Comparing Lessons On Biomechanics And The Realities Of Clinical Experience

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The podiatry profession places too much emphasis on the subtalar and midtarsal joints, according to Christopher Nester, BSc, PhD. (Photo courtesy of Arnold Ross, DPM)
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Author(s): 
Guest Clinical Editor: Bruce Williams, DPM

Q: What clinical revelations go completely against the grain of what you were taught about foot biomechanics or the use of foot orthoses in podiatry school?
A:
In school, Dr. Williams says he learned of the existence of forefoot varus and its role as a primary cause of excessive foot pronation. However, he says recent research has actually shown that forefoot varus rarely occurs and one can usually cast it out of the orthotic.
As far as rearfoot varus goes, Dr. Williams learned rearfoot varus posting will prevent pronation. In contrast, he says research is increasingly showing conclusive results that the rearfoot continues to pronate to the end range of motion despite the use of small to large rearfoot varus posted devices. He argues that the profession needs to “look elsewhere for the real cause of pronation related problems,” including the blockage of sagittal plane pivots in the forefoot and ankle.
Dr. Williams also disputes the conventional wisdom that only accommodative soft devices can effectively treat diabetic plantar ulcerations. If it were true, he says every podiatrist would have a perfect record of treating plantar foot ulcers. Dr. Williams says DPMs must realize that all diabetic patients have poor and asymmetrical foot function. If practitioners do not address this, especially in patients with diabetes, he argues that they will be fighting a “losing battle” to offload the ulcer and will not improve the overall foot function.
In his clinical experience, Dr. Nester has learned “there is no such thing as podiatric biomechanics” and that schools should only teach Newton’s paradigm of foot function.
“We do not need multiple ill-considered attempts to explain what is seen clinically via ‘pseudomechanics.’ These ‘stories’ to explain what is seen clinically inevitably conflict with each other and fail to fully explain the foot,” argues Dr. Nester. “Our podiatry students just need to learn biomechanical principles and understand what happens when forces are applied to the structures of the foot.”
Dr. Nester also believes podiatrists do not need to overcomplicate the prescription of orthotics. If practitioners understand the biomechanics, he believes they can decide what force they should apply to the patient’s foot and accordingly decide which components to add to an orthotic device. Given all the variables involved, Dr. Nester says it is too easy to turn orthosis prescription into an unnecessarily complex science.
Podiatry school taught Dr. Nester that the foot controls the lower limb but he has found in his clinical experience that the rest of the limb controls the foot. Although the foot can influence the capabilities of the proximal limb structures, he believes that the foot is poorly positioned mechanically to be the primary influence over the knee and hip. As Dr. Nester sees it, the profession ascribes too much importance to the foot in lower limb mechanics. Rather, Dr. Nester believes the foot “is just one of a number of interdependent structures we need to consider.”
In his post-education clinical experience, Dr. Payne has learned that motion and foot position are not necessarily associated with pathology and that changes in foot posture and motion patterns with an orthotic are not necessarily associated with a positive outcome. In addition, he has discovered that the subtalar joint neutral position is not as important as one assumed for foot orthoses outcomes.

Q: What research are you pursuing now and how may it ultimately effect how DPMs look at podiatric biomechanics and the use of foot orthoses to treat foot pain?
A:
Dr. Nester is studying how the bones of the midfoot and forefoot move during stance, and how podiatrists can best model this in experiments and in terms of clinical problems. He is also looking into the way the foot interacts with other joints and the importance of muscles in foot function.
Dr. Payne is researching what parameters orthotics change and which parameters are associated with positive outcomes. He is also studying the effects of orthotics on the windlass mechanism.
Although his private practice keeps him too busy to pursue research, Dr. Williams says he would like to work with “like-minded practitioners” and conduct simple studies that correlate his views of the function of the foot.

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