Flail Chest

Description

• 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

Etiology

• 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

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

• Described with low-energy mechanisms
• Complicated by osteoporosis