Association of Tibial Slope Morphology and Lateral-Medial Tibial Slope Asymmetry With Revision ACL Reconstruction in an Asian Cohort.

Abstract

Background: Graft failure after anterior cruciate ligament (ACL) reconstruction remains a significant clinical challenge, particularly in revision surgery. Increasing biomechanical and clinical evidence suggests that tibial slope morphology influences anterior tibial translation and ACL graft forces, potentially increasing failure risk. While posterior tibial slope has been implicated in graft failure, the relative contributions of medial tibial slope (MTS), lateral tibial slope (LTS), and slope asymmetry remain incompletely defined.

Purpose: To evaluate the association between tibial slope parameters and the risk of ACL reconstruction failure.

Study design: Cohort study; Level of evidence, 3.

Methods: A retrospective cohort study was conducted at a tertiary academic center in Singapore, including 204 patients who underwent primary (n = 120) or revision (n = 84) ACL reconstruction between 2009 and 2022. Preoperative magnetic resonance imaging (MRI) was used to measure MTS, LTS, and LTS-MTS asymmetry using standardized anatomic landmarks. Demographic, clinical, and intraoperative variables were collected, along with patient-reported outcome measures (PROMs), including the Lysholm Knee Score and Knee injury and Osteoarthritis Outcome Score. Receiver operating characteristic (ROC) curve analysis was performed to determine predictive performance and optimal cutoff values for tibial slope parameters. Multivariable regression analysis was used to identify variables independently associated with revision ACL reconstruction.

Results: Patients undergoing revision ACL reconstruction demonstrated significantly greater mean LTS (9.73°± 3.49° vs 7.91°± 3.12°; P < .01) and LTS-MTS asymmetry (1.68°± 3.99° vs 0.20°± 4.01°; P = .01) compared with patients undergoing primary reconstruction. No significant difference in MTS was observed between groups (P = .43). ROC analysis showed that LTS (area under the curve [AUC] 0.65; cutoff ≥7.65°) and LTS-MTS asymmetry (AUC 0.61; cutoff ≥1.85°) were significantly associated with the revision ACL reconstruction cohort, whereas MTS was not. Multivariable analysis identified LTS ≥7.65°, LTS-MTS asymmetry ≥1.85°, and concomitant meniscal tears as independently associated with the revision cohort. Higher tibial slope values were associated with lower PROM scores, although these differences were not clinically meaningful.

Conclusion: This study underscores the importance of evaluating LTS and LTS-MTS asymmetry on MRI in relation to revision ACL reconstruction status. LTS ≥7.65°, LTS-MTS asymmetry ≥1.85°, and concomitant meniscal tears were significantly associated with belonging to the revision group, highlighting the need for careful assessment of tibial morphology and consideration of these parameters during preoperative planning.