Preparation of bank bone using defatting, freeze-drying and sterilisation with ethylene oxide gas. Part 2. Clinical evaluation of its efficacy and safety.

We used bone allograft treated by defatting in chloroform and methanol, freeze-drying and sterilisation with ethylene oxide gas in operations on 396 patients. The purpose of defatting and freeze-drying is to facilitate subsequent sterilisation by eliminating a barrier to the diffusion of ethylene oxide gas into bone, to lower the residual levels of the ethylene oxide and its toxic by-products after sterilisation, to eliminate alloantigens and to make storage at room temperature possible. Postoperative infections confirmed by a positive bacterial culture occurred in 2 of the 396 patients receiving the allograft, which was prepared under clean, but not sterile, conditions, one of which was thought to be due to dehiscence of the wound, rather than to the allograft. There were also 3 probable infections. Histological sections of the area around the interface of the allograft and its bony bed showed: (1) osteoblasts lining the surface of the dead cortical bone of the graft with appositional new bone; (2) ingrowth of new bone into the Haversian canals, and (3) little infiltration of inflammatory small round cells. These findings indicated the ability of the bone to support new bone formation and to eliminate antigens. The low incidence of infection confirmed the efficacy of this method of sterilisation.