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Validation of a Deconvolution Technique for Quantifying Short-Term Wear in a Conventional and Highly Crosslinked Acetabular Components
Kurtz, S. M., Turner, J., Herr, M. P., Edidin, A. A.
Abstract
The reduction of volumetric wear continues to be one of the imminent challenges for the orthopaedic research community in the area of UHMWPE. Retrieval analyses are necessary to determine the relationship between in vitro hip simulator predictions and actual wear performance in vivo. In order to quantify short term wear in retrieved highly crosslinked acetabular components it is necessary to differentiate between the initial surface morphology (dominated by manufacturerís machining marks) and the smaller scale surface features associated with the in vivo adhesive/abreasive wear mechanisms. We have developed and validated a technique for deconvolution of as-manufactured versus in vivo generated surface topology from retrieved, highly crosslinked polyethylene acetabular inserts. Surface topology was characterized by white light interferometry with advanced texture analysis software. A Fourier transform algorithm was used to deconvolve the low-frequency features (i.e. waviness) such as machining marks, from the high-frequency features (i.e. roughness), most likely representing wear in retrieved components. Thirteen new (never implanted) and sixteen short-term (less than 24 months) conventional and highly crosslinked retrievals from different manufacturers were evaluated in this study. The wear surfaces in the short-term retrievals were deconvolved using the cut-off frequencies from the new inserts. The frequency distribution and magnitude of the machining marks were found to be material and manufacturer specific. This study highlights the importance of quantitative techniques, such as white light interferometry for distinguishing between initial and in vivo generated surface morphology. The topology observed in the crosslinked retrievals was consistent with the surface damage mechanisms previously observed in conventional UHMWPE components, namely third-body and adhesive/abrasive wear.
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