Implant survival and factors associated with failure of cemented custom-made distal femoral megaprostheses after tumor resection

Background: Distal femoral megaprosthetic reconstruction is a standard limb-salvage procedure after tumor resection. This study aimed to evaluate implant survival and associated factors, the incidence of mechanical failure, and functional outcomes following reconstruction with cemented custom-made distal femoral megaprostheses. Methods: Fifty-seven patients who underwent distal femoral tumor resection followed by reconstruction with a cemented custom-made distal femoral megaprosthesis between 2010 and 2024 were retrospectively analyzed. Implant survival was evaluated using Kaplan–Meier analysis, and associations with outcomes were assessed using Cox proportional hazards and Fine–Gray competing-risk regression models. The analyzed risk factors included age, sex, resection length, stem diameter, fixation length, and functional score. Functional outcomes were assessed using the Musculoskeletal Tumor Society (MSTS) score. Results: Implant survival remained above 60% at the latest follow-up, with survival rates of 100% at 12 months, 93.5% at 24 months, and 72.9% at 60 months. No clinical or implant-related geometric variables were significantly associated with implant survival. The cumulative incidence of mechanical failure was 7% at 48 months and approximately 15% at the latest follow-up, with no association between mechanical failure and resection length, stem diameter, or fixation length. Functional outcomes were favorable, with a mean MSTS score of 21.6 ± 3.9. Conclusion: Cemented custom-made distal femoral megaprostheses demonstrated satisfactory mid- to long-term survival following tumor resection. In this cohort, none of the evaluated variables were significantly associated with implant survival. The incidence of mechanical failure remained relatively low, and geometric implant parameters were not significantly associated with mechanical failure. Functional outcomes were favorable, with most patients achieving good or excellent MSTS scores.