Rapid Technologies in Medicine.

A study carried out by Dr. Michel Janssens & Drs. Jules Poukens, at AZM University Hospital (Netherlands) has clearly showed that Rapid Manufacturing may allow faster, more accurate and better planned implant surgeries than those that are possible with conventional techniques. This article, made into the Custom-Fit European Project framework shows the recent developments on custom

The use of Rapid Technologies (RT) in the medical environment has been demonstrated since its earliest times to be helpful. The need of unique parts, based on patient’s data, their high cost and complexity, the needs of medical imaging for diagnostic purposes and the doctors’ autonomic diagnosis have contributed to it.

Two cases studies were carried out which common flowchart is detailed in figure 1. This article explains the one about a jaw implant.



Figure 1: Generic flow of the process

The case study starts with a patient which has an infected conventional jaw implant (see figure 2).



Figure 2: The infected patient

To achieve a well comprehensive diagnosis, data acquisition is prepared by means of Computerised Tomography. Figure 3 shows images of the jaw using the Mimics software, based on the CT-images. The target is to extract the surface model of the bone defect.


Figure 3: CT-scan of the jaw

We accomplish the geometric aspect of the problem to make a detailed planning of the surgery. In the jaw case, the images show clearly how far the bone is infected. With this knowledge, the surgeon planned where to cut the jaw. The surface model was used to design two cutting guides that fit the jaw exactly (shown in figure 4).



Figure 4: Cutting guides designed based on the planning

Those implants are made of relative flexible material so they can be managed if necessary during the operation. Since the planning can now be done with a controlled accuracy, it is possible to design a custom fit implant based on the surface model of the defect and the planning of the surgeon (figure 5). Since there was a considerable amount of time between the scanning and the actual surgery, a serious clearance was taken into account in the design to compensate for the possibility that more bone needed to be removed.



Figure 5: The designed implant

The design of the implant itself requires the possibility to work easily with scanned data. The models coming from Mimics are surface models transferred through Standard Triangulation Language file that need to be converted into CAD-surfaces, which is a lengthy and difficult process. To avoid this problem, the design is done using 3Matic, software that does design directly on facet models (STL-files). Tests showed that the design in a conventional CAD system of the jaw implant took 3 times longer than the design in 3Matic.

To be produced, the implants need to fulfil the strict medical regulations on the materials. At this moment, the most commonly used material for implants is titanium. This is not the easiest material to process and neither the cheapest. The jaw implant was previously produced using conventional milling (see Figure 6) which compromise the design and generates material waste. Along with it, a model of the jaw in ABS using RM technologies (that does not generate waste) was made to practice the surgery on (Figure 7).



Figure 6: The jaw implant with de ABS jaw model



Figure 7: The jaw implant surgery

This new technique will improve the patients’ life. Fewer surprises would occur during the surgery for the method accuracy and the healing period of the patient could be reduced significantly. Lead times in planning, design and manufacturing are considerably reduced. Finally, the studied implants have better mechanical properties and integrate other anatomical features like blood vessels and nerves. Now the focus is established in the accuracy of CT-scans and materials development for them to be also biocompatible and bioresorbable. In the future, it should be possible to tune the materials in such a way that they can be made patient specific and will be replaced by natural bone after a period of time.

Visit Custom-Fit at http://www.custom-fit.org/

About Custom-Fit:

Custom-Fit is an industry led project to investigate the possibility of moving towards knowledge based manufacturing and customised production through integration of knowledge in Rapid Manufacturing, Information Technology and Material Science. Funded under the Sixth Framework Programme, the project involves 30 partners from around Europe. The aim is to create a fully integrated system for the design, production and supply of individualised products. It has targeted product for implementing the new technology, including motorcycle seats, helmets, implants and prosthesis.


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