6/12/2013

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Edward M. Wojtys, M.D.

University of Michigan

ACL Prevention

Programs

Conflicts of InterestNone

DisclosuresNIH/NIAMS—R01 AR054821

Coulter Foundation Grant

KIA Research—Consultant

Center for Organogenesis

NFL—Injury and Safety Panel

Sports Health—Editor

Damaging Forces

⇓

Failed

Dynamic Protection

⇓⇓⇓⇓

ACL Tears

ACL Injury Cascade

Mechanisms of Injury

?

Remains Unopened…

ACL Injury

Prevention

secrets

??

?

?

??

The Big Black Box

Scandanavian

registry:

•Median age ~25

•Range= 5-70 years

Granan Acta Orthop 2009

Danish registry

Lind Acta Orthop 2009

Adolescent females

Age Distribution

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Risk Factors for

Contralateral ACL

(Systematic Review – 13 Prospective)

Contralateral 1st Time

Risk Risk

Sward KSST 2010

# 1 Risk Factor for

Contralateral ACL Injury

Return to High

Level Activity

Sward KSST 2010

ACL Injury Prevention Programs

• Kinetics

• Kinematics

• Education

• Compliance

Females have 100% longer rise times in isometric force development.

Komi Acta Physiol Scand 1978

• 52 NCAA athletes– High risk sports of basketball, volleyball,

soccer

(12 male, 12 female)

– Low risk sports of cycling, rowing, running

(14 male, 14 female)

• Body-matched male/female pairs for age and sport

• Strength testing (Biodex)

• Rotational knee stiffness device

Gender Differences in Rotational

Knee Stiffness

Wojtys JBJS 2003

• Females increased volitional knee stiffness significantly less than males (p<0.05).

• Female athletes in pivot sports had lowest volitional increase in knee joint stiffness.

Female (pivot sport) 171%

Female (non-pivot sport) 198%

Male (non-pivot sport) 207%

Male (pivot sport) 258%

Gender Differences in Rotational

Knee Stiffness

Wojtys JBJS 2003

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Coordinated,

efficient muscle effort.

Engrams

Kottke Arch Phys Med 1980

ACL Injury Prevention

in Alpine Skiing

• Injury Mechanism Education

(Avoiding hazardous positions)

• Prospective

• 62% Reduction in ACL Injuries

Ettlinger AJSM 1995

ACL Prevention

Kinematics, Kinetics, Education

Neuromuscular Prevention

(Youth Soccer)

• Knee, ankle, lower extremity

• 60 teams - 32 trained

28 control

• Males & females

• Cluster randomized trial

• Stretches, eccentrics, agility,

jumping, & balance

Emery BJSM 2010

Injury Rate

Per 1,000 player hours

Trained – 2.08 injuries

Control 3.35

Neuromuscular Training is

Protective!

Emery BJSM 2010

Adolescent & Female

Football

• Stratified cluster randomized trial

• 230 Swedish clubs(121 – intervention)

• 4.564 players (12-17 y.o.)

• 15 min warm-up 2x week(core, balance, allignment)

Walden BMJ 2012

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ACL Injuries

Intervention – 7 (0.28%)

Control – 14 (0.67%)

Reduction in ACL – Injury rate

64%

Walden BMJ 2012

Knee Injuries - Soccer

• 1,506 females (13-19 y.o.)

• Community based intervention

• Motor skills, body control, & muscle

activation & education

Kiani Arch Int. Med. 2010

Intervention – 3 injuries

Incidence – 0.04/1000 player hrs

Control – 13 injuries

0.20/1000 player hrs

77% reduction knee injuries

90% reduction noncontact

Kiani Arch Int. Med. 2010

Prevention of Knee Injuries

• Systematic review (1966-2001)

• 328 studies identified � 14 included

• 5 brace studies � Negative

• 3 shoe cleats / ski boot-binding � ?

• 6 prospective, neuromuscular � Positive

Thacker J Sports Med Phys Fit 2003

Knee Ligament Injury Prevention

(KLIP)

• 577 female athletes

(soccer, b-ball, v-ball)

862 controls

• 20 min / session – 2x / week

• Non randomized – coach resistance

No Reduction in ACL Injuries!

Pfeiffer JBJS 2006

Injury Prevention - Soccer

• Randomized trial – high and low risk

Intervention and control

• Ankle, knee, hamstrings, groin

• Training compliance (HR)

27.5% Ankle

29.2% Knee

21.1% Hamstrings

19.4% Groin

Engebretsen AJSM 2008

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Effectiveness of ACL

Injury Prevention

• Meta-analysis of prospective

controlled studies

• 909 studies identified

9 included

Sadoghi JBJS 2012

Caraffa 1996

Gilchrist 2008

Heidt 2000

Hewett 1999

Mandelbaum 2005

Petersen 2002

Petersen 2005

Pfeiffer 2006

Sadoghi JBJS 2012

Sadoghi Studies

• Scientific quality – low

• Issues – blinding, randomization,

few matched pairs, drop-out rates

• Only 1 study with power analysis

• Study outcome heterogeneity

• 5/9 – soccer

• Low numbers

Sadoghi JBJS 2012

Pooled Risk Ratio

Females 0.48 95% C.I. = 0.26-0.89

Males 0.15 95% C.I. = 0.08-0.28

ACL injury risk reduction significant

for females 52% (p=0.021) and

males 85% (p<0.001)

Sadoghi JBJS 2012

Meta-Regression

Balance Board � no effect (p=0.712)

Video assistance � no effect (0.914)

F/U duration � no effect (0.437)

Year of publication � no effect (0.358)

On the pooled risk

Sadoghi JBJS 2012

? Best Program ?

• Study heterogeneity

• At least 10 min – 3 x / week

Neuromuscular

Sadoghi JBJS 2012

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Meta-Regression (Training)

Preseason vs. playing season reduced risk by 19.1% (p=0.691)

Sadoghi JBJS 2012

ACL Injury Prevention and

Performance Enhancement

• Systematic Review (1995-2011)

• 57 Studies – 42 Programs

Sportsmetrics

Myklebust

17 Studies KLIP

PEP

11 (HOLM)

Noyes Sports Health 2012

ACL Injury Incidence Reduction

(AE*)

PEP and Sportsmetrics

*Athletic Performance Improvements

Noyes Sports Health 2012

Clinical Incidence Rate

Injuries

Athletes

At Risk (N)

ACL Injury Rate

Injuries

Athletic

Exposures (AE)

Sportsmetrics

ACL Injury

Reduction

• Very successful

Improved Athletic

Performance

• 60-120 min / 3x week

• Pre-Season

Noyes Sports Health 2012

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PEP

• Very Good

In-Season – 20 min before practice

? Athletic Performance ?

Noyes Sports Health 2012

ACL Injury

Reduction

Prevention Programs

• Landing technique

• Cutting maneuvers

• Deceleration

Tailored to the Athlete

Sports Specific

Artificial Turf vs Grass

• Prospective Cohort –

2020 players (109 teams)

• Young female football players (2005)

Risk of Acute Ankle/Knee Injury was

Similar!

Steffen BJSM 2007

Field Turf vs. Grass

(NFL)

• Descriptive Retrospective Study

• 2000-2009 (5360 team/games)

Injury Rate 67% on Field Turf

Hershman AJSM 2012

Compliance

Athletic Injury

Performance Prevention

Balance

Summary

• Injury prevention hampered by lack

of ACL injury mechanism

understanding

• Still not sure what Sportsmetrics,

PEP, and other successful

programs change?

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Thank You

ACL Injury Prevention

(Meta-Analysis)

Plyometric Balance

Strength Training Training

*Most effective – females (<18 yo) soccer

Yoo KSST 2010

Warm-up Program

(cluster randomized trial)

• 1892 female footballers (13-17 y.o.)

• Foot, ankle, leg, knee, thigh, groin, & hip

• Strength, awareness, & NM control

Risk of all injuries, severe & overuse, was reduced!

(Lower extremity injury rate did not change)

Soligard BMJ 2008

ACL-R Risk Factors

Activity Level & Graft Type

• Case-control 21 pts – 42 matched

• Univariate logistic regression

Low vs. high activity – OR 5.53

(95% C.I. 1.18-28.61)

Allo vs. auto – OR 5.56

(95% C.I. 1.55-19.98)

Borchers AJSM 2009

Goals

Enhanced condition

Prevent muscle fatigue

Hamstring fatigue � Transverse plane

Control Deficits

Nyland JAT 1999

Hamstring Training

Eccentric > Concentric

(Improving quad/hamstring)

(* Professional soccer players)

Mjolsnes SJ Med Sci Sports 2004

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Gluteal Training(Abductors, Extensors, External Rot.)

• Plyometric training

Dynamic L.E. control & positioning at

ground contact

Chimera JAT 2004

Core

• Pertebation training

• Body sway control

Jamison MSSE 2012

Hamstring Strength

• Concentric vs. eccentric

• 21 well trained male soccer players

• 2x6 reps �3x(8-12) reps x2/weeks

load x 6 weeks

11% in eccentric torque (60)

No ∆ in concentric

Mjolsnes Scand JMS Sports 2004

Knee Injuries – Alpine Skiing

• Education program (1993-94)

20 intervention

22 control

• 179 serious injuries

• 62% reduction with education

Ettlinger AJSM 1995

Ski areas

Contra vs. Ipsilateral ACL Injury

• 63 ACL-R

• 39 controls

• 12 month f/u

• 16 ACL-R, 1 control � ACL

* Female ACL-R

16x injury rate (controls)

4x ACL

Paterno Clin J. Sport Med 2012

4x male risk – 2nd ACL

6x male risk – contra ACL

Paterno Clin J. Sport Med 2012

Female Athletes

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ACL Retear and

Contralateral Injury Risk

• Prospective cohort (Level II)

• 2y data – 235(273) 86%

• 7 retears (3%) 7 contra (3%)

Moon AJSM 2007

Ekstrand 75%

Vermont 62%

Cincinnati (Sportsmetrics) 72%

Wedderkopp 71-80%

Caraffa 87%

Santa Monica (PEP) 88%, 74%

Soderman 0%

Decrease in ACL tears

ACL Prevention Success Rates

Dissipate damaging forces

Education

Avoid hazards

(proper form, positioning, anticipation)

Neuromuscular Protection

Injury Situation

• 20 min warm-up (video)– 2-3 times/week for 12 weeks

• Avoidance techniques

• Stretch and strengthen

• Plyometrics

• Soccer agilities

PEP Program

Mandelbaum AOSSM 2002

1041 soccer trainees – 0.2 injuries/player

1902 soccer controls – 1.7 injuries/player

2002 88% ↓ in ACL Injuries

2003 74% ↓ in ACL Injuriesa

PEP Results

Mandelbaum AOSSM 2002, 2003

Protective System

Sensory receptor outflow causes

activation of muscle efferents generating

stabilizing muscle co-contractions

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Pertubation Training

Selective Muscle Use Patterns

• ↑ co-contraction (Q-H-G)

• ↓ muscle stretch reflex

Protective System

Protective Muscle

Contractions

Knee Joint Resistance

to Deformation

• Always present

• First line of defense

(Relaxed)

Intrinsic Stiffness

• Dependent upon the excitation provided by the alpha and gamma motoneurons.

• Can be modified with training.

Extrinsic Stiffness

Gender Differences in the

Contributions of the Musculature to Knee Shear Stiffness

Edward M Wojtys, MD

James A. Ashton-Miller, Ph.D

Laura J. Huston, M.S.

JBJS, 2002

Males 473%

Females 217%

(p=0.003)

% Increase in Stiffness

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Strength was not the predominant

contributor to knee stiffness.

Stiffness = -0.009x1 -17.8x2 +0.5x3 + ß

X1 = muscle strength (p=0.974)

X2 = gender (p=0.049)

X3 = subject’s height (p=0.666)

ß = constant = 51.9 (p=0.576)

Regression Model

Gender differences in active musculo -skeletal stiffness

--- Men

--- Women

HamstringsQuads

Female subjects demonstrated a 56-73%reduced active limb stiffness relative to the

male subjects

Granata J Elect & Kines 2002

Hopping Freq. Males Females % Diff

preferred 26 (9) 19 (8) * 27% *

2.5 Hz 31 (8) 24 (5) * 23% *

3.0 Hz 43 (8) 35 (7) * 19% *

* males significantly greater (p<0.05)

Stiffness Results (kN/m)

1. Leg stiffness in the female subjects was approximately 77% that seen in males.

2. Body mass did not adequately explain the gender effect.

Granata, 2002Gender Differences in the Muscular

Protection of the Knee Among BMI-Matched Athletes

JBJS May 2003

Study Hypothesis:No gender differences exist in internal tibial-

femoral rotation when maximally contracting

knee joint musculature.

1. Stimulates joint and muscle receptors to induce high level of Q-H-G co-contractions.

2. Improves whole body and single joint positions to ↓ loads on joints.

3. Plyometrics to improve MRT &TPT.

4. Skill training to isolate ideal movements than will generate lowest joint moments and best position for cutting and jumping.

Ideal ACL Training Program

Lloyd JOSPT 2001

80% reduction in rotatory laxity

with 938 N of compressive force

Rotatory Laxity of the Knee

Wang & Walker JBJS 1974

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• 200 – 400% increase with isometric contraction

• 1000% increase in conditioned athletes

Varus-Valgus Knee Stiffness

Markolf JBJS 1976

Multifactorial!

Hormones – not understood

Worrisome

Anatomy – difficult to change

Muscle Function – training programs

?? mechanism of action

Causes?

t = 0 t = 200 msec

• Lengthening ?• Isometric ?• Shortening ?

0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 00

0 . 2

0 . 4

0 . 6

0 . 8

1

1 . 2

1 . 4

1 . 6

1 . 8

v

Background

Lengtheninghamstrings produced the lowest relative ACL strain

Effect of Hamstrings

Withrow ORS 2006

Configuration

Mean (SD)

Max ACL

strain

(%)

Max impact

force

(N)

Max quad

force

(N)

Max

medial

hamstring

force (N)

Max

lateral

hamstring

force (N)

Shortening 3.0 (1.1) 1755 (275) 1579 (203) 168 (68) 183 (62)

Lengthening 0.8 (0.6) 2093 (370) 1161 (231) 338 (118) 394 (83)

Isotonic 3.6 (1.1) 1777 (256) 1546 (186) 92 (29) 103 (31)

No hamstring 2.9 (1.3) 1702 (224) 1514 (169) N/A N/A

Lengthening hamstring condition significantly decreased

anteromedial ACL relative strain in this jump landing model

Effect of Hamstrings

Withrow ORS 2006

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For a given increase in knee flexionangle, an increase in hip flexion angle

exists… that will lengthen the hamstring

muscle-tendon unit (MTU) in a jump

landing.

Lengthening

Contraction≈ 1.6

Isometric

or Shortening

contraction

Hypothesis Methods

• 3 cadavers• Open dissection and digitization of

origins and insertions of BF, SM and ST MTU

• Certus system kinematic measurements

• Calculate hamstring MTU length for knee angles between 0 - 90o at 0, 30 or 60o hip angles (3 trials each)

l Hamstring = f ( θKnee , θHip )

• Initial Knee &

Hip Angle 30°

• At Landing

–Hip ↑ 15°

–Knee ↑ 21°

Pflum 2004

0°30°60°0 2 0 4 0 6 0 8 0

3 3

3 4

3 5

3 6

3 7

3 8

3 9

4 0

4 1

Ham

str

ing L

ength

(cm

)

K n e e F le x i o n A n g le ( d e g )

C a d a v e r # 1 - B FBF

75°°°°60°°°°45°°°°30°°°°0°°°° Hip Angle

Russell et al. J. Athl. Train. 2006

Forward Hop

Conclusions

1. Hypothesis supported: A hamstring lengthening state can indeed occur - when the change in hip angle exceeds 57% of the change in knee angle.

2. Using drop landing test data, simulations suggest the hamstring MTU act in a quasi-isometric state during a drop landing

3. Reducing the knee flexion or increasing the hip flexion will lengthen hamstring MTU to help protect ACL, and vice versa.

0 0 .2 0 . 4 0 .6 0 . 8 1 . 00

0 .2

0 .4

0 .6

0 .8

1

1 .2

1 .4

1 .6

1 .8

Pooled Risk

Risk Ratio – 0.38

Prevention programs reduced risk of ACL tear by 62%

Sadoghi JBJS 2012

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Pooled Risk - Gender

Female risk reduction – 52%

Male risk reduction – 85%

Number needed to treat to prevent 1 ACL tear was 5-87

Sadoghi JBJS 2012