4.O.02 LONG TERM RESULTS IN KNEE RECONSTRUCTIONS WITH MODULAR UNCEMENTED PROSTHESES FIXED HINGE AFTER RESECTION OF BONE TUMORS: A COMPARISON OF TWO CONSECUTIVE DESIGNS OF THE SAME SYSTEM

Abstract

Between 1983 and 2006 at Rizzoli 669 knee modular uncemented prostheses were implanted after resection of the distal femur, total femur or proximal tibia. These prostheses include 126 KMFTR prostheses and 543 second generation HMRS prostheses. Patients were followed periodically in the clinic. Data was obtained from clinical charts and imaging studies with special attention to major complications requiring revision surgery. Revision for polyethylene wear was considered a minor complication, since it did not imply failure of the implant. Functional results were assessed according to the MSTS system. Since data could be misleading due to deaths in an oncologic population (although 2/3 of patients were cured or long survivors), to censore the implant unrelated events Kaplan-Meyer curves of implant survival were studied.

In 126 KMFTR group infection rated 13.5%, stem breakage 13%, aseptic loosening 9.5%; change of polyethylene rated 44%. In 543 HMRS prostheses infection rated 8.6%, stem breakage 3%, aseptic loosening 4.8%; revision for polyethylene wear rated 9.6%. Techniques of revisions and their outcome analysed showed about 2/3 of good results, but increased risk of further complications in revised implants. Functional results (MSTS system) were good or excellent in 80% of KMFTR prostheses and in 90% of HMRS.

Decrease of major complications in newer prosthetic design was statistically significant and possibly due to newer materials and modified stem design. Polyethylene wear also decreased significantly. Function was satisfactory in most patients without complications for both groups. Revision surgery is technically demanding and appropriate timing of revision is crucial, since early treatment can improve final outcome.