Biology of Bone Allograft and Clinical Application

Abstract

Bone allografts have become an accepted technology to replace bone loss as a result of tumor resection, trauma and failed total joint arthroplasty. Since fresh allograft invokes an immune rejection response, bone is usually processed by freezing or freeze-drying to reduce the immune response. The significance of biological events of incorporation include hemorrhage and inflammation, osteogenesis, osteoinduction, osteoconduction and effective remodeling to become a load bearing structure. The clinical parameters that enhance the chance of successful bone allograft incorporation are adherence to the American Association of Tissue Bank standards, appropriate graft selection for the clinical application, stable graft-host interface and preservation of the surrounding soft tissue and host blood supply. Cancellous allografts are usually completely incorporated, while cortical grafts remain an admixture of viable new bone and necrotic old bone for a prolonged period of time. Massive bone allografts used for reconstruction of the tumor resection have a long term successful outcome in about 80 percent of the procedures. Similar success is reported for its use in total joint revision surgery and other clinical applications.The major complications reported for grafting procedures are infection, bone graft fracture, nonunion at the graft-host juncture and, rarely, massive allograft resorption. Although bone allografting is a successful procedure, future improved technology to regenerate bone includes the use of adjunctive growth factors, cell based and regional gene therapies. Ultimately tissue