Metal-on-Polyethylene Total Hip Arthroplasty: Exploring wear and corrosion resistance through visual analysis techniques

Lead Research Organisation: Newcastle University
Department Name: Sch of Engineering

Abstract

Project Introduction
Metal-on-Polyethylene (MoP) is currently the most widely used bearing combination in total hip arthroplasty (THA) devices, accounting for 87.1% of cemented primary hip implants in the UK in 2017. MoP is typically used in small diameter devices in order to limit the production of Polyethylene (PE) wear debris, which causes osteolysis leading to aseptic loosening and failure. These small diameter bearings are widely used but these devices limit patient hip functionality and are susceptible to dislocation; this is the second leading cause of revisions following wear related failures such as osteolysis. These limitations are largely acceptable in older patients who tend to have relatively low functionality prior to implantation, but are problematic for younger patients who are usually more active. Larger diameter bearings combat these limitations, but the accompanying increase in surface area of the bearing results in increased wear debris production and possibly corrosion.

Therefore if it can be shown that, when using modern materials and manufacturing techniques, a large diameter MoP device can perform within acceptable wear and corrosion tolerances compared to existing devices, then the new large-bearing technology could be widely adopted. This would deliver the benefits of large diameter bearings such as larger range of motion and reduced risk of dislocation, , and would increase knowledge of orthopaedic wear and corrosion resistance in general, which could be applied to other implant technologies.

Objectives
The project will investigate and improve corrosion and wear resistance of a novel MoP THA device. This will involve experiments testing the wear resistance, corrosion resistance and fatigue life of sample implants. The main objectives of the project are summarized below:
Year 1: Literature review, design of experiments, manufacture of fixture and hip components, preliminary tests and review paper writing.
Year 2: Wear and corrosion studies, learning and developing XPS sample analysis knowledge, interim paper publication and conference presentation.
Year 3: Design and implement novel upgrades to hip simulator to provide enhanced testing parameters, validation paper publication, conference attendance and thesis commencement.
Year 4: Thesis preparation and finishing experiments, paper publication on updated experimental results, conference attendance and preparation of ISO and ASTM testing body recommendations.

The research undertaken in this project should aid wider adoption of large diameter MoP THA devices, delivering the advantages discussed previously to patients. Additionally, the knowledge gained from this project should improve understanding of wear and corrosion methods, which would lead to the production of hip implants that are more resistant to these; this could also be applied to other orthopaedic devices. To aid in this outcome new testing methodologies will be produced, to be shared with the orthopaedic community. Other outcomes include an assessment of the suitability of modern PE materials for use in large diameter MoP THAs, and the design of a surface analysis sample assessment protocol, for contribution to the National Joint Registry.

Why Newcastle University?
Newcastle University is a Leading UK research centre in the field of bioengineering. The research group is housed in the school of engineering, but also benefits from strong ties with the university's medical school, as well as the NHS, medical charities and leading industrial partners. The research group also benefits from the expertise of multiple leading academics in the field, as well as having an array of equipment and facilities such as NEXUS that will aid the progress of the project.

Publications

10 25 50
 
Description To date the project has achieved several objectives. Firstly, the validation of a new technique for measuring polymeric wear debris (Nanoparticle tracking analysis) from orthopaedic implants has been completed, showing it to be a comparable technique to current alternatives, but with several advantages such as greatly reduced measurement times. Secondly, a study has been undertaken to understand the wear behaviour of modern polyethylene materials when articulating against natural orthopaedic materials, with results from this being presented at WBC2020. Currently, ,studies are being undertaken to determine the wear performance of a novel hip implant and the properties of the synovial fluid substitute bovine calf serum, commonly used in in-vitro testing.
Exploitation Route This is an ongoing project and as such listed findings and outcomes are being used in current work. Once the project is complete more information on suggestions for future users will be made available.
Sectors Manufacturing

including Industrial Biotechology

Pharmaceuticals and Medical Biotechnology

 
Description Validation of Nanoparticle Tracking Analysis for the quantification of the size and concentration of polymeric wear debris particles 
Organisation Malvern Panalytical
Country United Kingdom 
Sector Private 
PI Contribution Sample generation and all tests were conducted by Newcastle University personnel.
Collaborator Contribution Malvern Panalytical provided access to equipment at their facility to be used by Newcastle University researchers. Additionally an employee of Malvern contributed to the formation of a research paper resulting from this work.
Impact A research paper has been generated describing the validation of the technique for measuring polymeric wear debris. This is currently under review. This collaboration has aided the possibility of future research collaborations.
Start Year 2017
 
Description Industry visit and talk 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Postgraduate students
Results and Impact I arranged for the managing director of Orthoplastics, a leading medical grade polymer supplier, to visit the University. This was aimed at increasing ties between the two organisations. The director gave a presentation on the company and their work whilst at Newcastle, which was attended by approximately 30 people. This comprised of postgraduate students, undergraduate students and academics.

Following that I arranged for a tour of our facilities and the research currently underway at Newcastle, including how orthoplastics' products are helping in this.

This lead to increased ties with Orthoplastics, including research assistance with regards to medical polymers and an invitation to visit their manufacturing facility. This is scheduled to occur in 2020.
Year(s) Of Engagement Activity 2019
 
Description Open day talks and Q&A 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Undergraduate students
Results and Impact Assisted on multiple engineering school open days for both undergraduate and postgraduate students. This primarily involves setting up a bioengineering research stand where prospective students and their families can look at work done in this field at Newcastle and ask questions about the topic and the degrees available to them. Additionally, open day work entails guiding prospective students around the campus and being there to answer any broader questions they may have about University life and Newcastle Upon Tyne in general.
Year(s) Of Engagement Activity 2018,2019