Flail chest is a very serious complication of blunt force trauma to the chest, such as that incurred in a car accident, which can lead to death if it is not treated. In patients with flail chest, part of the chest wall separates from the rest, and it moves in an opposite direction from the rest of the chest wall. This causes the chest to appear to be flailing or struggling as the patient breathes, explaining the name. This condition has been observed and discussed by the medical community for hundreds of years.

For flail chest to develop, the patient must have multiple sets of broken ribs. The ribcage and sternum are deliberately designed to be extremely sturdy, as they protect some very delicate organs. When multiple sets of fractures occur in just the right spots, part of the chest wall separates, causing an instability to develop. When the patient breathes in, the separated section moves inward, against the outward motion of the chest, and when the patient breathes out, the separated section protrudes, rather than sinking with the rest of the chest.

Patients with flail chest usually have difficulty breathing, and they are at risk of being internal injury as a result of the movement of the separated piece of the chest wall. Their chests are often bruised as a result of the injuries which caused the flail chest, and the chest is usually very tender to the touch. The flail chest also indicates that the patient may have underlying trauma such as damage to the lungs or heart, which can contribute to the patient's difficulty breathing.

Historically, flail chest was viewed as an extremely grave complication, both because of the underlying damage associated with it, and because of the problems caused by a separated chest wall. A variety of treatments were used to manage flail chest, with varying levels of efficacy, and patients often experienced a long and traumatic recovery period if they made it through the initial crisis.

Modern treatment for flail chest involves a full examination to determine the extent of the damage, paired with the administration of pain management medications to keep the patient comfortable. In cases where patients experience severe difficulty breathing, mechanical ventilation may be used to keep the patient properly oxygenated. Once the patient is stabilized, surgery can be used to address the flail chest. In the wake of the surgery, the patient may need to spend a great deal of time resting to give the broken ribs a chance to heal without strain.