Poster 316: Increased tibiofemoral rotation angle is associated with graft failure after anterior cruciate ligament reconstruction

OBJECTIVES: Coronal and sagittal malalignment of the knee are well-recognized risk factors for failure after anterior cruciate ligament reconstruction (ACLR). However, the effect of axial malalignment on ACLR graft survival is yet to be determined. This study aimed to evaluate whether increased tibiofemoral rotational malalignment, namely tibiofemoral rotation angle (TFA) and tibial tubercle-trochlear groove (TT-TG) distance, is associated with ACLR graft failure. METHODS: In this matched-control study, 151 patients who underwent revision ACLR due to graft failure (failure ACLR group) were compared to a matched-control group of 151 patients who underwent primary ACLR with no evidence of failure after at least 2-years follow-up (intact ACLR group). Patients were matched by sex, age, and meniscal injury during primary ACLR. Axial malalignment was assessed on preoperative magnetic resonance imaging (MRI) through the TFA and the TT-TG distance. Sagittal alignment was measured through posterior tibial slope (PTS) on MRI. Optimal TFA cutoff associated with graft failure was identified by a receiver operating characteristic (ROC) curve. Kaplan-Meier curve with log-rank analysis was performed to evaluate the influence of TFA on ACLR longevity. RESULTS: In the failure ACLR group, mean TFA was 5.8 ± 4.5 (range, -5 to 16) degrees while this mean was 3.0 ± 3.3 (range, -3 to 15) degrees in the intact ACLR group (p<0.001). Neither TT-TG distance nor PTS presented statistical differences between the groups. ROC curve suggested an optimal TFA cutoff of 4.5 degrees for ACLR graft failure. Considering this as a threshold, patients who presented TFA ≥ 4.5 degrees had 6.6-times higher likelihood of graft failure compared to patients with TFA < 4.5 degrees (p<0.001). Survival analysis demonstrated a 5-years survival of 81% in patients with TFA < 4.5 degrees, while it was 44% when TFA ≥ 4.5 degrees (p<0.001). CONCLUSIONS: Increased TFA was associated with increased odds of ACLR failure when the TFA was ≥ 4.5 degrees. Measuring the TFA in patients with ACL tears undergoing reconstruction may inform the surgeon about additional factors that may require consideration prior to ACL reconstruction for a successful outcome.