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Queen Mary University of LondonQueen Mary University of London
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School of Engineering and Materials Science
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PhD Thesis: The extraction and characterisation of wear particles from tissues around failed orthopaedic implants of different designs.

Author: YAMAC, Tuba

Year: 1999

Supervisor(s): Peter Revell

Wear particles of ultra-high molecular weight polyethylene (UHMWPE), metal and bone cement at the bone/implant interface have been implicated as the cause of total joint replacement loosening subsequent to the inflammatory response which they induce. The accurate characterisation of wear particles is necessary for further understanding of the mechanisms of loosening.
The work in this thesis has involved the utilisation of a method to separate the UHMWPE particles from tissue, detect them using scanning electron microscopy and characterise them according to specific mathematical parameters. For the first time, the number of particles accumulated in the tissue has also been determined. A novel method has been developed to extract metal wear particles from tissue and characterise them in a similar way using high resolution techniques.

The particle extraction methods were applied separately to samples obtained from a series of Freeman-type joint replacements. Differences in particle parameters between total hip and knee replacements and in samples from areas of focal bone resorption were investigated. UHMWPE and metal particles were extracted from the same tissue samples in cases which had been implanted with Bateman bipolar prostheses, allowing direct comparison of the two particle species. Also in this series, the factors affecting the wear rate of the implant were investigated, such as duration of implantation and oxidation of the UHMWPE following irradiation sterilisation. The retrieved implant surfaces were also studied in order to investigate the source of the UHMWPE particles.