Demineralization of bone transplants in vivo

Abstract

A standard experimental model was designed by creating midfibular fracture gaps in rats, for the study of grafts of decalcified allogeneic bone matrix (DABM), fresh autologous bone, fresh allogeneic bone, and decalcified xenogeneic bone matrix (DXBM). The results reveal that DABM implants were accepted by the host in fresh and chronic fibular gaps. There was a gradual increase in calcium concentration, which reached normal levels by the eighth postoperative week at fracture gap sites. DXBM grafts demonstrated very small concentration of calcium after 4 weeks, which was mainly due to formation of callus around the grafts; and 55 per cent of these grafts were rejected, as evidenced by exudate and exfoliation. Fresh autologous and fresh allogeneic bone transplants demonstrated a fall in calcium concentration in the initial 3-week intervals, then a gradual increase in mineralization, and the attainment of normal levels by the eighth postoperative week. All autologous bone grafts were accepted, whereas 45 per cent of fresh allogeneic bone grafts were rejected from the mid-fibular implanted sites. The study with autologous bone transplants was repeated, and the implanted bone was isolated from new bone for calcium estimation at various postoperative intervals. The results revealed gradual decrease in calcium concentration up to 4 weeks, and the later intervals could not be estimated because of difficulty in separation of implanted bone from the new bone. The results of these experiments suggest that calcified bone grafts (autologous or allogeneic) undergo partial or complete decalcification in tissues after implantation. Since this decalcification of bone could be accomplished in vitro, it would appear that the DABM grafts are worthy of trials in human osseous deformities.