Purpose: To evaluate the incidence of complications in distal femur reconstructions with modular prostheses, comparing fixed vs rotating hinge knee.
Methods: Retrospective analysis of implant survival, complications, and functional results of the Rizzoli series on distal femur megaprosthesis. Between 1983 and 2010, 687 distal femur tumour modular prostheses were implanted: 491 fixed hinge and 196 rotating hinge knee prostheses. Failures of the prostheses were classified in five types: type 1, soft tissue failure; type 2, aseptic loosening; type 3, structural failure; type 4, infection; type 5, tumour progression.
Results: Failure rate was 27 % (185/687). Implant survival to all types of failure was 70 % at ten years and 50 % at 20 years with no significant difference between fixed and rotating hinge knee prostheses (p = 0.0928). When excluding type 5 and type 1 failures, the overall survival was 78 % and 58 % at ten and 20 years. There was not a significant difference in implant survival to aseptic loosening (p = 0.5) and infection (p = 0.2) between fixed and rotating hinge knee prostheses. All cases of breakage of prosthetic components occurred in fixed hinge knee prostheses. Functional results, evaluated in 536 pts, were satisfactory in 91.4 % of cases with a mean score of 23.3 with a significantly better function for rotating hinge knee prostheses (p < 0.001).
Conclusions: The most frequent cause of failure was infection followed by aseptic loosening. Even if better results were expected for rotating hinge knee prostheses, there is no significant difference in overall implant survival. No cases of breakage of prosthetic components occurred in rotating hinge knee prosthesis. Functional results were significantly better for the rotating hinge knee prostheses.
Level of evidence: Therapeutic study, level IV (case series).
Keywords: Distal femur tumour prostheses; Fixed hinge knee prostheses; Modular tumour prostheses; Rotating hinge knee prostheses.