Short- and Long-term Failure of Modular Oncology Knee Prostheses

Long-term implant survivorship for modular oncology knee prostheses is essential because of improved oncological outcomes. The influence of variables such as location, chemotherapy, and cement are largely unknown. Modes of implant failure need to be determined. Eighty consecutive patients with bone tumors of the knee treated by a single surgeon with limb salvage and a modular knee prosthesis were retrospectively reviewed. Patient and implant survivorship were determined. Modes of device failure were noted. Function was evaluated using the Musculoskeletal Tumor Society scoring system. Data was subject to statistical analysis. Mean age was 34 years (range, 9–84 years) with a mean follow-up of 5.3 years (range, 2–13.5 years). Survival (minus stage III and benign) was 46/58 (79.3%). The most common tumor was osteosarcoma. Twenty patients (25.0%) required revision, 12 (60.0%) for stem loosening, 6 (30.0%) for bearing failure, and 2 (10.0%) for infection. The mean Musculoskeletal Tumor Society function was 24/30. Our study revealed an improvement in survival for patients with bone sarcomas compared to historical controls. However, long-term prosthetic survivor-ship was a problem. Stem loosening was the most common mode of failure. A higher failure rate was found for tibial tumors, and with chemotherapy. New bearings and methods for implantation need to be developed to improve long term implant survivorship.