Which of the following is an open chest injury?

An open chest injury occurs when there is a breach in the chest wall, allowing air to enter the pleural space. A sucking chest wound is characterized by a defect in the chest wall that allows air to be sucked in during inhalation, which can lead to a life-threatening condition known as a tension pneumothorax. This type of injury typically results from penetrating trauma, such as a gunshot or stab wound, and it requires immediate medical intervention to prevent respiratory failure and circulatory collapse.

While flail chest and rib fractures involve injuries to the ribs and can cause significant respiratory issues, they do not create an opening in the chest wall. Similarly, a spontaneous pneumothorax refers to the presence of air in the pleural space without an external wound, often due to rupture of air-filled blisters on the lung surface, rather than an injury that breaks the integrity of the chest wall. Therefore, the defining characteristic of an open chest injury makes a sucking chest wound the clear and correct choice among the options provided.