[Derotational Intertrochanteric Osteotomy in Habitual Dislocation of the Patella]

PURPOSE OF THE STUDY The preoperative planning in habitual dislocation of the patella should take into account all pathologies and the procedure should address all abnormalities. One of them might be also the rotational deformity of the femur. The purpose of this prospective study was to confirm the hypothesis that the only correction of pathological femoral anteversion by derotational intertrochanteric osteotomy (in the absence of another pathology) or the correction of femoral anteversion with simultaneous reconstruction of the patellofemoral joint provide adequate stability for the patellofemoral joint, with respect to the elimination of the risk of recurrent dislocation of the patella. MATERIAL AND METHODS In the course of 15 years, 17 patients (20 knee joints) with habitual dislocation of the patella were included in the study, in whom the CT scan also confirmed the femoral anteversion of 35° and greater. The group was female-dominant, often with BMI > 30. The mean age was 26 years. In 4 cases only derotational intertrochanteric osteotomy was performed, in 16 patients the osteotomy was followed by the stabilization of the patella in the knee region (always individually in dependence on the diagnosed pathology), of whom in 2 cases as the second step procedure because of thrombophilic disorders detected earlier. Immediately after the surgery, or at 6 weeks postoperatively (depending on the knee procedure done), individual rehabilitation was commenced. Partial weight bearing was recommended for the period of 3 months after the surgery. The mean follow-up period was 39 months (minimum of 36 months). RESULTS In one case a failure of osteosynthesis was observed and revision osteosynthesis with an intramedullary nail was performed. In all the other cases, primary healing of the osteotomy was achieved. The other complications were less significant (1 case of asymptomatic deep vein thrombosis of the lower limb, evacuation of subcutaneous haematoma in 1 case, 3 cases of the knee stiffness solved by manipulation under general anaesthesia at 6 weeks after surgery). Recurrent patellar dislocation was not observed in any of the patients. No pain in the upper thigh was reported by patients during the last follow-up control (at least 3 years postoperatively). Three female patients reported an isolated feeling of patellar instability. DISCUSSION There are very few studies focusing on the femoral derotational osteotomy for habitual dislocation of the patella in world literature. If any at all, they concern supracondylar and not intertrochanteric femoral osteotomy and the groups of patients were smaller than the group evaluated by us. CONCLUSIONS Preoperative planning for habitual dislocation of the patella should definitely reflect all pathologies. Therefore, the femoral derotational osteotomy should certainly be mastered by the orthopaedic surgeon, though it is a larger and more exacting procedure than patellar stabilizations in the knee region. Indications for this type of osteotomy should include anteversion greater than 30°, or 35°. The derotational intertrochanteric osteotomy alone or its combination with the stabilization of the patella in the knee region brings reliable results with no risk of recurrent dislocation. Key words: patella, habitual dislocation, femur, anteversion, derotational osteotomy.