This amazing set of robotic arms and hands create the same function and feel like it is a real thing. Two recent europrosthetic developments, published as a set of two studies in Science Translational Medicine this week, employed implanted electrodes to help imitate the control, freedom of movement, and sense of touch. The first development restored the power to sense familiar sensations, while the second recreated genuine motor control – both have been tested in real-life by amputees.
Case Western Reserve University’s Dustin Tyler and his team made a prosthetic hand that connects to under-the-skin electrodes. Two to three electrodes were fitted around major nerve bundles in two adult males who were deprived of their hands due to accidents. Post implantation surgery, the men had no problems performing routine tasks.
The team also boosted sensory perception by firing electrical pulses across the men’sprosthetic hands. Altering the intensity of the stimulation stirred discrete neurons with different patterns—mimicking what happens in our hands naturally when we touch and grip. Later on, the patients disclosed that they felt as if they were grabbing objects with a natural extension of their body, rather than an external tool. ‘The work revives sections of the brain that generate the sense of touch,’ Tyler says. ‘When someone loses his hand, the inputs that activate these areas are lost as well.’
Routine sensations were restored over multiple points all over the hand. Two men were blindfolded and their statements were recorded. One man stated he felt like cotton ball was brushing against the back of his prosthesis, while the other felt water was gushing through his artificial hand. The reason was that signals were communicated via a computer into nerves in their arms and to their brains. They have more control over their hands – in fact like shown in the picture, one recipient could even hold a cherry tomato. They did routine tasks with dexterity like: grabbing (and not crushing) grapes, pulling stems off cherries, and squeezing toothpaste onto a toothbrush.
In a second study, a team led by Max Ortiz-Catalan from Chalmers University of Technology recreated the freedom of movement of a natural arm. They constructed a “osseointegrated” arm that connected straight to the bone, nerves, and muscles of an adult male. The male’s arm was amputated above the elbow. The fake arm is affixed to the bone in the stump by a titanium rod serving as an extension of the skeleton.
This osseointegrated concept employs implanted electrodes woven under the skin to dispense a steady supply of sensory feedback, helping to activate nerves for more accurate control. The recipient fitted with prosthesis was able to perform well tasks like: clamping his trailer load to tying his children’s skates, even occasionally sleeping with it attached—without any problems.
“We have employed osseointegration to make a long-term stable fusion between man and machine, where we have unified them at discrete levels. The “prosthetic arm” is connected to the skeleton, thus bestowing mechanical stability,’ Catalan explains in a university statement.