We report our results in 24 children with malignant primary bone tumours of the distal femur treated with a Stanmore extendible endoprosthesis (SEER). This consists of a femoral component that can be lengthened, a constrained knee and an uncemented sliding tibial component which crosses the proximal tibial physeal plate perpendicularly.

The average age of the patients at diagnosis was ten years and the mean follow-up was 4.7 years (2.5 to 7.9). The mean growth of the affected tibia was 76% (18 to 136) and of the fibula 83% (15 to 750) of the growth of the unaffected limb.

Measurement of growth arrest lines showed that the mean growth of the proximal tibial physis on the affected side was 69% (43 to 100) of that of the normal side. The great variability in the growth of the physis cannot yet be explained.

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.

The use of endoprostheses for limb salvage in primary bone tumours is highly specialised. Studies have shown no significant difference in survival, function or quality of life between patients with limb salvage and those with amputation.

We have derived a formula for calculating the ongoing costs of limb salvage with an endoprosthesis which is based on actual costs and uses historical data to show the likelihood of further surgery or revision. Comparative data for amputation are also shown. Using current prices, the cost-effectiveness of surgery with an endoprosthesis is clearly demonstrated.

We reviewed the surgical treatment and oncological results of 40 patients with pathological fractures from localised osteosarcoma of the long bones to determine the outcome of limb salvage in their management. All had had adjuvant chemotherapy. There were 26 males and 14 females with a median age at diagnosis of 18 years (2 to 46) and a median follow-up of 55 months (8 to 175).

We performed limb salvage in 27 patients and amputation in 13. The margins of resection were radical in five patients, wide in 26, marginal in six, wide but contaminated in two and intralesional in one. Local recurrence developed in 19% of those treated by limb salvage and in none of those who had an amputation. The cumulative five-year survival of all the patients was 57% and in those treated by limb salvage or amputation it was 64% and 47%, respectively (p > 0.05).

Limb-sparing surgery with adequate margins of excision can be achieved in many patients with pathological fractures from primary osteosarcoma without compromising survival, but the risk of local recurrence is significant.

Improvement in the life expectancy of patients with primary bone tumours has led to increased emphasis on limb salvage and preservation of function.

Between 1979 and 1994 we used custom-made endoprostheses in 18 patients to reconstruct diaphyseal defects after excision of primary bone tumours. The mean age at operation was 26 years (9 to 64) and the median follow-up 65 months (6 to 188).

Fifteen patients have survived and are free from local or metastatic disease. Local recurrence developed in one patient. Using the modified Enneking functional scoring system, 77% of the patients achieved 80% or more of their premorbid functional capability. Mechanical loosening, limb shortening and secondary osteoarthritis were the main complications. There were no infections.

We conclude that diaphyseal endoprostheses offer a good clinical and functional outcome in the lower limb.

We 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.