Bionic Hands Mimic Human Control With Sensation of Touch
By Michelle Fay CortezOct 8, 2014 6:13 PM ET
New advances in prosthetic devices
are allowing people with artificial hands to tell when they’re
holding something without even looking, and pluck a stem from a
cherry without bursting it, two studies have shown.
Different groups in the U.S. and Europe today reported key
breakthroughs in connecting healthy nerves to a prosthesis,
giving patients whose hands or arms have been amputated better
control of the devices and, for the first time, returning at
least some of the sensation of touch.
In one study, U.S. surgeons connected electrodes to nerves
in a man’s forearm that were stimulated when someone placed
something in his bionic hand. The procedure allowed the patient
to tell when he was touching something without having to see it.
In the other report, Swedish scientists surgically connected a
titanium rod to existing bone, nerves and muscles in an
undamaged part of the arm, then ran wires through the prosthesis
helping the patient control its use more precisely.
“What is fascinating about this is the perception of touch
actually occurs in the brain, not in the hand itself,” said
Dustin Tyler, an associate professor of biomedical engineering
at Case Western Research University in Cleveland, who led the
U.S. effort. “Losing the limb is just losing the switch that
turns that sensation on or off.”
Patient wearing a prosthetic limb directly attached to the skeleton and neuromuscular... Read More
Both results were reported today in the journal Science
Translational Medicine.
Igor Spetic, 48, said he vividly remembers the first time
he felt his right hand again, two years after it was amputated
following an industrial accident. Researchers working to craft
his prosthetic pulled a curtain to limit his view and then
placed a large, hard block into his palm.
‘Amazing’ Feeling
“I hadn’t felt anything other than pain for two years,”
he said by telephone. The new sense of feeling “was amazing. It
felt like my hand was actually working, that I didn’t have a
prosthetic. That’s how close to reality it was for me.”
The new hand allows Spetic to perform routine tasks in a
laboratory without serious thought or concentration, he said,
including picking up and drinking from a flimsy water bottle
without squirting it all over or plucking stems from a cherry
without bursting it.
There are currently 19 spots on the prosthetic that Spetic
can feel. That’s likely to double or triple within a year, Tyler
said in a telephone interview.
‘Refined’ Sensation
“The thing we like is that we can get that refined of
sensation,” Tyler said. “There was skepticism before we did
this work that we could get that kind of control. Now we know
this has the potential for a true restoration of sensation for
people when they are missing their hand.”
Source: Tyler Lab, Cleveland VA Medical Center via EurekAlert
An illustration of the nerve interface.
Spetic said the most unexpected benefit was the end of his
phantom pain, which he often felt as if he was fiercely
clenching his fist. “That was a bonus they didn’t anticipate,”
he said.
When researchers vary the intensity, frequency and location
of the stimulation, it allows Spetic to pick up the signals for
different fabrics such as burlap and cotton, textures like
sandpaper, and motion such as a pulse or water running across
his hand. There remain several steps ahead.
For now, the sensors on his prosthetic arm are taped to the
outside of the device, making it impossible to use at home. The
researchers are working on an integrated system that would be
sturdy enough for routine use. The sensors also can’t yet
distinguish between textures, so Spetic only feels unique
sensations beyond a tingling or pressure when the researchers
deliver the stimulation.
Swedish Study
The Swedish scientists, meanwhile, developed a fully
integrated robotic arm. Their patient, identified only as
Magnus, has used the device at home and work for the past year,
even sleeping with it attached.
The tight connections allow Magnus, a truck driver, to have
more precise, natural control over the arm. He can tie his
children’s shoes, catch a ball out of the air and even crack an
egg on command, according to their report in the journal. Using
his old electric prosthesis, an egg or ball would fly out of his
hand if he moved too quickly or extended his arm too far.
“The major contribution of our work is we have this
interface that allows implanted electrodes to become clinically
viable,” said Max Ortiz Catalan, a research scientist at
Chalmers University of Technology in Gothenburg, Sweden.
“Patients can take them home and use their prosthesis for their
activities of daily living. We know it’s reliable and long-term,” he said in a telephone interview.
Ortiz Catalan is planning a larger study of the devices,
currently used only for Magnus, next year. The Cleveland
researchers already are working with another amputee and
companies to try to devise a prosthetic that incorporates the
sensors into the device itself.
(An earlier version of this story misspelled Spetic’s last
name.)
To contact the reporter on this story:
Michelle Fay Cortez in Minneapolis at
mcortez@bloomberg.net
To contact the editors responsible for this story:
Reg Gale at
rgale5@bloomberg.net
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