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Making the Most of Movement: Gait Analysis and Bracing
By Sherry Metzger Gait analysis, an in-depth observation of how a
person walks or performs certain functions, is an important
therapist tool in bracing the orthotic or prosthetic patient.
Historical work on defining the gait cycle is useful in assessing
motion and determining normal versus pathological gait. Today gait
is analyzed using a combination of high-tech equipment and trained
therapists' observations.
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From left: Sarah Parsons, MSPO, CO; Chris Hovorka, MS, CPO; an engineering student at Georgia Tech; and David Fritz, MSPO. Photograph courtesy of Georgia Tech |
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"Learning the gait cycle is fundamental," explains
Chris Hovorka, MS, CPO, director of the Master of Science in
Prosthetics and Orthotics (MSPO) degree program at the Georgia
Institute of Technology (Georgia Tech), Atlanta. "Understanding how
a person moves helps us solve problems. We understand the
parameters of normal versus abnormal patterns of movement and use
the principles of biomechanics to help individuals use less energy
for movement or develop better strategies for movement."
The Georgia Tech MSPO is currently the only entry-level master
of science program in prosthetics and orthotics available in the
world. Hovorka, a clinical practitioner, says students in the
program learn "translational research" or how to connect laboratory
research to clinical practice. "Students study body movement
(kinesiology and clinical gait analysis) for at least a year," he
says. "Then they apply that to a person who has lost a limb or has
neuromuscular/skeletal deficits."
The Gait Cycle
The gait cycle describes the pattern of walking, beginning when
one foot contacts the ground and ending when the same foot contacts
the ground again. The gait cycle comprises two main phasesstance
and swingwhich account for approximately 60 percent and 40 percent
of the cycle, respectively. While the events that occur during
these two phases are not universally agreed upon, for the purposes
of this article, those events are defined as follows:
The stance phase is divided into loading
response, midstance, terminal stance, and pre-swing. Loading
response, when the foot makes initial contact with the ground, is
labeled pathological when the entire foot or toes hit the ground
first rather than the heel. Midstance begins with the contralateral
toe-off and ends with the center of gravity over the supporting
foot. Terminal stance begins here and ends with the heel of the
contralateral foot leaving the ground. Finally, pre-swing
corresponds to the cycle's second period of double limb support,
contralateral initial contact, and toe-off.
The swing phase consists of initial swing,
mid-swing, and terminal swing. Initial swing is the period from
toe-off to maximum knee flexion. Mid-swing is from maximum knee
flexion until the tibia is perpendicular to the ground, and
terminal swing begins there and ends on initial contact.
During the normal gait cycle, the weight-loading period of one
leg corresponds with weight-unloading of the trailing foot. In
other words, while one foot is accepting the weight of the body,
the other foot is rolling off the ground. Throughout the cycle, arm
swing corresponds to the contralateral leg to maintain balance.
Gait Analysis
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Georgia Tech MSPO students learn to use some of the latest gait analysis systems. |
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Gait analysis involves an understanding of the
gait cycle as well as the measurement of kinematics and kinetics.
Kinematics is the science of motion and provides a description of
the extent, speed, and direction of the movements of joints or body
segments. Kinetics refers to the forces that produce movement such
as gravity, inertia, and ground reaction (external forces) and
joint motion and muscle activity (internal forces).
Observational gait analysis is the primary clinical tool for
therapists and consists of using checklists to note gait deviations
as either present or absent. Though useful, these types of analyses
are often unreliable. However, orthotists and prosthetists can use
a variety of portable and affordable high-tech devices to make
kinematic and kinetic measurements. For example, the GAITRite
system, manufactured by CIR Systems Inc., Havertown, Pennsylvania,
is a portable walkway that can track, report, and graph
measurements such as cadence, velocity, and stride length. "This is
a 'clinician-friendly' tool," says Hovorka. "It has its
limitations, but it does provide some quantification that a
therapist can use."
A more sophisticated method of analysis, called Dartfish, is
used to optimize athlete performance and aide the judgment of
certain subjective events, such as diving, where detailed
information about body segment movement is needed. "When used
together, the loading information that GAITRite can provide along
with the angle measurements Dartfish makes, result in a better
understanding of movement," Hovorka comments. "However, the gold
standard, which is accepted to be the most reliable, is the Gait
Analysis Laboratory (GAL)."
GAL consists of force detection built into the flooring in a
walkway and infrared cameras that detect motion of individual body
segments via specialized markers strategically placed on the
patient. "[These labs] provide detailed information about the way a
person moves," says Hovorka. "However, they are expensive, not
portable, and require highly trained individuals to operate the
equipment, or biomechanists." Biomechanists have extensive
knowledge about biological movements; often their education
includes a master's degree or doctorate. In addition to digital
optical camera and force-plate analysis, GALs may include
electromyography (EMG), a study of muscle activity. Though muscle
activity varies between individuals and depends on external
variables, normal muscle activity during each phase of the gait
cycle has been researched and recorded. High-tech devices provide
values that are then interpreted by trained gait analysis
specialists who translate goniometric, metabolic, and kinetic
measurements into appropriate patient care.
"[In using these tools] our main goal is to problem-solve," says
Hovorka. "Whether it's teaching a child to stand for the first time
using an orthosis or helping someone to move using less energy,
getting a better understanding of how the person moves can help us
solve those problems."
When normal gait cycle biomechanics are understood and tools
have been used to analyze a patient's movement and compare it to
"normal," then the orthotist and prosthetist can develop devices to
help the patient move more naturally while using less energy.
Making Movement More Efficient
"Movement science involves understanding a movement problem,
developing a solution, and helping a person create a new movement
strategy," summarizes Hovorka. "We design bracing to position the
joints in a different alignment. The more joints an orthotic or
prosthetic device crosses, the greater the limitation of motion
will be at those joints and the more energy a person will have to
use to move. There's a fine line for how much bracing to use."
Because pathological gait results in excessive energy
expenditure, many disabled children abandon walking from the
beginning, and adults dealing with new circumstances, such as
amputation, find basic movements exhausting. The most common gait
disturbances seen in amputees involve abnormal load acceptance,
load relief, and swing phase clearance, though the level of
amputation determines the extent. Pathological gait is also found
in spinal and neuromuscular impaired patients.
An energy efficient gait pattern is one that moves a person's
center of gravity (COG) forward with minimal vertical and lateral
displacement. Pelvic rotation, knee-ankle-foot interactions,
lateral pelvic drop, and knee flexion affect vertical displacement.
Lateral displacement of COG is limited by the genu valgus, a
structural feature of the knee. Appropriate bracing across the genu
valgus, hip, and ankle can lesson energy demands by addressing COG
displacements.
Orthotic Management
An orthosis can support a structural deformity of the ankle
and/or foot to help alleviate predictable gait deviations. The five
most common foot pathologies are rearfoot varus, forefoot varus,
equinus, plantarflexed first ray, and forefoot valgus and rearfoot
valgus. Each involves some degree of inversion or eversion of the
foot or ankle. Orthotic management of these conditions includes
supporting the foot with a medial heel, lateral forefoot, or medial
forefoot wedge. The three primary types of orthoticsrigid,
semi-rigid, and softprovide the appropriate bracing to influence
function, dynamic balancing, and shock absorption, while minimizing
pressure sores.
Because an AFO can substitute for weak dorsiflexor muscles
during swing phase and weak plantarflexors during stance phase,
they are often recommended for patients with gait deviations from
muscle weakness. By supporting the forefoot, an AFO can prevent the
common problem of foot drop in swing phase. The orthotist aligns
the AFO in dorsiflexion or plantarflexion depending on the specific
gait displacement. Because proper foot and ankle biomechanics
contribute to normal gait, creating proper alignment between the
foot and the ground using foot orthoses and controlling the motion
of the ankle, rearfoot, and forefoot reduces the risk for abnormal
mechanical strain on the knees, hips, and spine.
Some types of AFOs and other bracing store and release energy
when needed for normal gait, preventing premature foot drop as well
as providing stability at midstance and propulsion during toe-off.
The energy released by the orthosis at terminal stance propels the
leg up and forward, and the swinging limb helps the body, or center
of gravity, to move forward. The appropriate ratio of stance and
swing phase (60:40) allows the energy from one step to transfer to
the next so the patient experiences less fatigue. In addition, in
the absence of normal muscle function, the orthosis counteracts the
forces tending to buckle the limb in stance. Therefore, an orthotic
device is judged on how well it can control limb movement during
the swing phase and load bearing during stance phase.
By correcting and stabilizing the deviations in joint alignment,
proper bracing can help patients establish a more stable and energy
efficient gait. KAFOs and HKAFOs improve gait just as AFOs do, by
providing joint stability and alignment over more joints. Because
more energy is expended when a brace encompasses more joints, the
reciprocating gait orthosis (RGO) couples the left and right
orthoses so that hip extension in either one tends to force the
other hip joint into flexion, providing coordinated motion between
the legs and less energy expenditure.
"Using the normal gait cycle as the benchmark, we can breakdown
a person's movements into measurements," concludes Hovorka. "We can
take those measurements and offer treatments that will improve the
person's movement strategy; making movement [more natural] and less
fatiguing."
Sherry Metzger, MS, is a freelance writer with degrees in
anatomy and neurobiology. She is based in Westminster, Colorado,
and can be reached at sherry@opedge.com . 
Table Of Contents - May 2007
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