Augmentation Techniques for Meniscus RepairLeili Ghazi zadeh, MSc1 Anik Chevrier, PhD2 Jack Farr, MD3 Scott A. Rodeo, MD4

Michael D. Buschmann, PhD2

1Biomedical Engineering Institute, Ecole Polytechnique de Montreal,Montreal, Quebec, Canada

2Department of Chemical Engineering, Ecole Polytechnique deMontreal, Montreal, Quebec, Canada

3Cartilage Restoration Center, OrthoIndy, Greenwood, Indiana4Department of Orthopaedics, Hospital for Special Surgery, NewYork, New York

J Knee Surg

Address for correspondence Michael D. Buschmann, PhD,Department of Chemical Engineering, Ecole Polytechnique deMontreal, 2900 boul Edouard-Montpetit, Montreal, Quebec H3T 1J4,Canada (e-mail: michael.buschmann@polymtl.ca).

Menisci are semilunar-shaped fibrocartilaginous structures1,2

that play central load bearing and load distribution roles in theknee joint.3 Population-based data suggest that meniscaldamage is present in at least one-third of the knees ofmiddle-aged or elderly individuals4 and meniscus-deficientknees are more likely to develop radiographic evidence ofosteoarthritis (OA)5 and increased degeneration over time.6

Although there has been a recent increase in the number of

meniscus repairs performedyearly in theUnitedStates,7onlyasmall portionof allmeniscal tears are considered repairable sothat current surgical treatment of symptomaticmeniscal tearsoften involves partial removal of torn meniscus, whichincreases the risk of developing OA.8–10 Tear properties suchas tear pattern, length, depth, size, stability, location (medialvs. lateral andwhere geographically in each), chronic or acute,patient profile (age, health, symptoms), and joint stability are

Keywords

► meniscus repair► augmentation

techniques► platelet-rich plasma► chitosan

Abstract Menisci display exquisitely complex structure and play an essential weight-bearing rolein the knee joint. A torn meniscus is one of the most common knee injuries which canresult in pain and mechanical abnormalities. Tear location is one aspect whichdetermines the endogenous healing response; tears that occur in the peripheraldensely vascularized zone of the meniscus have the potential to heal while the healingcapacity is more limited in the less vascularized inner zones. Meniscectomy was oncewidely performed, but led to poor radiographic and patient-reported mid- and long-term outcomes. After the advent of arthroscopy, orthopaedic opinion in the 1980s hasbeen swaying toward salvaging or repairing the torn meniscus tissue to preventosteoarthritis rather than performing meniscectomy. Meniscus repair in young activeindividuals has been shown to be effective, reproducible, and reliable if indications aremet; however, only a small proportion of all tears are considered repairable withavailable technologies. Biological augmentation techniques and meniscus tissueengineering strategies are being devised to enhance the likelihood and rate of healingin meniscus repair. Preclinical and clinical studies have shown that introduction ofcellular elements of the blood, bone marrow, and related growth factors have thepotential to enhance meniscus repair. This article reviews the current state of clinicalmanagement of meniscus tears (primary repair) as well as augmentation techniques toimprove healing by meniscus wrapping with extracellular matrix materials, trephina-tion, synovial rasping and abrasion, fibrin/blood clot placement, and platelet-richplasma injections. In addition, the rationale for using polymer/autologous bloodcomponent implants to improve meniscus repair will be discussed.

receivedOctober 11, 2016accepted after revisionMarch 9, 2017

Copyright © by Thieme MedicalPublishers, Inc., 333 Seventh Avenue,New York, NY 10001, USA.Tel: +1(212) 584-4662.

DOI https://doi.org/10.1055/s-0037-1602247.ISSN 1538-8506.

Original Article

all important factors affecting the rate ofhealing andshouldbeconsidered before patients undergo meniscus repair.

One of the major impediments in repairing a damagedmeniscus is that only the outer rim of the tissue is vascular-ized.11–13 Since wound healing in adult tissues is triggered bythe products released with blood clotting, the capacity fornatural repair is optimal in the periphery of the meniscusand diminished in the inner margins.14 Tear location thusbecomes critical, and tears occurring in the peripheral vascu-larized portion of the meniscus are the most amenable tohealing and thus, repair. Healing is more difficult in the caseof other tear patterns such as radial, horizontal, fragmented, orwhite–white (W-W) displaced bucket handle and in the case ofcomplex, chronic, or degenerative tears.15,16 When meniscaltears occur in the peripheral vascularized area of themeniscus,repair by suturing leads to satisfactory clinical improvement in70 to90%ofpatients.Nonetheless, theclinical failure rate canbeas high as 20 to 24% depending on, among other factors, thestatus of the anterior cruciate ligament (ACL),17 while incom-plete healing corresponding to structural failure is yet higherthan the clinical failure rate.18 Although previously consideredto be irrepairable, the current trend is to suture tears that occurin the innernonvascularizedmargins,with reportsofsurprisingclinical success in up to 68% of patients,19 while here againstructural failure can be much higher. There remains a need todevelop reproducible and efficient meniscus repair augmenta-tiontechniques. Thepurposeof thecurrent reviewis todescribethecurrentclinicalmanagementofmeniscus tearsanddifferentrepair augmentation techniques that are available includingmeniscus wrapping with extracellular matrix (ECM) materials,trephination, synovial rasping, and abrasion, aswell as applica-tion of exogenous fibrin/blood clots and platelet-rich plasma(PRP). Finally, the rationale for using chitosan–PRP implants toimprove meniscus repair will be discussed.

Current Clinical Management of MeniscusTears

Meniscus tears are among the most common type of kneeinjuries,20,21 and treatment of meniscal tears accounts forhalf of the arthroscopic procedures performed in the UnitedStates.22 Overall, meniscus tears fall into two overlappingcategories: either traumatic or degenerative.15 Age, gender,work-related kneeling, squatting, or climbing stairs areamong the risk factors for developing degenerative tears,while acutemeniscal tears tend to be sports-related23 under-standing that an acute tear can occur in a degeneratingmeniscus. Meniscus lesions in young children are predomi-nantly due to acute trauma or congenital meniscus variantsuch as discoidmeniscus. In older children theyare a result ofaccident/sport and in adults, they aremore chronic tears thatoccur because of trauma, degenerative disease, or a combi-nation of both. In adults, medial meniscus tears are oftenassociated with cartilage lesions and/or concomitant liga-ment damage.16 Medial and lateral meniscus tears areusually categorized based on the anatomic location of thetear, vascularity of the tissue where the tear occurs, and thetear pattern (radial, longitudinal, horizontal, circumferential,

root lesions, bucket handle, oblique/flap tears, and complexdegenerative tears).16,24 Meniscal root tears are defined asradial tears or an avulsion of the insertion of the menis-cus.25,26 Due to failure of the meniscus to convert axial loadsinto hoop stresses, these types of injuries alter load sharingand the continuity of circumferential fibers leading to pro-gressive arthrosis-like changes in the knee. Initially, a ramplesion was defined as a longitudinal tear of the peripheralattachment of the posterior horn of the medial meniscus atthe meniscocapsular junction of > 2.5 cm in length. Due todifferent anatomical locations, there is no current agreementregarding the definition of meniscal ramp lesions. Someauthors suggest that ramp lesions are associated with injuryto the meniscotibial ligament attachment of the posteriorhorn of the medial meniscus, while others say it is producedbya tear of the peripheral attachment of the posterior horn ofthe medial meniscus.27,28 Patient-reported history of recenttrauma or prior injury followed by symptoms of meniscalinjury (instability, locking, effusion, and tibiofemoral jointline pain) as well as physical examination of the knee (jointline tenderness, effusion, and limitation of range of motion)allows for diagnosis of a meniscal tear.15,29

Treatment algorithm of meniscus lesions has evolved tre-mendously in recent years (►Fig. 1). The decision as towhether conservative nonsurgical treatment should be pre-ferred to surgical treatment is highly dependent on the size,pattern, and location of the tear; the patient’s age, healthstatus, and activity level; and the surgeon’s experience.16

Although a considerable number of patients having traumaticor degenerative meniscus lesions are treated nonoperatively,meniscus lesions that seem to be mechanically unstable,complex tears, and mostly degenerative meniscus lesionsthat are symptomatic are often removed by meniscectomy.24

Arthroscopic partial meniscectomy (APM) is still the mostfrequent orthopaedic procedure in orthopaedic surgery,although there is evidence that more conservative treatmentsshould be preferred as the first-line treatment when notassociated with an acute tear, such as with an ACL tear.30–33

Indications for meniscus repair include symptoms di-rectly attributable to the tear, reducibility of the tear, goodtissue integrity, and favorable tear characteristics (e.g., singlevertical) in one plane in the red–red (R-R) or red–white (R-W) zones of the meniscus or when an ACL is recon-structed.15,29,34 The following tears are generally consideredless amenable for repair: chronic tears with plastic defor-mity, complete tears with oblique, horizontal cleavage, orcomplex degenerative pattern in the W-W zone of themeniscus.29,34,35 Longitudinal tears < 10 mm are oftenstable and are therefore often left untreated. Incompleteradially oriented tears that do not extend into the outerperiphery are less likely to heal and are often left untreatedor treated by debridement of the unstable edges. Repair of aradial tear to the periphery is usually encouraged to reducethe risk of having a nonfunctional meniscus. The presence ofeither untreated instability or OA is also a contraindicationfor meniscus repair. It has been demonstrated that meniscusrepair at the time of ACLR is highly correlated with superiorhealing rates over “isolated” meniscus tear repairs.15

The Journal of Knee Surgery

Augmentation Techniques for Meniscus Repair Ghazi zadeh et al.

Recently, there has been a shift toward attempting repair oftears previously deemed irrepairable since preservation ofthe meniscus structure is expected to maintain meniscusfunction and prevent degenerative changes to the joints.16

Satisfactory results have been reported for repair of somehorizontal cleavage tears36 and radial tears,37 for tearsextending into the avascular portion of the meniscus38 andfor patients 40 years and older at the time of surgery.39

Rehabilitation after meniscus repair surgery usually beginswith early active range of motion and restoration of strengthexercises, followed by a return to low-impact daily activitywithin 1 month and return to sports usually at 4 to 6months,when appropriate functional goals are reached and thepatient no longer has point tenderness over the repair site.40

Surgical repair of meniscal tears can be performed withinside–out, outside–in, and all-inside techniques. Tears inthe anterior or body of the medial or lateral meniscus areeasily accessed with the outside-in technique. For far poster-

ior tears, the inside–out or all-inside techniques are pre-ferred. Although inside–out techniques with verticaldivergent sutures are still suggested to be the “gold standard”for meniscus repair, all-inside techniques have the advan-tages of reduced surgical times, ease of use, and low risk ofdamage of neurovascular structures16,34 and comparablehealing rates in several studies.41–45 Early meniscal repairdevices such as the meniscal arrows and meniscal screwshave been associated with chondral damage and have beengradually replaced by suture-based devices. Recently, the all-inside circumferential compression stitching technique hasbeen developed for tears that are difficult to treat withtraditional all-inside techniques.46 Level I and Level II studiescomparing different meniscus repair techniques reportfailure rates between 9 and 43% and anatomic healing ratesbetween 65 and 100% (►Table 1). A systematic review of 13studies reporting the outcomes of meniscal repair at aminimum of 5 years reported a pooled failure rate of 23%

Fig. 1 Treatment algorithm of meniscus lesions. (Adapted from Mordecai et al, 2014.110)

The Journal of Knee Surgery

Augmentation Techniques for Meniscus Repair Ghazi zadeh et al.

Table

1LevelI

andLeve

lIIc

linical

stud

iesof

men

iscu

srepa

ir

Study

Design

Inclusioncriteria

Typeof

tear

trea

ted

Surgical

approa

chSa

mple

size

(%males)

Mea

nag

e(y)

FU rate

(%)

Mea

nFU times

(mo)

Outcome

mea

sures

Definition

offailu

reRe

sults

Brya

ntet

al(200

7)41

Leve

lIRa

ndomized

controlledtrial

Patien

tswitharedu

cible

vertical

men

iscal

tear

>10

mm

inleng

than

dno

t>

3mm

disp

lace

dinto

thejointin

theR-R,o

rR-W

zonethat

was

amen

able

torepa

irus

ingsu

turesor

arrows

Vertical

tears

intheR-Ror

R-W

zone

(1)All-inside

withmen

iscu

sarrows(n

¼51

)(2)Inside–

out(n

¼49

)Syno

vial

abrasion

65%withco

ncomitan

tACL

reco

nstruction

100(62)

2586

28Re

tear

rate

WOMET

ACLQofL

RofM

Retear

was

determ

ined

byrepe

atarthroscop

icev

alua

tion

ofpa

tien

tswithfollo

w-upfor

symptom

sof

persistent

orne

wpa

in,c

atch

ing,

orlockingthat

was

possibly

relatedto

themen

isca

lrepa

ir

Retear

rateswere22

%for

both

grou

psClin

ical

outcom

esimilar

forbo

thgrou

psOpe

rating

timelong

erin

Group

2

Kise

etal

(201

5)11

1Leve

lIRa

ndomized

controlledtrial

Patien

tsag

ed18

–40ywith

anMRI-v

erified

vertical,

long

itud

inal

men

isca

ltea

r,10

–40mm

long

,locatedin

thepe

riph

eralor

themiddle

thirdof

themen

iscu

s,witha

preservedce

ntralb

ucke

tha

ndle

eligibleforred

uction

andrepairwithall-inside

tech

niqu

e

Vertical

long

itud

inal

tearsin

theR-R

orR-W

zone

(1)All-inside

withmen

iscal

arrows(n

¼21

)(2)All-inside

withFasT-Fix

(n¼

25)

Raspingof

tears

22%withco

ncomitan

tor

earlierACLreco

nstruc

tion

46(57)

2610

0for

reope

ration

61for

clinical

24Re

operation

rate

KOOS

Tegn

er

Reop

erationwithin2yas

aco

nseq

uence

ofco

mplaintsdu

eto

reruptureor

impa

ired

prim

aryhe

aling

Reope

ration

rateswere

43%forGroup

1an

d12

%forGroup

2(significant)

Clin

ical

outcom

esimilar

forbo

thgrou

ps

Albrech

t-Olsen

etal

(199

9)42

Leve

lII

Rand

omized

controlledtrial

Betw

een18

and40

yRe

liablepa

tien

ts(noab

use)

Full-thickn

ess

rupture>

10mm

inleng

thLess

than

6mm

from

the

caps

ule

Noform

eripsilateral

men

iscu

ssu

rgery

Noco

mplexruptures

Noarthroscop

icarthritis

Inform

edco

nsen

tpriorto

surgery

Longitudina

lvertical,

bucket-han

dle

tears

(displaced

orin

situ)in

the

R-Ror

R-W

zone

(1)All-inside

withmen

iscu

sarrows(n

¼34

)(2)Inside–

out(n

¼34

)Ra

spingof

tears

27%withco

ncomitan

tACL

reco

nstruction

68(81)

2696

3–4

Seco

nd-lo

ok

arthroscop

yClin

ical

exam

ination

Men

isci

werede

fine

das

healed

iftherewas

noresidua

ltea

rleft

andas

partially

healed

ifthere

was

aresidua

lcleft

less

than

10mm

andthe

men

iscu

swas

othe

rwise

stab

leto

prob

ing

Allothe

rarthroscopic

caseswerede

fine

das

nonh

ealed

91%of

patien

tsha

dhe

aled

orpa

rtially

healed

inGroup

1co

mpared

with

75%in

Group2

(non

sign

ifica

nt)

Ope

rating

timelong

erin

Group

2

Han

teset

al(200

6)11

2Leve

lII

Rand

omized

controlledtrial

Longitudina

lfull-thickn

ess

tear

grea

terthan

10mm

inleng

thLo

cation

ofthetear

less

than

6mm

from

the

men

isco

capsu

larjunc

tion

Noform

ermen

iscu

ssu

rgery

Noev

iden

ceof

arthritis

during

arthroscop

yFixation

ofthemen

iscu

susingon

lyon

etech

niqu

e(nohy

brid

fixation

)

Longitudina

lfull-thickn

ess

tearsin

theR-R

orR-W

zone

(1)Outside–

in(n

¼17

)(2)Inside–

out(n

¼20

)(3)All-inside

withRa

pidL

oc

(n¼

20)

Raspingof

tears

51%withco

ncomitan

tACL

reco

nstruction

57(77)

2710

022

Clin

ical

exam

ination

IKDC

UsingBa

rrett’scriteria,a

repa

ired

men

iscu

swas

cons

idered

healed

ifthere

was

nojointlin

etend

erne

ss,effusion

,and

ane

gativeMcM

urray’s

test

Ifon

eor

moreof

these

parameterswas

presen

t,theresultwas

classified

asafailu

re

Hea

lingrateswere10

0%forG

roup1,

95%forG

roup

2,an

d65

%forGroup

3(significant)

Clin

icalou

tcomeworstfor

Group

3Ope

rating

timelong

erfor

Group

1

Järveläet

al(201

0)11

3Leve

lII

Rand

omized

controlledtrial

Trau

matic

long

itud

inal

unstab

lemen

iscaltea

rin

theR-Ror

R-W

zone

Less

than

6mo’

timede

lay

betw

eentheinjury

andthe

operation

Absenc

eof

dege

nerative

men

isca

ltea

ror

OAof

thekn

eeNoprev

ioussu

rgeryof

the

knee

Trau

matic

long

itud

inal

unstab

letears

intheR-Ror

R-W

zone

s

(1)All-inside

withmen

iscal

screws(n

¼21

)(2)All-inside

withmen

iscu

sarrows(n

¼21

)Ra

spingof

tears

33%withco

ncomitan

tACL

reco

nstruction

42(69)

3110

027

Clin

ical

exam

ination

Lysh

olm

IKDC

MRA

Partialm

eniscalresec

tion

atseco

nd-look

arthroscop

ybe

causeof

persistentkn

eepa

inor

mec

hanicalsym

ptom

sof

catching

ofthekn

ee

Failu

rerateswere17

%for

Group

1an

d30

%for

Group

2(non

significant)

Clin

ical

outcom

esimilar

forbo

thgrou

psMorech

ondralda

mag

efor

Group

1

The Journal of Knee Surgery

Augmentation Techniques for Meniscus Repair Ghazi zadeh et al.

Table

1(Con

tinue

d)

Study

Design

Inclusioncriteria

Typeof

tear

trea

ted

Surgical

approa

chSa

mple

size

(%males)

Mea

nag

e(y)

FU rate

(%)

Mea

nFU times

(mo)

Outcome

mea

sures

Definition

offailu

reRe

sults

Barber

etal

(200

5)43

Leve

lII

Nonran

do-

mized

prospec

tive

cohortstud

y

Patien

tswithlong

itud

inal

men

isca

ltea

rsin

theR-Ror

R-W

zoneof

themen

iscu

s

Longitudina

ltearsin

theR-R

zone(<

3mm

from

the

syno

vial

men

isca

ljunc

tion

)or

intheR-W

zone

(3–5

mm

from

thesyno

vial

men

isca

ljunc

tion

)

(1)A

ll-inside

withBioS

tinge

r(n

¼47

)(2)Inside–

out(n

¼29

)(3)Hyb

ridof

both

(n¼

13)

Raspingof

tear

trep

hina

tion

82%withco

ncomitan

tACL

reco

nstruction

85(64)

2784

27Lysh

olm

Tegn

erCincinn

ati

IKDC

Clin

ical

exam

ination

Iden

tified

during

seco

nd-

look

arthroscopy

dueto

persistentsymptom

s

Failu

rerateswere9%

for

Group

1,0%

forGroup

2,an

d15

%forGroup

3(non

sign

ifica

nt)

Clin

ical

outcom

esimilar

forallg

roups

Noch

ondral

damag

edu

eto

device

Choi

etal

(200

9)44

Leve

lII

Nonran

do-

mized

prospec

tive

cohortstud

y

Patien

tswhoun

derwen

tACLreco

nstructionsus

ing

hamstring

tend

onau

tograft

combine

dwithrepairs

ofthemed

ialm

eniscu

sin

asing

lece

nter

byasing

lesurgeo

n

Longitudina

ltearsof

the

posteriorho

rnof

themed

ial

men

iscu

sin

theR-Ror

R-W

zonewithor

withou

tad

ditiona

lpo

steriorho

rntearsof

the

lateral

men

iscu

s

(1)All-inside

withsu

tures

(n¼

14)

(2)Inside-out

(n¼

34)

Raspingof

tear

100%

withco

nco

mitan

tACL

reco

nstruction

48(92)

2810

036

Lysh

olm

Tegn

erLach

man

Pivo

t-shift

Arthrometer

Clin

ical

exam

ination

MRI

Themen

iscu

swas

cons

idered

healed

ifthere

was

nofluidsigna

lwithin

themen

iscu

son

MRI

71.4%of

men

isci

were

healed

inGroup1an

d70

.6%in

Group2as

per

MRI

Clin

ical

outcom

esimilar

forbo

thgrou

ps

Spindleret

al(200

3)45

Leve

lII

Nonran

do-

mized

prospec

tive

cohortstud

y

Med

ialm

eniscalrep

airs

ofthepe

riphe

ralthirdor

junc

tion

ofthepe

riphe

ral

thirdwiththemiddle

third

performed

bythesenior

surgeo

nwithpa

tella

rtend

onACLreco

nstruc

tion

during

ace

rtaintimepe

riod

Longitudina

l,bu

cket-han

dle

and

dege

nerative

tears

(1)Inside–

out(n

¼47

)(2)All-inside

withmen

iscu

sarrows(n

¼98

)10

0%withco

nco

mitan

tACL

reco

nstruction

145(55)

2486

Med

ian

48KO

OS

WOMAC

SF-36

Lysh

olm

IKDC

Clin

ical

successwas

define

das

noreope

ration

forfaile

dmed

ialm

eniscal

repa

ir

Failu

rerateswere18

%for

Group

1an

d8%

forGroup

1(non

significant)

Clin

ical

outcom

esimilar

forbo

thgrou

psTh

ree-ysu

ccessrates

(proportion

swithno

reope

rations)were88

%forGroup

1vs.89

%for

Group

2

Bied

ert(200

0)52

Leve

lII

Rand

omized

prospec

tive

cohortstud

y

Patien

tswithan

isolated

andpa

infulm

edial

intrasub

stan

cemen

isca

llesion

,withclinical

symptom

sof

amen

iscal

tear

andaMRIlinea

rhigh

grad

e2signa

linten

sity

inthemed

ialm

eniscu

s

Isolated

and

painfulm

edial

intrasub

stan

cemen

isca

llesion

s

(1)Con

servative

therap

y(n

¼12

)(2)Arthroscopicsu

ture

repa

irwithacce

ssch

anne

ls(n

¼10

)(3)Arthroscopicminim

alcentral

resection,

intram

eniscalfi

brin

clot

and

suture

repair(n

¼7)

(4)Arthroscopicpa

rtial

men

iscectom

y(n

¼11

)

40(53)

3010

027

Clin

ical

exam

ination

IKDC

Radiog

raph

sMRI

Not

define

dNea

r-normal

orno

rmal

find

ings

for75

%pa

tien

tsin

Group

1,90

%in

Group

2,43

%in

Group3,

and

100%

inGroup

4(significant)

Abbrev

iations

:ACL,

anteriorcruc

iate

ligam

ent;FU

,follow-up;

IKDC,Interna

tiona

lKne

eDocu

men

tationCom

mittee;

KOOS,

Kne

eInjury

andOsteo

arthritisScore;

MRA,m

agne

ticreso

nanc

earthrograph

y;MRI,

mag

neticreso

nanc

eim

aging;OA,os

teoarthritis;

QofL,

qualityof

life;

RofM

,rang

eof

motion;

R-R,red–red

;R-W,red–w

hite;SF

-36,

Short-Fo

rm36

;WOMAC,Western

Ontario

andMcM

asterUnive

rsities

Osteo

arthritisIndex

;WOMET

,Western

Ontario

Men

isca

lEva

luationTo

ol.

The Journal of Knee Surgery

Augmentation Techniques for Meniscus Repair Ghazi zadeh et al.

with no difference between the different techniques (out-side–in, inside–out, or all-inside with arrows).17 Anothersystematic reviewof 27 studies also reported no difference infailures, clinical scores, or complications between inside–outand all-inside repairs (excluding meniscal arrows andscrews).47 In a third systematic review of 31 studies, theauthors were unable to determine which all-inside devicehad the lowest failure rate.48 A meta-analysis of 21 studiesreported a higher failure rate of 16% for all-inside meniscalrepair versus 10% for inside–out meniscal repair, bothperformed concurrently with ACLR.49 Nerve injuries areassociated with inside–out technique and implant-relatedproblems are the most common complications with all-inside technique.50 In all of the above-mentioned studies,the authors highlighted the present lack of prospectivestudies with long-term follow-up and the low level ofevidence of available data.

Long-term comparisons of meniscus repair versus menis-cectomy are scarce and there remains a lack of high-levelevidence to guide the surgical management of meniscaltears.51 A randomized prospective comparative studyshowed normal or near-normal findings in 100% of patients(n ¼ 11) treated with APM versus 90% of patients (n ¼ 10)treatedwith arthroscopic suture repair with access channelsat 27 months follow-up.52 In a retrospective study following41 patients up to 96 months, failure rates were 14% in therepair group and 10% in the partial meniscectomy group.53

Clinical outcomes were similar for both groups and no OAprogression was noted, but preinjury levels were regainedonly in the repair group. Another retrospective study com-pared patients treated with inside–out suturing (n ¼ 67) ormeniscectomy (n ¼ 24) and showed more pain in the lattergroup.54 In a retrospective study with 10 years follow-up of32 patients, Lutz et al (2015) showed higher functional andquality of life scores for repaired vertical lesions in stableknees compared with meniscectomized knees.55 Radio-graphic scores were improved for the repaired group sug-gesting a close correlation between functional andradiographic scores and protective effect of meniscus repairagainst OA. Finally, recent systematic reviews and meta-analyses concluded that, although meniscus repairs wereassociated with higher reoperation rate, they result in betterlong-term patient-reported outcomes and activity levelscompared with meniscectomy.56,57 The Multicenter Ortho-paedic Outcomes Network (MOON) prospective longitudinalcohort study reported that a subset of patients treated withmeniscus repair at the time of ACLRhad an overall failure rateof 14% and significant clinical improvement that wassustained for 6 years.58

Augmentation of Meniscus Repair throughTrephination, Rasping, and Abrasion

Vascularity of the meniscus is an important determinant forhealing.11,12 The vascular supply of the meniscus is agedependent and the adult meniscus receives vascularityfrom the perimeniscal capillary plexus, which comes fromthe superior and inferior branches of the medial and lateral

genicular arteries. Multiple preclinical and clinical studieshave demonstrated that lesions in the vascular portions ofthemeniscuswith access to the peripheral blood supply havethe potential for producing a healing response which issimilar to what occurs in other dense fibrous connectivetissues during healing, including hemorrhage, proliferation,differentiation, and remodeling. Injuries in the peripheralzones of the meniscus are filled primarily and initially with ahighly cellular fibrin clot which acts as a scaffold for repaircells that migrate, proliferate, differentiate, and synthesizerepair tissues. Scar tissue remodeling may then take monthsto mimic the meniscus structure and function. Trephinationinvolves the creation of vascular access channels that runfrom the vascular portions of the peripheral meniscustoward the more central avascular area to enable bleeding,clot formation, cell migration, and repair. Several preclinicalstudies have shown that trephination channels enhance thehealing of avascular meniscal tears.

Arnoczky and Warren investigated healing response ofthe meniscus in a dog model at different time points post-injury.11 The creation of vascular access channels resulted incomplete healing of avascular lesions by synthesis of fibro-vascular scar tissue which was similar to fibrocartilaginousmeniscus tissue after 10 weeks. The healing responseappeared to originate from the peripheral synovial tissues.Zhang et al used trephination to treat longitudinal incisionsin the avascular area of the meniscus in a unilateral model indogs and investigated the role of synovial tissues during thehealing process.59 Trephined meniscus repaired first byformation of a granulation tissue which gradually maturedinto scar tissue. Zhang et al repaired longitudinal meniscustears located at the avascular portion of the meniscus bysuturing and trephination in 20 goats.60 At 25 weeks post-surgery, 4 out of 20 defects were fully repaired and 16 werepartially repaired. The amount, distribution, and organiza-tion of collagen bundles were similar to that of normalmeniscus, suggesting that repair tissue has the potential toremodel and mature with time. Cook and Fox tested poly-L-lactic acid bioabsorbable conduits designed to maintaintrephination channels in surgically created longitudinalavascular meniscus tears in 25 dogs.61 Treatments with theconduits in conjunction with suturing resulted in functionalhealing with bridging tissue and biomechanical integrity in71% of avascular meniscal defects, while no healing wasobserved with trephination and suturing. Peripheral displa-cement of the device was commonly observed althoughneither conduit was completely dislodged into the jointnor articular cartilage damage was noted.

Trephination has also shown some benefits in clinicalstudies (►Table 2). Fox et al repaired symptomatic incom-plete meniscus tears (vertical and longitudinal) in 30patients by using arthroscopic trephination and 90% ofpatients reported satisfactory to excellent subjective resultsafter 20 months.62 Zhang and Arnold repaired longitudinaltears by a tooth-like tip trephine device and inside–outarthroscopic horizontal sutures.63 At an average follow-upof 47 months, seven patients had symptomatic meniscalretear (failure rate of 25%) in the suture group, while two

The Journal of Knee Surgery

Augmentation Techniques for Meniscus Repair Ghazi zadeh et al.

Table

2Clin

ical

stud

iesof

men

iscu

srepa

irau

gmen

tation

bytrep

hina

tion

,rasping,

andab

rasion

Study

Design

Inclusioncriteria

Typeof

tear

trea

ted

Surgical

approa

chSa

mple

size

(%males)

Mea

nag

e(y)

FUrate

(%)

Mea

nFU

times

(mo)

Outcome

mea

sures

Definitionoffailu

reRe

sults

Zhan

gan

dArnold

(199

6)63

Leve

lIII

Patien

tswithlong

itud

inal

tearsof

thewhite

zone

atmid-third

area

from

periphe

ralrim

toinne

rrim

ofmen

iscu

s

Long

itud

inal

tears

(1)Inside

–ou

tan

dtrep

hina

tion(n

¼36

)(2)Inside

–ou

t(n

¼28

)95

%withco

nco

mitan

tACLreco

nstruc

tion

64(N

/S)

2210

047

Clin

ical

exam

ination

Patie

ntsco

mplaining

ofrecu

rren

ceof

knee

swellin

gan

dep

isod

esof

lockingor

catching

with

sign

ofjointlinetend

erne

ss,

pain

with

squa

tting,

orpo

sitiv

eMcM

urray’stest

wereco

nsidered

topo

ssibly

have

aretear

ofthe

men

iscu

s

Failu

rerateswere6%

inGroup

1an

d28

%in

Group

2(significant)

Shelbo

urne

andRa

sk(200

1)64

Leve

lIII

Patien

tswith

nond

egen

erative

periphe

ralv

ertica

lmed

ial

men

iscu

stearsthat

were

deem

edsalvag

eable

Periphe

ralv

ertical

med

ialm

eniscu

stears>

1cm

inleng

th

(1)Abrasion

and

trep

hina

tion(n

¼23

3)(2)Left

insitu

(n¼

139)

(3)Inside

–ou

t(n

¼17

6)(4)Notear

(n¼

526)

100%

withco

ncomitan

tACLreco

nstruc

tion

548

2379

Objective58

Subjec

tive

88Clin

ical

exam

ination

Noy

es

Clin

ical

failu

reof

men

iscal

trea

tmen

twas

described

asan

ypa

tien

twho

requ

ired

subs

eque

nt

arthroscop

yformen

iscal

symptomsthat

required

remov

alor

further

repa

ir

Failu

rerateswere6%

inGroup

1,10

.8%in

Group

2,13

.6%in

Group

3,an

d2.9%

inGroup

4(non

sign

ifica

nt)

Group

3repo

rted

morepa

inan

dlower

activity

levels

Shelbo

urne

and

Heinrich(200

4)11

4Leve

lIII

Patien

tswhoha

dlateral

men

iscu

stearsthat

were

left

insitu

orun

derw

ent

abrasion

andtrep

hina

tion

Posteriorho

rn,radial

flap

,pe

riphe

ral,or

posteriortears

(1)Abrasion

and

trep

hina

tion(n

¼43

)(2)Left

insitu

(n¼

289)

100%

withco

ncomitan

tACLreco

nstruc

tion

332(57)

2372

79Noy

esIKDC

Radiog

raph

s

Subs

eque

ntsurgeryfor

thelateralm

eniscu

sFailu

rerate

was

2.4%

Clin

ical

outcome

simila

rforbo

thgrou

ps

Shelbo

urne

etal

(201

5)65

Leve

lIII

Patien

tswhoha

dan

isolated

ACLtear,

periphe

ralv

ertica

lno

ndeg

enerativemed

ial

men

iscu

stear

trea

ted

withtrep

hina

tionalon

e,no

lateralm

eniscu

stears,

norm

alradiog

raph

sbe

fore

surgery,

andno

bilateral

knee

invo

lvem

ent

Periphe

ral

nond

egen

erative

med

ialm

eniscu

stears

atleast1cm

inleng

th

(1)Trep

hination

(n¼

419)

(2)Notear

(n¼

462)

100%

withco

ncomitan

tACLreco

nstruc

tion

881

2269

Objec

tive

85Su

bjec

tive

45Objective

74Su

bjec

tive

IKDC

Cincinn

ati

Patien

tswereco

nside

red

toha

veasymptom

atic

med

ialm

eniscu

stear

after

surgerywhe

nthey

soug

httrea

tmen

tforsu

bseq

uent

injury

ordisabling

symptomsthat

resu

lted

inasu

bseq

uentop

eration

forpa

rtialm

edial

men

isce

ctom

y

Failu

rerateswere

16.3%in

Group

1an

d5.8%

inGroup

2(significa

nt)

Clin

ical

outcome

simila

rforbo

thgrou

ps

Foxet

al(199

3)62

Leve

lIV

Patien

tswhoha

dpreo

perativesu

bjec

tive

andob

jectivefind

ings

ofa

men

isca

ltea

r,co

inciding

withtheco

mpa

rtmen

tof

thekn

eewithan

inco

mpletemen

iscaltea

r,at

thetimeof

arthroscop

y

Vertical,long

itud

inal

tearsthat

were

inco

mplete

Trep

hination

17%withco

nco

mitan

tACLreco

nstruc

tion

30(83)

3397

20Clin

ical

exam

ination

Lysh

olm

N/S

90%pa

tien

tsreported

goodto

exce

llent

subjec

tive

resu

lts

Talle

yan

dGrana

(200

0)70

Leve

lIV

Patien

tswithpa

rtial

stab

lemen

isca

ltea

rswho

weretrea

tedwith

paramen

isca

lsyn

ovial

abrasion

atthetimeof

ACLreco

nstruction

Long

itud

inal,do

uble

long

itud

inal,an

dradial

Syno

vial

abrasion

100%

withco

ncomitan

tACLreco

nstruc

tion

40(50)

2210

040

Clin

ical

exam

ination

Arthrometer

Tegn

erModified

AAOS

Failu

rewas

define

das

asymptomatic

men

isca

ltear

requ

iringsubsequ

ent

surgery

Failu

rerate

was

11%

Morefailu

reson

the

med

ialside

(non

sign

ifica

nt)

Tetiket

al(200

2)69

Leve

lIV

Patien

tswhoha

dmed

ial

jointlin

epa

inthat

interfered

withda

ilyliving

activities

Horizo

ntal

tearsin

the

posteriorha

lfof

the

med

ialm

eniscu

s

Raspingof

tear

Syno

vial

abrasion

0%withco

ncom

itan

tACL

reco

nstruc

tion

25(68)

2310

015

UK-ACL

Excelle

ntresu

ltwas

nopa

in,n

osubjec

tive

symptoms,

fullreturn

tosp

orts,n

oob

jective

patholog

icfind

ings

88%pa

tien

tsclassified

asexce

llent

(Con

tinue

d)

The Journal of Knee Surgery

Augmentation Techniques for Meniscus Repair Ghazi zadeh et al.

patients in the trephination and suture group showedsymptomatic meniscal retear (failure rate of 6%). Shelbourneand Rask repaired peripheral vertical medial meniscustears > 1 cm in length (100% with concomitant ACLR) byusing different techniques.64 Failure rate was 6% for the 233patients who had undergone abrasion and trephination.Shelbourne and Dersam repaired radial flap tear, posteriorhorn tear, and peripheral tears in the lateral meniscus usingabrasion and trephination or left the tears in situ at the timeof ACLR.54 Overall failure rate was 2.4% at 79 months andclinical outcome was similar for both groups. Shelbourne etal repaired peripheral nondegenerative medial meniscustears at least 1 cm in length by arthroscopic trephinationduring ACLR.65 Failure rate was 16.3% at 5.6-year follow-upand trephination-treated tears showed 95% normal radio-graphs. However, none of these studies objectively evaluatedanatomic meniscus healing using an imaging study orsecond-look arthroscopy.

Other augmentation techniques involve rasping themenis-cal tear and slightly abrading the synovium. Okuda et alsurgically created full-thickness longitudinal lesions in theavascular zone, the medial meniscus in a rabbit model andrepaired it by rasping on the surface of the meniscus from theparameniscal synovium to the injured portion.66 Earlymacro-scopic and histological evaluation showed hypertrophic syno-vial tissue invading the lesion from the parameniscalsynovium. Fibrous repair was complete in all layers of theinjured portion in the rasped meniscus at 16 weeks. Theyconcluded that rasping of parameniscal synovium withoutsuturing couldbe anuncomplicatedway toaugmentmeniscushealing. Ochi et al created full-thickness longitudinal tears inthe avascular zone of themedialmenisci in a rabbitmodel andassessedmechanismsofmeniscushealing following raspingofthe parameniscal synovium and meniscus surface.67 Immu-nohistochemistry showed that the rasped surface stayedhighly positive for interleukin-1α, transforming growthfactor-β1 (TGF-β1), platelet-derived growth factor (PDGF),and proliferating cell nuclear antigen at 1, 7, 14, and 7 dayspostsurgery and then gradually declined. They suggested thatrasping could stimulate chondrocytes in themeniscus surfacearea to synthesize specific types of growth factors and cyto-kines, and such synthesized proteins can stimulate the meta-bolismof thechondrocytesandattract thesynovial tissuewithits rich vascularity to the injured site to aid in healing.

Synovial abrasion and rasping have also been appliedclinically (►Table 2). Uchio et al treated full-thickness andpartial-thickness longitudinal tears in 47 patients by raspingthe tear and synovial abrasion.68 Healing rate was a reported92%. They found no effect of age, sex, time between injury andrasping, time between rasping and second-look arthroscopy,and concomitant ACLR on the healing rate. However, healingwas better for partial-thickness tears, shorter tears, tears nearthe capsule, and tears in stable menisci. Tetik et al reportedrepairing horizontal tears in the posterior half of the medialmeniscus in 25 patients by rasping of the tear and synovialabrasion.69 After 15 months follow-up, 88% of the patientswere classified as excellent (no pain, no subjective symptoms,full return to sports, no objective pathologic findings). TalleyTa

ble

2(Con

tinue

d)

Study

Design

Inclusioncriteria

Typeof

tear

trea

ted

Surgical

approa

chSa

mple

size

(%males)

Mea

nag

e(y)

FUrate

(%)

Mea

nFU

times

(mo)

Outcome

mea

sures

Definitionoffailu

reRe

sults

Uch

ioet

al(200

3)68

Leve

lIV

Patien

tstrea

tedby

rasp

ingat

apa

rticular

centerdu

ring

ace

rtain

timepe

riod

Full-thickn

essan

dpa

rtial-thickn

ess

long

itud

inal

tears

Raspingof

tear

Syno

vial

abrasion

67%withco

nco

mitan

tACLreco

nstruc

tion

47(42)

2410

021

Seco

nd-lo

ok

arthroscop

yArthrometer

“Nohe

aling”

indicated

that

thetear

leng

thha

dno

tshortene

dat

the

repa

ired

site

orane

wtear

hadde

velope

d

8%didno

the

alNoeffect

ofag

e,sex,

thetimebe

twee

ninjury

andrasp

ing,the

timebe

twee

nrasping

andseco

nd-lo

okarthroscop

y,an

dco

ncomitan

tACL

reco

nstructionon

healing

Hea

lingbe

tter

for

partial-thickness

tears,

shortertears,

tearsne

arthecaps

ule,

tearsin

stab

lemen

isci

Abbrev

iations

:AAOS,

American

Assoc

iation

ofOrtho

pae

dicSu

rgeo

ns;A

CL,an

terior

cruc

iate

ligam

ent;FU

,follow-up;

IKDC,Interna

tion

alKne

eDocu

men

tationCom

mittee;

N/S,n

otspec

ified

;UK-ACL,Unive

rsityof

Kentuc

kyAnteriorCruciateLiga

men

ttest.

The Journal of Knee Surgery

Augmentation Techniques for Meniscus Repair Ghazi zadeh et al.

and Grana repaired longitudinal, double longitudinal, andradial tears in 40 patients by synovial abrasion at the time ofACLR.70 Overall failure rate was 11% (4% for lateral meniscusand 21% for medial meniscus) at 3.3-year follow-up.

All of the earlier studies indicate that trephination, rasp-ing, and abrasion are easy treatment modalities that cancontribute to meniscus repair. In fact, these augmentationtechniques are often used in conjunction with outside–in,inside–out, or all-inside repair (►Table 1). One potentialdrawback of trephination is that the trephination channelsmay damage the peripheral circumferential fibers and haveadverse effects on the biomechanical properties of themeniscus. In addition, self-collapse and channel closurecould lead to blocked cell migration. Furthermore, it is stillnot knownwhether a single large or multiple small channelsare more efficient for meniscus healing. One limitation ofsynovial abrasion and rasping is that they appear to be lessefficient in repairing tears that are far from the capsule.

Augmentation of Meniscus Repair withFibrin/Blood Clots

Meniscus healing is a complex process that is associated withmany cellular and molecular events, including hemorrhage,clot formation, granulation, vascularization, cell ingrowth, cellinfiltration, ECM synthesis, scar tissue formation, and scarremodeling. Depending on the lesion location and size, healingprocesses may differ. The wound hematoma contains a spec-trum of PDGFs as well as clot components which are chemo-tactic and are expected to promote proliferation anddifferentiation of cells. Fibrin glue, exogenous fibrin clots,and in situ formingfibrin clots have all been used inpreclinicaland clinical studies to augmentmeniscus repair.Microfractureof the intercondylar notchwas also introduced to enhance therepair of isolated meniscus tears by inducing blood and bonemarrow (BM) elements into the joint.71 Although the exactmechanisms of action of fibrin clots have not been completelyelucidated at this point, they appear to have the potential toaccelerate tissue healing in meniscus.

Ishimura et al72 surgically created full-thickness lesions inavascular areas on the anterior segment of the medialmeniscus in a rabbit model. Autologous plasma-derivedfibrin glue used in conjunction with BM cells (BMC) accel-erated histological maturation of the repair tissue andimproved repair compared with the acellular fibrin glue byitself at 12 weeks. Ishimura et al73 arthroscopically repaired40 meniscal tears in 32 patients using purified fibrin glue. At3 years follow-up, two patients had recurrence of meniscalsymptoms and underwent partial meniscectomy. Second-look arthroscopic evaluation rated 20 out of 25 repairs asgood (80%), 4 as fair, and 1 as poor. In another study, Ishimuraet al74 used purified fibrin glue to repair 61 menisci in40 patients. The rate of recurrence of tears in the R-R zoneor R-W zone was 10% at an average follow-up of 8 years,whereas it was 17% for tears in the W-W zone. Second-lookarthroscopy in 27 patients revealed that 77% of repairs wereconsidered good, 11.5% fair, and 11.5% poor. In the study byArnoczky andWarren,11 implantation/placement of exogen-

ous fibrin clot into stable full-thickness defects in the avas-cular medial portion of meniscus in dogs improved thehealing response via proliferation of fibrous connectivetissue, which gradually remodeled into fibrocartilaginoustissue. Filling the lesion area with a fibrin clot provided ascaffold matrix and secretion of mitogenic components torecruit cells that probably originated from the adjacentmeniscal tissue and synovial membrane.

Ritchie et al surgically created unilateral peripheral long-itudinal tears in the meniscus in a goat model to assess theeffect of two different adjunctive healing techniques.75 Goatsin Group I received inside–out horizontal mattress sutures,goats inGroup II received inside–out suturesplusplacementofan exogenous fibrin clot inside the defect as a healingenhancer, and goats in Group III received inside–out sutures,rasping, and synovium abrasion. Healing rates were 100% inGroup I, 17% inGroup II, and 87.5% inGroup III, which suggeststhat the use of the adjuncts was not necessary. Port et al76

surgically created a full-thickness lesion in avascular zones ofthemeniscus in agoatmodel andassessed applicationoffibrinclot and autologous cultured adherent BMC in the site of thedefect by histology and mechanical testing. In this case,administration of cultured BM-derived cells in combinationwith exogenous fibrin clot failed to improve meniscal healingby16weeks.Nakhostine et al77created5 to7 mmlongitudinalfull-thickness incisions in the avascular portion of the menis-cus in an ovine model, which were further injected with 3 mLof blood clot through a trephination channel running from theperiphery of themeniscus to themidportion of the lesion. Theaddition of exogenous blood clot in this model without addi-tional stabilization was not sufficient to promote completehealing of torn menisci.

Fibrin/blood clots have also been used clinically (►Table 3).van Trommel et al treated five patients who had a tear of theposterolateral aspect of the lateralmeniscuswith suturing andplacement of an exogenousfibrin clot in the seamof the tear.78

Healing was complete for the three patients who were avail-able for follow-up. The authors suggested that applicationofanexogenousfibrin clotmight improvehealing of tears located inthe avascular portion of the meniscus. Biedert compared theeffect of four different methods, including conservative ther-apy (n ¼ 12), arthroscopic suture repair with channels(n ¼ 10), arthroscopic central resection and intrameniscaladministration of fibrin clot by suture repair (n ¼ 7), andAPM (n ¼ 11), for treatment of isolated and symptomaticpainful horizontal grade 2 meniscal lesions (intrasubstancemeniscal lesions) on themedial side in 40 patients.52Only 43%of the patients treated with administration of fibrin clot hadnormal or near-normal evaluation at follow-up. Jang et al79

reported a novelmethod fordeliveringfibrin clots to the targetareaofmeniscal tear byarthroscopic techniquetoaugment therate of healing. In this technique, the sutured fibrin clot ispassed through a plastic transparent shoulder cannula to thedesired location by pulling off the needle. They reported asuccess rate of 95%. Ra et al80 used fibrin clot as an alternativeeffective method for treatment of complete radial tear ofmeniscus by arthroscopic inside–out repair suturing in 12patients. They found improved clinical scores and complete

The Journal of Knee Surgery

Augmentation Techniques for Meniscus Repair Ghazi zadeh et al.

Table

3Clin

ical

stud

iesof

men

iscu

srepa

irau

gmen

tation

byfibrin/blood

clots

Study

Design

Inclusion

criteria

Type

oftear

trea

ted

Surgical

approa

chSa

mplesize

(%males)

Mea

nag

e(y)

FUrate

(%)

Mea

nFU

times

(mo)

Outco

me

mea

sures

Definitionoffailu

reRe

sults

Bied

ert(200

0)52

LevelII

Rand

omized

pros

pective

coho

rtstud

y

Patien

tswithan

isolated

andpa

infulm

edial

intrasubs

tanc

emen

iscal

lesion

,withclinical

symptom

sof

amen

isca

ltear

andaMRIlinea

rhigh

grad

e2signa

linten

sity

inthemed

ialm

eniscu

s

Isolated

andpa

inful

med

ialintrasu

bstanc

emen

iscallesions

(1)Con

servative

therap

y(n

¼12

)(2)Arthroscopicsu

ture

repairwithacce

ssch

anne

ls(n

¼10

)(3)Arthroscopicminim

alce

ntralresec

tion

,intram

eniscalfi

brin

clot

and

suture

repa

ir(n

¼7)

(4)Arthroscopicpa

rtial

men

iscectom

y(n

¼11

)

40(53)

3010

027

Clin

ical

exam

ination

IKDC

Radiog

raph

sMRI

Not

define

dNea

r-no

rmal

orno

rmal

find

ings

for

75%pa

tien

tsin

Group

1,90

%in

Group

2,43

%in

Group

3,an

d10

0%in

Group

4(significant)

Ishim

uraet

al(199

1)73

LevelIV

Patien

tswho

had

arthroscop

icmen

isca

lrepairusingfibrin

glue

Longitudina

land

bucket-han

dletears

Fibringlue

Reduc

tion

withsu

turing

inun

stab

letears

32(25)

1863

for

seco

nd-lo

okarthroscopy

46 6for

seco

nd-

look

arthroco

py

Seco

nd-lo

okarthroscop

yPa

tien

tsco

mplaine

dof

men

iscalsym

ptom

sFailu

rerate

was

6%20

repa

irsratedas

good

,4as

fair,

and1

aspo

orby

arthroscopic

evalua

tioncriteria

Ishim

uraet

al(199

7)74

LevelIV

Patien

tswho

had

arthroscop

icmen

isca

lrepairusingfibrin

glue

Longitudina

land

bucket-han

dletearsin

allzon

es

Fibringlue

Reduc

tion

withsu

turing

inthecase

ofun

stab

letears

Rasping

oftear

84%withco

ncomitan

tACL

reco

nstruc

tion

40(33)

2068

for

seco

nd-lo

okarthroscopy

96 10for

seco

nd-

look

arthro-

scopy

Seco

nd-lo

okarthroscop

yPa

tien

tsco

mplaine

dof

men

iscalsym

ptom

san

dreceived

partial

men

iscectom

y

Failu

rerate

was

15%

77%repa

irsratedas

good

,11.5%

fair,

and

11.5%po

orby

arthroscopic

evalua

tion

criteria

Recu

rren

ceof

men

isca

lsym

ptom

sco

rrelated

with

insu

fficien

cyof

the

reco

nstruc

tedACL,

repa

irof

freshtears,

andrepa

irsrequ

iring

supp

lemen

tary

men

isca

lsutures

vanTrom

mel

etal

(199

8)78

LevelIV

Patien

tsthat

had

complete

radial

split

atthelevelo

fthepo

pliteu

sfossaex

tend

ingfrom

the

periphe

ryto

thece

ntral

part

ofthelateral

men

iscu

s

Radial

tears

Outside-in

Exog

enou

sfibrin

clot

Rasping

oftear

20%withco

ncomitan

tACL

reco

nstruc

tion

5(N

/S)

2060

71Se

cond

-look

arthroscop

yMRI

Men

iscu

swas

deem

edto

behe

aled

ifthere

was

nofluidim

bibition

into

thesubstance

ofthefibroca

rtila

geon

MRI

Allcaseshe

aled

Kamim

uraan

dan

dKimura(201

1)81

LevelIV

Patien

tswho

had

horizo

ntal

clea

vagetears

withmen

iscal

degen

eration

Horizon

talc

leavag

etears

All-inside

withFasT-Fix

Exog

enou

sfibrin

clot

9(N

/S)

N/S

100

12Se

cond

-look

arthroscop

yN/S

Cleft

hadclos

edan

dha

dhe

aled

withalaye

rof

vascularsyno

vial

tissue

extend

ingov

ertheprox

imal

surface

ofthelateralm

eniscu

s

Kamim

uraan

dKimura(201

4)82

LevelIV

Patien

tswho

hada

horizo

ntal

clea

vagetear

asso

ciated

with

degen

erationiden

tified

usingMRIand

arthroscop

yClin

ical

find

ings

limited

to

Horizon

talc

leavag

etears

All-inside

withFasT-Fix

Exog

enou

sfibrin

clot

17%withco

ncomitan

tACL

reco

nstruc

tion

18(60for

seco

nd-lo

ok

arthroscop

y)

3656

41 7for

seco

nd-

look

arthro-

scopy

Lysholm

IKDC

Tegn

erSe

cond

-look

arthroscop

y

N/S

Com

plete

healingin

70%of

patien

tsas

assessed

byarthroscopy

The Journal of Knee Surgery

Augmentation Techniques for Meniscus Repair Ghazi zadeh et al.

healing in most patients on follow-up magnetic resonanceimaging and second-look arthroscopy. Horizontal cleavagetears with meniscal degeneration indications are difficult toheal.36 Kamimura and Kimura showed functional joint im-provement and meniscal healing in patients with horizontalcleavage tear with meniscal degeneration (difficult-to-treatinjuries) treated with FasT-Fix (Smith and Nephew) verticalsutures and placement of exogenous fibrin clots within thecleft.81 At 12 months follow-up, they82 showed 70% completehealing rate and improvement of Lysholm, International KneeDocumentation Committee subjective scores, and Tegner ac-tivity level. They suggested that this technique could beconsidered as a treatment option for younger patients with astable knee with a degenerative horizontal cleavage tear. Tobiologically augment repair of meniscal tears, Sethi et aldeveloped a simple intra-articular technique to deliver bloodclots by abrading the synovium and allowing the blood to rundown the synovial wall and into the meniscal cleft, poolingthere and forming a clot adherent to the edges of the separatedmeniscal tear close to the tear site.83 The authors claimed thattheir techniquehas a fewadvantages over using the exogenousfibrin clot such as being simple, easy to handle, safe,minimallyinvasive (doesnotdependonexogenouspreparation), doesnotrequire theassistanceofoperating roomstaff, anddoesnot adda significant amount of time to the meniscal repair.

Although using fibrin/blood clots in the context ofmeniscal repair has yielded equivocal and conflicting resultsin preclinical and clinical settings, this remains a simple andeasy option to potentially augment healing in the setting ofmeniscus repair. Further high-level evidence is still required.

Augmentation of Meniscus Repair withPlatelet-Rich Plasma

PRP is currently used in the sports medicine and orthopae-dics fields to treat different conditions such as tendinopathyor OA.84,85 PRP contains various types of growth factorsincluding PDGF, TGF-β, vascular endothelial growth factor,epidermal growth factor, insulin-like growth factor-I, fibro-blastic growth factor, and hepatocyte growth factor. Intheory, using PRP to augment meniscus repair appears tobe reasonable. Although some orthopaedic surgeons haveincorporated PRP for meniscus repair in their practice,preclinical and clinical data are still lacking. In addition,much of the difficulty in interpreting the effects of PRP is thedocumented variability of the contents of each specificpreparation and that PRP is not a uniform product.

In a study by Ishida et al,86 a gelatin hydrogel scaffold wasused as a drug delivery system for growth factors secreted byPRP to enhance the healing of meniscal defects in a rabbitmodel. The combination of gelatin–PRP was compared withtwo other groups including platelet-poor plasma and controlfor the intervals of 4, 8, and 12weeks. Theirfindings suggestedthat the combination of hydrogel and PRP supports meniscalcell proliferation and the synthesis of an extracellular matrix,which is rich in glycosaminoglycan. In addition, they foundgreater messenger RNA expression of biglycan and decorin.Zellner at al87 created a circular 2-mm punch meniscal defectTa

ble

3(Con

tinue

d)

Study

Design

Inclusion

criteria

Type

oftear

trea

ted

Surgical

approa

chSa

mplesize

(%males)

Mea

nag

e(y)

FUrate

(%)

Mea

nFU

times

(mo)

Outco

me

mea

sures

Definitionoffailu

reRe

sults

apo

sitive

McM

urray’stest

orpa

indu

ring

mov

emen

t,espe

cially

infullflex

ion

Tende

rnessof

the

femorotibialjointlin

eNolim

itationof

rang

eof

motion

Janget

al(201

1)79

LevelIV

Patien

tswho

hadaradial

tear

that

was

deem

edrepairable

Radial,long

itud

inal

inR-W

zone,

tran

sverse

andob

lique

tears

Suturing

Exog

enou

sfibrin

clot

Rasping

oftear

Syno

vial

abrasion

41(N

/S)

N/S

100

8Se

cond

-look

arthroscop

yMRI

N/S

Failu

rerate

was

5%

Raet

al(201

3)80

LevelIV

Patien

tswho

had

complete

radial

tearsof

themen

iscu

s

Radial

tears

Inside–

out

Exog

enou

sfibrin

clot

Rasping

oftear

Syno

vial

abrasion

17%withco

ncomitan

tACL

reco

nstruc

tion

12(92)

N/S

100

30 11forMRI

IKDC

Lysholm

MRI

Seco

nd-lo

okarthroscop

y

N/S

Com

plete

healingin

92%pa

tien

tson

MRI

Abbrev

iations

:ACL,

anteriorcruc

iate

ligam

ent;FU

,follo

w-up;

IKDC,Interna

tion

alKn

eeDocu

men

tation

Com

mittee;

MRI,mag

neticreso

nanc

eim

aging;N/S,no

tspec

ified

;R-W,red–

white.

The Journal of Knee Surgery

Augmentation Techniques for Meniscus Repair Ghazi zadeh et al.

in theavascular zoneof rabbitmeniscuswhichwas theneitherleft emptyor treatedwith biodegradablehyaluronan–collagencomposite matrices loaded/seeded with PRP, BM, BM/me-senchymal stem cells (MSC) precultured in chondrogenicmedium (CM) for 2weeks or BM/MSCwithout any preculture.Their findings illustrated thatMSCs appear to be necessary formeniscal healing in repair of punch defect model in rabbit. Inline with their previous findings, Zellner et al88 showedseeding of MSC on biodegradable hyaluronan–collagen com-posite matrices, which were precultured in CM produced/generated extensive and organized matrix mimicking nativemeniscus by better biomechanical integration after 12 weeksof histological/mechanical assessment. In both of the earlierstudies, the groups treatedwith hyaluronan–collagen compo-site matrices and PRP did not do better than the emptycontrols. In another study, Shin et al89 compared the effectof leukocyte-rich PRP (L-PRP) on healing of the horizontalmedial meniscus tears in a rabbit model. The horizontal tear(6 mm in width and 1.5 mm in length) were created in theanterior horn of themedialmeniscus andwere either injectedwith L-PRP or left untreated. Histological findings revealedtherewere no significant differences in quantitative histologicscoring between the two groups at 2, 4, and 6 weeks aftersurgery. Lee et al90 created 2-mm full-thickness circulardefects in the anterior portion of the inner two-third of theavascular zone of the medial meniscus in rabbits which werefilledwith fibrin glue or 10% PRP. Upon retrieval after 8weeks,the lesions in both the control and PRP groupswerefilledwithfibrous and fibrillated connective tissue and did not show anymeniscal cartilage formation.

To our knowledge, there are only a fewclinical studies thatuse PRP application for treatment of meniscal lesions(►Table 4). Pujol et al91 used PRP to augment repair andpromote meniscal healing of horizontal cleavage meniscaltears repaired with an open approach. In this case–controlstudy, 34 young patients underwent either a standard openmeniscal repair (n ¼ 17) or the same surgical repair withintroduction of PRP in the lesion (n ¼ 17). They found thatclinical outcome was slightly improved in the PRP group.Griffin et al92 performed 35 isolated arthroscopic meniscusrepairs, 15 of whichwere augmentedwith PRP. In contrast tothe above-mentioned study, they showed that outcome wassimilar after meniscus repair without and with PRP. Theauthors stated that an appropriate larger sample size isneeded to elucidate the beneficial effect of PRP.

Augmentation of Meniscus Repair byWrapping

Meniscus wrapping techniques were first described byHenning et al who used fascial sheath coverage and exogen-ous fibrin clot to treat meniscal tears93,94 (►Table 5). Thefibrin clot was believed to act as a scaffold and also providechemotactic and mitogenic factors and stimuli to assist thereparative process. The authors’ stated opinion was that thefascia sheath worked by partially encapsulating the menis-cus and decreasing the effect of early washout of the exo-genous clot injection.94 The surgical technique involved

rasping of the parameniscal synovium, peripheral whiterim, and tear surface of the fragment. The meniscus itselfwas sutured using inside–out technique and then a fasciasheath taken from the distal anterolateral thigh was suturedover the meniscus to cover the repair. Finally, an exogenousfibrin clot was injected under the sheath. Complex tearsincluding doubleflap, double longitudinal and radial tears allshowed improved healing with the addition of the sheathand fibrin clot.93 Complete or partial healing was seen in 26of the 31 repairs treatedwith this technique.94However, thistechnique is considered inadequate for radial tears in themiddle portion of the middle one-third of the lateral me-niscus.94 This technique also has the disadvantage of beingtechnically demanding and time-consuming. In 1996, Barrettand Treacy reported that Henning et al’s technique had notbeen widely adopted partly due to the technical difficulty insecuring the sheath around the repaired meniscal tear.95

Then, they described repair of complex tears in the medialand lateral menisci that involved combining T-fix (Acufex)and inside–out approaches as an improvement to the origi-nal technique. The technique consisted of rasping the syno-vium and the tear, inside–out repair of the meniscus,anchoring and suturing of the fascial sheath using T-fix,and inside–out sutures, as well as injection of a blood clotunder the sheath. They concluded that this technique wasmuch easier than that previously described and suggestedthat it could be used to improve repair of complex tears.

Jacobi and Jakob have been advocating for many years fortreating complex human meniscal tears, which otherwisewould have a poor clinical probability of healing, with acollagen wrap as an adjunct. This meniscus wrapping techni-quewas introduced in 2003 and first used to treat 30 patientswho had complex tears, delayed traumatic tears with degen-erative aspects, or repeat sutured tears, all in the R-WorW-Wzone.96 In this study, 15 complex tears, 11bucket-handle and4horizontal tears were treatedwith this technique. The tears inthe meniscus were first fixed by preliminary inside–outsutures. Chondro-Gide matrix (Geistlich Pharma) was thenintroduced through an arthroscopic cannula and multiplesutures were added (up to 10), to complete the fixation ofthe membrane on the meniscus and the meniscus tear. Theporous layer was laid down facing themeniscal defect to favorcell invasion and attachment and allow the in-growth of cellsand a newly formed tissue. The compact layer acts as occlusivescaffold with smooth surface to prevent cells from diffusinginto the synovial fluid. Three patients had a symptomaticfailure (10%) at mean follow-up of 2.5 years, while all other27 cases (90%) were asymptomatic. It is believed that themembrane acts as an internal bioreactor or scaffold andattracts cells that are released from the synovial fluid byrasping and bleeding inside the joint. Thus, healing becomespossible even in unfavorable conditions with this technique.Similar to the fascial sheath technique, this procedure istechnically demanding and time-consuming.

Meniscus wrapping with a cross-linked Chondro-Gidederivative was similarly used in a preclinical study in agoat model.97 Surgically induced 6-mm horizontal tears inthe avascular portion of the meniscus were closed with a

The Journal of Knee Surgery

Augmentation Techniques for Meniscus Repair Ghazi zadeh et al.

Table

4Clin

ical

stud

iesof

men

iscu

srepa

irau

gmen

tation

byplatelet-richplasma

Stud

yDesign

Inclusion

criteria

Type

oftear

trea

ted

Surgical

approac

hSa

mple

size

(%males)

Mea

nag

e(y)

FU rate

(%)

Mea

nFU times

(mo)

Outcome

mea

sures

Definitionof

failu

reRe

sults

Griffinet

al(201

5)92

LevelIII

Patien

tswho

unde

rwen

tarthroscop

icmen

iscu

srepa

irdu

ring

apa

rticular

periodat

one

center

and

wereolde

rthan

18years

Bucket

hand

lean

dho

rizo

ntal,

periph

eral

horizo

ntal,

periph

eral

long

itud

inal,

horizo

ntal,

long

itud

inal

atR-W

junc

tion

,long

itud

inal,

bucket-han

dle,

vertical

and

undersurface

tears

Inside

–ou

tAll-inside

Outside

–in

App

licationof

Cascade

PRF

delivered

arthroscop

icallyan

dsuturedinto

the

repa

irsite

usinga

PDSsuture

0%with

conc

omita

ntAC

Lreco

nstruc

tion

35(80)

15withPR

P20

witho

utPR

P

3110

048

IKDC

Tegn

er-Lysho

lmRe

turn

tosp

ort

Return

towork

RofM

Know

nrecu

rren

ceof

reop

eration

Failu

rerateswere

27%in

PRPþ

grou

pan

d25

%in

PRP�

grou

pClin

ical

outcom

esimila

rforbo

thgroup

s

Pujole

tal

(201

5)91

LevelIII

Patien

tsyo

unge

rthan

40yearswitha

symptom

atic

horizo

ntal

clea

vage(grade

2or

3)of

the

men

iscu

san

dpe

rsisting

pain

afterco

mplete

med

ical

trea

tmen

t(rest,

physiotherap

y,intra-articu

lar

injections

ofco

rticos

teroids)

fora

tlea

st6mo

Horizon

tal

clea

vage

tears

extend

inginto

theav

ascu

lar

zone

Ope

nsu

turing

Injectionof

GPS

IIIPR

Pdirectlyinto

the

repairlesion

prior

toclos

ure

Rasp

ingof

tear

0%with

conc

omitan

tACL

reco

nstruc

tion

34(71)

17withPR

P17

witho

utPR

P

3010

032

KOOS

IKDC

MRI

Failu

rewas

define

das

areop

erationon

thesamekn

eefora

men

isce

ctom

yor

aniterative

repa

irof

the

samemen

iscu

s

Failu

rerateswere

5.8%

inPR

Pþ

grou

pan

d11

.8%in

PRP�

grou

pClin

ical

outcom

eswereslightly

improv

edby

the

addition

ofPR

P(painan

dsports

activity

subc

ateg

ories)

Abbrev

iations

:ACL,an

terior

cruc

iate

ligam

ent;GPS

III,g

ravitationa

lplateletseparationsystem

III;FU,follow-up;IKDC,Interna

tion

alKne

eDocu

men

tation

Com

mittee;

KOOS,

Kne

eInjury

andOsteo

arthritisScore;

MRI,mag

neticreso

nanc

eim

aging;PR

F,platelet-richfibrin;PD

S,po

lydiox

anone

;PR

P,platelet-richplasma;

RofM

,rang

eof

motion;

R-W,red–

white.

The Journal of Knee Surgery

Augmentation Techniques for Meniscus Repair Ghazi zadeh et al.

Table

5Clin

ical

stud

iesof

men

iscu

srepa

irau

gmen

tation

bywrapp

ing

Stud

yDesign

Inclus

ioncriteria

Typeof

tear

trea

ted

Surgical

approac

hSa

mple

size

(%males)

Mea

nag

e(y)

FU rate

(%)

Mea

nFU times

(mo)

Outco

me

mea

sures

Definitionof

failu

reRe

sults

Hen

ning

etal

(199

0)93

LevelIV

Patien

tsag

ed14

–45y

withun

stab

letorn

men

iscu

swho

unde

rwen

trepa

irdu

ring

apa

rticular

period

Sing

lelong

itud

inal,

doub

lelong

itud

inal,

triple

long

itud

inal,

radial,flap

,ho

rizo

ntal

split,a

ndbu

cket-han

dle

tears

Rasp

ingof

tear

Suturing

Wrapp

ingwithfascial

shea

thExog

enou

sfibrin

clot

92%withco

ncom

itan

tACLreco

nstruc

tion

153(N

/S)

2310

04

Arthrogram

Seco

nd-lo

okarthroscop

y

Hea

lingov

erless

than

50%of

the

vertical

height

was

considered

afailu

re

Failu

rerate

was

12%

Failu

rerate

grea

terfor

complextears

Exog

enou

sbloo

dclots

decrea

sedfailu

rerate

inisolated

tears

(41–

8%)

Exog

enou

sbloo

dclots

withfascialshe

ath

decrea

sedfailu

rerate

inco

mplextears

(22–

11%)

Hen

ning

etal

(199

1)94

LevelIV

Patien

tswithun

stab

leco

mplextearsthat

unde

rwen

trepa

irdu

ring

apa

rticular

period

Doub

lelong

itud

inal,

doub

leflap

andradial

tears

Rasp

ingof

tear

Suturing

Wrapp

ingwithfascial

shea

thExog

enou

sfibrin

clot

81%withco

ncom

itan

tACLreco

nstruc

tion

31withshea

th(N

/S)

58witho

utsh

eath

inprev

ious

series

(N/S)

N/S

100

6to

9Arthrogram

Seco

nd-lo

okarthroscop

y

Hea

lingov

erless

than

50%of

the

vertical

height

was

considered

afailu

re

Failu

rerateswere8%

withshea

than

d24

%witho

utshea

th

Jaco

bian

dJako

b(201

0)96

LevelIV

Patien

tswithtearsin

theR-Ror

R-W

zone

,co

mplextears,

delayed

trau

matic

tearswith

dege

nerative

aspe

cts,

orrepe

atsu

tures

Com

plex,

bucket-

hand

le,and

long

itud

inal

tears

Inside

–ou

tWrapp

ingwithco

llage

nmatrix

33%withco

ncom

itan

tACLreco

nstruc

tion

30(63)

N/S

100

30Clin

ical

exam

ination

Persistenc

eof

symptom

sFailu

rerate

was

10%

Piontek

etal

(201

6)99

LevelIV

Fullthickn

ess,

combined

men

iscaltea

rgrea

terthan

20mm

inleng

thHorizon

tala

ndradial

tear

Tear

locationreaching

morethan

6mm

from

themen

isco

caps

ular

junc

tioninclud

ingthe

avascu

larzo

neBo

thde

gene

rative

and

nond

egen

erative

men

isci

(i.e.,ho

rizo

ntal

andradial

tears,

invo

lvingtheW-W

and

R-W

zone,

aswella

sex

tensivetearsof

the

bucket-han

dle

type)

Com

bined

(horizontal

andradialo

rlong

itud

inal

compon

ent)

and

complexmen

iscaltea

rs(tea

rex

tend

edthroug

hav

ascu

larzo

nesor/and

compos

edwithtw

oor

more

morpho

logical

tear

pattern)

All-inside

withFasT-Fix

Wrapp

ingwithco

llage

nmatrix

40%withco

ncom

itan

tACLreco

nstruc

tion

53(75)

3794

24IKDC

Lysh

olm

Barret

MRI

WORM

S

Failu

reifat

the

follo

w-upproce

sspa

tien

tun

derwen

tpa

rtial/co

mplete

men

isce

ctom

yor

knee

replacem

ent

Failu

rerate

was

4%Clin

ical

outcom

eim

prov

edin

86.8%of

theintend

edto

trea

tcases

Non

homog

eneo

ussign

alwitho

utmen

iscaltea

rin76

%of

caseson

MRI

(WORM

Sgrad

e1)

Abb

reviations

:ACL,

anterior

cruc

iate

ligam

ent;FU

,follow-up;

IKDC,Interna

tion

alKne

eDocu

men

tation

Com

mittee;

MRI,mag

neticreso

nanc

eim

aging;N

/S,n

otspec

ified

;R-R,red–

red;

R-W,red–

white;W

-W,

white–w

hite;WORMS,

Who

leOrgan

MRIS

core.

The Journal of Knee Surgery

Augmentation Techniques for Meniscus Repair Ghazi zadeh et al.

single suture introduced with the inside–out technique. Themenisci were then wrapped with a collagen membrane andfibrin glue was used to seal the membrane (as a tissueadhesive). In some animals, meniscus wrapping was com-bined with injection of expanded autologous chondrocytes.Meniscus wrapping by itself improved healing at 3 monthscompared with suturing alone, but this improved outcomewas not observed at the 6-month repair period. Combiningthe meniscus wrapping and autologous chondrocyte injec-tions improved repair at both 3 and 6 months time points.

In 2012, Pionteket al reportedon the developmentof a fullyarthroscopic wrapping technique to treat meniscal lesions.98

This arthroscopic method combines suturing techniques withthe use of a collagenmembrane towrap themeniscus and theoptional application of BM aspirate or concentrate deep to themembrane. In this technique, the tearswerefirst suturedwithall-inside FasT-Fix sutures (Smith andNephew). Themeniscuswas then wrapped with collagen matrix and BM aspiratedfrom the tibial proximal epiphysis was injected under thematrix into the tears. The authors stated that the techniquewas technically challenging, but they believed that the use ofcollagen matrix and addition of BM aspirate will create favor-able conditions, which may increase the rate of meniscushealing. The 2-year follow-up data of tears treated witharthroscopic suturing and wrapping technique were pre-sented in a subsequent article.99 Inclusion criteria for thisstudy included full-thickness tears greater than 20 mm inlength, horizontal, radial tears, and extensive bucket-handletears, tears located at greater than 6 mm from the capsularjunction including the avascular zone, as well as both degen-erativeandnondegenerativemenisci.Of the48casesanalyzed,only 2 patients underwent subsequent partial meniscectomyand were considered failures. Subjective and clinical assess-ment scores were improved at 2 years postoperative in thepatients. The authors reported 13 severe adverse events butspecified that none of the events was related to the procedureormaterialused. Theyconcludedthat this technique issafe andpromising and can be used by surgeons to repair menisciwhich would otherwise be removed.

Rationale for Using Polymer Stabilized PRPto Augment Meniscus Repair

Chitosan is a positively charged partially acetylated glucosa-mine-based polysaccharide that can act as a scaffold andadhere to negatively charged tissue surfaces to mediate tissuerepair. Near-neutral solutions of chitosan–glycerol phosphate(GP) can be mixed with whole blood to create hybrid clots100

that significantly resist retraction.101 We have previouslydemonstrated that chitosan–GP/blood clots can be injectedover marrow stimulated cartilage defects and yield repairtissues with improved biomechanical and biochemicalproperties compared with microfracture or microdrillingalone.101,102 Some of the mechanisms responsible for thisimproved repair are an increase in inflammatory and mar-row-derived stromal cell recruitment to the microdrill holes;increasedvascularizationandsubchondralbone remodelingatearly postsurgical time points from day 1 and 56 days when

compared with microdrilled control holes103; polarization ofmacrophage phenotype toward the alternatively activatedprowound healing lineage104; increased bone remodelingand osteoclast activation leading to better repair tissue inte-gration105; and stimulated secretion of anabolic wound repairfactors from M2a macrophages.106

Recently, we have developed freeze-dried formulations ofchitosan that can be solubilized in PRP to form injectableimplants that solidify in situ.107 These freeze-dried formula-tions contain chitosan, a lyoprotectant and a clot activator.Wefound that chitosan molecular size, chitosan concentration,and lyoprotectant concentration control the performancecharacteristics of these implants and have identified formula-tions that show promise for meniscus repair. In two pilotstudies,108,109meniscus repair in ovine models was improvedby application of freeze-dried chitosan–PRP implants. Chito-san–PRP implants induced cell recruitment to the tears, repairtissue synthesis, and remodeling at 3, 6 weeks, and 3 monthspostsurgery leading to the design of an ongoing pivotal animalstudy. Chitosan–PRP implants may be able to overcome someof the shortcomings of current augmentation techniques toimprove restoration of meniscus structure and function.

Conclusion

Meniscus tears are among the most common knee injuriesrelated to trauma or aging. Understanding of the structure,vascularity, biomechanics, and pattern of tears is importantand could facilitate the orthopaedic surgeon’s selection ofoptimal treatment. Current trends are shifting toward salva-ging the meniscus tissue and meniscus repair with good tofair satisfactory long-term outcome. Evidence shows thatnonsurgical approaches/management can be successfulespecially in the short term if tears are not symptomatic.Diverse augmentation techniques have been developed tointroduce marrow elements and blood components into thejoint to increase healing in the avascular zone of the menis-cus. Further development of these approaches and bioactivematerials may improve repair of currently irrepairable me-niscus tears.

Conflict of InterestA.C. and M.D.B. hold shares; M.D.B. is a Director and J.F.and S.R. are clinical advisors or Ortho Renegerative Tech-nologies Inc.

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