Frans Smeets Frans Smeets

Rapid Prototyping: 3D solutions for physicians and researchers

Written by  Margot Krijnen Monday, 12 June 2006 00:00

Making implants during surgical procedures: The future begins in Maastricht

It sounds like something from the distant future, but one day it will become reality. Staff of the engineering department IDEE (Instrument Development Engineering & Evaluation) have been designing and producing implants that can be inserted into patients whilst they are undergoing surgical procedures. The Faculty of Medicine of Universiteit Maastricht is the first faculty to use this new technology. But how does Rapid Prototyping work? Frans Smeets, head of IDEE, explains.

You have to see it to believe it. Imagine a cupboard the size of an oven fitted with a window. Within that space, a model of, say, a skull is built up – layer by layer from very thin threads of synthetic material that are heated and squeezed out of openings under high pressure (extrusion). The temperature in the cupboard is just high enough to slowly fuse the layers of synthetic material, but just low enough to build up the model. Gradually, an exact copy of a human skull takes shape. A skull that you can take in your hands and physicians can work on, for example, to prepare for a complicated surgical procedure or to design an implant. How is it possible that Rapid Prototyping can make such complex 3D models?

Frans Smeets is very proud of the RPT – the name given to this device by him and his colleagues. “The RPT works by using a 3D printing technique. Everything starts with a digital 3D image. You can obtain such images by, for example, using a CT scanner (computer tomography) or MRI (magnetic resonance imaging), but also a laser scan or a CAD design (computer aided design). We also have software (MIMICS) that is capable of segmenting the 3D data from digital files from the CT scanner by, for example, filtering out the bone structures. The output of this segmentation process will be a file with all the bone structures of a skull, for instance. We can retrieve this file into our CAD system (Pro-Engineer), with which we can carry out digital operations such as modelling implants, sawing templates, drilling templates, or cutting templates. Currently, implants are mostly made from titanium using a computer-operated (CNC) cutting technique, because titanium is a biocompatible material that is well tolerated by the body. For the synthetic materials of the RPT machine, this has yet to be proven, and new biocompatible materials will have to be developed.”

Jaw fragment

These days, the RPT machine is used for the production of models of skulls, jaws and suchlike on the one hand, and for the manufacture of aids (templates) in order to simplify surgical procedures on the other. The surgeon and the IDEE designer work closely together. Frans Smeets says, “To give you an example, a surgeon had to make a jaw fragment for a patient. He wanted to make this implant from the patient’s own bone material by taking a piece of bone from somewhere else in his body, say, the shoulder blade. Using software, a model is made from the bone fragment required, on the basis of a 3D CT scan. Based on this model, an exact cutting template is then produced with the RPT to cut the bone implant. This has the huge advantage that there is no need for the surgeon to produce an exact fit during surgical procedures. Thanks to the cutting template that had been made to measure exactly for the shoulder blade in question, he can create an implant of autologous bone material that fits perfectly. He can then insert the implant in the correct spot elsewhere in the body. Tailor-made templates or aids can also be made for the insertion of the implant. Partly thanks to the combination of CAD and RPT technology, the surgeon can make preparations for the surgical procedure outside the operating theatre to a large extent. Moreover, these procedures require considerably less time, the risk of mistakes is reduced, and precious time in the operating room is saved resulting in considerable financial savings as well.”

Only hard synthetic materials can be processed with the current RPT machine. But in the future, this technology will offer more options. Eventually IDEE also want to start working with soft materials that exactly resemble skin in terms of colour and structure, in order to create, for example, an ear prosthesis. In addition, Frans Smeets is also thinking of soft linings for helmets for skull corrections in children or tailor-made braces, splints and corsets.

Together with the surgeons of the Facial Surgery Department (University Hospital Maastricht), IDEE currently participates in two EU projects (Custom Fit and Custom IMD) in the areas of materials, software and RPT techniques. That may result in new developments over the next few years. With the current new machine, IDEE is already moving toward the era of fully ‘computerised’ production of 3D models from hard synthetic materials. The end of these developments is not yet in sight, and it is expected that IDEE will have several machines at its disposal, for all the various options. IDEE therefore seeks to forge close cooperation with DSM and other parties.

No restrictions

Why Rapid Prototyping? Where did the demand for this technology come from? “Especially the surgical groups increasingly started asking for models of skulls and suchlike,” Smeets explains. “The researchers are another target group. In the past, we were not able to produce the complex 3D shapes for laboratory or research components. But thanks to the RPT, there are no longer any restrictions. In fact, it is possible to create all 3D shapes with the computer. Using cutting or other CNC machining techniques, you will encounter restrictions that the RPT technology does not have. People active in anatomy education have already shown a real interest as well. With the RPT, we can make realistic models of body parts or organs for specific training programmes. And we should not forget to mention local companies. For them, we mostly work in the area of industrial design. For example, we make prototypes of an ergonomic mouse developed by the Erasmus MC and the company Hippus NV. Moreover, we work for companies such as Cybermind, Pie Medical, Anatech, DADC (DSM) and Bakken Research.”

By investing in relevant new technology, IDEE creates new opportunities for scientific and clinical research, as well as education. For this purpose, the department closely cooperates with a number of surgeons from the University Hospital Maastricht and the Biomedical Technology Department of the Technical University Eindhoven and the University of Leuven. It is expected that, in the coming years, the RPT technology will be a platform for many new developments. Smeets says, “Technically speaking, this is a splendid development, which will revolutionize our way of thinking as well. RPT opens up a whole new world of 3D possibilities – a new way of thinking.”

We and others envisage many new opportunities. Thanks to the RPT, we will, in essence, be able to offer tailor-made solutions for individuals around the world.” At the end of the interview, he presents us with a product from the RPT: a small open case in which a ball is turning around without making any contact. All made from one piece in the RPT. Frans Smeets is right. The possibilities are unlimited.

IDEE is the engineering department of the Faculty of Medicine, which enables unique research by developing unique equipment in Life Sciences. If you are interested in the RPT technology, please contact Milou Stassen at +31 (0)43-3881371 or This email address is being protected from spambots. You need JavaScript enabled to view it. to make an appointment.

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