Effect of gamma irradiation on mechanical properties of human cortical bone: influence of different processing methods

Abstract

The secondary sterilisation by irradiation reduces the risk of infectious disease transmission with tissue allografts. Achieving sterility of bone tissue grafts compromises its biomechanical properties. There are several factors, including dose and temperature of irradiation, as well as processing conditions, that may influence mechanical properties of a bone graft. The purpose of this study was to evaluate the effect of gamma irradiation with doses of 25 or 35 kGy, performed on dry ice or at ambient temperature, on mechanical properties of non-defatted or defatted compact bone grafts. Left and right femurs from six male cadaveric donors aged from 46 to 54 years, were transversely cut into slices of 10 mm height, parallel to the longitudinal axis of the bone. Compact bone rings were assigned to the eight experimental groups according to the different processing method (defatted or non-defatted), as well as gamma irradiation dose (25 or 35 kGy) and temperature conditions of irradiation (ambient temperature or dry ice). Axial compression testing was performed with a material testing machine. Results obtained for elastic and plastic regions of stress-strain curves examined by univariate analysis are described. Based on multivariate analysis it was found that defatting of bone rings had no significant effect on any mechanical parameter studied, whereas irradiation with both doses decreased significantly the ultimate strain and its derivative toughness. The elastic limit and resilience were significantly increased by irradiation with the dose 25 kGy, but not 35 kGy, when the time of irradiation was longer. Additionally, irradiation at ambient temperature decreased maximum load, elastic limit, resilience, and ultimate stress. As strain in the elastic region was not affected, decreased elastic limit resulted in lower resilience. The opposite phenomenon was observed in the plastic region, where in spite of the lower ultimate stress, the toughness was increased due to the increase in the ultimate strain. The results of our study suggest that there may be an association between mechanical properties of bone tissue grafts and the damage process of collagen structure during gamma irradiation. This collagen damage in cortical bone allografts containing water does not depends on the temperature of irradiation or defatting during processing if dose of gamma irradiation does not exceed 35 kGy.

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

“…The sterilization of bone allografts through high dose gamma irradiation has certain limitations because of the reported detrimental effects of ionizing radiation on mechanical properties of the bone (Barth et al, 2011;Bailey, 1967;Salehpour et al, 1995;Currey et al, 1997;Hamer et al, 1996;Allaveisi et al, 2015Allaveisi et al, , 2014Seto et al, 2008;Cornu et al, 2000;Grieb et al, 2006;Kaminski et al, 2012;Russell et al, 2012). Therefore, the radioprotective methods such as free radical scavenger treatments as well as fractionation of the E-beam irradiation have been proposed to overcome this limitation (Hoburg et al, 2011;Wei et al, 2013).…”

Radiation sterilization of tissue allografts: A review

“…Significant increase in the elastic limit and resilience was observed on irradiation at 25 kGy. Maximum load, elastic limit, resilience, and ultimate stress were found to decrease on irradiation at ambient temperature [89] . The results of study suggest that the damage of collagen structure by gamma radiation may effect the mechanical properties of bone grafts [89] .…”

“…Maximum load, elastic limit, resilience, and ultimate stress were found to decrease on irradiation at ambient temperature [89] . The results of study suggest that the damage of collagen structure by gamma radiation may effect the mechanical properties of bone grafts [89] . No noticeable effect of gamma irradiation on mechanical properties of defatted trabecular bone allografts was observed [90] .…”

“…Irradiation of bone grafts was carried out on dry ice or at ambient temperature. Significant decrease in the ultimate strain and toughness was found on irradiation with both the doses [89] . Significant increase in the elastic limit and resilience was observed on irradiation at 25 kGy.…”

“…Zhang et al [88] showed that there was no statistical significant difference between irradiated and non-irradiated groups for both deep-frozen allograft and freeze-dried tricortical iliac crest allografts at a radiation dosage of 20-25 kGy. Kaminski et al [89] studied the effect of 25 kGy and 35 kGy gamma radiation on mechanical properties of nondefatted or defatted compact bone grafts. Irradiation of bone grafts was carried out on dry ice or at ambient temperature.…”