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 adult population through LPTS-MBA ratio. 

 

Methods: A retrospective case-control study was performed with patients from a tertiary hospital who underwent primary ACL surgery and had a pre-operatory magnetic resonance imaging (MRI). These subjects were matched by age and sex in a 1:1 ratio to patients who had a MRI without ACL tear. LPTS and MBA were measured on MRI scan. Quantitative data are presented in the median ± interquartile range. Identification of independent risk factors or primary ACL tear was performed using multivariable logistic regression. Receiver operating characteristics curves detected any variable with strong discriminative capacity. 

 

Results: 95 patients with primary ACL tear confirmed on MRI were matched with 95 controls (N=190). Most of them were males with a median age of 26 years. In ACL tear group, the median value of LPTS-MBA ratio was 0.20 (interquartile range (IQR), 0.11-0.37) versus 0.12 (IQR, 0.08-0.19) in control group (P=0.001). LPTS had a median value of 4.20º in ACL tear group (IQR, 2.05-7.35º) and 2.90º in controls (IQR, 2.05-5.00º) (P=0.026) while MBA was 19º (IQR, 16-24º) versus 26º (IQR, 24-30º) (P=0.001), respectively. Logistic regression showed that LPTS (odds ratio (OR) 1.20, 95% confidence interval (CI) 1.03-1.42, P=0.021) and MBA (OR 0.78, 95%CI 0.71-0.85, P=0.001) were independent predictors. The area under the curve (AUC) of LPTS-MBA ratio was 0.69, higher than that of LPTS alone (AUC=0.61) but lower than that for MBA (AUC=0.82). 

 

Conclusions: LPTS-MBA ratio is increased in primary ACL tear patients. LPTS and MBA are independent predictors of primary ACL tear. LPTS-MBA ratio is better than LPTS alone for predicting primary ACL tear; however, MBA was the strongest predictive variable. 

 

Level of evidence: III, case-control study.