Factors Affecting Tibial Tuberosity-Trochlear Groove Distance in Recurrent Patellar Dislocation.

Background The tibial tuberosity-trochlear groove (TT-TG) distance is used to determine the necessity of tibial tubercle osteotomy. We conducted this study to determine the extent to which each of the tibial tuberosity lateralization, trochlear groove medialization, and knee rotation angle affects the TT-TG distance in both normal and patella dislocated patients and thereby scrutinize the rationale for tuberosity transfer based on the TT-TG distance. Methods: Retrospective analysis of rotational profile computed tomography was done for patella dislocated and control group patients. Femoral anteversion, tibial torsion, knee rotation angle, tuberosity lateralization, and trochlear groove medialization were assessed in all patients. Relationship of these parameters with the TT-TG distance was investigated to evaluate their effects on the TT-TG distance. Results: We observed that the patellar dislocation group, compared to the control group, had increased TT-TG distance (mean, 19.05 mm vs. 9.02 mm) and greater tuberosity lateralization (mean, 64.1% vs. 60.7%) and tibial external rotation in relation to the femur (mean, 7.9 degrees vs. -0.81 degrees). Conclusions: Tuberosity lateralization and knee rotation were factors affecting patellar dislocation. These factors should be considered in addition to the TT-TG distance to determine the need for tibial tubercle osteotomy in patients with patellar dislocation.