Researchers take one step closer to neural-controlled bionic legs for safer mobility

We've seen our fair share of prosthetic arms and computer interfaces operated with little more than the firing of a synapse, but legs? They're a different story: balancing and propelling a sack of (mostly) flesh and bone is a much more complicated task than simply picking up a sandwich. Thankfully, the Rehabilitation Institute of Chicago's Center for Bionic Medicine is now one step closer to thought-controlled lower-limb prosthetics. As pictured here, the researchers' early simulations showed that amputees could control a virtual knee and ankle with 91-percent accuracy, by way of pattern recognition software to interpret electrical signals delivered through nine different muscles in the thigh -- patients think about moving, thus lighting up the nerves in varying patterns to indicate different motions. The ultimate goal is to hook up bionic legs through the same way, which would offer a greater range of motion than existing prosthetics, making tasks like walking up and down stairs safer. Now all we need is a quadruple amputee willing to pick up a badge and slap on an eye-tracking microdisplay.

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The Rehabilitation Institute of Chicago Announces Preliminary Results Demonstrating Neural Control in Lower Limb Amputees
Research published in the JAMA marks the first significant step towards RIC's future development of a neural-controlled

CHICAGO (April 20, 2011) – The Rehabilitation Institute of Chicago (RIC), ranked the "#1 Rehabilitation Hospital in America" by U.S. News & World Report since 1991, announced today preliminary results demonstrating real-time neural control of knee and ankle motions for lower limb amputees. Results from the early-stage research, authored by Dr. Levi Hargrove of RIC's Center for Bionic Medicine, were published in the April 20 issue of the Journal of the American Medical Association (JAMA).

Prosthetic Leg"Our preliminary results demonstrate successful neural control of both the ankle and knee joints and represent a significant step in our efforts to develop a neural-controlled prosthetic leg for the millions of people living with lower limb loss worldwide," said Dr. Levi Hargrove, PhD, Center for Bionic Medicine, Rehabilitation Institute of Chicago. "There is much work to be done, but what we have found is a meaningful sign for a future of more advanced prosthetic control and artificial limbs for lower limb amputees."

More than one million American's live with lower limb amputations with more than 130,000 new lower limb amputations occurring each year – almost six times the number of upper limb amputations.1 With lower limb amputees forming a large portion of the amputee population, there is a significant unmet need for the development of a neural-controlled prosthetic leg. However, there are challenges in transitioning the current bionic technology for upper limbs to lower limbs due to some inconsistencies in recording neural, or electromyographic (EMG), signals. While research to-date has provided some insight into overcoming these challenges, additional studies are needed to evaluate and develop a novel lower limb neural interface.2

Dr. Hargrove's research published in JAMA investigates real-time neural control in four lower limb amputees and four non-amputee control participants, measuring the EMG signals in nine lower limb muscle sites during lower limb movement. Through real-time tests, all participants were instructed to move a virtual lower limb through a variety of motion patterns on a computer screen. Metrics were based on accuracy of movement, the time it took to complete the motion and the percentage of successfully completed motions.

Results from the trial showed all participants were able to control their knee and ankle from neural information measured in the thigh. The average motion completion rate for knee and ankle movements (knee flexion/extension and ankle dorsi-flexion/plantar flexion) was high at 97.2 percent for amputee patients and 95.1 percent for control participants. The average motion completion times for knee and ankle movements were 2.53 seconds for amputee patients and 1.94 seconds for control participants. The average accuracy of movement rates were 91 percent for amputee patients and 89 percent for control participants.

Findings from Dr. Hargrove's study complement RIC's continued success in providing upper limb amputees with neural control of prostheses, through its Targeted Muscle Reinnervation (TMR) procedure and development of the world's first neural-controlled bionic arm. TMR, pioneered by Todd A. Kuiken, M.D., Ph.D. of the RIC in 2002, is an innovative surgical procedure that re-routes brain signals from nerves severed during amputation to intact muscles, allowing patients to control their robotic prosthetic devices by merely thinking about the action they want to perform. The procedure has benefitted, to date, more than 50 upper limb amputees worldwide.

"These findings in JAMA also showed that real-time ankle control was attainable by only using EMG signals from the thigh muscles, leading me and my colleagues to believe that TMR surgery may not be necessary for amputees to regain control of knee and ankle movements with prostheses," said Dr. Hargrove. "We look forward to applying these findings to our continued research investigating neural control in lower limb amputees and the future development of advanced physical knee and ankle prostheses."
About The Bionic Arm

RIC's Center for Bionic Medicine, led by Todd Kuiken, MD, PhD, pioneered a procedure called Targeted Muscle Reinnervation (TMR), in which the amputee's own nerves that once went to their arm and hand are reconnected to healthy muscles, allowing the neural information to be used to control a computerized prosthesis more naturally-the user simply thinks about what they want the arm to do. The "Bionic Arm," or neural-controlled myoelectric arm, is driven using electrical signals from the reinnervated muscles, now activated by the user's own thought-generated nerve impulses. These impulses are sensed, via surface electrodes, from the reinnervated muscles and carried through to the mechanical arm, causing the arm to move. RIC's "Bionic Arm" technology has been very successful in more than 50 patients worldwide, including several U.S. service members who lost limbs in combat.
About The Rehabilitation Institute of Chicago

The Rehabilitation Institute of Chicago (RIC) is the nation's #1 ranked provider of comprehensive physical medicine and rehabilitation care to patients from around the world and is the leader in research and development of the most cutting-edge treatments and technology in its field. Through aggressive medical protocols, RIC guides the patient care process toward a better patient outcome-involving repair, regeneration, and recovery of brain, spinal cord, and musculoskeletal function.

RIC holds an unparalleled market distinction with a record six federal research designations awarded and funded by the National Institutes of Health and the Department of Educations' National Institute of Disability and Rehabilitation Research in the areas of spinal cord injury, traumatic brain injury, stroke, neurological rehabilitation, outcomes research, and rehabilitation engineering research.

RIC, founded in 1954, has been designated the "#1 Rehabilitation Hospital in America" by U.S. News & World Report every year since 1991 and attributes its leading standard of care in part to its innovative research and discovery, particularly in the areas of bionic medicine, robotics, neural regeneration, pain care, and better outcomes. RIC operates its 165-bed flagship hospital in downtown Chicago, as well as a network of 30 sites of care located throughout the city and surrounding suburbs that provide additional inpatient care, day rehabilitation, and outpatient services. RIC also maintains strategic alliances with leading healthcare providers throughout the state of Illinois and Indiana.