Megaprosthesis Revision Caused by Aseptic Loosening and Nonunion of the Structural Allograft in Patients Younger Than

Background: The use of structural allografts is aimed to restore the resected bone segment in order to maintain enough bone stock for future revisions. The aim of this study was to describe the mechanical failures of Allograft Megaprosthesis Composite (AMC) revised to Modular Megaprosthesis (MMP) due to nonunion of the structural allograft in patients younger than 40 years. Material and methods: A retrospective revision in a referral hospital for the treatment of musculoskeletal tumors was performed between January 1st 2009 and January 31st 2012. We looked in the surgical records of the musculoskeletal tumors unit for all of the procedures coded as “megaprosthesis-revision-arthroplasty”. We included patients younger than 40 year-old in which primary reconstructive surgery at any segment of the lower limb was performed by means of AMC, and revision surgery was performed by means of MMP. We looked in those records for information regarding integration of the structural allograft to the native bone. Six revisions from AMC to MMP were performed: 5 knees and 1 hip. The mean age at the time of revision surgery was 28.83 year-old (range 18-38). Primary oncological diagnoses were: 4 osteosarcomas of the distal femur, one Giant Cell Tumor (GCT) of the femoral head and 1 GCT of the proximal tibia. Results: In none of the cases integration of the structural bone allograft to the native bone was observed, reason why it had to be completely resected in all patients. The reason for revision surgery in all cases was aseptic loosening secondary to nonunion of the structural bone allograft. Mean time elapsed from implantation of AMC to revision surgery to MMP was 103 months. Mean time elapsed from revision surgery to last follow-up visit was 26 months. Conclusion: Structural bone allografts in limb salvage surgery after massive tumor resection, may not be the best reconstructive option because the high probability that the grafted bone segment might not integrate to the native bone, even in young patients, may lead to prosthetic failure because of aseptic loosening.