Bridging of large chronic osteoperiosteal gaps by allogeneic decalcified bone matrix implants in rabbits.

A circumferential complete osteoperiosteal gap (1 to 1.5 cm) was produced in the diaphysis of ulna of rabbits, and the ipsilateral radius was kept intact. In no case did spontaneous bridging of the gap occur. By 6 weeks after the creation of the gap the bone ends became smooth and tapered towards the ipsilateral radius and the defect was observed to be filled by thin fibrous tissue. Established defects at least 6 weeks old were then bridged by inserting a snugly fitting allogeneic bone matrix implant. The bone matrix was prepared by demineralization of tubular bones from healthy rabbits, using 0.6 M HCl, preserved in 75% alcohol and used within 3 weeks. The fate of the implant was observed clinically, radiologically, histologically by tetracycline fluorescence for up to 12 weeks. Radiologic evidence of bone formation was present in a majority by 6 weeks, and complete bridging of the gap was seen in 75% of cases by 12 weeks after implantation. Most of the initial bone that formed was the woven bone, i.e., immature bone formed directly from the mesenchymal cells, or formed in membrane, though areas of enchondral ossification were also observed in some cases. By 12 weeks, the bone had remodeled almost to the texture of a mature tubular bone. Successful bridging of chronic massive bone defects by allogeneic bone-matrix was confirmed in 75% of cases.