Essential Treatment Tips For Flexible Flatfoot

Author(s): 
By Richard O. Lundeen, DPM, and Stephen M. Offutt, DPM, MS

The treatment of symptomatic flexible pes planovalgus is a topic that stirs up considerable controversy among practitioners. This is especially true in the pediatric arena where there is a common belief that the child will “grow out of it.” For many foot specialists who see the damaging effects of excessive pronation among adults, the realization is all too obvious that much of this pathology can be curbed if it is addressed in childhood. Shockingly, some even deny the existence of the condition.
Etiological factors of flexible pes planovalgus fall into two broad categories: pediatric and adult. Pediatric flexible pes planovalgus is typically congenital. Torsional abnormalities, muscular imbalance, ligamentous laxity, neuropathy, obesity, agenesis of the sustentaculum tali, calcaneovalgus, equinus, varus or valgus tibia, compensated forefoot varus, limb length discrepancy and os tibiale externum are just some of the possible causes. On the other hand, adult flexible pes planovalgus is nearly always an acquired condition that is often secondary to posterior tibial tendon dysfunction (PTTD). In this circumstance, the clinical presentation is synonymous with a Johnson and Strom late stage I and stage II.
Biomechanically, the condition hinges around the cornerstone of peritalar subluxation. Peritalar subluxation occurs secondarily to excessive pronation of the subtalar joint, which is often associated with posterior contractures of the triceps surae. The foot functions on a maximally pronated subtalar joint which, upon weightbearing, unlocks the midtarsal joint. This results in an unstable forefoot, making efficient weightbearing and load transfer impossible. The forefoot proceeds to dorsiflex on a plantarflexing rearfoot, which leads to collapse of the arch.
The concept of planal dominance should be addressed. A high subtalar joint axis will primarily compensate in the transverse plane. Conversely, the low subtalar joint axis will compensate more in the frontal plane.

Reviewing Pertinent Diagnostic Findings
Understanding the clinical presentation of the flexible pes planovalgus is paramount when it comes to appropriate treatment selection. A closed kinetic chain exam will reveal collapse of the longitudinal arch with concomitant internal tibial rotation, heel valgus and forefoot abduction. You’ll see tibial rotation during the gait examination as demonstrated by patellar “squinting” or medial deviation through the midline. Often, you’ll observe medial talar bulging. You may also see pronation continue throughout midstance with little resupination. The “too many toes sign,” as described by Johnson, is indicative of the forefoot abduction.1 You should also note a positive Hubscher maneuver.

An open kinetic chain examination often will demonstrate an arch while subtalar joint range of motion will display excessive eversion. In the case of PTTD, you will surely note edema and pain along the posterior tibial tendon course.
You may see radiographic deviations of some or perhaps all of the following angles: talocalcaneal (Kite’s), cuboid adduction, talometatarsal angle and talonavicular congruity. Lateral radiographs will show deviations in calcaneal inclination, lateral talocalcaneal, talar declination, Meary’s angle, cyma line break and medial column sag at the talonavicular and/or naviculocuneiform joints. Axial projections may demonstrate calcaneal valgus and you should use them to rule out ankle valgus, which may have a similar presentation. In the juvenile or the adult patient, you may also note adaptive changes due to the deforming pronatory forces.

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