A sternal fracture is a fracture of the sternum (the breastbone), located in the center of the chest. The injury, which occurs in 5–8% of people who experience significant blunt chest trauma, may occur in vehicle accidents, when the still-moving chest strikes a steering wheel or dashboard or is injured by a seatbelt. Cardiopulmonary resuscitation (CPR), has also been known to cause thoracic injury, including sternum and rib fractures. Sternal fractures may also occur as a pathological fracture, in people who have weakened bone in their sternum, due to another disease process. Sternal fracture can interfere with breathing by making it more painful; however, its primary significance is that it can indicate the presence of serious associated internal injuries, especially to the heart and lungs. A sternal fracture is a fracture of the sternum (the breastbone), located in the center of the chest. The injury, which occurs in 5–8% of people who experience significant blunt chest trauma, may occur in vehicle accidents, when the still-moving chest strikes a steering wheel or dashboard or is injured by a seatbelt. Cardiopulmonary resuscitation (CPR), has also been known to cause thoracic injury, including sternum and rib fractures. Sternal fractures may also occur as a pathological fracture, in people who have weakened bone in their sternum, due to another disease process. Sternal fracture can interfere with breathing by making it more painful; however, its primary significance is that it can indicate the presence of serious associated internal injuries, especially to the heart and lungs. Signs and symptoms include crepitus (a crunching sound made when broken bone ends rub together), pain, tenderness, bruising, and swelling over the fracture site. The fracture may visibly move when the person breathes, and it may be bent or deformed, potentially forming a 'step' at the junction of the broken bone ends that is detectable by palpation. Associated injuries such as those to the heart may cause symptoms such as abnormalities seen on electrocardiograms. The upper and middle parts of the sternum are those most likely to fracture, but most sternal fractures occur below the sternal angle. Because of the high frequency of associated injuries, clinicians are taught to suspect that a patient has multiple severe injuries if a sternal fracture is present. Sternal fracture is commonly associated with injuries to the heart and lungs; if a person is injured with enough force to fracture the sternum, injuries such as myocardial and pulmonary contusions are likely. Other associated injuries that may occur include damage to blood vessels in the chest, myocardial rupture, head and abdominal injuries, flail chest, and vertebral fracture. Sternal fractures may also accompany rib fractures and are high-energy enough injuries to cause bronchial tears (ruptures of the bronchioles). They may hinder breathing. Due to the associated injuries, the mortality rate for people with sternal fracture is high, at an estimated 25–45%. However, when sternal fractures occur in isolation, their outcome is very good.