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Surgical precision with engineering accuracy

26 January 2021

Surgical precision with engineering accuracy

In cooperation with doctors, engineers, 3D designers and metalworking specialists, a thoracic surgery procedure has been further developed in Pécs - the patients are already past the first successful surgeries.

Young people’s adaptation difficulties, and in more severe cases, lung and heart damage can be caused by a developmental disorder known as the funnel chest or shoemaker's chest (pectus excavatum), which is characterized by a midline dent in the anterior thoracic wall. More than two hundred surgeries are performed in Hungary every year to correct the disorder that affects every six thousandth child. Recently, a process with 3D printing technology was developed in Pécs, which lasts for a significantly shorter time and has far fewer potential complications than the previous ones. The breakthrough was achieved by the almost unprecedented cooperation of doctors, engineers, 3D designers and metalworking professionals, and it could be a huge opportunity in surgical procedures if it becomes practice. Thoracic surgeon Zalán Szántó who invented the new method and has successfully performed it several times, provided us with the details.


Written by Gábor Szabó (ed. Miklós Stemler)


- How widespread is this developmental disorder and what complications does or can it cause in those who suffer from it?

- It is also a matter of somewhat subjective judgment as to when we can say someone has a funnel chest. Some have a shorter sternum, and their chest is therefore pushed inwards towards the inside of the chest. It is more common in young boys; there is one case in approximately six thousand births. Perhaps we should rather call this an anatomical variation. It can be dangerous because, in more severe cases, it can compress the hearts and lungs of the patients, but perhaps this is not the most dangerous thing but the shape of the unusually formed chest, which will be especially spectacular in adolescence. For an unfolding soul, this is a great burden; they do not dare to undress on the beach or show up in front of others. In Hungary, about fifty patients are operated on in adult thoracic surgery, while in paediatric surgery, where it is more common, approximately two hundred, two hundred and fifty patients are operated on in total every year.

- That is a pretty high number. Is surgery always necessary?

- It is not necessary to have surgery in all cases, it may become less and less noticeable as the child grows, but most of the funnel chests do not go away. Unfortunately, the often recommended sport and swimming alone cannot eliminate this disorder because we are usually facing a complex problem. Thus, we encounter primarily a cosmetic complaint, the correction of which can significantly facilitate the patient's later life. Interestingly, since the disease shows a family cumulation, parents were often able to experience the related difficulties themselves. If the condition is so mentally stressful for the patient that it causes problems in everyday life, surgery is definitely recommended. It is important that the procedure is performed before the ossification process is complete. Until then, we can form a curved, barrel-like, normal chest shape, i.e., the “sinking” will no longer be in it, which will improve the expansion of the chest later. This can be more significant at a later age.

- Until what age is this disorder operable?

- This ossification process is completed at the age of 22-23, 25 at the latest. Practically it can be corrected well until this age.

- I believe that formerly the surgery of these types of disorders were rather serious interventions, they were performed in a complicated and burdensome way for the patient. Currently, by implanting a plate inserted under the sternum, the chest is raised to the appropriate position. How burdensome is this intervention for the patient and how complicated is it to perform?

- It is much less burdensome for the patient than the conventional surgeries were, in which we performed longer incisions on the chest and then detached the associated muscles and partially cut through the ribs and inserted two plates under the sternum. The new method was developed by Donald Nuss, a Canadian paediatric surgeon who is still practising (he is also an honorary citizen of the University of Pécs - he gave a lecture on chest deformities at the invitation of UP a few years ago), and the old procedure is hardly used. Nuss did two important things: first, he did not implant the plate from this midline incision. The midline incisions - around the sternum - always heal much harder, more slowly, with a larger scab than the lateral ones, which in turn heal nicely. On the other hand, he replaced these short plates with a single longer one, which he implanted from the side. Thus, especially at a younger age, correction can be solved much easier. This then revolutionised this type of care to such an extent that in a few years, everyone around the world did and still does it with this surgical technique. Traditional open surgery, named after a surgeon called Ravitch, is only used if for some reason the Nuss procedure is not possible; due to a complication of a previous surgery or a particularly high degree of deformity. At our clinic, we have not had to perform such a traditional surgery in years.

- Not so long ago, you have performed two surgeries based on the new procedure, but you have significantly developed it further. What was the problem with the current procedure that you considered worth solving?

- During corrective surgery, all steps of the procedure were traditionally performed by the surgeon, including the design of the final form of the prosthesis to be implanted. This requires a great deal of focus and precision during the surgery, not least from the point of view of the doctor since it requires almost engineering design vision and metalworking experience. I believe that any possibility for error must be reduced to zero.

- With which we have arrived at the actual novelty, which is meant to achieve this accuracy. Where did this new technique come from?

- Initially, I designed the plates to be implanted based on the patients' chest images, which had to be "only" refined in the operating room. I did not even ask for an X-ray of the chest, but a CT scan – it is important to add that there are now gentle CT procedures that do not burden the body more than a plain chest X-ray. This gives a more accurate picture of the chest, a better view of what we need to do. I still did not feel professional enough about this although it was much more accurate. Even then, I was thinking about how to solve the fact that based on the CT image, according to an algorithm we created, the computer could draw in a personalised manner what shape and size of plate should be implanted into the chest that fits perfectly. It was necessary not only to see the image of the patient's chest, but also to be able to tell its geometry and flexibility.

- This is how 3D designers and engineers came into play, and last but not least, metalworking professionals. What does the process look like in practice?

- This method has four pillars: the radiologist who produces the image of the chest and uses a special algorithm to determine the flexibility of the chest as well; the 3D designer who designs the plate to be implanted based on the images, also using an algorithm created directly for this purpose; then we need a manufacturer - in our case Matro Kft. in Pécs - who has the skills and equipment to make the plate based on the 3D plans, and finally there are we, the surgeons, who implant it. With the most modern CT equipment available at the University of Pécs Department of Medical Imaging, it is possible to perform the necessary examinations with the lowest radiation exposure, which is well tolerated even by the body of our young patients. The 3D team of our university fits the plate onto the resulting image, the length and curvatures of which provide the opportunity for the best possible correction of the given difference. Of course, the method used for the calculations combines the experience gained during our previous surgeries, which expands with each intervention.

- It is not common for a manufacturer or company that does not specifically specialise in the production of surgical kits or prostheses to come into the picture. How did you find them?

- Matro Kft. is one of the most renowned metal industry companies in Pécs, they participate in several university collaborations. I knew that they could solve unusual tasks with great flexibility, with a well-prepared team of engineers and constructors. It was reassuring that as an inexperienced physician in this field, we could entrust the pros with the task. When I performed these two surgeries, I not only wanted to put the theory into practice, but also to go through the whole process, step by step, to get to know the manufacturing as well. We do not buy the raw material from them anyway, it is a flat plate made of special medical steel, but they are able to form it for us with an accuracy of one tenth of a millimetre.

- To what extent has this been an interprofessional learning process, i.e. to what extent should an engineer be a doctor and to what extent should a doctor be an engineer in this case?

- I think those who want and bring themselves to do it, they can find the harmony between engineering and medicine. It took statics, design, but also knowledge of metalworking so everyone could talk to each other to make it into one chain. The radiologist also had to add his experience, as did the 3D designer at the UP 3D Center who understood this problem and the structure of the chest and the manufacturing process itself can give us plenty of pluses we would never have thought of before.

- What changes has all this brought to the surgery itself, so that the plate does not have to be bent in the meantime, but there is practically a ready-made, personalized surgical set? I guess it definitely reduces the duration of the surgery.

- Such a surgery from the first incision to the last suture is about three-quarters of an hour, fifty minutes. We were able to reduce it by about fifteen or rather twenty minutes because we do not have to deal with metalworking there. That is, we managed to shorten the length of the intervention by 30 percent.

- Obviously, the risk is significantly reduced by this, if we only think about the time spent under anaesthesia.

- That is right, and we can be absolutely sure that this plate fits this patient 100%, and this reduces the chances of complications that may result from poor sizing to virtually zero due to the accuracy of the metalworking. After the implantation, it will not push where it should not, but it will push and it will support right where it needs to. It will fit in its place and bring exactly the result we previously designed in 3D.

- I know that the experience is still relatively recent, but are the patients already experiencing the results? For example, do they suffer less or recover faster than those who underwent surgery according to the previous practice?

- I do not expect such a change in this regard, as the manner and purpose of the surgery itself have not changed. The chest needs to be corrected, which obviously causes discomfort, and that depends on the extent of the difference. I would rather say that this way we can be sure that it hurts because we have corrected the difference and not because the prosthesis supports in the wrong place or its shape is not right. For the patients, the real advancement is that they are safer due to the shortening of the duration of the surgery and the absence of complications. And we can say for sure that we have achieved the amount of correction allowed by the chest. Moreover, the limits of the correction can also be determined. Perhaps it is easier to see when, in the case of a significant deformity, this type of intervention cannot be performed because it would involve too much pain or fracture risk. The whole procedure is personalised from the beginning.

- Such surgeries are performed in several places in the country. When do you think this procedure developed here could spread elsewhere? Since accuracy depends on the preparation of the surgery in this method, you can also help other surgeons and patients by using the knowledge and expertise of the professionals here to design a patient’s prosthesis based on their diagnostic reports, which the company manufactures and it is implanted in another hospital. Can this happen?

- I think it can surely happen, all the more so because, as mentioned earlier, in addition to purely surgical tasks, the design of such a correction plate is a complex task. It does not even have to be part of the surgery. Moreover, it is much more reassuring for the surgeon that after a surgical appointment and a CT, a customised plate is available “automatically” that is just waiting to be implanted. I, as a surgeon, would certainly be pleased if, after consulting a young man with such a problem in the outpatient clinic, I send him for a CT and the next time we meet I already have the plate in my hand and I just have to implant it. Otherwise, we can communicate with any of the CT centres, and remote diagnostics has come to the forefront in the current period. In principle, there is no obstacle in designing the plate here at the university clinic based on the diagnostic reports of a patient examined elsewhere, then manufacturing the prosthesis for them and sending it to the surgeon.

- Obviously, because of the coronavirus, these surgeries are also postponed, but for those affected, it is fantastic progress. What will be the next step?

- First, the optimisation of the algorithm we use. It would be great if we could make it even more advanced by involving artificial intelligence or large database analysis. We can also improve the production because the company is currently using plates of a given length but they can produce them of different length, and it has even occurred to design and build machinery for this. We can also start working with them to solve the intervention with even less pain and even less inconvenience with the help of plate metalworking. Other shapes or thinner or other types of plates can be considered, and I can even imagine that in the long run we will not use a plate, but some other material that is even lighter, even smaller, but just as strong and flexible. It remains to be seen, but we would head in those directions.

- Lots of innovation, a lot of people's time and work have been included in this project so far. What will be the fate of this, ultimately will it become a patent or protocol, what is the fate of such an innovation in general anyway?

- I think that the algorithm already mentioned, which can determine the necessary parameters, can be a patent. As for metalworking, I cannot yet say if it requires any special knowledge that could become a patent. If, for example, we can later use not metal but a “shoe tree” made with some kind of biotechnology, that could be such a direction again. We cannot say any better about the thoracic surgery than how we have implanted this prosthesis so far, I do not think there would be a change there.

- If this becomes a protocol, it will require the cooperation of many professionals with specific knowledge. What could be the way? Will the professionals come here to learn this, or will the surgical kits be produced in Pécs?

- I think both are viable options. It is not inconceivable that here will be the all-inclusive prosthesis manufacturing centre where they come before any surgery and here will be Europe’s largest funnel chest correction plate production line. I can imagine that in the future, radiologists will have a built-in algorithm, a programme that they will use when they have such a patient. In Hungary, it is possible that the capacity of a single company would be sufficient for this.

- What is the return on health of this method, in addition to the obvious medical benefits?

- Shorter duration of surgery, correction can become more accurate with less complications, but it can also help promote the technique of 3D design among doctors. By making complications avoidable and making the intervention shorter and safer, I am sure these will reduce the overall cost of this intervention.

- Ultimately, can you now say that this is what you were looking for, this is the accuracy because of which you have embarked on the development?

- Yes, I think that with the refinement of Professor Nuss’s revolutionary surgery we can perform it completely customised in the most precise way currently available. This is exactly what launched this initiative, but with the innovative and modern ideas emerging from working together, we have also exceeded the initial plan. We are confident that this step will further improve the healing and recovery of our patients. As the father of two adolescent children, I can also feel the worry of our little patients and their parents about the surgery, so maybe even then, the awareness that a serious team is working in the background for the best results helps.


UP 3D Centre: PTE3D

PTE Faculty of Engineering and Information Technology - Biomedical Engineering MSc

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