Tips and tricks in major limb replantation - Subtalar Dislocations

2018-10-31 03:00:04 |

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 $Lateral Xray shows medial subtalar dislocation with associated posterior tubercle fracture$ $Post-reduction sagittal CT shows displaced posterior tubercle fracture$
    - 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

Classification

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

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