Do Sex-Specific Differences Exist in ACL Attachment Location? An MRI-Based 3-Dimensional Topographic Analysis

BACKGROUND: Female sex is an independent risk factor for an anterior cruciate ligament (ACL) injury, as the incidence of an ACL rupture is 4- to 6-fold higher in female athletes compared with their male counterparts. The ACL attachment location as a potential risk factor for the increased ACL rupture rate in women has never been reported in the literature. PURPOSE/HYPOTHESIS: The purpose of the present study was to investigate the 3-dimensional topographic anatomy of the ACL bundle attachment in female and male patients, with and without an ACL rupture, and identify potential sex-related differences. We hypothesized that the ACL attachment location would be significantly different between men and women, in both the intact- and ruptured-ACL states. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Magnetic resonance images of the knee from 90 patients (55 men, 35 women) with a ruptured ACL and 90 matched controls (55 men, 35 women), who suffered a noncontact knee injury without ACL rupture, were used to create 3-dimensional models of the femur and tibia. The ACL bundles’ origin and insertion were outlined on each model, and their location was measured using an anatomical coordinate system. A 2-way analysis of variance was used to compare the ACL attachment location between male and female patients, with and without an ACL rupture. RESULTS: No significant differences were found between female and male participants regarding ACL attachment location (femoral origin and tibial insertion). Patients with a ruptured ACL demonstrated a significantly different ACL origin compared with the participants with an intact ACL by an average difference of 8.9% more posterior (P < .05) and 4.0% more proximal (P < .05) in men and 13.0% more posterior (P < .05) and 5.5% more proximal (P < .05) to the flexion-extension axis of the knee in women. CONCLUSION: The ACL attachment location should not be considered a risk factor for the increased ACL rupture rates in female compared with male athletes. However, a more posterior and proximal location of the femoral ACL origin might be a predisposing factor to an ACL rupture regardless of sex.