The Bionic Arm Has Arrived

Four people now have been outfitted with robotic arms attached to nerve tissue and controlled by the brain:

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 his pectoral muscle. The grafts receive thought-generated impulses, and the muscle activity is picked up by electrodes. These relay the signals to the arm's computer, which causes motors to move the elbow and hand, mimicking a normal arm.

"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.

Kuiken added: "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.

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 clavicle. When he mentally closed his missing hand, a signal could be detected on the pectoral region below the clavicle, 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. "The patient had substituted sensation of touch, graded pressure, sharp-dull and thermal sensation."

Sullivan said of the thought-controlled arm: "When I use the new prosthesis I just do things. I don't have to think about it."

The robotic arm does not yet send sensory data back to the brain, but that capability is apparently just around the corner.

Luke would be proud.