W e have made a retrospective study of 1001 custom-made prostheses used as replacements after surgery for bone tumours. There were 493 distal femoral, 263 proximal femoral and 245 proximal tibial prostheses. Aseptic loosening was shown to be the principal mode of failure of the implants, and 71 patients had revision for aseptic loosening of a cemented intramedullary stem.The probability of a patient surviving aseptic loosening for 120 months was 93.8% for a proximal femoral replacement, 67.4% for a distal femoral prosthesis and 58% for a proximal tibial implant. In patients with distal femoral replacements the age of the patient at the time of operation and the percentage of bone resected were related to the risk of aseptic loosening. Young patients with distal femoral prostheses in whom a high percentage of the femur had been replaced had the poorest prognosis for survival without aseptic loosening. The percentage of bone removed had a significant effect in the proximal tibial replacement group, but the age of the patient did not. By contrast, neither the age nor the percentage of bone removed was a factor after proximal femoral replacement.The significance of these findings is discussed in relation to mechanical factors.

A brief intensive chemotherapy regimen of DOX/CDDP has produced excellent long-term results, which are similar to those that have been achieved in cooperative group studies of longer, more complex multiagent chemotherapy, and provide the basis for a direct comparison in the next EOI study.

W e have performed endoprosthetic replacement after resection of tumours of the proximal tibia on 151 patients over a period of 20 years. During this period limb-salvage surgery was achieved in 88% of patients with tumours of the proximal tibia. Both the implant and the operative technique have been gradually modified in order to reduce complications. An initial rate of infection of 36% has been reduced to 12% by the use of a flap of the medial gastrocnemius, to which the divided patellar tendon is attached. Loosening and breakage of the implant have been further causes of failure. We found that the probability of further surgical procedures being required was 70% at ten years and the risk of amputation, 25%. The development of a new rotating hinge endoprosthesis may lower the incidence of mechanical problems.Limb salvage for tumours of the proximal tibia is fraught with complications, but the good functional outcome in successful cases justifies its continued use. J Bone Joint Surg [Br] 1999;81-B:488-94. Received 24 June 1998; Accepted after revision 13 October 1998 The proximal tibia is the second most common site for primary bone tumours. Some 12% to 15% of osteosarcomas, 11% of Ewing's sarcomas and 6% of chondrosarcomas will be located here.

We treated 35 patients with primary malignant tumours of the periacetabular area by resection and prosthetic reconstruction of the defect. At a mean follow-up of 84 months, 15 patients (43%) were free from disease. The most common complications were deep infection (26%), local recurrence (24%) and recurrent dislocation of the hip (17%). The surviving patients achieved an average of 70% of their premorbid function. This method of reconstruction has a high morbidity and should be performed only at specialist centres, but the functional and oncological outcomes are satisfactory.