To evaluate the outcome of multilevel surgery including femoral derotational osteotomy, and analyze the effect of bilateral femoral derotational osteotomy on the gait of spastic diplegia.

The medical records of 26 spastic diplegics, who had undergone a bilateral intertrochanteric femoral derotational osteotomy, bilateral distal hamstring lengthening, bilateral rectus femoris transfer, and bilateral heel cord lengthening, were evaluated. There were 16 boys and 10 girls with a mean age of 7.6 years. The pre- and post-operative gait analysis, functional assessment score, and physical examination were archived and analyzed.

In the physical examination, the femoral anteversion, hip flexion contracture, and popliteal angle decreased significantly, while the ankle range of dorsiflexion increased significantly. In three dimensional gait analysis, the cadence remained constant while the walking speed improved significantly. In transverse plane kinematics, the mean pelvic rotation did not show any difference but foot progression angle fell into the normal range after surgery. In the sagittal plane, the maximal hip extension and H3 power generation improved significantly, while the mean anterior pelvic tilt decreased significantly. The functional assessment score improved from 7 to 9, which was significant.

The walking ability of spastic diplegia with in-toeing, stiff knee and tip toeing gait improved after single stage multilevel surgery including a femoral derotational osteotomy. Femoral derotation osteotomy without psoas lengthening improved the anterior pelvic tilt despite the distal hamstring lengthening