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Polyethylene acetabular liner rim damage in total hip replacements

Pryce, Gregory Max (2019) Polyethylene acetabular liner rim damage in total hip replacements. PhD thesis, University of Leeds.

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Abstract

Total hip replacement surgery is a successful orthopaedic intervention with over 90,000 procedures carried out annually; however, some implants still fail. The failure of THRs in the first year have been related to mechanical failure, such as dislocation and/or implant fracture. The mechanical failure of polyethylene liners has been mainly associated with damage at the rim of liners, due to edge loading and/or impingement. Implant failure typically leads to the revision of the implant, which is more costly and predominately less successful for the patient; therefore, the occurrence and consequence of impingement and dislocation are required to be understood to reduce mechanical failure of future THRs. The aim of this project was to investigate and characterise rim damage of polyethylene liners of THRs. To understand the occurrence of impingement, a geometric model was developed that incorporated THR components into a bone model and investigated impingement during different dislocation-prone activities. The model was applied to investigate the effect that varying the surgical positioning of the acetabular component and the component design has on the likelihood of impingement. In terms of the positioning of the acetabular component, increasing the inclination and anteversion of the acetabular cup reduced the risk of impingement. Varying the design of the liner from a neutral to a lipped liner caused more frequent impingement, and reducing the neckshaft angle reduced the frequency of impingement. To understand what rim damage is caused by impingement, methods were developed to quantitatively assess rim damage of polyethylene liners and to experimentally replicate clinically relevant rim damage due to impingement. The method applied motion and load inputs to simulate a clinically relevant activity, and was applied to investigate the effect of varying the severity of impingement and medial-lateral load has on the severity of damage. Increasing the severity of impingement was found to increase the severity of rim damage and the amount of separation of the head. To check the clinical relevance of the results from the developed geometric model and the experimental method, a series of retrieved polyethylene liners of the same design were reviewed; damage was visually assessed, rim damage quantified, and invivo orientation of components were measured. Overall the series of developed methods have been used to assess and characterise rim damage of polyethylene liners, and the methods have the potential to assist with the pre-operative planning of THR surgeries, pre-caution post THR surgery and aid with the design process of future designs of implants.

Item Type: Thesis (PhD)
Academic Units: The University of Leeds > Faculty of Engineering (Leeds) > School of Mechanical Engineering (Leeds) > Institute of Medical and Biological Engineering (iMBE)(Leeds)
Depositing User: Mr Gregory M Pryce
Date Deposited: 28 Nov 2019 16:28
Last Modified: 28 Nov 2019 16:28
URI: http://etheses.whiterose.ac.uk/id/eprint/25448

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