Associated Coalitions of Tarsal Bones: Review of the Literature and Presentation of a Classification.

Associated coalitions of tarsal bones, either unilateral or bilateral, may be classified to developmental or syndromic types. There are no specific patterns for osseous or nonosseous configurations of associated tarsal coalitions. Associated developmental tarsal coalitions can be categorized into dual, threefold, massive, and total tarsal coalitions according to the number and sites of the involved joints. Dual coalitions are more common than other types. Among dual tarsal coalitions, the most frequent combination is talocalcaneal (TC) and calcaneonavicular coalitions, also referred to as double coalition, followed by combination of TC and talonavicular coalitions. The most frequent threefold coalition is the triple coalition, defined as concomitant TC, calcaneonavicular, and talonavicular coalitions. Massive tarsal coalition is defined as a nonsyndromic abnormality with involvement of more than three intertarsal joints or occurrence of a concomitant coalition outside the intertarsal joints, that is, tarsometatarsal joints and/or between metatarsal bases. Total tarsal coalition is the synostosis between all tarsal bones. Syndromic multiple tarsal coalition is a part of a hereditary complex skeletal malformation such as different phocomelia, craniosynostosis, and tarsal-carpal coalition syndromes. This literature review discusses associated coalitions, focusing on anatomical classification, workup, and treatment.