Prosthetics – Research offers new possibilities

Whether it’s discreetly thanks to a skin-toned look or in an eye-catching way owing to technical details – the way people wear prosthetic devices today depends on their wishes and preferences. Due to modern manufacturing processes and ever higher design standards, for many, they have become a way to express a lifestyle they increasingly want to communicate.

Usually, this applies equally to upper and lower limb prosthetic devices. Having said that, before a prosthesis becomes a finished product, comprehensive research is paramount to test new materials and manufacturing techniques.

Researchers at the George Mason University in Virginia, USA, are working on improving the way muscle activity is recorded. By wearing a small band on the forearm, ultrasound waves sense muscle activity deep inside the tissue. Preliminary results show that this method allows greater control of upper-body prosthetics, including fine-tuned motor control of the fingers and thumb. While this research is still solely conducted in the laboratory and with the help of machine learning algorithms, the scientists are not the only ones in their quest to improve the manageability of prosthetic arms. Researchers at the University of Illinois are likewise developing prosthetic arms that stimulate nerves with mild electrical feedback. The control algorithm regulates the current, so a prosthetics wearer feels steady sensation, even when the electrodes begin to peel off or when sweat builds up. The researchers point out that their primary goal is for wearers to no longer just perceive the prosthetic hand as a tool but rather as an extension of the body.

In Germany, one employee at the Karlsruhe Institute of Technology (KIT) and his company VINCENT Systems have developed a modular system for artificial prosthetic hands featuring a sense of touch. The system can be used by nearly every age group and injury level. Find out more about the prosthetic hand that weighs as much as a human hand in our REHACARE.com interview.

Researchers at the Leiden University in the Netherlands have created a so-called metamaterial that has a flexible response to external influences. In the future, this material, which was produced by using the 3D printing process, could also help to improve prosthetic devices because it is able to adapt to constant body movements. However, further research is still needed in this area.

That being said, so-called generative manufacturing processes such as 3D printing are definitely already suited to quickly and cost-effectively produce prosthetic components. "A major advantage is that prosthetics and orthotics can be custom-made to fit the patient," says Manuel Opitz, CEO of Mecuris GmbH. "3D printed products can also be more easily equipped with added options such as water resistance, integrated features (like a bottle opener) or a bionic outer contour."

In 2017, Mecuris launched its first 3D-printed CE-certified prosthetic foot on the market, which is also corrosion resistant to salt. What’s more, the Munich-based company also offers saltwater-resistant cosmetic products, whose design can be customized to the respective prosthetic feet.

Jérémy Lefint is a research associate at the Fraunhofer Institute for Manufacturing Engineering and Automation (IPA) and also attests to the benefits of 3D printing processes: "Not only can you print the support structure this way, but also various joints, dampen mechanisms, and sensors. In addition to cosmetic requests, you can also accommodate customizations."

From 2008 to 2015, Jannis Breuninger worked at the Fraunhofer IPA until he became the Director of Product Development at Mecuris when the company was founded in 2016. Since then, the Fraunhofer IPA and Mecuris have continued to collaborate – including joint work on internal projects or official test orders for newly developed prosthetic feet.

Another major advantage of 3D printing is the digital documentation and improved quality assurance. "The anatomy and dimensions of the prosthesis wearer are stored like a digital plaster cast," says Opitz. "This makes it possible to produce a secondary prosthesis - for bathing or (water) sports purposes - much faster." Anatomical changes could also be checked with millimeter accuracy during follow-up care with this process. "This complies with the latest EU regulatory requirements. For the first time, this allows manufacturers to produce custom prosthetic devices in compliance with CE standards."

Despite all the advantages that 3D printing already has to offer, it should be noted that certain work processes in prosthetic maintenance and care continue to require the expertise and skill of an orthopedic technician. Someone like Frank Purk from Hamburg, for example. He can envision 3D printed individual components such as knees and feet. However, when it comes to a shaft, he prefers to get involved in the process. Meanwhile, he is more confident as it pertains to the overall production of orthotics – "especially since they are cost-effective." After all, he says "this would also fit well with our system, which is becoming increasingly standardized." Find out what the Hamburg-based orthopedic technician reveals about prosthetic design and functionality in a recent interview with REHACARE.com.

Whether it’s with tried and tested methods or with the help of 3D printing - the production and design of prosthetic devices is as complex and unique as the people who wear them. Meanwhile, the demands and requirements of this assistive technology will continue to be based on real-life situations of users, prompting the industry sector to be equally dynamic and flexible.