EQUINE DEMINERALIZED BONE-MATRIX - RELATIONSHIP BETWEEN PARTICLE-SIZEAND OSTEOINDUCTION

The osteoinductive capability of four particle sizes of equine deminer alized bone matrix (DBM) was evaluated. Matrix particles were implante d in brachiocephalicus muscle pouches in six horses and were harvested 8 weeks later. Matrix particle sizes of 2.0 mm3 to 4.0 mm3 and 5.0 mm 3 to 10.0 mm3 were associated with osteoinductive activity and minimal signs of local inflammation. The two smaller particle sizes (0.425 mm 3 to 0.850 mm3 and 0.850 mm3 to 2.0 mm3) were minimally osteoinductive and were associated with a greater local inflammatory response. Micro scopic events associated with new bone production in the two largest p article sizes included the presence of new osteoprogenitor cells in ma trix vascular spaces, multinucleated osteoclast-like giant cells, and the formation of cartilage, osteoid, and new mineralized bone. The two smaller particle sizes were associated with increased fibrous tissue ingrowth and the presence of increased numbers of inflammatory cells. The temporal events of osteoinduction in response to heterotopic impla ntation of allogeneic DBM were delayed in horses when compared with ot her species. Although the demineralization technique used was effectiv e in previous investigations on other species, incomplete demineraliza tion occurred in the two smaller particle sizes that was not detected until after DBM implant harvest. The demineralization process may need to be altered for equine bone and precise monitoring for complete dem ineralization before implantation is required. Equine DBM is osteoindu ctive in muscle pouch sites in horses but matrix particle size does af fect osteoinductive capability. (C) Copyright 1994 by The American Col lege of Veterinary Surgeons