Fractures of the Talus
The Talus ("Astragalus") is unique: it has no muscular attachments and is 60% covered by cartilage. Its precarious retrograde blood supply makes it highly susceptible to Avascular Necrosis (AVN).
1. Mechanism & Anatomy
- Aviator's Astragalus: Hyperdorsiflexion injury (rudder bar in plane crashes or car accidents).
- Blood Supply: Enters via the neck (Artery of Tarsal Canal) and flows backward to the body. Neck fractures cut off this supply.
2. Hawkins Classification (Neck Fractures)
- Type I: Undisplaced. (AVN risk 0-13%).
- Type II: Displaced + Subtalar subluxation. (AVN risk 20-50%).
- Type III: Displaced + Subtalar + Ankle dislocation. (AVN risk 80-90%).
- Type IV: Type III + Talonavicular dislocation. (AVN risk 100%).
3. Important Signs
Hawkins Sign:
Subchondral osteopenia (radiolucency) seen on X-ray at 6-8 weeks post-injury.
Significance: It indicates the bone is alive (vascular resorption is occurring). It is a GOOD prognostic sign (No AVN).
Subchondral osteopenia (radiolucency) seen on X-ray at 6-8 weeks post-injury.
Significance: It indicates the bone is alive (vascular resorption is occurring). It is a GOOD prognostic sign (No AVN).
4. Management
- Type I: Cast in Equinus (Plantarflexion) to relax dorsal traction.
- Displaced: Urgent ORIF ( screws). Anatomic reduction is critical to prevent arthritis.
25 Practice MCQs
Q1. The major risk associated with Talus fractures is:
Answer: A). Due to retrograde blood supply.
Q2. Hawkins Sign indicates:
Answer: A). Subchondral atrophy means blood is reaching the bone.
Q3. Hawkins Type III fracture involves dislocation of:
Answer: A). The body is extruded posteriorly.
Q4. How many muscles attach to the Talus?
Answer: B). "The lonely bone".
Q5. Aviator's Astragalus is caused by:
Answer: A). Neck hits the anterior tibia.
Q6. The most common site of fracture in the talus is:
Answer: A). Where the blood supply enters.
Q7. "Snowboarder's Fracture" affects the:
Answer: A). Often misdiagnosed as an ankle sprain.
Q8. Canale View X-ray is best for viewing:
Answer: A). Optimized oblique view for the neck.
Q9. Blood supply to the talar body flows:
Answer: A). Similar to scaphoid and femoral neck.
Q10. Management of undisplaced neck fracture (Type I):
Answer: A). Protect blood supply.
Q11. Subtalar Arthritis is a common complication because:
Answer: A). The talus sits on the calcaneus.
Q12. What is the "Artery of the Tarsal Canal"?
Answer: A). Supplies most of the body.
Q13. Os Trigonum is:
Answer: A). Can cause posterior impingement in dancers.
Q14. Treatment for Hawkins Type II, III, IV:
Answer: A). To decompress the vessels and restore anatomy.
Q15. Which tendon runs posterior to the talus?
Answer: A). Between the medial and lateral tubercles.
Q16. Skin necrosis is a risk because:
Answer: A). Tented skin dies quickly.
Q17. Osteochondral lesions of the talar dome (OLT) usually occur:
Answer: A). DIAL a PIMP (Dorsiflexion-Inversion -> Anterior Lateral; Plantarflexion-Inversion -> Medial Posterior).
Q18. Weight bearing is restricted for:
Answer: A). Prevents collapse if AVN occurs.
Q19. Blair Fusion is used for:
Answer: A). Salvage procedure.
Q20. Malunion of the neck leads to:
Answer: A). Patient walks on the outside of the foot.
Q21. MRI is useful for:
Answer: A). More sensitive than X-ray.
Q22. Talar head fractures involve which joint?
Answer: A). Causes painful midfoot arthritis.
Q23. Screws are usually placed:
Answer: A). Perpendicular to the fracture line.
Q24. Talus is wider:
Answer: A). Provides bony stability in dorsiflexion.
Q25. Subtalar dislocation is also called:
Answer: A). Talus stays in ankle mortise; foot dislocates.
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