University of MinnesotaProfessor and Vice Chair

Past Medical Director of Intercollegiate Athletics

Agel, Arendt, et al., AJSM, 2005

BASKETBALLACL Injury Rate, 1989-98

0.29

0.09

Agel, Arendt, et al., AJSM, 2005

SOCCERACL Injury Rate, 1989-98

0.32

0.13

Agel, Arendt, et al., AJSM, 2005

• No significant change in rate of ACL injury in men or women over a 15 yr period

Mihata LC et al., AJSM 2006

Elizabeth A. Arendt, M.D.

Page 1 of 8

Hunt Valley Consensus ConferenceJune 1999

Hunt Valley Consensus ConferenceFebruary 2005

International Olympic CommitteeCurrent Concepts Statement

Lausanne Feb. 2008

An Update on ACL Injury Risk & Prevention (Retreat #5) Greensboro March 2010

BJSM, June 2008

J. Athletic Training 45:499-508, 2010

• Estrogen / progesterone – most obvious / most studied hormonal

• Relaxin– Powerful ligament relaxer

• Testosterone– are we missing a potential protective effect??

• Material Property level : ligaments / tendons

• Neuromuscular level : central or peripheral

• Cellular level : ligament structure /composition

collagen / proteoglycans

Model: primate

26 animals (26 ACL/26 PT)

2 yearsligament failure test

No correlation between ACL or Patellar tendonmaterial properties and estrogen levels

Arendt et al., AJSM, 2006

If there is a hormonal effect on knee function –

it is unlikely at the ligament

“material properties” level

How else could hormones have an effect?

? Neuromuscular mechanism ?

Elizabeth A. Arendt, M.D.

Page 2 of 8

• 3,150 athletes participated

– 2 basketball seasons, 1 soccer season

– 209 schools

• no OCP (64%) / used OCP (36%)

• RESULTS: No difference in the rate of

non-contact ACL or ankle sprain injury

based on use of oral contraceptives

Arendt et al., Med. Science & Sport, 2006

A meta-analysis (9 studies)

• Anterior knee laxity was greater in the ovulatory phase than the luteal phase and least in the follicular phase

• More injuries in the follicular phase.

• Inadequate data exists to make any conclusive statement regarding the effects of the menstrual cycle on knee laxity and on ACL injury rates.

Zazulak BT, Hewett TE, et al.: Sports Med 2006

Menstrual cycle phase & ACL Injury

Inconclusive data

Published studies to date support an increase in NC-ACL injuries in the pre-ovulatory phase

! No reasonable theories as to mechanism !

• Examine the interaction among hormones, mechanical loading, neuromuscular response, & ACL mechanical properties in the physically active (fe)male

• Examine ACL injury in genome-wide association studies to establish possible genetic components to ACL injury

.

R. Kevin Flynn, Alexandra Kirkley, et.al.,

Am. J. Sports Med. 2005

Conclusion: The COL12A1 AluI RFLP in exon 65 is associated with ACL ruptures in females.

The results suggest that females with an AA genotype are at a 2.4 times increased risk of ACL ruptures.

Posthumus M, van der Merwe W, Martin P Schwellnus, Malcolm Collins, et al.

Br. J. Sports Med. May 2009

Vicki L. Wilke, DVM, PhD, DACVS

Elizabeth A. Arendt, M.D.

Page 3 of 8

• Incidence– 20% of cases seen at veterinary teaching

hospitals for lameness

• Surgery recommended in dogs >35 #– 50% have

bilateral CCLR

– Cost: ~$1- 4,000/ knee

• Higher genomic similarity with human

• Dogs experience similar, spontaneously occurring diseases as humans– Similar physiology

– “Breeds”: partially inbred, genetic isolates

Kirkness et al. Science 2003

• Identification of genetic mutation(s) that cause or

predispose individuals to disease • genetic counseling

• Identification of environmental factors that influence

genetic expression of disease (phenotype)• smoking, body weight, exercises

• Identification of genetic intervention to prevent

progression of disease to end-stage

• Females more typically had the posterolateral tibial bony contusion pattern compared to males

Fayad LM et al. Skeletal radiology 2003

• Females have a lower incidence of

full-thickness articular lesions in

ACL-injured knees.

Rotterud JH et al., AJSM 2011

• Control Limb Rotation under Pelvis

• Land with a flexed knee and hip

• Plant / Pivot with knee and foot within vertical cylinder of upper body

• Heidt 2000

• Olsen 2005

• Johnson 1995

• Mandelbaum 1995

• Henning 1990

• Hewett 1999

• Mandelbaum 2005

• Mykelbust 2003

• Caraffa 1996

• *Pfeiffer 2004

• *Soderman 2000

• *Wedderkopp 2003

BOLD decreased knee injury riskUnderline decrease ACL injury risk

* No effect in injury risk

Elizabeth A. Arendt, M.D.

Page 4 of 8

and

• Alter dynamic loading of the knee joint through neuromuscular and proprioceptive training (eg) “Knee over toe position” / avoid at risk positions

• Recommended elements : Strength / power exercises, neuromuscular training, plyometrics &agility exercises , warm-up.

• Although results are promising, ACL injury rates & the sex disparity have not yet diminished.

The ideal prevention program has yet to be identified

• The protective effects of ACL injury-prevention training programs appear to be transient.

• Field assessment and screening tools show promise for identifying “at risk” individuals.

• Best age to target screening not yet identified.

• ACL injury mechanisms / prospective risk factors --- the same in pediatric and adult populations?

• the use of the drop vertical jump (DVJ) test to assess the risk of ACL injury in female athletes (pkneeAdMom)

• N =1855 over 3 yrs. HS/ college level

• 20 (+) ACL matched to 45 uninjured

RESULTS: no association pKAM & NC-ACL

Goetschius J, et.al., JSM 2013

• Which biomechanical / neuromuscular profiles (trunk, core, hip) cause noncontact ACL rupture?

An understanding of the causes is central to identifying how to screen at risk individuals

• Is gross failure of the ACL caused by a

single episode or multiple episodes?

• Are ACL injuries governed by a single or multiple neuromuscular / biomechanical profile(s)?

• Mixed conclusions if SEX is a risk factor– Re-injury of initial ACL

– Injury to contra-lateral knee

Elizabeth A. Arendt, M.D.

Page 5 of 8

• Femoral notch width is a good predictor of ACL size (area and volume) in M but not F

• Femoral notch angle is a good predictor of ACL size in F but not in M.

• Compared with ACL uninjured people, injured individuals have smaller ACLs

Chandrashekar N et al., AJSM 2005Chaudhari AM et al., AJSM 2009

• Both condyles have a 7-10 degree posterior inclination with respect to the shaft of the tibia (tibial slope)

Compliments of Charlie Brown, M.D.

• The lateral condyle is flat or convex

• The medial condyle is concave

Compliments of Charlie Brown, M.D.

• The lateral condyle has a smaller radius of curvature posteriorly than the medial condyle

Compliments of Charlie Brown, M.D.

• There is a 6 mmincrease in anteriortibial translation forevery 10 degreeincrease in anteriortibial slope

H. DeJour and Bonnin, JBJS, 1994

Lazar et al., Knee Surg, Sp Trauma, Arthros Nov 2007

• Measured MRI geometry of lateral joint

Ho: ACL Injured athlete has more highly convex joint surfaces.

• N = 173 : NC-ACL athletes age & activity matched to non-injured athletes

RESULTS: all Females / + ACL males

• shorter tibial plateau length (femur) femur more convex articulating surfaces

Wahl,et.al., JBJS 2012

• Cadaver study: N = 20

Ht. & Wt. matched M/F knees

Simulated pivot / landing

RESULTS: ACL x-sectional area & lateral tibial slope were significant predictors of peak AM-ACL strain (R2 = .59; P = .001).

Lipps D, et.al., AJSM 2012

Elizabeth A. Arendt, M.D.

Page 6 of 8

• Patients with a contralateral ACL injury demonstrated

significantly tibial IR, ER compared to healthy

volunteers.

• Females demonstrated

internal & external

rotation, as well as

rotational compliance

compared with males

(p< 0.001)

Branch T, Arendt E, et al., KSST, 2009

• Prospective 4 yr.cohort study, West Point cadets (n=859)

• Recorded multiple P.E. / Xray variables

• Results

– Incidence of NC-ACL injury in

class of 1999 2.1% in males

6.8 % in femalesUhorchak et al., AJSM, 2003

Uhorchak et al., AJSM, 2003

• Patellar tendon -inclination angle & posterior tibial slope are independent risk factors for ACL injury.

• Examining radiographs may offer a simple tool for estimating ACL injury risk for an individual athlete. Brown G, Arendt E, et al.,

poster AOSSM annual meeting 2012

Lateral Tibial Posterior Slope and Early GraftFailure Following ACL Reconstruction

J. Christensen, MD, et.al.

• Case-control format

• 1998-2009

• Skeletally mature

• Matched cohort

– Early ACL graft failure

(<2 years from primary surgery)

vs

– Intact ACL grafts at minimum 4 year follow-up ©2MFME

slide

– Age (± 5 years)

– Gender

– Date of primary surgery(± 5 years)

– Graft type

• BTB autograft

• Hamstring autograft

• Allograft

• Mean time to graft rupture in early failure group one year (0.6-1.4 years)

• Mean follow-up of the matched control group 6.9 years (4.0–13.9 years) with no evidence of graft rupture

• Tibial rotation

• Anatomic alignment (genu varum)

• Size and Convexity of Tibial slope

HIGH RISK of ACL INJURY

Elizabeth A. Arendt, M.D.

Page 7 of 8

ACL Injury

Hormones

Laxity

Q-angle

Notch Width

NM Strategies

Prior Injury

Reductionist View : Breakdown into Parts

• The sum of the parts

equal the whole

• Assumes each part

contributes equally

• Random mixing of

parts are ignored

Quatman & Hewett, BJSM, 2009

Less Reductionist View

Feedback loops, interrelations andweighting of relationships

• Can not reduce parts and retainmeaning of the whole

• Assumes parts are not equal

• Assumes non-random mixing is important

Quatman & Hewett, BJSM, 2009

ACL Injury

Hormones

Laxity

Q-angle

Notch Width

NM Strategies

Prior Injury

AnatomicFactors

HormonalFactors

?Sex?Laxity Factors

Neuro-muscularFactors

Women should be more like

men

Sports Medicine Institute University of Minnesotawww.sportsdoc.umn.edu

Elizabeth A. Arendt, M.D.

Page 8 of 8