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Year |
2001 |
|---|---|
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Question Number |
152. |
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Category |
Select |
Question
Sterilization of ultra-high molecular-weight polyethylene by irradiation in an inert environment (argon, nitrogen, or vacuum) is recommended because it
1. increases crystallinity
2. prevents free radial formation
3. prevents immediate oxidative degradation
4. prevents component shrinkage
5. provides better sterility
Figures
Answer (click for answer)
The answer is 3. Sterilization of UHMWP in oxygen is not recommended because it has been linked to fatigue failure of joint replacement bearings. Radiation dissociates molecular bonds and produces free radicals. In the presence of oxygen, these free radicals react with oxygen molecules. This reaction causes embrittlement of the polyethylene and an associated loss of its mechanical properties. This process begins immediately and continues during the implant’s shelf life and in vivo.
Reference: ("Biomaterials in Total Joint Arthroplasty," in OKU6, 1999, pp. 47-53)