An unusual cause of ankle pain: fracture of a talocalcaneal coalition as a differential diagnosis in an acute ankle sprain: a case report and literature review

Table 1 Radiological characteristics of talar coalitions

coalition	x-ray	CT	MRI
*calcaneonavicular*	osseous bridging	not necessary	not necessary
*talonavicular*	osseous bridging	not necessary	not necessary
*talocalcaneal*	- talar beak navicular overriding the talus	coronal and axial planes	T1 and T2 sequences
	- talar beak navicular overriding the talus	- osseous coalitions bony bridging	- bony coalition
	- C sign bony bridging between talus and calcaneal sustentaculum		- bony coalition
			- fibrous coalition
			- cartilaginous coalition
		- non-osseous coalitions facet narrowing, reactive changes (e. g. cysts, hypertrophy), downward slope or broadening of sustentaculum	fat suppressed sequence (STIR)
	- narrowing of the posterior subtalar joint		fat suppressed sequence (STIR)
	- narrowing of the posterior subtalar joint		- bone marrow edema (fracture)
	- rounding of the lateral talar process
	- lack of depiction of the middle facets on the lateral radiograph
	- short talar neck
	- dysmorphic sustentaculum tali
	Combination of signs sensitivity/specifity 100 %/ 88 %

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