Tarsal coalition is a common abnormality of the hindfoot skeleton that only rarely leads to symptoms. These symptoms occur most commonly in adolescence but rarely can be found also in adults. Although most coalitions are congenital, as the consequence of autosomal dominant inheritance, coalitions also can be acquired by degenerative joint disease, inflammatory arthritis, infection, and clubfoot deformities. Fifty percent of all coalitions are bilateral. Talocalcaneal and calcaneonavicular coalitions are most commonly found, and patients frequently have more than one coalition in the same foot. Clinical symptoms of the tarsal coalition frequently follow a sequence of sprains or other minor injuries to the involved foot. This leads to a rigid, painful foot. The pain is worsened by continued activities. The frequently cited peroneal spastic flatfoot is an uncommon means of identifying a tarsal coalition. The diagnosis of the tarsal coalition is made on the oblique radiograph of the foot, which demonstrates the calcaneonavicular coalition. Computed tomography (CT) and magnetic resonance imaging scans show the presence and extent of other coalitions. Secondary signs for the presence of a coalition are talar beaking, anteater nose sign, and C sign. These secondary signs can be demonstrated best on a lateral view of the involved foot. Local anesthetic blocks under image intensifier or CT guidance can identify areas of joint degeneration, which are caused by the altered biomechanics of the foot. Initial treatment should consist of conservative therapy in the form of support or immobilization of the involved foot, change in the activities of the patient, and nonsteroidal anti-inflammatory medication. Surgical treatment in the form of a resection of the coalition should be reserved for those patients for whom conservative therapy has failed. Subtalar or triple arthrodesis should be reserved for those patients for whom all other therapy has failed.
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