April 15, 2011
Scientists are developing an entirely new type of prosthetic arm and hand that allows a patient to regain not only movement, but also the sense of touch.
American soldiers who have lost limbs in the wars in Afghanistan and Iraq often end up at Walter Reed Hospital in Washington, D.C., for rehabilitation and to get fitted with prosthetics. Dr. Todd Kuiken, of the Rehabilitation Institute of Chicago, works with these patients who provide him with feedback on a bionic arm he developed. Kuiken's work has focused on creating an artificial arm which can respond to the wearer's mind.
"What we do is use the nerves that are still left. Although the arm is lost," he says.
Nerves from the amputated arm are attached to the remaining muscle, either in the chest or in the bicep. Nerves that control flexing the hand or closing it are attached in different locations.
Electrodes placed on the muscles act as antennas and when the brain sends an electrical nerve impulse to these antennas, the electrode activates the prosthetic arm or hand to move accordingly.
Glen Lehman lost his right arm in Iraq. With his new limb, he can carry a tray or open a refrigerator door, almost without thinking.
"It gives you the freedom of mobility back. Trying to do some things with one hand is kind of difficult," he says. "If you can imagine opening a jar of peanut butter or maybe some jelly or spreading it on toast, something as simple as making a peanut butter and jelly sandwich. It's very hard to scoop something out and spread it with one hand."
Patients can even have nerves from their hands and finger tips transferred to muscles in their biceps. This gives them the sensation of touch.
"If you touch that newly re-innervated skin, the patient feels as if you're touching their missing hand," says Kuiken. "They can feel light touch down to one gram of force. They can feel hot and cold, normal thermal thresholds, but they feel it in their missing hand."
According to Kuiken, prosthetics technology is at the point where we're likely to see a growing number of advanced artificial limbs that will help amputees lead normal lives.