Table 1.

Prevalence, clinical significance and differential diagnosis of the most common types of accessory ossicles around the ankle and hindfoot

Ossicle		Prevalence	Clinical significance	Differential diagnosis
Os trigonum		1–25%	Os trigonum syndrome	Posterior ankle impingement, Cedell’s fracture, Shepherd’s fracture
Os sustentaculi		0.3–0.4%	Coexisting talo-calcaneal coalition	Fractures of the sustentaculum tali
Os calcaneus secundarius		0.6–7%	–	Fracture of the anterosuperior calcaneal process
Os subtibiale		0.9%	–	Avulsion fractures
Os subfibulare		2.1%	–	Avulsion fractures
Rare	Os supratalare	–	–	Avulsion fractures
	Os talotibiale