Smaller Lateral‐to‐Medial Tibial Plateau Ratios Are Strongly Correlative With Anterior Cruciate Ligament Tears and Reconstruction Failures

PURPOSE: To compare the anterior-posterior distance ratio of the lateral-to-medial tibial plateau (LTP/MTP) among 3 patient groups: those with intact anterior cruciate ligaments (ACLi), primary ACL tears (ACLp), and failed ACL reconstructions (ACLf). METHODS: We retrospectively identified skeletally mature patients (16-40 years) who underwent knee magnetic resonance imaging between May 2013 and March 2022. Patients were included if they had adequate radiographs and magnetic resonance imaging available and were required to have a minimum of 2 years of follow-up for confirmation of ACL status. The anterior to posterior distance of the LTP and anterior to posterior distance of the MTP were measured on axial T1 magnetic resonance imaging to compute LTP/MTP. Tibial eminence width was measured between tibial spine peaks on coronal T1 magnetic resonance imaging. Posterior tibial slope (PTS) was calculated on lateral knee radiographs. Multivariate logistic regression identified predictors of ACLp and ACLf. RESULTS: Demographic characteristics: age, sex, and body mass index were no different between groups. The intraclass correlation coefficients for the morphometric measurements ranged from 0.750 to 0.902 indicating good to excellent agreement among the 3 raters and intrarater reliability testing. Mean PTS was significantly higher in ACLf (12.1 ± 2.9°) compared with ACLi (10.3 ± 2.0°) and ACLp (10.6 ± 2.6°) (P < .001). The mean LTP/MTP ratio was significantly lower in ACLp (0.79 ± 0.06) and ACLf (0.77 ± 0.06) versus ACLi (0.84 ± 0.06) (P < .001). In logistic regression comparing ACLp to ACLi, a lower LTP/MTP ratio was the only significant morphologic predictor (odds ratio [OR], 0.87; 95% confidence interval [CI]: 0.80-0.95). In contrast, when compared with ACLi, ACLf were significantly predicted by a lower LTP/MTP ratio (OR, 0.82; 95% CI: 0.74-0.91), higher PTS (OR, 1.38; 95% CI: 1.14-1.73), and narrower tibial eminence width (OR, 0.70; 95% CI: 0.51-0.94). A direct comparison found that higher PTS, narrower tibial eminence width, and higher body mass index were significantly associated with ACLf versus a ACLp. For every 1-degree increase in PTS, the odds of a retear versus ACL increased by 38%. CONCLUSIONS: This study identifies the LTP/MTP ratio as a key anatomical risk factor for ACL injury. Specifically, a smaller LTP/MTP ratio was associated with a significantly higher odds of both primary ACL tears and subsequent retears relative to individuals without ACL injury. LEVEL OF EVIDENCE: Level III, retrospective comparative study.