Identifying Risk Factors from Preoperative MRI Measurements for Failure of Primary ACL Reconstruction: A Nested Case-Control Study with 5-Year Follow-up.

Background: Identifying patients at high risk for failure of primary anterior cruciate ligament reconstruction (ACLR) on the basis of preoperative magnetic resonance imaging (MRI) measurements has received considerable attention. In this study, we aimed to identify potential risk factors for primary ACLR failure from preoperative MRI measurements and to determine optimal cutoff values for clinical relevance.

Methods: Retrospective review and follow-up were conducted in this nested case-control study of patients who underwent primary single-bundle ACLR using hamstring tendon autograft at our institution from August 2016 to January 2018. The failed ACLR group included 72 patients with graft failure within 5 years after primary ACLR, while the control group included 144 propensity score-matched patients without failure during the 5-year follow-up period. Preoperative MRI measurements were compared between the 2 groups. Receiver operating characteristic (ROC) curve analyses were conducted to determine the optimal cutoff values for the significant risk factors. Odds ratios (ORs) were calculated, and survival analyses were performed to evaluate the clinical relevance of the determined thresholds.

Results: A greater lateral femoral condyle ratio (LFCR) (p = 0.0076), greater posterior tibial slope in the lateral compartment (LPTS) (p = 0.0002), and greater internal rotational tibial subluxation (IRTS) (p < 0.0001) were identified in the failed ACLR group compared with the control group. ROC analyses showed that the optimal cutoff values for IRTS and LPTS were 5.8 mm (area under the curve [AUC], 0.708; specificity, 89.6%; sensitivity, 41.7%) and 8.5° (AUC, 0.655; specificity, 71.5%; sensitivity, 62.5%), respectively. Patients who met the IRTS (OR, 6.14; hazard ratio [HR], 3.87) or LPTS threshold (OR, 4.19; HR, 3.07) demonstrated a higher risk of primary ACLR failure and were significantly more likely to experience ACLR failure in a shorter time period.

Conclusions: Preoperative MRI measurements of increased IRTS, LPTS, and LFCR were identified as risk factors for primary ACLR failure. The optimal cutoff value of 5.8 mm for IRTS and 8.5° for LPTS could be valuable in the perioperative management of primary ACLR.

Level Of Evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.