Scientists at Imperial College London have developed a prosthetic arm that detects spinal nerve signals and can be controlled by thought.
They believe that patients sense they are moving a phantom arm, imagining simple manoeuvres such as pinching two fingers together.
Technology embedded in the arm then interprets electrical signals sent from spinal motor neurons and uses them as commands.
A study published in the journal Nature Biomedical Engineering claims more signals from spinal motor neurons in parts of the body undamaged by amputation can be detected than from remnant muscle fibres in the shoulder or arm, which are often damaged.
Robotic arm prosthetics currently on the market are based on the latter, limiting them to just one or two grasping commands, and are discarded by around 40-50 per cent of users globally as a result.
Dr Dario Farina, who is based at Imperial College London, carried out much of the research while at the University Medical Centre Gottingen.
Dr Farina said: “When an arm is amputated the nerve fibres and muscles are also severed, which means that it is very difficult to get meaningful signals from them to operate a prosthetic.
“We’ve tried a new approach, moving the focus from muscles to the nervous system.
”This means that our technology can detect and decode signals more clearly, opening up the possibility of robotic prosthetics that could be far more intuitive and useful for patients. It is a very exciting time to be in this field of research.”
The healthcare project was conducted in conjunction with Dr Farina’s co-authors in Europe, Canada and the USA.
Researchers carried out lab-based experiments with six volunteers who were either amputees from the shoulder down or just above the elbow.
After some physiotherapy training, the amputees were able to make a more extensive range of movements than would be possible using a classic muscle-controlled robotic prosthetic.
They came to this conclusion by comparing their research to previous studies on muscle-controlled robotic prosthetics.
Volunteers were able to move the elbow joint and do radial movements – moving the wrist from side to side – as well as opening and closing the hand. This means that the user has all basic hand and arm functions of a real arm.
Further refinements are needed to make the technology more robust, but researchers suggest the current model could be on the market in the next three years.
The work was supported by the European Research Council, the Christian Doppler Research Foundation of the Austrian Federal Ministry of Science, Research and Economy and the European Union’s Horizon 2020 research and innovation programme.