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Sci-Tech

Prosthetic hands get smart -- and a sense of touch

Prostheses are morphing into mind-controlled extensions of the human body that let their wearers feel what they're touching.

Bryan Christie Design

This is part of CNET's "Tech Enabled" series about the role technology plays in helping the disability community.

Garrett Anderson almost broke his grandmother's hand while trying to give it a gentle squeeze.

The retired US Army sergeant — who had lost his right arm below the elbow in 2005 while on patrol in Iraq — couldn't tell how much pressure he was applying with his prosthetic hand. It's a common problem.

When we hold a pen, shake a hand or cup an eggshell, we instinctively know how much pressure to exert without crushing the object. Such sensory feedback isn't possible with most prosthetic hands, which let amputees grip an object but can't tell them how much pressure they're using.

Anderson, 41, has been doing his part to change that. For the past three years, he's been testing prototypes that let him feel again.

"I can feel touching my daughter's hand or touching my wife's hand, or picking up a hollow eggshell without crushing it," Anderson says of his work with Psyonic, a startup operating out of the University of Illinois' Research Park, in Urbana-Champaign. Psyonic expects to provide commercial prostheses with pressure sensing next year, and ones with sensory feedback sometime after that.

Technology is on the threshold of turning the unthinkable into reality. Awkward, unfeeling prostheses are morphing into mind-controlled extensions of the human body that give their wearers a sense of touch and a greater range of motion.

Along with sensory feedback, Psyonic's rubber and silicone prosthesis uses machine learning to give its wearers intuitive control. The Modular Prosthetic Limb from Johns Hopkins University promises to deliver "humanlike" strength, thought-controlled dexterity and sensation. It's currently in the research phase. And Icelandic company Ossur is conducting preclinical trials on mind-controlled leg and foot prostheses. These and other advances could make it dramatically easier for amputees to perform the sorts of tasks most people take for granted.

Hand signals

Like many prostheses already on the market, Anderson's Psyonic hand is what's called a myoelectric prosthesis, which means it's controlled using electrical signals generated by the remaining muscles in his arm. The muscles in his forearm tell his fingers to flex and extend, for example.

When Anderson thinks about moving his hand, electrodes in the prosthetic hand measure the electrical signals from his forearm, while pattern-recognition software detects if he wants to open or close his hand, pinch his fingers together or make a fist, for example. In effect, his thoughts control his artificial hand.

But it's the prosthesis' sensory feedback — thanks to pressure sensors in its fingertips — that lets Anderson shake hands without breaking bones, hold a delicate eggshell while blindfolded or hammer a nail into a board. When he touches an object, those sensors let him feel vibrations, tingling or pressure.

Thought control

Without something like pattern-recognition software, a myoelectric prosthesis can be hard to control.

That was certainly true for Jodie O'Connell-Ponkos, a horse trainer in Ghent, New York, who'd lost her hand in an industrial meat grinder when she was 16. She often struggled to get her prosthesis to work because it was hard to line up the sensors to her arm muscles.

"The arm would almost make me feel like a failure sometimes," says O'Connell-Ponkos, 49. "It was more cumbersome to wear than not to wear, so I chose to just walk away from it."

More than 20 years later, in 2015, she was fitted with a prosthetic hand from German company Ottobock that had been souped up with a controller from Coapt, in Chicago.

Similar to Psyonic's prosthesis, Coapt's system decodes the electrical signals from an amputee's remaining muscles. Equally important, it also uses a pattern-recognition algorithm to translate intention into movement.

O'Connell-Ponkos now uses her artificial hand for everything from tying her shoes and putting her hair in a ponytail to chopping wood and training horses. "There's not much I haven't figured out how to do," she says. "I don't call it a prosthesis. I actually call it my arm."

Coapt's technology has been on the market since 2012 and is compatible with a variety of prostheses from eight companies.

Such technologic advances aren't limited to the upper body.

Ossur, based in Reykjavik, Iceland, has begun an effort to develop thought-controlled leg and foot prostheses. For these to work, surgeons would implant a small myoelectric sensor into amputees' remaining leg muscles. The sensor receives the brain's subconscious electrical impulses and — with the help of a separate processor— reroutes the signals to the prosthesis. The goal: to let amputees move and walk without consciously thinking about it.

"You're giving back what we refer to as the 'voluntary control' to the patient," says Kim DeRoy, executive vice president of research and development at Ossur. "And that is something that, for many patients, is missing."

Looking ahead

The future of prostheses is all about implants.

Jesse Tyler Ferguson Spring 2018 Cover

See more from CNET Magazine.

Mark Mann

Specifically, researchers are exploring the use of small, pill-shaped implants inserted deep into a muscle — allowing for finer, more-accurate control.

But that's not their only potential benefit if Dustin Tyler's research pans out. The professor of biomedical engineering at Case Western Reserve University is developing a technique that could trick the brain into thinking sensations are coming from the missing, flesh-and-blood hand.

The effort involves placing a cuff of electrodes around the amputee's remaining nerves and connecting those cuffs to a small device implanted in the chest that, in turn, activates those nerves. A Bluetooth connection will link the chest implant to the prosthetic arm, so that when the arm touches something, it activates the nerves. Tyler thinks implants could get FDA approval within the next 10 years.

"It's really that human experience that we're starting to restore," he says. "I don't think we should underestimate the value of that." 

This story appears in the spring 2018 edition of CNET Magazine. Click here for more magazine stories.

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