A study in Science Translational Medicine documents how scientists were able to successfully characterize and implement bionic leg technology in three amputees to help them merge with their bionic prosthetic legs as they climb over various obstacles without having to look.
The amputees report using and feeling their bionic leg as part of their own body, thanks to sensory feedback from the prosthetic leg that is delivered to nerves in the leg’s stump.
Djurica Resanovic lost his leg in a motorbike accident several years ago which resulted in amputation above the knee. Via the neuroprosthetic leg technology, Resanovic was successfully merged with his bionic leg during clinical trials in Belgrade, Serbia.
“After all of these years, I could feel my leg and my foot again, as if it were my own leg,” Resanovic says about the bionic leg prototype, in a media release from Ecole Polytechnique Fédérale de Lausanne.
“It was very interesting. You don’t need to concentrate to walk, you can just look forward and step. You don’t need to look at where your leg is to avoid falling.”
The scientists were from a European consortium led by Swiss Institutions, ETH Zurich and EPFL spin-off SensArs Neuroprosthetics, with clinical trials in collaboration with institutions in Belgrade, Serbia.
“We showed that less mental effort is needed to control the bionic leg because the amputee feels as though their prosthetic limb belongs to their own body,” explains Stanisa Raspopovic, ETH Zurich professor and co-founder of EPFL spin-off SensArs Neuroprosthetics, who led the study, in the release.
“We show that the feedback is crucial for relieving the mental burden of wearing a prosthetic limb which, in turn, leads to improved performance and ease of use,” he adds.
Wearing a blindfold and earplugs, Resanovic could feel his/her bionic leg prototype thanks to sensory information that was delivered wirelessly via electrodes surgically placed into the stump’s intact nervous system. These electrodes pierce through the intact tibial nerve instead of wrapping around it.
Resanovic continues, “I could tell when they touched the [big toe], the heel, or anywhere else on the foot. I could even tell how much the knee was flexed.”
Resanovic is one of three leg amputees, all with transfemoral amputation, who participated in a three-month clinical study to test the new bionic leg technology.
Thanks to detailed sensations from sole of the artificial foot and from the artificial knee, all three patients could maneuver through obstacles without the burden of looking at their artificial limb as they walked. They could stumble over objects yet mitigate falling. Most importantly, brain imaging and psychophysical tests confirmed that the brain is less solicited with the bionic leg, leaving more mental capacity available to successfully complete the various tasks, the release explains.
“We develop the sensory feedback technology to augment prosthetic devices,” explains Francesco Petrini, CEO and co-founder of SensArs Neuroprosthetics, and who is guiding an effort to bring these technologies to market, in the release.
“An investigation longer than 3 months, with more subjects, and with in-home assessment, should be executed to provide more robust data to draw clinically significant conclusions about an improvement of the health and quality of life of patients.”
The bionic leg prototype is equipped with seven sensors all along the sole of the foot and one encoder at the knee that detects the angle of flexion. These sensors generate information about touch and movement from the prosthesis. Next, the raw signals are engineered via a smart algorithm into biosignals which are delivered into the stump’s nervous system, into the tibial nerve via intraneural electrodes, and these signals reach the brain for interpretation.
“We believe intraneural electrodes are key for delivering bio-compatible information to the nervous system for a vast number of neuroprosthetic applications. Translation to the market is just around the corner,” comments Silvestro Micera, co-author of the publication, EPFL’s Bertarelli Foundation Chair in Translational Neuroengineering, professor of Bioelectronics at Scuola Superiore Sant’Anna, and co-founder of SensArs Neuroprosthetics.
[Source(s): Ecole Polytechnique Fédérale de Lausanne, Science Daily]
