When I was in training, there was a significant separation between biomechanics and surgery of the foot and ankle. In fact, in my school, we had a department of biomechanics and a department of surgery. I think most podiatrists consider these to be somewhat separate fields, with biomechanics equating to “orthotic therapy”, and “surgery” covering the invasive treatments.

This thought process has permeated even the very semantics of how we talk about what we do as podiatrists. Think of the terms conservative and surgical. These terms are commonly used by national, regional, and local speakers, as well as individuals in practice, to denote two general options of treatment, as in, “Let’s treat this conservatively with orthotics, and if those fail, we’ll do surgery.”

First, these terms are highly inaccurate. If I have a patient with an abscess in the foot, the more “conservative” option is to perform an incision and drainage. I think it’s fair to say that giving intravenous antibiotics and watching to see how the patient does would be the more radical and less conservative option. Call them what they are: nonsurgical and surgical treatment.

This, though, is more than simply a semantic debate, and the separation between biomechanics and surgery has been a detrimental one that has limited both our understanding and utilization of the treatment options available to us. It’s time to unify biomechanics and surgery.

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“The separation between biomechanics and surgery has been a detrimental one that has limited both our understanding and utilization of the treatment options available to us.”

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What if I told you that many of the treatment methods we utilize during foot orthosis therapy do basically the same thing as certain surgical procedures? This is true as long as you think in a certain way about how we treat the lower extremity. Let’s talk about a slightly different treatment paradigm that I will argue is more effective than past methods.

In the past, the primary mantra was, “Make the foot straight.” Flatfoot pathology was treated with foot orthoses, the goal of which was to keep the subtalar joint closer to an ideal neutral position and to allow the foot to compensate for other positional issues. Subtalar pronation is a compensation for tibial varum, for example. Similarly, surgical treatment was focused on correcting radiographic angles, such as aligning the bisection of the talus and first metatarsal (Meary’s angle) and correcting the dominant plane of deformity (planal dominance) in, for example, flatfoot disorders. These purely positional approaches took the unstated view that a straight foot was a healthy foot.

If the point was to make a foot straight, then why not just fuse joints to force a foot into that ideal straight position? We have since learned that a perfect arch and completely straight foot are not the way average humans function. It’s known, for example, that a majority of asymptomatic patients function with an inverted forefoot to rearfoot relationship.¹

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“We have learned that a perfect arch and completely straight foot are not the way average humans function.”

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Kinetic (Force-Driven), Not Kinematic (Positional)

Modern biomechanical and, in fact, surgical research, appear to be moving away from this kinematic, or positional, approach, and toward a kinetic, or force-driven, view. We have learned that foot orthoses don't function by changing the position of the foot. Instead they change forces, which lead to joints functioning in improved ways.²

We also increasingly see in the surgical research evidence that those procedures that previously addressed a certain dominant plane actually modify the forces that act on the foot, thereby improving foot function.

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“Modern biomechanical and, in fact, surgical research, appear to be moving away from this kinematic, or positional, approach, and toward a kinetic, or force-driven, view.”

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Let’s take an example to clarify this idea: the medial displacement calcaneal osteotomy (MDCO). The prior way podiatrists viewed this procedure was that it addressed a frontal plane dominant flatfoot. However, over time we have learned that – more significantly – medializing the calcaneal posterior tubercle causes an increase in the ground reaction forces medial to the subtalar joint axis, causing an increase in a supinatory torque. It also has the effect of converting the Achilles into a relative supinator of the subtalar joint (rather than a pronator, when it was more laterally located). This push-pull effect has been shown to decrease the forces on the posterior tibial tendon and medial arch of the foot and reduce the amount of plantarflexion work of the Achilles complex^3,4– all good things in patients with flatfoot-related disorders such as adult acquired flatfoot/posterior tibial tendon dysfunction.

Does this happen to sound familiar to anyone? A medial heel skive or a varus rearfoot post will accomplish much the same thing, albeit a little less powerfully, given that we aren’t surgically manipulating the foot. It is basically the same pressure and force manipulation but from an external rather than internal location.

There is an arena in podiatry where this type of thought process already occurs: the diabetic foot. We are intimately aware of the importance of plantar pressures and their effects on the neuropathic foot. We off weight diabetic neuropathic foot ulcers to heal them. No one talks about putting the diabetic foot in neutral position to heal a plantar first metatarsal head ulcer. We often do Achilles tendon lengthening procedures with our forefoot amputations because we are well aware of the decrease in forefoot pressures the TAL accomplishes.

With all of this said, how can we incorporate these concepts into our daily decision-making processes? Here’s my suggestion:

A Case to Illustrate

Let’s close out our discussion on this with an example. Mrs Jones is a 50-year-old with plantarmedial heel pain that presents to your office. Her history is suggestive of plantar fasciitis. Her examination demonstrates a pes planus foot type with medially deviated subtalar joint axis, an everted resting calcaneal stance position, flexible forefoot supinatus, and gastrocnemius equinus with pain on palpation of the plantar fascial insertion. You are also well aware that plantar fasciitis is not an inflammatory process but rather a degenerative one.⁵ You have already completed steps 1 and 2 of the process.

Step 3 of this patient’s treatment focuses specifically on these identified issues. As part of your treatment algorithm, you might prescribe a night splint (to improve ankle range of motion) and custom foot orthosis with medial heel skive (to increased orthosis reactive force medial to the subtalar joint axis) and forefoot valgus post (known to reduce strain on the plantar fascia). Steroid injections would not be a first line treatment, since this is a degenerative rather than inflammatory process. If these nonsurgical methods fail, then surgical treatment might reasonably consist of a gastrocnemius recession and plantar fascial microdebridement rather than fasciotomy.

A “New” Paradigm Unifying Biomechanics with Surgery

This paradigm has the potential to simplify our approach to patient issues by unifying biomechanics and surgery, but, like all things in medicine, requires further investigation. We need to know, for example, exactly how every foot orthosis modification affects foot kinetics. Similarly, we will need new technologies to investigate how surgical procedures affect actual patients rather than cadavers.

Try this method on your next patient and see how it goes. Good luck and best wishes.