Cases

Plating systems currently available on the market to treat bone fractures usually offer standard form plate designs which do not always conform flawlessly to a patient’s anatomy. In the treatment of some peri-articular fracatures, this can be rather problematic. This fact was noted by Prof. Dr. Stockmans , who has used Mimics to change the design of a hand plating system for an optimal fit to the shape of the bone. The complete product cycle, from concept to market, was reduced to a mere fraction of the time it would have normally taken to change the implant design.

A fracture of the fifth metacarpal bone, which connects the little finger to the wrist, is commonly called a boxer’s fracture (see figure 1). The fracture occurs most often at the neck of this bone when punching an immovable object with a closed fist. In this punch, the end of the little finger’s metacarpal bone bears the brunt of the impact and is most likely to break.

To allow the fracture to heal, it is necessary to stabilize the fracture. Orthopaedic device manufacturers supply surgeons with plating systems for repairing the metacarpal. However, these plating systems of the orthopaedic device companies did not offer a plate with optimal contouring for the treatment of this particular fracture, resulting in unstable anchoring (see figure 2).

After noting this problem, Prof. Dr. Stockmans and medical device company Stryker turned to Mimics to make several design changes, reflecting the anatomical shape of the fifth metacarpal. He imported CT scanner images of the metacarpal V and an STL file of the implant into Mimics. After making 3D reconstructions of the metacarpal V bone, he was able to position the plate virtually on the bone. To accomplish this, he used real patient data from his personal patient database. To design a plate with anatomical fit, Prof. Dr. Stockmans virtually cut the standard plate into pieces with the cutting tools available in the Mimics Simulation module. Then he repositioned the different parts to attain a perfect fit to the bone (see figure 3). The different parts were subsequently merged to create a redesigned, anatomically correct metacarpal V plate.

Using patient-specific data for the metacarpal plate’s redesign gave Prof. Dr. Stockmans confidence that the plate would provide an improved fit on metacarpal V anatomy and successfully serve the purpose of immobilization. Based on Prof. Stockmans' design suggestion, prepared in Mimics (see figure 4), Stryker's design engineers created a design meeting the anatomical as well as the manufacturing requirements (see figure 5). The time consuming design stage of prototype production for validation and optimization could be omitted.

Thanks to Mimics’ powerful and user-friendly design and access to patient-specific data, Prof. Dr. Stockmans and Stryker were able to complete the entire process – from concept to market – in fewer than three months. It normally would have taken one to two months longer. Typically such a design is devised through trial and error, involving the manufacture of prototypes which endure many design changes in the face of anatomical incompatibilities encountered during clinical trials. Mimics’ surgery simulation feature allows verifying the design virtually and performing virtual design modifications, thus avoiding design iterations and thereby significantly reducing the time to market (see figure 6). Since the implant conforms perfectly to the patient’s anatomy, operation times can be reduced, and surgeons no longer have to bend the implant during surgery to make it fit onto the patient’s bone. Mimics thus provides a direct link between the surgeon and the implant design engineer.