A Guide To Orthotic Therapy For Adult-Acquired Flatfoot

Author(s): 
Paul R. Scherer, DPM

   We know from the literature that adult-acquired flatfoot is not a simple pathology of the tibialis posterior muscle or tendon. Staging of the disorder is necessary for proper clinical decision making.

   Goldner and co-workers suggested tendon repair and Johnson and colleagues described synovectomies for the early stages, transfers for the middle stages and arthrodesis for the later stages.4,9 However, few clinicians are satisfied with the surgical approach to this pathology and deformity, even in these early stages. Although the appearance of the foot is more normal anatomically, clinical experience has shown that patients are rarely satisfied with functional results. Patient satisfaction with conservative external stabilizers is greater than with surgical intervention.10

   Non-surgical treatment of adult-acquired flatfoot using custom foot orthoses does not correct the pathology but does seem to slow the progression to definitely reduce symptoms and limit or reverse disability. One must coordinate the course of treatment with the staging of the deformity. Most authors recommend orthotic therapy for the initial management of symptoms.3,4,6 The proper staging allows physicians to direct non-surgical care at the specific stage, providing the most effective treatment outcomes.

Keys To Effective Orthotic Therapy For Stage I AAF

The primary pathology in stage I seems to be, according to most of the related literature, tendinitis of the tibialis posterior tendon and one should treat it accordingly.1,4-6 Immobilization in a rigid walking boot with a high midsole rocker rests the tendon and allows recovery with the least amount of attenuation.

   The midtarsal joint, which is stabilized by the tibialis posterior, has significant sagittal plane motion in gait. Using a walking boot that immobilizes the foot in only the frontal and transverse planes places a greater lever arm of force on this joint and stretches the tendon when it really needs to rest. A high midsole rocker on the walking boot allows, during gait, the sagittal plane motion to occur external to the foot, therefore resting the tendon.10

   Using a stabilizing custom pathology-specific functional foot orthosis following the reduction of symptoms provides a more stable or rigid “bag of bones,” and restores normal motion with less effort from the tendon. The device should be rigid and deep, and should maintain a more normal alignment of the subtalar joint and longitudinal arch while limiting midtarsal joint motion. This reduces the need for stabilization efforts on the part of the tibialis posterior.

   The type of custom device used in one clinical report was the University of California Biomechanics Laboratory (UCBL)-type device, which is made from a neutral negative cast.10 This study demonstrated that the in-shoe device “provided superior restoration of both arch and hindfoot kinematics.” The similarly designed Root custom functional foot orthoses, with a deep heel cup, top cover and sweet spot for the navicular tuberosity, provide the same support with a much greater acceptance and adherence. This is because the Root device fits into most contemporary shoes, which is not the case with the UCBL orthosis. If the patient will not wear the device, then it cannot be effective.

   The addition of a medial heel skive would improve such a device by shifting the effective ground reaction force (GRF) more medially, resisting eversion of the calcaneus and unlocking the midtarsal joint.11 Widening the midsection of the orthosis by adding a medial flange expands the surface area of the orthosis and allows better control. The flange also improves orthotic comfort by distributing force over an expanded surface area.

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