Wear measurement of polyethylene components in total knee replacement

The total knee replacement (TKR) was designed to provide final-stage treatment for patients to replace the damaged biological tissues and help the patient to carry out daily normal activities. Determination of wear of the polyethylene knee inserts has been an important subject in improving the longevity of TKR. Accurate wear measurement methodologies are essential to differentiate between the performance of different materials and designs because the geometry changes can be small and can consist of both wear and creep. The aim of this study was to develop a coordinate based threedimensional volumetric determination methodology using CMM and Micro-CT measurement techniques. The validation of the methodology was carried out using a FE model and computational volume removal test. Afterwards, the volumetric determination method was used to calculate the volume loss from computational and experimental tests of volume removal and creep deformation. Finally, the methodology was applied to evaluate both simulator and retrieval specimens. The studies indicated the presented volumetric determination methodology was not dependent on pre-wear data, CAD model or original design drawings and can be used for both simulator and retrieval analysis at relevant levels of wear and creep. It can also be applied to the biotribological study of other polyethylene components, since wear and damage can be assessed visually and volumetrically. The comparison between CMM and Micro-CT methods suggested that the CMM has higher accuracy and better repeatability. Whilst the methods developed in this thesis were suitable for laboratory and computational wear determination, they are not suitable for all specimens in retrieval study due to the greater amount of wear and damage on the surface.