Posterior talar process fracture

Posterior talar process fractures may involve the medial or lateral tubercle of the posterior process of the talus. The posterior talofibular ligament attaches to the lateral tubercle and flexor hallucis longus runs between these two tubercles. The unfused ossification center of the lateral tubercle forms the os trigonum.

Terminology

A Shepherd fracture refers to a fracture of the lateral tubercle of the posterior process. An elongated lateral tubercle of the posterior process of the talus is referred to as a Stieda process, so occasionally these fractures are described as Stieda process fractures.

A Cedell fracture is a fracture of the medial tubercle of the posterior process.

Fractures of the entire posterior process of the talus are extremely rare

Pathology

Mechanism of injury
  • injury to lateral tubercle is caused by inversion or extreme equinus
  • injury to medial tubercle is uncommon and is caused by forced dorsiflexion and pronation

Radiographic features

Plain radiograph

Lateral process fractures are best visualized on lateral projections. The os trigonum may be mistakenly identified as a fracture on plain radiograph.

CT

Best imaging modality for identifying posterior process fractures. CT is indicated when clinical suspicion is high but radiographs are negative.

Treatment and prognosis

Short leg cast or ankle brace is used until signs of union appear. If there is non-union, then excision of the fragment is undertaken.