Researchers at Chalmers University of Technology in Sweden have developed a new technique that could allow above-elbow amputees to better use robotic prostheses, including making individual finger movements. Unlike below-elbow amputees, these patients have a more limited number of remnant muscles with which to produce fine control of multiple bionic structures, such as bionic fingers. To address this, these researchers performed a surgical procedure on an above-elbow amputee and reconfigured his peripheral nerves to create small neuromuscular constructs that are served by an array of sensors. This dramatically increased the ability of the amputee to exert specific control on multiple elements of a robotic prosthetic, and may represent a road map to increase the dexterity and control of such patients.
Robotic prostheses are a huge leap in empowering amputees to regain some of their ability to perform daily tasks. However, amputations vary in where they are performed on a limb. In general, for upper limb amputees, below-elbow amputations leave numerous small residual muscles that could potentially be leveraged to help control aspects of the robotic limb, such as the movement of individual fingers. For above-elbow amputations, however, there are fewer options in terms of remaining muscles that can be used to control the prosthetic.
To address this, these researchers have created a new approach that could give above-elbow amputees more choice. They performed the procedure on an amputee who volunteered for the project, and surgically dissected the peripheral nerves in his residual upper arm and redirected some of them to small free muscle grafts that also included small electrodes. In effect, this created a whole series of artificial neuromuscular constructs that could be used by the patient to activate individual components of a bionic limb.
The new neuromuscular architecture was connected to a bionic limb through a titanium implant that the team surgically added to the residual bone, providing more strength and comfort compared with the classic ‘socket’ fitting. When the patient activates the neuromuscular constructs in specific patterns, AI algorithms interpret his intentions with regard to specific movements of his bionic limb.
“In this article, we show that rewiring nerves to different muscle targets in a distributed and concurrent manner is not only possible but also conducive to improved prosthetic control,” said Max Ortiz Catalan, a researcher involved in the study. “A key feature of our work is that we have the possibility to clinically implement more refine surgical procedures and embed sensors in the neuromuscular constructs at the time of the surgery, which we then connect to the electronic system of the prosthesis via an osseointegrated interface. A.I. algorithms take care of the rest.”
See some videos explaining and demonstrating the research below:
Study in journal Science Translational Medicine: Improved control of a prosthetic limb by surgically creating electro-neuromuscular constructs with implanted electrodes