McGovern Thomas F, Ammeen Deborah J, Collier John P, Currier Barbara H, Engh Gerard A
Anderson Orthopaedic Research Institute, Alexandria, Virginia 22306, USA.
J Bone Joint Surg Am. 2002 Jun;84(6):901-6. doi: 10.2106/00004623-200206000-00002.
The mechanical toughness of polyethylene that has been sterilized by gamma irradiation in air decreases after a long shelf life. The purpose of the present study is to report the high failure rate after unicondylar knee replacements performed with polyethylene bearings that had been sterilized with gamma irradiation in air and implanted after a shelf life of < or = 4.4 years.
Between December 1997 and January 2000, seventy-five unicondylar knee replacements were performed in sixty-two patients. All patients were followed both clinically and radiographically. A revision operation was offered when the patient had pain, swelling, and radiographic evidence of rapid polyethylene wear. The effect of aging of the polyethylene during storage was evaluated by dividing the knees into three groups on the basis of shelf life and comparing them with regard to the rate of revision and the observed wear of the polyethylene. Four retrieved components were examined for the presence of oxidation.
At a mean of eighteen months after the arthroplasty, thirty knees had been revised and seven were scheduled for revision. The rate of polyethylene wear increased as the shelf life increased. There was a significant inverse linear correlation between the shelf life of the polyethylene and the time to revision (p < 0.01, r (2) = 0.64). All retrieved components had greater-than-expected wear with pitting and delamination of the surface. Seven components had fractured, and ten had both fractured and fragmented. Analysis of four components confirmed severe oxidation of the polyethylene.
The present study demonstrated early, severe wear of tibial polyethylene bearings that had been sterilized by gamma irradiation in air and stored for < or = 4.4 years. This risk can be minimized by ensuring that implants have not been sterilized with gamma irradiation in air and stored for several years.
在空气中经伽马射线辐照灭菌的聚乙烯，其机械韧性在较长保质期后会降低。本研究的目的是报告使用在空气中经伽马射线辐照灭菌且保质期小于或等于4.4年的聚乙烯轴承进行单髁膝关节置换术后的高失败率。
1997年12月至2000年1月期间，对62例患者实施了75例单髁膝关节置换术。所有患者均接受临床和影像学随访。当患者出现疼痛、肿胀以及聚乙烯快速磨损的影像学证据时，建议进行翻修手术。根据保质期将膝关节分为三组，评估储存期间聚乙烯老化的影响，并比较它们的翻修率和观察到的聚乙烯磨损情况。对四个取出的部件进行氧化检测。
平均在关节置换术后18个月时，30例膝关节已进行翻修，7例计划进行翻修。聚乙烯磨损率随保质期延长而增加。聚乙烯的保质期与翻修时间之间存在显著的负线性相关性（p < 0.01，r² = 0.64）。所有取出的部件磨损均超过预期，表面出现点蚀和分层。7个部件发生断裂，10个部件既有断裂又有破碎。对四个部件的分析证实聚乙烯存在严重氧化。
本研究表明，在空气中经伽马射线辐照灭菌并储存小于或等于4.4年的胫骨聚乙烯轴承会出现早期严重磨损。通过确保植入物未在空气中经伽马射线辐照灭菌并储存数年，可将这种风险降至最低。
