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It can restore a sense of touch to those missing limbs - and could revolutionise prosthetics.

Researchers have revealed two patients fitted with radical new artificial limbs that interface directly with their skeleton and nervous system.

They were able to identify objects that touched their skin, and do everything from chop wood to drive trucks. 

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Keith Vonderhueval, a Swedish truck driver, was one of the first  to receive the technology, which interfaces directly to his skeleton and nerves.

One, a man who lost his right hand in an industrial accident four years ago can feel objects again thanks to a bionic hand with a sense of touch.

Wearing a blindfold Igor Spetic, 48, was aware of arm hairs rising when a researcher brushed the back of his artificial device with a cotton ball.

He said: 'I knew immediately it was cotton.'

Nerves that used to relay the sense of touch to the brain are stimulated by contact points on seven millimetre 'electrode cuffs' that encircle major nerve bundles in the arm.

Once the cuffs have been connected to the right nerves Spetic can feel the back of his hand and fingers being touched when the corresponding locations on the prosthetic come into contact with things ranging from rough sandpaper to smooth metal.

The system - which is limited to the lab at this stage - has worked for two-and-a-half years in Spetic's case and 18 months for a second patient in the trial Keith Vonderhueval.

Similar research involving prosthetic hands has reported sensation lasting one month and - in some cases - the ability to feel began to fade over weeks.

Because of Vonderheuval's and Spetic's continuing progress researchers are hopeful the method can lead to a lifetime of use and optimistic a system can be developed for use at home within five years.

Spetic has a physically challenging job as a truck driver in northern Sweden, and since the surgery he has experienced that he can cope with all the situations he faces - everything from clamping his trailer load and operating machinery, to unpacking eggs and tying his children's skates, regardless of the environmental conditions.

Patient wearing a prosthetic limb directly attached to the skeleton and neuromuscular system.

What's more Spetic's phantom pain - which he described as a vice crushing his closed fist since the hand was sliced off by a forging hammer while making an aluminium jet part - subsided almost completely.

Vonderhueval - who had less phantom pain after losing his right hand and much of his forearm in an accident - said his is also almost gone.

Both men said the first time they were connected to the system and received the electrical stimulation was the first time they'd felt their hands since their accidents.

In the ensuing months they began feeling familiar sensations and were able to control their prosthetic hands with more dexterity.

Igor Spetic Holding a Cherry Tomato

Professor Dustin Tyler, of Case Western Reserve University in Ohio, said: 'The sense of touch is one of the ways we interact with objects around us.

'Our goal is not just to restore function but to build a reconnection to the world. This is long-lasting, chronic restoration of sensation over multiple points across the hand.'

'The work reactivates areas of the brain that produce the sense of touch. When the hand is lost the inputs that switched on these areas were lost.'

Surgeons implanted three electrodes in Spetic's forearm - enabling him to feel 19 distinct points - and two in Vonderhuevel's upper arm enabling him to feel 16.

HOW IT WORKS

The direct skeletal attachment is created by what is known as osseointegration - a technology in limb prostheses pioneered by associate professor Rickard Branemark and his colleagues at Sahlgrenska University Hospital in Sweden.

The artificial arm is directly attached to the skeleton, thus providing mechanical stability.

Then the human's biological control system, that is nerves and muscles, is also interfaced to the machine's control system via neuromuscular electrodes. 

This creates an intimate union between the body and the machine; between biology and mechatronics.

The patient's arm was amputated over 10 years ago. 

Before the surgery, his prosthesis was controlled via electrodes placed over the skin.

Vonderhueval - who lost his hand in 2OO5 - said: 'The sense of touch actually gets better. 

'They change things on the computer to change the sensation. One time it felt like water running across the back of my hand.'

When they began the study published online by the journal Science Translational Medicine the sensation Spetic felt when a sensor was touched was a tingle.

To provide more natural sensations the researchers have developed algorithms that convert the input from the sensors taped to a patient's hand into varying patterns and intensities of electrical signals.

The sensors themselves aren't sophisticated enough to discern textures - they detect only pressure.

The different signal patterns - passed through the electrodes - are read as different stimuli by the brain. 

The patterns are still being fine-tuned and Spetic and Vonderhuevel who both live in Ohio appear to be becoming more attuned to them.

A blindfolded Vonderhuevel has held grapes or cherries in his prosthetic hand - the signals enabling him to gauge how tightly he's squeezing - and pulled out the stems.

He said: 'When the sensation's on it's not too hard. When it's off you make a lot of grape juice.'

Prof Tyler believes everyone creates a map of sensations from their life history enabling them to correlate an input to a given sensation.

He said: 'I don't presume the stimuli we're giving is hitting the spots on the map exactly but they're familiar enough the brain identifies what it is.'

In addition to hand prosthetics Prof Tyler believes the technology can be used to help those using prosthetic legs receive input from the ground and adjust to gravel or uneven surfaces.

Beyond that the neural interfacing and new stimulation techniques may be useful in controlling tremors, deep brain stimulation and more.