A majority of sternal fractures occur transversely across the midbody, but may also be seen at the manubrium. In general, the sternum is initially imaged with PA and lateral chest radiographs, but more sensitive dedicated sternal views are also available when clinical suspicion is high. The lateral chest x-ray provides more value in identifying sternal fractures and their degree of displacement than the PA view. With the advent of later generation CT scanners and their expanded use in trauma patients, CT often identifies sternal fractures and is greater in sensitivity and specificity than plain radiographs. CT is also useful to identify associated thoracic or cardiopulmonary injuries, which are of greater clinical importance than the fracture itself.
Sternal fractures are usually associated with direct blunt traumatic injury to the chest sustained in a motor vehicle crash, but stress fractures may also be encountered. Sternal fractures are painful injuries resulting in decreased respiratory excursion and pulmonary atelectasis, so outpatient management should consist of adequate analgesia and incentive spirometry. Sternal fractures may be associated with acute life-threatening intrathoracic injuries such as cardiac contusion, mediastinal injury and bleeding, aortic injury, flail chest, pneumothorax or hemothorax, pulmonary contusions and lacerations, and compression fractures of the ribs and thoracic spine. Because of the high morbidity and mortality of concomitant injuries, a high index of suspicion should be held for associated injuries when sternal fracture is diagnosed.
Figure 4.2 ▪ Sternum Fracture.
A, B: An axial and a sagittal CT image of the chest in another patient show a mildly displaced sternal fracture with hematoma formation about the fracture site. Anteriorly displaced sternal fractures, such as this, have a high association with flexion injury of the thoracic spine.
Identification of associated injuries carrying high morbidity and mortality is of paramount importance when considering the diagnosis of sternal fracture.
Dedicated sternal views are more sensitive than PA and lateral chest radiographs in identifying sternal fractures by changing the viewing angle and exposure of the radiograph. These should be considered when clinical suspicion is high and chest radiographs are negative, unless a CT is to be performed.
A clue to look for a subtle sternal fracture on CT is retrosternal hematoma formation.
Anteriorly displaced sternal body fractures are commonly associated with flexion injuries of the thoracic spine.
Fractures of the medial third of the clavicle and sternoclavicular dislocations are difficult to visualize on plain radiographs of the shoulder or the chest. Because of radiographic technique, some subtle injuries will be better detected on dedicated clavicular views. If one suspects a displaced sternoclavicular injury, a contrasted CT scan should be obtained. CT is important not only in determining if underlying structures are being compressed by the medial clavicle but also perhaps in elucidating associated intrathoracic injuries. Findings may include demonstration of sternoclavicular disruption, fractures of the sternum and clavicle, mediastinal hematoma, and vascular injury to aorta and its branches or the superior vena cava. These injuries usually occur in the setting of high-energy trauma and concomitant intrathoracic injuries such as pneumothoraces, pulmonary contusions, and head and neck injuries are commonly present.
Injuries to the sternoclavicular joint are potentially life-threatening by causing injury to underlying vital mediastinal structures. Dislocations at the sternoclavicular joint may be either anterior or posterior, with posterior dislocations potentially resulting in injury to adjacent structures through direct anatomical compression. Anterior dislocations can occur as the arm is forcefully abducted above the head. Patients with anterior dislocations tend to have much less pain than patients with retrosternal dislocations. Posterior dislocations may be accompanied by other symptoms depending on the structure being compressed such as hoarseness, stridor, or venous congestion of the head and neck. Both dislocations have pain exacerbated by movement of the upper extremity.
Anterior dislocations can be treated with conscious sedation and closed reduction. Once reduced, the clavicle should be immobilized for 4 to 6 weeks. If recurrent dislocations occur, surgical fixation may be required. Posterior dislocations may require urgent reduction if significant compression of underlying structures is present.
The medial aspect of the clavicle may not be adequately visualized on plain radiographs. If the clinical setting suggests a sternoclavicular dislocation, contrasted CT scan of the chest provides more information on not only the extent of the clavicular injury but also the status of the underlying vascular structures, trachea, and lung.
Many sternoclavicular dislocations in patients younger than 25 years old are actually fractures through the physeal plate and represent Salter–Harris type I or II fractures.
Plain chest radiography is generally the initial study used to detect rib fractures, although the overall sensitivity of CXR is poor. Sensitivity can be increased by recognizing thickening of the extrapleural soft tissues commonly accompanying these injuries. If higher sensitivity is desired, oblique rib views can be obtained. Plain radiography may miss fractures occurring in the costal cartilages unless the cartilage is heavily calcified. CT scanning is far more sensitive than plain radiographs in detecting rib fractures, but the test is generally unnecessary unless other injuries are of concern.
Figure 4.6 ▪ Subtle Rib Fracture.
Oblique image of the right thorax demonstrates a minimally displaced fifth anterolateral rib fracture. Note the slight amount of extrapleural soft tissue thickening accompanying this acute injury (arrow). See the section “Diagnosis: Flail Chest” for additional examples of rib fracture.
Rib fractures are clinically suspected based on history of direct trauma to the area of the chest and pain exacerbated by movement, inspiration, cough or sneezing, and palpation of the injured area. Depending on the amount of energy transferred, rib fractures may be isolated or associated with underlying injuries. For patients with isolated trauma to the chest without major force, the choice of an upright PA chest x-ray is a reasonable option. Rib radiographs are rarely necessary, as the results do not change management in most cases.
Patients whose mechanism of injury, physical exam, or symptoms suggest underlying pulmonary or abdominal injury, the clinician may elect to proceed to CT scan. CT is more sensitive for detecting injury to underlying lung and pneumothorax. A contrasted CT is used to diagnose injury to pulmonary vasculature and detection of intra-abdominal and retroperitoneal injuries. Isolated rib fractures are not life-threatening in and of themselves, but are extremely painful and may cause life-threatening complications, especially in elderly patients with borderline pulmonary reserve. Due to splinting of the chest wall, there is limitation of deep breathing and subsequent atelectasis and resultant pneumonia. For this reason, pain control, incentive spirometry, and pulmonary toilet are the mainstays for the treatment of rib fractures.
Conventional upright PA view is far more sensitive for detection of rib fracture than a supine portable AP (“trauma”) view; CT may show fractures not otherwise visible on plain radiographs.
For patients with normal CXR in whom it is important to determine the presence of isolated rib fracture, ultrasound at the site of maximal tenderness may be of benefit. The fracture and subperiosteal hematomas can be detected in the osseous and cartilaginous portions of the rib. However, ultrasound is less helpful in detecting upper rib and subscapular fractures.
PA and lateral views of the chest serve to evaluate for complications of rib injury, such as pneumothorax, pulmonary contusion, or hemothorax. Dedicated rib views for localization of nondisplaced fractures are generally unnecessary.
With scapulothoracic dissociation, chest x-ray may show significant lateral displacement of the scapula, indicating severe injury to the upper extremity and what amounts to a closed amputation of the extremity. Patients often have associated fractures of the clavicle, scapula, and humerus that may be evident on plain radiographs as well as intrathoracic injuries best demonstrated on CT scan. Selective angiography is needed to diagnose injuries to the subclavian and axillary arteries. MRI is the imaging modality of choice for associated brachial plexus injuries and may also demonstrate muscular and ligamentous injuries in detail.
Scapulothoracic dissociation is a rare injury most often resulting from motor vehicle collisions, especially in motorcyclists. The injury is associated with complete or partial injuries to muscles of the shoulder girdle, brachial plexus, and arteries supplying the upper extremity. Patients may complain of motor weakness and decreased sensation of the arm along with severe pain. Neurovascular injuries may be difficult to detect in intubated patients, underscoring the importance of adequate imaging in the multisystem trauma patient. On physical examination the shoulder area may be massively edematous or the upper extremity may be mottled, making vascular injury more apparent. Complete injuries to the brachial plexus may result in the need for amputation because the limb is rendered functionless.
Test strength and sensation of the upper extremity in all distributions of the brachial plexus and assess vascular integrity in all patients with fractures of the scapula and clavicle.
Compare the distance from the medial border of the scapula to midline on both sides of the thorax with the arms in similar position. A widening of this space may indicate scapulothoracic dissociation.
If patient’s condition allows, obtain MRI to further delineate injuries to the brachial plexus.
Complete disruption of the brachial plexus (even more so than vascular injury due to collaterals) portends dismal prognosis for limb salvage.
Figure 4.7 ▪ Scapulothoracic Dissociation.
A, B: Very wide separation and displacement at the acriomioclavicular joint with separation of the scapula from the chest wall. C: An arteriogram in the same patient with abrupt cutoff or occlusion of the left subclavian artery (arrow). (Image used with permission from David A. Taber, MD.)
Flail chest occurs when there are fractures of 3 or more consecutive ribs with at least 2 fracture sites of each rib, creating a free-floating segment of the thoracic wall. Most patients with flail chest have other associated intrathoracic traumatic injuries. Plain chest radiographs may demonstrate multiple consecutive rib fractures, but CT scan better identifies the flail segment and other associated thoracic injuries such as pneumothorax and pulmonary contusion.
The diagnosis of flail chest can be made clinically by observing a paradoxical motion of the chest wall in a spontaneously breathing patient. With inspiration, the uninjured chest moves up and out while the flail segment is pulled inward due to the movement of the flail segment in response to negative intrathoracic pressure. This flail segment causes focal chest wall instability and atelectasis, pneumonia, and ARDS. Flail chest may not be obvious clinically in an intubated patient and the diagnosis may have to be made radiographically. The force that fractures the segment of ribs is usually enough to cause significant underlying pulmonary contusion. Depending on the patient’s underlying pulmonary reserve, the extent of the lung injury, and the size of the flail segment, patients may require mechanical ventilation. If the flail chest is an isolated injury, the patient will need aggressive pulmonary toilet and pain control for the multiple rib fractures. If the size of the flail segment is large enough, a traumatic pulmonary herniation can occur through this defect. This is a rare injury and usually occurs through the anterior chest wall where there is little soft tissue support.
On chest x-ray, segmental rib fracturing may not be obvious, as often only 1 of the 2 fracture planes is visible.
CT scan may detect lung herniation through the flail window that mandates urgent surgical repair if large or causing ventilatory compromise.
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