Measurement and Characterization of Wear in Shoulder Replacements

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Around 7000 people undergo primary shoulder replacement surgery every year in the UK whilst around 700 undergo revision surgery according to the National Joint Registry. The primary surgery involves replacement of the shoulder joint due to a number of causes such as osteoarthritis or cuff tear arthropathy. There are three types of shoulder replacements: total, reverse and partial shoulder replacement. The most frequently performed primary procedure was the reverse polarity total shoulder replacement, carried out in 51% of procedures. This was followed by the standard polarity total shoulder replacement, carried out in 30% of procedures (NJR).Currently gravimetric methods are used to quantify wear in the UHMWPE component for in vitro simulator testing to develop new implants. Due to a lack of available methods limited work has been performed regarding retrieval analysis. Also due to the lower number of surgeries performed and lower number of retrieved implants when compared to hip replacements there is a lack of in depth retrieval studies evaluating the performance of shoulder implants. This project will focus on developing wear measurement methods that can be used for analysis of retrieved implants where no pre wear data is available. The developed methods will be compared with gravimetric methods to verify the accuracy and evaluate repeatability. The methods will allow for a better understanding of the wear process and will enable the visualization of the wear area, quantification of volume as well as surface changes. A range of coordinate and surface measurement instruments will be used to gather data from the bearing surface and the mating surfaces of the replacement with bespoke analysis procedures being developed to address the particular geometry of the shoulder implant.