Femoral derotation osteotomy for recurrent patellar dislocation.

Purpose: Excessive femoral internal torsion is an important risk factor for patellar dislocation. The aim of the present study was to estimate the effect of derotational osteotomy of the femur on the tibial tubercle trochlear groove (TTTG) distance or patellar tilt angle (PTA) and to report our clinical outcomes of recurrent patellar dislocation after femoral derotation osteotomy.

Methods: A retrospective analysis of 16 patients (17 knees) with recurrent patellar dislocation treated by femoral derotation osteotomy in our department from January 2016 to February 2019 was carried out. The procedure was performed with supracondylar femoral derotation. A few procedures were combined with soft tissue procedures. Knee function was evaluated by using the International Knee Documentation Committee (IKDC) score, Kujala score, Lysholm score, visual analog scale (VAS) score and patient satisfaction. Additionally, CT was used to assess the influence of femoral derotational osteotomy on TTTG distance and PTA.

Results: The average femoral antetorsion angle before surgery was 33° (SD ± 5°), and the intraoperative correction angle was 23° (SD ± 4°). A total of 17 femoral derotation osteotomies in 16 patients with patellar instability [11 females, 5 males, aged 20.8 (range 15-41) years] were included in the study. No dislocation occurred within 26.5 months after follow-up (range 12-49 months). The IKDC score, Kujala score, Lysholm score and VAS score significantly improved. The preoperative TTTG distance was 15.63 mm (SD ± 2.07 mm), and it was 14.69 mm (SD ± 1.78 mm) at the follow-up. The PTA decreased from 26.35° (SD ± 6.86°) to 11.65° (SD ± 2.85°). The powers of TTTG and PTA measurements are 0.78 and 1.00, respectively and all of these differences were statistically significant.

Conclusions: Derotational osteotomy of the femur for the treatment of recurrent patellar dislocation can achieve good clinical results, including improved TTTG distance and PTA and improved knee function.