Bionic arms controlled by a patient’s thoughts are a radical improvement on existing artificial arms, according to researchers. Existing prosthetic arms rely on a patient twitching the muscles in the stump of their damaged arms. But because the muscle is damaged, an amputee may only be able to carry out limited movements, such as one or two grasping actions.The limited range of movements is a reason why up to 50 per cent of amputees abandon their electronic arms at present.
But by linking the nerves from the spine into an intact piece of muscle, either in the patient’s chest or biceps, patients were able to carry out a much wider repertoire of movements.These included opening and closing the hand, rotating the wrist and moving the arms up and down. To control the new prosthetic, the patient simply has to think like they are controlling a phantom arm. By imagining the desired action, such as pinching two fingers together, the signal is carried by the nerves to the muscle. Electronic sensors on the skin surface pick up the signals, which then control the robotic arm. Ultimately it is hoped that more commands could be programmed into the robotic prosthetic, allowing more actions.
Dr Dario Farina, now based at Imperial College London, and colleagues in Europe, Canada and US led the research. He said yesterday: ‘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 researchers carried out lab-based experiments with six volunteers at the University of Vienna, who were either amputees from the shoulder down or just above the elbow. After 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.
While improvements are expected, the authors hope to have the prosthesis on the market in the next three years. A variety of ‘bionic arms’ are being tested by researchers. While an alternative approach is using brain implants, the advantage of using a nerve from the spine is that the approach is compatible with existing prosthetic arms – and no wires need to be inserted into the brain to control the device.
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