Motion Analysis Lab: The Science of Movement

Adapted from the Fall 2011 issue of Discovery to Recovery

In the Leon Root, MD, Motion Analysis Lab, physical therapists and biomechanical engineers use high-tech computerized systems to measure patients' movements. "The Motion Analysis Lab brings together physical therapists, engineers, and surgeons to investigate the origin and progression of musculoskeletal disease and to evaluate conservative and surgical treatment options for patients," says Howard Hillstrom, PhD, the Lab's director.

Lisa Cannegieter, PT, DPT, with child in Motion Analysis Lab
Lisa Cannegieter, PT, DPT, a rehabilitation specialist with child in Motion Analysis Lab

All studies conducted in the Motion Analysis Lab are designed to help our patients move more efficiently and comfortably. Research ideas come directly from work with patients, and studies are designed with the goal of improving patient outcomes.

"We try to improve patient care through research," says Lisa Drefus, PT, DPT, a pediatric physical therapist who conducts research in the Lab. "Research in the Lab answers practical clinical questions – what works best for a child."

Watching Kids Move

David Scher, MD, a pediatric orthopedic surgeon and co-medical director of the Motion Analysis Lab, treats many children with cerebral palsy (CP), an umbrella term for a group of non-progressive conditions of the brain that affect movement, posture, and gait. Says Dr. Scher, "I could not accomplish what I do for my patients with CP without the resources of the Motion Analysis Lab."

Children with CP often have interrelated symptoms in many regions of their bodies. Their inefficient gait patterns may be improved through various combinations of surgery and physical therapy. To confirm diagnosis and guide treatment selection, their pre-surgical diagnostic process routinely includes a three hour clinical movement analysis, or "gait analysis," in the Lab.

Example of 3D gait analysisFollowing a detailed physical exam to assess range of motion and muscle strength, therapists attach small reflective markers and apply wires to each relevant muscle (using dynamic electromyography or EMG) to quantify how the child moves in three dimensional (3D) space. The child walks back and forth across the Lab while being videotaped from both the side and front with high definition video cameras and a 3D twelve-camera motion capture system, providing therapists and physicians with data on how the child moves from the side, front, and top-down perspectives.

The gait analysis reveals the child's cadence (rate of steps), velocity (speed), length of step, and swing time (how long the leg is in the air during each step). EMG signals measure when each muscle turns on and off during each phase of walking.

To determine the forces driving their movement, children's kinetics are measured as they walk over specialized scales embedded within the floor, known as "force plates." There is also a matrix of small force sensors called a "plantar pressure measuring device" that can quantify pressures on the sole of a foot as the child walks. Dr. Scher relates this tool to "computerized footprints in the sand."

Research to Improve Mobility

Gait analysis provides valuable data for HSS physicians, engineers, and physical therapists who conduct collaborative gait research in the Lab. This research includes children and adults with CP, arthritis, and many other diseases and injuries that affect movement. Typically, research stems from surgeons' and therapists' clinical observations, and asks some form of this question: Does a surgery or treatment result in a measurable improvement in the patient's ability to move efficiently?

The studies described below analyze movement in children with cerebral palsy, Blount's disease, and typically developing toddlers. In every case, the goal is to help our pediatric patients move with increased ease.

In CP: The Ankle-Knee Connection

Therapists are collaborating with physicians on several studies in the Lab to determine which surgical treatments have good outcomes for children with cerebral palsy. When surgery is performed on ambulatory children with CP, the goal is to optimize their gait by helping them walk more efficiently and comfortably.

In one study, Lisa Drefus is working closely with Dr. Scher and others to determine whether children with hemiplegia (CP on one side of the body) need surgery on both the ankle and the knee, or whether their knee problem could resolve once the ankle and foot are correctly aligned through ankle surgery alone.

Often, children with hemiplegia receive two surgeries, but clinicians question if altered knee patterns are the result of a compensation pattern from the foot position. If this were the case, knee motion would improve without surgery once the foot position was fixed.

Early data show that parameters may exist that will help surgeons identify which patients' knee patterns are compensatory vs. a true impairment.

After Blount's Surgery

Children with Blount's disease typically have abnormal alignment at their knee joint, which results in a bowlegged gait that can be corrected through surgery. After surgery, the children look normal, but it is not immediately clear whether the surgery has had positive functional effects in addition to aesthetic effects.

To discover whether Blount's surgery improves the way children walk, a multidisciplinary team of HSS investigators, led by Roger Widmann, MD, chief of Pediatric Orthopedic Surgery, was formed that includes physicians, engineers, physical therapists, and an exercise physiologist. The team will conduct a series of pre- and post-surgical gait tests, a patient self-assessment questionnaire, and an energy efficiency exam that measures oxygen consumption (VO2 Max testing). Working together, investigators hope to discover if Blount's surgery improves functional ability.

Answering Age-Old Questions

Should typically developing toddlers wear stiff or flexible shoes when learning to walk? Parents and pediatricians have long debated this question, but there were no data on the subject until Dr. Hillstrom, Dr. Scher, and HSS pediatric physical therapists Melanie Buckland, PT, DPT, ATP, and Corinne Slevin, PT, DPT, MS, conducted a Stride Rite-sponsored comparative gait analysis on toddlers in the early stages of walking. Children participated in gait tests that measured stability, walking, and foot pressures while barefoot and in four different shoes that varied in flexibility. Researchers found that early walkers may walk faster, fall less, and exhibit plantar loading similar to being barefoot while wearing a flexible shoe.

Should toddlers with flexible flat feet wear in-shoe orthotics? The Lab is seeking funding to research this widely debated question and to learn if orthotics help children with flexible flat feet move with less pain or discomfort as they grow into adults.

Learn more in HSS's biannual publication, Discovery to Recovery.

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