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[Changes in crystallinity by sterilization and processing of ultrahigh molecular polyethylene used in
1Klinik und Poliklinik für Allgemeine Orthopädie, Westfälische Wilhelms Universität, Münster.
Purpose Of The Study:
We wanted to analyze crystallinity changes during sterilization in raw and in UHMWPE components for total joint arthroplasty manufactured.
Materials And Methods:
To analyze the crystallinity DSC measurements and to determine the relative crystallinity infrared spectroscopy was performed. The DSC measurements were based on a comparison between the melting enthalpy of one known material to the unknown material.
Results:
The raw manufactured non-sterilized sample showed a value for the DSC-measured crystallinity of 55.5%; the sample after gamma-sterilization without air was 56.0%, and with air 56.5%. The crystallinity after ethylene-oxide sterilization was 57.7% and after autoclavation 57.9%. The manufacturing time from the raw to the arthroplasty part showed some what different results. The average crystallinity of the samples differed between 55.4% and 61.6%. The best results were achieved in ETO-sterilized samples and one gamma-sterilized sample without air. The highest values were seen for the Hylamer.
Conclusion:
In summary, the best values for crystallinity were seen in both raw and completed arthroplasty products with ETO sterilization. For medical use cancerogenous factors must be excluded. Gamma-sterilization without air can be accepted as well. Increasing the crystallinity too much can lead to more wear debris.