CT imaging of blunt chest trauma
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Thoracic injury overall is the third most common cause of trauma following injury to the head and extremities. Thoracic trauma has a high morbidity and mortality, accounting for approximately 25% of trauma-related deaths, second only to head trauma. More than 70% of cases of blunt thoracic trauma are due to motor vehicle collisions, with the remainder caused by falls or blows from blunt objects.
The mechanisms of injury, spectrum of abnormalities and radiological findings encountered in blunt thoracic trauma are categorised into injuries of the pleural space (pneumothorax, hemothorax), the lungs (pulmonary contusion, laceration and herniation), the airways (tracheobronchial lacerations, Macklin effect), the oesophagus, the heart, the aorta, the diaphragm and the chest wall (rib, scapular, sternal fractures and sternoclavicular dislocations). The possible coexistence of multiple types of injury in a single patient is stressed, and therefore systematic exclusion after thorough investigation of all types of injury is warranted.
The superiority of CT over chest radiography in diagnosing chest trauma is well documented. Moreover, with the advent of MDCT the imaging time for trauma patients has been significantly reduced to several seconds, allowing more time for appropriate post-diagnosis care.
High-quality multiplanar and volumetric reformatted CT images greatly improve the detection of injuries and enhance the understanding of mechanisms of trauma-related abnormalities.
KeywordsBlunt trauma Lungs CT
Chest trauma is classified as blunt or penetrating, with blunt trauma being the cause of most thoracic injuries (90%). The main difference lies in the presence of an opening to the inner thorax in penetrating trauma, created by stabbing or gunshot wounds, which is absent in blunt chest trauma . Blunt thoracic injuries are the third most common injury in polytrauma patients following head and extremities injuries . Although half of thoracic injuries are minor, 33% require hospital admission . Overall, blunt chest trauma is directly responsible for 25% of all trauma deaths  and is a major contributor in another 50% of trauma-related deaths. Moreover, chest trauma is the second most common cause of death, following only head trauma, and is by far the most common cause of death in the young age group between 15 and 44 years old . Most blunt thoracic injuries are caused by motor vehicle crashes (MVC; 63–78%), with the remainder (10–17%) caused by falls from heights and a minority from blows from blunt objects or explosive devices .
Portable chest radiography is the initial imaging method used at the emergency workup of the polytrauma patient, and it is useful for detecting serious life-threatening conditions, such as a tension pneumothorax or haemothorax, mediastinal haematoma, flail chest or malpositioned tubes. However, the superiority of CT over chest radiography has been documented in the literature; CT detects significant disease in patients with normal initial radiographs and in 20% will reveal more extensive injuries compared with the abnormal initial radiographs, necessitating a change of management . CT is far more effective than chest radiography in detecting pulmonary contusion, thoracic aortic injury and osseous trauma, especially at the cervicorthoracic spine. MDCT has dramatically decreased imaging times and offers readily available multiplanar reformatted images or more sophisticated volume-rendered and MIP images. Therefore, it has been established as the gold standard for the imaging evaluation of chest trauma and trauma in general .
This review focusses mainly on the typical CT findings as well as the pitfalls associated with the wide spectrum of types of injury in the thorax, including injury of the pleura (haemothorax, pneumothorax), the lung parenchyma (contusion, laceration, lung herniation and blast lung), the trachea and airways, the aorta, the heart and pericardium, the oesophagus, the diaphragm and the thoracic wall. The possible coexistence of multiple types of injury is stressed.
Biomechanics of injury/trauma
Four main mechanisms of injury are responsible for chest trauma: direct impact to the chest, thoracic compression, rapid acceleration/deceleration and blast injury.
Injuries from a direct impact are usually less dangerous and affect mainly the soft tissues of the chest wall (haematomas, rubbings). Occasionally, a localised injury to the osseous part of the chest wall can occur (rib fracture, sternal fracture and sternoclavicular dislocation) or, rarely, direct impact forces may be transmitted through the chest wall to the deeper organs, causing serious injury to the heart, lung or large mediastinal vessels.
In thoracic compression injuries intrathoracic structures strike a fixed anatomical structure—such as the chest or the spine—causing organ contusion or rupture. Thoracic compression may cause contusion or laceration of the lung parenchyma, pneumothorax or haemothorax, tracheobronchial fractures as well as rupture of the diaphragm.
In decelaration injuries the production of shearing forces causes direct compression against fixed points. This type is the most common and potentially lethal injury, and may cause major tracheobronchial disruption, cardiac contusions, aortic and diaphragmatic rupture .
Finally, with the increasing use of improvised explosive devices in terrorist attacks, blast injuries are occurring at an increasing rate. Explosion results from the instantaneous conversion of a solid or liquid material into gas after detonation of an explosive material. The blast pressure wave that is created exerts forces and pressure differentials mainly at air-tissue interfaces within the body, mostly affecting the pulmonary, gastrointestinal and auditory systems (primary blast injury). Secondary blast injuries result from objects propelled by the explosion, impacting the individual, while tertiary injuries follow when the individual is being propelled by the explosion [8, 9].
Thoracic CT only
4 × 1.25 16 × 1.25 64 × 0.6
Thorax: part of whole body CT
25–40 or 75 s
It is crucial to detect even a small pneumothorax in the trauma patient, as this can significantly enlarge under positive mechanical ventilation in the ICU or during general anaesthesia and endotracheal tube placement. Consequently, a prophylactic chest tube placement is considered  in small asymptomatic pneumothoraces (<20%), although controversies exist about this practice in the literature . However, there is growing evidence that occult pneumothorax can be safely treated without thoracostomy in non-ventilated patients .
- Type 1
Compression rupture injury (the most common type) is centrally located, can become very large and is produced by compression of the lung against the tracheobronchial tree.
- Type 2
Compression shear injury is produced when the lower lobes are suddenly squeezed against the spine. It is located paraspinally and may be tubular in morphology (Fig. 5).
- Type 3
Rib penetration tear is peripherally located, is small and round and is usually associated with pneumothorax (Fig. 6).
- Type 4
The adhesion tear is seen adjacent to a previous pleuropulmonary adhesion and is almost always seen at surgery or at autopsy. Lung tissue surrounding a laceration retracts—because of the lung elastic recoil—leaving a round or oval cavity that may be filled with air (pneumatocele), blood (haematocele or haematoma) or both, creating an air-fluid level (haematopneumatocele). A laceration, although it may be filled with air, is usually surrounded by lung contusion and therefore is hidden on a chest radiograph during the first 2–3 days, until the contusion begins to resolve. CT, on the other hand, is significantly superior to chest radiography in detecting even a small laceration and in revealing the overall extent of the lacerations . Lacerations (Fig. 1) may range from a solitary lesion to multiple confluent small ones presenting a “Swiss cheese appearance” . Lacerations resolve more slowly than contusions, and clearance may take weeks or even months, and they may end in residual scarring . Uncommonly, lacerations may be complicated by a pulmonary abscess, enlarge through a ball-valve mechanism or form a bronchopleural fistula , or it may be associated with acute pulmonary embolism (Fig. 5).
Herniation of the lung parenchyma is an uncommon manifestation of blunt chest trauma, and it can occur through a congenital or a traumatic chest wall defect such as multiple rib fractures or sternoclavicular or costochondral dislocations. Surgical repair is indicated when the patient is symptomatic or if the patient needs intubation and general anaesthesia as herniation may increase with positive-pressure ventilation [24, 31].
Pneumomediastinum, the Macklin effect
Heart and pericardium
Aorta, great vessels
Soft tissue haematoma
Soft tissue haematomas may occur during direct compression trauma when rib fractures cause laceration of veins or arteries. Soft tissue haematoma may become life-threatening if the patient is under anticoagulant therapy. If it is arterial in origin, embolisation is indicated. Breast haematomas can be serious in direct impact or compression injuries .
Coexisting and associated injuries
Pulmonary contusion, laceration
Upper rib fracture (first three ribs)
Brachial plexus, subclavian vessels
Lower rib fractures (last four ribs)
Airway injury, oesophageal injury
Airway injury, lung injury, oesophageal injury
Sternoclavicular fracture (posterior sternoclavicular dislocation)
Mediastinal vessels, tracheal injury, oesophageal injury
Haemopneumothorax, lung injury, spine and clavicle fracture, subclavian vessels, brachial plexus
The authors would like to thank the following radiologists for their valuable contributions: Aristi Kouri (Nicosia, Cyprus), Christoforos Schizas (Nicosia, Cyprus), Jean Seely (Ottawa, Canada), Rennae Thiessen (Vancouver, Canada), Argiro Voloudaki (Heraklion, Greece).
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