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Understanding the reactivity of CoCrMo-implant wear particles

DOI: 10.1038/s41529-018-0029-2 DOI Help

Authors: Mohamed A. Koronfel (Imperial College London) , Angela E. Goode (Imperial College London) , Johanna Nelson Weker (Stanford Synchrotron Radiation Lightsource) , Stephen E. R. Tay (Imperial College London) , Camilla A. Stitt (Imperial College London) , Thiago A. Simoes (University of Leeds) , J. Frederick W. Mosselmans (Diamond Light Source) , Paul Quinn (Diamond Light Source) , Rik Brydson (University of Leeds) , Alister Hart (Royal National Orthopaedic Hospital) , Michael F. Toney (Stanford Synchrotron Radiation Lightsource) , Alexandra E. Porter (Imperial College London) , Mary P. Ryan (Imperial College London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Npj Materials Degradation , VOL 2

State: Published (Approved)
Published: March 2018
Diamond Proposal Number(s): 4843 , 9797

Open Access Open Access

Abstract: CoCrMo-based metal-on-metal hip implants experienced unexpectedly high failure rates despite the high wear and corrosion resistance of the bulk material. Although they exhibit a lower volumetric wear compared to other implant materials, CoCrMo-based implants produced a significantly larger 'number' of smaller wear particles. CoCrMo is nominally an extremely stable material with high Cr content providing passivity. However, despite the Co:Cr ratio in the original alloy being 2:1; chemical analyses of wear particles from periprosthetic tissue have found the particles to be composed predominately of Cr species, with only trace amounts of Co remaining. Here a correlative spectroscopy and microscopy approach has shown that these particles dissolve via a non-stoichiometric, and geometrically inhomogeneous, mechanism similar to de-alloying. This mechanism is previously unreported for this material and was not apparent in any of the regulatory required tests, suggesting that such tests are insufficiently discriminating.

Journal Keywords: Characterization and analytical techniques CoChrome Implants

Subject Areas: Biology and Bio-materials, Chemistry


Instruments: I20-Scanning-X-ray spectroscopy (XAS/XES)

Other Facilities: SSRL

Documents:
s41529-018-0029-2.pdf