Blunt Chest Trauma

• Rapidly available, initial screening study for evaluation of blunt thoracic trauma 1-4

• In the context of blunt trauma where there is concern for spinal injuries, this is usually supine

• Life-threatening injuries requiring immediate management such as haemothorax and tension pneumothorax are readily demonstrated on CXR 5

• Contrast-enhanced computed tomography (CT) is the modality of choice for diagnosing suspected thoracic injury in trauma, including blunt thoracic aortic injuries and thoracic spine injuries 6-11

• CT of chest in trauma patients has superior sensitivity and specificity, especially for blunt thoracic aortic injury and thoracic spine fractures. It can also provide more detail about abnormalities demonstrated on CXR. However, there is disagreement on whether chest CT should be routinely performed in all patients with a history of blunt trauma 12-15. Many guidelines recommend against the excessive use of CT when it is not warranted, however there are no specific criteria 4, 16, 17

• Currently, the decision to proceed to CT must be based on clinical judgement, taking into account the mechanism of injury, patient risk factors, clinical signs and symptoms, CXR findings, other investigations and disposition to avoid unnecessary overuse

• The majority of blunt aortic injuries are caused by high energy mechanisms with rapid deceleration of the thorax, including motor vehicle crashes, pedestrian vs car, falls, and crush injuries 6, 18-23

• There is a correlation between thoracolumbar spine (TLS) fractures and falls greater than 3m, ejection from a motor vehicle, motorcycle crashes, high-velocity injuries and pedestrians struck by motor vehicles 9. The mean collision speed of patients sustaining thoracic and lumbar spine injuries is 40 km/h 24

• Other major visceral injuries such as cardiac, tracheobronchial tree, oesophageal or diaphragmatic injury occur more commonly in penetrating trauma. When they occur in blunt trauma, there are usually other severe injuries present as they occur in very high-energy transfer mechanisms, most commonly motor vehicle crashes, with or without crush injuries 7, 25, 26

• Fear of missing potentially life-threatening injuries has led to increased use of chest CT, including as part of the “pan scan”, however this approach has its disadvantages, including:

• increased risk of radiation-induced cancer, particular in young populations 13, 27

• increased cost 13

• increased time in emergency departments 28

• Despite routine CT use, there has been no increase in the number of detected life-threatening injuries (28). A number of studies have reported that routine chest CT rarely identifies injuries that would have changed management 14, 15, 29. Common occult injuries detected on CT include small pulmonary contusions, rib fractures and small pneumothoraces not requiring chest drain insertion

Clinical decision rules to predict clinically significant injury on chest CT

• Observational studies have identified features that were significantly associated with significant thoracic injuries requiring intervention, including thoracic aortic injuries. A number of authors have attempted to define clinical decision making tools that identify patients at low risk of thoracic injury in blunt chest trauma, using a combination of clinical findings, mechanism of injury and CXR findings

• Use of these rules aims to reduce the number of normal chest CTs performed

• These clinical decision rules are yet to be externally validated

• A limitation of these studies is that they do not identify whether CT findings change management compared with CXR findings alone

• Currently, there are no clinical decision rules to identify which patients, with injuries on CXR, will not benefit from additional CT 

A high index of suspicion is advised in high-energy mechanisms of injury such as high-speed road trauma >60 km/h or falls from height

• In a haemodynamically stable patient, normal ECG and normal troponin has a high negative predictive value for cardiac trauma 34, 35

• In patients with haemodynamic instability, arrhythmias or elevated troponin, transthoracic echocardiography (TTE) can be used to identify causes of unexplained hypotension or arrhythmias including pericardial effusions and tamponade, wall motion abnormalities and valvular lesions 35, 36. However, TTE should not be used as a screening modality for cardiac trauma 35

• In cases where TTE is technically difficult, transoesophageal echocardiography (TOE) may be used if available 36

• Cross-sectional imaging with ECG-gated CT or MRI helps differentiate structural injuries from myocardial infarction and blunt cardiac injury (e.g. myocardial contusion) 25, 35-37

• MRI is generally not feasible in unstable patients

• Cardiac contusion is one of the most common cardiac injuries in patients with blunt chest trauma, reportedly affecting 3-56% of patients 38. It occurs most commonly in motor vehicle crashes, either from a direct blow to the chest (e.g. chest hitting steering wheel) or in rapid deceleration (as the heart strikes the internal sternum). The right ventricle is more commonly affected, as it is situated more anteriorly in the chest. Symptoms may range from palpitations or precordial pain to haemodynamic instability

• Other blunt cardiac injuries may include injury to internal cardiac structures such as the ventricular septum, valves, chordae tendineae, papillary muscles. Damage to the cardiac musculature or coronary vessels may result in a traumatic pericardial effusion and tamponade, requiring urgent intervention 39

Indications for radiological screening of thoracolumbar spine (TLS) trauma include:

• high-energy mechanism of injury

• neurologic signs consistent with TLS injury

• back pain or pain on palpation

• concomitant c-spine fracture

• altered mental status

• evidence of intoxication with ethanol or drugs

High-energy mechanisms of injury include falls >3 m, high-velocity motor vehicle crashes, pedestrian vs vehicle or any other high-velocity injury.

• Tracheobronchial injuries (TBI) are rare but potentially life threatening. They occur more commonly in penetrating trauma but can occur in significant blunt trauma 26

• CT can show evidence of TBI but bronchoscopy is the diagnostic modality of choice to confirm or exclude TBI 40-42

• In older studies, CT was able to identify the site of TBI in 71-94% of cases 43, 44. A recent observational study included 5 cases of TBI that were all detected on CT 45

• Rapid detection depends on a high suspicion of injury. TBI should be suspected if the patient has severe dyspnoea, haemoptysis, subcutaneous emphysema, mediastinal or cervical air on radiograph, or a persistent pneumothorax or air leak following chest tube insertion 41, 42

• The hallmark of the intrathoracic tracheal injury is persistent, progressive, and severe pneumomediastinum unrelieved by tube thoracostomy 46

• Diaphragmatic injuries (DI) can be a diagnostic challenge. Reported prevalence varies greatly with 0.46-8% of patients developing some form of DI after major blunt trauma to the lower chest or abdomen 47-49. The majority (75%) of DI involves the left hemidiaphragm, and left sided abdominal organs (particularly stomach & spleen) are most commonly found herniating into the chest 50

• DI rarely occurs in isolation, and is often accompanied by more serious injuries to other organs. This may delay diagnosis of DI and affects up to 66% of patients at initial presentation 51. Due to the progressive herniation of visceral organs and potential strangulation, delayed diagnosis is associated with 50% morbidity and mortality rate 51

• Plain chest radiographs (CXR) may sometimes demonstrate obvious DI (e.g. presence of herniated viscera within the chest cavity), although signs can be subtle. The accuracy for diagnosis of DI is relatively low - 27-60% of left-sided injuries and 17% of right-sided injuries 52. Sensitivity is reported around 24-50% 52

• Improvements in CT have made it generally the modality of choice for diagnosing diaphragmatic injuries (53). CT has a sensitivity of 71-100% and specificity approaching 100% 52, 54-56

• MRI can be used as a problem-solving tool when findings are inconclusive at CT, but is not suitable for unstable patients 52, 53, 57. Respiratory and cardiac-gated sequences minimise motion artefact 53

• Injury to the oesophagus is often accompanied by injury to adjacent structures, including the trachea and vascular structures 58

• Both plain films and CT are unable to demonstrate direct signs of oesophageal rupture, although they show indirect signs like mediastinal haematoma, pneumomediastinum, and pneumothorax 58-60

• When injury to the oesophagus is suspected, both contrast studies and endoscopy can be used to confirm the diagnosis 46, 58, 59. Previously oesophagography was the mainstay of oesophageal evaluation, a fluoroscopic examination involving swallowing contrast material. Contrast swallow can now also be administered with CT 60

Thoracic Aorta Injury (Suspected)

Thoraco-Lumbar Spine Injury (Suspected)