Increased lateral, but not medial, posterior tibial slope is associated with early graft failure following anterior cruciate ligament reconstruction.

BACKGROUND AND STUDY AIM: Excessive posterior tibial slope (PTS) has been identified as a biomechanical factor contributing to the risk of anterior cruciate ligament (ACL) injuries and graft failures. Notably, medial and lateral PTS (MPTS and LPTS) may have distinct influences on these outcomes. This study aims to investigate the impact of MPTS and LPTS on the likelihood of ACL graft failure. PATIENTS AND METHODS: This retrospective study included 43 patients who underwent revision ACL reconstruction between 2011 and 2018 due to graft failure within two years of primary surgery. These patients were matched with a control group of 43 individuals who underwent ACL reconstruction without graft failure. Medial and lateral posterior tibial slope (MPTS and LPTS) were measured using the Hudek method on magnetic resonance imaging (MRI) and compared between the two groups. Clinical evaluation included the preoperative Tegner activity score, pivot-shift test, Lachman test, and Lysholm score, as well as the postoperative pivot-shift test, Lachman test, and Lysholm score assessed at the two-year follow-up. RESULTS: The mean LPTS was significantly higher in the ACL revision reconstruction (RR) group compared to the primary reconstruction (PR) group (6.8 ± 3.6 vs. 3.2 ± 5.7, p < 0.05). However, no significant difference was observed in MPTS between the groups (3.0 ± 3.5 in the RR group vs. 2.4 ± 4.5 in the PR group, p = 0.56). Receiver operating characteristic (ROC) analysis determined an LPTS cut-off value of 6.0°. The Lachman test was positive in all patients preoperatively and became negative postoperatively in both groups. There was a significant improvement in pivot-shift grades from preoperative to postoperative evaluations in both groups. Both groups demonstrated significant improvement in Lysholm scores from preoperative to postoperative assessments, with no significant differences between the groups in either preoperative or postoperative scores. CONCLUSION: An increased LPTS (> 6.0°) is a significant risk factor for early ACL graft failure. Therefore, routine preoperative measurement of LPTS is recommended to identify patients at higher risk.