Adult Acquired Flatfoot
The adult acquired flatfoot (AAF) is a progressive, symptomatic (painful) deformity resulting from gradual stretch (attenuation) of the tibialis posterior tendon as well as the ligaments that support the arch of the foot.
Although the posterior tibialis tendon plays a significant role, this pathology has recently been recognized as involving failure of other interosseous ligaments, such as the spring ligament. Due to the complexity of this pathology, posterior tibial tendon dysfunction (PTTD) is now referred to as adult acquired flatfoot. Severe flatfoot associated with AAF can lead to other problems, such as plantar fascial tension, tendon pain, rearfoot subluxation, and ankle osteoarthritis.
Clinical Goal for Orthotic Treatment
Foot orthoses prescribed to treat AAF should reduce the excessive pronatory forces acting across the subtalar joint (STJ) axis. The orthoses must be very controlling with significant surface area contacting the foot. The modifications should increase supinatory torque across the STJ axis. Custom foot orthoses are appropriate for treatment in the early stages of AAF (Stage I and II). As this pathology progresses, foot orthoses are not an appropriate treatment and practitioners can consider ankle-foot orthoses (AFOs) for nonsurgical treatment. ProLab clients can discuss appropriate treatment options with a Medical Consultant.
To prescribe this device, check “Posterior Tibialis Dysfunction” under the Pathology Specific Orthoses portion of Part 1 of the prescription form.
AAF Prescription Recommendations
- Polypropylene Shell - semirigid
- Deep Heel Cup
- The deep heel cup increases surface area medial to the STJ axis applying a supinatory torque
- Wide Width and Medial Flange
- A wider distal width combined with a medial flange significantly increases surface area under the arch. This effectively supports the arch and limits excessive pronation.
- Standard Cast Fill
- Standard fill is used since many of these patients also have equinus. If no equinus is present, use minimum fill for greater control.
- Medial Heel Skive – 4mm or 6mm
- The medial heel skive increases force medial to the STJ axis to reduce excessive STJ pronation and heel eversion. Either a 4mm or 6mm skive is appropriate.
- 0/0 Rearfoot Post
- The rearfoot post helps stabilize the orthosis in the shoe
- EVA Cover to Toes
This orthosis is designed to reduce the extreme pronatory forces associated with the AAF and to attempt the realignment of the rearfoot. The combination of increased width, deep heel cup and the medial heel skive increase supinatory force across the STJ axis. ProLab clients can contact a Medical Consultant with any questions.
A Guide to Conservative Care For Adult-Acquired Flatfoot, by Paul R. Scherer, DPM
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