Orthotics Are Not Biomechanics

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Kevin A. Kirby, DPM

Over the past quarter century of lecturing at national and international seminars on the topics of foot and lower extremity biomechanics, foot orthotic therapy and sports injuries, I have had the pleasure to meet many podiatrists who share my interest in these subjects. We understand that since biomechanics is the science that examines the forces acting upon and within a biological structure and the effects produced by such forces, we will be able to more effectively help our patients who suffer from pain and dysfunction within their feet and lower extremities if we gain a better comprehension of foot biomechanics.

   However, there is also a large number of podiatrists who do not believe that the science of biomechanics of the foot and lower extremity should be one of their educational priorities. They seem to think that “foot surgery” and “biomechanics” are mutually exclusive of each other. In fact, many of these podiatrists seem to think that “foot orthotics” and “biomechanics” mean the same thing.

   An amusing example of how some podiatrists seem to think that “biomechanics” and “orthotics” are synonymous occurred last year while I was lecturing at a seminar in Florida. My wife, a retired elementary school teacher, was along with me at the seminar and overheard an interesting conversation outside the lecture hall. One podiatrist asked another, “Do you do biomechanics in your practice?” “No, I don’t see any need for it. I don’t do biomechanics,” replied the other podiatrist.

   After my lecture was finished, my wife couldn’t wait to ask the question, “How does a podiatrist not do biomechanics? I overheard two podiatrists talking outside the lecture hall and one of them said that he didn’t do biomechanics. How does someone who treats something as mechanical as the foot every day not do biomechanics?”

   I married a very smart woman.

   For years, I have heard podiatrists make these same types of comments. “I focus more on surgery in my practice and don’t do biomechanics.” Since when did the act of making or adjusting foot orthotics for patients become the only time a podiatrist “did biomechanics”?

   When a podiatric surgeon surgically shifts the first metatarsal head laterally during a bunionectomy procedure to realign the transverse plane position of the first metatarsophalangeal joint, isn’t the podiatrist altering the forces acting within the foot by doing this procedure and, by definition, “doing biomechanics”? When a podiatric surgeon performs a posterior calcaneal medial displacement osteotomy for posterior tibial tendon dysfunction that medially shifts the location of ground reaction force and medially shifts the location of Achilles tendon tensile force relative to the subtalar joint axis, isn’t the podiatric surgeon, by definition, “doing biomechanics”?

   “Doing biomechanics” doesn’t just mean making and adjusting foot orthotics for patients. Whether all podiatrists realize it or not, understanding the science of biomechanics — or how forces acting on and within the foot mechanically affect the foot to create pain and deformity — is how podiatrists make their living every day of practice. Whether they never measure an angle on a foot, never put plaster on a foot, never grind an orthotic and/or never glue a pad on an orthotic, podiatrists still “do biomechanics” every day that they treat patients.

   The foot, the mechanical organ that lives at the end of the human leg and that podiatrists have been trained and licensed to treat, is regularly subjected to more external force than any other part of the human body. Every time podiatrists place a pad inside a shoe, trim an offending toenail, shave down a corn, debride and offload a diabetic ulcer, do an osteotomy, transect a ligament, lengthen or transfer a tendon, and/or do an arthrodesis, they are “doing biomechanics.”

   Foot surgery alters the internal structure of the foot in order to decrease the pathological loading forces acting on injured structures of the foot and lower extremity. Foot orthotics alter the locations, magnitudes and temporal patterns of external forces acting on the plantar foot to decrease the pathological loading forces acting on injured structures of the foot and lower extremity. Foot surgery and foot orthotics are both biomechanical forms of treatment, one internal, the other external.

   Yes, performing foot and ankle surgery, wound care, routine care, and padding and strapping are all biomechanical forms of treatment. However, no matter how you look at it, orthotics aren’t biomechanics. Until podiatrists fully comprehend this important and critical concept, our profession will never be able to mature into the scientifically-based medical profession that our patients all deserve.

   Dr. Kirby is an Adjunct Associate Professor within the Department of Applied Biomechanics at the California School of Podiatric Medicine at Samuel Merritt University in Oakland, Calif. He is in private practice in Sacramento, Calif.

   Dr. McCord retired in December 2008 from practice at the Centralia Medical Center in Centralia, Wash.

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