Table 2.

Prevalence, clinical significance, and differential diagnosis of the most common types of variants and accessory ossicles in the forefoot

Ossicle	Prevalence		Clinical significance	Differential diagnosis
Hallucal sesamoids	Multipartite (gen medial)	2.7–33.5% bilateral—22–85%	Potential sesamoiditis (osteoarthritis—osteonecrosis)	Sesamoid fracture (multipartite)
	Absence	rare
Lesser metatarsal sesamoids	2nd digit	0.4%	Asymptomatic (Infection from surrounding soft tissues)	–
	3rd digit	0.2%
	4th digit	0.1%
	5th digit	4.3%
Interphalangeal joint sesamoids	2–13% ossified 73% nodule in cadaver series		Interposition in joint dislocation. Limitation to joint mobility and painful callosity have been reported	–
Os vesalianum	0.1 to 1%		Very rarely a source of pathology Painful conditions similar to the os peroneum syndrome have been reported	Avulsion fractures of the apophysis and base of the fifth metatarsal
Os intermetatarseum	1.2–10%		Pain on palpation of the dorsum of the foot (superficial and deep peroneal nerves compression)	Small fractures of the base of the second metatarsal in Lisfranc fracture—dislocations