By Sandra Basu
WASHINGTON — Last fall, Tim Hemmes, a 30-year-old quadriplegic at the University of Pittsburgh Medical Center (UPMC) was able to control an advanced mechanical arm using nothing but his brain signals.
Hemmes, paralyzed seven years earlier after a motorcycle accident damaged his spinal cord, was the first to participate in a trial to determine whether a spinal-cord injury patient could control an advanced prosthetic arm by thoughts.
With a grid of electrodes placed on the surface of the brain to control the prosthetic arm, Hemmes was able to reach up to touch hands with his girlfriend for the first time since the accident.
“Seeing Tim reach out with a mechanical arm to touch his girlfriend was an unexpected and poignant bonus for all of us who are involved with this exciting project,” co-principal investigator Michael Boninger, MD, director of the UPMC Rehabilitation Institute, said in a statement.
The advanced prosthetic arm used in the project, known as the Modular Prosthetic Limb (MPL), was built at Baltimore’s Johns Hopkins University Applied Physics Laboratory (APL) and was funded by Defense Advanced Research Projects Agency (DARPA) and dubbed Revolutionizing Prosthetics.
Revolutionizing Prosthetics was begun by DARPA in 2006 to expand prosthetic arm options for troops, a need that has been driven by the reality of war. In 2011 alone, statistics from the Armed Forces Health Surveillance Center indicate that 240 deployed servicemembers suffered at least one arm or leg amputation.
The Modular Prosthetic Limb was used by wounded troops at the Walter Reed National Military Medical Center for the first time on Jan. 24, 2012. – U.S. Navy Photo
While lower-limb prostheses have enabled some troops to return to duty, DARPA program manager Army Col. Geoff Ling said that “by providing increased upper-prosthetic capability that option may someday be available to servicemembers with upper-limb loss.
“When the Revolutionizing Prosthetics program was launched, the state of upper-limb prosthetic technology was far behind lower-limb technology. Advancing upper-limb technology was judged to be harder, and it wouldn’t have happened without a significant research-and development-investment, such as the $153 million budgeted by DARPA,” he told U.S. Medicine in a written statement.Military Develops New Prosthetic Devices Controlled by Brain Signals Sidebar
Independent Household Mobility Is Goal with Limb Amputations
One of the primary goals for patients with multiple limb amputations is to help them achieve Independent household mobility. While a wheelchair was traditionally used for that purpose, smaller houses with non-accessible spaces make that impossible.
One solution is the use of so-called “house legs,” shortened prostheses, which allowed increased mobility and independence for individuals with bilateral above-knee amputations, according to an article published earlier this year in the Journal of Surgical Orthopaedic Advances. 1
The article describes lessons learned at Walter Reed National Military Medical Center in Bethesda, MD, about providing advanced therapy and prosthetics for combat casualties. With Army Col. Paul F. Pasquina, MD, chief of Walter Reed’s Integrated Department of Orthopaedics and Rehabilitation among the authors, it also provides guidelines for all providers involved in the care of individuals with amputation.
“Feedback has been overwhelmingly positive from patients and family members who credit the ‘house legs’ for allowing them to be more independent in performing routine household activities,” the authors write. “Moreover, shortened prostheses have been shown to require less oxygen consumption and cardiac response than full-length prostheses, advocating their use for elderly patients and civilians who would otherwise be considered poor prosthetic candidates.”
They recommend that house legs be designed to be lightweight, use anatomical suspension and allow for patients to be able to put them on and remove them quickly.
The article also discusses some of the unique challenges of injuries from Iraq and Afghanistan, noting that the “relatively high number of combat casualties with very proximal lower-limb amputations” is spurring efforts to find ways to help these patients walk upright.
In addition, issues such as hip disarticulation and/or hemipelvectomy coupled with a colostomy can make socket design and prosthetic fitting even more challenging.
For patients with high bilateral levels of amputation, walking with prosthetics may not be a possibility, the authors write, recommending, “Therefore, it is imperative that clinicians pay considerable attention to customizing seating systems and wheelchair fittings to achieve independent mobility.”
They suggest that future development of robot devices may provide more options for these patients in coming years.
The article also emphasizes the importance of an ongoing fitness program for wounded warriors with amputation. It notes that low-impact aerobic activities, such as cycling, provide the required safety and efficiency, adding that specially-designed bicycles are available, including hand crank, recumbent and upright models.
- Harvey ZT, Loomis GA, Mitsch S, Murphy IC, Griffin SC, Potter BK, Pasquina P.
Advanced rehabilitation techniques for the multi-limb amputee. J Surg Orthop Adv.
2012 Spring;21(1):50-7. PubMed PMID: 22381511.Military Develops New Prosthetic Devices Controlled by Brain Signals Cont
The 9-pound MPL undergoing research provides 22 degrees of motion and independent movement of the fingers. It provides nearly as much dexterity as a natural limb and, like a natural limb, is designed to respond to a user’s thoughts, according to APL.
‘‘House legs’’ are simply shortened prostheses that are light- weight and easy to don and doff much akin to slippers. This design and concept addresses needs of household ambulation to very active aswell as very inactive persons with bilateral transfemoral and knee disarticulation amputation levels.
“No other arm has the level of dexterity and sensorization that this arm is. It is the most advanced arm in the world,” Michael McLoughlin, who serves as the program manager at the APL, told U.S. Medicine.
McLoughlin said the ultimate objective is to provide a prosthetic that has a level of functionality approaching that of the lost limb.
“That means to be able to form a very complex grasp and to be able to use it very intuitively,” he said. “When we start thinking about interfacing with the nervous system, the real power of what we are doing is that, for the amputee, they are really thinking about moving their arm, they are not learning how to do something new,” he said.
Putting together an advanced system such as this has required widespread expertise, McLoughlin explained, with numerous industry, government and academic contributors.
In addition to working with the University of Pittsburgh and the California Institute of Technology for their experience in brain-computer interfaces, APL is partnering with the University of Chicago for its expertise in sensory perception and with the University of Utah for its expertise to develop implantable devices suitable for interfacing with the human brain.
“This has always been a technically extremely challenging program, on a number of levels — just building the arm that has all the ability of a natural limb is very challenging. The brain-computer interface, just understanding what to do with the signals and how to interpret neural patterns and convert those into the motions of the arm, that is challenging,” McLoughlin said.
In the case of Hemmes, an electrocortigraphy (ECoG) grid “adapted from seizure-mapping brain electrode arrays was placed on the surface of his brain during surgery,” according to a UPMC release. The researchers used computer software developed in earlier studies to interpret the neural signals sensed by the brain grid. When Hemmes imagined flexing his thumb, a brain signal pattern was created, then interpreted by the computer, allowing him to perform tasks with the prosthetic.
Research on direct brain control of this advanced prosthetic continues. It was announced last year that DARPA-funded researchers at UPMC and the California Institute of Technology would conduct pre-clinical trials with five spinal cord-injured volunteers, testing brain control of mechanical limbs.
The Defense Advanced Research Agency’s Revolutionizing Prosthetics program seeks to expand prosthetic arm options for today’s wounded warriors. Photo from DARPA website.
In another project with Walter Reed National Military Medical Center, a prosthetic controlled in a less invasive manner is undergoing testing. Rather than implanting electrodes in the brain, as may be necessary with spinal cord injured patients, noninvasive surface electrodes allow control for patients who have the functionality to use it.
“We want to be able to adapt the technology to a very wide range of patients,” McLoughlin said. “So someone who is an amputee that has a fairly intact peripheral system, to someone who has a spinal-cord injury or other neurodegenerative condition that is no longer able to utilize their arms, would be able to utilize the prosthetics. We try to adapt to what the patient needs.”
With a long history of point of care testing at both of its predecessor organizations, the Walter Reed National Military Medical Center (WRNMMC) laboratory services staff were keenly aware of the advantages of using portable testing devices to obtain rapid patient assessments.
Lifting weights is one way servicemembers keep in peak physical condition during deployment.