New Surgery Makes Artificial Arms Easier to Control

A new type of surgery may give amputees better control over their artificial arms, allowing them to point a finger, grasp a baseball bat or even give someone a pinch, U.S. researchers said on Tuesday.

The findings represent the latest advances in a surgical technique to use nerves severed by amputation to control artificial limbs.

The technique involves reconnecting amputated nerve fibers to muscles in the chest and using electrical impulses from those nerves to operate a special motorized artificial arm.

"Now, instead of saying I want to close my hand, a patient can say, 'I want to be in a finger-pointing mode and close my hand, or I want to have a fine pinch grasp, or a power grasp like you hold a baseball bat,'" said Dr. Todd Kuiken of the Rehabilitation Institute of Chicago, who reported his findings in the Journal of the American Medical Association.

Currently, most prosthetic arms are powered by body motion. Motion in the upper shoulder is transferred through a cable to operate the hand, wrist or elbow. But this method only allows people to use one joint at a time and takes a lot of training.

"It's not too intuitive," Kuiken said in a telephone interview. He said restoring nerve function offers a much more natural way to control the devices and allows people to move more than one joint at once.

"We've got about 30 patients around the world who have gotten this procedure," Kuiken said.

In his latest findings, Kuiken's team has shown that the re-attached nerves can be used with a next-generation type of prosthetic device to perform complex elbow, wrist and hand movements, better mimicking the function of the lost limb.

The prosthetic devices have antennas that capture electrical impulses from the nerves. These signals are processed by a computer, which directs the arm to perform needed motion, Kuiken said.

"Now, a patient can think 'I want to close my hands this way', and with these complex hands, it will actually do it," he said.

Kuiken said devices in the study were prototypes, and more work is needed before they will be widely available for patients.

Dr. Gerald Loeb of the University of Southern California in Los Angeles, said in a commentary the work was "exciting and promising."

"With increasing functional capabilities, patients with upper-extremity amputations may derive exceptional benefit form prosthetic arms, just as legions of patients with lower-extremity amputations now lead remarkably normal and even athletic lives."