HomeNews & MediaFeatured StoriesArmed with Ideas: APL Leads Prosthesis Development Team 

August 3, 2006

Armed with Ideas: APL Leads Prosthesis Development Team

A team of APL scientists and engineers has embarked on one of the Lab's most ambitious projects: to develop a next-generation mechanical arm that will look, feel, perform and be controlled like a natural limb.

The work is being done as part of the Defense Advanced Research Projects Agency (DARPA) Revolutionizing Prosthetics program, a bold effort to provide the most advanced medical and rehabilitative technologies for military personnel injured in the line of duty. APL has been awarded a $30.4 million contract to start the first phase of Revolutionizing Prosthetics 2009, a four-year $55 million program that aims to develop an advanced prosthetic arm that will allow a user to button a shirt, tune a radio, feel the warmth of a loved one's hand, or even return to active duty in their previous capacity.

APL's S. Harshbarger, along with a core group of engineers, scientists and medical professionals from APL, the Johns Hopkins School of Medicine, the Whiting School of Engineering, and the Bloomberg School of Public Health, will lead an interdisciplinary team of government agencies, universities and private firms to implement DARPA's vision.

Harshbarger is quick to downplay the media's characterization of the end-product as similar to the one Luke Skywalker gets in The Empire Strikes Back, after Darth Vader severs his hand.

"We want to be careful not to overstate expectations," he says, though he's no stranger to engineering solutions to seemingly insurmountable tasks. At the Lab, and in prior positions, Harshbarger has established a track record of developing, managing and delivering high technology solutions on multi-million dollar programs for DARPA and the Department of Defense.

Still, he treads lightly when making promises about this project. "This is truly a ‘DARPA hard,' high-risk, high reward project," Harshbarger says. "We are going to need breakthrough research in neural control, sensory input, advanced mechanics and actuators, and prosthesis design and integration to pull this off in four years, when DARPA is expecting us to deliver the product, ready for clinical trials. When it happens, it's literally going to revolutionize the prosthetics field and, more importantly, transform the lives of patients who have suffered limb losses."

Because of advances in body armor, soldiers are surviving wounds that would have been fatal in past conflicts; but these soldiers often have massive injuries that require the amputation of an extremity. According to DARPA, more than 300 soldiers from the War in Iraq alone have returned home with major amputations.

Harshbarger says there have been significant improvements in upper extremity prosthetics in recent years. The state-of-the-art myoelectric arm, for example, allows users to control hand and arm movements by deliberately flexing a muscle or through mechanical movement. Still, he says, "these devices have relatively limited degrees of motion and can generally allow control of only one motion at a time."

Technically speaking, existing technology allows for about three degrees of freedom of movement; Harshbarger's team is aiming for a device able to perform at strengths, speeds and angles with 22 degrees of freedom (including shoulder) to match the performance of the human arm while maintaining the person's ability to control the arm.

"Our guiding philosophy is that the patient's brain is more likely to be able to learn to use the prosthetic limb if its mechanics and controls behave similarly to the system that the brain learned initially," Harshbarger says. However, he concedes, understanding the body's signals may be the most daunting task of all for engineers.

"Our challenge is to advance the base of scientific understanding related to neural control mechanisms and physiological function of the human limb, while at the same time developing innovative engineering solutions that can be successfully implemented," he adds.

"DARPA is very clear on this; they will not tolerate delivery of a box of parts," Harshbarger states. In fact, the defense research agency is looking for his team to deliver usable improvements on existing technology at the end of each of the first two years of the project and they want the technology ready for clinical trials in only four years.

"There is no time for us to recreate the wheel," he says. So, he has pulled expertise from across the Lab and the broader Hopkins enterprise and assembled a formidable array of brainpower from several disciplines to tackle the technical challenges while addressing real patient needs.

"We have handpicked a team that has decades of experience in prosthetics and related areas," he says. "We are literally standing on the shoulders of giants in their respective fields. This team is comprised of the best folks who've been pushing the envelope and are poised with many of their most recent advances finally ready to be implemented."

The APL team includes investigators from several top-tier universities and includes Otto Bock Health Care of Austria, one of the world's leading manufacturers of prosthetic devices. A complete list of subcontractors is available online at http://www.jhuapl.edu/newscenter/pressreleases/2006/060209.asp.

"Developing this broad consortium and providing both the technical and managerial leadership for the design and systems integration of this advanced limb is an example of what APL does best," says Dr. Smith, APL's business area executive for Biomedicine. "We focus on programs where we can make critical contributions to our nation's critical challenges. I can think of no better example of a critical contribution than having a positive impact on the quality of life and future opportunities for our injured soldiers."