A team led by Swiss institutions has developed bionic legs that allow amputees walk freely while thinking about different activities other than controlling the device. The study published on Wednesday in the journal Science Translational Medicine showed that tiny electrodes implanted in the patients' thigh nerve give them natural sensations of touching the ground with the foot. Leg amputees tend not to trust the prosthesis and to rely too much on the healthy leg since the prosthesis is not connected with the brain. Scientists from multiple European institutions including ETH Zurich placed an insole with seven sensors under the prosthetic foot and one encoder at the knee that detects the angle of flexion. The signals from the insole and knee are translated into impulses of current, generating information about touch and movement. The raw signals are engineered by a smart algorithm into biosignals which are delivered to the residual peripheral nerve through tiny electrodes implanted into the nerve itself, according to the study. Then, those signals are conveyed to the brain, which is able to perceive what happens and to adjust the walking accordingly. "This is the first prosthesis in the world for above-knee leg amputees equipped with sensory feedback," said Stanisa Raspopovic, ETH Zurich professor who led the study. "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," said Raspopovic. Djurica Resanovic is one of the three amputee volunteers in the study. "You don't need to concentrate to walk, you can look forward and step, you don't need to look where your leg is to not fall," said Resanovic. "First time that I feel my leg, my foot," Resanovic stressed. Now, all three patients can maneuver through obstacles without the burden of looking at their artificial limb as they walked. Also, brain imaging showed that the brain is less solicited with the bionic leg, allowing more mental capacity to do other tasks. Scientists are working to translate the technology into the bionic hand and nerve stimulation for heart-transplant patients. Source
