Scripted by Katherine Dempsey, animated by Next Media Animation
By Katherine Dempsey
The way you walk or run can help health care professionals learn more about how to improve different kinds of mobility treatment and gauge how well treatment works. Doctors, therapists and researchers use three-dimensional gait analysis to see how to best help people with arthritis, cerebral palsy and other conditions in addition to gathering data that can help prevent and treat injury.
Rush University Medical Center’s Human Motion Analysis Laboratory uses gait analysis to capture motion and pick up on forces exerted by the way a person walks. Orthopedic surgeon Shane Nho of Midwest Orthopedics at Rush is using the method as part of a study to demonstrate the effectiveness of a surgical procedure called hip arthroscopy in correcting femoral acetabular impingement, or FAI, by proving that people move better after the surgery. The condition typically results from deformities (bumps) on the femur and hip socket, Nho said. It can cause pain and inhibits normal hip movement, and doctors believe it can lead to hip arthritis. Hip arthroscopy smooths out the bone, eliminating the deformities, he noted.
Someone with femoral acetabular impingement (FAI) walking, as depicted by motion-capture technology used in Rush University Medical Center’s Human Motion Analysis Laboratory. Courtesy of Robert Trombley, Human Motion Analysis Laboratory
People in Nho’s study can opt to participate in a motion analysis that involves walking and squatting in the Rush lab while wearing reflective markers (small balls) placed on the body. They’re tested before and after surgery, and their movements are compared to the movements of unaffected people to see how significant the difference is, he said. Plus, the study stacks up the way a patient moves before surgery against the way he or she moves after the surgery. The study also collects other data, like range of motion and strength. Data collection is on-going, but Nho says he thinks the gait analysis would supply extra information to confirm that when hip arthroscopy is used to correct FAI, the surgery helps the hip do its job better.
“I think it would prove what we already think we know,” Nho said.
Dr. Najia Shakoor, a rheumatologist at Rush University Medical Center, has used gait analysis to study people with knee osteoarthritis for the last several years. She examines the knee adduction moment, or the amount of force that people apply to the knee’s inner side when they walk. Calculating the knee adduction moment is a way to measure how much load (force) the person is exerting on the knee and it measures whether the person is putting too much force on the inner knee.
Other gait analysis research has demonstrated that osteoarthritis severity, likelihood of pain, and faster progression is linked to more extreme knee adduction moment, she said. Based on findings that barefoot walking and walking in minimalistic shoes were both associated with a decreased knee adduction moment, Shakoor and co-investigators have tested out a “mobility shoe” – a minimalistic, flexible, lightweight shoe – that imitates what it’s like to walk in bare feet. They’ve found that these shoes decrease loading at the inner side of the knee.
Shakoor’s current study investigates how the mobility shoes might be causing changes in foot motion that in turn might be lessening knee load at the inner side of the knee. Along with motion captured via a typical gait analysis with reflective markers on the body, the gait analysis also examines the amount of foot pronation by using additional markers on the feet. Plus, it assesses the foot pressure distribution via a pressure mat. The foot pressure and foot pronation will be compared to the amount of force on the inside of the knee to look for a relationship between pronation and pressure and loading over time, she said. Study participants – who wear the mobility shoes – are tested three times over a period of six months.
If her team can determine whether there’s a link between changes in foot motion and decreased loading over time, Shakoor said, that knowledge can help doctors better treat people dealing with knee osteoarthritis so those people can decrease loading.
Researchers can use gait analysis to look for connections between gait and injury. Karrie Hamstra-Wright, a clinical associate professor of kinesiology and nutrition at the University of Illinois at Chicago, uses three-dimensional gait analysis system in an ongoing study with members of UIC’s cross-country team. She’s looking to help those runners get more information about gait patterns that might be leading to overuse injury. and how injury might affect their gait. Participants get a pre-season gait analysis, and later Hamstra-Wright takes the group of team members who were injured and compares it against the non-injured runner group, searching for contrasts in gait between the groups.
She pointed out that she hasn’t yet noticed any specific gait pattern being a risk factor for overuse injury among these runners, with the caveat that the sample size is still not quite big enough.
“We definitely have quite a bit of time to go before I would expect to see any significant changes,” said Hamstra-Wright, who is also a 2:52 marathoner.
The system Hamstra-Wright and Jones use – called 3D GAIT, another gait analysis system – involves walking or running on a treadmill while cameras capture motion by emitting near-infrared light to reflective markers located on the pelvis, thighs, calves and feet, said Reed Ferber, director of the Running Injury Clinic in Calgary, Canada. Ferber came up with the idea for the system, and the Running Injury Clinic put it into practice in 2008. Out of 39 physical therapy and chiropractic clinics and 14 research sites across the globe using 3D GAIT, UIC is the only place in Illinois using it.
Michael Jones, a clinical assistant professor at UIC, is using 3D GAIT to help in understanding more about why iliotibial band syndrome occurs among runners. ITBS, an overuse injury, results from repetitive stress between the side of the femur and the IT band, which extends down the outside of the thigh and affixes itself on the knee. It’s the second most common reason for side knee pain among runners. Jones’s study combines running data from the gait analysis with measurements of sensation and hip and back strength to try to figure out how those three variables link to ITBS. He wants to gain insight into the influences at play to eventually help improve treatment for people with the injury.
“As a physical therapist, I treat people with IT band syndrome,” Jones said. “I’d like to know more about why it happens.”
3D GAIT isn’t just for runners, Ferber noted; it’s also been used to evaluate walkers, people with knee osteoarthritis and athletes who compete recreationally.
3D GAIT and Rush’s motion analysis lab both use reflective markers (little balls) that are placed on the body. Multiple cameras emit near-infrared light, which bounces off of the markers and back into the lenses of the cameras, letting them determine very precisely where in space the markers are located. Both systems can capture movement with millimeter accuracy. The three-dimensional nature allows for gathering images from multiple planes of motion, unlike a one-camera setup. Rush has five force plates that measure the ground reaction force while the person is walking, and a computer calculates rotational forces (torque) acting on body parts. That, in turn, makes it possible for researchers to see atypical forces that are acting on joints of the body. 3D GAIT can get information from 40 to 50 footfalls within about 30 seconds and can break down the data in about 10 seconds, pointed out Ferber, who is also an associate professor of kinesiology at the University of Calgary.
An undergraduate at the University of Illinois at Chicago helps clinical associate professor Karrie Hamstra-Wright with a study using gait analysis to examine the interplay between gait and injury among UIC cross-country runners. Here, he demonstrates pronation, one of 17 biomechanical variables observed with a gait analysis system.
Data from the system goes into a database containing information from more than 3,000 physically active people who have undergone running or walking analyses. It measures 17 biomechanical gait variables such as “peak pronation,” “peak knee rotation” and “peak pelvic drop.” When a person gets a gait analysis using 3D GAIT, a normal range is determined for each of the 17 variables relative to people in the database of the same gender. The person being analyzed can see if they fall outside of that range. That lets doctors and others use scientific data to note how someone’s gait patterns are different than average, Ferber said. Plus, when they make calls about treatment, they can ground those calls in hard facts, he said.
The aim, as Ferber notes, is to “predict injury” for runners and ultimately people who do general physical activity. When people like doctors and physical therapists use 3D GAIT, they can help identify gait problems that might end up in injury and pinpoint the kind of injury that a person might get, he said. Plus, the system can quite accurately figure out appropriate therapy for an injury.
Gait analysis can help kids, too. At the Motion Analysis Laboratory at Shriners Hospitals for Children – Chicago, gait analysis is applied to a variety of clinical purposes. Orthopedic surgeon Peter Smith frequently uses it to help figure out suitable treatment for children with cerebral palsy who have complicated manners of walking.
Jaryn Smith, 19 – one of Smith’s patients but no relation to him – has cerebral palsy that affects both of her legs. She’s been coming to Shriners since 2000 and has undergone many gait analyses, including before and after her surgeries there. She said she thinks gait analysis has helped people at the hospital to know what requires improvement.
“They’re helping me walk better,” she said, referring to hospital staff.
At the Motion Analysis Laboratory, children wearing reflective markers (small Styrofoam balls covered in tape) walk back and forth on a walkway. The cameras emit near-infrared light, which bounces off of the markers and back into the lenses of the camera, recording the person’s motion. Force plates measure how much force the person’s body exerts on the ground as he or she walks, and that lets computer software calculate rotational forces exerted on the joints. Children also wear wireless electrodes on their skin on distinct muscles, which picks up on when those particular muscles fire.
Software can figure out attributes of the child’s movement, such as joint angles and positions, how quickly the joints move, length of the space between his or her steps, and forces that act on the joints while he or she moves, Graf noted. Doctors and physical therapists and others at Chicago Shriners Hospital can compile all the data gathered to prescribe treatment and also see how a patient changes throughout time. They look at whether the person is using certain muscles improperly (via the electrode data), whether abnormal forces are acting on the joints (via the force plate data) and pressure distribution on the bottom of the foot (via pressure mat data).
Data collection for research also takes place at the motion analysis lab at Chicago Shriners Hospital. Joseph Krzak, senior motion analysis laboratory physical therapist, conducted research for his Ph.D. in kinesiology, nutrition, and rehabilitation at UIC, studying children with hemiplegic cerebral palsy (which directly impacts just one side of the body) with equinovarus foot and ankle deformity. He and co-investigators conducted the study throughout the last five years, and it’s currently in press. They collected their data at Chicago Shriners Hospital.
Equinovarus foot and ankle deformity results from cerebral palsy. When children are affected by the deformity, they point one of their feet inward and walk on the toes of that foot. This can result in pain and greater risk of trips and falls, Krzak said. Children must also use extra energy to get from place to place; what’s more, it can cause skin issues and it might be hard for kids to locate shoes that fit them.
Depending on the child, equinovarus deformity can affect different foot segments in different ways. Krzak wanted to describe how various groupings of foot bones are affected in order to distinguish distinct foot types that children with this particular deformity have. That insight could help doctors, physical therapists and orthotists (who make braces and splints) better decide what kinds of treatments would best help individual patients. Analogous treatment would help people who display the deformity in analogous ways, he said.
Krzak and the other researchers used a biomechanical model – the Milwaukee Foot Model – to investigate how different parts of a kid’s feet moved, how much those foot parts were moving abnormally when compared with “typically-developing” children, and the directions of abnormal foot movements. The Milwaukee Foot Model allows for more detailed motion-tracking of small bones in the foot. It’s a “specialized” kind of gait analysis, said Gerald Harris, the motion analysis lab technical director, in an email.
“We can identify which particular parts of the foot are moving differently than a group of typically-developing children that don’t have cerebral palsy,” Krzak said.
Krzak’s team found four kinds of equinovarus, grounded in which foot segments were moving irregularly and the
direction of those movements. More knowledge about how separate foot parts are moving unlike the foot parts of typically-developing kids can lead to more insight about distinct kinds of equinovarus, Krzak said. In turn, doctors, physical therapists, and orthotists can use that knowledge to better determine proper treatment for a child with equinovarus deformity and allow for better post-treatment results.
Gait analysis systems add up to the search for better treatment, diagnosis and prevention for problems that impact the legs and feet of millions of people.