ACL Injuries in Women Athletes 2011

Dr. Connie Lebrun MDCM, MPE, CCFP,

Dip. Sport Med, FACSM

Clinical Director Glen Sather Sports Medicine Clinic

University of Alberta, Edmonton, Alberta, CANADA

ACL Injuries in WomenManagement and

Prevention

©2010The Amercian College of Sports Medicine. Published by Lippincott Williams & Wilkins, Inc. 2

Figure 1Complex Integrative Morphological and Mechanical Contributions to ACL Injury Risk.McLean, Scott; Beaulieu, Melanie

Exercise & Sport Sciences Reviews. 38(4):192-200, October 2010.DOI: 10.1097/JES.0b013e3181f450b4

Figure 1 . Combined effects of fatigue and decision making on key knee joint biomechanical parameters during a high-impact single leg landing task. As fatigue progressed, statistically significant (P Med Sci Sports Exerc. 2009; 41(8):1661-72. Copyright (C) 2009 Lippincott Williams & Wilkins. Used with permission.]


TABLE.Complex Integrative Morphological and Mechanical Contributions to ACL Injury Risk.McLean, Scott; Beaulieu, Melanie


TABLE. Research studies investigating explicit links between morphological and knee joint biomechanical factors associated with anterior cruciate ligament (ACL) injury risk.




Figure 2 . A custom designed manual loading device was used to apply combined 3D loads to male and female cadaveric knee specimens (A). Using these and resultant ligament strain data, specimen-specific regression models were developed that could predict peak anterior cruciate ligament (ACL) strain magnitudes to within 0.51% +/- 0.01% and 0.52% +/- 0.06% of measured data, and within 0.61% +/- 0.11% and 0.57% +/- 0.05% of validation data (not used in model development) respectively (B). Application of combined valgus (45 Nm), internal rotation (20 Nm) and compressive (300 N) loads at a fixed knee flexion angle (40 deg) and three discrete anterior tibial shear load magnitudes (50 N, 100 N and 150 N) resulted in predicted peak female ACL strains that were significantly greater than male ACL strain values (C). [Adapted from Mizuno K, Andrish JT, van den Bogert AJ, McLean SG. Gender dimorphic ACL strain in response to combined dynamic 3D knee joint loading: implications for ACL injury risk. Knee. 2009; 16(6):432-40. Copyright (C) 2009 Elsevier. Used with permission.]




Figure 3 . Associations between key knee joint anatomical indices and peak stance phase knee joint biomechanical variables during a single-leg landing task. Specifically, peak anterior knee joint reaction force was significantly positively correlated with lateral posterior tibial slope (LTS) (A). Peak knee joint internal rotation angle was significantly positively correlated with the ratio between medial and lateral posterior tibial slopes (MTS:LTS) (B). Peak knee abduction angle was significantly positively correlated with both MTS:LTS and the ratio between the tibial plateau width and the intercondylar distance (TPW:ICD) (C). [Adapted from McLean SG, Lucey SM, Rohrer S, Brandon C. Knee joint anatomy predicts extreme in vivo knee joint mechanics during single leg landings. Clin Biomech. 2010;In press. Copyright (C) 2010 Elsevier. Used with permission.]




Figure 4 . Conceptual model depicting integrative morphological and biomechanical contributions to knee joint and anterior cruciate ligament (ACL) loading during high-impact landing maneuvers. Explicit combinations of postural alignment and knee joint anatomical and laxity factors are posited to implicate within the ACL injury risk via the generation of large knee joint and resultant ACL load states. For the associated figure, ABd = abduction; IR = internal rotation; Ant Shear = anterior tibial shear; Fx = force in the x-axis direction; Fy = force in the y-axis direction; Fz = force in the z-axis direction; Mx = moment about the x-axis; My = moment about the y-axis; Mz = moment about the z-axis.




Figure 5 . Surrogate (integrative forward dynamic and finite element) modeling techniques proposed to successfully investigate anterior cruciate ligament (ACL) causality based on integrative neuromechanical and morphological factors. Systematic and/or random perturbations can be applied at each level of the modeling pipeline, based on quantified variations in each measure, to determine ACL injury risk arising through individual-specific neuromechanical and morphological vulnerabilities.

Are Women More at Risk?

Anatomy of ACL

Origin from lateral femoral condyle

Insertion to tibial plateau medial to anterior horn of lateral meniscus

ACL Injury

“Commonest cause of the ex-athlete”

1 in 10 female athletes (N.C.A.A.)

2-6 times higher incidence than males in same sport

NATIONAL COLLEGIATEATHLETIC ASSOCIATION

INJURY SURVEILLANCE SYSTEM (ISS)

Sport Year ISSBegan

Soccer (/) 1984/83

Softball 1984

Ice Hockey () 1984

Field Hockey () 1984

Basketball (/) 1986/86

Spring Football 1986

Sport Year ISSBegan

Football 1982

Volleyball () 1982

Gymnastics (/) 1983/84

Wrestling 1983

Baseball 1983

Lacrosse (/) 1984/83

Based on exposure rates

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

'89 '90 '91 '92 '93 '94 '95 '96 '97 '98 AllYears

Inju

ry R

ate

(per

100

0 A

-E)

Women

Men

SOCCERACL Injury Rate, 1989-98

0.32

0.13

2.8 X

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

'89 '90 '91 '92 '93 '94 '95 '96 '97 '98 AllYears

Inju

ry R

ate

(per

100

0 A

-E)

Women

Men

BASKETBALLACL Injury Rate, 1989-98

0.29

0.09

3.5X

Mechanism of ACL Injury

Non-contact mechanism (80%)

Rapid but awkward stop

The position of “no return”

ACL tears in 70 ms

Gender Differences?

Risk Factors:Environmental

Anatomic

Hormonal

Biomechanical

Anterior Cruciate Ligament Injury in the Female Athlete

Intrinsic factors:AlignmentHyperextensionPhysiological rotatory laxityACL sizeNotch size and shapeHormonal influencesInherited skills and coordination


Extrinsic factors:StrengthConditioningShoes Motivation


Combined (partially controllable):Proprioception (position sense/balance)Neuromuscular activation patternsSport-specific skills (acquired)

Gender Differences?

Non-Contact Anterior Cruciate Ligament Injuries: Risk Factors

and Prevention Strategies

A Consensus Conference held at Hunt Valley, Maryland on June 10, 1999

Sponsored by AAOS, AOSSM, NCAA, and NATA

Organized by Letha Y. Griffin, M.D., Ph.D.Elizabeth A. Arendt, M.D.

Hunt Valley Consensus ConferenceJune 1999

Reviewed research to date: Anatomic risk factors Hormonal risk factors Biomechanical/neuromuscular risk factors

Reviewed videos on non-contact ACL injuries

Reviewed existing neuromuscular programs

GOALS:

to increase awareness of “at risk” population

to stimulate increased research efforts

Hunt Valley Consensus ConferenceJune 1999

Hunt Valley Consensus Conference: June 1999

HORMONAL RISK FACTORS

No consensus that sex specific hormones play a role in increased ACL injuries in females

No evidence to recommend modification of sports or hormonal modification for females

Remains a “fertile” area for future research

Existence of Hormone Receptors in Ligaments

Relaxin receptor sites :Found in female ACLNOT found in male ACL

Degroo et al.,Trans Ortho Res Soc, 2001

Model: human ACL, 5 & 5 cell culture

Model: Sheep ACL fibroblasts Cyclic estrus function Estrogen receptors

present in sheep ACL fibroblasts

No effect of physiologic levels of estrogen on cell proliferation or collagen synthesis

Effects of Hormones - Cellular Mechanisms

Seneviratne et al.Trans. Ortho. Res. Soc, 2000

Effects of Hormones-Mechanical Properties of Ligaments

Model: mouse knee jointmechanically quantified drawer test

Estrogen + Relaxin ligament stiffness

Levine et al.,Ortho Trans, 1999


Model: sheep38 animals (38 ACL/10MCL)6 monthsligament failure test

No effect of estrogen level onmechanical properties of ACL or MCL

Strickland et al.,Trans of Ortho Res Soc, 2000


Model: primate26 animals (26 ACL/26 PT)2 yearsligament failure test

No correlation between ACL or Patellar tendon material properties and estrogen levels. Arendt et al.,

ISAKOS, 2001

Estrogen and progesterone receptor sites have been reported in human ACL cells.

Relaxin receptor sites have been reported in female ACL cells.

The effect of relaxin, or relaxin plus estrogen may merit further investigation.


EstrogenProgesterone

Hormone Levels and ACL Injuries

Population : 17 Norwegian females (8 on BCP)team handball players

menstrual phase at time of N-C ACL injurymenstrual history questionnaire

Myklebust et al., Scand Med Science and Sport, 1998


Fewer injuries occurred during mid-cycle.

Trend toward in luteal phase

Myklebust, et al, Scand Med Science and Sport, 1998


No correlation between cycle phase & NC-ACL injury

Boynton et al.,AOSSM, 2000

Population : 61 female recreational skiers

Date of injury, cycle length, use of oral contraceptives

Date of next menstrual cycle used to calculate phase of cycle in which injury occurred


Population : 83 College female varsity athletes.

(25 on birth control pills) Menstrual phase at time of N-C ACL No data on onset of next menses

No significant difference in NC-ACL injury & day of menstrual cycle.Trend toward in follicular stage

Arendt et al.,Journal of Gender Specific Medicine, 2002


Centered moving average

Smooth out time dependency of the number of injuries

Arendt et al., Journal of Gender Specific Medicine, 2002


Arendt et al., Journal of Gender Specific Medicine, 2002

Cannot detect exact location ofhigh risk time interval

Non-linear regression model

There is a significant difference in the time dependency of the number of injuries


Population : 65 females (8 on OCP)Sports related NC-ACL injuryMenstrual phase at time of injuryUrine specimens within 24 hFirst day of next cycleUrine analysis for total estrogen, progesterone, and

lutinizing hormone metabolites

Wojtys et al,AOSSM, 2001


LH Levels

Progesterone

Estrogen

X X X X X X X X

X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X XX X X X X X X X X X X X X X X X X X X X X X

LH

Con

cent

rati

on

leve

lsE

stro

gen

leve

ls

(pg/

ml)

Pro

gest

eron

e le

vels

(n

g/m

l)

X = ACL injury Poor correlation between urine metabolites and athlete recollection of cycle

Higher number of ACL injuries during mid-cycle

No data on how metabolites were used to define stages of cycle Wojtys et.al.,

AOSSM, 2001


Population : 35 females (25 College / 12 H.S.)

Sports related NC-ACL injurySaliva sample within 48 hours of injury

26/37 (70%) injured ACL in follicular phase

.

Slaughterbeck et al.,NATA, 2001


Hormones and Tissue Laxity

Population: 26 high school female athletes Normal menstrual cycle Prospective single blinded 8 week study KT-1000 measurements taken prior to practice Repeated measurement of KT-1000 over 8 weeks Menstrual cycles charted No difference in KT-1000 with phase of the

menstrual cycle

Karageanes et al.,Clin J Sports Med, 2000

Hormone Research

Criticisms:One or two measurements not enough

to capture female physiologyNormative standards not well definedSmall #’s unlikely to capture hormonal

variabilityMost studies have large S.D. bars

Conclusion

Menstrual cycle phase & musculoskeletal injury

Inconclusive data

Neuromuscular mechanism (?)

Consensus Statements: 1999 Anatomic Risk Factors

No consensus on role of the intracondylar notch

No consensus on role of ligament size

Consensus Statements: 1999Anatomic Risk Factors

No consensus on role of anatomic alignment

Anatomic Risk Factor ACL Size

Size of ACL: less force is required to rupture a smaller ligament

Anatomic Risk FactorsACL Size

Cadaver knees ( N =16 )Direct measurement techniqueSmaller ACL (cross-section) in

females compared to males

Muneta et al.,AJSM, 1997


Measured ACL width on MRI

Males ACL (6.1mm) > females ACL (5.2mm) Did not control for height and weight

Staubli etal.,Arthroscopy, 1999


Measured ACL (cross-section) on CT scan

Male ACL (47.1mm) > female ACL (35.1mm)

Controlled for height and weight

Jackowski et al.,(Thesis, London, Ont.) 2001

Anatomic Risk Factors ACL Size

Measured ACL cross-section on MRI Case control study:

matched for gender, age, and activity 20 F ACL deficient knees: contralateral

knee compared to 20 controlsACL deficient group had smaller x-sect

(31mm) than controls (42.9mm)Willits et al.,AOSSM, 1999

THE FAMILIAL PREDISPOSITION

TOWARDS TEARING THE ACL: A CASE-CONTROL STUDY

K. Flynn BSc C. Pedersen MSc

A. Kirkley, MDC. Lebrun, MD

Peter J. Fowler, MDThe University of Western Ontario,

London

Anatomic Risk FactorsACL Size

Based on data to date it appears that the increased rate of ACL tears seen in patients with narrower notches may simply be a manifestation of a smaller ACL.

Is the smaller ACL appropriate for the size / strength of the individual ????

If no -- is it due to gender, hormones, training??

Anatomic Risk Factor Tibial Slope

Tibial Slope: in the “quads active” mechanism of ACL injury, the tibia is planted & the quadriceps contracts resulting in sufficient force to cause excessive posterior translation of the femur in relation to the tibia, resulting in tearing of the ACL.

The greater the tibial slope the easier it is for the femur to “slide” down the slope thus tearing the ACL


There is a 6 mm increase in anterior tibial translation for every 10 degree increase in anterior tibial slope

DeJour and Bonnin,JBJS, 1994

Tibial Slope ACL Deficient Knees


Tibial slope measured on CT scan

No difference in males (8.3 degrees) vs. female (8.1 degrees) varsity athletes

Jackowski et al.,(Thesis, London, Ont.) 2001


XR measurementcase control study: 50 ACL deficient

knees to age matched PF kneesno significant difference in ACL

deficient knees (9.7 degrees) to controls (9.9 degrees)

Meister et al.,Amer J Knee Surg, 1997


Absolute measurement not contributory (?)

Slope plus muscle contraction combined effect (?)

Prevention Strategies for Anatomic Risk Factors

Anatomic risk factors are difficult to alter

Little agreement regarding which anatomic factors may be significant, hence no prevention strategies recommended at this time.

Hunt Valley Consensus ConferenceVideos of ACL Injuries

54 videos of ACL injuries were collected in preparation for consensus conference

22/54 in basketball: 15 women, 5 men, 2 ?

Mechanism of injury: jump stop, jump landing, sudden deceleration

ACL Injured on Landing

Knee slightly flexed

Knee in valgus, external rotation

ACL Injured on Landing

Knee slightly flexed

Knee in valgus, external rotation

Videos of ACL InjuriesConclusions

Most common positions at injury were landing from a jump, jump stop, sudden deceleration

Injured leg was usually not extended, but less than 30º flexion

Research Needs: Non-Contact ACL Injuries

What is the mechanism of injury in non-contact injuries to the ACL?

Video data conflicts with in vitro data concerning ACL failure mechanisms

Injury Mechanisms – Body Positions

Knee Biomechanics (in vitro)

External loads of valgus and external rotation do not load the ACL between 100 and 300 flexion

Quadriceps activation can load the ACL between 100 and 300 flexion; this is increased if no hamstrings activation

Consensus Statements: 1999Biomechanical Risk Factors

At this time, neuromuscular factors appear to be the most important reason for the differing ACL injury rates between males and females

Strong quadriceps activation during eccentric contraction a major factor in injury to ACL

Neuromuscular Prevention Programs

Henning - Griffis ProgramCaraffa ProgramWedderkopp’s ProgramCincinnati ProgramFrappier Program (Fargo, N.D.)Santa Monica Program (PEP)Norwegian Awareness Program

Norwegian Awareness Program

Three types of excercises with progression:

1. Floor

2. Airex balancemat

3. Balance board 5 weeks 2-4 x per week Then 1 x week through the season

(Oct-April)

Results After 99\00 Season: All 3 Divisions

ACL-skader Elite, 1. og 2. divisjon

Måned

J uni J uli Aug Sept Okt Nov Des J an Feb Mars Apr Mai

Antall A

CL s

kader

0

5

10

15

20

25

30

35

1998-1999

1999-2000

Conclusion:

Only 29% of the teams carried out the program according to the planElite teams had the best compliance

Exercise quality improved when led by physical therapists

Compliance may be improved by:More informationChanges in type of excercises Improved info to the coachSign a contract with the team

New and More Sports Related Training Programs

Handball related excercises Fakes Two-leg landing Less static excercises

Increased skill-level Increased number of

two-persons drills Increased knowledge

and motivation for players

Floor Exercises – Progression

Run w\take off Jump and two-leg

landing Jump-in fake Turn around jump Jump in with two

leg landing

Air Mat Progression

Receive ball on one leg

Jump shot with two leg landing

One leg landingTwo and one leg

”fight”Jump in with

turnround

Baps Board Progression:

Two leg passes Knee flex two leg

and one leg Passes one leg One leg ball

dribling w\closed eyes

Two leg and one leg ”fight”

All Divisions


Month

Aug Sept Oct Nov Dec J an Feb March Apr May

No of ACL in

jurie

s

0

5

10

15

20

25

30

35

1998-1999

1999-2000

2000-2001

1999-00: 5 of 23

2000-01: 7 of 17

Elite Division


Month

Aug Sept Oct Nov Dec J an Feb March Apr May

No of ACL in

jurie

s

0

2

4

6

8

10

12

14

1998-1999

1999-2000

2000-2001

1999-00: 4 of 6

2000-01: 3 of 5

Conclusion:

An awareness program reduced ACL injuries in Norwegian team handball by 40% overall and 50% at elite level

Conclusions

Prevention of ACL injuries is possible:Neuromuscular trainingFocus on knee positionChange the plant and cut

and landing technique

Possibilities for better results with more control of the training


What are strategies for preventing non-contact ACL injuries?

What do all these programs have in common?


Proprioception trainingIdentifying at risk motions and

positions. Train avoidance techniques when possible

Training programs that enhance body control, in particular rotational control of the limbPelvifemoral muscles (hip extension, hip

abduction, abdominals)


What specific neuromuscular factor accounts for the difference in ACL injury incidence between males and females? - most studied risk factor to

date is GENDER

Take “3” to Save the KNEE

Accentuate Balanced Body Motion

Control Limb Rotation

Land with Bent Knee and Hip

Education

ACL Injuries in Women Athletes 2011