Sternal fractures occur anytime there is blunt trauma to the chest, particularly the upper to midportion of the chest. The sternum consists of three bones, of which the body of the sternum is the largest bone and the one most often fractured. It occurs secondary to a motor vehicle accident about 60-90 percent of the time, mostly because of the great deal of force required to fracture this thick bone.
Most of the victims tend to be female and over fifty because they are likely to have thinner sternums and more osteoporosis, leading to weaker bones. Surprisingly, being restrained in a seat belt increases the rate of sternal fracture injury when compared to not being restrained. This is possibly because a strap crosses the sternum and the forces of the auto accident go directly on the sternum.
In one study done over 6.5 years in Melbourne, Australia, 272 patients had radiological evidence of sternal fractures. Only six of the 251 patients that sustained their fracture in a motor vehicle accident were not restrained. The rest were restrained properly and yet suffered this severe type of fracture. Some of these patients suffered underlying cardiac contusions leading to heart arrhythmia, underlying pulmonary bruising, vascular injury and bleeding between the heart and the pericardial sac resulting in pericardial tamponade (a serious heart condition that results in low cardiac output and death if not treated promptly.)
In the study, about 3 percent of all serious car accidents resulted in x-ray evidence of sternal fractures. Not too many patients had a secondary heart arrhythmia and only 0.7 percent of these patients died as a result of their injury. The patient with this type of injury who is under the age of forty can be treated in a short-stay ward with conservative treatment, according to the study’s authors. Because the incidence of cardiac arrhythmia was low, an EKG can be done but the patients do not need to have prolonged cardiac monitoring because the incidence of underlying heart injury is low.
The sternal fracture is best picked up doing a lateral chest x-ray that can show slight displacement and disruption of the cortex of the bone, particularly in the midportion of the sternum. If there is displacement, there is a greater chance of injury to the underlying structures of the chest wall, such as the heart and lungs. These people need to be monitored carefully. Nondisplaced fracture patients tend to do very well and heal over a six week period of time. Because the sternum doesn’t move, the patient may need no type of protection other than a chest band for comfort.
Severely displaced fractures may need surgical intervention. This involves using a plate and screws to hold the displaced fracture ends together. Usually the plate is kept within the patient indefinitely.
It is important to note that the vast majority of sternal fracture patients are completely and correctly restrained in their vehicle and that the fracture is not localized to the driver. Even though restraints increase the risk of sternal fracture, they likely decrease the risk of overall death from motor vehicle accidents.