Spastic hemiplegic cerebral palsy and the femoral derotation osteotomy: effect at the pelvis and hip in the transverse plane during gait.

Gait analysis techniques were used to evaluate the outcome of the femoral derotation osteotomy in children with hemiplegic cerebral palsy. Seventy-one patients were evaluated and classified according to the Winters and Gage scale. Nine of the 13 patients classified as type IV underwent a femoral derotation osteotomy. Postoperatively, all nine patients demonstrated less internal hip rotation, pelvic retraction, and internal foot progression angle. Before surgery patients improve the foot progression by an externally biased hip position within the hip rotation arc. After surgery the hip position is allowed to be more centered within the rotation arc without compromising foot progression. Interestingly, the changed hip position during gait was significantly less than the magnitude of the derotation osteotomy. When contemplating postoperative outcome, consideration of hip position within the arc of rotation and pelvic retraction should be given to avoid undercorrection and residual pelvic compensation with femoral osteotomy based solely on foot progression.