Thoracic Trauma

Chapter 6 Thoracic Trauma

Chest injuries are responsible for 25% of all trauma-related deaths. Injuries are classified as blunt trauma if the chest wall remains intact and penetrating injury if the chest wall is breached. Blunt traumatic injury comprises approximately 90% of cases and is most frequently caused by motor vehicle accidents and falls. These injuries are related to the deceleration force at impact. In penetrating injury, the major risk is to mediastinal vascular structures along the path of the projectile or other penetrating object. Although penetrating injury represents only about 10% of chest trauma, it may have a higher prevalence in urban trauma centers.

The plain chest radiograph, as part of the trauma series (i.e., anteroposterior chest radiograph, anteroposterior pelvis radiograph, and cross-table lateral view of the cervical spine) is typically the initial means of diagnostic imaging for all cases of trauma. The trauma series identifies injuries that have the potential for being immediately life threatening (e.g., tension pneumothorax) or iatrogenic insults that may occur from the injudicious placement of tubes and lines during resuscitation (e.g., right mainstem bronchus intubation) (Box 6-1). However, the importance of chest radiography for clearing major chest trauma victims has considerably diminished, and computed tomography (CT) has become the primary imaging modality for all hemodynamically stable trauma patients. This represents a rather significant change in practice compared with less than a decade ago.

CT realized significant gains in speed, accuracy, and utility with the advent of volumetric scanning (i.e., spiral, helical CT) in the early 1990s. Further major advances have occurred in the past decade with multidetector CT (MDCT) imaging. These gains have proved extraordinarily beneficial in the evaluation of trauma patients. Consequently, CT is often requested despite a relatively unremarkable chest radiograph, particularly for the multitrauma patient for whom CT of the head, cervical spine, abdomen and pelvis has become routine. CT images of the chest should be acquired after the administration of intravenous contrast material (IVCM) using an injection rate of at least 2 to 3 mL/sec and with collimation no greater than 1 to 3 mm, although images may be reconstructed at greater thickness (e.g., 5 mm). As further advances in CT speed develop, the trauma series, including the chest radiograph, may be replaced by primary evaluation with CT.


Rib Fractures

Injuries to the chest wall, particularly rib fractures, are common (Box 6-2). The complications of rib fractures, such as pneumothorax and splenic injury, are often of greater consequence than the fractures themselves. Rib fractures are frequently not detected on the initial chest radiograph because an undisplaced or minimally displaced fracture, or a costovertebral separation are radiographically occult. Multiple rib views are not necessary because the treatment for clinically suspected rib fractures is the same whether they are shown by radiography or not. In children, rib fractures are uncommon because of the elasticity of the cartilage. The presence of multiple rib fractures, particularly if of various ages or if posteriorly located is strongly suggestive of child abuse. In adults, multiple, bilateral, healed or healing fractures are often associated with repeated falls and frequently indicate alcoholism or chronic drug use.

Rib fractures are an important indicator of the trauma mechanism, providing information about the vector and severity of the applied forces, as well as indicating the possible complications (Fig. 6-1). Fractures of the first three ribs raise concern for more severe traumatic injury since these can be associated with airway, spinal, or vascular injury (Table 6-1). Ninety percent of patients with tracheobronchial injury have rib fractures at this site. However, only 3% to 15% of patients with upper rib fractures have brachial plexus or vascular injury; CT’s ability to effectively screen for these injuries permits the highly selective use of other modalities. For example, angiography is reserved for those patients for whom clinical or CT findings are inconclusive or warrant a more specific approach to investigation. Fractures of the lower three ribs should raise suspicion for splenic, hepatic, or renal trauma (Fig. 6-2) and should prompt an abdominal CT study to evaluate for these solid visceral injuries (Fig. 6-3).

Table 6-1 Rib Fractures

Location Associations or Complications
First three pairs Spinal or vascular injury, tracheobronchial rupture
Last three pairs Hepatic, splenic, renal injury
Multiple sites Flail chest
Multiple healed, adult Alcoholism
Multiple healed, child Child abuse

Several plain chest radiographic findings may indicate splenic trauma. Displacement of the gas-filled fundus of the stomach medially and anteriorly by hematoma and/or signs of left diaphragmatic rupture indicate a greater likelihood of splenic injury. Segmental rib fractures involving more than three contiguous ribs or single fractures involving five consecutive ribs constitute a flail chest (Fig. 6-4). Severe respiratory compromise may develop as a result of the paradoxical movement of the flail segment during respiration. For this reason some institutions have begun to perform open reduction internal fixation (ORIF) of flail segments using hardware plates.

Extrapleural hematomas frequently accompany rib fractures. On the chest radiograph, the hematoma may appear as a focal, lobulated opacity that has a convex margin with the lung. Unlike pleural fluid, these hematomas do not alter configuration with changes in patient position. Extrapleural hematoma at the apices may be caused by subclavian vessel hemorrhage as a result of the initial trauma or after central line placement (Fig. 6-5). Aortic injury can also result in a left apical extrapleural hematoma, manifest as increased opacity above the left lung apex. More inferiorly, extrapleural hematoma is usually the result of injury to intercostal vessels. Hemorrhage from intercostal vessels may result in a rapidly developing hemothorax, or even exsanguination. Angiography with embolization can be life saving (Fig. 6-6).

Sternal Fractures

Sternal fractures occur in less than 10% of patients with major thoracic trauma and may be associated with injury to the mediastinal vascular structures or myocardial contusion, the diagnosis was most easily made on the lateral chest radiograph (Fig. 6-7A). Today, coronal or sagittal reformations or three-dimensional renderings of the chest CT readily show sternal fracture as well as the degree of fracture displacement (see Fig. 6-7B). Sternoclavicular dislocations can be difficult to identify on the chest radiograph, but CT can readily show them. Most dislocations are anterior and are of little clinical significance. Posterior dislocations are more concerning given their greater association with injuries to adjacent mediastinal vessels, trachea, and esophagus.

Spinal Injury

Spinal injury is common in cases of high-velocity trauma where up 30% of patients with significant thoracic trauma have spinal injuries. More than 60% of fracture dislocations in the thoracic spine are associated with neurologic defects. This compares with a prevalence of 32% in the cervical spine and 2% in the lumbar spine (Box 6-3). Early identification of spinal fractures may prevent irreversible and potentially devastating cord injury. Thoracic spine radiographs are not necessary for trauma patients who have undergone volumetric chest CT. Studies have shown that coronal and sagittal reformatted images are more sensitive, specific, and accurate for detecting and characterizing spinal injuries. Most fracture dislocations occur at the thoracolumbar junction (Fig. 6-8). Multiple fractures are found in 10% of patients and eighty percent of these injuries are noncontiguous. The radiologic features to be considered include abnormal vertebral shape, location, size, and density. The “rule of 2 s” applies (Box 6-4).


Feb 28, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on Thoracic Trauma

Full access? Get Clinical Tree

Get Clinical Tree app for offline access