Talar neck fracture

Talar neck fractures extend through the thinnest cross-sectional portion of the talus, just proximal to the talar head. They represent one of the most common types of talus fracture (~30-50%), along with chip and avulsion fractures of the talus (~40-49%). These fractures are commonly associated with subtalar dislocation and/or posterior body fractures ⁴.

Mechanism

These fractures usually result from forced hyperdorsiflexion of the ankle with associated axial loading. There may be a rotational component with hindfoot supination and impact on the medial malleolus ⁶. They are usually a result of high-energy mechanisms. There is a 20-38% incidence of open injuries and 50% incidence of other associated injuries ⁶.

Radiographic features

Plain radiograph

• Canale view: 15° internal rotation, with 15° tube angle from vertical (similar tube angle to an AP foot) better demonstrates the fracture ⁵

CT

• useful adjunct to plain radiograph to identify subtle incongruities and assist with pre-operative planning

• undisplaced type I fractures may potentially be misclassified and the majority of talar neck fractures are not able to be classified according to the Hawkins classification ⁶

• the majority of apparent isolated talar neck fractures are actually talar body fractures with extension into the neck ⁶

Classification

Hawkins classification ¹:

• type I: undisplaced fracture

• type II: displaced fracture with subluxation or dislocation of the subtalar joint and a normal ankle joint

• type III: displaced fracture with the body of talus dislocated from both subtalar and ankle joint

Canale and Kelly ² described a rare type IV category which in addition to features described for type III there is dislocation or subluxation of the head of the talus at the talonavicular joint.

Treatment and prognosis

• type I fractures: short leg cast or boot for 8 to 12 weeks, non-weight bearing for at least 6 weeks

• type II-IV fractures:

  • initial management

    • urgent closed reduction in the emergency department with CT to confirm the position and assist with pre-operative planning ⁶

  • definitive management

    • may require initial percutaneous pinning prior to definitive open reduction - internal fixation (ORIF) to allow adequate time for soft tissues to settle ⁶

Complications

• hardware complications

  • loosening

  • backing out

  • hardware or peri-hardware fracture

  • infection

• tendon entrapment or injury

• risk of osteonecrosis increases with increasing classification type

  • type I fractures have a 0-15% risk

  • type II fractures have a 20-50% risk

  • type III fractures approach a 100% risk

  • type IV fractures have a 100% risk

• post-traumatic arthritis ⁶

  • subtalar (50%)

  • tibiotalar (33%)

• mal-union ⁶

  • varus mal-union (25-30%)

History and etymology

The classification of talar neck fractures was described by Dr Leland G Hawkins in 1970 ¹.

See also

• Hawkins sign