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.