Talar Fractures & Dislocation

Talar bone fracture are classified according to the anatomic location as lateral process, posterior process, talar head, talar body and talar neck fractures.

Talar fractures account for 2% of all lower extremity injuries and 5–7% of all foot injuries. The talus acts as a link between the ankle, subtalar and transverse tarsal joints.

About 70% of the talar surface is covered by articular cartilage along its five weight-bearing surfaces and hence almost any talar fracture involves a joint. It is devoid of muscle or tendon attachments and its vascular supply is dependent entirely on fascial structures. As a result, capsular disruptions can result in osteonecrosis.

See Also: Ankle Anatomy

Talar Neck Fracture

Talar neck fractures occur commonly with forced dorsiflexion and were historically known as the ‘aviator’s astragalus’ as it was common when planes impacted the ground and the rudder bar forcefully dorsiflexed the foot resulting in a talar neck fracture.

The talar neck fractures by forced impaction on the anterior margin of the tibia during hyperdorsiflexion. This is most commonly seen with motor vehicle accidents or a fall from a height.

Clinical Evaluation

Patients present with swelling of the ankle with tenderness of the talus and subtalar joint and painful foot movements. About 15–25% of fractures are open and due to high-energy mechanism injuries. Prolonged dislocation with tenting of the skin may result in pressure necrosis on the overlying soft tissues, compromising soft-tissue integrity and resulting in possible infection. Emergency reduction of the talus under sedation prior to sending the patient for radiographs is recommended. Foot compartment syndrome is rare but possible and must be carefully looked for in patients with severe swelling.

Radiology

In addition to the standard anteroposterior (AP) and lateral radiographs of the ankle, a Canale view is obtained. This provides an optimum view of the talar neck. CT is helpful to delineate the fracture morphology and assess articular involvement. Fractures that appear non-displaced on plain radiographs may show unrecognized comminution or articular step-off on CT scan.

Talar Neck Fracture Classification

The original classification of talar neck fractures by Hawkins had three types of fractures, and Canale and Kelley added a fourth type:

1. Type I Non-displaced .
2. Type II Associated subtalar subluxation or dislocation .
3. Type III Associated subtalar and ankle dislocation .
4. Type IV Type III with associated talonavicular subluxation or dislocation.

Types II, III and IV are associated with progressive severity in disruption of vascular supply to the fracture fragments:

1. In type I fractures, the incidence of osteonecrosis is 0–15%
2. Type II, it is 20–50%,
3. Type III it is 20–100%
4. Type IV it is usually 100%

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Talar Neck Fractures Treatment

The management depends on the degree of displacement. Type I fractures can be treated with a short leg cast for 8–12 weeks. The patient should remain non-weight bearing for 6 weeks until clinical and radiographic evidence of fracture healing is present.

Many surgeons however prefer surgical treatment to avoid the risk of late displacement. This fracture pattern is amenable to percutaneous internal fixation with ‘lag screws’ from a posterolateral insertion site. Displacement greater than 2 mm requires surgical management to avoid further vascular and soft-tissue compromise.

Immediate closed reduction is indicated, with emergency open reduction and internal fixation (ORIF) for all open or irreducible fractures, particularly those with residual subluxation, dislocation or pressurized soft tissues. If open reduction is necessary, all major fragments should be salvaged. Primary arthrodesis is usually avoided.

Surgical approaches include the anteromedial, posterolateral, anterolateral and the combined anteromedial– anterolateral. The combined approach is used only when greater visualization of the talar neck is needed. Internal fixation is usually accomplished with two interfragmentary lag screws or headless screws placed perpendicular to the fracture line. The screws can be inserted in antegrade or retrograde fashion. Posterior-to-anterior directed screws have been demonstrated to be biomechanically stronger.

A short leg cast or removable boot should be placed postoperatively for 8–12 weeks, and the patient should be kept non-weight bearing.

The Hawkins sign represents osteopenia that is seen beneath the subchondral surface of the talar dome and is seen at 6–8 weeks after the fracture, indicating talar revascularization. Absence of this sign in radiographs performed at 6 weeks indicates possible avascular necrosis. If osteonecrosis is suspected, MRI may be useful in making an early diagnosis.

See Also: Lateral Ankle Sprain

Talar Head Fractures

Fractures of the head of the talus constitute 5–10% of talar injuries.

Two mechanisms of injury have been suggested: axially directed loading and compression of the talar head and a dorsal compression fracture on the anterior tibial plafond.

Plain radiographs may define the fracture clearly, but a CT scan is often necessary for definitive diagnosis and evaluation of displacement.

The fracture of the head with loss of support of the talonavicular joint may be associated with clinical instability of the triple joint complex. Injuries to the calcaneocuboid and subtalar joints are common with this injury.

Displaced fractures of the head of the talus should be treated with open reduction and internal fixation with cancellous lag screws using an anteromedial approach. Care should be taken to not strip any remaining vascular supply of the head. Early motion can be started from approximately 2 weeks after surgery and delayed weight bearing is initiated at a minimum of 6 weeks. Osteonecrosis of the fractured segment of the head has been reported to be 10%, and, if degenerative arthrosis occurs, talonavicular arthrodesis may be indicated.

Lateral Process Talar Fractures

Lateral process fractures, also described as snowboarder fractures, are created by forced dorsiflexion and external rotation of the foot.

This fracture is commonly missed on initial presentation on plain radiographs of the ankle. CT is helpful to ascertain the extent of the fracture, which may encompass a significant portion of the lateral aspect of the posterior facet.

Fractures with less than 2 mm displacement are treated nonoperatively in a short leg cast for 6 weeks, followed by 6 weeks in a removable weight-bearing cast. Fractures with more than 3–4 mm displacement or involving >10% of the articular surface should be fixed using lag screws.

Posterior Process Fracture

Posterior Process Fracture of the talar bone involve the posterior 25% of the articular surface and include the posteromedial and posterolateral tubercles. They occur during forced ankle inversion whereby the posterior talofibular ligament avulses the lateral tubercle or by forced equinus and direct compression. The posterolateral tubercle is more frequently involved, and flexion and extension of the hallux may exacerbate symptoms because of the close proximity of the flexor hallucis longus tendon in its posterior groove.

Diagnosis of fractures of the posterior process of the talus can be difficult, and should be suspected when a patient previously diagnosed to have an ankle sprain does not improve by 6 weeks. Non-displaced or minimally displaced fractures without significant subtalar involvement are treated with a short leg cast for 6 weeks whereas displaced fractures are treated operatively. If the fragment is large with significant subtalar joint involvement, it should be fixed. If the fragment is small or diagnosed late, primary excision is performed.

Body of Talar Fractures

It is important to distinguish talar body fractures from talar neck fractures. These injuries are identified as talar body fractures if the inferior fracture line was proximal to the lateral process of the talus and as talar neck fractures if the inferior fracture line was distal to the lateral process of the talus.

Although the incidence of osteonecrosis is similar between talar neck and talar body fractures, a higher incidence of post-traumatic subtalar osteoarthrosis has been noted after talar body fractures. Non-displaced talar body fractures have a reported incidence of osteonecrosis of 25%; however, with displacement, the rate increases to 50%.

Diagnosis should be made by a plain radiograph, and CT may be indicated for complete evaluation of the fracture pattern and displacement.

Displaced fractures should be treated with ORIF. An 88% incidence of osteonecrosis or post-traumatic arthritis has been reported, with worse results occurring in comminuted and open fractures. Comminuted fractures of the body of the talus with gross displacement are difficult to treat with uniformly poor longterm results. Accurate replacement of the fragments is often impossible and procedures such as talectomy or calcaneotibial fusion are required. As the results of talectomy are usually poor, calcaneotibial fusion combined with talectomy is preferred. The foot is painless and stable, and enough compensatory movement usually develops in the midtarsal joints to enable the patient to walk with a fairly elastic gait.

Subtalar Dislocation

Subtalar dislocation refers to the simultaneous dislocation of the distal articulations of the talus at the talocalcaneal and talonavicular joints. The dislocations are closed in approximately 75% of patients. Most (85%) of the dislocations are medial (the foot is dislocated medial to the talus), although lateral, anterior and posterior dislocations have been reported.

Forced inversion of the foot results in a medial subtalar dislocation, whereas eversion produces a lateral subtalar dislocation. All subtalar dislocations require closed reduction. Under adequate analgesia with knee flexion and longitudinal foot traction, the foot deformity is accentuated to ‘unlock’ the calcaneus. The deformity is then reversed and reduction occurs with a ‘clunk’.

Post-reduction CT should be performed to fully ascertain the extent of associated osteochondral injuries and congruency of reduction of the subtalar joint. Intraarticular fragments blocking congruent reduction require surgical excision. Irreducible dislocations occur in 32% of patients owing to entrapment of bone or soft-tissue structures.

With medial dislocations, the talar head can become trapped by the capsule of the talonavicular joint, the extensor retinaculum or extensor tendons, or the extensor digitorum brevis muscle.

With a lateral dislocation, the posterior tibial tendon may be entrapped. Open reduction is required in such instances and is usually performed through a longitudinal anteromedial incision for medial dislocations and a sustentaculum tali approach for lateral dislocations.

References & More

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3. Canale ST, Kelly FB Jr. Fractures of the neck of the talus. Long-term evaluation of seventy-one cases. J Bone Joint Surg Am. 1978 Mar;60(2):143-56. PMID: 417084. Pubmed
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7. Vallier HA, Nork SE, Benirschke SK, Sangeorzan BJ. Surgical treatment of talar body fractures. J Bone Joint Surg Am. 2003 Sep;85(9):1716-24. doi: 10.2106/00004623-200309000-00010. PMID: 12954830. Pubmed
8. Mercer’s Textbook of Orthopaedics and Trauma, Tenth edition.