Lateral Femoral Condyle Angle Is an Anatomic Risk Factor for Anterior Cruciate Ligament Primary Injury and Secondary Graft Rerupture.

Abstract

PURPOSE: To define the lateral femoral condylar angle (LFCA)-a parameter measuring condylar inclination-and assess its predictive capacity for primary and recurrent anterior cruciate ligament (ACL) injuries. METHODS: Patients aged 18 to 50&#x2009;years who underwent primary ACL reconstruction between 2017 and 2022 were screened. Those with graft rerupture were matched 1:1:1 by sex, age, body mass index, and meniscal status to ACL-intact controls and patients without graft failure during a minimum 48-month follow-up. LFCA was measured as the angle between the long axis of the distal femur and the axis of the lateral femoral condyle, alongside 38 established parameters using preoperative 3.0-T magnetic resonance imaging scans. Intergroup differences were assessed with one-way analysis of variance; multivariate regression and receiver operating characteristic analyses identified independent predictors and evaluated predictive performance. RESULTS: The study included 540 patients (180 per group: primary ACL injury, rerupture, controls). One-way analysis of variance revealed a significant gradient in LFCA across controls (81.3&#xb0;, 95% CI: 80.8-81.8&#xb0;), primary injuries (81.9&#xb0;, 95% CI: 81.5-82.3&#xb0;), and reruptures (84.2&#xb0;, 95% CI: 83.7-84.6&#xb0;) (P&#x2009;<&#x2009;.001). In multivariate models adjusted for baseline factors, LFCA independently predicted primary injury (odds ratio [OR]&#x2009;=&#x2009;1.27, 95% CI: 1.13-1.42, P&#x2009;<&#x2009;.001; area under the curve [AUC]&#x2009;=&#x2009;.576) and rerupture (OR&#x2009;=&#x2009;1.46, 95% CI: 1.21-1.76, P&#x2009;<&#x2009;.001; AUC&#x2009;=&#x2009;.704). Combined models incorporating LFCA with tibial slopes, notch angle, and notch height achieved an AUC of .847 for primary injury prediction, whereas models with LFCA, lateral condylar flexion curvature radius, slope asymmetry, and tibial AP distance reached an AUC of .817 for rerupture. LFCA alone with lateral condylar flexion curvature radius yielded an AUC of .777 for rerupture prediction. Sex-stratified analyses confirmed LFCA predicted rerupture in both male patients (OR&#x2009;=&#x2009;1.44, 95% CI: 1.19-1.75) and female patients&#xa0;(OR&#x2009;=&#x2009;1.49, 95% CI: 1.16-1.92), and primary injury in male patients&#xa0;(OR&#x2009;=&#x2009;1.30, 95% CI: 1.15-1.48). CONCLUSIONS: LFCA is an independent predictor of ACL injury, showing particular strength in identifying Asian patients at high risk for graft rerupture. LEVEL OF EVIDENCE: Level III, retrospective case-control study.