ETHYLENE-OXIDE STERILIZATION IMPAIRS ALLOGRAFT INCORPORATION IN A CONDUCTION CHAMBER

Bone allograft processing often includes treatment with hydrogen perox ide for protein denaturation and sterilization by irradiation or ethyl ene oxide, The effect of these treatments on the osteoconductive prope rties of the graft was tested by measuring the new bone ingrowth dista nce into processed cancellous bone grafts in rats, Forty graft pairs w ere taken from rat tibias, and were frozen, defatted in chloroform-met hanol, and dried, In addition, 1 graft of each pair was treated with 2 % hydrogen peroxide, 2.5 Mrad irradiation, or by a Steri-Vac hospital ethylene oxide chamber, The grafts were placed in bone conduction cham bers and implanted in rat tibias, Six weeks after implantation, the ch ambers were emptied, and the new bone ingrowth distance and scintimetr ic activity were measured, Ethylene oxide treatment impaired the new b one ingrowth distance by 68% and reduced the scintimetric activity by 51%. Another 10 defatted grafts, which had been ethylene oxide treated together with the grafts for implantation, were analyzed for levels o f residual ethylene oxide, ethylene chlorohydrin, and ethylene glycol, Ail the measured residuals were below the detection limit of 20 parts per million, which was below the level recommended by the United Stat es Food and Drug Administration, Ethylene oxide sterilization was more deleterious for bone allografts than expected.