Type one – avulsion of tuberosity by tendon of posterior tibial muscle
Type two – dorsal lip fracture
Type three – fracture of body of navicular
Dorsal avulsion fracture:
Due to plantar displacement of foot followed by inversion or eversion dorsal tibionavicular part of deltoid ligament avulses dorsal cortex of bone
Tenderness and oedema at fracture site
Short leg cast for 4-6 weeks
Fractures of navicular tuberosity:
Up to 25% of all navicular fractures
Usually an avulsion fracture with forced eversion of foot – avulsed by posterior tibial tendon
Differential diagnosis – type II accessory navicular
Treatment – nonweightbearing with posterior splint to hold foot inverted and plantarflexed or short leg cast with good support for arch
Fracture of body of navicular:
Varity of mechanisms
Uncommon; ~2% of all fractures
Two types – avulsion fracture and axial compression fracture.
Usually due twisting injury.
Have swelling and pain. Pain often disproportionate to extend of injury.
On x-ray can see piece of cortical bone avulsed
Axial compression fracture:
1) transverse fracture in body – dorsal fragment smaller than rest of body of bone
2) fracture line runs from dorsolateral to plantarmedial in body of talus
3) fracture with central or lateral comminution and major medial fragment