Outcomes of Megaprosthesis Reconstruction for the Salvage of Failed Osteoarticular Allograft Around the Knee implanted before Skeletal Maturity in Primary Bone Sarcoma: A Case-Series

Objectives: Functional expectations following the salvage of a failed osteoarticular allograft are poorly described. In this study, we aim to evaluate functional outcomes, implant survival, and complications of the megaprosthesis in salvaging a failed osteoarticular allograft around the knee.Methods: We retrospectively reviewed the medical profiles of 21 skeletally mature patients who underwent megaprosthesis reconstruction to salvage a failed osteoarticular allograft around the knee implanted before skeletal maturity. The location of reconstruction was the proximal tibia in 13 patients and the distal femur in eight patients. Knee function was evaluated by the Musculoskeletal Tumor Society (MSTS) score and the Toronto Extremity Salvage Score (TESS).Results: The mean age of patients was 16±1.7 years. The mean interval between the primary (allograft) and secondary (megaprosthesis) reconstructions was 59.4±23.6 months. At an average follow-up of 51.2 months, the mean knee range of motion was 101.2±15.6°. The mean MSTS score and TESS were 83.6±7 and 86.6±7.9, respectively. The mean limb length discrepancy was 2.5±1 cm before and 0.36±0.74 cm after the operation (P 0.001). Six postoperative complications (28.6%) occurred in this series, including one wound dehiscence, one periprosthetic fracture, two acute infections, one aseptic loosening, and one delayed periprosthetic infection. Only the last two complications required revision. Accordingly, the two- and five-year implant survivals were 95.7% and 90%, respectively.Conclusion: Megaprosthesis is a viable option for salvaging failed osteoarticular allografts around the knee. It also provides the opportunity to correct the limb length discrepancy. Level of evidence: IV