Femoral Tunnel Malposition, Increased Lateral Tibial Slope, and Decreased Notch Width Index are Risk Factors for Non-Traumatic Anterior Cruciate Ligament Reconstruction Failure

To identify risk factors for patients who sustain non-traumatic ACLR failure. A retrospective analysis was performed on patients undergoing primary or revision ACLR in our institution between 2010 and 2018. Patients sustaining insidious-onset knee instability without history of trauma were identified as non-traumatic ACLR failure and assigned to the study group. Control group of subjects who showed no evidence of ACLR failure with minimum 48-month follow-up were matched in a 1:1 ratio based on age, sex, and body mass index. Anatomic parameters including tibial slope (LTS, MTS); tibial plateau subluxation (LTPsublx, MTPsublx); notch width index (NWI); and lateral femoral condyle ratio (LFCR) were measured on magnetic resonance imaging (MRI) or radiography. Graft tunnel position was assessed using 3D-CT and reported in four dimensions: deep-shallow ratio (DS ratio) and high-low ratio (HL ratio) for femoral tunnel, anterior-posterior ratio (AP ratio) and medial-lateral ratio (ML ratio) for tibial tunnel. Inter- and intra-observer reliability were evaluated by the intraclass correlation coefficient (ICC). Patients’ demographic data, surgical factors, anatomic parameters, and tunnel placements were compared between the groups. Multivariate logistic regression and receiver operating characteristic (ROC) curve analysis was used to discriminate and assess the identified risk factors. A total of 52 patients who sustained non-traumatic ACLR failure were included and matched with 52 control subjects. Compared to patients with intact ACLR, those who sustained non-traumatic ACLR failure showed significantly increased LTS, LTPsublx, MTS and deceased NWI (all P