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Bionic arm guided by thoughts alone

A new prosthesis taps into conscious commands carried through the nerves to the chest, where receptors pick them up.

By ASSOCIATED PRESS
Published September 14, 2006

DAYTON, Tenn. - Jesse Sullivan has two prosthetic arms, but he can climb a ladder at his house and roll on a fresh coat of paint. He's also good with a weed-whacker, bending his elbow and rotating his forearm to guide the machine. He has even mastered a more sensitive maneuver - hugging his grandchildren.

The motions are coordinated and smooth because his left arm is a bionic device controlled by his brain. He thinks, "Close hand," and electrical signals sent through surgically re-routed nerves make it happen.

Doctors describe Sullivan as the first amputee with a thought-controlled artificial arm.

Researchers encouraged Sullivan, who became an amputee in an industrial accident, not to go easy on his experimental limb.

"When I left, they said don't bring it back looking new," the 59-year-old Sullivan said with a grin, his brow showing sweat beneath a fraying Dollywood amusement park cap. At times he has been so rough with the bionic arm that it has broken, including once when he pulled the end off starting a lawnmower.

"We're excited about collaborating with the military," said the developer of Sullivan's arm, Dr. Todd Kuiken, director of neuroengineering at the Center for Artificial Limbs at the Rehabilitation Institute of Chicago, one of 35 partners now in a DARPA project to develop a state-of-the-art arm.

Sullivan's bionic arm represents an advance over typical artificial arms, like the right-arm prosthesis he uses, which has a hook and operates with sequential motions. There is no obvious delay in the motions of Sullivan's flesh-colored, left arm. Until now, it has been nearly impossible to re-create the subtle and complex motion of a human arm.

"It is not as smooth as a normal arm but it works much smoother than a normal prosthesis," Kuiken said.

High-tech science makes the bionic arm work. A procedure called "muscle reinnervation," developed by Kuiken and used on five additional patients so far, is the key.

For Sullivan, it involved grafting shoulder nerves, which used to go to his arms, to the pectoral muscle in his chest.

"The nerves grow into the chest muscles, so when the patient thinks, 'Close hand,' a portion of the chest muscle contracts," according to an institute fact sheet.

About three months after the surgery, Sullivan first noticed voluntary twitches in his pectoral muscle when he tried to bend his missing elbow, the institute said. By five months, he could activate four different areas of his major pectoral muscle.

Trying to flex his missing elbow would cause a strong contraction of the muscle area just beneath the collarbone. When he mentally closed his missing hand, a signal could be detected on the pectoral region below the collarbone, and when he tried to open his hand there was a separate signal. Extending his elbow and hand caused a contraction of the lower pectoral muscle.

When Sullivan's chest was touched he "had a sensation of touch to different parts of his hand and arm," the institute said.

"When I use the new prosthesis I just do things. I don't have to think about it," Sullivan said.

[Last modified September 14, 2006, 01:10:04]