The current investigation includes a retrospective review of the experience of five Institutions with distal femur megaprostheses for tumor over a twenty year period, to analyze the incidence and etiology of failure, using a new classification system based upon the failure modes. Between 1974 and 2008, 2174 patients underwent primary limb preservation for a benign or malignant extremity tumor using a metallic megaprosthesis at five Institutions, 951 (43.7%) were distal femur replacements. Retrospective analysis of complications according to the Letson and Ruggieri Classification was performed and Kaplan-Meier curves of implant survival were defined. Segmental megaprosthetic reconstruction failures were categorized as mechanical and non-mechanical failures.Introduction
Methods
Purpose was to evaluate the incidence of complication in lower limb reconstructions with modular prostheses comparing cemented versus uncemented stems in two different orthopedic tumor Centers.
From 2002 and 2007, 238 modular prostheses of same design with a rotating hinge knee, were implanted in the lower limb as primary reconstruction in these two Centers. In 130 cases the prosthesis was implanted with cemented stems and in 108 cases with uncemented stems. Sites included: 120 distal femur, 61 proximal femur, 46 proximal tibia, 10 total femur and in 1 case both distal femur and proximal tibia. Histologic diagnoses included: 89 osteosarcoma, 13 Ewing sarcoma, 21 chondrosarcoma, 19 sarcoma, 55 metastasis, 17 TGC, 7 MFH, 11 other diagnoses and 6 non oncologic cases. Major prostheses-related complications were analysed and functional results according to Muscolo Skeletal Tumor Society system, at a mean follow up of 2.03 yrs. Also a statistical evaluation with Kaplan Meier curves, a comparative statistical analysis with Wilcoxon test and multivariate Cox regression analysis were performed.
Infections occurred at mean time of 1.3 yrs, sites included: 9 distal femurs, 4 proximal femurs, 5 proximal tibias, 2 total femurs. Aseptic loosening occurred at mean time of 2.3 yrs, sites included: 3 proximal tibias, 2 distal femurs, 2 proximal femurs. Rate of aseptic loosening was higher for cemented stems 5/130 (3.85%) vs uncemented 2/108 (1.85%). This difference is not statistically significant. Infection rate was 10% (13/130) for cemented stems and 6.5% (7/108) for uncemented stems. This difference is statistically significant at comparison of survival curves logrank test. Average MSTS function score was 83.5%. Multivariate Cox regression analysis showed that the significant factor favourable reluted with lower incidence of complications was the use of uncemented stems.
