منو منو

Subtalar Dislocations


  • 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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