Validation of a micro-CT technique for measuring volumetric wear in retrieved acetabular liners

In this study, a novel micro-CT-based technique for evaluating wear in retrieved acetabular liners was introduced and validated. Six UHMWPE acetabular components ranging in implantation time from 2.7 to 14.4 years were collected and evaluated with the use of a high-resolution micro-CT scanner. The components were scanned with a uniform volumetric resolution of 74 microns (16-bit precision) with the use of a 1,024 x 1,024 in-plane image matrix. Manual rigid 3D image registration of the interior hemispherical portion of the acetabular cup with geometric primitives by trained observers allowed for isolation, visualization, and measurement of the wear volume. Results for these six components indicated an average wear rate of 65 mm(3)/year. Overall scanner error was quantified gravimetrically and associated with a maximum uncertainty of 0.6%. Intra-- and interobserver uncertainty analysis showed the method to be both accurate and repeatable.