Surgical technique: Unicondylar osteoallograft prosthesis composite in tumor limb salvage surgery.

BACKGROUND: After resecting tumors confined to one femoral condyle, a unicondylar osteoarticular allograft can be used for reconstruction without sacrificing the uninvolved condyle. However, unicondylar osteoarticular allografts have been associated with a high rate of joint degeneration. We describe a unicondylar osteoallograft prosthesis composite reconstruction replacing only one side of the joint to reduce compartment degeneration and avoid contamination of the tibia, but the survival, function, and complications of a unicondylar osteoallograft prosthesis composite are unclear. DESCRIPTION OF TECHNIQUE: We located a bone resection plane intraoperatively as planned before surgery using a computer-assisted navigation system. The tumor then was removed en bloc and the unicondylar defect filled with a size-matched allogeneic unicondyle. The allograft cartilage was removed. Thereafter, the condyle of the femoral component was resurfaced with a unicompartmental knee prosthesis to form a unicondylar osteoallograft prosthesis composite, however the tibia was left undisturbed. Navigation allowed precise apposition between the unicondylar osteoallograft prosthesis composite and host bone to ensure mechanical alignment and congruency of the joint surface before fixation with a plate.
METHODS: We retrospectively reviewed 12 patients who underwent unicondylar osteoallograft prosthesis composite reconstructions after unicondylar resection for tumors. One patient died from tumor-related causes without unicondylar osteoallograft prosthesis composite failure after 18 months. We observed the survival rate of unicondylar osteoallograft prosthesis composite reconstruction and related complications. Function and radiographs also were documented according to the Musculoskeletal Tumor Society (MSTS) functional scoring system and the International Society of Limb Salvage radiographic scoring system. The minimum followup was 8 months (median, 37 months; range, 8-65 months).
RESULTS: At last followup, 10 of the 12 unicondylar osteoallograft prosthesis composite reconstructions were still in place. Three reconstructions failed owing to two local recurrences (both treated with amputation) and there was one infection (treated with revision and maintenance of the implant at last followup). The average MSTS functional score at last followup was 27 points and the radiographic score 91%.
CONCLUSIONS: Our observations suggest unicondylar osteoallograft prosthesis composite reconstruction might be a reliable technique with relatively few major complications and at least short-term maintenance of the tibial cartilage. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.