To control the prosthetic, the patient has to think like they are controlling a phantom arm and to imagine some simple manoeuvres, such as pinching two fingers together. Sensor technology interprets the electrical signals sent from spinal motor neurons and uses them as commands.
The Imperial team says that, by detecting signals from spinal motor neurons in parts of the body undamaged by amputation means more signals can be detected by the sensors connected to the prosthetic. Ultimately, they believe, more commands could be programmed into the robotic prosthetic, making it more functional.
Dr Dario Farina, from Imperial’s Department of Bioengineering, said: “When an arm is amputated, the nerve fibres and muscles are also severed, which means it is 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 our technology can detect and decode signals more clearly, opening the possibility of robotic prosthetics that could be more intuitive and useful for patients.”
To create the technology, the researchers decoded and mapped some of the information in electrical signals sent from the re-routed nerve cells and then interpreted them in computer models. These models were then compared to models of patients with functioning arms. Specific motor neuron signals were then encoded as commands into the prosthetic’s design.
Ultimately, the scientists say they want to decode the meaning behind all signals sent from the motor neurons, so they can program a full range of arm and hand functions in the prosthetic. In theory, this would mean the user could use the prosthetic almost as seamlessly as if it was their own arm.
The next step will involve extensive clinical trials with a much wider cross section of volunteers so the technology can be made more robust.