Tarsalcoalitions

Tarsalcoalitions are congenital or developmental unions between two or more tarsal bones in the foot that limit motion of the subtalar or midtarsal joints. They result from abnormal ossification or failure of segmentation of adjacent bones and may be osseous, cartilaginous, or fibrous in composition. Coalitions are often bilateral and may remain asymptomatic until adolescence, when increased activity or ossification produces pain and stiffness.

The most common types are calcaneonavicular and talocalcaneal coalitions, which together account for the majority of cases. Typical symptoms include activity-related hindfoot pain, decreased subtalar motion, recurrent ankle sprains, and development of a rigid or painful flatfoot. Physical examination may show reduced inversion-eversion and a hindfoot valgus.

Diagnosis begins with plain radiographs, which can suggest coalition; specific signs such as the "C-sign" on lateral views can indicate talocalcaneal involvement. Computed tomography provides detailed bone anatomy and is preferred for surgical planning, while magnetic resonance imaging is useful for identifying cartilaginous or fibrous coalitions and associated soft tissue changes.

Initial treatment is conservative: activity modification, nonsteroidal anti-inflammatory drugs, immobilization or casting for acute flares, custom orthotics, and physical therapy. Corticosteroid injections may provide temporary relief. Surgical options are considered when conservative care fails and include coalition resection (often with interposition) for younger patients with minimal arthritic change, or arthrodesis of affected joints for degenerative cases. Outcomes are generally favorable with appropriate selection of therapy, though long-standing coalitions can predispose to adjacent joint arthritis.