Salvatore J.A. Sclafani
Trauma imaging may be used to provide rapid and broad surveys when clinical evaluation is likely to be incomplete or unreliable or used to characterize recognized injuries as part of treatment planning. And it may be used to guide observational, operative, and minimally invasive decisions. Therefore, trauma imaging may inform clinical diagnosis and can guide, but not make, management decisions.
Imaging strategies are affected by the proximity of available imaging technology to the resuscitation area, the capabilities of the imaging equipment, the experience and availability of radiology technologists performing emergent imaging procedures, and timely access to expert interpretation and reporting.
The timing of diagnostic imaging should reflect the needs of individual patients and the local system. With some exceptions for image-guided endovascular hemostasis, hemodynamically unstable patients should be resuscitated prior to imaging according to accepted guidelines and recommendations. In order to enhance efficiency, triage priorities for imaging should be based on the acute needs for accurate information that can be used to direct treatment of the patient. Close cooperation and open communication between the emergency physicians, traumatologists, consultants, nurses, imaging technologists, and radiologists are always necessary to optimize any imaging assessment.
One chapter cannot reasonably teach interpretation of diagnostic images. Therefore, a general approach to the role of imaging in the evaluation of selected clinical scenarios is presented, while pointing out the advantages and disadvantages of a given imaging strategy.
INITIAL IMAGING FOR THE ASSESSMENT OF BLUNT TRAUMA
As part of the secondary survey of victims of blunt trauma, an imaging survey of the chest (supine anteroposterior [AP] chest with 10° of caudal angulation of the central x-ray beam), pelvis (supine AP pelvis), and cervical spine (horizontal-beam, cross-table lateral cervical spine obtained with bilateral arm pull) may be performed, if clinical evaluation alone is deemed insufficient (Fig. 15-1). The goals of these initial imaging studies are to identify life-threatening, but clinically occult, injuries such as an unstable pelvic fracture, hemomediastinum, or instability of the cervical spine.1,2
FIGURE 15-1 Trauma series. This 27-year-old unrestrained left rear seat passenger sustained multiple injuries, superfluous in a high-speed side-impact crash. (A) Anteroposterior (AP) recumbent chest radiograph shows hyperexpanded and hyperlucent left hemithorax with “deep sulcus” sign (short white arrow) and rightward mediastinal shift (double-ended arrow) due to left tension pneumothorax. Short black arrows show multiple displaced rib fractures. Asterisk shows irregularity of left hemidiaphragm, which strongly suggests herniation of abdominal contents through left diaphragmatic laceration. (B) AP pelvis radiograph shows lateral-compression-type pelvic ring disruption consisting of bilateral iliopubic and ischiopubic ramus and left sacral fractures (long arrows) with sacroiliac joint disruptions (short arrow). (C) Cross-table lateral cervical spine radiograph is grossly normal to C5. Therefore, this constitutes a nondiagnostic study. Craniocervical alignment should be assessed and may be easily overlooked. Dens–basion distance (white double-ended arrow) is normally no greater than 12 mm. Posterior axial line represents cephalad extension of posterior cortex of C2 body (and is normally no more than 12 mm posterior or 4 mm anterior to basion) (black double-ended arrow). Anterior atlantodens interval is normally no greater than 3 mm in adults and 5 mm in children (8 years and younger). Laminar point of C2 (laminar points are most anterior extent of neural canal margin of lamina) should be within 1.5 mm of line connecting laminar points of C1 and C3. (D)Coronal image of right upper quadrant from focused abdominal sonography for trauma (FAST) shows free intraperitoneal fluid in anterior subhepatic (Morison’s) space (arrows), compatible with hemoperitoneum.
The trauma resuscitation “ABCD” strategy may be extended to this “trauma series.” Verification of the integrity of the airway (and other tubes and lines) should be specifically made on the x-rays of both the chest and lateral cervical spine. Radiographic pulmonary opacities associated with hypoxemia include pulmonary contusions, aspiration pneumonitis, and atelectasis (including collapse due to aspirated dental or foreign debris). Tension pneumothorax and hemothorax are typically detected on clinical examination, while clinically occult pneumothoraces or hemothoraces are commonly shown by chest x-rays as a “deep sulcus” sign and generalized hemithoracic opacity, respectively. Other injuries, such as rupture of the hemidiaphragm, flail chest, pneumopericardium, and pneumomediastinum and hemomediastinum, are often diagnosed or suggested by initial conventional x-ray findings. Hemodynamic instability may be due to extraperitoneal hemorrhage from disruption of the pelvic ring. Biomechanically unstable disruptions of the pelvic ring are almost always shown on AP radiographs and may be associated with injuries to the bladder and urethra. In addition, pelvic x-rays may show hip dislocations and fractures of the acetabulum and proximal femur.
A technically adequate (C1–T1) lateral x-ray of the cervical spine provides a reasonable “screening” study to identify most unstable cervical injuries. It may provide important information regarding the best technique for airway control and may confirm that spinal shock from a vertebral fracture is the cause of unexplained hypotension.
Focused Abdominal Sonography for Trauma (FAST)
FAST is performed as part of the secondary survey in victims of torso trauma (see Chapter 16). It is a temporally (2–5 minutes) and anatomically limited real-time sonographic examination whose core components include a direct sonographic search for free fluid in the pericardial sac, both upper abdominal quadrants, and the intraperitoneal recesses adjacent to the urinary bladder. Scanning is optimally performed in two orthogonal planes (e.g., longitudinal and transverse), and intraparenchymal and retroperitoneal injuries are generally not sought but are sometimes seen. FAST may be extended to detect a hemothorax and pneumothorax. Commercially available, portable handheld real-time imaging devices are technically adequate to perform FAST.
FAST is uniformly accurate for the detection of intraperitoneal fluid with moderately large volumes >400 cm3 (at smaller volumes, accuracy varies with user experience).3–5 Unfortunately, isolated hepatosplenic injuries with minimal or no hemoperitoneum represent as many as one third of solid organ injuries.6,7 Fortunately, small isolated intraparenchymal lesions with less than 250 mL of intraperitoneal blood rarely require endovascular or surgical intervention (liver <1%, spleen <5%).8 False-positive interpretation of FAST images can result from improper machine settings (gain), sonolucent perinephric fat (which is rarely sonolucent in both axial and coronal scanning planes), fluid-filled loops of bowel, bladder, various types of fluid-filled intra-abdominal cysts, and physiological or nontraumatic free fluid (ascites). FAST is widely available, inexpensive, and noninvasive, uses no ionizing radiation, and can be repeated serially. In the setting of patients admitted with severe hemodynamic compromise or obvious hemorrhagic shock, FAST can establish the abdomen as a source of hemorrhage within a few seconds.
The FAST does, however, require operator training and experience for reliable performance and interpretation, and these can limit its value. In addition, FAST is not very valuable in patients with pelvic fractures as a hemoperitoneum may be present in the absence of visceral injury. Another important limitation of FAST is that isolated injuries to the bowel and retroperitoneal injuries are not reliably detected. While a systematic review of the literature would not support the use of FAST as a replacement for DPL and computed tomography (CT) in blunt abdominal trauma, many trained surgeon-sonographers use it on a daily basis with great accuracy.9
Hemodynamically stable patients who have suffered blunt trauma with a clinical presentation suspicious for injury to the bowel (e.g., lap belt sign and associated Chance or flexion-distraction injury to the thoracolumbar spine) or hematuria (e.g., gross hematuria in all age groups, microscopic hematuria defined as >50 red blood cell count per high-power field in individuals 16 years old and younger, or in those older with at least one documented episode of hypotension) should undergo intravenous contrast-enhanced CT of the abdomen and pelvis.
COMPREHENSIVE IMAGING FOR BLUNT POLYTRAUMA
Victims of blunt multiple trauma often receive portable imaging in the trauma suite and are then triaged based on their hemodynamic status to the operating room, intensive care unit, or angiography suite for ongoing resuscitation or remain in the trauma center for completion of secondary and tertiary surveys, including initial imaging. Typically, this consists of CT for clinically appropriate imaging (e.g., head, neck, chest, abdomen, and pelvis) for the most severely injured, but hemodynamically stable patients. Subsequently, conventional x-rays of the extremities and spine may be obtained. Less severely injured individuals may take a slightly different route with conventional x-rays preceding CT and directed at abnormalities found by clinical examination or prior imaging.
There are some who advocate the “pan scan,” also known as the “head to toe” CT, as a method of detecting many injuries. This paradigm advocates utilization of high-resolution thin collimation image acquisition to include CT scanning of the head, face, soft tissue of the neck, the chest, the abdomen, and pelvis, including the acetabulum and the spine. While it does provide excellent coverage, it exposes patients to much radiation and is not recommended as a general rule. On the other hand, the “pan scan” has value in a high-volume facility with considerable imaging resources and the need for rapid screening.
Multidetector Computed Tomography (MDCT)
MDCT scanners have changed the way CT is used in imaging trauma.10,11 MDCT scanners, with 16 or more detectors, can provide nearly equivalent resolution in any imaging plane with progressively shorter scan times. This greatly improves the quality of both two-dimensional (multiplanar) and three-dimensional reformations. The rapidity of multidetector helical scanning and enormously improved designs of x-ray tubes allow for single-session scanning from cranial vertex to pelvic ischia in less than 90 seconds.12,13 This includes two- and three-dimensional reformations of the thoracic and abdominal aorta, maxillofacial skeleton, cervical and thoracolumbar spines, and pelvis and acetabulae.
With appropriate anticipation and proscription, scanning parameters allow raw axial data to be reconstructed using different thicknesses (e.g., 5-mm-thick slices for abdominal viscera and 2.5-mm-thick slices for CT aortography). Thus, individual thin-section imaging of parts of the body in addition to the CT survey is superfluous, increases ionizing radiation unnecessarily, and increases time-out of the critical care area. This previous standard of detailed specialized imaging of the face and spine should be abandoned.
Computed Tomography of the Head
Axial noncontrast CT scanning remains the reference standard in patients with acute craniocerebral trauma, guiding initial decisions regarding the clinical management.14,15 Indications for CT of the cranium include the following: (1) objective evidence of closed injury to the brain, including decreased level of consciousness; (2) cranial or facial deformity; (3) hemotympanum; or (4) evidence for leakage of cerebrospinal fluid (Figs. 15-2 to 15-4). Clinical criteria reliably predict significant intracranial injury (ICI) and help determine which patients will require CT scanning of the head. In children,17 significant ICI is extremely unlikely in any child who does not exhibit at least one of the following high-risk criteria: (1) evidence of significant skull fracture; (2) altered level of alertness; (3) neurological deficit; (4) persisting vomiting; (5) scalp hematoma; (6) abnormal behavior; or (7) coagulopathy.16 More generically, minor trauma to the head may lead to surgically important injuries to the brain, and liberal utilization of CT is appropriate among individuals who have sustained “high-risk” mechanisms. These clinical criteria are not as reliable in the elderly patient.17 Single-photon emission CT (SPECT) may be helpful in initial diagnostic evaluation of patients with mild traumatic brain injury (MTBI), particularly for those with normal CT findings and associated post-traumatic amnesia (PTA), postconcussion syndrome (PCS), and loss of consciousness.18
FIGURE 15-2 Epidural hematoma. Helmetless bicyclist in crash. (A) Lateral scout scanogram shows linear lucency compatible with fracture (arrows). (B) Axial computed tomography (CT) displayed at bone window shows minimally displaced right parietal skull fracture with overlying subgaleal hematoma. Fracture is marked by white arrow and barely visible hyperintensity of extra-axial blood collection by arrowheads. Bone windows are inadequate to identify intracranial hemorrhages. (C) Axial CT at brain windows shows epidural hematoma (arrowheads), associated midline shift (short arrow), and subgaleal hematoma (asterisk). (D) Axial CT at level of the suprasellar cistern, brain windows, shows epidural hematoma (black asterisk), asymmetric widening of perimesencephalic cistern (arrow), which suggests impending uncal herniation. (Reproduced with permission from D. K. Hallam.)
FIGURE 15-3 Blunt head injury: Diffuse axonal injury. This 48-year-old helmeted female motorcyclist sustained diffuse axonal injury. (A) Axial computed tomography (CT) at level of lateral ventricles demonstrates intraventricular hemorrhage (asterisk), “tear” hemorrhage in posterior limb of internal capsule (white arrow). Black arrow denotes splenium of corpus callosum, which appeared normal by CT. (B) Axial magnetic resonance imaging (MRI) using FLAIR shows clot in right lateral ventricle as extended region of low signal (asterisk), edema associated with tear hemorrhage (white arrow), and splenium of corpus callosum (black arrow) to better advantage. (C) MRI gradient recalled echo (GRE) sequence shows low signal intensity of magnetic susceptibility due to hemorrhage in region of posterior horn of internal capsule (white arrow) and in right lateral ventricle (asterisk). Splenium of corpus callosum has region of mildly increased signal intensity compatible with edema (black arrow). In general, the more central findings of diffuse axonal injury, the greater the degree of neurological disability. (Reproduced with permission from W. A. Cohen.)
FIGURE 15-4 Patterns of herniation. (A). Axial computed tomography (CT) at level of suprasellar cistern shows extensive subarachnoid hemorrhage extending from lateral aspect of suprasellar cistern (1), into the sylvian fissure (2), circumferentially about brainstem and perimesencephalic cistern (3), along tentorium (4), and interpedunculate cistern of mesencephalon (5). Entrapment of lateral ventricles is shown as dilatation of temporal horns (white arrows). Brainstem appears relatively lucent and heart shaped, with pointed inferior portion of heart due to “beaking” of mesencephalon due to upward herniation. (B) Subfalcine shift. Axial CT, at brain windows, at level of lateral ventricles shows marked rightward subfalcine shift (black arrow), quantified as distance from third ventricle to line connecting anterior and posterior portions of sagittal sinus (which tend not to shift due to their fixed relation to calvarium). Note extensive hemorrhage in left frontal parietal region extending into left ventricle. (Reproduced with permission from W. A. Cohen.) (C) Uncal herniation. Axial CT at level of middle cranial fossa shows large left temporal hematoma (black asterisk) associated with left uncal herniation (small white arrows). Enlargement of right temporal horn (large white arrow) is compatible with obstruction to cisternal system. (Reproduced with permission from A. B. Baxter.) (D) Combined upward and downward herniation. This is a 38-year-old with posterior leukoencephalopathy due to hypertension. Axial CT at level of suprasellar cistern shows enlargement of lateral ventricles and right temporal horn (long white arrows). Suprasellar cistern is poorly seen. Perimesencephalic cisterns are absent and posterior aspect is beaked, compatible with superior herniation from posterior fossa. Upward herniation is also shown by the cerebellar vermis filling the subtentorial cisternal space (multiple small arrows). (Reproduced with permission from W. A. Cohen.) (E) Same patient as in (D). Sagittal T1-weighted magnetic resonance imaging shows tonsillar herniation through the foramen magnum (arrowheads), as well as superior herniation of cerebellum and mesencephalon at level of tentorium (white arrow).
Images are reconstructed using both bone and soft tissue algorithms and viewed at bone windows and two different soft tissue windows (“brain” and “blood”).
CT scanning is highly sensitive for the detection of extra-and intra-axial hemorrhage and mass effect, as well as for soft tissue injuries to the globe and paranasal sinuses. In patients with diffuse axonal injury, however, CT may even be normal and discordant between the severity of the clinical brain injury and radiographic findings. On a cautionary note, skull fractures aligned in the plane of scanning may be subtle, and review of the scout views used to plan the CT head study may alert the clinician to such fractures. Except for medicolegal imaging of nonaccidental trauma (child abuse), conventional x-rays of the skull are usually not necessary.19,20
Computed Tomography of the Maxillofacial Skeleton
Indications for specific facial CT scans include the following: (1) deformity or instability of the maxillofacial structures found by physical examination; (2) deformity, opacification, or fracture of the periorbital or paranasal sinus shown on head CT; and (3) clinical evidence for leakage of cerebrospinal fluid (Fig. 15-5). The mnemonic “LIPS-N” (lip lacerations, intraoral lacerations, periorbital contusions, subconjunctival hemorrhage, or nasal lacerations) provides a helpful tool during clinical examination of trauma patients, also, given the high association between any of LIPS-N lesions and facial fractures.21Absence of opacification of a paranasal or periorbital sinus on CT generally excludes surgically important injury to the maxillofacial skeleton.22
FIGURE 15-5 Facial fracture: zygomaticomaxillary complex (ZMC) fracture with associated nasoethmoidal orbital complex fracture. This 54-year-old male sustained a blow to the face in a motorcycle crash. (A) Anteroposterior (AP) scanogram shows loss of symmetry to orbital volumes, with elliptoid enlargement of right orbit. Associated indistinctness of orbital floor and lateral maxillary sinus walls is also present. Opacification of right maxillar sinus is shown. (B) Axial computed tomography (CT) image at the level of zygomatic arches shows depression and overriding apposition of impacted zygomatic arch fracture (lateral white arrow), posterolateral maxillary sinus wall disruption (posterior arrow), and segmental comminuted fracture of anterior maxillary wall (anterior arrow). Medial to this anterior arrow is the base of the nasofrontal process of the maxilla with a fractured nasolacrimal duct just posterior to it. Internal rotation of the nasofrontal process of the maxiilla and associated fracture of the nasolacrimal duct are not portions of ZMC fracture and represent an associated nasoethmoidal orbital complex fracture. (C) Coronal CT reformations shows separation of right frontozygomatic suture (lateral and superior arrow), disruption of orbital floor (white arrow projected over orbit), and lateral maxillary wall (inferior white arrow). (D) Sagittal CT reformation shows associated vertical fracture of right ascending ramus of mandible, with anterior subluxation at temporomandibular joint (white and black arrows, respectively). (E) Three-dimensional CT reformation gives an overview of complex fracture of zygomaticomaxillary region and right mandibular fracture. It is important to note that spatial resolution is lost with three-dimensional reformations, although spatial comprehension is often improved. (F) Three-dimensional CT reformation shows depression of right zygomatic arch and loss of projection of the right zygoma (flat cheek).
Images need be acquired in only one plane, usually the axial, with reformations in the orthogonal plane, or as reconstruction from a CT of the cranium obtained from an appropriately prescribed study (i.e., 1.00- to 1.25-mm slice thickness). Spiral CT, and especially MDCT, can be reformatted into 2D reformations in the orthogonal planes (e.g., coronal, sagittal, oblique sagittal) and 3D reformations, using 1.0- to 1.25-mm thick sections in the axial plane, without loss of image quality and accuracy, stress on the neck, and further radiation.
Primary axial images are obtained using 1.0- to 1.25-mm slice thickness from above the frontal sinus to the hard palate or maxillary alveolus. These are commonly extended to include the mandible to aid surgical diagnosis, especially in children, as fractures of the condyle of the mandible are the most commonly missed maxillofacial fractures in this age group.23–25 Reformations in the coronal and sagittal planes should be perfectly orthogonal to the axial images. Reformations in the sagittal plane may be performed either relative to the coronal plane or as sagittal oblique reformations parallel to the optic nerve, if evaluating for blowout fractures of the orbital floor.26
While CT is highly accurate at detecting and characterizing surgically important injuries, it does not show the magnitude of osseous fragmentation found at surgery in complex fractures. Orbital and maxillary fractures should heighten suspicion of more complex fractures. Although its incremental diagnostic value is small, 3D-CT reformation appears to be the best imaging method for the global portrayal of complex maxillofacial injury patterns such as Le Fort–type fractures. This technique provides valuable information on spatial relationships and is particularly useful in planning operative treatment.27–30
On the other hand, axial and 2D reformations best portray defects in soft tissue, interposition of osseous fragments, and herniations of soft tissue (e.g., orbital floor blowout fractures) and are best for quantifying size of fractures.26,31
Maxillofacial CT delivers a significant radiation dose to the orbits and to the soft tissues of the neck (e.g., thyroid). This is an important consideration when imaging children.32
Imaging for Soft Tissue Injuries of the Neck
Clinical findings for blunt injury to the aerodigestive tract include subcutaneous crepitus, hemoptysis, hoarseness, neck pain, and abrasions or hematomas (e.g., from the shoulder harness of a three-point restraint; Figs. 15-6 and 15-7). In the absence of a pneumothorax, x-ray findings that suggest injury to the aerodigestive tract include parapharyngeal or precervical emphysema, soft tissue swelling, or fracture of the larynx or hyoid bone on the lateral image of the cervical spine. X-rays of the neck for the soft tissues, however, are superfluous as the image resolution is inferior and the imaging findings are not substantive. CT is the standard of care for imaging this area.
FIGURE 15-6 Soft tissue neck injury. This is a 15-year-old male motorcyclist with “clothesline injury,” causing tracheal and esophageal transection. (A) Lateral view of cervical spine shows extensive subcutaneous emphysema (white arrows). Endotracheal cuff balloon is abnormally large (diameter >3 cm), compatible with soft tissue injury, abnormal airway, or tracheomalacia. In general, the presence of precervical or parapharyngeal emphysema in neck without pneumothorax should raise question of airway or digestive tract injury. (B) Axial computed tomography (CT), lung windows. Cervical tracheal disruption is shown between two short white arrows at posterior and left side of trachea. Extensive parapharyngeal and precervical emphysema is present (long arrows). (C) A different 27-year-old man sustained thyroid cartilage fracture in strangulation. Axial CT at level of thyroid cartilage, soft tissue windows. White arrow points to paramedian thyroid cartilage fracture. Thyroid cartilage fractures typically occur within 2 or 3 mm of anterior junction of the lamina of the thyroid cartilage and are thought to be due to wishbone-like spreading of thyroid cartilage as it is driven against the vertebrae. Overriding apposition of fracture fragments shortens the vocal cord on the affected side, causing hoarseness and lower voice.
FIGURE 15-7 Esophageal injuries. (A) Gunshot wound in Zone II of the neck of a teenager. Barium extravasation directly enters the airway from a high laryngoesophageal fistula (circled). (B) Gunshot wound traversing Zone I into the right chest. Barium swallow shows leak on both the left side of the cervical esophagus (curved arrows) and the right thoracic esophagus (straight arrow). (C) A 27-year-old male sustained a low transverse mediastinal gunshot wound entering left, exiting right. Gastrografin esophagram shows leak into the right chest (straight right arrow) and into the peritoneal cavity (curved black arrow).
Noncontrast MDCT of the neck to visualize the larynx requires thin-section axial imaging from the hyoid bone to the sternal notch. Images are reconstructed using both bone and standard (soft tissue) algorithms and portrayed at bone and soft tissue windows, respectively.
CT is often most helpful in the evaluation of laryngotracheal injuries when deformed anatomy or extensive hemorrhage makes direct or indirect endoscopy more difficult. A careful search for open injuries (e.g., air adjacent to cartilaginous fractures) guides the need for intervention for debridement and mucosal closure. CT can assist in the grading of laryngotracheal injuries, but tends to understage compared to endoscopy or open exploration. The search should begin in the region of the valleculae and extend anteriorly along the larynx and trachea. The most common injuries are those to the thyroid cartilage. Fractures of the thyroid cartilage typically occur within 2–3 mm of the anterior crest of the two lateral laminae. Comminuted fractures of the laminae generally result from higher energy and direct impact injuries to the larynx, and are more commonly associated with thyrocricoid dislocation. Also, CT can demonstrate subluxations and dislocations of the arytenoid cartilage. Most tracheal disruptions are in the membranous portion of the trachea and will heal with conservative therapy. Soft tissue emphysema immediately adjacent to the trachea suggests an injury in this location. A search for a fracture of a tracheal ring is often fruitless unless the fracture is displaced. Coronal reformations through the trachea may show separation (vertical diastasis between tracheal rings) of the trachea compatible with more serious grades of injury.
A blunt injury to the esophagus is uncommon. It generally occurs in the proximal third, especially in the cervical esophagus. On the other hand, a penetrating injury to the esophagus is more common and may involve any portion of the esophagus.
A definitive diagnosis requires contrast esophagography or endoscopy or both, because neither is sufficiently accurate to exclude injuries, especially in patients who are intubated or unconscious. Barium sulfate is the contrast agent of choice for suspected esophageal injuries at or above the carina where aspiration is a concern. Water-soluble contrast media are less accurate in identifying leakage and are inflammatory when aspirated into the airway. Gastrografin should be avoided because it is hypertonic and results in pulmonary edema if aspirated into the airway. When there is concern of an injury to the distal esophagus or stomach, barium should be avoided because it can result in granulomas and peritonitis. Therefore, water-soluble contrast media should be used first when peritoneal contamination is a concern.
Rapid filming is necessary. In all but the most cooperative patients, the author injects thin barium through a feeding tube or a nasogastric tube to obtain full distention of the esophagus. The patient is placed in an oblique projection with a feeding tube or nasogastric tube positioned at the region of penetration. To obtain full distention, 50 mL contrast agent is rapidly injected, during which time fluoroscopic cineradiographs are obtained at 2–3 frames/s.
IMAGING FOR VASCULAR INJURIES OF THE NECK
Blunt carotid and vertebral injury (BCVI) (Fig. 15-8A) is now known to be much more common than previously appreciated. Vascular imaging of the neck is warranted in injury patterns associated with a high risk of blunt injury to the carotid and vertebral arteries, including the following: fracture of the cervical spine (especially involving C1–C3, involving the transverse foramina or extension into foramen magnum), neurological deficits not explained by findings at brain imaging, new-onset Horner’s syndrome, high-energy facial fractures (Le Fort II or III), fracture of the skull base involving the foramen lacerum, or soft tissue injury in the neck (neck belt sign and “hangings” sufficient to cause central anoxia).33,34 Catheter angiography is indicated emergently in patients with an expanding cervical hematoma, active extravasation from nose, mouth, or ears, or a cervical bruit in individuals younger than 50 years old.35 Angiography is the primary diagnostic tool in symptomatic BCVI because it allows for rapid utilization of endovascular therapy for bleeding and identifies patients at risk for embolic stroke.33,36 The sensitivity of duplex Doppler US is inadequately low (38.5%) for directly depicting BCVI. Therefore, CT angiography using MDCT, with a sensitivity of 90–100%, is the imaging test of choice in patients with less obvious signs of vascular injury because it allows rapid acquisition of a vascular assessment without delaying a rapid trauma workup.37–39
FIGURE 15-8 Blunt carotid and vertebral injury. (A) This 40-year-old lawyer complained of severe chronic unrelenting headaches. Prior history included a whiplash injury as a driver. Vertebral arteriogram shows fusiform dilatation of the vertebral artery at the level of the skull base (circled in white). This likely represents long-term effect of BCVI. A 2.8 French microcatheter was negotiated through the tortuous vertebral artery. Then coils were placed proximal and distal to the fusiform aneurysm with relief of headaches. (B) A 22-year-old man sustained a gunshot wound of Zone III of the neck and face. He was exsanguinating. Internal carotid arteriogram showed transection of the internal carotid artery high near the skull base and well above the angle of the mandible (arrow) with active oral hemorrhage (circled). The internal carotid artery was embolized with coils and patient made full neurological recovery.
CT arteriography of the neck is obtained following a timing bolus performed at the C6 level using 20 mL of contrast at 3 mL and a slice thickness of 5 mm. Based on the timing bolus, the CT arteriogram of the neck is acquired. Reformations, including those that are three-dimensional, performed as multiplanar volume reformations (MPVR) with maximum-intensity projections, are obtained.
PENETRATING VASCULAR INJURIES OF THE NECK
The imaging algorithm used to evaluate penetrating neck trauma is very complex. It depends on the mechanism of injury, the locations of entry and exit wounds, the hemodynamic and neurological assessment, and the likelihood of injury. Gunshot wounds may cause a blast injury involving intima, and shards and fragments of bone and metal can cause artifacts in the area that make interpreting a CT difficult. Catheter-based arteriography is advised for such wounds. When the likelihood of asymptomatic injury is low, CT arteriography may play a role in management of such patients.
Location of penetration is a key driver of the imaging workup for a suspected vascular injury. Zone III, above the angle of the mandible, is difficult to assess clinically and to explore operatively. There are extensive vessels at risk, including the internal carotid artery, the external carotid artery and branches, the vertebral artery, and the accompanying veins. Thus, imaging plays a vital role in these patients. Selective internal and external carotid arteriography, vertebral arteriography, and four-vessel intracranial arteriography all play important roles in detecting and evaluating such injuries. Indeed, arteriography is so valuable for the evaluation and treatment of bleeding in this zone that aggressive steps to resuscitate the unstable patient and control bleeding by packing are warranted to allow angiography to proceed. Most vascular injuries in Zone III are best managed by the interventional radiology service (Fig. 15-8B).
Zone II, between the inferior margin of the mandible and the manubrium/clavicles, is evaluated easily by a physical examination. If the common carotid artery or the internal jugular vein require repair, operative exposure is relatively simple and unobstructed. Thus, little imaging is necessary after penetration when “hard” signs of a vascular injury (see Chapter 41) are present. Treatment of asymptomatic patients is more controversial.
In Zone I, the area inferior to the manubrium/clavicles, the brachiocephalic vessels, trachea, or esophagus may be injured, and rapid exsanguination may occur. As a result, symptomatic patients may undergo urgent exploration without imaging.
When patients are stable or asymptomatic, immediate angiography has great value in excluding injury, in detecting vascular injuries that can be treated nonoperatively by embolization or insertion of a stent or stent graft, and in facilitating surgical exploration. CT angiography can be considered as a screening test because it often determines trajectory and the presence of hemorrhage. Penetrating injuries to Zones I and III of the neck are best evaluated with catheter-based imaging in the hemodynamically stable patient. CT of the neck and chest may allow analysis to determine whether penetration is in proximity to the great vessels or even whether vessels are injured. Unfortunately, artifacts are often present when bullets are adjacent to the area or the contrast medium is administered from the arm. As intimal injuries to the great vessels may be life-threatening, these artifacts limit the usefulness of CTA in Zone I and, possibly, in Zone III.
Computed Tomography of the Cervical Spine
In adults and older children (≥10 years old), validated clinical prediction rules (i.e., National Emergency X-Radiography Utilization Study Group [NEXUS] and the Canadian Cervical Spine Rule) can reliably determine those trauma victims who need imaging of the cervical spine. Another clinical prediction rule helps determine which imaging modality is most cost-effective. Specifically, Blackmore et al.40developed a clinical prediction rule to determine pre-imaging risk of fracture in select patients about to undergo a helical CT to survey the cervical spine for fracture and soft tissue injuries (Figs. 15-9 to 15-12). For the application of this clinical prediction rule, it is assumed that the patient will already be undergoing CT of the cranium. Any one of three mechanisms of injury or any one of three clinical findings puts the patient at a pretest risk of greater than 5% of harboring an injury in the cervical spine. High-risk mechanisms of injury include the following: a high-speed motor vehicle crash >35 mph or >50 km/h combined impact, motor vehicle crash with a death at the scene, or a fall from a height of >10 ft or >3 m. Clinical parameters suggesting an increased risk for injury to the cervical spine that are associated with a high-risk mechanism include the following: a significant closed injury to the brain (or intracranial hemorrhage shown by CT of the cranium), acute neurological deficits referable to the cervical spine (acute myelopathy or radiculopathy), or either pelvic fracture or multiple extremity fractures. Hanson et al.41 validated the clinical prediction rule prospectively and showed its application by separating victims of blunt trauma into a high-risk group (12% prevalence of acute injury to the cervical spine) and a low-risk group (0.2% prevalence of injury to the cervical spine). In infants (<1-year old) and younger children (<9 years old) no validated rule exists. In general, patients with greater severities of injury have an elevated risk of injury to the cervical spine. Conventional x-rays will depict essentially all clinically important fractures and dislocations in patients aged 9 years and younger. CT is not indicated in younger children and infants to screen the cervical spine, nor in search for other occult injuries causing neurological deficits.42,43 CT should be reserved as a staging/treatment planning procedure among patients with a known bony abnormality.
FIGURE 15-9 Upper cervical spine, coronal reformations from computed tomography (CT). (A) Coronal reformation of craniocervical junction CT shows pathological widening of right lateral atlantoaxial interval (double-ended arrow), widening of left occipital condyle–C1 lateral mass interval, and bony flake due to left type 1 dens fracture (long arrow). These findings are compatible with atlanto-occipital dissociation. (B) Coronal reformation of the craniocervical junction shows transverse type 2 dens fracture (white arrow). Black arrow marks tubercle on C1 for the insertion of transverse atlantal ligament. Asterisk marks osteophyte at superior margin of C1 portion of anterior atlantodens articulation, a common finding in older patients. (C) Coronal reformations in a patient who sustained high-energy trauma show type 3 dens fracture (white arrows), which is minimally distracted. (D) Coronal reformations from survey CT of cervical spine focused at craniocervical junction. Black arrow demonstrates displaced type 2 dens fracture. White arrows show a right lateral mass fracture of C1. Intra-articular (lateral mass) fractures of C1 less often have involvement of transverse atlantal ligament unlike Jefferson burst fractures, which are more commonly extra-articular or minimally intra-articular.
FIGURE 15-10 Upper cervical spine, sagittal reformations from computed tomography (CT). (A) Left parasagittal CT reformation. This 3-year-old was run over by a trailer. The upper, long, white arrow shows a vertically and coronally oriented fracture of occipital condyle. The two lower arrows show superior articular surface of C1 lateral mass, with anterior subluxation of head. (B) Midline sagittal reformation shows hyperextension teardrop fracture at C2 (white arrows) in a 20-year-old man. (C) Midline sagittal CT reformation shows a combination of anterior subluxation of C2 relative to C3 (white arrow), as well as posterior displacement of lamina of C2 relative to C1–C3 line as manifestation of hyperextension hangman’s fracture of C2. (D) Sagittal mid-plane CT reformation shows diastasis of type 2 dens fracture (double-ended arrow). Distraction of >3 mm is commonly associated with disruption of anterior and posterior longitudinal ligaments.
FIGURE 15-11 Lower cervical spine, sagittal reformations from computed tomography (CT). (A) This 84-year-old woman sustained C5 hyperextension injury in a fall. Lateral cervical spine shows extensive spondylosis but no obvious fracture to vertebral bodies. However, white Xs mark laminar points and show definite retrolisthesis of C5 on C6. Careful attention to laminae, particularly in the elderly, is good practice in detecting translational abnormalities. (B) Same patient as in (A). Sagittal reformation in midline from CT shows complex fracture of C6 with marked neurocanal narrowing at C5 body–C6 laminar level. Disruption of flowing osteophytosis of anterior longitudinal ligament (ALL), seen in diffuse idiopathic skeletal hyperostosis, should be presumed grossly unstable. Extent of anterior, appositional osteophytes is marked by “W” and is fairly typical of diffuse idiopathic skeletal hyperostosis. (C) Midline sagittal CT reformation shows flexion teardrop fracture of C6 in a 79-year-old man. Mechanistic classification of these fractures is based on relation of height relative to width of avulsed fragment (H and W). Teardrop fracture (black arrow) separates anterior inferior corner of C6 vertebral body from its corpus. In this case, H is greater than W, compatible with hyperflexion injury. In lower cervical spine, hyperextension injuries tend to have greater width than height of their corner fragments and can be from anteroinferior or anterosuperior corner. Note this relation is different at C2, where hyperextension fragments typically have greater height than width, due to peculiar shape of anteroinferior corner of C2. (D) Parasagittal CT reformation shows oblique corner fracture through the C7 lateral mass, with anterior and inferior displacement of C6 lateral mass relative to inferior cervical spine (white arrow).
FIGURE 15-12 Multimodality correlations: cervical spine. A patient with C6-7 fracture dislocation underwent pre-reduction lateral conventional radiograph (A), post-reduction sagittal reformation (B) from axial computed tomography (CT), and MRI of the spine and cord (C) and (D). (A) White Xs mark laminar points and connecting them shows disruption of spinolaminar line at C6–C7. Arrow points to fractures of inferior articular process of C6. Sagittal CT reformation (B) shows improved alignment of vertebral bodies but persistent encroachment of neural canal from bony fragments from body and posterior elements (arrow). (C and D) Sagittal magnetic resonance imaging performed using short tau inversion recovery (STIR) and gradient recalled echo (GRE) sequences following reduction of C6–C7 fracture dislocation. Single asterisk shows precervical edema and double asterisk edema in posterior spinal musculature. Long white arrow shows a region of cord swelling with heterogeneous signal, suggesting cord transection at C6 level. Short arrow shows abnormal signal within C6–C7 disk space. GRE sequences (D) show decreased signal at C6 level within the center of the cord that is compatible with hemorrhage (white square), which portends poorer neurological prognosis than edema alone.
Axial slices of thickness of 1.25–3.0 mm are obtained from the skull base through the T4 vertebral body. Images are typically reconstructed at half the slice thickness interval for creation of parasagittal and coronal reformations. Reformations are typically contiguous 2.5- to 3.0-mm thick images and can be reconstructed using either a bone or soft tissue algorithm, but evaluated using bone windows. Generally, the information gathered from these reformations is sufficient and makes plain x-rays unnecessary.
Since helical CT produces large numbers of axial images, the review of the examination is substantially facilitated by use of picture archiving and communication systems (PACS) workstations and the so-called scroll functions. In addition, use of cross-referencing tools on the PACS workstation facilitates identification of specific vertebral levels.
In many ways, the coronal reformations may be viewed using the same approach as standard frontal x-rays such as the open mouth views of the craniocervical junction and the AP view of the cervical spine, while viewing of the sagittal reformations can be performed with guidelines used for the lateral cervical spine. Particular attention in parasagittal images to the alignment at C0–C1 will avoid missing a subtle incongruity of this typically perfectly matched joint, a finding suggestive of atlanto-occipital instability. Similarly, careful evaluation of sagittal reformations will avoid oversight of “in-plane” (axial plane) fractures, such as type II fractures of the dens and fractures of the horizontal spinous process/lamina. Nonetheless, careful attention to axial images is necessary to detect fractures involving the craniocervical junction,44 transverse processes (potential vertebral artery injury), margins of vertebral bodies, pedicles, lateral mass, or lamina and spinous processes.
The sensitivity of this survey CT for acute bony injuries to the cervical spine is above 95% with specificity around 95%. Although CT does not directly show soft tissue injuries to the spine, focal kyphosis, focal lordosis, and widening of the disk space can be used as with conventional x-rays to suggest associated injuries to soft tissue. Some authors feel that clinically important injuries to soft tissue causing biomechanical instability are almost always evident on technically adequate CTs of the cervical spine (especially on the sagittal and parasagittal reformations).45
Conventional X-Rays of the Spine
Clinical decision rules and expert recommendations provide guidelines as to who does not require an image survey of the cervical spine.46-49 Basically, oriented asymptomatic individuals without findings on a physical examination following trauma do not require subsequent imaging. Imaging of the thoracic and lumbar spine following blunt trauma is indicated when patients present with one or more of the following: (1) signs or symptoms of local injury (pain, tenderness, interspinous step-off); (2) depressed level of consciousness, including intoxication; (3) acute myelopathy or radiculopathy referable to the thoracolumbar spine; and (4) major distracting injury, including concomitant injuries to the cervical spine.50,51
Given the differences in the incidence of injury to the cervical spine in children and the differences in their distribution (far more common in the upper cervical spine) relative to adults, an examination limited to frontal and lateral views is acceptable.52 In infants 0–4 years of age and in children 5–9 years of age, AP, lateral, and open mouth views are satisfactory. All patients aged 10 and over require a minimum of three views to as many as five or six views to adequately survey the cervical spine. The minimum views include an AP view of the craniocervical junction (open mouth view), an AP view of the subdental cervical spine, and a lateral view of the cervical spine that extends down to the C7–T1 interspace. To supplement these three views, bilateral trauma oblique views and a swimmer’s lateral are often used. These views of the lower cervical spine including the cervicothoracic junction are intended to be more conclusive, but are of limited resolution. Trauma oblique views are obtained without moving the patient. The imaging cassette is placed on the surface of the table or gurney on which the patient is lying and positioned such that its leading edge is near the patient’s midline and its inferior edge is beneath a portion of the patient’s shoulder girdle. The x-ray beam is angled at 45° to the plate with the central beam centered on the anterior aspect of the patient’s neck, with approximately 10–15° of cranial angulation. Trauma oblique projections obtained in this fashion show the posterior elements and the end plates of the vertebral body.
Films of the thoracic and lumbar spine are usually obtained as separate sets of frontal and lateral projections. The upper thoracic spine may require the addition of a swimmer’s lateral view, if one has not been previously obtained as part of a cervical spine series, to show the cervicothoracic junction and upper thoracic spine. In general, if pathology is identified, the authors recommend “coned” views of the affected vertebral body. This represents more collimated images centered on the level of abnormality.
When examinations of the cervical or thoracic spine are technically inadequate, it is almost always due to the inability to adequately visualize the cervicothoracic junction and the upper thoracic spine. Swimmer’s lateral views are generally obtained with one arm elevated above the head and the other arm in caudal traction. Obviously, when there are fractures of the upper extremity, it may be either difficult or impossible to humanely obtain such studies in a conscious patient. It is possible for experienced observers to substitute carefully evaluated trauma oblique views for swimmer’s views; however, most centers would use CT in a targeted fashion when the conventional x-rays are inadequate to view this area. To reinforce the point, it is necessary to see the top of T1 on the cervical spine and the bottom of C7 on radiographs of the thoracic spine.
One of the common errors made in evaluating the cervical spine is mistaking developmental variations for pathology (Fig. 15-11). Common variations at the craniocervical junction include the following: fusion of C1 to the occiput, which may be partial or complete; failure of fusion or development of the posterior elements of C1; pseudospreading of C1 relative to C2, which may mimic Jefferson burst fractures (most common in the 0- to 4-year age range, but may be seen up through puberty); pseudosubluxation of C2 on C3 in pediatric patients, which can be recognized as normal by a normal C1–C3 spinolaminar line; and os odontoideum (an anomalous bone that replaces all or part of the dens axis and is not attached to the atlas).
In the thoracic and lumbar spine, the authors recommend a careful count of the vertebral bodies on the frontal examination to establish the correct levels, based on the number of rib-bearing (thoracic) and non-rib-bearing (lumbar) vertebrae. On the lateral view, it is important to look at the corners of the vertebral bodies, especially the anterior superior corner, which is affected in approximately 90% of all vertebral body fractures. On the frontal view, it is most important to evaluate the adjacent end plates for continuity, the lateral margins of the vertebrae, the posterior elements for pathological interspinous and interpediculate widening, and horizontal lucencies that would suggest horizontal soft tissue and/or osseous disruption of a flexion-distraction-type injury.
Once an abnormality is identified on conventional x-rays, CT and/or MRI may be used to further characterize the injury for planning of treatment and provide information on the patient’s prognosis.
Computed Tomography of the Thoracolumbar Spine
Among patients undergoing CT of the chest and/or abdomen, a review of axial images in bone algorithm and bone windows, sagittal reformations, or lateral and AP scanograms (topograms) may be used in lieu of conventional x-rays to study the thoracic and lumbar spine.53 Liberal use of CT for the further evaluation of vertebral body deformities that are thought to be related to trauma based on conventional x-rays is highly recommended. In addition, patients with high-risk mechanisms and impressive signs or symptoms without abnormal x-rays (e.g., a palpable step-off suggesting disruption of the posterior elements) should undergo a thoracolumbar CT to detect occult minimal burst fractures or Chance or flexion-distraction-type injuries.
A 2.5–3.0-mm axial slice thickness is used to acquire images from two vertebral body levels above an abnormality through two vertebral body levels below. Images are reconstructed using both bone and soft tissue algorithms; however, acquisition of the entire thoracic or lumbar spine is advised as it allows more accurate determination of the location of injury. Sagittal reformations are made in both algorithms and viewed at bone and soft tissue windows, respectively.
In the thoracic or lumbar spine, it is important to have some reference to the scanogram or to the reformations to allow accurate assessment of the vertebral levels imaged. In addition to careful evaluation of the vertebral elements, some attention should be paid to possible injuries to ribs, aorta, sternomanubrial junction, and the kidneys. If flexion-distraction or Chance fractures are detected, careful attention should be directed to the abdominal aorta, bowel, and retroperitoneal structures, including the ureteropelvic junction.
Magnetic Resonance Imaging of the Spine
The principal indications for MRI are to characterize soft tissue injuries associated with fractures and luxations of vertebral bodies and to assess the neural elements (Fig. 15-12). An MRI is indicated in individuals who have no conventional x-rays or CT abnormality, but who have an acute myelopathy or radiculopathy (spinal cord injury without radiographic abnormality [SCIWORA]). The use of MRI is frequently controversial in the setting of dislocation of bilateral or unilateral facets (see Chapter 23). Some advocate initial reduction followed by MRI, but this is a practice that varies from institution to institution. In general, urgent MRI is appropriate when there is an evolving neurological deficit or neurological deficits without explanation.
Edema of the spinal cord has a much better prognosis than hemorrhage into the cord, and MRI in the subacute setting can help make this distinction, as well as detect epidural hematomas that may require decompression. Evaluations of the disk spaces, ligaments, and facet joints, including the cranio-occipital articulation, are best made with MRI.
Sagittal and axial T1-weighted and fluid-sensitive sequences (e.g., T2-weighted STIR) are standard. Gradient echo sequences are useful in detecting an artifact of magnetic susceptibility, a finding in the acute and subacute setting that allows more reliable assignment of a fluid collection to being blood. When assessing the transverse atlantal ligament, images should be obtained in the axial plane parallel to Ranawat’s line (a line from the anteriormost portion of the anterior tubercle of C1 to the most posterior aspect of the posterior arch of C1).
MRIs have been used to “clear” the cervical spine in obtunded or unexaminable patients with otherwise normal imaging (CT or high-quality conventional radiographs).54,55 The absence of abnormal high signal intensity in ligaments and discs effectively excludes biomechanically significant injuries; however, an abnormal signal does not imply instability. At this time, MRI has not been shown to accurately grade injuries to the posterior longitudinal ligament (PLL) or anterior longitudinal ligament (ALL).
Flexion and Extension X-Rays of the Cervical Spine
Among individuals who are completely alert and who have normal x-rays and tenderness at the posterior midline, flexion and extension radiographs may be used to assess ligamentous stability (Fig. 15-13). Some centers have recommended the use of passive (guided by the physician) flexion and extension studies using fluoroscopy. While this may be appropriate in very limited circumstances in the hands of physicians of considerable experience, the published data are not sufficiently strong to warrant generalization.
FIGURE 15-13 Flexion–extension radiograph: cervical spine showing subtle instability at C2–C3. This 24-year-old male bicyclist was struck by a car from behind and posterior midline tenderness of upper cervical spine was palpated. (A) Upright lateral out-of-collar radiograph shows loss of usual cervical lordosis without focal kyphosis or translation. Precervical soft tissues are normal. (B) Upright lateral flexion radiograph of cervical spine shows no gross interspinous widening or loss of parallelism of facet joint. Reference lines are drawn from posteroinferior corner of C3 to most inferior aspect of C3 spinous process. Perpendicular to that line from posteroinferior corner, a line is used as a reference for translation of C2 relative of C3, as demonstrated by double-arrowed line. (C) Upright lateral extension radiograph of cervical spine again shows no gross widening of anterior disk space. Using same reference for translation of C2 on C3, 2.5 mm of difference at C2–C3 disk space is demonstrated between flexion and extension, compatible with partial, dynamic instability.
A qualified physician should be in attendance if the examination is performed shortly after injury (hours vs. days), and the patient needs to be completely alert and able to assume an upright posture and precisely follow commands. An initial x-ray is obtained with the patient upright and with the cervical spine in a neutral position. This examination is reviewed by the physician overseeing the examination. If this examination is normal, the patient is asked to actively extend to the maximum and an x-ray is obtained. The patient’s cervical spine is then returned to a neutral position. This extension x-ray is evaluated in a manner similar to that taken with the cervical spine in a neutral position. If normal, the examination is repeated with maximum effort at flexion, and an x-ray is obtained.
Standards for an adequate examination vary from a range of motion of 30° to 90°. The test is intended to study the capacity of the spine to resist physiological stresses, however, and the mean normal range of motion in adults is approximately 90°. If the patient’s midline tenderness is in the upper or mid-cervical spine, it is not critical to see the C7–T1 interspace. If the discomfort is in the lower cervical spine or more diffuse, the entire area of abnormality needs to be visualized.
Evaluation of cranio-occipital stability by conventional x-rays is based on the detection of translation and distraction between the basion and the cervical spine. If the flexion–extension x-rays are abnormal in the acute or subacute setting, MRI is pursued. If the examination does not show an adequate range of motion, the patient’s spine is immobilized (hard collar) and the examination is repeated in 2 weeks (if the patient remains symptomatic).
Computed Tomography of the Chest
Chest CT is generally performed to evaluate adult victims of high-energy blunt trauma (especially those with chest pain, deformity, or hypoxia),56 with particular attention to the mediastinal contents (Figs. 15-14 to 15-18). Children presenting with hypotension, elevated respiratory rate, abnormal physical examination, depressed consciousness, and femur fractures after blunt trauma are at a substantially increased risk for an intrathoracic injury.57 In this setting, CT provides significant information about the lungs, pleural cavities, and chest wall. Indications for evaluating the mediastinum are principally to exclude injury to the intrathoracic aorta and great vessels (sensitivity 97–99%58). The role of MDCT in the diagnosis of acute traumatic aortic injury has been evolving, and it is believed to be most cost-effective in the following circumstances: when patients are already undergoing another CT examination (e.g., CT of the head, abdomen, and pelvis); are at risk for injury to the thoracic aorta because of high-energy mechanism, associated injuries, or age (>50 years old); or have a previously abnormal study (chest x-ray). A decision rule has been proposed by Blackmore et al.59 in which individuals with two or more of the following are at high risk for aortic injury: age >50, unrestrained occupant in motor vehicle crash, hypotension, thoracic injury (rib fracture, pneumothorax, pulmonary contusion, or laceration), abdominopelvic injury (fracture of lumbar spine or pelvic ring, injury requiring laparotomy), fractures of appendicular skeleton, or injury to the brain.
FIGURE 15-14 (A–C) Blunt traumatic rupture of the thoracic aorta in a 47-year-old driver. (A) Noncontrast CT of the chest showed evidence of periaortic hemorrhage (white circles). (B) Axial CTA of the chest clearly shows disruption of the descending aorta at the aortic isthmus (arrow). (C) Catheter aortography adds little in this case: increased opacity at the area just distal to the left subclavian origin may represent contrast extravasation posteriorly.
FIGURE 15-15 (A–C) Aortic injury. Subtle CTA and obvious catheter aortogram. A 71-year-old male was involved in a high-speed crash. (A) Composite of CTA shows relatively subtle extravasation from descending aorta (arrows). (B) Catheter aortography shows medial and lateral bulges (arrows). (C) This injury was treated by stent graft.
FIGURE 15-16 (A–E) Gunshot injury of the aortic arch not detected on catheter aortography. A 24-year-old male sustained a gunshot wound of the back with mediastinal traverse. He was hemodynamically stable but paraplegic. (A) Portable chest radiography showed hemothorax and a very wide indistinct mediastinum with a bullet in the mediastinum. (B and C) Right and left anteroposterior catheter aortograms did not show any evidence of an injury. (D) However, suspicion of an aortic injury persisted. Therefore, a CT arteriogram was performed. This shows that the bullet had traversed the spine and fragmented into parts that went to the right and the left (dashed arrows). The left fragments penetrated the posterior arch and exited the anterior arch of the aorta (arrows). (E) Surface-rendered reformations clearly show the path of the bullet.
FIGURE 15-17 Mediastinal hematoma caused by nonaortic injury. (A) This 75-year-old man was injured in high-speed motor vehicle crash with sternal fracture. Anteroposterior (AP) recumbent chest shows widening of right paratracheal stripe (H), with maintenance of normal para-aortic arch and aortopulmonary window (#1 and 2, respectively). (B) Same patient as in (A), axial computed tomography (CT) shows anterior mediastinal hematoma (asterisk). Note maintenance of normal fat surrounding descending aorta (arrow). (C) AP chest radiograph performed on 19-year-old unrestrained driver in head-on motor vehicle crash shows multiple injuries, including T6 and left shoulder fractures. Widening of right paratracheal stripe (H), obscuration of aortic arch (black arrow), and abnormal right paraspinal line (white arrows) suggest mediastinal hematoma. In absence of osteophytes, right paratracheal stripes are not typically seen in young adults and their presence locally should direct search for underlying pathology. Left paraspinal line is typically seen due to descending aorta and should not be seen as continuous line between the lower chest and the apex of lung. Continuous left paraspinal line from apex to diaphragm is pathognomonic for mediastinal collection, such as hematoma in setting of trauma. (D) Same patient as in (C); axial CT following intravenous contrast shows extensive posterior mediastinal hematoma (asterisks). Note inset showing sagittal plane translational fracture-dislocation of T6.
FIGURE 15-18 Pulmonary contusion (A and B) and laceration (C and D) due to blunt-force injury. (A) This 22-year-old woman was in a high-speed motor vehicle crash. Anteroposterior (AP) recumbent chest shows peripheral nonanatomic patchy opacity (bracketed arrows). Pulmonary contusions are typically present by the time patient presents to the hospital and may evolve for 48–72 hours. Progression thereafter should be considered a complication, such as pneumonia or adult respiratory distress syndrome. Typically, pulmonary contusions resolve within 1 week. (B) Same patient as in (A); contrast-enhanced axial CT shows subpleural location of patchy opacities compatible with contusion against rib cage (arrows). Atelectasis is seen in right posterior hemithorax. (C) This 22-year-old male passenger was involved in a side-impact crash with significant intrusion into passenger compartment. AP recumbent chest shows extensive pulmonary opacities, with mixed lucency seen in left mid-lung (arrow) and multiple displaced rib fractures (arrowheads). Mediastinal contours are also abnormal with obscuration of aortic arch, aortopulmonary window, and widening of right paratracheal stripe. (D) Contrast-enhanced axial computed tomography in same patient as (C) shows large anterior pneumothorax (asterisk), dense opacification throughout left lung compatible with contusions, and air-fluid level within cystic structure compatible with lacerations (arrow). Post-traumatic pulmonary opacities associated with pneumothorax should properly be called lacerations.
Axial images are obtained with a slice thickness of 2.5 mm from the thoracic inlet to at least the bifurcation of the abdominal aorta and through the perineum if there is a known fracture of the pelvic ring. The 2.5-mm images are reconstructed at 1.25-mm intervals for the purposes of developing the multiplanar volume-rendered reformations and three-dimensional reformations useful for portraying the anatomy of the aorta and great vessels. Reconstructing the images at 5 and 2.5 mm can be used for evaluating the chest and abdomen, and thoracolumbar spine, respectively, at bone and soft tissue algorithms and windows.
In patients unable to receive contrast, noncontrast CT can be effective in detecting a mediastinal hematoma (Fig. 15-17A) and guiding the patient to evaluations such as transesophageal echocardiography, magnetic resonance angiography, etc.
CT is generally the most cost-effective survey study for patients at modest to moderate risk for injury to the thoracic aorta. The role of CT aortography is evolving, and this technique has mostly replaced that previously held by catheter angiography. Findings on CT can be divided into direct and indirect. Direct findings are visualization of pseudoaneurysms, intimal flaps, and pseudocoarctation (due to subadventitial dissection). A mediastinal hematoma, however, is an indirect finding. To suggest an aortic injury, a mediastinal hematoma should be contiguous with the aortic wall and should not be separated from the aorta by a rim of fat (Fig. 15-17B). Thus, in very thin patients or in patients with extensive edema and pleural or parenchymal opacification, determination of whether or not a mediastinal hematoma has obliterated juxta-aortic fat can be difficult. Complex atheromatous disease can make interpretation of the examination difficult, particularly for more subtle injuries. Finally, artifacts of the technique, including aortic pulsations and beam hardening due to dense contrast in adjacent venous structures, may make interpretation difficult.
It is particularly important in the presence of an abnormal examination to delineate the anatomy of interest to the trauma surgeon, such as the distance from the most proximal point of injury to the takeoff of the left subclavian artery or any anomalous branches. This information is readily provided by CT, particularly with three-dimensional and multiplanar reformations. These capabilities have begun to alter the role of angiography from its traditional role of diagnosis, staging, and pretreatment planning to one more often used for resolving diagnostic conundrums raised by CT or transesophageal echocardiography, or as part of treatment (e.g., placement of aortic stent grafts).
CT is the most sensitive diagnostic method for detection of acute blood in the pericardium.60 It is also among the most sensitive methods for detection of injuries to the chest wall, pleural cavities, or lungs. It is less sensitive in the detection of injuries to the hemidiaphragm (sensitivity is 65–70%) or the tracheobronchial tree. For suspected diaphragmatic injuries, especially herniations through a diaphragmatic tear, coronal and sagittal multiplanar reformations are useful, as they better display characteristic findings.
Computed Tomography of Abdomen and Pelvis
Abdominopelvic CT is one of many adjunctive tests to assist the trauma surgeon in the evaluation of otherwise occult intraabdominal injury or to aid in characterization of injuries previously detected by other diagnostic tests (e.g., DPL or FAST; Figs. 15-19 to 15-24). Usual indications include abdominal signs (e.g., lap belt sign) or symptoms (e.g., pain and tenderness) following high-energy trauma. The combination of left costal margin and pleuritic chest pain is an independent predictor of splenic injury and warrants diagnostic evaluation.61
FIGURE 15-19 (A–C) Three examples of diaphragmatic rupture seen on three modalities. (A) Portable chest film on admission demonstrates an elevated left hemidiaphragm. There is compression of the gastric air in the fundus, consistent with compression as the stomach traverses the diaphragm. (B) Upper gastrointestinal imaging demonstrates a narrow area of barium entering the chest. Note again the compression. (C) Scout film after embolization of a ruptured spleen shows similar compression of the gastric shadow as seen in (A). Patient was explored, the hernia reduced, and the diaphragm repaired. A Grade IV nonbleeding lacerated spleen was left undisturbed.
FIGURE 15-20 Examples of contrast extravasation in the abdomen. (A) Laceration of the left lobe of the liver with arterial extravasation exiting the liver and spreading in the peritoneum. Note that the extravasation is as dense as the aorta and denser than the stomach. This enables differentiation of GI contrast and vascular contrast. Sometimes a bone “window” allows better discrimination by widening the gray scale. (B) Extravasation posterior to the stomach (arrow) in the lesser sac represents GI extravasation from the duodenum at the ligament of Treitz. (C) Extravasation mixed with air indicated bowel perforation. (D) Extravasation (black arrow) adjacent to thick-walled (white dots) colon indicates colonic perforation by gunshot wound. (E) Contrast extravasated within the perinephric space indicates urinary leakage. (F) Extravasation in the mesentery is of similar density to the aorta and vena cava. It represents a mesenteric tear with active bleeding.
FIGURE 15-21 Patterns of injury: “the central package.” This 54-year-old male motorcyclist sustained multiple injuries, including laceration of horseshoe kidney, duodenal contusion, bladder rupture, and anteroposterior (AP) compression fracture of pelvic ring. (A) AP radiograph of pelvis. Greater than 2.5 cm diastasis of pubic symphysis is compatible with disruption of sacrospinous, sacrotuberous, and anterior capsular ligaments of sacroiliac joints. Appearance supports AP compression mechanism and is associated with increased risk for intra-abdominal, intrathoracic, and head injuries. (B) Axial computed tomography (CT) abdomen at L3–L4 level in the arterial phase. White arrow shows median fracture of horseshoe kidney with posterior perinephric hematoma (asterisks). This is arterial phase image because there is dense opacification of aorta directly posterior to neck of horseshoe kidney without opacification of the inferior vena cava immediately to its right. Arterial phase images best demonstrate active extravasation and pseudoaneurysms. (C) Axial CT at level of third portion of duodenum shows paraduodenal hematoma (asterisk), suggestive of duodenal injury. (D) Axial CT at level of right acetabulum shows widening of symphysis and extraperitoneal bladder laceration as contrast in anterior abdominal wall (asterisk). Posterior wall of bladder is irregular with double densities within urine contrast compatible with hematoma (arrowheads).
FIGURE 15-22 Patterns of injury: “the left package.” This 22-year-old male driver was injured in a side-impact crash with substantial intrusion to driver’s side of car. Multiple injuries sustained. (A) Anteroposterior (AP) scanogram from computed tomography (CT) of chest, abdomen, and pelvis shows extensive opacity of left mid- and lower lung fields compatible with contusion, a deep sulcus (arrow) at left costophrenic angle compatible with left pneumothorax, and multiple left-sided rib fractures (arrowhead). Patient is intubated, and there is right upper lobe collapse. (B) Axial CT of upper abdomen during parenchymal phase shows injury of the anterior portion of left kidney (medial arrow) and splenic laceration with sentinel clot (black and white arrows, respectively). Although rib fractures are not shown on current image, subcutaneous emphysema in left chest wall and distal extent of small pneumothorax are shown. (C) Oblique sagittal reformation from CT aortography shows complex segmental intimal injury to proximal descending aorta in the typical location (arrows) and pseudoaneurysm formation due to acute traumatic aortic injury. Air-fluid levels (arrowheads) are compatible with pulmonary lacerations.
FIGURE 15-23 Patterns of injury: “The right package.” This 22-year-old unrestrained passenger was ejected from car in side-impact high-speed crash. (A) Anteroposterior (AP) view of pelvis shows bilateral iliopubic and ischiopubic ramus fractures (white arrows) and disruption of right sacral arcuate lines (arrowheads); findings are compatible with lateral compression fracture due to right lateral impact. (B) Axial contrast-enhanced abdominal CT shows free intraperitoneal fluid (asterisks) due to complex collection of liver lacerations (arrow) extending to the intrahepatic inferior vena cava. The relatively uniform enhancement of hepatic parenchyma suggests that the hepatic veins are not occluded. (C) Axial computed tomography through S1, bone windows, shows through-and-through fracture of S1 ala, which traverses S1 neuroforamina (white arrows). Such through-and-through fractures are typically associated with biomechanical instability.
FIGURE 15-24 Grade IV renal laceration. This 14-year-old sustained an injury in a fall from a dirt bicycle while jumping. (A) Contrast-enhanced axial CT scan, soft tissue windows, performed in parenchymal phase shows perinephric hematoma on left (asterisk) adjacent to laceration that extends into renal hilum (arrows). Right kidney shows normal pyelographic phase. Free intraabdominal fluid is due to Grade III splenic laceration (not shown). (B) Contrast-enhanced axial computed tomography (CT) obtained in arterial phase shows wedge-shaped defect in left kidney (arrowheads) compatible with laceration and infarct extending to capsule secondary to segmental arterial occlusion. (C) Contrast-enhanced axial CT at level of kidneys shows thrombus within collecting system (black arrows), perinephric hematoma, and contusion of posterior aspect of kidney, just below laceration seen on image (A). Perinephric hematoma surrounds kidney. (D) In such complicated cases, delayed images (10 minutes) are highly valuable in assessing associated urinary leakage. Ten-minute delayed images show a type III extravasation of contrast-enhanced urine from anterior and medial pole of kidney into the perinephric space (black arrow). Striated nephrogram is present posteriorly (white arrow), compatible with contusion adjacent to laceration.
Among patients with distracting injuries (e.g., femur or pelvic ring fractures), physical examination may lead to an underdiagnosis of surgically important intra-abdominal injuries in up to 15%. In addition, abdominopelvic CT is the principal means of both detection and characterization of renal injuries among adults with gross hematuria, children with microscopic hematuria (>50 red blood cell count per high-power field), or microscopic hematuria among adults who have had one or more episodes of systolic hypotension.
Indications for CT cystography include hematuria and fracture of either the pelvic ring or acetabulum or hematuria and free intraperitoneal fluid. In the absence of hematuria, cystography is not necessary.
A “dual-phase” intravenous contrast-enhanced study is used to acquire 5-mm slice thickness from the lower chest to the bifurcation of the abdominal aorta during the mid-portal venous phase and from the iliac crest to the perineum following a brief delay to avoid “outrunning” the intravenous bolus and to allow opacification of the distal ureters. Images are reconstructed using a standard algorithm and viewed at soft tissue and bone windows. In those patients whose arterial or parenchymal phase images demonstrate a renal injury, a series of images through the upper urinary tract is repeated after a 10-minute delay using 5-mm slice thickness to detect and quantify the extravasation of urine.
CT cystography typically is performed prior to the administration of intravenous contrast (Fig. 15-25). Two techniques are applicable. The first utilizes the CT scanograms in the frontal and lateral views as “scout films.” The bladder is then distended with 400 mL of 30% contrast media after which frontal and lateral scanograms are repeated looking for extravasation. If none is seen, the bladder is emptied and additional frontal and lateral scanogram images are performed to look for subtle leakage. In the second method, 100 mL of 5% iodinated contrast is instilled. If this shows no extravasation, additional contrast is instilled into the urinary bladder until 40 cm of water pressure is achieved and 2.5-mm axial images are obtained through the bony pelvis. No postdrainage scanning is obtained. Images are reconstructed using a soft tissue algorithm and reviewed at soft tissue and bone windows. This author prefers the first method as evacuation of the contrast before axial imaging enables better detection of subtle pelvic intraperitoneal hemorrhage.
FIGURE 15-25 (A–D) Lower genitourinary injuries. (A) A 38-year-old male was hit by car leaving a bar. Retrograde cystography shows streaky contained contrast media on the left side of the bladder. (B) CT scan of the pelvis in a woman who was struck by a car shows streaky contained extravasation surrounding the bladder and extending into the obturator spaces. Streaky contained contrast medium indicates retroperitoneal extravasation and is consistent with tears of the retroperitoneal surfaces of the bladder. (C) Retrograde cystogram shows contrast media extending into the left subphrenic space (asterisk) and the left paracolic gutter (curved arrow). Note how the contrast surrounds loops of bowel in pelvis (arrows). This is consistent with tear of the dome of the bladder and free spillage into the peritoneal cavity. (D) A 25-year-old male motorcyclist sustained pelvic fractures. Retrograde urethral injection of contrast media clearly shows extravasation extending up into the pelvis from a posterior urethral injury above the urogenital diaphragm.
The arterial-weighted parenchymal phase images are particularly useful for the detection of extravasation, especially if a pseudoaneurysm or arteriovenous fistula is present. Extravasation of venous contrast is seen in 5–10% of victims of high-energy blunt trauma. Splenic hemorrhage is the most commonly appreciated area of isolated extravasation; however, fractures of the pelvic ring are most commonly associated with multiple sites of extravasation.62The amount of hematoma associated with disruptions of the pelvic ring directly correlates with the likelihood of an angiographically demonstrable arterial injury (200 cm3, 5% arterial injury; more than 500 cm3, approximately 50% arterial injury)63 (Figs. 15-30 and 15-31). Nonetheless, otherwise unexplained continued hemodynamic instability in patients with blunt pelvic fractures warrants angiographic evaluation, even if the initial CT showed noextraperitoneal hematoma (Figs. 15-26 and 15-27).64
FIGURE 15-26 Fatal bleed from internal iliac arteries: 28-year-old female hit by bus. AP pelvic digital subtraction angiogram shows exsanguinating hemorrhage from the internal iliac arteries bilaterally. This was treated with placement of a distal aortic occlusion balloon prior to emergent surgery. Note the small size of the iliac arteries due to spasm and profound hypovolemic shock.
FIGURE 15-27 Left superior gluteal artery bleed. Left posterior oblique (LPO) digital subtraction pelvic angiogram in this 56-year-old male post-motorcycle accident and pelvic fracture reveals a large active bleed from a left superior gluteal artery transection. Such injuries often require occlusion by coil embolization because the bleeding comes from the trunk of the superior gluteal artery.
Regarding splenic (Fig. 15-28) and hepatic lacerations, detection of extravasation is a more powerful guide to the need of intervention than is grading of the organ injury. The detection of lacerations that extend to the hepatic veins is of particular importance in the liver, as these have a strong predictive value for failure of nonoperative management when associated with large (>10 cm) hypoperfused regions.65Adrenal hemorrhage is relatively common, particularly on the right. In general, it is not of clinical importance unless bilateral, and even then, post-traumatic hypoadrenalism is rare.
FIGURE 15-28 Splenic laceration and active extravasation: 43-year-old-male post-MVC. Contrast-enhanced axial CT abdomen shows anterior splenic laceration with active focal extravasation (long arrow).
CT is relatively insensitive to the detection of isolated injury to the bowel. Findings may include thickened bowel wall, asymmetric mural enhancement, and free fluid not explained by other injuries (Figs. 15-29 and 15-30). Nonetheless, when interloop fluid is present, this is very suspicious for a transmural injury to the bowel even in the presence of injury to a solid organ and even immediately following DPL (Fig. 15-20F). One note of caution regarding free intraperitoneal fluid is that women of childbearing age have small amounts of fluid (±50 mL) in their pelvis. Patients who have been vigorously resuscitated (especially if they are >24 hours from their injury) may have ascites and interloop fluid present due to a capillary leak syndrome. Acute and subacute hemorrhage typically measures 40–70 Hounsfield units (H), while urine, bowel contents, and ascites measure closer to water (e.g., 0–30 H).
FIGURE 15-29 Small bowel perforation: 14-year-old-boy, unhelmeted bicycle rider hit by car, sustained small bowel perforation. Intravenous contrast-enhanced axial CT shows three findings consistent with small bowel (jejunal) injury: (1) diffusely enhancing and thickened jejunum loops within the left side of the abdomen, with a focal hypoenhancing segment compatible with at least partial transmural injury (short arrow); (2) high-density interloop fluid within the mesentery adjacent to abnormal bowel (arrowhead) strongly suggests transmural bowel laceration; (3) small amount of pneumoperitoneum (long arrow) collecting within mesentery. Extra-alimentary air almost always correlates with transmural laceration of bowel.
FIGURE 15-30 Shock-bowel syndrome: 11-year-old-girl sustained fall from height. Intravenous contrast-enhanced axial CT abdomen shows flat (slit-like) IVC, diffusely dilated small bowel loops with slightly thickened and enhancing walls, and extensive mesenteric and retroperitoneal edema. Reduced splanchnic blood flow due to underresuscitation results in capillary leak and prolonged transit time for intravenous contrast. This constellation of findings is consistent with shock bowel. Also note moderate intraperitoneal fluid from DPL.
FIGURE 15-31 Pelvic ring fracture: lateral compression type. This 36-year-old unrestrained woman in rollover motor vehicle crash sustained injuries to right upper and lower extremities. (A) Anteroposterior (AP) conventional radiograph of pelvis shows disruption of right-sided arcuate lines at S1 and S2 (black arrows), left iliopubic ramus at pubis (white arrow), and right ischial pubic ramus near synchondrotic scar (black arrowhead). (B) Inlet view of pelvis better shows the disruption of anterior sacrum at right alae (black arrows), left pubic (white arrow), and right ischial pubic ramus (black arrowhead). (C) Axial computed tomography (CT) shows impacted fracture of right S1 ala, lateral to neuroforamen (arrow). Frequency of injury to sacral nerve roots is greatest when fractures involve medial aspect of the neural canal (Denis zone 3), lowest when lateral to the neuroforamen (Denis zone 1), and intermediate when involving neuroforamen (Denis zone 2). (D) Axial CT image at superior margin of symphysis pubis demonstrates an impacted fracture of posterior margin of left pubis (arrow).
CT performs slightly better at detection of diaphragmatic ruptures than conventional x-rays, with a sensitivity of 60%. A normal contour of the diaphragm and no pleural collections or adjacent airspace disease effectively exclude injury to the diaphragm. Another pitfall in the search for diaphragmatic injuries is the increasing prevalence of fibrous replacement of diaphragmatic muscle among older (>65 years old) individuals, which may mimic the so-called discontinuous diaphragm sign of a ruptured diaphragm.66,67
Computed Tomography of the Pelvis and Acetabulum
CT is generally indicated for unstable fractures of the pelvic ring, as determined by physical examination or appearances on conventional x-rays (simultaneous anterior and posterior displacement of fractured pelvic ring) (Figs. 15-31to 15-35). Acetabular CT is indicated following reduction of hip dislocations to detect entrapped intra-articular debris and for the evaluation of unstable fractures. Finally, individuals who sustain bilateral sacral fractures benefit from a sacral CT obtained with coronal imaging of S1–S3 and sagittal reformations.
FIGURE 15-32 Pelvic ring fracture: anteroposterior (AP) compression type. This 55-year-old male sustained an injury during a 7-m fall onto concrete. (A) AP radiograph of pelvis shows symphyseal diastasis (double-ended arrow); right ischiopubic ramus fracture, which is minimally displaced (arrowhead); and disruption of right sacral arcuate lines (black arrows). Right femur is abducted (white arrow), a finding that is common with fractures of femoral shaft that this patient also sustained. (B) Inlet view of pelvis (obtained with 45° angulation caudally) better shows disruption of arcuate lines (white arrows) and again shows pubic symphyseal diastasis. (C) Axial CT at the lumbosacral junction shows through-and-through fracture (arrows) of right lateral mass of S1 with 6 mm of lateral and 8 mm of anterior translation. (D) Axial CT image at ischial tuberosities shows oblique sagittal fracture through right ischial pubic ramus (white arrows). Orientation of ischial fractures often reflects mechanism injury (sagittal plane fractures due to AP compression or vertical shear; transverse or axial plane fractures due to lateral compression).
FIGURE 15-33 Vertical shear injury with unstable sacral fracture. An “H”-shaped sacral fracture was sustained in 40-ft fall. This was associated with right calcaneus and T12 compression fractures. (A) Anteroposterior (AP) pelvis CT scout shows disruption of arcuate lines bilaterally (arrows). Such finding requires excellent lateral view of sacrum to exclude transverse components of the fracture to create either “H”- or “U”-shaped sacral fractures, which are typically biomechanically unstable. This can rarely be obtained. Computed tomography (CT) better evaluates this area as coronal reformations of thin-section axial CT. (B) Axial CT shows bilateral through-and-through sacral fractures (arrows) that are transforaminal in their course. At this level, no transverse fracture is appreciated. (C) Coronal oblique CT reformation shows bilateral lateral mass fractures (arrows), as well as a portion of transverse fracture (arrowhead). (D) Sagittal CT reformation clearly shows transverse fracture (arrow).
FIGURE 15-34 Acetabulum: transverse acetabular fracture with associated posterior wall fracture. This 25-year-old unrestrained male backseat passenger partially ejected in high-speed motor vehicle crash. (A) Anteroposterior (AP) view of pelvis shows disruption of iliopectineal and ischiopubic lines adjacent to acetabulum, with medial and proximal displacement of distal fragment (white arrow). Note that no fracture involving obturator foramen is evident, and no supraacetabular extension fracture is shown to suggest a column fracture. Black arrow shows concentric-shaped region of radiodensity due to overlap of tectum and femoral head, characteristic of dislocation. Position of femur in adduction and internal rotation is characteristic for posterior dislocation. Asterisk shows eyebrow-shaped radiopacity of displaced posterior wall fragment. (B) Left obturator oblique again shows transverse fracture (black arrow) and posterior wall fragment (asterisk), following relocation of posterior hip dislocation. Careful attention to shape of femoral head allows detection of subtle fractures associated with dislocation. Femoral head fractures may be either shear injuries or impaction fractures (the latter, similar to Hill-Sachs fractures associated with anterior shoulder dislocations). (C) Left iliac oblique shows location of posterior wall fragment (asterisk) and better shows transverse fracture course through anterior wall. (D) Axial computed tomography (CT) image at the level of tectum shows a sagittal plane fracture (arrows) characteristic of transverse fractures of acetabulum. Transverse fractures typically divide acetabulum into superior and lateral moiety, which maintains its connection to the intact hemipelvis, and a medial and inferior moiety in continuity with ischium. In this case, CT was obtained prior to reduction, and femoral head (H) is posterior to tectum (circular radiodensity just anterior to dislocated femoral head). The most inferior portion of posterior wall fracture fragment (PW) is also shown.
The general goal of imaging for unstable fractures of the pelvic ring and acetabulum is to aid in surgical planning. CT scans of acetabular fractures are performed for the assessment of fracture types,68secondary congruence of the hip (e.g., are the fracture fragments symmetrically oriented about the intact femoral head?), evidence for marginal impaction (e.g., subarticular bone depressed or impacted, and not showing secondary congruence), detection of a fracture of the femoral head, and detecting intra-articular debris. There is approximately a 15% concurrent rate for fractures of the pelvic ring and acetabulum.
CT of the pelvis typically uses a slice thickness of 2.5–5 mm in the axial plane from the level of the L5 transverse processes to the ischia. Images are reconstructed using a bone algorithm and reviewed at bone and soft tissue windows. If using an MDCT scanner, 5-mm thicknesses can be obtained by coupling two contiguous 2.5-mm channels and thus allow scanning of the acetabulum without additional radiation. Similarly, 2.5-mm slice thicknesses obtained from multidetector scanning may be reconstructed at 1.25-mm intervals when bilateral sacral fractures are present to obtain oblique coronal (in plane of S1–S3 sacral promontory) and sagittal reformations of diagnostic quality.
Acetabular CTs are usually performed using a slice thickness of 2.5–3.0 mm in the axial plane through the acetabulae, with 5-mm slick thickness in the remainder of the bony pelvis. Occasionally, sagittal and coronal reformations may be helpful in better depicting anatomy.
In assessing CT for a disruption of the pelvic ring, it is important to correlate with at least an AP x-ray of the pelvis. A top to bottom, posterior to anterior approach of reviewing images is recommended, such that the review is initiated at the level of L5 looking for avulsions of the transverse processes due to the iliolumbar ligament and the posterior superior iliac spine due to the strong posterior sacroiliac ligaments. The sacroiliac joints are subsequently assessed for their side-to-side symmetry and integrity of their subchondral white lines. The anterior surface of the sacrum is carefully evaluated for “buckle” fractures due to internal rotation of the hemipelvis as seen with the most common fracture mechanism, internal rotation of the hemipelvis due to a lateral impact (lateral compression mechanism). Fractures of the sacrum are assessed relative to the neural canals, particularly at S1 and S2, the neural foramina from S1 to S5, and the origins of the sacrospinous and the sacrotuberous ligaments. Fractures of the iliopubic and ischiopubic rami are assessed for their orientation (lateral compression fractures typically show orientation in the axial plane or coronal plane, while AP compression and vertical shear fractures will show orientation in the sagittal plane). The normal pubic symphysis is never more than 1 cm in width in normal subjects, regardless of age. When the pubic symphysis is traumatically wider than 2.5 cm, disruptions of both sacrospinous and sacrotuberous ligaments are assumed. In the posterior ilium, it is important to look for avulsion fractures of the posterior superior iliac spine, so-called crescent fractures, as these are strongly associated with biomechanically unstable fractures in the presence of disruption of the anterior pelvic ring. The axial images give good evaluation of the amount of internal or external rotation, but underestimate the amount of flexion or extension of a hemipelvis relative to the intact pelvis. Furthermore, evaluation of the amount of pelvic hematoma may be helpful in determining the need for angiography for embolization. Localization of these hematomas is a good predictor of associated pelvic vascular injuries.
Pelvic CT is not a dynamic study, and the assessment of biomechanical instability may be difficult. Certainly, the combination of a crescent fracture from the posterior superior iliac spine and displaced, anterior pelvic ring fractures will be unstable under anesthesia. The stability of other patterns, however, is not so predictable, even though CT images provide a great deal of anatomic and conceptual (injury pattern) information. Therefore, conventional x-rays are necessary as guides to intraoperative reduction.
Evaluation of the acetabulum with CT is usually accomplished by an initial rapid survey, in which obvious fractures are ignored and the observer completes the general survey. If fractures involve the acetabulum, the goal is to determine what remains attached to the intact hemipelvis and describe and characterize the major fracture fragments and their relation to each other and the femoral head. Initiating the search at the anterior surface of the sacrum, evaluating symmetry of the sacroiliac joint, and following along the cortical margin of the sciatic buttress to the tectum provide an anatomic approach that extends from the intact hemipelvis toward the fracture. Assessment of the posterior through anterior walls, the ischium for the posterior column, the pubis and symphysis for evaluation of the anterior column, the iliac wing for superior extension, and the secondary congruence between the femoral head and tectum allows for a more complete recognition of fracture fragments.
Conventional radiography is for evaluation of long bones showing obvious deformity, instability, palpable crepitus, pain, and swelling. For periarticular regions, conventional x-rays are indicated for deformity, instability, decreased range of motion, pain, and swelling. The Ottawa ankle and knee clinical prediction rules add considerable precision to specificity.69–71
For long bones (Fig. 15-36), two orthogonal views are obtained, including an AP view and lateral projection centered at the midshaft. Projections should include the joint above and the joint below the long bone, or the end of the bone. Periarticular regions (joints) (Figs. 15-37 to 15-41) should have two orthogonal views and one or two oblique views, centered at the midportion of the articulation.
FIGURE 15-35 Acetabulum: both column fractures. This 63-year-old man sustained left acetabular fracture in 12-ft fall onto concrete. (A) Anteroposterior (AP) conventional radiograph of pelvis shows disruption of both iliopectineal and ischiopubic line on left, and disruption of left ischiopubic ramus. (B) Left obturator oblique view shows so-called spur sign, characteristic of both column fractures. Spur (arrow) represents intact iliac bone connected to sacroiliac joint, exposed due to medial migration of unstable anterior hemipelvis. Judet obliques are named for affected side, such that when obturator foramen is visible en face, image is termed an obturator oblique, and when iliac wing is imaged en face with foreshortening of obturator foramen, the view is termed iliac oblique. Oblique views give best conventional film representation of acetabular anatomy. (C) Axial computed tomography (CT) image obtained just above tectum shows comminuted coronal plane fracture of left acetabulum. White arrow marks intact supraacetabular ileum and is piece of bone that accounts for “spur” seen on obturator oblique views of affected hip (B). On CT, column fractures, whether anterior, posterior, or both columns, are typically shown as coronal plane fractures. (D) Sagittal CT reformation shows separation of acetabular roof from intact hemipelvis, characteristic of both column acetabular fractures. (E) Oblique coronal plane reformation from axial CT shows good secondary congruence between femoral head and free-floating tectum. Disruptions of medial acetabular wall, as well as supra-acetabular wall, are demonstrated.
FIGURE 15-36 Long-bone fracture: Monteggia. Lateral view of proximal forearm shows anterior convex angulation of midshaft fracture of ulna. Anterior dislocation of radius at radiocapitellar articulation is present. While Monteggia and Galeazzi fractures are well-known long-bone fractures with associated dislocations at adjacent joint, the evaluation of any long-bone fractures should include careful evaluation of adjacent joints. (Reproduced with permission from CC Blackmore.)
FIGURE 15-37 Periarticular fracture: coronoid process fracture of elbow. (A) Anteroposterior (AP) radiograph of left elbow shows displaced coronoid process (arrow). Elsewhere, joint appears congruent. (B) Lateral view of left elbow shows tip of coronoid process fracture (arrow). Coronoid process fractures can be graded by amount of coronoid process involved, such that larger coronoid process fracture fragments are more likely to result in elbow instability. (C) Axial computed tomography (CT) obtained because mismatch between radiographic and clinical findings of instability shows highly comminuted fracture of coronoid process (arrows). Radial head (R) and olecranon process (O) appear normal. (D) Sagittal CT reformation shows nearly all the coronoid process is involved in fracture. Secondary congruence between trochlea and olecranon–coronoid process is fair. (E and F) Three-dimensional “surface-rendered” CT reformations more graphically demonstrate transverse and distal extent and displacement of coronoid process fracture.
FIGURE 15-38 Periarticular injury: shoulder dislocation. (A–C) Anterior dislocation sustained by a 52-year-old struck by falling tree on his back. (A) An anteroposterior (AP) radiograph with medial location of humeral head relative to glenoid (circle). (B) Postero-oblique radiograph of humeral head and glenoid (dotted line). Note that amount of overlap of scapula is less on this posterior oblique view than it is on anterior view (A), characteristic of anterior dislocation. (C) An axillary view; shows anterior location of humeral head relative to glenoid (upward pointing arrow and circle, respectively) on axillary lateral view. (D and E) Posterior dislocation sustained in a 42-year-old man who fell during a seizure. Posterior oblique radiograph (D) shows overlap of glenoid (circle) and medial aspect of humeral head (dotted line). (E) An axillary projection that shows the location of the humeral head posterior to glenoid (oval). Posterior margin of the head is denoted by downward pointing black arrow. Three downward pointing white arrows show impaction on anterior margin of humeral head, so-called trough fracture or reverse Hill–Sachs deformity.
FIGURE 15-39 Periarticular fractures: intra-articular intercondylar distal femur fracture. This 20-year-old man was involved in a highspeed motor vehicle crash as a belted driver. (A) Anteroposterior (AP) radiograph of knee shows transverse T-type fracture of distal supracondylar femur, with intra-articular extension into intercondylar notch (arrows). (B) Lateral radiograph of knee shows transverse supracondylar component (arrow), from which femoral condyles have dissociated. In addition, lateral femoral condyle shows coronal plane, comminuted fracture of posterior aspect of condyle (arrowheads). In up to 40% of intra-articular intracondylar fractures caused by high-energy mechanisms, such coronal plane fractures (Hoffa’s fracture) may be overlooked. (C) Axial computed tomography (CT) shows a sagittal plane fracture extending into midportion of trochlea of the patellofemoral joint and a comminuted coronal plane fracture of posterior aspect of lateral femoral condyle (arrow). (D) Coronal plane reformation from axial CT shows T-type intra-articular fracture with dissociation of medial and lateral femoral condyles (white lines). Asterisk marks developmental variant, nonossifying fibroma. (E) Sagittal reformation from axial CT in central portion of lateral knee joint compartment shows coronal plane fracture of posterior femoral condyle (Hoffa’s fracture) as marked by arrow. Asterisk notes nonossifying fibroma, a benign developmental variant.
FIGURE 15-40 Periarticular fractures: tibial plateau fracture (Schatzker 2). This 46-year-old man fell on the stairs. (A) Anteroposterior (AP) radiograph of knee shows valgus angulation due to collapse of lateral femoral condyle into a split depressed fracture of tibial plateau (arrows). (B) Axial image from computed tomography (CT) shows depressed left (asterisk) and split (arrows) portions of split depressed fracture. Note extension of comminuted fracture lines into medial tibial plateau across posterior aspect of proximal tibia and into intercondylar eminences, where anterior eminence (A) is minimally displaced. (C) Coronal reformation from axial CT shows split (arrow) and depressed (asterisk) portions of Schatzker type 2 fracture. Also note apparent elevation of anterior tibial eminence (A), on which anterior cruciate ligament inserts. Less striking step-off is seen in central portion of medial tibial plateau. (D) Three-dimensional CT reformation graphically demonstrates depression and lateral displacement of articular surface and lateral rim of tibial plateau, respectively. Also shown on this view is fracture of proximal fibula.
FIGURE 15-41 Periarticular fractures: calcaneus and Lisfranc fractures of midfoot. This 51-year-old restrained driver in a high-speed motor vehicle crash sustained multiple extremity and torso injuries. (A) Lateral conventional radiograph shows intra-articular fracture of calcaneus (upward pointing arrow denotes primary fracture plane; asterisk shows double density of central lateral fragment of posterior subtalar joint of calcaneus). Downward pointing arrow shows displacement of one of the metatarsal bases with an adjacent cuneiform fracture. (B) Axial computed tomography (CT) image at level of base of sustentaculum tali shows varus deformity through primary fracture (arrow). Secondary fracture plane extends toward anterior process (bracket). It is important to note continuity of cortex of medial wall of anterior process, as it influences distal extent of necessary fixation. (C) Sagittal reformation from axial CT shows primary fracture plane (upward arrow) with centrolateral fragment rotated into its superior extent. (D) Coronal reformation shows comminuted fracture of posterior facet of calcaneus due to bursting of body by lateral process (LP) of the talus. Centrolateral fragment is shown by asterisk. White arrow denotes lateral dislocation of peroneal tendons from peroneal groove in posterior fibula. (E) Axial CT at level of sinus tarsi, soft tissue window, shows lateral and anterior dislocation of peroneal tendons surrounded by hemorrhage and edema (white arrow). (F) Three-dimensional reformation from axial CT, medial oblique projection, shows divergent dislocations of great toe and third to fifth metatarsal bases (arrows).
Analysis of the long bone should allow assessment of the direction of the force that created the fracture pattern (e.g., twisting injuries result in spiral fractures; bending injuries result in wedge fractures). In general, higher-energy injuries tend to be more comminuted and displaced. If there is a mismatch between the apparent amount of comminution and the reported energy of the injury, osteoporosis or otherwise pathological bone should be suspected.
For periarticular regions, subluxations are suggested by partial or complete loss of congruity of the joint, the appearance of a so-called white line due to overlapping of bones, and disruption of expected alignment of adjacent articulating structures.
Careful attention to soft tissues (e.g., focal swelling, obliteration of normal fat pads, joint effusions) is helpful for subtle or otherwise occult fractures (e.g., elbow, knee, and wrist).
Computed Tomography of Appendicular Joints
CT of appendicular joints (e.g., shoulder, supracondylar femur, tibial plateau, pilon, and calcaneus) is indicated for “displaced” intra-articular fractures (e.g., 1–2 mm at the wrist or scapula, and glenoid, 5–10 mm at the tibial plateau) or unstable fracture patterns (Figs. 15-37 to 15-41). CT may be very helpful in presurgical planning and in the detection of otherwise occult fractures.
In most patients, CT should be performed after provisional placement of traction or reduction. Slice thicknesses of 0.5–1.25 mm in the axial plane may be used in all appendicular joints to acquire raw data and may be reconstructed using bone algorithms. Initial reformations are usually obtained perpendicular to the joint of interest and orthogonal to source data and initial reformation planes. Three-dimensional volume-rendered reformations should be made from reconstructions created using standard (soft tissue) algorithms and variable (user-defined) opaqueness.
Use of traction prior to imaging allows ligamentotaxis to indirectly reduce fracture fragments and support indirect assessment of the integrity of soft tissue attachments to major bony fragments. Specifically, bone fragments that do not move or reduce on stretch are presumed to be no longer attached to soft tissue and may require debridement or direct repositioning. In addition, CT facilitates the assessment of intact bone and the integrity of subchondral bone (e.g., need for bone grafting).
CT for injuries to the scapula allows for the assessment of intra-articular step-offs, displacement of 1–2 mm or more, and the determination of stability of shoulder projection (which is determined by an intact clavicle, acromion, basiacromion, and glenoid neck). In addition, function of the supraspinatus and infraspinatus muscles may be disrupted in the presence of scapular spine fractures that are displaced for 10 mm or more.
Catheter angiography is the definitive method of evaluating arterial blood vessels for injury and of identifying active arterial hemorrhage. While CT angiography is frequently favored for imaging of many traumatic conditions, it has rarely been validated against the “Gold Standard” of catheter angiography. A notable exception is the screening of traumatic injury of the thoracic aorta that has replaced catheter angiography for many patients.
Advantages of catheter angiography are many. It allows simultaneous detection and treatment of a wide variety of traumatic vascular injuries. It is a very specific method of identifying bleeding at the submillimeter diameter of vessel. It can evaluate many sites of bleeding simultaneously. It has an excellent safety record, especially when using iso-osmolar nonionic contrast agents, coaxial micropuncture access, digital subtraction techniques, coaxial microcatheters, and steerable guidewires.
Disadvantages are cost, the delay necessary to assemble the team of radiologists, technologists, and nurses, the lack of suitability as a screening test, and the risks of radiation exposure. Technical expertise is limited to predominantly subspecialty-trained interventional radiologists (although endovascular surgeons and cardiologists may develop this expertise on an individual basis). These disadvantages are magnified when the likelihood of injury is low. Thus, noninvasive vascular techniques such as CT angiography should be explored under controlled studies to further assess their accuracy and appropriateness in such situations.
Transcatheter Endovascular Therapies
Endovascular techniques have become a broadly accepted way of controlling traumatic hemorrhage for a variety of reasons. Catheter-based hemostasis allows precise control from a remote site that avoids exacerbation of venous hemorrhage, introduction of pathogens, and hypothermia that may result from open exposure. It is especially valuable for hemorrhage that is remote or hidden from view and requires laborious time-consuming exposures or that is the result of multiple small bleeding sites that are not easily detected or controlled during operative exploration.
Endovascular techniques include embolization, stenting, stent grafting, and temporary balloon occlusion. They may be definitive or an adjunct to operative exposure. The methods of embolization include particulate or microcoil embolization of small vessels, proximal and distal large vessel isolation of a bleeding vessel, and conduit coil occlusion to cause selective temporary hypotension of the bleeding zone.
Stenting, which facilitates blood flow beyond an injury, has largely been replaced by covered stent grafts that exclude lacerations, transections, and arteriovenous fistulae while maintaining flow through the conduit. Endografts are made of a variety of porous materials such as expanded polytetrafluoroethylene and are reinforced by a metallic skeleton that apposes the stent graft to the native artery. Reports of midterm patency, while limited at this time, are beginning to show that these are durable options to vascular repairs.
Contraindications to endovascular techniques are highly dependent on skills, teamwork, and hemodynamics; however, there are some injuries that are difficult for rapid surgical control and endovascular techniques have a role, even in the unstable patient.
Arch Angiography for Acute Blunt-Force Traumatic Aortic Injury
Blackmore et al.59 have published a clinical prediction rule as an aid to determine which patients should be screened for traumatic aortic injury. Usual indications are either direct (pseudoaneurysm, intimal flap) (Fig. 15-42) or indirect (juxta-aortic hematoma) CT findings, especially if the abnormality involves the ascending aorta. If patients are going directly to angiography for evaluation of disruptions of the pelvic ring and the mediastinum is not normal on a chest x-ray, catheter arch angiography is the preferred “screening” modality; otherwise, CT is the preferred modality for patients at >0.5% risk for aortic injury.72 Modern CT angiographic techniques are quite exquisite in demonstrating aortic injuries as well as providing coronal and sagittal reformations that can illustrate the important relationships and variants necessary for surgeons to create a treatment plan.
FIGURE 15-42 Traumatic aortic pseudoaneurysm. A 30-year-old-male following high-speed motor vehicle accident. Left anterior oblique (LAO) digital subtraction arch aortogram shows traumatic aortic pseudoaneurysm extending proximal to the left subclavian artery. Of note, the aortic diameter and the distance from the left subclavian artery are important when considering endovascular therapy.
Among selected patients sustaining aortic injury who are not operative candidates, endovascular stent grafts have been advocated as either temporizing or definitive therapy.
Typically, a 5 French pigtail catheter is guided to the ascending aorta via a femoral arterial approach. Patients are positioned and imaged in both 35° right anterior oblique (RAO) and left anterior oblique (LAO) projections, using injection rates of approximately 25–30 mL/s for 40–60 mL volume (depending on hemodynamic status) and positioning to include the great vessels and diaphragm.
The arteriographic appearance is classical. Linear filling defects indicate torn and ruffled intimal lining; expansion of the lumen, typically at the ligamentum arteriosum, indicates the presence of a pseudoaneurysm. This is sometimes associated with distal narrowing of the contrast column.
Associated injuries should also be identified. Injuries of the brachiocephalic branches may occur instead of or in association with aortic injury. Bleeding from the internal mammary or the intercostal arteries is easily overlooked without diligence.
Hepatic Angiography for Blunt-Force Lacerations
Visceral catheter angiography is appropriate to evaluate hepatic lacerations (Fig. 15-43), especially in patients with a labile hemodynamic status or those with active extravasation or vascular abnormalities on a contrast-enhanced CT. Gross hemodynamic instability and profound shock, however, usually mandate urgent celiotomy. Of course, angiography may have a role after a “damage control” operation.
FIGURE 15-43 Liver laceration. (A) CT of the upper abdomen reveals a Grade V liver laceration with pseudoaneurysm of the right hepatic lobe in this 18-year-old male status post-high-speed MVA. (B) Right hepatic angiogram identified the pseudoaneurysm. Note the size of the feeding vessel in relation to the 5 French diagnostic catheter. Selective coil embolization was performed through a microcatheter. When selective catheterization is not possible, the liver is quite tolerant of wide arterial embolization due to the dual blood supply provided the portal veins are patent.
Hepatic fracture lines seen on CT that traverse the hepatic triad more often result in bleeding than those fractures that are parallel to the triad. Extravasation of CT contrast tends to be associated with a positive arteriogram, but the decision to use angiography should primarily be based on clinical status rather than the CT appearance. Lack of enhancement of segments of the liver on CT is a very important finding. It represents a large hematoma in the liver, occlusion of the portal triad, or injury of the hepatic outflow from that segment. It is vital to distinguish nonenhancement from a hematoma. A large hepatic hematoma pushes the hepatic fragments away from each other, and unopacified or opacified hepatic vessels are not seen in a hematoma. If the area of nonenhancement has vessels running through it, it suggests an occlusion of the portal vein and hepatic artery or injury to a hepatic vein. Therefore, CT nonenhancement of the liver is a clear indication for urgent angiography if at all possible to confirm such injuries and to control arterial hemorrhage. As surgical exploration of damaged hepatic veins may be quite difficult, hepatic embolization and observation of a nonbleeding hepatic venous injury can be lifesaving. And, as noted above, hepatic angiography has an important role in the management of penetrating liver injuries that are isolated to the liver, as well as a secondary procedure.
Selective catheterization of both the celiac trunk and the superior mesenteric artery (SMA) is essential due to the high rate of hepatic vascular variants, particularly the aberrant replaced right hepatic artery from the SMA. Imaging should be continued through the late portal venous phase. Moreover, it is important to determine whether there is patency of portal flow prior to embolization of the hepatic artery.
Critical findings include arterial extravasation, spasm and occlusion, or shunting and fistula to portal or hepatic venous structures. Embolization of discretely abnormal vessels can be performed using a number of methods. A diffusely abnormal parenchymal injury with arterial bleeding may be safely embolized with Gelfoam due to the dual blood supply of the liver (hepatic arterial and portal venous). Embolization of hepatic arteries in the absence of portal flow increases the risk of developing an infarction or abscess. Depending on the location of bleeding and on the difficulty with catheterization, particulate embolization is the fastest technique; however, single microcoil embolization is preferred if time and circumstances allow. While formation of a postprocedure abscess is a complication of embolization, outcomes are favorable by integrating percutaneous image-guided drainage into the scheme.
Splenic Arteriography for Blunt-Force Lacerations
A patient who is hemodynamically unstable is not a candidate for angiography and embolization. Other patients who have an injury of the spleen diagnosed on CT are candidates for nonoperative therapy with good results. CT is not a reliable predictor, however, of which patients are best managed by bed rest compared to those patients who require hemostasis. When a CT demonstrates active arterial extravasation or a parenchymal vascular abnormality, one should consider angiography. Unfortunately, there is not good correlation between the CT grading system and outcome of treatment. Many Grade IV injuries can be observed and some Grade I injuries become worse, rebleed, and require definitive procedural therapy. The author and his surgical colleagues observe (i.e., bed rest) most Grade I injuries, but advocate liberal use of angiography for triage of most other CT-diagnosed splenic injuries, especially in those patients with a significant hemoperitoneum or transient hypotension. Patients with high-grade injuries on CT should be imaged by angiography early to avoid transfusion or delayed rupture. The absence of arteriographic extravasation is a highly reliable predictor of successful nonoperative therapy regardless of grade. Identification of active arterial extravasation is the standard indication for endovascular treatment.
Diagnostic angiography of the celiac trunk is followed by selective splenic artery catheterization with a 5 French catheter. If splenic artery anatomy permits, and a solitary pseudoaneurysm or focus of extravasation is seen, distal coil embolization at the site of injury can be attempted. This is especially true in a patient in whom the extravasation extends beyond the splenic capsule into the peritoneal cavity. It should be remembered that distal superselective embolization is associated with the development of more postprocedure splenic infarctions and abscess, though these are uncommon. Finally, most patients have tortuous splenic arteries and most extravasations are multiple.
Diffuse intrasplenic extravasation is far more common, and superselective occlusion of these multiple sites would be very time consuming and less effective. Also, the splenic tortuosity that results from medial displacement of the spleen by the perisplenic hematoma often prevents rapid catheterization (Fig. 15-44). In such cases, embolization of the proximal splenic artery by coils placed distal to the dorsal pancreatic branch and proximal to the pancreatic magna branches is advocated to reduce the arterial pressure head at the injury site while allowing perfusion through collateral vessels. Such collaterals prevent splenic infarction by maintaining splenic perfusion through connections between the left gastric and the short gastric arteries, between the dorsal pancreatic artery and the pancreatica magna branches, between the right and left gastroepiploic vessels, and others (Fig. 15-45).
FIGURE 15-44 Splenic intraparenchymal false aneurysms. Digital subtraction angiogram of the splenic artery reveals multiple focal extravasations in this 56-year-old male status post-MVA. Selective embolization is not desirable because so many vessels are injured and selective catheterization would be difficult due to splenic artery tortuosity. In such cases proximal splenic artery coil embolization proximal to the pancreatic magna branch is usually successful in controlling this hemorrhage.
FIGURE 15-45 Demonstration of long-term follow-up of splenic artery embolization. A 40-year-old female pedestrian sustained blunt splenic injury after being struck by a motor vehicle 10 years ago. She was treated by coil occlusion of the proximal splenic artery with good results. During admission 10 years later for stab wound to the neck, the coils were detected. Splenic arteriography was performed. This demonstrated marked enlargement of the pancreatic collaterals that bridged the occlusion. Flow was rapid through these very large collaterals.
Complications are uncommon when proximal splenic artery embolization is performed. A poorly selected coil size may result in hilar occlusion if the selected coil is too small and migrates distally. Too large coils may migrate proximally to occlude the celiac axis or embolize into the aorta. As noted above, distal microembolization bypasses the collateral circulation and results in more loss of immune function.
Interventions for Renal Trauma
Low-grade renal injuries are usually well tolerated and do not require angiography, especially when caused by blunt trauma. Initial nonoperative management of blunt renal injuries with an intact pedicle is the common practice. High-grade injuries that result in massive hemorrhage are usually managed by nephrectomy. In other patients who are hemodynamically stabilized, angiography with intent to embolize bleeding is appropriate. Angiography is recommended for patients with CT evidence of a major renal injury and ongoing blood loss or persistent gross hematuria. Areas of nonenhancement on CT suggest a renal vascular injury, such as a polar avulsion or intimal stretch of the main renal artery with distal platelet embolization.
Penetrating renal injuries are more aggressively approached by angiography if nonoperative management is undertaken. Large perinephric hematomas, areas of nonenhancement, and extravasations on CT warrant angiography.
Aortography is helpful to assess injury of the origin of the renal artery, to exclude renal parenchymal injury perfused by accessory renal arteries, and to look for associated intraperitoneal and retroperitoneal bleeding sites. A selective renal arteriogram using a 5 French catheter is then performed. Most injuries will require use of a coaxial microcatheter and embolization of small branches. Coils are preferred as they can be carefully placed to prevent infarction of adjacent noninjured renal tissue, but surgical gelatin pledgets can be used, as well. Because renal branches are end vessels with little collateralization, infarction is likely, and the goal is to reduce these infarctions to a minimum.
The treatment of vascular injury in the renal pedicle continues to be a vexing problem, especially since delays in revascularization usually result in a renal infarction. Partial wall injuries that result in a pseudoaneurysm, false aneurysm, and segmental infarction often went unrecognized prior to the use of CT. Such injuries are detected currently before complete arterial thrombosis and renal infarction occurs. Therefore, arteriography is indicated when an injury in the renal artery is suspected. When such injuries are detected, treatment options are many, including operative revascularization, antiplatelet therapy and observation, and the application of covered stent grafts. Stent grafts can effectively seal full thickness injuries and cover exposed media that results in embolic infarctions. While long-term follow-up of series of these patients is lacking, the midterm (1–5 years) patency of stent grafts throughout the body remains high (Fig. 15-46).
FIGURE 15-46 (A–D) Renal artery injury. A 56-year-old man fell from a height of about 10 m. (A) During CT evaluation inhomogeneous enhancement of the spleen was detected. Central perinephric hemorrhage (asterisks) and irregularity of the renal artery (arrow) were seen. (B) Coronal reformation shows irregularity of the renal artery and thickening of its wall. (C) Aortography showed irregular enlargement of the proximal renal artery near the ostium (circled). Slight extravasation was seen on the later images. (D) Therefore, a stent graft was placed over the area of injury. The vessel wall was then smooth, and no extravasation was seen. Two-year follow-up arteriography showed continued patency and no stenosis.
Blunt Pelvic Fractures
Blunt pelvic fractures with crushing or shearing tear the small branches of the internal iliac artery that accompany ligaments, muscles, and tendons. Injuries tend to be multiple and bilateral, and from several branches. In addition, bony fragments can penetrate or perforate vascular structures. Examples include a fracture of the superior pubic ramus injuring the internal pudendal or obturator artery, a fracture of the iliac wing through the sciatic notch injuring the superior gluteal artery, and disruption of the sacroiliac joints injuring the lateral sacral arteries.
Pelvic fractures are potentially life-threatening injuries that are caused by high-energy impact trauma and account for about 3% of skeletal injuries. They are the third most common lethal injury after motor vehicle crashes. The majority of patients with pelvic fractures do not require massive transfusion (greater than 6 U) as bleeding in most cases is likely to be venous or osseous in nature and is self-limited. Radiological intervention is not commonly needed in patients with routine pelvic fractures. Severe hemorrhage, however, occurs in 3–10% of patients, and mortality rates may be as high as 50% in patients with unstable pelvic fractures. Thus, the use of angiography in patients with pelvic fractures is highly dependent on the hemodynamic status, the type of fracture pattern, the transfusion requirements, and the presence or absence of hemoperitoneum.
Most of the indications for angiography in blunt pelvic trauma have remained the same for more than 30 years and are listed as follows:
1. Hemodynamic instability in a patient with a pelvic fracture with no or little hemoperitoneum detected by FAST or diagnostic peritoneal lavage
2. Pelvic fracture and transfusion requirement of greater than 4 U in 24 hours
3. Pelvic fracture and transfusion requirement of greater than 6 U in 48 hours
4. Pelvic fracture and a large or expanding hematoma identified during celiotomy
5. CT evidence of large retroperitoneal hematoma with extravasation of contrast
6. Need for detection and treatment of other injuries during angiography
With MDCT the detection of extravasation of contrast has been used as an indication for follow-up pelvic angiography. Of course, CT is not as reliable as clinical signs as extravasation may be venous in origin and not correlate with massive arterial hemorrhage. Although it should not delay angiography that is already indicated for pelvic hemorrhage, CT is helpful in localizing the vessels likely to be bleeding and in excluding associated abdominal and cerebrospinal injuries. Correlations of location of the hematoma and site of vascular injury include obturator space and obturator artery, presacral space and lateral sacral artery, space of Retzius and internal pudendal artery, and buttock and gluteal artery.
Femoral access is the preferred approach; however, catheterization may be difficult because of hypotension, tachycardia, and difficulty in palpating the vessels as the pelvic hematoma expands. Ultrasound or fluoroscopic guidance is very helpful in these situations. A 5 French aortic flush catheter is used for flush abdominopelvic aortography. This is valuable to screen the abdominal viscera and mesentery, to exclude aortoiliac and other retroperitoneal bleeding sources, and as a road map of the pelvic vessels. Bilateral internal iliac arteriography is mandatory to exclude bleeding sites since aortography may not identify all bleeding. From one access, both internal iliac arteries are sequentially catheterized and opacified. Then, external iliac arteriography is used to evaluate the external pudendal and external obturator vessels.
Multiple areas of extravasation are often identified. These may be bilateral and may involve multiple vascular beds. Extravasation is often punctate, but can be large, coarse, and extensive, also. The size of such extravasations may not correlate with the degree of blood loss. Vascular occlusions are common, as well. These can be due to thrombosis or vasospasm that often cannot be differentiated. Failure to treat these occlusions may result in recurrent hemorrhage when vasospasm resolves. Arteriovenous fistulas can occur, but are more common in penetrating trauma.
Because bleeding is usually multifocal and originates from multiple small blood vessels, embolization requires small particulate embolization. Large coil occlusion is as ineffective as surgical ligation of the internal iliac artery because bleeding soon resumes through numerous collateral circuits. Surgical gelatin pledgets are ideal because they are inexpensive, readily available, and often temporary lasting only a few weeks and allowing reestablishment of normal blood flow after the tissue has healed (Fig. 15-47A and B). Permanent particulate emboli, however, are often used because of their ease of use through a microcatheter (Fig. 15-48A and B). Embolization is technically successful in more than 90% of patients, and hemorrhage control is highly effective. Survival depends on many other factors including associated injuries, the presence of an open fracture, transfusion requirements, and delays to embolization.
FIGURE 15-47 (A and B) Multiple bleeds from pelvic fractures: 48-year-old male driver in a motor crash sustained pelvic fractures requiring transfusions. (A) Circles surround multiple bleeding sites from the region of the sacroiliac joint; from the pelvic side wall on the right hemipelvis emanate anterior and posterior branches of the right internal iliac artery and in the region (B) multiple points of extravasation were detected (circle). They are emanating from the left lateral sacral artery. Such diffuse hemorrhage is not amenable to superselective embolization because it would be too time consuming. Pledgets of surgical gelatin, 2–3 mm in size, can occlude these vessels effectively.
FIGURE 15-48 (A and B) A 26-year-old motorcyclist sustained unstable pelvic fractures during a crash. He developed expanding perineal and scrotal hematomas requiring red cell transfusion. (A) Left internal iliac arteriogram reveals a source of bleeding from the left internal pudendal artery (curved arrow). The more medial contrast stain (straight arrow) is a normal finding. It represents the blush of the perineal body and root of the ischiocavernosa muscle that is frequently seen on internal iliac arteriography of mails. (B) Because this was focal hemorrhage, selective embolization via 2.8 French catheter placed coaxially through the 5 French catheter was attempted and successfully achieved hemostasis.
Penetrating Pelvic Trauma
Penetrating trauma is an uncommon indication for pelvic angiography as most patients are hemodynamically unstable or have clear indications for exploratory celiotomy. Moreover, they are more likely to sustain injuries to large vessels. Because the retroperitoneum has been exposed by a penetrating wound, intraperitoneal bleeding is likely and direct exploration is warranted. Occasionally, angiography is valuable when operative control cannot be initially accomplished and damage control has been performed. Angiography and embolization prior to unpacking will avoid additional blood loss at a reoperation.
Large vessel conduit injuries require a very different endovascular strategy. When an injury to a noncritical internal iliac artery or branch has been missed at operation, but detected on postoperative angiography, coil occlusion of both the proximal and, whenever possible, the distal end of the vessel is the standard treatment.
Peripheral Vascular Injuries
A discussion of the use of interventional radiology in the treatment of extremity injuries must be preceded by a discussion of the use of imaging in the diagnostic workup of suspected vascular trauma in the extremities. The indications and contraindications depend on a variety of factors that are primarily related to clinical presentation and hospital course, and also to associated injuries, mechanism of injury, and signs of circulatory shock.
Vigorous or pulsatile external active hemorrhage, a rapidly expanding hematoma, or loss of pulses at the wrist or ankle mandates emergent operative exploration. Other patients with proximity wounds and stable hematomas, diminished pulses, or signs of an arteriovenous fistula may benefit from arteriography. The availability of stent grafts has also increased the utilization of angiography as a prelude to nonoperative management of some clinically significant vascular injuries.
While debatable to some, “proximity” angiography has value in asymptomatic patients with penetration that has passed close to the estimated path of major vessels. Vascular injuries occur in 3–8% of asymptomatic patients. Failure to diagnose arterial injuries may result in delayed hemorrhage or chronic arteriovenous fistulas with claudication, venous insufficiency, and congestive heart failure. Exclusion angiography avoids the time and effort needed to keep track of patients who are often negligent in their own follow-up.
The indications for the use of angiography in patients who have sustained fractures and dislocations are a more complicated matter. Vascular injuries resulting from fractures and dislocations are uncommon. Clinical evaluation is often difficult as the hematoma from a fracture may be quite large and indistinguishable from one associated with a vascular injury. Crush wounds, angulation deformities, and fracture hematomas may cause a pulse deficit by kinking, entrapping the vessel, or inducing spasm without an intrinsic vascular injury. A laceration into muscle may result in external blood loss without major vascular injury. Finally, a compartment syndrome may result in tissue ischemia without loss of pulses.
Almost all peripheral vascular injuries can be reached using a 5 French catheter from femoral access provided a long enough catheter is available. Angiography should be done in multiple projections with opaque marking of the entry and exit wounds demonstrating that the entire course of the wounding agent is within the field of view. Iso-osmolar nonionic contrast medium is the optimal agent for visualization. Multiple images in the arterial, capillary, and venous phases are necessary.
The imaging signs of vascular injury include luminal narrowing, arterial extravasation, bulge of the wall, intraluminal filling defects, occlusions, and arteriovenous fistulas. The imaging signs are in some cases quite nonspecific. Luminal narrowing can result from spasm, mural thrombus, intramural hematoma, and extrinsic compression, while dilatation can result from a traumatic true aneurysm, traumatic false aneurysm (“pseudoaneurysm”), or arteriovenous fistula. Finally, occlusion can be caused by thrombosis or vasospasm.
The natural history of many injuries cannot be predicted by the angiographic appearance. Therefore, observation of some injuries is warranted. Equivocal findings such as luminal narrowing can be assessed by repeating angiography after infusion of an intra-arterial vasodilator, on a subsequent day. Small irregularities and intimal tears that are not flow restricting may be treated by antiplatelet therapy and will heal (Fig. 15-49A–D).
FIGURE 15-49 “Minimal injury” of the popliteal artery. Pedestrian who was struck by a motor vehicle sustained comminuted tibial plateau fracture of the left knee. Pulses were diminished and angiography was sought after incomplete reduction. (A and B) Initial popliteal arteriogram showed numerous filling defects consistent with intimal tears (white arrows). Patient was treated with aspirin. (C and D) Arteriogram 1 week later showed healing of the intimal tears.
Treatment of angiographically diagnosed vascular injuries is based on the criticality of the bleeding vessel, its size, location, and accessibility, the hemodynamic condition of the patient, and the type of lesion. Small vessels that are not essential for tissue perfusion can be treated by small particle embolization, using surgical gelatin pledgets or more permanent smaller agents. Permanent agents have no advantage, but in some instances are more easily administered through microcatheters than surgical gelatin. These agents are delivered by flow direction toward the path of least resistance, which is usually toward the bleeding site. Microcoils can be utilized for injury to a small vessel provided they can be delivered near enough to the injury site to avoid collateral recruitment that permits continued bleeding. Examples of vessels that can be treated by embolization of small particles include hemorrhage from a pelvic fracture, multifocal hepatic arterial hemorrhage, and injuries to small muscular branches in the extremities.
Injury to larger vessels such as those greater than 3 mm in diameter requires two techniques, one for essential vessels and one for expendable vessels. The treatment of essential vessels requires repair of the bleeding site while allowing continued blood flow. Thus, stent grafts can be deployed to cover the injured segment while allowing prograde flow (Fig. 15-50).
FIGURE 15-50 Thrombosis of popliteal artery with endovascular repair. A 46-year-old morbidly obese woman sustained comminuted tibial plateau fractures after a fall from curb. Pulses were absent. (A) Popliteal arteriogram shows complete occlusion of the mid-popliteal artery. (B) The catheter was quickly advanced to a location just above the occlusion and a guidewire advanced easily into the posterior tibial artery. An ePTFE reinforced stent graft was deployed between proximal and distal extent of the occlusion. (C) Follow-up popliteal arteriogram showed restoration of direct line flow. The entire procedure took less than 1.5 hours.
Nonessential conduits, such as branches of the profunda femoris artery or the brachial artery, or one of the arteries in the shank, can be safely embolized. Particulate embolization will flow past the injury and penetrate deep into the vascular bed. When conduits are injured, this insult to the vascular bed is unnecessary. Therefore, large vessel agents are used to occlude the damaged segment of the conduit while the vascular bed is perfused through collaterals (Fig. 15-51).
FIGURE 15-51 Example of vascular isolation by proximal and distal coil occlusion. A 22-year-old male sustained a single stab wound of the upper left chest resulting in very large hemothorax. (A) Subclavian arteriogram shows that there is active arterial hemorrhage from a lacerated fourth anterior intercostal branch of the left internal mammary artery. (B) Because there was continuity between anterior and posterior intercostals, it was necessary to advance a 2.8-French microcatheter across the laceration into the distal segment to deliver a coil distally before withdrawing the catheter and delivering a coil proximally.
Coils in various sizes, some containing threads or fibers to accelerate thrombosis, are the most common devices used to occlude a large vessel. A coil is sized to have a diameter large enough to prevent distal migration, but not too large to end up recoiling into a parent, nontarget vessel.
The technique of conduit isolation attempts to occlude both the proximal and distal vessels around the area of injury by coiling (Fig. 15-51). The goal is to exclude the vascular defect and prevent rebleeding through collateral vessels. This is highly desirable in most circumstances, but mandatory when treating arteriovenous fistulas. The guidewire is carefully maneuvered distal to the injured segment, but proximal to any branches, and coils are delivered. The catheter is then withdrawn, and coils are placed in the proximal segment.
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