Professor Gordon Blunn wearing suit and smiling. Life Solved text and logo in corner

3D printing technology to challenge ill-fitting or uncomfortable prostheses

  • 02 March 2021
  • 16 min listen

In this episode of Life Solved from the University of Portsmouth, we hear how the work of Professor Gordon Blunn and his team is revolutionising the way artificial limbs and joint replacements are integrated with the human body.

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Printing new body parts on demand: once this might have sounded like the stuff of science fiction, but a University of Portsmouth project is changing lives using 3D printing technology.

Professor Gordon Blunn leads the University's Health and Wellbeing programme and specialises in the biomedical engineering of the musculoskeletal system.

He's worked out a way to create longer-lasting, replacement bones and joints for bone cancer sufferers and those needing joint replacements. Gordon talks to us in Life Solved, the podcast exploring life-changing ideas from the University of Portsmouth.

Protecting young bone cancer survivors

Professor Blunn was particularly concerned with how to successfully treat children recovering from bone cancer as traditional metal implants can create painful problems for growing bodies.

Some of these patients are really very young and so we need these implants to stay in place for as long as possible and to grow as the patient grows. In the 90s, the success rate for a 10-year-old implant was only 60%. We want these implants to last a lifetime.

Professor Gordon Blunn, Theme Professor (Health and Wellbeing)

Avoiding repeated surgeries for patients is key as success rates lessen with every revision. As a solution, Professor Blunn and the team developed a porous structure that allows tissue and bone to grow through it, making the implant a part of the body’s structure.

Adapting with the body

As life expectancies increase and patients treated with implants can be young, sometimes hip or knee replacements need replacing, as wear and tear creates inflammation. Gordon thinks that by using 3D printing and porous materials, future joint replacements and other implants could not only fit better but also reduce the need for additional operations as time goes by

The new technology is also beneficial to amputees as the 3D printed structures can allow for tissue integration enabling external prostheses to attach directly to the skeleton avoiding the use of a traditional stump-socket device making it more comfortable for the wearer.

Infection is also a risk when using implants, but the team have thought of a way around that too. A ‘glue’ used to incorporate implant into the skeleton has been created using bone cells from the patient and the team is experimenting with incorporating antibiotics into this too.

Where you have implants that become loose there’s often an issue associated with loss of bone so you would actually enhance tissue integration using this glue.

Professor Gordon Blunn, Theme Professor (Health and Wellbeing)

Episode transcript:

Anna Rose: Thanks for downloading this podcast from the University of Portsmouth. Our interviews bring you world-changing ideas and ask the big questions, looking at research taking place here in Portsmouth.

Anna Rose: Today, we meet Professor Gordon Blunn, Theme Professor for Health and Wellbeing and Lead Professor for our University-wide Health and Wellbeing Research theme.

Gordon Blunn: My area of research is in biomedical engineering and in that field we're interested in particularly musculoskeletal engineering and that is associated with mobility and function of the skeletal system, the muscles, the tendons, the ligaments, the cartilage that go to make up that system.

Anna Rose: He's been using research into 3D printing of bones to make real change in the lives of people all over the world – those suffering with bone cancer, needing hip replacements and amputees, amongst others.

Gordon Blunn: 3D printing of bones can be used to develop specific implants for individuals and also be used to enhance ingrowth of bone into metal implants. They can be remarkably successful and transform.

Anna Rose: Gordon and his team have spent a lot of time looking at bone, cartilage, tendons and ligaments. A significant part of their research has been on recovery from bone cancer, particularly in children.

Gordon Blunn: 3D printing is used in the manufacture of prostheses. One of the applications for these prostheses is to treat bone cancers. These bone cancers occur in the shafts of long bones and to treat those cancers, the surgeon has to remove the cancerous bone and replace it with an implant. So in some circumstances, you're looking at replacing over half of a femur, for example, that is also associated with a knee joint replacement as well. In patients that have these big bone cancer prostheses and they're very large implants, fixation to the bone is a problem. And one of the things that we've done is enhance that fixation by having regions on the prosthesis, which are porous and these regions are made by 3D printing, laser metal sintering. That porous area allows bone to grow into the implant, throughout the implant and locks the implant into the skeleton so it no longer becomes loose.

Anna Rose: They made real change in the world via their research, particularly for children suffering with bone cancer. And they looked at the effect and opportunities of 3D printing in this field.

Gordon Blunn: 3D printing can be divided into 3D metal printing and 3D printing of polymeric structures. 3D metal printing, which is newer and is also called selective laser sintering, is where you have a metal powder and that is fused together by a laser beam or an electron beam. And in that way you can actually produce an implant which is customised and as it's metal, it's very strong and functional and can be used to develop specific implants for individuals and also be used to enhance ingrowth of bone into metal implants.

Gordon Blunn: Some of these cancers occur in very young patients, patients who are still growing in fact. One of the things that happens when you replace a significant portion of the bone is that you reset the part of the bone that is responsible for growth. This is called the growth plate, and it occurs at the ends of long bones. And in replacing the growth plate, you obviously prevent growth of that bone and that means that if you don't do anything about growth, that patient's growth is limited.

Gordon Blunn: So one of the things that we've done in these prostheses is to develop a growing prosthesis. The latest iteration of that which I've been involved with is the development of non-invasive growing prostheses. That's particularly important because previously as the adolescent or the child grew, they would come back into theatre and have a small operation and that prosthesis would be extended and that would be done intermittently throughout the child's life. The non-invasive prosthesis is where the implant is able to grow, essentially non-invasively. So you don't have an operation. You don't have an in-stay in hospital associated with that operation and you don't have a risk of infection associated with that operation.

Gordon Blunn: The non-invasive prosthesis is a bit like an electric motor. It has a magnet within the implant that is coupled to a gear system which drives a power screw, which extends the prostheses. The magnet in the implant is induced to turn by an external rotating magnetic field, which is produced by a series of electric coils. What happens is the patient comes into hospital, puts their leg into one of these coils, that gets turned on, it spins the magnet in the implant, which extends the prostheses. And the patient does this every so often to keep pace with the growth in their non-effective leg or arm.

Anna Rose: These 3D printed structures become a part of the body as soft tissue grows through it over time and makes it stable. As well as cancer patients, Gordon explained the potential uses for amputees.

Gordon Blunn: Amputees today are treated with a stump and a socket device. They have a stump over which fits a socket. That socket is attached to an external prosthesis. And these are successful but in some cases, stump socket devices don't work in all patients, particularly in the patients that have resections high up on their limbs. In other words, proximal resections where the socket has to be attached to only a small stump. For example, in transfemoral amputees, you often have sockets which extend under the groin and that can be really uncomfortable.

Gordon Blunn: So one of the things that is being developed at the moment is a prosthesis that actually is attached to the skeleton, to the bone, in a similar way that we attach the bone cancer prostheses to patients. Part of that prosthesis projects through the skin and the external part of the artificial limb is attached to the part that extends through the skin. In that way, you get more secure fixation, you don't have the issues associated with a stump-socket device, which often requires reengineering because we lose and gain weight. The stump-socket devices are often associated with rubbing and you can get the development of sores. So by having a prosthesis attached to the skeleton, by removing the stump-socket device, you alleviate all those problems.

Gordon Blunn: One of the important issues with these devices, as they pass through the skin, is maintaining a bacterial seal because you obviously have an implant that projects through an opening in the skin and bacteria have the potential to invade the body. So we're using 3D printed technology to enhance the attachment of the skin to the implant.

Gordon Blunn: Patients who were unable to use a sub socket device now are able to use an artificial prosthesis, and that's empowering for those patients. We have actually seen patients increase their physical activity significantly. Some patients actually swim with their prosthesis, which projects from their stump, which is incredible to see. People ride bikes, people climb hills, they can be remarkably successful and transforming.

Anna Rose: This kind of implant could have an effect on an even bigger proportion of the population than amputees and cancer patients. As we live longer, this research could help more people in need of hip and knee replacements.

Gordon Blunn: So knee and hip replacements are fairly standard. Actually, around 80-90,000 hip replacements are used every year in the NHS, mainly to treat patients who have osteoarthritis. And osteoarthritis is a condition where the cartilage on the surface of your bone, which makes up your joint, becomes worn and becomes very painful.

Gordon Blunn: The issue with some of these hip replacements, although they are remarkably successful and can last a considerable amount of time, is that some of them become loose and have to be revised. Around 10 percent of hip replacements are actually revision operations. Loosening is associated with bone loss around the prostheses and porous metals made by 3D printing have the potential to be used to enhance bone growth and bone loss around the implant.

Anna Rose: Gordon focussed on creating 3D implants that can be in place for longer amounts of time as more and more people are needing long-lasting hip and knee replacements. Avoiding repeated surgeries is another benefit of this technology.

Gordon Blunn: Hip joint replacements, they have been really successful. Currently, there is no cure for osteoarthritis and patients get osteoarthritis or can get osteoarthritis at a relatively young age into their 50s, for example. And where that osteoarthritis is severe, the only option is to use a joint replacement. You can imagine that if you're relatively young, for example, in your 50s and you have a joint replacement, which you hope would last for the remaining part of your life, they are really effective up to about 20 years. This means that if you're young and you have a hip replacement, you may be faced with a revision operation.

Anna Rose: And importantly, since we're all living longer, this will increase the lifespan of the implants, too.

Gordon Blunn: OK, so 3D printing, you are able, of course, to manufacture custom implants. You can design in areas where you get the musculoskeletal system to attach to that implant so it becomes part of the body, essentially. We know definitely that if you get good integration of the prosthesis with the skeleton, with the bone, that that significantly reduces revision surgery. Interestingly, 3D printing is also used in spinal surgery to fuse vertebrae in patients that have back pain.

Anna Rose: Clever stuff. Gordon and his team have been working on a kind of glue to bind this new 3D printed mechanism together.

Gordon Blunn: A glue, which is actually made from the patient's own blood, can be sprayed onto the surface of the prostheses, which has the potential to enhance bone formation. This glue, which is produced at the time of surgery, can be used to incorporate stem cells. These stem cells can be obtained from patients at the time of surgery, from a bone marrow aspirate, obtained from the iliac crest.

Gordon Blunn: That bone marrow aspirate is prepared during the surgical procedure and incorporated into part of the glue in the form of a spray, which can be coated onto the surface of the prostheses. This glue sets and you deliver a layer of stem cells onto the surface of the implant. So one of the things that you could do with this glue is that you can incorporate antibiotics into the glue. One of the issues associated with hip and knee joint replacements is infection, and about one percent of implants become infected. That is disastrous, really, because bacteria like to grow on inert surfaces and become more resistant to antibiotics given systemically because they form a film on that surface called a biofilm. So if you can prevent bacteria attaching to the implant through the use of an antibiotic containing glue, you will hopefully prevent infection.

Anna Rose: Thanks for listening to this episode of Life Solved from the University of Portsmouth. You can find out more about the work of Gordon and his team as well as our other projects by going online to port.ac.uk/research. If you want to share your thoughts on this programme, you can follow us on social media and shout about this podcast using the hashtag Life Solved.

Anna Rose: Next time, we'll hear from the Portsmouth lecturer who's picking apart the language of the media to expose harmful ideologies.

Alessia Tranchese: These are two representations of the same event, and the idea is the language is all about choice. You can say he raped her, she was raped, you are describing the same event. But there is always a reason why we choose to say things in a certain way. We're always choosing from a pool of options, but we choose one. And if we choose that, and especially if we choose it repeatedly so there is a pattern, then that means that there is something that...

Anna Rose: Make sure you subscribe in your podcast app to get every episode of Life Solved automatically. And please do tell us what you think with the review and rating if you get a moment. From the team in Portsmouth, thanks for listening. We can't wait to share another fascinating discovery next time.

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