The Impact of Differential Posterior Tibial Slope on Clinical Outcomes Following Revision ACL Surgery: A Retrospective Single-Centre Study

Background: Recent evidence has suggested that patients undergoing anterior cruciate ligament (ACL) revision surgery tend to have a larger differential posterior tibial slope compared to healthy individuals. The impact of differential slope on patient reported clinical outcomes following revision ACL surgery remains unclear. Methods: Patients undergoing revision ACL surgery between 2019 and 2024 in our institution were eligible for inclusion. The primary outcome was the change in subscales of the Knee injury and Osteoarthritis Outcome Score (KOOS) from preoperative to at least 1 year postoperative. Medial and lateral posterior tibial slopes were measured independently by four assessors on preoperative magnetic resonance imaging (MRI) scans. The correlation between change in KOOS and the mean differential posterior tibial slope (dPTS) was calculated by using Pearson’s correlation statistic. Results: Data from 31 revision ACL cases were analysed. There were statistically significant postoperative improvements in all five KOOS domains (Symptoms p = 0.036, Pain p = 0.004, Daily Living p = 0.002, Sport and Recreation p < 0.001, Quality of Life p < 0.001). There was a statistically significant correlation between mean differential slope and change in KOOS Symptoms (p = 0.007), Pain (p < 0.001), Sport and Recreation (p = 0.034), and Quality of Life (p = 0.010), but not with Daily Living (p = 0.070). Conclusions: In patients undergoing ACL revision reconstruction, greater differential posterior tibial slope is associated with poorer patient-reported outcomes. MRI-based assessment of dPTS demonstrated moderate single-rater and good average-rater interobserver reliability, potentially aiding in preoperative risk stratification and patient management.