A Guide To Orthotic Therapy For Adult-Acquired Flatfoot

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Author(s): 
Paul R. Scherer, DPM

   Hintermann and colleagues observed that radiographs and MRIs were unreliable when it came to diagnosing dysfunction of the tibialis posterior tendon.7 They designed the first metatarsal rise sign to help recognize and treat adult-acquired flatfoot at an early stage when the foot is still supple. Patients perform the test standing with equal weight on both feet. When the leg is passively and externally rotated, the first metatarsal head immediately rises off the ground in a patient with a dysfunctional tibialis tendon while it remains on the ground in a normal patient. Hintermann and co-workers compared the use of this test in 21 patients and found that it was always positive whereas the “too many toes” sign and single heel raise were positive in approximately 80 percent of the patients.

   Abboud and colleagues described a test for adult-acquired flatfoot and tibialis posterior function that has a seated patient, with feet dangling above the ground, attempt to touch the plantar surfaces together.8 This attempt at inversion and plantarflexing should happen symmetrically. If one foot lags behind the other, it is a positive sign of tibialis posterior dysfunction.

   The Hubscher maneuver is simply a forced dorsiflexion of the hallux while the patient is bilaterally weightbearing.3 Plantarflexion of the first ray, inversion of the rearfoot and external rotation of the lower leg demonstrate integrity of the rearfoot ligaments. Patients with tibialis posterior weakness will have a negative test demonstrated by motion of the rearfoot but patients with disruption of the rearfoot ligaments will have a positive test in which the rearfoot will not move.

Reviewing The Different Stages Of Adult-Acquired Flatfoot

By acknowledging that adult-acquired flatfoot is not a simple failure of a tendon and recognizing the host of assessment and examination tools and criteria that one can use, we can utilize this information to stage or classify the various forms of the disease before treatment.3,4,6

   Stage I AAF, as described by the Richie modification of the Johnson and Strom classification, demonstrates little or no structural changes, weightbearing or non-weightbearing.3,4 The presenting symptom is tendinitis associated with either symmetrical or unilateral flatfoot. Usually, the patient can still perform a heel raise on the symptomatic side but with greater hesitation and less endurance than an unaffected patient. Symptoms of stage I resolve within two weeks with bracing and anti-inflammatory therapy, and this positive response is diagnostic of this stage. The rearfoot remains flexible and the Hubscher maneuver is negative as are the lag and first metatarsal rise tests.

   Stage II AAF is characterized by a change in the weightbearing morphology of the foot, particularly the lowering of the longitudinal arch and abduction of the forefoot distal to the midtarsal joint, producing the signature “too many toes” sign.3 These changes are due to an actual tendinosis, not simply a tendinitis of the tendon. The patient can rarely perform a simple heel raise. These signs are usually a result of the attenuation or rupture of the tibialis posterior tendon, and are associated with a positive supination lag test and a positive first metatarsal rise test. The rearfoot remains flexible but the Hubscher maneuver is now positive.

   Stage III AAF is characterized and easily differentiated from stages I and II by the rigidity of the rearfoot.3,4 Forced weightbearing manipulation of the rearfoot into a more neutral position is not possible. Radiographs usually demonstrate moderate to severe arthritic changes at the posterior facet of the subtalar joint and degeneration of subchondral bone at the talonavicular joint. The patient with stage III AAF will fail the heel raise, lag and first metatarsal rise tests as well as the Hubscher maneuver.

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