About the Project
The chosen PhD candidate will investigate the wear of ultra-high molecular weight polyethylene, which is a material used for joint replacement implant bearings.
Polyethylene is one of the most commonly used polymers for medical implants and devices. Over 100,000 polyethylene hip replacement and 100,000 knee replacement operations are performed in England and Wales each year. The population of the UK is aging, the number of operations are increasing each year, and more joint replacements are being performed in younger patients. This creates a significant societal burden, and it is crucial that the implants themselves last as long as possible to minimise the risk of further surgery.
Polyethylene is used as a bearing material in joint replacements because it has a very low wear rate, but implants are also expected to last decades, some wear is unavoidable. The consequences of implant wear are severe. Polyethylene wear debris is known to cause osteolysis (loss of bone) and implant loosening, which is the most common cause of replacement failure (National Joint Registry 13th Annual Report). Excessive implant wear can alter implant function and in severe cases cause fracture.
Wear simulator testing is the most common method used to predict implant wear, but it is costly, tends to involve repetitive motions rather than representing the variety of activities and movements of the natural joint, and results do not always predict clinical findings.
The aim of this project is to improve our understanding of polyethylene wear by examining the influence of different loading patterns on the chemical structure of polyethylene and its mechanical properties. From this data a numerical model will be created to represent the behaviour which could be implemented into finite element software packages.
We are looking for a highly motivated candidate with a strong background in materials, engineering, finite element analysis, or related area to research this important issue. The project will involve a combination of laboratory testing and finite element simulation work.
By the end of the doctorate the candidate will:
• have extensive knowledge of biomaterial safety and design
• have been trained in a wide range of materials characterisation techniques
• be able to develop numerical models to represent polymeric materials and perform computational simulations to predict behaviour
• be an expert in polyethylene biomaterials
• have presented their work at, at least, one international conference and built up a network of contacts
This research project aims to answer the following questions:
1. How does the crystallinity and alignment of the polyethylene surface change in response to different loading conditions (e.g. translation, rotation, impact, and combinations)
2. How do any chemical changes influence the mechanical properties, such as polyethylene wear
3. Are these differences consistent for different polyethylene resin types and manufacturing treatments (such as highly cross-linked polyethylene)
4. Do retrieved implant samples demonstrate equivalent material changes to those created in the laboratory?
5. Can a material model be created to accurately predict polyethylene wear in a clinical scenario?
The candidate will have the opportunity to work with researchers within the medical device industry in the later stages of the project, as well as potentially collaborating directly with surgeons and clinical staff. Furthermore, the University of Bath provides a wide range of training courses, teaching opportunities, and career support for PhD students.
There will be opportunities to collaborate with the medical device industry and create contacts internationally.
Applicants should have, or expect to achieve, a first class Masters degree in one of the following areas: materials science, biomedical engineering, engineering, chemical engineering, engineering, physics, or similar related discipline. Applicants must have good written and verbal English communication skills.
Funding Notes
A Home/EU award will cover tuition fees, a training support fee of £1,000/annum, and a tax-free maintenance payment of £14,553 (2017-8 rate) for up to 3.5 years.
An Overseas award (3 years): Provides tuition fee, £1000 per year Training Support Grant, but no stipend.
The successful applicant will ideally have graduated (or be due to graduate) with an undergraduate Masters first class degree and/or MSc distinction (or overseas equivalent).
English language requirements must be met at the time of application to be considered for funding.