Flail Chest



  • Free-floating segment of chest wall:
    • 3 or more adjacent ribs are fractured in 2 or more places
    • Rib fractures in conjunction with sternal fractures or costochondral separations
  • The free-floating segment of chest wall paradoxically moves inward during inspiration and outward during expiration
  • The principal pathology associated with flail chest is the associated pulmonary contusion:
    • There is no alteration in ventilatory mechanics owing to the free-floating segment


  • Blunt thoracic trauma
  • Fall from a height
  • Motor vehicle accident
  • Assault
  • Missile injury
  • Ribs usually break at the point of impact or posterior angle:
    • Ribs 4–9 most prone to fracture
    • Weakest point of ribs is 60-degree rotation from sternum
  • Transfer of kinetic energy to the lung parenchyma adjacent to the injury:
    • Disruption of the alveolocapillary membrane and development of pulmonary contusion
    • Arteriovenous shunting
    • Ventilation/perfusion mismatch
    • Hypoxemia
    • Respiratory failure may result

Pediatric Considerations
  • Relatively elastic chest wall makes rib fractures less common in children
  • Presence of rib fractures implies much higher energy absorption

Geriatric Considerations
Much more susceptible to rib fractures:
  • Described with low-energy mechanisms
  • Complicated by osteoporosis

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