Increased posterior tibial slope is associated with failure after anterior cruciate ligament primary repair.

Abstract

To determine whether preoperative posterior tibial slope (PTS) and intercondylar notch morphology are associated with arthroscopic anterior cruciate ligament primary repair (ACLPR) failure 2-5 years postoperatively, and to explore the association of the difference between medial and lateral PTS (MPTS and LPTS), and magnetic resonance imaging (MRI) versus radiograph slope agreement. This retrospective secondary analysis included a prospectively collected, single-surgeon cohort of patients aged ≥18 years who underwent ACLPR for selected proximal anterior cruciate ligament (ACL) tears between 2008 and 2021 with 2-5 years of follow-up. MPTS, LPTS and anterior/posterior notch width (aNW and pNW) were quantified on preoperative MRI; PTS was additionally measured in a radiograph subset. Failure was defined as objective knee laxity (side-to-side difference ≥ 3 mm, Lachman ≥ 2 or pivot-shift ≥ 2) and/or patient-reported symptomatic instability, including telemedicine follow-up. Associations with failure were assessed using univariable and multivariable logistic regression and exploratory analyses included receiver operating characteristic/area under the curve and time-to-failure analyses. Among 249 patients (51.4% female; mean age 39.4 ± 10.8 years) with median follow-up of 3.2 years (interquartile range 2.4-5.0), 24 (9.6%) met failure definition. After adjustment for age and suture augmentation, increased PTS was associated with failure per 1° increase (MPTS: odds ratio [OR] 1.62; 95% confidence interval [CI] 1.35-1.96; LPTS: OR 1.35; 95% CI 1.17-1.55; both p < 0.001), while older age was associated with lower odds of failure. In exploratory analysis, directed ΔPTS (MPTS-LPTS) was associated with failure (adjusted OR 1.27; 95% CI 1.07-1.51; p = 0.008). Intercondylar notch width was not associated with failure. MRI and radiographic-based slope measurements correlated (MPTS r = 0.706; LPTS r = 0.590; both p < 0.001). In this selected cohort of patients undergoing arthroscopic ACLPR, greater MPTS and LPTS and younger age were associated with higher odds of failure at 2-5 years, while notch width was not. These findings suggest that PTS may help contextualise risk when counselling patients considered for ACLPR. Level IV, case series.