Cases

A man who suffered from an infection of his conventional jaw implant is smiling again. He received a new, custom-fit implant that could be designed by using Mimics and 3-matic software. Within the framework of a European Integrated Project called Custom-Fit , Dr. Jules Poukens performed the case study at the University Hospital of Maastricht, the Netherlands, with the assistance of IDEE (University of Maastricht). This case clearly illustrates that it is possible to use rapid manufacturing technology for the design and insertion of implants. Rapid manufacturing technology enables faster, more accurate, better planned implant surgeries than is possible with conventional techniques.

Making a detailed diagnosis

The patient’s conventional jaw implant had become infected (see Fig. 1). Starting with CT-images of his mandibula, Mimics extracted a surface model of the bone defect which clearly displayed the extent of the infection (see Fig. 2).

Planning, simulating and optimizing surgical procedures

The combination of the CT-images and surface model of the defect can be used for other purposes besides diagnosis. Because these images give a clear picture of the complete patient anatomy, they can help the surgeon predict challenges he will meet during surgery. The insights and knowledge he gains enable him to forecast an optimal procedure for cutting the mandibula. Another solution lies in patient-specific, intra-operative guidance systems, developed and patented by Materialise, that accurately transfer the treatment plan to the patient at the time of surgery. In this case, the surface model was used to design two cutting guides that fit the mandibula exactly (shown in Fig. 3).

Designing a custom-fit implant

Conventional implants are made of relatively flexible material, which means that they can be shaped and reshaped to fit during surgery. This shaping process can take a lot of time in the operating room. Thanks to Mimics and 3-matic software, a custom implant can be designed in advance, thus reducing the length of the surgery. The design of a custom implant involves the incorporation of scanned data. Since anatomical data is extremely complex and organic in shape, it is very difficult to develop a model from them with conventional CAD-systems. With Mimics, on the other hand, it takes only minutes to transform scanned data into a complete 3D computer model.
Conventional CAD systems usually can import files that result from scanning. In order to perform operations on such data, the user must first put them through the lengthy, difficult process of reverse engineering. 3-matic software completely eliminates the reverse engineering step, allowing the user to work directly on the scanned data. Tests showed that designing a jaw implant with a conventional CAD system took three times longer than designing it in 3-matic.

In this case, IDEE used 3-matic software to design the jaw implant (see Fig. 4). Because of the considerable time span between the moment when the patient was scanned and his actual surgery, the odds were that the infection in the bone would have spread. To compensate, the designer added extra large flanges for any additional bone that might need to be removed.

A further advantage of working with 3-matic is the ability to combine organic, scanned shapes together with engineering components (such as fixtures). For example, when designing this jaw implant, the designer could quickly create the holes to fix the implant onto the existing bone with conventional titanium screws.

Planning translated into precision surgery

Next, the implant design was produced through conventional milling, while the cutting guides and a 3D model of the jaw were made in ABS by fused deposition modeling. The team used this model to practice the surgery (see Fig. 5).

During surgery (see Fig. 6), the surgeon used the different cutting guides to cut the patient’s jaw easily. He was thus able to translate the treatment plan to the operating theatre with maximal accuracy. Next, the implant was screwed onto the existing bone using conventional titanium screws. The custom-designed implant turned out to be an absolutely perfect fit.

The combination of virtual planning, the ABS model and the cutting guides substantially enhanced the surgical intervention’s precision, efficiency and simplicity. Thanks to the skill of the surgeon (Drs. Jules Poukens), this patient has a life again.