Sterilization of Allograft Bone: is 25 kGy the Gold Standard for Gamma Irradiation?

Abstract

For several decades, a dose of 25 kGy of gamma irradiation has been recommended for terminal sterilization of medical products, including bone allografts. Practically, the application of a given gamma dose varies from tissue bank to tissue bank. While many banks use 25 kGy, some have adopted a higher dose, while some choose lower doses, and others do not use irradiation for terminal sterilization. A revolution in quality control in the tissue banking industry has occurred in line with development of quality assurance standards. These have resulted in significant reductions in the risk of contamination by microorganisms of final graft products. In light of these developments, there is sufficient rationale to re-establish a new standard dose, sufficient enough to sterilize allograft bone, while minimizing the adverse effects of gamma radiation on tissue properties. Using valid modifications, several authors have applied ISO standards to establish a radiation dose for bone allografts that is specific to systems employed in bone banking. These standards, and their verification, suggest that the actual dose could be significantly reduced from 25 kGy, while maintaining a valid sterility assurance level (SAL) of 10(-6). The current paper reviews the methods that have been used to develop radiation doses for terminal sterilization of medical products, and the current trend for selection of a specific dose for tissue banks.

PDMS-SiO2-TiO2-CaO hybrid materials – Cytocompatibility and nanoscale surface features

“…Sample discs were sterilized using gamma irradiation dose of 25 kGy, the dose usually recommended [30,31] to achieve a Sterility Assurance Level (SAL) of 10 -6 and a procedure already described [19].…”

A biocompatible hybrid material with simultaneous calcium and strontium release capability for bone tissue repair

“…Cut discs were sterilized using a total gamma irradiation dose of 25 kGy, the dose usually recommended [20,21] to achieve a Sterility Assurance Level (SAL) of 10 -6 (the probability of a micro-organism to survive after the process) when the natural contamination level and microorganism types cannot be calculated, in a procedure already described [22].…”

Growth factors in orthopaedic surgery: demineralized bone matrix versus recombinant bone morphogenetic proteins

“…The final sterilisation may have a secondary toxic effect or alteration of the osteoinduction if ethylene oxide, glutaraldehyde or formaldehyde is used while merthiolate, gamma irradiation (≤25kGray) or electron beams preserve the osteoinductive properties [5,24,[78][79][80][81][82].…”