Wear zones on retrieved metal femoral heads from metal-on-polymer hip prostheses
2013 (English)Conference paper, Poster (Other academic)
Total hip joint replacement is one of the most commonly performed orthopaedic procedures; in 2010 in Sweden alone almost 16 000 primary procedures were performed. The implants have a relatively high success rate of 95% after 10 years. However, adverse biological reactions to wear particles can cause inflammation, bone resorption and later loosening of the implant. Aseptic loosening is the most common cause for revision surgery, causing 73% of the failures. The amount, size and shape of the wear particles will depend on the bearing surfaces in the hip joint and affect the biological response. Understanding the wear patterns of the bearing surfaces is therefore of great importance. Previously surface analysis in combination with cross-section studies have mainly focused on metal-on-metal implants.
In this study explanted femoral heads that had worn against polyethylene in vivo were investigated, all retrieved due to aseptic loosening. The heads were made of cobalt chromium alloy or stainless steel. The surface roughness was studied using an optical profiler while the surface appearance and chemistry were studied in scanning electron microscopy and energy-dispersive X-ray spectroscopy. The subsurface microstructure was studied in transmission electron microscope.
It was found that the surface appearance varied significantly over the femoral head. Typically, the wear-zone on the top of the sphere of the cobalt chromium implant was dominated by scratches. Around the sides, the wear pattern changed depending on the orientation of the implant in vivo. On the sides of the head another typical wear zone was found, dominated by irregular Mo-Cr-rich areas. Often the worn surface showed a combination of these two zones. For the stainless steel head the scratches were more dominant on the sides than on the top. Subsurface investigation on a femoral head showed substantial twinning near the surface.
Place, publisher, year, edition, pages
Metallurgy and Metallic Materials Medical Materials
IdentifiersURN: urn:nbn:se:uu:diva-221305OAI: oai:DiVA.org:uu-221305DiVA: diva2:708443
19th International Conference on Wear of Materials (WOM), Portland, United States, 14–18 April 2013