Ries M D, Weaver K, Rose R M, Gunther J, Sauer W, Beals N
The Mary Imogene Bassett Hospital, Cooperstown, NY 13326, USA.
Clin Orthop Relat Res. 1996 Dec(333):87-95.
The oxidation level of ultrahigh molecular weight polyethylene specimens sterilized by gamma irradiation in either air or Ar gas was compared with that of unsterilized and ethylene oxide sterilized ultrahigh molecular weight polyethylene. The fatigue strength of ultrahigh molecular weight polyethylene specimens sterilized by gamma irradiation in air was compared with that of unsterilized and ethylene oxide sterilized ultrahigh molecular weight polyethylene. At the specimen surface, oxidation was highest for ultrahigh molecular weight polyethylene gamma irradiated in air, lower for ultrahigh molecular weight polyethylene gamma irradiated in Ar gas, and absent in unsterilized and ethylene oxide sterilized ultrahigh molecular weight polyethylene. At a depth of 3.5 mm below the specimen surface, oxidation levels were equivalent for ultrahigh molecular weight polyethylene gamma irradiated in either air or Ar gas whereas unsterilized and ethylene oxide sterilized specimens were again unoxidized. Thus, even in an inert atmosphere, oxidative degradation of gamma irradiated ultrahigh molecular weight polyethylene occurs. The 10 million cycle fatigue strength was similar for unsterilized and ethylene oxide sterilized ultrahigh molecular weight polyethylene whereas the fatigue strength of gamma irradiated in air ultrahigh molecular weight polyethylene was lower. Results of this study show that ethylene oxide gas does not degrade ultrahigh molecular weight polyethylene whereas gamma radiation in air causes changes in the polymer that adversely affect its mechanical properties. Ethylene oxide gas is a viable alternative to gamma radiation in air that avoids oxidation and fatigue strength degradation known to accompany irradiation of ultrahigh molecular weight polyethylene polymer bearing surfaces in total joint implants.
将在空气或氩气中通过伽马射线辐照灭菌的超高分子量聚乙烯样本的氧化水平，与未灭菌以及经环氧乙烷灭菌的超高分子量聚乙烯的氧化水平进行了比较。将在空气中通过伽马射线辐照灭菌的超高分子量聚乙烯样本的疲劳强度，与未灭菌以及经环氧乙烷灭菌的超高分子量聚乙烯的疲劳强度进行了比较。在样本表面，在空气中进行伽马射线辐照的超高分子量聚乙烯氧化程度最高，在氩气中进行伽马射线辐照的超高分子量聚乙烯氧化程度较低，而未灭菌以及经环氧乙烷灭菌的超高分子量聚乙烯则未发生氧化。在样本表面以下3.5毫米深处，在空气或氩气中进行伽马射线辐照的超高分子量聚乙烯的氧化水平相当，而未灭菌以及经环氧乙烷灭菌的样本再次未被氧化。因此，即使在惰性气氛中，伽马射线辐照的超高分子量聚乙烯也会发生氧化降解。未灭菌以及经环氧乙烷灭菌的超高分子量聚乙烯的1000万次循环疲劳强度相似，而在空气中进行伽马射线辐照的超高分子量聚乙烯的疲劳强度较低。本研究结果表明，环氧乙烷气体不会使超高分子量聚乙烯降解，而在空气中进行伽马射线辐照会导致聚合物发生变化，从而对其机械性能产生不利影响。环氧乙烷气体是空气中伽马射线辐照的可行替代方案，可避免已知伴随全关节植入物中超高分子量聚乙烯聚合物轴承表面辐照而出现的氧化和疲劳强度降低问题。
