The effect of gamma irradiation on a xenograft tendon bioprosthesis

Radiation sterilisation of xenograft prostheses has been shown to cause damage to the material. Such damage has been imputed to affect the mechanical and biological properties and may contribute to long-term failure. This study has examined the effect of 25 kGy (2.5 Mrad) of gamma radiation on the mechanical and physicochemical properties and the biological function of a xenograft tendon bioprosthesis derived from glutaraldehyde cross-linked kangaroo tail tendon. The ultimate tensile stress of nonirradiated glutaraldehyde cross-linked tendon was greater than that of fresh frozen tendon, but irradiated cross-linked tendon did not differ. Irradiation did not alter the response to prolonged collagenase exposure. There was a decrease in overall apparent cross-link density (as determined by thermal denaturation temperature). After 12 months implantation, there was a slightly more active cellular response around irradiated tendon and the very peripheral fibres were infiltrated, but the mechanical properties of the retrieved implants were the same for irradiated and nonirradiated material. Gamma irradiation would appear to be a satisfactory method of sterilisation for glutaraldehyde cross-linked tendon materials. However, as damage to the cross-linked structure was detected in this study, it may not be appropriate in other applications.