Talar Neck Fractures

Talar neck fractures are 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 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 body of the talus. Body has four parts – talar dome, central part, lateral process and posterior process.

The dome is shaped like 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 article on blood supply of the talus]

Talus bone is supplied by three sources

Posterior tibial artery

• via artery of tarsal canal (dominant supply)
• supplies majority of talar body

Deltoid branch of posterior tibial artery

Supplies medial portion of talar body

may be only 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 now-a-days 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

Patient would generally present with severe injury to the foot and ankle. A  a complete medical history and physical examination are done to assess the injury, profile of the patient and state of limb.

Status of the soft tissue such as 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 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 talus. It is more useful in determination of avascular necrosis of the talus.

Treatment of Talar neck Fractures

Nonoperative  Treatment

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 stepoff.

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 anesthe- sia may accomplish  this  task but 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, secondaryproblems 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, 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 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 implant which can be used are k-wires, mini and small fragment screws, cannulated screws and mini fragment plates.

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 osteonecrostic 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, possible collapse in due course, narrowing of joint space, and occasionally fragmentation of the talar body.

Posttraumatic arthritis

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 lateral border of the foot.

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