Robotics Research Gives Life to Artificial Limbs

April 2011
By George I. Seffers, SIGNAL Magazine
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Staff Sgt. Andre Murnane, ARNG, became the first National Guard Special Forces soldier to jump with a prosthesis on August 1, 2010.

Future prostheses could open new doors for injured soldiers, including an option to return to their units.

The U.S. Army is giving soldiers who have lost limbs a higher quality of life, including allowing some to remain on active duty or to return to combat if they choose. In part because of research conducted through the Army’s Advanced Prosthetics and Human Performance program, individuals who have lost limbs are jumping out of airplanes or commanding troops in combat.

The research covers both prosthetics and orthopedics, according to Troy Turner, portfolio manager for advanced prosthetics and human performance at the Army’s Telemedicine and Advanced Technology Research Center (TATRC), Fort Detrick, Maryland. Turner oversees a number of programs and projects, some more advanced than others, which are funded through congressional earmarks.

Jason Ghannadian, TATRC program manager for advanced prosthetics, explains, “Our mission is to turn every service member back to the fullest quality of life, whether they want to return to their civilian lives or get back to the war. A lot of them want to know how long until they can get back to their unit,” he says. “The goal is to let all of them get back, if they want, and to not have prosthetics be like a death sentence forcing them to sit behind a desk the rest of their lives.”

As of February 1, the Army has treated 1,180 amputee soldiers returning from Iraq and Afghanistan since 2003, according to Turner. Approximately 19 percent have endured an upper extremity amputation, meaning they have lost a hand, part of the arm or the entire arm. About 80 percent have lost a foot, a lower leg or an entire leg on the battlefield. Some have sacrificed more than one limb.

Amputee soldiers wishing to return to combat face a number of challenges, and they need manufactured body parts that are lightweight and durable and that will work under extreme conditions. In July, Turner, Ghannadian, and a team of about 10 people from industry, the Department of Veterans Affairs and Walter Reed Army Medical Center headed to the beach to test an advanced version of a computerized leg known as C-Leg. The test involved a former Paralympic swimmer wearing a C-Leg. A storm the night before had left the water choppy and somewhat dangerous, creating some anxiety for the team, but the test went so smoothly, according to Turner, it was almost anticlimactic.

Immediately following the beach test, Ghannadian reveals, the swimmer flipped the artificial leg device over and drained from it a considerable amount of water, illustrating that the electronics were completely inundated. “It’s like taking your cell phone or your laptop and throwing it in the ocean or covering it with mud and then still being able to use it,” Turner adds.

C-Leg originally was created by Otto Bock, a German firm. It is a common, commercially available prosthetic device that offers a fully microprocessor-controlled knee joint, a natural gait pattern, wireless remote control and safe, smooth walking at different speeds and on all surfaces.

But that is not enough for soldiers. “In the military context, we needed a knee that would perform like the best knees but that would do more than that. Instead of having battery power that would last eight or 10 hours, we needed a knee that would last for four or more days of constant use. Instead of support while walking at a certain slow-ish pace, we needed a faster pace. We also needed a knee that could be used in harsh environments,” Turner explains. “The military doesn’t just work in offices in clean environments. A knee needs to work in mud and sand and salt water and fresh water. If a person’s on patrol and has to cross a ditch, [he] can’t stop to change a knee. We need a knee that can be submerged in those harsh environments.”

Turner describes a hypothetical scenario with a soldier on patrol in an urban environment. If he steps out from behind a building and hears a suspicious noise, most conventional prostheses would not have the mobility control to allow him to slip quietly back behind the building. “We needed a knee that would allow the user to walk backwards,” he continues.

The advanced C-Leg has been offered to about 30 soldiers who had worn the previous version of the device. Next, it will be offered to veterans through the Department of Veterans Affairs and then likely will be made more widely available, Turner reveals.

The Spring Ankle with Regenerative Kinetics (SPARKy) is another TATRC-funded project. Developed by researchers at Arizona State University, SPARKy uses a robotic tendon to stretch springs when the ankle rolls over the foot, allowing the springs to propel the artificial foot forward for the next step. The four-pound device allows users to walk on a variety of surfaces, including grass, cement and rocks, and to climb up and down stairs. SPARKy is expected to become commercially available this year through a spinoff company called Spring Active.

A team of West Point cadets, one of whom interned at TATRC, built on the SPARKy technology to develop an artificial foot for service members. If all goes as planned, Turner says, a soldier will wear the device while running the Army physical fitness test later this month.


Staff Sgt. Jake Kessler, USA, ties a figure-8 knot into his harness rope as he prepares to climb a 50-foot rock with the heels of his prostheses.

TATRC funding also supported creation of the PowerFoot BiOM, a device developed by Dr. Hugh Herr, a researcher at the Massachusetts Institute of Technology. Herr has created his own company, iWalk, which markets the device. The PowerFoot BiOM is a bionic lower-leg system that replaces lost muscle function and allows the user to walk in a more natural way, without the hard work often required to use artificial limbs. It uses precision robotic engineering to provide power from one step to the next, and it simulates the action of the ankle, Achilles’ tendon and calf muscles by propelling the amputee upward and forward during each walking step.

TATRC works closely with other agencies doing similar research for different constituencies. The Department of Veterans Affairs, for example, coordinates research for veterans, and the National Institutes of Health does the same for civilians. The goal, according to Turner, is to eliminate redundancy and ensure that worthwhile projects find funding. Turner and his team also share information with the Revolutionizing Prosthetics program team at the Defense Advanced Research Projects Agency (DARPA). The Revolutionizing Prosthetics program is a more than $100 million effort intended to create a fully functional arm that will be linked directly to the brain and controlled entirely by thought. Ideally, the device will work as well as a natural limb, offering the sense of touch and the dexterity to play guitar. Prototypes currently are undergoing human testing.

Meanwhile, TATRC hopes to build on DARPA’s neural research to improve control for lower extremity prostheses. One possibility, Turner suggests, is to have the equivalent of a personal computer bus controlling various prosthetic and orthopedic devices used by each soldier. He explains that currently when multiple devices—a knee and an ankle, for example—are used, they are entirely independent of one another.

“We’re talking literally about communications devices—ones and zeroes being passed—between prosthetic devices. We’re talking about a bus system that can share data so that the devices can talk to each other and know what each other is doing and know how to behave,” Turner says. Theoretically, if one device runs low on power, it should be able to draw power from another. Or, if the soldier has a powered, processor-controlled knee linked with a more conventional ankle, the ankle could include a bar code so that the knee can identify it and adjust its performance according to whichever model ankle is being used. “I believe this is off-the-shelf technology. It’s not brain science,” he says, adding that it may be a simple matter of linking existing technologies in ways not yet attempted. Turner suggests that future soldiers could find themselves downloading the latest software application for a knee or an arm.

TATRC also is funding research with Sigenics, a Chicago firm that offers one possible solution for more effectively controlling prostheses. The company builds tiny electrodes that can be either surgically implanted or injected into the body. These Implantable Myoelectric Sensor (IMES) devices amplify brain signals and work together throughout the body to send those signals directly to the artificial limb. “One of our challenges is that we have to bring down the costs. Right now, each sensor costs about $10,000,” reveals Philip Troyk, Sigenics president. He adds that the devices will be available for field trials within the next year and also may be effective for rehabilitating paralyzed limbs so that they move once again. Once the Sigenics sensors are in place, the amputee could upgrade easily to new devices as technology advances, Troyk says.

Sigenics is teamed with Alion, a McLean, Virginia, firm that will develop a three-dimensional (3-D) modeling and simulation tool to aid in upper extremity prosthetics research. The tool might also prove useful for creating a 3-D model of a patient’s arm for surgeons if, for example, the arm has been mangled by an improvised explosive device on the battlefield, reveals Terry Philippi, Alion’s program manager.

Unlike some military research and development, TATRC’s work will not lead to a one-size-fits-all solution that meets a specific set of requirements. That is because every soldier is different, with different needs, different body types, physical reactions and preferences.

The research underway and the products that result from that research are adding value beyond the military mission. Regardless of whether injured soldiers remain in the military or return to civilian life, those who have lost limbs face similar challenges. Relatively minor motions can be a major chore. Fidgeting while standing in line or stepping back from a curb when a car approaches can be dangerous, and quality of life moments, such as feeling a child’s touch while walking hand-in-hand, can be impossible.

It is hard to predict what the future might hold, according to the experts leading the research efforts. “The  result may be that all of this stuff becomes obsolete, and somebody figures out how to grow a new arm or leg. That could be the ultimate goal, to be honest,” Turner says

Otto Bock:
DARPA Defense Sciences Office:
Spring Active:

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