Effects of high-dose gamma irradiation on tensile properties of human cortical bone: Comparison of different radioprotective treatment methods.

There are growing interests in the radioprotective methods that can reduce the damaging effects of ionizing radiation on sterilized bone allografts. The aim of this study was to investigate the effects of 50kGy (single dose, and fractionated) gamma irradiation, in presence and absence of l-Cysteine (LC) free radical scavenger, on tensile properties of human femoral cortical bone. A total of 48 standard tensile test specimens was prepared from diaphysis of femurs of three male cadavers (age: 52, 52, and 54 years). The specimens were assigned to six groups (n=8) according to different irradiation schemes, i.e.; Control (Non-irradiated), LC-treated control, a single dose of 50kGy (sole irradiation), a single dose of 50kGy in presence of LC, 10 fractions of 5kGy (sole irradiation), and 10 fractions of 5kGy in presence of LC. Uniaxial tensile tests were carried out to evaluate the variations in tensile properties of the specimens. Fractographic analysis was performed to examine the microstructural features of the fracture surfaces. The results of multivariate analysis showed that fractionation of the radiation dose, as well as the LC treatment of the 50kGy irradiated specimens, significantly reduced the radiation-induced impairment of the tensile properties of the specimens (P<0.05). The fractographic observations were consistent with the mechanical test results. In summary, this study showed that the detrimental effects of gamma sterilization on tensile properties of human cortical bone can be substantially reduced by free radical scavenger treatment, dose fractionation, and the combined treatment of these two methods.