Background

Advances in diagnosis and treatment should mean that hindquarter amputation is now rarely needed. Unfortunately this is not the case. We have performed 166 of these amputations in the past 36 years. We have investigated the reasons why this procedure is still required and the outcomes following it.

Purpose

To identify the incidence and reasons for revision of the Oxford prosthesis (OXF) in New Zealand.

Since 1970, 2200 primary endoprosthetic replacements have been carried out at our Unit for bone tumours. 3% were carried out in the 1970s, 21% in the 1980s, 33% in the 1990s and 43% since 2000.

The most common diagnosis was osteosarcoma (839)(38%) followed by metastatic disease (18%) and chondrosarcoma (13%). The most common site was the distal femur (35%) followed by the proximal femur and proximal tibia. The least common sites were the scapula and distal radius. The mean age at operation was 35 but varied widely, being 19 in patients with osteosarcoma and 58 for those with metastases. 239 extendable prostheses were inserted in children. 50% of the patients were alive at 10yrs and 42% at 20yrs. 7% required an amputation either for local recurrence or infection.

The failure rate of the prostheses varied by age and site, with pelvic and proximal tibial replacements having the highest risk of infection and proximal humeral replacements the lowest risk of any complication. The failure rates of the most common prostheses (distal femur and proximal tibia) have improved over time and are now ~ 1.5% per year. Hydroxyapatite collars have largely resolved the problem of aseptic loosening. Silver coated prostheses have been used in 48 complex cases with encouraging results in controlling infection. Functional scores averaged 80% and were the same for revision as for primary implants.