This is a two-part article detailing the involvement of the JHU Applied Physics Laboratory in a project to revolutionize prosthetic arm control. Today's article explains the current need for prosthetics and the project's purpose. Next week's article will highlight the progression of the APL in achieving their goal.
Al Gore may feel personally responsible for creating the Internet, but the real credit may reside elsewhere. DARPA, or the Defense Advanced Research Projects Agency, is an agency of the U.S. Department of Defense pioneering technological innovations from the Internet to one of its most ambitious projects to date: the development of a prosthetic arm that will look, feel and be controlled like a natural limb.
Currently contracted by DARPA, the JHU Applied Physics Laboratory has been awarded $30.4 million to initialize the project's first phase. Named the DARPA Revolutionizing Prosthetics Program, the four-year, $55 million project is targeted toward the large number of soldiers injured during Operation Iraqi Freedom.
In addition to injuries due to the War in Iraq, every year, over 50,000 new amputees are documented. Lower-limb amputees are more common than upper-limb amputations, comprising about 90 percent of total amputees in the U.S., whereas those with amputations proximal to the elbow make up two percent of the total amputee population. Seventy percent of all upper-limb amputees have amputations distal to the elbow, or have lost fingers or arms below the elbow. In the U.S., approximately 25,000 people are known to have complete loss of one arm. Those with complete arm and/or hand amputation are the target beneficiaries of this project.
The causes for upper-limb amputation vary widely and include trauma, cancer, cardiovascular disease, infection, nerve injury and congenital anomalies. The most common causes are trauma and cancer followed by cardiovascular disease; trauma accounts for 77 percent of total amputations. Diabetes and the associated complications of poor blood circulation in the limbs are the main causes of cardiovascular amputations. With the War in Iraq, combat injuries also comprise a large source of amputees, especially because of improvements in battlefield medicine that allow a higher percentage of injured combatants to survive the initial injury. These injuries are often massive, requiring amputation of the limb.
Most prosthetics currently on the market are stiff and feel unnatural; only about half of all upper-limb amputees receive prosthetic devices. The devices most commonly chosen are geared toward aesthetic appeal, not functionality, indicating that many amputees will tolerate a decrease in the function of the prosthesis for an increase in cosmetic appeal.
The driving philosophy behind the DARPA project is to revolutionize prosthetic arm control by hard-wiring its control mechanisms directly into the brain. Since the brain is already programmed for limb control, it is feasible to redirect those same control mechanisms to the prosthetic arm. Once this control system is understood, it must be integrated into an innovative engineering design that can be easily implemented.
A major barrier to this effort will be understanding the brain's interfacing methods to the hand in order to create and enact motor control schemes, with respect to planning, feedback and coordination. Another potential barrier to the success of a neurally integrated prosthetic is the necessity of procedures to install the neural interface. There will certainly be a patient population that, either due to pure reluctance or complications such as immune system compromise, will balk at the necessity of additional surgery following amputation. Additionally the neural integration promises to have a long development cycle that will not produce immediate results.
Led by Stuart Harshbarger, the DARPA Revolutionizing Prosthetics Team encompasses a core group of engineers, scientists and medical professionals from the APL, the Johns Hopkins School of Medicine, the Whiting School of Engineering and the Bloomberg School of Public Health. The team will be assisted by researchers from top-tier universities across the country and internationally recognized manufacturers of prosthetic devices including the BioStar Group and Otto Bock Health Care of Austria.
How does one go about fooling the brain into controlling an arm that it has already lost? How closely can a real limb be reproduced by plastic and circuit boards?
Quite frankly, no one is really sure.
