What is the definition of a flail chest?

Flail Chest Definition

Flail chest is a clinical finding characterized by paradoxical movement of a chest wall segment during respiration, resulting from a contiguous segment of 3 or more consecutive ribs fractured at 2 or more places. 1, 2

Key Distinction: Clinical vs. Radiographic Finding

• Flail chest is the clinical finding of paradoxical chest wall movement with breathing 1
• Flail segment is the radiographic finding on imaging showing the anatomic injury pattern (≥3 consecutive ribs fractured in ≥2 places) 1
• This distinction is critical but not universally recognized among clinicians, leading to confusion in patient management 1

Anatomic Criteria

The radiographic definition requires:

• Minimum of 3 consecutive ribs 1, 3, 4
• Each rib fractured in at least 2 places 1, 3, 4
• Creates a "floating" segment of chest wall that moves independently 1

Clinical Presentation

• Paradoxical chest wall movement: The flail segment moves inward during inspiration (when the rest of the chest expands) and outward during expiration 2, 4
• Patients typically present with rapid breathing, respiratory distress, and may develop shock, especially when combined with pulmonary contusion 2
• The paradoxical movement represents mechanical instability of the chest wall 1

Field Recognition

• EMS providers rarely diagnose "flail chest" specifically in the field 1
• The broader term "chest wall instability or deformity" more accurately describes what can be identified in the prehospital environment 1
• This terminology ensures additional blunt chest trauma (such as multiple rib fractures) will be recognized and appropriately triaged 1

Clinical Significance

• Flail chest is a marker of severe injury and is associated with increased risk of respiratory failure and mortality compared to multiple rib fractures without flail 1, 5
• The underlying pulmonary contusion with inflammatory reaction and right-to-left shunting contributes significantly to hypoxia and poor outcomes 3
• Patients with flail chest have higher rates of mechanical ventilation (86% vs 42%), respiratory complications (64% vs 26%), and longer hospital stays compared to patients with multiple rib fractures without flail 5