Talar neck fractures are a most common fracture of talus and account for about 50% of the talar fractures.
Talar neck fractures are high high-energy injuries which are usually caused by forced dorsiflexion with the axial load.
Ipsilateral lower extremity fractures common with these fractures.
Anatomy of Talus
Read about anatomy of talus.
Talus consists of head, neck, and body. Talar head is projected anteromedially to articulate with navicular bone and sustentaculum tali.
The talar neck connects head of the talus with the body of the talus. The body has four parts – talar dome, central part, lateral process, and posterior process.
The dome is shaped like a pulley, being convex from front to back but slightly concave from medial to lateral. It articulates with tibial plafond to form ankle joint and participates in plantarflexion and dorsiflexion.
It has articular facets medially and laterally that articulate with the malleoli, as well as an inferior articular facet that articulates with the posterior facet of the calcaneus.
Inversion and eversion, as well as plantarflexion and dorsiflexion, take place at the posterior subtalar joint.
This is a projection on the posteroinferior aspect of the talar body and is nonarticular. The flexor hallucis longus tendon courses between medial and lateral tubercles of the posterior process.
Fractures of the posterior process can affect the flexor hallucis longus. The posterior process of the talus can be present as a separate ossicle, the os trigonum.
The lateral process of the talus protrudes beneath the tip of the fibula. The posterior subtalar facet extends into this region, and fractures of the lateral process often involve that joint inferior surface articulates with
Blood supply of Talus
[Read the article on the blood supply of the talus]
Talus bone is supplied by three sources
Posterior tibial artery
- via artery of the tarsal canal (dominant supply)
- supplies majority of the talar body
- Deltoid branch of the posterior tibial artery
- Supplies medial portion of the talar body
- May only be remaining blood supply with a displaced fracture
Anterior tibial artery
supplies head and neck
Perforating peroneal artery via artery of tarsal sinus
supplies head and neck
Classification of Talar Neck Fractures
Type I
- Nondisplaced fractures
- 0-13% chances of avascular necrosis
Type II
- Displaced fracture with subtalar dislocation
- 20-50% risk of avascular necrosis
Type III
- Displaced fracture with subtalar and tibiotalar dislocation
- 20-100% risk of avascular necrosis
Type IV
- Displaced fracture with subtalar, tibiotalar, and talonavicular dislocation
- 70-100% risk of avascular necrosis
Mechanism of Injury of Talar Neck Fractures
Most fractures of the talar neck are caused by a severe dorsiflexion force. Earlier the most common cause of this fracture was forced dorsiflexion of the foot against the rudder bar in a plane crash. Hence the term aviator’s astragalus was given to this fracture. But nowadays the most common causes are motor vehicle accidents and falls from height.
Following the talar neck fracture, the body of the talus locks in the ankle mortise. The remainder of the foot, including the head of the talus and the os calcis, displaces medially through the subtalar joint.
Continuation of the dorsiflexion force ruptures the intraosseous ligaments like the posterior talofibular and talocalcaneal ligaments. The body of the talus is forced posteromedially out of the mortise with the neck fracture, pointing laterally and superiorly. In more than 50% of such cases the medial malleolus fractures obliquely or vertically.
Clinical Presentation of Talar Neck Fractures
The patient would generally present with a severe injury to the foot and ankle. A complete medical history and physical examination are done to assess the injury, profile of the patient and state of the limb.
Status of the soft tissue such as an open wound, skin damage and swelling should be carefully assessed.
Imaging
X-ray
Ap and lateral views of ankle and foot are the x-rays to begin with. Canale view provides an optimal view of talar neck. It is taken in maximum equinus, 15 degrees pronated. The beam of x-ray is 75 degrees cephalad from horizontal
CT scan
CT scan is able to provide 3D view and degree of displacement, comminution, and articular congruity. It can assess ipsilateral foot injuries as well.
MRI
There is not much role of MRI in acute injury of the talus. It is more useful in the determination of avascular necrosis of the talus.
Treatment of Talar Neck Fractures
Nonoperative Treatment
The emergency reduction should be attempted in all the cases to bring fragments as close to anatomy and to protect internal structures from undue stress and secondary injury.
Hawkins type I fractures can be managed by short leg cast for 8-12 weeks. However, a CT scan should be done to rule out articular step off.
Avascular necrosis is a rarity, and late secondary arthritis of the subtalar joint is also uncommon.
Operative Treatment
Operative treatment is considered in form of closed reduction/open reduction and fixation should be performed in Hawkins II-IV fractures.
Type II Fractures
Anatomical restoration of the neck is essential to restore congruity to the subtalar joint, which, in turn, will restore the normal plantigrade position of the foot. A closed reduction with general anesthesia may accomplish this task but the absolutely anatomical reduction is often not achieved. Therefore, early anatomical open reduction and internal fixation of this injury should be followed.
If the surgical approach does not interfere with the remaining medial blood supply, significant avascular necrosis will be rare. After anatomical reduction, the secondary problem in that joint and in the foot will be avoided, resulting in a satisfactory outcome.
Type III, IV Fractures
A fracture of the talar neck with dislocation of the talar body is a surgical emergency. The extruded body lies posterior to the medial malleolus. To prevent secondary neurovascular injury, the urgent reduction is done.
Open reduction is done and once the body of the talus has been restored to its normal position, the talar neck fracture should then be stably fixed with cancellous lag screws.
If the fracture is highly comminuted or too contaminated, discard the extruded talus body and a fusion is performed.
comminuted or contamination of the wound would make sepsis likely in an open fracture. In
Prophylactic antibiotics must be administered in all patients for surgery.
Talus fractures are approached by either anteromedial [between tibialis anterior and posterior tibialis] or anterolateral [Between tibia and fibula proximally, in line with 4th ray] approached.
The various implants which can be used are k-wires, mini and small fragment screws, cannulated screws and mini fragment plates.
The patient is kept non-weight-bearing for 10-12 weeks
Wounds are closed in layers but it is the best to leave the lacerated portion of the wound open.
Complications of Talar Neck Fractures
Avascular Necrosis or Osteonecrosis
In type I or type II talar neck fractures, the risk of avascular necrosis is minimal, whereas in type III injuries necrosis is virtually certain.
The osteonecrotic changes may be recognized around 6-8 weeks following the injury on the x-rays.
Talar body initially shows increased density compared to the surrounding bone. This is because the surrounding bone is vascular and is undergoing disuse atrophy.
With revascularization occurs, there is rarefaction of subchondral bone, a possible collapse in due course, narrowing of joint space, and occasionally fragmentation of the talar body.
Posttraumatic arthritis
The subtalar joint is most commonly involved to undergo arthritic changes [50%], followed by tibiotalar join [30%]
Malunion
Malunion often occurs in varus. This complication can be prevented by anatomic reduction. It leads to decreased subtalar eversion, stiff foot due to decreased movements of midfoot and hindfoot due to decreased subtalar eversion. The weight bearing goes to the lateral border of the foot.
- 3Shares
3
Leave a Reply