Reconstruction with Unconventional Endoprostheses after Resection of Primary Distal Femoral Bone Tumors: Implant Survival and Functional Outcomes.

 To evaluate the survival time, the failure rate and its causes, and the functional results of cemented endoprostheses, with a polyethylene body, used after resection of primary bone tumors of the distal femur.  A retrospective study including 93 primary and 77 review procedures performed between 1987 and 2014. Survival was obtained by the Kaplan Meyer analysis, and the risk factors for implant failure were assessed through the Cox proportional risk model. The causes of endoprosthesis failure were classified according to Henderson et al. into five types: soft-tissue failure, aseptic loosening, structural fracture, infection, and tumor recurrence. The functional evaluation was performed using the functional classification system of the Musculoskeletal Tumor Society (MSTS) of bone sarcomas of the lower extremity, Brazilian version (MSTS-BR).  Osteosarcoma was the most common diagnosis; 64.5% of the patients were younger than 20 years of age; the mean follow-up was of 124.3 months. The failure rate of the primary implant was of 54.8%, and the mean survival was of 123 months. The estimated survival of the primary implant was of 63.6%, 43.5%, 24.1%, and 14.5% in 5, 10, 15, and 20 years respectively. The most common cause of failure was type 2 (37.3%). Age ≤ 26 years and right side were risk factors for failure. The mean MSTS-BR score was of 20.7 (range: 14 to 27). The results obtained for the failure rate and survival of the implant are in accordance with those of the literature, so the procedure herein studied is adequate and yields satisfactory functional results, even in the long term.