[Future of bone allografts in massive bone resection for tumor]

Currently cryopreservation offers the best means of preserving bone tissue for allografts. At -196 degrees C all enzyme activity is halted and tissue preservation is unlimited. Perfect sterilization, adapted cryoprotection and controlled freezing and thawing are now part of the well-controlled process of bone preservation in bone banks. At implantation, the mechanical properties of cryopreserved bone is as good as or better than fresh bone, although the diaphyseal cortical bone is more fragile. Anatomic and physiologic reconstruction of the graft area is a major factor in graft resistance. It takes approximately three weeks for vessels to penetrate cancellous allografts and at least one month for total revascularization. The delay may reach several years for cortical bone. The immune response of the host is determined by the antigenic properties of the leukocytes in the bone marrow as well as the blood vessels and nerves. The protein-mineral complex itself has little antigenic effect. A certain number of non-specific immune reactions result from transfusions almost always performed with bone grafting. At the present time, there is no artificial material capable of providing a mechanically acceptable substitute for allograft bone in limb reconstruction. Allograft bone currently stocked in bone banks provides a biologically and clinically acceptable means of reconstruction after major bone loss. Other factors such as public acceptance and administrative authorizations will also play an important role in the future of massive reconstruction with bone allografts.