Gamma Radiation Sterilization Alters Microscopic Damage Processes in Dense Cancellous Bone

INTRODUCTION Structurally intact, cancellous bone is an attractive grafting material because it can allow a greater degree of ingrowth by host tissues than cortical bone and may also be used as structural support for other biomaterials used to deliver osteogenic agents. Gamma radiation sterilization is a commonly used technique for reducing the risk of disease transmission with allograft, but is associated with reductions in the strength and resistance to fracture of cortical bone tissue [1]. Radiation doses commonly used in sterilization (25-35 kGy), however, have not been associated with alterations in elastic modulus or ultimate stress of cancellous bone [2,8]. Furthermore, it is not known how gamma radiation sterilization influences the yield properties of cancellous bone. Because cancellous bone experiences tissue damage at strains well below yield [5,7], alterations in tissue resistance to crack propagation associated with gamma radiation sterilization may alter yield properties as well as the amount and type of microscopic tissue damage formed during loading. The long-term goal of this study is to improve the performance of dense cancellous bone allograft. The specific goals of this study were to: 1) determine the effects of gamma radiation sterilization on the compressive yield properties of dense cancellous bone; and 2) determine the effects of gamma radiation sterilization on the type and amount of microscopic tissue damage generated in cancellous bone after yield.