Experimental spinal fusion with decalcified bone matrix and deep-frozen allogeneic bone in rabbits

The effects of allogeneic decalcified bone matrix (DBM) on the formation of bone between the spinous processes of the rabbit vertebrae was compared with the effects of allogenic deep-frozen cortical bone (AFB). Autologous cancellous bone (ACB) chips were used for a control substance. Healing was estimated by gross anatomical roentgenologic and microscopic methods one, two, four and six months after the operation. The ACB and DBM transplants gave comparable results. A stable bony bridge was formed at one month, and this was seen to strengthen during the follow-up time. Both transplanting materials were accepted by the host without foreign body reactions. Inflammatory cell accumulations and sequesterated particles were not seen in any of the specimens with ACB and DBM transplants. The DBM induced new bone formation and the transplanted material was resorbed within two months after the operation. The AFB transplants did not induce the new bone formation, but the implanted fragments in contact with the host bone were surrounded by the callus, which produced a bony bridge but only as late as four months after the operation. After six months, the bridging was incomplete and sequestered bone particles were still seen in some of the specimens. The AFB transplants were slowly resorbed and accumulations of inflammatory cells were present at least six months postoperation. The results indicate that in rabbits, decalcified bone matrix is a better substitute for autologous bone than the allogeneic deep-frozen cortical bone.