Swiss researchers have developed a prototype prosthesis allowing above-knee amputees to regain the sensitivity of the lost limb.
“It’s the first time I feel my leg, my foot”. Thanks to a prototype equipped with sensors and linked to the nervous system, developed by researchers from the ETH Zurich University, in Switzerland, and the start-up SensArs Neuroprosthetics, above-knee amputees have been able to regain sensitivity of the lost limb, allowing them, among other things, to make the difference between walking on tarmac or in the sand. The results of this study were published on October 2 in the journal Science Translation Medicine.
It is thanks to a sensory sole placed under the prosthetic foot, as well as sensors located in the knee, that this prosthesis is so special. The signals sent are translated by the device into electrical impulses, the language of the human nervous system. Tiny electrodes, implanted in the nerve, then lead them to the residual device. The signals from the residual nerves are then transmitted to the brain, allowing the patient to perceive what is happening on and under the prosthesis. He can thus sense obstacles and avoid falls.
Thus, unlike those who are equipped with a conventional prosthesis, amputees no longer need to think about their movement when they walk or to overstretch the valid leg. Another notable advantage of the new prototype: it reduces patients’ “phantom limb pain”. This term qualifies the pain felt as coming from an amputated limb. They take place when neurons in the area of amputation lead to send pain messages to the brain.
Increase in stamina
“It’s the first time I feel my leg, my foot,” says Djurica Resanovic, one of the two volunteers who participated in the study which lasted three months. During the trials, while blindfolded and with earplugs plugged, he was able to tell where his foot was touched by another person and how much the knee was bent.
“Using this prosthesis improved the quality of their walking and increased their endurance, both in the laboratory and in a real environment,” note the researchers in reference to the volunteers.
In 2015, Austrian researchers obtained a similar result in a below-knee amputee. But this is the first time that such a prosthesis has been put in place for a lower limb amputated above the knee, say the scientists. “We have developed the first leg with sensations intended for significant invalids, above the knee amputees, which allows to overcome unexpected obstacles without falling, or to climb stairs very quickly. Both of these tasks are extremely difficult, if not impossible, for amputees who wear commercial prostheses,” says Stanisa Raspopovic, professor at ETH Zurich.
A four-year clinical trial is planned
“We are developing sensory feedback technology to augment prosthetic devices,” says Francesco Petrini, CEO and co-founder of SensArs Neuroprosthetics. “An investigation of more than 3 months, with more subjects, and with an in-home assessment, should be carried out to provide more robust data in order to draw clinically meaningful conclusions on an improvement in the health and quality of life of the patients. patients,” he concludes. This is why the researchers have just launched a clinical trial over four years to implant their prosthesis in “a significant number of patients” and follow them over a longer period.
Currently, a lot of work is being done to try to make life easier for amputees, whether to reduce their pain or help them regain lost sensations. A few months ago, French researchers from the CNRS and Aix-Marseille University announced that they had succeeded in developing a prosthetic arm capable of detecting the movements of the phantom limb.
Then, in September, American scientists revealed that they had made an electronic glove, to be worn over a prosthetic hand, capable of providing softness, warmth, appearance and sensory perception similar to that of the human limb.
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