LAUREL – Signing a credit card receipt, opening a door knob and typing on a keyboard are everyday activities that most people perform without a second thought. For Marine Capt. Jonathan Kuniholm those activities are arduous.
Kuniholm, 34, of Durham, N.C., lost most of his right forearm and hand to an improvised explosive device when his platoon was ambushed in Iraq on New Year’s Day 2005. He has had a motorized prosthetic since April. He has three different hands that can be interchanged to do various tasks, but Kuniholm is not happy with the current level of technology.
“The human hand has (many) degrees of freedom,” he said. “What we have right now basically has two.”
Researchers at Johns Hopkins University Applied Physics Laboratory aim to change that in the next four years. Work began this month on a $30.4 million defense contract to design and build the world’s most advanced prosthetic arm.
The project aims to create a prosthetic with 22 ranges of motion that will mimic the movement of a natural limb and allow the user to have a sense of touch, temperature and spatial location. It must also fit the size constraints of a human arm and be capable of 18 hours of continuous operation.
Kuniholm, who is now working toward his Ph.D. in biomedical engineering at Duke University, hopes to work on the project to advance current prosthetic technology.
“I’m an interested user, and I want something that closely duplicates the uses of the hand that I used to have,” he said. “But I’m committed to doing it for everyone who has lost a limb.”
The best current commercial prosthetics have as many as three ranges of motion: elbow, wrist and hand, according to Kraig Helberg, a prosthetist for C.D. Denison Orthotics & Prosthetics in Baltimore. The user can only perform one type of motion at a time, resulting in a movement that looks unnatural.
The university was awarded the competitive contract from the Defense Advanced Research Projects Agency, the Defense Department’s central research and development organization. The contract finances the first two years of the project, with a $24.4 million option for the next two years. More than 30 subcontractors from the United States and Europe have signed on to work with the project.
Current motorized prosthetics are controlled by myoelectric signals — when the user flexes a muscle, an electronic signal on the skin is picked up by sensors causing the battery-powered motor to move the arm.
Helberg said many more people come to him wanting myoelectric prosthetics than actually end up getting them. He explains how different they are from a human arm and tries to fit each patient with a prosthetic that suits his or her needs.
“Not everybody who is an amputee is gadget-tolerant,” Helberg said.
Project leader Stuart Harshbarger said because they are cumbersome to use, many people who have myoelectric prosthetics instead opt to use a traditional hook or a purely cosmetic prosthetic.
“The challenge is to build this advanced technical device that is actually usable, meets peoples’ needs, is acceptable and people will use it,” Harshbarger said.
The war in Iraq has given the Defense Department a vested interest in prosthetic technology. Better body armor and medical treatment are saving soldiers’ lives, but many still lose limbs. According to an ABC News report, 9 percent of soldiers injured in Iraq died, compared to 24 percent in the Vietnam War and 30 percent in World War II. Walter Reed Army Medical Center in Washington has treated more than 300 soldiers who have lost limbs.
Research is being done on how the new devices will meet the requirements of the contract. One possibility the lab is studying involves operating the prosthetic with impulses received directly from the brain.
Harshbarger’s team is also investigating the possibility of power sources other than batteries. Even with advances in rechargeable battery technology, there is still a fundamental limit to how much energy can be stored in them, Harshbarger said. One option involves using a catalyst and reactant such as hydrogen peroxide to create pressurized gas that powers the arm.
All of the options will be considered in the first two years, and a definitive plan for each subsystem will be presented to the Research Projects Agency. Harshbarger is certain the project will yield important discoveries, even if it is not optioned for the second two years.
“There’ll be technologies at the end of year one that patients can actually use and benefit from,” he said.
Harshbarger, who has worked in the lab for five years, said this is the most personally significant project he has ever worked on.
“There’s no more compelling critical challenge than trying to restore functionality to people who have given their service to their country.”
– 30 – CNS-2-24-06