Subtalar instability. Etiology, diagnosis, and management.

Subtalar instability is an evolving disorder that seems to cause a portion of chronic hindfoot instability. It can be seen as an isolated problem, or more commonly, in combination with ankle instability. There seems to be many injury mechanisms, most of which seem to involve supination of the hindfoot, and all seem to attenuate the lateral ligaments of the ankle and subtalar joints. As the condition progresses, and additional sprains occur as a result of the alteration in subtalar joint mechanics, the remaining ligaments become attenuated. There are many methods described to diagnose subtalar instability, but no conclusive test has been devised. Thus, the diagnosis must be inferred from an accurate history, physical examination, conferring radiographic studies, and failure of nonoperative management (often, for ankle instability). As with other hindfoot injuries, many patients improve with conservative measures. These measures are early (ice and immobilization) and late (bracing and proprioceptive training). When patients do not improve or cannot tolerate bracing, recent studies have shown there is a role for ligamentous reconstruction. Most procedures attempt to recreate the lateral ligament structures, including the calcaneofibular, the cervical, and the interosseous talocalcaneal ligaments, which seem to have the best stabilizing effect on the hindfoot. With the advent of newer procedures and more aggressive surgical management, there may be a role for early anatomic repair and rehabilitation.