RESUMEN
PURPOSE: High tibial osteotomy with internal tibial derotation (high tibial derotation osteotomy = HTDRO) is a common surgical treatment in patients with patellofemoral malalignment alone or in combination with patellofemoral instability. Operative techniques and theoretical calculations may assume that correction of the tibial tubercle-trochlear groove (TTTG) distance is related to the amount of torsional correction. The purpose of this investigation was to predict the change in TTTG distance in HTDRO through a clinical study. METHODS: Twenty-one consecutive cases of derotational HTO were evaluated by torsional CT scanning in terms of the pre- and postoperative tibial torsion and TTTG distance. Changes in the TTTG distance were related to the changes in the amount of torsional correction. The change in patellar height was measured pre- and postoperatively, and the Caton-Deschamps Index (CDI) was calculated. RESULTS: The mean change in tibial torsion was 13.9°, and the mean change in the TTTG distance was 6.3 mm. A strong relationship (0.90) between the change in torsion and the change in TTTG distance from pre- to postoperative status was found (p < 0.001). No statistically significant change in CDI could be seen between the preoperative [mean value (MV) 1.0] and postoperative (MV 1.1) periods. CONCLUSIONS: In patients with patellofemoral instability or patellofemoral maltracking with both a high tibial external torsion and a high TTTG distance, a derotational HTO can correct both bony deformities. Patella height does not change significantly with this surgical technique. With 1° of torsional correction, the TTTG distance decreases 0.45 mm with our surgical technique of derotational HTO.