Repair of critical long bone defects using frozen bone allografts coated with an rhBMP-2-retaining paste

Massive frozen stocked allogeneic bone grafts are often used to reconstruct large bone defects caused by trauma or tumor resections. However, the long-term failure rate of such massive allografts was reported to be 25% because of infection, fracture, and nonunion. In this study, we evaluated the ability of a recombinant human bone morphogenetic protein (rhBMP)-2-retaining paste to promote the osteogenic potential of frozen stocked allogeneic bone grafts to repair intercalated femoral shaft defects in a rat model.

After confirming the transplantation intolerance between two rat strains (Wistar and Lewis) by skin transplantation from Lewis rats to Wistar rats, an 8-mm-long bone segment was removed from the Wistar rats, and a frozen stocked allograft coated with the rhBMP-2-retaining paste from the Lewis rats was placed into the defect and subjected to intramedullary fixation with an 18-gauge injection needle pin. The allografted femurs were evaluated by radiographic, histologic, and biomechanical examinations at specified time points.

The results revealed successful repair of critical-size cortical bone defects by implanting frozen stocked allografts coated with the rhBMP-2-retaining synthetic biodegradable carrier paste from an immunologically intolerant host.

This experimental study suggest that allogeneic bone grafting in combination with rhBMP-2 and its local delivery system may represent an innovative approach to the reconstruction of bone defects.