Newswise — Clinical investigators at the University of Michigan, Ann Arbor, have used modern tissue engineering to develop an interface that could improve the function of prosthetic hands and possibly restore the sense of touch to patients who are fitted with the devices. They presented their updated findings at the 95th annual Clinical Congress of the American College of Surgeons.
Their research arose from a need for better prosthetic devices for troops wounded in Afghanistan and Iraq. “There is a huge need for a better nerve interface to control the upper extremity prostheses,” according to Paul S. Cederna, MD, FACS, one of the principal investiga-tors. “The wounded soldiers coming back from Iraq and Afghanistan sustain very severe upper extremity injuries but survive thanks to body armor.” The Department of Defense has provided extensive funding to support these research efforts.
The University of Michigan researchers aimed to overcome the shortcomings of existing robotic prosthetics, which have only limited motor control, provide no sensory feedback and can be uncomfortable and cumbersome to wear. “Most of these individuals are typically using a prosthesis design that was developed decades ago,” Dr. Cederna said. “This effort is to make a prosthesis that moves like a normal hand.”
When a hand is amputated, the nerve endings in the arm continue to sprout branches, growing a mass of nerve fibers that send flawed signals back to the brain. The researchers created what they called a “bio-artificial neuromuscular junction,” composed of muscle cells and a nano-sized polymer placed on a biological scaffold. Neuromuscular junctions are the body’s own nerve-muscle connections that enable the brain to control muscle movement.
That bioengineered scaffold was placed over the severed nerve endings like a sleeve. The muscle cells on the scaffold and in the body bonded and the body’s native nerve sprouts fed electrical impulses into the tissue, creating a stable nerve-muscle connection. In laboratory rats, the bioengineered interface relayed both motor and sensory electrical impulses and created a target for the nerve endings to grow properly. “The polymer has the ability to pick up signals coming out of the nerve, and the nerve does not develop and grows an abnormal mass of nerve fibers,” Dr. Cederna explained.
Results in laboratory rats indicate the interface may not only improve fine motor control of prostheses, but can also relay sensory perceptions such as touch and temperature back to the brain. Laboratory rats with the interface responded to tickling of feet with appropriate motor signals to move the limb, according to Dr. Cederna.
The Department of Defense and the Army have already provided $4.5 million in grants to support the research. Meanwhile, the research team has submitted a proposal to the Defense Advance Research Project Agency to begin testing the bioengineered interface in humans in three years.
William Kuzon, Jr., MD, PhD, FACS; David C. Martin, PhD; Daryl R. Kipke, PhD; Melanie Urbancheck, PhD; and Brent M. Egeland, MD, have also participated in the study.