A Simple Method of Planning and Performing a Proximal Femoral Varus-Shortening-Derotation Osteotomy for Hip Dislocation in Cerebral Palsy Using a Blade-Plate

Femoral varus, derotation and shortening osteotomy is part of the surgical treatment of hip subluxation and dislocation in children with cerebral palsy. In such cases, a post-operative neck-shaft angle of 110–120° is desirable as well as 0–15° anteversion. Standard techniques of planning a femoral osteotomy require accurate knowledge of proximal femoral deformity, but in cerebral palsy this may be difficult to measure owing to excessive anteversion and difficulties with positioning for radiographs. We have developed and used a method that does not rely on preoperative radiographic measurements or the use of the femoral diaphysis for reference. Our method is focused on achieving the desired postoperative neck-shaft and anteversion angles mentioned above. The centre of the femoral neck is used as a reference and the chisel for a blade plate is applied 20–30° varus to this neutral axis. Osteotomy cuts are then made parallel to the chisel and perpendicular to the femoral shaft. The chisel is replaced with a 90° blade plate and the osteotomy is reduced, derotated and fixed to the femoral shaft. The final neck-shaft angle is therefore 90° plus 20–30°, ie the desirable 110–120°. This position is achieved without knowledge of the angle of the wedge of bone removed by the osteotomy. This technique has been performed in 16 hips in 10 patients with cerebral palsy during one year. The final neck shaft angle fell within the desired range in 12 hips (75%). We have found this technique to be a simple and reliable means of achieving correction in patients in whom accurate preoperative estimate of the femoral neck shaft angle is not possible.