Extending Reach of Prosthetic Arms

Todd A. Kuiken, M.D., Ph.D., a physiatrist at the Rehabilitation Institute of Chicago and professor at Northwestern University, has pioneered a technique known as targeted muscle reinnervation (TMR), which allows a prosthetic arm to respond directly to the brain’s signals, making it much easier to use than traditional motorized prosthetics. This technique, still under development, allows wearers to open and close their artificial hands and bend and straighten their artificial elbows nearly as naturally as their own arms.

“The idea is that when you lose your arm, you lose the motors, the muscles and the structural elements of the bones,” Kuiken explained. “But the control information should still be there in the residual nerves.” He decided to take the residual nerves, which once carried the commands from the brain to produce arm, wrist and hand movements, and connect them to the chest muscles so that the signals can be used to move the artificial limb.

Nearly a dozen patients who have undergone TMR so far have motorized prosthetic arms that produce two arm movements: open and close hand and bend and straighten elbow. But in a new study from the Journal of Neurophysiology, published by The American Physiological Society, Kuiken and his colleagues demonstrate that TMR has the potential to provide an even greater number of arm and hand movements, beyond the four they’ve already achieved. The researchers have begun work with two U.S. Army medical centers to help soldiers who have lost limbs.

The result? When the patient thinks ‘close hand’ the hand closes. Contrast this with current motorized prosthetic arm technology: The patient has to learn to use new muscle groups to move the prosthetic arm; can perform only one movement at a time; and must contract two muscles at once to achieve a new movement.

“It’s not very common to flex your chest muscle to close your hand or bend your wrist,” said Kuiken. “Quite frankly, most people with a unilateral shoulder disarticulation amputation don’t wear a prosthesis at all: It’s just too cumbersome.”

COMPAMED.de; Quelle: The American Physiological Society