Efficacy and Safety of Ethylene Oxide Sterilization of Allogeneic Bone for Human Transplantation: A Forty-year Experience

Abstract

Context: Since the year 2000, allogeneic tissues utilized for operations in humans in the United States have commonly undergone terminal sterilization with gamma irradiation. Ethylene oxide sterilization of tissues processed for human implantation has been abandoned Objectives: (1) To record the long-term successful experience of a precursor transplantation laboratory in the provision of human bone and fascia sterilized with “cold cycle” ethylene oxide; (2) to report the successful experience of a single neurosurgeon operating in a community hospital using only this bone to fuse and stabilize the lumber spine without instrumentation; (3) to review historic and contemporary scientific evidence for the biologic and biomechanical effects of ethylene oxide gas and gamma irradiation exposure on tissues, along with their virucidal, fungicidal and bactericidal properties for surface and interstitial sterilization. Design: Records from the Western Transplantation Services (WTS) laboratory were scrutinized documenting the 18 years of its existence (1978-1996) as well as the voluminous, carefully preserved records of patient interactions, preoperative, operative, and postoperative records archived over three decades from 321 patients undergoing 339 operations by a single neurosurgeon utilizing 1,135 tricortical iliac crest wedges sterilized with ethylene oxide. Main Outcome Measures: Rates of infection and neoplasia in allograft recipients or in laboratory personnel from preparation and distribution of over 50,000 ethylene oxide sterilized allografts provided by a single processing laboratory; lumbar spine fusion rate and complications attributable to grafts among patients receiving these implants. Results: Over 50,000 allografts distributed from Western Tranplantation Services resulted in no reported infections or neoplasia in any recipient and no neoplasia among technicians processing four tissues with exposure to ethylene oxide. Fusion rate among patients undergoing uninstrumented posterior lumbar interbody fusion (PLIF) with tissues distributed by this laboratory was 96% with no reported infections and no allograft fractures. Complication rate of 4% related to the operation and not the performance of the allografts processed by the laboratory. Conclusions: Ethylene oxide sterilization of allogeneic tissues for human transplantation is a safe, efficacious method and merits reconsideration as a remarkably unique surface and interstitial tissue sterilant that is bactericidal, fungicidal and virucidal without compromise of biomechanical integrity of grafts at doses achieving these sterilizing effects.