DARPA’s RP Arms in Transition: From Miracle into Reality

Home > Articles > DARPA’s RP Arms in Transition: From Miracle into Reality
By Judith Philipps Otto

"Whatever the mind of man can conceive and believe, it can achieve."

-W. Clement Stone, American author (1902-2002)

What child doesn't love a good fairy tale, where miracles are conceived in dreams and achieved with the wave of a wand? In the real world, however, miracles are far more challenging to conjure-they take preparation, commitment, brainpower, and hard work that endures even after the hallelujahs from the initial announcements have faded. In the wake of the wave of excitement surrounding the development and introduction of two working prosthetic arm prototypes created through the Defense Advanced Research Projects Agency's (DARPA) Revolutionizing Prosthetics (RP) program, dedicated teams have continued to quietly and purposefully turn these prototypes into commercially available realities-and those realities could be realized in as few as six months.

DEKA Arm Nears Rollout Stage



DARPA RP program manager Col. Geoffrey Ling, MD, PhD, who has led the program since its January 2006 inception, reveals that the "Luke" arm developed by DEKA Research and Development Corporation (DEKA), Manchester, New Hampshire, is expected to be FDA 510(k) approved for production by the end of this performance period. "They are heading into final first-stage investigations, going toward commercialization," Ling says. "The final design review is coming up, and that's the one that's going to go into production. Hopefully by the end of this year, we'll have a commercially produced arm. This is no longer a science fair project; we're really on the way. We want this to get to as many people as we can."

Stewart Coulter, PhD, project manager for DEKA's high-capability "Luke" prosthesis confirms, "We're working very hard toward getting it into production quickly. We are continuing to push it."

Photographs of the Modular Prosthetic Limb (MPL) courtesy of the Johns Hopkins University Applied Physics Laboratory (JHU APL).

Last year's generation 2 arm has now been tested on more than 30 subjects and has logged more than 3,000 use hours over 15 months, Coulter says. "Twenty-six of these subjects used the arm in VA-funded research studies, which provided feedback from veteran, active duty, and civilian subjects, as well as occupational therapists and prosthetists from three VA hospitals and one Army rehabilitation center. After getting this feedback from the target population and incorporating that information into the current gen 3 model, the team is finalizing the design, preparing it for clinical studies, and getting ready to roll it out.

"I'm very excited about the changes that we've been able to make as a result of the feedback," Coulter adds. "We're really looking forward to getting the new version out there and [having] people take advantage of that."

MPL Arm Progresses to Human Testing

Further landmark news concerns the Modular Prosthetic Limb (MPL), which was created and unveiled at the Johns Hopkins University Applied Physics Lab (JHU APL), Laurel, Maryland, in December 2010. The arm's modular design makes it adaptable to a wide range of injuries. The MPL has the capacity to be neurally controlled via an interface to the brain and is on the verge of being tested on human subjects.

"We're really on the cusp of a significant scientific breakthrough-demonstrating that a human will be able to control the prosthetic arm," Ling says.

The first patient, he explains, is not an amputee, but an individual with high cervical spinal cord injury (SCI) quadriplegia. Ling notes that the patient will be provided with the opportunity "to use their brain to control this prosthetic arm. Our expectation is that this patient will be able to perform many of the activities of daily living that we take for granted, such as eating, drinking, and aspects of personal hygiene. We're very, very excited about this."

Program leaders laud the U.S. Food and Drug Administration (FDA) selection of the MPL as the pilot medical device for its new Innovation Pathway, a program which in early March added the Centers for Medicare & Medicaid Services (CMS) as a collaborator in supporting and expediting the development of unique new technologies.


"Traditionally the FDA doesn't provide a lot of interaction during the approval process, so the Innovation Pathway program is all about really getting the FDA involved much earlier in the process," says Mike McLoughlin, APL program manager and JHU Whiting School of Engineering instructor. "Now there is more developer interaction with the FDA. This FDA program was designed specifically for devices that are very innovative or unique."

Ling's enthusiasm about the Innovation Pathway program is palpable. "It is unprecedented," he exclaims, "to have both the FDA and Medicare/Medicaid trying to see how they can coordinate their efforts with a developer! This was really a golden opportunity to all come together."

With everyone pulling cooperatively to support progress, "the key thing," Ling says, "is that we're now showing what is possible. We can change expectations, and that's what we really want to do." (Editor's note: For more information about the FDA Innovation Pathway program, visit www.oandp.com/articles/news_2011-02-08_02.asp)

The RP program was conceived as a four-year effort, McLoughlin says, "but DARPA decided they really wanted to make sure the arm got into human use, so they decided to undertake an additional phase to make sure that happened."

McLoughlin and the MPL team are now one year into that additional, funded three-year testing and development phase. He reports that the current MPL arm, now ready for testing, is a fully articulated arm with 22 degrees of freedom that is comparable in size and weight to the arm of a 50th-percentile male. "We are getting queued up to work later this year with the University of Pittsburgh [Pennsylvania] on human subject tests that will involve the use of cortical arrays or brain implants in individuals with SCI and quadriplegia. Basically, we will look at their ability to operate the arm. It's really an exciting time in the program."

Because products designed for use by human subjects must use technology that is well founded and thoroughly tested, not all researched aspects of the MPL will be incorporated in the version being tested. "Some of the newer, emerging aspects will be great a few years from now, but the timing isn't right to include them into today's model," McLoughlin says. "Our focus is more at a systems level. We want to demonstrate the capability to capture signals from the brain, understand how to use them to control the arm, and even look at how we could use the stimulation of the brain to restore sensation. It's a much broader focus on solving the whole problem. Other efforts are looking at very specific pieces of the problem."


McLoughlin looks forward to partnering with the University of Pittsburgh (Pitt) team to implement the first human subject trials, with an anticipated June or July start date.

Mike Boninger, MD, director of the Pitt Medical Center Rehabilitation Institute and chair of the Department of Physical Medicine and Rehabilitation, says the process is going well. The project has gained approval from Pitt's Institutional Review Board (IRB) and FDA approval is expected soon, so he anticipates that testing subjects should begin on schedule. "Part of the reason that things have gone well is that we have been preparing for this for years," he says.

Boninger has been working with Andrew Schwartz, PhD, professor of neurobiology at Pitt, who has been able to get a non-human primate to control a robotic arm with six degrees of freedom. Such robotic arms don't mimic the capabilities of the human hand, however, so Schwartz and Boninger were eagerly anticipating the March arrival of the advanced MPL arm and the opportunities it would bring to determine not only how it works in non-human primates, but in the planned human studies as well. (Editor's note: For more information about Boninger's research, visit www.oandp.com/articles/news_2011-02-22_01.asp)


In preparation for implanting the first SCI subject, Boninger and his team have been working with patients in an epilepsy monitoring unit.

"Patients there have intractable epilepsy or seizures, and one way doctors resolve those seizures is to put an electrode grid on top of the brain," he explains. "The electrode grid enables neurologists to precisely locate where the seizure activity occurs, and then a neurosurgeon can do a procedure that gets rid of the area where the seizures start. The patients with epilepsy are admitted to the hospital and have a part of their skull removed-a craniotomy. An electrode grid is then laid on top of their head. Then the clinical team waits for them to have a seizure." While they wait, team members collect experimental data while the patient tries to play a computer game or control a virtual robotic arm.

During this process, Boninger's team continues to make discoveries. "This is a relatively new field; we're finding new information all the time," he says. "For example, we've learned that by implanting a very small electrode grid over the motor cortex of the brain, we were able with good accuracy to decode individual finger movement. That's the start of being able to control a prosthetic down to the level of the individual fingers."

The challenge of exploring unknown territory is immense-and irresistible. As McLoughlin notes, "APL is an organization that has probably launched over 60 spacecraft in our history, and we've done a lot of really complex technical things. This is probably one of the most complex projects I've ever worked on. We have a really great dedicated team here that has put forward a really outstanding effort to make sure this all comes together. We've had some surprises along the way and will probably have more to come, but we've been able to deal with them and be successful."

Non-DARPA Initiatives

The spirit of commitment and achievement to bring these remarkable prostheses within the grasp of the amputee and SCI populations has resulted in several entities pursuing related studies. Ling mentions the National Institutes of Health (NIH), which has funded a number of investigations looking at alternative strategies for controlling the MPL arm-"using their own money to try to broaden the scientific investigation, which is tremendous," Ling enthuses. "Their proposal request specified that it has to run the DARPA arm. What we're getting is efficient use of the taxpayers' resources to do a very good thing," he points out.

And although McLoughlin emphasizes that the JHU APL works hard to transfer technology by facilitating the development of a commercial source that will undertake the challenge of manufacturing the ultimate MPL arm, they won't become manufacturers themselves.


Stuart Harshbarger, chief science officer at Orthocare Innovations, Oklahoma City, Oklahoma, and principal research scientist at JHU, is more closely tied to the ultimate manufacture of the MPL. The former MPL project manager stepped down from that role in order to concentrate on facilitating the transition of some of the DARPA technology into clinical practice and commercial availability. His partnership with Orthocare Innovations offers him the opportunity to do just that.

"We're taking a lot of the lessons learned and practical knowledge from the DARPA RP2009 program and working with various program partners whose specific intellectual property has been developed," he says. "Our goal is to develop a new series of derivative upper-extremity technology-which we call the Contineo multi-grasp hand. While it can grasp and hold...it's not as fully capable as the high-dexterity MPL hand-but it's a very capable device that could hopefully be made widely available and affordable to new amputee users as well as the existing customer base," Harshbarger notes.

Harshbarger's focus is to see that appropriately tailored, derived technology from the RP2009 program is moved into the clinical environment, and the Contineo multi-grasp hand is well on its way, with a beta version just a few months away from the patient evaluation stage.

"We've been working with a number of patient candidates using a virtual environment type of interface, similar to and derived from RP2009 technology," he explains. "It allows a subject to see how they can control the new hand system using a graphic model, a visual model of the new hand, and whatever controls they may have available in their native limb."

Orthocare's clinical partners are helping to identify patients with an interest and a "robust ability" to control the Contineo hand. "The testing has really been quite remarkable," he notes, "fueling some...growing momentum and activity around transitioning. The hand is a good next practical step that we believe will have significant capability beyond what is commercially available. The multi-grasp hand and the accessory modules being developed are anticipated to be directly compatible with a fully capable RP2009 limb system, providing for a continuum of options in the long run-ranging from relatively affordable to optimally capable," he adds.

Harshbarger expects Orthocare Innovations to have units in beta testing by the middle of this year and early versions released commercially by the end of the year. In addition, the company is developing a number of related modules, such as a wrist accessory to be used with the multi-grasp hand.

The MPL Fountain of Youth: DARPA's HIST Project Begins

DARPA recently launched a new program related to RP2009. Headed up by Jack Judy, PhD, and dubbed Histology for Interface Stability Over Time (HIST), the program was launched in 2010 to explore and extend the longevity of the neural implants that allow the brain to control the MPL prosthesis.

Ling stresses that the current lifespan of such interfaces has steadily improved and now covers about five years, but prolonging the performance life of the implant is naturally desirable. Implants fail primarily because the brain treats them as invaders and tries to protect itself by isolating them-a process known as gliosis, which over time can prevent the electrodes from functioning.

Oddly, Ling points out, gliosis does not affect all electrodes. "We're not sure why it affects some and not others, but that's the way it is."

Gliosis is more complex than an inflammatory cortical tissue rejection process, he explains; it is a cellular reaction similar to scar formation. "It could be mediated by a lot of different factors, so classic anti-rejection drugs probably would not work," while their potential side effects might create a situation that is worse than the one they were employed to correct.

"The initial phase of the HIST project will have to be done in a pre-clinical non-human model so [researchers] can see if they are actually making an appropriate impact on the gliosis," Ling continues. "Once that's done, they'll move forward, working closely with the FDA and CMS, following the Innovations Pathway program being pioneered by the MPL arm testing."

Ultimately, when these related programs successfully conclude in the not-too-distant future, we can look forward to seeing upper-limb amputees fitted with prostheses that are equipped with a sense of touch; are able to feel heat and cold; can point, flex, rotate, hoist, tuck, and grip with the appropriate pressure; and last a human lifetime-perhaps even longer.

Judith Philipps Otto is a freelance writer who has assisted with marketing and public relations for various clients in the O&P profession. She has been a newspaper writer and editor and has won national and international awards as a broadcast writer-producer.

To read about the ongoing progress of DARPA's Revolutionizing Prosthetics Program, see the following articles in The O&P EDGE:

"DARPA Revolutionizes Prosthetics: How and Why?" November 2007

"Armed for the Future: DARPA's Revolutionizing Prosthetics Project Nears Completion," December 2009

"What's Next: DARPA's Revolutionizing Prosthetics Projects Get a Grip on Reality," April 2010