Abstract
Background Current classifications emphasize the morphology of the coalition, however, subtalar joint facets involved should also be emphasized.Objective The objective of this study was to develop a new classification system based on the articular facets involved to cover all coalitions and guide operative planning.Methods Patients were diagnosed with talocalcaneal coalition using a CT scan, between January 2009 and February 2021. We classified the coalition into four main types according to the shape and nature of the coalition: I, inferiorly overgrown talus or superiorly overgrown calcaneus; II, both talus and calcaneus overgrew; III, coalition with an accessory ossicle; (I-III types are non-osseous coalition) IV, complete osseous coalition. Then each type was further divided into three subtypes according to the articular facets involved. A, the coalition involving the anterior facets; M, the coalition involving the middle facets, and P, the coalition involving the posterior facets.Results There were 106 patients (108 feet) included in this study. Overall, 8 feet (7.5%) were classified as type I, 75 feet (69.4%) as type II, 7 feet (6.5%) as type III, and 18 feet (16.7%) as type IV. Twenty-nine coalitions (26.9%) involved the posterior facets only (subtype-P), 74 coalitions (68.5%) involved both the middle and posterior facets (subtype-MP), and five coalitions (4.6%) simultaneously involved the anterior, middle, and posterior facets (subtype-AMP). Type II-MP coalition was the most common.Conclusion A new classification system of the talocalcaneal coalition to facilitate operative planning was developed.