In New Procedure, Artificial Arm Listens to Brain

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 bearhugs children at the three Kiddie Cottage day care centers she owns in Knoxville, Tenn.

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.