Scientists at the Medical University of Vienna and Imperial College London developed a new method for precisely detecting the nerve signals remaining after an arm amputation and utilizing them to control an artificial arm, which could form the basis for the development of the next generation of prostheses.
As part of the Natural BionicS project funded by the European Research Council, novel 40-channel microelectrodes were implanted in the muscles of three participants with transhumeral amputations, which had previously been reconnected to nerves through targeted muscle reinnervation.
By combining surgical reinnervation with implantable microelectrodes, the researchers succeeded in directly measuring the activity of individual motor neurons—the nerve cells in the spinal cord that transmit movement commands to the muscles—and linking their signal patterns to specific movement intentions. To achieve this result, the participants mentally performed various movements with their phantom arm.
“Using our method, we were able to precisely identify the nerve signals that underlie, for example, the stretching of a finger or the bending of the wrist,” said Oskar Aszmann, MD, head of the Clinical Laboratory for Bionic Limb Reconstruction at the Department of Plastic, Reconstructive and Aesthetic Surgery at the Medical University of Vienna.
Analysis of the recorded, highly differentiated nerve signals also showed that complex movement intentions remained intact in the nervous system even after amputation and can be mathematically reconstructed. This means that the information can be used in future for the precise control of bionic prostheses.
“This is a crucial step towards making the control of bionic limbs more natural and intuitive,” said Aszmann, an author of the related study.
In the long term, these findings will lead to the development of a so-called bioscreen, a system that visualizes the complex neural patterns of human movements and thus forms the basis for new generations of prostheses, the researchers said.
Editor’s note: This story was adapted from materials provided by the Medical University of Vienna.
The open-access study, “Implanted microelectrode arrays in reinnervated muscles allow separation of neural drives from transferred polyfunctional nerves,” was published in Nature Biomedical Engineering.
