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