Updated: 10/22/2018

Subtalar Dislocations

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Questions
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Introduction
  • Epidemiology
    • incidence
      • rare
        • accounts for 1% of all dislocations
    • demographics
      • more common in young or middle-aged males
  • Pathophysiology 
    • 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 
  • Prognosis
    • post-traumatic arthritis is common
    • poorer 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
Anatomy
  • Articulation
    • inferior surface articulates with posterior facet of calcaneus
    • talar head articulates with
      • 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
    • 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 fractures
      • 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 (extruded talus)
      • 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 Shows incidence, mechanism and treatment of subtalar dislocations
          • 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
 

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Questions (6)
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(OBQ09.123) A 37-year-old female sustains the injury seen in Figures A and B. At long-term follow up, degeneration of which of the following joints has been shown to have the highest rate of patient symptoms? Review Topic

QID: 2936
FIGURES:
1

Tibiotalar joint

5%

(30/594)

2

Talonavicular joint

12%

(72/594)

3

Calcaneocuboid joint

1%

(5/594)

4

Lisfranc joint

10%

(60/594)

5

Subtalar joint

71%

(424/594)

ML 2

Select Answer to see Preferred Response

PREFERRED RESPONSE 5

(OBQ08.216) A 30-year-old male falls off the roof and sustains the injury seen in Figure A. Multiple attempts at a closed reduction are made, but are unsuccessful. Entrapment of which of the following structures is the most likely etiology? Review Topic

QID: 602
FIGURES:
1

Peroneal tendons

20%

(460/2256)

2

Posterior tibial tendon

60%

(1355/2256)

3

Extensor retinaculum

2%

(53/2256)

4

Anterior tibial tendon

3%

(61/2256)

5

Flexor hallucis longus

14%

(319/2256)

ML 3

Select Answer to see Preferred Response

PREFERRED RESPONSE 2

(OBQ12.150) Which of the following is true when comparing Figure A to Figure B? Review Topic

QID: 4510
FIGURES:
1

Figure B is more likely to have an associated fracture

8%

(446/5512)

2

Figure A is more likely to be blocked from closed reduction by the extensor digitorum brevis

12%

(662/5512)

3

FIgure A is more likely to be open

54%

(2988/5512)

4

FIgure B is more likely to be blocked from closed reduction by the posterior tibial tendon

19%

(1042/5512)

5

Figure A more likely to be stable following closed reduction

6%

(318/5512)

ML 4

Select Answer to see Preferred Response

PREFERRED RESPONSE 3

(OBQ09.76) A 34-year-old male falls 10 feet from a balcony and is brought to the emergency room with the deformity seen in Figure A. Radiographs shown are shown in Figure B and C. Which of the following structures can block closed reduction of this injury pattern? Review Topic

QID: 2889
FIGURES:
1

Flexor hallucis longus tendon

12%

(421/3527)

2

Extensor digitorum brevis muscle

62%

(2184/3527)

3

Posterior tibial tendon

20%

(718/3527)

4

Tibialis anterior tendon

5%

(176/3527)

5

Plantar fascia

0%

(13/3527)

ML 3

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PREFERRED RESPONSE 2

(OBQ04.153) A 40-year-old male suffers the isolated injury shown in figure A with no associated fractures. What joint is dislocated in this radiograph? Review Topic

QID: 1258
FIGURES:
1

Tibiotalar

1%

(10/873)

2

Talonavicular

95%

(830/873)

3

Calcaneocuboid

3%

(30/873)

4

First metatarsophalangeal

0%

(0/873)

5

First tarsometatarsal

0%

(1/873)

ML 1

Select Answer to see Preferred Response

PREFERRED RESPONSE 2
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