Increased Lateral Posterior Tibial Slope Is Associated With a Greater Rate of Lateral Meniscal Injury in Acute Noncontact Anterior Cruciate Ligament Ruptures.

PURPOSE

To determine whether there is an association between increasing posterior tibial slope and meniscal tears in a group of patients with isolated, noncontact and acute anterior cruciate ligament (ACL) ruptures from a large ACL registry.

METHODS

Our institution's ACL Registry was consulted to identify patients between the age of 18 and 45 years who underwent primary ACL reconstruction between January 2019 and July 2022 for acute, noncontact ACL rupture. Patients with pre-existing meniscal pathology, chronic ACL reconstructions, revisions, and multiligament knee injuries were excluded. Preoperative magnetic resonance imaging scans were used to measure lateral and medial posterior tibial slope. Meniscal injuries seen during arthroscopy were recorded on the basis of operative reports. Independent cohorts were created on the basis of the presence or absence of a meniscal tear. Two-tailed Student t tests were used to compare average medial and lateral posterior tibial slopes between groups. Separate analyses were performed for the presence of isolated lateral meniscal tears, isolated medial meniscal tears, and both medial and lateral meniscal tears. Multivariable logistic regression models were generated to evaluate other potential risk factors for each tear outcome, including age, sex, and body mass index (BMI). Receiver operating characteristic curve analysis was conducted to explore the potential of identifying an optimal threshold for predicting the presence of a meniscal tear based on lateral posterior tibial slope.

RESULTS

In total, 1,056 patients ultimately met inclusion criteria. There were 498 (47%) patients with any meniscal tear, 346 (33%) patients with lateral meniscus tears, 245 (23%) patients with medial meniscus tears, and 93 (9%) patients with both medial and lateral tears. The average lateral and medial posterior tibial slopes were 5.5° (-4.2° to 13.4°) and 5.7° (0° to 15.7°), respectively. Increased lateral tibial slope was associated with a statistically significant increase in rate of any meniscal tear (adjusted odds ratio 1.10, 95% confidence interval 1.04-1.16, P < .001) and lateral meniscal tear, specifically (adjusted odds ratio 1.11, 95% confidence interval 1.04-1.18, P < .001). In regression analysis, male sex and body mass index ≥35 were found to increase the risk of all meniscal tear types. With a receiver operating characteristic curve analysis identifying lateral posterior tibial slope threshold values that resulted area under the curve ranges from 0.55 to 0.57, we were unable to identify an optimal threshold for posterior tibial slope in predicting meniscal tears.

CONCLUSIONS

In this single-institution, registry-based study, increasing lateral posterior tibial slope was associated with a greater rate of meniscus injury in acute ACL ruptures, whereas medial tibial slope demonstrated no correlation. No optimal threshold of posterior slope could be identified above which the odds of a meniscal tear were significantly elevated. Regression analysis identified BMI ≥35 and male sex as independent risk factors for meniscal tear in this select population.

LEVEL OF EVIDENCE

Level III, comparative retrospective case series.