Ethylene oxide sterilisation of allogenic bone implants

Area of Science:

• Biomaterials Science
• Sterilization Technology
• Microbiology

Background:

• Bone allografts require effective sterilization to prevent disease transmission.
• Ethylene oxide (ETO) gas is a common sterilant for medical devices, but its efficacy in bone matrices needs thorough evaluation.
• Freeze-dried bone processing is utilized to preserve bone structure and facilitate storage.

Purpose of the Study:

• To assess the penetration and efficacy of ethylene oxide gas in sterilizing freeze-dried bone matrices.
• To determine the microbiological kill rate and assess potential barriers within bone.
• To evaluate the suitability of spore indicators for monitoring the bone sterilization process.

Main Methods:

• Evaluation of ethylene oxide gas penetration through cancellous and cortical bone matrices.
• Determination of the D-value (decimal reduction time) for a defined microbiological load on bone.
• Use of commercial ethylene oxide sterilizer cycles.
• Monitoring sterilization with free-floating spore indicators.
• Preliminary analysis of ethylene oxide residuals in processed bone.

Main Results:

• Ethylene oxide gas rapidly diffused through both freeze-dried cancellous and cortical bone.
• A standard ethylene oxide sterilization cycle achieved a sixfold overkill of the microbiological load.
• Minor variations in kill rates were observed based on bone type and thickness, but were negligible compared to the overall efficacy.
• Spore indicators effectively monitored the sterilization process.
• Preliminary results indicated no leachable toxic residuals in processed, freeze-dried bone.

Conclusions:

• Ethylene oxide gas sterilization is highly effective for freeze-dried bone matrices.
• The sterilization process provides a substantial margin of safety (overkill).
• Spore indicators are reliable for monitoring bone sterilization.
• Ethylene oxide sterilization of freeze-dried bone appears safe regarding toxic residuals.