A MODIFIED PERIACETABULAR OSTEOTOMY TO TREAT SPASTIC HIP DYSPLASIA

Abstract

Severe acetabular dysplasia with established dislocation of the hip represents a common problem in cerebral palsy. Once significant dysplasia is present little remodeling of the acetabulum occurs with femoral osteotomies alone. Pelvic osteotomies should address the problem of acetabular deficiency in order to restore optimal coverage of the femoral head. Standard innominate oste-otomies are not recommended for neuromuscular hip dysplasia. To address the lack of postero-lateral coverage in this population, a modified periacetabular osteotomy was performed.

Between 1991 and 2000 a total of forty-four patients (fifty-two hips) with total body involvement CP underwent this procedure at a mean age of nine, four yrs. The modification includes only one bicortical cut at the posterior corner at the sciatic notch. The cut extends down to the triradiate cartilage, if present, and through the former site of the triradiate cartilage after closure of the acetabular growth plate in adolescence. Additional procedures included: open reduction, femoral varus osteotomy, and soft tissue releases. Follow-up included a subjective and clinical evaluation. Radiographic assessment included measurements of the migration percentage and acetabular index, evidence of AVN, and premature closure of the triradiate cartilage.

The mean follow-up period for these patients was 3.5 years (1.0 to 8,1 yrs) after surgery, and 70% of the patients had reached skeletal maturity at that time. The median acetabular index improved from 30% pre-operatively to 18% at follow-up. The median migration percentage was 71% preoperatively, and zero at follow-up. A re-dislocation occurred in one hip, and a re-subluxation in another. All other hips were stable and well contained at follow-up. There were three hips showing signs of postoperative femoral head defects . Premature closure of the triradiate cartilage was not noted. The care-givers had the impression that the surgery had improved personal care, positioning/transferring, and comfort.

This osteotomy reduces the volume of the elongated acetabulum and provides coverage by articular cartilage. It provides coverage particularly at the posterior part of the acetabulum. Compared to other techniques this modified periacetabular osteotomy has only one posterior cortical cut which extends down to the sciatic notch. Since this cut is cortical, the fragment can be mobilized extensively and it allows placement of a graft and a better posterior coverage.