Anatomical Components Associated With Increased Tibial Tuberosity–Trochlear Groove Distance

BACKGROUND: Increased tibial tuberosity–trochlear groove (TT-TG) distance is an important indicator of medial tibial tubercle transfer in the surgical management of lateral patellar dislocation (LPD). Changes to TT-TG distance are determined by a combination of several anatomical factors. PURPOSE: To (1) determine the anatomical components related to increased TT-TG distance and (2) quantify the contribution of each to identify the most prominent component. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: Included were 80 patients with recurrent LPD and 80 age- and body mass index–matched controls. The 2 groups were compared in TT-TG distance and its related anatomical components: tibial tubercle lateralization (TTL), trochlear groove medialization, femoral anteversion, tibiofemoral rotation (TFR), tibial torsion, and mechanical axis deviation (MAD). The Pearson correlation coefficient (r) was calculated to evaluate the association between increased TT-TG distance and its anatomical parameters, and factors that met the inclusion criteria of P < .05 and r ≥ 0.30 were analyzed via stepwise multivariable linear regression analysis to predict TT-TG distance. RESULTS: The LPD and control groups differed significantly in TT-TG distance, TTL, TFR, and MAD (P < .001 for all). Increased TT-TG distance was significantly positively correlated with TTL (r = 0.376; P < .001), femoral anteversion (r = 0.166; P = .036), TFR (r = 0.574; P < .001), and MAD (r = 0.415; P < .001), and it was signficantly negatively correlated with trochlear groove medialization (r = −0.178; P = .024). The stepwise multivariable analysis revealed that higher TTL, excessive knee external rotation, and excessive knee valgus were statistically significant predictors of greater TT-TG distance (P < .001 for all). The standardized estimates that were used for evaluating the predictive values were larger for TFR compared with those for TTL and MAD. CONCLUSION: TTL, TFR, and MAD were the main independent anatomical components associated with increased TT-TG distance, with the most prominent component being TFR. The association of TT-TG distance to each component analyzed in our study may help guide surgical planning.