GENDER DIFFERENCES IN NONCONTACT ANTERIOR CRUCIATE LIGAMENT INJURIES

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After the passage of Title IX in 1972, women began competing in organized sports in large numbers. There was concern that women would have significantly higher injury rates than men. For the most part, these fears were unfounded. Sports injury rates between men and women are similar and, in general, seem to be sport-specific rather than gender-specific.27, 37, 94, 99 There is, however, an increased predisposition (two to eight times) to anterior cruciate ligament (ACL) rupture in women.* There are many theories and much research devoted to explaining why this difference in injury rate exists.

Research has focused on intrinsic and extrinsic factors. Intrinsic factors are those that are individual, physical, and psychosocial.6 Intrinsic factors include joint laxity, hormonal influences, limb alignment, notch dimensions, and ligament size. The intrinsic causes tend to be more sex-specific and may not be modifiable. Most research into the cause of ACL injuries has been directed toward intrinsic causes. Extrinsic factors are those related to the type of sport, the environmental conditions, the conditioning of the athlete, and the equipment used.6 Unlike most intrinsic factors, extrinsic factors are potentially controllable or changeable. Extrinsic factors include conditioning, experience, skill, strength, muscle recruitment patterns, and landing techniques. Extrinsic factors are difficult to measure objectively in a functional, sport-specific way, making research in these areas challenging.

This article briefly reviews the epidemiology of ACL injuries and looks at potential contributing factors to the gender difference in ACL injury rate. In addition, prevention strategies and their usefulness are examined. The indications for surgery and outcomes after ACL reconstruction in men and women are reviewed, and ACL graft choice in women is discussed.

Section snippets

EPIDEMIOLOGY

Thousands of ACL reconstructions are performed every year. To date, the most comprehensive data base available has been the National Collegiate Athletic Association (NCAA) injury surveillance system69; however, this is composed of varsity college athletes and the data collected may not be representative of the broader population of athletes.

It is unclear whether ACL incidence varies significantly with age or what the peak age for ACL injury is in a particular sport or in either sex. Studies

Ligamentous Laxity

Ligamentous laxity is one of the intrinsic factors that has been postulated as contributing to ACL injury. Two questions need to be answered to address this issue: Does increased ligamentous laxity translate to an increased ACL injury rate? Do women have more ligamentous laxity than men?

In 1970, Nicholas found that male football players who had increased looseness had a higher incidence of knee ligament rupture.70 Others agreed that joint laxity determined by similar tests predisposed people to

Conditioning

Many articles refer to a significantly decreased level of baseline conditioning in women.* As levels of conditioning improve, there is a leveling out of injury rates between men and women.17, 37, 98 The bulk of the literature about conditioning level is related to overall injury rate rather than specifically addressing ACL injury rate; however, many authors have extrapolated this data to ACL injury rate.5, 12, 45, 64 In a deconditioned

PREVENTATIVE MEASURES

Not all noncontact ACL injuries can be prevented; however, an impact on injury rates can be made with early instruction in preventative skills: learning how to fall, to jump, and to cut. Plyometric training can reduce landing forces and improve strength ratios,40 which theoretically could lead to a decrease ACL injury rate. ACL injury prevention programs have been successful.15, 24, 39 These programs employ strategies that range from increasing hamstring activation and modifying jumping and

Gender Comparisons After Reconstruction

Few studies have been published comparing outcomes of ACL surgery on the basis of gender. In a comparison of male and female patients undergoing autogenous ipsilateral central bone patellar tendon bone ACL reconstructions, Barber-Westin found similar results on the Cincinnati knee rating scale. At 26 months postoperatively, in 94 patients (47 men and 47 women), there was no difference in complications.7 The failure rate was 6% in female patients and 4% in male patients. Men and women did

HUNT VALLEY CONSENSUS SYMPOSIUM

In June 1999, a consensus conference was held in Hunt Valley, Maryland. A panel of experts on ACL injuries met to discuss what was known about ACL injuries, prevention strategies, and directions for further research. The following is a summary of their findings:32

  • Anatomic Risk Factors

    • No consensus on the notch's role in ACL injury can be reached.

    • There are insufficient data to relate lower extremity alignment to ACL injury.

  • Environmental Factors

    • Shoe-surface coefficient of

SUMMARY

Female athletes have an increased incidence of ACL rupture. The cause of this increased injury rate is unclear, but it is most likely from a complex interplay between multiple variables. The relative risk of incurring an ACL injury is still low. The increased risk of ACL injury in women compared with men should not discourage female participation in sports. Instead, the focus should be on strategies to prevent injuries. Intrinsic factors are difficult or impossible to change; modifiable risk

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    Address reprint requests to Kimberly G. Harmon, MD, Sports Medicine Clinic, Hall Health Primary Care Center, Box 354110, University of Washington, Seattle, WA 98195–4410

    *

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