Effect of Sagittal TTTG on Graft Failure After Anterior Cruciate Ligament Reconstruction

Background: Anterior cruciate ligament reconstruction (ACLR) is a common orthopedic procedure with generally favorable outcomes, yet graft failure remains a significant challenge, particularly in young and active patients. While various anatomical and biomechanical risk factors for graft failure have been proposed, the influence of the sagittal tibial tubercle–trochlear groove (sTTTG) distance, representing anterior–posterior alignment of the tibial tubercle, has not been sufficiently explored. This study aimed to evaluate the association between sTTTG and ACL graft failure and assess contributing biomechanical variables, including tibiofemoral rotation (TFR), posterior tibial slope (PTS), and knee flexion angle. Methods: For this secondary analysis, a retrospective matched case–control study was conducted, involving 151 patients with ACL graft failure who underwent revision ACLR and 151 controls with intact grafts after a minimum 2-year follow-up period. sTTTG was measured on axial MRI as the anteroposterior distance from the trochlear groove to the tibial tubercle, perpendicular to the posterior femoral condylar axis. Secondary measurements included TT-TG, TFR, medial and lateral PTS, and knee flexion angle. Group differences as well as factors predictive of sTTTG were analyzed. Results: The ACLR failure group demonstrated a significantly lower sTTTG distance compared to controls (0.5 ± 4.6 mm vs. 2.4 ± 4.8 mm, p = 0.001). Logistic regression analysis revealed that a 1 mm increase in sTTTG was associated with an 8% reduction in revision risk (OR = 0.93 per 1 mm increase; 95% CI, 0.88–0.97; p = 0.003), although the predictive accuracy was low (AUC = 0.6). Multivariable analysis identified lateral PTS and knee flexion as significant independent predictors of sTTTG. Conclusions: A decreased sTTTG distance was significantly associated with ACL graft failure, underscoring the relevance of sagittal tibial tubercle positioning in ACL biomechanics. While not an independent clinical decision-making tool, sTTTG appears relevant to graft failure and may be considered in future risk assessment strategies.