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.

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.

Inclusion Criteria:

• Patients diagnosed as talocalcaneal coalition by CT or MRI at the outpatient
• Underwent arthroscopic talocalcaneal coalition resection due to failure of conservative treatment

Exclusion Criteria:

• The affected side underwent other foot and ankle operations
• Combined with other ankle diseases
• Refused to participate in the study

Patients that were diagnosed with talocalcaneal coalition using a CT scan, between January 2009 and February 2021.