Advanced management of rib fractures requires understanding the biomechanics of flail chest, the pathophysiology of associated pulmonary contusion, and the rationale for regional analgesia techniques. Flail chest occurs when three or more contiguous ribs are each fractured in two or more locations, creating a free-floating segment of chest wall that is mechanically disconnected from the respiratory bellows. During spontaneous inspiration, the intact chest wall expands outward as the diaphragm descends, generating negative intrapleural pressure. The flail segment, no longer tethered to the skeletal framework, is drawn inward by this negative pressure (paradoxical motion), reducing the effective tidal volume. During expiration, positive intrathoracic pressure pushes the segment outward while the intact wall moves inward. This paradoxical respiratory movement not only reduces minute ventilation but also creates pendulum-like airflow (pendelluft) between the lungs, where air from the injured side moves to the contralateral lung during inspiration rather than exiting through the trachea, further impairing gas exchange. The force required to produce a flail chest invariably causes underlying pulmonary contusion, which is the primary determinant of morbidity and mortality rather than the chest...