Mid-term Functional Outcomes and Complications rates in Knee Megaprosthesis for Non-Oncologic limb Salvage Surgeries: A Comprehensive Analysis

Purpose To retrospectively evaluate the clinical and radiological outcomes of revision total knee arthroplasty using knee megaprosthesis in patients with severe bone loss from non-oncologic causes. Methods Between 2008–2020 forty patients were evaluated with 33 month mean follow up (interquartile range: 28–61) and 72-year median age (IQR: 65–77). Radiographic analysis and a functional outcomes were carried out in the preoperative and at the final follow-up using Oxford Knee Score (OKS), Knee Society Score (KSS), Visual Analogue Pain Scale (VAS) and Musculoskeletal Tumor Society Score (MSTS). Complications were classified according to the Henderson classification system. Results Three different implant systems were used: Endo-Model® M Link in 21 cases, OSS™ Orthopedic Salvage System Zimmer Biomet in 18 cases, and the MDT prosthesis in one case. Indications were: 57% (24) prosthetic joint infection (PJI), 15% (6) aseptic loosening, 15% (6) severe osteomyelitis, 5% (2) fractures, 2.5% (1) femoral stem rupture and 2.5% (1) instability. The survival rate at 50 months was 52% (95% CI: 35% − 67%). Postoperative median MSTS score was 16 points (10–25), KSS objective: 73 (67–78), satisfaction: 30 (20–39), expectation: 12 (6–15), functional: 60 (34–70), VAS: 3 (0–8), and OKS: 24 (14–38). Clinical improvement (MCID) was assessed in 22% (9) for functional KSS, and 17% (7) for objective KSS. Twelve out of forty (30%) had positive postoperative cultures and complication occurred in 55% of the series. According to Hendersons classification: 36.4% (8) were aseptic loosening, PJI 31.8 (7), soft tissue failure 22.7% (5) and structural failures 9.1% (2). Conclusion The utilization of knee megaprosthesis in severe bone stock deficiency is a good option for limb salvage surgeries with an acceptable mid-term outcomes. Level of evidence IV