Purpose: Use of massive knee prostheses in the treatment of malignant tumours allows excellent short-term oncological and functional results. The purpose of our work was to demonstrate that these good early results later require several revisions.
Material and methods: From 1981 to 1986, 48 patients, mean age 13.8 years (9–19) were treated for osteosar-coma of the knee by chemotherapy and resection. Six patients had metastases at the time of diagnosis. Resection involved the distal femur in 34 cases, the proximal tibia in 13 and both extremities in one case. Mean resection was 20 cm (12–29). Reconstruction was achieved with a cemented GUEPAR. Twenty of the initially implanted prostheses had a rotatory mechanism. Reconstruction of the diaphyseal segment was generally achieved with massive metal or polyethylene prostheses and in three cases with a prostheses sleeved on an allograft. After resection of the proximal tibia, reconstruction of the extensor system was achieved with the vastus medialus.
Results: Results were assessed retrospectively at a mean follow-up of eleven years (4 months – 20 years). Seven patients were lost to follow-up. At last follow-up of available patients, 34 were in remission, 14 had died, giving an actuarial survival rate at 15 years of 72%. For the 48 prostheses initially implanted, seven were revised for loosening, four became infected (two secondarily), four femoral stems fractured and two rotatory mechanisms fractured. All the prostheses followed more than three years required at least one surgical revision. Only eight of the initially implanted prostheses are still in situ after 15 years, giving an actuarial survival probability of 39±17%. Certain prostheses were changed four times. If all revisions are included, the 32 surviving patients have had 84 prostheses. Most of the recent revisions were indicated for hinge wear and to avoid changing the inserts within too short an interval. At last follow-up, one patient has undergone amputation, one has a rota-tionplasty, and one has an arthrodesis, all for infection. The functional results at last follow-up are good or excellent in 19 cases, fair in five, poor in three and could not be evaluated in 21 (14 deaths and seven lost to follow-up).
Discussion: Reconstructions using massive prostheses are associated with a high rate of mechanical complications making surgical revision inevitable. These complications are mainly due to wear of the hinge itself. The use of better designed prostheses in terms of mechanical properties should reduce the rate of mechanical complications. When the tumour extension spares the epiphysis, use of biological, non-prosthetic reconstruction methods should be preferred.
