Introduction
Talus fractures are relatively uncommon injuries, but can be associated with significant complications. The talus is involved in about 2% of all lower extremity injuries and about 5-7% of foot injuries. It is the most important bone of the foot to stabilize and mobilize soon after injury. Talus fractures are usually associated with hyperdorsiflexion of the ankle as the talar neck impacts the anterior margin of the tibia, such as in a motor vehicle accident or fall from height.
Anatomy
The talus articulates superiorly with the tibia and fibula in the ankle mortise and the calcaneous and navicular inferiorly. Body weight is transmitted through the tibia to the superior surface of the talus. The anterior portion of the body is wider than the posterior portion giving stability to the ankle. The neck of the talus connects to the head which connects to the navicular and calcaneous and is the most vulnerable to fracture. The talus has no muscular or tendinous attachments, but has a groove for the flexor hallicus longus tendon. The majority of the talus is covered by articular cartilage. It articulates with the spring ligament inferiorly, the sustentaculum tali posteroinferiorly and the deltoid ligament medially.
The major blood supply to the body is from the artery of the tarsal canal (posterior tibial artery). Other blood supply is by arteries to the sinus tarsi (peroneal and dorsalis pedis arteries), the deltoid artery (posterior tibial artery) which supplies the medial body, and the superior neck vessels (anterior tibial artery).
Classification
The most commonly used classification system is the Hawkins classification of talar neck fractures.
- Type I - nondisplaced talar neck fracture
- Type II - displaced with subluxation or dislocation of subtalar joint
- Type III - displaced with dislocation of body from ankle mortise
- Type IV - displaced with subluxation or dislocation of talonavicular joint
Other types of fractures include talar head fractures, talar body fractures, lateral process fractures, and posterior process fractures.
Presentation
Patients present with foot pain with painful range of motion and crepitus. Swelling and tenderness of the talus and subtalar joint may be present.
Differential Diagnosis and Associated Injuries
Other fractures of the foot and ankle are commonly seen. Also consider subtalar dislocation and total dislocation of the talus.
Radiology
AP, lateral and mortise x-rays of the ankle and AP, lateral and oblique views of the foot should be ordered. The canale view provides the best view of the talar arch. CT is useful for assessing fracture pattern, displacement, and articular involvement. CT, MRI and Technetium bone scan can be used to evaluate for occult fracture. MRI can help detect avascular necrosis.
Treatment
Treatment for Hawkins Type I involves a short leg cast or boot for 8-12 weeks and to remain non weight-bearing for 6 weeks. For Hawkins Type II-IV, ORIF is recommended. Lateral process fracture treatment is determined by displacement. If there is less than 2mm displacement, then use a short leg cast or boot for 6 weeks and remain non weight-bearing for 4 weeks. If there is more than 2mm displacement, ORIF is recommended. Posterior process fracture treatment is also determined by displacement. Nondisplaced or minimally displaced posterior process fractures are treated with a short leg cast for 6 weeks and remaining non weight-bearing for 4 weeks, while for displaced fractures, ORIF is recommended. Non displaced talar head fractures are treated with a short leg cast molded to preserve the longitudinal arch and partial weight-bearing is recommended for 6 weeks. ORIF is necessary for displaced talar head fractures.
Complications
The prognosis for talus fractures is related to the degree of damage to its blood supply. Complications are related to the degree of displacement. One of the most common complications of talus fractures is avascular necrosis due to injury to the artery of the tarsal canal which supplies the body, and branches of the dorsalis pedis and peroneal arteries which supply the head and neck. Risk of avascular necrosis is stratified according to the Hawkins classification:
- Hawkins Type I: 0-15%
- Hawkins Type II: 20-50%
- Hawkins Type III: 20-100%
- Hawkins Type IV: 100%
Open fractures can occur in up to 15-25% of injuries reflecting the high-energy mechanism of injury. There is an infection rate of up to 40% in open talus fractures. Post-traumatic arthritis occurs in 40-90% of cases. Delayed union or nonunion occurs in approximately 15% of cases and malunion is also a concern. Other complications include skin slough secondary to prolonged dislocation, interposition of the long flexor tendons, and foot compartment syndrome.
Outcomes
ORIF results in lower rates of nonunion, shorter time to union, earlier weight-bearing, better anatomical reduction, and lower rate of avascular necrosis than closed treatment.
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