Comparison of the in vivo wear rates of 43 surgically retrieved direct compression molded and ram extruded ultra high molecular weight polyethylene acetabular components.

The objective of this study was to investigate retrieved ultra high molecular weight polyethylene (UHMWPE) liners from Total HIp Arthroplasty (THA) revisions. The amount of in vivo wear on compression molded v. ram extruded and machined acetabular liners was the focus of comparison between 43 surgically retrieved samples. The principal experimental methods were scanning electron microscope (SEM) observations and a fluid displacement method to quantify volumetric wear. SEM observations revealed similar wear mechanisms between the compression molded and ram extruded and machined UHMWPE retrieved liners. More third body wear corresponded with more volumetric in vivo wear. This study found that the ram extruded and machined UHMWPE liners had a significantly larger average wear rate than the compression molded UHMWPE liners. In order to determine whether the observed difference in wear rates can be attributed to the different types of UHMWPE processing, a more controlled experiment would have to be performed.