Survival, Failure Modes, and Risk Factors After Limb Salvage Surgery with Modular Megaprosthetic Reconstruction

Background/Objectives: Modular megaprosthetic reconstruction is a central limb-salvage strategy after major skeletal resection, but long-term outcomes remain limited. This study aimed to evaluate patient and implant survival, complication burden, Henderson failure modes, and associated risk factors. Methods: We retrospectively analyzed 340 consecutive patients undergoing modular megaprosthetic reconstruction at a tertiary referral center from 2003 to 2024 for primary malignant bone tumors, metastatic disease, or complex revision- or trauma-related indications. Kaplan–Meier methods estimated patient, implant, and complication-free survival. Implant failure and first recorded Henderson failure modes were additionally assessed using competing-risk methods. Cox regression evaluated risk factors, with multivariable modelling focused on Type IV infection. Results: Median follow-up was 5 years. Patient survival was 71.4% at 5 years and 61.3% at 10 years and was poorer in metastatic disease (p < 0.001). Implant survival was 78.0% and 70.3%, respectively. Complications occurred in 133 patients (39.1%). Type IV infection was the most frequent first failure mode (49, 14.4%), followed by Type I soft-tissue failure (40, 11.8%). The cumulative incidence of infection was 14.6% at 5 years and 15.3% at 10 years. Previous surgeries at the operative site (hazard ratio [HR] 2.30 per additional surgery, 95% confidence interval [CI] 1.90–2.80), operative time (HR 1.005/min, 95% CI 1.002–1.008), and diabetes mellitus (HR 2.30, 95% CI 1.25–4.25) were independently associated with infection and remained significant after expanded adjustment. Conclusions: Implant survival remained 70.3% at 10 years, but complications were frequent. Infection was the dominant first failure mode, and prior local surgery, longer operative time, and diabetes identified higher-risk patients. These findings support individualized risk assessment, preventive planning, and long-term surveillance.