Proximal tibial derotation osteotomy for torsional tibial deformities generating patello-femoral disorders.

INTRODUCTION: Torsional abnormalities of the leg may cause instability and pain in the patellofemoral joint. Although derotation osteotomies seem logical to address these conditions, there are very few surgical results reported in the literature. HYPOTHESIS: Isolated tibial derotation osteotomies relieve patellofemoral pain and instability even in the event of combined femoral and tibial torsion abnormalities. AIM: Test this hypothesis in a retrospective and continuous series of thirty-six tibial derotation osteotomies and define the factors of success and failure. PATIENTS AND METHODS: Thirty-six derotation osteotomies of the proximal tibial metaphysis were performed between 1995 and 2006 in 29 patients (five men and 24 women, an average of 26.5 years old±7.4 (18-44)) followed-up for a mean 4.7 years. There was confirmed patellar instability in five knees, and patellofemoral pain without instability in 31. A proximal metaphyseal osteotomy was performed to correct excessive external tibial rotation as well as to recenter the tibial tubercle after anterior tibial cortex elevation. All patients were followed-up and the clinical data were analysed according to criteria from the Lille score [specifically designed for patellofemoral joints (100 point score)] and the IKS score. All patients had a preoperative radiological evaluation [(including measurement of torsion abnormalities in 32 cases by computed tomodensitometry (CT scan))]. The mean preoperative external tibial torsion measured on CT scan was 36.2°±9.48 (26-51°) and the mean femoral anteversion was 19.4°±9.5 (8-36°).
RESULTS: Twenty-seven patients (94%) were satisfied or very satisfied. The Lille score increased from 54.8±16.9 (30-92) preoperatively to 85.2±14.2 (36-100) at follow-up. The mean IKS knee scores and function increased from 56±14.8 (45-94) to 94±12.1 (60-100) and from 71±18.4 (30-100)-96±11.9 (50-100). Patellofemoral dislocations did not occur in any of the five cases with instability. Mean derotation was 25° measured with a mean tibial torsion measured clinically at follow-up 8.6°±7.2 (0-30). Two reoperations were necessary, (one knee manipulation under general anesthesia, and in another the fibular fibrous arch had to be released). One case of regressive palsy of the common fibular nerve was observed. Union of the osteotomy was obtained in all patients. DISCUSSION: This series is one of the largest series published to date. Isolated medialization of the anterior tibial tubercle only partially corrects these morphological abnormalities. In cases of associated excessive femoral anteversion we recommend surgery to the tibia alone because results were comparable in groups with and without excessive anteversion of the femoral neck. LEVEL OF EVIDENCE: level IV. Retrospective study.