Written by Todd DePastino
Twenty years ago, the prospect of a bionic arm controlled by the mind of an amputee was the stuff of science fiction.
But last year, Harry Van Riper volunteered for a VA feasibility study for just such a “smart” limb. If he receives it, Harry will be able to pinch, grab, point, and grip by sending signals from his brain.
The specific technology Harry is furthering is called “osseointegration” (OI) the direct attachment of a robotic prosthetic limb to the bone itself, making it a permanent part of the body and nervous system.
Inside the implant is a sensor that will attach to severed nerves remaining in Harry’s shoulder. The sensor transmits signals from the brain to the prosthesis, which will enable Harry to use his hand intuitively.
OI technology is being tested and improved at the George E. Wahlen VA in Salt Lake City, Utah. Scientists there are working to improve socket attachment and reduce complications resulting from the invasive procedure.
Harry has made two trips to Salt Lake City to be assessed as a possible recipient of a new left arm. One big thing makes Harry an especially promising candidate. As a “transhumeral” (above the elbow) amputee, Harry still has active nerve endings in his shoulder receiving brain signals.
Fifty-five years after Harry lost his left arm, Harry’s brain still thinks it’s attached. In Harry’s mind, he can make a fist, open a door, and sip a cup of coffee using his phantom left hand. The down side to such ability has been “phantom pain”—the experience of real pain in the missing limb. In the first years of Harry’s rehabilitation, his phantom pain was excruciating. It only got better with exercise.
That those nerve endings are still alive means they can relay neurological signals that can, in turn, be captured, interpreted, amplified, and translated into instructions guiding movement in a bionic arm. It all happens in a flash so that the arm moves naturally, as if it were native to the body.
Think about that. The mere intention arising in Harry’s brain to move a finger will cause the micro-computer in Harry’s shoulder to run that neural signal through an algorithm that produces action in a robotic finger.
The implications of this technology are staggering. This system has the potential to give movement to the paralyzed and to liberate those with “locked in syndrome”—people who can think, but not communicate.
The technology also works in reverse. Sensory inputs in the fingers and hand can pulse signals from the environment back up the arm to Harry’s brain, allowing Harry to adjust his grip or position, just as with a biological arm.
The science behind this technology is, of course, extraordinarily complex. The techniques used to separate thick nerve bundles into smaller fibers enabling precise control, to amplify faint nerve signals, and to employ machine-learning algorithms to interpret those signals are unimaginably delicate.
Given Harry’s age and the fact that he’s gotten along well for 55 years without a left arm, you may wonder why he’s submitting to the demanding battery of tests needed for a bionic arm.
“I don’t need the arm,” says Harry. “I’ve never considered myself disabled. I live perfectly without it.”
But, as a man of science and a devout Christian, Harry believes his participation in this study is another way to serve.
“I taught college biology for my career, and I understand and am intrigued by the science behind this technology. More important, I know these new prosthetics will help countless people in the future. Children with missing limbs will be fitted with an implant, and then right-sized bionic arms will be snapped in as they grow. If my participation helps these kids in the future, then I’m happy to do it.”