Posterior tibial tendon insufficiency. Isolated fusion of the talonavicular joint.

In selected patients, fusion of the talonavicular joint can be an effective treatment of adult flatfoot deformity. Restriction of motion and altered hindfoot mechanics, however, are a consequence of talonavicular fusion and can lead to accelerated arthrosis of adjacent joints. In patients with severe long-standing deformity, medial displacement calcaneal osteotomy may be a necessary adjunct to talonavicular fusion for adequate correction of heel valgus.