Posterior tibial slope as a risk factor for anterior cruciate ligament tears: a retrospective study using automated measurement

Background:The association between anterior cruciate ligament (ACL) tears and posterior tibial slope (PTS) is well established; however, large-scale retrospective cohort studies in East Asian populations remain limited.Therefore, using a cohort from a tertiary hospital, this study aimed to investigate the difference in PTS between patients with ACL tears and matched controls.Methods: Patients aged 18 years were included in both the ACL tear and control groups, excluding those with histories of lower limb surgery, tibial fractures, amputations, or posterior cruciate ligament injuries.Propensity score matching (1:1) was performed based on age, sex, and body mass index.Using a validated, landmark-based algorithm, PTS measurements were automatically obtained from lateral knee radiographs.Results: After 1:1 propensity score matching, each group included 377 patients.The mean PTS was significantly higher in the ACL tear group (11.10 2.98) than in the control group (10.08 3.43) (P < 0.001).No significant differences were found in age (ACL tear, 35.96 13.79 years; control, 35.40 15.20 years, P = 0.60), body mass index (ACL tear, 25.28 3.88; control, 24.96 4.33, P = 0.29), or sex (ACL tear, 78.5% male; control: 78.8% male, P > 0.999).When a cutoff value of 9.42 was applied, the incidence of ACL tears was significantly higher in individuals with PTS 9.42 (55.3%) than in those with 9.42 (40.8%) (P < 0.001). Conclusion:This study shows that a greater PTS is significantly associated with ACL tears in an East Asian cohort, as patients with ACL injuries had an average PTS roughly 1 higher than that of matched controls.