Lateral Process

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Two processes, lateral & posterior project from body of talus.

  • Either process may be fractured, either as isolated injury or association with other ankle or talar injuries.
  • It is frequently confused with an ankle sprain.
  • Nonunion is a frequent complication of displaced lateral process fracture.

Lateral process:

  • Broad based, wedge shaped prominence of lateral talar body with an articular surface dorsolaterally for fibula and inferomedially for anterior aspect of posterior facet.
  • Lateral talocalcaneal, cervical, bifurcate and anterior talofibular ligaments originate from the tip of this process.

Mechanism of injury:

  • Occurs when the foot is dorsiflexed and inverted (such as occurs with "snow boarding").
  • Shearing stress is transmitted from the calcaneus to the lateral process, causing a fracture of variable size which may enter into the posterior facet.

Associated injuries:

  • Subtalar dislocation.
  • Vertical fractur of medial malleolus.
  • Talar neck fracture.

Classification: (Hawkins)

  • Non articular chip fracture.
  • Single large fragment involving both talofibular articulation & subtalar joint.
  • Comminuted fracture involving both articulations.
     

Clinical Findings:

  • Point tenderness over lateral process just anterior & inferior to the tip of the lateral malleolus.
  • May resemble an ankle sprain.
  • Patient may note persistent pain and loss of motion if fracture extends into posterior facet of subtalar joint.
     

Radiographs:

  • Fracture may involve up to 1/3 of posterior facet of subtalar and/or ankle joint.
  • Note that radiographs will frequently underestimate the size of the fracture fragment.
  • Broden's view: medial & lateral oblique axial views will help evaluate posterior facet.

Mortise View:

  • Help define size of fragment & amount of articular involvement.
  • Taking the mortise view in plantarflexion along with 20-25 degrees of internal rotation will place the lateral process in profile, and will flex the forefoot out of the way.

CT Scan:

  • Allows accurate sizing and assessment of articular displacement of posterior facet.

Non Operative Treatment:

  • Size of fracture fragment & degree of displacement will determine clinical outcome.
  • Larger fragments will be more likely to involve posterior facet.

Nondisplaced fractures:

  • Treated with nonweightbearing cast immobilization for approximately 4-6 weeks.


Nonunion is a frequent complication of displaced lateral process fractures that are treated nonoperatively.

Operative Treatment:

  • Nonreduced, displaced fractures may lead to nonunion, with residual malalignment of the subtalar joint & persistent pain.
  • Large fragments are treated with ORIF.
  • Fractures larger than 1 cm and fractures with more than 2 mm displacement probably should be treated surgically.
  • Small comminuted fragments are treated with excision of fragments

Complications:

  • Nonunion is frequent complication of displaced lateral process factures that are treated nonoperatively


Subtalar arthrosis:

  • Whether treated operatively or nonoperatively, many patients will develop subtalar arthrosis & may require late subtalar arthrodesis.