Outcomes of Megaprosthetic Reconstruction After Tumor Resection of the Distal Femur and Proximal Tibia: A Single-Center Retrospective Study of 241 Cases

Background: Megaprosthetic reconstruction is the standard of care for limb salvage after tumor resection around the knee, but the full burden of unplanned revision surgery is rarely reported as a structured composite outcome. We evaluated 241 consecutive patients over 21 years at a tertiary orthopedic oncology center. Methods: This retrospective cohort included 241 patients (160 distal femur, 78 proximal tibia, three combined) treated between 2003 and 2024. Revision-free survival (RFS, composite of any unplanned revision or amputation) and amputation-free survival were estimated by Kaplan-Meier analysis; independent predictors were identified by Cox regression. A pre-specified major-event composite (amputation, implant removal, or recurrence resection) was used for sensitivity analysis. Results: Mean age was 34.9 ± 19.5 years; mean follow-up was 120.2 months. Negative resection margin (R0) was achieved in 85.5% (206/241). Unplanned revision was required in 25 patients (10.4%); overall limb salvage was 92.9%. Five-year RFS was 73.8% (distal femur) vs. 65.0% (proximal tibia; p = 0.084), and 5-year limb salvage was 88.9% vs. 84.3% (p = 0.081). Surgical margin was strongly associated with outcome: 5-year RFS 75.4% (R0) vs. 48.7% (R1/R2; p < 0.001); 5-year limb salvage 90.6% vs. 71.5% (p = 0.003). On exploratory multivariate Cox analysis, proximal tibia site and positive margin were associated with worse revision-free survival; within the proximal tibia subgroup, absence of gastrocnemius flap coverage was also associated with worse outcome (interpreted with caution given the small flap subgroup, n = 11, and limited event count). Conclusions: In this single-center series, megaprosthetic reconstruction around the knee achieved acceptable revision-free survival and limb salvage. Surgical margin status was the strongest independent predictor of both endpoints, reinforcing the well-established importance of oncologic margin quality and site-specific soft tissue strategies.