ACL Injury Prevention ACL Injury Prevention ProgramsPrograms

Michael D. Lee, MD

ACL TearsACL Tears

•250,000 to 300,000 per year

•$20,000 to $50,000 per reconstruction

•$800 to $3000 out of pocket

•PT: $1000+

ACL ReconstructionACL Reconstruction

•6% ipsilateral knee (2-10%)

•12% contralateral knee (8-16%)

•about 1 in 5 will have another ACL tear

Failure Rate

Wright et al., JBJS, 2011

ACL RevisionACL Revision

•14%

Failure Rate

Wright et al., JBJS, 2012

ACL TearsACL Tears

•ACL reconstructed knee is not “normal”

•lifelong increased risk of OA

•best treatment: prevention

Female RiskFemale Risk

•4 - 6 times male risk

•Title IX 1972 Act

•Female participation 5 times at college level

•Female participation 10 times high school level

ACL InjuriesACL Injuries

•70% are non-contact injuries

•Non-contact injuries are theoretically preventable

Risk FactorsRisk Factors

•non-modifiable

•modifiable basis for prevention

Non-modifiable Risk Non-modifiable Risk FactorsFactors•anatomic

•genetic: COL5 risk in some females

•developmental

•hormonal•Ge

•G

Notch StenosisNotch Stenosis

•Theory: small notch impinges on ACL

•Several studies support this theory

Notch Width IndexNotch Width Index

Notch SizeNotch Size

•Smaller notch = smaller ACL?

•+ correlation of ACL size and notch width index

•Smaller ACL found in ACL injured patients compared to controls

Ligamentous LaxityLigamentous Laxity

•Generalized LL a significant risk for ACLI

•Studies show knee hyperextension in ♀ soccer and bball players a risk for ACLI

Tibial SlopeTibial Slope

Tibial SlopeTibial Slope

•Increased slope increases ACLI risk

•Increased slope increases ACL strain

Hormonal FunctionHormonal Function

•ACL fibroblasts have estrogen receptors

•Estrogen affects tensile properties of ligaments

•Increased ACLI risk in pre-ovulatory menstrual phase (first 1/2 of cycle)

Hormone FunctionHormone Function

•Retrospective studies show decreased risk of ACLIs with BCPs

•Theory: stabilize hormonal functional through cycle

Neuromuscular MaturationNeuromuscular Maturation•No ACLI difference in pre-adolescent ♀vs ♂

•4 -6 x risk for females after maturation

•only males have a n-m spurt with increase in power, strength and coordination

•post-maturation jump mechanics differ

Modifiable Risk FactorsModifiable Risk Factors

•ligament dominance•quadriceps dominance•leg dominance•trunk dominance

Neuromuscular Imbalance

Ligament DominanceLigament Dominance

•responsible for valgus collapse

•supporting ms groups don’t adequately contract to absorb ground reaction forces

•this increases the forces placed thru static restraints

Ligament DominanceLigament Dominance

•all LE muscles contribute to dynamic stability

•posterior kinetic chain most important for ACLI prevention (glutes, hamstrings, gastro-soleus)

•improper PKC recruitment during landing causes higher knee abd. moments and increases load on ACL

Valgus Collapse

Quadriceps DominanceQuadriceps Dominance•♀ preferentially activate quads in landing

•results in stiff-legged, extended landing posture rather than safer flexed position

•hamstrings are ACL-agonists, reducing anterior tibial translation

•Quads are ACL-antagonists, exerting strain on ACL

Quadriceps DominanceQuadriceps Dominance

•an erect or extended knee landing posture activates the quads

•quadriceps contraction increase anterior shear stress to knee

•protective pull of hamstrings is lost

•plyometric training can increase HS:Quad torque or strength ratio

Leg DominanceLeg Dominance

•women rely more on one leg compared to men

•leg dominance defined as measurable muscle asymmetry

•limited evidence to support LD as a definite risk factor

Trunk DominanceTrunk Dominance

•inability to control trunk in space allows greater movements outside of safe zone

•creates larger moments on the LE

•ACL injured females in one study had significantly more max. trunk displacement in all directions compared to controls

EnvironmentalEnvironmental

•most important is shoe-surface interface

•larger (longer) cleats and rubber floors are risk factors in several studies

FatigueFatigue

•may decrease dynamic stability

•Chappell et al: increased ant shear force and valgus moments, and decreased flexion angles in jump study in fatigued vs non-fatigued state

•data support but clinical research lacking to validate this theory

Prevention FocusPrevention Focus

•balance•strength•proprioception•endurance•plyometrics•stability

Prevention BiomechanicsPrevention Biomechanics

•decrease peak landing forces, knee abduction forces and HS/Quad strength ratio

•increase knee flexion with landing

•importance of feedback can’t be overemphasized

Goals

Clinical StudiesClinical Studies

•Hewett et al. 1999, 1263 athletes: increased ACLI in untrained group

•Mandelbaum “PEP” program: Prevent injury and Enhance Performance. 20 min. soccer program replaces warm-up. Reduced ACLI 74-88% over 2 years

Clinical StudiesClinical Studies

•Gilchrist et al.: 1435 female Div. I soccer players. Non-contact ACLI rate 3.3 x less in trained group

•Caraffa et al.: Proprioceptive training 600 soccer players. ACLI 8 x higher in untrained group

Meta-Analyses of ACL PPMeta-Analyses of ACL PP

•Hewett 2006: 6 studies, concluded that N-M programs have sign. effect on reducing ACLIs

•Yoo 2010: ACLI PP best for < 18 y.o., female, and emphasis on plyometric and strength training.

•Sadoghi 2012: significant, positive effect of ACLI PP. ♀ RRI = 52%. ♂ RRI = 85%

ScreeningScreening•Meyer: ♀ separated into hi/low risk groups from motor analysis of drop vertical jump. Significant decrease in knee abduction moments in hi risk group with ACLI PP training.

•DiStefano: “LESS”: Landing Error Scoring System. Those with higher risk scores improved most with ACLI PP

ScreeningScreening

•Studies consistently identify at risk athletes

•identification methods presently are too labor intensive for large scale implementation.

ComplianceCompliance

•Poor

•athletes and coaches prefer to focus on performance rather than injury prevention

ComplianceCompliance

•Performance is usually enhanced with ACLI PP

•Improved: LE strength, vertical jump height,squat strength, single leg hop distance, sprint times

RecommendationsRecommendations

“ all female athletes should undergo an ACL PP until more reliable methods of identification of at-risk athletes are developed. The training sessions should emphasize proper technique and should be performed year-round.”

Journal of Bone and Joint Surgery 2013

Questions?Questions?