If you missed last spring’s news from the VA Medical Center (VAMC) in Providence, R.I., don’t feel bad. Lots of people did, though it’s hard to imagine how: It was about as astonishing as medical advances get. Two volunteer research subjects, a man and a woman, both stroke victims with paralysis in all four limbs and the torso, were able – using only their minds – to manipulate an advanced prosthetic arm using a direct neural interface. After several weeks of practice and calibration, the subjects were able to activate a microelectrode array, implanted in the motor cortex just beneath the skull, to direct the arm’s movements in three-dimensional space. One of the subjects, Cathy Hutchinson, was able to lift a bottle and drink, for the first time in 15 years.

Dr. Robert Jaeger, director of Deployment Health Research in the VA’s Office of Research and Development, describes the Providence demonstration, led by Department of Veterans Afairs (VA) researchers and professors at Brown and Harvard universities, as a serendipitous combination of two technologies, developed separately and in parallel. The first was a brain/computer interface, BrainGate, developed jointly by Brown neuroscience researchers and a private biotechnology company, that works by detecting the firing patterns of neurons associated with specific motions, and translating them into instructions for a device. The second technology was a sophisticated robotic arm developed by DEKA Integrated Solutions Corporation under the Defense Advanced Research Projects Agency’s (DARPA’s) Revolutionizing Prosthetics program, launched in 2006 to advance the state of upper-limb technology for service members.

“Originally they developed the BrainGate as an experimental device to try to restore the ability of subjects to type on a computer keyboard,” said Jaeger, “and they were successful in that. And it just so happened that one of the great dreams in prosthetics was the control of an advanced prosthetic device by a brain/computer interface.”

BrainGate, Jaeger explained, was originally developed for patients with locked-in syndrome, a condition in which a person is awake and alert but unable to move or communicate verbally due to paralysis of nearly all voluntary muscles. “Originally they developed the BrainGate as an experimental device to try to restore the ability of subjects to type on a computer keyboard,” said Jaeger, “and they were successful in that. And it just so happened that one of the great dreams in prosthetics was the control of an advanced prosthetic device by a brain/computer interface.” It was, relatively speaking, easy to integrate the DEKA arm into an interface that already had protocols written for controlling computers, wheelchairs, or other devices.

Despite their confidence in the technology, researchers were unsure of how it would perform once the human element was introduced. But even Jaeger was surprised to see how quickly Hutchinson was able to acquire control of the arm and perform simple tasks with it. “I thought they were going to take months trying to get that to work,” he said. “And it turned out to be a matter of weeks.”

Why this breakthrough is important to the VA can be understood through reading the casualty statistics compiled by the Congressional Research Service in February 2013. More than 1,715 troops who have served in Afghanistan or Iraq have undergone battle-injury amputations, the vast majority of which have been “major limb” amputations of the leg, arm, hand, or foot. Six percent of wounded veterans returning from Iraq have lost a limb. In addition to these younger service members, many older veterans have undergone amputations necessitated by diabetes or other vascular disorders, and others have suffered a loss of sensory functioning – vision or hearing – that may be alleviated by prosthetic devices. Since 2000, the VA estimates that the number of veterans accessing healthcare for prosthetics and sensory aids has increased by more than 70 percent.

Last year’s BrainGate demonstrations represented the cutting edge of VA’s collaborative effort to restore function to veterans – to integrate body, mind, and machine. The VA, through the efforts of its Rehabilitation Research and Development Service and associated Centers of Excellence, leads an array of studies aimed at an increasingly ambitious set of objectives to restore full function to veterans. It seeks to build on the demonstrated capabilities that allow performance of a few simple tasks to enable service members to do anything they want – even return to service, if they wish.

 

Toward Wearable Robotic Limbs

DARPA invested in upper-limb prostheses to develop advanced capabilities with near-natural control. Leveraging advances in actuator and processing technologies, DARPA aims to expand options available to upper-extremity amputees commensurate with advances that had been made in lower-extremity prosthetics. There are two main reasons why lower-limb prosthetics are, relatively speaking, more advanced than upper limbs. The first, explained Jaeger, is that there’s simply been more demand for them: “VA has got better at the service delivery of advanced lower-extremity prosthetics,” he said. “The lower-extremity prosthetic world has a much richer base of manufacturers and a much wider selection of advanced limbs than upper extremities because there are far more lower-extremity amputees than upper-extremity amputees.”

Much of the VA’s lower-limb prosthetic research is conducted by the Center of Excellence for Limb Loss Prevention and Prosthetic Engineering at the VA Puget Sound Health Care System in Seattle, Wash., where researchers aim to prevent lower-limb amputation among veterans with vascular disease, and to develop and match lower-limb prosthetics with the needs of amputees. Given the range in ages and expectations of today’s veterans – some of whom want to run marathons or go rock climbing, and some of whom want simply to get up from a wheelchair to move about the kitchen – the VA prosthetics care program is charged with delivering a variety of alternatives. VA researchers and their partners have developed a number of lower-extremity prostheses, some of them power-assisted, balanced by gyros, smoothed by hydraulic cylinders, and controlled by microprocessors and accelerometers, that will help veterans do almost anything a human leg can enable them to do, and to walk with increasingly natural gaits.

The second reason why leg prosthetics are more developed is that the arm, hand, and fingers are incredibly sophisticated – an engineering marvel, capable of 29 degrees of freedom, or planes of movement, through the combined actions of the shoulder, elbow, wrist, and fingers. Until recently, the available prosthetic arms were equipped with hands that could only open and close in a crude grip; everyday tasks such as typing on a keyboard, or even turning a doorknob, were out of the question.

Many upper-limb tasks, so simple to most people, still prove maddeningly difficult for amputees because they are not simply mechanical tasks – they require sensory input. “If you’re gripping a water bottle you don’t want to crush the thing,” said Jaeger. “If you’re gripping a mug of coffee, you want to be able to have control of it and grip it hard enough so that it’s not going to slip out of your hand and burn you.”

The second-generation DEKA arm used in last year’s BrainGate trial was the most sophisticated upper-limb prosthetic VA researchers had ever worked with. It’s a motorized mechanical arm, controlled by devices activated by the user’s foot and shoulder, and capable of 10 degrees of freedom. Users can insert a key in a lock and turn it, use a power tool, or raise their arms overhead.

Many upper-limb tasks, so simple to most people, still prove maddeningly difficult for amputees because they are not simply mechanical tasks – they require sensory input. “If you’re gripping a water bottle you don’t want to crush the thing,” said Jaeger. “If you’re gripping a mug of coffee, you want to be able to have control of it and grip it hard enough so that it’s not going to slip out of your hand and burn you.”

The DEKA arm is fitted with a “sensory prosthesis” or “tactor” – a small vibrator whose frequency intensifies with the force of the hand’s grip. “You can’t literally sense how hard you’re gripping,” Jaeger explained. “But we can measure how hard you’re gripping and translate that into a vibration that your body can sense in another, alternate way.”

At the end of fiscal year 2012, VA researchers completed a three-year optimization study of the DEKA arm in which 31 volunteer users, many of them veterans and service members, gave feedback on the arm’s design and performance during thousands of hours of tasks. Input from this study informed DEKA’s design of the arm’s most recent version, the third-generation, or “Gen3,” arm, which is now being examined by users in VA-funded take-home trials.

“The take-home study is interesting,” Jaeger said, “because before the take-home study, we only had data in the laboratory – and in the laboratory and VA Medical Center there are engineers, occupational therapists, and M.D.s hovering around, and if anything isn’t going right, somebody fixes it right away. But when the arm is actually being worn in the home environment, and nobody else is around – other than the wearer and their family members – if something goes wrong, they’ve got to be able to troubleshoot and fix it.” The take-home trials so far have revealed the arm to be, if anything, more reliable than researchers and users had hoped, and have laid the groundwork for making the device commercially available.