Mechanical strength of cortical allografts with gamma radiation, in Acta Orthop Belg

versus ethylene oxide (ETO) sterilization on the mechanical strength of cortical bone grafts. Tibias were collected from cadavers of mature goats. Sixty test specimens were randomized into four groups : fresh (no processing), frozen (freezing at –70°C), gamma-irradiated, and ETO-sterilized specimens. Torsion, three-point bending, and compression testing were separately performed with a material testing machine. Parameters studied included maximum stress, strain, deflection, extension, load, shear modulus, and E-modulus. Compared with findings for the fresh specimens, findings were as follows for gammairradiated specimens : maximal shear modulus, reduced by 48% ; shear stress, by 55% ; deflection, by 71% ; bending stress, by 51% ; bending strain, by 74% ; extension, by 60% ; and compression strain, by 50%. However, there were no reductions in those parameters for the frozen specimens or the ETOsterilized specimens. These findings confirm that shear, bending, and compression strength of cortical allografts are weakened by gamma irradiation at room temperature. To maintain optimum mechanical properties, ETO sterilization of allografts is better than gamma sterilization, especially for cortical bone, because it is usually used in load-bearing settings.