Presentation
Patient with a history of diabetes presents with pain in the plantar foot.
Patient Data
Reduced bone density of tarsal bones is noted with well preserved joint space.
Os peroneum and os tibiale externum are noted.
A green circle has been placed around the os peroneum.
Case Discussion
Geist classification:
Type 1 accessory navicular bone also known as os tibiale externum
2-3 mm sesamoid bone embedded within the distal portion of the posterior tibial tendon
no cartilaginous connection to the navicular tuberosity and may be separated from it by up to 5 mm
accounts for 30% of accessory navicular bones
usually asymptomatic
Type 2 accessory navicular bone
accounts for ~55% (range 50-60%) of all accessory navicular bones
triangular or heart-shaped
typically measures around 12 mm
connected to the navicular tuberosity by a 1-2 mm thick layer of either fibrocartilage or hyaline cartilage
eventual osseous fusion to the navicular tuberosity may take place
Type 3 accessory navicular bone
an especially prominent navicular tuberosity called a cornuate navicular
thought to represent a fused type 2 and is occasionally symptomatic as a result of painful bunion formation over the bony protuberance