The angle of the lower portion of the posterior cruciate ligament assists in the diagnosis of partial anterior cruciate ligament tears

PurposeTo compare the difference of angle of the lower portion of the posterior cruciate ligament (PCL) measured via magnetic resonance imaging (MRI) in patients with and without partial anterior cruciate ligament (ACL) tears and to investigate the effectiveness of the angle of the lower portion of the PCL in diagnosing partial ACL tears.MethodsFrom January 2022 to December 2022, a cohort of consecutive patients presenting with ACL tears who underwent ACL reconstruction and patients with isolated meniscus tears undergoing arthroscopic surgery were enroled for this study. The angle of the inferior portion of the PCL comprises alpha and beta angles, and the posterior offset of the lateral condyle were measured on the MRI and compared between the partial ACL tear and control groups. Receiver operating characteristic curves, the areas under the curve (AUCs) and the 95% confidence intervals (CIs) were calculated to identify cutoff values for diagnosing partial ACL injuries.ResultsFollowing an assessment of cohort eligibility and matching for age and sex, 100 patients were included in this study. The mean age of the cohort was 46.1 +/- 10.3 years. The AUC for the alpha angle was 0.88 (95% CI, 0.82-0.94), with a sensitivity of 0.74 and specificity of 0.84 for predicting partial ACL ruptures; the alpha angle cutoff value was 73.6 degrees (diagnostic odds ratio (OR), 14.10; 95% CI, 5.33-37.28). The AUC for the beta angle was 0.86 (95% CI, 0.79-0.93), with a sensitivity of 0.64 and a specificity of 0.92 for predicting partial ACL ruptures; the beta angle cutoff value was 73.3 degrees (diagnostic OR, 14.54; 95% CI, 5.76-36.68).ConclusionsA small alpha angle and a large beta angle were associated with partial ACL tears. The angle of the distal portion of the PCL was simple to measure and reproducible, enhancing the diagnosis of partial ACL tears.Level of EvidenceLevel III.