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16 September 2019

SmartSurgery: 3D printing implants

Professor Kawal Rhode is working on clinical projects at Guy’s and St Thomas’ NHS Trust which are starting to reshape the future of affordable, directly implantable body parts for better healthcare.

New Scientist Live 2019

“I think 3D printing technology will be widespread," Professor Kawal Rhode, Professor in Biomedical Engineering, said. 

With the work of his team, the future is already taking shape. 

Professor Rhode is currently working on clinical projects at Guy’s and St Thomas’ NHS Trust which are starting to reshape the future of affordable, directly implantable body parts for better healthcare. 

Working with thoracic surgeon Mr Andrea Bille and PhD student Antonia Pontiki for the last 18 months, Professor Rhode and his team have been using 3D printing to create rib and sternum replacements when they have been affected by cancer. 

Normally, in this situation, the chest wall is replaced with gauze but it affects how patients will be able to breathe after surgery: it’s not particularly good for lung mechanics. This is also far from ideal in terms of cosmetics.

Enter 3D printing. The process to create custom implants with 3D printing commences much like it does now, by scanning patients using CT imaging before they have their surgery. These scans are used to build 3D computer models of the bones that are going to be removed such as a part of a rib, a set of ribs or the sternum. 

Then these models are 3D printed in low-cost plastic, which can take up to 24 hours to print, a negative (mold) is created using silicone which is then sterilized and sent to theatre during surgery. That mold is subsequently used to create a new rib or a new sternum using bone cement, an approved material which can be implanted. 

Other trials have seen objects printed in titanium which is prohibitively expensive. But one of the unique features of Professor Rhode’s work is that it's an astonishingly low-cost way of doing a customized bone implant. 

“The cost of the printing and making the silicone molds and everything is exceptionally low-cost. We focused on building very low-cost technology which is not going to add to the overall cost of the procedure and make it prohibitive to introduce.” 

A future in 3D

3D printing is currently a multi-stage process, and wanting to ensure its simplicity, researchers are now exploring the possibility of directly printing the implants using a material that can also be directly implanted. 

PEEK is an approved material commonly used in dental implants, is an acrylic analogue that is bio-compatible but difficult to print. While commercial printers exist, they are, of course, prohibitively expensive. 

Professor Rhode and his team are in the process of building a custom printer that can print this material for under £1000 and then directly print the ribs and sternum using this printer.

“It will be a one-stop-shop to really go from scan to implant and it also gives us a lot of flexibility in terms of customizing that implant in a much more flexible way to get better interfacing between with the bones that are already there,” Professor Rhode said.

Using 3D printing for soft tissue

At the other end of the biological material spectrum, the team is also developing printers for soft material which are more tissue mimicking: ‘phantoms’. These are models which can be used in devices, in testing of devices and in training for surgeons and doctors undertaking minimally-invasive keyhole procedures.

Realistic anatomical models are built with the optimal material, silicone. But the problem is you can’t directly print silicone.

"We’ve been looking into printing with a number of newly available materials and we’ve done some extensive testing on a material called LAYFOMM,” Professor Rhode said. 

“We’ve actually been able to use it to print life-size hearts which we are currently used in a simulator to help with developing new devices for procedures in heart disease.”

“The other thing we’ve managed to do using printing in terms of realistic anatomical models is to make some very realistic aortic valves – normal and pathological ones – again using printing to create molds and then to make these valves out of silicone using two-part molds.”

These valves, says Professor Rhode, are totally functional, are put into a flow-circuit and can be pumped and operated just like a real aortic valve. 

“We can use that to validate a number of things: computational algorithms that deal with valve flow and mechanics and we can use it to test new devices for treatment of valve disease.”

There are also obvious benefits when it comes to design modifications as this can be done very quickly and at very low-cost as material costs are low and production cycle is quicker. 

“The development cycle of research technology has suddenly been reduced by an order of magnitude. Previously if I wanted some complex part built, I’d have to send it off to a workshop or service where they’d have to machine the parts or manufacture them and there might be several weeks to wait,” he said. This was evident during the team’s involvement with the iFind Robot project, where the pace of the research was boosted due to the efficiency with printing.

“With 3D printing we just make that cycle as short as possible and in robotics, printing has helped to reduce the development cycle as has the ready availability of low-cost components.”

A better future for patients 

“In terms of the technology, we have 3 aims,” Professor Rhode said. 

“One aim is to improve things for the patient, that might be outcomes, various aspects of the patient care pathway, and their experience of that.”

“Or technology should be economically viable and maybe make some improvements in terms of the economy of the patient care pathway.”

Thirdly, explains Professor Rhode, is that maybe the technology would have benefit for the healthcare professionals. Thinking needs to be centered around how 3D printing can best achieve these things. 

Taking into consideration Professor Rhode’s current lung cancer surgery clinical trial, preliminary testing has found that those patients who have been repaired using the 3D printing technique, have very good lung mechanics post-surgery compared to patients who just had gauze repairs. 

Additionally, it cuts down time in the surgery room and can very easily be cost neutral technology which delivers these other improvements, either to the healthcare system or to the patients. 

But does this kind of success work on a case-by-case basis, or in time will 3D-printed body parts translate seamlessly into surgical procedures? 

“At the moment we’re dealing with inert implants like bone, but other King’s colleagues like Professor Lucy Di-Silvio are working on creating living bones using printing to create scaffolds and then populating the scaffolds with osteoblasts.”

Researchers like Professor Rhode think that this is the long-term objective for 3D printing as well as printing using biological material. 

“It is going to be something that people have already shown feasibility of and now going forward I think it is going to come into routine practice.” 

“3D printing is an exponentially rising technology so I think we’re going to feel it’s impact sooner rather than later.”

In this story

Kawal Rhode

Professor in Biomedical Engineering and the Head of Education at the School of Biomedical Engineering and Imaging Sciences