Effects of Gamma Irradiation on the Mechanical Properties of Human Cortical Allograft Bone

Musculoskeletal allografts are used widely in tumour and reconstructive surgery. Gamma irradiation has been used to sterilise allograft bone but its effect on the biomechanical properties of osseous tissue is not fully elucidated. In this study, we have examined the effect of gamma irradiation on the mechanical properties of human cortical bone. An examination was carried out of the three-point bending, compressive strength, and fracture toughness of human femoral cortical bone irradiated at doses of 15, 25, and 50. kGy, in comparison with non-irradiated control bone. We found that gamma irradiation degrades the mechanical properties of bone as evidenced by three-point bending and toughness assays. A 6% reduction in ultimate three-point bending stress was observed at 15. kGy, 23% at 25. kGy and 30% at 50. kGy. There was a 12% reduction in toughness at 15. kGy, 13% at 25. kGy and 22% at 50. kGy. The effect on ultimate compressive stress was less marked, with no significant effect seen below a 50. kGy radiation dose. In summary, given the low incidence of disease transmission from allograft bone, it is believed that where large structural allografts are concerned, the possible benefits of gamma irradiation need to be balanced against its detrimental effects on the resistance of the bone to catastrophic mechanical failure.