In this study we highlight the advantages supported by long term results of using our external fixator system for femoral derotation osteotomy as part of our management regime for developmental dysplasia of the hip. Out of all the children in the East Kent area who present with a dislocated hip each year about 4 require a femoral derotation osteotomy in order to maintain a good position after either open or closed reduction.

The system has been used since 1981. 51 patients (56 hips) were reviewed with a follow up between 5 and 18 years with a mean of 11 years. The age at diagnosis ranged from shortly after birth to 42 months with a mean of 12 months. The treatment involved a protocol in which traction was applied for 4 weeks preoperatively if the hip was high and open or closed reduction was selected according to the result of an arthrogram. 33 of the 51 patients received traction and 23 patients (25 hips) had an open reduction. Following reduction the hips were immobilized in a spica for 6 weeks after which the femoral osteotomy using the fixator was performed. A second 6 week period of spica immobilization followed after which the fixator and spica were removed. We had 16 complications including 3 patients who developed AVN of the femoral head. 8 patients required an additional 16 operations.

We assessed the patients clinically and radiologically using the Severin’s grading system. At final follow up over 85% of patients were assessed to have a clinical grade of 1 and 2 and over 70% a radiological grade of 1 and 2.

Our technique of external fixation has several advantages over conventional methods of fixation of the femur: a) the avoidance of a 2nd open procedure to remove the implant, b) the accuracy of the femoral derotation using the goniometer and c) the achievement of femoral fixation without the need for image intensifier screening.