What radiographic finding is indicative of tarsal coalition?

The presence of a widened talonavicular joint is a key radiographic finding indicative of tarsal coalition. Tarsal coalition refers to the abnormal connection between two or more tarsal bones, most commonly the calcaneus and talus, or the talus and navicular. This congenital condition can lead to altered biomechanics in the foot, resulting in a range of symptoms including pain and limited movement.

When examining radiographs of a patient with tarsal coalition, the talonavicular joint may appear widened due to compensatory changes in the joint alignment and structure. This widening is a direct result of the altered relationship and motion between the bones involved in the coalition, which affects the normal anatomy and spacing of the surrounding joints.

In contrast, other options like fractures of the talus, calcaneal spurs, or joint effusions do not specifically indicate tarsal coalition and are associated with different conditions or injuries. A fracture would show as a break in the bone continuity, a calcaneal spur typically signifies chronic plantar fasciitis rather than a coalition, and joint effusion pertains to fluid accumulation in the joint cavity, which could arise from various injuries or inflammatory conditions but is not characteristic of tarsal coalition.