What condition is characterized by a fracture of two or more adjacent ribs allowing for free movement of the fractured segment?

Flail chest is defined as a condition in which two or more adjacent ribs are fractured in multiple places, resulting in a segment of the chest wall becoming detached from the rest of the thoracic cage. This leads to paradoxical movement of the fractured segment, where the segment moves opposite to the direction of the chest's expansion and contraction during breathing. When inhaling, the flail segment gets sucked inwards, and during exhalation, it moves outward. This abnormal movement can impair ventilation and significantly decrease lung capacity.

The other options represent different medical conditions:

Flail segment is a term that describes the same phenomenon as flail chest, but flail chest is the more commonly accepted term in medical practice.

Tension pneumothorax occurs when air enters the pleural space and cannot escape, leading to increased pressure that ultimately collapses the lung on the affected side and pushes mediastinal structures to the opposite side.

A greenstick fracture is a type of fracture that is incomplete, often seen in children where the bone bends and cracks on one side but does not break all the way through.

Both tension pneumothorax and greenstick fractures do not correlate with the specific characteristics of rib fractures that allow movement of a flail