CLINICAL USE OF BONE ALLOGRAFTS

Modern techniques of bone allograft surgery provide a treatment modali ty for management of difficult skeletal defects. In oncological limb-s alvage surgery, allograft reconstructions permit re-establishment of s keletal continuity and function after a wide resection of bone tumour. Bone allografts are increasingly used in salvage of difficult bone st ock deficiencies following failed total joint replacements. Union betw een the allograft and the host bone takes place slowly and the use of autogenous bone graft at the graft-host junction is recommended for in duction of repair. Internal repair (revascularization and substitution of the original graft bone with new host bone) also progresses slowly and seems to be confined only to the superficial surface and the ends of the graft. Biomechanically, a massive allograft may serve a struct ural function in the absence of advanced revascularization and creepin g substitution processes. Infection of an allograft is a disastrous co mplication, whereas non-union of the graft-host junction and fracture of the graft are amenable to surgical treatment. Ostochondral allograf ts tend to show gradual deterioration of the articular cartilage with time, necessitating occasionally late resurfacing arthroplasty. It is evident that there is more active immune response to osteochondral gra fts than was thought previously. Bone allografts induce cell-mediated and antibody-mediated cytotoxicity specific for donor antigens similar to that seen after organ transplantations. Not only the basic mechani sms of bone allograft rejection but also the clinical features of bone allograft rejection are poorly characterized. Clinically, new non-inv asive imaging techniques should be applied in determining the metaboli c activity of bone in order to find the optimal loading of healing all ografts. Although the clinical results of massive bone allografts are still not completely predictable, the method has proved to be a techni cally and biologically feasible alternative for non-biological skeleta l reconstructions.