Medel Francisco J, Kurtz Steven M, Hozack William J, Parvizi Javad, Purtill James J, Sharkey Peter F, MacDonald Daniel, Kraay Matthew J, Goldberg Victor, Rimnac Clare M
Implant Research Center, School of Biomedical Engineering, Science and Health Systems, Drexel University, 3401 Market Street, Suite 300, Philadelphia, PA 19104, USA.
J Bone Joint Surg Am. 2009 Apr;91(4):839-49. doi: 10.2106/JBJS.H.00538.
In the 1990s, oxidation was found to occur in ultra-high molecular weight polyethylene total joint replacement components following gamma irradiation and prolonged shelf aging in air. Orthopaedic manufacturers developed barrier packaging to reduce oxidation during and after radiation sterilization. The present study explores the hypothesis that polyethylene components sterilized in a low-oxygen environment undergo similar in vivo oxidative mechanisms as inserts sterilized in air. In addition, the potential influence of the different sterilization processes on the wear performance of the polyethylene components was examined.
An analysis of oxidation, wear, and surface damage was performed for forty-eight acetabular liners and 123 tibial inserts. The mean implantation time was 12.3+/-3.7 years for thirty-one acetabular liners that had been gamma sterilized in air and 4.0+/-2.5 years for the seventeen acetabular liners that had been gamma sterilized in inert gas. The mean implantation time was 11.0+/-3.2 years for the twenty-six tibial inserts that had been sterilized in air and 2.8+/-2.2 years for the ninety-seven tibial inserts that had been gamma sterilized in inert gas. Oxidation and hydroperoxide levels were characterized in loaded and unloaded regions of the inserts.
Measurable oxidation and oxidation potential were observed in all cohorts. The oxidation and hydroperoxide levels were regional. Surfaces with access to body fluids were more heavily oxidized than protected bearing surfaces were. This variation appeared to be greater in historical (gamma-in-air-sterilized) components. Regarding wear performance, historical and conventional acetabular liners showed similar wear penetration rates, whereas a low incidence of delamination was confirmed for the conventional tibial inserts in the first decade of implantation.
The present study explores the impact of industry-wide changes in sterilization practices for polyethylene. We found lower oxidation and oxidation potential in the conventional acetabular liners and tibial inserts that had been gamma sterilized in inert gas as compared with the historical components that had been gamma sterilized in air. However, we also found strong evidence that conventional components undergo mechanisms of in vivo oxidation similar to those observed following gamma irradiation in air. In addition, gamma sterilization in inert gas did not provide polyethylene with a significant improvement in terms of wear resistance as compared with gamma sterilization in air, except for a lower incidence of delamination in the first decade of implantation for tibial inserts.
20世纪90年代，人们发现超高分子量聚乙烯全关节置换部件在伽马射线辐照及在空气中长时间储存老化后会发生氧化。骨科器械制造商开发了阻隔包装以减少辐射灭菌期间及之后的氧化。本研究探讨了这样一个假设，即在低氧环境中灭菌的聚乙烯部件在体内经历的氧化机制与在空气中灭菌的内衬相似。此外，还研究了不同灭菌工艺对聚乙烯部件磨损性能的潜在影响。
对48个髋臼衬垫和123个胫骨内衬进行了氧化、磨损及表面损伤分析。31个在空气中进行伽马灭菌的髋臼衬垫的平均植入时间为12.3±3.7年，17个在惰性气体中进行伽马灭菌的髋臼衬垫的平均植入时间为4.0±2.5年。26个在空气中灭菌的胫骨内衬的平均植入时间为11.0±3.2年，97个在惰性气体中进行伽马灭菌的胫骨内衬的平均植入时间为2.8±2.2年。对内衬的加载区和未加载区的氧化及氢过氧化物水平进行了表征。
在所有队列中均观察到可测量的氧化及氧化电位。氧化及氢过氧化物水平存在区域差异。接触体液的表面比受保护的承重表面氧化更严重。这种差异在传统（空气中伽马灭菌）部件中似乎更大。关于磨损性能，传统髋臼衬垫和历史髋臼衬垫的磨损穿透率相似，而在植入的第一个十年中，传统胫骨内衬的分层发生率较低。
本研究探讨了聚乙烯灭菌方法行业范围内变化的影响。我们发现，与在空气中进行伽马灭菌的历史部件相比，在惰性气体中进行伽马灭菌的传统髋臼衬垫和胫骨内衬的氧化及氧化电位更低。然而，我们也发现有力证据表明，传统部件在体内经历的氧化机制与在空气中伽马辐照后观察到的相似。此外，与在空气中进行伽马灭菌相比，在惰性气体中进行伽马灭菌并未使聚乙烯的耐磨性有显著改善，不过胫骨内衬在植入的第一个十年中分层发生率较低除外。
