Sterilization of Partially Demineralized Bone Matrix: The Effects of Different Sterilization Techniques on Osteogenetic Properties

Transplantation of allogenic bone requires the thorough examination of donors as well as the careful processing and storage of samples in order to minimize potential infection. Other problems associated with allogenic transplants such as low osteoinductive properties and immunological reactions led to the development of partially demineralized bone matrix (PDBM). This highly osteogenic bone extract is largely free of antigens and easy to produce. However, in order to exclude the potential risk of infection, PDBM should be sterilized prior to implantation. It was the purpose of this study to investigate the influence of various sterilization techniques on the osteoinductive properties of PDBM. Seventy-six drill defects with a diameter of 0.6 cm in the tibia of 11 Merino sheep were filled with PDBM as well as autogenic or allogenic cancellous bone. Prior to implantation the PDBM was sterilized using autoclavation, gamma irradiation, ethylene oxide, or ethanol. Twelve empty drill holes served as controls. The extent of new bone formation was ascertained by histological, fluorescent-optical, and microradiographical examinations 3 and 6 weeks postoperatively. Furthermore, the amount of newly formed bone was measured quantitatively. Apart from autoclaved PDBM, all matrix grafts showed excellent new bone formation after sterilization, exceeding the results of allogenic cancellous bone.