Additive manufacturing methods of 3D printing are increasingly opening up new paths in medical technology.
Alex Berry, founder of Sutrue (UK), and Richard Trimlett, consultant at the Royal Brompton Hospital, are focusing strategically on AM for applications in cardiology. Is it possible to improve the “golden hands” of an experienced heart surgeon? Yes, it is. Using the example of a machine for performing sutures during operations and a cardiac stabiliser for endoscopic heart operations, Sutrue shows how operations on the heart can be performed more safely. Heart operations are soon to become faster and safer. And there is even more good news: patients are recovering faster.
Sutures following operations are still stitched up today in almost the same way as they were in the days of the ancient Egyptians. Alex Berry discovered that around 240,000 medical professionals a year globally suffer needlestick injuries as a direct consequence of this stitching. Even experienced operators are confronted with the drawbacks and inaccuracies of previous suturing methods. To change this trend, Sutrue developed an instrument which automatically passes any curved needle with a suture through the tissue of a patient. The requirements placed on the automated suturing device were that the stitches are made quickly, are positioned precisely, are reproducible and are made with the necessary force. The better and more quickly the suturing can be performed, the shorter the operation is for the patient as well. And a clean stitch also leads to better recovery.
The perfect mechanics of an automated instrument: Suture quickly, reproducibly and cleanly in a heart operation
The extremely slender suturing device is inserted via a conventional endoscope the size of a drinking straw during the heart operation and moved into position. Its head can rotate and be pivoted in order to find any desired batch of tissue. The needle rotates softly and with pinpoint precision during suturing. This is possible thanks to a complex miniature gear mechanism that drives the needle. The entire gear mechanism is an AM assembly. What this innovation actually means for the operator is that the suture is pulled through quickly and cleanly and the stitch is automatically set in place. A few small stitches in arteries or in delicate structures are now possible. Each stitch can be performed with reproducible accuracy using the suturing device. Complicated operations in particular can be performed faster and more safely. Thanks to the suture device, up to three rotations of a needle per second are now possible, instead of one stich per 25 seconds while doing by hand. This reduces the risk associated with the operation for both, patients and surgeons.
Idea of stabilising the heart muscle during the operation
In Great Britain alone, around half a million people live with a heart defect. Treatment with drugs only delivers very minor improvements to patients and often an operation on the heart is the only way to save a person’s life. In Great Britain, cardiovascular disease is the second most common cause of death, accounting for 27% of deaths, after cancer, which accounts for 29% of all deaths. During open-heart surgery, the surgeon needs the heart muscle to be stabilised for an intervention to be made. Richard Trimlett outlines the task: “We're doing a beating heart operation so the heart is in use by the body but we need to hold the small area that we're working on still. With the chest open we can put a big suction device in but when we're doing keyhole surgery we need very small parts that we can pass in and out. What we don't want to do is disadvantage the patient by offering them an inferior stability of the heart so that the quality of the operation isn't as good when you do it as a keyhole. I said to Alex, 'could you make something that comes apart in pieces, pass through a very small incision that we can use to hold the heart stable? Could we make it to throw it away and even customise it to the different shapes and sizes?’” For Richard Trimlett it was clear that the heart stabiliser should be small, be capable of being dismantled, and be designed with exposed channels pre-assembly. The role of the stabiliser is to keep the heart muscle still at the precise point where the surgeon wants to make an intervention. Alex Berry took on the task and presented a biocompatible prototype of the heart stabiliser: one part made of plastic (SLS) and one part made of metal (LaserCUSING). The component consists of a rod on which the U-shaped heart stabiliser is inserted, like a stamp. The surgeon presses the stabiliser onto the operating site that he wants to keep still to make an intervention.
Short development time and care for the patient
The heart stabiliser was successfully developed in just three months. Previously, it was not uncommon for such a new development to take up to ten years. The component itself is printed by ES Technology on an Mlab cusing from Concept Laser in the space of three to four hours. It consists of a metallic basic body and several plastic suction points that aspirate by means of a vacuum. Both parts are joined together using a sandwich technique. “The solution is estimated to have cost only around £15,000 to develop. Comparable conventional developments used to cost upwards of a million pounds,” says Berry to illustrate the relative sums involved. But from Richard Trimlett’s point of view, it is primarily the patient who benefits from the new instruments using in heart operations. Here he cites an average rehabilitation time for the patient of around six months following a conventional surgical intervention. “Initial experience indicates,” according to Richard Trimlett, “that patients undergo a demonstrably gentler procedure and can recover after just three to four weeks.”
Cooperation between surgeons and Sutrue
The Sutrue Team have been involved in the development of medical operating equipment for more than 10 years. A precise analysis of the operating method is absolutely essential to allow suitable medical instruments to be developed. To achieve this, surgeons work together closely with expert medical consultants, such as Richard Trimlett. Trimlett, who is a cardiologist, attempts to translate the specifications and wishes into a specific set of requirements. With Alex Berry from Sutrue, he has access to a manufacturing expert who transfers the requirements into CAD designs and geometries. Sutrue has been working with AM methods for around (ten) 7 years. “AM makes it possible to produce geometries that cannot be achieved using traditional manufacturing methods. In addition, the parts have greater performance capacity or functional precision, or else they are extremely delicate or small. This is often precisely what the surgeon was previously lacking,” explained Alex Berry.
Sutrue relies on machine technology from Concept Laser
ES Technology, Concept Laser’s UK distributor, manufactures the parts for the automated suturing device on an Mlab cusing machine using the LaserCUSING process, also known as 3D metal printing. The Mlab cusing is particularly suitable for manufacturing delicate parts where a high level of surface quality is demanded. The special thing about the compact machine is its very user-friendly, pull-out drawer system that is very safe at the same time. This includes both the build chamber with dose chamber and the storage container. It allows a rapid change of material without the risk of any contamination of powder materials. The patented drawer system is available with three different sizes of build envelope (50 x 50 x 80 mm3, 70 x 70 x 80 mm3, 90 x 90 x 80 mm3). Also available now is its “big brother,” the Mlab cusing 200R, which allows even greater productivity thanks to a doubling of the laser power from 100 watts to 200 watts. In addition, a larger build envelope has been created and this increases the build volume by as much as 54% (max. 100 x 100 x 100 mm3).
In this case, the machine technology from Concept Laser makes it possible to produce the teeth of the gear mechanism, which are just 0.4 mm long. Up to 600 parts can be printed on one single build plate. After the tooth system has been removed from the powder bed, it does not require any finishing thanks to the very high accuracy of the metal-powder-based process. Stainless steel 316L is used. Alex Berry explains: “In addition to the restrictions on geometry, conventionally milled or cast parts have a few other drawbacks. It takes a great deal of time to get to the finished prototype. In addition, the costs are very high. In 3D printing the parts are produced very quickly and at a fraction of the previous costs of prototyping. But the potential for bionic designs, reproducibility, miniaturisation and not least the reduction in the number of parts and outlay on assembly is also vast. If one looks at the full spectrum of optimising manufacturing and product design coupled with an increase in functionality, 3D printing is capable of revolutionising medical instruments.”
Richard Trimlett and Alex Berry already see an even greater challenge on the horizon. The buzzword is artificial hearts, that is to say mechanical pumps that perform the function of the heart. The previous models have weaknesses. AM could lead to new thinking in this area. The pump could be designed to be smaller. The really intriguing thing, according to Richard Trimlett, is the possibility of integrating electromagnetic functions for moving the pump. These are just a few of the basic considerations for redesigning mechanical heart pumps. AM seems to be inspiring the experts in the field of cardiology.
How has the Mlab cusing helped to create a medical instrument:
- Design freedom is key for redesign of traditional instruments
- Delicate and complex parts through high accuracy
- High density (over 99,5%) and high surface quality (e.g. suturing device, optimised parts needed no post-processing)
- Drastically reduced development times and costs
- No tooling costs and reduced waste
- Ready for production: many parts in parallel in consistent quality (e.g. 600 parts in one build plate/ 10 parts for each suturing device)
- Materials are established and certified for use in medicine.
Benefits for patients and medical professionals:
- Turning a conventional surgical intervention to a minimally invasive surgery (e.g. cardiac stabiliser, leads to a better patient recovery)
- Safe and fast suturing method through guided and reproducible stitches (e.g. suturing device, up to 3 rotations of a needle per second, instead of 1 per 25 seconds by hand)
- Gentler procedure for patient and less risk for medical professionals
- Optimised medical instruments for a better outcome
- Reduced operative time leads to less stress for the patient and reduced costs.
Questions to Alex Berry, Director of Sutrue (UK)
Although fascinating stories from the world of 3D printing are not uncommon, Sutrue’s story still amazed us. Alex Berry from Sutrue had lots to recount when we met him at a conference in Bamberg (Germany). He told us about two developments of products for use in cardiology and in the interview he also explained what motivates him and Sutrue:
Editor: Can one talk about additive manufacturing having made a breakthrough in medical technology?
Alex Berry: Yes and no would be the balanced answer. I would say Yes in relation to dental laboratories or implant manufacturers. Here specific materials are used for specific patients and metal-based solutions are probably very widespread nowadays. In the case of medical instruments, we are some way off exploiting all of the possibilities on offer. The importance of AM is still underestimated today. Sutrue is one of the pioneers that have sought to use 3D parts to offer better and more efficient solutions than were previously possible.
Editor: So is there still a need for more information? What reasons would you cite?
Alex Berry: A medical instrument is the “tool of the trade” for a doctor or surgeon. But doctors and surgeons are not designers or manufacturing experts. They are highly specialist skilled artisans with a strong background in theory and practical experience of working in hospitals and operating rooms. It is quite common to find surgeons who perform 200 or 300 operations a year in a specific region of the body. These highly specialist people have very precise ideas about how a specific instrument could be improved. Ultimately, what is helpful for the doctor is to have dialogue or guidance from an outside party to find out exactly how a tool can be designed more effectively. These bridge-builders are people like Richard Trimlett. Richard talks to the surgeons and attends operations to understand what an instrument should look like and how it can do a certain job better. We then come together with these ideas and develop prototypes. This is followed by trials and further modifications to the design until the final solution is produced. This is an interactive process that takes a certain amount of time. However, with AM nowadays this can again also be done very quickly. What used to take years can now be accomplished in three, six or nine months. However, for the automated suturing device we still had a development period of six years. But it was only toward the end that we were able to make enormous progress with 3D printing. I am convinced that when it comes to medical instruments we will be able to achieve a great deal more with AM. The freedom of geometry, miniaturisation, short development times and other benefits of AM can be exploited even more widely. The process almost calls for a redesign of previous solutions.
Editor: How did you get your references?
Alex Berry: In every business there are customers that maintain a close dialogue in which each party is good at listening to the other. We were then able to try out our promises with a few pilot customers. The sector is small after all and everyone knows everyone else. You quickly get into conversations – and also quickly get to follow-up projects. Richard Trimlett is of course a very important driving force for Sutrue. His expertise and contacts in cardiology are significant sources for our developments. This allows us to focus our products very closely on the particular application and develop them further during everyday use in the operating room. Fundamentally I must say: Our products tell a story. The story is test, test, test. You could also call this an evolutionary design and redesign process. It is only when many surgeons state every day in the operating room: Yes, this is clearly better than our old instruments that you can be satisfied.
Editor: How significant are SLS or SLM for your product solutions?
Alex Berry: Sutrue has long been engaged in the full range of rapid prototyping and prototyping methods. These also include SLS, which is laser sintering with plastics, or SLM, which is selective laser melting of metals. This is slightly easier with metals because the original materials are certified for use in or on the body. In the last 10 or 15 years, AM has made huge progress here. It can now be said that laser melting has established itself as an interesting option. We can assemble very many parts in parallel on a build plate. These parts have exceptional geometries or ergonomic or bionic principles. Not least we can very quickly trial a prototype without using any tools in order to improve the application. Metal AM has massively changed the way we look at our products and we can develop solutions in terms of design and function that were unthinkable just a few years ago.
Editor: How did you end up choosing Concept Laser as the plant and machine manufacturer?
Alex Berry: AM has always fascinated me. This is simply because you can produce prototypes very quickly. Development used to take six months and the component cost £1,500. But the end product was not even convincing. This was initially also the case with the automated suturing device. In 2015 I came across ES Technology. The company is based in Kingston Bagpuize, Oxfordshire. ES Technology has an Mlab cusing machine from Concept Laser and a great deal of experience in the 3D printing of metals. The results on the Mlab cusing were fantastic. The system performed much better than other 3D metal printer, we tried at the same time. We began to fabricate our prototypes with the STL data. AM provides us with a huge opportunity to keep on improving prototypes. We were able to optimise the design again and again and continuously improve the focus on the application. It was, as I would call it, a “design journey” before we actually had a properly functioning automated suturing device on the table. The secret is a miniature gear mechanism which allows the needle to rotate very smoothly and whose head can be rotated and tilted so that the surgeon can use the instrument optimally in an endoscopy. Even an experienced surgeon with “golden” hands will appreciate this assistance.
Editor: How do you want to market your products?
Alex Berry: Sutrue is a “think & engineering tank.” We do not especially want to market our solutions ourselves. Customers can acquire a license and we then provide them with the 3D printing data. With the appropriate industrial 3D machine technology, our product can be printed out anywhere in the world.
Editor: What are your plans for the future?
Alex Berry: I may be an idealist because with AM solutions we can help to develop and advance surgery. I think this is hugely exciting. We are thinking ahead in very different directions. It is now possible to have additive solutions but also hybrid solutions in which traditional machining processes are combined with laser melting. At the same time, we can now set about modifying the geometries to suit the process so that parts or assemblies can be manufactured more quickly or easily or also embrace new performance criteria or functional integrations. When it comes to functional integrations, temperature control, cooling or even sensor technology can be incorporated. In terms of miniaturisation, AM also provides a great deal of potential for the future. The short development times and optimisation options for prototypes are also very interesting. We should also not forget that, as well as technical advancement, AM solutions also offer huge advantages in terms of costs. Added value and economic efficiency can be significantly enhanced as a result. These are all very interesting topics. In principle, any conventional component can be reconceived with AM: redesign will probably be our consistent theme in the future.
Editor: Thank you for the interview.