Researchers from ETH Zurich and a company called SensArs have developed a new interface to connect a leg prosthesis with the residual nerves left in the thigh of two patients who had an above the knee amputation. The goal was to provide the people with sensory input from the prosthetic foot.
One challenge that the researchers are trying to overcome is to remove the phantom pain that many amputees feel. One participant in the study is Savo Panic who says that despite not having his lower leg, he feels pain in his big toe, foot, heel, ankle, and calf.
The team wanted to see if providing biofeedback from the prosthetic could help the amputees to walk more comfortably naturally and help reduce pain. In the tests, the prosthetic foot had tactile sensors on the sole and collected data on knee movement that was provided by the electronic knee joint.
Each of the volunteers had tiny electrodes placed into their thigh that connected to the residual nerves there, and they stayed for three months. The team used algorithms to translate information from the tactile and motion sensors to impulses of current that the nervous system could understand. The participants underwent tests that alternated with the feedback and without. The results of those tests made it clear that the feedback was very helpful and made walking less physically demanding.
The team says that the user’s oxygen consumption was reduced while walking. The team also found that the amputees needed to concentrate less on walking with the feedback. The feedback system allowed the users to walk more quickly as well. The interface can also be used for nerve stimulation to reduce the phantom pain the amputees feel. The team says that further in-home studies are needed.