PREPARATION OF BANK BONE USING DEFATTING, FREEZE-DRYING AND STERILIZATION WITH ETHYLENE-OXIDE GAS .1. EXPERIMENTAL EVALUATION OF ITS EFFICACY AND SAFETY

We devised a method of sterilising bone allografts which consists of d efatting in chloroform and methanol, freeze-drying and sterilisation w ith ethylene oxide gas. The purpose of defatting and freeze-drying was to facilitate subsequent sterilisation by eliminating the barrier to diffusion of the gas into bone, to lower residual levels of ethylene o xide and its toxic by-products, to eliminate alloantigens and to make storage possible at room temperature. The efficacy and safety of the m ethod were evaluated by testing the sterilisation of infected bone fro m 6 patients with active chronic osteomyelitis, the penetration of eth ylene oxide into human femoral heads treated by this or by freeze-dryi ng or freeze-thawing, and the desorption of ethylene oxide and its tox ic by-products from pieces of bone treated by these methods. All the s amples of infected bane tested negative for bacteria after treatment. The gas penetrated into the central area of the femoral heads in a few hours. Residual levels of ethylene oxide and its toxic by-products we re much lower in the treated bone than in freeze-dried or freeze-thawe d bone, and decreased quickly in flowing air. Prior defatting and free ze-drying facilitated penetration of ethylene oxide into bone during s terilisation and the desorption of ethylene oxide and its toxic byprod ucts after sterilisation. Preparation under clean, but not sterile, co nditions and storage at room temperature make bone banking more practi cal and efficient.