OrthoNet

Flatfoot in Adults-2

Posterior Tibial Tendon Dysfunction
- Tib post inserts into the plantar aspect of the navicular and into the medial and middle cuneiforms
- main function of the tendon is to invert the subtalar joint (stabilizes the hindfoot with gastrocs) and adduct the forefoot; inverting the heel stabilizes the subtalar joint.
- the peroneus brevis is the main antagonist, everting the subtalar joint and abducting the forefoot
- if the tib post is weak, the peroneus brevis is a significant deforming force (conversely, if peroneus brevis is disrupted, the hindfoot is pulled into varus and the forefoot into adduction by tib post)]
- tib post dysfunction is largely a degenerative problem, preceded by synovitis.
- the history is that of a slow progressive discomfort
- physical demonstrates significant sagging of the medial malleolus and talar head, with the forefoot abducted. Standing on toes is difficult, and the calcaneus will not invert.
- ankle joint motion is usually good, but subtalar motion is variable, as is transverse tarsal motion; these are important to note in planning treatment
- muscle strength can be tested by resisted inversion in plantarflexion (to decrease the influence of tib ant) and in maximal eversion.
- look for the relationship between the forefoot and the hindfoot; as the hindfoot falls into valgus, the forefoot may swing into varus and this deformity may become fixed. This may need to be corrected.

Approach:
- careful physical exam to note synovial thickening, subtalar motion, ankle motion, transverse tarsal motion, and the degree of hindfoot versus forefoot rotation.
- if synovitis is the major problem, try an NSAID and cast immobilization
- if chronic and rigid, try foot orthosis
- if flexible, try an orthosis or UCBL insert
- Surgery: reconstruction or fusion
- for reconstruction, the foot must be supple in both the hindfoot and forefoot; if the mobility is not present, or the forefoot varus is too advanced, a tendon transfer will fail.
- tendon transfer is probably superior in young patients with supple feet
- Mann describes a technique of reconstructing tib post with flexor digitorum longus strung up into the navicular.
-Arthrodesis - the basic premise is that the more flexible the foot, the less disability the patient has
- what to fuse depends on what the anatomy is. Options include
- isolated subtalar fusion if there is a supple, easily correctable transverse tarsal joint and no fixed forefoot deformity
- talonavicular arthrodesis - if subtalar joint and forefoot are flexible.
- double arthrodesis - talonavicular and calcaneocuboid - if subtalar joint is supple
- triple arthrodesis - must get the hindfoot back to neutral or 5o of valgus

Rheumatoid Arthritis
- has a predilection for the forefoot, with ankle involvement.
- rarely involves the tarsometatarsal joints
- treatment involves immobilization, perhaps AFO; surgery should be aggressive before huge deformity exists.