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AOSpine Masters SeriesAdult Spinal Deformities
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AOSpine Masters SeriesAdult Spinal Deformities
Series Editor:
Luiz Roberto Vialle, MD, PhDProfessor of Orthopedics, School of Medicine
Catholic University of Parana State
Spine Unit
Curitiba, Brazil
Guest Editors:
Law rence G. Lenke, MDJerome J. Gilden Distinguished Professor
Orthopaedic SurgeryProfessor, Neurological Surgery
Chief of Spinal Surgery
Director of the Advanced Deformity Fellowship
Washington University School of Medicine
St. Louis, Missouri
Kenne th M.C. Cheung, MBBS(UK), MD (HK), FRCS, FHKCOS, FHKAM(Orth)Head, Depart ment of Orthopae dics & Traumat ology
Jessie Ho Professor in Spine Surge ry
The University of Hong Kong
Queen Mary Hospita l
Pokfulam , Hong Kong
With 92 f gures
Thieme New York • Stut tgar t • Delh i • Rio d e Janeiro
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Thiem e Med ical Publishers , Inc.
333 Seventh Ave.
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Library of Congress Cataloging-in-Publication Data
AOSpin e m aste rs se ries. v. 4, Adu lt sp inal d eform ities / ed itors , Luiz Robe rt o Vialle, Law ren ce G. Len ke,Ken net h M.C. Che un g.
p. ; cm.
Adu lt spinal deform ities
Includes bibliographical referen ces and index.
ISBN 978- 1-626 23-1 00-9 (alk. pap er) —ISBN 978-1 -626 23-10 1-6 (eISBN)
I. Vialle, Luiz Rober to , ed itor. II. Len ke, Law rence , 1960 – , ed itor. III. Che un g, Ken ne th M. C., ed itor.
IV. Title: Adult sp inal d eform ities.
[DNLM: 1. Spinal Diseases—sur ger y. 2. Orth ope dic Proced ure s—m eth od s. 3 . Spin e—sur ger y. WE 72 5]
RD768
617.4'71—dc23 2015 00197 9
Copyright ©2015 by Thieme Medical Publishers, Inc.
Impo rtant note: Medicine is an ever-changing science undergoing continual development. Research and
clinical experience are continually expand ing our knowledge, in par ticular our kn owledge of proper
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ISBN 978-1- 62623 -100- 9
Also available as an e-boo k:
eISBN 978-1-6 2623- 101-6
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Volum e 1 Metastat ic Spina l Tum ors
Volum e 2 Prima ry Spinal Tum ors
Volum e 3 Cer vical Degen erat ive Cond itions
Volum e 4 Adu lt Spinal Deform ities
Volum e 5 Cer vical Spine Trau m a
Volum e 6 Thoracolumba r Spine Traum a
Volum e 7 SCI and Regeneration
Volum e 8 Back Pain
Volum e 9 Pediatric Spina l Deform ities
Volum e 10 Spinal Infect ion
AOSpine Masters Series
Luiz Robert o Vialle, MD, PhDSeries Editor
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Series Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
Luiz Roberto Vialle
Guest Editors’ Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
Law rence G. Lenke and Kenneth M.C. Cheung
1 Preo pe rat ive Eva lu at io n and Op timizat io n for Su rge ry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Scott C. Wagner, Daniel G. Kang, Ronald A. Lehm an, Jr., and Law rence G. Lenke
2 Decision Making in Adu lt Deform ity Surgery:
Decom pression Ve rsu s Sh or t or Lon g Fu sion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Kenneth M.C. Cheung an d Jason P.Y. Cheung
3 Th e Use o f Ost eot omies for Rigid Sp in al De formit ie s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 8
Stephen J. Lew is and Sim on A. Harris
4 Indications and Techniques for Sacral-Pelvic Fixation in Adult Spinal Deform ity . . . . . . . . . 45
Kristen E. Jones, Robert A. Morgan , and Dav id W . Polly, Jr.
5 Instrumentation Strategies in Osteoporotic Spine: How to Prevent Failure? . . . . . . . . . . . . . 56
Ahm et Alanay an d Caglar Yilgor
6 The Inciden ce and Managem en t of Acute Neurologic Com plications
Follow in g Com p lex Ad ult Sp in al Defor m it y Su rge ry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 8
Joseph S. Butler and Law rence G. Lenke
7 Po st op erat ive Co ron al Deco mpensat io n in Ad u lt De formit y . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8
Yong Qiu
8 Measu r in g Ou tco me and Va lu e in Ad u lt De formit y Su rge ry . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5
Robert W aldrop an d Sigurd Berven
9 Ju n ct ion al Issu es Fo llow in g Ad ult Defo rmit y Su rge ry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 06
Han Jo Kim , Sravisht Iyer, and Christopher I. Shaf rey, Sr.
Contents
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viii Contents
10 Biomechan ics and Mater ia l Science fo r Deformi ty Correc tion . . . . . . . . . . . . . . . . . . . . . . . . . 120
Manabu Ito, Yuichiro Abe, an d Rem el Alinga lan Salm ingo
11 Pseudarthrosis and Infect ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
Michael P. Kelly an d Sigurd Berven
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
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Spine care is advancing at a rapid pace. The
challenge for today’s spine care professional is
to quickly synthesize the best available evi-
dence and expert opinion in the man agem ent
of spine pathologies. The AOSpine Masters
Series p rovides just that —each volume in th e
series delivers pathology-focused expert opin-
ion on procedures, diagnosis, clinical wisdom,
and pitfalls, an d highlights today’s top rese arch
pap ers.To bring the value of its masters level edu-
cational courses and academ ic congresses to a
w ider au dience, AOSpine h as assem bled inter-
nationally recognized spine path ology leaders
to develop volumes in th is Masters Series as a
vehicle for shar ing their exper iences and expe r-
tise and providing links to the literatu re. Each
volume focuses on a current compelling and
somet imes cont roversial topic in spine care.
The unique and e cient format of the
Masters Series volumes quickly focuses the
attention of the reader on the core informa-
tion critical to understanding the topic, while
encouraging the rea der to look furth er into the
recomm ended literature.Through this approach, AOSpine is advanc-
ing spine care w orldwide.
Luiz Roberto Vialle, MD, PhD
Series Preface
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Adu lt spin al deform ity (ASD) is a clinical prob-
lem of increasing prevalence, and thus physi-
cians and patients worldwide are aware of it.
With increasing longevity, the normal degen-
eration of the spine may lead to various ASD
prob lem s such as lum bar degenerat ive scolio -
sis with or without accompanying spinal ky-
phosis. In addit ion , ASD in clu des a sp ect rum
of preexistent childhood deformities, such as
scoliosis or kyphosis, that slowly progress tosymptomatic stages over adulthood. Clinical
manifestations may include progressive de-
form ity, poten tial spinal im balance, and spinal
stenosis, w ith resultant a xial or lower extre m -
ity symptomatology. Health-related quality-
of-life assessmen ts often d em onstrate severe
adverse e ects of ASD that can inter fere w ith
m any aspects of physical, emot ional, and psy-
chological well-being. Wh en clinical and rad io-
graphic scenarios warrant, surgical intervention,
ranging from simple decompressions to com-
plex total spine recon st ruct ion s, sh ou ld be con -
sidered in appropr iate patient s.
We have assembled a global panel of spe-
cialists to share w ith us the ir experience in the
m anagem ent of ASD, from evaluation to t reat-
ment, and including such issues as instru-
m ent ation and surgical techniques, as well as
prevent ing and m anaging complica t ions. Tho r-
ough patient evaluation, both m edical and sur -
gical, is warranted, with patient selection forindicated surgical intervent ion one of the m ain
keys to a successful outcome. Pertinent issues,
such as bone density evaluation and p reopera -
tive optimization, must be addressed w ith the
use of intraoperative adjuvants to ensure sta-
ble in ternal xat ion to the sp inal colum n in
pat ients requ ir ing st ab ilizat ion w ith or w ith-
out rea lignm ent . For pat ients w ith progressive
deformity producing segmental, regional, or
global malalignment, various corrective strat-
egies are discussed to safely realign the spinal
colum n u sing various forms of spinal osteoto-mies w ith adjuvant spinal instrum entation to
secure the spinal segments in their realigned
pos it ion. Spin al xat ion techniqu es are espe-
cially challenging whe n instr um ent ing the sac-
ropelvic unit in long constructs. The various
form s of osteotom ies utilized range from sim -
ple facet excis ions to ext rem ely co mplex thre e-
colum n osteotom ies such as pedicle subtr action
and vertebral colum n resection techniques that
are occasionally required for patient s w ith se-
vere deform ity w ith accompanying im balance.
Ensu ring n eu rologic safety du ring ASD surgery
is paramount, because these operations have
an early neurologic complication rate that is
not insigni cant and can lead to permanent
de cits. All of th ese essent ial pre ope rat ive and
intraope rative factors are discussed in det ail.
Even with initial surgical success, the long-
term success of surgery for ASD is controver-
sial. Variou s factors, such a s wo un d infection s,
pse udarthrosis, and adjacent segm ent pat hol-ogy, the most common being proximal junc-
tiona l kyph osis (PJK), can lead to d ete riorat ion
Guest Editors’ Preface
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xii Guest Editors’ Preface
of the clinical outcomes over time. The dura-
bilit y of clin ica l outcom e m easures for these
pat ients is an im por tant focus along w ith the
nan cial implications for treating ASD patient s.
Thus, as in all areas of medicine, the value
prop os it ion o f tre at ing ASD pat ients, bot h w ithnonoperative and operative procedures, must
be as certained to just ify the w ide spect rum of
interventions available. As in all areas of sur-
gery, selecting the appropriate patient and per-
forming the least aggressive surgery to solve
the clinical problem w hile ensuring long-term
success is the opt imal app roach.
We hope this book will help spine surgeons
from around t he world navigate the often con-
troversial and complicated clinical issues in-
volved in th e m an agem en t of ASD pat ient s, so
that the outcome can be maximized and the
complications m inimized.
Law rence G. Lenke, MD
Kenneth M.C. Cheung, MBBS(UK), MD (HK),
FRCS, FHKCOS, FHKAM(Orth )
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Yuichiro Abe, MD, PhD
Att en ding Spine Surgeon
Depar tm ent of Orth opaed ic Surgery
Eniwa Hospital
Eniw a, Jap an
Ahm et Alanay, MD
Professor
Departm ent of Orthoped ics andTraumatology
Facult y of Med icine
Acibadem University
Istan bu l, Turkey
Sigurd Berven , MD
Professor in Residen ce
Director of Spine Fellowsh ip an d Residen t
Edu cation Program
Depar tm ent of Orth opaed ic Surgery
Univers ity o f Californ ia–San Fran cisco
San Fran cisco, California
Jose ph S. Butler, PhD, FRCS (Tr&Orth )
Clinical Fellow
Spina l Deform ity Unit
Royal Nation al Ort hop aed ic Hospita l
Stan m ore, Middlesex , United Kingdom
Jas on P.Y. Cheung, MBBS, MMedSc, FHKCOS,
FHKAM(Orth), FRCSEd(Orth )
Clinical Assistant Professor
Depar tm ent of Ort hopae dics & Traum atology
The University o f Hong Kong
Queen Mary Hospital
Pokfulam , Hong Kong
Kenneth M.C. Cheung, MBBS(UK), MD (HK),
FRCS, FHKCOS, FHKAM(Orth)Head, Depar tm ent of Orth opaed ics &
Traumatology
Jessie Ho Professor in Spine Surger y
The University o f Hong Kong
Queen Mary Hospital
Pokfulam , Hong Kong
Sim on A. Harris, MA, MB, BChir, FRCSC
Fellow
Departm ent of Orthoped ics
Toron to West ern Hospital, University of
Toronto
Toronto, Ontario, Canada
Manabu Ito , MD, PhD
Director
Cen ter for Spine a nd Spina l Cord Disorde rs
Nat ional Hosp it al Organizat ion Hok kaido
Medical Cen ter
Sapporo, Japan
Contributors
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xiv Contributors
Sravish t Iyer, MD
Orthopaedic Surgery Resident
Hospital for Special Surgery
New York, New York
Krist en E. Jones , MDFellow
Depar tm ent s of Orth opaed ic Surgery and
Neuro su rgery
University of Minnesot a
Mineapolis, Minnesota
Daniel G. Kang , MD
Spin e Surgery Fellow
Depar tm ent of Orth opedic Surgery
Washington University
St. Louis, Missouri
Michael P. Kelly, MD, MSc
Assistant Professor of Ort hop ed ic Surger y
Assistant Professor o f Neurological Surgery
Depar tm ent of Orth opedic Surgery
Washingt on University School of Med icine
Sain t Louis, Missouri
Han Jo Kim , MD
Assistant Professor of Ort hop aed ic Surger yCo-Director of Edu cation
Spine Ser vice
Hospital for Special Surgery
New York, New York
Ronald A. Leh m an , Jr., MD
Professor of Ort hop aed ic Surgery
Professor of Neurological Surger y
Washingt on University School of Med icine
BJC Instit ut e o f Health
St. Louis, Missouri
Law ren ce G. Lenke, MD
Jerome J. Gilden Distinguished Professor
Distinguished Professor of Orthopaedic Surgery
Professor of Neurological Surger y
Chief of Spin al Surger y
Directo r of the Advanced Deform ity
Fellowship
Washingt on University School of Med icine
St. Lou is, Missour i
Step hen J. Lew is , MD, MSc, FRCSC
Associate Professor
University of Toront o
Depar tm ent of Surgery
Division of Ort hop aed ics
Toronto Western Hospital for SickChildren
Toronto, Ontario, Canada
Robert A. Morgan, MD
Assistant Professor
Orth opaed ic Surgeon
University of Minnesot a
Minneapolis, Minnesota
David W. Po lly, Jr., MDProfessor and Chief
Spine Ser vice
University of Minnesot a
Depar tm ent of Orth opaed ic Surgery
Minneapolis, Minnesota
Yong Qiu , MD
Professor an d Direct or
Depar tm ent of Spine Surgery
Nan jing Drum Tow er Hosp it alMed ical Schoo l of Nanjing University
Nan jing, Jiangsu Province, China
Rem el Alingalan Salm ingo , PhD
Visiting Researcher
Biomedical Enginee ring
Tech nica l University of Den m ark (DTU)
Engineer
JJ X-Ray A/S
Tech nica l University of Den m ark (DTU)
Scion
Kongens Lyngby, Den m ark
Chris topher I. Shaf rey, Sr., MD
John A. Jan e Professor of Neuro logical
Surgery
Professor of Ort hop aed ic Surger y
Depar tm ent of Neurological Surgery
University of Virginia School o f
Medicine
Char lot tesville, Virgin ia VA
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Contributors xv
Scot t C. Wagner, MD
Instr uctor of Surgery
Division of Surgery
Departm ent of Orthopaed ics
Uniform ed Services University of the Healt h
SciencesWalter Reed Nation al Militar y Medical Cen ter
Bethesda, Maryland
Robert Waldrop, MD
Fellow in Spine Surger y
Depar tm ent of Orth opaed ic Surgery
Univers ity o f Californ ia–San Fran cisco
San Fran cisco, California
Caglar Yilgor, MD
Assistant Professor
Departm ent of Orthoped ics and
Traumatology
Facult y of Medicine
Acibadem UniversityIsta nb ul, Turkey
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! Introduction
Adu lt spinal deform ity is an umbrella term en-
compassing various developm ent al, progres-
sive, or degen erative conditions t hat contribute
to an altered three-dimensional structure of
the h um an spine. There are t hree m ain types of
adult spinal deformity: t ype 1, de n ovo, or pr i-
m ary de generative scoliosis; type 2 , unt reated
adolescent idiopathic scoliosis that has pro-gressed into adu lthood; and t ype 3, secondary
scoliosis related to altered vertebral anatomy
due to previous surgery, trauma, or metabolic
bon e dise ase.1 A second ar y form of adult scoli-
osis is iatrogen ic imb alance cau sed by previous
spinal surger y.2 The m ost clinically imp orta nt
and m ost comm only encountered t ypes of adult
deformity are t ypes 1 and 3.1
Str uctu ral curves that develop in adulthood
(type 1) generally begin and then progress as
the intervertebral disks degenerate with nor-
mal aging. As disk degeneration progresses,
pos terior ele m ent incompet ence leads to axia l
rotation of the spinal motion segments, with
perm anent ro tator y deform it y in turn leading
to ligamentous laxity and eventual lateral lis-
thesis of the vertebral bodies.3 Destr uction of
the d iskoligam entou s comp lex and e nsuing de-
generation of the facet joints leads to ab norm al
m otion at each vertebral segment , subsequen tly
causing reactive chan ges such as osteophytosisat th e en d plates, facet joint hypert rophy/cysts,
and ligamentu m avum hypertrophy. In addi-
tion, the concavity of the m ajor and fractional
curve can cause foram inal narrowing, w hich is
often furthe r exacerbated by disk degeneration
and loss of foram inal height (up/dow n foram-
inal stenosis). These changes cause nar rowing
of the spinal cana l (cent ral and lateral recess)
and ne ural foramen ,1 and collectively contrib-
ute to t he clinical symptom s of adult scoliosis
or spinal deformity. Thus, understanding the
complex pathomechanics and anatomy of thisdegenerat ive p rocess is vital for spine surgeons
considering per form ing deform ity su rgery. As
the population ages and life expectancy in-
creases, the prevalence of degene rative a dult
spinal deformity w ill continu e to increase.2 In
fact, the impact on overall public health and
disability of the United States population by
adult degenerative scoliosis cannot be over-
stated, and there will likely be an increased
num ber of these pat ients electing surgical cor-
rection of their deformity and treatment of
their symptom s.2,4
! Epidemiology
New -on se t adult degenera t ive deform it ies are
considered in the context of a popu lation older
than 40 years of age, without a prior h istory of
adolescen t idiop ath ic scoliosis (AIS). Adu lt sco-liosis can b e asymp tom atic, and the inciden ce
of spinal curves of less tha n 10 d egrees m ay be
1
Preoperative Evaluation andOptimization for Surgery
Scott C. Wagner, Danie l G. Kang, Ronald A. Lehman, Jr.,
and Law rence G. Lenke
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2 Chapte r 1
as h igh as 64%.5 In fact, 30%of elderly patien ts
w ithout a previous history of spinal deform ity
w ill develop new str uctu ral abnorm alities, w ith
m en and wom en a ected equally (in contrast to
adolescent idiopathic scoliosis, in which girls
are more com monly a ected than boys).3 Pa-tient s w ith progressive degenerative spinal de-
form ities typically present in the sixth de cade
w ith various symptom s, frequently including a
combination of back pain, radiculopathy, and
neurogenic claudication.3 Adult degenerative
deformities tend to progress up to 6 degrees
per year, ave raging 3 degre es per year, if left
untreated,3 and radiographic parameters that
p re dict a high risk for progression inclu de a
Cobb an gle greater th an 30 degrees, lateral olis-
thesis greater than 6 m m , and a large degree of
apical rotation.3 However, open su rgical spina l
deformity correction in adu lt patients is asso-
ciated w ith a com plication rate of up to 8 6%,
including a 7.8%rate of early wound infection,
and is typically associated w ith large am ount s
of int raoperat ive blood loss, deep w ound infec-
tion, and p ulmonary em bolism .4,6,7
Therefore, thorough preoperative evalua-
tion and opt imization is absolutely param ount
when considering surgical treatment of adultspinal deform ity, because this patient popu la-
tion is often elderly, with m ultiple associated
comorbidities, and at h igh r isk for m edical and
surgical complications.8 A multidisciplinary
app roach, including the p rima ry care p rovider,
an internist, an endocrinologist, a cardiologist,
as well as the t reating spine surgeon, should be
unde rtaken in the perioperative evaluation pro-
cess to minimize the potential medical risks
and maximize the functional bene ts.
! Clinical Evaluation
Initial Assessment
The initial assessment must include taking
a comprehensive history and performing a
thorough physical examination. A previous
diagnosis of spinal deform ity (e.g., adolescent
idiopathic scoliosis, kyphosis, congenital de-formity), a history of prior spine surgeries, as
well as any previous imaging studies demon-
strating progression of degenerative changes
and deformity w ill provide clinical cues to ap -
pro priat ely gu ide the rem ainder of th e w orku p.
Patients typically present with a combination
of various comp laint s, including uppe r or lower
back pain , ra diat ing low er ext rem it y pain orweakness, paresthesias/numbness, neurogenic
claudication, di culty with gait or upright
pos ture, and progress ion of their defor m it y.
Changes in body hab itus/postu re (par ticularly
chan ges in th e t of cloth ing), di culty w ith
gait or decreased walking distance tolerance,
and changes in the use of assistive devices are
elicited du ring the h istory-t aking process. Back
pain is t he m ost com m on pre sent ing symptom ,
and complaints of pain must be di eren tiated
with regard to axial versus radicular symp-
toms. Isolated low back pain may represent
par asp in al m uscle fat igu e or m echanica l in st a-
bilit y at the painful segm ent ,1 with increased
pain severit y oft en su ggest ing signi cant sag-
ittal and coronal imbalance.3 If radicular pain
is present in addition to axial pain, duration/
onset of symp tom s, exacerbating activities, and
laterality of the symptoms provide guidance
for p otent ial decomp ression.1,3 Radicular ex-
tremity pain can be caused by an acute diskherniation, localized foraminal or lateral re-
cess nerve root compression from osteophytes/
spondylotic chan ges, foram inal compression on
the concave side of the fractional curve, or t rac-
tion on the convex side of the deformity, or
m ay be related instead to single- or m ultilevel
central stenosis. Neurologic de cits are less
com m on in adult deform ities, but w hen pres-
ent are often related to segmental instability
causing foraminal compression or congenital
spinal stenosis, w hich is exacerbated by degen-
erative changes causing further central canal
stenosis.1 The operative approach should take
into consideration the extent and t ype of de-
compression and fusion constr uct, if any, that
is indicated based on the patient’s symptom-
atology, as well as any recent changes or pro -
gression of symptom s.1
The clinical exam ination includes assessment
of a shift in the trunk, and the relationship of
the h ead to th e pelvis in th e coronal and sagit-tal plane is noted. Asymm etr y of the shoulder
or pelvic girdles provides useful information
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Preoperative Evaluat ion and Optimization for Surgery 3
w ith regard to th e severity of the deform ity, as
do pelvic obliquity and leg-lengt h discrep an cy.
Othe r subt le clues to severity an d pr ogression
of the deformity include skin creases around
the trun k/abdomen and standing posture (e.g.,
pelvic re t roversio n, h ip /k nee ex ion). Havingthe p atient perform forward an d lateral bend-
ing during the exam can provide important
prognost ic in for m at ion, as the r igid it y of the
curve can a ect the overall outcom e of nonop -
erative and subsequ ent op erative intervent ion.
Hip and knee exion contractu res should also
be assessed w ith t he pat ient lying in t he supine
posit ion on the exam inat ion table. Then, w ith
the patient lying in the prone position on the
table, the exibility of the curve without grav-
ity can be dete rm ined, and th e pat ient’s ability
to tolerate the prone position and overall phys-
ical condit ioning can be a ssessed. The p atien t’s
inability to t urn prone indepen dently may in-
dicate signi cant deconditioning and th at the
pat ient is a high -r isk su rgical candidat e). Neu-
rovascular examination includes overall gait
assessmen t, motor strength, deep ten don re-
exes, sensation and cranial nerve function,
as well as extremity pulse assessment.3 The
pat ien t sh ould also b e exa m in ed for long t ractsigns, as myelopathy m ay be a componen t of
severe thora cic deform ity, as well as to ensur e
that the patient does not have concomitant
cervical stenosis.
Radiographic Evaluation
Radiographic evaluation includes full-length
standing anteroposterior and lateral radio-
graphs of the spine, with the patient’s knees
and hips straight, as well as supine full-length
lms to provide information regarding any
spontaneous deformity reduction with gravity
forces removed. Cobb angle measu rem ent s and
radiographic determ ination of spinopelvic im-
balance provide crit ica l in form at ion, as t he d e-
gree of the curve and t he extent of imbalance
can necessitate discussion of operative inter-
vention at the time of initial evaluation. For
the purpose of preoperative planning, these
m easurem ent s are imp erative. Rotatory sublux-ation, the presence and location of osteophyto-
sis, and a ny ant eroposterior or lateral listhesis
are noted. Magnetic resonance imaging (MRI)
is routinely obtained , particularly in th e p res-
ence of radicular pain or neu rologic symptom s,
though it is not uncomm on for th ese older pa-
tients t o be u nable to und ergo an MRI for var-
ious reasons (e.g., presence of a pacemaker).Also, in the revision setting, previous spinal
instrum ent ation m ay cause signi cant im age
art ifact and di culty in MRI interpr etation. In
such patien ts, comp uted tom ography (CT) my-
elogram is obtained instead of MRI, and pro-
vides information regarding signi cant areas
of stenosis. We also rout inely obtain a CT scan
in adult spinal deform ity patients for preoper-
ative p lanning, wh ich e nables evaluation of the
extent of spondylotic changes and the levels/
areas of autofusion, helps deter m ine th e feasi-
bilit y an d sizing of sp inal xat ion poin ts, an d, in
the revision set ting, helps ana lyze th e location/
size of any previous decom pressions, the heal-
ing of previously fused regions, and the position
of previous spinal instru m ent ation. In ad dition,
at our institution, the CT scan is useful in pa-
tient s w ith complex deformity (e.g., congenital/
segmen tation abnorm alities, signi cant angu-
lar deformity, previous postsurgical changes)
through t he u se of a thre e-dim ensional acrylicm odel for p reoperat ive p lanning, and can also
be use d in t raop erat ively to iden t ify topo-
graphic landmarks and guide placement of
instrumentation.
Provo cative Testing
Selective nerve root/transforaminal cortico-
steroid injections can also be used to provide
diagnostic inform ation as w ell as a th erape ut ic
e ect.1 We use selective ner ve root/transforam-
inal injections in patients with a component
of radicular/lower extremity pain to help de-
term ine the speci c ner ve root causing symp -
tom s, provide tem porar y relief prior to su rgical
treatm ent , and ultim ately to localize the levels
in which decompression may result in symp-
tom relief. However, th e u tility of select ive ne rve
root/transforaminal injections remains unclear,
as the lack of response to t he injection m ay be
attributable to the injection technique or to poor pat ient re ca ll. We sp eci cally ask the pa-
tient about the immediate relief of symptoms,
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4 Chapte r 1
w ithin 5 to 10 m inutes follow ing the injection,
as a criterion for a diagnostic injection (symp-
tom s likely arising from th at level of injection).
In contrast, an injection causing relief hours
or days later m ay be a function of the system ic
anti-in ammatory e ect following systemicabsorption of the corticosteroid. Similarly, in
our experience, epidural corticosteroid injec-
tions provide limited diagnostic information,
as the corticosteroid medication distributes
throu ghout m ultiple levels and is also absorbed
system ically. However, we o er ep idura l cort i-
costeroid injections for patients w ith signi cant
central or lateral recess stenosis to poten tially
provide tem porary r elief of sym ptom s an d im -
prove physica l fu nct ion to e nable pre op era t ive
optim ization of tn ess and m obility. We do not
routinely use facet blocks or diskography for
diagnostic assessment in the adult spinal de-
form ity patient.9 However, in patien ts w ith iso-
lated axial back pain an d ar thr itic facet changes
on imaging stud ies, facet blocks m ay be ut ilized.
Because the pain generator can be located at
any point in t he spine relative to t he a pex of
the curve, facet blocks are performed sequen-
tially at di erent levels to isolate speci cally
which motion segments are causing the pain,with subsequent relief of symptoms after in-
ject ion/a blat ion.1
! Nonoperative Manageme nt
A trial of nono perat ive m anagem ent is indicated
for almost all patients presenting with adult
spinal deformities, particularly curves of less
than 30 degrees, less than 2 mm of listhesis,
and if the constellation of symptom s is relatively
m inor. In contradistinction to th e t reatm ent al-
gorithm of adolescent idiopathic scoliosis, th ere
is no role for bra cing in adu lt spinal deform ity
pat ients3 because th e progression of the cur ve
is related to degenerative changes and me-
chanical instab ility, and not longitu dinal growt h
of th e axial skeleton . The refore, th e ben e t of
tem porar y pain relief is out weighed by the p o-
tential deconditioning of the paraspinal mus-cles an d by skin complications resulting from
brace trea tm ent in th is pat ient pop ulat ion.3,10
However, in rare cases in w hich the pain source
cannot be adequately localized, thoracolum-
bar or t horacolu mbosacral o rthoses (TLO/TLSO)
m ay be considere d for tem porar y stabilization
and pain relief.1 Low-impact core strengthen-
ing programs an d ph ysical therapy are utilizedto improve patient reserves as well as to stabi-
lize the surrounding musculature to provide
improved support to the spinal column.3 Non-
stero idal ant i-in am m ator y drugs (NSAIDs) are
used t o p rovide relief of axial and, occasionally,
radicular pain an d n eurogenic claudication. We
do not routinely provide n arcotic pain m edica-
tions for nonoperative treatment, and pain
management specialists are consulted to pro-
vide multimodal therapy with optimization of
non narcotic pain m edications (e.g., gabapent in,
pre gabalin ), althou gh som et im es sh or t p eriods
of narcotics or pain m edications may be n eces-
sary. Also if ope rat ive tre atm en t is decided, we
encourage reduction or complete discontinua-
tion of any narcotic pain m edications to avoid
di cult pain m anagement in the postoperative
period.
! Surgical Indications
Indications for surgery in th ese pat ients include
failure of nonoperative pain m anagement w ith
signi cant ly dim inished qua lity of life/fun ction ,
or progression of deformity/imbalance, with
correlation between radiographic and clinical
ndings. As previously mentioned, lumbar
curves greater than 30 degrees or with 6 m m
of listhesis in a ny plane a re considered for sur-
gery because the deformity is at high risk for
progressio n. Also , pat ients w ith annual defor-
mity progression greater than 10 degrees or
with increasing listhesis (lateral, anterior, or
poste rior ) greate r than 3 m m, and w hose sym p-
tom s are progressively worsening, are o ered
surgical stabilization. Ultimately, the decision
to proceed w ith surgical management is predi-
cated on several major factors, including the
pat ient’s symptom at ology, age, genera l m edi-
cal health, and t he p atient’s expectations w ithregard to the out come of such a signi cant pro-
cedure.1 If surgical options are to be pursu ed,
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Preoperative Evaluat ion and Optimization for Surgery 5
medical optimization of the patient and de-
tailed preope rative surgical planning are a bso-
lutely critical to promote the success of the
treatment plan.
! Optimization for Surgery
As previously m ent ioned, the present ing age of
pat ients w ith adult sp inal deform it ies is typ i-
cally between 60 and 70 years, and systemic
m edical com orbidities are com mon .1,3 Diabetes
and cardiac and vascular disease can signi -
cantly impact the surgical outcome, particu-
larly for a large reconst ru ctive procedu re, given
the potential for considerable intraoperative
blood loss and overall surgica l t im e.1,3 Postop-
eratively, elderly patients also require longer
rehabilitation, given t heir decreased cardiopul-
m onary reserves.1 Therefore, consultation w ith
the anesthesiologist and the patient’s primary
care provider is recommended to pursue an
interdisciplinary approach for stratifying the
pat ient’s perioperat ive m edica l r isks and op t i-
m izing medical com orbidities prior to proceed -
ing with surger y.Halpin et al11 and Sugrue et al 12 described
the ir high-r isk protocol for pat ients u nde rgoing
major spinal surgery: patients are considered
high risk if the surgeon an ticipates longer than
6 hour s of operative time, more th an six vert e-
bral levels w ill be included, o r that the pro ce-
dure will be staged, or if the patient presents
w ith signi cant m edical comorbidities. In these
authors’ protocols, all high-risk patients are
evaluated by a hospitalist an d anesth esiologist,
and various param eters are evaluated an d opti-
mized, including nutritional status, pulmonary
statu s, cardiac and renal function, and he patic
function.11,12 The case is then discussed at a
conferen ce for h igh-risk spine procedu res th at is
atten ded by all m anaging providers before op-
erative clearan ce is granted.11 At ou r institu tion,
the use of similar goal-directed, evidence- based
prot ocols to coor din at e the ca re of com plex
pat ien ts has im prove d outcom es and ove rall
pat ient sat isfact ion postop era t ively.12
Nut rit ional s tat us of the ad ult sp inal d efor-
m ity patient sh ould be assessed preope ratively.
This evaluation is typically accomplished by
measuring serum albumin, prealbumin, total
prot ein , a nd t ransferr in , w hich provide in for -
mation regarding patient protein reserves.13
Patients with albumin levels less than 3.5 g
per d eciliter h ave been s how n t o h ave a s ign i -cantly higher risk of complications and m or-
tality.14 Prealbumin levels below 11 mg per
deciliter require nutritional support, and be-
cause these levels are not a ected by hydration
status, prealbumin is the recommended mea-
surem ent tool for assessing nut ritional stat us.14
Any insu ciency in the nutr itional state iden -
ti ed preope ratively should be corrected prior
to surgery, consulting with a nutritionist if
necessary. The d uration of nut ritional support
is dependent on the severity of the malnour-
ished state and the patient’s general health,
bu t generally is 6 to 12 w eeks in order t o at tain
approp riate nutr itional optim ization, although
some patients may require a longer period.
Postoperative nutrition is an important aspect
for all patients following spinal deformity
surgery, particularly with complex spinal re-
construct ive procedures that enta il signi cant
m etabolic deman d. There is often a balance in
timing for the start of nutrition by mouth andreturn of bowel function (i.e., bowel sound,
atus, and bowel m ovem ent). Star ting an oral
diet too early may result in ileus or obstruc-
tion, wh ich can signi cantly increase th e pa-
tient ’s pain and limit early rehabilitat ion e orts,
whereas unnecessarily delaying the start of
nutrition may fail to meet metabolic require-
m ent s to optimize healing and rehabilitation in
the postoperat ive p eriod. Therefore, in certa in
cases, part icularly follow ing complex spin al re-
constructive procedures, we at tempt placem ent
of a small bowel feeding tube (SBFT) on post-
operative day 1, with the goal to begin tube
feed s by postop erat ive day 2. If th ere is di -
culty in placing th e SBFT distal to t he pylorus,
we begin parenteral nutrition support through
central access. We continue small bowel tube
feeds or parenteral nutrition support until
the patient is tolerating adequate nutrition by
mouth.
Perioperative blood management is an as- pect of adult sp in al deform it y su rgery that
requires particular attention. Low preoperative
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6 Chapte r 1
hem oglobin concentration and increased num -
ber of levels fuse d have been sh ow n to be
signi cant risk factors for allogeneic blood
transfusion at the time of surgery.15 The risks
associated with transfusion are myriad, and
include benign febrile reaction, infectious dis-ease transmission, and anaphylaxis. Therefore,
e orts to redu ce the potent ial need for tran sfu-
sion should be undertaken preoperatively. In
the absence of any contraindications, we rec-
omm end t hat patients w ith adult spinal defor-
mity take iron supplements for 2 to 4 weeks
prior to s urgery.14 The re is evidence to suggest
that preoperative recombinant human eryth-
ropoietin (rhEPO) adm inistrat ion in the p reop-
erative period can reduce the transfusion rate
without increasing complications.16 However,
at our institut ion this is not a com m on pract ice
given t he signi cant exp en se of rhEPO, an d, in
our experience, its lim ited e ectiveness in the
adu lt spinal deform ity patient . We t ypically use
other perioperative adjunctive measures and
blood m anage m ent st ra tegies, w hich inclu des
the use of intravenous anti brinolytics (e.g.,
tranexamic acid), cell saver, and topical hemo-
stat ic agent s (e.g., Surgi o, th rom bin), as well
as paying meticulous attention to hemostasisthroughout the procedure (including packing
o segmen ts w ith rolled surgical sponges to
redu ce blood loss wh en at tent ion is focused on
decompressing or instrum enting more cepha-
lad or caud ad spina l levels).
Open anter ior surgical deform ity correction
for severe spinal deform ity has been shown to
have detr imen tal e ects on postoperative pul-
monary function, particularly in older adult
pat ients or pat ients w ith preexist ing lung dis-
ease.17,18 Although pu lmon ary function testing
is not routinely performed preoperatively, we
typically evaluate patients with pulmonary
symptom s, di culty with or poor endurance
w ith daily activity an d am bulation, or comp lex
or severe thoracic deform ity (often with planned
three-colum n osteotomy). We use pulmonar y
function testing in th ese patient s to stratify the
risk of poten tial postoperative pulm onar y com -
plica t ions, and we o btain a p ulm on ary sp ecial-
ist consultation for per ioperative optim ization.Also, preope rat ive sm oking cessation is imp er-
ative for at least 8 w eeks prior to surgery.
Typically, major deformity correction and
fusion has been accomplished via combined
anterior/posterior approaches; th e an terior re-
lease with fusion is achieved via a thora cotomy
or thoracoabdominal approach, followed by
posterior inst rum entat ion, which provid es im - proved fusio n rat es and be t ter ove rall corre c-
tion.19 However, it is postulated t hat d isruption
of the thoracic cage during the anterior ap-
pro ach lead s to injury to t he r espirator y m ech -
anism.18 Because of this theor y, there h as been
interest in posterior-only management of se-
vere deform ities (e.g., via t hree -colum n osteot-
omies such as pedicle substraction osteotomy
[PSO] or vert ebra l colum n resect ion [VCR]) an d
in the theoret ical bene ts of obviating the an -
terior approach on pulmonary function. There
is some evidence that posterior-only surgery
can achieve sim ilar postoperat ive ra diographic
outcomes19; however, patien ts w ith such severe
deform ities often presen t w ith chronic restr ic-
tive lung disease, with m inim al potent ial for
improvemen t in lung function despite correc-
tion of the thoracic deformity, and a recent
study found that, in adult patients, utilization
of VCR for severe deformity correction did
not improve postoperative pulmonary func-tion.18 Preoperat ive pulm onar y funct ion test-
ing, therefore, may be worthwhile in patients
w ith signi cant thoracic deform ities and base-
line pulmonary disease to establish potential
reserves. Thus, it is imp orta nt to counsel older
pat ients w ith m ore severe deform it ies t hat de-
spite the correction a orded by the surgery,
wh ich m ay require extensive osteotom ies, pul-
m onar y function may not imp rove signi cantly
pos top erat ively.18
Hypovitaminosis D, although extremely
common, is often missed in the preoperative
setting, despite the potentially serious com-
p licat ions ar isin g from th is de cie ncy. It is
estimated that more than half of all general
m edicine inpatients are de cient in vitam in D,
though the prevalence in patients undergoing
spine surgery remains largely unexplored.20 A
recent stu dy from a single institu tion foun d an
overall vitamin D de ciency rate of 57%in pa-
tients undergoing spinal surgery of any kind,and t he rate for patient s with diagnosed spinal
deform ity w as 18 %; th is relatively low preva-
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Preoperative Evaluat ion and Optimization for Surgery 7
lence is likely att ributable to an increased rate
of vitam in D supp lemen tation in this cohor t.20
It is thus important to consider this diagnosis
and recom men d ade quate vitam in D intake for
pat ients w ith diagnosed sp inal deform it y, es-
pecially p re op erat ively, as calciu m m et abo lismis extremely important in the prevention of
osteoporosis.
Along with hypovitaminosis D, osteoporo-
sis is also very com m on in this patient p opula-
tion. The management of this serious disease
requires the cooperation of a mu ltidisciplinary
team. Postmenopausal women are at a high
risk for d evelopmen t an d p rogression of oste-
oporosis, which can lead to fragility fractures
and increased mortality; however, older men
may also present with osteoporosis, and any
clinical suspicion should prompt an initial
workup . The World Health Organization (W HO)
recomm ends that all peri- and postm enopausal
wom en u ndergo screening for low bone m in-
eral density (BMD),21 and dual-energy X-ray
absor pt iome tr y (DEXA) is th e gold stan dard for
assessment of BMD. We obtain DEXA BMD
measurements of the lumbar spine and hips
for all preop erat ive pat ient s, regardless of age
or gender, to identify osteoporotic patientswh o may require optimization/treatm ent w ith
consultation of an endocrinologist or primary
care provider prior to surger y. Postm enop ausal
women diagnosed with osteoporosis should
also receive 1,500 m g calcium and 400 IU vita-
m in D daily. The re also exist medical modalities
for optimization of BMD, including bisphos-
phon at es , p arat hyro id hor m on e (t eripara t ide),
estrogen modu lators or horm one replacement ,
and calcitonin. The use of these medications
should be m onitored in consultation with the
pat ient’s endocrinologist or prim ary care pro -
vider. Identifying patients with osteoporosis
pr ior to su rgery facilitat es t reat m ent and op t i-
m ization of their BMD, and can improve surgi-
cal outcom es by optim izing th e xation strengt h
of the sur gical instrum ent ation and ultim ately
improve bone healing/fusion.
Cardiopulmonary, nutritional, and bone-
quality assessments are vital in this patient
pop ulat ion. Com or bidit ies a re in tuit ively m orecommon in the adult deformity population
wh en compared with t he adolescent idiopathic
scoliosis population, and the presence an d se-
verity of these comorbidities guide the initial
management of the deformity. Although there
has been some evidence that osteopenia and
osteoporosis do not play a signi cant role in
the progression of adult spinal deformity,3 in pat ients ele ct ing to proceed w ith su rgical cor -
rection of scoliosis th e p resence of osteoporo-
sis can a ect the ability to obtain purchase in
the bony spine. In p atients over 50 years of age
und ergoing spine surger y of any type, the inci-
dence of osteoporosis has been reported to be
14.5%for me n and 51 .3%for wom en.22 Indeed,
osteoporosis is associated w ith rep orted fusion
rates a s low a s 56%, as well as iatrogen ic inst a-
bilit y and fract u re follow ing su rgery.23 Sur-
veys have found that most orthopedic spine
surgeons feel uncomfortable managing the
treatm ent of osteoporosis after it has been di-
agnosed24 ; therefore, prompt referral to pri-
mary care providers or endocrine specialists
for partial or complete management of osteo-
poros is prior to an y planned su rgical proce-
dure is recomm ended.
Lastly, psychosocial factors m ust be con sid-
ered. Mental health issues are common in the
older adult popu lation, and the p resence of de- pression , an xiety, psych osis, or o ther prem orbid
psych ological condit ions ca n adverse ly a ect
surgical outcomes and patient perception of
surgical success.11 These factors can be m an-
aged by e ectively utilizing a team of social
workers or case man agers and psychiatric sup -
por t , an d shou ld n ot be ove rlooked p rior to u n-
der taking major spinal deform ity surgery.
! Preventing Complications
Medical comp lications surrou nding ad ult spi-
nal deformity surgery can range from mild to
extrem ely severe, with an overall comp lication
rate ranging from 40 to 86%in patien ts und er-
going d eform ity surger y.25 Thorough atte nt ion
to the preoperative medical optimization pro-
cess can r educe t he inciden ce of postoperative
complications, and str ategies to m inimize suchcomp lications sho uld be judiciously em ployed.
The m ost comm on m inor complication in th e
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8 Chapte r 1
pos top erat ive period is urinary t ract in fect ion
(UTI), with a re por ted rate of 9%.25 UTIs can b e
prevented pre - and in t ra op erat ively by appro -
priat e st erile technique during inse rt ion of the
catheter, unrestricted catheter drainage, early
removal, and, in some instances, instillation of be nign ba ct eria in the urinary t ra ct .25 Pulmo-
nary abnormalities, including atelectasis and
pneum on ia, are a lso very com m on in th is p op -
ulation. These complications can be p revented
in the preop erative setting via sm oking cessa-
tion at least 8 we eks prior to surgery, as noted
above, as well as approp riate use of bronchodi-
lators or pulm onar y rehabilitation p rotocols.25
Of course, many oth er intra- and p ostoperative
strategies exist to m inim ize th e nu m erous com-
plica t ions that m ay occu r, bu t t hese a re beyon d
the scope of this chapt er.
! Preoperative Planning
Levels of Treatment
Six levels of operative t reatm ent were described
by Silva an d Lenke3 in 2 010: I, decomp ressionalone; II, decompression and limited instru-
m ente d p osterior spinal fusion; III, decompres-
sion and lumbar curve instrumented fusion;
IV, decompression w ith an terior an d p osterior
spinal instr um en ted fusion; V, th oracic in-
strumentation and fusion extension; and VI,
inclusion of osteot om ies for speci c deform i-
ties. Each level represent s a u nique ap proach t o
surgical m anagem ent of adu lt spinal deform ity,
p re dica te d on the constellat ion of symptom s
reported by the patient, and d esigned to pro-
vide independent symptom management. For
pat ients w ith neurogenic claudicat ion alon e
secondar y to cent ral canal stenosis, level I treat-
m ent , which ent ails lim ited decomp ression, is
app ropriate. These patient s often presen t with
minimal back pain, and radiographic analysis
may reveal small osteophytes with less than
2 mm of subluxation. Additionally, these pa-
tient s should have no cosm etic or major defor-
mity complaints, and the coronal and sagittal balance m ust be w ithin re ason , as isolat ed cen-
tral decompression in the presence of curves
greater tha n 30 degrees (or with kyph osis) can
lead to worsening of the deformity.3 A rela-
tively large series found that coronal imbalance
greater than 4 cm correlated with decreased
overall patient-related ou tcome scores on the
Scoliosis Research Society-22 (SRS-22) scale
an d t he Oswestr y Disability Ind ex (ODI),26 andthus these param eters are extrem ely impor tant
in th e su rgical decision-making process. How-
ever, for the relatively well-balanced patient
with m ore than 2 m m of subluxation, the addi-
tion of posterior instr um ent ation at th e level of
the decomp ression imp roves stability and con-
stitutes level II of treatment. If such patients
also have comp laint s of signi cant lumb ar pain
associated with the lumbar deformity greater
than 30 degrees, but maintain global sagittal
and coronal alignme nt, the e ntire lumbar curve
m ust be included in the instrum ented region,
wh ich const itutes level III of treat m ent .3 Trans-
foraminal lumbar interbody fusion (TLIF) may
also be utilized as an adjunct when fusing to
the sacrum to imp rove xation and fusion at the
tran sitional lumbosacral jun ction.3
Loss of lumbar lordosis, often associated
with at-back syndrome in adult deform ity pa-
tient s, is often m anaged via an ant erior fusion
approach. Utilizing anterior fusion in additionto poste rior xation const itut es level IV an d
provid es bo th load sh ar ing t o re duce posterior
strain and a dditional ceph alocaudad foram inal
decompression.3 In addition to the aforemen-
tioned criteria, patients with additional sagit-
tal imbalance can be managed by expanding
the fusion proximal to t he thoracolum bar junc-
tion, which constitutes level V of treatm ent .3
It is also important that anterior osteophytes
be m inim al, an d sign i cant thoracic kyphosis
contraindicates this t reatmen t approach.3 Once
signi cant sagittal or coronal imbalance has
developed, spinal fusion without adjustment
of global alignm en t will be insu cient to
control symptom s. A recent retrospective stud y
exam ining the role of preoperative coronal and
sagittal balance found that postoperative cor-
rection of sagittal balance was the strongest
predictor of clin ical ou tcom es, whereas another
study has suggested that severe preoperative
coronal imbalance predicts worse functionalrecovery.7,26 Historically, patients with severe,
rigid spinal deform ities have been managed w ith
combined anter ior/posterior app roaches; how-
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Preoperative Evaluat ion and Optimization for Surgery 9
ever, there has been increased interest in the
use of complex three-column osteotomies to
enab le an all poster ior approach, however inter-
est in the u se of complex three-colum n osteoto-
mies to enable an all posterior approach; the
use of these osteotomies constitutes Level VIof surgical m anagem ent . These comp lex three-
colum n osteotom ies require highly experienced
surgeons and a specialized operating room team
to ensure optimal outcomes and the highest
level of safety, and even with this expertise
the re is still a 30 to 40% rate of complications
following th ese p rocedures.17
! Chapter Summary
Patients with adult spinal deformity represent
some of the m ost complex surgical candidates
in the population, and estimates suggest that
the number of patients electing to undergo
surgical correction will continue to increase.
Adu lt scoliosis comp rises a diverse sp ect ru m o f
disease, w ith m ultiple potent ial etiologies and
natural histories, and as such there is no one
single approach to management that can beapplied to a ll adult deform ity patient s. Radio-
graph ic, clinical, an d subject ive nd ings m ust
be assessed preop erat ively by a m ult id isci-
p lin ary team . Because these pat ients typ ica lly
prese nt aft er the sixt h decade of life , w it h
m ultiple associated m edical com orbidities, the
spine surgeon must be aware of the potential
for signi cant risk exposure in the pe riopera-
tive setting. A multidisciplinary approach to
pre op era tive evaluat ion m ust be employe d,
and t he p atient’s prim ary care provider, inter-
nist, endocrinologist, and cardiologist should
be act ively engaged in det erm in ing if the pa-
tient is appropriate for surgery and in prepar-
ing the pat ient for th e procedu re. If the patient
is not cur rent ly being evaluated for major med-
ical conditions common to this population,
such as restrictive lun g disease or osteoporosis,
the spine surgeon may be the rst provider to
initiate assessmen t and recomm end treatm ent.
The complexity of the t hree- dime nsional path-oanatomy and associated biomechanics that
can signi cantly a ect postoperat ive outcom es
must be understood and respected, and the
preop erat ive eva luat ion and op t im iza t ion for
surgery process must be tailored to each in-
dividual patient. With ap propriate patient se -
lection, understanding of all treatment options
and decision algorithms, as well as under-
standing the importance of a team approachto perioperative medical management, spine
surgeons can expect good results for their pa-
tients undergoing surgical treatment for adult
spinal deformit y.
Pearls
Back pain is the m ost com mon complaint in adu lt
spinal deformity patients.
If claudication symptoms are present in addition
to axial pain complaints, laterality of the pain
provides gu idance for poten tial de com pre ssion
and likely instrum ent ed fusion.
The rigidity of the curve can be assessed both
clinically and radiographically, and a ects overall
outcom es of nonop erative and subsequen t oper-
ative intervention.
Full-length standing anteroposterior and lateral
radiographs o f the spine are essent ial, and supine
full-length lms provide informat ion regard ing
any spontaneous deformity reduction related to
gravity. Indications for surgery in these patients include
failure o f nonope rative p ain manag ement , as well
as correlation between radiographic and clinical
ndings.
Consultation with the anesthesiologist and the
patient’s p rima ry ca re provider is recom men de d
to ensure an multidisciplinary approach for strat-
ifying the patient’s perioperative medical risks
and optimizing medical comorbidities prior to
pro ceed ing with surge ry
Preoperative pulmonary function should be
evaluated, as increased impairment or minimal
improvement in pulmonary function can be ex- pe cted postop era tively, and patients should be
informed abou t this matt er.
Hypovitaminosis D and osteoporosis are ex-
tremely common in this patient population,
and, given the signi cant de trimenta l e ect on
fusion rates and potentially overall clinical out-
comes, should be managed in consultation with
an endocrinologist.
Operative candidates can be classi e d based on
severity and type of their symptoms, as well as
pre op era tive radiograph ic nd ings.
Consideration should be given to posterior-only
deformity correction t echniques, which m ay re-
duce m orbidit y associated with the ante rior tho -
racotomy or thoracoabdom inal approaches.
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10 Chapte r 1
Pitfalls
Bracing is not rout inely utilized in adu lt spinal de-
formity patients and may result in decondition-
ing a nd skin comp lications.
Failure to identify and evaluate osteoporosisand subsequently failing to optimize BMD may
result in subopt imal xation and const ruct /fusion
failure.
Patients may ex the ir knees and hips, with sub-
sequent pelvic retroversion, to compensate for
xed sagitt al imba lance, and t he surgeo n should
ensure that radiographs are obt ained withou t
these compensatory mechanisms.
Narcotic pain me dicat ions should not be routine ly
prescribed preoperatively, and patient s with sig-
ni cant narcotic pain medication use preopera-
tively should be weaned to optimize postopera-
tive pain management.
Failure to identify preoperative nutritional de -
ciency may result in poor wound hea ling, di -
culty with rehabilitation, and prolonged fusion
healing. Complex three-column osteotomies require highly
experienced spine surge ons and a spe cialized op-
erating room team to ensure optimal outcomes
and the highest level of safety. Therefore, the
spine surgeo n should always consider every othe r
option or technique to obtain realignment and
opt imize balance (e.g., positioning, poste rior soft
tissue/ligament releases, facetectomies, poste-
rior column osteot omy) rather t han use a three-
column osteotomy.
References
Five Must- Read Reference s
1. Aebi M. The adu lt scoliosis. Eur Spine J 2005;14 :925 –
94 8 PubMed
2 . Mes n A, Len ke LG, Brid we ll KH, et a l. Does pre op -
erative narcotic use adversely a ect outcom es and
complications after spinal deformity surgery? A com-
par iso n of non nar cot ic- w ith nar cot ic- usin g grou ps.
Spine J 2014;14: 2819–28 25 PubMed
3. Silva FE, Len ke LG. Adu lt de gene rat ive scoliosis: eva-
luation and management. Neurosurg Focus 2010;
28:E1 PubMed
4. Mum m an en i PV, Sha rey CI, Len ke LG, et a l; Mini-
mally Invasive Surgery Section of the International
Spine Study Group. The minimally invasive spinal
deform ity surgery algorithm : a reproducible rational
framework for decision making in minimally in-
vasive spinal deformity surgery. Neurosurg Focus
2014;36:E6 PubMed
5. Schwab F, Dubey A, Gamez L, et al. Adult scoliosis:
p revalence, SF-36, an d nut r it ional par am et er s in an
elderly volunteer population. Spine 2005;30:1082–
1085 PubMed
6. Schwab FJ, Hawkinson N, Lafage V, et al; Interna-
tional Spine Study Group. Risk factors for m ajor per i-
operative complications in adult spinal deformity
surgery: a multi-center review of 953 consecutive
pat ien ts. Eur Spin e J 20 12 ;2 1: 26 03 –2 61 0 PubMed
7. Daubs MD, Lenke LG, Bridwell KH, et al. Does cor-
rection of preoperative coronal imbalance make a
di erence in outcom es of adult patients w ith defor-
m ity? Spine 2013;38:476–483 PubMed
8. Acost a FL Jr, McClen don J Jr, O’Sha ugh ne ssy BA, et a l.
Morbidity and mor tality after spinal deform ity sur-
gery in patients 75 years and older: complications
and predictive factors. J Neurosurg Spine 2011;15:
667–674 PubMed
9. Grubb SA, Lipscom b HJ, Suh PB. Resu lts o f sur gical
treatment of painful adult scoliosis. Spine 1994;19:
1619–1627 PubMed
10. van Dam BE. Nonope rative treat m ent of adult scolio-
sis. Orthop Clin North Am 1988;19: 347–351 PubMed
11. Halpin RJ, Sugr ue PA, Gould RW, et a l. Stan dar dizing
care for high-r isk patient s in spine surgery: the Nor-
thwestern high-risk spine protocol. Spine 2010;35:
2232–2238 PubMed
12. Sugr ue PA, Halp in RJ, Koski TR. Trea tm en t algor ith m s
and protocol practice in high-risk spine surgery.
Neu rosurg Clin N Am 20 13 ;2 4: 21 9– 23 0 PubMed
13. Klein JD, Hey LA, Yu CS, et al. Perioperative nutri-
tion and postoperative complications in patients
undergoing spinal surgery. Spine 1996;21:2676–
2682 PubMe d
14. Kelly MP, Hu SS. Nutrition and pain management in
the adult sp inal deformity p atient . Scoliosis Research
Society e-text. http://etext.srs.org/. Accessed August
30, 2014
15. Nut ta ll GA, Horlocker TT, San tr ach PJ, Oliver WC Jr,
Dekutoski MB, Bryan t S. Predictor s of blood t ran sfu-
sions in spinal instrumentation and fusion surgery.
Spine 2000;25:596–601 PubMed
16. Shap iro GS, Boach ie-Adjei O, Dhaw likar SH, Maier LS.
The use of Epoetin alfa in complex spine deformity
surger y. Spine 2002;2 7:2067–2 071 PubMed
17. Aue rb ach JD, Len ke LG, Brid we ll KH, et a l. Major
complications and comparison between 3-column
osteotomy te chniques in 105 consecutive spinal defor-
m ity procedures. Spine 2012;37:1198–1210 PubMed
18. Bumpa ss DB, Len ke LG, Brid we ll KH, et al. Pulm onar y
function improvemen t after vertebral column resec-
tion for severe spinal deformity. Spine 201 4;39:587 –
59 5 PubMed
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Preoperative Evaluat ion and Optimization for Surgery 11
19. Good CR, Len ke LG, Brid we ll KH, et a l. Can poste rio r-
only surgery pr ovide similar radiograph ic and clinical
results as combined an terior (thoracotomy/thoraco-
abdom inal)/posterior app roaches for adult scoliosis?
Spine 2010;35:210–218 PubMed
20 . Sto ker GE, Buch ow ski JM, Bridw ell KH, Len ke LG,
Riew KD, Zebala LP. Preoper ative vit am in D st atu s of
adults u nde rgoing surgical spinal fusion. Spine 20 13;
38:507–515 PubMed
21. Lane JM, Nydick M. Osteoporosis: current modes of
pre vent ion an d t re at m en t . J Am Acad Orthop Surg
1999;7:19–31 PubMed
22. Chin DK, Park JY, Yoon YS, et al. Preva len ce o f ost eo -
porosis in pa tien ts requir ing sp ine surger y: inciden ce
and signi cance of osteoporosis in spine disease. Os-
teoporos Int 2007;18:1219–1224 PubMed
23. Park SB, Chu ng CK. Stra tegies of spin al fusion on os-
teoporotic spine. J Korean Neurosurg Soc 2011;49:
317–322 PubMed
24 . Dipao la CP, Bible JE, Biswas D, Dipaola M, Grauer JN,
Rechtine GR. Survey of spine surgeons on attitudes
regarding osteoporosis and osteomalacia screening
and t reatm ent for fractures, fusion surgery, and p seu-
doar throsis. Spine J 2009;9:5 37–544 PubMed
25. Baron EM, Alber t TJ. Medical comp lications of su rgi-
cal treatment of adult spinal deformity and how
to avoid th em . Spine 2 006;31(19, Suppl):S106–S118
PubMed
26. Glassm an SD, Ber ven S, Bridw ell K, Horton W, Dima r
JR. Correlation of radiograph ic param eters and clini-
cal symptom s in adult scoliosis. Spine 2005 ;30:682–
68 8 PubMed
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! Introduction
Degenerative scoliosis most comm only a ects
the lumbar spine in the elderly. It occurs as a
result of facet and disk degeneration, leading to
increased loads and resulting deformity. The
preva lence o f adult scoliosis in the elderly p op -
ulation m ay be as h igh as 6 8%,1 and this num-
ber w ill only in crea se as p eop le live lon ger a nd
wan t to m aintain th eir activity levels. Unt reatedscoliosis can lead t o pain, spinal osteoar th ritis,
worsening deformity, spinal stenosis with ra-
diculopathy, coronal and sagittal imbalance,
associated m uscle fatigue, and psychological ef-
fects from poor cosmesis and redu ced m obility.
The m anagem ent of adult deformity is con-
troversial, with a lack of high-quality evidence
to guide treatment, such as determining the
best candidat es for conse rvat ive versu s su rgi-
cal treat m ent , and t he best surgical procedu res
for speci c clinical scen arios. Nevert heless, pa-
tients tend to present w ith back or leg pain, and
concerns about deformity progression need to
be ad dressed. Thus, an understandin g of the pos-
sible causes is important before appropriate
recom m endations for treatmen t can be made.
! Diagnosis o f Back Pain
One of the most common presenting yet
di cult-to-discern comp laints of degenerat ive
scoliosis is back pain. The p ain m ay be stat ic or
m echanical, localized or regional, or associated
with buttock or leg pain, and there may even
be neurologic symptom s. It is im por tant to
elicit a thorough h istory docum ent ing the pain’s
severity, its aggravating and relieving factors,
and its funct ional lim itations that a ect work
or recreation or r educe t he patient ’s ability to
walk distances. This information helps eluci-
date the cause of the pain, and thus helps indeterm ining the appropriate treatment .
Axial back pain can be cause d by de genera-
tion of the intervertebral disk (diskogenic) or
disk height loss leading to segm ent al instability
(degenerative spondylolisthesis). There could
also be single- or m ultisegment facet joint de-
generation. All these ndings are part of the
degen erat ive cascade a s described by Kirkaldy-
Willis et al.2 Thus, a thorough clinical exam-
ination w ould include careful palpation of the
lumb ar spine, its mu sculature, and the sacroil-
iac joints, to look for areas of local tenderness
that would help pinpoint path ology. Additional
characteristic ndings include the presen ce of
an “instability catch” or the patient’s experi-
ence of a catching pain in the lower back wh ile
rising from a forwa rd-leaning posture, wh ich
requires supporting their weight by putting
their hands on their knees. The patient may
also have a “painful catch,” in w hich th e ra ised,
straightened leg is unable to move down butsuddenly drops due to a shar p pain in th e lower
back. Bot h sympto m s could point to the pres -
2
Decision Making in Adult DeformitySurgery: Decompression VersusShort or Long Fusion
Kenneth M.C. Cheung and Jason P.Y. Cheung
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Decision Making in Adult Deformity Surgery 13
ence of spinal instability, likely from a degen-
erative spondylolisthesis.
Back pain can a lso result from postur al im-
balance in bot h the co ro nal and sagit tal planes.
This imbalance is often referred to as the “cone
of economy” as discussed by Jean Dubousset.3 The cone is projected from the feet u p, and so
the trunk is only within a narrow range. This
concept relates to the par t of the cone w here
the body can rem ain balanced without extern al
support and using m inim al e ort. The mu scular
e ort required in an upright posture is much
greater wh en th e cone is exceeded, and correc-
tion should be considered .
Coronal imbalance of the spine can lead to
tr uncal translation and r ib-on-p elvis impinge-
m ent . Sagitt al plane deform ities include di -
culties in stan ding upright, resulting in mu scular
fatigue a nd discom fort from comp ensating for
the global sagittal kyphosis. These global de-
form ities may furthe r stress th e sacroiliac and
hip joints and lead to buttock and groin pain.
Usually the location of the pain is quite accu-
rate in determining the problematic site, but
the sacroiliac and h ip joints a re comm on sites
of misdiagnoses of back pain and should be
thoroughly assessed by clinical examination.Shoulder or pelvic asym m etr y and shoulder or
rib prom inence are clues for coronal deform i-
ties. Although a forw ard-leaning post ure could
be re lat ed to m uscle fat igue cause d by sagit tal
imbalance, it could also be due to a xed ky-
phot ic deform it y of the sp ine it self or a re su lt
of hip extensor weakness. In addition, during
the gait assessment, patients may have wors-
ening kyphotic posture due to m uscle decom -
pensat ion associated w ith pro longed walking.
Radiological assessment of causes of back
pain wou ld require fu ll- lengt h st anding pos-
teroanterior and lateral radiographs of the
spine, which must include, at a minimum, C7
to th e h ip joint s, but ideally wou ld include C1
to the hip joints, so that balance parameters
can be easily m easured . Flexion an d exten sion
views are useful, and in our expe rience, stand -
ing exion and prone traction radiographs show
the maximum displacement of a spondylolis-
thesis and its maximum reduction.4,5 Addi-tional m agnetic resonan ce imaging (MRI) of the
lumbar spine is needed to assess neurologic
impingeme nt as well as to rule out other causes
of back pain. Sometimes, because of the se-
verity of the d eform ity, a comp uted tom ogra-
phy (CT) m yelogram could be a use fu l adju nct
to identify the exact location of nerve root
compression.Radiological instab ility is com monly de ned
by the degree of slip (Fig. 2.1), and t he change
in slip angle (Fig. 2.2 ) and disk height (Fig. 2 .3).
These radiographic features can be found on
standing lateral radiographs (degree of slip)
and dynam ic exion-exten sion lateral radio-
graphs (slip angle and disk height). Oblique
lms can be t aken to look for a pars d efect. For
measurement of the degree of slip, a line is
Fig. 2 .1 Measureme nt of the degree of slip. A line
is dropped from the poste rior border of the cranial
vertebrae to the caudal vertebrae. The distance
from this point to the posterior border of the caudal
vertebrae is divided by the total vertebral body
width of the caudal vertebrae. Grade 1 is de ned as
0 to 25%, grade 2 is "25 to 50%, grade 3 is "50 to
75%, and grade 4 is "75 t o 100%.
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14 Chapte r 2
drawn from the posterior border of the cranial
vertebrae to t he caud al vertebr ae. The d istan ce
from this point to the posterior border of the
caudal vertebrae is divided by the total verte-
bral bo dy w idth of t he caudal verteb rae. Grad e
1 is de ne d as 0 to 25%, grad e 2 is "25 to 50%,
grade 3 is "50 to 75%, and grade 4 is "75 to 100 %.
Spond yloptosis is de ned as m ore than 100%
slip. A slip of greater th an 50%is un stable an d
associated with progression and lumbosacral
kyph osis. The slip angle of an L5-S1 spond ylo-
listhesis is measured by a line drawn perpen-
dicular to the posterior aspect of the sacrum
and a line drawn along the inferior end of theen d plate of L5. In th e cran ial segm en ts, the slip
angle is made by the superior end plate of the
caudal vertebra and the inferior end plate of
cranial vertebra. For measuring disk height, a
line is drawn from the midline inferior end
plat e of the cranial verteb ra to the upper end
plat e of the caudal verteb ra. A ra t io bet ween
this distance and the midline vertebral height
of the cranial vertebrae is compared on dy-
namic views. In these cases, fusion surgery
is indicated to prevent p rogression of the in-
stability, correct any segmental deformity,
and treat the axial back pain caused by spinal
instability.
Full-length stand ing coronal and sagitt al ra-
diographs are used for assessmen t of the over-all coronal and sagitt al balance using the cente r
sacral vertical line (Fig. 2.4) and C7 plum bline
Fig. 2 .2 Measureme nt of the slip angle. The angle
is made by the superior end plate o f the caudal
vertebrae and t he inferior end plate of the cranial
vertebrae. The slip angle of a L5-S1 spondylolisthesis
is measured by a line perpendicular to the posterior
aspect of sacrum and a line drawn along the inferior
end of the end p late of L5.
Fig. 2 .3 Measurem ent of the d isk height. A line is
dropped from the midline inferior end plate of the
cranial vertebrae to the upper end plate of the
caudal vertebrae. The ratio be twee n t his distance
and the midline vertebral height of the cranial
vertebrae is compared on dynamic views.
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Decision Making in Adult Deformity Surgery 15
(Fig. 2 .5). The b isector of the cen ter sacral ver-
tical line is also useful for nd ing th e proximal
neutral vertebra. Sagittal balance is measured
by the C7 sagit tal p lum bline, an d lum ba r lor -
dosis is usually measured from the upper end
plat e of T12 to the end plat e of S1. Shoulderheight, apical verteb ral translation of the th o-
racic and lum bar curves, curve m agnitudes, and
exibility should be documented. Common
local deform ities seen on radiographs include
an L2-L3 apex deformity, lateral listhesis or
Fig. 2 .4 Measurem ent of cent ral sacral vert ical line.
Using the top of the iliac crest to contro l for tilting,
a vertical perpendicular line is drawn up from t he
center of S1. The proximal neutral vert ebra can be
bisected from this line, and in this gure it would
be L2.
Fig. 2 .5 Measureme nt of sagitt al C7 plumb line is
done by dropping a vert ical perpendicular line to
the horizontal from the C7 vertebral body and
comparing its horizontal position with the position
of the poste rosuperior corner of the S1 superior end
plate. Sagitt al imbalance is norm ally conside red to
be > 5 cm deviat ion from the S1 posterosupe rior
corner, and in this gure the re is a positive sagitt al
balance.
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16 Chapte r 2
rotatory subluxation (Fig. 2.6), lum bar hypol-
ordo sis, an d shor t reciprocat ing curves. Latera l
listhesis or rotatory subluxation is measured
by t he h or izontal d ist an ce be tween the supero-
lateral corner of the caudal vertebra and the
inferolateral corner of cephalad vert ebra. Bend -
ing radiographs can di eren tiate sti curves
from exible curves, but is m ore impor tan t for
deciding on the instrumentation levels during
surgery. MRI is useful to assess disk degen era-
tion an d spinal sten osis. Deform ity correctionis required for these symptoms and may re-
quire more complex operations such as osteot-
om ies and long fusions.
! Diagnosis o f Leg Pain
The classic presen tat ion of nerve root comp res-
sion is buttock pain that radiates to the lower
extremities and neurogenic claudication. Ra-dicular or leg pain points t o spinal or foram inal
stenosis caused by facet joint an d ligamen tum
avum hypertrophy, foraminal narrowing due
Fig. 2 .6 Late ral subluxat ion is measured by the
horizontal distance bet ween t he supe rolateral
corner of the caudal vertebra and the inferolateral
corner of the cephalad vertebra.
to vertebral rotatory subluxation, or reduct ion
of the inte rped icular distance on th e concavity
of the curve. These patients usually develop
bu rning or ach ing pain st ar t ing in the but tock
that radiates down the appropriately involved
derm atom e to the lower leg. Clinical identi ca-tion of the involved de rm atom e provides a good
clue to t he likely nerve root a ected . This can
then be con rmed if there is corresponding
weakn ess in th e sam e m yotome. Typically, im -
pingem ent of th e L4 n er ve root lead s to an te rior
shin numbness with ankle dorsi exion weak-
ness (t ibialis anter ior), an L5 ne rve root involves
the posterolateral calf and foot dorsum, with
extensor hallucis longus weakness, and an S1
ner ve root involves the posterior calf and sole,
w ith weakn ess of the exor hallucis longus.
Neu rogenic claudication com m on ly presents
w ith insidious onset of but tock, thigh, and calf
pain t rigge re d by walking. The usu al disa bilit y
is thus diminished walking tolerance. Vascular
claudication is an imp orta nt di erent ial diag-
nosis. Patients w ith vascular claudication m ay
also present with diminished walking toler-
ance due to calf cramping on exertion or a
sensation of tightn ess that p roceeds from dis-
tal to proximal. This contrasts to neurogenicclaudication whe re d iscom fort with num bness
pro ceeds fro m proxim al to dist al. Object ive
sensory examination should pinpoint the spe-
ci c der m atom e or suggest wh ich ner ve root is
compressed. Motor we akness u sually suggests
a m ore long-standing n erve compression. Vas-
cular examinat ion should be performe d, includ-
ing observation for troph ic changes in th e skin
and nails of the lower limbs and diminished
distal pulses, which wou ld suggest a vasculo-
genic cause for the pain.
Radiographic assessment was described
above (see Diagnosis of Back Pain).
! Factors that May Lead to
Curve Progression, Hence
the Need for Surgical
Treatment
In general, the issue of whe the r curves progress
is debated in th e literatu re, and t he rate of pro-
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Decision Making in Adult Deformity Surgery 17
gression is highly variable. Curves may pro-
gress 1 to 6 degrees pe r year (average 3 degrees
per year ).6,7 Risk factor s for progre ssion include
a pr ior history of progression an d rad iograph ic
risk factors such as a symm etrical disk degen-
eration, lateral disk wedging, and osteophyteformation.8–10 Comparing the two sides of a
spinal segm ent , less than 80% of lateral disk
wedge and more than 5 mm of lateral osteo-
phyte di ere nce m ay indicate an unst able seg-
ment .9 Progression has been suggested t o occur
w ith Cobb angles greater t han 30 de grees, loss
of lum bar lordosis, apical rotation larger t han
Nash-Moe grad e 2 (convex pedicle m igrates 25%
of the vertebral body width and the concave
pedicle gradually disappea rs), lat era l list hesis
of 6 mm or more, or a prominent or deeply
seated L5 disk (in relationship to the inter-
crestal line).11–14 The presence of rotatory
subluxation, lateral spondylolisthesis, and disk
degeneration in the upper lumbar levels also
suggests a risk of progressive deformity.12 Due to
spine coupling, rotatory deformity of th e spine
is related to t he d evelopme nt of lateral spondy-
lolisthesis. Thus, apical vertebral rotation may
also predict scoliosis progression. Spinal seg-
m ent s proxim al to the scoliosis share t he loadto comp ensate for spine im balance. With d isk
degeneration, this compensatory mechanism
fails, an d p rogressive deform ity occurs. Fusion
surgery is required to prevent curve progres-
sion, and the length of fusion is dependent on
the presen ce of coronal or sagitt al imbalance.
! ManagementManagement of adult deformities should be
tailored to each patient because the symptom-
atology is di eren t in ever y case. Treat m en t is
dependent on the experience of the surgeon,
the patient ’s preference, the p atient’s age and
functional status, magnitu de of deform ity, the
rate of progression, and the presen ce of comor-
bidit ies. Som et im es the cause of pain is di -
cult to di eren tiate based solely on clinical and
radiological exam ination. In these cases, trans-foraminal epidural injections, selective nerve
root blocks, and facet joint blocks are comm only
utilized to iden tify the pain gen erator.
Non op era t ive m anagem ent is usu ally re -
served for patients with mild symptoms aris-
ing from stenosis, radicular or back pain, curve
m agnitude of less than 30 degrees, lateral sub-
luxation of less than 2 mm, and reasonable
coronal and sagitt al balance.14 Com m on indi-cations for surgery include axial back pain,
symptom atic deform ity, neurologic symptom s,
and dissatisfaction w ith appea rance. The nal
decision shou ld be a balance of the m agnitude
of surgery, th e qu ality of life gain, and t he risk
of surgical complications. Patients with severe
deform ity may require m ajor surgery to achieve
full correction, and the risk of complications
w ill dram atically increase. Complication rates of
up to 80%have been reported in some series.15,16
Conversely, decompression only or limited fu-
sion m ay be su cient to provide reasonable
and lasting relief for patients. The following
sections discuss the au thors’ experience in su r-
gical decision making, choosing between de-
compression only and sh ort or long fusion, and
the pitfalls of man aging adu lt deform ity.
! Critical Factors in Decision
Making for Surgery
The goal of surgery for these p atients sh ould be
to perform th e smallest operation possible that
would help relieve the symptoms and prevent
a recurre nce. We nd it helps to break down
the componen ts of patient complaints in order
to make an app ropriate decision.
1. Leg pain
a. Nerve root comp ression/spinal stenosis—
local decompression
b. Degenerative spon dylolisthes is—local de-
comp ression ± fusion
2. Back pain
a. For local degeneration or instability—
short fusion
b. For ex ible or corre ct able sagit tal or cor -
ona l imbalan ce—long fusion
c. For sti or un correct able sagittal or coro-
na l im balan ce—long fusion + osteot om ies
3. Progressive deformitya. Long fusion to prevent progression, sel-
dom would be performed alone in the
absence of symptom s above
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18 Chapte r 2
! Surgical Decision Making
Decompression Only
Decompression alone is indicated for p atients
with neurogenic claudication without back pain or a sym ptom at ic or progress ive defor-
mity. Decompression is usually in the form
of posterior fenestration or laminectomy, al-
though other approaches, including anterior
indirect decompression and endoscopic trans-
foraminal approaches, have been described.
Each approach has m erit and w ould be depen-
dent on the surgeon’s experience. A detailed
discussion of the ir relative m erits is beyond th e
scope of this chapter. As a general principle,
in those patients undergoing decompression
alone, as much facet joint and as many poste-
rior ligame ntous str uctu res as possible should
be pre se rved to re duce the risk of future pro -
gression and iatrogenic instability.
One shou ld always be prepared t o carry out
a local fusion if more extensive bon e resect ion
is necessary. This is not uncommon as such
individuals often have tight spinal canals, and
incidental durotomies are not infrequent. If a
w ide lam inectomy is perform ed for the repair,a local fusion with pedicle screw xation m ay
be advisable.
Usual indications for decompression-only
surgery include leg pain with minimal or no
back pain , Cob b angles o f less than 30 degre es,
less than 2 m m of lateral subluxation, and n or-
mal coronal and sagittal balance indicated by
the center sacral vertical line and C7 plumb-
line.14 Despite combined back and leg symp-
toms that m ay warrant fusion, decompression
alone may be indicated for patients with sig-
ni cant ly high surgical risk. This may be the
be st op t ion for an eld erly pat ient w ith neuro-
genic claudication, a m ild deform ity, and poor
bo ne qu alit y. Pat ients undergoing decompre s-
sion alone should always be war ned of a risk of
progression of the deform it y that m ay re qu ire
a fut ure fusion procedu re.
FusionFusion surgery is indicated for th e tre atm ent
of back pain du e to de generative changes or in-
stability, as well as to prevent progression of
th e deform ity. It m ay be performe d alone or in
combination with decompression in patients
w ith radicular symp tom s. Shor t fusion m ay be
useful to stabilize curves with signi cant ap i-
cal rotation or when translation or lateral lis-thesis is greater than 3 m m .6,12,17,18 However, if
the re is symptom atic coronal or sagitt al im bal-
ance, realignm ent and long fusion is advisable.
Determination of fusion levels for adult
scoliosis is based o n th e severit y of spinal de-
form ity and the global appea rance and degen-
erative changes of the entire spinopelvic axis.
There is no universal agreement on the length
of fusion an d th e selection meth od of the en d
vertebrae for instrum entation.
Short fusion within the deformity not ex-
ceeding the end vertebrae aim s to stabilize th e
spinal segm ents w ithout correcting the wh ole
deform ity. Its m ajor advantage is th e lower risk
of complications from the anesthesia or the
surgery; th us it is indicated in th ose with back
pain but w ithou t coron al o r sagit tal im ba lance.
Long fusions or fusions exten ding beyond t he
end vertebrae is useful for correction of large
curvature s with coronal or sagittal imbalance,
but th is procedure needs to be balanced againstincreased comp lication rates.
Typical patient s wh o may be m anaged w ith
short fusions (Fig. 2.7) are those w ith smaller
Cobb angles (less than 30 degrees) and minor
rotatory subluxation (lateral subluxations of
more than 2 mm ).14 Back and leg pain an d seg-
mental instability caused by wide decompres-
sions can all be treated w ith short fusions.
Long fusions (Fig. 2.8), which generally
m eans fusion to L5 or th e sacrum , and to T10
or above, yield bette r sur gical correct ion of the
scoliosis and restoration of lumbar lordosis.
They are typically indicated for p atients wh ose
curves are likely to p rogress, such as patient s
w ith Cobb angles greater th an 45 degrees, m ore
than 2 mm of lateral subluxation, and coronal
and sagittal imbalance.14 The aim of the long
fusion is to achieve balance in both the coronal
and sagitt al planes, not absolute Cobb an gle cor-
rection.19 Glassman et al 20 demonstrated that
pos it ive sagit tal balan ce is the sin gle biggest pre dict or of clin ica l symptom s in ad ult defor-
m ity and takes priority over other para m eters.
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Decision Making in Adult Deformity Surgery 19
Thu s, long fusions sho uld always be considered
in patients with global coronal or sagittal im-
balance to ach ieve bet ter funct ional ou tcom es .
It should be borne in mind th at instrum en-
tation sh ould not e nd at the level of junctional
kyph osis or spon dylolisthesis. Any level of se-vere rotatory subluxation should be included
within the fusion block. To balance the spine,
the most horizontal vertebra should be the
upper instrumented vertebra (UIV).21 Instru-
m ent ation should not end at a level with p os-
ter ior column d e ciency, w ith listhesis in any
direction, at a level of a rotated segmen t, with
junct ional kyp hosis, at the ap ex of the defor-mity in the coronal or sagittal plane, or at a
degene rated level.
Fig. 2.7a–e A 71-year-old man with com plaint s of
axial back pain and bilate ral lower limb claudication.
(a) The patient has degenerat ive scoliosis from L3 to
L5, with a Cobb angle of 25 degrees. (b) L3–4 and
L4–5 spondylolisthe sis and sp inal stenosis were
noted. (continued on page 20)
a
b
(text cont inues on page 23)
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20 Chapte r 2
Fig. 2.7 a–e (continued) (c) The L5-S1 was well
hydrated, and there was no oblique take-o .
(d,e) Shor t fusion from L3 to L5 was performe d
with good correction of the segmental instability.
c
d
e
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Decision Making in Adult Deformity Surgery 21
Fig. 2.8 a–d A 58-year-old man with axial back pain
and lumbar hypolordosis. There is (a) an oblique
L5-S1 with de generat ive changes and (b) a positive
sagitt al imbalance. (continued on page 22)
a
b
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22 Chapte r 2
Fig. 2.8 a–d (continued ) (c) The pat ient was treated
with an L3 pedicle subt ract ion osteotomy and
posterior spina l fusion from T10 to the sacrum with
S1 and iliac instrument at ion. (d) Good restoration
of sagittal balance is observed postoperatively.
c
d
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Decision Making in Adult Deformity Surgery 23
Upper Instrumente d Vertebra for
Long Fusions
In gen era l, for long fusions, the aut hor s’ prefer-
ence is to en d at T10 or above, because instru -
m ent ation an d fusions ending at T12 to L1 have been show n t o have a h igher revision rate, likely
related to the hypermobile t horacolumbar re-
gion as it transitions from an immobile tho-
racic spine to a m obile lum bar spine. There are
also chan ges in facet orient ation from coronal
to sagittal and changes in sagittal alignment
from kyph osis to lordosis. Exten ding th e UIV to
T10 (level with tru e r ibs) or fur the r p roxim ally
can provide relative protection to t he a djacent
segment with the increased stability provided
by the rib cage. The rib cage lengt hens the
transverse dimensions of the spine and gives
the thoracic spine greater resistance to bend-
ing stresses in m ultiple p lanes. T11 or T12 do es
not have costostern al articulations; hence, these
levels lack the biomechan ical advantage of th e
upp er levels.
In add ition, other factors that could a ect
long-term survival of that segment need to be
taken into consideration. These factors include
healthy adjacent spinal segments with no de-generation or instability in any plane, and a
UIV adjacent to spinal segments with normal
sagitta l, coronal, and axial alignm ent and near-
neu tral rotat ion. The UIV should lie w ithin t he
“stable zone” de ned by the cente r sacral ver-
tical line, before surgery, or could be placed
into that zone a fter surgery.
Curre ntly, there is no consen sus stu dy avail-
able to recommend T10 instrumentation in all
pat ient s to im prove long-term resu lt s. Dis-
advantages of the UIV above T10 include in-
creased risk of perioperative complications,
and with longer instrumentation across the
thora colum bar spine th ere is also a greater risk
of pseudar throsis. Thu s, the rat ionale for stop -
ping at T10 m ay not be ap plica ble in all cases.
Important decisions on the extent of instru-
mentation and fusion should depend on the
pos it ion of t he UIV in rela t ionsh ip to t he globa l
spine. An exte nsion to T5 or even higher w ould
depend on th e ability of the lumbar surgery tocorrect th e sagittal imbalance. With control of
more spinal segments, better sagittal balance
m ay be achieved m ore easily.
Ultimately, th e surgical procedure shou ld be
tailored to each patient’s needs and based on
the goal of achieving a well-balanced, stable,
pain less, an d dura ble sp ine w ith the few est
num ber of fused segment s wh ile reducing the
risk of complications associated with large-scale op erations.
Low er Instrumente d Vertebra for
Long Fusions
For th e lower instru m ent ed vert ebra (LIV), m ost
long fusions will extend to the sacropelvis or
stop at L5. In adolescen t idiop ath ic scoliosis, it
m ay be possible to stop at L3 or L4 in a lum bar
curve, but be cause of str uctu ral chan ges and a
xed tilt found at the caudal spinal segments
like L4-L5 in adult deformity, stopping at a
m ore cranial segment is gene rally not ad vised.
Stopping at L5 en ables retent ion of the lum bo-
sacral m otion, avoidance of sacroiliac (SI) joint
stress, decreased operative time and instru men-
tation complications, and a lower pseud art hro-
sis rate. Pelvic xation can also be avoided . On
the other hand, this procedure places a lot of
stress at th e L5-S1 disk, being the only residua lmobile segment, and the patient needs to be
warned of future breakdown and th e need for
surgery to fuse this segment. In general, for
m any pat ient s, th e L5-S1 disk is already degen -
erated, and in su ch cases it is probably better to
fuse to the sacrum. Preservation of the L5-S1
disk enables some pelvic motion, which may
be im por tant for som e funct ional dem ands of
pat ients, such as r id ing a bicycle.
Fusion to th e sacrum is required for disk de-
gener ation at L5-S1, spon dylolisth esis or spina l
stenosis at the sam e segm ent , as well as oblique
take-o at L5-S1 or in fractiona l cur ves greate r
than 15 degrees.22 Balancing is di cult w ith-
out fusion down to the sacrum in cases of
oblique take-o at L5-S1. In addition , th e fora-
men is smaller on one side, leading to unilat-
eral L5 radiculopathy. It is not uncommon to
see pat ients w ith foram inal, central, or lateral
recess ste nosis at L5-S1. If stenosis is p resen t
at L5-S1 an d m ore exten sive decomp ression isrequired, fusing down to th e sacrum is inevi-
table. The obvious disadvantages of fusion to
the sacropelvis include increased operat ive tim e
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24 Chapte r 2
and m ore exten sive surgical dissection to reach
the sacru m . Anter ior colum n supp ort m ay also
be re qu ired to reduce the rat e of pseudarthro -
sis. Lost m otion at L5-S1 may also alter t he pa-
tien t’s gait.
Osteotomies may be required if less than30%deformity correction can be obtained on
bendin g radiographs. This is not uncom m on
because adult deform it ies ar e usu ally st i . To
avoid overloading the instrumentation at the
m etal–bone interface, releases and rebalancing
would be required. There are t wo t ypes of sag-
ittal imbalance in adult deformity. First, the
spine is globally balanced but a segm ent al por-
tion of spine is at or kyph otic. Second , th ere
is global and segmental imbalance. Coronal
imbalance can also be classi ed into two types
w ith the sh oulders and p elvis tilted in opposite
directions or w ith tilting in the sam e direction.
Posterior column osteotomies are the best
choice for segmental imbalance of the spine.
A prere quisite w ould be m obile d isk spaces to
allow extension correction. If the disks are al-
ready degenerated and sti , ante rior release is
also required. If the bone stock is inadequate,
anterior structural grafts can be used to im-
prove fusio n rat es. For globa l im ba lance, bot hSmith-Petersen and pedicle subtraction osteot-
omies can be used. Typically, a Smith-Petersen
osteotomy is indicated if the weight-bearing
line falls w ithin 3 cm of the sacrum , and a p ed-
icle subtra ction osteotom y is reserved for cases
w ith poor bone stock, and it can provide 30 de-
grees of lordotic correction. In patients with
combined coronal and sagitt al im balance, ped-
icle subtraction osteotomies are a viable op-
tion if the shoulders an d pelvis are tilted in the
same direction, but a vertebral column resec-
tion is the better option if the shoulders and
pelvis a re t ilted in op posite direct ions.
Anterior procedures are required only in
rigid d eform ities that are not p assively correct-
able with posterior instrumentation. They are
usually used only in combination with poste-
rior instr um ent ation, as inte rbody fusions alone
may not be able to correct the overall sagittal
alignment.23 Anter ior spinal fusion can furth er
correct lumbar hypokyphosis and imbalance, p rovid e in direct decompress ion by foram inal
distraction, prevent posterior instrumentation
failure by load sha ring, and decrease t he r ate of
pseudar thro sis , which is e sp ecially co m m on in
smokers, diabetics, and osteoporotic patient s.14
! Complications
Adult deformity surgery is challenging, and
there are many associated complications. Re-
por ted complica t ion rat es reach 80 % for adult
deform ity, with up to 58%of patient s requiring
reoperation.15,16 These degene rative conditions
usually occur in the elderly with multiple co-
m orbidities such as pulmon ary and card iac dis-
ease, osteoporosis, and nutritional de ciency.
These conditions shou ld be prope rly optim ized
prior to su rgery to d ecrease periop erat ive risks .
Any of the ab ove comorbidities m ay a ect the
tim ing of surgery a s well as the scale of surgi-
cal correction.
Deform ity correction can indirectly decom -
pre ss the neural st ruct ure s by rod derot at ion,
cantilever reduction maneuvers, and particu-
larly by increasing vertebral disk height with
anter ior interbody fusion. Overdistraction onthe concave side may lead to loss of lumbar
lordosis. To redu ce rigid cur ves, poste rior col-
umn osteotomies at multiple levels are likely
required to mobilize the spinal segments. Fu-
sions should avoid stopping at a level of ro-
tatory subluxation to prevent aggravating the
subluxation.
With limited instrumentation and fusion,
degeneration may be accelerated in the re-
m aining cur ve as a result of adjacent segm ent
disease. Stopping the fusion within the de-
formity may provoke these adjacent segment
pro blem s. Stopping the fusio n at the thor aco-
lumb ar junction also leads to adjacent segmen t
disease cranial to th e segm ent of fusion. Fusion
to T10 or above m ay avoid t his. However, some
consider adjacent segment degeneration un-
preventable in fusio n surgery as it could be d ue
to th e nat ural age-related p rogression of a de-
generative process coupled with the postsurgi-
cal e ect of spinal sti en ing created by fusionor instrum entation procedures.24,25
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Decision Making in Adult Deformity Surgery 25
Proximal adjacent segment degeneration
is detected by progressive narrowing of disk
height, progressive decrease in lordosis or in-
crease in kyphosis, osteophyte form ation, scle-
rosis of an adjacent end plate, or translation
in the coronal or sagittal planes. Proximal junct ional prob lem s su ch as ad jacent segm ent
degeneration, compression fracture, or screw
failure in th e UIV occurs m ore frequen tly with
fusions en ding at T11 to L2 as comp ared w ith
those at T10 or above.26
For the LIV, depending on fusion to L5 or to
the sacrum , di eren t comp lications m ay occur,
including L5-S1 disk degenerat ion, loss of cur ve
and balance correction, iliac screw implant
prob lem s, and pse udarthro sis . If the fusio n is
stopped at L5 where there is xed sagitt al im-
balance and disk degenera t ion at L5-S1, the
rate of disk degeneration w ill furt her increase,
leading to loss of sagitta l pro le correct ion and
L5-S1 spon dylolisth esis.22 In osteoporot ic bone,
fusion to L5 has a high risk of xation failure, as
the L5 pe dicles are m ostly cancellous an d t here
are trajectory problems in obtaining a medial
angle for placing th e p edicle screws. Failure of
L5 screws w ith loosening leads to k yphosis or
hypolordosis of the L4-L5 segment. L4-L5 ky- phos is m ay be tolerat ed in a sh or t fusio n, b ut
with longer fusions the degree of sagittal im-
balance becom es an issue.
Fusions to the sacru m sh ould be reserved for
L5-S1 spondylolisthesis, stenosis, oblique take-
o , m oderate or severe L5-S1 degenerat ion, and
pr ior lam inect om y. Problem s w ith lon g fusions
to the sacru m include higher complication rates
du e to a large-scale op erat ion, risk of sacroil-
iac joint degeneration, altered gait mechanics
and increased pseudar throsis. Instrum entation
complications for these long fusions include
bre akage and back-ou t or loosening of screws.
To avoid this, S1 screws should be bicortical
through the promontory anteriorly. S1 screws
should also be d irected m edially to avoid pen -
etrating the L5 nerve root. Bone grafting an-
terior to L5-S1 and iliac screws may further
protect the S1 xat ion. To im prove the L5-S1
xation, distal hooks, iliac screws, and inter-
bod y cages for anterior colum n su ppor t ar ealso options. Hooks are an alternat ive xation
especially in osteoporotic bone but m ay cause
sten otic problem s at L5-S1.
Iliac screws entail the risk of pullout 27 and
are usua lly more p rom inent . Screws should be
bu ried if possib le, but , in th in p at ients, re m oval
may be required and should be done around2 years afte r xat ion. Technica lly, iliac screw s
are m ore di cult to insert with previous pos-
terior iliac bone harvesting. There is also a
higher pseudarthrosis rate at L5-S1, but this
m ay be salvaged by revision surgery w ith an te-
rior reconstru ction and iliac xation as well as
using bone morphogenetic protein to improve
fusion rates. The lowest pseudarthrosis rate of
L5-S1 fusions is associated w ith complete sacro-
pelvic xation an d su rger y in pat ients younger
than 55 years of age.28
! Chapter Summary
In adult deform ity, the re is di culty in m atch-
ing a patient’s symptoms and concerns with the
surgical plan. Clinicians must weigh potential
gains and risks, and all surgical decisions should
be individ ually tailore d to the pat ient . Com or - bidit ies sh ou ld be addre ssed p rior to su rgery to
avoid p er ioperat ive complications. Usually, the
surgical opt ions include decomp ression alone,
decompression with limited arthrodesis, and
deformity correction with long fusion (Table
2.1). Decompre ssion surgery is reser ved for pa-
tients with leg pain but minimal or no back
pa in, scoliosis Cobb an gles less t han 30 degrees ,
less than 2 m m of subluxation, no th oracic hy-
perk yp hos is, and acceptable coron al and sagit -
tal balance, or if they have a poor premorbid
state. For short fusions, patients should have
scoliosis Cobb angles less th an 30 d egrees, seg-
mental instability (more than 2 mm of lateral
sublu xation ), back and leg pain , no signi cant
imbalance issues, and, if destabilizing, decom-
pressio n is re qu ired for adequ at e re lief of sp i-
nal stenosis an d n erve r oot comp ression. Long
fusions are reserved for scoliosis Cobb angles
greater than 45 degrees, more than 2 m m of sub-
luxation, and coronal and sagitt al imbalance. Toavoid complications related to instrum en tat ion,
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26 Chapte r 2
fusion shou ld not end at a level with junctionalkyphosis or spondylolisthesis, posterior col-
um n de ciency, a rotated segm ent , a level at
the apex of the deformity, or a degenerated
level. Levels of rotatory subluxation must be
included within the fusion block. For balance,
the m ost hor izont al verteb ra shou ld be th e UIV.
Extension of the fusion to T10 p rovides th e in-
creased stability o ered by th e rib cage. The
LIV at L5 is only feasible with a normal L5-S1
disk, and no spondylolisthesis or spinal steno-
sis or oblique take- o at L5-S1. Fusions to the
sacrum should b e avoided if possible to avoid
iliac screw implant problems, pseudarthrosis,
sacroiliac joint problem s, and gait d istu rban ces,
bu t is u sually m an datory for lon g-stan ding sag-
ittal and or coronal imbalances.
Pearls
All surgical decisions for degenerative scoliosis
should be individually tailored to the patient. Decompression surgery is reserved for patients
with leg pain, minimal or no back pain, scoliosis
Table 2 .1 Deco mpressio n Surgery Only Versus Short Fusion Versus Long Fusio n
Sympto m or
Condition Decompression Only Short Fusion Long Fusion
Pain Radicular pain, minimal
or no back pain
Back and leg pain Back and leg pain
Scoliosis Cobb angle < 30
degrees
Cobb angle < 30 degrees Cobb angle > 30 degrees
Subluxation < 2 mm < 2 mm > 2 mm
Overall balance Acceptable coronal andsagitt al balance
Acceptable coronal andsagitt al balance
Global coronal andsagittal imbalance
St abilit y St able m ot ion segm ent Segm ent al inst abilit y, > 50%
pars/ facet excision fordecompression
Segm ental and regional
kyphosis
Ope rat ed le vels St enot ic le vels only Rotatory subluxat ionsegme nts within fusion
block, segm en tal
instability caused by widedecompression
UIV: T10LIV: L5 if no degeneration,
spondylolisthesis,
stenosis or obliquetake-o at L5-S1
Lim it at ions Cannot a ddress global ba lance, progressive
deformity, segme ntalinstability with wide
decom pre ssion
Higher surgical risk, cannotaddress global balance,
adjacent level disease
Highe st surgical risk,compromised xation
with osteoporosis, highrisk of pseudarthrosis,
iliac screw prominence
Abbreviations: UIV, upp er inst rum ented vert ebra; LIV, lower instrumented vert ebra.
Cobb angles less than 30 degree s, less than 2 mm
of subluxation, no thoracic hyperkyphosis, accept-
able coronal and sagittal balance, or those with
po or p remorb id state.
Short fusions are for scoliosis Cobb angles less
than 30 de grees, segm ent al instabilit y, back and
leg pain, and no signi cant imbalance issues.
Long fusions are for scoliosis Cobb angles greater
than 45 degrees, more than 2 mm of sublux-
ation, and coronal and sagitta l imb alance.
Extension of th e fusion to T10 provides increased
stab ility o ered by the rib cage.
The m ost horizont al vert ebra should be the UIV.
Pitfalls
Fusion should not end at a level with junctional
kyphosis or spondylolisthesis, posterior column
de ciency, a rotated segm ent , at the ape x of the
deformity, or a dege nerated level.
Avoid the LIV ending at L5 with an abn orm al
L5-S1 d isk, spo ndylolisthesis, sp inal stenos is, or
oblique take-o at L5-S1.
Fusions to t he sacrum should be avoided if possi-
ble due t o the increase d risk of iliac screw implan t
pro blems, pseu dart hro sis, sacroiliac joint pro b-
lem s, and gait disturbances.
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Decision Making in Adult Deformity Surgery 27
References
Five Must -Read Referen ces
1. Schwa b F, Dub ey A, Gam ez L, et al. Adu lt sco liosis:
pre valence, SF-36, an d nut rit ion al pa ram et er s in an
elderly volunteer population. Spine 2005;30:1082–
1085 PubMed
2 . Kirka ldy-Willis WH, Wedge JH, Yon g-Hin g K, Reilly J.
Pathology and pathogenesis of lumbar spondylosis
and stenosis. Spine 1978;3:319–328 PubMed
3. Dubousse t J. Thre e-d ime nsion al analysis of th e sco-
liotic deformity. In: Weinsteid S, ed. The Pediatric
Spine: Princip les and Pra ctice. New York: Raven Press;
1994
4. Luk KD, Che un g KMC. Lum bar spin al in st ab ility.
Hong Kong Journ al of Orthopa edic Surgery 1998 ;2
5. Luk KD, Chow DH, Holmes A. Vertical instability in
spondylolisthesis: a traction r adiographic assessme nt
technique and the principle of managem ent. Spine
2003;28:819–827 PubMed
6. Bradford DS, Tay BK, Hu SS. Adult scoliosis: surgical
indications, operative management, complications,
and outcomes. Spine 1999;24:2617–2629 PubMed
7. Grubb SA, Lipscomb HJ, Coonrad RW. Degenerative
adu lt onset scoliosis. Spine 1988 ;13:24 1–245 PubMed
8. Benner B, Ehni G. Degenerative lumbar scoliosis.
Spine 1979;4:548–552 PubMed
9. Jim bo S, Kobayas hi T, Aon o K, Ats ut a Y, Mats uno T.
Epidemiology of degenerative lumbar scoliosis: a
comm unity-based cohort study. Spine 2012;37:1763–
1770 PubMed
10. Kobaya sh i T, Ats ut a Y, Takem itsu M, Mat su no T,
Takeda N. A prospective study of de novo scoliosis
in a community based cohort. Spine 2006;31:178–
182 PubMed
11. Grubb SA, Lipscom b HJ. Diagnost ic nd ings in pain-
ful adult scoliosis. Spine 1992;17 :518–527 PubMed
12. Pritchet t JW, Bort el DT. Degen erat ive sym ptom atic
lum bar scoliosis. Spine 19 93;18:70 0–703 PubMed
13. Robin GC, Spa n Y, Ste inb er g R, Makin M, Men czel J.
Scoliosis in the elderly: a follow-up study. Spine
1982;7:355–359 PubMed
14. Silva FE, Len ke LG. Adu lt de gen erat ive scoliosis: eva -
luation and management. Neurosurg Focus 2010;
28:E1 PubMed
15. Car reon LY, Puno RM, Dima r JR II, Glassm an SD, John -
son JR. Perioperat ive com plications of poster ior lum -
ba r decom pre ssion an d ar th ro des is in old er ad ult s. J
Bone Joint Surg Am 2003;85 -A:2089–20 92 PubMed
16. Edwards CC II, Bridwell KH, Patel A, Rinella AS, Berra
A, Len ke LG. Long a du lt de form ity fus ions t o L5 an d
the sacrum. A matched cohort analysis. Spine 2004;
29:1996–2005 PubMed
17. Sapkas G, Efstat hiou P, Bad ekas AT, Ant on iadis A,
Kyratzoulis J, Meleteas E. Radiological parameters as-
sociated w ith t he evolution of degener ative scoliosis.
Bull Hosp Jt Dis 1996;5 5:40 –45 PubMed
18. Tribu s CB. Degen erat ive lum bar scoliosis: evaluation
and management. J Am Acad Orthop Surg 2003;11:
174–183 PubMed
19. Simm ons ED. Surgical treat m ent of patient s w ith
lumb ar sp inal stenosis w ith associated scoliosis. Clin
Orthop Relat Res 2001 ;384:45– 53 PubMed
20. Glassm an SD, Ber ven S, Brid well K, Hor ton W,
Dim ar JR. Correlation of radiograp hic param eter s and
clinical symptom s in ad ult scoliosis. Spine 2 005;30:
682–688 PubMed
21. Simm ons ED Jr, Simm ons EH. Spin al ste nos is w ith
scoliosis. Spine 1992 ;17(6, Supp l):S117– S120 PubMed
22. Bridwell KH. Selection of instr um ent ation an d fusion
levels for scoliosis: wher e to star t an d w here t o stop.
Invited submission from the Joint Section Meeting
on Disorders of the Spine and Peripheral Nerves,
March 2004. J Neurosu rg Spine 2004;1:1 –8 PubMed
23. Cho KJ, Suk SI, Park SR, et al. Shor t fusion versu s lon g
fusion for degenerative lumbar scoliosis. Eur Spine J
2008;17:650–656 PubMed
24 . Ghiselli G, Wang JC, Bha tia NN, Hsu W K, Dawson EG.
Adjacent segment degeneration in the lumbar spine.
J Bone Joint Sur g Am 2 004 ;86- A:14 97–1 503 PubMed
25. Kum ar MN, Baklan ov A, Chop in D. Corr elation be-
twe en sagittal plane changes and adjacent segment
degeneration following lumbar spine fusion. Eur
Spine J 2001;10:314–3 19 PubMed
26. Shu ebar ger H, Suk SI, Mardjet ko S. Debate: deter -
mining the upper instrumented vertebra in the ma-
nagement of adult degenerative scoliosis: stopping
at T10 versus L1. Spine 2006;31(19, Suppl):S185–
S194 PubMed
27. Weist ro er JK, Perr a JH, Lonste in JE, et a l. Com plica -
tions in long fusions to th e sacrum for adult scoliosis:
m inimum ve-year analysis of fty patien ts. Spine
2008;33:1478–1483 PubMed
28 . Kim YJ, Bridw ell KH, Len ke LG, Rhim S, Cheh G. Pseu-
darthrosis in long adult spinal deform ity instrum en-
tation and fusion to the sacrum : prevalence and r isk
factor analysis of 144 cases. Spine 2006;31:2329–
2336 PubMed
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! Introduction
The use of spinal osteotomies in severe spinal
deformities has enabled corrections that were
not considered possible in the past. With ad-
vanced posterior-based techniques, excellent
corrections are achieved through a single ap-
proach , shor tening the d urat ion of surgery and
redu cing the n eed for multiple position chan ges
dur ing surgery. Although t he m ajority of cor-rections can be perform ed from th e posterior
direction, selective deformities may require
combined an terior procedures.
With the improvement in surgical tech-
niques and neuromonitoring modalities, ob-
taining correct ions of severe spinal deform ities
is now both possible an d reason ably safe.1 Thor -
ough kn owledge of advanced an atomy, careful
pre op erat ive planning, an d sp ecialized inst ru-
me ntation and implants provide the necessary
tools for successful surgery. This chapter re-
views t he various osteotom ies, the indications
for their use, as well as the methods of maxi-
m izing corrections and m inimizing both short-
and long-term complications.
! Planning the Deformity
Correction
Although deciding whet her or n ot to operate is
the rst m ain decision to be made, planning the
ner d etails of the procedure will help ensure a
smooth er ow of the surgery. The main plan-
ning should be d one p reoperat ively, and an a l-
gorithm for key decisions shou ld be esta blished
pre op era t ively and discussed w ith the pat ient
and fam ily. For exam ple, if th e pat ient d oes not
wish to assume the increased risk associated
with achieving a more complete deformity
correction, it is important to discuss what can
be achieved w ith lesser re leases. Con versely, if
correction is a key comp onen t of the patient ’sexpectat ions and t he su rgical team can reliably
achieve t hese goals safely, a th ree-colum n oste-
otomy can be performed if lesser osteotomies
are unsuccessful.
Determining the Flexibility
of the Deformity
Using the least risky procedure to obtain a cor-
rection is key to the safe outcome of deform ity
surgery. If a similar correct ion can be obtained
through multiple posterior column releases, a
three-colum n osteotomy m ay not be necessary.
Determ ining the exibility of the curve can
often be di cult, and intraoperat ive adjust-
m ents m ay be required in cases wh ere the curve
is m ore sti or less sti tha n expected.
Helpful clues to cur ve exibility include th e
pre se nce of w ide disk sp aces, disk sp aces that
open and close on bending lms, and curve
magnitudes that decrease when the p atient isin the prone position or w ith tra ction views. If
computed tomography (CT) imaging demon-
strates ant erior fusions, either congenital or from
3
The Use of Osteotomies forRigid Spinal Deformities
Ste phe n J. Lew is and Simo n A. Harris
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The Use of Osteotom ies for Rigid Spinal Deformities 29
p revious surgery, th ese fu sions w ill not corre ct
with posterior releases, and three-column os-
teotomies will be required. In contrast, good
corrections can be a chieved w ith poster ior col-
um n releases through previous posterior fusion
masses that h ave not undergone previous an-terior fusions. Proper preope rative worku p w ith
long-cassette anteroposterior (AP) and lateral
side bend ers, CT scan, and m agnetic resonance
imaging (MRI) should be done preoperatively,
so that the best possible preoperative plan
can be made. Newer technologies with three-
dime nsional (3D) printers can provide surgeons
w ith preop erative m odels of the spine, to even
bet ter pre pare for the ult im at e pro cedure .
Exposure
Excellent exposure is an essential component
of the procedu re. Severe deform ities can m ake
this m ore challenging; however, taking the t ime
to obtain the necessary exposure will greatly
facilitate implant insertion, and generally im-
prove t he ow of t he p rocedure . It is im por tant
to ident ify the spine levels, areas w ith previous
decompre ssions, fusion m asses, and previous
implants. In cases of revisions, knowledge of p rev ious sp in al in st rum entat ion w ill ensu re
that t he required instrum ents are available to
facilitate implant removal.
Spinal Cord Blood Flow
The blood ow to the spinal cord ente rs thedura t hrough vessels that t ravel with th e exit-
ing nerve root. Although n erve roots a re com -
m only sacri ced in th oracic-level osteoto m ies,
taking a ner ve root at the level of the arte ry of
Adamkiewicz could lead to signi cant detri-
m ent t o the spinal cord circulation.2 This arter y
has variable anatomy, but is present between
T8 and L1 on the left side in the majority of
peop le. When consid ering ost eotom ies a rou nd
the thoracolum bar junction, protecting and sav-
ing the nerve roots may preserve key sources
of blood ow.
For thoracolumbar three-column osteoto-
mies, preoperative angiography can be per-
formed to determ ine the exact location of the
arte ry of Adam kiewicz. The ar ter y run s a char-
acteristic intradural “hairpin” loop on imag-
ing3 ( Fig. 3.1). The location of the artery may
in uen ce the choice of level of th e osteotom y,
and th e surgeon m ay choose a level other t han
the ap ex if the ar ter y is present at t he ap ex. In- ju ring this vessel, especially in the pre sence of
Fig. 3.1a,b Spot image (a) and inverse (b) shots
of angiography of the left T11 segme ntal arte ry
showing the characteristic intradural hairpin loop
(white arrow), represent ing the artery of Adam -
kiewicz. In th is pat ient , the vessel enters the dura
through t he left T11 forame n and forms the loop
that extends up to T10. With the vessel arising two
levels proximal to the apex, a vert ebral column
resect ion was performed at L1 without incident .
a b
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30 Chapte r 3
hypotension, can lead to a loss of intraopera-
tive motor evoked potential (MEP) monitoring
that is often delayed from the time of injury.
With spinal cord infarction as one of the m ain
risks of spinal cord level osteotomies, knowl-
edge of and at tention to th is artery m ay help preven t th is devast at in g com plicat ion , esp e-
cially in patient s with previous anter ior proce-
dures, whe re segmen tal vessels may have been
ligated.
Fixation
Achieving adequ ate and stable xation is es-
sent ial to obtaining and m aintaining deform ity
correction. Although the pedicle screw is themain anchor in the majority of constructs, al-
ternatives such as hooks, laminar screws, fu-
sion mass screws or hooks, wires, and bands
should be considered whe n ped icle screw xa-
tion is not possible.4 Obtaining adequat e prox-
imal anchors is generally the key determinant
of successful constructs in thoracic osteoto-
mies. Osteotomies should not be attempted
unless solid proxim al and distal xation is es-
tablished. Careful planning from the preop era-
tive im ages will help to ident ify and select t he
approp riate anchor for each level.
During osteotom y closure, various m ethod s
can be utilized to protect the main implants.
Tem porar y devices or implant s can be u sed to
close th e osteotom ies, such as cent ral rod con-
structs, sparing the main screws.5 The use of
per iapical reduct ion scre w s, tubes, or ot her
extenders on the screws, linking of multiple
anchors to th e rod before cantilevering the re-
duction, and the use of a three- or four-rodtechnique with connectors can facilitate reduc-
tion of the osteotom y and correction of the d e-
form ities wh ile protecting the m ain anchors.
Determining the Desired
Correction
The imaging should be carefully studied to
identify the deform ity and determ ine the t ype
and m agnitude of the desired correction. Care-ful underst anding of the nor m al sagittal align-
m ent, the pelvic param eters, and th e m agnitude
of the deformity will help to identify which
osteotomies would be required to gain the de-
sired correction.6,7
For xed kyph otic deform ities, correct ion
w ill be achieved t hrough a nter ior length ening,
pos terior shor tening, or a com binat ion of both.For coronal deformities, correction will be
achieved through concave lengthening, convex
shorte ning, or a combination of both. For xed
lordosis, correction can be achieved through
anterior shortening, posterior lengthening, or
a com bination of both. For m ultiplanar d efor-
mities, it is important to identify the primary
deform ity or deform ities, and tailor an osteot-
omy or combination of maneuvers to achieve
the desired correct ion. For example, for a xed
kyphotic scoliosis, a combination of posterior
shorte ning and convex shorten ing could be the
pr im ary m od e of correct ion. If a verteb ra l col-
um n re section (VCR) were to be per form ed, a
larger anterior cage placed on the concavity
could maximize correction. For xed hyper-
lordosis, a form al anter ior release or resection
could be combined with posterior colum n re-
leases to achieve the d esired correction.8
The magnitude of the deformity must be
considered. Rough estimates of potential cor-rection th rough a single osteotomy include 10
degrees of sagitt al or coronal plane correction
through a single posterior column release, 30
to 35 d egrees of sagitt al and 10 to 15 d egrees of
coronal plane throu gh a single pe dicle subtrac-
tion osteotomy (PSO), and 30 to 50 degrees of
correct ion th rough a VCR in th e coron al or sag-
ittal plane.9,10 For a VCR, more correction will
be ach ieved t hrough a d efor mity w ithou t a pre -
vious fusion compared with one that is previ-
ously fused , as correction w ill be achieved only
through the osteotomy site and not th rough the
adjacent segments in cases of previous fusion
masses. Properly estimating the desired cor-
rection relative to t he deform ity w ill help plan
the num ber and types of osteotomies required
to achieve th e desired correction.11
Deciding the Leve l of the
OsteotomyFor p osterior column releases (Sm ith Petersen ,
Ponte), multiple periapical osteotomies will
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The Use of Osteotom ies for Rigid Spinal Deformities 31
help achieve a gradual, multilevel correction
for deformities with m obile ant erior colum ns.
For t hr ee- column osteoto m ies (PSO, PSO vari-
ants, VCR), the preferred vertebra would be at
the apex of the deformity, not t ilted in th e cor-
onal or sagittal planes, and would be appro- pr iat e for proxim al an d dist al xat ion. Other
considerations include the location of the ar-
tery of Adam kiewicz and the presence of pseu-
darthrosis in cases of revisions, in which cases
it would preferable be include the nonfused
levels in th e osteot omy.
Planning an Osteoto my
Putting all the information together will help
to determ ine the best opt ion for deform ity cor-
rection. A represen tative case is a 66-year-old
woman with ankylosing spondylitis (Fig. 3.2).
Preoperative im aging w ith long-cassette radio-
graphs and CT demonstrated the autofusion
of her spine. Her chief complaints are sagitt al
imbalance and di culty w ith forw ard gaze.
Her pelvic incidence m easures 55 degrees, thelumba r lordosis 10 degrees, w ith a sacral slope
of 5 degrees and a pelvic tilt of 50 degrees.
With th e desired lum bar lordosis being 10 de-
grees less than the pelvic incidence, and the
desired pelvic tilt being less than 25 degrees,
she wou ld require ~ 35 degrees of lum bar lor-
dosis. This can best be achieved throu gh a single
lum bar PSO.
As for her th oracic spine, she has signi cant
complaints related to her gaze. Her thoracic
kyphosis from T5 to T12 m easures 25 degrees,
wh ich is within the norm al range. Her T2-T5,
Fig. 3.2 a–d Represent ative case of a 66-year-old
woman with ankylosing spondylitis as demonstrated
on the p reoperative st anding posteroant erior radio-
graph (a) and the sagitt al CT reconstruction (b).
Abnorm al sagit ta l alignm ent is characterized by
a low sacral slope (SS), high pelvic t ilt (PT) and
insu cient lum bar lordosis (LL, T12-S1) for the
given pelvic incidence (PI). To maintain a balanced
relationship of the PI and LL, an L2 ped icle subt rac-
tion osteotomy (PSO) was performed. Forward gaze
was improved with a T3 PSO to correct the p roximal
tho racic kyphot ic deformity. Stabilizat ion of t his
correction was achieved with a C2 to pelvis construct
as demonstrated on the standing postoperative
long-casset te posteroant erior (c) and lateral (d)
radiographs.
a b c d
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32 Chapte r 3
however, m easures 45 d egrees, which is greater
tha n th e 10 to 15 degrees expected for this re-
gion. A single PSO in t his region w ould p rovide
the n ecessary correction to improve her gaze.
This patient und erw ent a T3 an d an L2 PSOs
with a C2-to-pelvis stabilization through asingle-stage procedur e, addressing both of her
deformities and providing her with the neces-
sary sagittal balance.
Single Proce dure or Staged
Although it m ay be preferable to complete t he
surgery in one stage, certain factors may ne-
cessitate performing the procedure in two or
more stages. These factors include excessive
bleeding, long durat ion of t he su rgery, medica l
comorbidities, and di culties w ith neu rom on-
itoring. Recognizing th ese di culties pre ope r-
atively may help to electively plan performing
these surgeries over two separate days. The
bene ts of st aging include m inim izing op era -
tive team fatigue, postpon ing the bleeding por-
tion of the procedure to the second day, and
the possibility of obtaining prop er im aging to
check the position of the instrum entation pr ior
to th e second stage. The t iming betw een stagesis controversial. Some advocate a short time
of 1 to 2 days, wh ereas others recomm end 1 to
2 weeks to allow p atients to achieve their nor-
mal nutritional status before proceeding. Lo-
gistical issues of operative time and surgical
team availability, as well as patient and fam-
ily issues, also need to be considered in the
decision.
The Surgical Team
Having a strong, cohesive surgical team with
open communication is essential to the suc-
cess of these complex reconstructions. Ideally,
the team should include an experienced spine
surgeon and anesthesiologist, skilled surgical
assistant s, a nursing team fam iliar w ith the in-
strum entation and procedure, an experienced
neuromonitoring and radiology technologist,
and a blood conservation team . Open com m u-
nication is impor tant , and such issues as blood pressu re par am et ers, b lood conse rvat ion st rat -
egies, neurom onitoring changes, and inform a-
tion about the surgical eld and the stage of
the procedure should be reviewed frequently
throughout the case.12
Obtaining Fusion Across the
Osteotomy
Obtaining a solid fusion across the osteotomy
is imp orta nt in preventing early imp lant failure
at t he level of the osteotom y. Although m ultiple
rods can increase t he rigidity of the construct s,
having stable anterior and posterior columns
w ith bridged struct ural bone across all defects
is key to obtaining fusion. Anterior grafts are
not su cient to overcom e large posterior col-
umn defects. Resected ribs can be preservedin the procedure an d used to bridge posterior
column defects following osteotomy closure.13
Techniques of fashioning the rib and the host
bed, w ir ing r ibs in place, or usin g m in i-screw s
from the craniofacial intern al xation sets to
secure the ribs will help re-create the struc-
tu ral continu ity of the p osterior column .
! Osteotomy OptionsSpinal osteotom ies can be divided into six main
types14 ( Fig. 3 .3):
Posterior colum n:
1. Partial facet
2. Complete facet
Partial body:
3. Pedicle subtr action osteot omy (PSO)
4. Transd iskal ped icle subt raction osteotomy
Complete body:5. Ver teb ra l colum n resect ion (VCR)
Multiple vertebra e:
6. Multiple vertebr al colum n resection
In this classi cation, the approa ch m odi er
was added. If the procedure was performed
from posteriorly, the osteotom y would h ave a
“P” after th e n um ber. If a combined anter ior
and posterior sur gery w as pe rformed , an “A/P”
would be added after the number. For exam-
ple, if a PSO was p erform ed fro m poster iorly, itwould be considered a type 3P osteotomy. A
VCR performed through a combined anterior
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The Use of Osteotom ies for Rigid Spinal Deformities 33
and posterior approach wou ld be considered atype 5 A/P.
Types 1 and 2: Posterior Column
Osteotomies
Release of the facet joints an d th e post erior lig-
am entous stru ctures, including the ligament um
avum , provides signi cant m obility to the pos-
terior column . For any correction to occur, the
anterior column has to be mobile. With thecombination of a m obile anter ior column and a
released posterior column, signi cant correc-tion can be achieved in both the coronal and
sagitt al planes (Fig. 3.4). For kyphosis correc-
tion, this osteotomy provides a combination of
po ster ior sh or te ning and ante rior lengthening.
Type 1 o steotom ies involve resection of th e
infer ior facets. This can pr ovide some m obilit y
in th e poster ior colum n. Type 2 osteotomies
involve removal of the superior facet and liga-
mentous structures. Resection of the superior
facet is the key to the release. This can beachieved w ithout resecting the inferior facets,
Fig. 3 .3a–f Schemat ic of the compre-
hensive anatom ic spinal osteotom y
classi cation proposed by Schwab et al.
In th is classi cat ion, Type 1 (a) is a part ial
facet resect ion, t ype 2 (b) is a complete
facet resect ion, t ype 3(c)
is a ped iclesubtraction osteotomy, type 4 (d) is a
transdiskal pedicle subtract ion osteotomy,
type 5 (e ) is a vert ebral column resect ion,
and type 6 (f) is a multi-level vert ebrec-
tomy. (From Schwab F, Blondel B, Chay E,
et al. The comprehensive anatomical
spinal oste otomy classi cation. Neurosur-
gery 2014;74:112–120, discussion 120.
Reprinte d with perm ission.)
a b c
d e f
Fig. 3 .4a–f Long cassett e standing (a) posteroante-
rior, (b) lateral, and (c) sagitt al computed tomogra-
phy (CT) reconst ruction of a 17-year-o ld boy with an
L2 congenital kyphosis. Note the global compe nsa-tion of the deformity through thoracic and lumbar
hyperlordosis. Posterior column osteotomies were
pe rform ed at L1-L2 and L2-L3, with correct ion of
the deformity and stabilization from (d) L1 to L3,
allowing for (e ) th e spont aneous no rmalization of
the thoracic kyphosis and a decrease in (f) thecompensatory lumbar hyperlordosis.
a b c d e f
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34 Chapte r 3
especially when signi cant distraction of thefacets occurs, as is the case w ith large kyphot ic
deformities. Preservation of the inferior facet
during the osteotomy can help to maintain
poste rior -colu m n bone stock , aid ing in the p os-
terior fusion. Use of a hook-based temporary
central rod to facilitate osteotomy closure fol-
lowing the posterior column release produced
~ 10 degrees of correction per osteotomy level
in the t horacic spine (Fig. 3 .5).
Type 3: Pedicle Subtraction
Osteotomy
The PSO is a posterior-based closing-wedge
osteotomy. It is ideally suited for kyphosis
correction and can reliably produce 25 to 35
degrees of lordosis even in the presence of a
solidly fused anter ior colum n15 ( Fig. 3.6). Per -
forming the PSO asymmetrically can enable
concomitant coronal plane correction. A PSO
can be performed in both the thoracic andlum bar spines. In cases of pelvic inciden ce (PI)
and lumb ar lordosis (LL) m ismatch w ith an as-
sociated abnormally high PI, a sacral PSO can be perform ed to decrease the PI an d nor m alize
th e PI–LL relat ionsh ip.16
The main complications associated with
PSOs are bleeding, potential nerve root injury
or ent rapm ent, and pseudarthrosis. The tech-
nique is discussed below. Careful attention to
detail can help m inimize the poten tial m orbid-
ity that can be seen with th ese cases.
Technique
Multiple variations of the technique h ave bee n
described, but the principles of the procedure
are com m on to all of them .
Decompression
Following exposure an d implant insertion, the
pedicle is iso lat ed fro m all of it s bon y at tach-
ments: laterally, the transverse process; dis-
tally, the pars; and proximally, the superiorfacet. A complete laminectomy of the involved
level is performed as well as of some or all of
Fig. 3.5a,b (a) Schem atic of a poste rior column
osteotomy with resection of the superior facets.
(b) Osteotomy closure is achieved with a temporary
central hook-rod construct reducing the inferior
facet to the proximal surface of the pedicle. Note
the exible anterior column allowing ant erior
lengt hening with oste otomy closure. (From Lewis SJ,
Goldstein S, Bodrogi A, et al. Comparison of pedicle
subtraction and Smith-Pete rsen osteotom ies in
correct ing thoracic kyphosis when closed with a
central hook-rod construct. Spine 2014;39:1217–
1224. Reprinted with perm ission.)
a b
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The Use of Osteotom ies for Rigid Spinal Deformities 35
the adjacent levels to ensure adequate space
for th e d ural sac cent rally up on closure. Com -
plete resect ion o f th e p edicle is requ ired t o cre-
ate a single foram en for t wo n erve roots—the
ner ve root of the osteotomy level as well as thener ve root of the level proxim al. The complete
pos te rior ele m ents of the verteb ra of the os te-
otomy level should be resected. A triangular
poste rior -b ased w edge o f bone is then rem oved
from the body, leaving a small amoun t of ante-
rior bone of the vertebral body. The anterior
colum n acts as a h inge du ring closure.
For thoracic-level osteotomies, the trans-
verse processes are rem oved to reveal the m e-
dial rib. The r ib is dissecte d free from all its soft
tissue attachm ent s, taking care to avoid ente r-
ing the pleura l space. The r ib is the n cut 5 to
6 cm lateral from th e vertebra. Subpe riosteal
dissection is done to free up the medial rib,
wh ich is then d etached from the lateral aspect
of the vertebral body. Dissection along the
lateral pedicle and body is then performed to
free th e m ediastinum from the ventral verte-
bra l bod y. Spoon re t rac tor s can then be placed
around th e anterior vertebra to furth er protect
the m ediastinal str uctu res. Retract ing the spi-nal cord should be avoided dur ing the decom -
pre ssion to m in im ize iat rogenic in ju ry.
Minimizing Bleeding During the Osteotomy
The epidural veins run a predictable course;
ident ifying, coagulating, and cut ting the m can
m inimize blood loss dur ing the procedu re. The
veins run t hrough the epidural fat and sh ould
be coagulat ed w hile separa t ing the fat from the
dura. A second series of veins run along the
medial aspect of the pedicle, distally along
the cour se of th e exiting ner ve root and proxi-
mally over the pedicle and deep to the su-
perior facet . W hen reach ing arou nd ventrally,
care should be made to avoid the segmental
vessels running along the midportion of the
lateral vertebral body. As well, failure to sepa-
rate the plane of the mediastinum from theventra l body can lead to signi cant m ediasti-
nal venous bleeding during dissection lateral
to the vertebral body. It is imperative to stay
along the lateral aspect of the vertebra w hen
dissecting an teriorly.
Osteotomy Closure
Closure of the osteotomy is perform ed after en -
suring adequate rese ction of the posterior wall
of the vertebral body and after complete re-section of the p edicles has bee n pe rform ed. If
di culty is encoun tered closing the osteotomy,
Fig. 3.6 a–e Long casset te stand ing (a) lateral and(b) sagitt al CT reconst ruction of a 67-year-old man
who underwent a previous anterior and posterior
L2-L4 fusion for an L3 bu rst fracture. Intraoperat ive
views with (c) th e t emporary cent ral rod in place
and postoperative long casset te (d) late ral and(e ) sag it ta l T2 m agne tic resonance imaging (MRI)
dem onstrating restored sagitt al alignme nt following
an L3 PSO and T10 to pe lvis construct .
a b c d e
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36 Chapte r 3
the surgeon should consider resecting more
bon e an ter iorly for adequ at e decom press ion.
Inadequate bone resection is the m ain reason
osteotom ies do not close.
To judge th e red uction of the p osterior col-
um n, the inferior facet of th e level proximal tothe osteotomy can be preserved and reduced
to the superior facet of the level distal to the
osteotomy. This w ill ensure a stable posterior
column with structural bone continuity and
preve nt oversh or tening during closu re. Closu re
can be achieved through the use of a hook-
based centra l ro d (Fig. 3.7), through com pres-
sion of the periapical anchors w ith tem porary
short rods, or with th ree- or four-rod constructs
using side-to-side rod connectors. If posterior
colum n continuity cannot be achieved th rough
osteotomy closure, struct ural bone graft (from
adjacent ribs or large spinous processes) can be
used to ll the posterior defects.
Type 4: Transdiskal Variant
Modifying the proximal resection of the PSO
to exten d across th e d isk space provides for a
greater resection and enables bone-on-bone
contact th rough th e ante rior colum n. This vari-
ation is particularly useful in cases of diskitis
w ith kyph otic collapse (Fig. 3 .8) and posttrau-
m atic kyphosis.17
PSO w ith Previous Ante rior Implants
Anterior implants at the level of the planned
osteotomy present a challenge wh en perform -
ing posterior-based procedures. The implants
can be rem oved either th rough a form al ante-
rior approach or through an anterior reach-
around procedure from a p osterior approach18
(Fig. 3.9). Posteriorly th e tran sverse processes
are rem oved, and dissection is performe d along
the lateral aspect of the pedicle. The anterior
implant s are ident i ed. Taking care to preserve
the exiting nerve root, a m etal cutting bur can
be used to cu t the anterior ro d proxim al an d
distal to the ante rior screw. Som e of the lateral
bod y is then re m oved to ident ify the neck of
the screw, which is then cut with the bur. The
segment of the anterior screw with the at-
tached rod is rem oved. The osteotom y is then
Fig. 3.7a,b Schematic of (a) a p edicle subt raction
osteotomy closed with (b) a cent ral rod. Note the
reduction of the inferior facet of the proximal level
to the superior facet of the distal level, re-creatinga new facet joint and continuity of the posterior
column. (From Lewis SJ, Goldstein S, Bodrogi A,
et al. Comparison of pedicle subtraction and
Smith-Pete rsen oste otom ies in correct ing t horacic
kyphosis when closed with a cent ral hook-rod
construct. Spine 2014;39:1217–1224. Reprintedwith perm ission.)
a b
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The Use of Osteotom ies for Rigid Spinal Deformities 37
perfor m ed in the usu al fash ion and the re-
m aining shaft of the screw is rem oved w ith the
vertebral body resection (Fig. 3 .10 ).
Type 5: Vertebral Column
Resection
For large m ultiplanar deform ities, resection of
a complete vertebral body can provide the
mobility in the spine to achieve the neededcorrection.19 Severe kyp hot ic deform ities, like
those seen following tu berculosis, often requ ire
more extensive resections involving multiple
vertebrae to achieve the needed correction.
Common indications for VCR include severe
kyphoscoliosis, congenital deformities (Fig.
3.11 ), and rigid deform ities secondar y to pre -
vious surgery.20
The procedure is performed in a similar
fashion to a PSO. Although the PSO is often
perfor m ed for p r im arily sagit tal plane defor -
m ities, the VCR can a ccom m odate m ultiplanardeform ities. These deformities often have m ajor
rotational an d translational components, causing
Fig. 3.8a–h Long cassette (a) lateral and (b) sagit talT2-weighted MRI of a 73-year-old woman with
known tuberculosis unresponsive to medical
treatm ent . Note t he destruct ion and kyphotic
collapse of the T10-T11 d isk space and (c) adjacent
vert ebral bodies with an associated e pidural abscess
noted on (d) gadolinium-enhanced T1-weighted
MRI. Long casset te (e ) posteroant erior and
(f) lateral views demonst rate a T4 to L2 post erior
reconstruction. (g ) A transdiskal pedicle subt raction
osteotomy was performed by resecting the posterior elemen ts and ped icles of T11, the
proximal vert ebral body of T11, the T10-T11 disk,
and t he d istal vertebral body and end p late of T10.
(h) A new vertebral body was creat ing by reducing
the proximal body of T10 to the dista l verteb ral
body of T11. Note t he inferior face t o f T10 was
reduced to t he supe rior facet of T12 to maintain
the integrity of the poste rior column.
a b
c
d e f
g h
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38 Chapte r 3
Fig. 3.9 a–h Long casset te (a) posteroant erior and
(b) lateral view, sagittal T2 MRI (c) , and CT coronal
(d), sagitta l (e ), and rep resent at ive axials (f) of a
69-year-old woman with coronal and sagittal
malalignm ent following a previous ante rior T12to L5 fusion and circumferent ial extension to t he
sacrum and pe lvis. Thoracic kyphosis (T5-T12)
measures 45 deg rees, lumbar lordosis (T12-S1)
measures 7 degrees, the pelvic incidence measures
51 degrees, the sacral slope m easures 5 degrees,
and t he sagit tal vertical axis measures 12 cm.
(g,h) The pat ient underwent an o set L2 pedicle
subtraction osteotomy through a poste rior
approach and proximal extension to T4, as de mon-strated in the standing postoperative long-casett e
posteroanterior (g ) and lateral (h) ragiographs.
The L2 anterior screw was removed from the sam e
posterior approach .
a b c d e f g h
Fig. 3.10 a–e (a) Int raoperative view of the lateral
and ant erior dissection performed to ident ify the
previously placed anterior instrum entat ion t hrough
a posterior exposure. Note the preservation of the
exiting nerve root. A me ta l-cut ting high-speed drill
is used t o cut the ante rior rod proximal and d istal to
the screw. After rem oval of some o f the lateral
vertebral body, a further cut is made along the neck
of the screw. (b) The screw head with t he at tached
rod is removed. (c) The shaft of the screw is
extracted when completing the oste otomy. (d,e) A
schemat ic demonstrates the removal of the ante rior
implant. (From Lewis SJ, David K, Singer S, et al.
A technique of ante rior screw removal through a
posterior costo transversectomy approach for
posterior-based osteo tomies. Spine 2010;35:
E471–E474. Reprinted with perm ission.)
a
b
c d e
signi cant challenges to the exposure, the dis-
section, and the decomp ression, especially on
the concave side (Fig. 3.12a,b). Care must be
taken when dissecting around the vertebral
bod y on the concavit y, t o ensu re that the dis-section does not ente r the m ediastinum . Simi-
larly, with the severe rotation, the spinal cord
will be shifted against the concavity (Fig.
3.12c,d), making it vulnerable to injury with
removal of the concave pedicle. These chal-
lenges are not as di cult w hen per form ing a
PSO for sagitt al plane deform ities.
The step s for a VCR are similar t o t hose fora PSO: exposure, followed by insertion of im-
plan ts, removal of the transverse processe s, re-
m oval of the m edial ribs and rib head s, exposu re
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The Use of Osteotom ies for Rigid Spinal Deformities 39
Fig. 3.11 a–g (a) Anteroposterior and (b) lateral
long cassette radiographs of a 19-year-old man with
congenital kyphoscoliosis. (c,d) Three -dimensional
reconstructions demonst rates a T11 hem ivertebra
at t he ape x of the de formity. The pat ient under-
went (e ) posterior resect ion of T11 and T12 and(f,g) post erior reconstruct ion from T5 to L4. A
port ion of the re sected vertebra was use d as an
ante rior strut be tween T10 and L1 to maintain the
integrity of the anterior column. Closure of the
osteotomy was performed with proximal to distal
convex rod placeme nt with the t emporary concave
rod, with loosened set screws in place t o preventtranslation.
a b c d e f g
Fig. 3.12a–d Axial (a) CT and (b) MRI of a non-
rotate d t horacic spine with kyphosis. Note the
position of the rib heads and the cent ral position of
the spinal cord. (c) Comparat ive CT of a pat ient with
a severe scoliosis. Note the marked rotation of the
vertebra, the convex late ral vertebral body abut ting
the posterior aspect of the convex rib, the very
ventral position of the concave rib, and the posterior
position of the convex rib head. (d) Axial MRI shows
the spinal cord shifted aga inst the concave rib.
a b
c d
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40 Chapte r 3
of the ventral vertebral body, posterior de-
compression, removal of the concave pedicle,
tem porar y concave rod, convex rem oval of the
pedicle , and re lease of the proxim al a nd dist al
disks. The vert ebral body can be rem oved p iece-
m eal or en b loc. For piecem eal rem oval, a shellof vent ral vertebr al body cortex can be left be-
hind to protect the med iastinal structures and
serve as a barrier for the anterior strut graft
or cage. For en-bloc resection, circumferential
release of the disks needs to be performed to
perm it adequ at e release and re m oval. Rele ase
of the concave side of the disk is the m ost di -
cult. Often th e adjacent m edial ribs on th e con-
cavity need to be rem oved to provide su cient
access for the release. The tap for the pedicle
screws can be u sed as a joystick from the con-
vexity t o facilitate th e com plete rem oval of the
vertebral body. The use of proper retractors to
protect the m edias t inal st ruct ures during an-
terior body resection is paramoun t.
When performing VCR with marked rota-
tion, it is easiest to enter t he canal through t he
convex foramen to start the decompression.
The complete posterior elem ent s of the level
to be resected should be removed, along with
the laminae of the adjacent levels. This will provide good visualizat ion of the sp in al cord
up on oste otom y closure. The con cave pedicle is
carefully rem oved an d a tem porar y rod is then
placed on the con cavit y. The m ajorit y of the
remaining dissection and vertebrectomy can
be perform ed fro m the convex it y w ithou t the
temp orary rod being in t he w ay.
A structural anterior support graft, either a
par t of the resect ed verteb ra or a cage, is in -
serted anteriorly to guide the reduction and
preven t over sh or ten ing. A lam inar sp read er can
be use d to dist ra ct ventrally from the concave
side to facilitate the graft/cage insertion. Clo-
sure of the VCR should be done with a convex
rod. The t em pora ry concave rod is left in place,
with the set screws loosened, preventing trans-
lation without hindering osteotomy closure.
Redu ction is often easiest from proximal to dis-
tal. Single- and dual-rod reduction techniques
have been described. Redu cing a p roxim al and
distal convex rod to a central connector hasalso been described. Being familiar with mul-
tiple techniques and the equipment available
will enable the surgeon to tailor the m ethod to
the given situation.
Type 6: Multilevel Vertebral
Column ResectionSevere kyph otic angular d eform ities, often sec-
ondary to remote infections, are amenable to
pos te rior-based vertebr al re se ct ions. A sin gle
level is often insu cient . Multiple levels of th e
remnants of the deformed vertebrae are re-
sected (Fig. 3 .13 ). Follow ing resect ion, ven tr al
distraction aids in length ening the an terior col-
umn for placement of an anterior cage/strut.
Posterior shorten ing through t he rod w ill com -
plete the corre ct ion.
! Osteotomies for Fixed
Lordosis
The correction of xed hyperlordosis requires
a combination of anterior shortening and pos-
terior lengthening. This is most reliably ac-
complished t hrough a form al anterior release
followed by a p osterior correction (Fig. 3.14).Similar to severe kyphosis, w here the vertebral
column is displaced poste riorly, in xed hype r-
lordosis the spine is displaced ventrally. This
ventral displacement favors an anterior ap-
pro ach , w ith the sp ine be ing su per cial t o the
anterior abdominal wall. In cases of thoracic
hyperlordosis, severe narr owing of the m edias-
tinum occurs, w ith bronchial comp ression oc-
curring in th e m ore severe cases. Even in cases
w ith respiratory issues, these p atient s paradox-
ically bene t from formal anterior approaches
to decrease the lordosis and help increase the
kyphosis, thereby increasing the anteroposte-
rior diam eter of the m ediastinum , relieving the
br on ch ial com pre ssion.
Anterior shortening can be accomplished
with multiple-level diskectomies for global
hyperlordosis or through resection of disk and
bo ne for m ore foca l deform it ies (Figs . 3.15 an d
3.16). A posterior-column release and instru-
me ntation is then perform ed. Contouring the pos te rior ro d in the approp riate sagit tal plane
w ill th en reduce th e lordotic deform ity. Form al
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The Use of Osteotom ies for Rigid Spinal Deformities 41
Fig. 3.13 a–e (a) Anteroposterior and (b) lateral
views of a 59-year-old m an with severe kyphosis
secondary to remote infect ion. (c) CT sagitt al view
shows four vert ebrae autofused ventrally with a
severe focal kyphosis, and hyperlordosis of the d istal
lumbar and thoracic spines. (d,e) Long casset te
radiographs demonstrating correction following
multilevel vertebrectomy, placement of an anterior
cage, and posterior T6 to pelvis instrumentation.
a b c d e
Fig. 3.14 a–d Supine (a) anteroposterior and
(b) late ral long casset te radiographs of a 17-year-old
boy with severe neuromuscu lar lordoscoliosis with
previous Baclofen pum p inse rt ion. (c,d) Following
L1 to S1 anterior diskectom ies, intraoperative
traction and a posterior T2 to pe lvis instrumentation
and fusion was performed.
a b c d
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42 Chapte r 3
Fig. 3.15a–f (a) Anteroposterior and (b) lateral
long cassette radiographs of a 47-year-old woman
with a remote Harrington rod instrumentation
and fusion for adolescent idiopat hic scoliosis. She
presented with distal degenerat ion and sag ittal
malalignment. (c,d) An L3 pedicle subt ract ion
osteotomy and ante rior lumbar interbody fusions at
L4–5 and L5-S1 were performe d, resulting in xed
lumbar hyperlordosis. Because of the patient ’s
severe unhappiness with her sagitt al alignme nt,
an ant erior L2–3 diskect omy and resection of the
proximal port ion of the L3 vertebral body followed
by a L2–3 post erior colum n release were perform ed.
The poste rior fusion m ass release was gent ly
distracte d and held open with mesh cages, while
an ap propriately contoured rod was inserted from
distal to proximal to reduce the o steotomy.
(e,f) This resulted in a more balanced sagit ta l plane.
(From Lewis SJ, Gray R, David K, Kopka M, Magana S.
Technique of Reverse Smith Petersen osteotomy
(RSPO) in a patient with xed lumbar hyperlordosis
and negative sagittal imbalance. Spine 2010;35:
E721–E725. Reprinted with perm ission.)
a b c d e f
Fig. 3.16 a–c Late ral radiographs of the pat ient in
Fig. 3.15 demonstrating (a) the L3 pedicle subtrac-
tion osteotomy and (b) the planned resection for
the reverse Smith–Petersen osteotomy. (c) Close-up
lateral view of the lumbar spine following closure of
the combined anterior/posterior osteotom y. (From
Lewis SJ, Gray R, David K, Kopka M, Magana S.
Technique of Reverse Smith Petersen osteotomy
(RSPO) in a patient with xed lumbar hyperlordosis
and negative sagittal imbalance. Spine
2010;35:E721–E725. Reprinte d with permission.)
a b c
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The Use of Osteotom ies for Rigid Spinal Deformities 43
pos te rior dist ra ct ion after the circu m ferential
release m ay cause unwan ted distraction of th e
entire spine instead of just the posterior column,
making the reduction to an under-contoured
rod the preferred m ethod.
! Chapter Summary
The approach to severe spinal deform ities has
signi cantly changed with the improved tech-
niques, imaging, and instrumentation that
are available. An improved outcome will be
achieved w ith careful preoperative planning, a
deep understanding of the deformities, and
th e knowledge and ability to perform t he vari-
ous correct ion techn iques. Creating an environ-
m ent with experienced and skilled surgical and
per ioperat ive team s w ill help to predict and
manage the complexities associated with the
successful treat ment of these challenging cases.
Pearls
Obtaining appropriate preoperative imaging
studies can help to bett er understand the com- plexities o f the de form ity and the patient’s anat-
omy, and to plan for potent ial di culties in the
pro cedure.
Careful preoperative clinical and radiographic
evaluat ion will help to assess the exibility of the
deformity, to determ ine the xation options, and
to decide on the location, number, and type
of osteotom ies required to achieve the desired
correction. Accurate intraoperative spinal cord monitoring,
including mot or evoked pot ent ials, is essen tial to
the safe comp letion of these procedures. Under-
standing the timing and magnitude of neuro-
mo nitoring changes will direct key intraope rative
decisions.
Although ped icle screw instrume ntat ion is the p ri-
mary method of curve control, alternative xation
methods such as fusion mass screws or laminar
hooks are importan t b ackup strategies, especially
in revision surgery or dysplastic anato my.
Pitfalls
The artery of Adamkiewicz has a variable anat-
omy from T8 to L1, mo st com mon ly on the left
side. When considering ost eoto mies around t he
thoracolumbar junction, protecting and saving
the nerve roots may preserve key sources of blood
ow.
Careful and controlled reduct ion of three -column
osteotomies is essential to prevent cord trans-
lation and subsequent injury. Complete visuali-
zation o f the cord and harmonious collaboration
with the surgical team , electrophysiological moni-toring team , and nursing sta is essen tial for spi-
nal cord safet y.
References
Five Must -Read Referen ces
1 . Dorw ard IG, Len ke LG. Osteotom ies in the pos ter ior-
only treatment of complex adult spinal deformity:
a com parat ive review. Neurosurg Focus 201 0;28:E4
PubMed
2. Dom m isse GF. The blood su pp ly of th e spina l cord. A
critical vascular zone in spinal surgery. J Bone Joint
Surg Br 1974;5 6:225–2 35 PubMed
3. Boll DT, Bulow H, Black ha m KA, Ascho AJ, Schm itz
BL. MDCT angiogra phy o f the spina l vasculatu re a nd
the artery of Adamkiewicz. AJR Am J Roentgenol
2006;187:1054–1060 PubMed
4. Lewis SJ, Arun R, Bodrogi A, et al. The use of fusion
mass screws in revision spinal deformity surgery.
Eur Spine J 2014;23(Suppl 2):18 1–186 PubMed
5. Lew is SJ, Golds te in S, Bod rogi A, et a l. Com pa rison o f
pedicle su bt ra ct ion an d Smith-Pe ter se n oste otom ies
in correcting thoracic kyphosis when closed with a
central hook-rod construct. Spine 2014;39:1217–
1224 PubMed
6. Schw ab F, Patel A, Ungar B, Farcy J-P, Lafage V. Adu lt
spinal deformity-postoperative standing imbalance:
how m uch can you tolerate? An overview of key pa-
rameters in assessing alignment and planning cor-
rective surgery. Spine 2010; 35:2224– 2231 PubMed
7. Rose PS, Bridwell KH, Lenke LG, et al. Role of pelvic
incidence, thoracic kyphosis, and patient factors on
sagittal plane correction following pedicle subtrac-
tion osteotom y. Spine 2009;34 :785–79 1 PubMed
8 . Lewis SJ, Gray R, David K, Kopka M, Magan a S. Tech -
nique of Reverse Smith Petersen osteotom y (RSPO) in a
pat ien t w ith xed lum bar hyp er lordosis an d negative
sagittal imbalance. Spine 2010;35:E721–E725 PubMed
9. Cho K-J, Bridwell KH, Lenke LG, Berra A, Baldus C.
Comparison of Smith-Petersen versus pedicle sub-
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44 Chapte r 3
traction osteotomy for the correction of xed sagit-
tal imb alance. Spine 2005 ;30:2030 –2037, discussion
2038 PubMed
10. Dorward IG, Lenke LG, Stoker GE, Cho W, Koester LA,
Sides BA. Radiogr aph ic and clinical out com es of pos-
terior column osteotomies in spinal deformity cor-
rection. Spine 2014;39:870–880 PubMed
11. Bridw ell KH. Decision m aking regard ing Sm ith-
Petersen vs. pedicle su btraction osteotomy vs. ver-
tebral column resection for spinal deformity. Spine
2006;31(19 , Supp l):S171–S178 PubMed
12. Jar vis JG, Str ant zas S, Lipkus M, et al. Respo nd ing to
neurom onitoring changes in 3-colum n posterior spi-
nal osteotom ies for rigid pediatric spinal deform ities.
Spine 2013;38 :E493–E503 PubMed
13. Lewis SJ, Kulkarni AG, Rampersaud YR, et al. Poste-
rior colum n re construction with autologous rib graft
after en bloc tumor excision. Spine 2012;37:346–
35 0 PubMed
14. Schwa b F, Blonde l B, Chay E, et al. The com preh en sive
anatomical spinal osteotomy classi cation. Neuro-
surgery 2014;74:112–120, discussion 120 PubMed
15. Lafage V, Schwab F, Vira S, et al. Does vertebral level
of pedicle subtraction osteotomy correlate with de-
gree of spinopelvic parameter correction? J Neuro-
surg Spine 2011;14:184–191 PubMed
16. Lafage V, Bha ru cha NJ, Schw ab F, et al. Mult icen te r
validation of a formula predicting postoperative
spinopelvic alignment. J Neurosurg Spine 2012;16:
15–21 PubMed
17 . Halper n EM, Bacon SA, Kitagaw a T, Lew is SJ. Poster ior
transdiscal three-colum n shortening in th e surgical
treatment of vertebral discitis/osteomyelitis with
collapse. Spine 201 0;35:13 16–1322 PubMed
18 . Lew is SJ, David K, Singer S, et al. A techn ique of ant e-
rior screw rem oval through a posterior costotransver-
sectomy approach for posterior-based osteotomies.
Spine 2010;35: E471–E474 PubMed
19. Ham zaoglu A, Alanay A, Ozturk C, Sarie r M, Karad er-
eler S, Ganiyusufoglu K. Posterior vertebral column
resection in severe spinal deform ities: a total of 102
cases. Spine 2011;36 :E340–E344 PubMed
20 . Len ke LG, O’Lea ry PT, Bridw ell KH, Side s BA, Koest er
LA, Blanke KM. Poster ior vert ebra l column rese ction
for severe pediatric deformity: minimum two-year
follow-up of thirt y- ve consecut ive patien ts. Spine
2009;34:2213–2221 PubMed
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! Introduction
Fusion attempts across L5/S1 in adult spinal
deformity are plagued by a high rate of pseu-
dart hrosis and implant breakage/failure du e to
the unique anatomic and biomechanical char-
acteristics of the lumbosacral junction.1,2 In
a single-institution review of adult deformity
pat ients w ith const ruct s great er than fou r lev-
els, construct s ending at S1 had a signi cantlyhigher rate of pseudarthrosis compared with
constru cts end ing at L5 or m ore cepha lad lev-
els.1 Othe r pseu dart hrosis risk factors were age
older than 55 years, more than 12 levels in-
cluded in the construct, and T10-L2 kyphosis
of greater than 20 degrees. The addition of
sacral-pelvic xation increases the strength
and stability of constructs spanning the lum-
bosacral junct ion and is a form idable too l in
the spinal deform ity surgeon’s arm am entar ium
for correcting spinal imb alance.
! Anatomic and
Biomechanical
Considerations
As a transition zone from the mobile lumbar
spine to the sti pelvis, the lumb osacral junc-tion exper iences signi cant forces challenging
arthrodesis attempts across the segment. De-
spite bearing axial loads of more than double
bod y weigh t , the osseou s anatom y of the sa-
crum p rovides relatively litt le strength for x-
ation.3 The sacrum consists of a thin rim of
cortical bone surrounding a cancellous core,
w ith large pedicle diamete r precluding the e n-
gagement of both medial and lateral cortical
walls via ped icle screw instr um ent ation.
The lumbosacral junction is a biomechani-
cally distinct location that is subjected to thehighest level of translational shear force and
the most limited range of motion within the
spine, with the L5/S1 disk bearing the largest
summation of load vectors.2,4–6 These u nique
stresses, combined with the relatively small
am oun t of sacral cort ical bon e available for x-
ation, result in increased pseudarthrosis and
implant breakage/failure in long instrumenta-
tion constru cts end ing at S1.2,7
McCord et al6 introduced the concept of the
lumbosacral pivot point at the junction of the
L5-S1 disk and the middle osteoligamentous
colum n to describe the considerable exion
moments and cantilever forces acting at the
lumbosacral junction. Extending xation an-
terior to this pivot point increases construct
strength. Screw insertion into the ilium pro-
vides th e longest xation length ante rior to
this pivot point, and w as found to be t he on ly
instrum entation type at t he lum bosacral junc-
tion that signi cantly increased the maximumexion moment at failure. Compared with the
weak cancellous composition of the sacrum , the
4
Indications and Techniquesfor Sacral-Pelvic Fixationin Adult Spinal Deformity
Kriste n E. Jones, Robe rt A. Morgan, and David W. Polly, Jr.
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46 Chapte r 4
pos ter ior iliu m o ers abu ndant cort ica l bon e
for anchoring instrumentation and enables
increased screw length and diameter, making
sacral-p elvic xation a useful tech nique for in-
creasing constr uct strength .
! Indications for Sacral-Pelvic
Fixation
The rigid xation provided by sacral-pelvic
instrum ent ation is a useful adjunct to treating
a wide array of pathological entities. Sacral-
pelvic xa t ion is in dicat ed for lu m bos acral
arth rodesis extending ceph alad to th e L2 ver-
tebra, augmentation for poor quality or os-
teoporotic bone, sacrectomy for tumor or
infection, un stab le sacral fractur es, correct ion
of at-back syndrom e via lumb ar osteotomy,
correction of pelvic obliquity, and high-grade
spondylolisthesis.8 The addit ion of iliac xa-
tion in these conditions signi cantly reduces
the stress placed on S1 instrumentation and
increases construct strength.
As w ith all spinal surgery, selection of the ap-
propriate ap proach for each individual pat ientand m eticulous atten tion to surgical technique
is the key to successful treatment. Although
sacral-pelvic xation is not required for many
pat ients undergoing lum bosacral ar thro des is,
th e force vectors required for th e creation an d
m aintena nce of proper sagittal alignm ent rela-
tive to the patient’s individual bone quality
m ust be considered.
! Sacral-Pelvic
Instrumentation Selection
and Techniques
Sacral Fixation
Screws at S1 can be placed th rough th e pedicles
in a medially convergent m ann er w ith bicort ical
end-p late or tricortical purchase, or through th e
ala in a divergent m anner (Fig. 4 .1a). Sublami-nar h ooks and w ires and S2 pedicle screws can
be used to su pplem ent S1 pedicle /a lar screw s
bu t shou ld n ot be relied on for anchor ing a long
construct.
S1 Pedicle Screw s
The sizable medially convergent sacral pedicles
accomm odate large screw length an d diameter
while simultaneously preventing “ lling” the
pedicle to ach ieve bicortica l purchase of the
m edial and lateral pedicle w all with a single
screw. The largely cancellous sacral pedicles
provid e relat ively lit t le pullo ut st rengt h in
un icortical xation, an d un icortical ped icle
screws should be avoided.3 Bicortical xation
anchored into the anterior sacral cortex pro-
vides increased p ullout strength compared w ith
unicortical S1 pedicle screws; however, addi-
tional trajectories can be employed to further
enh ance pu llout str ength . Luk et al9 compared
bicor tical S1 ped icle screw insert ion torque and
pullout st re ngt h to that of S1 pedicle screws
advanced through the S1 superior end plate.
S1 pedicle screws traversing the end plate
had signi cantly higher inser tional torque and
pullout st re ngt h compar ed w ith bicortica l S1
screws.Tricort ical xation, de ned as a screw tra-
jector y tow ard the m edial sacral pro m on tor y,
captures purchase in the dorsal, anterior, and
superior end-plate cortex (Fig. 4.1b). Lehman
et al10 found that this tricortical trajectory
doubles the insertional torque compared w ith
bicort ica l S1 pedicle screws par allel to the S1
end plate. Tricortical S1 screw strengt h has n ot
been direct ly compared w ith t rans– end-plate
screw strength; both provide enh anced strength
compared with typical bicortical purchase
paralle l to the S1 end plate. Triangu lat ion of
the pedicle screw t rajectory increases pullout
strength compared with straight-ahead trajec-
tory and should be u niversally emp loyed.
Sacral Alar Screw s
Alar screw insertion ut ilizes a lateral trajectory
into low-d ens ity cancellous sacral bone. Bicor-
tical alar xation is techn ically possible butfraught w ith risk of injuring the L5 n erve root s
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Indications and Techniques for Sacral-Pelvic Fixat ion in Adult Spinal Deformity 47
Fig. 4.1a,b Sacral screw trajectories. (a) Trajecto-
ries for S1 pedicle (A) and alar (B) screw placement.
(b) Intraoperative view de monst rating probe
insertion in tricortical S1 screw trajectory. Tricortical
purchase ut ilizing dense sacral promontory cort ical
bone should be employed to m aximize screw
pullout st rength.
a
b
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48 Chapte r 4
or comm on iliac vessels draped ante riorly across
the ala.3 Thus, alar screws are ut ilized m ainly as
unicortical supp lement s to bicortical/tricort ical
S1 p edicle screw const ru cts. A Chop in or Colo-
rado p late or a Tacoma block can be u tilized to
connect S1 and alar screws. Disadvantages ofthis technique include constrained screw st art -
ing point and p otent ial imp airm ent of the ideal
trajectory.
Sacral Sublaminar Wires and Hooks
Although sublaminar wires and hooks lack
su cient biom echanical strength to serve as
anchors to long constructs, they can be used
as supp lements for short-segment fusions.3,11
Hooks are optim ally placed in th e do rsal sacral
neuroforamina where improved cortical pur-
chase can b e achieved. The Harrington instru-
mentation system initially employed sacral
hooks as anchors to long constructs, but the
rate of pseudarthrosis and hook dislodgment
at L5/S1 was u naccept ably high. Sacral sub lam -
inar wires and hooks should not be used as
anchors to long constr ucts.
S2 Screws
S2 pedicle screw strength is typically limited
by a sh or t pedicle lengt h and a locat ion dor sa l
to the lumbosacral pivot point described by
McCord et a l6 an d Kebaish. 11 S2 pedicle screw s
and S2 screws directed laterally into th e ala can
be used as adjunct su ppor t to sh or t-segm ent
fusions but lack the biom echanical stren gth to
anchor long construct s.12
Jackson Intrasacral Rod Technique
Jackson intra sacral rods are inserted vertically
throu gh th e ala from S1 to th e level of S2 an d
the n can be connecte d to a constr uct including
S1 p edicle screws. Insert ion is techn ically dif-
cult and can be preclude d by alar anatomic
variations. This technique h as been shown to
be biom ech anically in fer ior to a lu m bosa cral
pedicle screw s– iliac screw const ruct and ism ent ioned for historical context only.5
Transsacral Fixation
Kellogg Spee d rst describe d tra nsver tebra l
strut grafting at L5/S1 from an anterior ap-
pro ach for pat ients w ith high -grade spon dylo-
listh esis. The Speed techn ique involves dr iving
a bular stru t graft through the L5 vertebral
bo dy and in to the sacrum via an te rior expo-
sure, and is a u seful technique in lieu of inter-
bo dy cage placem ent , w hich has an increas ed
risk of anterior subsidence for patients with
high-grad e spondylolisthesis.13
Due to the risk of the anterior exposure to
the lumbosacral junction, including injury to
the great vessels during mobilization or sym-
pat het ic plexu s dysfu nct ion cau sin g re trograd e
ejaculation in m ales, H.H. Bohlman popu larizedthe posterior approach for tran svertebra l b-
ular strut grafting at L5-S1 for patients with
high-gra de spon dylolisthesis. Ante rior xation
through L5/S1 can also be performed via a
paracoccyge al approach in a m in im ally in -
vasive fashion u tilizing synth etic imp lants . As
with all constructs, the addition of posterior
colum n sup port increases stability.
Iliac FixationAnchor ing a constr uct with iliac xation cre-
ates a longer lever arm to resist cantilever
forces across the lumb osacral junct ion via ex-
tension ant erior to the lum bosacral pivot point,
increasing biomechanical strength of sacral-
pelv ic const ruct s.6 Incorporation of the ilium
into a construct o oads stress from sacral
screws an d decreases the r ate of sacral instru-
m entation failure and pseudart hrosis across the
lumb osacral junction.4,14
Transiliac Fixation
Harrington Threaded Sacral Rod
Developed for pelvic xation in adjun ct w ith
Harr ington distraction rod s, this device is men-
tione d for historical pur poses. Two sep arate
pos te rior iliac incis ions are used to inse rt the
threa ded rod th rough the p osterior iliac wings
with compression applied. Pseudarthrosis rateshave been rep orted above 40%m and t he d is-
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Indications and Techniques for Sacral-Pelvic Fixat ion in Adult Spinal Deformity 49
traction forces of Harrington rods can result in
sagitta l plane imba lance.2,8
Kostuik Transiliac Bar
Inser ted from the m idline, the Kostuik tran sil-iac bar is placed 1 to 2 cm anter ior to the pos-
terior superior iliac spine and then attached
via custom connectors to S1 pedicle or alar
screws. The bar is sm ooth and has a contoure d
shape that accommodates the midline sacral
dorsal prominence, and has been reported to
have a h igh fusion rate of up to 97%.8
Iliac Fixation
Luque L-f xation
The rst to develop segment al instru m entation,
Luque exten ded lum bosacral construct s to the
pelvis usin g L-shaped ro ds w hose ends were
inserted into the posterior ilium at the poste-
rior sup erior iliac spine. This circum vented the
distraction problem associated with the Har-
rington technique and improved fusion rates,
but pist on ing occu rring be t ween the rod s de-
creased t he stability of th e Luqu e L- xation intorsion and exion.2,8
Galveston Technique
Ben L. Allen and Ron L. Ferguso n d evelope d t he
Galveston te chnique in t he 1980s. Sm ooth rod s
inserted from th e poster ior superior iliac spine
into the ilium were connected to segmental
lumbosacral instrumentation. Rod contouring
required signi cant expertise. To obviate the
need for this, rods with pre-bent sagittal con-
tour and bilateral iliac xation were created in
a single piece.3 This constru ct still required sub-
stantial rod management skills. Because the
smooth rods had inferior pullout strength com-
pared w ith thread ed screws, iliac screw s quickly
be cam e a m ore p op ular m et hod of xation .
Iliac Screws
Iliac xation with single or stacked unilateralor bilateral screws is performed with fully or
par t ially threa ded screw s. The pullout st rengt h
and rotational stability is superior to non-
threa ded rod techniques. The star ting point for
screw insertion is at the level of the posterior
super ior iliac spine w ith a t rajectory targeting
either the supra-acetabular notch or th e ante-rior superior iliac spine (Fig. 4.2). The screw
trajectory is planned via visualization of the
“iliac teard rop” on eith er uoroscopy or com-
pu ted tom ography (CT) im age gu idance. The
iliac teardrop is a region above th e acetabulum
bo rd ering t he m edial iliac w all, the lat era l iliac
wall, and the zenith of the sciatic notch. The
screw achieves greatest pu rchase in th e lateral
margin of the teardrop, directed through the
cortical bone just above the sciatic notch. San-
tos et al15 analyzed various screw lengths and
diamete rs and found a signi cant increase in
insertional torque for iliac screws of length
" 80 mm and diameter " 9.5 m m . No di eren ce
in insertional torque existed bet ween the supra-
acetabular notch and the anteroinferior iliac
spine- directe d tr ajectory. Given t he r isk of ace-
tabular joint violation w ith th e supra-acetabular
trajectory, the authors concluded that optimal
iliac screws are inserted in the anteroinferior
iliac spine trajectory w ith length " 80 mm anddiameter " 9 .5 mm .
Iliac screws can be used in combination w ith
sacral screws to provide increased construct
strength and are biomechanically superior to
oth er pelvic xation opt ions. Com par ing th e
Galveston techn ique to iliac screws in a series
of 20 neuromuscular scoliosis patients, iliac
screws enabled better correction of pelvic
obliquity and d ecreased implant breakage.16
In a biom echanical compar ison bet ween the
m odi ed Galveston technique with iliac xa-
tion but no S1 xation versus S1 pedicle screws
plus iliac screw s, or S1 and S2 screws w ithou t
iliac xat ion, Tis et al17 found that constructs
w ith iliac screws conferred signi cant strength
via decreased range of motion in multidirec-
tional exibility testing and increased load to
failure.
Bridwell’s group 4 performed a laboratory
investigation compar ing m ultidirectional exi-
bi lit y and exu ra l load to failure am on g thefollowing constru ct t ypes: lum bosacral pedicle
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50 Chapte r 4
screws, interbody cage, and iliac screws. Iliac
screw or interbody cage placem ent signi cantly
redu ced m ultidirectional exibility at the lum -
bosacral junct ion com pared w ith pedicle screws
alone, but iliac screw xation was superior in
protect ing sacral screws from pullout or p low -
through.4
Lebwohl et al5 performed a laboratory bio-m echanical analysis compar ing construct sti -
ness, S1 screw strain, and u ltimate failure load
among several techniques of supplementary
sacral xation, using S1 ped icle screws with
and w ithout S2 screws, as well as an int rasacral
rod and iliac screws. All techniques decreased
the S1 screw strain in exion-extension, but
only iliac screws decreased S1 screw strain in
axial loading. In destru ctive testing w ith exionloading, only iliac screw s signi can tly increased
Fig. 4.2 a–d Iliac screw placement u sing intraopera-
tive computed tomography (CT)-based framelessnavigation. (a) Iliac screw insert ion point is at the
posterior superior iliac sp ine, d irected toward the
anterior inferior iliac spine. (b) The teardrop view
is utilized t o opt imize screw purchase in the lateral
cort ical wall, just above t he sciatic notch . (c) The
sagittal view is used to dem onstrate screw angula-
tion toward the anterior inferior iliac spine, avoiding
violation of the acetabulum. (d) Stacked iliac screw
construct in patient with progressive deformity from
high-grade spondylolisthe sis p reviously fused in
situ, requiring sacral oste otomy for deformity
correction.
a
b
c
d
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Indications and Techniques for Sacral-Pelvic Fixat ion in Adult Spinal Deformity 51
the load to failure. The auth ors concluded that
th e add ition of iliac xation signi cant ly in-
creases the biomechanical strength of sacral
constructs.
A signi cant d isadvant age to iliac screws is
the potential prominence of the screw headat th e p oster ior sup er ior iliac spine (PSIS). Al-
though the starting point can be m odi ed or
the PSIS notched to allow bur ying of the screw
head, implant prominence cannot be com-
pletely e lim inat ed. Anot her d isadvantage is the
requirement of an o set connector for seg-
me ntal lumbosacral instrum entation.
Transsacral Iliac Fixation
S2-Alar-Iliac Screws
Developed to addre ss the problem atic imp lant
pro m inence and o se t locat ion of iliac screw s,
S2-alar -iliac (“S2-iliac”) screws are associated
with a lower complication rate related to im-
p lan t prom in ence-relat ed pain , necess it at ing
screw rem oval, compare d w ith t raditional iliac
xation.11 Implant prominence is minimized,
with th e m ean distance of the insertion point
to the skin 15 m m deep er for the S2-iliac tech-nique compared with traditional iliac screw
inser tion at th e PSIS.18 The S2-iliac screw st ar t-
ing point is 2 to 4 m m lateral and 4 to 8 m m
caudal to the dorsal S1 foramen, with a tra-
je ct or y tow ard the anterior infer ior iliac sp ine
(Fig. 4.3a) at an angle of ~ 40 degrees lateral
and 20 to 30 d egrees caudal.11,18 The iliac tear-
drop is again employed for trajectory align-
ment. Unlike traditional iliac screws, S2-iliac
screws do not typically require an o set con-
nector for joining rods to lum bosacral pedicle
screw constructs (Fig. 4.3b). Biomechanical
test ing of S2-iliac screws has sh own e quivalent
stability to conventional iliac screws.19 The
S2-iliac screw trajectory results in crossing the
sacroiliac joint, which has not been shown to
be prob lem at ic in the rst 5 year s o f follow-up
of this technique, but which requires ongoing
surveillance (Fig. 4.3c,d). Although haloing
around iliac screws m ay be observed in over
25%of patien ts, iliac screw pu llout o r breakageis very r are.1,11,14
Adjunctive Anterior
Interbody Support
Polly and colleagues 20 found that load-b earing
interbody structural grafts increase construct
sti ness and therefore can decrease the strainon posterior instrumentation, in addition to
increasing th e su rface a rea available for arth ro-
desis. They also found that the location of the
interbody graft in the sagittal plane has bio-
m echanical signi cance, with ant eriorly placed
grafts having increased sti ness compare d with
central or posteriorly placed inter body grafts.
Comp ared w ith stand- alone pedicle screw and
combination pedicle-iliac screw constructs,
pedicle -iliac screw const ruct s com bined w ith
interbody cages signi cantly redu ce segmen tal
movement across the lumbosacral junction in
laboratory analysis.4
! Patient Positioning
Patients undergoing sacral-pelvic instrumenta-
tion via open or minimally invasive technique
should be positioned prone on an operating
table that enables the creation or m aintenance
of anatomic lumbar lordosis. Fixation of the
lumbosacral junction in a at or kyphot ic an-
gulation m ust be absolutely avoided due to the
resultant sagitt al imbalance. Allowing th e abd o-
men to hang freely w ithout ventral compression
helps minimize intra-abdominal pressure and
venous bleeding.
! Operative Technique s
Sacral Fixation
Pedicle screw pullout stre ngth is increased by
m edialization of insert ion trajectory compared
with “straight-ahead” insertion without me-
dial angulation of the screw tip.3,12 An obese
bo dy hab itus, an iliac crest ove rh an g, o r t rian -
gulated vertebral bodies may presen t obstacles
to adequ ate m edialization of pedicle screw t ra- jectory (Fig. 4.4a). If this problem is encountered
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52 Chapte r 4
Fig. 4.3 a–d S2-alar-iliac screws. (a) Int raoperative
CT-guided planning dem onstrating st arting point
and trajectory of S2-alar-iliac screw. (b) Postoperative
CT scan showing alignment of S2-alar-iliac screw
head with lumbosacral pedicle screws, eliminat ing
the need for an o set connector typically required
by trad itional iliac scre ws. (c,d) X-rays dem onst rat-
ing usage of S2-alar-iliac screws to anchor long
construct for deformity correction.
a b
c d
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Indications and Techniques for Sacral-Pelvic Fixat ion in Adult Spinal Deformity 53
while using a midline open skin incision, the
bailout technique re qu ires sp lit t ing the fascia
in a paramedian fashion for a transmuscular
approach to enable a more lateral starting
point and m edializat ion of the t ra jector y. Vigi-
lance is required to prevent an unintended
straight-ahead trajectory from violating the
ante rior sacral or lum bar cortex with resultant
injury to neurovascular structures. The aortic
bifu rcat ion occurs at ap proxim ately L4/ L5, w ith
the common iliac vessels traveling laterally
from t he b ifurcat ion. The L4 and L5 ne rve root s
traverse the anterolateral sacral cortex pr ior to
join ing the lum bosacral p lexu s located at the
level of the sacral ala, and t he colon is in close
opposition to the ventral surface of S2. A rela-
tive “safe zone” exists in the ventral midline
of the sacral promon tory; h owever, individual pat ient vascular anat om y sh ould be in cid en-
tally visualized an d ap preciated on preope ra-
tive spine imaging prior to proceeding with
instrumentation.
Iliac Fixation
Misdirection o f iliac or S2-iliac screw s th rough
the sciatic notch can cau se injur y to the su pe-
rior gluteal artery or sciatic nerve, which is a
rare but serious complication. Violation of the
acetabulum m ust be avoided. Fam iliarization
with the iliac teardrop view enables correct
screw t rajectory selection.
Placeme nt of screws into th e ilium requires
signi cant insertional torque that can cause
breakage o f th e screw driver unless care is t ake n
to sequentially tap the screw trajectory com-
plete ly to the des ired depth. Once iliac screw
insertion is initiated, one should not pauseduring insertion, as the mechanical thermal
energy generated by screw insertion in the
Fig. 4.4 a–c Complicat ions of sacral-pelvic xat ion.
(a) Failure t o adequately direct pedicle screws in
me dial trajectory, combined with signi cant screw
pe rforation of ant erior cortex, result ing in screws
abutting internal iliac veins b ilate rally. (b,c) Asymp-
tom atic halo formation (arrows; dotted line) around
iliac screws doe s not necessita te revision unless
resulting in pain or lumbosacral pseudarthrosis.
a
b
c
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54 Chapte r 4
bone assis ts in temporar ily lessening inser t ion al
torque, a bene t that is lost whe n screw inser-
tion pauses. Iliac screw head prominence and
o set distance from lum bosacral pedicle screw
heads is minimized utilizing the S2-alar-iliac
trajectory.
Revision of Screws
As mentioned, iliac screws may undergo as-
ymptomatic haloing (Fig. 4.4b,c). Unless pain,
implant breakage, or instability of the constr uct
occurs, screw revision is not required. If iliac
screw rep lacem ent is required, using larger di-
am eter screws confers more stability than using
longer screws.
! Chapter Summary
Sacral-p elvic xation is a power ful tool for in-
creasing the st rength and sta bility of lumb osa-
cral construct s. Extrem e biomechan ical forces
at th e lum bosacral junct ion and relatively poor
bon e qu alit y of the sacrum re su lt in a h igh ra te
of lumbosacral pseudarthrosis and implantfailure in adult spinal deformity correction.
Sacral-p elvic xation is indicated for lum bo-
sacral arthrod esis extend ing ceph alad to th e L2
vertebra, augm ent ation of construct s for poor-
quality or osteoporotic bone, sacrectomy for
tumor or infection, unstable sacral fractures,
correction of at-back syndrom e via lumb ar
osteoto my, correct ion of pelvic obliquit y, high-
grad e spon dylolisth esis, or as a salvage me cha-
nism d uring revision for pseu dart hrosis.
Sacral xation is optim ally per form ed using
bi- or t ricort ica l S1 m edially direct ed pedicle
screws. Alar and S2 screws an d h ooks through
the dorsal sacral foramina may be added for
supplementation, but lack the biomechanical
strengt h to anchor long constr ucts in adult spi-
nal deform ity. Care m ust be t aken to opt imize
screw size for cort ical pu rchase w hile avoiding
injury to neurovascular structures anterior to
the lumbosacral junction.
Iliac xation is opt ima lly per form ed using
iliac or S2-alar-iliac threaded screws, in a tra-
jector y toward the antero in fer ior iliac sp ine,
with length " 80 mm and diameter " 9.5 mm.Know ledge of sacral-pelvic anatom y and u se of
the iliac teardrop view on intra operat ive imag-
ing is key for iliac screw p lacemen t.
The addition of interbody structural grafts
increases the surface area for arthrodesis and
sti ness of the construct and should be per-
formed for long constructs at the lumbosacral
junct ion.
The spinal deformity surgeon must have
excellent knowledge of indications, instru-
mentation options, and techniques of sacral-
pelvic xat ion . Fam iliar ization w ith sacra l-p elvic
anatomy is necessary to optimize the size
and trajectory of instrumentation and avoid
complications.
Pearls
Sacral-pelvic xation increases the strengt h and
rigidity of constructs spanning the lumbosacral
junc tion. Iliac xation decrease s the rate of sacral instru-
mentation failure and reduces the incidence of
lumb osacral pseud arthrosis.
S2-alar-iliac screws provide stron g biome chanical
xation, m inima l implant prominen ce, and favor-
able implant alignment with lumbosacral pedicle
screws for ease o f rod con touring.
Pitfalls
Sacral pedicle and alar screws have inadequate
strength to anchor constructs extending cepha-lad t o L2, predisposing t he p atient t o lumbo -
sacral pseu dart hrosis unless sacral-pelvic xation
strategies are em ployed.
Aceta bular joint impingem ent or sciatic not ch vi-
olation with resultant neurovascular injury can
occur during p lacement of iliac screws un less in-
traoperative imaging with teardrop view is used.
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Indications and Techniques for Sacral-Pelvic Fixat ion in Adult Spinal Deformity 55
References
Five Must -Read Referen ces
1. Kim YJ, Bridw ell KH, Len ke LG, Cho KJ, Edw ards CC II,
Rinella AS. Pseuda rth rosis in ad ult sp inal deform ity
following multisegmental instrumentation and ar-
throdesis. J Bone Joint Surg Am 2006;88:721–728 PubMed
2. Kostuik JP. Treatment of scoliosis in the adult thora-
columbar spine with special reference to fusion to
the sacr um . Orthop Clin North Am 198 8;19:371 –381
PubMed
3. Santos ER, Rosn er MK, Per ra JH, Polly DW Jr. Spinopel-
vic xation in deform ity: a review. Neurosurg Clin N
Am 2007;18:373–384 PubMed
4. Cun nin gha m BW, Lew is SJ, Long J, Dm itr iev AE, Lin-
ville DA, Bridwe ll KH. Biom ech an ical evaluat ion of
lumbosacral reconstruction techniques for spondy-
lolisthesis: an in vitro porcine model. Spine 2002;27:2321–2327 PubMed
5. Lebwohl NH, Cunningham BW, Dmitriev A, et al.
Biome chanical compar ison of lumb osacral xation
techniques in a calf spine model. Spine 2002;27:
2312–2320 PubMed
6. McCord DH, Cun nin gha m BW, Sho no Y, Myers JJ,
McAfee PC. Biomechanical analysis of lumbosacral
xation. Spine 1992;17(8, Suppl):S235–S243 PubMed
7. Kim YJ, Brid well KH, Len ke LG, Rine lla AS, Edw ards C
II. Pseudarthrosis in primary fusions for adult idio-
pat h ic scolios is: incid en ce, ri sk fac to rs , an d ou tcom e
analysis. Spine 2 005;30:4 68–474 PubMed 8 . Mosh irfar A, Rand FF, Spon seller PD, et al. Pelvic xa-
tion in spine surger y. Historical overview, indications,
biom echan ica l re levan ce, an d cu rre nt te chniqu es . J
Bone Joint Surg Am 2005;87(Suppl 2):89–106 PubMed
9. Luk KD, Chen L, Lu WW. A stronger bicortical sacral
pedicle s crew xation t hro ugh t he S1 e ndplat e: an in
vitro cyclic loading and pull-out force evaluation.
Spine 2005;30:525–529 PubMed
10 . Leh m an RA Jr, Kuklo TR, Belmon t PJ Jr, Ande rsen RC,
Polly DW Jr. Advan tage of ped icle screw xation di-
rected into the apex of the sacral promontory over
bicor t ica l xa tion : a biom echan ica l an alysis . Spin e2002;27:806–811 PubMed
11. Kebaish KM. Sacropelvic xation: techniques and
complications. Spine 2010;3 5:2245– 2251 PubMed
12. Koller H, Zenn er J, Hem p ng A, Fer rar is L, Meier O.
Reinforcement of lum bosacral instru me ntation u singS1-pedicle screws combined with S2-alar screws.
Oper Orthop Traumatol 2013;25:294–314 PubMed
13. Cunningham BW, Polly DW Jr. The use of interbody
cage devices for spinal deformity: a biomechanical
per sp ec t ive. Clin Orthop Relat Res 20 02 ;3 94 :7 3– 83
PubMed
14. Tsuchiya K, Bridwell KH, Kuklo TR, Lenke LG, Baldus
C. Minimum 5-year analysis of L5-S1 fusion using
sacrop elvic xation (bilateral S1 an d iliac screw s) for
spinal deformity. Spine 2006; 31:303–3 08 PubMed
15. Santos ER, Sembrano JN, Mueller B, Polly DW. Opti-
m izing iliac screw xation: a biomecha nical stud y onscrew length, trajectory, and diameter. J Neurosurg
Spine 2011;14:219–225 PubMed
16 . Peelle MW, Len ke LG, Brid we ll KH, Sides B. Com pari-
son of pelvic xation techniques in neu rom uscular
spinal deformity correction: Galveston rod versus
iliac and lumbosacral screws. Spine 2006;31:2392–
2398, discussion 2399 PubMed
17 . Tis JE, Helgeson M, Lehm an RA, Dmit riev AE. A bio-
m echanical comparison of di erent types of lumbo-
pelvic xat ion. Spin e 2 00 9; 34 :E866 –E872 PubMed
18. Cha ng TL, Spons eller PD, Keba ish KM, Fishm an EK.
Low pro le pelvic xation: anatom ic param eters forsacral alar-iliac xation versus trad itional iliac xa-
tion. Spine 2009;3 4:436–4 40 PubMed
19. O’Brien JR, Yu W, Kaufman BE, et al. Biomechanical
evaluation of S2 alar-iliac screws: e ect of length
and quad-cortical purchase as comp ared w ith iliac
xation. Spine 2013;38: E1250–E1255 PubMed
20. Polly DW Jr, Klem m e W R, Cun ningh am BW, Bur net te
JB, Haggerty CJ, Oda I. The biomechanical signi -
cance of anterior colum n sup port in a simulated sin-
gle-level spin al fusion. J Spina l Disord 20 00;1 3:58 –62
PubMed
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! Introduction
Osteoporosis is an imbalance between bone
form ation and resorption that primarily a ects
trabe cular bone . Progressive bone m ineral loss
and concomitan t bony architectu re changes re-
sult in pain, deformity, increased risk of frac-
tu re, and possible ne ural compression.
The spine is the m ost comm on site of osteo-
porot ic fr act ure s. Althou gh m ost pat ients w ithacute vertebr al comp ression fractures imp rove
regardless of the t reatm ent ap plied, no patient
experiences spontaneous restoration of the
vertebral he ight and achieves a realigned spine.
Therefore, spinal instru m ent ation is event ually
required for some pat ients.
With aging comes a higher incidence of
comorbidities that further complicates the
management of osteoporotic spine. The el-
derly today have more active lifestyles than
did the elderly of previous generations, and
they refuse to accept disability an d d eform ity
as a part of the aging process. Modi able
conditions su ch as p ulmon ary, coronar y, and
cerebrovascular disease an d diabetes m ellitus
should be addressed in collaboration with the
consulting medical and anesthesiology spe-
cialists to m inimize the surgical risk and op ti-
mize the outcome. Patients who smoke, have
a nut ritional de ciency, are dep ressed, or are
subject to oth er life stressors shou ld be coun-seled preoperatively to reduce the impact of
these factors.
Performing adult spinal reconstruction in
pat ients w ith os teop enia re qu ires careful pre -
operative planning, as osteopenia has impact
on both idiopathic and degenerat ive disorders.
Similarly, careful preoperative planning is re-
quired when performing a reconstruction on
younger patients with secondary osteoporosis
due to factors such as hypercort isolism, hyper-
thyroidism, hyperparathyroidism, alcohol abuse,
and immobilization.In p atients with low bone m ineral density
(BMD), spinal imp lant s cann ot be p laced as se-
curely as in patients with normal BMD, and
thus application of corrective forces through
the weak bone–implant interface is di cult. To
avoid failure in such situations, it is imp orta nt
to understand the biomechanics of the osteo-
porot ic sp ine an d to re cognize that os te op oro-
sis is a system ic disease. The m ain su rgical goal
should be set to tre at the symptom s. This chap -
ter discusses the pre- and postoperative mea-
sures that can be taken in treating patients with
osteoporosis, and the surgical strategies that
can be u sed to re duce t he r isk of failure.
! Understanding the
Modes o f Failure in
Osteoporotic Spine
In the osteoporotic spine, the two most com-
m on surgical problem s are failure of the xation
5
Instrumentation Strategiesin Osteoporotic Spine:How to Prevent Failure?
Ahmet Alanay and Caglar Yilgor
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Instrument ation Strateg ies in Osteoporot ic Spine 57
or of the bone –implant inter face, and a djacent
segmen t failure, either of wh ich m ay result in
pseudar thro sis .
In the early postoperative period, pedicle
and adjacent vertebral fractures are the most
common failures, whereas in the late phase, pse udar throsis w it h in st rum entat ion failu re ,
adjacent disk degene ration, and late compres-
sion fractu res w ith progressive kyph osis occur
m ore frequently.
Because t he osteoporotic spine is less able to
withstand force, even the stresses and strains
th at are e nt ailed in th e activities of daily living
can cause postoperative implant failure, which
may present as a sudden pain, a neurologic
problem , or im plant pro m inence.
Fixation Failure
Because the elastic modulus of the bone is
smaller than th at of the imp lant, and because
the force tran smissions follow t he path of least
resistance, the bone surrounding the screws
fails before t he implant does. This phe nom e-
non is called screw toggling, and , under repet i-
tive cycling loading, pedicle screws t ypically fail
by cephalocaudal toggling. The n loosening andeventu ally pullout occur, stripping or fracturing
the pedicle. The t hinne r lateral wall of the pe d-
icle is more often fractured than the medial wall.
The p acking of a stripp ed screw h ole with cort i-
cocancellous graft does not usu ally augment t he
pullou t strength o f osteop orot ic pe dicles, which
is a possible salvage m ethod in healthy bone.1
In a cement -augmented pedicle, the screw
can be pu lled out alone, causing no dam age to
the bone or the cement, or the screw and the
cement can be pulled out together, creating
either an enlarged h ole in th e pedicle or a ped-
icle fracture.
The dorsal lamina has a thicker cort ical shell
than does the ventral aspect, which contributes
to its success in the osteoporotic spine. The
main failure mechanism of the laminar hooks
is lam ina breakout, breaking the “ring” form ed
by the lam ina, posterior verteb ra l bo dy, and
m edial pedicle walls.
Fracture of the upp er-instrum ented vertebrais anoth er comm only seen failure in the osteo-
porot ic spine.
Adjacent Segment Problems
After xation of the osteoporotic spine, almost
80%of the proxim al junctional kyph osis occurs
due to adjacent vertebra fractures.2 Instability
and adjacent disk degeneration are other pos-
sible m echanisms of adjacent segm ent failure.
The p reoperat ive statu s of the adjacent seg-
ment and disk is the greatest predictor of the
developm ent of postoperative adjacent segm ent
failure. One m ust avoid end ing a fusion adjacent
to a severely degenerated disk or to a segme nt
w ith xed obliquity or subluxation.
Nonunion and Pseudarthrosis
Similar to a h ealthy bone, an osteop orotic boneis also subject to pseudarthrosis, especially in
fusions extending to the sacrum . Known r isk fac-
tors include thora colum bar kyphosis, positive
sagitt al balance greater than 5 cm , presen ce of
hip osteoar thr itis, and incomplete sacropelvic
xation.
! Preoperative Measures
Quantifying Bone Quality
Grad ing scales from X-rays, du al-en ergy X-ray
absorpt iomet ry (DEXA), quant itative compu ted
tom ography (QCT), and m icroden sitomet ry can
be used to diagnose and qu ant ify os te op oros is
in an adult surgical candidate. QCT provides
separate BMD estimates of trabecular an d cor-
tical bone, and has a higher sensitivity due to
its imaging in a cross-section al plane. Althou gh
QCT is useful in predicting the fracture risk,
there is no clear consensus on a correlation
between the qu ant it y of os teop oros is and the
type of strategies that shou ld be applied.
The DEXA values acquired from th e fem oral
neck should be interpreted with caution be-
cause the bone density in t he spine decreases
earlier than in other skeletal sites in the early
pos tm enop ausa l years due to turnover in th is
highly trabecu lar bone. Bone den sity at various
skeletal sites begins to coincide at a bou t age 70.Also, DEXA acquired from th e verteb rae m ay
be fa lse ly elevat ed due to de generat ive ch an ges.
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58 Chapte r 5
Therefore, the surgeon must be ready to deal
with a weak bone regardless of the preopera-
t ive DEXA values .
Medical TreatmentIt is well documented in the literature that
BMD correlates w ith imp lant p ullout strengt h.
Therefore, preop erative m edical treat m ent w ith
bisp hosp honates, recombin an t parathyroid hor-
mone (rPTH), calcitonin, selective estrogen
receptor modulators, calcium, or vitamin D
should be considered. It is also important to
determ ine wh ether the bene t of m edical treat-
m ent is su cient enough to o set the delay in
surgical treatmen t.The choice, timing, and duration of post-
operative pharmacological treatment for osteo-
porosis also remain con trover sial because these
drugs m ay inter fere w ith bone healing.
! Intraoperative Measures
The loss of the quan tity as w ell as the architec-
tu re of the osteop orotic bone m ay increase the
risk of spinal surgery or make the surgical
goals di cult to achieve. In these situ ations ,
speci c pedicle screw characteristics and in-
sert ion techniques can be adopted , and su rgical
strategies such as addressing the pathom orphol-
ogy of the osteoporotic vertebrae, han dling soft
tissue m eticulously, enhan cing anchor points,
applying prophylactic vertebroplasty, using
interbody support, and protecting the bone–
implant interface are utilized to improve therate of successful xation. These techniqu es
and strategies are discussed in the following
subsections.
Pathomorphology o f the
Oste oporot ic Vertebrae
It is well established th at th e bone quality varies
in di eren t part s of the vertebrae . The verte-
bra l bod y it self is the m ost a ected par t of theosteoporot ic vertebrae. The lam ina, on th e other
han d, wh ich is pred om inantly cortical, is rela-
tively spared and is potentially a stronger an-
chor. The morphometry of the pedicles are
variable. This pattern of bone loss causes the
pedicle screw xat ion t o be le ss e ect ive in the
osteoporotic bone. The xation of the ped icle
screws is achieved either by taking advantageof the relatively stronger cortical bone w ithin
the pedicle by increasing the screw diameter
and avoiding tap ping the screw path , or by aug-
menting the pedicle screw in various ways.
Sublam inar xation w ith w ires, cables, hooks,
and bands is also a good alternative because
the lamina is less a ected by osteoporosis.
The BMD also var ies in di erent r egions of
the sacrum . Medial side h as a h igher BMD than
the lateral side, and the superior sacral end
plat e h as t he h igh est . The screw s shou ld there -
fore be directed m edially in a t riangular fash-
ion an d toward t he sacral promontory.
The T2 pedicle is generally stronger than
T3–T6 p edicles, making T2 a good opt ion for
screw xation or pedicle hooks as a strong
upper an chor point.3
Pedicle Screw Factors
No conse nsu s h as yet been reach ed on the op -timal screw diameter, length, and shape for
xation in the osteoporotic bone. However,
several p edicle screw characteristics, together
with th e hole preparation and screw insertion
tactics, are shown to achieve a bette r xation
and p revent implant failure.
Pedicle Screw Characte ristics
Double-th readed ped icle screws have a cancel-
lous thread ed t ip followed by a cortical thread.
The w ider pitch of cancellous threa d p rovides
additional grip in the cancellous bone, and
the screw advances faster with higher inser-
tion torque. The cortical thread in the pedicle
area provides higher grip and less toggle du e to
denser threads.4
Conical (tapered) screws also increase in-
sertional torque, but they cannot be reversed
or backed ou t, because doing so eradicates th e
screw’s cont act w ith the b one.The expand able ped icle screw u ses a n ovel
screw design th at enables the d istal part of the
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Instrument ation Strateg ies in Osteoporot ic Spine 59
screw to enlarge within the vertebral body as
a posteriorly directed force is applied to the
screw to resist pullout failure. The tip of the
screw becomes anchored against the inne r cor-
tex of the dorsal vertebral body, resulting in a
76%increase in holding strength in compari-son to convent ional pedicle screws,5 by taking
advantage of the relatively uncompromised
cortical bone rather than depending solely on
weakene d osteop orotic cancellous bone. How-
ever, in patients with severely low BMD, ex-
pandable screw s m ay be unable to ove rcom e
the extreme biomechanical disadvantage, re-
sulting in failure. Moreover, screw revision
rem ains an issue in th e clinical application of
these screws.
Pedicle Screw Tract Augme ntat ion
It is possible to augmen t th e ped icle screw t ract
by pre paring the hole, inject ing polym et hyl-
m etha crylate (PMMA) bone cem ent into the
hole, and inserting th e screw afterw ards. Aug-
mentation may also be done with bioactive
ceme nts, calcium p hosph ate, or calcium sulfate
using trad itional or fenestr ated ped icle screws.
Coating the pedicle screw w ith hydroxyapatiteis a time-dependent augmentation technique
that increases osteointegration.
Cement Augmentation and Fenestrated Screws
A cadaveric b iome chan ical ana lysis of PMMA-
augm ente d pedicle screw xation using a novel
fenestrated bone tap increased the pullout
strength by 199%and 162%in primary and re-
vision p rocedu res, respect ively.6 Clinical ser ies
also demonstrated good outcome with no
screw loosening, m igration, or pullout detected
in th e follow- up X-rays, no fractu re at the aug-
m ente d levels, and no imp lant failure requiring
reintervention.7,8
Although PMMA augme ntat ion of the pedi-
cle screws provides good xation in patient s
with low BMD, it is not free of complications.
Extravasat ion, intr acan al leakage, hypoten sion,
increase in pulmonar y artery p ressure, pulmo -
nar y ceme nt em boli, super cial infections, andthermal nerve injuries were reported. There-
fore, strategies were developed to reduce the
likelihood of cement leakage. Higher viscosity
cement can be used, and uoroscopy can pro-
vide additional assistance. It is generally recom -
m end ed to inject 1 to 3 m L of ceme nt becau se
using a larger am ount fails to dem onstrate an y
signi cant bene t in pullout strength .6
Attention was also paid to the method of
PMMA augm ent ation. Injecting cemen t into a
cavity prepared by an in atable balloon fol-
lowed by insert ion of the p edicle screw dem on-
strated almost twice the pullout strength of
screws augmente d w ith standard cemen t injec-
tion.9 Fenestrated screws have been used m ore
recently, with promising results.10 Although
clinical long-term results are yet to be seen,
there is a potential theoretical advantage of
using fenestr ated screws over injecting ceme nt
followed by screw insertion. Injecting the ce-
me nt into the prepared hole lls the tract, and
wh en inserting the p edicle screw, the cem ent
coats the screw threads and thereby reduces
e ect ive screw purcha se. Altern atively, cem en t
injection through a fenestrated screw enables
the cem ent to in ltrate in the vertebral body
without altering the bone–implant interface.11
Although it is widely used with promising
results, PMMA is toxic, is unable to undergoremodeling after microfracture within the ce-
m ent , and is di cult to rem ove in revision
surger y. Hence, osteob iologic cem en t is an area
of interest and development for screw aug-
m ent ation. Calcium ph osphate an d calcium su l-
fate avoid the exother m ic reaction and reduce
the risk of leakage. Moreover, they are bio-
resorbable and poten tially osteoconduct ive, and
integrate in the nat ural process of bony rem od-
eling. A cadaveric study comparing osteobio-
logic cement and PMMA for the use of screw
augme nt ation found no signi cant di eren ces
in axial pullout stre ngth.12
Hydroxyapatite Coating
The increased osteointegration of the hydroxy-
apatite-coated pedicle screws is time depen-
dent ; w ith tim e, optim um stability is achieved.
It has been shown in an osteoporotic animal
model that hydroxyapat ite-coated pedicle screwsare 1.6 times m ore resistant to pu llout an d th at
they have superior biological bonding to the
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60 Chapte r 5
surrou nd ing bone, occurring as early as 10 days
after surger y.13 However, th ey do not allow for
the application of add itional forces dur ing in-
traoperative correction maneuvers.
Inse rtion Technique and
Inse rtional Torque
The star ting point, hole preparat ion, tap ping, the
insertion a ngle, and the trajectory of a pedicle
screw, as well as its length, depth of penetra-
tion, and diamet er, a ect its insert ional torque
and the reby its resistance to failure.
Length of Screw and Depth of
Screw Penetration
The length of a pedicle screw is linea rly related
to its pullout stre ngth . As the screw p enet rates
furth er into the vertebr al body, the cu tout load
to failure increases. By engaging the ventral
cortex of the vertebral body, screws can be
p laced in a bicor t ical fash ion to provid e up
to an ad ditional 30%of pullout strength .14 The
risk–bene t ratio should be considered, and
care m ust be t aken to avoid injur y to adjacent
structures w hen using this technique.
Diameter
The d iam eter of the p edicle screw shou ld be as
w ide as possible to enable better cortical bone
purch ase. Increasing the diam eter increases t he
pullout st re ngt h in m ilder cases; how ever, in
severe osteoporosis the p ullout force is low re -
gardless of th e screw diamete r. Instead, using
larger diam eters m ay cause d ilation or fracture
of the p edicle that d ecreases its strengt h.15
Starting Point, Insert ion Angle, and Trajectory
When the screws are placed parallel, the vol-
um e of cancellous bone betw een t he t hreads
of the screw deter m ines the resistance to pull-
out for each screw. Triangulated screws provide
bet ter p ullout st rengt h w ith a lar ger volum e o f
cancellous bone available for resistance to p ull-
out because the construct is contributed by thevolume of bone within the trapezoid area in
the vertebr al body form ed by longer and tr ian-
gulated screws.16
Thoracic Spine
In t he anatom ic trajectory, the screw is in line
w ith the ped icle axis and the refore is directed
to the inferior corner of the vertebral body in
the sagitt al plane. In th e straightforw ard te ch-
nique, the screw is parallel to th e vertebral end
plat e an d t rian gu lat ion in the t ransve rse plane
can be achieved. This technique provides at
least 39%h igher m axim um insertional torque
and 27%greater pullout strength.17 Pedicle-r ib
screws increase the e ective transverse diam-
eter wh en compared w ith the pedicle alone and
can be used for safer insertion of the screws,although it m ay decrease the pullout strength
by 25 %.18 The sta rting point sh ould be selected
in accordance w ith the t rajectory used.
Lumbar Spine
Placing the pedicle screws in convergence also
increases the pullout strength in the lumbar
spine.
Sacrum and PelvisSacral xation is a big challenge in the osteo-
porot ic sp ine. Restorat ion of the sagit tal bal-
ance is more imp ortant than the xation itself.
When the fusion is extended to the sacrum
and a long fusion is performed, multiple and
bicort ica l screw xat ion sh ou ld be use d in ad-
dition to considerat ion of ante rior colum n sup -
por t or iliac xation. The t ricort ica l t echniqu e,
which entails directing the screws into the
sacral promontory, increases the insertional
torque.19
Hole Preparation and Tapping
Appropriate preparation of the hole improves
screw purchase. High insertional torque im-
proves the screw pullout st re ngt h. In hea lthy
vertebral bodies, the screws are placed after
tapping to avoid microfracturing within the
dense bony matrix of the bone during screw
insert ion. In osteoporotic cancellous bon e, how-ever, tapping results in rem oval of bone w ithin
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Instrument ation Strateg ies in Osteoporot ic Spine 61
the pedicle track and prevents bone compres-
sion around t he screw t hread s. Even screw re-
m oval and imm ediate reinsertion decreases the
m echanical insert ion torque. Therefore, und er-
tapp ing or not tap ping at all is advised in oste-
oporotic bone. When compared with same-sizetapping, under-tapping by 0.5 and 1.0 mm
increases the insert ional torque by 47% and
93%, resp ectively.20
Under-t apping is m ore bene cial in the lum -
bar sp ine than in the thoracic sp ine. This m ay
be due to the fact that the thor acic pedicle
screws are probably more dependent on cor-
tical purchase w ithin the ped icle walls.
Enhancing Anchor PointsThe weak link in the osteoporotic spine in-
strumentation is the implant–bone interface.
Fixation strategies for osteoporotic bone are
targeted toward taking advantage of the rela-
tively stronger cortical bone. Anchor options,
in addition to screws, include hooks, wires,
cables, and b ands.
Load Sharing by Multileve l Fixation
Because th e implant–bon e interface in th e os-
teoporotic bone is prone t o failure, the num ber
of points of xation m ust be increased to dis-
tribute the contact forces more evenly. Longer
construct s w ith at least thre e sets of xation
points at e ach end can be bene cial, keeping in
mind t he added morbidity entailed w ith using
additional screws.
As previously stated, using hooks, wires, ca-
bles, an d ban ds as w ell as cross- links h elp in im -
proving the p er form an ce of the p edicle screw s.
Select ion of Fusion Leve ls
End-instrumented vertebrae should be care-
fully selected. Ending the construct in a ky-
phot ic region or at the apex of kyphosis shou ld
be avo ided.
Anoth er frequen t decision-m aking dilem m a
in the osteoporotic spine is wh ether or not to
fuse to sacrum. Certain scenarios that requirelum bosacral xation are symp tom atic L5-S1
spond ylolisth esis, over 15 degre es of scoliosis
at the L5-S1 segmen t, and th e nee d to achieve
prop er sagit tal ba lance.21 Stop ping at L5 ent ails
the risk of increased adjacent segm ent disease,
wh ereas fusing to the sacru m is found to have
more complications.21 L5 pedicles are usuallyshort and cont ain more cancellous bone. There -
fore, it may be r isky to end a long fusion at L5
in osteoporotic patients because L5 pedicle
screws m ay fail.
Cross-Link
The use of a rigid or semirigid cross-link, es-
pecially w hen the screws are t rian gu lat ed, in-
creases the torsional sti ness by making the
construct per form e ectively as a quadr ilateral
frame. The use of a cross-link is especially ad-
vantageous in longer constr ucts, as it p revents
rods from telescoping.
Hoo ks, Wires , Cables, and Bands
The use of sublaminar and pediculolaminar
hooks, wires, cables, and bands takes advan-
tage of the cortical bone composition of the
spinal lam ina.A polyester band may be used to increase
the surface of bony contact and to t any anat-
omy. It m ay be used in a sub laminar, subpa rs,
tran sversal, or lam inotran sversal fashion to en -
able translation, distraction and compression,
in situ be nding, and rod derotat ion.
Prophylactic Vertebroplasty
In the setting of osteoporosis, junctional fail-
ure, especially in th e cran ial levels, is not a rar e
occurrence. Prevention is the best way to
overcome adjacent segment failure. Prophy-
lactic vertebroplasty ent ails cemen t augm ent a-
tion of the adjacent noninstrum ented segmen t/
segments. Although there is a paucity of clini-
cal and biomechanical studies, prophylactic
vertebroplasty seem s to be helpful in de creas-
ing the revision arthrodesis rates because of
adjacent vertebr ae fractures.22
Furt her stu dies are needed to clarify the op -timum amount of cement required and how
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62 Chapte r 5
many levels should be prophylactically ce-
m en ted . E cacy at the distal adjacent level
also need s to be furt her an alyzed.
Interbody Support in
Osteoporotic Spine
Ante rior column supp ort is bene cial in load
sharing because the graft or cage lessens the
stress directed toward t he screw–rod constru ct.
Anterior interbody support may further im-
prove sagit tal sp in al balance and rat es of
arthrodesis.
Inter body grafts serve a m ore critical role at
the cau dal end of the constru ct, particularly atthe lumb osacral jun ction. Grafts can be placed
w ith a bias toward the concavity of the defor-
m ity to assist correction. Figs . 5.1, 5 .2, and 5.3
Fig. 5.1a,b (a) Preope rative post eroante rior X-ray. (b) Preoperat ive lateral X-ray.
a b
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Instrument ation Strateg ies in Osteoporot ic Spine 63
dem onstrate the u se of the intraoperative m ea-
sures m entioned above in a 64-year-old pat ient
with a BMD of –3.2 complaining of back and
leg pain.
In severe oste oporosis, th ere is a risk of sub -
sidence of the graft or cage into the end plates
that may lead to anterior column collapse
and subsequent kyphotic deform ity. The cage
should be placed to contact the peripheral
apophyseal ring where the cortical bone is
stronger. A graft with an elastic modu lus that is
similar to th e nat ive bone also reduces the r isk
of subsidence. Choices of interbody graft m ate-
rials include bon e (au tograft or allograft), m etal,
carbon ber, polyaryleth eret he rketon e (PEEK),
and other synthet ic mater ials. Iliac crest auto-
graft is typically the be st m atch, but it is asso-ciated with well-established harvest-related
morbidity.
Role of Ante rior Fixation in the
Oste oporotic Spine
Cont inuous loading of ant erior screw constructs
on a low-BMD spine can lead to screw cutout.
Although newer implant designs demonstrate
improved anchorage,23 anterior xation has alim ited role in th e osteoporot ic spine because it
is the m ost a ected part of the vertebrae.
Role of Semirigid Fixation in the
Oste oporot ic Spine
The loading of the spine in various axes of
motion creates increased stress at the bone–
implant inter face. The di eren ce of the r igidity
within th e instrum ented and n oninstrumentedsegments of the spine can accelerate adjacent
segment degeneration and potentially cause
pse udarthrosis. Sem irigid xation m ay p rovide
su cient stab ilization to facilitat e bony fusion
wh ile per m itting some degree of exibility to
o oad stress at the adjacent segm ent and the
bo ne–im plant in terface .
Protection o f the Bone–Implant
Interface
Hand ling int raoperative soft tissue m eticulously,
providing extensive release , perform ing oste-
otomies to increase exibility and thu s m ini-
m ize the corrective forces, maint aining sagittal
alignm ent , and obt aining a solid fusion ar e es-
sential for the protection of the bone–implant
interface.
Meticulous Soft Tissue Handling
Care should be taken to preserve the supra-
spinous ligamen t, int raspinous ligamen t, and
Fig. 5.2a,b (a) Preoperative sagitt al magnetic resonance imaging (MRI) view. (b) Preoperative transverse
MRI view.
a b
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64 Chapte r 5
Fig. 5.3a,b (a) Last follow-up posteroanterior X-ray
of the same patient demonstrating the use of
cement-augmented pedicle screws, ante rior
interbody support, prophylactic vertebroplasty,
and cross-link. (b) Last follow-up lateral X-ray of
the same patient dem onstrating the use of ceme nt-
augmented pedicle screws, ante rior interbody
support, p rophylact ic verteb roplasty, and cross-link.
a b
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Instrument ation Strateg ies in Osteoporot ic Spine 65
ligament um avum between the cranial fused
level and th e adjacent segm ent , as well as be-
tween the cranial levels of fusion. Doing so
provid es a segm ent of higher p oste rior tensio n,
wh ich m ay prevent the developmen t of junc-
tional deformity and instability. Supra- andinfra-adjacent facets should be preser ved and
the cranial disk space should not b e violated
w ith pedicle screws.
Exte nsive Release
The release of the d iskoligamen tous an d bony
constraints such as diskectomy, facetectomy,
or various osteotomies should be optimized
before r educt ion to d ecrease the st ress ap plied
to the bone–implant interface w hen perform -
ing spinal corrective m ane uvers.
Maintaining Sagittal Alignment
Aligning th e oste oporot ic spine to physiologi-
cal coronal and sagittal contours neutralizes
the deforming forces, reduces the junctional
forces, and d ecreases the ener gy required for
ambulation.
Obtaining Fusion
Obtaining a rapid and solid fusion ensures
long-ter m spinal stability, redu cing th e load on
instruments and on the relatively poor bone–
implant interface. A thorough fusion p rocedure
with appropriate bone-bed preparation and
approp riate use of bone grafts or substitu tes is
the refore of par ticular imp orta nce in the oste-
oporotic spine. The u se of bone m orph ogenetic
pro te in m ay facilit at e an earlier an d m ore vig-orous fusion, and d ecrease th e risk of implant-
related failure. The use of bone morphogenetic
pro te in m ay also be associat ed w ith complica -
tions related to soft tissue swelling, inappro-
priat e bon e form at ion ar ou nd n eura l elem ents,
and subsequ ent ra diculitis.
! Postoperative Measures
Enh ancing the purchase of intern al xation and
pro te ct ing t he bo ne–im plant in terface by han-
dling soft tissue meticulously, providing ex-
ten sive releases, maint aining sagittal alignm ent ,
and using anter ior interbody suppor t decreases
the demand on xation in the postoperative
period. Ext ernal br ace im m ob ilizat ion and re -
striction of the spine r ange of motion a s wellas physical therapy and reh abilitation are m ea-
sures that can be taken in the postoperative pe-
riod to serve the sam e pu rpose. As stated ea rlier,
the timing of postoperative pharmacological
osteoporosis treat m ent re m ains cont roversial.
If a brace is to be used, it must be custom-
molded p ostoperat ively, after surgical deform ity
correct ion is established . Rehab ilitation sh ould
focus on gait training, balance, and general
conditioning, together with range-of-motion
and exibility exercises of th e hip an d kne e.
There is no consensus yet on the duration of
br ace applicat ion.
! Chapter Summary
Prim arily a ecting the tr abecular bone, osteo-
poros is causes progre ssive bon e m ineral loss
and concomitant bony architecture changesthat result in pain, deformity, increased frac-
ture risk, and possible neural compression.
Although most patients with acute, painful
vertebral compression fractures improve re-
gardless of the treatment applied, no patient
spontaneously restores the vertebral height
and achieves a realigned spine. Spinal instru-
m ent ation is eventu ally required in som e oste-
oporotic patient s. In the sett ing of osteoporosis,
however, the xation of the spinal implant s is
insecure, and application of corrective forces
through a weak bone–imp lant interface is di -
cult, comp licating the surgical treatm ent . The
rst step for an adult spinal surgical candidate
is the diagnosis and quant i cation of the oste-
oporosis. Unde rstan ding the biom echanics and
the modes of failure of the osteoporotic spine
is important. The vertebral body itself is the
most a ected part of the osteoporotic verte-
br ae. The lam ina, o n the ot her han d, w hich is
predom inantly cort ica l, is relat ively spar ed andis potentially a stronger an chor. The m orph om -
etry of the pedicles is variable. Failure of the
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66 Chapte r 5
xation or of the bone–imp lant inter face, adja-
cent segment failures, and pseudarthrosis are
the t hree m ain problems in osteoporot ic spine.
Several pre- and postoperative measures may
be taken, as well as app lying several su rgical
strategies intraoperatively to prevent failure.The pedicle screw characteristics together
with hole preparation and screw insert ion
tact ics are show n to achieve a bette r xation.
Ante rior column supp ort is bene cial in load
sharing, improving sagittal balance and re-
ducing the rates of arthrodesis. The results of
cement augment ation of the pe dicle screws and
the adjacent noninstrum ented vertebrae seem
prom ising, bu t it is not a com plicat ion-free
procedure.
Pearls
In elective cases, increasing t he BMD preoperat ively
with parathyroid hormone might be considered.
Under-tapping is advised in the osteoporotic
bone to increase the inse rt iona l torque.
Triangulated screws provide better pullout
strength, with a larger volume of cancellous bon e
available for resistance to pullout because the
construct is contributed by the volume of bone
within the trapezoid area in the vertebral bodyformed by the longer a nd t riangulated screws.
The use of a cross-link is especially advant ageous
in longer constructs, as it prevents rods from
telescoping.
The use of hooks, wires, cables, and bands take
advantage of the relatively stronger cortical bone
for xation of osteop orot ic bon e.
Cem ent -augmen ted p edicle screws are advanta-
geo us for bet te r xation and for allowing add i-
tional correct ive forces.
Prophylact ic vert ebrop lasty is helpful in decreas-
ing t he revision art hrodesis rates because of adja-
cent vertebrae fractures.
The release of the diskoligamentous and bony
constraints such as d iskectom y, facetect omy, or
various oste oto mies should be opt imized before
reduction when performing spinal corrective
pro cedures to de crease the st ress app lied to the
bo ne –implant inter face.
A custom-m olded posto perative brace h elps pro-
tect the bone–implant interface.
Pitfalls
Avoid ending a fusion adjacent to a severely
de gene rated disk or to a segm ent with xedobliquity or subluxation.
DEXA scans in elderly patients must be inter-
pret ed with caution because degenerative changes
may falsely elevate th e BMD values.
In th e oste oporotic bone, tap ping results in re-
moval of bone within the pedicle track and
prevent s bo ne compression aro un d the screw
threads.
Avoid ending a construct in a kyphotic region or
at t he a pex of kyphosis.
Avoid dam aging the supra- and intraspinous liga-
ment s and ligamentum avum between the cra-
nial fused level and the adjacent segm ent , as well
as bet ween the cranial levels of fusion.
Avoid damaging the supra- and infra-adjacent
facets and violating the cranial disk space with
pe dicle screws.
References
Five Must- Read Reference s
1. Halvorson TL, Kelley LA, Thom as KA, Wh itecloud TS
III, Cook SD. E ect s of bon e min era l densit y on ped icle
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2. DeWald CJ, Stan ley T. Inst ru m ent ation- related
complications of multilevel fusions for adult spinal
deformity pat ients over age 65: surgical considera-
t ions and treatmen t options in patients w ith poor
bo ne qu alit y. Sp in e 2006 ;3 1(1 9, Sup pl): S14 4–S1 51
PubMed
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cal cadaveric analysis of polymet hylmethacr ylate-
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2007;7:47–53 PubMed
7 . Chan g MC, Liu CL, Che n TH. Polymethylm etha crylate
augmentation of pedicle screw for osteoporotic spi-
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Instrument ation Strateg ies in Osteoporot ic Spine 67
nal surger y: a novel techn ique. Spine 200 8;33:E317–
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8. Aydogan M, Oztu rk C, Karat opr ak O, Tezer M, Aksu N,
Hamzaoglu A. The pedicle screw xation with verte -
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12 . Roh m iller MT, Schwa lm D, Glat te s RC, Elalayli TG,
Spengler DM. Evaluation of calcium sulfate paste for
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13 . Hase gaw a T, Inu fus a A, Imai Y, Mikaw a Y, Lim TH,
An HS. Hydroxyapatite-coating of pedicle screws im-
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14 . Zind rick MR, Wilt se LL, Wide ll EH, et al. A biom e-
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15 . Yazic i M, Pekm ezci M, Cil A, Alan ay A, Acar oglu E,
Oner FC. The e ect of pedicle expan sion on pe dicle
m orph ology and biom echanical stability in the im -
mature porcine spine. Spine 2006;31:E826–E829
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16 . Hadjipavlou AG, Nicodem us CL, al-Ham da n FA, Sim -
mons JW, Pope MH. Correlation of bone equivalent
m ineral density to pull-out resistan ce of triangulated
ped icle screw const ruct . J Spin al Diso rd 19 97 ;1 0:
12–19 PubMed
17. Leh m an RA Jr, Polly DW Jr, Kuk lo TR, Cun nin gha m B,
Kirk KL, Belmo nt PJ Jr. Str aight- forwa rd versu s an ato-
mic trajectory technique of thoracic pedicle screw
xation: a biomechanical analysis. Spine 2003;28:
2058–2065 PubMed
18 . White KK, Oka R, Mah ar AT, Low ry A, Gar n SR. Pullout
strength of thoracic pedicle screw instrumentation:
comparison of the transpedicular and extrapedicular
techniques. Spine 200 6;31:E355–E358 PubMed
19 . Leh m an RA Jr, Kuk lo TR, Belmon t PJ Jr, And er se n RC,
Polly DW Jr. Advant age of ped icle screw xation d i-
rected into the apex of the sacral promontory over
bicor t ica l xat ion : a biom echan ica l an alysis . Spin e
2002;27:806–811 PubMed
20. Kuk lo TR, Lehm an RA Jr. E ect of variou s t ap pin g
diameters on insertion of thoracic pedicle screws: a
biom echan ica l an alysis. Spin e 20 03 ;2 8: 20 66 –2 07 1
PubMed
21. Bridwell KH, Edwards CC II, Lenke LG. The pros and
cons to saving the L5-S1 motion segment in a long
scoliosis fusion constru ct. Spine 2003;28 :S234–S242
PubMed
22 . Chian g CK, Wan g YH, Yan g CY, Yan g BD, Wa ng JL.
Prophylactic vertebroplasty may reduce the risk of
adjacent intact vertebra from fatigue injury: an ex
vivo biomechanical study. Spine 2009;34:356–364
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23. Goldhah n J, Reinh old M, Stau ber M, et al. Impr oved
anchorage in osteoporotic vertebrae with new im-
pla nt designs. J Orthop Res 2006;24:917–925 PubMed
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! Introduction
Signi cant advances have been m ade in adult
spinal deformity (ASD) surgery over the past
several years. Improvements in pedicle screw
technology and the increasing use of three-
column osteotomies have m ade m ore powerfuldeformity corrections possible. Nonetheless,
loss of neurologic function after ASD surgery
remains a serious and potentially devastating
complication, with profound conseque nces for
health -related qua lity of life. Int raoperative neu-
rophysiology mon itoring has be come a reliable
and e ective moda lity to optimize neu rologic
safety d ur ing ASD surger y.1,2 Furth erm ore, the
increasing use of im age-guided navigation sys-
tems has led to signi cant improvements in
th e accuracy of ped icle screw placem ent .3,4 This
chapter discusses the management of acute
ne urologic com plications in com plex ASD sur-
gery and proposes a treatment algorithm t o deal
w ith these complications in safe and e ective
manner.
! Prevalence
The incidence of neurologic complications in
ASD patients un dergoing deform ity correction
surgery has been di cult to deter m ine. Mul-
tiple aws exist in the published data, w ith a
lack of high-qu ality prosp ect ive st ud ies, signif-
icant d ata var iability, an d a lack of rigorous an d
validated measurements of neurologic func-
tion. Nonetheless, the incidence of neurologic
de cits following ASD surger y has been p re-viously report ed as ran ging from 0% to over
10%.5– 9
Two previous studies, one from a single in-
stitution, an alyzed prospectively collected d ata
to identify comp lications, but n either on e used
a validated scoring system to quantify neuro-
logic funct ion.10,11 All studies could more ac-
curately be described as retrospective studies
of prospect ively collected dat a. But an accurate
rate of neu rologic comp lications after complex
ASD surgery is critical for informed decision
making for both patients and surgeons. Fur-
thermore, it is crucial to be able to measure
changes in neurologic complication rates in a
standa rdized fashion so as to accurately evalu-
ate new techniques, technologies, and thera-
pies in ASD su rgery.
The Scoli-Risk-1 t rial is a recen t p rospective,
multicenter observational study attempting to
accurately assess the neurologic complication
rate following complex ASD surgery using theAm er ican Spinal Injur y Associat ion (ASIA) scor-
ing system (Fig. 6.1).12 A total of 276 pat ients
6
The Incidence and Managementof Acute Neurologic ComplicationsFollow ing Complex Adult SpinalDeformity Surgery
Joseph S. Butler and Law rence G. Lenke
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Neurologic Complicat ions Following Adult Spinal Deformity Surgery 69
Fig.6.1
TheAmericanSpinalInjuryAssociation(ASIA)scoringsystem.
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70 Chapte r 6
were enrolled from 15 international centers.
At hospital discharge, 23.1% of patients had a
m easurable lower extre m ity motor de cit (i.e.,
less tha n 5/5 m otor strength in all ve m ajor
leg muscles) decreasing to 17.8%at 6 weeks
and 10.7% at 6 mon ths postoperat ive. Thisstudy gives a clearer indication of the expected
neurologic complication rate in ASD patients,
pot ent ially se t t ing a st andard for future clin ica l
trials aim ed at lowering the rate of postopera-
tive neuro logic de cits.
! Mechanisms of Neurologic
ComplicationsThere are several proposed causes of intraop -
erative neurologic de cits during ASD sur-
gery. Int raop erat ive spinal cord, caud a equin a,
or nerve root de cits may result from direct
neurologic trauma during instrumentation
such as t he p lacem ent of pedicle screws, hooks,
or sublaminar w ires. Furt her m ore, intraope ra-
tive corrective maneuvers may lead to neuro-
logic de cit secondary to either d istract ion of
the neural elements or excessive tension onlocal vasculature, leading to decreased blood
ow and cord ischemia. Spinal cord ischemia
may also result from prolonged extreme hy-
pot ension (m ean ar ter ial p ressure [MAP] < 55
mm Hg), hypoxia secondary to decreased he-
moglobin level, or vascular compromise after
ligation of the segm ent al vessels in an anter ior
procedure.13
! Patient Evaluation and
Preoperative Planning
Neurologic complicat ions are m os t st rongly
associated with prolonged complex surgery, a
large am ount of blood loss, combined anter ior/
pos ter ior procedures , m ult ist age su rgery, con-
genital kyphosis or scoliosis, large or rigid spinal
cur ves (Cobb a ngle > 90 degre es), preexisting
myelopathy or neurologic de cit, and intra-medullary spinal cord tumors. Further risk
factors include tethered cord, Arnold-Chiari
malformation, syringomyelia, and split cord
malformations.
A complete patient history and thorough
physical exam inat ion st ill rem ain e ssent ial ele-
ments to an adequate preoperative workup.
Patients should be assessed for a history ofcongenital deformities such as kyphosis and
scoliosis, neu ro brom atosis, and skeletal dyspla-
sia, which would infer a considerably increased
risk of iatrogenic neurologic complications. The
physical exam inat ion sh ou ld inclu de a thre e-
dimensional assessment of the spine to evalu-
ate pat ient postu re, neurologic statu s, hip exion
contract ures, leg length inequality, pelvic obliq-
uity, body habitu s, and nut ritional status. Me-
ticulous examination of the motor, sensory,
and re ex fun ction as well as gait assessmen t
is critical in screening patients for potential
intraspinal and brainstem anomalies such as
teth ered cord, Arn old-Chiari m alform ation, sy-
ringomyelia, and split cord malformations.
Adeq uate rad iological im aging is crucial for
optim al surgical and n eurologic outcome. How-
ever, it is technique-dep ende nt, requ iring vi-
sualization of the entire spine in the coronal
and sagittal planes, including the hip joints,
with all im aging taken w ith the patient stand-ing with th e knees fully extende d for accurate
measurement of sagittal balance (sagittal ver-
tical axis [SVA]), th oracic kyph osis, lum bar lor-
dosis, and spinopelvic parameters including
pelvic in cid ence (PI), sa cral slop e (SS), an d pel-
vic tilt (PT). Lateral dynamic standing lumbar
X-rays m ay ident ify focal instab ility or sp ond y-
lolisthesis. Ben ding lms an d sup ine X-rays
w ithout th e e ects of gravity help assess the
exibility of a deformity. Once the appropri-
ate radiographic studies have been obt ained,
the sagittal and coronal balance can then be
assessed.
Magnetic resonance imaging (MRI) is used
as a routine p reoperat ive radiographic study to
assess central can al stenosis, facet hyper troph y,
pedicu lar anom aly, foram inal encroachm ent ,
and degenerat ive d isk disease. It also helps de-
term ine the p resence of intraspinal anom alies.
Patients with suspected low bone m ass or with
established osteoporosis should have a dual-en ergy X-ray absor pt iome tr y (DEXA) scan p er-
form ed to optim ize surgical planning.
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Neurologic Complicat ions Following Adult Spinal Deformity Surgery 71
! Intraoperative Preparation
Meticulous intraoperative preparation is re-
quired for the safe and e ective man agement of
intraoperative complications. Before induction
of anesthesia, the surgical team should discusswith the anesthesia and neuromonitoring
teams and operating room sta the patient’s
m edical situation, the inten ded procedu re, and
surgical time frame. An arterial line may be
used to monitor MAP. Somatosensory evoked
potent ial (SSEP) and m otor evoked pot ent ial
(MEP) leads a re p laced and checked before th e
pat ient is turned to the prone pos it ion. The
upper extremities are padded and posit ioned
to avoid stret ch or compr ession of th e brachial
p lexu s, and ca re is t aken to ensu re that the
pressure areas are well padded. Forced-air
warming blankets prevent hypothermia, par-
ticularly in pr ocedures of long durat ion.
Maintaining adequate blood pressure is es-
sential. However, a balance should be main-
tained to minimize intraoperative blood loss
and t ransfusions, yet en suring adequate spinal
cord p erfusion . A MAP of < 55 m m Hg has been
associated w ith an increased risk of spinal cord
ischemia.14 However, mild hypotensive anes-thesia is often used to minimize blood loss,
par t icu larly during the surgical a ppro ach , with
the MAP maintained at 65 to 70 mm Hg. Ap-
proxim ately 30 m inutes before per form ing cor-
rective man euvers, the an esthesia team should
gradually elevate the MAP to > 70–80 mm Hg
to maintain adequate cord perfusion during
spinal column manipulation and deformity
correction.
! Intraoperative
Neuromonitoring
Stagnara Wake-Up Test
The Stagnara wake-up test has been widely
used in the intraop erative assessme nt of neu -
rologic function. It assesses primary motor
cortex, anterior motor pathways of the spinalcord, ner ve roots, and periph eral ner ves. How-
ever, it gives only a gross approxim ation of th e
function of these elements and does not di-
rectly m easure any components of the sensory
system.15 This test involves a tem porar y redu c-
tion in anesthesia, after which the patient is
asked to move the upper and lower extremi-
ties. The test is limited, as it is entirely relianton patient compliance and cannot be u sed in
pat ients unab le to follow com m ands because
of intellectual and developmental disability,
young age, or p reoperat ive w eakness. The test
itself carries risk, including self-extubation,
loss of intravenous access or of safe patient-
pos it ion ing on the t able, air em bolism , and
posto perat ive re collect ion of t he event .
The w ake-up test w as historically the bench-
m ark for intra operative neu rologic assessmen t,
and is still used at som e center s in conjunct ion
with advanced neuromonitoring techniques
as a means of con rming neurologic status.
Properly administered, the wake-up test should
be 100% accurate in detect ing gross m ot or
changes.15 Although th e limitations of the te st
prevent assessm ent of ne m otor ch an ges, it
w ill alert t he surgeon to the m ost clinically sig-
ni cant neurologic de cits. It is used when
there is any problem obtaining spinal cord
monitoring (SCM) signals (such as in a patientw ith th oracic myelopathy) and also in p atient’s
who have had SCM changes meeting evoked
potent ial w ar ning cr iteria w hen the re spon ses
cannot be improved. It also should always be
perform ed at the e nd of t he surgical p rocedure
pr ior to the pat ien t’s leaving th e ope rating room.
Som atosensory Evoked Potentials
Somatosensory evoked potentials assess the
po ster ior colu m ns of the sp inal cord , in ad dit ion
to the cerebral cortex and mixed peripheral
ner ves. The posterior column s are respon sible
for proprioception as opposed to pain and te m -
pera ture . Althou gh pro priocept ive loss is n ot as
debilitating as a mot or de cit, it can have a sig-
ni cant imp act on activities of daily living. As
SSEPs are sensitive to focal posterior column
and global spinal cord issues, they act as a good
surrogate for othe r n eural p athw ays. However,
there are situations when a motor de cit mightnot be d em onstrated on SSEP m onitoring. For
example, anterior vascular territory comprom ise
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72 Chapte r 6
w ithout concomitan t posterior vascular changes
m ight not be addressed by SSEP mon itoring.
Somatosensory evoked potentials continue
to be the most frequently used intraoperative
monitoring method to assess the integrity of
the dorsal column but cannot be relied on tomonitor motor function directly. Reports of
post operat ive paraparesis in the abs ence of
intraoperative SSEP signal change underscores
this importan t lim itation.16 SSEP de pend ability
falls o wh en applied to patient s w ith preex-
isting neurologic conditions. Individual nerve
root injury is not e ect ively monitored by SSEPs.
Missed nerve root or isolated motor pathway
complications are not failures of the m odality
bu t rat her are issues outsid e of SSEP mon itor ing
capability, highlighting t he need for a lternat ive
or adjunct m onitoring approaches. Warn ing cri-
ter ia for SSEPs at out inst itut ion include greater
than a 60% decrease in amplitude or a 10%
increase in latency of the signal as compared
w ith baseline values.
Motor Evoked Pote ntials
Motor evoked poten tials m onitor corticospinal
tract activity via stimulation at the level of themotor cortex or spinal cord and are selective
for motor pathways. MEP monitoring relies
on intervening thalamic synapses to prevent
ant idrom ic ring of spinal sensory tracts. The
stim ulation site for t ran scranial MEP (tcMEP) is
the cerebral cortex. MEP end-point data are as-
certained from the spinal cord (D-wave) or
from t he end m uscle compound m otor action
pot en t ial (CMAP). Stim uli are prese n ted as
single high voltage or multiple small stimuli.
Sources of stimulation include magnetic and
electrical. For magnetic tcMEP, a coil over the
cortex provides the stimulation. Electrical
stimulus of the motor cortex is provided by
subdermal electrodes. Although occasionally
associated w ith scalp edem a and u nreliable re-
cordings, corkscrew electrodes are preferable
given their low impedance and secure posi-
tioning in the scalp. Peripheral data are com-
m only elect rom yograp hic via CMAP. The CMAP
is best m onitored at sites rich in corticospinaltract innervation such as the distal limb mus-
cles. Com m on r ecording sites are abductor pol-
licis brevis or adductor hallucis brevis with
viable alternat ives of long forearm exors and
extensors in the upper extremity and tibialis
ante rior in the lower extrem ity. Although the re
does not app ear to be any monitoring advan-
tage to increasing the number of monitoredm uscles, increased m uscle group test ing might
p rovid e a be ne t in ident ifying pos it ioning-
related injury.
Electromyography
The clinical applications of electromyography
(EMG) an d its speci city for the m otor system
led to the introduction of spontaneous EMG
(sEMG) recordings. sEMG myotomes are pre-
selected to coordinate with operative levels,
and m uscle relaxants m ust not be utilized du e
to dam pen ed or even absen t activity. Continu -
ous electrical activity to a myotom e is recorded
and observed and may be indicative of root
irritation. When a n er ve root is noted to be ex-
cessively ma nipu lated or imp inged, tr igger ing
a burst of activity, with more severe nerve
manipulation and stretch of a nerve root train
activity is also noted. One would gen erally note
silen ce if th e n erve root is cleanly severed. Dis-tal recording sites are typically paired w ith an
intramuscular needle or wire electrodes in-
serted after induction but before surgery.
Triggered EMG (tEMG) has also been used
as it is postulated that a high stimulus inten-
sity tEMG w ill dem onstrate an int act cortex of
a ped icle hole through wh ich a screw is passed.
In application, bone has high impedance re-
quiring high thresh old to stimulate the adjacent
ner ve. Wh en tEMG requires high stim ulation,
it demonstrates the integrity of the pedicle
cortex and lack of perforation. Direct stimula-
tion of a m isplaced pedicle h ole with a breach,
can activate th e adjacent ner ve root and evoke
a CMAP in t he appr opriate m yotom es at lower
stimulus intensities than would be expected
with an imperforate pedicle cortex. Clinical
correlation is of course re quired , but t EMG at-
tempts to p rovide data on a pathway from p ed-
icle screw or tract to the distal site an d can be
used in thoracic spine operations if the rectusabdominis or intercostals musculature are
m onitored as th e distal recording site.
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Neurologic Complicat ions Following Adult Spinal Deformity Surgery 73
! Multimodality
Intraoperative Monitoring
Somatosensory evoked potentials are the
m ost comm on neurom onitoring modality em-
ploye d, bu t a re not always a su cient p roxy for
all cord function. Failing to recognize the lim-
itation s of SSEPs can lead t o devast ating conse -
quen ces. It m ust be em pha sized th at no single
m odality su cient ly m onitors all spinal cord
pat hways . If the goal of in t raop era tive neuro -
m onitoring is to detect the onset of de cits for
bot h se nso ry and m ot or pat hways, then no
single modality meets the goal; however, a
combination of testing met hods m ight. Multi-
modality intraoperative monitoring uses allelectrophysiological techniques and can pro-
vide intraop erative inform ation about the n eu-
ral structu res at risk. It per m its assessm ent of
bot h asce nding and descending p at hways con-
curren tly, providing a cert ain degree of redu n-
dancy because many types of intraoperative
injuries will compromise both motor and sen-
sory pathways.
! Intraoperative Neurologic
Complications
Signi cant ASD surgery requires continuous
neu rom onitoring, especially dur ing placeme nt
of instrumentation and deformity correction.
Imm ediate action is required whe n dam age to
the spinal cord or a peripheral nerve is sus-
pect ed at any t im e during the pro cedure in
response to changes of > 50% am plitu de and
> 10% laten cy in t he SSEP/MEP signa ls. An
algorithm m ay aid the p rimar y surgeon in de-
termining the causative factor and initiating
appropriate treatment. Reassessment of neu-
romonitoring signal strength is performed after
each step. The speci c timing of each of the
steps listed below is not un iversal; rathe r, tim -
ing should be determined on a case-by-case
basis. Each subs equ ent st ep is in it iat ed if the
pat ient fails to dem onst rat e im prove m ent inneu rologic function after the previous sequen-
tial corrective maneu vers have been p erformed.
Here is a general checklist of factors to con-
sider w hen SCM changes occur:
Ten- Item Che cklist in Respo nse to Losing
SCM Data or Meeting Warning Criteria
(SSEPs or Neurogenic MEPs)
1. Check with personne l to ma ke cert ain SCM data
issue is real (experience matters).
2. Be aware that an increase in blood pressure
(MAP " 80–90 mm Hg/systolic blood pressure
> 120 mm Hg) may require a quick dose of epi-
nephrine/norepinephrine or a dopamine drip;
provide blood pro duct s if ne ed ed (he mog lobin
# 9).
3. Release any tract ion on pat ient’s spinal column
(halo, halo-fem oral, etc.).
4. Palpate the dura, checking for impingem ent (ifspinal canal is open), such as prior oste otomies/
laminectomies.
5. Reverse any correct ive maneuver; also consider
shortening of spinal column.
6. Con rm the absence of spinal subluxation.
Consider using temporary bilateral rods during
closure.
7. Consider implant malposition (screw/hook/wire)
if temporally related, which might indicate dural
impingement.
8. Order a wake-up test if the monitoring data
have not improved or reached baseline. Also,
this is a good time to take a deep breath and
re ect on possible add itiona l issues.
9. Con rm that elevated MAP is being maintained.
10. Consider apical spinal cord decompression to
relieve tight neu ral tissue.
Increase Spinal Cord Perfusion
Im m ediately following iden ti cation of neu ro-
monitoring signal changes, the hemodynamic
and oxygenation status of the patient should be op t im ize d to im prove perfusio n to the sp i-
nal cord. The MAP is elevated t o > 80 m m Hg or
20% above baseline.17 Hemoglobin and blood
glucose levels are evaluated and corrected if
required. Body temperature should be main-
tained at > 36.5°C to opt imize ne urom onitoring.
These measures have been shown to increase
spinal cord per fusion.18
Stagnara Wake-Up Test
Changes in neuromonitoring signal suggestive
of persistent n eurologic de cit m ay be cause
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74 Chapte r 6
for considering a con rmatory test. Prior to
the induction of anesthesia, patients should be
counseled t hat t hey w ill be asked to per form
several commands upon awaking from anes-
thesia. Frequent assessment of the patient’s
neuromonitoring status is recommended asinstrum entat ion is placed and corrective ma-
neuvers per form ed. This enables the surgeon
to most reliably pinpoint the possible incit-
ing factor, such as a malpositioned implant
or tension on the cord caused by corrective
maneuvers. Thus, potentially problematic in-
strum entation can be rem oved or correction
relaxed while waiting for the patient to
awaken from an esthesia for the wake-up test.
However, one must also understand that a
time lag can occur bet ween the application of
a corrective force (e.g., distraction) and the
dim inut ion/loss of SCM signals. Thu s, pru den t
responses to any SCM change that meets the
warning criteria must be made based on the
many factors involved, including the MAP,
any recent correction m aneuvers, and th e type
of data .
Release of Correction
The surgeon shou ld consider releasing the ten-
sion on the spine when all parameters (e.g.,
MAP, temperat ure, he m oglobin level) have been
reasonably addressed and there is still an ab-
sence of expected motor function with the
wake-up test. After release of correction, a
second wake-up test can be considered w hen
SSEP/MEP signals ind icate pe rsisten t abnor m al-
ity. If an improvemen t in th e wake-u p test or
in ne urom onitoring is discovered after t he re-
lease of surgical correction, the surgeon has
the option of fusing the spine in situ or at-
tempt ing a m ore modest correction. When no
improveme nt in neu rologic funct ion is elicited
after the release of tension, all screws and
hooks shou ld be rea ssessed. The stability of the
spine also shou ld be evaluated . Wh en re m oval
of instrum entation would compromise the sta-
bilit y of the sp inal colum n, su ch as a fter verte-
bra l bod y resect ion, th e surgeon m ay be forced
to maintain the existing instrumentation andfuse the spine un der the least amoun t of ten-
sion. If osteotom ies have bee n p erforme d, the
canal should be exam ined for fragments of bone,
Gelfoam , or bone wax, wh ich m ay be contrib-
uting to cord comp ression.
Pedicle screw position should be critically
exam ined in light of a mon itoring chan ge. The
pos it ion of each screw can be re assessed usingone m easure or a com bination of several. High
stimu lation th resholds of each xation point,
as indicated by triggered electromyography,
th eoret ically indicate intracort ical screw p osi-
tion secondary to increased resistance to cur-
rent ow through cort ical bone. Any ped icle
screw w ith a m arkedly lower electromyogra-
phy th resh old (< 60%) in relat ion to the rest
of the construct should be reassessed, as this
m ay ind icate a p ossible ped icle wall breach.19
Screw position can also be evaluated with the
use of intraop erat ive uoroscopy. A ped icle
screw tip past the midline of the vertebral
bod y not ed on posteroa nterior radiographs is
suggestive of a medial pedicle breach. In the
pre se nce of any o r all of thes e signs, t he screw
may be removed to reassess the tract with
direct palpation. A small laminotomy may
also be performed to evaluate the integrity
of the medial pedicle cortex with or without
screw removal. Early removal of instrumen-tation m ay increase th e possibility of neu ro-
logic improvement, provided the spine will
not be signi cantly destabilized with rem oval
of instrum entation.
The ability to obtain adequ ate postope rative
imaging studies is one potential advantage
of removal of instrumentation. The quality of
computed tomography (CT) and MRI scans is
superior when no instrumentation is present
to create ar tifact. Even titan ium construct s can
pro duce ar t ifac t on CT or MRI scans. An MRI
scan may be done in the p resence of titanium
instrumentation; otherwise, a CT scan can be
ordered . If the instru m ent ation is retained and
stan dard CT or MRI scanning is inconclusive, a
CT m yelogram can be p erform ed. If an ab nor -
mality (e.g., screw malposition, hematoma)
is identi ed, urgent return to the operating
room is indicated for decompression or re-
m oval of instrum ent ation. If su cient im aging
can be performe d and there is no identi ablesite of compression, close patient observation
is adequ ate.
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Neurologic Complicat ions Following Adult Spinal Deformity Surgery 75
! Steroid Protocol
Although its u se is debated, m ethylpredniso-
lone is currently the only recognized pharma-
cologic inter vention for the treat m ent of acute
spinal cord injury (SCI).13 The use of steroidshas not been extensively studied in the intra-
operative setting; however, we currently ad-
minister steroids to patients who have a
continued negative w ake-up test (i.e., absence
of motor fun ction) after release of tension from
corrective an d distractive man euvers. The cu r-
rent re comm end ed protocol is a loading int ra-
venous bolus dose of 30 mg/kg administered
over 15 minutes, followed by 5.4 mg/kg/h as
a 23-hour infusion (if started within 3 hoursfrom the time of injury).13 The u se of met hyl-
predniso lone for the m anage m ent of in t ra op -
erative SCI is not well documented. Thus, the
surgeon mu st weigh the potential bene ts of
improved ne urologic recover y against t he pos-
sible increased risk of infection. The Am erican
Association of Neu rological Surgeon s/Congress
of Neurological Surgeons (AANS/CNS) Joint Sec-
tion on Disorders of the Spine and Peripheral
Nerves Guidelines Com m it tee has indicated
that methylprednisolone for either 24 or 48hours is an option in th e treatm ent of patients
w ith acute SCIs that shou ld be und ert aken only
w ith the kn owledge that t he evidence suggest-
ing harm ful side e ects is more consistent th an
any suggestion of clinical ben e t.
Intravenous lidocaine (2 mg/kg) for vasodi-
latation has been described for treatment of a
pos tulat ed ischem ic sp inal cord after segm en-
tal vessel ligation.20 In experimental animal
models, intrathecal and intravenous vasodila-tors have been shown to enhance spinal cord
perfusio n and neuronal protect ion. How eve r,
we h ave no clinical experience w ith this m edi-
cation and thus cannot comment speci cally
on its u sefulness.
! Postoperative Manageme nt
A patient w ith an intraope rative ne urologic in-sult should be admitted to the intensive care
unit postoperatively for close monitoring of
hem odynamic parameters as w ell as for neuro-
logic examinations. MAP must be maintained
at > 80 m m Hg w ith the judicious use of intra-
venous uid replacem ent , blood tran sfusion (if
indicated), or vasopressors wh en necessary to
m aintain cord per fusion. A $-agonist (e.g., do- pam ine) can be u sed to m ain tain m ean ar ter ial
blood pressu re if uid re placem ent alon e is in-
su cient . A neu rologic examinat ion should be
perform ed an d docum ented every h ou r for t he
rst 12 to 24 hours. This may pose a problem if
the p atient rem ains intubated and sedated. In
this case, it is paramount that the patient be
lighten ed from sedation on an h ourly basis for
e ective assessmen t of neu rologic function.
! Delayed Postoperative
Neurologic Complications
Neu rologic complica t ions in the postop erat ive
per iod sh ou ld be m anaged w it h the sa m e dil-
igence and meticulous care as described for
an intraoperative SCI. Although relatively un-
common, delayed postoperative SCI may be
attr ibuted to progressive spinal cord ischem iasecondary to traction or to the developm ent of
an epidural hem atoma.
As w ith an y acute SCI, ade quat e pe rfusion of
the spinal cord is paramount. Blood pressure
should be meticulously monitored, and MAP
should be m aintained at > 80 mm Hg in an ef-
fort to sust ain spinal cord pe rfusion. Vasopres-
sors (e.g., dopam ine) m ay be required to attain
adequate blood pressure and cord perfusion.
Hemoglobin levels should also be checked to
avoid excessive postoperative anemia. Patient
temp erature should be maintained above 36.5°C.
A steroid protocol m ay be initiated as indicated
above for the patient with continued neuro-
logic loss.
Obtaining imaging studies before retu rning
the patient to the operating room may aid in
delineat ing the cause of the de cit. This will
enable the surgeon to plan th e proper course of
action, whet her that involves reexploration for
localized decomp ression of an evolving epiduralhem atom a, release of correction, or rem oval of
instrumentation to correct spinal cord isch-
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76 Chapte r 6
emia secondary to excessive tensioning. Reim-
aging with CT or MRI scans can be omitted if
obtaining these studies would result in a sub-
stantial time delay. Early decompression may
improve neurologic outcome for the patient
with new -onset neurologic de cit in the acute pos top erat ive period. Con versely, if no abnor -
m ality is iden ti ed on CT or MRI scan, the p a-
tient m ay be observed closely with sup port ive
treatment.
! Chapter Summary
The surgical treatm ent of comp lex adult spi-
nal deform ity has advanced signi cantly in re-cent times with the use of pedicle screw-based
instrumentation and the increasing role of
complex three-colum n osteotomies to optimize
deformity correction. The correction of large
magnitude coronal and sagittal plane defor-
m ity is becoming more com m on. However, th e
technical demands involved in restoration of
spinopelvic alignm ent and sagitt al and coronal
balance in large-m agnitude deform it ies has a
signi cant risk of neu rologic complications, w ith
pot ent ially devast at ing clin ica l an d funct ion al
sequelae. It is important that spinal surgeons
use an algorithm for the safe and e ective m an-
agement of neu rologic sequelae associated w ith
ASD surgery so as to opt imize patient m anage-
m ent an d functional outcome.
Pearls
Neurologic safety during spinal de form ity sur-
gery requires preoperative p reparation, intraop -
erative multimodality spinal cord m onitoring, and
po stop era tive d iligence .
A com bina tion of SSEP, MEP, and EMG mon itor-
ing is necessary for comprehensive assessment
and evaluation of neurologic function during ASD
surgery.
Appropriate responses to any loss of degradation
of SCM data and to warning criteria should in-
clude a spectrum of responses aime d at optimiz-
ing spinal cord b lood supply and m inimizing a ny
direct or indirect tension or pressure on the neu-
ral element s.
To con rm the patient ’s neurologic integrity, one
must always perform a detailed motor exam of
the lower extremities at the end of the surgical pro cedure be fore th e pa tient is extuba te d and
leaves the operating room .
Pitfalls
One must ident ify tho se patients who are at high
risk of neurologic complications during ASD sur-
ger y, including t hose with p reexisting neuro logic
abnormalities, an abnormal neural axis on MRI
exam, or large and sti kyphot ic deformities.
Not resp onding to or trusting t he SCM pe rsonnel
and da ta in a timely fashion can have devastat ing
neurologic sequelae. One must be careful with those patients kept
intubated/sedated following extensive ASD sur-
gery in order not to miss a delayed neurologic
complication due to the inability to obtain an
adequ ate ne urologic exam o n a frequent b asis.
References
Five Must- Read Reference s
1 . Dorman s JP. Establishing a standard of care for neu-
rom onitoring dur ing spinal deformity sur gery. Spine
2010;35:2180–2185 PubMed
2 . Malhot ra NR, Sha rey CI. Intra ope rat ive electr oph ys-
iological monitoring in spine surgery. Spine 2010;
35:2167–2179 PubMed
3. Gelalis ID, Pasch os NK, Pakos EE, et al. Accur acy o f
ped icle s crew placem en t: a sys te m at ic re view o f pro-
spective in vivo stud ies compar ing free han d, uoro-
scopy guidance and navigation te chniques. Eur Spine
J 2012;21 :247–25 5 PubMed
4. Tian NF, Hua ng QS, Zho u P, et al. Ped icle screw in ser -
tion accuracy with di erent assisted met hods: a sys-
tematic review and meta-analysis of comparative
stud ies. Eur Spine J 2011;20:846 –859 PubMed
5. Daubs MD, Len ke LG, Cheh G, Stob bs G, Brid we ll KH.
Adult spinal deformity surgery: complications and
outcomes in patients over age 60. Spine 2007;32:
2238–2244 PubMed
6. Kim YB, Len ke LG, Kim YJ, et a l. The m orbid it y of
an anterior thoracolumbar approach: adult spinal
deform ity patients with greater than ve-year fol-
low-up. Spine 2009;34:822–826 PubMed
7. Kim YJ, Brid well KH, Len ke LG, Cheh G, Baldu s C. Re-
sults of lumbar pedicle subtraction osteotomies for
xed sagittal im balance: a m inimum 5-year follow-up
study. Spine 2007;32:2189–2197 PubMed
8. Lap p MA, Brid we ll KH, Len ke LG, et al. Long-
term complications in adult spinal deformity pa-
tients having combined surgery a comparison of
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Neurologic Complicat ions Following Adult Spinal Deformity Surgery 77
p r im ar y to rev ision pat ien ts. Spine 200 1; 26: 97 3–
983 PubMed
9. Rhee JM, Bridwell KH, Lenke LG, et al. Staged poste-
rior sur gery for severe adult spinal deform ity. Spine
2003;28:2116–2121 PubMed
10 . Bridw ell KH, Lew is SJ, Len ke LG, Bald us C, Blanke K.
Pedicle subtraction osteotomy for the treatment of
xed sagittal imbalance. J Bone Joint Surg Am 2003;
85-A:454–463 PubMed
11 . Buch owski JM, Brid we ll KH, Len ke LG, et al. Neuro-
logic complications of lumbar pedicle subtraction
osteotomy: a 10-year assessment. Spine 2007;32:
2245–2252 PubMed
12 . Len ke LG, Feh lings MG, Sha rey CI, et al. Prosp ect ive,
multicenter assessment of acute neurologic compli-
cations following complex adult spinal deform ity sur-
gery: t he Scoli-Risk-1 trial. Spine 2014 subm itted
13. Winter RB. Neurologic safety in spinal deform ity sur-
gery. Spine 1997; 22:1527 –1533 PubMed
14. Owen JH. The application of intr aoperat ive m onitor-
ing during su rgery for spinal deform ity. Spine 1 999;
24:2649–2662 PubMed
15. Vauzelle C, Stagn ara P, Jouvin rou x P. Fun ction al m on-
itoring of spinal cord activity dur ing spinal surger y.
Clin Orthop Relat Res 19 73;93:17 3–178 PubMed
16. Lesser RP, Raud zen s P, Lüd ers H, et al. Postope rat ive
neurological de cits may occur despite unchanged
intraoperative som atosensory evoked poten tials. Ann
Neuro l 19 86 ;1 9: 22 –2 5 PubMed
17 . Naslund TC, Hollier LH, Mon ey SR, Facu nd us EC,
Skenderis BS II. Protecting the ischemic spinal cord
dur ing aort ic clamp ing. The in uen ce of anest hetics
and hypot her m ia. Ann Surg 1992;215:40 9–415, dis-
cussion 415–416 PubMed
18. Raynor BL, Len ke LG, Kim Y, et al. Can tr iggere d elec-
trom yograph thresh olds predict safe thoracic pedicle
screw placement? Spine 2002;27:2030–2035 PubMed
19. Bracken MB, She par d MJ, Holford TR, et a l. Adm ini-
stration of methylprednisolone for 24 or 48 hour s or
tirilazad m esylate for 48 h ours in th e treatm ent of
acute spinal cord injury. Results of t he Third National
Acute Spinal Cord Injury Randomized Controlled
Trial. National Acute Spinal Cord Injury Study. JAMA
1997;277:1597–1604 PubMed
20 . Klem m e WR, Bur khalte r W, Polly DW Jr, Dahl LF,
Davis DA. Reversible ischemic myelopathy during
scoliosis surgery: a possible role for intravenous li-
docaine. J Pediatr Orth op 1999; 19:763– 765 PubMed
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! General Introduction of
Adult Scoliosis
Adult scoliosis is de ned a s an abnorm al defor-
m ity in an a dult, with Cobb angle greater than
10 degrees in the coronal plane, with or with-
out sagittal imbalance or ab norm al pelvic ori-
entation.1 In the elderly population, a variety
of prevalence rates have been repor ted as a re-sult of di erences in de nitions of scoliosis,
sample size, ethnicity, and screening tools. In
a study of volunteers who were over 60 years
of age, Schwab et al2 found that 68% of the
subject s met t he de nition of scoliosis. As re-
por ted by Xu et al ,3 the prevalence of scoliosis
was 13.3%in a cohort of 2395 adu lts older t han
40 years o f age.
Adult scoliosis may stem from progression
of scoliosis during childhood or adolescence
(Fig. 7 .1), or m ay be new ly developed in adu lt-
hood through degenerative changes (Fig. 7.2).
The former condition is referred to adult idio-
pat h ic scoliosis, w hereas the lat ter is term ed
degen erat ive scoliosis or de novo scoliosis. In
contrast to adolescents, adults with scoliosis
characteristically present w ith back pain, ra-
diculopat hy, an d ne urogen ic claud ication. Cos-
m esis is a concern of some young adult scoliosis
pat ients. They oft en complain of waist asym -
metry and ribs abutting the pelvis, as a resultof im balance in the coronal plane or th e sagit-
tal plane.
For ad ult scoliosis, non ope rat ive care is usu -
ally the rst-line treat ment option. Nevert heless,
surgery may be inevitable when nonoperative
m easures fail. The prim ary ind ications for sur-
gery of adu lt scoliosis are (1) progressive defor-
m ity, (2) poor spinal balance causing funct ional
di culties, (3) large deform ity th reate ning
cardiopulmonary compromise, (4) neurologic
m anifestations, (5) persistent pain t hat fails to
respond to nonoperative treatm ent, and (6) un-acceptable cosmetic appearance.1,4–6 Bess et al, 7
in a multicenter review of 290 patients with
adult scoliosis, reported that operative treat-
ment for older patients was primarily driven
by pain and disabilit y, independent of rad io-
graphic measurements, and, for younger pa-
tients, by increased coronal plane deformity.
Although ope rative m anagem ent of adult scoli-
osis is a growing ch allenge, a variety of sur gical
options h as been em ployed, include p osterior,
anterior, or combined approaches. Silva and
Lenke6 proposed six distinct levels of surgical
options for adult degenerative scoliosis: I, de-
compression alone; II, decompression and
limited instrumented posterior spinal fusion;
III, decompression and lumbar curve instru-
m ente d fusion; IV, decomp ression w ith an te-
rior and posterior spinal instrumented fusion;
V, thoracic instrum ent ation and fusion exten -
sion; and VI, inclusion of osteotomies for spe-
ci c deform ities.Fusion levels should start proximally at a
stable vertebra, typically above T6 or below
7
Postoperative CoronalDecompensation in Adult Deformity
Yong Qiu
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Postoperative Coronal Decompensation in Adult Deformity 79
T10, and end distally at a neutral and stable
vertebra. The proxim al level never start s at t hethora cic kyph osis apex, avoiding proxima l junc-
tional kyphosis, wh ereas t he distal level never
ends at a level with rotatory subluxation. The
decision of whether to include L5 or the sa-
crum in the fusion is controversial.8,9 Fusion
distally to L5 o ers the th eoretical bene ts of
preserved lum bosacral m ot ion, sh or ter su rgi-
cal time, and a decreased likelihood of pseu-
darthrosis; on the other hand, it carries the
potential for accele rate d sym pt om at ic advan ced
degeneration at the L5/S1 disk, which in turn
ultimately results in axial discomfort, radicu-
lopathy, and loss of lumbosacral lordosis. In
contrast to L5, fusions extende d to th e sacrum
achieve a higher stability of xation as well as a
be t te r cor rect ion of sagit tal im ba lance, but this
procedure also runs the risk of an increasin g
chance of pseudarthrosis, a greater frequency
of major complications, and a higher rate of
instrum entation failure.8,9 A recent study a lso
found fusion to th e sacrum to be one of the riskfactors of proximal junctional kyph osis.10 Non-
controversial indications for fusion to the sa-
crum include the following6: (1) an oblique
take-o of L5 on the sacrum , (2) a lum bosacralfractional cur ve > 15 degrees, (3) advanced de -
gene ration of the L5/S1 disk or th e L5/S1 facet
join ts, (4 ) L5/S1 sp on dylolisthesis, and (5) p rior
history of decompression at this segment.
Wh en fusion to the sacrum cannot be avoided,
it is important to perform an interbody fusion
be tween L5 and S1 to decrease the risk of a
nonunion.
! Di erentiating Between
Degenerative and
Idiopathic Scoliosis
An essent ial prem ise of the treat m ent of spinal
deformity in particular is understanding its
etiology. Aebi1 developed in 2005 a classi ca-
tion for adult scoliosis based on the etiology:
type 1, de novo scoliosis; type 2, progressive
idiopath ic scoliosis; t ype 3a, secondary degen-erative scoliosis, due to a preexisting condition,
either intrinsic (adjacent curve) or extrinsic
Fig. 7.1 a–e (a,b) A 57-year-old wom an with a
history of ado lescent idiopat hic scoliosis. (c–e) Both
coronal and global sagitt al balance was well main-
tained, and t he L2/3 d isk height was much bet ter
preserved on the convex side t han on the concave
side.
a b c e
d
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80 Chapte r 7
Fig. 7.2 a–d Adult de generat ive scoliosis in a
65-year-old woman. (a) Stand ing X-ray lms showed
a right-sided lumbar curve, rotatory subluxation at
L3/4, and reg ional kyphosis from L3 to L5 as well as
sagittal imbalance. (b) Magnetic resonance imaging
of advanced disk degene ration showed dark disks
with narrowed disk height . (c,d) Computed
tomography scans demonstrated the vacuum
phenomenon as well as canal stenosis in the lowe r
lumbar region.
a b
c d
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Postoperative Coronal Decompensation in Adult Deformity 81
(lower limb length discrepancy) to the spine;
and type 3b, scoliosis secondary to metabolic
bon e disease . How ever, it is di cu lt to di er-
ent iate t he clinical etiology in elderly patient s
who are unable to provide either a medical
history or information about their spinal de-formity. As there is a paucity of information
in th e literature, this chapter d escribes several
experience-based radiographic criteria t hat may
help to di erentiate between d e novo and idio-
pat hic scoliosis .
Apical Disk Height
In de novo scoliosis, asymmetrical disk de-
generation has been regarded as the initiatingfactor that contributes to the occurrence of
degenerat ive scoliosis. Asymm etric degenera -
tion in the apical disks leads to asymmetric
disk collapse, ind ucing a cur vature by pivoting
on the apical facet joint at the concave side,
wh ich in turn exacerbates more degeneration
of the disks on the concave side than on the
convex side and then start the vicious circle.
Bao et al11 also found that regional lum bar disk
degenerat ion correlated w ith th e coronal Cobb
angle, con rm ing that asymm etric disk degen-eration contributed to th e developm ent of de
novo scoliosis. We observed that the convex
disk height w as signi cant ly less in de novo
scoliosis (Fig. 7.2) than in idiopathic scoliosis
(Fig. 7 .1).
Curve Pattern
The m ajority of degen erat ive scoliosis a ect s
the lumbar or t horacolumbar spine, and t heircurve pattern s may be di erent from th at of
idiopathic scoliosis. Because the original patho-
genesis of de n ovo scoliosis is th e degen erat ion
of disk and facet joints, the ap ex of the lum bar
curve is often located at the intervertebral
space. The m ost comm on ap ex of de novo sco-
liosis is the inter verteb ral space of L2/3 or L3/4,
often with a shorter curve span. In addition,
the levels involved in the degenerative curve
are gene rally thre e to four levels, wherea s four
to six levels are more common in idiopathic
curves.
Regularity of Apical Vertebra
In add ition to cur ve patter ns, the apical verte - br a in de novo sco liosis is ofte n irre gu larly
wedged. Osteophytes, end-plate abruption, and
osteoporotic minor fracture are comm only seen
in degenerat ive vertebrae, so the sh ape of ver-
tebra m ay not be regularly trap ezoid. In con-
trast, wedging of apical vertebra, if any, is
usu ally regular in idiopath ic lum bar scoliosis.
Compensatory Curve Above the
Main Curve
Regular compensatory curves proximal to the
m ain cur ve in idiopath ic scoliosis m ay develop
during adolescence, and serve as a way to re-
ba lan ce the dist al thoraco lum bar/ lum bar curve
in the coronal plane (Fig. 7.1). That explains
why global coronal imbalance is less frequen t
in adolescent idiopathic scoliosis cases with
double curve patte rns, owing to the compensa-
tory curve and its compensatory ability from
the diskal, pelvic, and certainly spinal muscu-
lar structure as well. This balancing pattern
m ay continu e into adulthood and last for a long
time. This featu re of compensatory curves could
serve as an imp ortan t rad iograph ic sign to dif-
feren tiate these tw o entities.
Patient s with de n ovo scoliosis often presen t
early w ith coronal or sagittal imbalance due to
the less e ective compensative curves above
the imbalance. In contr ast w ith sagitt al im bal-
ance, there is paucity of informat ion in the lit-eratu re on th e inciden ce of coronal im balance
in de novo scoliosis. Based on our study,11
about one third of patients with d e novo sco-
liosis may presen t w ith coronal im balance due
to a lack of compensatory curves. Similar to
the functional scoliosis seen in young individ-
uals with disk herniation or other lower back
diseases, tr unk shifting is not un comm on in de
novo scoliosis with sten osis because of the p ain-
alleviating mechanism. This trunk shifting or
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82 Chapte r 7
coronal imbalance with spinal curve may be-
com e structural with time.
Correlation Betw een the Cobb
Angle and Imbalance
The discrepancy between the Cobb angle and
imbalance in de novo scoliosis is an interest-
ing nd ing. Degen erat ive cur ves always are
shorter th an t he idiopathic curves and have a
smaller Cobb angle. As mentioned earlier, cor-
onal imbalance is an important feature of de
novo scoliosis, whatever the Cobb an gle, whereas
signi cant imba lance is mostly witnessed in
adult idiopathic scoliosis with severe curves.
The refore, a sm all Cobb an gle with obvious cor-
onal imbalance indicates that the curve might
be degenerat ive (Fig. 7 .2).
Correction Ability o f Rotatory
Subluxation
Ver tebral rotat ory su bluxat ion (VRS) is a tr iax-
ial deform ity, pre dom inan tly at t he L3/L4 level,
w ith fem ale predom inance. Although it is m ore
likely to occur in patients with de novo scolio-
sis at the early stage of th e d eform ity, it couldalso occur du ring the late course of adult idio-
pat hic sco liosis . At ou r center, we fou nd that
the correct ability of VRS under tract ion or on
side-bend ing lms could be used to di erent i-
ate de novo scoliosis and idiopath ic scoliosis. In
the form er, redu ction of VRS und er t raction or
on side bending may not be achieved because
of the rigidity from vertebral degeneration at
the subluxation level, including disk collapse,
osteophytes, and spont aneou s vert ebral or facet
fusion. In contrast, in idiopathic scoliosis, VRS
could be partially reduced un der tr action or on
side bending.
Discrepancy Between the Cobb
Angle and Rotatory Subluxation
At our center w e n oted t hat VRS was m ore like
to occur wh en t he Cobb angle increased in cases
of idiopathic scoliosis. However, in de novo
scoliosis, VRS may occur at its ea rly stage, and
its onset and severity may not necessarily be
correlated w ith th e Cobb angle. In ot her words,
VRS in de novo scoliosis may develop even in
cases with a sm all curve.
The Origin o f Stenosis
According to th e de nition of de novo scoliosis,
its primar y cause is the degenerat ion of spine,
including disks, the m uscle–ligament s comp lex,
and the facet joint. Lumbar stenosis is more
comm only seen in p rima ry degene rative scoli-
osis than in adult idiopathic curves. Therefore,
radicular leg pain and claudication should be
m ore comm on in de novo scoliosis, even w ith
small curves. This is in accordance with our
clinical observation th at m echanical back pain
is the m ost comm on complaint in m any adult
idiopath ic scoliosis patients d ue to deformit y-
induced paraspinal muscle fatigue, whereas
neu rogenic back pain in comb ination with leg
pain is t he m ost com m on complain t in de n ovo
scoliosis patien ts (Fig. 7.2 ).
Lum bar Lordosis
In addition to di eren t curve presen tations in
the coronal plane, sagitt al alignm ent m ay also
be di ere nt be tween de novo and idiopat hic
scoliosis, especially in th e early stages. Lum bar
lordosis m ay rema in norm al in idiopathic sco-
liosis because disk height may be maintained
for a long time. In de novo scoliosis, however,
lumb ar lordosis m ay not be preserved because
of early disk collapse. Bao et al11 also dem on-
strated t hat d e novo scoliosis patient s with se-
vere disk degeneration have lumbar hypolordosis
or kyphosis (Fig. 7.2). Moreover, osteoporotic
fracture is more frequen tly observed in de novo
scoliosis, particularly in female patients, greatly
contributing to lumbar kyphosis, whereas in
idiopathic scoliosis, the degenerative patholo-
gies are not the primary cause, and osteopo-
rotic fractu re m ay be less com m on.
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Postoperative Coronal Decompensation in Adult Deformity 83
! Contribution of Disk
Degeneration to Spinal
Imbalance and Curve
Severity
Spine imbalance in the sagittal or coronal
plane has an im por tant im pact on the health
status and treatment options in patients with
de novo scoliosis. Sagittal im balan ce is closely
correlated with poor health-related quality of
life (HRQOL). Import an tly, it h as been w ell doc-
um ente d that coronal imbalance is also one of
the m ain causes of unsat isfactory app earan ce,
impaired function, and back pain.12 Because
the established consensus in terms of the ori-
gin of de novo scoliosis is that it is triggered
by asym m et rica l disk degenerat ion, ou r team
conducted a stu dy speci cally focused on th e
correlation between disk degeneration and
spinal imbalance.11
We quanti ed disk degener ation using the
P rrm ann classi cation, wh ich describes ve
grades of disk degene ration on m agnetic reso-
nan ce imaging.13 Each grad e of disk was scored
w ith a speci c num ber to enable doing calcu-
lations; for exam ple, grad e I was given a scoreof 5, whereas grade V was given a score of 1.
Thus, higher scores represent ed h ealthier disk
conditions.
The results of our study revealed that disk
degeneration at the lower end vertebra (EV)
was strongly correlated with sagittal imbal-
ance (Fig. 7.2). We found that the grad e of the
lower EV disk reached a mean degeneration
score of 2.32, being the second m ost severely
degenerated disk after the apical disk. There
m ay be th ree stages of disk degenerat ion, cor-
related w ith stability an d m otion: dysfunct ion,
instability, and stabilization. With moderate
disk degenerat ion, the disk might be come u n-
stable. Also, there m ight b e a tend ency for in-
stability to lie in m oderately degenerated disks
with well-preserved disk height, whereas
mobility may decrease and restabilize in the
collapsed disks. This nding supp orted our as-
sum ption t hat lower EV disk degeneration w as
more responsible for the sagittal imbalance
because it s st abilit y was jeopardized. How-
ever, we failed to nd signi can t correlation
be tween coro nal im ba lance an d disk degener-ation. Cert ainly, degenerat ion of th e posterior
elements, including the facet joints and the
paraspinal m uscle, is anot her accepte d factor
accounting for de novo scoliosis; therefore, it
is assumed that unstable posterior elements
instead of disk degeneration may be the im-
por tan t cause of coro nal im balance in lum ba r
degenerative scoliosis. The degenerative facet
join ts w ith os teoa rthrit is m ay be the prim ary
cause, or may be se condary to t he loss of disk
height, leading to vertebral instability an d in-
creased segmental axial mobility, which may
contribute to coronal imbalance. Asymmetric
atrophy of paraspinal muscles is another pos-
sible factor in uencing coronal balance. The
degree of instability varies in each individual,
ba sed on the slip in the sagit tal plane, t ra ns-
lational dislocations in th e coronal plane, and
three-dimensional rotational subluxation.
Correlation between the Cobb angle and
apical disk degeneration was also noted. Them ore degenerat ion the ap ical disk presented,
th e larger is the Cobb an gle. Such a close rela-
tionship between degeneration of the apical
disk and the Cobb angle can be explained by
the path ology of degene rative scoliosis: asym -
m etric degenerat ion in the apical disk will lead
to asym m etr ic disk collapse, inducing the spine
to bend the apical facet joints, which in turn
exacerbates the degeneration of the concave
side. In addition, we also found that regional
lumbar disk degeneration grade is correlated
with sagitt al malalignm ent , including an an te-
verted C7PL and lumbar kyphosis (Fig. 7.2).
Decreases in lumbar lordosis in patients with
disk degeneration, as evidenced in our study,
explain w hy de n ovo scoliosis patients w ith se-
verely degenerate d disks had lum bar hypolor-
dosis or kyph osis.
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84 Chapte r 7
! Coronal Balance of
Adult Deformity
Coronal Balance Assessment
The concept of balance of the spine has beenextensively described by the Scoliosis Research
Society (SRS). The concept imp lies th at, in bot h
the coronal and sagitt al planes, the hea d is po-
sitioned correctly over th e sacrum and pelvis, in
bot h a t ran sla t ional and an angu lar sense . Fro m
the frontal view of the trunk, balance implies
horizontal shoulders and th e tru nk evenly dis-
tribute d about t he vertical line pa ssing through
th e cent er sacral vert ical line (CSVL). Spina l bal-
ance in the coronal plane can be determ ined as
the displacem ent of the m ost cephalad verte-
bra fro m the CSVL in bo th a dist an ce (frontal
plane o set) an d an angle (o set angle). In p rac-
tice, the de ned cephalad vertebra usually is
C7 or T1 (Fig. 7.3). Compen sation in th e coronal
plane is usu ally referred t o as the t ra nsla t ion o f
the midpoint of C7 in relation to CSVL (mea-
sured in the same man ner as coronal balance
[CB]). It prim arily describes t he position of the
head over the pelvis. Decompensation occurs
when this alignment strays from the midline
by m ore t han a thre sh old value speci ed by theinvestigators, usually repor ted as 2 cm.
The w ord balance implies a static alignm ent
in the standing (or unsupported seated) posi-
tion, whereas compensation and decompensa-
tion refer to the result of dynamic alignm ent .
In detail, compensation signi es the active
process of becom in g balanced, w hereas de-
compensation indicates a failure to achieve
balance , e sp ecia lly aft er an in terven t ion su ch
as surgery.
Relationship Betw een Coronal
Balance and Quality o f Life
In patients with adult scoliosis, the impact of
sagittal balance on clinical health status has
Fig. 7.3 a–c Examples of the classi cation of the
coronal balance pat te rn in adult scoliosis. (a) Type A
in a 64-year-old woman without obvious t runcal
asymmetry. (b) Type B in a 63-year-old woman with
the trunk shifting toward the concave side. (c) Type C
in a 61-year-old woman with the t runk shifting
toward the convex side.
a b c
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Postoperative Coronal Decompensation in Adult Deformity 85
been extensively discussed, w here as the im -
pac t of coron al balance on fu nct ion al ou tcom es
is less clear. In contrast to patients with idio-
pat h ic scoliosis, pat ien ts w it h degenerat ive
lumbar scoliosis have an increased likelihood
of imbalance in the coronal plane. Because ofasymm etrical degenerat ive changes and verte-
bra l wedging in the apica l region, coron al im -
balance is fre qu ently ob se rved. According to
the study by Daubs et al,14 13 of 85 (1 5%) adu lt
scoliosis patients with preoperative coronal
imbalance had worsening coronal balance of
m ore than 1 cm after surgery. This nding sug-
gests that th e inciden ce of postoperative imbal-
ance in the coronal plane is underest imated .
It ha s been found that coronal imbalance cor-
relates w ith signi cant clinical m anifestation s
such as p elvic obliquit y, sitting or sta nd ing im -
balance, as w ell as severe cosm et ic t runca l de-
form ity. Moreover, coronal im balan ce is one of
the m ain und erlying causes of the progression
of deformity, back pain, and functional com-
prom ise . Axia l pain usu ally derives fro m the
convexity of the curve, and leads to furth er de -
terioration of coronal imbalance. Radicular pa in
and neurogenic claudication mainly originate
from the compression on the concavity of thecurve, or from dynamic overstretching on the
convex side.1 Deterioration of these sym ptom s
runs in parallel with the increase in coronal
imbalance to som e exten t. To address th ese
prob lem s, it is im por tant to corre ct the pre op -
erative coronal imbalance.
To help elucidate the factors th at are m ost
crucial for im proved ou tcomes, several studies
have attem pted to correlate radiographic nd-
ings with clinical symptoms in adult scoliosis.
Glassm an et al15 repor ted that signi cant coro-
nal imbalance was associated with pain and
dysfunction in unoperated patients, and coro-
nal imbalance was not as critical a parameter
as sagittal imbalance in prediction of symp-
tom s. However, Daubs et al14 showed that sagit-
tal balance is the stron gest predictor of imp roved
functional outcom es in ad ult scoliosis patients.
They found that restoring sagittal balance in
pat ients w ith com bined coro nal an d sagit tal
imbalance seems to be the key to improvingthe functional outcomes. In terms of patients
w ith coronal imbalance alone, improveme nt in
coronal balance was a signi cant pre dictor of
improved surgical outcom es.14
In som e stu dies, coronal im balance has also
be en re por te d to lead to d ecreas ed HRQOL and
increased risk of implant failure in adult scoli-
osis patient s.15–17 In the study by Glassman etal,15 signi cant coronal imbalance of greater
than 4 cm w as associated w ith more p ain and
dysfun ction for unop erated pat ients but n ot for
operated patient s. Ploumis et al16 reported that
pat ients w ith coro nal im balance of great er
than 50 m m showed worse physical function
scores. Cho et al17 demonstrated that preoper-
ative coronal imbalance led to more implant
failures, requiring removal of the implant.
Therefore, improved postoperative coronal
balance sh ou ld be the goal in order to im prove
th e HRQOL as w ell as to r edu ce th e n eed for re -
vision surgery. At our center, postoperative
coronal imbalance was one of the factors that
contributed to implant failure.
Decom pensation in the
Coronal Plane
As mentioned above, decompensation in the
coronal plane implies dynamic malalignmentof the spine, com m only measu red a s CB (trans-
lation of th e cen ter of C7 in relat ion to CSVL)
beyon d a sp eci ed threshold value. In adoles-
cent idiopathic scoliosis patients, decompen-
sation was usually de ned as coronal imbalance
of more than 2 cm (measured in the same
manner as CB). In adult scoliosis patients, the
thresh old value of decomp ensation in th e cor-
onal plane varied am ong stud ies. Glassm an et
al15 reported the association between coronal
imbalance of greater than 4 cm and deteriora-
tion in clinical symptoms in nonoperated pa-
tients. Daubs et al14 and Ploumis et al 16 de ned
coronal imbalance as C7PL > 4 cm and > 5 cm
lateral to CSVL, respectively. In a recent study,
with emphasis on coronal imbalance in adult
spinal deform ity patients t reated w ith long fu-
sions, Ploum is et al18 also emp loyed a criterion
of 4 cm.
In a stu dy by th e SRS th at classi ed ad ult
scoliosis according to t he King/Moe and Len keclassi cations, coronal im balance was consid-
ered to be one of the global balance m odi ers.19
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86 Chapte r 7
Im balance was considered to be presen t if the
C7PL was located > 3 cm t o th e r ight or left of
th e CSVL. We recen tly sur veyed a consecu tive
series of degen erat ive lum bar scoliosis pat ients
to evaluate coronal balance, with the balance
thre shold set at 3 cm . We found a high preva-lence of preoperative coronal imbalance in
adults with degenerative lumbar scoliosis. In
these patients, imbalance occurred either on
the concave side, namely C7 deviating toward
the concave side of the m ain curve w ith refer-
ence to CSVL (Fig. 7 .3b), or on th e convex side,
w ith C7 deviating toward th e convex side (Fig.
7.3c).
Postoperative CoronalDecompensation
Postoperative coronal decompensation is a major
complication in adult scoliosis.14,18 In ad dition
to the Daubs et al14 nding repor ted above (see
section Relationship Between Coronal Balance
an d Quality of Life), Ploum is et a l,18 in a cohort
of 54 adult patient s treated w ith long fusions,
found p ostoperat ive coronal decompen sation in
seven patients with preoperative coronal im-
balance and in fou r w ithou t , at six weeks p ost-operatively. At a m inimum 2-year follow-up , four
m ore patients w ithout initial im balance were
observed with coronal decompensation. The
authors reported that postoperative coronal
decompen sation was found in an increased num-
ber of adult spine deformity patien ts.18 But so far,
the underlying factors that predict postopera-
tive coronal decomp ensation rem ain unclear.
In theory, decreased compensation of the
segments above and below the fusion pre-disposes the patient to postoperative coronal
decompensation. Multiple deformity- and
surger y-related factors are probably associated
with the occurrence of postoperative coronal
decompensation.
Deformity-Relate d Facto rs
We found that the preoperative coronal im-
balance pat te rn plays an im por tant ro le in the
occurrence of postoperative coronal decomp en-sation. A curve with imbalance to the convex
side predisposes to further decompensation,
par t icu larly w hen osteotom ies of the posterior
elements, such as Smith-Petersen osteotomy
(SPO), or th rough t hre e colum ns, such as ped-
icle subtraction osteotomy (PSO), are under-
taken.6,20 For cases with imbalance to t he convex
side, compression maneuvers on the convexside at t he level(s) of the osteotom y, wh ich a re
perform ed to close the os teot om y gap, m ay
lead to further inclination of the trunk toward
the convex side. As in congenital thoracolum-
bar kyp hoscoliosis, we also not ice d that pa-
tient s with preop erative convex im balance had
a higher rate of postoperative coronal decom-
pensat ion after thre e-colum n osteotom ies.
At the same time, decreased compensation
above and below the instr um ent ation also play
an import ant role in the d evelopm ent of post-
operative coronal decompensation, because
the compensation potential of the unfused
segments comes mainly from the disks and
parave r teb ral m usculature. Hence , the m or e
degenerative changes the adjacent vertebrae
cephalad or caudal to the fusion levels mani-
fest, the worse the potential ability for these
unfused segments to compensate, resulting in
an increasing likelihood of postoperative coro-
nal d ecompen sation.
Surgery-Related Factors
Among the surgery-related factors that have
impact on the occurre nce of postoperat ive cor-
onal decompen sation, the lower instrume nted
vertebra (LIV) selection is of upmost impor-
tance. Ending LIV at a vertebra that cannot
becom e hor izontal during su rgery carr ies the
poten tial r isk of postop erat ive decom pen sat ion .
If th ere is a resid ual ob liquit y of LIV in t he cor-
onal plane, an inclination of the tr un k is bound
to occur, because the disk below LIV provides
lim ited range of m otion. As m ent ioned pr evi-
ously, we found that the disks of the lower
lumb ar region showed signi cant degenerative
changes. The physiological funct ion of these disks
is correspond ingly comp rom ised. Apparen tly, fu-
sion distally stopping at a vertebra th at cann ot
be com e hor izontal places the coro nal ba lance
pat te rn at r isk of decom pen sat ion aft er surger y.In addition, proper determination of the
upp er instru m ente d vertebra (UIV) can dim in-
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Postoperative Coronal Decompensation in Adult Deformity 87
ish the inciden ce of coronal decomp ensation.
A location of UIV below t he en d ver tebra of the
m ain curve can result in inclination of the fu-
sion with reference to the CSVL. If fusion ex-
tend s into the thoracic region, however, a m uch
m ore cepha lad location of the UIV tha n th e en dvertebra also carries the risk of decompensa-
tion, because it lowers the n um ber of thoracic
vertebrae with compensation potential. More-
over, inclination of UIV to the convex side of
the main curve probably impedes balance in
the coronal plane through the adverse impact
on the auto-compensation mechanism.
An inapp ropriate osteotomy algorithm m ay
contribute to postoperative coronal decompen-
sation as well. Three -colum n osteotom ies usu-
ally begin at the apex and from the convex
side.20 This is e ective in the correction of
cases with p reoperative coronal imbalance to
the concave side. For a case with preexistent
imbalance to the convex side, however, such a
maneuver might aggravate the imbalance be-
cause of the comp ression forces at the osteoto-
m ized site from the convex side.
In practice, surgeons perform sagittal bal-
ance restoration more than in the coronal
p lane, and the balance pat tern and the com - pensa tion pot ent ial in the coron al p lane are
sometimes ignored. Such an attitude toward
coronal plane balance is evidently an under-
lying risk factor for postoperative coronal
decompensation. Multiple studies have dem on-
strated that coronal imbalance accompanied
by sagit tal im balance is a m or e com m on clin i-
cal scenario.14,16,19 Therefore, adequate atten-
tion need s to be paid n ot only to the sagittal
p lane but also t o t he coron al p lane. In p at ien ts
complaining of sagittal imbalance, Bridwell20
classi ed the coexistent coronal imbalance
with into type A and type B. In type A, the
pat ient ’s sh ou lders and pelvis are t ilt ed in op-
pos ite direct ions; the sh ou lder is elevat ed at
the side where the pelvis is lower. Conversely,
w ith type B, both the shoulders and the pelvis
tilt in the same direction. An asymmetrical
PSO is often useful in correcting type A bi-
p lanar deform it ies.21 The more radical tech-
niques such as vertebral column resection(VCR) are som et ime s useful for the rar e t ype B
deformities.20
! Prevention o f
Postoperative Coronal
Decompensation
A Nove l Classi cation of CoronalBalance Pattern
A discrepancy exists between sagittal imbal-
ance, which is well account ed for in th e t radi-
tional treatment algorithm, and imbalance in
the coronal plane, wh ich th e algorithm ignores.
Furthermore, postoperative coronal decom-
pensat ion is an im por tan t complicat ion that
a ects surgical outcom e and increases the re-
vision rate. To address this problem, we have
established a novel classi cation regard ing cor-onal balance pat tern s for adult scoliosis.
This classi cat ion is based on CB, w hich is
m easured as th e distance of the m idpoint of C7
relative to the CSVL on standing posteroante-
rior X-ray lms (Fig. 7 .3). Ver tebral alignm en t in
the coronal plane is considered to be balanced
if CB is less th an 3 cm at eith er side; oth er w ise,
it is considered to be im balanced. Patients w ith
a balanced coronal pattern are categorized as
typ e A (Fig. 7 .3a). Patients w ith an im balanced
coronal pattern (CB m ore th an 3 cm ) are cate-
gorized as type B if the imbalance is on the
concave side of the m ain curve (Fig. 7 .3b) and
typ e C if th e imb alance is on th e convex side of
the m ain curve (Fig. 7 .3c).
Osteotomy Options Based on
This Classi cation
For a coronal pattern of type A or type B, the
three-column osteotomy, if necessary, should
be perform ed r igh t at t he apex from the convex
side, so as to restore lumba r lordosis and to re-
establish coronal balance when the compres-
sion forces are app lied to close th e osteotom y
gap. This osteotom y opt ion is ver y e ect ive in
correcting patients with a type B coronal pat-
tern. But in type C patients with preoperative
coronal im balance on the convex side, this os-
teotomy option m ight be inappropriate due to
the compression forces at th e ap ex. Although itis rare, intraoperative dislocation after three-
colum n osteotom y can occur as a severe com-
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88 Chapte r 7
plicat ion, due to compulsive ly re ct ifying the
imbalanced trunk, which is accompanied by a
relatively rigid lumbosacral hemicurve.
To restore a balanced spine with t he tr unk
centrally over the pelvis, a novel osteotomy
strategy has been suggested for cases withtyp e C (Fig. 7 .4). First, a th ree- column osteot-
omy needs to be performed at a more distal
level, usually at th e L4 ver tebra or th e L4/5 disk
from the concave side of the m ain curve to re-
store the balance of the trunk over the pelvis.
Second, the apical region is then corrected.
In cases with kyphosis, an additional three-
column osteotomy can be done at the apex.
The optimal strategy of osteotomy for type C
begins from the concave side, and convert s
the previous imbalance pattern into a type A
pat tern.
In a ddition, an asym m etrical PSO might be
an alternate option for patients with a type C
pat tern. Toyone et al21 described t he technique
of asym m etrical PSO through w hich a coronal
correction was well achieved upon closure of
the osteotom y wedge on the convex side.
! Revision Surgery for
Instrumentation Failure
Due to Postoperative
Coronal Imbalance
Long spinal instr um ent ation is often indicated
in adult spinal deformity, which immobilizes
a long span of spinal segmen ts, leading to in-
creased m otion of the adjacent segm ents an d
the potential for degenerative pathology. Be-
cause the lumbosacral junction presents high
mechanical demand, a high rate of complica-
tions has been well docum ented for long fusions
to the sacrum . One of the implant-related com-
plicat ions is ro d fra ct ure , w hich is associated
w ith th e use of iliac screws or sm all-diamet er
rods, operating at inappropriate fusion levels,
resulting in postoperative coronal imbalance,
and failing to add ress sagitt al imbalance.
Postoperat ive coronal imbalance often re-quires add itional revision surgery. In our prac-
tice, the inciden ce of rod breakage is 15% in
adult spinal deformity patients (9/59) with a
minimum of 2-year follow-up, particularly in
pat ients w ith postop era tive re sid ual k yp hosis.
We speculate th at rod fracture m ay partly result
from overloaded mechanical forces imposed
on instrumentation in cases with postopera-tive coronal im balance (Fig. 7 .5).
The use of iliac screws might increase the
risk of implant failure because of the increased
sti ness of the lumbosacral constructs. The
excessive stress of rod contouring is necessary
to connect iliac screws and S1 pedicle screws,
bu t it can lead to ro d fra ct ure .22 In particular,
we found that, in patients with postoperative
coronal decompen sation, the location of the rod
fracture is often close to the level of the iliac
crest or th e osteotom y level (Fig. 7 .6).
Postoperative coronal imbalance th at is com-
plica te d by a symptom at ic rod fra ct ure is a de-
nitive indication for revision surger y. Several
m odalities have been emp loyed to x the frac-
tured rod. Traditionally, the entire incision is
reopened an d the fractured rod is replaced with
a new one. Alternatively, revision with a com-
binat ion of in -lin e rod connector s an d cross-
links can restore th e sti ness of the original
construct w ithout the need to replace the en-tire construct. To reinforce the local construc-
tion of the fractured rod and decrease the risk
of comp lications, we u se satellite rod s (Fig. 7 .6).
This local direct-repa ir strategy requ ires the
reopening of only the area surrounding the
fractured rod rather than the entire opening
along the instrumentation. More importantly,
satellite rod s can en able the restoration of cor-
onal balance through local comp ression at t he
convex side or distraction at the concave side.
Recently, we st arte d u sing the satellite r ods in
the index surgery at the osteotomy level or
wh en the instrum entation bridges the lumbo-
sacral junct ion.
! Chapter Summary
Adult scoliosis may stem from the progression of
scoliosis in children or ad olescents (idiopath ictype), or may newly develop in adulthood
through degenerative changes (degenerative
(text cont inues on page 93)
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Postoperative Coronal Decompensation in Adult Deformity 89
Fig. 7.4a,b (a) A 65-year-old woman withdegene rative scoliosis and a t ype C coronal
ba lance pat tern. Lum bar kyphosis and severe
sagitt al imba lance was note d. As per t he
surgical algorithm, a long fusion from T6 to
S1 was starte d with osteotomy at L4/5 to
ba lance the spine in the coronal plane
followed by a pedicle subtraction osteotomy
(PSO) at L1. (b) At 2-year follow-up, the spinal
ba lance was well maint ained.
a
b
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90 Chapte r 7
Fig. 7.5a–h (a,b) A 56-year-old woman with
degene rative lumbar kyphoscoliosis complicate d by
lumbar st enosis. Posterior spinal fusion from T5 to
pelvis was done t oget her with L4-L5 decompre ssion.
(c,d) Postoperative coronal imbalance was noted.
(e ) Both rods were fractured at 8 months’ follow-up.
(f) Revision surgery with a domino connector was
pe rform ed to restore coronal balance, which was
well maintained at (g,h) 2 years, follow-up.
a b c d
e f g h
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Postoperative Coronal Decompensation in Adult Deformity 91
Fig. 7.6 a–e (a,b) A 64-year-old woman with
degenerative lumbar scoliosis was treated with
Luque instrumentat ion 9 years ago in another
hospital. Poste rior instrume ntat ion from T5 to S1
with an L1 PSO was performed in the revision
surgery.(c)
However, immediate postoperativecoronal imbalance toward the convex side was
noted. (continued on page 92)
a
b c
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92 Chapte r 7
Fig. 7.6 a–e (continued ) (d) Two years later, the
rod fractured at t he right side of L2. (e ) A second
revision surgery was per forme d with sat ellite rods.
Both coronal and sagitt al balance was restored at
6 m onths’ follow-up.
d
e
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Postoperative Coronal Decompensation in Adult Deformity 93
type). Surgical interventions are mainly in-
dicated for patients complaining of pain and
disability. In our experience, several factors
di erentiate between degenerative and idio-
pat hic sco liosis . In degenerat ive sco liosis , d isk
degeneration contributes to the occurrenceof spinal imbalance. Disk degeneration at the
lower end vertebra strongly correlates with
sagittal imbalance, whereas that at the apex
correlates with cu rve m agnitude. In degen era-
tive lumba r scoliosis, imbalance in the coronal
plane is fre qu ently obse rved an d usu ally asso-
ciated w ith deter ioration of symptom s such as
back pain and rad icu lop at hy. A r ecent su rvey
found a high rate of preoperative coronal im-
balance in degenerat ive lum bar sco liosis , on
either the concave or the convex side. Correc-
tive surgery m ight result in coronal decompen -
sation in adult scoliosis patients, leading to
trunk shifting and possibly implant failure.
Deformity- and surgery-related factors might
lead to t his complication.
A novel classi cation system has bee n de-
vised for the coronal balance pattern in adult
scoliosis: typ e A, balanced; t ype B, imb alanced
on th e concave side; and type C, im balanced
on the convex side. For a preoperative coronal pat tern of t yp e A or B, t he thre e-colum n oste -
otomy should be p erform ed right at the apex
from the convex side. For type C, the optimal
strategy of osteotomy begins from the concave
side of the main curve, at a more distal level,
usu ally at the L4 vert ebra or L4/5 disk, followed
by corre ct ion of the apica l re gion. For inst ru-
m ent ation failure due to postoperat ive coronaldecompensation, revision surgery focuses on
reinforcing th e local constr uct ion, using in-line
rod conn ector s, cross-links, or satellite rod s.
Pearls
Consult the classi cation system that has been
devised for preo perative coronal balance p att ern
in adult scoliosis.
Ident ify the factors that di erent iate de gene ra-tive and idiopat hic adult scoliosis.
Keep in m ind that disk degen eration may con-
tribute to sp inal imbalance and curve severity.
Evaluate t he risk factors of postop erat ive coron al
decompensation.
Be aware of revision options for instrumentation
failure due to postoperative coronal imbalance.
Pitfalls
Postope rative coronal decompen sation can o ccur
after osteotomy at the apex.
Postoperative coronal decompensat ion may result
in instrume nta tion failure and loss of correction.
References
Five Must -Read Referen ces
1. Aebi M. The adult scoliosis. Eur Spine J 2005;14:
925–948 PubMed
2. Schwa b F, Dub ey A, Gam ez L, et al. Adu lt sco liosis:
pre valen ce, SF-36 , a nd nut rit ion al par am et er s in an
elderly volunteer population. Spine 2005;30:1082–
1085 PubMed
3. Xu L, Sun X, Huang S, et al. Degenerative lumbar
scoliosis in Chinese Han popu lation: prevalence and
relationship to age, gender, bone mineral density,
and body mass index. Eur Spine J 2013;22:1326–
1331 PubMed
4. Glassm an SD, Schw ab FJ, Brid we ll KH, Ond ra SL, Ber -
ven S, Lenke LG. The selection of operative versus
nonoperative treatm ent in patients w ith adult scoli-
osis. Spine 20 07;32:93 –97 PubMed
5. Smith JS, Sha rey CI, Ber ven S, et al; Spinal Deform ity
Study Group. Operative versus nonoperative treat-
m ent of leg pain in adu lts with scoliosis: a ret rospec-
tive review of a prospective multicenter database
with two-year follow-up. Spine 2009;34:1693–1698
PubMed
6. Silva FE, Len ke LG. Adu lt d egen er ative s coliosis:
evaluation and ma nagem ent . Neurosurg Focus 2010;
28:E1 PubMed
7. Bess S, Boachie- Adjei O, Bur ton D, et a l; Inter nat ional
Spine Study Group. Pain and disability determine
treatm ent m odality for older patients w ith adult sco-
liosis, wh ile deformit y guides treatm ent for younger
pat ien ts. Spine 2 00 9; 34 :2 18 6– 21 90 PubMed
8. Bridwell KH, Edwards CC II, Lenke LG. The pros and
cons to saving the L5-S1 motion segment in a long
scoliosis fusion construct. Spine 2003;28(20, Sup-
pl): S234– S242 PubMed
9 . Polly DW Jr, Hamill CL, Brid well KH. Debat e: t o fu se
or not to fuse to the sacrum, the fate of the L5-S1
disc. Spine 2006;31(19, Suppl):S179–S184 PubMed
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94 Chapte r 7
10 . Yagi M, King AB, Boach ie-Adjei O. Incid en ce, r isk fac-
tors, and natural course of proximal junctional ky-
phos is: su rg ica l outcom es re view of ad ult id iop at h ic
scoliosis. Minim um 5 years of follow-u p. Spine 2012;
37:1479–1489 PubMed
11. Bao H, Liu Z, Zhu F, et a l. Is t he sacro -fem oral-p ubic
angle predictive for pelvic tilt in adolescent idio-
pat h ic sco liosis pa t ien ts? J Spin al Diso rd Tech 20 14 ;
27:E176–E180 PubMed
12 . Mac-Thion g JM, Transfeld t EE, Mehb od AA, et a l. Can
c7 plumbline and gravity line predict health related
quality of life in adult scoliosis? Spine 2009;34:
E519–E527 PubMed
13. P rr m ann CW, Metz dor f A, Zanet ti M, Hodler J, Boos
N. Magn et ic res on an ce classi cat ion o f lum ba r in ter -
vertebral disc degeneration. Spine 2001;26:1873–
1878 PubMed
14 . Daubs MD, Len ke LG, Bridwe ll KH, et a l. Does cor rec-
tion of preop erative coronal im balance make a di e-
rence in outcomes of adult patients with deformity?
Spine 2013;38:476–483 PubMed
15. Glassm an SD, Ber ven S, Bridw ell K, Horton W, Dima r
JR. Correlation of radiograph ic param eters and clini-
cal symptom s in adult scoliosis. Spine 2005 ;30:682–
68 8 PubMed
16 . Ploum is A, Liu H, Mehb od AA, Transfeld t EE, Win -
ter RB. A correlation of rad iographic and functional
m easurem ent s in adult degenerat ive scoliosis. Spine
2009;34:1581–1584 PubMed
17. Cho W, Mason JR, Sm ith JS, et a l. Failur e of lum bop el-
vic xation after long constru ct fusions in patients
with adult spinal deformity: clinical and radio-
graphic risk factors: clinical article. J Neurosurg
Spine 2013;19:445–453 PubMed
18. Ploum is A, Simpson AK, Cha TD, Herzog JP, Wood KB.
Coronal spinal balance in adu lt spine deform ity pati-
ents w ith long spinal fusions: a minimum 2–5 year
follow-up study. J Spinal Disord Tech 2013 Sep 27.
[Epub ah ead of print] PubMed
19. Lowe T, Berven SH, Schwab FJ, Bridwell KH. The SRS
classi cation for adult spinal deform ity: building on
the King/Moe and Lenke classi cation systems. Spine
2006;31 (19, Suppl):S119–S125 PubMed
20. Bridwell KH. Decision m aking regarding Sm ith-
Petersen vs. ped icle subtra ction osteotom y vs. verte-
br al colum n re se ct ion for sp inal deform it y. Spin e
2006;31 (19, Supp l):S171–S178 PubMed
21. Toyone T, Shib oi R, Ozawa T, et a l. Asym m et rica l ped-
icle subtraction osteotomy for rigid degenerative
lumbar kyphoscoliosis. Spine 2012;37:1847–1852
PubMed
22. Sche er JK, Tan g JA, Deviren V, et al. Biom ech an ical
analysis of revision str ategies for rod fract ure in p ed-
icle subtraction osteotomy. Neurosurgery 2011;69:
164–172 , discussion 172 PubMed
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! Introduction
The de nition of a health-related outcome var-
ies in the literature an d m ay encomp ass a spec-
tru m of m easures. Clinical outcom e is the en d
result of health care delivered to patients or
pop ulat ion s, and entails su ch considerat ions
as quality, patient -based assessment , and value
of care. Measuring outcomes is complex, and
there is no single m easure that sum m arizes the pat ient’s exp erience, the hospital persp ect ive,
the payer perspective, and the treating physi-
cian’s p erspect ive. Therefore, outcomes must be
considered broadly and encompass a spectrum
of perspectives and m easures. This chapter d is-
cusses measures of health-related quality of
life (HRQOL), an d the a pp lication o f these m ea-
surem ent s in assessing outcom es of spinal de-
form ity surgery.
Outcome m easuremen t is an important as-
pect of su rgeon accountabilit y an d is vit al in
determining the quality and value of health
care. Quality may be evaluated based on pro-
cess measures, objective health outcomes,
pat ient-re por te d ou tcom e m ea su re m ents, an d
cost of care. Value is a broad er m easure that in-
corporates an analysis of both quality and
cost. This chapter provides an overview of
various outcome measures used for spinal de-
form ity, and ndings from the literature on
outcom es in adult spinal deform ity surgery.
! Process Measures
Process m easures are a re ection of how care
is delivered. Examples include compliance
with antibiotic or thromboembolic prophy-
laxis guidelines, the u se of surgical “tim e-ou ts”
before su rgery, preop erat ive risk assessm ents
of patients, and implementing postoperative
care protocols for the prevention of common
po stop erative com plication s. The utilit y of pro -cess measures depends on how reliably they
are linked to clinical outcomes. For example,
m easuring comp liance with pre operat ive anti-
biot ic gu idelines is u sefu l in that it m ay p re dict
a reduction in the incidence of surgical site
infections. Although th ey are an indirect m ea-
sure of quality, the implementation and mea-
surement of such guidelines are important in
standard izing care an d imp roving quality.
! Physiological Outcome
Measures
Physiological ou tcomes repre sent clinical h ealth
metrics that may be measured objectively. In
adult spinal deformity, these may include ra-
diographic outcomes, implant survival, and
fusion rat es. Cobb angle, sagitt al vert ical axis
(SVA), and spinopelvic parameters including
8
Measuring Outcome and Valuein Adult Deformity Surgery
Robert Waldrop and Sigurd Berven
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96 Chapte r 8
pelvic in cid ence (PI), pelv ic t ilt (PT), sa cral
slope (SS), an d lum bar lordosis (LL) are a ll im -
por tan t radiogra phic m ea su rem ents in sp inal
deformity. Although these outcomes are easy
to measure and interpret , i t is important to
evaluate clinical measurem ent s in relation t otheir correlation with quality measurements
(e.g., do radiographic outcom es pre dict reope r-
ation rates?).
! Quality Measures
Traditional measurements of quality include
outcom es such as operative tim e and length of
hosp ital stay, as w ell as rates of comp lications ,
reoperations, and readmissions. Such measures
provide im por tant in form at ion that m ay be
used to comp are the p erforma nce of individual
providers and hospitals and to es tablish m et -
rics for pe rforman ce and goals for qua lity im -
prove m ent . However, ove rall qu alit y of ca re
encompasses mu ch more than these tradition-
ally reporte d quality met rics.
Quality metrics are valuable in identifying
outliers, and in improving care processes and pat hways. How eve r, overall qu alit y m easure s
are distinct from pat ient-cente red clinical out-
come measures. One important concern re-
garding reliance on quality measures is the
poss ib ilit y that m easu rin g qu alit y alone m ay
lead to a focus on outcomes that are not pa-
tient-centered. If the target for outcome were
only length of stay or avoidance of readmis-
sion, the n th at goal m ay incentivize signi cant
undertreatment of complex spinal disorders.
Fig. 8 .1 provides an examp le of a case in wh ich
a patient un derw ent a limited decompression
and posterior-based tethering procedure for
a comp lex spinal deform ity. Measured by only
length of stay or com plications of care, the lim -
ited decompression surgery would be rated as
a high-quality outcome. However, the patient
had n o improvem ent in he r health status or in
her deformity measures. The patient under-
wen t a revision surger y 3 years after th e index
procedure an d w as t reated w ith a three-colu mnosteotomy for multiplanar realignment of the
spine. The revision sur gery resu lted in a longer
stay, higher cost, and more risk and potential
for comp lication th an the index surger y. How-
ever, the p atient rep orted a dr am atic imp rove-
men t in health status that is not captured by
the quality metrics alone. It is important to
avoid myopic focus on qu ality m etr ics w ithoutgiving priority to patient-centered measures
of clinical outcom es in spinal deform ity.
! Patient-Reported
Outcomes
Although process measures, physiological out-
comes, and trad itional quality m etr ics are im-
por tant too ls for assessin g health care qu alit y,
they do not re ect the patient’s health care
experience or the impact of care on HRQOL.
There has been an increasing emphasis on pa-
tient- based health assessme nts in recent years.
Patient-reported outcome measures (PROMs)
may include a spectrum of domains to assess
HRQOL. Frequently used domains include
disability/functional status, pain and other
symptom s, em otional/psychological w ell-being,
general health status, and satisfaction withhealth care experience. The Visual Analogue
Scale (VAS) for pain assessm ent is anoth er com -
mon ly used outcome m easure.
Measurement tools for patient-reported out-
comes include both disease-speci c and gen-
eral health status measures. Disease-speci c
measures focus on domains associated with a
par t icu lar con dit ion or pat ient pop ulat ion, an d
have the advantage of increased responsive-
ness to change (ther e is a m ore reliable change
in outcome score as the underlying condition
changes) compared with general health status
m easures. Examp les of speci c outcome tools
includ e th e Scoliosis Research Societ y (SRS-22)
questionnaire, the Oswestry Disability Index
(ODI), and th e Neck Disability Ind ex (NDI).
General health status outcomes tools are
advantageous in that they may be used in any
pat ient pop ulat ion and allow for bro ad com -
par isons across a spect rum of m edica l an d sur-
gical conditions. However, they are often lessresponsive to changes in par ticular conditions
or disease states. Examples of gene ric pro les
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Measuring Outcom e and Value in Adult Deformity Surgery 97
Fig. 8.1a,b (a) A 73-year-old woman
presented with sag ittal and coronal
plane deformity, back pain, and
neurogen ic claudicat ion. She was
unable to live independent ly. The
patient was t reate d with a limiteddecompression and a posterior-based
tet hering device. Although the length
of stay was 3 days, and the re was no
complication or readm ission within 90
days, the re was also no improvement
in radiographic or patient-cente red
clinical outcomes, and the patient
remained disabled. (b) Postoperative
X-rays 2 years after a revision surgery
in which the patient was treated with a
three -column osteotomy for realign-
ment of the spine. The pat ient stayedin the hospital for 6 days and her
pe rioperative course was com plicated
by a supravent ricular t achycardia that
required cardioversion. At 2-year
follow-up, she was living independently
and walking without limits.
a
b
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98 Chapte r 8
include t he Shor t Form 36 (SF-36), Shor t Form
6 Doma ins (SF-6D), th e EuroQOL ve dim en -
sions questionnaire (EQ-5D), and the Health
Utilities Ind ex (HUI).
Both general health statu s m easures and cer-
tain disease-speci c outcom e tools m ay be usedas indirect m easures t o calculate u tility scores.
A ut ility score re ects societal preferen ces for a
health state. Di eren t health states are rated
on a continuous scale from 0 to 1, with the
value re ect ing a m easu re of well years of life.
Utility scores derived from patient-reported
outcome questionnaires using validated in-
struments provide information on a patient’s
health status and the value that society places
on t hat health state. Consideration of a ut ility
score over time yields a quality-adjusted life
year (QALY), calculated as t he ut ility score m ul-
tiplied by the nu m ber of years that h ealth state
is maintained. Thus, the durability of an out-
com e re sult s in increased QALYs over t ime. A
QALY is an ou tcome m easure that represen ts a
standa rdized unit for compar ison across elds
and can be assigned value by society.
! Commonly Used Outcome
Measurements
The follow ing instrum ent s are comm only used
pat ient -repor ted outcom e m easu rem ents in
adult spinal deform ity that h ave validated con-
version s t o u tility scores /QALYs.
Short Form 36 (SF-36) and ShortForm 6 Domains (SF-6D)
The SF-36 is a w idely used generic health sur-
vey consisting of 36 quest ions w ith four physi-
cal health scales (physical funct ioning, physical
role lim itation, bodily pain, and general h ealth)
and four mental health scales (vitality, social
functioning, emotional role limitation, and
mental health). The SF-6D is an abbreviated
version of the SF-36 t hat h as been established
as a preference-based health state classi ca-tion th at m ay be converted to a ut ility score.1
EuroQOL Five Dimensions
Questionnaire (EQ-5D)
The EQ-5D is anoth er validated and w idely used
general health questionn aire that is used to es-
tab lish a ut ility score. It includes ve healthdimensions: mobility, self-care, usual activities,
pain/discom for t , an d anxie ty/depressio n.
Scoliosis Research Society
Questionnaire
The Scoliosis Research Society (SRS) question-
naire measures how spinal deform ity a ects a
pat ient’s HRQOL based on ve dom ains: pain ,
function, self-image, men tal he alth, and satis-
faction. The 22-item questionnaire (SRS-22) is
the most widely used and validated version,
although several other versions exist (SRS-24,
SRS-29, SRS-30). SRS-22 has been validated as
a reliable instrument with high internal con-
sistency, responsiveness, reproducibility, and
discriminator y capacity for patients w ith adult
deformity.2,3 A m odel has been established for
translating SRS-22 scores to SF-6D scores to
deter m ine utility scores.4,5
Oswestry Disability Index (ODI)
The ODI mea sure s HRQOL in p atien ts w ith low
back pain . It rat es a pat ien t ’s d isabilit y score
base d on 10 m easu res: pain , perso nal ca re,
sitt ing, stan ding, walking, lifting, sleep ing, sex
life, social life, an d t raveling. Highe r scores cor -
respond to a greater degree of disability. The
ODI is a validated and w idely used m easure that
can be reliably translated to a ut ility score.6
! Cost and Value
In our cur rent health care e conomy, cost has be-
come an increasingly important consideration
in the assessmen t of health care inter ventions.
Econom ic analyses of health care intervent ions
include cost-m inimization stud ies, cost-e ec-
tiveness an alyses, an d cost-u tility ana lyses. Anassessment of costs may include direct costs,
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Measuring Outcom e and Value in Adult Deformity Surgery 99
charges, and reimbursements. Indirect costs
such as loss of productivity due to time o
from work, transpor tation to health care facili-
ties, and th e cost of caregivers m ay also be in-
clude d in cost analyses and incorporate a w ider
view of total costs from a societal perspect ive.Although cost in itself is an impor tan t con-
sideration, the value of care provides th e m ost
meaningful assessment of a health care inter-
vention. Value of care en compasses both out-
com e and cost and is de ned as the net bene t
of care relative to t he net cost of care, or wh at
we get for wh at we spend. The m easurement
of bene ts and costs in spine surgery is not
uniform and m ay vary depen ding on the per-
spective of the stakeholder in the health care
economy. Hospitals and other health care facil-
ities may emphasize outcomes and costs that
a ect a single admission such as length of
hospit al stay, imp lant u tilization, and com pli-
cations. Third-party payers often focus on
outcomes and costs in a medium-term time-
frame including readmissions within 90 days
or the cost of outpatient care. The value of a
health care intervention to the physician and
pat ient is es tablished ove r a longer t im efram e
than a single admission; its imp act is m easured based on HRQOL over a lifet im e.
Cost-ut ility stud ies provide t he m ost useful
information about the value of a health care
intervention because a utility score is able to
captu re a patien t’s preference for di eren t health
states over tim e. An outcom e m easure th at di-
rect ly re ects HRQOL and is tran slatable across
disease states, such as QALYs, is an imp ort ant
prerequ isite for est imat ing th e value of or thope-
dic care. The length of follow- up is also an im-
por tan t considerat ion when measuring value, as
the cost of a single episode of care will be signi -
cantly discounted by the duration of the ben e t.
! Outcomes of Adult Spinal
Deformity Surgery
Several stu dies have reported various outcomes
for the operative and nonoperative manage-ment of adult spinal deformity. Estimates of
the prevalence of adult spinal deform ity in the
United States range from 2.5 to 25%7 However,
many of these patients do not seek medical
care for their condition, and of those who
do, many m ay have successful ma nageme nt of
their symptoms without surgery. Nonopera-tive care may include physical therapy, core
strengt hen ing, weight loss/aerobic activity, pain
m edications, steroid injections, and altern ative
m odalities such as acupunct ure and chiroprac-
tic care. For m ost patien ts, a trial of nonop era-
tive care should be initiated before sur gery is
considered. Exceptions include patients with
neurologic de cits or signi cant instability.
Surgery may also be indicated in patients
w ith p rogressive curves, substantial deform ity-
related pain, and those who have failed ap-
prop riat e nonop erat ive t reat m ent . Stu dies of
operative and nonoperative management of
adult spinal deformity h ave d emon strated im-
proved pat ient-re por ted ou tcom es w ith su rgi-
cal man ageme nt.8–12
In a review art icle on ad ult spinal deformity,
Youssef et al13 sum mar ize the ndings of 49
studies rep ort ing outcomes for various sur gical
strategies including decomp ression alone ver-
sus decompression with fusion; anterior, pos-terior, or combined surgical approaches; the
use of vertebr al osteotomies; an d levels of in-
strumented vertebrae. A variety of outcome
m easuremen ts are reported for each technique.
Radiographic Outcomes
A systematic review of adult scoliosis outcomes
by Yadla et al14 found a range in Cobb angle
correction from 9.1 to 53.9 degrees (m ean 26 .6
degrees, representing an average 40.7%curve
correction) in a ser ies of 49 ar ticles pu blished
be tween 195 0 and 2 00 9 w ith m in im um 2-yea r
follow-up.
Radiographic outcomes h ave also been com-
pared be twee n di erent su rgical ap proaches .
Crand all and Revella15 foun d no signi cant dif-
ference in coronal curve correction between
pat ient s undergoing pos ter ior in st rum ented
fusion in addition to either anterior lumbar
interbody fusions (ALIF), with an average cor-rection 69.5%, or t ransforam inal lumb ar inter-
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100 Chapte r 8
bod y fusion (TLIF), w ith an ave rage corre ct ion
68.7%. A liter atu re r eview by Mun dis et al16 re -
por te d im proved coronal and sagit tal correct ion
with a lateral transpsoas approach compared
w ith open anter ior procedures. A retrospective
report by Pateder et al17 comparing patientswh o under went posterior only surgery (n = 45)
versus combined anterior-posterior surgery
(n = 35) found no signi cant di eren ce in coro-
nal or sagittal curve correction between the
two groups.
Youssef et al13 also reviewed radiographic
outcom es for di eren t types of posterior oste-
otomies including Smith-Petersen osteotomy
(SPO), pedicle subt ract ion osteotom y (PSO), and
vertebral column resection (VCR). These tech-
niques are used to achieve varying degrees of
lordosis correction and restoration of sagittal
balance. SPO provid es the sm alle st degr ee of
curve correction, achieving up to 10 degrees
of lordosis per vertebral level; however, multi-
level osteotomies may achieve a large overall
correction. Repor ts of PSO have dem onstrated
an average 30 degrees of lordotic correction
per level. In a comparison of SPO an d PSO, Cho
et al18 found an average total correction of 33
degrees for patients undergoing three or moreSPOs and 31.7 degrees for patient s un dergoing
PSO, but a signi cant ly lower imp rovemen t in
sagitta l balance for t he SPO group tha n for th e
PSO group. VCR achieves the highest degree of
curve correction. Suk et al19 reported a mean
deformity correction of 59%(109.0 degrees to
45.6 degrees) in 16 patients who u nderw ent
pos ter ior VCR. Papadop oulos et al20 reported
that of 45 patients w ho under went p osterior
VCR, the average correction of kyphosis was
from 108 degrees to 60 degrees with one pa-
tient sustaining a complete spinal cord injury.
Complications
The inciden ce of comp lications is an imp orta nt
quality m easure in adu lt spinal deform ity. Re-
por ted com plica t ion rates for sp inal deform it y
surgery are high, but a stan dardized de nition
or classi cation for repor ting complications in
the literature has not been established. Com- plicat ion rat es have be en classi ed in various
ways, including major versus m inor comp lica-
tions, early versus late complications, and sur-
gical versus medical complications. Reported
complications in deformity surgery include
pseudar throsis, adjacent segm en t d isease, dura l
tears, super cial or deep wound infections,implan t complications, neu rologic de cits, epi-
dural hematoma, wound hem atoma, pulmonary
embolism, deep vein thrombosis, systemic com-
pl icat ions, and deat h . The in cid ence of com -
plica t ions m ay b e in uenced by pat ient factor s
(e.g., age, comorbidities, severity of deformity)
or sur gical factor s (e.g., app roach t ype, need for
osteoto my, nu m ber of levels fused).
The 49 ar ticles reviewed by Yadla et al14 re-
por t complicat ion ra tes rangin g from 0 to 53 %,
with a combined total of 897 complications
am ong 2 ,175 pat ient s (41.2%). Char osky et
al31 repor ted an overall 39%comp lication rate
among 306 patients over age 50 undergoing
adult deformity surgery with either an ante-
rior on ly, posterior on ly, or comb ined app roach.
Sansur et al22 reviewed a total of 4,980 cases
of adult scoliosis from the SRS morbidity and
mortality database and found an overall com-
plica t ion rat e of 13.4% and a m or talit y ra te of
0.3%. Signi can tly higher complicat ion rat esresulted from revision sur geries, osteotom ies,
and combined anterior-posterior surgery.
Youssef et al13 summarized several studies
repor ting complication rates of various p roce-
du res. Tran sfeldt et al23 repor t a 10%complica-
tion rate among adu lt deform ity patients w ho
unde rwent decompression alone compared with
56% in patients wh o underwent decompres-
sion and fusion. Burn eikiene et al24 reported a
31% inciden ce of system ic comp lications and
49%ha rdware or surgical technique comp lica-
tions in 29 patients undergoing TLIF. Compli-
cations of ALIF may include vascular injuries,
ilioinguinal and iliohypogastric nerve injuries,
damage to the bladder or ureters, pseudar-
th rosis an d su bsidence, ileus, lymph ocele, and
retrograde ejaculation.13,25 Most of these com -
plicat ions are uncom m on , althou gh ra tes of
m ajor and m inor complications vary in th e lit-
eratu re. In a stu dy of 447 p atients, McDonnell
et al26 found a complication rate of 11% form ajor comp lications and 24%for m inor compli-
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Measuring Outcom e and Value in Adult Deformity Surgery 101
cations. Comp lications of th e lateral t ranspsoas
approach are often related to manipulation of
the lumber plexus. In a prospective multi-
center evaluation of 107 adult degenerative
scoliosis patients undergoing extreme lateral
inter body fusion, Isaacs et al27 reported a 12.1%m ajor comp lication rate.
Reoperations
Scheer et al28 an alyzed dat a from a prospe ctive,
multicenter adult spinal deformity database,
and exam ined th e rates, indications, timing, and
risk factors for reoperat ion as well as the e ect
of reope ration on HRQOL m easu res. In a coh ort
of 352 patients (268 with at least 1-year fol-
low-up), they found a total reoperation rate
of 17%, the m ajority of w hich occurred w ithin
1 year of the index operation. The most com-
mon indications for reoperation included in-
strumentation complications and radiographic
failure.
There w as a 19% reoperat ion rate for pa-
tients undergoing a three-column osteotomy
and a 16% reoperation rate for patients not
requiring three-column osteotomy; however,
three-colum n osteotomy was not signi cantly predict ive of reop era t ion at 1 year. The upper-
m ost instrum ented vertebra was also not pre-
dictive of reoperat ion. There w ere no signi cant
di erences in the Am erican Societ y of Anes-
thesiologists (ASA) grade, Charlson comorbid-
ity index rating, preop erative body m ass index
(BMI), or smoking history between patients
wh o did not undergo reoperation and those wh o
did. Patients wh o needed reoperation w ithin 1
year h ad w orse ODI and SRS-22 scores at 1-year
follow-up than did patients not needing reop-
erat ion. However, th ere wa s no signi cant dif-
ference in HRQOL scores at 2 years between
pat ients w ho re qu ired re op era t ion at 1 year
and those wh o did not.
Other studies have dem onstrated similar re-
ope rat ion rates , ran ging from 10 to 21%.21,29–31
Reasons for revision surgery in adult spinal
deformity include pseudarthrosis, curve pro-
gression, infection, painful/prom inent implant s,
adjacent segment disease implant failure, andneuro logic de cits.29,30
HRQOL Outcomes in Adult
Spinal Deformity
Despite high comp lication and reope ration rates
in adult spinal deform ity surgery, patient sat-
isfaction with these procedures is high. Bothcondition-speci c and genera l HRQOL outcomes
that can be converted to utility scores and
compared across the literature are important
prere qu isi tes for det erm in ing the value of sp i-
nal deform ity surgery.
Several prospective m ulticenter st udies have
dem onstrated the bene ts of operative treat-
men t of adult spinal deform ity compared with
nonoperative care in regard to patient-rep orted
health m easures includ ing ODI, SRS-22, EQ-5D,
and numeric rating scale scores for leg and
ba ck p ain .8–12
Yad la et al14 reported th at in the 49 studies
included in their systematic review, ODI and
SRS were the most commonly used patient-
ba sed ou tcom e inst rum ents, w ith 11 st udies
reporting pre- and postoperative ODI scores
and 10 studies reporting pre- and postopera-
tive SRS scores. The re w as an average decre ase
of 15.7 points (range 3.1–32.3) in ODI score
am ong 911 patient s. This imp rovem ent in dis-ability outcome correlates with previous re-
por ts of signi can t clin ical im prove m ent of
ODI scores ran ging from 4 to 15 p oints.32 Of th e
999 patients with pre- and postoperative SRS
scores in Yadla et al’s review, the re w as a m ean
increase in SRS scores of 23.1 points, well
above the minimal important di erence for
SRS scores of 13 point s rep ort ed b y Bagó et al.33
You ssef et al13 summarized the results of
studies reporting HRQOL outcomes for pa-
tien ts und ergoing various surgical approa ches.
Crandall and Revella15 found nonsigni cant
di ere nces in VAS and ODI out come s betw een
pat ients undergoing posterior fusion w ith ei-
ther ALIF or TLIF. Mundis et al16 foun d signi -
cantly improved VAS and ODI scores in a
literature review of the lateral approach for
adult spinal deformity. Various studies have
reported improved patient-reported outcomes
following PLIF, including improved ODI, SF-36,
and VAS scores.34–36 Good et a l 37 reported sim-ilar SRS and ODI scores for bot h p oster ior on ly
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102 Chapte r 8
and combined fusions, with both having im-
provem ents a t 2-ye ar follow-up.
Cost and Value in Adult
Spinal DeformitySeveral recent articles have reported on the
costs of adult spinal deformity surgery. Mc-
Carth y et al38 studied t he tot al costs of 484 pa-
tient s undergoing operat ive treatm ent of adult
spinal deformity with an average follow-up
of 4.8 years, and found an average total hospi-
ta l cost of $120,394. Total cost for pr ima ry su r-
gery averaged $103,143, which increased to
$111,807 at 1-year follow-up and $126,323 at
4-year follow-u p. Hospital read m issions wererequ ired in 130 p atien ts (27%), w ith an aver-
age readmission cost of $67,262. Another cost
analysis by McCarthy et al39 found higher di-
rect costs w ith increasing age, length of hospi-
tal stay, length of fusion, and fusions to the
pelvis.
Cost-utility studies of adult spinal defor-
mity are lacking in the literature. Although
several recent ly published system atic reviews
repor t on cost-ut ility analyses in spine care,40,41
none of the reviewed articles include valueassessments in adult deformity. One study by
Glassm an et al42 examined the costs and bene-
ts of non ope rative care for adult scoliosis, an d
questioned the value of nonoperative treat-
m ent given the ir ndings of a $10,815 m ean
treatment cost over a 2-year period with no
signi can t chan ge in HRQOL.
! Improving Outcomes inDeformity Surgery
Measurem ent of clinical outcom es and value is
an imp orta nt goal in spine surger y and is criti-
cal in establishing accountability for the end
resu lt of care. Ern est A. Codm an w as a sur geon
in the early 20th centu ry and a pioneer in ad-
vocating outcom e m easureme nt an d report ing.
He proposed an “end results system ” in wh ich
pat ients’ symptom s, diagnos is, t reat m ent , andoutcom es would be tracked over tim e in an ef-
fort to redu ce complications and improve qual-
ity of care. At the time, Codman’s ideas were
seen as radical and m et w ith strong resistance,
leading to his dismissal from his faculty posi-
tion at Massachusetts General Hospital. Al-
though great strides have been made since
Codman’s time in recognizing the importanceof outcome measurement, there is still much
room for improvement in the e ort to establish
regular and reliable system s for outcom e m ea-
suremen t and reporting.
There is a high variability in spine surgery
w ith regard to surgical rates, surgical strategies,
and costs.43–45 High variability indicates a lack
of consensus on the optimal treatment strat-
egy and a need for fur the r comp arative e ec-
tiveness re search. Redu cing variability in spine
surgery requires an evidence-based approach
to care. The establishm ent of large m ulticente r
pro cedural an d diagnos is- based regist ries for
spine surgery has been an important step to
improving outcom e measurem ent and report -
ing. These registries provide a reliable system
for th e rep ort ing of comp lications, clinical out -
comes, and HRQOL out comes, and facilitat e t he
evaluation of alternat ive intervent ions in com-
parat ive e ect iveness rese arch . With the ac-
curate measurement of complications, qualitym ay be improved t hrough the establishm ent of
clinical protocols based on stand ards of care in
an e ort to reduce complications. The w ide-
spread use of patient-reported outcome tools
that m ay be translated to a u tility score is nec-
essary to address t he lack of cost-u tility a naly-
ses and value-b ased assessmen ts in adult spinal
deformity. An increased emphasis on measur-
ing and im proving value in spine care w ill re-
sult in improved outcomes and reduced costs
over time. Although we support an e ort to
redu ce variability in spine surgery th rough an
eviden ce-based app roach to care, we also rec-
ognize th at care is not m onolithic, and patient
and physician preference must be considered
to obtain optimal outcomes.
! Chapter Summary
Surgical treatm ent of adult spinal deform ity is
a high-cost intervention that consistently draws
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Measuring Outcom e and Value in Adult Deformity Surgery 103
the attention of the lay press and the me dical
pro fessio n due to a perceived lack of e ect . In
the evolving health care economy, dem onstra-
tion of value, through cost data coupled with
pat ient-re por ted ou tcom es , w ill be cr it ica l in
m aintaining patient access to care. To best p ro-tect our patients’ ability to receive care that
can e ect change in the ir health stat us, it is
imperative for spinal surgeons to understand
and collect patient reported outcomes. Surgi-
cal treatment of adult spinal deformity has
been sh ow n to have a signi cant e ect on pa-
tient-reported outcomes. Although the initial
cost of spinal deformity surgery is high, the
cost pe r QALY decreases w ith increasing d ura -
bilit y of the intervent ion. Thu s, it is imperat ive
that we as a profession continue to track and
report secondary interventions and compli-
cations of care, so that optimal intervention
strategies can be created. Determination of
appropriate quality metrics and process mea-
sures for the delivery of spine care can help
achieve improved patient outcom es and poten-
tially lower cost, thus maximizing societal re-
tu rn on investm ent for the care of adult spinal
deformity.
Pearls
In a value-based health care econom y, m easures
of cost an d clinical outcome are importan t t o de -
ne cost-e ective inter vent ions.
Patient-centered measures of outcomes provide
the most useful assessme nt of value of inte rven-
tions in deformity surgery.
Utility scores are a useful measure of general
health status preference that has a de nable unit
of well-years of life/year.
Cost pe r QALY is a measu re o f value th at is sensi-
tive to the m agnitude of the health status change
and t he durability of change.
Selection of disease-speci c, pat ient -reported out-
come should consider validated met rics that can
poten tially be co nver ted to a utility score.
Pitfalls
Sole focus on quality metrics and process mea-
sures creates a dissociation bet ween intervent ions
and pat ient-centered outcomes.
Optimizing qualit y and p rocess metrics in the ab -
sence of patient-centered information may in-
correctly guide evidence-based care, and provide
incen tives for inappropriate care.
Cost-minimization strategies or focus on cost
without regard to e ect of treatment on patient
reporte d ou tcome s will not b e a value-optimizing
strategy.
References
Five Must -Read Referen ces
1. Brazier J, Roberts J, Deverill M. The estimation of a
pre fer en ce-ba se d m ea su re of hea lth fro m the SF-36 .
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ford DS. Stu dies in th e m odi ed Scoliosis Resear ch
Society Outcomes Instrument in adults: validation,
reliability, and discriminator y capacity. Spine 2003;
28:2164–2169, discussion 2169 PubMed
3. Bridwell KH, Berven S, Glassman S, et al. Is the SRS-
22 instru m ent resp onsive to change in adult scoliosis
pat ients having prim ar y sp inal deform it y su rgery?
Spine 2007;32:2220–2225 PubMed
4. Bridwell KH, Cats-Baril W, Harrast J, et al. The valid-
ity of the SRS-22 instr um ent in an adult spinal defor-
mity population compared with the Oswestry and
SF-12: a study of response distribution, concurrent
validity, internal consistency, and reliability. Spine
2005;30:455–461 PubMed
5. Brazier JE, Rober ts J. The estim ation of a prefere nce-
ba se d m ea su re of hea lth from the SF-12 . Med Care
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6. Carr eon LY, Glassm an SD, McDono ugh CM, Ram per -
sau d R, Ber ven S, Sha inline M. Pred icting SF-6D ut i-
lity scores from the Oswestry disability index and
numeric rating scales for back and leg pain. Spine
2009;34:2085–2089 PubMed
7. Unite d Stat es Bone a nd Joint Init iative. The Burd en of
Musculoskeletal Diseases in the United States, 2nd
ed. Rosem ont , IL: Amer ican Academ y of Orth opaed ic
Surgeons; 20 11
8. Everet t CR, Patel RK. A system atic literat ure review of
nonsurgical treatment in adult scoliosis. Spine
2007;32(19 , Supp l):S130–S134 PubMed
9. Sm ith JS, Sha rey CI, Ber ven S, et al; Spinal Defor-
mity Study Group. Improvement of back pain with
operative and n onoperative treatm ent in adults with
scoliosis. Neurosurgery 2009;65:86–93, discussion
93–94 PubMed
10. Li G, Passias P, Kozanek M, et a l. Adu lt sco liosis in pa -
tient s over sixty- ve years of age: outcomes of oper-
ative versus nonoperative treatment at a minimum
two-year follow-up. Spine 2009;34 :2165–2170 PubMed
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104 Chapte r 8
11 . Smith JS, Sha rey CI, Ber ven S, et al; Spinal Defor-
mity Study Group. Operative versus nonoperative
treatm ent of leg pain in adu lts with scoliosis: a ret-
rospective review of a pr ospective m ulticenter da-
tabase with two-year follow-up. Spine 2009;34:
1693–1698 PubMed
12. Bridw ell KH, Glassm an S, Horton W, et al. Does
treatment (nonoperative and operative) improve
the two-year quality of life in patients with adult
symptomatic lumbar scoliosis: a prospective multi-
center evidence-based medicine study. Spine 2009;
34:2171–2178 PubMed
13 . You ssef JA, Orndo r DO, Patt y CA, et al. Cur rent st a-
tus of adult spinal deformity. Global Spine J 2013;
3:51–62 PubMed
14 . Yad la S, Malt en fort MG, Ratli JK, Har rop JS. Adu lt
scoliosis surgery outcomes: a systematic review.
Neu ro su rg Focu s 2 01 0; 28 :E3 PubMed
15. Cran dall DG, Revella J. Tran sforam inal lum bar inte r-
body fu sio n ver su s a nte r ior lum ba r in te rb od y fu sio n
as an adjunct to posterior instrum ented correction
of degenerative lumbar scoliosis: three year clinical
and radiographic outcomes. Spine 2009;34:2126–
2133 PubMed
16. Mundis GM, Akbarnia BA, Phillips FM. Adult defor-
mit y correction th rough m inimally invasive lateral
approach techniques. Spine 2010;35(26, Suppl):
S312–S321 PubMed
17 . Pate de r DB, Keba ish KM, Cascio BM, Neubaeur P, Ma-
tusz DM, Kostuik JP. Posterior only versus combined
anterior and posterior approaches to lumbar scolio-
sis in adults: a r adiographic analysis. Spine 200 7;32:
1551–1554 PubMed
18 . Cho K-J, Bridw ell KH, Len ke LG, Ber ra A, Bald us C.
Comparison of Smith-Petersen versus pedicle sub-
tract ion osteotom y for the correction of xed sagittal
imbalance. Spine 2005;30:2030–2037, discussion
2038 PubMed
19 . Suk S- I, Chun g E-R, Kim J-H, Kim S-S, Lee J-S, Choi
W-K. Posterior ver tebral column resection for severe
rigid scoliosis. Spine 2005;30: 1682–16 87 PubMed
20 . Papadopoulos EC, Boach ie-Adjei O, Hess WF, et al;
Found ation of Orthop edics and Comp lex Spine, New
York, NY. Early out com es an d com plication s of post e-
rior vertebr al colum n rese ction. Spine J 2013 Apr 2 5.
[Epub ah ead of print] PubMed
21 . Cha rosky S, Guigu i P, Blam ou tie r A, Roussou ly P, Cho -
pin D; Stu dy Group on Scolio sis . Com plica t ion s an d
risk factors of prima ry adu lt scoliosis surgery: a m ul-
ticenter study of 306 patients. Spine 2012;37:693–
70 0 PubMed
22 . Sansu r CA, Sm ith JS, Coe JD, et a l. Scoliosis r ese arch
society morbidity and mortality of adult scoliosis
surger y. Spine 2011;36 :E593–E597 PubMed
23 . Transfeld t EE, Topp R, Mehb od AA, Win te r RB. Surgi-
cal outcom es of decom pression, decomp ression with
limited fusion, and decompression with full curve
fusion for degene rative scoliosis with radiculopathy.
Spine 2010;35:1872–1875 PubMed
24. Bur ne ikien e S, Nelson EL, Mason A, Rajpal S, Serx-
ne r B, Villavicencio AT. Com plication s in p atien ts u n-
dergoing combined transforaminal lum bar interbody
fusion and posterior instrumentation with defor-
m ity correction for degen erative scoliosis and spinal
stenosis. Surg Neurol Int 201 2;3:25 PubMed
25. Than KD, Wang AC, Rahman SU, et al. Complication
avoidance and m anagemen t in anterior lum bar inter-
body fusion . Neurosu rg Focu s 2011; 31 :E6 PubMed
26 . McDonn ell MF, Glassm an SD, Dima r JR II, Pun o RM,
Johnson JR. Perioperative complications of a nter ior
pro cedu re s on the sp ine. J Bone Join t Sur g Am 19 96 ;
78:839–847 PubMed
27 . Isaacs RE, Hyde J, Goodr ich JA, Rodge rs WB, Phil-
lips FM. A prospect ive, nonran dom ized, multicenter
evaluation of extrem e lateral inte rbody fusion for the
treat m ent of adult degene rative scoliosis: periopera-
tive outcomes an d comp lications. Spine 2010 ;35(26,
Suppl):S322–S330 PubMed
28 . Sche er JK, Tang JA, Sm ith JS, et a l; Inte rn at iona l Spin e
Study Group. Reoperation rates and impact on out-
come in a large, prospective, multicenter, adult spi-
nal d eform ity dat abase: clinical article. J Neurosurg
Spine 2013;19:464–470 PubMed
29 . Pichelm an n MA, Len ke LG, Bridwe ll KH, Good CR,
O’Lear y PT, Sides BA. Revision rat es following p rim ar y
adult spinal deformity surgery: six hundred forty-
three consecutive patients followed-up to twenty-
two years postoperative. Spine 2010;35:219–226
PubMed
30 . Kelly MP, Len ke LG, Bridw ell KH, Agar wal R, Godzik J,
Koester L. Fate of the adult revision spinal deformity
pat ient: a sin gle in st it u t ion experience. Spin e 20 13 ;
38:E1196–E1200 PubMed
31. Acosta FL Jr, McClendon J Jr, O’Shaughnessy BA, et al.
Morbidity and mor tality after spinal deform ity sur-
gery in patients 75 years and older: complications
and predictive factors. J Neurosurg Spine 2011;15:
667–674 PubMed
32. Fairb an k JC, Pynse nt PB. The Oswes tr y Disabilit y
Index. Spine 2000;25:2940 –2952, discussion 2952
PubMed
33. Bagó J, Pér ez- Gru eso FJS, Les E, Her nán de z P, Pel-
lisé F. Minimal impor tan t di eren ces of the SRS-22
Patient Questionnaire following surgical treatment
of idiopathic scoliosis. Eur Spine J 2009;18:1898–
1904 PubMed
34 . Wu C-H, Wong C-B, Chen L-H, Niu C-C, Tsai T-T, Chen
W-J. Instrumented posterior lumbar interbody fu-
sion for pat ients w ith degen erative lumba r scoliosis.
J Spinal Disord Tech 2008;21:310–315 PubMed
35. Zimm er m an RM, Moham ed AS, Skolasky RL, Robin-
son MD, Kebaish KM. Fun ction al outcom es an d com -
p licat ions after pr im ary sp inal s urge r y for scoliosis
in adults aged forty years or older: a prospective
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Measuring Outcom e and Value in Adult Deformity Surgery 105
study with minimum two-year follow-up. Spine 2010;
35:1861–1866 PubMed
36 . Tsai T-H, Huang T-Y, Lieu A-S, et al. Funct ional o ut -
come analysis: instrum ented posterior lum bar inter-
bo dy fu sio n for degen er at ive lum ba r sco liosis . Act a
Neu ro ch ir (Wien) 201 1; 15 3: 54 7– 55 5 PubMed
37. Good CR, Lenke LG, Bridwell KH, et al. Can posteri-
or-only surgery provide similar radiographic and
clinical results as combined anterior (thoracotomy/
thoracoabdominal)/posterior approaches for adult
scoliosis? Spine 2010;35 :210–21 8 PubMed
38. McCar th y IM, Hostin RA, Am es CP, et a l; Int er na -
tional Spine Study Group. Total hospital costs of
surgical treatment for adult spinal deformity: an
extended follow-up study. Spine J 2014;14:2326–
2333 PubMed
39. McCarthy IM, Hostin RA, O’Brien MF, et al; Interna-
tional Spine Study Group. Analysis of the direct cost
of surgery for four diagnostic categories of adult spi-
nal deform ity. Spine J 2013;13:1843– 1848 PubMed
40. Indr aka nt i SS, Web er MH, Takem oto SK, Hu SS,
Polly D, Berven SH. Value-based care in the man-
agemen t of spinal disorders: a systemat ic review of
cost-u tility an alysis. Clin Ort hop Relat Res 2012 ;47 0:
1106–1123 PubMed
41. Kep ler CK, Wilk ins on SM, Radcli KE, et a l. Cost -
utility analysis in sp ine care: a systematic review.
Spine J 2012;12:676–6 90 PubMed
42 . Glassm an SD, Car reon LY, Sha rey CI, et a l. The cost s
and bene ts of nonoperative managem ent for adult
scoliosis. Spine 2010;35 :578–582 PubMed
43. Irw in ZN, Hilibra nd A, Gust avel M, et a l. Var iation in
surgical decision m aking for de generat ive spinal dis-
orders. Part I: lumbar spine. Spine 2005;30:2208–
2213 PubMed
44 . Sand er s JO, Haynes R, Light er D, et al. Var iation in
care among spinal deformity surgeons: results of a
survey of the Shriners hospitals for children. Spine
2007;32:1444–1449 PubMed
45. Deyo RA, Mirza SK. Tren ds a nd variation s in th e u se
of spine surger y. Clin Orthop Relat Res 200 6;443:1 39–
14 6 PubMed
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! Introduction
Proxim al junct ional kyph osis (PJK) was rst
de ned and characterized in the literature by
Glattes and colleagues.1 These authors pre-
sented a retr ospective series of 81 adult defor-
m ity patients and de ned abn orm al PJK using
two criteria: (1) proximal junctional sagittal
Cobb angle " 10 degrees ( Fig. 9 .1) and (2) post-
operative proximal junctional sagittal Cobbangle at least 10 degrees greater than the pre-
operative m easuremen t. They reported an in-
cidence o f PJK of 26%,1 and have been supported
by su bsequ ent st udies re por ting ra tes of PJK
ran ging from 17 t o 61.7%.2,3 Although PJK is
generally asymptomatic, there is a subset of
pat ients (1.4–4%) w ho present w ith symptom s
requiring furt her surger y.4,5
Risk factors for the development of PJK in-
clude advanced age, surgical app roach, greater
rigidity of construct, greater magnitude of
sagitt al correction, the p resence of preexisting
proxim al kyp hosis, dam age to the pos ter ior
ligamentous complex, damage to the adjacent
facet when instrumenting the upper instru-
m en ted ver tebra (UIV), xation to th e ilium ,
type of instrumentation (hooks versus pedicle
screws), and the presence of osteoporosis.1,2,6
Given t he large num ber of iden ti ed risk fac-
tor s, the et iology of PJK is most likely mu ltifac-
tor ial in nat ure . Noneth eless, advanced age is afactor that seem s to be u niform across the m a-
jorit y of st udies. In a ddit ion, th e curre nt litera-
tur e suggests that PJK m ay be m ore prevalent
than the rates initially reporte d 20 years ago.
This chapter synthesizes our current un-
derstanding of PJK in adults by reviewing the
literatu re u nde rlying the various etiologies of
PJK, discussing the impact of PJK on clinical
outcome s, exam ining the risk factors th at lead
to revision surgery due to PJK, providing con-
sensus exper t opinion on possible m ethod s for
minimizing PJK development, and describingindications for surgical treat m ent .
! Etiology and Risk Factors
for Proximal Junctional
Kyphosis
The etiology of PJK is m ultifactorial an d can b e
divided into surgical, radiograph ic, and p atient -related factors. These are sum m arized in Table
9.1. We w ill closely exam ine the literat ure ab out
these various causes.
Surgical Factors
Disruption of the Posterior Soft Tissues
In t he ir classic pap er, Panjabi and W hite 7 high-
lighted the role of the posterior spinal liga-
m ent s in prevent ing excessive motion betw eenthe vertebrae. Given these ligaments’ role as a
stabilizer in th e spine, the disrup tion of poste-
9
Junctional Issues Follow ing AdultDeformity Surgery
Han Jo Kim, Sravisht Iyer, and Christopher I. Sha rey, Sr.
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Junc tional Issues Following Adult Deformity Surgery 107
rior soft tissues has always been viewed as a
potential contribu tor to the develop m en t of PJK.
The relative contribution of the posterior
soft tissues has been examined in a cadaveric
model.8 The authors of this study performed
one of several procedures on m otion segmen ts
obtained from six hum an cadavers. These pro -
cedures included bilateral transverse h ook site
preparat ion, sublam inar h ook site p re par at ion,
pedicle screw placem ent , supra- an d in tersp i-
nous ligamen t t ransection, and tran section of all
poster ior st ructures. Follow ing these inte rven -
tions, the auth ors measured the torque need ed
to produce 2.8 degrees of angular displace-
men t, and, based on th is measuremen t, calcu-
lated the total exion sti ness of the motion
Fig. 9.1a,b The proximal junct ional sagitt al Cobb
measurem ent (proximal junct ional angle). This is
de ned as the Cobb angle between the inferior end
plat e of the upper instrum en ted vert ebra and the
superior end plate of the vertebra two levels above.
(a) Postoperative radiograph. (b) Radiograph at
6 months t hat m eet s both criteria of proximal
junctional kyphosis (PJK): proximal junct ional angle
> 10 degrees and a progression of the proximal
junctional angle > 10 deg rees.
a b
Table 9.1 A Summ ary of Various Risk Factors for PJK Proposed in the Literature
Surgical Radiographic Patient-Specif c
• Disruption of poste rior soft tissues• Rigidity of instrume ntat ion
• Combined ante rior-posterior approach/fusion
• Upper instrumented vertebrae in the upperthoracic spine
• Fusion to the sacrum• Degree of correction
% Increased lumbar lordosis% High SVA corre ct ion
% Failure to respect global sagit ta lalignment
• Increased preoperative thoracickyphosis
• Increased preope rative proximal
junctional angle
• Advanced age
• High BMI• Osteoporosis
Abbreviations: BMI, body mass index; SVA, sagit tal vertical axis.
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108 Chapte r 9
segment . Their data showed that sectioning the
supra- and int erspinous ligamen ts led to a sig-
ni cant ( p = 0.02) loss of exion sti ne ss. They
found that the posterior ligamentous complex
contributed 6.59% to the sti ness of the m o-
tion segmen t and that the sti ness loss couldroughly double (12.62%) w ith t he exposure re-
quired for placement of instrum entation at th e
same motion segment .
Similarly, a biom echanical mo del developed
by Cam m ar at a et a l6 showed th at complete fac-
etectomy and posterior ligament resection both
independently increased the proximal junc-
tional kyphotic angle; com bining th e tw o pro-
cedures resulted in an even greater increase in
th e kyphot ic angle.
Denis et al9 present ed a series of 67 patient s
with Scheuermann’s kyphosis treated with an
instru m ente d fusion. They highlighted t he im -
por tance of the posterior ligam entou s st ruc-
tu res in their series. They separate d th eir cohor t
of patients w ith PJK into a group w here the fu-
sion stopped short of the proximal end verte-
bra as well as a grou p w here the proxim al end
vertebra w as include d in t he fusion. The latte r
group had three patients who developed PJK.
All thre e wer e noted t o have disrup tion of the ju nct ional ligam entum avum w ith su blam i-
nar hooks or sublaminar wires. In all, the au-
thors noted that disruption of the posterior
ligaments was implicated in 25%(5/20) cases
of PJK obser ved in th eir se ries.
Although the above ndings all hint at the
importan ce of the p osterior structures, the tru e
impact of posterior dissection has been di cult
to isolate in clinical studies. Although all sur-
geons would agree that disruption of the m us-
cular, ligamen tous, and bony t issue likely occurs
cephalad to th e UIV, the degree of disruption is
di cult to quant ify, let alone standa rdize.2 De-
spite this limitation, the spinal reconstructive
community generally agrees that damage to
the posterior soft tissues likely contributes to
th e d evelopm en t of PJK.2
Rigidity of Instrumentation
In addition to the posterior soft tissues, nu-merous investigators have commented on the
rigidity of instrum ent ation as a risk factor for
development of PJK. This has been a focus in
the eld, par ticularly in light of the m ore rigid,
all-pedicle screw constructs that have gained
in popularity over the p ast tw o decades.
The biomechanical study by Cammarata et
al6 described in the prior section nicely high-lights t he impact of increasing construct rigid-
ity on t he proxim al junct ional angle. Similarly,
Thaw rani et al10 used a porcine cadaver model
to show that transverse process hooks pro-
vided decreased sti ness compare d with an all
pedicle screw con st ruct . In t he a ll pe dicle screw
group, the majority of the motion occurred
at t he m otion segmen t im med iately proxima l
to th e UIV, wherea s this tran sition w as m ore
gradual in the t ransverse process group.
However, clinical stu dies h ave not clearly af-
rm ed the nd ings of the above biomechan ical
studies.5,11,12 Y.J. Kim et al 12 found th at the use
of all pedicle screw construct s wa s associated
with an increased rate of PJK compared with
hybrid or hook constructs ( p = 0.04), but this
di erence did not rem ain signi cant when ad-
ju st ing for age ( p = 0.33). Similarly, other pub-
lished series of adult scoliosis patients have
not demonstrated that all pedicle screw con-
stru cts were m ore likely to be associated w ithPJK tha n w ere hybrid screw–hook constr ucts.5
Hassanzad eh an d colleagues11 published a series
of 47 consecutive adult patients with 2-year
follow-up who underwent long spinal fusion
w ith h ooks or screw s at t he UIV. They found
no instances of PJK in the 20 patients treated
w ith a hook at t he UIV compare d w ith a 29.6%
(8/27 patients) rate of PJK in the screws group
( p = 0.01).
Surgical Approach
Som e t ypes of surgical approach h ave also been
associated w ith PJK. Y.J. Kim an d colleagu es12
found that a com bined anterior and posterior
approa ch was a risk factor for developmen t of
PJK, even w hen adjusted for age ( p = 0.04). This
nding has been consistently shown to be th e
case in othe r ser ies as well.13,14 In a ret rospec-
tive series of 249 patients (adults and adoles-
cents) who underwent surgery for idiopathicscolios is, H.J. Kim et al14 performed a m ultivar-
iate analysis to identify risk factors for the de-
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Junc tional Issues Following Adult Deformity Surgery 109
velopm ent of PJK. They found that patient s w ho
underwent an anterior-posterior approach were
th ree tim es as likely (odds rat io [OR], 3.04; 95%
con den ce int er val [CI], 1.56–5.93) to develop
PJK compared with individuals who under-
wen t posterior-on ly fusion. Additionally, a com - bined anter ior and p osterior approach was one
of the few factors that could be consistently
identi ed as a risk in a system atic review of the
eld.2
Upper Instrume nte d Vertebrae
The cont ribut ion of the UIV to th e development
of PJK was suggested in the initial description
of the phenomenon. Glattes and colleagues1
foun d a signi cant ly higher level of PJK w he n
the instr um ent ation stopped at T3 (53%) when
comp ared w ith T4 (12.5%) ( p = 0.02). A subse-
quent larger series from the same institution
did show that an upper thoracic UIV (T2–6)
demonstrated a higher prevalence of PJK
(33.67%, 33/9 8) compa red w ith lower t horacic
and upp er lum bar UIV ( p = 0.036). 12 However,
this di erence did not rem ain signi cant wh en
adjusting for age ( p = 0.65). 12 The UIV, along
with a combined anterior-posterior approach,was only one of two independent risk factors
associated with the development of PJK in a
series of 249 pat ients.14
Bridw ell et al15 found that p atients w ith more
advanced PJK (PJK " 20 degrees) were more
likely to have a lower n um ber of levels fused (8
versus 11) and were more likely to have a UIV
in the lower thoracic spine ( p < 0.001). Ha et
al16 examined the di eren ce betw een a UIV in
the lower and upper thoracic spine an d found
that the mechanism of failure was di erent
bet ween the two scenarios . Failu re occu rre d
sooner ( p < 0.01) and was more likely to occur
due to fracture in the lower thoracic spine,
whereas subluxation was more prevalent in
the upper thoracic spine.
Other series, however, failed to identify the
UIV as a risk facto r for d evelopm en t o f PJK.5,17 A
systematic review found low-level evidence
that the UIV was am ong th e r isk factors associ-
ated w ith t he developm ent of PJK.2
The m echanism of how th e UIV m ight con-
tribute to the development of PJK is incom-
plete ly understood. Pro posed theor ies inclu de
both dam age to the adjacent facet join t that can
occur more easily in th e up per t horacic spine18
as well as the interface between the mobile
cervical and relat ively stat ic th oracic spine.1
Instrumentation to the Sacrum/Ilium
In cases of adult scoliosis, extension of the
fusion to the sacropelvis and the subsequent
increase in sti ness of the constru ct has been
thought to contribute to the development of
PJK. In th eir ser ies o f adult pat ien ts , Y.J. Kim
and colleagues12 found a higher rate of PJK in
pat ients w hose low er inst rum ented verteb ra
(LIV) was S1 compared with patients with an
LIV of L5 or above (51 %vs 3 0%, p = 0.009). This
remained a strong trend ( p = 0.059) even afte r
adju stin g for age. Yagi et al5 observed a sim ilar
tren d; in their series, fusion to the sacrum was
associated w ith a signi cantly higher incidence
of PJK (an increase of 27.6%, p = 0.02). A more
recent clinical series also found that patients
w ith PJK requ iring revision wer e m ore likely to
have fusions exten ding to the pelvis (74% vs
91%, p = 0.02). 19 Fusion to the sacru m was also
associated with an increased risk of progres-sion of PJK to greate r th an 2 0 degrees.15
Magnitude of Correction
More recently, as we have begun to un dersta nd
the import ance of global sagittal alignm ent , in-
vestigators have sought to dete rm ine if param -
eters of sagittal alignment correlate with the
incidence of PJK. In gene ral, stud ies have foun d
that an increase in sagittal balance correction
and an increase in lumbar lordosis correlate
w ith th e developm en t of PJK.5,17,19,20 The m ech-
anism underlying this increased rate of PJK is
un know n. In t he ir retrospect ive ser ies, H.J. Kim
et al19 found that patients requiring revision
sur gery for PJK ha d a lum bar lordo sis (LL) th at
was closer to t he p elvic inciden ce (PI), w he reas
th ose w ithou t PJK had a LL m uch lower t han PI.
Their ndings are sim ilar to those of Maruo
and colleagues,17 who showed that increasing
LL more than 30 degrees was associated witha signi cant ly higher incidence of PJK (58% vs
28%, p = 0.003).
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110 Chapte r 9
Similarly, patients requiring revision surgery
with PJK had a lower postoperative sagittal
vertical axis (SVA) (0.8 vs 4.1 cm) and a higher
m agnitu de of SVA correct ion (9 vs 4 cm ) com-
pared w ith those w ithou t PJK.19 These nd ings
are gen erally in keep ing with th ose of Yagi andcolleagues,5 w ho saw th at a SVA correct ion
greate r th an 5 cm led to a 5 0%inciden ce of PJK
( p = 0.01). Anoth er ser ies of 54 pat ients d em on-
strat ed th at t he risk of PJK decreases by 30 %for
every centimeter increase in the C7-plumb-
line.20 In the same series, the C7-plumbline
had ret urn ed closer to its preoperat ive position
in all pat ient s by na l follow -up (average 2.23
years).
The interplay betw een th oracic kyphosis and
lumb ar lordosis, that is, the global sagitt al align-
ment (GSA), is also becoming an increasingly
import ant concept in u nde rstand ing PJK. In t he
same study where they looked at sagittal cor-
rec tion , Yagi and colleagues5 showed that a
non ideal postop erat ive GSA (th oracic kyph osis
[TK] + LL + PI > 45°) led to a 7 0%r ate of PJK ( p <
0.001). Maruo et al17 also showed that ideal
global sagittal alignm ent protected against t he
development of PJK. The importance of spinal
balance is also high ligh te d by Mendoza- Lat tesand colleagues,20 who found that the di erence
be tween TK and LL was inversely pro por t ional
to t he risk of developing PJK.
Taken together, these studies add to our
growing understanding of global sagittal bal-
ance. They suggest that the goal of restoring
th e SVA to 0 cm m ay not be opt ima l for all pa-
tient s. Inde ed, studies of asymptom atic volun-
teers h ave consistent ly shown increased age to
be corre lat ed w ith great er SVA.21,22 They also
highlight the need for further studies to es-
tablish the optimal spinopelvic parameters
for surgeons to target (i.e., to understand the
di eren ce bet we en LL + 9° and LL – 9°).19
Radiographic Factors
Preoperative Thoracic Kyphosis
High preoperative TK may predispose to PJK
in both adult and pediatric populations. Inthe adult population, Maruo and colleagues17
showed that preoperative TK greater than 30
degrees was a risk factor for developing PJK
(62% vs 29%, p = 0.002). Similarly, Mendoza-
Latt es and colleagues20 found th at patients with
PJK ha d a larger d i ere nce be twe en TK an d LL
at baseline ( p = 0.012). These patients also
prese nted w ith low er sacral slope and signs of pelvic ret roversio n.
Proximal Junctional Angle
Lee and colleagues ,23 one of the rst groups to
descr ibe PJK in pat ient s w ith idiopat hic scolio-
sis, found that a preoperative PJ angle greater
than 5 degrees was a risk factor for develop-
ment of subsequent junctional kyphosis. This
work h as been supp orted by Denis et al’s9 se -
ries of Scheuer m ann patient s. The large m ajor-
ity of cases of PJK obser ved in t hat ser ies were
noted w hen the p roximal extent of the fusion
did not include t he kyph otic proxim al end ver-
tebra. Maruo and colleagues17 were able to
demonstrate that a proximal junctional angle
(PJA) greate r t han 10 d egrees ( p = 0.016 ), in ad-
dit ion t o a PI > 55° ( p = 0.037), was a r isk factor
for t he developm en t o f PJK.17
Patient Factors
Patient -speci c factor s such as advanced age,
high body mass index (BMI), the presence of
osteoporosis, smoking, and the presence of
other comorbidities are always important to
consider prior to spine surgery. Not surpris-
ingly, m any of th ese factors have been linked to
th e developm en t of PJK. In t he adu lt liter atu re,
increasing age has been associated with the
incidence of PJK and PJK requiring revision in
num erous case series.1,2,15,19,24
Interestingly, the link between high BMI
and the development of PJK is less clear in the
literature. Bridwell et al15 were able to show
th at h igher BMI ( p = 0.015) and the presen ce of
a comorbidity ( p = 0.001) were associated w ith
th e developm en t of PJ angle > 20 degrees . How-
ever, other series from the same institution
have failed to show th e sam e link betw een high
BMI and PJK (de ned in th e trad itional m ann er
using 10 degrees as a cuto ).19,24
Given that a large proportion of PJK occurs
du e to fract ure at t he UIV,17 i t is not sur prising
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Junc tional Issues Following Adult Deformity Surgery 111
that osteoporosis plays a critical role in the
developm en t of PJK. In o ne series, osteop orotic
pat ients ove r the age of 65 w ho underwent a
m inimum ve-level fusion were found to have
pedicle and compression frac ture s at a rat e of
13%, w ith PJK occurr ing in 26%of pat ien ts .25 Ina small series of 10 adult patients, Watanabe
and colleagues26 found th at osteopenia and p re-
operative comorbidities were common among
pat ients w ith proxim al verteb ra l fra ct ure an d
subluxation. Case series in ad ult pat ients h ave
found that osteoporosis is m uch m ore preva-
lent in individuals with PJK than in those
without.24
! Timing of Proximal
Junctional Kyphosis
The m ajority of th e cases of PJK are ident i ed
w ithin the rst year postoperat ively.5,14 The
pat ients w ho do go on to develop PJK progress
to abou t on e ha lf (53%) of th eir tot al degree of
PJK by 3 months.5 Sim ilar ly, Y.J. Kim an d col-
leagues12
repor ted th at 59%of progression ofthe PJA occurs within the rst 8 weeks. Maruo
et al17 rep orted that 62%of cases with PJK were
ident i ed with in 8 weeks, w ith fractu re being
the m ost comm on cause.
! Clinical Outcomes Afte r
Proximal Junctional
Kyphosis
Clinical outcomes after PJK are summarized in
Table 9.2. In gener al, m ost stud ies have show n
that most cases of PJK are asymptomatic, and
that this condition does not substa nt ially alter
clinical outcome. There are, however, two re-
cent series th at do show that patient s with PJK
have increased p ain levels compared w ith those
pat ients w ithou t PJK.19,24 The di erence in pain
levels between the t wo groups met the m ini-m al clinically import ant di erence.24 The in-
cidence of symptom atic pain (i.e., upp er back
pain re por ted by the pat ient at follow-up) w as
also markedly higher in the group with PJK
(29 .4% vs 0.9%, p < 0.001). These more recent
results highlight the importance of furthering
our understanding of PJK; as we shall see in
the following sections, the early descriptionsof PJK as a rad iograph ic nd ing th at wa rra nt s
follow-up m ight be understating the t rue im-
pact of t he condit ion.
Investigators are now turning a closer eye
to t he concept of symp tom atic PJK to see h ow
these cases might impact clinical outcomes.
Yagi an d colleagu es5 found t hat th eir patients
w ith symptom atic PJK had a signi cantly higher
Oswestry Disability Index (ODI) score com-
pared w it h pat ien ts w it hou t PJK.5 Similarly,
H.J. Kim et al19 foun d lower ODI and pain score s
in patients with PJK and lower pain scores in
pat ients undergoing revis ion for PJK. Impor -
tantly, they found lower outcomes across all
domains of the Scoliosis Research Society (SRS)
questionn aire in patient s with PJK, though th ese
outcome s did not reach statistical signi cance.
! Revision Surgery forProximal Junctional
Kyphosis
The m ajority of cases of PJK are a symp tom atic
and d o not require inter vention. Repor ted rates
of revision d ue to PJK have ra nged from 1.4 to
11.2%w ith pain being the most comm on rea-
son for revision.4,19,27,28
Severe cases of PJK can lea d to signi can t
sagittal imb alance an d disability. In a sm all se-
ries of 10 patients, Watanabe et al26 reported
vertebral subluxation and severe neurologic
de cit in two of the ir 10 patient s as a result of
progressio n of PJK.
Hart et al28 reported on a case series from
the Invasive Species Specialist Group (ISSG) da-
tabase. Their de nition of proximal junct ional
failure (PJF) was “severe PJK,” which was furt he r
de ned as a change of more than 10 degrees of
kyphosis between the UIV and the vertebratwo levels above the UIV (UIV +2), along with
one or more of the following: fracture of the
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114 Chapte r 9
vert ebral bod y of UIV or UIV +1, post er ior os-
seoligamentous disruption, or pullout of in-
stru m ent ation at the UIV. In t heir ser ies, they
identi ed 57 patients from a series of 1,218
consecutive adult patients wh o met this de -
nition of PJF (4.68 %). Of th e 5 7 ca ses of PJF, 27(47.4%) un der wen t revision su rgery w ithin 6
m onth s of the ir index ope ration. Of the causes
of PJF, fract ure was t he m ost com m on (56%),
followe d by soft tissue failure (3 5%) an d screw
pullout (9%). Of the r isk factor s ident i ed for
revision surgery, a combined an ter ior/posterior
approach ( p = 0.001) an d h ighe r PJK angu lation
( p = 0.034) were found to be signi cant . Of th e
various modes of failure, only the presence
of traum atic mechan ism of failure, wh ich oc-
curred in six patients, was deemed to predis-
pose p at ients to a revis ion ( p = 0.019). A higher
SVA also tren ded towa rd be ing a signi cant
p redictor of re vision ( p = 0.090) along with
fem ale sex ( p = 0.066). The overall rate of revi-
sion su rgery w as 2.21%.
A similar st udy w as cond ucte d by Yagi and
colleagues4 as p art of the Comp lex Spine Study
Group. They utilized a consecutive series of
1,668 p atients t reated for adult spinal defor-
m ity and greater than ve levels of fusion.The ir series had longer follow-up (2 to 12 year,
m ean 4 .3 years), and they also focused on pa-
tient s older th an 50 at th e time of surgery. They
de ned PJF as PJK requ iring revision an d iden -
ti ed 23 p atien ts (1.4%). The large m ajority of
th ese 23 patien ts (17 patient s, 74%) had be en
revision surgery cases at the tim e of their long
segment fusion and all had received posterior
ped icle scr ew con st ruct s. Osteop enia w as prev-
alent (10/23, 43 %), but, inte rest ingly, non e of
these patients h ad osteoporosis. Sixteen patients
were revised for intolerable pain, another six
for a neurologic de cit, an d one for head pt osis.
The a uth ors found that a m ajority of these fail-
ures occurred early, with a mean time to PJF
(revision) of 10.5 ± 9.3 m onth s; 87%h ad be en
revised within 2 years of surgery. H.J. Kim et
al19 reported that a higher lum ber lordosis and
an increase d SVA correct ion ar e r isk factors for
revision due to PJK. They reported a revision
rate of 10 .7%.Moving forward, important work remains
to be d one regard ing our u nd erst an ding of PJF.
A classi cat ion system for PJK an d a clear de -
nition of PJF are needed before we progress
tow ard d e nin g the r isk factors for PJF. Add i-
tionally, the optimal magnitude of correction
also rem ains to be determ ined.
Preve nting Proximal Junctional
Kyphosis
To date, no de nitive m ethods have been de-
scribed to prevent PJK, although several ap-
proaches h ave bee n su ggested . Two studies h ave
repor ted on t echnical tricks to reduce the inci-
dence of PJK.11,29,30 Hassanzadeh et al 11 found
no insta nces of PJK in 20 patient s treate d w ith
a hook at the UIV compare d w ith a 29.6%(8/27
pat ien ts) rat e of PJK in pat ien ts w ho were
treated with a pedicle screw at the UIV ( p =
0.01). Additionally, they found that patients
w ith hooks had signi cantly higher funct ional
scores compared with those w ith screws ( p <
0.01). These data have not been replicated to
date.
Given that vertebral fractures represent a
com m on et iology for PJK an d PJF, invest igators
have also studied the impact of prophylactic
one- and two-level vertebroplasty above longfusions. Results rep orted include both biome-
chanical29 and clinical 30 data. In a biom echani-
cal mo del using 18 cad averic spines, Kebaish e t
al29 were able to show a signi cant redu ction
in vertebral compression fractures when two-
level vertebroplasty (UIV and UIV +1) was
comp ared w ith on e-level (UIV only) or no ver-
tebroplasty. A clinical series from the same
group followed 38 patien ts w ith tw o-level ver-
teb rop last y (UIV an d UIV +1) for 2 years .30 They
re por te d a low er r ate o f PJK or PJF (PJK 8%, PJF
5%, com bined 13%) th an previou sly published
rates. Their stu dy did n ot include a control co-
hor t (i.e., patients w ho h ad n ot received verte-
bro plast y), and did not sh ow any signi cant
di erences in clinical outcomes between the
group s w ith an d w ithou t PJK or PJF.
Fina lly, Yan ik et al31 reported on a series of
60 patient s treated for Scheuer m ann k yphosis.
To reduce th e sti ness of the proximal con-
struct, they studied the impact of leaving twoscrew t hreads out of the posterior cortex whe n
placin g pedicle screws at the UIV. They theo-
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Junc tional Issues Following Adult Deformity Surgery 115
rized that this would reduce the sti ness at the
proxim al aspect of t he con st ruct . At an ave rage
of 2-year follow-u p, they found that the screws
w ith thread s left out of the cortex ha d a lower
PJ angle (4.44 ± 1.55 d egrees vs 8.08 ± 2.96 de -
grees) when compared with standard pediclescrew insertion ( p = 0.001). This grou p also h ad
no cases of PJK, compared with a 17.2%(5/29,
p = 0.02) rate with the standard screw tech-
nique. Finally, they were also able to show an
improveme nt in the p hysical compon ent of the
Short Form 36 score in the group treated with
the modi ed screw insertion.
Revision Strategies
The approa ch to t he patient w ith PJK is sim ilar
to the app roach to th e patient w ith other sagit-
tal plane deform ities. Our indications for a re -
vision op erat ion are as follows:
1. Progressive deform ity
2. Pain th at has failed non operative measures
for man agem ent
3. Implant prominence with imminent skin
bre akdow n
4. Neurologic de cit or cord comp ression
The decision ab out th e UIV level selection is
based on several facto rs, bu t generally sp ea k-
ing, PJK cases w ith a UIV in t he lower th oracic
spine should be extended u p to the upper th o-
racic spine, and cases w ith a UIV in th e u ppe r
thoracic spine should be extended up to T1–2
or into th e cervical spine.
Osteotomies may also be necessary in the
treatm en t of PJK. Osteoto my selection is based
on th e r igidit y of PJK. Flexib le PJK (Fig. 9 .2) can
usually be treated without an osteotomy, or
with a posterior column only osteotomy (Fig.
9.2d), w herea s rigid d eform ities (Fig. 9 .3) may
necessitate a three-column osteotomy (i.e.,
pedicle su btract ion ost eot om y or vertebral
colum n resection) (Fig. 9.3c). Flexibility can be
assessed with hyperexten sion or supine radio-
graphs as well as the scout images on some
comput ed t om ography (CT) scans (as long as a
head support was not used du ring the scan).
For cases where a neurologic de cit orsymptomatic cord compression is present, a
vertebral column resection m ay be necessary
to decompress the kyphotic area where the
cord compression is likely to be present. Ana-
tomic realignment is essential to relieve the
cord compression.
The goal for the revision operation should
avoid the temptation for overcorrection; in-stead , the goal sho uld b e an SVA close to 4 to
5 cm. Overcorrection can lead to a recurrence
of PJK and necessitate ad ditional operat ions and
unn ecessary risk for pat ients.
! Chapter Summary
Proximal junct ional kyphosis is de ned u sing
two criteria: (1) proximal junctional sagittal
Cobb angle " 10 de grees, and (2) postoperative
proxim al junct ion al sagit tal Cobb angle at least
10 degrees greater than the p reoperative mea-
surement .1 PJK is gene rally an ea rly postop er -
ative phenomenon, and most cases typically
are recognized in the rst year after surgery.5,14
Rates of PJK reported in the literature range
from 17 t o 61 .7%.2,3
Proxim al junct ional kyph osis is likely multi-
factorial in origin. Risk factors for the devel-opment of PJK can be categorized as surgical,
radiographic, and patient-related factors. Ad-
vanced age appears to be the most important
pat ient-re late d r isk factor. Surgical r isk factor s
to consider include greater m agnitude of sag-
ittal correction, dam age to the adjacent facet
wh en instr um ent ing the UIV, dam age to the
posterior ligam entou s complex, a com bined
anter ior and posterior appr oach, xation to the
ilium, and certain t ypes of instr um ent ation. Of
the ab ove, the m agnitude of correction is par-
ticularly im por tan t, as an SVA of 0 cm m ay not
be op t im al for all pat ients.21,22 A higher post-
operative LL and an SVA correction of greater
than 5 cm have both been associated with th e
development of PJK.17,19 To date, no de nit ive
methods have been described to prevent PJK.
Some investigators have described technical
tr icks to red uce t he inciden ce of PJK.11,31
Patients with PJK are generally asymptom-
atic. However, recent stud ies have show n t hatthese patients may have increased pain levels
and worse functional outcome measures.19,24
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116 Chapte r 9
Fig. 9.2 a–d A pat ient present ing with PJK who was
treate d with extension of the posterior fusion and
posterior ost eotom ies only. (a) Late ral radiograph.
(b) Hyperextension view, clearly showing a exible
deformity. (c) Computed t omography (CT) scan.
(d) Preope rative (left) and postoperative (right)
standing radiographs.
a b
c d
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Junc tional Issues Following Adult Deformity Surgery 117
In the subset of patients who are symptom-
atic, pain is the m ost com mon complaint and
th e m ost com mon reason for revision. Repor ted
rates for revision for PJK range from 1.2 to
11.4%.4,19,27,28 Patien ts requ iring revision for PJK
are gene rally approache d similarly to patient s
with other sagittal plane deformities. Osteoto-
m ies may be necessary and are chosen based on
the rigidity of the PJK. When revising PJK, the
tem ptat ion for overcorrect ion should be avoided.
Fig. 9.3 a–c A pat ient with a rigid deformity.
(a) Preoperat ive image s of the proximal
kyphotic de formity. (b) CT scan and recum bent
lm show a solid fusion extending up to the
uppe r instrume nted vert ebra (UIV) with a rigid
deformity. This patient required a three-columnoste otomy to correct the PJK. (c) Pre- and
postrevision radiog raphs.
a
b c
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118 Chapte r 9
Pearls
The appropriate magnitude of correction and
global sagitt al alignme nt are critical to a chieving
successful outcomes and avoiding the develop-
me nt of PJK. An SVA of 4 cm is a reaso nab le go al,especially for those patient s over 60 years of age.
Proximal junct ional kyphosis is an early postoper-
ative ph enom enon, a nd m ost cases can t ypically
be observed with in 2 to 6 months post operatively.
Similarly, cases of junctional failure typically are
evident within the rst year.
When revising cases of PJK, it is crucial to con-
sider the rigidity of th e deform ity, as exible PJK
may be treated with instrumentation and fusion
only, witho ut an ost eoto my or poste rior column
osteot omies only.
Pitfalls
Careful att ent ion m ust be paid to global sagitt al
alignment; attempting to aggressively correct all
pa tients to an SVA of 0 cm has be en sho wn to
pre dispose patients to PJK. Althoug h no consen sus exists on prevent ing PJK,
surgeons must pay close attention to the integ-
rity of the posterior soft tissues and the rigidity
of the construct, and m ust select an appropriate
UIV. Failure to consider t hese factors may lead to
the developm ent of PJK.
Although most cases of PJK are asymptomatic,
these pat ient s may have increased pain and worse
functional scores. They must be followed regu-
larly to ensure stable kyphosis and acceptable
outcomes.
References
Five Must- Read Reference s
1 . Glatt es RC, Bridw ell KH, Len ke LG, Kim YJ, Rinella A,
Edwards C II. Proximal junctional kyphosis in adult
spinal deform ity following long instru m ente d poste-
rior spinal fusion: inciden ce, outcomes, and risk fac-
tor ana lysis. Spine 2005 ;30:1643 –1649 PubMed
2. Kim HJ, Len ke LG, Sha rey CI, Van Alst yn e EM, Skelly
AC. Proximal junct ional kyphosis as a distinct form
of adjacent segment pathology after spinal defor-
m ity surgery: a system atic review. Spine 201 2;37(22,
Suppl):S144–S164 PubMed
3 . Lee JH, Kim JU, Jan g JS, Lee SH. Analysis of t he inc i-
dence and risk factors for the progression of proxi-
m al junct ional kyphosis following surgical treat m ent
for lumbar degenerative kyphosis: minimu m 2-year
follow-u p. Br J Neurosu rg 2014 ;28:252 –258 PubMed
4. Yagi M, Rahm M, Gaines R, et a l; Comp lex Spin e
Study Group. Characterization and surgical outcomes
of proximal junctional failure in surgically treated
pat ien ts w ith ad ult sp inal de for m it y. Spin e 2 01 4; 39 :
E607–E614 PubMed
5. Yagi M, King AB, Boach ie-Adjei O. Incid en ce, risk
factors, and natural course of proximal junctional
kyphosis: surgical outcomes review of adult idiopa-
thic scoliosis. Minimum 5 years of follow-up. Spine
2012;37:1479–1489 PubMed
6. Cam m arat a M, Aub in CE, Wang X, Mac-Thion g JM.
Biomechanical risk factors for proximal junctional
kyphosis: a detailed numerical analysis of surgi-
cal instrum entat ion variables. Spine 20 14;39:E500–
E507 PubMed
7. Panjabi MM, White AA III. Basic biom echa nics of th e
spine. Neurosurgery 1980;7:76–93 PubMed
8 . Ande rso n AL, McI TE, Ash er MA, Bur ton DC, Glatte s
RC. The e ect of posterior th oracic spine an atom ical
structu res on mot ion segment exion sti ness. Spine
2009;34:441–446 PubMed
9. Denis F, Sun EC, Winter RB. Incide nce a nd risk factors
for proximal and distal junctional kyph osis following
surgical treatmen t for Scheuerm ann kyphosis: m ini-
m um ve-year follow-up. Spine 2009;34: E729–E734
PubMed
10 . Thaw rani DP, Glos DL, Coom bs MT, Bylski-Aust row
DI, Sturm PF. Transverse process hooks at upper in-
strumented vertebra provide more gradual motion
tran sition than p edicle screws. Spine 2014; 39:E826–
E832 PubMed
11. Hassanzadeh H, Gupta S, Jain A, El Dafrawy M, Sko-
lasky RL, Kebaish KM. Type of an chor at t he proxim al
fusion level has a signi cant e ect on the inciden ce
of proximal junctional kyphosis and outcome in
adults after long po sterior sp inal fusion. Spine Defor-
mity 2013;1:299–305
12 . Kim YJ, Bridw ell KH, Len ke LG, Glat te s CR, Rhim S,
Cheh G. Proximal junct ional kyphosis in adult spinal
deformity after segmental posterior spinal instru-
m entation and fusion: m inim um ve-year follow-up.
Spine 2008;33:2179–2184 PubMed
13 . Wan g J, Zhao Y, Shen B, Wang C, Li M. Risk fact or
analysis of proximal junctiona l kyphosis after poste-
rior fusion in patients with idiopathic scoliosis. In-
ju ry 201 0; 41 :4 15 –4 20 PubMed
14 . Kim HJ, Yagi M, Nyugen J, Cun nin gha m ME, Boach ie-
Adjei O. Com bined a nter ior-poster ior surger y is the
most important risk factor for developing proximal
junct ional kyphosis in id iop at h ic sco liosis . Clin Or-
thop Relat Res 2012;470 :1633–1 639 PubMed
15 . Bridwe ll KH, Len ke LG, Cho SK, et al. Proxim al ju nc-
tional kyphosis in pr imary adult deformity surgery:
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Junc tional Issues Following Adult Deformity Surgery 119
evaluation of 20 degrees as a critical angle. Neuro-
surgery 2013;72:899–906 PubMed
16 . Ha Y, Maru o K, Racin e L, et al. Proxim al jun ct ional
kyphosis and clinical outcom es in adult spinal defor-
mity surgery with fusion from the thoracic spine
to the sacrum : a comp arison of proximal and distal
upper instrumented vertebrae. J Neurosurg Spine
2013;19:360–369 PubMed
17. Maru o K, Ha Y, Inou e S, et al. Predictive facto rs for
proxim al junct ion al ky ph os is in lon g fu sio ns to the
sacrum in adult spinal deformity. Spine 2013;38:
E1469–E1476 PubMed
18. Helgeson MD, Shah SA, Newt on PO, et al; Harm s
Stud y Group. Evaluation of pr oxim al junct ional ky-
phos is in ad ole sce nt id iop at h ic sco liosis follow ing
pe dicle screw , hook, or hybrid in st rum en tat ion . Spine
2010;35:177–181 PubMed
19 . Kim HJ, Brid we ll KH, Len ke LG, et a l. Patien ts w ith
proxim al junct ional kyp hos is r equ ir ing revision su r-
gery have higher postoperative lumbar lordosis and
larger sagittal balance corrections. Spine 2014;39:
E576–E580 PubMed
20 . Mend oza- Lat tes S, Ries Z, Gao Y, Weinste in SL. Proxi-
mal junctional kyphosis in adult reconstructive
spine surgery results from incomplete restoration
of the lumbar lordosis relative to the magnitude of
the thoracic kyphosis. Iowa Orthop J 2011;31:199–
20 6 PubMed
21 . Vedan ta m R, Len ke LG, Kee ne y JA, Brid we ll KH. Com -
par iso n of st an ding sagit tal sp inal al ign m en t in as -
ymptom atic adolescents and adults. Spine 1998;23:
211–215 PubMed
22. Gelb DE, Lenke LG, Bridwell KH, Blanke K, McEnery
KW. An analysis of sagittal spinal alignment in 100
asymptomatic middle and older aged volunteers.
Spine 1995;20:1351–1358 PubMed
23 . Lee GA, Bet z RR, Clem en ts DH III, Huss GK. Proxim al
kyphosis after posterior spinal fusion in patients w ith
idiopathic scoliosis. Spine 1999;24 :795–79 9 PubMed
24. Kim HJ, Bridwe ll KH, Len ke LG, et al. Proxim al ju nc-
tional kyph osis results in inferior SRS pain subscores
in adult deformity patients. Spine 2013;38:896–901
PubMed
25. DeWald CJ, Stanley T. Instrumentation-related com-
plica t ion s of m ult ilevel fu sio ns for ad ult spinal d efor-
mity patients over age 65: surgical considerations
and treatment options in patients with poor bone
quality. Spine 2006;31(19 , Supp l):S144– S151 PubMed
26. Wata na be K, Len ke LG, Brid we ll KH, Kim YJ, Koest er
L, Hensley M. Proximal junctional vertebral fracture
in adults after spinal deform ity surgery using ped icle
screw const ruct s: analysis of m orph ological featu res.
Spine 2010;35:138–145 PubMed
27. Ream es DL, Kasliw al MK, Smit h JS, Ham ilton DK,
Arlet V, Sha rey CI. Time to developm en t, clinical and
radiographic characteristics, and management of
proxim al junct ion al kyphos is follow ing a dult thor a-
colum bar instr um ente d fusion for spinal deformity. J
Spina l Disord Tech 2 014 PubMed
28. Hart R, McCar thy I, O’Brien M, et al. Iden ti cation o f
decision criteria for revision surgery am ong patient s
with proximal junctiona l failure after surgical treat-
ment of spinal deformity. Spine 2013;38:E1223–
E1227 PubMed
29. Kebaish KM, Martin CT, O’Brien JR, LaMotta IE, Voros
GD, Belko SM. Use of vert ebrop lasty to preven t
p roxim al junct ion al fr ac ture s in ad ult d eform it y su r-
gery: a biome chanical cadaveric study. Spine J 2013;
13:1897–1903 PubMed
30. Martin CT, Skolasky RL, Mohamed AS, Kebaish KM.
Preliminar y results of the e ect of proph ylactic ver-
tebroplasty on the incidence of proximal junctional
complications after poster ior spinal fusion to th e low
thor acic spine. Spine Deform ity 2013;1:1 32–138
31 . Yan ik HS, Kete nci IE, Polat A, et al. Prevent ion of
p roxim al junct ion al kyph os is a fter p oste rior s urger y
of Scheuermann kyphosis: An operative technique.
J Spinal Disord Tech 2014 Jul 29. [Epub ahead of
p rin t] PubMed
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! Introduction
The rst application of a metallic implant to
the human spine was reported by Hadra1 in
1891. Silver w ires were placed in th e t horacic
spine for treatment of a spinal fracture. The
most important historical event in spinal re-
construction surgery was the invention of the
Harrington instrumentation in the middle of
the 20th century.2 Paul Harrington developedthese spinal im plants, consisting of hooks and
rods m ade of stainless steel, for treat ment of se-
vere spinal deformity and fracture-dislocations
of the spine. Since the introduction of his de-
vice, surgeries to correct and stabilize the
spine with m etallic imp lants have undergone
dramatic development, and surgeries using
metallic implants to correct and stabilize the
dam aged spine became kn own as spinal instru-
m ent ation surgery. The Harrington instr um en-
tation surgery was m odi ed by his successors,
who added sublaminar wires, tapes, and pedi-
cle screws.3 Since 2000, pedicle screws and
rods have been widely used for spinal defor-
mity surgery due to their biomechanical su-
periorit y. Of the biom at erials used for sp inal
deform ity surgery, titanium alloys are th e m ost
pop ular m at erial at the prese n t t im e due to
their imp roved biocompatibility and because
they en tail fewer m etal-related art ifacts in mag-
netic resonance imaging (MRI).4 Historically,stainless steel and cobalt-chromium (Co-Cr)
were discovered much earlier than titanium
alloys (Table 10 .1). Spinal implants made of
stainless steel or Co- Cr are cur ren tly used for
pat ient s w it h r igid sp in al cu rves due to their
superior mechanical properties to titanium
alloys.
There is no consensu s on how t o select m e-
tallic m aterials for spinal deformity correction
today, and spine surgeons de pen d on th eir per-
sonal experience through t heir m edical career.This chapter discusses met allic spinal imp lants
and the biomechanics of the deformity cor-
rection of the spine. It is imperat ive th at pra c-
titioners be fam iliar w ith th ese topics, as they
are indispensable in providing patients with
safe and e ective spinal deform ity correction.
! Mechanical Properties
of Metals
Metals have a com m on patt ern of stress–strain
curve consisting of th e elastic deform ation zone
and the plastic deform ation zone. In t he elastic
deformation zone, the stress–strain relation-
ship is linear and th e m etal deform s in propor-
tion to the applied force (Fig. 10.1). After the
yield point, the stress–strain curve of metals
becom es non linea r. If increas ing force is applied
to a me tallic imp lant, the implant w ill reach th eultim ate strength and nally ruptu re or break.
10
Biomechanics and Material Sciencefor Deformity Correction
Manabu Ito , Yuichiro Abe, and Remel Alingalan Salming o
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Biom echanics and Mate rial Science for Deformity Correction 121
Although all meta ls follow th e sam e pat tern of
stress–strain relationship, the re are di eren ces
in their yield strength and ultimate strength
and t he slope of the stress–strain curve. Within
the elastic deform ation zone, met als are able
to retur n to th e original shape a fter the force
is removed. Once metals were over-bent to
th eir plastic deform ation zone, the m etal is notable to return to the original shape and p erm a-
nent deformation of metallic implants occurs.
If plastic deform ation of th e rod s occurs after
scoliosis corre ction , signi cant loss of correc-
tion may result, and the original purpose of
correcting the spinal deform ity would not be
ful lled. For this reason, it is important for
spine surgeons to know how much force is
put on the sp inal im plan ts during corre ct ion
pro cedure s and m echanica l re spon ses of the
m etallic implants t o the forces created by cor-
rection procedures.
The m etals curren tly used for spinal defor-
m ity surgery include stainless steel, pure tita-
nium, titanium alloys, and Co-Cr alloys. The
m echanical prope rt ies of each met al are shown
in Fig. 10.2 . Commercial pure titanium (cpTi)
has four grades based on its mechanical prop-
ert ies. Grade 1 h as th e h ighest value of elon-
gation at break, but it has the lowest tensile
strength. As the grade increases, the tensilestrengt h increases, and t he cap ability of elonga-
Table 10.1 History of Metallic Implants Used for
Spine Surge ry
Year Event
1890s Application of sliver wires for spinal
fractures1910s Development of stainless steel
1920s Development of cobalt-chromium
alloys (Vitallium® in 1932)
1940s Development of SUS316, 317 stainlesssteel (Harrington instrumentat ion)
1960s Development of titanium alloys(Grade 1–4: com me rcially pure
titanium, other titanium alloys:Ti-6Al-4V, Ti-6Al-7Nb,
Ti-6Al-2.5Fe, Ti-13Zr-13Ta, et c.)
Abbreviation: SUS, steel use stainless.
tion decreases. The tensile strength of Ti alloys
is m uch higher th an th at of pure titanium , but
the elongation capacity of Ti alloys is the low-
est am ong all the t ypes of titanium . Although
titanium rods are bent by surgeons during sur-
gery to the desired contour, the mechan ical sti -
ness of titan ium decreases signi cantly around
the bending points. Co-Cr shows the highest
tensile strength and relatively high break p oint
for elongation. This sti er m echanical proper ty
of Co-Cr is favored by sp ine su rgeon s for t reat -
m en t of rigid spina l deform ities. Sta inless steel
(grade, SUS316 L) is a litt le we aker in its t en sile
strength compared with Co-Cr, but it shows
m uch bet ter elongation dura bility. New stain-
less steel m aterials w ith higher ten sile strengt h
have been invente d re cently and w ill be avail-able for surger y very soon.
Fig. 10.1 The st ress–strain curve of a typical
struct ural me tal. Line A shows the apparent st ress
and line B shows the true stress. Point 1 shows the
ultimate strength, and point 2 shows the yield
strength . A material demonstrate s rupture at point
3. The area of linear relationship between the stress
and strain indicates the elastic deformation region
before point 2. After point 2, t he st ress increases
up to t he ultimat e te nsile strengt h (point 1) in
region 4. Beyond point 1 , a neck forms where thelocal cross-sectional area signi cant ly decreases
and t he m aterial becomes weaker in region 5.
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122 Chapte r 10
! Changes in Mechanical
Properties of Rods
After Manual Bending
(Table 10 .2)
Because t he m etallic rods supp lied by m edical
device companies for use during surgery are
straight, the surgeon needs to bend them by
hand to the desired contour just before per-
form ing the correction procedure. With regard
to the rods’ mechanical properties, the yield
strength of titanium alloy rods with a 5.5-mm
diameter decreases from 803.9 N to 324.0 N
(40.3%) after t hree -point ben ding by 20 d e-
grees.5 The yield strength of titanium alloy rods
w ith a 6.0-m m d iameter is reduced 54.1%after20-degree three-point bending. Co-Cr alloy
rods with a 6.0-m m diameter showed the sam e
tendency as the 6.0-mm titanium alloy rods,
w ith their yield signi cantly decreasing to 56.4%
after 20-degree three-point bending. If multi-
ple rod bending op erat ions were perform ed,
even the m echan ically sti est Co- Cr rods can
exhibit a signi cant reduction in their mechan-
ical prope rt ies. Spine sur geons should be aw are
of the reduction in mechanical properties of
each m etal to avoid m echanical failures of rods
Fig. 10.2 The relationship bet ween tensile strength
and elongation at t he break of each met al. There are
four grades for comm ercial pure titanium (cpTi),
with small di erences in mechanical prope rties.
Though titanium alloys show greater te nsile
strength than cpTi does, the break points of
titanium alloys under elongation are much lower
than those of cpTi. Sta inless steel shows the highest
capab ility for elongat ion and Co-Cr shows the
highest tensile st rength among all.
Table 1 0.2 Changes in Mechanical Properties After Rod Bending5
Yield Strength (N) No Bend
Bend Back
One Time
20-Degree
Bend
40-Degree
Bend
6.0-mm Ti rod 1,004 748 (74.5%) 544 (54.1%) 509 (50.6%)
6.0-mm Co-Cr rod 865 689 (79.6%) 488 (56.4%) 476 (55.0%)
Sti ness (N/m m)
6.0-mm Ti rod 160 151 (94.6%) 143 (89.2%) 120 (74.9%) 6.0-mm Co-Cr rod 317 278 (87.8%) 261 (82.3%) 208 (65.8%)
Abbreviations: Ti, titanium; Co-Cr, cob alt-chromium.
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Biom echanics and Mate rial Science for Deformity Correction 123
dur ing surgery and postoperative follow-u p pe-
riods before solid bony fusion is obtain ed.
The mechanical forces on spinal implants
decrease over time after surgery, as biological
bon y fusio n m at ure s and becom es solid . The
maximum force on the spinal implants mayoccur d uring the correction procedure . Precise
in-vivo forces on spinal implants during cor-
rection p rocedures are still unkn own. Previous
biom echanica l st udies have t r ied to m ea su re
in-vivo forces on rods by various engineering
methods.6,7 It is di cult to obt ain in-vivo dat a
during operative procedures due to ethical re-
strictions, and r eliable in-vivo data in spinal de-
formity correction are lacking. Medical devices
such as m etallic rods and screws for spinal de-
form ity should be designed and man ufactured
based on the biom echanica l and biologica l en-
vironment in which they will be used in the
human body. Reliable in-vivo biomechanical
information regarding the force on spinal im-
plants during spinal d eform it y corre ct ion m ay
advance the safety and e ectiveness of defor-
m ity surgery in the future.
! Viscoelasticity of the Spine
The spinal column, consisting of bone, liga-
m en ts, and inter vertebral disks, is a comp osite
material with signi cant viscoelasticity. Vis-
coelastic materials show two biomechanical
characteristics: creep ph enom enon and stress
relaxation. The creep phenomenon states that
when stress is held constant, the strain on the
m aterial increases w ith t ime. Stress relaxation
states that wh en t he strain is held constant, the
stress decreases with t ime.
Considering th e viscoelastic prope rt y of the
spine, rapid correct ion procedures such as quick
rod rotation m aneuvers may m ake th e spine
m uch sti er and may hinder e cient spinal
correction, resulting in a lower correction rate
than the surgeon anticipated preoperatively.
Thu s, dest abilization p rocedu res, such as bilat-
eral facetect om ies, diskectom ies, an d release of
costotransverse ligaments, are very importantin obtaining better correction. Besides these
technical issues, the biomechan ical pr inciples
indicate that slow rod rotation an d tran slation
procedures can ob tain be t ter nal correct ion
rates. After the correction procedure is com-
plete d, the ro d w ithin an elas t ic deform at ion
range will tend to spring back to the original
shape due to the stress relaxation e ect aftercorrection procedures (Fig. 10.3). Fast rod ro-
tation m ay cause signi cant increase of m e-
chanical loads on the implants and result in
dramatic changes in the shape of the rods. If
the forces on the rods were within the elastic
deform ation zone of met al, the rods wou ld still
have a potent ial to retu rn to the original shape.
Spine surgeons shou ld be fam iliar with the m e-
chanical character istics of m etals and t he sp inal
column to obtain better correction rates and
provide pat ients w ith sa fe surgery.
! Correction Procedures for
Adolescent Idiopathic
Scoliosis
There are m any surgical procedures to correct
adolescent idiopathic scoliosis (AIS) reportedafter the introdu ction of the Harrington instru-
mentation. The Cobb angle correction on an-
teroposter ior (AP) radiographs was 40% w ith
Harrington rods, 55%with the dual-rod multi-
hook system (CD, Cotrl-Dubousset instru m ent ),
and 65% with th e dual-rod multiple pedicle
screw constru cts in th e coronal plane. Recent
studies reported t hat p edicle screw constructs
in the sagittal plane increased the lordosis of
the thoracic spine.8 While the surgeon is per-
form ing the direct vertebr al rotation techn ique
to decrease rotational deformity around the
apex of the thoracic curve, the m ajor force on
the spine pushes the th oracic rib hump down
to lessen the rotational deform ity of the spine,
wh ich eventu ally causes dekyphosis in the th o-
racic spine .9
There have been several attempts to create
thoracic kyphosis by posterior spinal instru-
mentation surgery. Because a titanium rod is
mechanically weaker than a stainless steel orCo-Cr rod, some surgeons ut ilized stainless steel
or Co-Cr rods rathe r th an t itanium rods so as
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124 Chapte r 10
not t o yield to th e force on the rods. Anothe r
m ethod was to use an in-situ rod bending tech-
nique after a single rod-rotation to create tho -
racic kyph osis. One of th e prob lems of an in-situ
rod-bending procedure is that a m uch greater
load would be applied to the pedicle screws
around the area of rod bending, which may
increase the possibility of vertebral fractures
or screw loosening due to a higher concentra-
tion of mechanical force on the screws. Also,
multiple rod-bending procedures will reduce
the original mechanical strength of the metal-
lic implant .
There have been new surgical techniques
for correcting spinal deformity to maintain or
create th oracic kyphosis. One technique is th e
vertebral coplanar alignment (VCA) reported
by Vallesp ir et al.10 This technique u ses slotted
tubes attached to each pedicle screw on the
convex side of the th oracic cur ve. Two longitu-
dinal rods are inserted an d separated along theslots, driving the t ubes into on e plane, ma king
th e axis of th e vertebrae coplanar, th us correct-
ing transverse rotation and coronal translation.
For creating th oracic kyphosis, the e nds of the
tubes are spread in the thoracic spine. After
locking a de nitive rod on the concave side
and retrieving tubes on the concave side, the
convex-side rod is inserted and tightened . The
curve correction rate in the m ain thoracic curve
was 73%on average, and the average preope ra-
tive th oracic kyphosis of 18 degrees re m ained
un changed after surger y. Anoth er techn ique is
the simultaneous translation technique using
two rods as reported by Clement et al.11 This
technique uses polyaxial pedicle screws and
polyaxial claw s consist ing of a ped icle h ook and
an opposing transverse counter-hook placed
at th e m ost cephalad end of the rod. The t wo
6.0-mm t itanium rods are bent rst and are in-
serte d pre-or iented. Redu ction of the d eform ity
is obtained by gradu al and alternate t ightening
of all nuts on both rod s, allowing the vertebrae
to gradually approach the rods. Another tech-nique uses a Universal clamp consisting of a
woven polyester band, a t itanium alloy clamp,
Fig. 10.3 The shape changes of the t wo rods on
both side s of the curve before (red) and just aft er
(blue) rod rotation and 1 week after surge ry (white).
The original contours of the two rods showed
signi cant reduct ion just after the rod rotation
procedure. The rods, however, tended to spring
back to the ir original shapes as long as the forces
were within the elastic deformat ion zone of the
meta l (titanium a lloy). The m echanical stress on
rods tends to decrease with t ime due to the
stress-relaxation e ect of the spine.
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Biom echanics and Mate rial Science for Deformity Correction 125
and a locking screw as w ell as pe dicle screws.12
Pedicle screws were placed in two or m ore ver-
tebrae at th e distal extrem ity of the curve with
m onaxial screws on t he convex side an d poly-
axial screws on th e concave side. Thoracic levels
were instrumented with three to seven sub-lam inar Universa l clamp s (UCs) on th e concave
side an d one sublam inar UC at the apex on th e
concave side. Correction of the thoracic curve
was p erform ed using posterom edial translation
by t igh tening the UCs for the spine t o appro ach
the pre-ben t double rods.
The kinem atic concept of how to correct th e
deform ity with p edicle screws is show n in Fig.
10.4 . The ap ex verteb ra should be m oved from
ante rior to posterior and from lateral to me dial
with two anchor points corresponding to the
tips of pedicle screws. The screw tip on the
concave side should be moved more posteri-
orly than that of the convex side. By providing
a bigger bend to the concave side rod than to
the convex side rod and rotating the two rodssimultaneously, the screw tip of the concave
side at the apex of the curve m oves m ore pos-
teriorly than that of the convex side does. This
technique w as reported by Ito et al13 and named
the simultaneous double rod rotation tech-
nique, which allows simultaneous correction
of the coronal plane d eform ity and restoration
of the thoracic kyphosis. The biomechanically
strongest correction procedu re, which utilized
a solid frame between the pedicle screws on
Fig. 10.4 The locations of the apex vertebra in the
axial plane. The apex vertebra is located antero-
laterally before surgery and the vertebra is to be
relocated post eromedially during surgery. The
pedicle screw at t he apex vert ebra on the concave
side of the curve should be m oved m ore toward
the back (red line) than that on t he convex side (blue
line) to relocate t he apex vertebra to the normal
position. In the simultaneous double rod rotat ion
technique,13 the concave side rod should be bent
more than the convex side rod, which allows the
head of the pe dicle screw on t he concave side t o
move m ore toward the back than that on the
convex side.
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126 Chapte r 10
bot h the convex and concave sid e of t he cu rve,
was reported by Chang and Lenke.14 By con-
necting the t wo rods w ith a solid meta l frame,
the spinal implant is able to produce the most
pow erful force on the spin e, but the s t re ss con -
centration m ay not occur on speci c pediclescrews.
! Intraoperative Mechanical
Forces on Rods During Rod
Rotation Maneuvers
During rod rotation procedures to correct the
deformed spine three dimensionally, the in-
serted rods frequently show dram atic contour
changes due to signi cant mechanical loads
on th e rods and screws. A recent biom echani-
cal study has used nite elemen t analysis of
the mechanical properties of metals and the
geometrical changes of metallic rods before
and after surgery.15–17 These auth ors measured
three-dime nsional (3D) contour chan ges of the
rods before and after surgery using postopera-
tive 3D computed tomography (CT) images.
Speci c m athem atical assumptions and bound-
ary conditions were put into the computer sim -ulation . In the ir nite eleme nt ana lysis (FEA)
m odel, the distal end of the rod was xed com-
plete ly, an d the upperm ost end was ab le to
m ove p arallel to the axis of the t run k. By calcu-
lating the forces on rods in AIS patients with a
single thoracic curve, pullout forces of about
150 N were exerte d on t he concave side screws
aroun d th e apex of the cu rve if pedicle screws
were inserted at all the fusion levels (implant
dens ity 100%) (Fig. 10.5). At bot h e nds of the
rods, push-in forces of about 200 N were on the
pedicle screw s on the concave side of the cu rve.
Push-in forces on ped icle screws ra rely result in
clinical problem s, but pullout forces on screws
can lead to screw loosening or bony fractures,
wh ich can create serious complications for th e
Fig. 10.5 The force on each pedicle screw during
rod rotat ion p rocedure in an ado lescent idiopathic
scoliosis (AIS) patient. The contour of the concave
side rod shows signi cant reduct ion, and pullout
forces around the apex of the curve have reached
about 200 N according to the calculation. At both
ends of the concave side rod, maximum pushing-in
force was exert ed on the pe dicle screws. The m inus
sign indicates pull-out force on each screw. The tot al
amoun t of the force acted on t he concave side rod
has topped 1,400 N.
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Biom echanics and Mate rial Science for Deformity Correction 127
spinal cord or great vessels. According to the
FEA m odel, the pu llout forces on ped icle screw s
around t he ap ex of the curve m ay exceed 500 N
if the n um ber of pedicle screws were redu ced.
Maximum pullout forces of thoracic pedicle
screws in cadaveric spines are about 600 N, sothat there may be an increasing risk of screw
pullouts a ro und the apex in pat ients w ith rigid
curves and fewer pedicle screws.
One of the e ective solut ions to reduce me-
chanical forces on pedicle screws is to place
cross-links or a fram e over the t wo rod s. Many
rod rotation procedures utilize only the con-
cave-side rod for correction of scoliosis, and
the convex-side rod is placed after comp letion
of rod rotation of the concave side. In these
correction procedures, the force on the con-
cave side rod is m uch higher th an th at on th e
convex side rod. The re sults show ed th at 50%of
the rod contour on the concave side was lost
after rod rotation m aneuvers and the opposite
side rod showed a lmost no chan ge in its shape .
If a cross-link was placed between the two
rods, 15%of the total load was shared by the
convex side rod, which showed some contour
changes. The biomechanically strongest con-
struct with pedicle screws is bilateral screw p lacem ent w it h a cross- lin k, w hich for m s a
triangular shape in each vertebra. From this
biom echanica l poin t of v iew, verteb ra l colum n
manipulation with a rigid frame cross-linking
the two rods and pedicle screws is the most
pow erful corre ct ion pro cedure in sp inal defor-
m ity surgery.14
! Implant Density andCorrection Rate
According to the present consensus among
spine experts worldwide, AIS curves of less
than 70 degrees w ith exibility need less tha n
80%of screw density.18 From a biome chanical
standpoint, a small number of anchors with
less rigid m etallic rods are not a ble to correct
the spinal deform ity su cient ly because they
can sustain only small amoun ts of mechan icalload. It seem s reasonable to assum e th at m ore
implant density and more rigid rods will pro-
vide bette r correction rates and nal outcom es.
Several recent stud ies, however, found that the
nal outcome of the surgical correction did
not show any signi cant improveme nt even if
surgeons used m ore rigid and thicker rods w ith
a higher implant density.19,20 Implant densityand mechanical sti ness of the rods are of
some importance to obtain better correction
rates. The more impor tan t steps to a ect the
nal outcome of deformity correction may be
perform ing pre op erat ive cu rve exib ilit y and
destabilization pr ocedures, such as Ponte oste-
otomies, before performing correction proce-
dures including rod rotation and t ranslation.
! Chapter Summary
Harrington started to use his spinal implants,
consisting of hooks and rod s m ade of stainless
steel, for treat m ent of spinal deform ity almost
50 years ago. Since the introdu ction of his de-
vice, surgeries to correct and stabilize the spine
with m etallic implants have shown dram atic im-
provem ent in thre e-dim ensio nal corre ct ion of
the cu rves; an excellent correction rate has beenobtained in recent years by using pedicle screws
and r igid rods. Titanium alloys are th e most pop -
ular material for recent spinal surgery due to
their biocompatibility and fewer m etal-related
artifacts on MRI. However, bending a titanium
rod multiple times may lead the material to
plast ic deform at ion, w hich m akes it signi -
cantly weaker m echanically. Surgeons should
be fam iliar w ith the m ech an ica l chara cter ist ics
of each m aterial used for deform ity surgery and
refrain from excessive manual bending of the
rods to maint ain the original me chanical prop-
erty of each metal. Spinal implants made of
stainless steel or Co-Cr are commonly used for
correction of rigid spinal deformities, such as
severe scoliosis and rigid kyphosis, because of
their superior mechan ical sti ness and ability
to obtain b ette r correction rates. Surgical treat-
m ent of spinal deformity requires fam iliarity
with spinal biomechanics and the mechanical
characteristics of each biomaterial. This chap-ter discussed the fundamen tals of biom echan-
ics of spinal deformity correction, mechanical
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128 Chapte r 10
behaviors of m et allic implan ts, in-vivo forces o n
rods and pedicle screws, biom echanical bene-
ts of destab ilization procedures for rigid curves,
and viscoelastic proper ties of the spine. Reade rs
can ap ply the concepts of spinal biom echanics
and material science to their own correction procedures to p rovide their pat ien ts w ith a safe
and e ective surgical procedure an d excellent
clinical outcomes.
Pearls
Spinal deformity correction relies on metallic
imp lants such as screws, hooks, and rod s.
Popular metals used for spinal implants are tita-
nium alloys, stainless steel, and cobalt-chromium.
Each me ta llic mate rial has di eren t mechan ical
behaviors for th e st ress–strain relat ionship and
repetitive loading.
The viscoelastic property of the spine should be
considered when operating on cases with rigid
large spinal deform ity.
Pitfalls
Mechan ical load s on spinal imp lants d uring cor-
rection procedures often exceed the limit of
bo ne st i ness, which may lead to surge ry-relate d
complications.
Di erent deformity correction procedures have
be ne ts and limitat ions.
Rapid rod rotation for rigid deformity correction
will signi cant ly increase mechanical loads on the
spinal imp lant.
References.
Five Must- Read Reference s
1. Hadra BE. Wiring of the vertebrae as a means of
imm obilization in fracture and Pott’s disease. The
Times and Register, Medical Press, Philadelphia,
1891:1–8
2. Harrin gton PR. Treat m en t of scoliosis. Corr ect ion and
intern al xation by spine instru m ent ation. J Bone
Joint Surg Am 1962;44- A:591–6 10 PubMed
3. Suk SI, Lee CK, Kim WJ, Chu ng YJ, Par k YB. Seg-
men tal pedicle screw xation in the treatment of
thoracic idiopathic scoliosis. Spine 1995;20:1399–
1405 PubMe d
4. Uhtho HK, Bard os DI, Liskova-Kiar M. The advan-
tages of titan ium alloy over stainless steel plates for
the inter nal xation of fractures. An experim ent al
study in dogs. J Bone Joint Surg Br 1981;63-B:427–
48 4 PubMed
5. Dem ura S, Murakam i H, Hayashi H, et al. The in u-
ence of rod contouring of di eren t spinal constru cts
on strength an d sti ness. Orthope dics, in press
6. Wang X, Aub in CE, Crand all D, Labelle H. Biom ech an -
ical modeling and analysis of a direct incremental
segmental translation system for the instrumenta-
tion of scoliotic deformities. Clin Biomech (Bristol,
Avon) 2011;2 6:548–55 5 PubMed
7 . Aubin CE, Labelle H, Chevr e ls C, Desr och es G, Clin J,
Eng AB. Preoperative planning simulator for spi-
nal deformity sur geries. Spine 2008;33 :2143–2152
PubMed
8. Sucato DJ, Agrawal S, O’Brien MF, Lowe TG, Richards
SB, Lenke L. Restoration of thoracic kyphosis after
operative treatment of adolescent idiopathic scolio-
sis: a mu lticenter comparison of three surgical ap-
p ro aches . Spin e 2 00 8; 33 :2 63 0– 26 36 PubMed
9 . Lee SM, Suk SI, Chu ng ER. Direct vert ebra l rot ation :
a new technique of three-dimensional deformity
correction with segmen tal pedicle screw xation in
adolescent idiopathic scoliosis. Spine 2004;29 :343–
34 9 PubMed
10 . Vallespir GP, Flores JB, Trigu eros IS, et a l. Ver teb ra l co-
plan ar align m en t: a st an da rd ized te chniqu e for th ree
dimensional correction in scoliosis surgery: techni-
cal description and preliminar y results in Lenke typ e
1 curves. Spine 2008;3 3:1588– 1597 PubMed
11. Clem en t JL, Cha u E, Geo ray A, Vallad e MJ. Sim ult a-
neous translation on two rods to treat adolescent
idiopathic scoliosis: radiograph ic results in coronal,
sagittal, and transverse plane of a series of 62 pati-
ents w ith a m inimu m follow-up of two years. Spine
2012;37:184–192 PubMed
12. Mazd a K, Ilha rr ebo rd e B, Even J, Lefevre Y, Fitou ssi F,
Penn eçot GF. E cacy and safety of post erom edial
translation for correction of thoracic curves in ado-
lescent idiopathic scoliosis using a new connection
to th e spine: the Universal Clamp. Eur Spine J 2009;
18:158–169 PubMed
13. Ito M, Abum i K, Kotan i Y, et al. Sim ulta ne ous dou ble-
rod rotation technique in posterior instrum entation
surgery for correction of adolescent idiopathic sco-
liosis. J Neurosurg Spine 2010;12 :293–30 0 PubMed
14. Chan g MS, Len ke LG. Ver tebr al de rot ation in a doles-
cent idiopathic scoliosis. Oper Tech Orthop 2009;
19:19–23
15. Salmin go R, Tad an o S, Fujisak i K, Abe Y, Ito M. Cor rec-
tive force analysis for scoliosis from implant rod
deformation. Clin Biomech (Bristol, Avon) 2012;27:
545–550 PubMed
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Biom echanics and Mate rial Science for Deformity Correction 129
16 . Salm ingo RA, Tad an o S, Fujis aki K, Abe Y, Ito M. Rela-
tionship of forces acting on implant rods and d egree
of scoliosis correction. Clin Biomech (Bristol, Avon)
2013;28:122–128 PubMed
17. Salm ingo RA, Tad an o S, Abe Y, Ito M. In ue nce o f im-
plan t r od cu rvat ure on sagit tal co rre ct ion o f sco liosis
deformit y. Spine J 2014;14:143 2–1439 PubMed
18. de Kleuver M, Lew is SJ, Ger m scheid NM, et al. Opti-
m al surgical care for adolescent idiopathic scoliosis:
an international consensus. Eur Spine J 2014;23:
2603–2618 PubMed
19. Prin ce DE, Matsu m oto H, Cha n CM, et al. The e ect of
rod diameter on correction of adolescent idiopathic
scoliosis at two years follow-up. J Pediatr Orthop
2014;34:22–28 PubMed
20. Che n J, Yang C, Ran B, et al. Cor re ction of Len ke 5
adolescent idiopathic scoliosis using pedicle screw
instrum entation: does implant density in uence the
correction? Spine 201 3;38:E946–E951 PubMed
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! Introduction
Adult spinal deformity (ASD) is among the
m ost challenging pathologies treate d by spine
surgeons. Preoperative preparation to correct
neu ral elem ent compression as well as coronal
and sagittal malalignment requires strict at-
tent ion to detail and n ear-pe rfect technical ex-
ecut ion. Surger y to treat ASD can be fru strat ing,
however, as a seemingly “perfect” surgery maystill be complicated in th e both n ear- an d long-
term per iods by comp lications requiring unan -
ticipated revision surger y. Two such com m on
complications are pseudar throsis and infection.
Our group has reported a 9%rate of unantici-
pat ed se cond pro cedure s in adult s undergoing
prim ar y surgery for ASD, where pseuda rthrosis
(4%) and infect ion (1%) were com m on causes
for revision.1 Even more trou blesome w as a 21%
rate of repeat revision surgery, where pseu-
dar th rosis (5%) an d in fect ion (2%) we re again
tw o comm on causes.2 These nu m bers are in line
with reports from other cohorts; thus, pseu-
dart hrosis remains a comm on cause of revision
surgery in prim ary and revision ASD.3,4
! Pseudarthrosis
Successful fusion requires optimal biologicaland biomechanical environm ent s, wh ich rely on
bot h pat ient select ion and su rgical technique.
Although advances in imp lant te chnology and
osteobiologics have improved union rates, pseu-
darthroses persist in as many as 16%of three-
column osteotomy patients.5,6 This is a r esult
of the risk factors for pseu dart hrosis that e xist
by the nat ure of ASD surgeries. Lon g-segm ent
fusions are at a higher risk for pseudarthrosis
because of the large su rface area of bon e that
m ust hea l. In add ition, the com monly employed
m idline approach is associated w ith a den er-vation of the paraspinal musculature, with an
associated d ecrease in vascularity to th is mus-
culature. This is an insult to the local healing
environment. ASD surgeries are not uncom-
m only associated w ith spinal stenosis, requir-
ing decomp ression, or r igid coronal and sagitt al
plane deform it ies, re qu ir ing posterior colum n
osteotomies. The greater the amount of bone
resected, the greater the theoretical risk of a
pseuda rthrosis d evelop ing. Desp ite m od er n im-
plants, a long segm en t fusion w ill rem ain som e-
what mobile, through elastic deformation of
the constru ct. This microm otion, in som e cases,
m ay be excessive, w ithout the rigidity required
to promote fusion. In the absence of a fusion
mass, implants will almost certainly fracture.
This m ay occur a s early as 6 m onth s to 1 year,
though w e h ave en countered pseudarthrosis
that present ed a late as 7 years postope ratively
(Fig. 11.1). Finally, ASD often involves fusion
of junctional segments (e.g., lumbosacral junc-tion, thoracolum bar junction), wh ich are at a
higher risk of nonu nion.6 In som e cases, ante-
11
Pseudarthrosis and InfectionMichae l P. Kelly and Sigurd Berven
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Pseudarthrosis and Infect ion 131
rior column support, through either a trans-
foraminal lumbar interbody fusion (TLIF) or
an anter ior lum bar in terbody fusion (ALIF), mayassist w ith imp roving un ion rates. Approp riate
use of recombinant human bone morphoge-
netic protein-2 (rh-BMP2) at t he lumbosacral
ju nct ion m ay obv iat e the use of TLIF/ALIF at
L5-S1.
Nico t in e exp os ure is associated w it h de-
creased fusion rates in spine surgery. In the
case of ASD, the risk of nonunion with multi-
level surgery is great a nd, in ou r p ractice, sur-
gery is not o ered to patients wh o are unable
to cease nicotine use. To test for nicotine use,
we routinely check urine cotinine levels. This
m etabolite of nicotine is excreted in t he u rine
and o ers reliable values for active and pa ssive
exposure to cigarette sm oke, m aking it a suit-
able screening test for this patient popu lation.
Nicot ine has proven an t ian giogenic e ect s on
fusion m asses, increasing th e likelihood of non-
union. Furth erm ore, nicotine has been shown to
have an adverse in uence on patient-repor ted
outcomes in several areas of spine surgery,independent of other risk factors, further de-
creasing th e p otent ial for success with surgery.
Given the costs an d r isks associated w ith spinal
deformity surgery, nicotine cessation is neces-
sary. In most cases, we require 3 months of preop erat ive abst inence, to prove that the ces-
sation is lasting.
Osteop orosis is increasingly com m on in ASD
pat ients, as t he age of p at ients seeking surgery
rises. Perhap s even m ore comm on is hypovita-
minosis D, which has been shown to be com-
mon in general orthopedic surgery practices
and in spine surger y–speci c practices.7 Vita-
m in D plays an essent ial role in bone m etabo-
lism and hom eostasis, and low vitam in D levels
are associated w ith osteom alacia (hypominer-
alized bone). We routinely check serum 25-
hydroxyvitam in D levels at pre ope rative visits,
and w e prescribe supplemen tation with oral
vitamin D as needed. In most cases, 50,000
Int ern ation Units (IU) w eekly for 6 we eks, fol-
lowed by 1,000 IU daily. In addition, we rec-
ommend supplementation with 1,000 mg of
calcium daily. In some cases, hypovitaminosis
D exists du e to som e oth er system ic pathology,
rather than malnutrition. For these patients,we consult en docrinologists w ith a par ticular
interest in bone m etabolism .
Fig. 11.1 A 50-year-old woman prese nte d 8 years
afte r L3 pedicle subtract ion osteotomy with broken
implants and pseudarthrosis causing xed sagit tal
plane m alalignm ent . She was treated with revision
posterior spinal fusion; not e t he four rods spanning
the level of the pedicle subtraction.
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132 Chapte r 11
As previously mentioned, however, osteo-
poros is is a com m on com orbidit y encountere d
by sp in e su rgeon s. This is of conce rn to su r-
geons, as bone mineral density (BMD) is di-
rectly correlated with insertional torque and
pullo ut st rengt h. St rengt h of screw purchase ,in tu rn, a ects fusion rates by deter m ining the
dura bility and r igidity of the constru ct and its
stability while the fusion mass matures. We
routinely obtain bone densitometry tests such
as dual-energy X-ray absorptiometry (DEXA)
scans preoperatively. These tests provide the
tr ue value of th e BMD and th e T-score, which
is the number of standard deviations above
or below the mean for young-adult reference
stan dard s. Osteop orosis is de ned as a T-score
of –2.5 or lower. Osteopen ia exists at betw een
–1 and –2.5 st an dard deviat ions. When order-
ing a DEXA scan, one must remember that
in many cases the lumbar spine BMD may be
falsely elevated due to spondylosis, with end-
plate sclerosis and os teop hyte form at ion (Fig.
11.2). The DEXA scan shou ld include den sities
at the hip and distal radius. We have found
th e d istal radius p art icularly useful for m aking
the diagnosis of osteoporosis, which facilitates
pharm acologica l m an agem ent of t he diso rd er.
Although a multitude of options exist for
the management of osteoporosis, only one
anabolic therapy exists, teriparatide (Forteo,
Eli Lilly, Ind ianap olis, IN).8 Ter iparat ide is a re-combinan t form of a port ion of the p arathyroid
hormone (PTH). Although PTH increases os-
teoclastic act ivit y, via osteoblast signaling, pul-
satile administration of teriparatide increases
osteoblastic activity to a greater degree, in-
creasing bone format ion. An adverse e ect of
teriparatide observed in animal models was os-
teosarcoma formation, however, and patients
with risk factors for osteosarcoma, including
Paget’s disease and prior radiation therapy,
should avoid teriparatide exposure. In cases
of a contraindication to teriparatide, we often
emp loy denosum ab, a m onoclonal antibody that
binds re ceptor act ivat or of nuclear-' B (RANK)
ligand (RANKL). The b ind ing o f RANKL prevents
RANK activations, thereby suppressing osteo-
clast activation. This is an “anti-catabolic” mech-
anism of osteoporosis management, however,
similar to bisphosphonates. Both denosumab
and bisphosphonates delay callus maturation
in fracture models, which likely behave simi-larly to a fusion m odel, but t here is no hu m an
evidence to support a correlation between ex-
posure t o t hese ant i-catab olic m edica tions and
pse udarth ros is.8 Nonetheless, we attempt to
avoid bisphosphonate exposure early in the
spine fusion process, as there are animal data
to support a negative e ect of bisphospho-
nates. There is some eviden ce, however, that a
combination of teriparatide and bisphospho-
nate therapy may be ideal to maximize callus
form ation and rigidity, w ith early teriparatide
administration followed by conversion to bis-
phosphon at e therap y.
Surgical techn iques may play a role in instr u-
menting the osteoporotic spine as well. Spe-
cially designed screw t hread s have been show n
to increase insertional torque, which may ben-
e t the durability of a construct in osteopo-
rotic bone. Hydroxyapatite coating has also
been sh ow n to in crease screw purchase . As the
pedicle is often patu lous in the os teoporot icspine, one may choose to avoid tapping the
channel of the pedicle screw. If tapping is per-
Fig. 11.2 Upright and supine radiographs of a
65-year-old woman with degenerative lumbar
scoliosis. Note the hypertrophic osteoarthritis
through the apex of the deformity, which would
cause a falsely elevated bone mineral density.
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Pseudarthrosis and Infect ion 133
formed, it should undersize the anticipated
screw diameter by 1 mm or more. Screw di-
ameters should be maximized, at least 70%of
pedicle diam et er, t o ensu re an ap pro priate in -
terference t w ithin the pedicle. Screw length
should be maximized and, in extreme cases,one m ay choose to tap th e anterior cortex and
achieve b icort ical purchase of the screw, as this
w ill signi cantly improve pullout stren gth. One
should attem pt to leave the dor sal cortex int act
as well, as this may minimize screw toggling
and loosening.
Implant materials are a matter of prefer-
ence and are d ebated am ong spinal deform ity
surgeons. We prefer to use 5.5-mm cobalt-
chromium (Co-Cr) rods in cases of degenera-
tive scoliosis with poor bon e qu ality. In larger,
sti er reconstructions, we commonly use a
6.0-m m Co-Cr rod on t he “working side,” and
place a 5.5-m m Co-Cr on t he contralat era l sid e.
Som e surgeons pr efer com m ercially pure t ita-
nium rods, w hich are a bit less sti th an Co-Cr,
believing that th is w ill st re ss t he bon e–implant
interface less, thereby de creasing th e incidence
of adjacent segment problem s. Conversely, some
surgeons prefer 6.35-mm stainless steel (SS)
rods, believing this is the most durable metalfor spinal deformity surgery. In a series of spi-
nal deformity patients, implant fracture was
less comm on am ong those xed w ith Co-Cr
rods.9 In cases of thr ee-colum n osteotom y (i.e.,
pedicle su btra ct ion osteotom y, vertebra l col-
um n resection), dominoes are used to span t he
osteotomy level with more than two rods, in-
creasing the r igidity of the constru ct at th e os-
teotomy site and decreasing micromotion. In
any case, secure xation, with accurate screw
placem ent , is re qu ired alon g the lengt h of the
deformity. This increases the rigidity of the
construct , decreasing nonun ion rates. We per-
form high-den sity instru me ntation (1.8 screws/
level) in the vast m ajorit y of ASD surger ies. Al-
though this issue is debated regarding adoles-
cent idiopathic scoliosis, we feel strongly that
high-den sity instr um ent ation is needed in ASD.
In all cases instrumented to S1, we place
distal supporting screws, often S2-alar-iliac
(S2AI) or iliac screws.10 Iliac screws d istal to S1decrease strain on S1 xation in exion, m ini-
mizing micromotion at the lumbosacral junc-
tion. S2AI screws have been proposed as an
alternative to iliac screws, with a m ore vent ral
starting point and “in-line” tulip heads, facili-
tating rod placemen t. Midter m results of S2AI
screws are encouraging, and we employ this
technique frequently. A third option for distalxation is S2-alar screw s. These screw s o er
suppor t to S1 pullout, with out crossing or im-
mobilizing the sacroiliac joint. If one chooses
to use this method, attention must be paid to
the course of the L5 root, as it courses over the
front of the sacral ala. Bone graft materials
should consist of locally obtained autograft,
allograft, and iliac crest bone graft (ICBG) or
rbBMP-2. We routinely use fresh-frozen can-
cellous allograft, as its osteoinductive proper-
ties are likely better than those of cortical
chips. In long fusions, inadequate volumes of
ICBG may indicate the use of rh-BMP2 in an
o -label fashion. We have shown this to be an
e ective met hod of improving fusion rates. We
neithe r use nor advocate other so-called osteo-
biologic prod uct s, as the evidence to su ppor t
their use is weak. The dorsal elements should
be decort icated, u sing gauges or burs, to fre sh
bleeding bo ne. Bleeding bo ne is a re qu isite for
compet itive fusion rates. If using m ore th an t worods or cross-links, they are xed after bone
graft placement, to minimize disruption and
interference w ith contiguous grafting.
In the vast m ajority of cases, the diagnosis
of pseudarth rosis is made with t he p resence of
loose or fractured implants. We intervene w hen
ther e is a p rogression of deformit y or p ain. In
the absence of progression, we often observe
unilateral rod fractures. When both rods have
fractu red, we usually recomm end revision sur-
gery. In a small number of cases, a pseudar-
throsis may present as symptoms consistent
with neu ral elem ent compression (e.g., radicu-
lopathy, claud ication) due to scar tissue/ brous
callus accumu lation (Fig. 11.3). Comp uted to-
m ography (CT), w ith ne cuts and m etal sub-
traction, is the p referre d im aging m odality for
diagnosing pseudarthrosis.11 Flexion/exten sion
radiographs have been used, though they are
not as sen sitive as CT scann ing.
Management of pseudarthrosis consists ofrevision surgery. The use of rh-BMP2 in pos-
terolateral fusion revisions has received Food
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134 Chapte r 11
and Drug Adm inistrat ion (FDA) app roval. Wh enrevising a pseudarthrosis case, inspection of
the entire fusion m ass is recom men ded, as one
pse udarth ros is m ay beget anot her.12 In our
experience, most pseudarthrosis presents at
L5-S1, L4-L5, and at the thoracolumbar junc-
tion, in that order. Revision surgery often con-
sists of anter ior colum n sup port , if not already
done, in the form of a TLIF, ALIF, or transpsoas
interbody fusion. Options for graft material
include t itan ium , polyethe ret he rketone (PEEK),
and allograft. Our preferen ce is to use t itanium ,
as it bond s to bon e, increasing the stability of
the construct and likely improving fusion rates.
The p seudar throsis tissue sh ould be debrided,
as these tissues are unable to undergo mine ral-
ization and m ust be re m oved to achieve union.
In th e lumbar spine, we often p erform a posterior
column osteotomy through the pseudarthrosis
tissue an d compress through th e pseuda rthrosis.
In addition to encouraging fusion by exposure
of bleeding cancellous bon e, the osteotomy aidsin restoration of lordosis, taking tension o of
the fusion mass and prom oting compression at
Fig. 11.3 A 61-year-old man presente d with a
sagitt al plane malalignment and L4 radiculopat hy
due to pseudarthrosis. Note the vacuum disk within
the instrument ed levels, indicative of a
pseudarthrosis.
th e pseudar th rosis level. If rh- BMP2 is not used ,
we u se autogenou s iliac crest graft, as th e bio-
logic activity of allograft is not su cient to
create a comp etitive environm ent for fusion in
the setting of a previous pseudarthrosis. For
cases of lumbosacral junction pseudarthrosis,we ensure that we have adequate distal xa-
tion, consisting of ped icle screws at th e rst
sacral vert ebra an d iliac screws below t hat. In
the case of patulous, eroded S1 pedicles, we
place m ult ip le iliac screw s on ea ch sid e.
The postoperative routine is unchanged in
the m anagem ent of pseudart hrosis. No bracing
is used and th e patients are mobilized on post-
operative day 1. Strict activity precautions
are established, however, and patients are in-
structed on how to safely rise from bed and
are given a front-wheeled walker to use for 6
weeks to encourage an upright posture, dis-
couraging exion throu gh the revision fusion
m ass. Teriparatide the rapy is continued for a
minimum of 3 m onths after surgery. We do not
perform CT scanning for evaluat ion of fusio n
masses, as the exposure to radiation is exces-
sive, and ndings are un likely to a ect our man-
agem ent of the patient.
Careful attention to detail in preoperative planning, intraoperat ive p er form an ce, and post -
operative rehabilitation helps surgeons mini-
m ize pseudar throsis in their pract ice. Sm oking
cessation is absolutely mandatory to ensure
competitive results. Appropriate choices of bi-
ologics and instrumentation help increase fu-
sion rates. However, a nonunion rate of 0%is
not realistic, and t he informed decision-m aking
pro cess shou ld include d iscussion of t he r isk o f
reop erat ion for non un ion in ASD surger y.
! Infection
Perioperative surgical-site infection (SSI) is a
signi cant cau se of m orbidit y in ASD surger y,
with reported rates ranging from 0.3% to
20%.1,2,13 These rates include both super cial
and deep wou nd infections; the treatm ents and
imp lication s for each di er. In many inst an ces,a super cial infection can be managed on an
outpatient basis, with oral antibiotics alone.
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Pseudarthrosis and Infect ion 135
Conversely, a deep wound infection is a ca-
tastrophe, nearly universally managed with
rehospitalization, revision surgery, and pro-
longed intr avenou s ant ibiotics followe d by oral
antibiotics.
A review of the Scoliosis Research Society(SRS) Morbidity and Mortality database re-
vealed an overall infection rate of 2.1%in cases
perfor m ed by part icip at ing m em bers.13 This
cohort include d a heter ogeneous m ix of proce-
dures, including n oninstrum ented degenerative
lumbar surgeries, in addition to instrum ented
ASD procedures. Not surprisingly, less exten-
sive surgeries, including lumbar diskectomies
and minimally invasive TLIF procedures were
associated with lower rates of infection. Those
cases that w ere associated w ith instrumen ted
spinal fusions had higher rates of infection.
Neurom uscular scoliosis (1 4%) and pos tlam i-
nectom y kyph osis (5.1%) had the highest rates
of postoperat ive wou nd infection. Revision sur -
geries were m ore com m only a ected by infec-
tion s (3.3%vs 2.0%), an d d eep infect ions we re
m ore comm on in this situation as well.
Although the SRS database provides good
epidemiological data regarding rates of infec-
tions, it does not provide the granu lar data thatallow for ner conclusions regarding postoper-
ative infections in th e ASD popu lation. Several
smaller series have reviewed the rates of re-
oper ation for pat ients und ergoing ASD recon-
structions. Pichelmann et al1 published our
group’s exper ience w ith p rima ry ASD surger-
ies, not ing a rate of reoper ation for infection o f
1.4%and account ing for 15.5%of revision sur-
geries. One must note that this rate is likely
lower th an the t rue value, as super cial infec-
tions are unlikely to have undergone reopera-
tion. As a follow-up study, we reviewed the
rates of unan ticipated reoper ation for revision
ASD proced ures, noting infection in 14 %of re-
vision surgeries performed.2 These rates are
similar to those presen ted by others, with in-
fect ion accoun ting for 15%of revision surger ies
in ASD.3
Adult spinal deformit y surgeries are at h igher
risk for perioperative infection than other or-
thop edic or neurologic surgeries because of thelong durat ion, high est imated blood losses, large
surface ar eas, and exte nsive u se of implant s. It
stands to reason that t he longer a w ound is ex-
posed to air, t he m ore likely som e contam ina-
tion may occur. High estimated blood losses
are often associated with the need for periop-
erative allogeneic transfusions. Although allo-
geneic transfusions are associated with majorcomplications, such as t ransfusion-related acute
lung injury (TRALI), m ore com m on a re p er iop-
erative infections, including SSI, urinary tract
infections, and respiratory tract infections.14
The exposure t o allogeneic blood an d prote ins
is associated with an immunomodulatory ef-
fect that may depress the immune response
to pathogens, making the patient susceptible
to SSI. This relationsh ip has bee n sh own in less
extensive lumbar degenerative fusion proce-
dures and the sam e is likely tr ue in ASD.
Imp lants render p atients susceptible to deep
wound infections, as there is a race between
native cells and bacteria to t he implant surface.
Bacteria form a glycocalyx on implants, which
helps the m adhe re to the surface. The glycoc-
alyx “protects” the bacteria from antibiotics,
due t o poor pe net rance by antibiotics, and a lso
decreases the value of woun d culture, as bacte-
ria becom e adh eren t to the glycocalyx and are
not easily shed into the wound bed. There isevidence that titanium and cobalt chromium
imp lant s are less suscep tible to glycocalyx for-
m ation t han stainless steel. Our preference is
to u se Co-Cr rods for their m aterial propert ies
in ASD.
Patient demographics certainly help iden-
tify those at risk for developing SSI. Thus, as
w ith pseudar throsis, it is imp erative that t hese
pat ient s are id en t i ed and that approp riate
steps are taken to m inimize t he risk of SSI. A
comprehensive review of patients treated at
our institu tion, with an overall deep infection
rate of 2.0%, foun d th at a concom itan t diagno -
sis of diabetes had the strongest association
w ith a pe riope rat ive infection (odd s ratio [OR],
3.5).15 The impor tan ce of controlled blood glu-
cose levels was emphasized, as even patients
without a diagnosis of diabetes but with epi-
sodes of hyperglycem ia showe d a higher rate of
infection. These ndings were later supp orted
by Richards et al,16 w ho found an increased rateof infection in orthopedic traum a patients w ith
poorly controlled periopera tive bloo d glu cose
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136 Chapte r 11
levels. Obesit y (body ma ss index 30– 35 kg/m 2)
was also associated with an increased risk of
infect ion (OR, 2/2).
Preincision antibiotic prophylaxis is man-
datory, and antibiotics must be given at the
appropriate time. We have shown a 3.4-foldincreased risk of infection in those p atient s wh o
did not receive intravenous cefazolin within
1 hou r of incision. In a st ud y of ped iatric spinal
deformity surgeries, Milstone et al17 found a
similar relationship between infections and
inappropriate antibiotic administration tim-
ing. The choice of proph ylactic antibiotics m ay
vary by institu tion, but it shou ld consist of an
antibiotic with broad-spectrum gram-positive
coverage of comm on skin ora. At our insti-
tu tion, prophylaxis is pr ovided w ith cefazolin
and vancomycin. In the case of penicillin or
cephalosporin allergy, we use a ztreona m . Both
ant ibiotics are given w ithin 1 hou r of the skin
incision, with vancomycin started earlier to
provid e an ap pro priat e rat e of adm in ist rat ion
and to m inim ize the risk of red m an syndrome.
During surger y, we re-dose ant ibiotics at half
the time of normal administration. For exam-
ple, cefazolin is g iven every 4 hou rs , as it is nor -
m ally given every 8 h ours.Int ra-site ant ibiotics, comm only in t he form
of lyophilized vancomycin powder, adminis-
tered at th e time of wound closure are becom-
ing increasingly comm on. Several retrospect ive
analyses have shown decreased rates of SSI
w ith the institution of this technique. Sweet et
al18 published the rst report on this m ethod,
noting a decreased prevalence from 2.6% to
0.2%with the use of intra-site vancomycin in
adult spine patient s. This bene t has been sup -
por ted by several ot her st udies in adult and
pediat r ic sp ine su rgeries. The re have be en no
comp lications de nitively linked to the u se of
intra-site vancomycin powder, though there
are concerns about pseudarthrosis, anaphylaxis,
and “super-in fect ion.” Vancomycin is acidic and
changes the environment within the wound
bed, t hou gh no e ect on union ra tes has been
observed. Vancomycin powder is e ective in
eliminating gram-positive contaminants, but
some concern over an increase in gram-nega-tive an d p olymicrobial infection s exists. A sin-
gle random ized controlled trial did not suppor t
the e ectiveness of lyophilized vancomycin
pow der.19 Nonetheless, our expe rience m irrors
those of others, and we continue to employ
this pra ctice.
We place both super cial and dee p drains atthe time of wound closure. There is limited bu t
not strong evidence suppor ting their use in spi-
nal d eform ity surger y. Blank et al20 perform ed a
rand om ized t rial of surgical drains in patient s
undergoing surgery for adolescent idiopathic
scoliosis. They found increased rate s of wou nd
drainage in those patients treated without a
drain. The study w as under powered and thus
could not detect a di eren ce in infection rates,
however. It stan ds to reason that an ade quately
pow ere d s tudy wou ld su ppor t a decreased r at e
of postoperative infection w ith decreased wound
drainage. Postoperative drains h ave be en asso-
ciated with increased rates of perioperative
blood t ra nsfu sions, and this m ust be balanced
with the potential bene t of wound drainage.
Diagnosis of spine infections can often be
m ade w ith a history and physical exam ination.
Fevers and chills as well as lethargy/malaise
are comm on—the form er are more frequent
with acute infections, and the latter are m orecommon with chronic, deep infections. In the
case of acute infections, some m ay show w ound
eryth em a, uctu ance, and woun d drainage.
These signs are not ubiquitous, however, and
th e clinician m ust h ave some level of suspicion.
In chronic infections, a small draining sinus
is com mon , or a new and enlarging uctuant
mass may be present. Upon presentation, one
should draw a complete blood count an d serum
C-re act ive p rotein (CRP). We h ave found CRP to
be m ore usefu l t han the eryt hro cyte sedim en-
tation rate (ESR) in diagnosing postoperative
infections. In t he im m ediate postoperat ive pe-
riod, the half-life of CRP is ~ 2.5 days, whereas
th e k inet ics of ESR are of little u tility. Im aging
of the spine should begin with plain radio-
graphs, which may show evidence of screw
loosening, with halos, in cases of chronic in-
fection (Fig. 11.4). Follow ing plain rad iograph s,
CT or magnetic resonance imaging are of lim-
ited utility, as a seroma forms in all cases, re-gardless of bacterial contamination. Aspiration
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Pseudarthrosis and Infect ion 137
of a serom a and uid analysis m ay be per-
form ed w hen there is uncertainty regarding the
pre se nce of an in fect ion. Physician su sp icionand concern sh ould drive the d ecision to inter -
vene for a suspected infection.
Management of a super cial infection is
often su ccessful w ith ant ibiotics alone, as this is
usually a cellulitis related to th e surgical woun d.
Acute, deep wound infections are treated ag-
gressively in our p ract ice. The st an dard of care
is irrigation and debr idem ent . In th e woun d is
grossly contaminated, we may remove loose
graft. In the absence of gross contamination,
graft and implant s are retained . E ort should
be m ade to ach ieve good decontam inat ion of
the wound, so that implants can be retained.
Although t heir p resence as a foreign bod y might
concern surgeons, the instability caused by
implant removal will make eradication of the
infection m ore di cult. If th ere is any ques-
tion regarding the level of contamination of
the w ound, we place a wound vacuum -assisted
closure (WVAC) dressing and ret urn to t he o p-
erating room in 72 hours for repeat irrigationand debr idem en t, with p ossible WVAC change
Fig. 11.4 An 11-year-old girl with neuromuscular
scoliosis presente d with pain 11 mont hs after
posterior spina l fusion . Explorat ion revealed a deep
wound infect ion. Note the lucencies (arrows)
surrounding the midthoracic pedicle screws.
versus delayed primary closure. A chronic, de-
layed deep woun d infection is treated di erent ly,
however. These infections are m ore com m only
associated with less virulent bacteria, such as
Propion ibacterium acn es or Staphylococcus epi-
dermidis. As these bacteria are less virulent,and grow m ore slowly, intr aoperat ive cultures
should be taken and incubated for a longer
per iod than nor m al, 1 4 to 28 days . In cases of
chronic, delayed infection, we rem ove im plants
and con rm t he arthrodesis and the absence
of pseud ar th rosis. Patient s are followe d for ev-
idence of curve progression or pseudarthrosis
in follow-up and are re-instrumented only
wh en needed for deform ity progression.
When successfully treated, patients with
deep wound infection following ASD surgery
can expect good outcomes, equivalent to
those of patients who did not encounter this
complication.21
! Chapter Summary
Pseudarthrosis and infection are two comm on
reasons for revision surgery in adult spinaldeformity. Both of these pathologies have risk
factors that are m odi able by both th e patient
and the surgeon. Nicotine avoidance is m an-
datory in ASD, given the already high rate of
per ioperat ive com plicat ions assoc iat ed w it h
these surgeries. Evaluat ion of bone h ealth, with
bo ne m inera l densit y te st ing, and t reat m ent
of osteoporosis shou ld be routine. Approp riate
management of diabetes mellitus, including
tight control of perioperative blood glucose
levels, will help minimize risks of periopera-
tive infection. Ant ibiotic pro phylaxis shou ld be
given w ithin an h our of incision and be tailored
to prophylaxis against comm on ora in the
community.
As techn iques evolve, w ith concom itant im-
provem ents in im plants and b iologic therap ies,
the rates of these two complications will fall.
Ultimately, met iculous at tent ion to detail be-
fore, during, and after surgery w ill ma ximize
the likelihood of success and m inimize com- plicat ions in these pat ients.
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138 Chapte r 11
Pearls
Smo king cessat ion is necessary in ad ult spinal de-
formity surgery.
Evaluation for osteoporosis, with bone mineral
density testing, and appropriate pharmacologi-cal intervention should be performed in ASD
patients.
Teriparatide is an anabolic agent available for
managem ent of osteoporosis and may have some
be ne t in achieving art hro de sis.
Facetect omies must b e performed , and decort i-
cation of dorsal elements is necessary.
Recombinant hum an bone m orphogene tic pro-
tein-2 decreases rates of reoperation for pseu-
darthrosis in ASD.
Informe d consent spe ci cally ta ilored to t he use
of rh-BMP2 in bot h on-labe l and o -label app lica-
tions (addressing risks of pain, seroma, ectopic bone, and po te nt ial for malignancy) should be
sought from the patient.
Iliac or S2-alar-iliac screws should be placed rou-
tinely, when fusing to S1.
High-density (" 1.8 screws/level) constructs are
recommend ed in ASD.
Patient facto rs associate d with surg ical-site infec-
tions in ASD include high body mass index and
poorly con trolled diab et es m ellitus.
Prophylactic, intravenous antibiotics must be ad-
ministered with in 1 hour of incision.
Prophylactic, intra-site, lyophilized vancomycin
po wder may de crease rat es of surgical-sit e
infection.
Aggressive management of acute, deep wound
infections o ers patients a chance for equivalent
outcom es once the complication has resolved.
Pitfalls
Nicot ine exposure increases rat es of pseud ar-
throsis. One must resist t he de sire to o perate o n
pa tien t s who are using nicot ine prod uc ts an d
insist that they be compliant with smoking ces-
sation prior to surgery.
Implants and osteobiologics do not compensate
for poo r planning and e xecution of te chnique in
ASD. Poor planning and performance increase
rates o f pseudar throsis and surgical-site infection.
The use of rh-BMP2 without informed consent
from the p atient is ill-advised.
Inadequate debridement of pseudarthrosis
tissue increases the likelihood of recurrent
pseu dart hrosis.
Prophylactic antibiotics must be administered
within 1 hour of incision. Cefazolin should be
given e very 4 hours during surgery.
Poorly controlled postoperative blood glucose
levels increase t he risk of infect ion.
References
Five Must- Read Reference s
1. Pichelm an n M A, Len ke LG, Brid we ll KH, Good CR,
O’Leary PT, Sides BA. Revision rates following pri-
mary adult spinal deformity surgery: six hundred
forty-three consecutive patients followed-up to
twenty-two years postoperative. Spine 2010;35:
219–226 PubMed
2. Kelly MP, Len ke LG, Bridwe ll KH, Agar wa l R, Godzik J,
Koester L. Fate of the adult revision spinal deformity
pat ien t: a sin gle inst it ut ion experience. Spin e
2013;38:E1196–E1200 PubMed
3 . Richard s M. Unan ticipated revision surger y in adult
spinal deformity: an experience with 815 cases at
one institution. Spine 2014;39(26, Suppl 1):S174–
182 PubMed
4. Mok JM, Cloyd JM, Bradford DS, et al. Reoperation
after prim ary fusion for adult spinal deform ity: rate,
reason, and tim ing. Spine 2009; 34:832– 839 PubMed
5. Kim HJ, Buchow ski JM, Zebala LP, Dickson DD,
Koester L, Bridwell KH. RhBMP-2 is superior to iliac
crest bone graft for long fusions to the sacrum in
adu lt spinal deform ity: 4- to 14-year follow-u p. Spine
2013;38:1209–1215 PubMed
6. Kim YJ, Brid well KH, Len ke LG, Rhim S, Cheh G. Pseu-
darthrosis in long adult spinal deform ity instrumen -
tation and fusion to the sacrum : prevalence and r isk
factor analysis of 144 cases. Spine 2006;31:2329–
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7. Stoker GE, Buchowski JM, Bridwell KH, Lenke LG,
Riew KD, Zebala LP. Preoper ative vita m in D st atu s of
adults u nder going surgical spinal fusion. Spine 20 13;
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8. Hirsch BP, Unnanuntana A, Cunningham ME, Lane
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9. Smit h JS, Sha rey CI, Am es CP, et al; Inte rn at ional
Spine Study Group. Assessme nt of symp tom atic rod
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adult spinal deformity. Neurosurgery 2012;71:862–
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10. Kebaish KM. Sacropelvic xation: techniques and
complications. Spine 2010; 35:2245 –2251 PubMed
11. Car re on LY, Djurasovic M, Glassm an SD, Sailer P. Di-
agnostic accuracy and reliability of ne- cut CT scans
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Pseudarthrosis and Infect ion 139
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instrum ented posterolateral fusion w ith surgical ex-
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13 . Smit h JS, Sha rey CI, Sansu r CA, et al; Scoliosis Re-
search Society Morbidity and Mortality Committee.
Rates of infection after spine surgery based on
108,419 procedu res: a re port from t he Scoliosis Re-
search Society Morbidity and Mortality Committee.
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14. Woods BI, Rosario BL, Chen A, et al. The association
be twee n pe riop er at ive a lloge neic transfu sion volu m e
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lum bar sp ine su rgery. J Bone Joint Surg Am 2013;95:
2105–2110 PubMed
15. Olsen MA, Nepple JJ, Riew KD, et al. Risk factors for
surgical site infection following orthopaedic spinal
operations. J Bone Joint Surg Am 2008;90:62–69
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16. Richard s JE, Kau m ann RM, Zucker m an SL, Obre m s-
key W T, May AK. Relation ship of hype rglycemia a nd
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17. Milsto ne AM, Maraga kis LL, Tow ns en d T, et a l. Tim ing
of preop erative antibiotic prop hylaxis: a m odi able
risk factor for deep surgical site infections after p edi-
atric spinal fusion. Pediatr Infect Dis J 2008;27: 704–
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18. Swe et FA, Roh M, Sliva C. Intra wou nd app lication of
vancomycin for prophylaxis in instrumented thora-
colum bar fusions: e cacy, dru g levels, and patien t
outcomes. Spine 2011;36:2084–2088 PubMed
19. Tub aki VR, Rajasekar an S, She tt y AP. E ect s of usin g
intravenous antibiotic only versus local intrawound
vancomycin antibiotic powder application in addi-
tion to intravenous antibiotics on postoperative in-
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20. Blank J, Flynn JM, Bron son W. The use of post ope ra-
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21. Mok JM, Guillaum e TJ, Talu U, et a l. Clinical ou tcom e
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Note: Page references followed by f or t indicate p ages or tab les, respect ively.
A
Acetabu lum , iliac screw xation- related injur y to,
53, 54
Adjacent segm ent disease/failure, 24, 56–5 7,
65–66
proxim al, 25
Adolescent idiopath ic scoliosis
corrective procedu res for, 123– 127, 125 f, 126 f
fusion levels in, 23
pro gressio n to ad ult sco liosis , 78 , 79 f
unt reated, 1
Adu lt degen erat ive spinal deform ities, 1. See also
Adu lt scoliosis, degene rative (de novo)
clinical evaluation of, 2–4
epide m iology of, 1–2
pre op era t ive eva luat ion of, 2–4
pro gressio n ra te of, 2
Adu lt scoliosis, 1–11
classi cation of, 79, 81
de nition of, 78
degen erat ive (de n ovo), 80 f
apical disk height in , 80 f, 81coronal imbalance in, 81–82
de nition of, 78
di eren tiated from adu lt idiopath ic scoliosis,
79, 81–82, 93
lumbar kyphosis associated w ith, 80 f, 83
pat hology of, 83
spinal curve pattern s in, 81
stenosis-related, 82
surgical option s for, 78–79
tru nk shifting in, 81–82
fusion levels for, 18
idiopathic
as back pain cause, 82de nition of, 78
di eren tiated from adu lt degen erat ive scoliosis,
79, 81–82, 93
proxim al ju nct ional kyp hos is in , 11 0
nonop erative m anagemen t of, 78
surgical treat m ent of, indications for, 78
treatm ent d ecision making about, 12–27
Adu lt spina l deformit ies. See also Adu lt scoliosis
de nition of, 1
nonop erative m anagemen t of, 4, 17, 99
pat hogenes is o f, 1
pre se nt ing age of, 2 , 5
prevalence of, 99
progr ession of, 2 , 4, 17
typ es of, 1
Adult spinal deformity surgery
indications for, 4–5, 78, 99
levels of, 8–9
outcomes measures for. See Health-related quality
of life (HRQOL) m easu res
Album in levels, preope rative assessm ent of, 5
Am er ican Spin al Injur y Association (ASIA) scor ing
system , for spin al cord injur y, 68, 69 f, 70Ank ylosing sp ond ylitis, osteotom y plan ning for,
31–32, 31 f
Anterior approach. See also Comb ined ante rior/
pos te r ior a ppro ach
in ad ult scoliosis, 78
in rigid spinal deform ity surger y, 24
Anter ior column su pport
e ect on union rates, 130–131
in osteopo rotic spine, 62
in pseu doarth rosis revision surgery, 134
Ante rior xation, in osteop orotic spine, 63
Anterior lumbar interbody fusion (ALIF), 130–131,
13 4Arte ry of Adam kiewicz, in ost eotom y, 29–3 0, 29 f, 31
Index
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142 Index
B
Back pain, adu lt spinal d eform ity-related , 2, 9, 78
axial, 12, 85
clinical evaluat ion of, 2
diagnosis of, 12–16 , 13 f, 14 f, 15 f, 16 f
as indication for surger y, 17
mechanical, 82neurogenic, 82
radiologic assessm ent of, 13–1 6, 13 f, 14 f, 15 f
Biome chanics, of spinal deform ity correct ion,
120–129
implant mater ials, 133
intraoperative mechanical forces, 126–127,
12 6 f
me chanical proper ties of imp lants, 120–121
after man ual bending, 122–123, 122t
spinal viscoelasticity, 123, 1 24 f, 128
stress-strain curves, 120–121, 121 f
Bisphosphonates, 132
Blood m anagemen t, perioperative, 5–6
Blood t ran sfusions, comp lications and risks of,
6, 135
Bone grafts, 133, 134
Bone m ineral d ensit y (BMD)
correlation w ith
implant pu llout stren gth, 58, 132
insertional torque, 132
falsely elevated, 132, 132 f
low, as spinal imp lant failure cause, 56
in osteop orotic spine, 56, 58, 132, 138
pre op era t ive m ea su re m ent of, 7 , 57
Bracingcontraindication to, 4
pos to pera t ive, of ost eop or ot ic spin e, 65, 66
But tock pain, 13, 16
C
Cages, for osteop orotic spin e, 63
Cen tr al sa cral ver tical lin e (CSVL), 14–1 5, 15 f, 84
Claudication
neu rogenic, 2, 78, 82
di eren tiated from vascular claud ication, 16
level of surgical treatm ent for, 8
ner ve root comp ression-related, 16
pharm acot her ap y for , 4
relationship to coronal imbalance, 85
vascular, di eren tiated from neur ogenic
claud ication, 16
Cobb an gle, in ad ult spin al deform ities, 2, 82
correlation with apical disk degeneration, 83
discrepancy w ith rotatory su bluxation, 82
less than 30°, 18, 19 f, 25
pre op era t ive m ea su re m ent of, 3
in proximal junct ional kypho sis, 106, 107 t , 11 5
in spinal curve pr ogression, 17
as surgery outcome m easure, 95–96
Codm an , Ern est A., 102Combined anterior/posterior app roach
in ad ult scoliosis, 78
as proximal junctional kyph osis cause, 107 t ,
108–109, 114
as respiratory system injury cause, 6
Comorbidities, in adult spinal deformity patients,
5, 7, 56
Compensatory spinal curves, 81–82
Com plications, of adu lt spinal deform ity surger y,3, 24–25, 100–101. See also Neurologic
complications, of adu lt spinal deform ity
surgery; Pseudoarthrosis; Surgical-site
infections
causes of, 24–25
pre op er at ive assessm en t for, 5
pre vent ion of, 7–8
rate of, 17, 24
Com put ed to m ography (CT)
pos top era t ive, 74 , 76
pre op er at ive, 3, 57
of pseudoart hrosis, 133
Compu ted t omography m yelography
for back pain assessm ent , 13
intraoperative, 74
“Con e o f econo my,” 13
Cont ractu res, of hip or kn ee, 3
Corona l balance
in ad ult scoliosis, 84, 84 f
assessm ent o f, 14–1 5, 15 f, 84
Corona l comp ensat ion, de nition of, 84
Coronal decompensation. See also Coron al
imbalance
de nition of, 84, 85
pos top era t ive, pr eve nt ion of, 87– 88Corona l im balance
in ad olescent idiop athic scoliosis, 79 f, 81
in ad ult scoliosis
in adu lt degen erat ive scoliosis, 81–8 2
correlation w ith qu ality of life, 84–85
de nition of, 85–86
with associated sagittal imbalance, 87
e ects of, 13
greater than 4 cm , 8
pos top era t ive, 85
as instrum entat ion failure cause, 88, 90 f –9 2 f, 93
revision sur gery for, 88, 90 f –92 f, 93
pre op er at ive, 85
typ es of, 24
typ e A, 84 f, 87, 93
t ype B, 84 f, 87, 93
t ype C, 84 f, 87, 88, 89 f, 93
Cort icosteroid epidu ral injections, diagnostic, 4
Cost, of adu lt spinal deform ity sur gery, 95, 98–99
Cross-links
in osteop orotic spine, 61, 66
in ped icle screw xation, 127
C7 plum b line, 14–15, 15 f, 11 0
DDecompression, 8
e cacy of, 17
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Index 143
with fusion
anterior an d p osterior fusion, 8, 78
complication rat e of, 100
limited p oster ior fusion, 8, 78
lumbar cur ve instru me nted fusion, 8, 78
with pedicle subt raction osteotomy, 34–35
Decompression-only surgeryfor ad ult d egener ative scoliosis, 78
complication rat e of, 100
indications for, 18, 25
versus shor t or long fusion, 26 t
Degene rative cascade, of adu lt spinal deform ities,
12
Degree of slip, radiologic measu rem ent of, 13–1 4,
13 f, 14 f
Denosum ab, 132
Diabetes m ellitus, as su rgical-site infection risk
factor, 135–13 6, 138
Disk degener ation
correlation with spinal imbalance, 83
ima ging of, 16
lum bar, 17
Disk height, measu rem ent o f, 14
Dual-energy X-ray absorptiometry (DEXA),
pre op era t ive, 7, 57–5 8, 66 , 13 2
E
Elderly patient s
adu lt spinal deform ity onset in, 2, 5
spinal surger y-related comp lications in, 24
Electromyography
spontane ous, 72triggered, 72
Euro QOL Five Dim en sion s (EQ-5D) qu est ionn aire,
96, 98
F
Facet nerve blocks, 4
Fenest ration, poste rior, 18
Fibular str ut grafting, 48
Flat-back syndrome, with lumbar lordosis, 8
Fractures
of imp lants, 130, 133
osteop orotic, 7, 56, 65, 81, 82
as proximal junctional kyphosis cause,
110–111 114
Fusion. See also Interbody fusion/supp ort
in adu lt degene rative scoliosis, 78–7 9
ant erior, 24
with decompression, 8, 78, 100
indications for, 18–1 9
lim ited, 17
local, w ith pedicle screw xation, 18
long-segment, 18–19, 20 f –2 2 f, 23
complications of, 25, 130
versus decompression-only surgery, 26 t
indications for, 26, 26t w ith lower inst rum ent ed verteb ra (LIV), 23–24 ,
25–26
as pseu doar th rosis risk factor, 130
with uppe r instru me nted vertebra (UIV),
19, 23
in osteop orotic spine, 65, 132
to th e pelvis, as proximal junct ional kyphos is risk
factor, 109
to th e sacrum , 23–24, 25, 26, 79as proxim al junct ional kyph osis risk factor,
10 7t , 109
short-segme nt, 18, 19 f –20 f
indications for, 26, 26 t
G
Gait assessm ent , 3, 13
Galveston tech nique, 49
Groin p ain, 13
H
Harrington , Paul, 120, 127
Harrington instrum ent ation system
developm en t of, 120, 127
with sacral hooks, 48
Harrington t hreaded sacral rods, 48–49
Health -relat ed q ua lity of life (HRQOL) m easu res,
95–105
comm only used measures, 98
correlation w ith
coronal imb alance, 83, 85
sagittal imbalan ce, 83
cost an d value-related m easures, 95, 98–99
de nition of, 95
need for improvement in, 102 pat ient-re por ted m ea su re s (PROMs), 96, 98 , 10 3
physio logical m ea su re s, 9 5– 96
pro cess m easure s, 95
quality m easures, 96
radiographic outcomes, 99–100
ut ility scores, 96, 98, 103
Health Utilities Inde x (HUI), 96, 98
Hemoglobin levels, preo perat ive, 5–6
Hemostasis, intraoperative, 6
High-risk patients
decom pression- only surgery for, 18
pro toco l for, 5
Hydroxyapatite, as ped icle screw coating, 59–60,
13 2
Hyperglycemia, as surgical-site infection risk factor,
135–136, 138
Hypovitam inosis D, 6–7, 9, 131
I
Iliac screw xation, 48–5 1, 50 f, 53–54
asymp tom atic haloing of, 53 f, 54
complications of, 53, 54
implantation problem s with, 25, 26
in postoperative coronal imbalance revision
surger y, 88S2-alar- iliac, 51, 52 f, 53, 54
in fusions to S1, 133, 138
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144 Index
Ilium, fusion to, as proxim al junction al kyphosis
risk factor, 106, 109
Infections. See Surgical-site infections
“Instability catch,” 12–13
Instru m entat ion, spinal. See also Osteoporot ic spine,
instrum entat ion strategies for
implication for magnet ic resona nce imaging, 3levels of, 18
rigidity of, as proxim al junction al kyph osis risk
factor, 108
th oracic, w ith fusion exten sion, 8
Interbody fusion/suppor t
anterior lumbar (ALIF), 130–131, 134
complication rate o f, 100– 101
in osteopo rotic spine, 62–6 3, 64 f
in sacral-pelvic xation, 51
tran sforam inal lum bar (TLIF), 130–1 31
Intraop erative m onitoring. See Neuromonitoring,
intraoperative
Ischem ia, spinal, 75
J
Jackson int rasacral rod te chnique , 48
K
Kostuik transiliac bar, 49
Kyphosis
lumbar, adult degenerative scoliosis-related, 80 f, 83
osteotom y for, 30, 34–36, 35 f
pos tlam in ectom y, 13 5
proxim al ju nct ional , 79 , 10 6– 119
clinical outcom es after, 111, 112 t –11 3 t etiology of, 106–1 11, 115
pre vent ion of, 114– 11 5
revision surger y for, 111, 114–1 15, 116 f –11 7 f,
117, 118
risk factors for, 106– 111, 107 t , 11 5
tim ing of, 111
Scheu erm ann ’s, 108, 114–115
thoracic
osteotom y for, 31–32 , 31 f
pos ter ior spin al in st rum entat ion-r ela ted,
123–124
pos top er at ive, 11 0, 1 23– 124
pre op era t ive, 10 7 t , 110
techn iques for creation of, 123– 125
L
Laminectomy
in decompression-only surgery, 18
as kyph osis cause, 135
Leg-length discrepan cy, 2–3, 79, 81
Leg p ain, 16, 18 , 82
Lidocaine, as spinal cord ischem ia treatm ent , 75
Listhesis. See also Spond ylolisthesis
anteroposterior, 3
later al, 3, 16Lordosis
xed, osteotom y for, 40, 42 f, 43
lumbar
adu lt degene rative scoliosis-related , 80 f, 82
adu lt idiopath ic scoliosis-related, 82
anterior fusion app roach to, 8
with at-back syndrom e, 8
as proxim al junction al kyph osis risk factor,
107 t , 109, 110, 115radiological measurement of, 15
as spinal surgery outcome measu re, 95–96
Lower in stru m ent ed ver tebrae (LIV)
in long-segmen t fusion, 23–24, 25–26
in proximal junctional kyphosis, 109
Lum bar spin e. See also Lordosis, lum bar
degen erative adu lt scoliosis of, 81
pedicle scre w xat ion in , 60
Lum bosacral xation, in osteop orotic spine, 61
Lumbosacral junction
biom echan ics of, 45
sacral-pelvic xation of, 45–5 5
Lum bosacral pivot point , 45
Luque instr um entat ion, 91 f
Luq ue L- xat ion, 49
M
Magnetic reson ance imaging (MRI)
of disk degene ration, 16
lum bar, for back pain assessm ent , 13
pos top er at ive, 74 , 76
pre op er at ive, 3, 70
of spinal steno sis, 16
Mean ar ter ial pressu re (MAP), intra oper ative
m onitor ing of, 71, 73, 74, 75Metab olic bon e disease, as adu lt scoliosis cause,
1, 79
Metallic implan ts, for spinal deform ity correct ion,
120–129
for ad olescent idiopat hic scoliosis, 123– 127, 125 f,
126 f
nite elem ent ana lysis of, 126–1 27
fractures of, 130, 133
histor y of, 120, 121 t
implant d ensity, 133
relationship w ith correction rate, 127
infection of, 135
intraoperative mechanical forces on, 126–127,
126 f
m aterials for, 133
m echanical properties of, 120–121
after man ual bending, 122–123, 122 t
spinal viscoelasticity an d, 123, 124 f, 12 8
stress-st rain cur ves of, 120– 121, 121t
Methylprednisolone, 75
Microdensitometry, preoperative, 57
Motor evoked pote nt ial (MEP) intra oper ative
m onitor ing, 29–3 0, 43, 71, 72, 73, 74
N Nar cot ics pain m edica t ions, 4 , 10
Neck Disa bi lit y In dex (NDI), 96
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Index 145
Nerve ro ot com pre ssion , sym ptom s of, 16
Nerve ro ot /t ra nsfora m in al inject ions, d iagnos t ic,
3– 4
Neuro log ic co m plica t ions, o f ad ult sp in al deform it y
surgery, 68–77
delayed postoperative, 75–76
intraoperative managem ent of, 71intraoperative neuromonitoring for, 29–30, 43,
71–73 , 74, 75
mechan isms of, 70
pos top er at ive m an age m ent of, 75
pre op era t ive risk as sessm en t for, 7 0
pre valence of, 68–7 0, 68 f
steroid protocol for, 75
Neuro log ic d e cit s, p re op er at ive eva luat ion of, 2
Neuro m on itor ing, in tra op er at ive, 74 , 75
m otor evoked pote nt ial (MEP) m onitor ing, 29–3 0,
43, 71, 72, 73, 74
som atosen sory evoked pote nt ial (SSEP) m onitor-
ing, 71–72, 73, 74
Neurovascular e xam in at ion, pr eop era t ive, 3
Nicot ine. See also Smoking cessation
e ect on patient outcomes, 131
Non stero idal ant i- in am m at or y d rugs (NSAIDs), 4
Non union . See also Pseudoarth rosis
nicotine-related, 131
rates of, 133, 134
reope ration r isk of, 134
Nut rit ional st at us, p re op era t ive asse ssm ent of, 5 , 10
Nut rit ional su ppor t , in sp inal su rger y p at ien ts, 5
OObesity
as proxima l jun ctiona l kyphosis risk factor, 110
as sur gical-site infection r isk factor, 136, 138
Open anter ior surgery, pulm onary function e ects
of, 6
Osteop enia, 56, 111, 114, 132
Osteop hytosis, preope rative evaluation of, 3
Osteoporosis, in adult spinal deformity patients,
138. See also Osteoporotic spine, instru m en-
tat ion strategies for
bo ne m inera l densit y in , 56 , 58 , 13 2, 1 38
diagnosis of, 132
man agement of, 132, 138
pre op era t ive m edica l t re at m ent for, 58
as proxim al junction al kypho sis risk factor, 106,
110–111
in spinal surgery pat ient s, 7, 10
Osteoporotic spine, instrumentation strategies for,
56–67
adjacent segment failure in, 56–57, 65–66
anchor points en hancement, 61
anterior xation, 63
bo ne- im plan t in te rface p ro tect ion , 63 , 65
xation failure in, 56–5 7, 65–6 6
fusion, 132for instru me ntat ion failure p revention
intraoperative measures, 58–65
pos top era t ive m ea su re s, 6 5
pre op era t ive m ea su re s, 5 7– 58 , 66
interbody suppor t, 62–63, 64 f
nonu nion and, 57
ped icle scre w xat ion , 58 –61
insertion technique and insertion torque in,
60–61tract augmen tation in, 59–60
pro phylact ic ve r teb ro plast y, 61 –62 , 66
pse udoa rthro sis an d, 56 –5 7, 6 5– 66
sem i-rigid xation, 63
Osteotomy, 8. See also Vertebral column resection
(VCR)
closure of, 30, 35–3 6, 36 f
for xed lordosis, 40, 42 f, 43
with long-segment fusion, 24
ped icle su btra ct ion
closure of, 35–36 , 36 f
comparison w ith Smith-Petersen osteotomy, 36 f
complications of, 34
for coronal im balance corre ction, 88, 91 f
outcomes, 100
with previous anterior implants, 36–37, 38 f
revision surger y of, 131 f
for rigid spinal deform ities, 30, 31–3 2, 31 f, 33 f,
34–36, 35 f, 36 f
techn ique of, 34–3 6, 35 f
for typ e A coronal imba lance correction , 87
pos te r ior
outcom es of, 100
in pseu doarth rosis revision surgery, 134
Smith-Petersen, 36 f, 10 0as spinal cord infarction cause, 29–30
for proxim al junction al kyphos is, 115, 116 f, 11 7
for rigid spinal deform ities, 28–4 4
anterior app roach in, 28
closure of, 30
xation in, 30
fusion across, 32
level of osteotom y, 30–3 1
m ulti-level vertebre ctomy, 32, 33 f, 40, 41 f
num ber of osteotomies required, 30
pedicle su btra ct ion os teo to my, 30 , 31 –32 , 31 f,
33 f, 34–36 , 35 f, 36 f
p lann ing of, 28–3 2
pos terior a ppro ach in , 28
pos terior colum n os teot om y, 33 –3 4, 3 3 f, 34 f
as single procedur e, 32
as staged procedure, 32
transdiskal pedicle subtraction osteotomy, 32,
33 f, 36–37 , 37 f
typ es of, 32–4 0
three-column , 8–9, 10
for coronal imb alance correct ion, 87–88, 89 f
deform ity exibility determination in, 28–29
indications for, 28–2 9
level of, 31versus m ultiple posterior column releases, 28,
29
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146 Index
Osteotomy (continued )
for proxim al jun ctional kyph osis, 117 f
reope ration rate for, 101
spinal cord blood ow in, 29–30
spinal cord protect ion in, 43
surgical exposure in, 29
thoracolumbar, 29, 29 f Oswestry Disability Index (ODI), 8, 96, 98, 101–102,
11 1
Outcome m easures, in spinal deform ity surgery.
See Healt h- relate d q ua lity o f life (HRQOL)
measures
P
“Painfu l catch,” 12– 13
Pain man agement , in adult spinal deformities, 4, 10
Parathyroid horm one, 132
Patient-reported outcome measures (PROMs), 96,
98, 103
Pedicle rods, biomecha nical proper ties of, 120
Pedicle screw xation
altern atives to, 30, 43
intraoperative assessme nt of, 74
w ith local fusion, 18
in osteoporotic spine, 58–61, 132–133
as proxima l jun ctional kyph osis risk factor, 108
sacral, 46–48, 47 f
m edial insert ion tr ajectory for, 51, 53, 53 f
Pedicle screw s
biom echan ica l p ro per t ies o f, 120
hydroxyapatite-coated, 59–60, 132
m echan ical forces on, 126–127 , 126 f Pediculolaminar instrum entat ion, for osteoporot ic
spine, 61
Pelvic incidence (PI), as spinal d eform ity su rgery
outcome m easure, 95–96
Pelvic obliquit y, 2–3
Pelvis
fusion to, as proxima l jun ctiona l kyphosis risk
factor, 109
ped icle scre w xat ion in , 60
Periapical redu ction screw s, 30
Physical examin ation, preop erat ive, 70
Physiological outcome m easur es, 95–9 6
Polyme thylm eth acrylate (PMMA) bone cem ent , 59
Posterior app roach, 9. See also Combined anterior/
pos te r ior ap pro ach
in ad ult scoliosis, 78
in severe adu lt spinal deformit ies, 6
Posterior column release, multiple periapical
osteotom ies for, 30–3 1
Posterior spinal ligaments, surgery-related dis-
rupt ion of, 106–108, 107 t , 11 5
Postm enopau sal wom en, bone mineral density
screen ing in, 7
Postural imb alance, as back pain cau se, 13
Prealbum in levels, preop erat ive assessm ent of, 5Preoperative evaluation, of adult degenerative
spinal deformit ies, 1–4
Preoperative planning, of adult spinal deformity
surger y, 8–9
Process m easure s, 95
Provocative testing, preo per ative, 3–4
Proxim al jun ctional angle, in proxima l jun ctiona l
kyph osis, 107 t , 110
Pseudoar throsis, 130–134, 131 f, 13 3 f, 13 4 f diagnosis of, 133
Harrington threade d sacral rod-related,
48–49
L5-S1, fus ion- relate d, 25
long-segment fusion-related, 24
m anagemen t of, 133–134
rate of, 130
as revision surgery cause, 130, 133– 134
risk factors for, 130–13 3
sacral hook-related , 48
Psychological disorders, in adu lt spinal deform ity
pat ien ts, 7
Pulmonary disorders, postoperative, 8
Pulmonary function testing, preoperative, 6, 9
Q
Quality- adju ste d life yea rs (QALYs), 98, 99 , 103
R
Radicular pain, 4, 16, 82, 85
Radiculopathy, 2, 78
Radiographic measurements, of spinal deformity,
95–96
Radiograp hic outcom es, of adu lt spinal deform ity
surgery, 99–100Radiological imaging, preoperative, 3, 9, 70
Radiological instability, 13–14, 13 f
Recombinant human bone morphogenetic
pro te in -2 (rh -BMP2), 13 3– 134, 1 38
Recombinant human erythropoietin (rEPO), 6
Reop eration /revision surgery, 101
for oste otom y, 101
for ped icle xation osteoto my, 131 f
for post operat ive coronal imb alance, 88, 90 f –92 f,
93
for p seudoart hrosis, 130, 133–134
for sur gical complications corre ction, 24
surgical-site infection -related, 135
Rigid spinal d eform ities
combined an terior/posterior approach to, 8–9
osteotom y for. See Osteotom y, for r igid spinal
deformities
proxim al ju nct ional kyp hos is- re lat ed , 11 7 f,
11 8
Rod rotation m aneuvers, intraoperative m echanical
forces in, 126–12 7, 126 f
S
Sacral-pelvic xation, 45–5 5
adjunctive ante rior interbody support in, 51anatom ic and biomechanical considerations in,
45–46
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Index 147
indications for, 46
instrum entat ion selection and techniques for,
46–51
iliac xation, 48–51 , 50 f, 52 f
sacral xation, 46–4 8, 47 f
oper ative technique s in, 51, 53, 53 f
pat ien t pos it ioning for , 51Sacral slope, 95–9 6
Sacrum
bo ne m inera l densit y o f, 58
fusion to, 23–24 , 25, 26, 79
as proxim al junction al kyph osis risk factor,
10 7 t , 10 9
pedicle scre w xat ion in , 60
Sagittal alignm ent , global, 107 t , 109–110, 118
Sagittal b alance
pre op era t ive assessm ent of, 8
radiological assessme nt of, 14–15 , 15 f
as surgical outcom e pred ictor, 85
Sagittal imb alance
adu lt degen erative scoliosis-related, 83
with associated coronal imbalance, 87
correlation w ith d isk degenerat ion, 80 f, 83
in osteopor otic spine, 65
pre op era t ive eva luat ion of, 10
proxim al ju nct ional kyp hos is- re lat ed , 11 1
surgical correction of, 87
typ es of, 24
Sagittal plane d eform ities, 13
Sagittal p lum b line, C7, 14–15, 15 f, 11 0
Sagitt al vert ical axis (SVA), in p roxim al jun ction al
kyphosis, 107t , 110, 114, 115Sciatic ner ve, iliac screw xation-r elated injur y to,
53, 54
Scoliosis, 1. See also Adolescent idiopath ic scoliosis;
Adu lt scoliosis
neu rom uscular, as surgical-site infection risk
factor, 135, 137 f
pr im ar y d egenera t ive, 1
secondar y, 1
surgery-related, 1
Scoliosis Research Societ y, 84
Morbidity and Mortality d atabase, 135
SRS-22 quest ionna ire, 8, 11, 96, 98, 101–1 02
Sem i-rigid xation, in osteop orotic spine, 63
Severe adu lt spinal deform ities, surgical decision
making regarding, 17–26
Short Form 6 Domains (SF-6D), 96, 98
Shor t Form -36 (SF-36), 96, 98
Slip an gle, radiological m easure m ent of, 13–1 4,
13 f, 14 f
Sm oking cessation, preo perat ive, 6, 8, 131, 138
Som atosen sory evoked p oten tial (SSEP)
intraoperative monitoring, 71–72, 73, 74
Spee d techn ique, of bular str ut grafting, 48
Spinal cord injur y
acute, medical treatm ent for, 75delayed intraoperative, 75–76
Spinal cord per fusion, int raop erat ive, 73
Spinal cu rves
compensatory, 81–82
progr ession of, 16– 17
Spinal instab ility, diagnosis of, 12–13
Spinal surger y
decision m aking for, 17–2 6
high-risk protocol for, 5indications for, 17
as scoliosis cause, 1
Spin e, viscoelasticity of, 123, 124 f, 12 8
Spinopelvic imbalance, radiographic determination
of, 3
Spinopelvic parameters, as spinal deformity surgery
outcome m easures, 95–96
Spondylolisthesis
degenerative, 12
L5-S1
fusion sur gery for, 25
slip angle m easurem ent in, 14
lateral, 17
Stagnara Wake-Up Test, 71, 73–74
Sten osis, spinal
im aging of, 16
lumbar
as adu lt degen erative scoliosis cause, 82
at L5-S1, 23
as pseu doar th rosis risk factor, 130
Sublaminar instr um entat ion, 48, 61
Sublu xation, rotator y, 15–1 6, 16 f, 82
de nition of, 82
discrepan cy with Cobb an gle, 82
w ithin fusion block, 26 pre op era t ive eva luat ion of, 3
as spinal cu rve pr ogression risk factor, 17
Sup erior gluteal arte ry, iliac screw xation- related
injury to, 53
Surgical-site infections, 134–13 7
antibiotic prophylaxis/treatm ent for, 134–135,
136, 137, 138
diagnosis of, 136– 137, 137 f
man agement of, 137
as revision surger y cause, 130
risk factors for, 135–13 6, 138
T
Teripar atide, 132 , 134, 138
Thoracic instru me ntat ion, with fusion extension, 8
Thora cic spine, ped icle screw xation in, 60
Thora columb ar spine, adult degen erat ive scoliosis
of, 81
Thoracolum bar/th oracolum bosacral orthoses
(TLO/TLSO), 4
Transforaminal lumbar interbody fusion (TLIF),
130–131
Tran siliac xat ion, 48– 49
Tran ssacra l iliac xation , 51, 52 f
Transver tebral bular str ut grafting, 48Tricor tical xat ion, of sacral pe dicle screw s, 46,
47 f
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148 Index
U
Universal clamp t echniqu e, 124– 125
Upper instrum ented vertebrae (UIV)
in long-segmen t fusion, 19, 23
in proximal jun ctional kyphosis, 107t , 108 , 109,
110–111, 114, 118
Urinar y tract infections, per ioperat ive, 7–8, 135
V
Value, of health care, 95, 98–99
of adult spinal deform ity surger y, 102, 103
Vertebrae
apex/apical
in adu lt degen erat ive scoliosis, 81
in ped icle screw xation, 125, 125 f
osteoporotic, pathomorphology of, 58
proxim al neutra l, 15
Ver teb ral colum n re sect ion (VCR)
out comes of, 100
of proxim al jun ctional kyph osis, 115
of rigid sp inal deform ities, 32, 33 f, 37–40 , 39 f
of severe ad ult spina l deform ities, 6
for t ype B coronal imba lance correction , 87
Ver teb ral copla na r alignm en t (VCA), 124Vert ebrectom y, mult i-level, 32, 33 f, 40, 41 f
Vert ebroplast y, prop hylactic, in osteop orotic spine,
61–62, 66
Visual Analogue Scale (VAS), 96, 10 1
Vitam in D de ciency, 6–7, 9, 131
W
Wound infections, postoperative. See Surgical-site
infections
Recommended