Russian developers are close to creating an electronic leg prosthesis that can restore the patient’s ability to feel a limb. Surgeons implanted electrodes in the participant’s stump, which were connected to a sensor on an artificial foot. It generates an electrical signal that enters the human nervous system and is converted into sensations. Due to electrical stimulation, scientists managed to save a man from phantom pain. They also found out what types of sensitivity correspond to stimulation with current with different characteristics. According to the scientists, the results obtained are important for both fundamental research and applied problems.
And feel in a hurry
The specialists of the company “Motorika” on the basis of the FEFU Medical Center, together with colleagues from Skoltech, are developing a sensitive leg prosthesis. The scientists implanted electrodes into the patient’s stump and spinal cord. Through them, they managed to transmit signals from sensors installed on an artificial analogue of the foot to the human nervous system. In addition, the directed electrical impact made it possible to relieve the participant of the study from phantom pains.
“Our development solves two key problems of people with amputations at once: it stops phantom pains that are difficult to remove pharmacologically, and also returns lost sensations. Our hypothesis is that the feeling of prosthetic legs will save a person from excessive effort when walking, will allow in the future to develop a controlled bionic foot, protect the back from damage and asymmetric load, and also increase psychological comfort, since a prosthetic leg is no longer perceived as a means of rehabilitation or the gadget feels like its own limb,” said Yury Matvienko, head of invasive research at Motoriki.
Photo: Motorika
Study preparation
The next stage of research is scheduled for the second half of 2023. In it, a group of specialists will expand the sample of patients and try to capture a wider range of different sensations from stimulation of the nervous system, as well as new technical solutions in prosthetics.
The work on the prosthetic leg was preceded by two phases of research on the sensing of prosthetic arms that could also transmit sensation. The first phase of the study involved two people with a paired amputation of the upper limbs.
Photo: Motorika
Study preparation
During the surgery, the nerves in the patients’ forearms were connected to electrodes. Then the scientists found out what sensations the participants cause current pulses with different characteristics. It turned out that it could be, for example, squeezing the phantom hand, vibration in the fingers. Scientists installed pressure sensors on prosthetic hands that generated electrical impulses. With their help, patients were able, without looking, to touch to determine the small or large size of objects.
The second phase of the study involved three volunteers with various hand injuries who were also implanted with electrodes. In this study, in addition to the dimensions (large, medium, small) of objects, they were also able to distinguish between soft and hard.
Truth in your feet
“Past sensing surgeries for prosthetic arms have shown positive results, so we decided to move on and work on the lower extremities. We have now placed three electrodes on the peripheral nerves and the spinal cord. In this way, we are creating a system that will work with the consequences of amputation of both the upper and lower extremities,” said the neurosurgeon who performed the implantation, expert of the FEFU TsTI Center Artur Biktimirov.
Artur Biktimirov implants electrodes in the leg stump and spinal cord
Photo: FEFU
After experiments on the hands, scientists were able to observe similar sensations in patients in the areas of the foot and knee, Gurgen Sogoyan, a researcher at the Skoltech Center for Neurobiology and Neurorehabilitation, told Izvestia. According to the specialist, often the patient reported how he felt.
This allowed specialists to conduct additional electrophysiological experiments, for example, to record brain potentials during stimulation of electrodes using EEG. These studies are interesting from a fundamental point of view, but are also necessary for the applied development of neuroprostheses with concomitant suppression of phantom pain, the expert said.
Photo: FEFU
According to Mikhail Lebedev, chief researcher at IEPhB RAS, testing the prosthesis sensing system on patients with amputation of the lower extremities is an important stage of the project, since their innervation, control and sensations differ significantly from those of the upper ones. It is known that the foot is the most complex sensory organ necessary for controlling posture and walking. Also, the innervation of the legs is more dependent on the subcortical centers of the brain, so its features need to be carefully studied.
“The first results obtained are impressive, as they indicate the possibility of sensing the phantom foot and the reduction of phantom pain,” said Mikhail Lebedev.
The subject in a blind test determines the texture of surfaces
Photo: Motorika
As FEFU rector Boris Korobets explained to Izvestia, there are no analogues of such products. There are no prostheses in the world that would restore sensitivity. It is in Russia that developers, scientists and surgeons first teamed up to perform operations with invasive microelectronics, which ensures the interaction of bionics with the human body.
Now specialists all over the country are interested in this technology. The developers hope that the project will help people from different regions and abroad to return to their usual feelings.
