Fractures of the talus include a broad spectrum of injuries from occult fractures of the talar process to displaced talar neck fractures.
Talar fractures are rare. But they could be difficult to treat and potentially devastating to overall foot function.
Relevant Anatomy of Talus
The talus is a uniquely-shaped bone divided into three anatomic regions –body, head, and neck. The body is the largest part the talus. It articulates with the tibia and fibula to form an ankle joint.
The transverse diameter of the body is greater anteriorly than posteriorly to effect increased joint stability with dorsiflexion
Down below, the body articulates with the posterior facet of the calcaneus along with articulatory part of inferior part of the head and neck of the talus to form the subtalar joint.
The body is divided into 4 parts –
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 FHL. 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.
The neck of the talus is roughly cylindrical in shape and is considerably narrower than the body. The neck projects anteromedially and plantarwards from the dome and its inferolateral surface define the roof of the sinus tarsi and tarsal canal which separate it from calcaneus.
The primary blood supply to the body of the talus passes under the talar neck from the sinus tarsi and proceeds retrograde to supply the talar body. Fractures of the talar neck can compromise the vascularity of the body of the talus making it prone to avascular necrosis.
There is limited indirect perfusion of talus as there is no muscle or tendon attached to it.
Anastomoses with the tarsal sinus artery complete the vital vascular sling that travels along the undersurface of the talar neck. Branches from the anterior tibial and peroneal arteries supply the talus,.
The head of the talus is convex anteriorly. It articulates with the navicular distally and with the calcaneus inferiorly. Talonavicular and subtalar joint contribute the majority of motion essential to accommodative hindfoot function.
Different Types of Fractures of Talus Bone
Two major types of talus fractures are talar neck fractures and fracture of the talus other than the neck. The talar neck fractures constitute more than half of talus fractures and carry different treatment approach and prognosis than other talar fractures.
Each of these groups is briefly discussed below. They would be discussed in detail in their respective articles
Talar Neck Fractures
Talar neck fractures comprise more than half of the fractures of talus and commonly the result of high-energy trauma.
Frequently, these fractures are associated with other bony and soft-tissue injuries.
Mechanism of Injury
Talar neck fractures are high energy injuries
- The most common mechanism is a dorsally directed force on a braced foot, such as that encountered in head-on motor vehicle accidents. Talar neck fractures were once known as aviator’s astragalus. Pilots suffered the fracture during plane crashes in which their foot was dorsiflexed on the floorboard of the plane
- Inversion of the ankle, with impingement of the talar neck against the medial malleolus, is another
- The direct blow to the dorsum of the foot
Classification of Talar Neck Fractures
Undisplaced fracture is nondisplaced [ 0% to 13% incidence of osteonecrosis.]
Displaced fractures with subluxation or dislocation from the subtalar joint. [ 20% to 50% incidence of osteonecrosis]
Displaced fracture with subluxation or dislocation of the subtalar and ankle joint. [Almost 100% osteonecrosis]
Type III + talonavicular dislocation
Soft tissue injuries are severe.
Inability to reduce the fracture sufficiently to rest the soft tissue is an indication for immediate open reduction.
Plain radiographs to assess the fracture pattern must include a mortise or AP view of ankle [ assess congruency and the presence of a medial malleolar fracture], lateral view of the foot [will indicate the dorsal comminution and the presence of subtalar joint involvement.]
Canale view is modified the anteroposterior view to see the talar neck in a true anteroposterior projection. The foot is placed in maximal plantarflexion and everted 15°. The x-ray tube is positioned 75° from the horizontal with the beam directed cephalad. This would show a true anteroposterior view.
CT scanning can be used to confirm the presence of a subtle fracture and to evaluate the reduction
Closed treatment of type I fractures of the talar neck if a fracture is nondisplaced has been advocated.
or if an anatomic reduction can be maintained by closed means.
Percutaneous fixation with crossed K-wires or screws has been employed to obviate the need for plaster immobilization in equinus.
Reduction and immobilization displaced fractures should not be delayed.
Anteromedial, anterolateral, and posterolateral incisions are the three principal surgical approaches to the talus.
Stable fixation can be attained by a variety of constructs like screws, k-wires or minx.
Nonunion, arthritis, and osteonecrosis are common complications of talar neck fractures.
Osteonecrosis of a significant portion of the weight bearing surface with collapse is the most dreaded complication of talar neck fractures.
Talar Head Fractures
Fractures of the head of the talus account for less than 10% of all injuries to the talus. It is caused by a dorsiflexion force and axial compression. It can also occur secondary to talonavicular joint dislocation.
It may be associated with other foot fracture and dislocation of the talonavicular joint
AP and lateral radiographs of the foot usually would suffice. A Canale view permits better visualization of fractures oblique to the transverse or sagittal plane of the foot. Computed tomography defines the exact location and degree of displacement of these fractures. CT or MRI may be useful to assess the talonavicular joint but not required routinely.
Closed reduction of the fracture and plaster immobilization is the usual treatment. Nondisplaced fractures will heal in non weight bearing short leg casts
Open reduction and internal fixation is occasionally required especially with the instability of the talonavicular joint or disruption of the calcaneocuboid joint.
Usual surgery is the anteromedial approach and interfragmentary compression screws.
Talonavicular arthrodesis may be required if there are issues of fracture union or Inability to maintain stable internal fixation.
Fractures of the Body of the Talus
Fractures of the body of the talus account for over 25% of all injuries to the talus.
The injuries can be divided anatomically into osteochondral, lateral process, posterior process, and true body (dome) fractures.
Fractures of the talar dome may be further classified into coronal, sagittal, horizontal, or crush fractures.
The fractures of the body of talus occur by compression or shearing forces. Calcaneus, tibia, talar neck are usually associated with injuries.
For imaging, AP, mortise (15° internal oblique), lateral, and Broden views are done. CT scan is required to assess articular injuries, comminution, and any missed associated fracture. These fractures are associated with high incidence of subtalar arthritis.
Lateral Process Fractures
These are also known as snowboarder’s fractures. It is an eversion injury. The lateral process is caught between the lateral malleolus of the fibula above it and the calcaneus below it; the injury may also be caused by inversion and dorsiflexion.
Fractures of the lateral process may be easily missed as the injuries are mistaken for severe ankle sprains and require careful assessment of the x-ray.
Mortise view with the foot plantarflexed shows the lateral process easily. where the lateral process is best seen.
A CT scan will reveal an occult lateral process fracture suspected on plain film.
Short-leg, nonweight bearing casts are used for undisplaced fractures. Displaced fractures may require internal fixation or excision.
Chronic pain and nonunion may occur in the long run.
Fractures of the posterior process are also called Shepherd fracture. The fracture occurs due to Hyperplantarflexion or avulsion of the posterior talofibular ligament. It can also occur as a stress fracture in ballet dancers and to some extent athletes.
There could be associated talar body fracture and injury of injury of flexor hallucis tendon.
On x-rays, it is important to differentiate this injury from an os trigonum (a nonunited, accessory center of ossification of the posterior process)
Immobilization with or without plantarflexion of the ankle is the initial treatment.
If there are persistent symptoms and failure of the radiographic union, excision of the fragment may be considered.
It is usually caused by bony avulsion of the posterior tibiofibular ligament. These are difficult to detect and often could be missed.
The injuries could be associated with a subtalar dislocation and open talar dislocation. The treatment is often surgical.
Osteochondral fractures of the talar dome occur in association with severe ankle sprains, and for this reason, are often missed on initial presentation. They may be found anterolaterally or posteromedially on the dome of the talus. These are also called transchondral fractures.
The anterolateral fracture results from the impaction of the anterolateral aspect of the articular surface of the talus against the fibula, with an inversion force applied to the dorsiflexed foot.
The posteromedial osteochondral fractures result from impaction of the superomedial ridge of the talus against the tibial plafond when the plantarflexed foot experiences an inversion force.
AP and mortise views of the ankle are done. The sensitivity is increased if the mortise view is performed in plantarflexion and dorsiflexion.
CT or MRI may be needed to determine the size, location, and nature of the osteochondral fracture.
The pattern of a talar dome fracture depends upon the degree of ankle dorsiflexion and varus or valgus alignment when the foot is axially loaded.
Undisplaced coronal, sagittal, shear and horizontal fractures may be treated by nonweight bearing splints/casts until the fracture heals.
Displaced and unstable fractures need to undergo open reduction and internal fixation. • These include tears of the lateral collateral ligament of the ankle.
Pure axial compression crushes the talus and damages the articular cartilage of its tibiotalar and talocalcaneal articulations. These fractures carry the worst prognosis.
Complications of Talar Fractures
Fractures of the talus can lead to avascular necrosis (AVN), arthritis, and, when unrecognized, chronic pain and nonunion. These develop as follows:
AVN of the body of the talus develops primarily after a displaced fracture of the talar neck—which disrupts the blood supply to the talar body.
Arthritis is a common complication following talar fracture. The exact surgical reduction is a goal in the prevention of posttraumatic arthritis.
Chronic pain and nonunion can occur.