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Os Naviculare Accessorium

os naviculare accessorium

The accessory navicular (os naviculare accessorium) is an accessory ossicle adjacent to the navicular tuberosity, present in approximately 12 to 21 percent of the population in three types: Type I (os tibiale externum — sesamoid in tibialis posterior tendon), Type II (synchondrosis with the navicular — the most clinically significant), and Type III (fully incorporated cornuate navicular). Type II produces a medial foot prominence and is associated with flatfoot because the tibialis posterior tendon inserts abnormally on the accessory bone rather than the navicular tuberosity.

Region: Foot & Ankle

Clinical Relevance

Clinical Notes

Symptomatic accessory navicular syndrome produces medial midfoot pain aggravated by footwear pressure over the prominence and by walking. The synchondrosis can be stressed during walking and running, producing a stress reaction visible on MRI as bone oedema adjacent to the synchondrosis. Conservative management with orthotic arch support and footwear modification resolves most cases; surgical excision of the accessory bone with tibialis posterior tendon advancement (Kidner procedure) is performed for refractory cases.