ASEPTIC LOOSENING IN CEMENTED CUSTOM-MADE PROSTHETIC REPLACEMENTS FORBONE-TUMORS OF 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. Ase ptic loosening was shown to be the principal mode of failure of the im plants, and 71 patients had revision for aseptic loosening of a cement ed 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 p atient at the time of operation and the percentage of bone resected we re related to the risk of aseptic loosening. Young patients with dista l femoral prostheses in whom a high percentage of the femur had been r eplaced had the poorest prognosis for survival without aseptic looseni ng. The percentage of bone removed had a significant effect in the pro ximal tibial replacement group, but the age of the patient did not, By contrast, neither the age nor the percentage of bone removed was a fa ctor after proximal femoral replacement. The significance of these fin dings is discussed in relation to mechanical factors.