Cara Lewis, PT, PhD, an assistant professor of physical therapy at the Sargent College of Health & Rehabilitation Sciences at Boston University (BU), Massachusetts, has built a robotic gait-training device to correct what she calls a “hip-battering walk” that could lead to osteoarthritis.
A subject wears the orthosis while walking on a custom treadmill. The graphic representation of a patient’s skeleton is generated by a special computer program in the lab of Cara Lewis (right). Photograph by Vernon Doucette, courtesy of BU.
Lewis’ research involves using an orthosis for motor retraining rather than assistive technology although she says the assistive technology capability is something she envisions for the future. An expert on gait and musculoskeletal causes of hip pain, Lewis believes that the preponderance of young people, especially athletes and runners, being diagnosed with hip pain and fibrocartilage tears, is evidence that hip pain is caused by repetitive stress from an improper gait, which can progress to joint instability, and is not just a sign of wear and tear due to aging, according to an online BU Today article. Thus, Lewis says the target population for her orthosis includes those between the ages of 20 and 40.
“My goal is to intervene early on, so that osteoarthritis doesn’t progress-or doesn’t even develop,” Lewis was quoted as saying.
The orthosis is a pneumatically powered exoskeleton consisting of a brace for the waist and braces for each leg. Subjects wear the orthosis while walking on a custom treadmill with two plates measuring force separately for the left foot and the right foot. Subjects have electrodes placed on their legs to record their muscle activity. Subjects are also covered with reflective markers, which are monitored by several motion-capture cameras.
“The computer system picks up the marker positions and then can re-create a model of the skeleton,” she says. “From that we can tell differences in angles and figure out when we want to apply the robotic force, and how much.”
By pressing a button, Lewis releases air from a large pressurized tank into the orthotic actuators, which encourages gait correction. The subjects can feel what they are supposed to do rather than following verbal instruction.
“Because I have such precise control over the timing and amount of assistance, I can wean people off of the bad [gait] position,” she says. “And then they can walk normally on the street.”
Currently, the Sargent College lab is doing research, not intervention.
