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Micro-structural alterations within different areas of articulating surfaces of a metal-on-metal hip resurfacing system
Publikationstyp
Journal Article
Date Issued
2009-06-15
Sprache
English
Author(s)
Journal
Volume
267
Issue
5-8
Start Page
689
End Page
694
Citation
Wear 267 (5-8): 689–694 (2009)
Publisher DOI
Scopus ID
Publisher
Elsevier
Metal-on-metal hip arthroplasties have been successfully implanted for many years. During the last decade the metal-on-metal hip resurfacing has also experienced a renaissance. Both perform low wear rates due to nano-meter-scale wear particles. These particles represent a limitation causing harm to the human body. In order to investigate the emission of wear particles in ultra-low wear systems micro-structural changes in the subsurface-region have to be well understood. Previous studies of metal-on-metal total hip arthroplasties have revealed that an in situ formation of a nano-crystalline layer together with mechanical mixing enables the CoCrMo alloy to adjust to the current load situation and maintain a low wear rate. However, only little is known about the wear performance of hip surface replacements which are exposed to a different stress/strain situation. For this study a Durom hip resurfacing system (Zimmer, Warsaw, USA) with a 46-mm diameter was analyzed by means of transmission electron microscope (TEM) and electron energy loss spectroscopy (EELS) with energy filtered TEM (EFTEM). The results were compared to earlier findings for total hip arthroplasties. For the sampling locations three zones were chosen according to geometry and wear appearances: (1) primary articulating contact zone, (2) a zone which received edge loading and (3) inferior area of the cup. In the primary wear zone of the femoral component a nano-crystalline layer with a thickness of 250-400 nm and grain size of 25-40 nm occurred. This layer must be the origin of wear particle detachment. The EELS measurements showed no incorporation of carbon in-between the nano-crystals, whereas in THA samples it occurred down to a depth of 200 nm. This carbon is suspected to be of organic origin. In the second area a nano-crystalline layer of 100-150 nm exhibited a sharp border to another layer of orientated ε-martensite needles underneath. This paper will compare the different zones and relate the structure and chemistry to the differing load histories. The results will be compared to earlier findings for total hip arthroplasties.
Subjects
CoCrMo
Hip joint
Metal-on-metal
Microstructure
Sliding wear
TEM
DDC Class
610: Medicine, Health
620: Engineering