subtalar dislocation

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Subtalar dislocations is the simultaneous dislocation of the talonavicular and talocalcaneal joints, without tibiotalar or talar neck fractures .

Epidemiology

Subtalar dislocations comprise 1-2% of all dislocations.

Pathology

Mechanism

Subtalar dislocations are often associated with high energy trauma, usually, motor vehicle accidents or falls from a height. However, a significant proportion are also associated with seemingly trivial injuries, particularly during sports or twisting injuries of the foot.

Classification

Subtalar dislocations have been classified based on the position of the foot relative to the talus and the indirect forces that have been applied to cause significant and progressive ligamentous and capsular injury. These injuries can be either medial, lateral, anterior or posterior :

  • medial (75% of cases)
    • forced inversion of a plantarflexed foot followed by external rotation of the talus
    • initial rupture of the talonavicular ligament occurs followed by tearing of the interosseous ligament from anterior to posterior
  • lateral (15-20%): forced eversion of a dorsiflexed foot followed by external rotation of the talus. Initial rupture of the deltoid ligament followed by the interosseous ligament and the talocalcaneal joint, then dorsal talonavicular ligament rupture
  • posterior (2%): heavy forced plantarflexion followed by a talocalcaneal slip
  • anterior (1%): anterior traction of the foot on a fixed lower leg, followed by a talocalcaneal slip
Associations
  • lateral dislocations are usually from high energy mechanisms and are often associated with open injuries and neurovascular compromise
  • subtalar dislocations are frequently associated (more than 60%) with bony injuries including fractures of the lateral talar process and the sustentaculum tali

Radiographic features

Plain radiograph and CT
  • direction of dislocation and associated fractures can be estimated with anteroposterior and lateral radiographs
  • medial dislocation: on lateral views, talar head is superior to navicular
  • lateral dislocation: on lateral views, talar head is colinear or inferior to navicular

Treatment and prognosis

  • early reduction is warranted to limit further soft tissue injury and neurovascular compromise
  • if attended to quickly most subtalar dislocations can be reduced in a closed manner under sedation followed by immobilization
  • open reduction is indicated in failure of closed reduction or if the talus is blocked from reduction by interposing soft tissues and tendons
  • post reduction CT is recommended to assess for overlooked bony injury on plain radiograph
  • the prognosis for isolated subtalar dislocation is favorable, with most morbidity arising from reduced subtalar mobility and osteoarthritis 

Complications

Siehe auch:
und weiter:
Assoziationen und Differentialdiagnosen zu subtalare Luxationen: