DOS 2019

168 · DOS Abstracts No improvement of failure rate after resection of primary bone tumors and reconstruction with second-generation mega-prostheses Christina Holm, Michala Sørensen, Müjgan Yilmaz, Michael Mørk Petersen Orthopedic surgery , Rigshospitalet; Orthopedic surgery, Bispebjerg Hospital Background: Previous multicenter studies reports variable outcome and failure rates after mega-prosthetic reconstructions for tumors in the lower extremi- ties. Purpose / Aim of Study: Purpose of study was to evaluate if 1) use of sec- ond-generation mega-prosthesis for reconstruction after resection of primary malignancies result in lower incidence of implant failure and revision and also limb amputation compared to first generation prostheses, and 2) if the overall patient survival in a population based cohort of sarcoma patients has changed over time. Materials and Methods: A retrospective study of 72 consecutive patients (F/ M=30/42), mean age 44 (range 7-84) years with bone or soft tissue sarcomas (n=67) or aggressive benign bone tumors (n=5) having surgery between 2006 and 2016 with bone resection and reconstruction with mega-prostheses. Causes of failure were classified according to Henderson classification. Kaplan- Meier survival analysis was used for evaluation of overall patient survival. Fine and Gray competing risk analysis was used for assessing cumulative incidence of implant failure and limb amputation. Functional outcome was evaluated with the MSTS score Findings / Results: Forty-seven patients were alive at follow-up.Twenty- eight patients (39%) underwent revision for all causes. Overall 10-year patient survival was 61% (95%CI 48-74%) with no difference over time (p=0.9).Ten- year incidence of implant revision and implant failure was 25% (CI: 14%-36%) and 18% (CI: 9%-28%) respectively. No difference between first and second- generation prostheses was found (p=0.9 and p=0.2 respectively).Ten-year in- cidence of limb amputation was 11% (95%CI: 3%-18%).No difference between first and second-generation prostheses (p=0.9).The overall predominant failure mode causing revision was non-mechanical (51%). Mean MSTS score was 20 (67%) (range 0-30) Conclusions: Our results with second-generation mega- prostheses, justifies the use of limb salvage surgery regardless of patient diagnose and staging. We found no difference in implant failure or limb survival compared to our previ- ously published findings (Holm et al. Int Orthop 2018;42:1175-81). For future evaluations of tumor prostheses we advocate using competing risk analyzes in order to achieve valid estimates. 124.