Updated: 3/15/2022

Subtalar Dislocations

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

QID: 4510
FIGURES:

Figure B is more likely to have an associated fracture

8%

(518/6466)

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

12%

(752/6466)

FIgure A is more likely to be open

55%

(3531/6466)

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

19%

(1234/6466)

Figure A more likely to be stable following closed reduction

6%

(371/6466)

L 1 B

Select Answer to see Preferred Response

(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?

QID: 2936
FIGURES:

Tibiotalar joint

5%

(85/1565)

Talonavicular joint

12%

(193/1565)

Calcaneocuboid joint

1%

(21/1565)

Lisfranc joint

7%

(105/1565)

Subtalar joint

73%

(1142/1565)

L 2 B

Select Answer to see Preferred Response

(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?

QID: 2889
FIGURES:

Flexor hallucis longus tendon

12%

(513/4424)

Extensor digitorum brevis muscle

62%

(2721/4424)

Posterior tibial tendon

21%

(937/4424)

Tibialis anterior tendon

5%

(218/4424)

Plantar fascia

0%

(16/4424)

L 1 B

Select Answer to see Preferred Response

(OBQ08.175) What is the most common fracture associated with a lateral subtalar dislocation?

QID: 561

Distal fibular fracture

27%

(879/3298)

Cuboid fracture

33%

(1086/3298)

Calcaneus fracture

8%

(275/3298)

Talus fracture

26%

(859/3298)

Navicular fracture

5%

(172/3298)

L 5 C

Select Answer to see Preferred Response

(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?

QID: 602
FIGURES:

Peroneal tendons

20%

(708/3576)

Posterior tibial tendon

61%

(2172/3576)

Extensor retinaculum

2%

(76/3576)

Anterior tibial tendon

2%

(89/3576)

Flexor hallucis longus

14%

(509/3576)

L 3 C

Select Answer to see Preferred Response

(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?

QID: 1258
FIGURES:

Tibiotalar

1%

(19/1611)

Talonavicular

94%

(1517/1611)

Calcaneocuboid

4%

(58/1611)

First metatarsophalangeal

0%

(4/1611)

First tarsometatarsal

0%

(2/1611)

L 1 C

Select Answer to see Preferred Response

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