Key points
- Os supranaviculare – small accessory ossicle at the dorsal aspect of the talonavicular joint, dorsal to the navicular bone
- Also called os talonaviculare dorsalis, talonavicular ossicle or Pirie’s bone
- Rare, prevalence about 1%; usually an asymptomatic incidental finding on lateral foot and ankle radiographs
- Well-corticated margins and a matching navicular cortical edge favour ossicle over acute fracture
- Chief mimic is dorsal avulsion fracture of the talonavicular capsule – trauma history, pain and swelling, a linear irregular fragment or an associated dorsal talar head fracture favour fracture
- May fuse with the navicular forming a dorsal spur of no clinical significance; occasionally symptomatic with focal tenderness and bone marrow oedema on MRI, and reported in association with navicular stress fracture
References
- Ingalls J, Wissman R. The os supranaviculare and navicular stress fractures. Skeletal Radiol. 2011;40(7):937-41. PMID: 21484322.
- Azawi D, Mahsouli A, Vanhoenacker F. Os Supranaviculare as a Predisposing Factor to Navicular Stress Fractures. J Belg Soc Radiol. 2021;105(1):81. PMID: 34901742.
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