Thursday, November 4, 2010

Northwestern University Prosthetics-Orthotics Center helps improve assistive walking devices

From Medill Reports. In the picture, Brett Johnson, a Ph.D. student at the Northwestern University Prosthetics-Orthotics Center, models a Lower Limb Paralysis Simulator.

David Seaman, 31, is what some might call a super fan. His left foot is covered with miniature University of Florida gator logos. But it’s not a sock or a tattoo.

The sandy-haired father from Georgia has worn a prosthetic foot since 2004 after deciding to undergo an amputation slightly below the knee on his left leg.

“A lot of people make them look real, but it’s still fake so you might as well have fun with it,” he said with a smile.

Seaman lost half of his foot in a lawn-mowing accident when he was 12. He wore an orthotic, or assistive, device for 13 years before deciding the time and technology were right to make the switch to a prosthetic foot.

The orthosis, or brace, supported his foot but despite multiple surgeries it still caused tissue and muscle breakdown that resulted in blisters and sores.

By electing to have an amputation, Seaman had his foot replaced with a prosthesis, or artificial limb.

“Before I had my amputation I could play basketball but the next two days I would have to be on crutches because of the damage,” he said. After he switched to a prosthesis Seaman could play basketball all day, run, hike and play with his kids outside, he added.

“With the technology today, they’re able to completely replace everything instead of just trying to make something work,” he said.

Struck by the potential of prosthetics and orthotics to improve people’s lives, Seaman decided to become prosthetist and enrolled in Northwestern University’s nine-month certification program, he said.

“It’s a rewarding field both as a wearer and a provider because if it weren’t for prosthetics, I would be really limited in my life,” he said.

The Chicago-based Northwestern University Prosthetics-Orthotics Center works to improve orthotic and prosthetic devices. The center does research and education, according to lab manager Rebecca Stine, who supervises studies in the VA Motion Analysis Research Laboratory.

Stine said the lab, which is funded in part by the Department of Veterans Affairs, typically has 10 to 12 research studies going on at one time and four to five of these are conducted by graduate students completing their research.

Brett Johnson is working toward his Ph.D. in biomedical rehabilitation. His research focuses on seemingly minor adjustments that can have a big impact in the lives of people with lower limb paralysis—particularly those who use a Reciprocating Gait Orthosis, a brace-like assistive device which moves one leg forward when the other is pushed back.

The RGO, as it’s called, helps people with lower paralysis walk upright, Johnson said. But, it’s not a magic bullet and requires a lot of energy to operate.

Users can’t keep their hands free or walk at a functional gait, he said. For these reasons many people with lower limb paralysis prefer to use a wheelchair, Johnson added.

He is examining the motion and energy expenditure required to move in an RGO to determine whether small adjustments—such as adding a spring to help propel the leg forward—will make the device more efficient, requiring less effort from the user, he said.

But improving the RGO isn’t the only challenge. The research methods can be just as tricky.

To study the efficacy of the device Johnson has to monitor people using it. However, it’s often difficult for individuals with lower limb paralysis to find the time or resources to attend the multiple sessions the study requires, he said.

“They already have a lot on their plate,” he said. “They have to give up half a day for a research study, and there’s nothing really sexy about that,” he added, because the study doesn’t offer direct benefits such as new product testing.

Johnson tried another approach—using able-bodied volunteers as models for RGO-assisted walking.

But he couldn’t simply plop fully mobile people in the device and expect them to simulate the movements of a person with lower limb paralysis. “They will feel and use their legs,” Johnson said.

To address the problem, he designed a Lower Limb Paralysis Simulator with the help of the Ed Grahn, the center’s associate director.

The simulator allows fully mobile volunteers to participate in the study by preventing them from using their legs, which are suspended several inches off the floor.

They must learn to walk again—this time using crutches and the metal legs of the simulator.

For this particular study, volunteers were recruited from a network of colleagues and friends and compensated $100 for their participation in the training and data collection sessions, Stine said by e-mail.

Volunteer Kenneth Varner, 30, spent 15 training sessions of 45 minutes each mastering the device.

Varner knew Johnson through their Capoeira class, an African-Brazilian art form that combines martial arts, dance and music, and offered to help him out, he said.

The Chicago resident said the hardest part was learning to walk by twisting his hips instead of moving his feet.

“I was in a full body sweat and traveling nowhere,” he said about using the RGO without assistance for the first time.

To capture Johnson’s movements, researchers attached 43 tiny reflective spherical markers to his major joints and at intervals along the simulator. Cameras mounted around the perimeter of the walking area recorded the position of the markers, Stine said.

Researchers also collected information on Johnson’s movements through force plates in the floor. Stine compared the plates to a fancy bathroom scale and explained they can detect forces in three directions: side to side, front to back, and vertically.

The information was then passed to a computer which translated it into an animated stick figure that mimicked Varner’s movements.

By analyzing the computer-generated model, the pair can determine the range of motion of the joints, the timing of the steps and the forces being exerted through the arms and the simulator, Stine said.

The data are meaningful because they can help determine how much force a user is putting on the crutch and measure step length, Johnson said. This allows him to test whether changes to the device would help users put less weight on their arms or allow them to take bigger steps, he added.

For prosthetic wearers such as Seaman, little changes can make a big difference.

“Over the course of a full day, it means a person can go that much farther, that much faster,” he said.