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.
- 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.
- Subtalar dislocation.
- Vertical fractur of medial malleolus.
- Talar neck fracture.
- Non articular chip fracture.
- Single large fragment involving both talofibular articulation & subtalar joint.
- Comminuted fracture involving both articulations.
- 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.
- 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.
- 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.
- 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.
- Treated with nonweightbearing cast immobilization for approximately 4-6 weeks.
Nonunion is a frequent complication of displaced lateral process fractures that are treated nonoperatively.
- 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
- Nonunion is frequent complication of displaced lateral process factures that are treated nonoperatively
- Whether treated operatively or nonoperatively, many patients will develop subtalar arthrosis & may require late subtalar arthrodesis.