| Summary: | Due to the fact that a growing number of young patients require joint replacements, the expected lifetime of the prostheses is considerably increasing, and patient activities are becoming more demanding. New materials and designs are being introduced. The technical challenge lies in developing new designs, with high-performance materials, and low wear to improve prosthesis life. The main issue is to pre-clinically investigate the new materials and designs. Many researchers have reported wear in total knee replacements investigated in simulators. A single simulator test can be very expensive and take a long time to run. Computational wear modelling is an alternative attractive solution to these limitations, particularly when combined with experimental studies to provide input as well as validation. However, historical computational wear models have adopted the classical Archard's wear law, which was developed for metallic materials, and have selected wear factors arbitrarily from literature. It is known that such an approach is not generally true for polymeric bearing materials and is difficult to implement due to the dependence of wear factors on contact pressure as well as cross-shear. Therefore, these studies are generally not independent and lack general predictability. The objective of the present study was to develop a new computational wear model for the knee implants, where the wear volume dependent on sliding distance and contact area, based on an independent experimentally determined non-dimensional wear coefficient. The effects of cross-shear and creep on wear predictions were also considered. Independent experimental pin-on-plate multi- directional wear tests were conducted to provide the required input parameters. The output results from the new computational model were compared with the data from the experimental knee simulation tests in Leeds and parametric studies for different designs, materials and different operating conditions were conducted. The results suggested that the computational wear modelling, based on the new wear law and the independent -experimentally calculated non-dimensional wear coefficient, were more reliable, and therefore provide a more robust virtual modelling platform. In addition, the results showed that potential methods for increasing the expected total knee replacement lifetime might be to introduce less conforming knee replacement and to use cross-linked polyethylene as a bearing material.
|
|---|
