Triplanar Control for Foot Orthoses
November 2004 Issue
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.