3D-printed orthoses show promise but no silver bullet, study finds

BRUSSELS — 3D printers can help bring orthotics to remote communities, but the devices they create are still heavier and less durable than conventional ones, according to new research by Handicap International.

With an estimated 30 million people in low-income countries needing a prosthetic limb or orthotics, the NGO is trialing whether 3D printing can help overcome barriers such as a lack of trained personnel and limited access to orthopedic workshops.

In a study conducted between December 2017-April 2019 in Togo, Mali, and Niger, 100 patients received both 3D-printed and conventional orthoses — which assist, rather than replace, limbs — to treat conditions such as knee instability and foot drop. Patients received both in order to compare factors including weight, durability, and appearance.

Under the most common form of 3D printing — fused deposition modelling — the printers use data gleaned from a digital scanner to build up layers of filament melted down from the most appropriate material — in this case polypropylene. In Togo, patients’ limbs were scanned at remote orthopedic centers before the information was sent to the capital, Lomé, and improved by a trained specialist using software. The 3D model was then printed over about 24 hours and sent back to the orthopedic center for final touches, such as adding straps.

By contrast, conventional orthoses are typically made by taking a plaster mold, often at a specialist clinic in a major city, making access difficult for people in remote communities. This is then refined and used to make an orthosis by thermoforming a plastic sheet, also made of polypropylene.

Erwin Telemans, HI’s general director in Belgium, told delegates at a recent event that 3D printing has the potential to get closer to patients. Traditionally, Telemans said, “you may have a very well established orthopedic workshop in the capital and make a very major investment there, with an outcome of maybe 100 legs by the end of the year.”

The benefit of 3D printing is its reliance on scans, which can be taken remotely and sent over the internet, provided the connection is strong enough, to be made wherever the printer is.

Tom Saey from Mobilab, a research center involved in the study, said one challenge they encountered was finding 3D printers that were robust, accurate, and not overly complex, in order to facilitate repairs.

“If we needed to fly in an engineer to fix the printer each time it would be very expensive and not very efficient,” Saey told participants at the event, adding that this ruled out some of the most sophisticated industrial models in Europe.

Materials were also a challenge, with high humidity meaning some could begin to change shape after just a few days. The researchers changed from polyethylene terephthalate to polypropylene during the trial, in order to make the 3D orthoses lighter.

Overall, they found patients preferred the appearance of the 3D orthoses, as well as the process of scanning over the plaster mold. However, weight and durability were reported to be better when using conventional techniques.

HI now plans to prepare a five-year strategy on how to integrate 3D printing in its work and reach out to partners, such as universities, for potential collaborations.

“The idea is not to replace plaster and the old techniques,” said Christophe Van Geel, a rehabilitation specialist with HI. 3D printing has existed for 20 years, but is only now beginning to become cost-effective in the field, he said, adding that, “it will be one of the panoply of tools available.”

“Sometimes, we tend to overcomplicate things,” Telemans said. He recalled his experience, more than 20 years ago, fitting orthotic devices on children with polio in Khartoum. “They were made of iron rod just bent a little bit and kids could walk out of the room in a couple of hours,” he said.

“Innovation is also about finding all the right balance. Is 3D the solution? We’ll see.”