US scientists have restored a sense of touch to two bionic hand patients.
The men can now delicately pluck the stalks out of cherries.
Sensors on the artificial hand are used to send signals directly to the nerves, the study, published in Science Translational Medicine, said.
Meanwhile, a Swedish team has made a separate breakthrough in artificial limbs – anchoring bionic arms directly on to the bone to improve control.
One of the beneficiaries of the American work was Igor Spetic, who lost his right hand in an accident four years ago.
Igor Spetic was fitted with a bionic replacement, but it was incapable of feeling the world around him.
He had to carefully watch what he was doing and judge by eye whether he was squeezing too hard.
A team at Case Western Reserve University attached sensors to the bionic hand and in surgery fitted “cuffs” around the remaining nerves, which were capable of delivering electronic stimulation.
The team could send different patterns of electronic stimulation to the nerves using a computer. These were interpreted in the brain as different sensations.
The team “mapped” these sensations to 19 different locations on the hand, from the palm to the tip of the thumb, and matched the sensors to the different electronic patterns of stimulation.
They then moved on to pressure and textures. Igor Spetic can tell, while blindfolded, whether he is handling different materials such as Velcro or sandpaper.
He has been using the sensing hand for two-and-a-half years. Another patient has been using the system for one and a half years.
In both patients the modified hand had the added bonus of eliminating “phantom limb pain”, in which patients still feel pain from the hand that is no longer there.
Meanwhile, scientists at Chalmers University of Technology in Sweden say they have implanted the first bone-anchored bionic arm.
The technique known as “osseointegration” involved connecting the arm directly to the bone, nerves and muscles in the residual stump of the patient’s arm.
It gave the patient better control.