The association between passive anterior tibial subluxation and anterior cruciate ligament reconstruction failure.

PURPOSE: Increased passive anterior tibial subluxation (PATS) has been observed in patients with failed anterior cruciate ligament (ACL) reconstruction (ACLR). However, whether primary PATS is associated with future risk of graft failure and how PATS evolves over time remain unclear. This study aims to determine whether PATS measured at the time of the primary ACL injury is associated with graft failure and to characterize the longitudinal changes in PATS among patients with and without graft failure. METHODS: A retrospective review was conducted on patients who underwent primary ACLR between January 2019 and December 2023. A total of 131 patients with graft failure were propensity score-matched to 131 controls with intact grafts at a minimum 48-month follow-up (age, 28.9 ± 7.7 years; 61 females [23.3%]). Primary magnetic resonance imaging (MRI) evaluation was performed for all patients before primary ACLR. Secondary MRI evaluation was performed before revision surgery for the failure group (median [interquartile range {IQR}], 31.0 [19.1-58.0] months) and at 24 months post-operatively for the control group (median [IQR], 24.9 [23.9-27.4] months). Multivariable logistic regression and receiver operating characteristic curve analysis were performed to evaluate factors associated with graft failure. Multivariable linear regressions were performed to identify factors associated with longitudinal changes in PATS between the primary and secondary MRI evaluations. Statistical analyses were performed using R software. RESULTS: Significantly higher lateral (L-PATS) and medial (M-PATS) PATS at both the primary and secondary MRI evaluations were observed in the failed ACLR group compared with the control group (all p < 0.05). Patients with graft failure demonstrated significant longitudinal progression of PATS compared to those with intact grafts (p < 0.05). Primary L-PATS (odds ratio [OR], 1.166; p < 0.001) and lateral tibial slope (LTS) (OR, 1.193; p < 0.001) were identified as factors independently associated with graft failure, demonstrating moderate discriminative ability (area under the curve [AUC], 0.682 and 0.668). Graft failure, female sex and medial meniscus injury were independently associated with longitudinal increases in PATS (all p < 0.05). CONCLUSIONS: Increased L-PATS measured at the time of the primary ACL injury was associated with an increased risk of graft failure. Patients who experienced graft failure demonstrated significant longitudinal increases in both L-PATS and M-PATS compared to those with intact ACLR. LEVEL OF EVIDENCE: Level III.