Summary
Medial bony and meniscal slopes are higher in patients with unexplained failed ACLR, but synthetic ligaments and ACLR with technical errors failed with slopes similar to successful ACLR
Abstract
Purpose
Increased tibial slope is a known risk factor for non-contact anterior cruciate ligament (ACL) injuries. It is suggested that the meniscus may influence the antero-posterior stability of the knee joint by reducing postero-inferior slope. The primary objective of this study was to compare the tibial soft tissue and bony slopes in patients with failed and non-failed ACL reconstructions (ACLR). Our hypothesis was that patients with failed ACLR would have higher slopes than successful ACLR, and that unexplained failures would have higher slopes than failures with clear technical errors and failed synthetic ligaments.
Methods
Between 2015 and 2022, 130 patients with failed ACLR were retrospectively identified; 79 knees with adequate MRI scans were included for analysis. These were compared to 57 patients with successful ACLR. MRI measurements included lateral and medial tibial bony slope (LBS, MBS) and lateral and medial meniscal slope (LMS, MMS). Subgroup analysis was performed for failures with technical errors and for failed synthetic ligaments.
Results
In all patients, the LMS and MMS reduced the bony slope toward the horizontal without reaching statistical significance. Those with failed ACLR had significantly higher MBS (6.63°±2.96 vs. 4.61°±2.45, p<0.001) and MMS (5.17°±3.5 vs. 3.42°±2.76, p=.002). The Youden optimal threshold value of MBS =5.07° (sensitivity 80%, specificity 56.1%) yielded an odd’s ratio (OR) for failure of 5.12 (CI: 2.25-11.62; p<0.001). Revisions with technical errors and synthetic grafts had slopes that were not significantly different to successful ACLR.
Conclusion
Medial bony and meniscal slopes are higher in patients with unexplained failed ACLR, but ACLR with technical errors failed with slopes similar to successful ACLR. Increased medial slope values are a risk factor for surgical failure.