Triplanar Control for Foot Orthoses
By Marmaduke Loke Do corrective foot orthoses need to incorporate
triplanar control? Marmaduke Loke, Dynamic Bracing Solutions,
Encinitas, California, believes the answer is yes, and discusses
his reasons below:
Although my comments may be controversial to some people, I hope
for professional growth and answers to complex problems. I wish
many objective studies that are evidence-based will provide better
solutions for the people that depend on us.
I believe one has to define whether an accommodative foot
orthosis or a corrective foot orthosis is the goal. An
accommodative foot orthoses may or may not apply limited corrective
forces to the foot. Many are made the exact shape of the present
foot and condition; many apply an elevated longitudinal and or
transverse arch support with different levels of flexibility and
materials.
All casting methods will work well for accommodative foot
orthoses, and given the orthotist's choice, may have similar
results. It is my belief that in this category, Sole Supports
offers a duplicatable method of casting with foam impressions and
accomplishes more correction in its design. The foot orthoses that
are designed for the plantar surface of the foot with corrective
forces can only influence the triplanar control of the foot, not
provide it. Studies would best decide which methods of designing
foot orthoses have more influence on triplanar control with plantar
surface-designed foot orthoses.
Deviations Involve All Three Planes
The foot is made up of 26 bones that interact with each other in
all three dimensions. Each bone can deviate in one, two, or three
planes. Since the joints are triplanar in nature, the deviations
usually are involving all three planes. This complicates the
approach of solving pathomechanical foot conditions. The foot is
the foundation for the human body. The parameters of the mechanical
levers of the foot are small to maintain proper balance. Slight
deviations in the levers of the foot can affect balance and add
stresses to the joints and the structures that hold them. As
deviations increase in each plane, walking efficiency is decreased
and body compensations are increased to maintain balance.
Corrective Orthoses More Complex
Corrective foot orthoses are much more complex and must
incorporate triplanar control. Maintaining biomechanical correction
in the three dimensions demands foot orthoses that apply
three-point pressure systems to address the deviations in each
plane. Casting methods need to provide as many corrective forces as
possible built in to the cast. The casting is done weight bearing
if possible. Stronger casting materials, such as fiberglass casting
tape, must be used. I do believe future CAD/CAM scanning systems
are possible to replace the casting tape. Triplanar-control AFOs
are not as accepted by the patient/client and tend to be utilized
in moderate to severe foot conditions. They demand more room in a
shoe, but not as much as many AFO designs.
Drawbacks to Progress
There are many issues and drawbacks that prevent our profession
from moving to better end result solutions. Proper reimbursement
for the more complex work is at the forefront. The understanding
and learning curve to be successful with triplanar control in all
lower-limb orthoses has proven to be another. I believe that if the
reimbursement issue were solved, more clinicians would do what it
takes to learn it. The time commitment required to provide
triplanar care to each person in need is linked to the
reimbursement issue to justify the time commitment. Evidence-based
outcomes are proving these methods will be the future of lower-limb
bracing.
A Quantifiable Science
Orthotics and prosthetics are based on a mechanical science.
Mechanical science is quantifiable. The mechanical laws for humans
are the same for both orthotics and prosthetics. Prosthetics
controls and aligns in triplanar fashion to achieve its outcome.
Orthotics is more complex mechanically, because of the added bony
segments and all the possible deviations, contractures,
deformities, and neuromuscular issues to be solved in the three
planes. The orthotic dynamic alignment must be thought out
mathematically and done before the fittings.
If the same mechanical laws govern orthotics and prosthetics,
why do we not see free-dorsiflexion prosthetic feet? Why do we not
see three-fourths length prosthetic feet? Why do we not see
floor-reaction prosthetic feet that can be flexed with your hands?
Why do we not see many locked transfemoral prostheses? There are
many other questions like these, and the answers to these questions
are and should be the same as if you replace orthotics for
prosthetics in the questions.
Collecting data that demonstrates the best biomechanical outcome
should be the goal regardless of which casting method is used.
Walking efficiency demands good mechanics. If accommodative devices
do not alter the mechanics for the better, walking efficiency
benefits will not be realized.
We have developed and utilized methods driven by evidence-based
studies for our solutions and hope more and more of our profession
will do the same. Marmaduke Loke may be contacted at AdvProsth@aol.com. 
Table Of Contents - November 2004
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