Dr. Roy Aaron recalls the first time he donned a head-mounted display – a device resembling a helmet with goggles that displays computer-generated images for the eyes – and was suddenly immersed in virtual reality.
“They simulated a scene where I had to walk on a beam over like a gulley, a canyon,” Aaron said. “But of course the investigator was right next to me. In fact, he was holding my arm. I still wouldn’t do it. I dropped down and put my hands on the floor.”
The surprisingly realistic virtual experience can be unnerving, but it is an essential component of research being conducted by Aaron and his team of doctors, scientists and computer engineers, who are using such technology to develop a new generation of “biohybrid” prosthetic limbs that meld body and machine.
Aaron is the director of the Providence VA Medical Center’s Center for Restorative and Regenerative Medicine – a collaborative project of Brown University’s Warren Alpert Medical School, the Providence VA and the Massachusetts Institute of Technology to build better artificial limbs for soldiers returning home from Iraq and for other amputees.
The project, which was launched in late 2004 with a $7.2 million grant from the U.S. Department of Veterans Affairs, recently received a $200,000 grant from the R.I. Science and Technology Advisory Council to support the virtual-reality work.
“We’re trying to develop prosthetics that mimic normal function as closely as possible,” said Aaron, who is also a surgeon at Rhode Island Hospital and The Miriam Hospital and a professor of orthopedics at Brown Medical School.
“How do you hook up the muscles and the nerves so that when you think about moving your arm, the prosthetic actually moves?” Aaron continued. “Right now, all these things are passive – they’re done with rubber bands and strings and things like that, and they don’t really work that well.”
New artificial legs developed in the program will be tested on patients in virtual environments that offer amazingly realistic motion scenarios, Aaron said.
The STAC grant will enable researchers to build a virtual environment in which an amputee wearing a prosthetic leg is tested on a moving hydraulic platform surrounded by three-dimensional video projections.
Aaron said he would assemble a steering committee to oversee the research, and he hopes to have the virtual environment built and a site picked to conduct the research by this summer.
Other prostheses will be put to the test in a virtual environment called “the Cave,” an 8-foot by 10-foot by 10-foot cube owned by Brown. A subject enters the box wearing 3-D glasses that allows him to see himself in a virtual environment created by video images projected on every surface. The experience can even include sound, vibration and smells, creating an amazingly realistic experience, Aaron said.
Each virtual environment will enable researchers to assess how well newly developed prostheses perform in particular, realistic situations, Aaron said.
“Lets’ say he was a roofer who fell off a roof and lost a leg, or something like that – you can create the illusion of height without the person actually being anywhere,” Aaron explained. “You can simulate a rolling or pitching motion, so you can see if a person can stand on a boat, for example – important if you happen to be a sailor or a Marine who was injured.”
Blending body and machine
Ultimately, the Center for Restorative and Regenerative Medicine hopes to develop a new generation of prosthetic limbs that mesh an amputee’s own bone and tissue with high-tech hardware and function as naturally as possible, Aaron said.
Researchers at the center are working to improve a process known as osseointegration, in which titanium prostheses are anchored directly into living bone and skin. In particular, the researchers are trying to grow genetically altered skin cells that form a seal around the titanium rods, overcoming chronic problems of inflammation and infection that occur because the body naturally rejects the rods, preventing healing.
Other research is focused on developing prosthetic joints that respond to an amputee’s nervous system and are powered by microchips that function like muscles. Another team is working to develop a system that sends brain signals directly to prosthetic limbs, using a technology pioneered at Brown to help quadriplegics.
Yet another team is improving a technique that lengthens sheared bones, which can improve the fit of prosthetics for patients who lost a limb just below an elbow, knee, shoulder or hip.
Researchers are also developing ways to regenerate lost or damaged cartilage with help from drugs delivered in biodegradable polymer beads that cause the regeneration of cartilage cells.
“While unfortunately we can’t regrow an entire limb, we can regenerate pieces of tissue which, if they’re put in the right place at the right time, can have a lot of function,” Aaron said.
The war’s medical legacy
The VA funded the center in an effort to prepare for a surge of Iraq war casualties missing one or more limbs entering VA hospitals for long-term rehabilitation, Aaron said.
Because improvements in body armor and front-line emergency medical care have saved the lives of a greater percentage of soldiers wounded in Iraq than in other wars, more soldiers are returning home missing limbs, he said.
Ultimately, the war’s medical legacy could be the development of prostheses that function so naturally that amputees can live much as they did before losing a limb, Aaron said. The center’s work will also yield advances in many other fields, including sports medicine, and the treatment of paralysis and neurodegenerative diseases, he said.
“Right now our goal is to take care of these guys who come back with devastating limb injuries,” Aaron said. “Like in all wars, technologies developed for injured soldiers eventually make their way into civilian life.”
Developing superior prostheses also will contribute to research on the close relationship between emotional injury and physical injury, which could lead to a breakthrough in the treatment of post-traumatic stress disorder, he said.
“Anyone who’s taken care of injured patients knows that depression and anxiety … influence a person’s physical recovery,” Aaron said. “And we hope that the extent of a person’s physical recovery might influence their emotional state.
“As we develop new prostheses, we hope they will have a good effect on the overall person.”
