Courtesy: Prof Nabil Ebraheim, University of Toledo, Ohio, USA

Basic Anatomy of the Talus

• Approximately 70% of the talus surface is covered by articular cartilage.
• Talus consists of head, neck, body, lateral process, and posterior process.
• Large cartilage coverage contributes to high risk of post?traumatic arthritis after fractures.

Blood Supply of the Talus

• Primary blood supply comes from posterior tibial artery, dorsalis pedis artery, and perforating peroneal artery.
• Medial femoral circumflex equivalent concept does not apply; talus blood supply is relatively tenuous.
• Deltoid branch of the posterior tibial artery may be the only remaining blood supply in severe talar neck fractures.

Important Clinical Point

• Because the talus has limited vascular supply and large cartilage coverage, talar fractures have high risk of avascular necrosis (AVN) and arthritis.
• Subtalar arthritis is the most common complication.

Mechanism of Injury

• Talar neck fractures usually occur due to forceful dorsiflexion combined with axial loading.
• High-energy injuries such as motor vehicle accidents or falls are common causes.

Hawkins Classification of Talar Neck Fractures

• Type I: Non?displaced fracture – AVN risk about 10%.
• Type II: Talar neck fracture with subtalar subluxation or dislocation – AVN risk about 50%.
• Type III: Talar neck fracture with subtalar and tibiotalar dislocation – AVN risk about 90%.
• Type IV: Talar neck fracture with subtalar, tibiotalar, and talonavicular dislocation – AVN risk 90–100%.

Avascular Necrosis (AVN) of the Talus

• Risk correlates strongly with degree of fracture displacement.
• More severe fracture displacement leads to higher risk of AVN.
• AVN may appear as sclerosis on radiographs 3–6 months after injury.

Lateral Process Fracture of the Talus

• Also known as ‘Snowboarder’s fracture’.
• Presents with lateral ankle pain and may be mistaken for ankle sprain.
• CT scan is helpful for diagnosis.
• Non?displaced fractures treated with short leg cast and non?weight bearing for 6 weeks.
• Displaced fractures require surgery.
• Small displaced fragments may be excised.

Types of Lateral Process Fracture

• Type I: Avulsion fracture.
• Type II: Large fragment involving subtalar joint – usually requires surgical fixation.
• Type III: Comminuted fracture – often initially treated with casting.

Posterior Process Fractures

• Posterior process contains medial and lateral tubercles separated by groove for flexor hallucis longus tendon.
• Fracture is rare and frequently missed on initial radiographs.
• May mimic ankle sprain or os trigonum.

Hawkins Sign

• Subchondral radiolucent band seen in talar dome on mortise view at approximately 6–8 weeks after injury.
• Represents subchondral bone resorption due to preserved vascularity.
• Presence of Hawkins sign indicates good talar blood supply and low risk of AVN.
• Absence does not definitively confirm AVN but raises suspicion.

Radiological Evaluation

• Standard radiographs include AP, lateral, and mortise views.
• Canale view is used to visualize talar neck fractures.
• In Canale view: foot pronated 15°, maximally plantarflexed, beam directed 75° cephalad.
• CT scan is very useful for fracture characterization.
• MRI is sensitive for detecting early avascular necrosis.