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Traumatic injuries to the cervical spine.

Nowhere in radiography are the standards for imaging more important than in dealing with traumatic spine injury. This article provides an overview of cervical spine trauma and specifically addresses various injuries and how to image them.

This article is a Directed Reading. See the quiz at the conclusion.

After completing this article, readers will be able to:

* Describe the basic anatomy of the cervical spine.

* List and describe various forces involved in spinal injury.

* Discuss various cervical spine injuries.

* Present recommendations, limitations and diagnostic challenges of imaging cervical spine trauma.

* Address other patient considerations including safety and care.

In May 1995, Hollywood met heartache. Christopher Reeve, America's favorite superhero, broke his neck when he was thrown from his horse during an equestrian competition. His resulting paralysis was not enough to hold down this hero, though. Mr. Reeve was willing to share his disability struggles and to speak out, campaigning tirelessly for spinal cord injury and research.

Approximately 10 000 cervical spine fractures occur annually, comprising 2.6% of all trauma victims. These cervical spine injuries cause an estimated 6000 deaths and 5000 new cases of quadriplegia each year. (1) Motor vehicle accidents and falls account for 50% and 20% of these injuries, respectively. In fact, approximately 5% to 10% of unconscious patients who present to the emergency department as the result of a motor vehicle accident or fall have a major injury to the cervical spine. Sports-related activities account for another 15% of cervical spine injuries. Participants in sporting events such as diving, equestrian activities, football and gymnastics are considered to be at a high risk for spinal trauma. Of the new cervical spine fractures each year, as many as 47% of patients suffer neurologic complications resulting in devastating psychological, physical and financial losses. The mortality rate among trauma patients with cervical fractures who required intubation was 37%, with most deaths related to associated injuries, particularly head injury. (2) Perhaps the most concerning statistic is that 10% of all spinal-cord injured patients arrived at the emergency department neurologically intact. (3)

Normal Cervical Spine Anatomy

The purpose of the cervical spine is to protect the spinal cord and to support the skull while enabling diverse head movements. This is a big job considering that cervical vertebrae are smaller than the other spinal vertebrae.

The normal anatomy of the cervical spine consists of 7 vertebrae separated by intervertebral disks. (See Fig. 1.). The basic parts of a vertebra are an anterior body and a posterior arch which consists of the pedicles and laminae. One distinguishing feature of the cervical vertebrae is the presence of a transverse foramen in the transverse process.

[FIGURE 1 OMITTED]

The vertebrae are joined by a complex network of ligaments. These ligaments keep individual bony elements behaving as a single unit. In 1983, Denis (4) proposed a 3-column model of the spine. One can view the cervical spine as 3 distinct columns: anterior, middle and posterior. (See Fig. 2.) The anterior column consists of the anterior longitudinal ligament and the anterior two thirds of the vertebral body. The middle column is formed by the posterior longitudinal ligament and the posterior one third of the vertebral body. The posterior column is made up of the remaining ligamentous and vertebral structures. The anterior and posterior longitudinal ligaments maintain the structural integrity of the anterior and middle columns. The posterior column is held in alignment by a more complex ligament system.

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Upper Cervical Region: The Atlas (C1) and the Axis (C2)

The atlas and the axis are atypical vertebrae. (See Fig. 3.) The atlas (C1) is ring like and somewhat kidney shaped when viewed from above or below. It has no spinous process or body and consists of 2 lateral masses connected by anterior and posterior arches. The atlas carries the cranium and rotates on C2's large, flat superior articular facets.

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The axis (C2) vertebra is the strongest cervical vertebra. Its distinguishing feature is an odontoid process that is a tooth-like structure projecting from the vertebra. This odontoid process is often referred to as the dens. The dens is held tightly to C1 by the transverse ligament, thus stabilizing the atlantoaxialjoint, which is a pivot joint that allows rotational movements like shaking the head when saying "no." (See Fig. 4.) These ligaments provide further stabilization by permitting spinal column rotation and preventing posterior displacement of the dens in relation to the atlas.

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The C2-C3 Interface

Rotation of the axis on C3 is limited by a blocking mechanism that protects the vertebral artery from excessive torsion. This blocking mechanism is also found in the subjacent cervical vertebrae.

Lower Cervical Region

The lower cervical vertebrae are typical in structure with some exceptions. In this region, the laminae are slender and overlap to create a shingling pattern that increases with age. The seventh cervical vertebra is considered an atypical cervical vertebra because of its long spinous process that can be seen and felt in the back of the neck.

Cervical Spine Injuries and Neurologic Deficits

The technologist must appreciate the fact that injury to a vertebra does not directly correlate with injury to the spinal cord. Likewise, injury to the spinal cord does not require a vertebral fracture. In other words, a person may "break his neck" yet not sustain a spinal cord injury (SCI) when only the vertebrae are damaged but the spinal cord is not affected. In these situations, the individual may not experience paralysis after the bones are stabilized; however, as many as 39% of cervical fractures have some degree of associated neurologic deficit.

The effects of SCI depend on 2 factors: the type of injury and the level of injury. Furthermore, SCI can be divided into 2 types of injury--complete and incomplete. A complete injury means that there is no function below the level of the injury; there is no sensation and no voluntary movement, with both sides of the body equally affected. An incomplete injury means that there is some functioning, whether it is movement or sensation, below the primary level of injury.

The level of SCI is very helpful in predicting what parts of the body might be affected. In general, the higher up the spinal column the injury occurs, the more dysfunction a person will experience. Injuries to the cervical spinal cord result in paralysis of all 4 limbs, which is termed tetraplegia or, more often, quadriplegia. Injuries below the cervical spine result in paraplegia, a paralysis of the legs and portions of the trunk. Quadriplegia is slightly more common than paraplegia. Table 1 summarizes various motor deficits and mobility consequences for corresponding cervical fractures.

Beside a loss of sensation or motor function, individuals with SCI also experience other changes. Very high injuries (C1, C2) can result in a loss of many involuntary functions including the ability to breathe. SCIs may cause sexual dysfunction or dysfunction of the bowel and bladder. Other effects of SCI may include chronic pain, in addition to altered regulation of blood pressure, body temperature and the ability to sweat below the level of injury.

When an SCI occurs, there usually is swelling of the spinal cord that may incur further injury and loss of function. With time, the swelling will begin to dissipate and the individual may regain some functioning. In the event of an incomplete injury, the individual may recover some functioning as late as 18 months following the injury. However, only a very small fraction of individuals sustaining SCIs completely recover.

Cervical Fractures

Most cervical spine fractures occur at 2 levels. One third of fractures occur at the level of C2, while one half of injuries occur at the C6 or C7 levels. As reported in accident statistics, the most vulnerable segments to injury are the axis and C5-C6. According to the National Spinal Cord Injury Statistical Center's 2004 annual statistical report, (1) of the patients discharged with a cervical spine injury, 39% had injuries that occurred at C4-C6. According to the report, the atlas was the least involved of all cervical vertebrae.

Mechanisms of Injury

Nonangular stresses and rotational/angular forces are the 2 main mechanisms for spinal injury. Nonangular forces include compression and shear force. Rotational/angular forces include hyperextension, hyperflexion and hyperrotary forces.

Compression Forces. This mechanism is best explained as a force produced when a heavy object is placed on top of the head. Excessive compression forces on the neck commonly lead to facet jamming and fixation. In addition, these forces can cause fractures of the atlas or lower cervical bodies. The fractures may be vertical, oblique or bursting in nature.

Shear Forces. Undue shearing forces can disrupt ligaments and produce anterior or posterior subluxation. Also, these forces can create anterior or posterior fractures of the dens or cause anterior compressive fractures of the atlas or vertebral body.

Hyperextension Forces. This mechanism is best described as the force produced when a person strains to look up by bending the head back. The effects of forceful posterior bending include ligament sprain, wedging of a vertebral body, posterior subluxation and fractures of the atlas or vertebral body.

Hyperflexion Forces. An example of this mechanism is the force produced when a person strains to look down by bending the head forward. Excessive anterior bending may produce much the same effects as hyperextension forces.

Lateral Hyperflexion Forces. This is best explained as the force produced when a person attempts to place his or her ear on a shoulder. The effects of excessive lateral bending include dislocation and fractures of processes, including the odontoid process. In addition, lateral wedging of vertebral bodies may occur.

Hyperrotary Forces. This force is produced when a person strains to look over his or her shoulder. Extreme rotation of the longitudinal axis may produce ligament torsion, rotary subluxation, spiral loosening and atlasaxis dislocation.

Upper Cervical Fractures

C1 Atlas. Isolated fractures of the atlas are rare and divided into types I, II and III. (5) Jefferson first described the type II fracture pattern as a "burst" pattern. (6) This fracture can occur from a severe axial force causing compression. (See Fig. 5.) If the force is great enough, such as that which occurs in diving injuries, the vertebral arch or body of the adjacent vertebra literally bursts. Another fracture, the pillar fracture, is an isolated fracture of the lateral mass of C1. Regardless of fracture type, stability is defined as an intact transverse longitudinal ligament. The "Rule of Spence" is used to assess the integrity of this ligament and its stability. The rule states that on an open-mouth odontoid projection, the displacement of the lateral masses to a certain degree implies a ruptured ligament. All stable patients with a C1 fracture should have a magnetic resonance (MR) image taken to assess the integrity of the ligament. If the ligament is ruptured, this is considered the most unstable of all cervical spine fractures. (7)

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C2 Axis. Fractures of the axis also are divided into 3 types: dens, hangman's and other. (8) The dens fracture is the most common form and has 4 subtypes that are classified according to the fracture location, whether it be at the tip, base, body or some combination of the dens and vertebra. (See Fig. 6.) The hangman's fracture, originally named to describe the effects of hanging a person from a gallows, now refers to bilateral fracture of the pedicles of the axis caused by hyperextension or sudden deceleration. (See Fig. 7.) In present times, this type of fracture most commonly results from a car accident in which the victim strikes the windshield with his forehead. A hangman's fracture often causes death by suffocation, which nearly occurred during Reeve's tragic equestrian accident.

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Axis with Atlas Fractures. In the largest case series examining combined fractures, 43% of axis fractures and 16% of atlas fractures occur in unison. (9) There are 4 main fracture combinations. The most common is the C1-type II odontoid fracture, while the least common fracture pattern is the C1-hangman. Combination fractures of C1 and C2 should be evaluated by computed tomography (CT), with reconstruction whenever an isolated C1 or C2 fracture is seen. (10)

Lower Cervical Fractures

Lower cervical spine fractures are classified into 4 major subtypes according to the forces involved in the mechanism of injury: hyperflexion, hyperextension, compression and lateral flexion/shearing. (11-12)

Fractures Caused by Hyperflexion. The flexion tear drop fracture is a fracture of the inferior-anterior portion of a vertebral body, typically occurring at C2. (See Fig. 8.) It is often the result of diving into shallow water. This fracture is the most severe and unstable injury of the cervical spine.

[FIGURE 8 OMITTED]

Subluxation is defined as a partial dislocation of a bone in its joint. In terms of the spine, it is displacement of a vertebra. Anterior subluxation in the cervical spine occurs when posterior ligament complexes rupture. (See Fig. 9.) The anterior longitudinal ligament remains intact and no associated bony injury is seen. Because the anterior columns remain intact, this fracture is considered mechanically stable. However, most authorities approach this injury as if it were potentially unstable because of the significant displacement that can occur. A few very rare cases have reported neurologic deficit.

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Subluxation between 25% and 50% of the vertebral body is generally consistent with a unilateral facet dislocation (sometimes referred to as the "locked" vertebra), whereas subluxation of more than half of the vertebral body indicates a bilateral facet dislocation. (See Fig. 10.) This is an extremely unstable condition and is associated with a high prevalence of SCI. In addition, a significant number of bilateral facet dislocations are accompanied by disk herniation.

[FIGURE 10 OMITTED]

A clay shoveler's fracture is a forcible detachment of a spinous process caused by a sudden load on a flexed spine. (See Fig. 11.) This fracture occurs most often at C6, C7 or T1 and is the most stable of the cervical spine fractures.

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Fractures Caused by Hyperextension. An extension tear drop fracture is radiographically similar to the flexion tear drop fracture, involving the anterior-inferior portion of a vertebral body. However, this fracture is more stable than the flexion fracture.

A fracture of the neural arch of C1 occurs when the head is hyperextended and the posterior neural arch of C1 is compressed to the point of fracture. Because the transverse ligament and the anterior arch of C1 are not involved, this fracture is stable.

Fractures Caused by Compression. A burst fracture occurs when a downward compressive force is transmitted to lower levels in the cervical spine, causing the body of the cervical vertebra to shatter outward in a bursting pattern. (See Fig. 12.) The Jefferson burst fracture of C1 has been discussed previously as an upper cervical fracture. Burst fractures involve disruption of the anterior and middle columns. In addition, these fractures are much more severe than simple compression fractures because the bones spread out in all directions and may damage the spinal cord.

[FIGURE 12 OMITTED]

Fractures Caused by Lateral Flexion/shearing. Between 4% and 6% of cervical spine injuries occur from this mechanism. Occupants of a vehicle that has been broadsided will likely suffer this injury. The impact propels the victim's body in 1 direction while the head and neck go in the opposite direction. Examples of fractures include uncinate fracture, isolated pillar fracture (see Fig. 13), transverse process fracture and lateral vertebral compression.

[FIGURE 13 OMITTED]

Cervical Spine Stability

The stability of C3-C7 fractures is based on a 3-column theory described by Denis.(4,13) As previously described, the 3 spinal columns (anterior, middle and posterior) work in conjunction to provide stability to the spine. (See Fig. 2.) Column disruption can lead to mechanical instability of the cervical spine. If 1 column is disrupted, other columns may provide sufficient stability to prevent SCI. If 2 columns are disrupted, the spine may move as 2 separate units, thus increasing the likelihood of SCI. Fractures are considered unstable if more than 1 column is disrupted. The degree of instability depends on several factors, including degenerative changes related to aging, arthritic conditions, spinal stenosis and spina bifida, as well as the specific mechanism and location of the injury. Trafton (7) has ranked specific cervical injuries based on their degree of mechanical instability. The following list ranks cervical spine injuries in order of instability (most stable to least stable): (See Table 2.)

* Rupture of the transverse ligament of the atlas.

* Fracture of the dens.

* Flexion teardrop fracture.

* Bilateral facet dislocation.

* Hangman fracture.

* Extension teardrop fracture.

* Jefferson fracture.

* Unilateral facet dislocation.

* Anterior subluxation.

* Simple wedge compression fracture.

* Fracture of the posterior arch of C1.

* Clay shoveler's fracture.

Imaging the Cervical Spine

The first step in imaging the cervical spine is to determine if the patient actually needs imaging and, if so, which projections are appropriate. The criteria for imaging apply only to adults with no mental status changes, including drug or alcohol intoxication. The presence of the following should be noted:

* Neurologic deficits consistent with a cord lesion, such as sensory and motor deficits.

* Altered sense of reality due to head injury or intoxication.

* Complaints of neck pain or tenderness.

* Significant other injuries that may preclude any complaints about neck pain or tenderness.

Although some research suggests that these criteria also may be used in the management of verbal children, (14-16) caution is in order because the studies were small, and the ability of children to complain about pain or sensory changes can vary.

A CR Imaging Guidelines

The American College of Radiology (ACR) Committee on Appropriateness Criteria has developed guidelines. (17,18) for determining appropriate imaging examinations to diagnose specified medical conditions, namely spinal injury. These criteria are intended to guide professionals in making decisions regarding radiologic imaging and treatment. The ACR cautions, however, that using the guidelines blindly in a "protocol-driven" manner may result in many unnecessary studies.

Conventional Radiography

The ACR states that if the above criteria are met, plain-film radiographs are the mainstay of the initial imaging evaluation. The exam should include 3 projections: a true lateral projection, an anteroposterior projection; and an open-mouth odontoid projection. (See Fig. 14.) A lateral projection using the Twining method, commonly called the "swimmer's lateral," for T1 is frequently needed, especially in men. The importance of obtaining all these projections, described in more detail below, and demonstrating all of the vertebrae cannot be overemphasized. Although some missed cervical fractures are the result of image misinterpretation, the most frequent cause of overlooked injury is an inadequate film series) (19,20) (See Table 3.)

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Lateral projection. Approximately 85% to 90% of cervical spine injuries are evident in a lateral projection, making it the most useful image from a clinical standpoint. (See Fig. 14a.) However, some experts believe the single portable cross-table lateral radiograph, often obtained in the trauma room, should be abandoned. This projection is insufficient to exclude a cervical spine fracture and frequently must be repeated in the radiology department. (21-22)

For complete imaging, the lateral projection must include all 7 cervical vertebrae as well as the C7-T1 junction. If no arm injury is present, traction of the arms may help to demonstrate all 7 vertebrae on the lateral film. If all 7 vertebrae and the C7-T1 junction are still not visible, a swimmer's lateral, taken with 1 arm extended over the head, may remedy the problem. (See Fig. 15.) Because there is less scatter, a coned-down swimmer's lateral gives better detail than does the full cervical spine swimmer's projection, especially when using digital imaging.

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Anteroposterior projection. This projection is used to reveal the spinous processes of C2 to T1; however, it is the least useful projection from a clinical standpoint. (23) (See Fig. 14b.)

Odontoid projection. The open-mouth odontoid projection is used to evaluate an area that is difficult to demonstrate on a cross-table lateral image because of shadow superimposition. (See Fig. 14c.) It is used to assess trauma to C2. Occasionally, the tip of the odontoid process is not adequately visualized, and the technologist may use the Fuchs method, which is a modified projection to demonstrate the superior third of the odontoid tip. However, this projection is unreliable when the patient is in a cervical collar and the neck cannot be extended.

Oblique and flexion/extension radiographs. Plain-film imaging beyond lateral and anteroposterior projections may be useful in selected cases. Supine oblique studies aid in examining lateral masses, whereas flexion and extension projections are commonly used for patients with severe pain and tenderness but who have normal lateral and anteroposterior films. (24) These additional studies are not generally used for routine protocols.

Oblique projections are most valuable in adding 2 more images of the C7-T1 junction. This is considered a laminar projection because the image can reveal disruptions in the normal shingling appearance of the vertebral laminae. Because both of these functions can now be accomplished through the use of CT, the ACR states that the use of supine oblique projections is no longer necessary for patients who are undergoing cervical CT examination.

According to the Eastern Association for the Surgery of Trauma (EAST), a panel created to evaluate and develop evidence-based guidelines for controversial topics in trauma, a patient with significant midline pain requires flexion/extension projections to evaluate for ligamentous injury, which commonly arises from hyperrotational injuries. (25) (See Fig. 16) These radiographs should only be obtained in conscious patients who are able to cooperate. The patient should be able to limit the motion of his or her neck based on the occurrence of pain. Under no circumstances should cervical spine flexion and extension be forced, as this may result in SCI.

[FIGURE 16 OMMITED]

Although the literature still recommends flexion/ extension radiographs, the ACR states that these projections are not very helpful except to ensure that minor degrees of vertebral slippage in patients with cervical spondylosis (spinal osteoarthritis) are fixed deformities. (26,27) Furthermore, muscle spasms are common in injured patients and preclude an adequate examination in the acute setting. According to the ACR, flexion/ extension radiography is best reserved for follow-up of symptomatic patients, usually in 7 to 10 days after muscle spasms have subsided. Although the use of flexion/extension radiography can provide information concerning ligament instability, MR is the procedure of choice for demonstrating this anatomy.

Computed Tomography

There are 3 situations in which CT is necessary: when a fracture is seen, when a fracture is suspected and when the spine is poorly visualized on plain films. When a fracture is seen on the plain films, a CT of the cervical spine that extends 1 level above to 1 level below the injury is recommended. A significant number of patients will have additional fractures in the surrounding areas that are not seen on the plain films. (28) When radiography indicates a suspected fracture, patients should undergo CT. Research has shown that 22% to 42% of patients whose radiographs are inconclusive actually have fractures. (28,29) In several studies, CT has been shown to effectively rule out a fracture. (28,31)

CT is also advantageous for areas of the cervical spine that are poorly visualized. Between 9% and 26% of patients have inadequate plain films, generally of C1-C2 and C6-C7. (29,32) Schleehauf showed that 7% of those with inadequate plain films had positive CT scans. (29) More importantly, in a meta-analysis of more than 1500 blunt trauma patients over a 3-year period, CT detected 100% of cervical spine injuries that were undiagnosed by inadequate plain films. (30,29) The ACR recommends that patients who are not alert or conscious, are under the influence of a substance, or who have distracting injuries, cervical tenderness and neurologic findings (eg, sensory and motor deficits) should have, at a minimum, a 3-projection cervical radiographic series followed by helical CT scan. (20,33,34) The cervical CT examination should be performed immediately after a cranial CT scan while the patient is still in the CT suite. This is a time-effective and costeffective approach. (35)

Magnetic Resonance

According to EAST, an MR examination should be conducted within 8 hours for any patient presenting with a neurologic deficit. MR provides more information about the spinal cord than any other imaging study. (36-38) Such information includes intrinsic compression (from edema or hematoma formation) or extrinsic compression (from disk herniation or bony fragments). MR should be reserved for patients who have clear-cut neurologic findings and for those suspected of ligament instability. (39) The ACR states that MR should be used in cases of known or suspected soft-tissue injuries such as disc herniations, ligament tears, epidural hematoma and spinal cord edema or hematoma. (40-42) A recent review article by Saifuddin (43) goes further by recommending total spinal MR to screen for multiple noncontiguous injuries, which occur in about 20% of patients. (43) MR, however, is not adequate for evaluation of bony trauma.

Myelography with CT should be used in place of MR only if MR is not available and the patient cannot be safely transferred to a MR facility. The inherent risks of patient positioning required for myelography and CT exams are considerable; thus, supervised transport to an MR facility may pose less risk to the patient.

Comparison of Techniques

Plain Radiography vs CT

Schenarts and colleagues compared the sensitivity of CT (at C1-C2) to plain-film radiography (5-projection) in blunt trauma patients. (44) CT detected 96% of upper cervical fractures vs 54% detected by plain-film radiographs. Interestingly, no fractures were missed with the combination of radiography and CT. Other studies have shown similar results. (45,46) Another group, Berne and associates, (33) compared CT (at C1-T1) to plain-film radiography (3-projection) in similar patients over 8 months. Plain films were 61% sensitive in detecting cervical spine injury vs 90% with CT. As before, the combination of imaging techniques was 100% sensitive in detecting cervical spine injury.

CT vs MR

Velmahos and colleagues compared the sensitivity of CT and MR in detecting ligament injury in asymptomatic blunt trauma victims. The study revealed that isolated ligament injury without subluxation was detected in 25% of patients by CT vs 100% with MR. (47)

Other Cervical Spine Injuries Vertebral Artery

This injury is seen in up to 11% of cervical blunt trauma patients and presents as an expanding cervical hematoma. (48,49) Patients with vertebral subluxation, facet dislocations or foramen fractures are at increased risk for vertebral artery injury and probably should undergo additional imaging studies. (50)

SCIWORA

SCI without radiographic abnormality (SCIWORA) is defined as the presence of neurologic symptoms in the absence of radiographic findings. Recent evidence suggests a higher incidence of adults presenting with SCIWORA than previously thought. (51) The most common level of injury was C4. SCIWORA classically is seen in children with symptoms ranging from transient neuropathy to complete cord injury. Often a transient neuropathy will have a "lucid interval," only to return hours or days later. The SCIWORA syndrome occurs when the elastic ligaments of a child's neck stretch during trauma. This action causes the spinal cord to stretch, thus leading to neuronal injury or, in some cases, complete severing of the cord. (52) This situation may account for up to 70% of SCI in children and is most common in children younger than 8 years.

Ligament Injury

Although the combination of CT and radiography is adequate to evaluate the bony spine, the issue of ligament injury needs to be addressed. On plain films these injuries may be seen on lateral projections as a misalignment of the cervical vertebrae. Unfortunately, not all ligament injuries are obvious. Symptoms include focal neck pain in the absence of radiographic findings. Nevertheless, it is important to correctly recognize the injury because missed cervical trauma in a neurologically intact patient can result in neurologic deterioration. (20,53)

Whiplash

Mention should be made of whiplash patients, who have no radiologically demonstrable injuries and yet have a spinal sensory deficit or motor deficit. The clinical picture in whiplash injury varies greatly, ranging from simple headaches to neck pain and paresthesia in the hands. This syndrome was first described by Schneider, (54) who called it a central SCI. It usually results from hyperextension trauma, such as a face-first fall down stairs or a motor vehicle accident. Evidence shows that 50% of patients recover within 6 weeks; however, recovery may take up to 3 years. (55)

Challenges in Evaluating the Stability of the Cervical Spine

When a lateral film, such as a portable lateral c-spine image, is solely used to "clear" the cervical spine, approximately 15% of vertebral injuries are missed. In addition, plain-film studies have reported false-negative rates as high as 20% and a false-positive rate of 40%. (31) Although some missed cervical fractures, subluxations and dislocations are the result of film misinterpretation, the most frequent cause of overlooked injury is an inadequate film series. (19,20) Image quality becomes an important factor in a complete radiographic series, as well as obtaining the necessary projections to demonstrate all the vertebrae. Occasionally, it is impossible to fully visualize all 7 cervical vertebrae and, more importantly, the C7-T1 junction in a true lateral image. This may be due to limitations of patient mobility or, perhaps, shadow superimposition over questionable areas. A swimmer's lateral may adequately expose these areas.

If the original film series is inadequate or there are still questionable areas, the technologist may have to perform additional projections. If there is any question of an abnormality on the plain radiograph or if the patient has neck pain that seems to be disproportionate to the findings on plain films, a CT scan of the area in question should be obtained. Failure to fully demonstrate the spine has resulted in patient morbidity.

Aside from inadequate film series, there are other challenges of clearing the cervical spine. For example, the patient's neck should remain immobilized until a full cervical spine series can be obtained. However, the need for immobility often hinders completion of the series.

Another imaging challenge is the radiography of uncommon cervicocranial injuries such as occipitoatlantal dissociation and atlantoaxial rotation. These conditions deserve special consideration because they are difficult to diagnose radiographically. Occipitoatlantal dissociation is the generic term that includes occipitoatlantal dislocation and occipitoatlantal subluxation. While dislocations are more common and uniformly fatal, the subluxation is less frequent, and is rarely fatal.

Procedure Limitations

Although they may be considered adequate to rule out a fracture, cervical spine radiographs have limitations. Reportedly, up to 20% of fractures are missed on plain radiographs. (21,31,45) Many projections have unique disadvantages. The swimmer's lateral projection requires patient cooperation for positioning, which may pose a problem for the radiologic technologist. In addition, the superimposition of the clavicles, upper ribs and shoulder joints may obscure visualization of some of the vertebrae.

The open-mouth odontoid projection is considered unreliable for intubated patients due to its false-negative rate of approximately 16%. In addition, artifacts caused by the teeth overlying the dens may give the appearance of a fracture through the process. If there is any question of a fracture, the projection should be repeated without the teeth in the field of view. If it is not possible to exclude a fracture of the dens, CT can be used.

CT and MR imaging have limitations too. For example, fractures in the axial plane, including base of odontoid and some subluxations, may not be readily apparent with CT. (56) Also, CT is excellent for identifying fractures, but its ability to show ligament injuries is limited. (56) MR is used as an adjunct to plain-film radiography and CT scanning, especially to demonstrate soft tissue injury. Although MR approaches 100% sensitivity for the detection of ligament injury, there are several problems with this approach. First, there is a high false-positive rate. (57) Second, the clinical implications of many of these injuries are not yet known. Other problems with MR involve the physical nature of the procedure. Lack of availability and the time required for MR scanning limits its usefulness in the acute setting. (37,58) Often, MR involves the transportation of an unstable patient to a remote part of the hospital where resuscitation is difficult. Furthermore, resuscitation equipment with metal parts may not function properly within the magnetic field generated by the MR scanner. In addition, the radiologic technologist must be aware if a patient has any metallic implants or devices, which can be difficult to determine if the patient is unconscious or unable to communicate.

Diagnostic Imaging Challenges

The following situations place special demands on radiologic technologists when they perform a complete radiography study for patients with cervical spine trauma:

* Unconscious or uncooperative patients. These patients may not be able to communicate about their pain or remain still for various positions.

* Intubated patients. The odontoid projection may be compromised in these patients. Similarly, if airway anesthesia is inadequate, conscious patients may cough or vomit when the endotracheal tube is manipulated, causing significant patient movement. The vast majority of cervical motion is produced at the occipitoatlantal and atlantoaxial joints. The subaxial cervical segments are displaced only minimally. (59)

* Cervical collar problems. Not all collars are radiolucent.

* Area of injury. Localizing the area of injury may become a problem in several circumstances. For example, there may be multiple areas of injury that require imaging. Also, other injuries may mask a SCI and mislead the trauma team.

* Degenerative changes. Spondylosis is a degenerative disorder that may cause loss of normal spinal structure and function. Symptoms may mimic those of spinal injury.

* Pain without obvious finding. "Significant" neck pain is not defined and is determined by the treating physician. Extreme pain to 1 patient may feel like a simple itch to another. In addition, pain may be present in cases of SCIWORA, as discussed previously. Furthermore, neck pain from spondylosis is common and often mistaken for acute injury.

* Congenital changes. Congenital deformities of the spine are caused by anomalous vertebral development in the embryo. These changes in the spine shape and size may make it difficult to accurately assess vertebral damage. The 3 major patterns of congenital spinal deformity are hyperlordosis (exaggerated lumbar curve), kyphosis (a progressive spinal disorder that may cause a deformity described as humpback or hunchback) and scoliosis (abnormal curvature of the spine).

* Old injuries. Following a fracture, most vertebrae will "heal" and form a new union of bone. However, many conditions predispose bones to nonunion (eg, Down syndrome and rheumatoid arthritis). Furthermore, new trauma may be superimposed on old injuries. These old injuries may confound a diagnosis. It is important to get an accurate medical history of the patient to properly assess the injury.

* Adequate evaluation of the CT-T1 junction. The C7-T1 junction is a unique area that deserves much attention. It is a common site of developmental anomalies; it is a major site of arterial, lymphatic and neurologic traffic; and it is the juncture of the highly mobile cervical spine and the very limited thoracic spine. The features of the CT-T1 junction highlight the area's importance and contribute to the difficulty of adequately visualizing this region. Radiographs of this region are technically difficult to obtain, and in at least 26% of all trauma patients, this space is not visualized on the 3-view series. (60)

* Swimmer's lateral projection. If a patient's arms are in traction, a swimmer's lateral may have limited value.

* Pseudosubluxation. In physiologic misalignment caused by ligamentous laxity, pseudosubluxation can be confusing. Pseudosubluxation can occur at the C2-C3 level and, less commonly, at the C3-C4 level. Pseudosubluxation usually occurs in children, but it also may be seen in adults.

* Flexion-extension radiographs. A recent study noted that up to one third of all flexion/extension studies are inadequate due to limited range of motion. (61) According to the ACR, flexion/extension radiographs are not very helpful except to ensure that minor degrees of vertebral slippage in patients with cervical spondylosis are fixed deformities. (26,27) Furthermore, muscle spasms in acutely injured patients preclude an adequate examination in the acute setting. Additionally, cord injuries have been reported as a result of this maneuver. (62)

* Evaluation of stability. Stability can be difficult to assess in an acutely injured patient because the degree of instability depends on several factors, including degenerative changes and the specific mechanism and location of the injury.

Pediatric Considerations

Children and adults have structural differences in the cervical spine. These differences can alter injury patterns and cause distinct pathology in young children. Children have more elastic intervertebral ligaments and more horizontally aligned facet joints. This anatomy predisposes them to subluxation of the cervical spine without bony injury. To further compound this problem, immature neck muscles and a proportionally large head make pediatric cervical spines act like a fulcrum and thus increase the chance of injury. As the pediatric cervical spine matures, the fulcrum effect migrates from the upper cervical levels to the lower ones until it reaches C5. Most injuries occur at the C1-C3 levels in children younger than 8 years.

Other Patient Safety Considerations Emergency Procedures

When a cervical spine injury is suspected, the first step in the protocol is to minimize neck movement and further injury. The management of a patient with a potential SCI begins with the care of paramedics prior to transport. Ideally, the patient is immobilized in the neutral position on a full spine board with a cervical collar and side head supports. In addition, the shoulders and pelvis are strapped so that the neck is not the center of the body's rotation. The patient must be treated as if the spinal column were fractured, even when there is no external evidence. If a spinal misalignment or fracture is identified, the patient should be placed in skeletal traction with tongs as soon as possible, even if no evidence of neurologic deficit exists. In addition, steroids should be administered to the patient. The use of steroids for neurologic injury has become the standard to prevent secondary causes of SCI such as swelling. According to 3 North American Spinal Cord Injury Study reports, the recommended management for patients with SCI is administration of methylprednisolone within 3 hours of injury. (63-68) All in all, the number 1 treatment for spinal injury is prevention.

Radiation Protection

As with any radiologic study, the major overall goal is to produce high quality films without exposing the patient to excessive radiation. Collimation is important to radiographic detail and is a part of the overall practice of the ALARA (as low as reasonably achievable) principle. However, care should be taken not to collimate anatomic structures of the neck out of the radiographic image during the trauma survey.

The Role of the Radiologic Technologist

Education is the key to a good radiology department response to trauma. Often an emergency room physician must make a rapid initial diagnosis. Therefore, it is imperative that these studies be performed correctly and completely. Technologists should be aware of the indications for special projections of the cervical spine, including how to adequately visualize all vertebrae (especially C2 and the C7-T1 junction).

Trauma imaging requires the technologist to be aware of the patient's history, and to know the sequence of diagnostic imaging. For example, a gunshot injury or stabbing may require the chest to be imaged before neck and spine imaging. But, as a rule, spine imaging is the priority for motor vehicle accidents and diving injuries. The technologist must work quickly and decisively to complete imaging while the patient is treated by the trauma team. By remaining knowledgeable about current radiographic imaging standards, the radiologic technologist is armed with the proper knowledge that translates into safe quality patient care. Nowhere in radiography are the standards for imaging more important than when dealing with traumatic spine injury.

Directed Reading Continuing Education Quiz

DRI0005017 Expiration Date: Oct. 21, 2007* Approved for 2.0 Cat. A CE credits

Traumatic Injuries to the Cervical Spine

To receive Category A continuing education credit for this Directed Reading, read the preceding article and circle the correct response to each statement. Choose the answer that is most correct based on the text. Transfer your responses to the answer sheet on Page 75 and then follow the directions for submitting the answer sheet to the American Society of Radiologic Technologists. You also may take Directed Reading quizzes online at www.asrt.org. Effective October 1, 2002, new and reinstated members are ineligible to take DRs from journals published prior to their most recent join date unless they have purchased a back issue from ASRT.

* Your answer sheet for this Directed Reading must be received in the ASRT office on or before this date.

1. Which type of injury accounts for 50 % of spinal cord injuries?

a. falls

b. motor vehicle accidents

c. sports-related activities

d. gunshot

2. Ten percent of all spinal-cord injured patients arrive at the emergency department neurologically intact.

a. true

b. false

3. Which of the following cervical vertebrae are considered to be atypical?

a. C1, C2, C3

b. C1, C2

c. C1, C2, C7

d. C1-C7

4. Which of the following characteristics is a distinguishing feature of the axis?

a. extra long spinous process

b. ability to shingle with the lower vertebrae

c. facet for rib attachment

d. the dens

5. Which type of injury results in no function or sensation below the level of the injury?

a. complete

b. incomplete

c. primary

d. secondary

6. According to the National Spinal Cord Injury Statistical Center's 2004 annual statistical report, which vertebra was the least involved in cervical fractures?

a. atlas

b. axis

c. C4

d. C7

7. Which of the following mechanisms is a type of rotational/angular force?

a. compression

b. shear

c. hyperextension

d. subluxation

8. The "Rule of Spence" states that on an open-mouth odontoid projection, the displacement of the lateral masses to a certain degree implies the presence of:

a. a ruptured ligament.

b. a Jefferson burst fracture.

c. a whiplash injury.

d. spinal cord injury without radiographic abnormality (SCIWORA).

9. Which is the most common C2 fracture?

a. dens

b. hangman's

c. Jefferson

d. burst

10. Which of the following is true concerning a hangman's fracture?

1. its name describes the effects of hanging a person from a gallows

2. it refers to bilateral fracture of the pedicles of the axis caused by hyperextension or sudden deceleration

3. it most commonly results from a car accident in which the victim strikes the windshield with his or her forehead.

a. 1 and 2

b. 1 and 3

c. 2 and 3

d. 1, 2, and 3

11. The 4 major subtypes of lower cervical fractures are categorized according to:

a. level of injury.

b. stability of injury.

c. forces involved in the mechanism of injury.

d. cause of injury.

12. Which fracture is considered the most severe and unstable injury of the cervical spine?

a. flexion tear drop

b. extension tear drop

c. clay shoveler's

d. unilateral facet

13. Which fracture is considered the most stable fracture of the cervical spine?

a. flexion tear drop

b. extension tear drop

c. clay shoveler's

d. unilateral facet

14. The degree of instability depends on:

1. degenerative changes.

2. spinal stenosis.

3. the specific mechanism and location of the injury.

a. 1 and 2

b. 1 and 3

c. 2 and 3

d. 1, 2, and 3

15. The ACR states the initial imaging evaluation should include 3 projections: a true lateral, an anteroposterior, and a (n):

a. open-mouth odontoid.

b. swimmer's.

c. transaxillary.

d. oblique.

16. Which projection is the most useful from a clinical standpoint?

a. open-mouth odontoid

b. swimmer's

c. anteroposterior

d. lateral

17. The swimmer's projection is known formally as a

a. anteroposterior projection, Fuchs method

b. lateral projection, Twining method

c. open-mouth odontoid projection

d. oblique projection

18. Which type of projection is used to assess trauma to C2?

a. open-mouth odontoid

b. swimmer's lateral

c. anteroposterior

d. lateral

19. The ACR states that flexion/extension radiographs are best used to:

a. confirm that vertebral slippage in patients with spondylosis are fixed deformities.

b. demonstrate the occurrence of muscle spasms.

c. view a very unstable cervical injury.

d. evaluate the C7-T1 junction

20. When is CT necessary in cervical spine imaging?

a. a fracture is suspected

b. ligament tears

c. for patients with clear-cut neruologic deficits

d. spinal cord edema

21. MR is the modality of choice for evaluating of bony trauma.

a. true

b. false

22. Which situation may account for up to 70% of spinal cord injuries in children and is most common in children younger than 8 years?

a. whiplash

b. SCIWORA

c. axis fracture

d. atlas fracture

23. Which of the following roles are the responsibility of a radiologic technologist during imaging a cervical spinal injury?

1. ensure studies are done correctly and completely

2. be aware of the indications for special views

3. be aware of the patient's history and make adjustment to the sequencing of diagnostic images

a. 1 and 2

b. 1 and 3

c. 2 and 3

d. 1, 2 and 3

24. In which projection may artifacts caused by the teeth overlying the dens give the appearance of a fracture through the process?

a. closed-mouth lateral

b. oblique

c. open-mouth odontoid

d. swimmer's lateral

25. The sensitivity of MR for detecting ligament injury approaches -- %.

a. 100

b. 75

c. 50

d. 25

26. Symptoms of spondylosis may mimic those of spinal injury.

a. true

b. false

27. Children and adults have structural differences in the cervical spine. Which of the following differences can alter injury patterns and cause distinct pathology in young children?

a. less elastic intervertebral ligaments

b. more vertically aligned facet joints

c. proportionally smaller heads

d. immature neck muscles

28. Which junction must be clearly visualized in spinal trauma?

a. C1-C2

b. C2-C3

c. C7-T1

d. C1-C7

29. The number one treatment for spinal injury is prevention.

a. true

b. false

Answers to Directed Reading Quizzes DRI0003009 and DRI0003010

Directed Reading Quiz DRI0003009 "Sonographic Assessment of Fetal Skeletal Dysplasias" and Quiz DRI0003010 "Molecular Imaging Of Cancer: The Basics" were published in the Vol. 74, No. 6 issue of Radiologic Technology. The expiration date to submit these quizzes to ASRT was August 31, 2005. Answers to the quiz questions are:

DRI0003009

1. D

2. C

3. D

4. A

5. A

6. B

7. B

8. A

9. A

10. B

11. C

12. B

13. B

14. C

15. D

16. A

17. D

18. B

19. D

20. A

DRI0003010

1. C

2. C

3. A

4. D

5. C

6. C

7. C

8. A

9. A

10. B

11. B

12. B

13. B

14. C

15. B

16. D

17. C

18. A

19. C

20. A

[ILLUSTRATION OMITTED]

Acknowledgement

The images from the Harris & Harris Emergency Radiology Primer, found at www.uth.tmc.edu/radiology/test/ er_primer/index.html, were acquired from work supported by the John S. Dunn Research Foundation. References

Reprint requests may be sent to the American Society of Radiologic Technologists, Communications Department, 15000 Central Ave. SE, Albuquerque, NM 87123-3917.

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Jennifer Minigh, Ph.D., has more than 10 years of research and teaching experience in the areas of pharmacology, toxicology, molecular genetics, signal transduction and oncology. Dr. Minigh is the director of Medical Communication Consultants and serves as secretary and immediate past-president of the Ohio Valley Chapter of the American Medical Writers Association.
Table 1
Motor Deficits and Mobility Consequences
for Corresponding Cervical Fractures

Level of      Motor Deficits              Mobility
Injury                                  Consequence

C1, C2,    Paralysis of all 4      Power wheelchair (chin
C3, C4     limbs                   drive or sip-n-puff)

C5         Shoulder and biceps     Power wheelchair
           control without         (arm drive)
           control of wrist
           or hand

C6         Wrist control without   Manual and/or power
           hand function           chair-sliding board
                                   transfers

C7, T1     Dexterity problems      Manual chair transfers
           with the hand and       w/o sliding board
           fingers

Table 2
Common Injuries of the Cervical Spine.

Spinal    Injury                   Stability    Cause
Level     [Figure #]

C1        Jefferson fracture [5]   Moderately   Severe axial force
                                   unstable     causing compression

          Atlantoaxial             Highly       Unknown but often
          subluxation              unstable     occurs in patients
                                                with bone degeneration

C2        Hangman's fracture [7]   Unstable     Hyperextension or
                                                sudden deceleration

          Odontoid fracture [6]    Highly       Unknown
                                   unstable

C6, C7,   Clay shoveler's          Stable       Sudden load on a
T1        fracture [11]                         flexed spine

Any       Flexion teardrop [8]     Highly       Sudden and forceful
                                   unstable     flexion

          Bilateral facet          Highly       Flexion, or a
          dislocations [10]        unstable     combination with
                                                rotation

          Unilateral facet         Unstable     Flexion or a
          dislocations                          combination
                                                with rotation

Spinal    Injury                   Radiologic Findings
Level     [Figure #]

C1        Jefferson fracture [5]   Odontoid projection: displaced
                                   lateral masses of C1

          Atlantoaxial             Odontoid projection: asymmetric
          subluxation              lateral

C2        Hangman's fracture [7]   Lateral projection: bilateral
                                   pedicle fracture of C2

          Odontoid fracture [6]    May be difficult to see on plain-
                                   film radiographs; may require CT
                                   scanning

C6, C7,   Clay shoveler's          Forcible detachment of spinous
T1        fracture [11]            process; frequently an incidental
                                   finding

Any       Flexion teardrop [8]     Large wedge off the anterior
                                   aspect of the vertebra; alignment
                                   abnormalities

          Bilateral facet          Anterior displacement of more
          dislocations [10]        than half of the diameter of the
                                   vertebral body in the lateral view

          Unilateral facet         Anterior dislocation of 25% of a
          dislocations             cervical vertebra on lateral views

Table 3
Radiographic Evaluation of Adults

Projection        Assessments/Goals

Cross-table       Visualize all 7 vertebral bodies and the C7-T1
lateral             junction
                  Verify alignment of cervical spine by following
                    3-column model
                  Check individual vertebrae thoroughly for obvious
                    fracture or changes in bone density
                  Evaluate changes in prevertebral spaces
                  Check for fanning of the spinous processes
                  Note abrupt changes in angles

Swimmer's         Visualize all 7 cervical bodies and, more
lateral             importantly, the C7-T1 junction

Oblique           Verify proper shingling of vertebrae
                  Note if interlaminar space between 2
                    continuous laminae is increased

Odontoid          Verify proper alignment of the lateral masses
                    of C1 with respect to the odontoid process
                  Check for fractures or lateral displacement
                  Assess symmetry of the interspace between C1 and C2

Anteroposterior   Verify that a straight line connects the spinous
                    processes, thus bisecting the cervical spine
                  Note vertical splitting of any spinous process
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Author:Minigh, Jennifer
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Date:Sep 1, 2005
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