Combined Anterolateral Ligament and Anterior Cruciate Ligament Injury Is Associated With Increased Lateral Femoral Condyle Ratio

Purpose: to investigate the association between the lateral femoral condylar ratio (LFCR), the posterior tibial slope (PTS), and injury of the anterolateral ligament (ALL). Methods: Inclusion criteria were patients with acute anterior cruciate ligament (ACL) tear after noncontact injury during sports from October 1997 to May 2021. The LFCR and PTS were measured, and injury of the ALL was evaluated. Patients were divided into 2 groups: isolated ACL tear (isolated group) and combined ACL with ALL tear (combined group). The LFCR and PTS were compared between the isolated and combined groups. For each risk factor, the receiver operating characteristic curve, the area under the curve (AUC), and its 95% confidence interval (CI) were calculated to determine the cutoff for detecting increased risk of ALL injury. Results: There were 83 patients in the isolated group and 176 patients in the combined group. Demographics of the 2 groups did not differ significantly. The LFCR was significantly larger in the combined group than in the isolated group (P = .000). The PTS did not differ between the two groups (P = .405). The LFCR (odds ratio [OR] = 1.58; P = .000) was a significant factor. Age, body mass index, and PTS were not associated with an ALL injury. The AUC (0.79; 95% CI, 0.740.85) for the LFCR had a sensitivity of 73% and specificity of 76% to predict an ALL rupture. The calculated cutoff of 64.5 was associated with an increased risk for ALL rupture (OR = 8.65; 95% CI, 4.73-15.81) when compared with the isolated group. Conclusions: An increased LFCR was associated with the ALL injury. However, increased PTS was not associated with ALL injury. These findings need to be considered for clinicians in treating ACL tear patients at risk for an ALL injury. Level of Evidence: III, retrospective comparative prognostic trial.