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Thoracic wall injuries: Ribs, sternal and scapular fractures, and hemothoraces and pneumothoraces
While many thoracic injuries are potentially lethal, most patients will survive. The earliest description of surviving blunt and penetrating chest trauma are Neanderthal skeletons showing evidence of a healed penetrating trauma and blunt rib fractures. The Edwin Smith Papyrus, written circa 3000 bc , gave explicit instructions for the management of chest injuries, including soft tissue and bony injuries. In fact, 8 of the 43 cases discussed concerned chest injuries, suggesting that even at that time, chest injuries accounted for 20% to 25% of all trauma.
Trauma to the chest wall and the underlying lung parenchyma either in isolation or as part of multisystem trauma remains exceedingly common, and such injuries are a frequent source of trauma morbidity and mortality. Hemothoraces and pneumothoraces, although technically not injuries to the thoracic wall, occur commonly in conjunction with such injuries and will be considered here as well. Flail chest and its accompanying pulmonary contusion are more completely discussed elsewhere (Pulmonary Contusion and Flail Chest).
Incidence
Thoracic injuries remain common and are directly attributable for 20% to 25% of all trauma deaths. Chest injuries commonly accompany other injuries and contribute to organ failure in patients who have multiple injuries. Rib fractures are among the most commonly encountered injuries. In a review of over 7000 patients seen in a Level I trauma center, 10% had rib fractures; of these, 94% had associated injuries, with a 12% mortality rate. Half of patients with rib fractures required operation or intensive care unit (ICU) admission, one third developed complications, and one third ultimately required extended care in an outpatient facility.
Pneumothoraxes are found in over 20% of patients arriving to a trauma center, and hemothoraces are encountered with similar frequency. The incidence of both hemothoraces and pneumothoraces is often underestimated by plain films, as these injuries are much better visualized by computed tomography (CT) of the chest than the traditional supine anteroposterior (AP) chest radiograph.
Fractures to the bony thorax other than the ribs most commonly occur in the clavicles, which constitute 5% to 10% of all fractures. Fractures of the sternum and scapula are much less common (0.5% to 4% and 0.8% to 3%, respectively) and are more likely to occur in association with other injuries than clavicular fractures. The liberal use of chest CT has resulted in an increase in the identification of nondisplaced scapula and sternal fractures. Complete scapulothoracic dissociation is a rare but dramatic injury with severe associated neurovascular injury.
Mechanism of injury
Injuries of the chest wall vary enormously in severity. In routine emergency room settings, chest trauma may be incurred as a result of a low-energy impact and be relatively minor. Conversely, chest injuries sustained by patients treated in trauma centers following high-energy trauma from motor vehicle collisions are potentially severe and often life-threatening. The most common causes of chest wall injuries and rib fractures in adults are motor vehicle collisions, followed by falls and direct blows to the chest with blunt objects. Rib fractures are normally the hallmark of significant blunt chest trauma and increasing numbers of rib fractures are associated with increasing morbidity and mortality rates. The presence of greater than three rib fractures on plain chest radiograph in adults is a marker for associated solid visceral trauma and mortality risk and has been used as an indication for trauma center transfer. In hemodynamically stable patients, the presence of rib fractures doubles the rate of intraabdominal injuries detected by abdominal CT.
The different mechanisms of injury provide somewhat different patterns of injury. Penetrating injury causes parenchymal lacerations with hemopneumothoraces and little disruption of the bony skeleton. Blunt injury to the lung is most often due to displaced rib fractures and can result in hemopneumothoraces or pulmonary contusions. Pneumothoraces after blunt trauma occur through (1) alveolar rupture with resultant air leak due to a sudden increase in intrathoracic pressure; (2) laceration of the lung due to displaced rib fractures; (3) tearing of the lung in a deceleration injury; and (4) direct crush injury from a blow to the chest.
Vulnerable populations
It is important to recall that rib fractures in infants and younger children occur almost exclusively in the setting of child abuse. Thoracic wall injuries are less common in children owing to the resilience of their bony chest wall. Thus, children may suffer major intrathoracic injury without rib fractures, and the presence of any rib fracture in a child should be considered a marker for severe injury. The presence of acute rib fractures in a young child whose mechanism of injury is unclear or the finding of rib fractures of varying ages should also serve as an indicator for potential nonaccidental trauma (child abuse), and such cases should be reported immediately to the appropriate authorities.
Conversely, elderly patients with osteopenia will occasionally have extensive rib fractures from low-velocity mechanisms without any associated intrathoracic injuries. In older populations, falls followed by motor vehicle collisions become the predominant mechanisms of injury. For patients over the age of 65, rib fractures are associated with increased risk of complication and death. Patients identified as frail prior to injury are at particular risk. Patients of advanced age or frailty suffer from increased rates of pneumonia, respiratory failure, ICU stays, and mortality compared to their younger or more robust counterparts. Multiple studies have shown a correlation between the number of rib fractures and risk of mortality in this population.
Diagnosis
Physical examination
Expeditious inspection and palpation of the chest will provide much information regarding the patient’s injuries ( Fig. 1 ). Auscultation and percussion tend to be less reliable against the high ambient noise of the trauma emergency department (ED). Inspection of the chest should include assessment of obvious chest wall deformities, use of the accessory muscles, the symmetry of the chest wall at rest and during respiration, number and location of wounds, presence of open chest wounds, subcutaneous emphysema, and “flail” segments. Although tracheal deviation in the neck is classically cited as a sign of tension pneumothorax, it is rarely if ever seen, even in patients with gross mediastinal deviation on chest radiograph. Palpation of the chest wall further allows appreciation of the symmetry of chest wall motion and can reveal the presence of bony crepitus or mobile segments or subcutaneous emphysema. Auscultation in trauma has high specificity but very poor sensitivity, so focus should be placed only on the presence and symmetry of air entry. As breath sounds can be easily transmitted from the contralateral lung, the presence of breath sounds does not mean that significant pathology may be present. Conversely, absent or asymmetric breath sounds are very suggestive of significant chest trauma. In the unstable patient, this is an indication for intervention on clinical grounds and a contraindication for imaging studies. Thoracic percussion, even more than auscultation, is difficult to interpret in the trauma setting and is rarely useful.
Physical examination can often, but not always, reveal the presence of a hemopneumothorax. It should be suspected in hemodynamically unstable patients who are found to have greatly diminished or absent breath sounds on the affected side. The finding of any subcutaneous emphysema following blunt trauma or at some distance from a penetrating wound is ample evidence of a pneumothorax that requires treatment. An open pneumothorax is readily appreciated on examination. In these instances, additional imaging studies are not necessary prior to intervening, and confirmation of the hemothorax or pneumothorax occurs with the placement of a chest tube with evacuation of blood or air.
Radiographic studies
Radiographic imaging in the form of plain films, ultrasonography, and CT scan serve as valuable adjuncts in evaluating patients with known or suspected chest wall trauma.
Plain chest radiographs
The screening supine AP chest radiograph is the initial and sometimes most important study in the management of chest trauma. The trauma surgeon must be comfortable interpreting these films, which are often suboptimal owing to the patient’s body habitus, the supine position, the presence of a spine board, and the use of portable x-ray machines. The transition to digital radiology allows image manipulation and magnification to better identify pathology, overcoming many shortcomings of the previous analog technology. While it is tempting to evaluate the study directly from the x-ray machine, only gross pathology can be identified in this manner, as the image is often small and cannot be manipulated. It is our practice and opinion that all studies need to be reviewed on the computerized radiology system before the patient is transported for further imaging or procedures. Still, the portable AP chest radiograph has a high positive predictive value, as findings present on the initial chest x-ray are usually of great significance and can diagnose or exclude several life-threatening injuries.
Interpretation of the chest radiograph should be done in a consistent and systematic fashion. While there are many schema, our practice is to begin technical adequacy of the film followed by a review of the lung parenchyma and pleura. Lung expansion, pulmonary infiltrates or contusions, the position of the endotracheal tube (if present), and the presence of hemothoraces or pneumothoraces should be noted. The mediastinum should be evaluated for evidence of great vessel injury, which is suggested by mediastinal widening, blunting of the aortic knob, apical capping, or a medial displacement of the left main bronchus or of the nasogastric tube. Diaphragmatic elevation or injury should also be noted. Finally, any fractures of the bony thorax—ribs, clavicles, scapulae—should be sought. Alignment of the thoracic vertebrae can be appreciated on chest radiograph, but full imaging of the spine as well as specific radiographs of the bony thoracic structures should be deferred until the patient’s airway, respiratory, and cardiovascular status has been stabilized.
Radiographic imaging is extremely useful in the diagnosis of a hemothorax or pneumothorax. Indeed, in a hemodynamically stable patient, the diagnosis is often made on the portable AP chest radiograph obtained for the secondary survey. In the supine position, the AP chest radiograph will reveal hemothorax only when at least 200 to 300 mL of blood is present in the pleural space. Evidence of hemothorax is suggested by an overall opacification or haziness compared to the contralateral hemithorax as the fluid layers posteriorly ( Fig. 2 ). False “negative” appearing chest radiograph may occur in the setting of bilateral hemothoraces (no difference between the two sides) or when there is a simultaneous anterior pneumothorax (decreasing the relative density to be more similar to the other side). In the patient with penetrating chest trauma, the chest radiograph is best taken with the patient upright, which increases the sensitivity for both hemothoraces and pneumothoraces.
Ultrasonography
Ultrasonography has become important in the assessment of the acutely injured patient. The Focused Assessment with Sonography for Trauma (FAST) examination is adept at revealing intraabdominal hemorrhage and pericardial fluid collections in the trauma patient. In patients with suspected chest wall trauma, an Extended Focused Assessment with Sonography for Trauma (eFAST) examination can be performed to assess the pleural spaces for pneumothoraces. Pneumothoraces are best assessed with the linear probe at the midclavicular line between the second and third intercostal space. If lung sliding, or the shimmering appearance of the pleura, is seen between the two ribs, then a pneumothorax is likely absent. This technique can be especially useful in hemodynamically unstable patients with suspected pericardial tamponade or tension pneumothorax. Chest ultrasound has other uses and can also be useful in identifying hemothorax, rib fractures, and cardiac injuries in patients with chest trauma. However, the sensitivity and specificity of these adjunctive techniques have not been well studied and its exact use in the trauma bay outside of the FAST and eFAST has not been well defined.
Computed tomography
As routine truncal (chest, abdomen, and pelvis) CT scanning becomes common practice, thoracic injuries are diagnosed at an increased rate with greater precision. Many patients with blunt trauma have been found to have significant anterior pneumothoraces not seen on plain chest radiograph. The incidence of missed pneumothoraces on supine AP chest radiograph has been estimated to be between 20% and 35%. A patient with a relatively minor pneumothorax on chest radiograph who develops dyspnea and hypoxia may in fact have a clinically significant pneumothorax that is better visualized by chest CT. In stable patients, CT scanning also will reveal pleural fluid collections and help to distinguish them from parenchymal injury such as pulmonary contusion.
The appropriate management of the patient with “CT-only” pneumothorax is a matter of some controversy ( Fig. 3 ). The reported incidence of these occult pneumothoraces in blunt trauma patients is 2% to 8%. The available literature suggests that 20% of these patients will require tube thoracostomy. The decision to place a chest tube should be dictated by the patient’s overall status. Those patients who have multiple injuries, are in hemorrhagic shock, or have sustained a traumatic brain injury will not tolerate progression of even a small pneumothorax (see Fig. 3 ), and may benefit from early and expeditious tube thoracostomy. In those patients in whom the clinical picture appears stable, observation can be undertaken, with serial radiographs taken at 6 and 24 hours after diagnosis.
CT also reveal injuries not seen on initial chest radiograph in about two thirds of major trauma patients and can lead to therapeutic changes in 5% to 30% of cases ( Fig. 4 ). Specifically, chest radiography can miss over half of rib fractures seen on CT of the chest. For patients with rib fractures seen on initial chest radiograph, CT scan usually identifies a mean of two to three additional rib fractures. Despite the increased sensitivity of detecting rib fractures as well as lung contusions, pulmonary morbidity (pneumonia, respiratory failure) and mortality risk is only affected by rib fractures and pulmonary contusions that are visible on chest radiograph, indicating that increased sensitivity is not necessarily related to clinical significance.
CT scanning may reveal additional findings that are only suggested by an abnormal chest radiograph ( Fig. 5 ). Chest CT contributes significantly to the management of the traumatic patient in a number of specific situations. CT of the thoracic spine is the “gold standard” imaging modality for assessing vertebral body as well as posterior element fractures and is also helpful in imaging the spine at the cervicothoracic junction. In patients with the nonspecific finding of a widened mediastinum on chest radiograph, CT allows for definitive diagnosis of aortic and great vessel injuries.
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