Avulsion fractures of the navicular are classified by the AO/OTA as 83A fractures.
These extraarticular fractures are caused by a pull of the posterior tibialis tendon.
Often there is swelling, bruising, and point tenderness.
Extraarticular avulsion fractures are, as a rule, not associated with any deformity.
The higher-energy injuries (MVA or industrial/crush) are associated with significant soft-tissue trauma, and other injuries to the foot and deformity are more likely to be present.
This image shows an avulsion fracture of the navicular.
Mechanism of injury
These fractures are typically athletic injuries. They are most common in jumping sports when landing on the foot with eversion and abduction (like basketball). The patient presents with either immediate or delayed pain.