BALANCING EDUCATION AND RESEARCH IN MOTION ANALYSIS

by Amy Gross McMillan, PhD, PT

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Author in her lab

Department of Physical Therapy, University of Central Arkansas, USA

The University of Central Arkansas (UCA) is located in Conway, Arkansas, USA. Where is Arkansas, you ask? In the south central United States, between Oklahoma, Tennessee, Missouri, and Louisiana. Where is Conway? Half way between the towns of Pickles Gap and Toad Suck (don't ask - that would take an entire article to explain), and about 30 miles north of Little Rock.
University of Central Arkansas is home to one of only two physical therapy (PT) educational programs in the state. Our department currently offers a clinical doctorate in physical therapy (DPT) for those entering the field of PT. For those who are already PTs, we offer three post-professional programs, resulting in either an advanced MS, transitional DPT, or PhD degree. Needless to say, the faculty in this department does much teaching, but must also find time for research.

The Physical Therapy Center

In February 1999, the PT department moved into a new building, which included space for a motion analysis laboratory (finally!). Though the space was there, the lab was not actually equipped until late 2001, when we installed a Vicon 460 series with six M-series cameras, two AMTI force plates and a 16 channel Run Technologies, Inc. fiberoptic EMG system. Having absolutely no technical support (engineering, biomechanics, etc.) on campus or anywhere near us, we were slow in getting things up and running (with the help of lots of support from Vicon and AMTI). The main purpose of the lab is research and education, although there is much interest from PT clinicians in the area who want to bring their patients in for analysis, as there is no clinical gait lab in the state. Unfortunately, at this time we simply don't have the personnel to run a clinical gait lab. We do have several exciting research projects underway in the lab, and these will be briefly described in this article.

Dr Gross McMillan's young daughter taking part in a gait study using the Vicon 460 system

Doctoral Projects.

As our first contingent of PhD students enters the dissertation phase, we have several doctoral projects taking shape in the lab. All PhD students are PTs, and all have clinically related research topics. Stephanie Smith (advised by Reta Zabel, PhD, PT with consultation from Amy Gross McMillan, PhD, PT) has recently completed her data collection for a study comparing the coordination of sit to stand (STS) and sit to walk (STW) in young and elderly adults. Preliminary results appear to confirm her hypotheses that coordination for these two movements differ within each group (young and older adults), and between groups. Ms. Smith hopes to contribute to the body of knowledge about typical coordination for these functional tasks and provide clues as to how PTs can best help adult patients who cannot perform these tasks. Yasser Salem (advised by Dr. Gross McMillan) will soon begin data collection for his project which examines the effects of prolonged standing (in a standing frame) on gait characteristics of children with spastic cerebral palsy. While standers are commonly used in pediatric PT, there is little evidence to support their use, especially with children who are ambulatory.
Margaret McGee (advised by Dr. Gross McMillan) has collected pilot data in the lab for a project to determine the effects of hippotherapy on gait in children with cerebral palsy, Down's syndrome and other movement disorders. Hippotherapy is another therapeutic technique used in pediatric PT treatment, with little objective evidence as to its effects.
The work of Mr. Salem and Ms. McGee will hopefully strengthen the body of knowledge for these therapeutic approaches, leading to more evidence-based practice of PT in pediatrics.

Motion Analysis Lab. Department of Physical Therapy of University of Central Arkansas

Sit to Stand versus Sit to Walk in Children.

While involved in all of the projects mentioned above, Dr. Gross McMillan also has two of her own projects ongoing in the lab. The first is an investigation of STS versus STW in young children - essentially the same protocol but the other end of the lifespan from the adults in Ms. Smith's study mentioned above. Both studies seek to determine if children and adults change their coordination when they get up to walk versus simply standing up. Dr. Gross McMillan is currently collecting kinematic and force data on 2-5 year olds, using the Vicon 460 system synchronized with one AMTI force plate. We are using the full body marker set with the Plug In Gait model, with minimal adaptations for our needs. Because we are still in the data collection phase we have no results to share from this study, except to say conclusively that collecting data from 2, 3, 4, and 5 year olds is a bit more challenging than collecting data from 80 and 90 year olds!

Sit to stand versus sit to walk in young children

Stance Control Orthosis.

Perhaps one of the most exciting things happening in the lab right now is a project that was brought to us by an area orthotist. Gary Horton, of Horton's Orthotics Lab, Inc. in Little Rock, approached us about two years ago (before the lab was even functional) asking us to do some gait studies with patients who were wearing a new orthotic knee joint. Horton's Stance Control Orthosis (SCO) is a knee-ankle-foot-orthosis (KAFO) which incorporates a knee joint designed by Horton's Orthotics and manufactured here in Arkansas. The knee joint locks on weightbearing, providing the wearer with stance phase stability, and unlocks when unweighted, allowing for a free swinging knee during swing phase. Candidates for the brace are typically individuals with post-polio syndrome, spinal cord injury, spina bifida, etc., who have some control of the hip but not of the knee. Until now these individuals have walked with a locked KAFO, using a stiff-legged gait pattern typically using one or more compensations (e.g., circumduction, hip hiking, trunk lateral flexion) to help clear the involved lower extremity during swing. Obstacles such as ramps, stairs and uneven terrain can be quite a challenge when walking with a locked KAFO. By allowing swing phase knee flexion during gait, the SCO should provide a more symmetric gait with fewer compensations, lower energy expenditure, and improved functional mobility. Over time this should decrease wear and tear on joints such as the hips and back, thus decreasing secondary musculoskeletal pain and dysfunction. To test these hypotheses we conducted a pilot study with three subjects: two gentleman with post-polio syndrome who had bilateral involvement but needed an orthosis on the right lower extremity only, and one gentleman with right lower extremity paresis due to an acute nerve root injury. The subjects 1 and 2 with post-polio had used a locked KAFO prior to receiving the SCO, and had used the SCO for two years (Subject 1) and 6 weeks (Subject 2) prior to the study. Subject 3 had refused to wear the locked KAFO made for him after his injury, stating he just couldn't function with that brace. At the time of data collection he had been wearing the SCO for approximately eight months. All three subjects walked without an assistive device except for long distances.
The SCO allows the wearer to lock the knee completely if desired, and in this situation the brace is essentially a locked KAFO. Thus for this study, subjects did not change their orthosis, but simply locked the knee completely during the "locked" trials. During the SCO trials the knee functioned as designed, locking on weightbearing and moving freely during swing. To minimize effects of practice and fatigue, subjects randomly selected which condition they would perform in first.
All data were collected at UCA on the same day. Subjects first completed walking trials (at self-selected speed) in the motion analysis lab. They then completed an obstacle course including several types of obstacles commonly encountered in the environment (e.g., walking over carpet, walking through mulch and sand, stepping over obstacles, walking up/down ramps and stairs). Each subject was timed while they walked through the obstacle course one time in each condition (locked vs SCO). Following the obstacle course the subjects walked for 5 minutes in each condition at a comfortable pace (mean = 1.3 mph), while collaborator Kevin Kendrick, PhD collected heart rate data as an indication of energy expenditure (we do not yet have a metabolic cart at UCA). During data collection subjects were allowed to rest as needed.
Results from these three subjects indicate that all three subjects walked more symmetrically and with fewer compensations in the SCO vs. the locked KAFO. Figures of kinematic data are included as examples of subjects' improved, though not "normal", kinematics. All subjects also had improved spatiotemporal parameters in the SCO condition. Walking speed was faster for all three subjects, with increased cadence and increased stride and step length with the SCO. Subjects 1 and 2 completed the obstacle course faster in the SCO condition, while Subject 3 completed the course more rapidly in the locked condition. Subject 3 may have hurried through the course in order to get finished with the locked trial - he particularly disliked walking with his knee locked, and complained about it constantly. He may also have felt more comfortable on these unfamiliar obstacles when wearing the orthosis in the locked mode.
On the treadmill the subjects increased their heart rate from minute 1 to minute 5, an expected response to exercise. For subjects 1 and 2, this increase in heart rate was less when walking in the SCO vs. the locked orthosis, giving some indication that they walked more efficiently in the SCO condition. Subject 3 actually exhibited a decrease in his heart rate from minute 1 to minute 5 in the SCO condition. Anecdotal reports from all three patients indicate that they greatly prefer the SCO to the locked KAFO, that they feel more comfortable, are more functional, and "walk better" in the SCO.

Gait trial - Stance Control Orthosis

Obstacle course trial stance control orthosis

Treadmill walking trial, stance control orthosis

In summary, all three subjects exhibited improved spatiotemporal gait characteristics and a more symmetric gait pattern when walking with the SCO versus the locked KAFO. Two subjects completed an obstacle course more quickly in the SCO, and all three subjects appeared to walk more efficiently on the treadmill while wearing the SCO. Obviously there are many factors which affect heart rate, and we are currently borrowing a metabolic cart to get some pilot data on difference in energy use in the SCO vs the locked conditions. We are also planning a larger study to more thoroughly assess the effects of this very exciting orthotic advancement, which has the potential to change the lives of many individuals with lower extremity weakness.

Amy Gross McMillan, PhD, PT
Assistant Professor and Director of Research
Department of Physical Therapy
University of Central Arkansas, 312 PT Center
201 Donaghey Avenue, Conway, AR 72035
USA
amymac@mail.uca.edu