Armed for the Future: DARPA’s Revolutionizing Prosthetics Project Nears Completion

Home > Articles > Armed for the Future: DARPA’s Revolutionizing Prosthetics Project Nears Completion
By Judith Philipps Otto

In an exclusive interview with The O&P EDGE, Stuart Harshbarger discusses how the end game is shaping up for the Defense Advanced Research Projects Agency Revolutionizing Prosthetics 2009 Program.

As this issue of The O&P EDGE goes to press, the Defense Advanced Research Projects Agency (DARPA) will be rolling out the final model of its Modular Prosthetic Limb (MPL)-the culmination of a Herculean four-year effort by 30 universities and research institutions and more than 300 of the most gifted minds in our country's brain trust.

"It is, without any challenge, going to be the most highly dexterous advanced prosthetic limb system in the world," says Stuart Harshbarger, chief science officer at Orthocare Innovations, Oklahoma City, Oklahoma, and principal research scientist at Johns Hopkins University Applied Physics Laboratory (APL), Laurel, Maryland, who served as program manager for the project. "I don't think anybody can argue with that."

The assignment was enough to make the strong tremble: Team members were tasked to duplicate not only the complexity of a five-fingered hand with an opposable thumb, but an elbow, wrist, and shoulder to match-more than 22 separate ranges of motion in total-and to control them all via a direct connection to the wearer's mind; appropriate movements of the arm and hand had to be driven solely by intent or desire, rather than through any conscious focus on the mechanical steps required to accomplish each movement.

The scope and complexity of the challenge has been enormous-involving and coordinating the efforts of a host of applied neuroscience researchers, clinicians, biochemists, and electrical-mechanical computer engineers to address separate aspects such as human-like appearance, functional performance, and neural-interface technology that ranged from non-invasive to cortical control. The logistics of communication involved what Harshbarger refers to as a virtual corporate framework, with members integrated through a number of online virtual-collaboration tools, as well as frequent conference calls and onsite visits.

The results, however, are enough to make a sci-fi fan giddy. It's tempting to let the "wow!" factor lure one into comic-book babble about bionics, cyborgs, and manufactured superheroes. But once we get a grip, we see not just one sensational Big Idea-which has been called the 'Maserati of prosthetic limbs'-but Aladdin's treasure cave, filled with myriad gems of discovery and accomplishment-each a major miracle in its own right.

"There are a lot of jewels in terms of technology developments," Harshbarger agrees. "I believe the program is going to have really far-reaching consequences beyond upper-extremity prosthetics. We've already seen some of the technology from Phase One being applied for lower-extremity applications through alignment methods in knees and artificial legs. The technology didn't find its way into the final upper-limb solution, but it turned out to be almost an ideal solution for lower-extremity prosthetics; we're excited about that."

Harshbarger points to additional treasures gleaned from the program:

  • Some of the research using carbon nano-tubes for developing cosmetic coverings and sensors was viable, but premature and too expensive to move toward transition in the near term. It will likely become viable over time, once the manufacturing processes become less expensive and more commonplace.
  • Some materials can be used in conjunction with cosmetic coverings to develop thermal conductivity, enabling the thermal sensors in the limb itself to work better and more like the natural sensors in our native limbs.
  • Some materials can be ground up and processed in such a way that they exhibit strong hydrophobic properties (dispelling water). Ongoing research is being pursued to assess using this carbon nano-tube hydrophobic process in socket lining materials, where it could transport sweat and moisture away from the surface of the skin, improving patient comfort and reducing skin irritation.

"That's something that we would never have considered at the onset of the program but that sort of came out in the mix, as did a number of other discoveries," he reflects.

Harshbarger and Orthocare Innovations are committed to the dual-use nature of the technology. "In the process of building the prosthetic-limb system, we developed the most advanced, dexterous, human-like manipulators that exist in the world. If you look at the mobile-robotic platforms that have been used by the military to deal with improvised explosives and unexploded ordnance, it's clear that they could benefit from such improved dexterity. Many of the individuals that we're seeing as prosthetic patients are injured because of the lack of sophistication and lack of dexterous capability of these mobile platforms.

"Although this is something we didn't really consider up front, we're working now to integrate some more rugged, militarized ver­­sions of these terminal devices onto mobile-robotics platforms, making them efficient enough that human operators won't have to go into the hazardous zones themselves."

Impressive as the Revolutionizing Prosthetics 2009 (RP2009) program's far-reaching accomplishments are, Harshbarger shies away from superlatives.

"Some early reports fed the hype that these systems really are a natural replacement for the human limb and that they seamlessly integrate with the body. The prototypes we built two years ago are pretty remarkable, but they're a long way from that standard.

"Recognizing all of the social and rehabilitation issues that people with these level of injuries go through," he continues, "and considering the challenge of therapy and rehabilitation and the multiple socio-psychological aspects that the field deals with, I think it's a bit of a disservice to paint the program's achievements in that sort of science-fictionesque manner."

In fact, one of the MPL's primary advantages is its modular nature, rather than its glamorous, high-tech image. Designed to fit any level of injury, and capable of scaled performance levels, the MPL can be virtually all things to all upper-limb amputees. Even a scaled-down, reduced-capability version of the limb represents a significant improvement over the state of the art that exists today, Harshbarger says, "and at a much more modest price point."

The Challenges

Getting to this point wasn't easy, however.

"Probably the biggest challenge we faced was proving the principle of literally tapping right into the signals from the nervous system," Harshbarger says. "I'm particularly proud of the progress in development of the wide range of wireless neural devices that are now functionally working in their final packaging within the modular prosthetic-limb system. We were generally surprised and optimistic at the level of natural control and even, to some degree, sensory feedback that is possible using the targeted-muscle-reinnervation [TMR] procedure that Dr. Todd Kuiken brought to the team.

"The good news is that some of the technologies have advanced faster and have been more successful in terms of engineering than we anticipated. The challenge now lies in proving that these devices are safe and effective, through the FDA regulatory process-and to ensure that they can sustain chronic performance over many years of the individual's life."

Shepherding these integrated wireless implantable devices through the U.S. Food and Drug Administration (FDA) process-even though the devices are working and demonstrating the basic principle-requires another immense effort to collect data and then subsequently ensure the long-term viability of a novel system. Such an effort could take considerably longer than the entire research and development process to date.

"Nobody's ever done this before," Harshbarger points out. "There's never been a candidate human, so no one has any data to know how long these devices might remain viable. We're working hard on the right kinds of related medical research to answer those questions, but that's something that just...can't be done in the four-year window.

"That's the kind of thing that we hope that DARPA and some of our other government sponsors will support. Maybe Congress would step in to really ensure that this valuable interface work doesn't die on the vine because it has been very hard and very expensive-and there is clearly more work to do."

What Lies Ahead for the MPL?

Photograph of the MPL by Tom Van Doren, PhD, VP, Robotic Systems, HDT Engineering Services.

Harshbarger's personal commitment to the future of the MPL has motivated him to step out of his leadership role at APL and into his current position with Orthocare Innovations.

"I was moved by my fundamental belief that there's an opportunity to see this promise all the way through, not just as a nice demonstration in the research lab, but something that actually becomes a product, impacting the field and making a difference for users. By making the transition from the APL team to Orthocare, I'll be able to facilitate that commercial-transition process, negotiating manufacturing agreements in a manner that would have been impossible in my previous role."

Over the next year or more, he believes initial products emerging from the four-year program will begin to be available, at least for critical use. "We will see, over time, an entire portfolio of products that are derived from these efforts-products that address the full spectrum from 'significant step and low price point' to the full-up, highly capable limb system that is the best we can do with today's technology and a very significant government investment."

Orthocare Innovations, with support from several other performers, hopes to play a "very strong role," Harshbarger says, in making these products available to veterans, military service personnel returning to active duty, and civilians.

"Orthocare is in the process of working with a number of the partners in the program to establish a joint venture and to license the technology and all relevant intellectual property from the other participants, allowing the limb system to be built for commercial use. Subject to legal agreements, we hope to play a role-perhaps even the leading role-working in conjunction with some of the other key performers in the DARPA program to nurture the transition of this technology into an integrated system that can then be manufactured and delivered."

Once the MPL reaches commercial availability, reimbursement becomes a challenge for candidate users of the limb. Although the different terminal devices and hand configurations can eventually be sold to all consumers, payor approval may initially be difficult to obtain.

"Part of our effort will be to collect scientific data to show the efficacy of these systems versus some of the existing technology in terms of functional performance, user acceptance, and relative outcomes," Harshbarger says. "Such data should help us make the case that the payor and reimbursement communities should support these technologies over other options."

Was It Worth It?

Playing a key leadership role in a project that has already made history was the chance of a lifetime, Harshbarger admits. "In the final analysis, I believe we will have achieved all of the goals that DARPA set forth-and we will have also seeded lots of technologies that didn't appear to be either related or plausible when we started.

"I feel very good about it," he concludes. "I don't know if I could live long enough to do it over again, but I'm definitely proud of having been involved, and happy with the legacy that will come from it."

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.

A Brief RP2009 Timeline

The Revolutionizing Prosthetics 2009 program consists of two separate projects:

The two-year program's task was to utilize, synthesize, and adapt existing technologies in pursuit of a "strap-on-and-go" mechanical limb system that uses non-invasive control methods.

The four-year program's goal took on "a bit higher challenge," notes Stuart Harshbarger, chief science officer at Orthocare Innovations, Oklahoma City, Oklahoma, and principal research scientist at Johns Hopkins University Applied Physics Laboratory (APL), Laurel, Maryland: to revolutionize prosthetics with a completely new approach to developing a limb system that more closely mimics the human natural form and movements, controlling them with a whole range of different options. Those options include "everything from non-invasive or minimally-invasive techniques to a whole suite of wireless implantable devices that would tap into the residual signals within the body; the devices would record intermuscular activity or record directly from the peripheral nerve-or even, eventually, from the brain itself," Harshbarger explains.

January 2006: The original kick-off date both for a two-year program at DEKA Research and Development, Manchester, New Hampshire, which resulted in the introduction of the "Luke" (Skywalker) Arm; and for Harshbarger's four-year program at Johns Hopkins University (APL), which produced the Modular Prosthetic Limb (MPL) arm.

January 2007: The first fitting of the APL Prototype 1 on amputee Jesse Sullivan and other amputee participants.

August 2007: The introduction and demonstration of Prototype 2, which attracted significant media attention.

"Although Proto 2 approached all the active joints and packaging required for the program, it was a very, very early prototype model," Harshbarger stresses, explaining the reason for a certain amount of consternation among researchers concerning the manner in which the arm was hailed by the media as a fait accompli, at a time when its creators regarded it as far from prime time.

August-November 2007: The Luke arm ran its course and gained funding to support additional work related to clinical evaluations with the Veteran's Administration (VA)-which continues to conduct studies of its potential.

November-December 2009: The MPL arm undergoes small-scale evaluations to meet the remaining program objectives.

January 2010 will mark the official wrap-up date for the DARPA four-year program although Harshbarger anticipates some continuing federal support to facilitate the transition from DARPA as well as other government organizations such as the army and the VA.

"We hope that within the next year or so," Harshbarger says, "this subsequent phase will involve a similar program at the VA to allow a wider-scope clinical evaluation or optimization studies with our [limb] system and some of the other neural components that go along with it."

The timeline for such studies can be difficult to predict. The DEKA arm has been undergoing evaluations since 2007, but the study with the VA was only announced in January 2009 as it took some time to finalize agreements between DARPA and the VA. Now that a precedent has been established and the working partnership is in place between the Department of Defenese (DoD) and the VA, however, Harshbarger says he is hopeful that the MPL's progress into similar VA optimization studies will proceed smoothly and efficiently.