Revolutionary mechanical arm provides grip, feel

Team lead by Applied Physics Laboratory has come up with a prosthetic breakthrough, giving fine motor skills and sensory perception to amputees. Photos: Testing the prosthetic arm

Remember Luke Skywalker's amazingly lifelike arm replacement in The Empire Strikes Back? A similar type of realistic arm may be in store for injured soldiers.

The Johns Hopkins University Applied Physics Laboratory in Laurel, Md., announced Thursday that its team has developed a breakthrough prosthetic arm for the Defense Advanced Research Projects Agency Revolutionizing Prosthetics 2009 program.

The DARPA program is an initiative to produce by 2009 a mechanical arm that closely mimics the movement and sensory perception of a biological arm. It would then be provided for military personal hurt in the line of duty.

As of the end of February 2007, 897 service men and women have had amputations since the start of the Iraq War in 2003. Of those amputations, 612 were a complete limb, hand or foot, and 285 were fingers and/or toes only, according to Cynthia Smith, a spokeswoman for the Department of Defense, who was quoting figures from the Amputee Center at Walter Reed Army Medical Center.

Charged with leading the joint project, APL was awarded $30.4 million in February 2006 as part of the first phase of the program. The team comprises members from universities, private firms and government agencies.

Johns Hopkins' new Proto 1 arm restores significant function and sensory perception to the wearer and allows eight degrees of motion, according to a statement released by the university. Proto 1 was tested on patients at the Rehabilitation Institute of Chicago in January and February.

Through an attachment to healthy nerves, the Proto 1 enables the wearer to have a sense of touch and feel strength of grip. In the case of the Proto 1 arm, nerves in the pectoral area were used. The process is known as Targeted Reinnervation and was developed by Dr. Todd Kuiken, the director of the Neural Engineering Center for Bionic Medicine at the Rehabilitation Institute of Chicago.

The result was that a wearer was able to re-adjust the prosthetic thumb to manage different types of grips and possess fine motor skills for things like placing a checkers piece into a slot and removing a credit card from his pocket. He could stack plastic cups without crushing them by using sensory feedback to regulate the force of his grip.

The wearer was also able to swing his arms more naturally while walking, all with the use of sensory instead of vision.

"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," Kuiken said in a statement.

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