Determination of clinical wear in retrieved total hip replacement joints using shadowgraph and co-ordinate measurement methods

Over the last twenty years or so, a number of increasingly complex joint simulators
have been developed and manufactured to evaluate new designs of total joint replacement. This
has been in response both to the greater understanding of joint biomechanics and the increase in
regulatory and pre-clinical testing required by law to ensure patient safety and product reliability.
Upon simulation of this clinically relevant wear it is important that it can be accurately quantified
and assessed. Furthermore it is vital to be able to assess whether in vitro produced component
wear is representative of true clinical wear, in order to audit the capability of the laboratory
testing to replicate real-world patient relevant conditions. To achieve this methods have been
developed to accurately quantify in vivo total joint replacement wear from retrieved total hip
replacement components. This paper explores two methods for determination of such clinical
wear and discusses the relative advantages of using each. To do this a number of retrieved total
hip replacement acetabular components were assessed for both volumetric and linear wear using
previously developed shadowgraph and co-ordinate measurement techniques and the results
reported and compared.