Prosthetic and orthotic devices can help patients regain mobility and limb function post-stroke or amputation, but the process of creating custom devices takes time and labor. Researchers at the University of Michigan (U-M) are developing a system that uses 3D printing to create assistive devices that are better tailored to each individual in less than a day.

Functional body parts have been 3D printed for years, with the list including a titanium rib cage graft, prosthetic arms for amputees in war-torn Sudan, a hand-worn orthosis for a partially paralyzed Polish man, and even a supportive boot for a penguin named Purps. Companies like Sols and Wiiv set up services that let you scan your own feet at home to make custom 3D printed insoles.

The researchers from U-M's Orthotics and Prosthetics Center is trying to use 3D printing to set up a more permanent, professional procedure for quickly creating devices to get patients moving faster. Current devices are usually made by wrapping fiberglass tape around a patient's limb to create a mold. That's then filled with plaster to make a model, before hot, squishy plastic is molded around it to create a supportive device. Straps and other components may need to be added too, making the entire process very time-consuming and labor-intensive.

While all this is happening, patients are left waiting days or weeks before getting their hands on their new hands.

To speed up the process, the U-M researchers first take an optical scan of the body part in question – in this case, the ankle, to make foot braces used to help stroke victims regain mobility. Then, that 3D data can be fed into cloud-based software, which an orthotist can use to design the required device. From there, the finished device can be 3D printed in a matter of hours, not days.

"Eventually we envision that a patient could come in in the morning for an optical scan, and the clinician could design a high quality orthosis very quickly using the cloud-based software," says Albert Shih, lead researcher on the project. "By that afternoon, they could have a 3D-printed device that's ready for final evaluation and use."

Speed isn't the only advantage of the process. The 3D printed orthotics can be made to fit each patient more precisely, and they're much lighter than traditionally-built devices. That's thanks to being made with a "sparse structure," meaning they're semi-hollow, supported by tiny struts criss-crossing through the inside.

"Traditional hand-made orthotics are solid plastic, and they need to be a certain thickness because they have to be wrapped around a physical model during the manufacturing process," says Jeff Wensman, director of the U-M Orthotics and Prosthetics Center. "3D printing eliminates that limitation. We can design devices that are solid in some places and hollow in others and vary the thickness much more precisely. It gives us a whole new set of tools to work with."

With a virtual model saved to the cloud software, a clinic can simply print as many of the same devices as needed, and make slight adjustments to keep up with a patient's progress. Storing previous models can also be a great way to look back and see how they've been tracking over time.

Since the system uses affordable and accessible equipment, the plan is to release the software freely, so even small clinics can offer better and faster prosthetics and orthotics.

The researchers discuss the project in the video below.

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