Evaluation of Surface Finish and Dimensional Control of Tribological Metal-Ultra High Molecular Weight Polyethylene Pair of Commercially Available Hip Implants

Dimensional control and surface finish of the femoral head and acetabular liner are critical factors in the manufacturing process due to the risk of increased polyethylene wear, which is the primary cause of aseptic failure of a metal/polymer hip prosthesis. The aim of this study is to perform a dimensional and surface finish analysis to evaluate the reproduction and accuracy of the manufacturing processes of metal femoral heads and ultra high molecular weight polyethylene acetabular liners.

Four femoral heads and acetabular liners from 5 manufacturers were evaluated. The methods of evaluation followed the standards ISO 7206-2:2011 and ISO 21535:2010.

The diameter, sphericity, and roughness of the femoral heads from all the manufacturers were in accordance with the standard requirements. Only the sphericity showed a lack of repeatability among the manufacturers. The variability in sphericity was high among some manufacturers and low in others. The diameters of the acetabular liners of 2 manufacturers were not in accordance with the standard requirements. The repeatability of sphericity, thickness, and roughness of the acetabular liners were heterogeneous among the manufacturers, which means that some manufacturers need to improve quality control.

Our results showed a good dimensional and surface finish control of the manufacturing processes of the femoral heads. However, the same control was not shown during the manufacturing of the acetabular liners although all samples had a thickness and sphericity in accordance with the standard. A better quality control of the manufacturing process of ultra high molecular weight polyethylene acetabular liners should be made to improve the dimensional parameters of the acetabular liners and the tribological pair.