Wednesday, June 27, 2012

Restoring Capabilities: First Wounded Warrior Demonstrates APL's Revolutionary Prosthetic Arm

An Applied Physics Laboratory (APL)-developed prosthetic arm was controlled for the first time by electrical thought impulses in sessions at the Walter Reed National Military Medical Center in January. Tech. Sgt. Joe Delauriers—who lost both legs and his left arm in a September 2011 IED explosion in Afghanistan—was the first in a series of military members with upper-extremity amputations who will test the device this year and help Laboratory engineers continue to refine the technology.

This milestone is the latest in the Laboratory's Revolutionizing Prosthetics program, launched in 2006 to create a neurally controlled artificial limb that will restore full motor and sensory capability to upper-extremity amputees. Program Manager Mike McLoughlin says that after years of preparation, "it's gratifying to enter a phase where we are working with patients and amputees who can benefit from this technology.

(Top) APL's Courtney Moran, a prosthetic clinician, helps Tech. Sgt. Joe Delauriers affix the Modular Prosthetic Limb; (middle) Moran observes as Delauriers, Walter Reed researcher Brett Monson, and APL's Bobby Armiger monitor signals from the limb; (bottom) Delauriers controls the device. 
Credit: JHU/APL 

"The progress has been truly revolutionary," adds McLoughlin, the deputy business area executive for Research and Exploratory Development. "We have literally gone from the hook, that could only open and close, to a fully functional hand."

The latest prototype—known as the Modular Prosthetic Limb, or MPL—has nearly the same numbers of degrees of freedom as the human arm, and it was designed to adapt to varying degrees of amputations. Patients can control the device in several ways; from a technique known as targeted muscle reinnervation, which involves the transfer of residual nerves from an amputated arm into the chest of the patient, to the noninvasive process used with the wounded warriors at Walter Reed.

Delauriers controlled the device via surface electrodes that picked up signals generated by the muscles beneath the skin of his residual limb. Those electrical patterns were converted into actual movement, says Bobby Armiger, a biomechanics engineer in the Research and Exploratory Development Department who is heading up the clinical evaluations at Walter Reed.

Before the airman could use the arm, he had to undergo training using an APL-developed Virtual Integrated Environment (VIE), which allows patients to observe movement of a 3-D virtual arm. Using the VIE, recorded signals from the residual limb were correlated to the desired motion of the phantom limb.

"In just a few sessions, Joe was able to rotate his wrist, move the hand, and pinch the fingertips together," Armiger says.

This year, the project will also sponsor clinical evaluations of the MPL involving patients with upper spinal cord injuries to explore different control methods.

Physicians at the University of Pittsburgh Medical Center will surgically implant micro-electrodes in the brain of a paralyzed patient to record neural signals that control arm movement. "The goal for the first participant is to demonstrate that we can use these neural recording arrays to control external devices over a one-year period," McLoughlin says. "We hope that they will be able to control the position and orientation of, and perform highly dexterous movements with, the Modular Prosthetic Limb."

The next logical phase in the MPL's development is to incorporate a sense of touch, McLoughlin says. "There are more than 100 different sensors in the arm and hand that measure things like pressure, vibration, temperature, surface texture, and even the orientation of the prosthetic arm relative to your body," he explains.

"We've always had our eye on restoring capabilities to soldiers injured in combat," McLoughlin says. "But this project promises to transform the lives of not just the wounded warriors, but of patients with spinal cord injuries, the elderly, or anyone who has lost the ability of arm and hand function."

Contacts and sources:
Johns Hopkins Applied Physics Laboratory

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