Caption: Picture 2. Sternum, fractures. Frontal radiograph of the normal sternum.
Sternum, Fractures
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Background: Sternal fractures are often seen in association of deceleration injuries and/or direct blows to the chest. They occur in approximately 5% of all patients with blunt trauma. The introduction of seat-belt legislation has resulted in an increased frequency of these injuries. Most sternal fractures occur in the midbody, and they are typically transverse. Manubrial fractures are the next most common. Stress fractures are occasionally seen in athletes such as wrestlers, but they can also occur in women with osteoporosis and kyphotic thoracic spines.
Pathophysiology: Most sternal fractures are caused by blunt anterior chest trauma. Sternal fractures have an 18-62% risk of associated thoracic, mediastinal, or cardiac injury. Sternal fractures are also associated with compression fractures of the thoracic spine secondary to hyperflexion of the spine at the time of injury.
Frequency:
Mortality/Morbidity: A 25-45% mortality rate has been reported with sternal fractures as a result of frequently associated chest injuries, such as cardiac contusion, aortic rupture, pulmonary contusion, and thoracic spine compression fractures. Race: No racial preference exists. Sex: No definite sexual difference exists. Age: A large study from Greece showed that patients with sternum fractures have a mean age of 50.3 years (range, 15-93 y). Anatomy: The sternum has 3 parts: the manubrium, the body (corpus), and the xiphoid process (tip). The manubrium lies at the level of the third and fourth thoracic vertebrae (T3 and T4). Along the superior margin of the manubrium is the suprasternal or jugular notch. Both the clavicle and the first rib articulate with the manubrium. The sternal head of the sternocleidomastoid muscle inserts onto the manubrium. The joint between the manubrium and the body is called the manubriosternal joint. It forms the sternal angle, which is also the level of the second rib. In older people, this joint tends to be fused. The xiphoid process is cartilaginous in younger people and ossified in older people. Clinical Details: Trauma patients presenting to a hospital with sternal fractures are usually admitted for monitoring of associated blunt cardiac injury. The monitoring usually entails serial determination of cardiac enzyme levels (creatine phosphokinase–MB [CPK-MB]) and electrocardiography (ECG). Preferred Examination: The routine radiologic study of the sternum consists of a lateral projection and frontal views, which are obtained with the patient prone and rotated slightly off the midline in each direction. Normal anatomic variants, such as nonunited ossification centers, may sometimes cause a diagnostic dilemma. Limitations of Techniques: Initially CT studies were less sensitive than plain radiographs. The newer generation of multidetector-row CT units now allow for multiplanar and 3-dimensional (3D) reconstruction, which greatly improves accuracy. CT provides superior sensitivity and specificity but at greater cost and with radiation exposure. Ultrasonography has been proven to be as accurate as radiography in diagnosing sternal fractures. However, lateral radiographs remain the standard means of demonstrating grade of displacement.
DIFFERENTIALS
Cardiac contusion
X-RAY Findings: The lateral radiograph is usually the most valuable view for detecting sternal fractures and for determining the degree of displacement. Degree of Confidence: Almost all patients with sternal fractures complain of localized sternal pain. Therefore, correlation with the clinical presentation is important. False Positives/Negatives: Nonunited ossification centers and failure of bony fusion of the sternomanubrial and sternoxiphoid articulations can simulate fractures. The angulation is variable at both of these sites. |
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CAT SCAN Findings: Initially CT studies were less sensitive than plain radiography. The newer generation of multidetector-row CT units now allow for multiplanar and 3D reconstruction, which greatly improves accuracy. CT provides superior sensitivity and specificity, but at a greater cost and with radiation exposure. CT is particularly useful for assessing for associated injuries such as pulmonary contusion, pneumothorax, or retrosternal hematoma.
ULTRASOUND Findings: Ultrasonography is a useful way to demonstrate fractures of the sternum. Degree of Confidence: The sensitivity of ultrasonography is comparable to that of plain radiography, but conventional radiography remains the standard means of documenting a sternal fracture.
NUCLEAR MEDICINE Findings: Nuclear bone scanning may be needed if the initial radiographic findings are not definitive. Degree of Confidence: Total-body bone scans are sensitive for acute sternal trauma. However, the anatomic detail is limited, and correlation with the results of radiography or CT scanning is often necessary. |
PICTURES
Caption: Picture 1. Sternum, fractures. Lateral radiograph of the normal sternum.
Caption: Picture 2. Sternum, fractures. Frontal radiograph of the normal sternum.
Caption: Picture 3. Sternum, fractures. Posterior surface of the sternum.
Caption: Picture 4. Sternum, fractures. Lateral border of the sternum.
Caption: Picture 5. Sternum, fractures. Nuclear bone scan of fractures of the sternum (arrow) and ribs on the right side (arrowheads).
Caption: Picture 6. Sternum, fractures. Complete dislocation at the sternal angle.
Caption: Picture 7. Sternum, fractures. Upright frontal radiograph in the same patient as in Image 6 shows mild widening of the superior mediastinum after blunt trauma.
Caption: Picture 8. Sternum, fractures. Supine frontal radiograph after significant blunt trauma to the anterior chest wall shows marked mediastinal widening.
Caption: Picture 9. Sternum, fractures. Lateral radiograph in the same patient as in Image 8 shows a complete displaced fracture of the sternum (arrow).
