Date:12/02/2009 URL: http://www.thehindu.com/2009/02/12/stories/2009021256292200.htm
Front Page The prosthetic revolution Pam Belluck In new procedure, the artificial arm listens to the brain New York: Amanda Kitts lost her left arm in a car accident three years ago. But these days she plays football with her 12-year-old son, and changes diapers and bear-hugs children at the three day- care centres she runs. Ms. Kitts, 40, does this all with a new kind of artificial arm that moves more easily than other devices and that she can control by using only her thoughts. "I'm able to move my hand, wrist and elbow all at the same time," she said. "You think, and then your muscles move." Her turnaround is the result of a new procedure that is attracting increasing attention because it allows people to move prosthetic arms more automatically than ever before, simply by using rewired nerves and their brains. The technique, called targeted muscle reinnervation, involves taking the nerves that remain after an arm is amputated and connecting them to another muscle in the body, often in the chest. Electrodes are placed over the chest muscles, acting as antennae. When the person wants to move the arm, the brain sends signals that first contract the chest muscles, which send an electrical signal to the prosthetic arm, instructing it to move. The process requires no more conscious effort than it would for a person who has a natural arm. On Tuesday, researchers reported in the online edition of The Journal of the American Medical Association that they had taken the technique further, making it possible to perform 10 different hand, wrist and elbow movements, a substantial improvement over the typical prosthetic repertoire of bending the elbow, turning the wrist, and opening and closing the hand. "It's dramatically impacted the field," said Stuart Harshbarger, a biomedical engineer at Johns Hopkins University who is the program manager for a military-financed prosthetics study that includes research on the technique. "It's already being used by practicing clinicians and surgeons across the country. The ability to control a pretty robust prosthetic limb has surprised everyone with how good it is." Typically, a person with a prosthetic arm can make only a few motions, often so slowly that many people use the arms only for limited activities. There is a separate motor for each movement, said Gerald E. Loeb, a Professor of biomedical engineering at the University of Southern California, "and that motor has to be explicitly controlled," usually by the person consciously contracting muscles in the back or biceps. "Essentially up until now," Professor Loeb said, "subjects have controlled one motor at a time and had to think very carefully about what motor they wanted to control and how to move it instead of just thinking about moving it and being able to do it." Before Ms. Kitts had the reinnervation procedure in October 2007, for example, she had to move her back muscles a certain way to make the wrist rotate, and flex her triceps and biceps to move the elbow up and down. "It was a lot of work," she said. "It wasn't useful to me at all." The reinnervation method is part of a recent explosion of new ideas and techniques being explored as scientists try to help people better compensate for missing limbs or paralysis. The drive is being fuelled by increasing amputations from diabetes and military injuries and by advances in technology. Arms have become a particular focus. Science has long had success with prosthetic legs, but it is harder to mimic the complexity and dexterity of hands and arms. Efforts under way include more flexible and sensitive skin and arm designs, and wireless devices implanted in prosthetic arms to allow more natural movement. Researchers have also used sensors implanted in the brain to enable two monkeys to control a mechanical arm, and a paralysed man to move a cursor on a computer screen. - New York Times News Service To unsubscribe send a message to [email protected] with the subject unsubscribe. To change your subscription to digest mode or make any other changes, please visit the list home page at http://accessindia.org.in/mailman/listinfo/accessindia_accessindia.org.in
