Comparing Silicone Dynamic Orthotics with Traditional Orthotics by Computer
Analysis
Introduction
Traditional orthotics
have been around for over 60 years and they have been based on theories
about the foot and its mechanical function (aka "biomechanics")
for the last 100 years or so. Traditional orthotics control foot function
by holding the heel (rearfoot)
in a fixed position as it impacts with the ground.
The Silicone Dynamic
Orthotic (SDO) is an encased fluid orthotic and is based on the principles
of "fluid mechanics". These principles of physics go back centuries,
probably beginning with Archimedes. Today these principles are an axiom
of physics: "fluid moves in response to pressure to the area of least resistance
and greatest need". With a fluid orthotic, the high viscosity silicone
starts to slow down the motion of pronation
as soon as the heel strikes the ground. The fluid then moves forward,
filling the arch. As the fluid redistributes under the oncoming pressure,
it limits the excess arch movement. The fluid serves to cushion the foot
at the end of its range of motion and yet allows the foot to function in
its most natural way. By limiting the excess motion, the orthotic
minimizes overpronation.
At the same time, it biomechanically corrects metatarsal
pushoff (stepping off the ball of the foot). The pressure of the
metatarsals pushes a slight amount of silicone back toward the heel, preparing
the fluid for the next heel strike. Unlike stiffer traditional supports
which confine the heel and abruptly stop arch motion, SDO's "stabilize"
the heel by controlling arch movement.
We have a computerized system which allows us to compare the efficacy
of different orthotics. The system records the distribution of pressure
underneath the foot as a patient walks across our pressure-sensitive mat. The results we will review below are
from real people. It is the intention to compare the efficacy between
barefoot, traditional orthotics, and the SDO.
How to read and understand the "Tekscan" pressure measurement system
The color scale on the left of each picture represents the amount of pressure
seen on the bottom of the foot (aka "ground
reactive force"-GRF). Low GRF is in blue, moving toward red,
which indicates a higher GRF. This pressure is an indication of balance
and alignment in the foot . The higher the pressure, the greater
the degree of pronation and misalignment which has direct relationship
of balance, alignment and efficiency throughout the musculo-skeletal system.
The picture you see is an average of pressures accumulated through the
gait cycle (heel contact through toe-off). What is important is the pressure
under the ball of the foot which spreads and balances to the ground during
"pronation".
The more the ball of the foot pronates the more it allows the back of the
foot to pronate also. As the rearfoot further pronates the front
of the foot also has more room to pronate further. This motion goes back
and forth as far and as fast as it can. This then is "maximum"
pronation with each footstep and forms the balancing act of our foot and
how it relates to our body alignment.
Disclosure
In the following sequences of comparisons between the distribution of forces
and pressures in the foot with traditional orthotics and with the SDO,
understand that the individuals tested have been using their orthotics
with success (of varying degrees) in relation to their symptoms. Therefore,
we are not trying to say that traditional orthotics are bad, we are only
showing the difference in the efficiency of the way the two orthotics
work.
Tests
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