Marcio Antonio Babinski; Germano Camargo Fleury Passos; Beatriz Correa Rodriguez; Eduardo de Oliveira Carrilho Padula; Rodrigo Mota Pacheco Fernandes; Roberto Feres Junior & Lucas Alves Sarmento Pires

The os intermetatarseum is an accessory bone located in the foot, usually between the first 2 metatarsals and the cuneiform bone. It can be presented as free, articulated or in a fused fashion. It is a very unusual variation found in less than 13 % of the population. A 27-year-old patient presented to the emergency service due to an ankle lesion. Physical exam showed pain and limited range of motion while supporting partial load. Radiographic imaging showed a bony trace near the base of the first and second metatarsals, diagnosed as the os intermetatarseum. Formation of this supernumerary bone begins as a separate ossification center. Most cases are asymptomatic; however, compression of the deep peroneal nerve branches by the os intermetatarseum can lead to pain. Some authors suggest that the presence of this bone may cause hallux valgus. The intermetatarseum can lead to diagnostic confusion, mainly related to Lisfranc fracture. Its origin is still little understood.

KEY WORDS: Os intermetatarseum; Foot; Anatomical variation; Tarsal bones.

BABINSKI, M. A.; PASSOS, G. C. F.; RODRIGUEZ, B. C.; PADULA, E. O. C.; FERNANDES, R. M. P.; FERES JUNIOR, R. & PIRES, L. A. S. Os Intermetatarseum: A rare variation of great relevance. Int. J. Morphol., 41(6):1833-1836, 2023.