Reasons for Sterilization

• Contamination of bacteria from the gut
• Infection
• Contamination of tissue during recovery or processing
• Screening failure (infectious window), strict anaerobes, asymptomatic donor infection
• Emerging diseases

What is Sterilization?

Sterilization: A process which results in the inactivation of all forms of life. “Free from viable micro-organisms”

*American National Standard Institute/Assoc. for the Advancement of Medical Instrumentation – ANSI/AAMA ST67:2003 definition

What is “Sterile”

There is currently no single assay which can, with 100% confidence, determine if an item is sterile by the definition given above. Instead, the level of sterility of a population is calculated and expressed as an Sterility Assurance Level (SAL).

The ANSI/AAMA definines Sterility Assurance Level (SAL) as "The state in which the probability of any one product being contaminated is one in a million. Sterile = 10-6 SAL (1/1,000,000 = 10-6)"

“It is a functional definition of sterility and is used in industry because the absolute definition, the complete absence of viable organisms, is not possible to reliably verify. Simply stated, it’s like running an inverted lottery which results in at least a million winners to every one loser. Our patients are the winners by receiving treatment with a sterile product.” ***

***: Burns, S., New Gamma methods Increase Options for Allograft Materials, Medical Device & Diagnostic Industry, 29: 3, Mar 2007, ©Canon Communications LLC, also available at their website

Example of Sterility

Tissue must have a sterility assurance level of 10-6 (Medical Device level) for bacterial contaminants. Viruses are not included in this definition.

If average bioburden is 103
In this case, to achieve sterility a system must be validated to achieve 9 logs of inactivation (103 + 10-6 = 9 logs). The quantity of energy or chemistry required depends upon how susceptible the organisms are to the sterilization process.

Sterilization Challenges in Connective and Soft Tissue with and without bone.

Bacteria, their spores & viruses are present that require longer exposure to sterilant

Adequate penetration into the matrix of the tissue is needed for complete sterilization

It is essential to preserve the biomechanical and biological character of the allograft.
Sterilization Challenges in Connective and Soft Tissue

Micro-organisms (spores) & viruses are present that require longer exposure to sterilant

Adequate penetration into the matrix of the tissue is needed for complete sterilization

It is essential to preserve the biomechanical and biological character of the allograft.

Methods Used to Sterilize

• Ethylene Oxide
• Gamma Irradiation
• Chemical Sterilization
• Supercritical CO2

Click here to learn about the Clearant Process and how it sterilizes tissue.