USA: Bionic arm that works on thought-powered movement displayed in Washington

The first woman to be fitted with an experimental "bionic arm" displayed the technology on Thursday (September 14). The bionic arms re-directs severed nerves to send the brain's signals to the electronic motors in the prosthetic. Claudia Mitchell, 26, is one of six people to try out the arm, being developed by the Rehabilitation Institute of Chicago. Mitchell lost her arm in a motorcycle accident in 2004. Mitchell told reporters her older prosthetic arm would only do one thing at a time, either open her elbow or open her hand and had to concentrate on flexing her pectoral muscle, or the triceps, to power the arm. "Now I just think about it." Like many amputees, Mitchell, a former Marine, often left her old-fashioned artificial arm at home. "My other arm, it just didn't work well enough to bother wearing it," Mitchell said. The device is "a tank", admits Dr. Todd Kuiken, its developer. It weighs 11 pounds (5 kg) and one motor extends far beyond her shoulder, with wires and mechanical parts, including some of the six motors, clearly visible. The hand is covered with a flesh-colored sheath that resemble a rubber dishwashing glove, and the fingers move awkwardly. But they do move. What is unique about Mitchell's arm is the interface between body and machine. The arm allows the person to feel temperature, pressure and texture. Kuiken worked with plastic surgeon Dr. Gregory Dumanian at Chicago's North-western Memorial Hospital to move the five nerves that once controlled her arm, removed at the shoulder after Mitchell's accident. Dumanian placed the ends of the nerves close to the skin of the chest, where they re-grew close to the skin. Kuiken told reporters "What we're trying to do is restore function and we've got a long way to go. I think we've taken an important step in improving function. It's just a matter of restoring part of what's lost." When Mitchell thinks about moving her hand or arm, the nerves fire just as if they were still leading all the way down her arm and into the elbow and fingers. The signals are picked up by the electrodes on her skin, which in turn send commands to the six motors in the electronic arm. Her "take-home arm" has the electrodes in a plastic harness that fits over her shoulder and part of her chest. The "bionic" arm is far more fragile and so far can be only used in the lab at the Institute. The next step is to have the signals come back the other way, from the fingers on the prosthetic to the nerves in the chest and then the brain, so that Mitchell can feel pressure, heat or cold, and even a sharp edge. One hope is to perfect the arms for veterans who have lost limbs. Other teams are working to develop ways to control prosthetic devices using thought alone, without surgery to re-direct nerves. A team at Cyberkinetics Neurotechnology Systems Inc. in Massachusetts have a chip that, implanted into a patient's brain, allows him to control a computer. Teams at the University of Pittsburgh Medical Center and at Duke University have built arm devices that monkeys can power with their thoughts alone.

ITN Source | September 16, 2006

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