Revolution in Artificial Limbs Brings
Feeling Back to Amputees
By Josh Fischmann, for National Geographic
PUBLISHED FEBRUARY 22, 2014
Something is missing. Every amputee knows it, and it is more than the arm or leg they have lost.
They can get replacements for those limbs: substitutes made from metal and plastic, controlled by
advanced computer chips, with the ability to grip, to turn, to step. But they are tools, not part of the
patients themselves. They have no sensitivity, and no instant response to a patient's intentions.
Because of that lack of feeling and control, says Dennis Aabo Sørensen (pictured below), a 36-yearold from Denmark who lost his left hand in a fireworks explosion nearly a decade ago, he could tell
what he was touching with his prosthetic hand only by looking at it.
Now, for Sørensen and other amputees, all that is changing. Scientists announced they had wired
pressure sensors in the fingers of an artificial hand to sensory nerves in Sørensen's upper arm. He
grabbed a block, and his nerves tingled. "I could feel round things and soft things and hard things,"
he says. "It's so amazing to feel something that you haven't been able to feel for so many years." This
is more than a psychological boost; experiments show that sensory feedback vastly improves a
patient's ability to control a prosthetic, even to the point of picking stems off of fruit.
Article Adapted from: http://news.nationalgeographic.com/news/2014/02/140222-artificial-limbs-feelingprosthetics-medicine-science/
Here’s how it works. To create a sense of feeling, sensors were added to the prosthetic's fingers.
The sensors generated electrical signals as the fingers pushed on an object (step 1). However, these
signals could NOT be detected by the nervous system. Those signals were fed to a computer that
converted it into something the nervous system could understand (step 2 and 3). The new signal
was relayed to electrodes implanted under Sørensen's skin. These electrodes caused undamaged
sensory nerves in his stump to fire, sending messages to the brain (step 4). In response, he felt
different tingling sensations, depending on the amount of pressure he needed to apply to hold the
object. In this way, he gradually came to associate the tingles with different qualities, such as
hardness, softness, and roundness.
For a month, Sørensen went through a gauntlet of tasks designed to simulate the challenges of daily
living—reaching, turning, squeezing, pinching—things that Sorensen hadn't done in nine years.
Receiving sensory feedback from an object is a game-changer in the patient's relationship to the
world. Without such touch, for example, amputees have to watch their prosthetic hands to see if
they are gripping a paper cup too hard—often too late to prevent a spill.
WATCH A VIDEO CLIP at: https://www.youtube.com/watch?v=QtPs8d4JbwY
Article Adapted from: http://news.nationalgeographic.com/news/2014/02/140222-artificial-limbs-feelingprosthetics-medicine-science/