Improving Paraplegic


Joel Burdick's career path to helping paraplegics began when Reggie Edgerton, a UCLA professor focused on exercise physiology, saw him as a valuable partner. “My ability was in helping algorithms because of my work on the robot side,” says Burdick, a California Institute of Technology professor of mechanical engineering and bioengineering. “Our whole approach for spinal cord injury recovery is not just working on issues with stem or tissue but tapping into circuitry in the lower spinal chord.”

Another important piece of the puzzle was Rob Summers. A paraplegic, he was chosen partly for his athleticism but also for his gift for not getting discouraged. “He would be the least upset and least depressed if it didn’t work,” Burdick says. “There’s risk in doing surgery, and getting nothing out of it can be a psychological blow. He’s an amazing human being in terms of motivation and his willingness to work hard.”

Creating Patterns

For Summers, they had 16 individual electrodes implanted in the epidural. The idea is to create a pattern, sending a stream of pulses to excite the neurons and change the amplitude and pulse width. To give you an idea of the variance between Summers and another anonymous patient they’ve worked with, the ratio voltage level difference was a factor of 10 to 1. “Every spinal cord injury is different. The numbers vary so much from both our animal and human studies,” Burdick says. “The pattern of electrode stimuli has a billion ways it can go.”

Rob Summers in the harness that provides support while he receives electrical stimulation to his spinal cord. Image:



You would think the main goal in the study is to aid walking but Burdick says many paraplegics don’t even have that in their top five. “Many have issues like being on ventilators so walking wouldn’t be as important,” he says. “Higher on the list is bladder function.” The work with Summers had him not needing to use a catheter and gaining much more control of his bowel. In addition, major muscle growth occurred in his legs.

“After a period, he was able to show some voluntary motion,” he says. “He could wiggle his toe while standing or sitting, move his legs up and down. He had to be on a simulator to do that but these were very exciting and motivating.”

Burdick reminds us how much the participants put on the line because of how uncomfortable the process can be. “There can be muscle cramps, it can put pressure on their breathing apparatus,” he says. “Rob when first engaged had a drop in blood pressure.”

Tempered Expectations

What Burdick doesn’t want to do is give false hope. “We’re working with young men ranging from their early 20s to 30s,” he says. “Maybe we get strong results with people in their 40s and 50s but we don’t know. We’re not promising they’ll be walking around everywhere, you can’t do that.”

The human side of the research will understandably come along slower than what they can do in other areas of study due to regulatory issues. “What we’ve learned from both our animal and human studies is that every patient is different,” he says. “But that’s also the opportunity. You never know how someone can surprise you.”

Eric Butterman is an independent writer.

Every spinal cord injury is different. The numbers vary so much from both our animal and human studies. The pattern of electrode stimuli has a billion ways it can go.

Prof. Joel Burdick, Caltech


June 2013

by Eric Butterman,