‘Bionic’ Amputees Display Thought-Controlled UE Prostheses

A science fiction dream has moved into reality for a 26-year-old former US Marine and a 59-year-old grandfather of ten.

Appearing at a recent news conference in Washington, DC, the "$4-Million-Dollar Woman" and the "Bionic Man" caused a media sensation, generating news reports around the world.

Both are regaining their lives through the first generation of thought-controlled prostheses: simply thinking of the arm movement causes it to happen.

Claudia Mitchell, Ellicott City, Maryland, lost her left arm at the shoulder in a motorcycle accident in 2004. As she struggled to adjust to the loss, she read a Popular Science story about Jesse Sullivan, a bilateral upper-limb amputee who received the first bionic arms at the Rehabilitation Institute of Chicago (RIC), Chicago, Illinois, according to a story September 14 in USA Today . Now Mitchell has an arm even more advanced than Sullivan's. Sullivan, who appeared with Mitchell at the news conference and lives in Dayton, Tennessee, lost both his arms at the shoulder in May 2001 from an electrical accident suffered while working as a utility lineman.

How They Work

These giant leaps in prosthetic technology are the result of work of Todd Kuiken, MD, PhD, and others at RIC [Editor's note: see "New Discoveries, New Directions in O&P," The O&P EDGE , March 2006]. The key to this high-tech science is a procedure developed by Kuiken called "muscle reinnervation" in which shoulder nerves, which used to go to Sullivan's arms, have been grafted into his pectoral muscles, explained an article on CNN online. These grafts receive thought-generated impulses, and the muscle activity is picked up by electrodes, which relay signals to the prosthesis' computer, which in turn causes motors to move the muscle and hand. Said Sullivan, "When I use the new prosthesis, I just do things. I don't have to think about it."

"The nerves grow into the chest muscles, so when the patient thinks, 'Close hand,' a portion of the chest muscle contracts," the article explained. Kuiken, who is director of Neuroengineering at the RIC Center for Artificial Limbs, told CNN, "Basically it is connecting the dots. Finding the nerves. We have to free the nerves and see how far they reach" and connect to muscles. The arm enables Sullivan to use four movements: rotating upper arm, bending the elbow, rotating the wrist, and opening and closing the hand, sometimes simultaneously. Sullivan uses a conventional prosthesis as his right arm, which utilizes a hook and sequential motions.

When their chest muscles are touched, Sullivan and Mitchell feel sensations as though in their missing arms and hands. The RIC team is working on developing a prosthesis capable of feeling sensation when the hand touches something. "We hope to be able to close the loop with Claudia and have the sensation be there so that when she touches something, she feels a touch of her hand," Kuiken said, quoted by USA Today .

When Sullivan's chest was touched several months after his surgery, he "had a sensation of touch to different parts of his harms and arm," according to RIC, quoted in the CNN article. "The patient had substituted sensation of touch, graded pressure, sharp-dull, and thermal sensation."

Gregory Clark, associate professor of bioengineering and prosthetics researcher at the University of Utah, said a natural arm is capable of 22 discrete movements, as quoted by CNN. Sullivan's bionic arm is capable of four currently, although researchers are working to improve them.

Mitchell's current prosthesis has three motors, but she has been trying out a prototype with six motors, which will theoretically allow her to reach for things over her head, according to the Washington Post .

For Kuiken, the bionic limbs are the latest step in his 20-year effort to make a better upper-limb prosthesis, said staff writer David Brown in the Washington Post . According to Brown, Kuiken's laboratory has spent about $3 million on research and development, with more than $2 million provided by the National Institutes of Health (NIH).

RIC is now part of a multi-laboratory effort funded by nearly $50 million from the Defense Advanced Research Projects Agency (DARPA) to create more useful, natural artificial limbs for amputees, noted the Washington Post .

According to CNN and the Washington Post , 411 US troops in Iraq and 37 in Afghanistan have suffered injuries resulting in the loss of a least one limb.

Other recent prosthetic research effort has focused on implanting sensors that link devices to movement commands from the brain, noted USA Today [Editor's note: See "'Thought-Control' Prostheses Soon a Reality, The O&P EDGE , May 2005].

"Most people have been looking at trying to tap into the brain, but that has a number of challenges," Kuiken said, quoted by USA Today . "[Implants] are becoming more doable, but if something breaks, you have to have surgery to fix it. The exciting thing about this technique is we are not implanting anything into her body."

Mitchell is now a volunteer at Washington DC-area military hospitals. And some soldiers and Marines may apply to follow Mitchell's leads, since Kuiken is looking for amputees who have lost arms above the elbow.

Regaining Lost Skills

Mitchell is enjoying regaining so much of her former ability in daily-living skills. "I can open a spaghetti jar and hold it up at an angle and use a spoon to empty it out," she told USA Today. "Small things like that may seem trivial to a two-armed person, but it is very exciting to me."

As most women would, Mitchell wanted her new arm to look as attractive as possible. According to a BBC story, Mitchell said, "When we got the glove that goes over it, I asked them if I could put nails on it, and they said yes, so I headed straight for the nail salon. She [the manicurist] was pretty terrified; she was afraid that she was going to mess something up, but I assured her it was okay."

Mitchell told the BBC , "I am happy, confident, and independent."

Sullivan too has regained many arm and hand skills, noted CNN , which added, "And there's another task the bionic grandfather of ten looks forward to mastering: casting a fishing line."

--Miki Fairley

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