Purpose of the study: The rate of failure can be high for massive reconstruction prostheses after tumor resection. We studied the causes and possible factors of failure.
Material and methods: The series included 91 patients who underwent surgery from 1972 to 1994 for resection of a bone tumor involving the knee joint. A GUEPAR prosthesis was implanted in all cases for reconstruction (megaprosthesis in 58 cases and composite prosthesis in 33). The extensor system had to be reconstructed in 37 patients. A GUEPAR II implant was used in 73 patients; 48 of these implants had an antirotation system. The analysis was retrospective. Outcome was studied in terms of survival and independent factors predictive of failure unrelated to the tumor.
Results: Mean follow-up was 72 months. At last follow-up, 68 patients were living disease free. There were nine cases of rupture of the extensor system. Preservation of a continuous extensor system at the time of bone resection reduced the risk of rupture (p=0.036). Seven allografts fractured, two loosened, and six became infected. Use of an allograft did not reduce the risk of loosening (p=0.17). Intraxial laxity was observed in 17 patients. Use of an antirotation system was a factor of risk of intraxial laxity (p=0.0023) but not of aseptic loosening. Aseptic loosening was observed in 18 patients: 10 femur reconstruction and 8 tibia reconstruction. The difference was not significant (p=0.6). In all, 104 revisions were required in 53 patients; 36 revisions of the prosthesis, 23 of them for mechanical causes. Overall median survival, excepting tumor-related causes, was 130 months. It was 130 months for femur reconstructions and 117 for tibia reconstructions (p=0.57). Age, length of resection, tumor location, use of an allograft, and use of an antirotation system were not found to be significant prognostic factors for implant survival.
Discussion: As reported by many others, we found that the rate of failure of massive prostheses for infectious and mechanical causes remained high in patients treated for bone tumors involving the knee joint. Survival of massive implants is much lower than that of gliding prostheses.
Conclusion: Technical progress is required to improve the survival of massive implants used for the treatment of bone tumors involving the knee joint.
