Meniscal Bone Angle Is a Strong Predictor of Anterior Cruciate Ligament Injury

PURPOSE: To evaluate the influence of lateral posterior tibial slope (LPTS) and meniscal bone angle (MBA) on primary anterior cruciate ligament (ACL) tear risk in an adult population through the LPTS–MBA ratio. METHODS: A retrospective case–control study was performed with patients from a tertiary hospital who underwent primary ACL surgery and had preoperative magnetic resonance imaging (MRI). These subjects were matched by age and sex in a 1:1 ratio to patients who had an MRI without ACL tear. LPTS and MBA were measured on MRI scan. Quantitative data are presented in the median ± interquartile range (IQR). Identification of independent risk factors for primary ACL tear was performed using multivariable logistic regression. Receiver operating characteristics curves detected any variable with strong discriminative capacity. RESULTS: In total, 95 patients with primary ACL tear confirmed on MRI were matched with 95 controls (N = 190). Nearly 80% were male subjects, with a median age of 26 years. In the ACL tear group, the median value of LPTS–MBA ratio was 0.20 (IQR 0.11-0.37) versus 0.12 (IQR 0.08-0.19) in the control group (P = .001). LPTS had a median value of 4.20° in the ACL tear group (IQR 2.05-7.35°) and 2.90° in the control group (IQR, 2.05-5.00°) (P = .026), whereas MBA was 19° (IQR, 16-24°) versus 26° (IQR, 24-30°) (P = .001), respectively. Logistic regression showed that LPTS (odds ratio 1.20, 95% confidence interval 1.03-1.42, P = .021) and MBA (odds ratio 0.78, 95% confidence interval 0.71-0.85, P = .001) were independent predictors. The area under the curve (AUC) of LPTS–MBA ratio was 0.69, greater than that of LPTS alone (AUC = 0.61) but lower than that for MBA (AUC = 0.82). CONCLUSIONS: In this study, a reduced MBA was the strongest predictive variable associated with a primary ACL tear. A threshold of 22.35° of MBA was associated with an increased risk of ACL tear, with a sensitivity of 70% and specificity of 84%. A cut-off of 0.22 of LPTS–MBA was associated with an increased risk of ACL tear, with a sensitivity of 55% and specificity of 87%. LEVEL OF EVIDENCE: Level III, case–control study.