ACL prevention rev

ACL Injuries in the Female Athlete Prevention

Strategies

• 8th Annual Force Health Protection Conference

• 9 August 2005

Daniel I Rhon, MPT

CPT, United States Army Medical Specialist Corps

Physical Therapist

William Beaumont Army Medical Center

Anterior Cruciate Ligament

• One of two internal stabilizers

• Crucial ligament for the competitive athlete

ACL ANATOMY

• Necessary for athletes involved in cutting and jumping sports

ACL ANATOMY

• Strong ligament – essential for knee stability

Tears Common In Contact Sports

Incidence of ACL Injuries

• Annually ~ 200,000 ACL tears occur in the US

• Non-contact ACL injuries occur most commonly in both males & females

Noyes et al.

• The Cincinnati Sports Medicine Group reported that 78% of ACL injuries result from non-contact mechanisms, most commonly landing from a jump, cutting, or sudden deceleration

ACL Deficiency

– Often associated with meniscal cartilage damage

– And articular cartilage damage

– May not be repairable!

Sequelae of Meniscal Damage

• Experimentally even partial meniscectomy increases contact pressures (up to 350%)!

• Degenerative changes on X-rays much more frequent: 75% vs 5%

» Fairbanks, JBJS; 1948: 30B;664-670.

ACL Deficiency

• Isolated Tear:– Relatively easy

to reconstruct– BUT:

• Season ender• Patient

morbidity• Prolonged

rehab• Return to form• Loss to team

ACL Tear Risk

• Increased incidence in female athletes: – Basketball,

volleyball and soccer

• 4 times greater than in males!

ACL Tear Risk

• Incidence in General population:– 0.4/1000

• Incidence in high school female athletes:– 1/100

• Incidence in college female athletes:– 1/10

•200-fold increased risk over general population!

Proportional Increase of Injury?

• Knee injury highest for spring football followed by:

– Women’s gymnastics– Women’s soccer– Men’s wrestling– Men’s soccer– Women’s basketball.

Increased Rate of ACL Tears in Female Athletes

• WHY?– Complex Interactions– Multifactorial

• Intrinsic Factors• Extrinsic Factors

Impact of Title IX

• Title IX Educational Assistance Act of 1972

– Equal representation of scholastic sports for both men and women

• Since inception, female participation in athletics has increased from 300,000 TO 2.37 million

Financial Setback

• 1997 Costs for ACL repair/reconstruction:

- $17,000 (treatment & rehab)

• Total cost could exceed $646M / annually for HS/College athletes

Intrinsic Factors(Not Controllable)

• Smaller size or ACL• Greater rotatory laxity• Valgus mal-alignment• Hyperextension• Diminished proprioception• Hormonal influence (estrogen)• Intercondylar notch shape & width

(White KK., 2003)

(Flynn JM., 2002)

Female Anatomic Alignment

Physiological Extrinsic Factors (Modifiable)

Knee stiffness

Activation Patterns

Neuromuscular characteristics of dynamic restraints

Landing Differences

Knee Stiffness

• Knee stiffness is an important component in knee joint stability

• External loads applied to knee are resisted by passive (ligament) and active (muscle) restraints

• Hence, insufficient muscular stiffness posses increased risk for ligamentous damage

Knee Stiffness

(40 Female Div I athletes, 60 Male football players, 40 controls; male/female)

– Women’s knees looser than men’s– Women’s Quad and HS weaker (even when body

corrected by height and weight)– Women more dependent on quad to stabilize

knees

• Interestingly: Female athletes no better than female controls in activating HS to stabilize knee

Huston and Wojtys, Am J Sports, 1996

Knee Stiffness (cont)

• 24 ‘high risk’ athletes compared with 28 ‘low risk’ athlete

– Measured knee stiffness using weighted pendulum (both with and w/o mm activation)

• CONCLUSION: Collegiate female ‘high risk’ athletes exhibited less muscular protection of knee ligaments than did size and sport-matched male athletes

Wojtys et al, 2003

Muscle Activation Patterns

FEMALE

Quadriceps Dominant:

- Increases anterior load seen Anterior Tibial Translation

- Places increased stress on ACL (Antagonist)

MALE

Hamstring Dominant:

- Anterior Tibial Translation is Decreased

- ACL load is decreased significantly (Agonist)

Hewett et al, 1996

Preparatory and Reactive Muscle Activity

• Effectively coordinate muscle activity to protect a joint requires a quick reaction at the muscle level

• The time taken to generate muscle activity and produce an adequate force will determine dynamic stabilization

Lephart et al, 2002

Force Production w/shorter Electromechanical Delay (EMD)

• EMD is the latency period between preparatory and reactive muscle activation

• Men have a shorter EMD than women

• Thus, men demonstrate a quicker response time for force production than women Hakkinen et al, 1991

Osternig et al, 1983

Landing Characteristics

• High % of ACL injuries occur when the athlete lands from jump– Ground Reaction Force (GRF) 3-14x body weight

• Stiff legged landing increases GRF significantly– Gender differences seen in knee angles when

landing from jump

Landing Characteristics (cont)

• Huston, 2000

– 20 height matched subjects (10 men / 10 women)

– Unconstrained jumps at 20, 40, 60 cm

– Impact Landing: Women averaged 7° knee flexion compared with Men 16°

Land Characteristics (cont)

Landing Characteristics (cont)

• Malinzak et al, 1999

• Compared kinematic data on young healthy men and women during controlled running and cutting maneuvers

• Results from comparison – Less knee flexion (25° vs 29°)– Increased knee valgus (knees pointing inward)– Less hip flexion

ACL Tear Prevention

Is it Possible? YES!!

Several prospective studies have shown an 4 to 8-fold decreased rate on ACL tears in female athletes who are properly trained

Hewett TE, Lindenfeld TN, Riccobene JV, Noyes FR. The effect of neuromuscular training on the incidence of knee injury in female athletes. A prospective study. Am J Sports Med. 1999 Nov-Dec;27(6):699-706.

Mandelbaum BR, et al. AOSSM Annual Meeting, 2002, Disneyland FL

Training Program (Smarter not Harder)

• What now??

• An effective jumping and training program has shown significant improvements on all previously highlighted EXTRINSIC FACTORS associated with the increase in ACL injuries

• Properly trained female athletes can decrease their ACL tear rate equal to that of males

• Studies show that it can also increase your vertical leap by 10%

CD-ROM Exercise Program Demonstration

Specificity of Trainingis the Key to Injury

Prevention• Still a GREAT program with male population

• Preventing musculoskeletal injuries with PROPER exercises should be the backbone of orthopedic medicine

• Proper education is the forefront to success

CD-ROM Pre-Rehabilitation Exercise Program

QUESTIONS?

References• Flynn JM, Lou JE. Ganley TJ. Prevention of sports injuries in children. Current

Opinion in Pediatrics. 14(6):719-22, 2002 Dec.

• Gollehon DL, Torzilli PA. The role of the posterolateral and cruciate ligaments in the stability of the human knee. A biomechanical study.; Warren-RF J-Bone-Joint-Surg-Am. 1987 Feb; 69(2): 233-42

• Hewett et al, Plyometric Training in Female Athletes. Am J Sports Med. 1996

• Hewett et al, The Effect of Neuromuscular Training on the Incidence of Knee Injury in Female Athletes. Am J Sports Med. 1999.

• Huston LJ, Greenfield ML. Wojtys EM. Anterior cruciate ligament injuries in the female athlete. Potential risk factors. Clinical Orthopaedics & Related Research. (372):50-63, 2000 Mar.

• Lephart et al, Neuromuscular Contributions to Anterior Cruciate Ligament Injuries in Females. Rheumatology. 2002.

• Loud KJ, Micheli LJ. Common athletic injuries in adolescent girls. Current Opinion in Pediatrics. 13(4):317-22, 2001 Aug.

• Messina et al, The Incidence of Injury in Texas High School Basketball. Am J Sports Med. 1999.

References

• Odensten M, Gillquist J. Functional anatomy

• Walsh et. al. Sportsmetric: Neuromuscular Training to Prevent Knee Injuries. Cincinnati Sports Medicine Research and Education Foundation. 2002.

• White et al, EMG Power Spectra of Intercollegiate Athletes and Anterior Cruciate Ligament Injury in Females. Med and Sci in Sports & Exercise. 2003

• Wojtys et al. Gender Differences in Muscular Protection of the Knee in Torsion in Size-Matched Athletes. J Bone and Joint Surg Am. 2003

• Wojtys et al. Neuromuscular Performance in Normal and Anterior Cruciate Ligament – Deficient Lower Extremities. Am J Sports Med. 1996