Increased distal femoral torsion is a predictor of non-contact anterior cruciate ligament injury: a case control study

Abstract Background The Anterior cruciate ligament (ACL) is one of the most easily injured ligaments in the knee. Abnormal femur and knee rotation may lead to ACL injury, while an increased proportion of the lateral femoral condyle is also a potential factor in ACL injury. Therefore, distal femoral torsion (DFT) may be closely related to ACL injury. Thus, this study aims to investigate the associations of DFT with the risk of ACL injury and the severity of the injury. Methods 582 patients who received ACL reconstruction surgery between 2014 and 2019 were examined retrospectively, and 114 patients were selected for analysis. Among them, 32 experienced ACL and anterolateral ligament (ALL) injury (ACL + ALL-injury group), and 32 experienced only ACL injury (only ACL injury group). In addition, 50 patients with similar age and BMI, but without ACL or ALL injury, were selected as the control group. DFT was assessed via the surgical posterior condylar angle (sPCA) on MRI by a blinded researcher. Inter-group differences were assessed via ANOVA. An ROC (Receiver Operating Characteristic) curve was generated to elucidate the ACL injury risk, and to establish the appropriate threshold value. Result The average sPCA was 3.68 ± 1.26° among the ACL + ALL-injury and ACL-injury only patients. Notably, the 3.77 ± 1.15° sPCA among the ACL + ALL-injury patients, and the 3.58 ± 1.37° sPCA among the ACL-injury patients were markedly enhanced, compared to the 2.41 ± 1.48° value in control patients. The ACL + ALL patients displayed an augmented sPCA trend over ACL-alone patients, however, it did not reach significance. Moreover, based on the ROC curve, sPCA > 2.37° was indicative of an enhanced ACL injury risk among the ACL-intact individuals. Conclusion Based on our analysis, augmented sPCA values were intricately linked to enhanced ACL injury risk in non-contact ACL ruptured patients. Nevertheless, its usage as a predictor of ACL injury severity is scarce. The conclusions of this study will likely assist orthopedic surgeons in identifying patients who may benefit from targeted ACL injury prevention.