... incidence coincides with onset of puberty (Michaud

1
When does gender matter? How maturation relates
to ACL injury

• Kate Jackson, MEd, ATC

2
Introduction

• Estimated 80,000 -250,000 ACL ruptures occur per
  year (Garrick, 1999)
• Over 50 in 15-25 year old athletes
• 70 noncontact mechanism (Boden, 2000)
• Increased ACL injury risk for adolescent and
  adult females (Agel, 2005)

3
Introduction

• Pubertal stage may relate to rate and type of
  injury (Tursz, 1986 Adirim, 2003)
• Decreased incidence of fracture, increased
  incidence of sprain
• Increase in overall injury rate related to sports
  as boys and girls progress through pubertal stages

4
Introduction

• Onset of ACL injury incidence coincides with
  onset of puberty (Michaud, 2001 Shea, 2004)
• No difference in ACL rates between genders before
  onset of puberty Age 12 distinct shift in
  increased female sprain rates
• Gender bias in ACL injuries present after age 12

5
Proposed risk factors for ACL injury

• Environmental
• Surface
• Footwear
• Interaction between surface footwear
• Protective equipment
• Anatomical
• Q angle
• Static valgus
• Pronation
• BMI
• Femoral notch width
• ACL geometry/structure
• Hormonal
• Regulation of collagen synthesis and ligament
  degradation
• Laxity

• Neuromuscular
• Altered movement patterns
• Altered activation patterns
• Altered muscle stiffness

6
Neuromuscular Risk Factors

• Altered movement patterns
• Kinematic (range of motion)
• Kinetic (joint torque as measured by ground
  reaction force)
• Tibial shear

7
Altered Movement Patterns

• Consistent kinematic differences found between
  adult and adolescent males and females during
  laboratory based landing tasks (Ford, 2003
  Hanson, in press Hewett, 2005 Padua, 2002)
• Females display
• Decreased hip and knee flexion
• Increased hip internal rotation
• Increased knee valgus
• Increased anterior tibial shear

8
Altered Movement Patterns

• Prospective kinetic differences found between ACL
  injured and healthy adolescent females (Hewett,
  05)
• Injured group had larger knee valgus moments
• Higher ground reaction forces

9
Altered Movement Patterns

• Less published information looking at
  pre-pubertal males and females
• No kinematic differences shown between genders in
  pre-pubertals (Jackson, submitted) or before age
  12 (Yu, 2005)
• Differences in force management between genders
  in pre-pubertal population during sidestep
  cutting (Jackson)
• Inherent differences between genders regarding
  force management?

10
Neuromuscular Risk Factors

• Altered muscle activation patterns
• High levels of quadriceps activity
• Low levels of hamstring activity
• Decreased normalized strength
• Altered muscle stiffness patterns
• Muscle activation response time to movement or
  perturbation

11
Altered Muscle Activation

• Adult females of all levels exhibit quadriceps
  dominance during landing and cutting (Huston,
  1996 Malinzak, 2001 White, 2003)
• Eccentric contraction coupled with decreased knee
  flexion ? greater anterior tibial shear
• Decreased knee flexion minimizes posterior shear
  forces of the hamstrings

Borrowed from Darin Padua
12
Altered Muscle Stiffness

• Adult females have decreased stiffness of the
  hamstrings and quadriceps (Padua, 2002 Wojtys,
  2002 Blackburn, 2008)
• Decreased ability to dissipate external forces
• Increased joint motion
• Greater load placed on static restraints
  (ligament dominance)
• Increased risk for ACL injury
• No known studies investigating muscle stiffness
  in youth population

13

• What is happening during puberty that is
  changing neuromuscular control patterns and
  resulting in differences between adolescent and
  adult males and females?

14

• Borrowed from Carmen Quatman

15
Sex Differences in Pubertal Changes

• Prepubertal similar in
• Height
• Weight
• BMI
• Muscle width
• Bone width and length

• Pubertal different in
• Height
• Weight
• BMI
• Bone length
• Females have more hip internal rotation knee
  valgus
• Females have larger Q angles

16
Rapid Growth Significantly Affects

• Height
• Weight
• Length and mass of levers (tibia, femur)
• Center of mass
• Muscle strength, activation stiffness

(Myer, 2007)
17
What We Should Do

• Proposed females do not go through neuromuscular
  spurt similar to males
• Negatively affects trunk hip neuromuscular
  control

(Myer, 2008)
18

• What should we do?
• Examine
• Identify
• Implement

19
Examine

• Examine neuromuscular control performance
  (Hewett, 2005)
• Gender differences relate to risk factors for ACL
  injury
• Neuromuscular control patterns develop early and
  may continue to progress/change

20
Examine

• Examine the position of the entire body during
  jumping, landing and cutting?
• Lateral trunk lean
• Hip flexion
• Femur position
• Knee flexion
• Knee valgus
• Tibial external rotation
• Foot eversion

21
Identify

• Identify at risk individuals and intervene

Garret Griffin, 2006
22
Implement Prevention Programs

• What to include?
• Balance
• Strength
• Agility
• Plyometrics
• Risk awareness

23
Implement Prevention Programs

• How often and for how long?
• Optimal parameters are not known
• Adjust accordingly based on
• Population
• Level of injury risk
• Rate of improvement
• Information overload
• How much time is a coach willing to give you?
• Do not proceed past the point of improper
  mechanics

24
Implement Prevention Programs

• What age?
• Optimal age is not known, improvements seen in
  adolescent and adult groups
• Do not cause harm by overloading developing
  structures
• My opinion, younger is better keeping in mind the
  goal of the program
• Introduce awareness
• Establish proper mechanics
• Minimize risk factors

25
Questions?