Poster 261: Increased TT-TG and Tibial Slope are Independent Predictors of ACLR Failure

OBJECTIVES: Tibial tubercle-trochlear groove (TT-TG) distance is a surrogate measure of valgus and rotational stress on the anterior cruciate ligament (ACL) and may predict ACL injury. Increased posterior tibial slope has been associated with risk of ACL re-tear but no studies have evaluated TT-TG as a predictor of ACL re-tear. We hypothesized TT-TG distance and posterior tibial slope would be independent predictors of ACL graft re-tear. METHODS: All patients who underwent ACL revision surgery between 2010-2018 at a single institution were identified. A control cohort underwent primary ACL reconstruction (ACLR) between 2006-2015, with no evidence of graft failure at 8.1 ± 2.5 yrs post-op. Record review included anthropometrics, graft type, and estimated highest Tegner activity score at ≥ 6 months post primary ACLR. Magnetic resonance images (MRI) following native ACL tear (controls) or graft failure (revision cohort) were assessed for the following: 1) medial, lateral, and coronal tibial slope, 2) depth of tibial plateau concavity, 3) TT-TG distance, and 4) tunnel position. Logistic regression analyses were used to associate ACL graft failure with radiographic parameters, surgical variables, and demographics. Sensitivity analyses, excluding patients in the revision group with tunnel malposition, were performed to confirm multivariable results. RESULTS: Participants included 153 revisions and 146 controls. Controls were older than revisions (26.6 ± 8.8 yrs vs. 20.6 ± 7.3 yrs). Mean TT-TG distance and lateral tibial slope values were smaller for the control vs. revision group (TT-TG = 9.4 ± 3.9 mm vs. 11.2 ± 4.2 mm; lateral tibial slope = 6.2(o) ± 3.4° vs. 7.2(o) ± 3.6°). TT-TG distance and lateral tibial slope were associated with increased risk of ACL graft failure by multivariable analysis (OR: 1.14, CI: 1.07, 1.22, p < 0.001 and OR: 1.11, CI: 1.02, 1.20, p = 0.007, respectively). With sensitivity analyses, age at index surgery, TT-TG distance, and lateral tibial slope remained significant predictors of ACL revision. CONCLUSIONS: Increased TT-TG distance, increased lateral tibial slope, and younger age are associated with increased odds of ACL graft failure. These patients may require a more comprehensive strategy to reduce the risk of ACL re-tear.