Process Design to Prevent Prosthetic Infections

Lead Research Organisation: University of Birmingham
Department Name: Chemical Engineering

Abstract

Most prosthetics used to replace joint function in the body have a very low chance of infection (<2%). When prosthetics must be inserted following trauma or where individualised implants must be made for patients, the chances of infection are significantly increased and can be as high as 50%. Treatment requires removal of the prosthetic and the implantation of another material that releases high-levels of antibiotics to the site of infection and causes a major risk to the health of the patients. The excessive use of antibiotics is one of the factors that has provoked a rise in the frequency of bacteria that are resistant to antibiotics. Consequently, there is a significant need to develop processes and designs for implants that have enhanced resistance to bacterial contamination. In this project, we will use a combination of 3D printing and silver coating to refine current methods of processing and produce surfaces that are resistant to bacterial infection. We will work with clinicians and industrial partners to develop technologies that can be used with lots of different kinds prosthetics, however, our first target is to reduce infections following the implantation of a metallic plate in the skull.

Many different clinical conditions require that a surgeon makes a hole in the skull of a patient to allow for treatment. This allows the surgeon to relieve pressure, caused by swelling following head injury, or to work on the underlying brain tissue. Although most orthopaedic implants come in a range of sizes that can be made to fit patients, metallic implants that are used in the skull (and the defect), do not fit without further structural refinement. At the moment, these implants are made in hospitals by bending a titanium (or other metal sheet) over a 3D printed model of the defect and then polishing and dipping the surface in acid before sterilisation at more than 100oC. Although this kills the majority of contaminating bacteria, the incidence of infection following the implantation of these plates is much higher than with other metallic implants made outside the clinic (12-50% compared with 2%). If an infection occurs, the plate must be removed from the patient's skull, the site cleaned, and then another plate can be fixed in place. This process is dangerous for the patients since it increases risk due to anaesthesia, further infection and requires that the individual spends a period of time without a plate in place, meaning that the brain remains relatively unprotected.

We aim to use technology that has been developed in a previous EPSRC project (NIDMET) to reduce the incidence of infection following the fitting of a cranial plate. We will refine an existing additive layer manufacturing process so that we are able to produce something quickly, accurately, to a high quality and surface modified with silver such that it is resistant to microbial contamination and therefore unlikely to cause infection. If we are able to reduce the incidence of infection even down to that associated with orthopaedic implants, we will improve the life of a considerable number of patients reducing costs, in terms of days of hospitalisation and cost of treatment.

We will use additive layer manufacturing methodologies to address another major problem that is associated with cranial plates: artefacts that are created by the plate material in a type of MRI scanner that mean that the implant or implant site cannot be evaluated using this important imaging method. We will address incompatibility of the material with gradient field MR imaging using a process that is called topological optimisation. This is an operation that is undertaken by a computer to modify the structure of something so that it is possible to minimise the amount of material that is required for a particular structure. Minimising material, particularly around the edge of the implant, will reduce the imaging problems associated with cranial implants.

Planned Impact

Patients: This research will ultimately be of the most benefit to patients. The implications of a prosthetic related infection are clear, with pain, threat to life and temporary (or even permanent) loss of function being major associated risks. The costs of treating these infections and associated loss of working days are both significant and are a burden to the UK NHS and thereby also the taxpayer, meaning that this work would be of potentially significant benefit to both.

Clinicians: The findings of this project would also be of significant importance to the clinicians that are involved in fitting prosthetics that are associated with a higher than normal likelihood of failure. These infections would rarely be associated with poor surgical technique, yet they could be taken to reflect the practice of the fitting clinician, potentially causing severe reputational damage.

The medical technology sector: The work would be of great benefit to two small medical technology companies in the UK (Accentus Medical and Cavendish) and would help them to move their technologies more rapidly into the clinic, potentially (through partnership with the Birmingham Health Partner Hospitals and the military) into widespread use. This would subsequently be of benefit to the economy through job creation and the UK government through increased tax collection.

Educational beneficiaries: Such a multidisciplinary collaboration, particularly with an emphasis on technical development, clearly has great potential from the point of view of training and education. Implant design and regenerative medicine capture the imagination of the general public and are excellent out-reach tools to inspire future generations of researchers into the STEM subjects. We have also found significant educational value in opening many of our design problems to final year engineers (in an appropriate non-confidential manner) who enjoy tackling real-world problems. Clinical Research fellows have also found it very engaging to be involved in Professor Grover's basic science research projects. Overall, we believe that projects like PREVENTION are a fantastic opportunity to create a community of engaged learners who, more often than not, come together to create very innovative solutions to medical issues.

Publications

10 25 50
 
Description We have designed a process that allows us to reduce the capacity of an implant to become contaminated with biofilm and hence pose a risk of infection. We have also worked with commercial partners to implement their silver coating technology into our process map. Staff associated with the project have begun working on the development of novel alloys for the production of ALMd specimens that are intrinsically less likely to become infected.
Exploitation Route We are driving forwards now collaborations with SMEs who are keen to enter the MedTech Sector. These commercial partners (Betatype and Oxmet) have a significant interest in the design of structures and new innovative alloys, respectively. Additionally, our work with our current partners (Cavendish and Accentus) is approaching completion and they have received the results from our experiments. These results may be used to optimise processes.
Sectors Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology

 
Description We have been engaged by several SMEs on the basis of the work that we have published, to start working implementing their technologies in our system. Discussions are ongoing with Betatype and with Oxmet to prepare further Innovate proposals to fund this work going forwards.
First Year Of Impact 2018
 
Description University Studentship, matched against the award
Amount £90,000 (GBP)
Funding ID NA 
Organisation University of Birmingham 
Sector Academic/University
Country United Kingdom
Start 09/2016 
End 09/2019
 
Description University of Birmingham DIF fund
Amount £800,000 (GBP)
Funding ID Centre for Customised Medical Devices (two SLM printers and technical support) 
Organisation University of Birmingham 
Sector Academic/University
Country United Kingdom
Start 09/2018 
End 09/2028
 
Description Silver embedding on ALMd surfaces 
Organisation Accentus Medical
Country United Kingdom 
Sector Private 
PI Contribution We have set up a collaboration between ourselves, the University Hospital of Birmingham Maxillofacial Repair Department, the Royal Centre for Defence Medicine, Accentus Medical and Cavendish Implants. Within this collaboration, we seek to bring together process innovation in additive layer manufacturing and silver embedding to produce prescribed prosthetics with a lower chance of infection.
Collaborator Contribution Birmingham Maxillofacial Repair Departments - have allowed us to examine their processes and identify potential sources of infection. RCDM - have initiated work with us to investigate how our prosthesis modification technology can be used to reduce infection in transcutaneous prosthetics. Accentus are working with us to implement their novel silver coating process into our additive layeer manufacturing process. Cavendish implants are working in collaboration with us to provide cast alternatives for our additively manufactured implants.
Impact We have recently secured an EPSRC grant that will help us to move the collaboration forwards, hopefully to the point that it is of significant clinical value (EP/P02341X/1). The collaboration is highly multidisciplinary and involves industry (Accentus and Cavendish), medical practicioners (RCDM, UHB and Addison), materials scientists (Grover and Attalah), and Mechanical Engineers (Shepherd and Cox).
Start Year 2016
 
Description Silver embedding on ALMd surfaces 
Organisation Royal Centre for Defence Medicine (RCDM)
Country Unknown 
Sector Hospitals 
PI Contribution We have set up a collaboration between ourselves, the University Hospital of Birmingham Maxillofacial Repair Department, the Royal Centre for Defence Medicine, Accentus Medical and Cavendish Implants. Within this collaboration, we seek to bring together process innovation in additive layer manufacturing and silver embedding to produce prescribed prosthetics with a lower chance of infection.
Collaborator Contribution Birmingham Maxillofacial Repair Departments - have allowed us to examine their processes and identify potential sources of infection. RCDM - have initiated work with us to investigate how our prosthesis modification technology can be used to reduce infection in transcutaneous prosthetics. Accentus are working with us to implement their novel silver coating process into our additive layeer manufacturing process. Cavendish implants are working in collaboration with us to provide cast alternatives for our additively manufactured implants.
Impact We have recently secured an EPSRC grant that will help us to move the collaboration forwards, hopefully to the point that it is of significant clinical value (EP/P02341X/1). The collaboration is highly multidisciplinary and involves industry (Accentus and Cavendish), medical practicioners (RCDM, UHB and Addison), materials scientists (Grover and Attalah), and Mechanical Engineers (Shepherd and Cox).
Start Year 2016
 
Description Pint of science presentation 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact I gave a talk at one of the Birmingham pint of science events in which I talked about how materials could be used to replace parts of the body and how we can make better models of tissue formation.
Year(s) Of Engagement Activity 2018
URL https://pintofscience.co.uk/event/healing-with-materials