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Title: Deformation on impaction of a large diameter carbon fibre reinforced poly- ether-ether-ketone acetabular cup and its effects on the tribology of the bearing
Author: Everitt, Holly
ISNI:       0000 0004 2731 996X
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2011
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Limitations associated with current total hip arthroplasty implants, such as aseptic loosening and dislocation, have led to the investigation into alternative bearing materials such as Carbon Fibre Reinforced PolyEtherEtherKetone (CFR-PEEK). There are reports of press-fit acetabular cups experiencing excessive deformation on impaction into the acetabulum which could lead to unfavourable conditions for bone in-growth and could adversely affect the lubrication regime of the bearing. This may have implications for the use of a reduced modulus material such as CFR-PEEK. The aim of this project was therefore to investigate the level of deformation the prototype Biomet UK Ltd CFR-PEEK cup experiences on impaction into the acetabulum and to assess the effect this deformation would have on the tribological behaviour of the system. In order to achieve this aim three different test regimes were considered; rim loading, impaction into polyurethane foam and impaction into cadaveric bone. In each case, corresponding finite element models were created. To assess the impact cup deformation would have on the lubrication regime of the ceramic-on-CFR-PEEK bearing, friction testing was conducted on cups with various clearances. This study has shown that that the polyurethane foam model is the most suitable method for assessing the level of cup deformation which occurs due to the impaction of a press fit acetabular cup. Testing using cadaveric specimens revealed a high level of variation in both the size of cavity produced by reaming and the level of deformation experienced by the cup. As a result cadaveric testing is unlikely to give a reliable worse case result. It was also found that rim loading is not a valid method for investigating the deformation on impaction of acetabular shells. In order to use rim loading, the load equivalent to that experienced on impaction would have to be found empirically for each individual cup design and size via imperial measurement. The Biomet CFR-PEEK cup experienced a large diametric deformation on impaction of up to 1.084 mm. However, the large clearance between the head and the acetabular cup meant that the deformation of the PEEK cup did not result in jamming of the modular femoral head. The friction testing demonstrated that the bearing was insensitive to changes in clearance; therefore, provided the initial clearance is sufficient the deformation caused by press-fitting should not have an adverse effect on the friction and lubrication of the system.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available