Gamma Irradiated Bone Allografts Processed from Femoral Heads

Disease transmission and bacterial infection in bone allograft transplantation is of significant concern. Screening of donor for disease, bacterial testing and aseptic processing, substantially reduce risk, but do not completely eliminate the possibility of allograft associated infections. Sterilization by gamma radiation is a definitive method for eliminating microorganisms and can prevent life-threatening allograft associated infections. In the present study, microbiological evaluation of bone allografts processed from femoral heads excised during surgery was carried out. 126 femoral heads obtained from living donors were processed, freeze-dried and sterilized by gamma irradiation at 25 kGy. The bioburden and type of microbial contamination associated with bone allografts was determined based on morphological characteristics and biochemical tests. Resistance of bacterial contaminants to gamma radiation was evaluated by exposing the bacterial cell suspension to different doses of 1 to 6 kGy and analysing for the surviving bacteria. Average bioburden of processed bone allografts for different batches was found to be in the range of 1.84 x 102 to 3.88 x 103 CFU/g. 60.2% of the isolates were found to be Gram-positive organisms. The D10 value of bacterial isolates ranged from 0.56 to 1.68 kGy. Verification doses for different batches of processing were 5.87 to 9.46 kGy. All bone grafts exposed to the verification dose were tested culture negative. The results validate 25kGy dose for sterilization of bone allografts processed from femoral heads.