Revolutionizing Prosthetics 2009 Team Delivers First DARPA Limb Prototype

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Revolutionizing Prosthetics 2009 Team Delivers First DARPA Limb

Prototype

http://www.medicalnewstoday.com/medicalnews.php?newsid=69181

An international team led by the s Hopkins University Applied

Physics Laboratory in Laurel, Md., has developed a prototype of the

first fully integrated prosthetic arm that can be controlled

naturally and provide sensory feedback, and allows for eight degrees

of Freedom -- a level of control far beyond the current state of the

art for prosthetic limbs.

Proto 1, developed for the Defense Advanced Research Projects Agency

Revolutionizing Prosthetics Program, is a complete limb system that

also includes a virtual environment used for patient training,

clinical configuration, and to record limb movements and control

signals during clinical investigations.

The DARPA prosthetics program is an ambitious effort to provide the

most advanced medical and rehabilitative technologies for military

personnel injured in the line of duty. Over the last year, the APL-

led Revolutionizing Prosthetics 2009 (RP 2009) team has worked to

develop a prosthetic arm that will restore significant function and

sensory perception of the natural limb. Proto 1 and its virtual

environment system were delivered to DARPA ahead of schedule, and

Proto 1 was fitted for clinical evaluations conducted by team

partners at the Rehabilitation Institute of Chicago.

" This progress represents the first major step in a very challenging

program that spans four years and involves more than 30 partners,

including government agencies, universities, and private firms from

the United States, Europe, and Canada, " says APL's Stuart

Harshbarger, who leads the program. " The development of this first

prototype within the first year of this program is a remarkable

accomplishment by a highly talented and motivated team and serves as

validation that we will be able to implement DARPA's vision to

provide, by 2009, a mechanical arm that closely mimics the

properties and sensory perception of a biological limb. "

Making Use of Residual Nerves

The advanced degree of natural control and integrated sensory

feedback demonstrated with Proto 1 are enabled by Targeted Muscle

Reinnervation, a technique pioneered by Dr. Todd Kuiken at RIC that

involves the transfer of residual nerves from an amputated limb to

unused muscle regions in appropriate proximity to the injury. In

this case, the nerves were transferred to the pectoral area of the

patient's chest. This procedure provides for a more intuitive use of

a prosthetic arm and allows for the natural sensation of grip

strength and touch.

During clinical evaluation of the limb at RIC, Sullivan, a

patient of Dr. Kuiken, demonstrated substantial improvements in

functional testing, such as the ability to reposition his thumb for

different grips, remove a credit card from a pocket, stack cups

while controlling his grip force using sensory feedback verses

vision, and to walk using the free swing mode of the limb for a more

natural gait. Harshbarger says that critical to Proto 1's

development was closely working with patients such as Sullivan to

help the team understand the attributes patients look for in new

prosthetic limbs. The limb system also includes a natural-looking

artificial covering that was created using photographs of the

patient's native limb taken before the accident.

" The Rehabilitation Institute of Chicago continues to advance this

applied research and bring the application of the Targeted

Reinnervation technique to the forefront to benefit our nation's

service men and women, " says Dr. Kuiken, the director of the Neural

Engineering Center for Bionic Medicine at RIC. " The results we are

achieving in this highly collaborative project are very exciting and

I am confident that these discoveries will bring more natural

control of prostheses, better artificial limbs and make a difference

in the lives of amputees worldwide. "

More Advanced Prototype Within Reach

APL, which was responsible for much of the design and fabrication of

Proto 1, and other team members are already hard at work on a second

prototype, expected to be unveiled in late summer. It will have more

than 25 degrees of freedom and the strength and speed of movement

approaching the capabilities of the human limb, combined with more

than 80 individual sensory elements for feedback of touch,

temperature, and limb position.

" There is still significant work to be done to determine how best to

control this number of degrees of freedom, and ultimately how to

incorporate sensory feedback based on these sensory inputs within

the human nervous system, " Harshbarger says. " The APL team is

already driving a virtual model of Proto 2 with data recorded during

the clinical evaluation of Proto 1, and the team is working to

identify a robust set of grasps that can be controlled by a second

patient later this year. "

Another exciting development is the functional demonstration of

Injectable MyoElectric Sensor (IMES) devices - very small injectable

or surgically implantable devices used to measure muscle activity at

the source verses surface electrodes on the skin that were used

during testing of the first prototype.

" The IMES devices, coupled with TMR procedures, promise to increase

the fidelity of control and can be used in certain injury scenarios

to provide a significant improvement on their own merit, "

Harshbarger notes. Further neural integration work includes

fabrication of early devices to integrate directly with the

peripheral nervous system and the cortex.

" APL and DARPA are united in the mission to improve technology and

quality of life for our injured warfighters, " Harshbarger

continues. " There are a lot of people working very hard to

accomplish DARPA's vision of a final limb system that approaches the

natural appearance and control of the native limb. It remains a

significant challenge, but the progress to date should give hope

that the performance of the final RP 2009 limb will significantly

improve the capabilities of upper extremity prosthetic limbs. "

As the team prepares for further evaluations this summer, Proto 1 is

already generating considerable interest from government agencies

wanting to transition the prototype for use with other patients.

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Key Members of Proto 1 Development Include:

s Hopkins University Applied Physics Laboratory (program lead,

system integration, design, and development)

The University of New Brunswick, Canada (pattern recognition

algorithms)

Rehabilitation Institute of Chicago (mechanical components designed

by Weir).

Otto Bock of Vienna Austria (design and fabrication of mechanical

subsystems)

Chicago PT and Northwestern University (development of the 'tactor'

sensory feedback device

University of Southern California (collaborative development of the

virtual patient training and clinical interface system)

Sigenics, Inc. and Northwestern University Prosthetics Research

Laboratory (development of electronics for the IMES devices)

Alfred Mann Foundation (ceramic encapsulated packaging for IMES)

Other organizations working toward the goals of the Revolutionizing

Prosthetics 2009 Program can be found at

http://www.jhuapl.edu/newscenter/pressreleases/2006/060209.asp.