Galloway Award 2018

The latest recipient is Mohamed Koronfel (Imperial College), for his work on “Understanding the reactivity of CoCrMo-implant wear particles”, published in Nature|Materials Degradation (doi:10.1038/s41529-018-0029-2)
The Galloway Award requires students to simply send a copy of a submitted or published paper from the previous 12 months, rather than a separate technical report. The student must be the primary author of the work and preferably first author.
CoCrMo alloys have been considered as an attractive material for orthopaedic implants due to their high wear and corrosion resistance. However, in practice, the release of millions of wear particles per patient annually led to high failure rates of CoCrMo Metal-on-Metal hip implants. These wear particles invoke an inflammatory response in the patient, where immune system cells (macrophages) are recruited to attack the wear particles. The inflammation comes with an associated severe pain that often leads to revision surgery and implant removal (failure). Due to the unexpectedly high failure rates, lawsuits were filed in both the UK and USA against the implants’ manufactures. Furthermore, due to unknown long-term effect of these wear particles, clinical risks to patients may manifest even long after revision surgery. The macrophage cells, where wear particles were typically found in vivo, create a harsh acidic, oxidising environment which may lead to the release of potentially toxic and carcinogenic metal ions.
A number of studies characterised the state of wear particles inside macrophages in periprosthetic tissue (accessible after implant removal during revision surgery). Although CoCrMo alloys are nominally an extremely stable material and contain very high levels of Cr (Co 60 % : Cr 30 % : Mo 7 %), the post-surgery wear particles were composed mainly of Cr and only trace amounts of Co. This high-level of Co dissolution is unexpected given the alloy’s stable Cr-rich passive film. Studies on periprosthetic tissue after implant failure provide little insight into the dissolution stages and exposure history imposed on wear particles in vivo. In order to understand the in vivo reactivity of wear particles, in situ monitoring of their chemical and physical changes in simulated biologically relevant conditions was carried out, using X-ray absorption spectroscopy and transmission X-ray microscopy at synchrotron-radiation facilities, which provide high chemical sensitivity and in-situ measurement capabilities.
This work highlights the potential reaction mechanisms that would not have been evident from the required regulatory testing regimes. Additionally, the work demonstrates the potential of synchrotron-based approaches to provide dynamic chemical information on nanoscale systems under practical conditions.

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