Neural Prosthesis: Body and Mind
The goal of VA researchers is to create a more lifelike artificial limb, and ultimately this will involve the type of direct neural/mechanical interface demonstrated in the BrainGate trial. Because much of VA’s work is aimed at restoring function after the loss of a limb, most of its research in neural prosthetics – restoring motor, sensory, or cognitive functions inhibited by injury or disease – is aimed at restoring movement.
At VA’s Center of Excellence in Functional Electrical Stimulation (FES) – a consortium of the Cleveland VA Medical Center (CVAMC), Case Western Reserve University (CWRU), and MetroHealth Medical Center (MHMC) – researchers focus on applying electrical currents to either generate or suppress neural activity to help restore some functionality – walking, grasping and releasing objects, bladder control, respiration, or other functions. FES currents, introduced through small implanted electrodes, have been shown by VA researchers to greatly enhance the motor abilities of subjects.
The center’s researchers continue to investigate the applications of brain/computer interfaces such as BrainGate; the technical, social, and psychological issues associated with amputation and prosthetics use, including further evaluations of the DEKA arm; and studies in the use of robotics to restore motor function.
VA investigators hope to build on these successes and restore function, via brain-activated neuroprosthetics, to amputees fitted with “smart” artificial limbs such as the DEKA arm. Much of this work will be performed by researchers in Providence. The VA Center of Excellence for Neurorestoration and Neurotechnology, established at the Providence VAMC last fall, is developing and testing new technologies that restore function to veterans and others with conditions affecting the brain and movement – conditions that include limb loss, spinal cord injury, stroke, amyotrophic lateral sclerosis, and Parkinson’s disease. The center’s researchers continue to investigate the applications of brain/computer interfaces such as BrainGate; the technical, social, and psychological issues associated with amputation and prosthetics use, including further evaluations of the DEKA arm; and studies in the use of robotics to restore motor function.
Osseointegration: Body and Machine
Some of the most advanced technologies introduced by VA researchers appear in the form of prototypes developed by researchers at the Center for Advanced Platform Technology (APT), another VA/Case Western collaboration that combines the input of clinicians and a diverse group of scientists to solve rehabilitation problems for veterans.
The DEKA arm was developed with amputee volunteer feedback. Photo courtesy of the Johns Hopkins University Applied Physics Laboratory
In the spring of 2013, a VA/Case Western team led by APT investigators Paul Marasco and Jeffrey Capadona introduced a material to the world so new it doesn’t have a name yet: an artificial squid beak, composed of a scaffold of tiny cellulose nanofibers whose stiffness can be varied with exposure to ultraviolet light.
If it’s not immediately clear what a squid’s beak has to do with prosthetics, remember that a squid is basically made of soft, squishy tissue – all of it except its beak, which is made of a natural polymer, chitin, that’s harder than human tooth enamel and capable of slicing through the shell of a crab. By itself, it shouldn’t be able to attach itself to a squid; think of trying to hammer a nail into Jell-O. But the animal has created a damping mechanism – a mechanical gradient that varies the beak’s chemistry along its length, making it softer as it inserts into the squid’s biting muscle.
The mechanical junction of hard and soft materials, said Jaeger, has long been an issue for prosthetics researchers, who try to fit prosthetics comfortably against human skin with the use of a socket.
The mechanical junction of hard and soft materials, said Jaeger, has long been an issue for prosthetics researchers, who try to fit prosthetics comfortably against human skin with the use of a socket. “Your limb swells and shrinks,” he said, “and you get a phenomenon called pistoning, where you have a good fit to start the day, and then your limb may shrink a bit if you’re not active, and then all of a sudden when you go to walk it’s a sloppy fit and the limb goes up and down in the socket. Also there can be sweat, heat, and pressure sores. So the socket interface historically has been a problem.”
At just a few months old, APT’s squid-beak nanofibers aren’t going to be rolled out to amputees anytime soon, but VA researchers have for some time been working on another solution: osseointegration. By screwing a titanium rod directly into the bone, and then bolting the prosthesis onto the rod, clinicians can avoid a socket altogether and make the artificial limb a relatively seamless extension of the residual limb.
Gulf War veterans and VA intern Paul Yarbrough demonstrates to Prince Harry of Wales how he can use a portable drill, thanks to the DEKA arm, an advanced artificial limb being tested at the VA New York Harbor Healthcare System Manhattan campus. U.S. Army photo
Several complications have challenged osseointegration researchers for years, however, including the infection risk and immune response associated with a permanent opening in the skin. In 2011, VA researchers modified titanium implants in ways that created an effective “seal” in the gap around the rod, allowing both bone and skin cells to literally attach and integrate into the titanium surface. That research laid the foundation for a landmark event announced in May 2013 by a team of researchers and surgeons from the University of Utah and the Salt Lake City VAMC. Led by Roy Bloebaum, Ph.D., a research professor of orthopedics, bioengineering, and biology at the university and director of the VA’s Bone and Joint Research Laboratory, the team will perform the first-ever FDA-approved U.S. clinical trials for osseointegration, on 10 amputee subjects.
Osseointegration has only been attempted about 250 times, in Europe and Australia, with mixed results. When his team announced the news of the coming Salt Lake City trials, Bloebaum seemed hopeful that the many nagging problems with the procedure had been addressed, and that these new implants would help prosthetics patients live relatively pain- and hassle-free.
“We’re trying desperately to provide relief to the many veterans who have lost a limb,” he said. “Most of these people are very young and have many years to live. Our goal is to give them back all the abilities they had before they were injured.”
“We’re trying desperately to provide relief to the many veterans who have lost a limb,” he said. “Most of these people are very young and have many years to live. Our goal is to give them back all the abilities they had before they were injured.”
This article first appeared in the The Year in Veterans Affairs & Military Medicine 2013-2014 Edition