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Updated: Mar 15 2022

Subtalar Dislocations

Images - AP - Medial subtalar dislocation (e-rediography)_moved.jpg tissue injury.jpg photo subtalar dislocation.jpg
  • Summary
    • Subtalar Dislocations are hindfoot dislocations that result from high energy trauma.
    • Diagnosis is made clinically and confirmed with orthogonal radiographs of the foot.
    • Treatment is a trial of closed reduction but may require open reduction given the several anatomic blocks to reduction. 
  • Epidemiology
    • Incidence
      • rare
        • accounts for 1% of all dislocations
        • < 1 per 100,000 per year
    • Demographics
      • more common in young or middle-aged males
  • Pathophysiology
    • Mechanism
      • typically result from a high-energy mechanism
        • 25% may be open
          • lateral dislocations more likely to be open
    • Associated conditions
      • associated dislocations
        • talonavicular
      • associated fractures (up to 44%)
        • with medial dislocation
          • dorsomedial talar head
          • posterior process of talus
          • navicular
        • with lateral dislocation
          • cuboid
          • anterior calcaneus
          • lateral process of talus
          • fibula
  • Anatomy
    • Articulation
      • inferior surface articulates with posterior facet of calcaneus
      • talar head articulation 
        • navicular bone
        • sustenaculum tali
      • navicular bone
      • sustenaculum tali
      • lateral process articulates with
        • posterior facet of calcaneus
        • lateral malleolus of fibula
      • posterior process consist of medial and lateral tubercles separated by groove for FHL
    • Muscles
      • talus has no muscular or tendinous attachments
    • Blood Supply
      • posterior tibial artery
        • via artery of tarsal canal (most important and main supply)
          • supplies most of talar body
        • via calcaneal braches
          • supplies posterior talus
      • anterior tibial artery
        • supplies head and neck
      • perforating peroneal arteries via artery of tarsal sinus
        • supplies head and neck
      • deltoid artery (located in deep segment of deltoid ligament)
        • supplies body
        • may be only remaining blood supply with a talar neck fracture
  • Classification
    • Anatomic
      • Anatomic
      • (based on dislocation direction of midfoot/forefoot)
      • Medial dislocation
      • most common (65-80%)due to lateral malleolus acting as strong buttress, preventing lateral dislocation
      • results from inversion force on plantarflexed foot
      • sustentaculum tali acts as fulcrum for the neck of the talus to pivot around
      •  foot becomes locked in supination
      • associated with posterior process of talus, dorsomedial talar head, and navicular fracture
      •  reduction blocked by peroneal tendons, EDB, talonavicular joint capsule
      • Lateral dislocation
      • more likely to be open
      • results from eversion force on plantarflexed foot
      •  anterior process of calcaneus acts as fulcrum for the anterolateral corner of the talus to pivot around
      • foot becomes locked in pronation
      •  associated with lateral process of talus, anterior calcaneus, cuboid, and fibula fractures
      •  reduction blocked by PT tendon, FHL, FDL
      • Anterior dislocation
      • rare
      • Posterior dislocation
      • rare
      • Total dislocation
      • talus is completely dislocated from ankle and subtalar and talonavicular joints
      •  results from continuation of forces required for medial or lateral dislocation with disruption of talocrural ligaments and extrusion of talus from ankle joint
      • usually open
  • Presentation
    • Physical exam
      • foot will be locked in supination with medial dislocation
        • known as "acquired clubfoot"
      • foot will be locked in pronation with lateral dislocation
        • known as "acquired flatfoot"
  • Imaging
    • Radiographs
      • recommended views
        • AP
        • lateral
      • findings
        • medial dislocation
          • talar head will be superior to navicular on lateral view
        • lateral dislocation 
          • talar head will be collinear or inferior to navicular on lateral view
    • CT scan
      • indications
        • perform following reduction
      • findings
        • look for associated injuries or subtalar debris
  • Treatment
    • Nonoperative
      • closed reduction and short leg non-weight bearing cast for 4-6 weeks
        • indications
          • first line of treatment
        • 60-70% can be reduced by closed methods
    • Operative
      • open reduction
        • indications
          • open dislocations
          • failure of closed reduction
            • up to 32% require open reduction
            • medial dislocation reduction blocked by lateral structures including
              • peroneal tendons
              • extensor digitorum brevis
              • talonavicular joint capsule
            • lateral dislocation reduction blocked by medial structures including
              • posterior tibialis tendon is the most common
              • flexor hallucis longus
              • flexor digitorum longus
  • Techniques
    • Closed reduction
      • sedation
        • requires adequate sedation
      • reduction
        • typical maneuvers include knee flexion and ankle plantarflexion
        • followed by distraction and hindfoot inversion or eversion depending on direction of dislocation
      • post-reduction
        • perform a post-reduction CT to look for associated injuries
    • Open reduction
      • anesthesia
      • approach
        • dictated by direction of dislocation and associated fractures
          • medial dislocation
            • sinus tarsi approach to remove incarcerated lateral structures (EDB, etc.)
          • lateral dislocation
            • medial approach between tibialis anterior and posterior tibial tendon to remove medial structures (posterior tibialis tendon, etc.)
            • may still require sinus tarsi/lateral approach to remove subtalar debris
      • post-op care
        • if joint stable
          • place in short leg cast with non-weightbearing for 4-6 weeks
        • if joint remains unstable
          • place temporary transarticular pins or spanning external fixator
  • Complications
    • Post-traumatic arthritis
      • long-term follow up of these injuries show degenerative changes
      • subtalar joint most commonly affected with up to 89% of patients demonstrating radiographic arthrosis (63% symptomatic)
    • Stiffness
      • most common complication
  • Prognosis
    • Post-traumatic arthritis is common
    • Poor outcomes associated with
      • high-energy mechanisms
      • lateral dislocations 
        • result from higher energy mechanisms
      • open dislocations
        • high risk of infection due to
          • lack of muscle coverage
          • poor vascularity of soft tissues
          • difficulty cleaning contaminated joints
      • concomitant fractures involving the subtalar joint
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