Precision of wear measurement using the shadowgraph technique

The shadowgraph technique is a relatively easy-to-use and inexpensive method of wear measurement from explanted acetabular cups. In this technique, from a mould of the internal surface of the cup, measurements of linear wear and wear angle can be obtained, from which volumetric wear can be calculated. In this study the measurement precision of this technique was assessed and the influence of different observers and multiple moulds was also determined. It was found that linear wear coefficient of variation (CV)=1.49 per cent) can be more precisely determined than wear angle (CV=8.18 per cent) and that both the observer and the mould can significantly influence the results obtained, although the influence of the mould is considerably less than that of the observer.