Verschleißverhalten von Polyäthylen beim künstlichen Kniegelenkersatz

Polyethylene wear is a major cause of aseptic loosening of knee endoprostheses. In clinical use the long-term wear resistance of a specific tibial plateau in artificial knee-joints will depend on numerous factors, including the type of polyethylene from which it was fabricated, the fabrication, the type of sterilization used, the type of implant (high or low conformity knees), the duration of shelf-storage prior to implantation, duration of use in vivo, and depth within the polymer to which wear has progressed. The influence of each of these complex and interactive parameters on the long-term wear resistance of polyethylene components is discussed in this work. Therefore, goal of this work was the description of specific material-properties of polyethylene as the tibial plateau in artificial knee-joints. Especially the material-properties of ultra high molecular weight polyethylene (UHMWPE) as a bearing-component in knee-prostheses were demonstrated. After an introduction with basic knowledge about the material science of polymers, there is a digest about the history of UHMWPE as a tibial component in knee-prostheses. A description of major problems of polyethylene in clinical use is followed by a discussion of the available methods of sterilization of orthopaedic implants made of polymers. Good in vitro results in long-term-resistance were achieved by WIRTZ et al., minimizing mechanical wear of UHMWPE by stretch-modifying the structure of polyethylene. Translating these results to unidirectional tractive rolling on the tibial plateau in the knee joint suggests that a significant reduction in polyethylene wear can be expected. Optimizing the long-time results of artificial joint-prostheses is a very complex enterprise where a lot of further interdisciplinary research has to be done