The orthopaedic casts we are most familiar with consist of a soft inner cotton layer, and a hard plaster or fiberglass exterior. Although they do their job – which is to stabilize the patient’s bones as they grow back together – there are several disadvantages to traditional plaster casts. They are bulky and heavy, and when exposed to moisture, can cause the skin to become extremely itchy and even irritated.
The team at Michigan Tech developed a way to create patient-specific orthopaedic casts to treat bone fractures in the forearm and wrist, using the Materialise Mimics Innovation Suite as well as our 3D-printing facilities. First of all, they took a 3D surface scan of the patient’s arm using an open-air photogrammetric scanner – an XBOX 360 Kinect to be precise – to avoid radiation and to keep their methods cost-effective.
This gave them a 3D model of the patient’s arm, which they then imported into the Materialise Mimics Innovation Suite. Using 3-matic, the structure of the cast was designed to perfectly fit the patient’s arm, and using the Lightweight Structures Module a porous structure was incorporated into the design to allow maximum breathing space while keeping the same structural strength.
Finally, the end design was 3D printed in polyamide, using Laser Sintering at one of our production facilities. After putting the cast through quality tests to ensure it was rigid and durable enough for the job, a total of four patients volunteered to test the cast and collect user experience.
Dr. Jingfeng Jiang, leader of the project, commented: “The Lightweight Structures Module enabled us to rapidly design and create prototypes of these orthopaedic casts given any patient-specific wrist geometry. Furthermore, the software allowed us to export the virtual design directly to ANSYS for FEA analysis, so that we could make sure the model was strong enough to withstand different loading conditions.”
The study concluded that the 3D-printed casts successfully did their job, and that 3D Printing could be feasibly used to manufacture patient-specific casts – we hope to see more exciting developments about it in future!