Revolutionary Prosthetic Arm Advances

John Milani
John Milani, right, a VA prosthetics official, and Dirk van der Merwe, a DEKA engineer, applaud as VA prosthetic and sensory aids service director Frederick Downs Jr. drinks from a water bottle using an advanced prosthetic arm.
Photo reprinted with permission of the Department of Veterans Affairs.

In its May 1, 2008 issue, O&P Business News highlighted an advanced upper extremity prosthetic device, funded by the Defense Advanced Research Projects Agency (DARPA) and designed by DEKA Research and Development Corporation of Manchester, N.H., that would forever alter the path of current upper extremity prosthetics.

In little more than a year, those involved with the prosthesis have upgraded it and readied it for its first significant patient trial. The Department of Veterans Affairs (VA) gladly entered into an interagency memorandum of understanding with DARPA to conduct the study.

Second generation

Since last year, this advanced prosthetic arm, now referred to as the Generation II DEKA Arm, has undergone improvements in the weight of the device, its electrical and internal connections, and its resistance to moisture, Michael E. Selzer, MD, PhD, the VA’s director of rehabilitation research and development, said. The design team also has made the device’s active socket design more comfortable for amputees and improved the arm’s articulation.

The logistics of the prosthesis remain the same, however: the complete device offers a total of 18 degrees of freedom, including 10 powered degrees of freedom incorporating a powered shoulder, elbow, wrist, and multi-grasp hand. Each patient receives an arm tailored to his or her level of amputation.

Patients control the prosthesis in a variety of ways. One unique control method involves stepping on pressure points placed in the soles of their shoes.

“It’s kind of intuitive with people who have grown up using a mouse,” Billie Jane Randolph, PhD, PT, the VA’s deputy chief consultant for prosthetics and sensory aids, said.

While she hesitates to deem this prosthesis better than others currently available, she acknowledges its significant benefits to her patients.

“It’s important, as a therapist, to have several different options available to our upper extremity amputees,” Randolph said. “With the current technology, we cannot have an above elbow amputee lift an object overhead, and this prosthesis will allow that.”

She also said that some veterans who have tried the prosthesis have experienced improved grasp over other devices they have tried.

Prosthetic studies

Since the VA’s prosthetic trials — headed by Linda Resnik, PhD, PT, OCS, research health scientist at the Providence, R.I., VA Medical Center (PVAMC) and associate professor in the department of community health at Brown University — began in April, researchers have three ongoing study protocols, two in New York and one in Tampa, Fla. and they have completed screenings for an additional 12 veterans to be included in the study. The full approved protocol calls for a total of 20 to 40 participants, including both men and women with various levels of amputation.

First, Selzer told O&P Business News, VA researchers evaluate the individuals chosen for the study to determine that it is safe for them to participate, and then fit them with sockets. They place insoles with pressure sensors in the amputees’ shoes, and ask the amputees to practice putting pressure on different parts of their feet to control a simulated arm on a computer screen. Researchers also mount the prostheses on the sockets and train the patients to control the arms.

The protocol requires that patients perform a list of tasks, which researchers observe. Patients also provide narrative comments about their ease or difficulty in using the arm, and feedback regarding possible improvements.

This is the most important aspect of the study, she said. Frederick Downs, Jr., VA prosthetic and sensory aids service director, who is testing this prosthesis told her that it was incredible for him to pick up his BlackBerry and be able to hold it while typing on it. At press time, Downs was at DEKA in Manchester, N.H. getting fitted with the prosthesis as part of DEKA’s first take-home trial.

Although he has been invited to participate in a home trial sponsored by DEKA, the VA study does not allow participants to leave the facility wearing the prosthesis. The study’s formal investigation takes approximately 4 weeks per amputee, and researchers currently have only six devices.

Trial goals

Despite the military influence over the project, veterans and other military personnel will not be the only ones who benefit from this advanced technology. In fact, DARPA’s involvement has been limited to identifying the need for improvement in upper extremity prosthetic design as priority, providing funding and arranging the connection with DEKA.

DARPA’s interest stemmed from the high percentage of wounded warriors with upper extremity amputation, Randolph said.

“Until [Operations Iraqi Freedom and Enduring Freedom (OIF/OEF)], only about 3% of the amputations in the United States were upper extremity. During OIF/OEF, at one point, about 30% of [the military] amputee population was upper extremity, and it’s still much higher than the national average,” she said.

Randolph’s own goal for this project is to improve the quality of life for upper extremity amputees, whether that entails their ability to play the piano, use a power drill, go fishing, or return to military duty and use a firearm.

“As therapists, we say that when someone loses a lower extremity, they lose their mobility. When they lose their upper extremity, they lose their independence,” she said. “The goal is to restore their function as much as possible, and to help them regain as much independence in their lives as they can.”

Neural interfaces

VA researchers also are exploring different ways to control the prosthesis, namely through neural interfaces. John P. Donoghue, PhD, senior research career scientist at the PVAMC, and professor of neuroscience and engineering at Brown University along with co-investigator Leigh Hochberg, MD, PhD of the VA, Brown University and Massachusetts General Hospital and their team have begun trials for this technology.

Called BrainGate, this system is designed to pick up signals from the areas of the brain responsible for arm and hand movement, decode them into control signals, and connect them to devices placed outside, or even inside, the body, Donoghue said. The transmission of these signals creates the ability to move for people with paralysis brought on by stroke, spinal cord injury or other disorders like amyotrophic lateral sclerosis (ALS), or for people who have lost limbs.

“All of those people have the same issue: their brains can put out commands to move, but they can’t affect the movement,” he said. “The emphasis for our research is to find out how to get those signals out of the brain, what kind of signals to pick up and how to best turn them into useful command signals.”

A foot-powered prosthesis, even one with a sophisticated computer, could complete a limited number of commands, whereas a brain-powered prosthesis could have control and flexibility, and be natural to use. The question Donoghue’s study asks is whether it is possible to obtain enough information from the brain to turn it into useful output to create movement.

Donoghue and his team of researchers implant a tiny sensor — about the size of a baby aspirin, he said — into the patient’s head. This sensor comes equipped with a 100 little hairs that attach to the surface of the brain and sense brain signals related to arm movement.

While previous animal research suggested that this area of the brain would restructure after injury, early trial data suggests that the part of the brain that controls the arm maintains its structure and purpose.

“Not only does brain activity remain in this arm region of the brain, but immediately upon them thinking about moving, it becomes active, as if the arm were really moving,” he said. “For amputees, this is important because it means that, immediately upon picking up those signals, they’re suitable to control an arm.”

BrainGate trials

To test out this technology, Donoghue and his research team secured approval for a Food and Drug Administration (FDA) pilot clinical trial that will study people with tetraplegia to determine feasibility of the system. If these patients are able to control the prosthesis through brain power, then the technology has implications for amputees.

Implantation of the device requires a neurosurgical procedure similar to what is used to implant other devices for movement disorders, pain or hearing loss. The current version of the technology includes a plug, about the size of a penny, that remains on the patient’s head, where the wires exit the brain and attach to a computer that processes the brain signals.

The team is working with funding from the National Institutes of Health to develop a fully wireless system, but Donoghue told O&P Business News that such technology is several years away.

For now, study participants are asked to control a computer cursor and click using only their thoughts. This is a far reach from the advanced prosthesis’s 18 degrees of freedom, but they must start small to determine how the brain handles these commands, Donoghue said. He expects that the next question will be establishing the amount of control allocated to the brain versus the amount to a computer controlling the prosthesis.

VA researchers have received FDA approval to add 15 more patients to the four initial patients, and have moved on to the second pilot trial, called BrainGate II.

Patient benefits

“Everyone who is paralyzed could potentially benefit from this technology,” Donoghue said.

While total control of paralyzed limbs still is many years away, he hopes that this technology will be useful to control the advanced prosthetic device Resnik and her team are studying now.

“The arm is a spectacular advance over what is available now, in that it allows motions that are much like what you can do with your own arm,” he said.

But the current answer to controlling the device is far from ideal.

“[Foot pedal control] gets in the way of walking around and requires you to learn how to wiggle your toes to make it operate properly,” he said. “It works impressively well, but it requires using one movement to replace another.”

Ultimately, the patients are most excited about this technology. Donoghue recalled asking for feedback from one patient who had suffered from a brain stem stroke, which left her unable to speak. He set up the computer cursor so she could type, and asked what she thought of the technology.

“She typed out, ‘I love it.’ It was quite touching,” he said.

But injured patients are not the only ones interested in this information. Recently, O&P Business News was part of an information-gathering session with Jim Schaefer, producer at the Pentagon Channel, who plans to feature this technology on the channel’s monthly documentary program, “Recon.” This program, Schaefer said, will aim to inform the active duty service population about the future medical possibilities for those service members who become severely injured.

Long-term implications

Although Donoghue and the other researchers emphasize the long-term goals of this technology over the short-term, Donoghue remains optimistic about the end results. He cites the human ability to drive a car as an example of learning to use new devices.

“It’s immensely complex, but it becomes like an extension of our own body when we drive,” he said. “Early feedback from the use of the [advanced prosthesis] indicates, that this does quickly become much like a part of your own body.”

Donoghue’s first goal is the ability to move the arm around in space in three dimensions, under only willed command, he said.

“We will have success when you meet somebody and shake their hand, or they salute you, or they’re doing their job with their prosthetic limb, and you can’t tell the difference,” Donoghue said.

While his vision is still far away, he can see it clearly.

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Stephanie Z. Pavlou, ELS, is a staff writer for O&P Business News.

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