Bone induction using demineralized bone in the rabbit femur: a long-term study.

While traditional bone grafting is the standard for replacement of segmental bony defects, alternative options (avoiding morbidity of autologous grafts) are attractive and continue to be sought. This study attempted to determine whether demineralized bone powder could be used reliably to replace a significant bony deficit at a weight-bearing site. The long-term functional characteristics of this induced bone were analyzed to determine whether it maintained its strength and shape and reacted normally to physiologic stress over an extended period of time (12 months). In 55 New Zealand White rabbits, a 1-cm length of femur was removed (approximately 20 percent of the total length of the rabbit femur). The femur was then reconstructed with a titanium mandibular plate, leaving the gap intact. In 38 of the animals, this gap was filled with demineralized bone powder in an attempt to induce bone to form across the defect. In group 1 (n = 23), the mandibular plate remained in place for the duration of the study (12 months). In group 2 (n = 15), the plate was removed 8 weeks after placement of the demineralized bone powder, and the animals were followed for an additional 12 months. In group 3 (n = 10), nothing was placed within the bony gap. In group 4 (n = 7), the gap was repaired with autologous bone graft. All the animals that received demineralized bone powder completely filled the osteotomy gap with new bone within 6 to 8 weeks after implantation. None of control group 3 formed bone across the gap (p < 0.001). Eighty-six percent of control group 4 (autologous bone graft) successfully formed bone across the osteotomy gap. In addition, 90 percent of control group 3 had hardware failure within 8 weeks after surgery compared with 0 percent (0 of 38) of the group that received demineralized bone powder (p < 0.001). In group 1, analysis after 12 months revealed that the bone formed ultimately became thin and easily fractured, most likely because of shielding from stress loading by the mandibular plate. In contrast, in group 2 (in which the plate was removed after 8 weeks), the bone remodeled and hypertrophied in response to the physiologic stress of weight bearing and at the end of the 12-month period was essentially identical to normal femur. In certain circumstances, reconstruction of bony defects using bone-induction techniques may be as good as autologous bone grafting, with the advantage of limiting the donor-site morbidity for the patient.