Lower Cervical Spine Trauma Imaging and Diagnosis

Spinal trauma is classified according to the mechanism of injury and the presence or absence of stability. Various imaging modalities, including conventional radiography, conventional tomography, computed tomography, and magnetic resonance imaging, are available for assessment of the injured spine. ^{[1, 2, 3, 4, 5, 6, 7]}  The biomechanics of cervical spine injury are age-related; while younger children typically sustain cervical spine injuries during motor vehicle collisions, injuries in adolescents are often sports-related. Cervical spine injuries in children most commonly involve the upper spine, but complete lesions of the cord are associated more frequently with lower spine injuries. Spinal cord injury without radiographic abnormality (SCIWORA) is associated with sporting activities and child abuse, but dislocations most commonly result from motor vehicle–related trauma (especially among pedestrians), and C-spine fractures most commonly result from falls and dives. Despite the low incidence of cervical spine injuries in pediatric patients, increased efforts at prevention are demanded because of the high mortality rate (27%) and incidence of neurologic deficits (66%). ^[8]

In patients with blunt trauma presenting to the emergency department, cervical spine injuries are identified in 3-4% and thoracolumbar fractures in 4-7%. ^[9]

Predictors of mortality include younger age, motor vehicle–related mechanism, C1 dislocations, high injury severity score (>25), and associated closed head injuries. A high index of suspicion for SCIWORA is essential when evaluating adolescents with neck trauma associated with sporting injuries or victims of child abuse. ^[10]

(See the images below.)

Imaging modalities

Developments in imaging techniques allow an appropriate choice to be made quickly to diagnose cervical trauma. Clinical examination is used for diagnosis in the small group of patients with cervical trauma who do not require any imaging. Cervical trauma is seen at multiple levels in about 10% of cases, so imaging should include the upper and lower cervical hinges if treatment is to be instituted.

The quality of standard radiographs varies greatly. Their negative quality and predictive value decrease as the severity of the injury increases. CT scanning is the most efficient technique for not only detecting but also formally eliminating an injury. Whereas plain film was the preferred initial assessment modality throughout the 20th century, CT is now the preferred modality for the initial evaluation. ^{[11, 12, 1, 13, 14, 15, 16, 2, 17, 18, 3, 19, 20]}

The evidence for effectiveness of MRI for follow-up imaging after a negative cervical spine CT has been mixed and a number of published studies cast doubt on the cost-effectiveness. ^{[21, 22, 23, 24]}  MRI is indicated in patients with a neurologic deficit. MRI is also indicated in symptomatic patients with normal radiography findings when a bone bruise is suspected. ^[25] Ligamentous injuries, which are often missed on conventional radiographs and CT, represent an indication for dynamic MRI. MRI is indicated in cervical fractures that have spinal canal involvement, clinical neurologic deficits, or ligamentous injuries. MRI provides the best visualization of the soft tissues, including ligaments, intervertebral disks, spinal cord, and epidural hematomas.

Cervical spinal MR reveals noncontiguous spinal injury or upper thoracic spinal injuries in 28% of patients with cervical spinal injury. The mechanism of cervical spinal injury does not significantly affect the incidence of the noncontiguous or upper thoracic spinal injury. ^[26]

A portable crosstable lateral radiograph in the emergency department is frequently inadequate and needs to be abandoned, because, often, it is insufficient, requires several repeats, and cannot exclude a fracture. Once a clinical decision is made to evaluate a patient with radiography, adequate views must be obtained in the radiology department. The patient's neck should remain immobilized until a full cervical spine series can be obtained, although initial films may be taken through the cervical collar.

Pediatric cervical spine injury is relatively rare and estimated to occur in less than 2% of all pediatric trauma patients, as compared to 2-4% of adult trauma patients. Traumatic pediatric cervical spine injury can be more challenging to diagnose than adult injury. CT  is an appropriate initial imaging modality for pediatric cervical spine injury, and MRI serves as an additional modality when initial findings are equivocal. In a study of 100,769 pediatric trauma patients by Massoumi et al, across all included trauma centers, cervical spine CT scans were performed on 3.55% of children, while fewer than 1% of patients received either cervical spine MRI (0.38%) or x-ray (0.77%). ^{[27, 28, 29]}

Missed and delayed diagnoses

The most common reason for a missed cervical spine injury is a cervical spine radiographic series that is technically inadequate. ^[13] The incidence of delayed diagnosis ranges from 5 to 20%. In a study by Platzer et al, the diagnostic failure rate was 4.9%. In 44% of such cases, radiologic misinterpretation was responsible for the delayed diagnosis; in 28%, incomplete sets of radiographs were responsible; in 22%, the injury was missed because inadequate radiographs did not show the level of the injury; and, in one case (6%), the treating surgeon did not see the radiographs. The authors concluded that, for optimal examination of patients with suspected cervical spine injuries, a specific diagnostic algorithm is needed, including complete sets of proper radiographs with functional flexion/extension views, secondary evaluation of the radiographs by experienced staff, and further radiologic examinations (CT, MRI) if evaluation of standard views is difficult. ^[30]

World Federation of Neurosurgical Societies recommendations

The World Federation of Neurosurgical Societies (WFNS) Spine Committee published the following recommendations ^[31] :

Pediatric cervical spine injuries

• Children with neurologic spinal cord signs and without x-ray/CT-scan abnormalities should receive and MRI.
• Surgery is indicated for irreducible rotatory atlanto-occipital dislocation.
• Minerva cast may be used instead of Halo in children younger than 5 years with cervical spine fracture or dislocation without surgical indication.

SCIWORA recommendations

• Perform an MRI if the patient, after cervical trauma, has neurologic symptoms but x-ray/CT findings are nonconclusive.
• MRI findings in patients with SCIWORA correlate with symptoms and predict neurologic outcome.
• In patients with SCIWORA, conservative treatment should be preferred instead of surgical treatment. 

American College of Radiology guidelines

The American College of Radiology has published the following guidelines on spine trauma ^{[9, 32]} :

• Imaging is not recommended for initial imaging of patients ≥16 yr and < 65 yr with suspected acute blunt cervical spine trauma when imaging is not indicated by NEXUS (National Emergency X-Radiography Utilization Study) or CCR (Canadian C-Spine Rules) clinical criteria and the patient meets low-risk criteria.
• CT is preferred to radiographs for initial assessment of spine trauma. 
• CT angiography and MR angiography are both acceptable in assessment for cervical vascular injury. 
• MRI is preferred to CT myelography for assessing neurologic injury in the setting of spine trauma. 
• MRI is usually appropriate when there is concern for ligament injury or in screening obtunded patients for cervical spine instability.
• Imaging is not recommended for the initial imaging of children 3-16 yr with acute cervical spine trauma that meets low-risk criteria.
• Radiographs of the cervical spine are usually appropriate for the initial imaging of children 3-16 yr with acute cervical spine trauma with at least one risk factor with reliable clinical examination.
• Radiographs of the cervical spine are usually appropriate for the initial imaging of children younger than 3 yr with acute cervical spine trauma with a Pieretti-Vanmarcke weighted score of 2 to 8 points or more.
• Radiographs of the thoracic and lumbar spine are usually appropriate for the initial imaging of children younger than 16 yr with suspected thoracolumbar spine trauma. 

Indications for cervical spine radiography include altered mental status, intoxication, neck pain, midline neck tenderness, and neurologic deficit. Plain films provide rapid assessment of cervical spine trauma. Three views are the minimum requirement for a cervical spine series: (1) a true lateral view, which should include all 7 cervical vertebrae and the C7-T1 junction; (2) an anteroposterior (AP) view; and (3) an open-mouth odontoid view. These standard views may be obtained without the removal of a cervical collar and without requiring the patient to move his or her neck.

(See the images below.)

Plain radiography is inexpensive to perform, readily available, and noninvasive; does not involve the administration of intravenous contrast; and can be performed on virtually any patient.

Approximately 85-90% of cervical spine injuries are evident in lateral view radiographs. Radiography of the lateral cervical spine has a sensitivity of 82%, which, when combined with an AP view and odontoid view, rises to 93%. They remain the mainstay of assessing cervical trauma. Any views that require manipulation of an acutely injured patient are difficult to justify, considering the ready availability of cross-sectional imaging.

Plain radiography can be used to identify most cervical spine fractures and ligamentous injuries. Ligamentous injuries are often associated with cervical vertebral body malalignment, and some ligamentous injuries are elusive to plain radiography.

Flexion-extension views are indicated upon high index of clinical suspicion for ligamentous injury, as evidenced by focal neck pain, minimal malalignment on the lateral cervical radiograph, and no evidence of instability or fracture. These radiographs can be performed only in conscious patients who are allowed to move their neck, and neck motion is limited based on the occurrence of pain. The neck should not be forced into flexion or extension by the physician or technologist, since force may result in cord injury.

If visualizing all 7 cervical vertebrae and the C7-T1 disk space on a lateral cervical radiograph is difficult, traction of the arm is a useful maneuver, provided that the arm is uninjured. A swimmer's view is particularly effective in visualizing all 7 vertebrae and the C7-T1 disk space. While attempts are being made to obtain adequate plain radiographs, the patient should be maintained in cervical immobilization. If adequate plain films cannot be taken, CT scans should be substituted. Keep in mind that an inadequate plain film series is the most common reason for false-negative results.

Conventional radiography is generally considered adequate to rule out a fracture, but the rate of false-negative results is significant, at approximately 20%. This can be countered by proceeding to a CT scan when the plain radiography findings are negative in a patient who has neck pain disproportionate to radiographic findings. A CT scan is a sensitive means of identifying cervical fractures, but its ability to reveal ligamentous injury is limited. Conventional tomography may still be indicated if a type II dens fracture is suspected, although, with the advent of multidetector CT (MDCT), the need for conventional tomography would be limited.

Not all patients who arrive in the emergency department following multiple injuries require cervical radiography, even if they arrive with a cervical collar. Criteria for low-risk patients have been defined and can be used clinically to exclude cervical spine fractures. Clinically significant cervical spine injury is unlikely in a patient with a normal mental status who has no neck pain, no tenderness on neck palpation, no neurologic deficit, no other distracting injury, and no history of loss of consciousness.

Views required to radiographically exclude a cervical spine fracture include a PA view, a lateral view, and an odontoid view. The lateral view must include the entire cervical spine, including the C7-T1 disc space. SCIWORA syndrome is common in children and is an important diagnosis, since it responds to steroids, which limits the neurologic sequelae. These criteria apply only to adults and not to children because of concerns of an unreliable history from young children.

Some concern has been raised about case reports suggesting that occult cervical spine fractures will be missed if asymptomatic trauma patients do not undergo radiography of the cervical spine. A review of these reported cases does not meet the low-risk criteria in cervical spine radiography. ^[33] In alert patients with trauma who are in stable condition, the Canadian C-Spine rule (CCR) is superior to the National Emergency X-Radiography Utilization Study (NEXUS) with respect to sensitivity and specificity for cervical spine injury, and use of the former would result in reduced rates of radiography. ^[34]

Lateral view

A lateral view of the cervical spine constitutes the most important radiographic examination of cervical spine injury and is taken as a horizontal beam that can be obtained before the patient is moved. A lateral radiograph should be obtained and examined before any other views are taken. All 7 cervical vertebrae and the C7-T1 junction must be visualized, as the cervicothoracic junction is a common location for traumatic injury. Adequate visualization of C7-T1 may be limited by soft tissue in the shoulder region and can be enhanced either by traction on the arms (in the absence of arm injury) or by a swimmer’s view (one arm extended over the head). Occasionally, a repeat lateral radiograph with the cervical collar removed may clarify suspicious lesions.

Approximately 85%-90% of cervical spine injuries are evident in the lateral view, making it the most useful clinical view. The first observation to be made on a lateral cervical spine radiograph is the alignment of the vertebral bodies. The anterior and posterior margins of the vertebral bodies, the spinolaminar line, and the tips of the spinous processes all need to be aligned. Any "step" in the alignment is considered abnormal and should be regarded as evidence of ligamentous injury or an occult fracture; thus, cervical spine immobilization should be maintained pending definitive diagnosis.

If alignment is found to be normal, the spinous processes are examined for widening of the interspinous space. Widening suggests a ligamentous injury or fracture.

Next, spinal angulation should be assessed. An angulation of more than 11° at any level of the cervical spine is regarded as abnormal and, in the context of cervical spine injury, should be regarded as being secondary to a ligamentous injury or fracture until proven otherwise. The spinal canal should measure more than 13 mm wide on the lateral radiograph. A measurement of less than 13 mm may be a sign of impending spinal cord compromise.

Flexion and extension views

Flexion and extension views may be used if a pure soft tissue injury is suspected or if an injury of questionable stability is noted. The patient should perform the flexion and extension voluntarily. Flexion/extension views are absolutely contraindicated in unstable injuries.

Importantly, pseudosubluxation, which is a physiologic misalignment due to ligamentous laxity, can occur at the C2-C3 level and, less commonly, at the C3-C4 level. If the degree of subluxation is within the normal limits listed and the neck is not tender at that level, flexion-extension views may clarify the situation. Pseudosubluxation is more common in children than in adults. Pseudosubluxation should disappear with an extension view, but flexion-extension views should be taken only when fracture/dislocation has been excluded.

Anteroposterior view

The AP view is the least useful view from a clinical standpoint. The spinous processes should all align and lie in the midline. If one of the spinous processes is offset to one side, a rotation injury such as a facet dislocation should be considered. A clay shoveler’s fracture should be considered if a spinous process appears vertically split.

Oblique views

Some have suggested that additional lateral oblique views also be obtained, but these are best left to the discretion of the radiologist who will be reading the films. Oblique views are considered laminar views, because most of the pathologies that are depicted on these views result from disruption in the normal overlapping appearance of the vertebral laminae.

The appearance of the normal laminae has been likened to shingles on a roof, forming regular elliptical curves with equal interlaminar spaces. A posterior laminar fracture is usually evident as a break within the body of a single lamina. If the interlaminar space between 2 continuous laminae is symmetrically or asymmetrically increased, subluxation or unilateral facet dislocation should be suspected.

Simple wedge fracture

A simple wedge fracture shows a diminished height of the vertebral body anteriorly, associated with increased concavity and increased density due to bony impaction. The prevertebral soft tissue space is increased. The posterior column remains intact, making this a stable fracture.

Radiographic features of simple wedge fracture include the following:

• Buckled anterior cortex
• Loss of height of anterior vertebral body
• Anterosuperior fracture of vertebral body

Anterior subluxation

In anterior subluxation, the lateral cervical radiograph shows widening of interspinous processes, and anterior and posterior contour lines are disrupted in flexion views.

Radiographic features of anterior subluxation include the following:

• Loss of normal cervical lordosis
• Anterior displacement of the vertebral body more than 4 mm
• Fanning of the interspinous distance
• Associated compression fracture of more than 25% of the affected vertebral body
• Increase or decrease in normal disk space
• Fanning of the interspinous distance

Bilateral facet dislocation

In a bilateral facet dislocation, at the point of injury, the inferior articulating facets of the upper involved vertebra pass superior and anterior to the superior articulating facets of the lower involved vertebrae because of extreme flexion of the spine. Lateral cervical spine radiographs show an anterior displacement of more than half of the AP diameter of the vertebral body.

This is an extreme form of injury, is highly unstable, and is often associated with spinal cord injuries. Disk herniation is often associated with bilateral facet dislocation. Patients with such an injury need to be handled with extreme care, as further neurologic deficit may accrue if the injured disk retropulses into the canal during the application of cervical traction.

Radiographic features of bilateral facet dislocation include the following:

• Best seen on lateral radiograph
• Complete anterior dislocation of affected vertebral body by half or more of the vertebral body AP diameter
• Bow-tie or bat-wing appearance of the locked facets

Clay shoveler’s fracture

Clay shoveler’s fracture is best seen on a lateral radiograph as an avulsion/separation of the spinous process of a lower cervical vertebra. Thus, visualization of the C7-T1 junction in the lateral view is imperative. The fracture is seen in the AP view as a vertically split appearance of the involved spinous process. This is a stable injury and is usually not associated with a neurologic deficit.

Radiographic features of clay shoveler’s fracture include the following:

• Best seen on lateral view
• Ghost sign on AP view (double spinous process of C6 or C7 due to displaced fractured spinous process)

Unilateral facet dislocation

In unilateral facet dislocations, the lateral cervical spine radiograph shows an anterior displacement of the spine at the involved level of less than one half the diameter of the vertebral body. This is in contrast to the greater displacement seen with a bilateral facet dislocation. The AP view shows a disruption in the line connecting the spinous processes at the level of the dislocation. An oblique view shows disruption of the typical shingles appearance at the level of the involved vertebra. The dislocated superior articulating facet of the lower vertebra is seen projecting within the neural foramina.

Radiographic features of unilateral facet dislocation include the following:

• Best seen on lateral or oblique views
• Anterior dislocation of affected vertebral body by less than half of the vertebral body AP diameter
• Discordant rotation above and below involved level
• Facet within intervertebral foramen on oblique view
• Widening of the disk space
• Bow-tie or bat-wing appearance of the overriding locked facets

Burst fracture of the vertebral body

A burst fracture of the vertebral body is characterized by a vertical fracture line in the AP projection, associated with comminution and protrusion of the vertebral body both anteriorly and posteriorly in relation to the contiguous vertebrae in the lateral view. Posterior protrusion of the middle column may extend into the spinal canal and can be associated with anterior cord syndrome. A burst fracture always requires an axial CT scan or MRI to document the degree of middle column retropulsion. A burst fracture with a loss in height of more than 25%, retropulsion, or neurologic deficit is treated with traction. A fracture is considered stable if none of the aforementioned features exist.

Flexion teardrop fracture

Radiologic features of flexion teardrop fractures include the following:

• Prevertebral swelling, which is associated with anterior longitudinal ligament tear
• Teardrop fragment from anterior vertebral body avulsion fracture
• Posterior vertebral body subluxation into the spinal canal
• Spinal cord compression from vertebral body displacement; the cord compression is not usually visible on conventional radiographs
• Fracture of the spinous process

Whiplash

According to Ovadia et al, the initial radiograph taken in the emergency room is the best imaging modality and probably the only one needed routinely following whiplash injury. In their study, all patients underwent clinical examination and radiography on the day of presentation and at follow-up. MRI, CT scan, bone scan, and electromyographic (EMG) tests were performed upon request of the treating physician and correlated by the authors with the clinical findings. Cervical pain was the most common complaint (96%). ^{[35, 36]}

CT scanning is not mandatory in every patient with cervical spine injury. Most injuries can be diagnosed with plain films. However, the radiograph is questioned, CT of the cervical spine should be obtained. CT scan is particularly useful in fractures that result in neurologic deficit and in fractures of the posterior elements of the cervical canal, because the axial display eliminates the superimposition of bony structures. ^{[37, 38]}

The patient is scanned from the top of the vertebral body above the fracture or question of fracture to the bottom of the vertebral body below the fracture, with a slice thickness of 1.5 mm and 1.5-mm spacing. Sagittal and coronal reconstructions are a useful adjunct in all cases.

CT has many advantages. It is an excellent modality for characterizing fractures and identifying osseous compromise of the vertebral canal because of the absence of superimposition from the transverse view. The higher contrast resolution of CT provides improved visualization of subtle fractures, and CT also has the capability of sagittal, coronal, and oblique reconstructions, adding more clarity to the diagnosis of traumatic lesions.

MDCT supplements plain radiography and, in many centers, has supplanted plain radiography. CT appears to more sensitive, with lower rates of missed primary and secondary injury. In one series, 36% of patients with a single injury on plain radiography were found to have a second injury on CT.

The limitations of CT include difficulty in identifying fractures that are oriented in an axial plane, such as fractures of the odontoid peg, and an inability to show ligamentous injuries.

A lateral scout view of the head is always obtained when performing head CT. It is common knowledge that the lateral scout view may provide additional information, although a careful review may not be performed routinely. Careful evaluation of the scout view of the head, including the skull and neck, may yield valuable information that may not be visualized on the axial CT images. ^{[39, 40]}

MRI now has an established role in the assessment of spinal injuries, because many are associated with spinal cord and nerve root compromise, as well disk herniation. MRI provides excellent soft-tissue contrast, making it the study of choice for spinal cord survey, hematoma, and ligamentous injuries. In addition, MRI provides an excellent general overview because of its multiplane capability and the ability to depict the vertebral arteries. It involves no ionizing radiation exposure, the absence of which is particularly useful in the young patient. ^{[41, 42, 43, 4]}

The craniocervical junction is seen well on MRI. The anterior aspect of the foramen magnum is delineated, but the posterior margin is less constant in appearance. Compression and distortion of the medulla and upper cervical cord by bony and extramedullary lesions are seen easily.

Vertebral artery injury associated with craniocervical junction trauma can be detected with MRA, and MRI is less dangerous and more sensitive for soft tissue injury than conventional radiography. In addition, MRI is useful in differentiating between pathologic vertebral fractures related to metastatic malignancy and benign osteopenic insufficiency fractures.

MRI is particularly useful in the following situations:

• Trauma at the craniocervical junction
• Evaluation of spinal cord injuries associated with cervical spine fractures
• Follow-up of SCIWORA
• Neurologic deficit with negative radiographic findings
• When neurologic deficit does not correlate with the level of trauma
• Prior to surgical decompression or stabilization
• Evaluation of patients with persistent pain and negative radiographic findings
• Imaging long-term sequelae of spinal trauma, particularly when a new deficit develops in patients with past history of trauma

MRI scanning is being increasingly used as an adjunct to plain films, but the lack of wide availability and the relatively prolonged scanning time required limit its usefulness in the acute setting. Another major drawback is the limitation on the resuscitation equipment and stabilizing devices that can be used near MRI scanners.

MRI is considerably inferior to plain films or CT for posterior element fractures, but some fractures are better detected with MRI, such as intramedullary fractures and fractures in the axial plane (eg, Chance fracture). Another disadvantage with using MRI for acute trauma is motion artifact, as MRI is particularly sensitive to patient motion, but modern scanners may improve this.

Vaccaro et al determined that MRI is neither useful nor cost-effective in patients presenting with a fracture of the upper cervical spine without neurologic deficit. They conducted a prospective analysis of patients admitted with isolated upper cervical spine fractures who underwent MRI within 48 hours of the traumatic event. In patients with an identified neurologic deficit, MR findings changed the treatment of 25% of cases, whereas MRI findings did not change the treatment in patients without a neurologic deficit. ^[44]

Intraoperative ultrasonography is a noninvasive technique that has the potential of reducing spinal cord compromise when a posterior surgical approach is used for complex spinal fractures. Intraoperative ultrasonography has also been found to be useful in localizing posttraumatic subarachnoid and spinal cord cysts. Ultrasound imaging needs dedicated training and remains an operator-dependent technique.

In patients with spinal cord injuries that are occult on conventional radiographs, bone scintigraphy often demonstrates previously unrecognized injuries and may help target specific areas for further evaluation with cross-sectional imaging. Radionuclide scanning is particularly useful in elderly females with osteoporotic bones, which may be difficult to image with routine radiographs. In patients with osteoporosis, occult fractures may take 2-3 days following injury to demonstrate increased tracer uptake on bone scans. ^[5]

Although radionuclide scans add a functional element to conventional radiography and cross-sectional imaging, it is not the imaging of choice in emergent situations. The sensitivity of radionuclide scans is high, but the specificity is low.

Digital subtraction angiography is the most sensitive imaging study for assessing carotid and vertebral circulation, but, because of invasiveness, its role as a screening study for spinal cord trauma remains questionable. Angiography may have difficulties differentiating spasm and small disruption of the intima from other conditions, and the quality of angiograms may be degraded from motion artifact in a restless patient. ^[45]

Four-vessel cerebrovascular angiography remains the standard screening test for patients at risk for blunt cerebrovascular injury, but it is being challenged by less-invasive techniques such as CTA and MRA. Although the reported sensitivity of computed tomographic angiography (CTA) for the diagnosis of blunt cervical vascular injury has been inadequate, the advances in CT technology have improved the diagnostic sensitivity of CTA to at least the same level as invasive catheter angiography. CTA, using a 16-channel detector, can be used to accurately screen at-risk patients for blunt cervical vascular injury. ^{[6, 46]}

Fox et al reviewed combat-related penetrating cervical injury and found that CTA is useful in the delayed evaluation of stable patients, but retained fragments produce suboptimal imaging in the zone of injury. They reaffirmed that arteriography remains the criterion standard in the evaluation of cervical vascular trauma and that its use should be liberalized for combat injuries. ^{[47, 48]}