Does Gender Play a Role in ACL Reconstruction Outcome?

The anterior cruciate ligament (ACL) is one of the most frequently injured knee ligaments with an injury incidence of over 200, 000 cases per year, according to the University of California, San Francisco Department of Orthopedic Surgery’s website. By the numbers, more ACL injuries happen to men because a greater amount of men participate in sports. Women, however, have a higher risk of ACL injury due to lower extremity alignment, looseness in the joints, hormonal differences, and ACL size. According to National Collegiate Athletic Association (NCAA) statistics, women are 2 to 8 times more likely to experience an ACL injury from sports participation. Although it is well documented that women are more likely to sustain an ACL injury, several doctors wondered if females are predisposed to poor outcomes following ACL reconstruction.

John Ryan, M.D.; Robert A. Magnussen, M.D.; Charles L. Cox, M.D., M.P.H.; Jason G. Hurbanek, M.D.; David C. Flanigan, M.D.; and Christopher C. Kaeding, M.D. conducted a systematic review of the medical literature concerning the outcomes of ACL reconstruction by sex. Published in the March issue of The Journal of Bone and Joint Surgery, the review is titled, “ACL Reconstruction: Do Outcomes Differ by Sex?” The doctors evaluated a total of 13 studies in order to determine whether sex played a role in the outcome of ACL reconstruction. After reviewing the studies, determining several outcome measures, and assessing the results for homogeneity, the doctors performed a meta-analysis. The four outcome measures analyzed were “graft failure risk, contralateral ACL injury risk, knee laxity, and patient-reported outcome scores following ACL reconstruction.” They determined homogeneity with a chi-square test and performed the meta-analysis using a Mantel-Haenszel analysis with a random-effects model.

After analyzing each outcome measure, the doctors found no difference in “graft failure risk, contralateral ACL rupture risk, or postoperative knee laxity on physical examination.” The doctors did not find a clinically important difference in patient-reported outcomes. Seven studies evaluated graft rupture risk. Although the risk was 4.6% for men and 5.4% for women, the doctors found no difference after performing the meta-analysis. Three studies reported on contralateral ACL rupture; the risk for men was 4.0% and 7.4% for women. The meta-analysis still found no difference according to sex. Five studies included knee laxity, or Lachman test, findings. 37.5% of males and 39.8% of females showed a Lachman test grade greater than 0, which the meta-analysis deemed an insubstantial difference. Nine studies disclosed patient-reported outcome scores but the lack of consistency in measurement tools made the findings clinically unimportant.

Although the meta-analysis revealed no differences in the various outcome measures between the sexes, there was nonsignificant evidence of increased knee laxity and a higher risk of contralateral ACL rupture risk in female patients. Women have a higher risk of ACL tears, possibly as a result of a neuromuscular control deficit in the knee. The lack of difference in ACL reconstruction outcomes between men and women may be because women receive increased care addressing neuromuscular deficits after ACL reconstruction. It is also possible that the outcome differences between men and women were not detected in this review.