COULD PEOPLE WITH A PROSTHESIS EVER FEEL AGAIN?
Modern prosthetics have come a long way since the peg legs of the Civil War, and in the last few decades electronic components have also been incorporated. But these replacements don’t restore sensation for their wearers. Amputation cuts off nerves corresponding to appendages like fingers and toes and severs the sensory pathways that allow people to grip objects and feel the floor to balance, thereby hindering the ability to move. When these links are eliminated the body can’t communicate sensations to the brain, and when it comes to prosthetic devices—even modern ones with electronic components—communication between man and machine is limited. “The biggest gap is between what the prosthesis can feel and what the human can feel,” says MIT biomedical engineer Shriya Srinivasan.
After seeing the difficulties experienced by a friend with a prosthesis, Srinivasan began pondering how prosthesis wearers could experience the sense of touch. Her research lead to the development of the Cutaneous Mechanoneural Interface (CMI), a surgical technique coupled with a “biohybrid organ” device that creates and conveys nerve signals to the brain that replicate tactile sensations, thus improving the interface between man and machine by enabling seamless communication between device and body.
Although the CMI can be retrofitted for integration with an existing prosthetic device, ideally the proper arrangements would be made at the time of amputation so as to better reconstruct sensory fibers within the residual tissue and prepare the area to accept a digital device, because as Srinivasan emphasizes, it’s not enough to build a fancy device—the human body must be made ready to interact with it. According to Srinivasan, CMI has advantages over existing electronics-equipped prosthetics, which amputees may eschew because sensory information isn’t sent to the brain and their experience with the device can be frustrating: “The patient doesn’t have to learn a new sensation or a new way of communication—the Cutaneous Mechanoneural Interface communicates through natural pathways.” Ensuring better mobility and sensation conveyance makes it possible to mitigate some of the impacts of amputation and improve a patient’s quality of life and experience of the world. Thus the hope is that beyond reconnecting the body with the sensory abilities of a missing limb CMI will also reconnect amputees more fully with their lives and society.