Walter Reed Gait Laboratory Puts Amputee Troops Back in Step
By Fred W. Baker III
American Forces Press Service
WASHINGTON, Jun. 20, 2007 As today’s highly active servicemember amputees push their prosthetic devices to the limits, a lab at Walter Reed Army Medical Center here is gathering data that will help designers make the prostheses better, while enabling faster, more efficient recoveries for patients.
Walter Reed Army Medical Center Gait Lab engineer Brian Baum explains how data is gathered and displayed on a computer system. Once data is collected in the computer, it can be compared to that of a non-amputee or even data from the patient’s non-amputee side, allowing better analysis by the rehabilitation team. Defense Dept. photo by Fred W. Baker III
(Click photo for screen-resolution image);high-resolution image available.
At the Gait Lab, patient information is gathered using a high-tech, state-of-the-art computer system that combines reflective markers and cameras to gather data on how amputees move using their prostheses. Using oxygen and heart-rate monitors, the lab also can gather data on how much energy it takes for amputees to walk using prostheses.
“The patients want to put on a prosthesis and be able to feel comfortable walking, transition to running if they need to, and do whatever other activities they want,” said Barri Schnall, the physical therapist at the lab. “At this point, if they want to sprint or they want to run, they need to change out of their walking prosthesis and into their running leg or foot. When we give feedback to the prosthetic companies, they can use the data that we have and the information that we are providing to help achieve the goal of providing a universal type of prosthesis.”
To gather the movement data, reflective markers are placed at key joints on the patient, including the legs, arms and hips. Encircling the room are eight specialized cameras with light-emitting diodes, known as LEDs, that flash at 120 times per second and record in true three-dimensional volume the reflections of the markers in the various positions as the patient walks. The angle and position of every joint -- ankles, hips, arms, pelvis, etc. -- is recorded in real time and expressed on a stick figure rendition of the patient walking.
In addition, two force plates in the floor collect “kinetic” data, recording how hard the patient’s feet land on the floor and how much power is generated.
All measurements are taken in an area that is about 20 feet long, 6 feet wide and 7 feet high.
Once the data is collected in the computer, it can be compared to the motion of a non-amputee, or even data from the patient’s non-amputee side, allowing better analysis by the rehabilitation team.
“We can tell what deviations they have and what compensations they are using to help them walk,” lab engineer Brian Baum said. “We take this information and then sit down with the patient, the prosthetist, the physical therapist and the physicians to give them more objective information on ways they can better treat the patient.”
The team members work together to decide if it is better to change the alignment of the prosthesis, change out a component, make changes to the patient’s physical therapy, or a combination of the approaches.
A digital video camera also records the patient’s movements allowing a third-person view of movement patterns. Schnall said the variety of data and media is looked at individually and collectively to best help the patient.
“Everybody has a different way of learning,” Schnall said. “For some patients, the graphs really hit home. They’ll say, ‘Oh, my physical therapist has been telling me this, but thought I was doing it right.’
“Some people find the video is helpful. They have never seen themselves walk as an amputee other than in the mirror, but that really doesn’t hit home sometimes,” she said.
Patients’ movements are typically recorded and monitored over the course of three or more visits. The first is when the patient starts walking using a prosthesis, the second is when they are walking independently, and then finally just before the patient’s discharge. Patients can be evaluated on an as-needed basis as well, if, for example, they are having pain during walking. Gait analysis can help narrow the source and identify possible solutions.
The system is accurate in identifying where the reflective markers are to within one millimeter. This helps when detecting finer movement trends, Baum said.
“Our eyes can’t pick up that little movement. This system can. “(At first) you can pick up large issues, but when they start walking pretty well, this system really takes over and can look at the finishing touches,” Baum said.
More information is better when it comes down to helping patients learn how to use their prosthesis in active lifestyles, he said.
“We’re just trying to take as much information as possible from everybody, … put it all together, … and then use this information to help treat them and improve the rehabilitation process,” he said.
“This group is really pushing the envelope and really pushing the prosthetic companies to design more robust and more functional prostheses because these guys want to return to duty. They want to return to a very active lifestyle. They want to run marathons. They want to do things that a lot of amputees haven’t been able to do in the past, partly because of the technological limitations,” Baum said.
A new lab being built in the Amputee Care Center at the hospital will offer a much larger space with greater flexibility, allowing more data to be collected from activities such as running. The new lab will include a virtual-reality system with a large free-moving platform that allows patients to work through on-screen simulations such as standing in a boat or riding on a subway. This will help patients learn to develop muscles needed to function in the normal world, Baum said.
Data gathered by the lab allows experts to analyze, develop solutions, improve rehab processes, and improve prosthetic designs and orthopedic interventions, Schnall said. She said the investment in the technology is a small price compared with sacrifices the servicemembers have made and that using this technology to expedite their rehab process is critical.
“We owe them the best technology and the best opportunity to return in a timely fashion to be able to do whatever they want to do and whatever they were able to do (pre-injury),” she said.