Evaluation

of Cervical Vertebral

Injuries

By Richard H. Daffner

HE ASSESSMENT OF patients with suspected cervical vertebral injury is an area of great concern for both the clinician who must deal with these patients and the radiologist who must interpret cervical radiographs. Many of these patients are evaluated because of “protocol-driven” requirements to obtain cervical radiographs as well as the fear of malpractice litigation if an injury is missed. To complicate this matter, efforts at medical cost containment in recent years has prompted a reevaluation of indications for “routine” cervical radiography following trauma. Two excellent articles in recent years have addressed the subject.1,2This article will review the indications and technical aspects for cervical radiography, will briefly discuss the use of ancillary studies such as computerized tomography, polydirectional tomography, and magnetic resonance imaging, and will review the principles of radiographic diagnosis.

T

INDICATIONS

In many institutions, including large medical centers, any patient involved in a motor vehicle accident or serious fall undergoes routine radiographic examination of the cervical vertebral column. Many of these studies are “protocoldriven” for patients who fit into certain diagnostic categories. Many of these protocols follow the guidelines of the American College of Surgeons who recommend routine lateral cervical radiography for all patients who have suffered major trauma.” Unfortunately, many of these studies are not indicated. In 1989, Mirvis et al1 surveyed 125 North American hospitals that dealt with acute trauma care and found that 46% obtained cervical radiographs routinely in all patients suffering major blunt trauma. Among the patients studied, 34% were deemed to be mentally alert and without symptoms referable to the cervical region. The authors estimated that the cost of cervical radiography (and computed tomography in some cases) was in excessof $59,000.’ In 1990, Vandemark2 addressed this problem by suggesting a “risk-tailored” approach to cervical radiography.* He proposed four clinical .%minars in Roentgenology, Vol XXVII, No 4 (October),

risk categories to help determine those patients who needed radiographs and those who did not. This first category, “no risk,” included patients with no historical or physical findings suggestive of a neck injury. Most of these patients arrived in the emergency department with a cervical collar placed by paramedical personnel because of protocol. These patients would not need radiography. Patients in the “low-risk” category had a history for a mechanism of injury unlikely to have exceeded the physiological range of cervical motion. Even so, for these patients Vandemark recommended a three-view series consisting of lateral, anteroposterior, and atlantoaxial (odontoid) views. Patients with a “medium risk” were those who had a history or a mechanism of injury sufficient to have exceeded the physiological range of motion. Those with a “high risk’ included a history or a mechanism of injury very likely to have exceeded the physiological range of motion. For both of these categories, he recommended a five-view series that included oblique radiographs. The high-risk patients are mandated to be examined in the supine position and the medium risk could be examined in either supine or erect position.’ What constitutes a high risk for cervical injury? A number of historical and clinical factors may be taken into account to determine if the patient falls into the high-risk category. As a rule, patients may be considered high risk if any one of the following parameters are present: high-velocity blunt trauma; multiple fractures

ABBREVIATIONS AP, anteroposterior; CT, computerized MRI, magnetic resonance imaging

tomography:

From the Depatiment of Diagnostic Radiology. Allegheny General Hospital and The Medical College of Fetmqlvania. Allegheny Campus, Pittsburgh, PA. Address reprint requests to Richard H. Dajfner, MD, Department of Diagnostic Radiology, Allegheny General Hospital. 320 E North Ave, PittsbuTh, PA 15212-4772. Copyright 0 1992 by W B. Saunders Company OO37-198Xi92!2704-OOO4$5.OOlO

1992: pp 239.253

239

240

RICHARD Table 1. Parameters

of High-Risk Factors for Cervical Vertebral Injury

High-velocity blunt trauma Multiple, severe long-bone fractures Direct cervical region injury Altered mental status Fall from greater than 10 feet Drowning Severe head or facial injury Neck pain, tenderness, or deformity Abnormal neurological examination Thoracic or lumbar vertebral fracture History of pra-existing vertebral disease Modified

and reprinted

with permission.2

(closed or open); direct cervical region injury (includes patients with cervical pain, spasm, or obvious deformity); altered mental status (includes alcohol, drugs, and loss of consciousness); drowning or diving accident; falls of greater than 10 feet; significant head or facial injury; thoracic or lumbar vertebral fracture; and spinal rigidity from underlying disease such as ankylosing spondylitis. Table 1 summarizes the high-risk factors. It is the author’s feeling that any patient within this category should undergo a full series of cervical radiographs. At Allegheny General Hospital, a level I trauma center, there are approximately 1,800 major trauma admissions per year. The majority of these patients are victims of high-speed motor vehicle trauma. This group of patients includes approximately 250 patients per year with significant vertebral injury. Eighty-two percent.of these are due to motor vehicle accidents, and 17% due to falls. Because of this large selective group of trauma patients, cervical radiographs are obtained on the majority of admissions. As a result, very few patients with “minor” cervical injuries are encountered. In summary, the author endorses Vandemark2 who feels that patients should be assessedas individuals, and the decision to obtain cervical radiographs should be determined by clinical and historical risk factors. TECHNICAL

ASPECTS

Plain Radiography

Once the decision is made to obtain cervical radiographs, what constitutes an adequate examination? The author recommends a six-view radiographic series that is performed with the

H. DAFFNER

patient in the supine position. This series comprises lateral horizontal beam, anteroposterior (AI’) projection of the lower cervical column, atlantoaxial anteroposterior (open mouth, odontoid) projection, and bilateral supine trauma oblique views. There are still many emergency departments in the country that rely solely on the lateral radiograph. Gehweiler et a1,4have shown that a significant number of injuries may be missed if reliance is made solely on the lateral film. In this author’s opinion, the lateral view only is an inadequate examination and should be followed by the remaining views as soon as it is practically possible. Table 2 shows the efficacy of lateral radiographs for cervical trauma. As previously mentioned in our institution, all cervical radiographs on trauma patients are obtained with the patient supine. A portable x-ray unit is adequate for filming in most instances. The lateral view is obtained using a horizontal beam with a grid cassette. The film is placed adjacent to the patient’s head as close to Table 2. Efficacy of Lateral

Radiographs

for Cervical

Trauma

injury

Demonstrable

Atlanto-occipital dislocation Atlantoaxial dislocation Atlas fractures Posterior arch Anterior arch Burst (Jefferson) Lateral mass Transverse process Axis fractures Dens Vertebral body Vertebral arch (“hangman”) Lower cervical vertebral bodies Simple flaxion Burst Uncinata process Lower cervical vertebral arch Spinous process Locked facets Articular pillar Lamina Pedicle Transverse process Flexion sprain Extension sprain Flexion fracture, dislocation Extension fracture, dislocation

+ +

+ + t/+ + + + + + + tt+I-

+ + +

Reprinted from Imaging of Vertebral Trauma by R.H. Daffner with permission of Aspen Publishers, Inc., 0 1988.5

CERVICAL

VERTEBRAL

241

TRAUMA

Fig 1. Trauma oblique projection. (A) Positioning. The patient is supine. The film cassette (large arrow) is placed next to the patient’s neck. The x-ray tube is angled 35” to 40” off the horizontal with a 15” cephalad tilt. Long arrow shows the central ray. (Reprinted with permissions) (B) Trauma oblique radiograph in a patient with a unilateral jumped locked facet at C4-C5 on the right. This projection elongates the vertebrae. The pedicles (P) and articular pillars (A) are particularly well shown. Note the point of locking (arrow).

Fig 2. Hyperflexion sprain at C4-C5. (A) Supine lateral radiograph is normal. (B) Upright lateral radiograph of C4 on C5 (open arrow). Note the widening of the interspinous space at C4C5 (white arrow).

shows

anterolisthesis

242

the shoulders as possible. Traction is placed on the shoulders, when possible, in attempt to image C7. Under no circumstances should traction be applied directly to the patient’s head. A 40-in focal film distance is used.5 Once an adequate lateral radiograph has been obtained, the AP view is performed using a 20” cephalad angulation of the upright tube with the point of entry at the cricoid cartilage. Once again, 40-in focal film distance is used.5 The atlantoaxial view is obtained with the patient’s mouth open, when possible. This view may be delayed until the patient is able to fully cooperate. It may be necessary to remove the anterior portion of the cervical collar, that is immobilizing the patient’s neck. The supine oblique view (trauma oblique) is a radiographic projection that unfortunately, is not being used widely, although it has been in the radiographic literature since at least 1980.4-6 To obtain this view, the film is placed adjacent to the patient’s head and neck. The x-ray tube is angled 30” to 40” off the horizontal with a 15” cephalad tilt of the tube. This additional angulation improves demonstration of the cervical thoracic junction in all but the most obese patients (Fig 1). Although there is distortion caused by this view, it is excellent for showing vertebral bodies, the pedicles, the articular pillars, and the laminae. It also may show the posterior arch of the atlas.5 An additional view that is extremely valuable to obtain is the upright-lateral view. This projection is obtained because of the possibility of an occult hyperflexion sprain (Fig 2). This injury is the result of posterior ligamentous damage and it is often encountered in the absence of accompanying fractures. The supine lateral radiograph may be normal, but an upright view will result in the weight in the head producing kyphotic angulation, widening of the interspinous space, and facet widening.4J Lateral active flexion and extension views may be obtained in patients with malalignment or excessivestraightening. In our institution, we reserve flexion and extension views for those patients with minor degrees of anterolisthesis or retrolisthesis. In most instances, this abnormality is result of degenerative disc disease at the same level (Fig 3). The patient must be conscious and cooperative for this type of examina-

RICHARD

H. DAFFNER

tion. Under no circumstances should the patient’s head be passively moved for this study. Further evaluation of the cervical vertebral column may be obtained with either computerized tomography (CT) or pluridirectional tomography. CT is a viable adjunct once an abnormality is detected. It may be useful for assessingthe cervicothoracic junction in patients with large shoulders in whom adequate lateral radiographs cannot be obtained. However, the true value of this study is predicated upon the performance of sagittal reconstruction through the area of interest. CT examination should always include one full level above and one full level below all areas of suspected abnormality.5 This is recommended because injuries of contiguous vertebrae are not uncommon (Fig 4). Sections are obtained contiguously at 4- to 5-mm intervals. Filming is performed at both bone and soft tissue windows. For suspected injuries of Cl-B, a lateral scout film is used. For those of the lower column, a frontal scout film is used to avoid losing the cervicothoracic junction in the shoulder shadows.

Fig 3. Retrolisthesis from degenerative disease. There is retrolisthesis of C3 on Gl (arrow). Note the narrowed C3 disc space. Lateral flexion and extension views (not shown) showed the deformity to be fixed.

CERVICAL

VERTEBRAL

TRAUMA

243

Fig 4. Necessity for obtaining full contiguous sections on CT. (A) Lateral radiograph shows a burst fracture of C5. There is anterolisthesis of C4 on C5. C4 and C6 appear normal. Note the prevertebral soft tissue swelling. (B) CT scan through C4 shows a fracture through the articular pillar on the left side (arrow). (C) CT section through C5 shows the burst fracture of the body. Note the fractures of the lamina on the left (arrows). (D) CT section through C6 shows fractures through the body as well as through the lamina on the left (arrow). (E) Frontal radiograph shows, in retrospect, the fractures through the articular pillar of C4 (wide arrow) and through C6 (long arrow). These fractures might have been overlooked had a CT examination only of C5 bean performed. (Reprinted from Imaging of Vertebral Trauma by R.H. Daffner with permission of Aspen Publishers, Inc.. ‘c 1988.5)

Polydirectional tomography may also be used to supplement plain-film and CT examination. Polydirectional tomography is used to best advantage in evaluating fractures of the dens, articular pillars, horizontal fractures, and to assessthe cervicothoracic junction. In addition, conventional frontal tomograms are the best method to differentiate a Mach band and a dens fracture of C2.5

Magnetic resonance imaging (MRI) is now used routinely on all patients at our institution with neurologic deficit following vertebral injury. MRI is useful in determining the relationship of bony fragments that may have been displaced into the vertebral canal to encroach upon the spinal cord. It can also show the extent of soft tissue damage associated with the injury. However, the main value is the evaluation of the

RICHARD

Fig 5. Teardrop fracture of C5. Note the large teardrop fragment off the anteroinferior aspect of the body of C5. There is retrolisthesis of the body of C5 (curved arrow) end widening of the facet joints of C5-C6 (straight arrow).

spinal cord following injury. MRI will be covered in further detail elsewhere in this issue. PRINCIPLES OF DIAGNOSIS

“Fingerprints” of Vertebral Injury Vertebral fractures occur in predictable and reproducible patterns. The same force applied to the cervical, thoracic, or lumbar column will produce injuries with remarkable similarity in appearance. In the cervical region, there are three basic mechanisms of injury-flexion, extension, and rotation. Flexion injuries are the most common type encountered in the cervical region. They accounted for 79% of the injuries encountered in a review of injuries at our institution.’ ‘“Fingerprints” of flexion injuries include compression, fragmentation, and burst of vertebral bodies; “teardrop” fragments of the anteroinferior vertebral body margins; wide interspinous space; anterolisthesis; disrupted posterior vertebral body lines; locked facets; and narrow disc space above the level of injury. A “teardrop” fracture of a patient in a diving accident illustrates many of these “fingerprints” (Fig 5).

H. DAFFNER

Extension injuries were encountered in 19% of our cervical injuries.7 Three broad categories may be found in the cervical region-the “hangman” type fracture of C2, the hyperextension sprain, and the hyperextension fracture dislocation. The “hangman” fracture is the most commonly encountered and classically involves the posterior arches of C2. However, quite often the posterior portion of the vertebral body of C2 is involved as well (Fig 6). The hyperextension sprain is encountered most commonly in elderly individuals who have suffered a fall and an abrasion or laceration to the chin. These patients generally have severe neurological deficit as the result of the spinal cord having been compressed by osteophytes (Fig 7A). Radiographically, there may be very little to account for the neurological abnormality other than severe degenerative disc disease.However, the hallmark of this injury is widening of an intervertebral disc space (Fig 7B). The extension fracture dislocation is a severely disruptive injury that may initially appear like a flexion injury because of the anterolisthesis of the vertebral bodies. However, the spinolaminar line remains intact, and the interspinous space is normal indicating that this is not a flexion injury.4J The “fingerprints” of extension injuries include widened disc space; triangular avulsion fracture from the anterosuperior aspect of the vertebral body; retrolisthesis; neural arch frac-

Fig 6. Hangman fracture of C2. The fracture through the neural arch of C2 is apparent (long arrow). There is also enterolisthesis of the body of C2 on C3 (wide arrow).

CERVICAL

VERTEBRAL

TRAUMA

245

Fig 7. Hyperextension sprain. (A) Drawing shows the mechanism. (Reprinted wfth permission.6) (B) Lateral radfraph in an elderly patient shows widening of the C6 disc space. There is a small avulsion fracture just anterior to the disc space (open arrow). Note the retrolisthesis of C6 on C7 (long arrow).

tures; and anterolisthesis with normal interspinous space and spinolaminar line. Rotational injuries are very uncommon in the cervical region. Fewer than 2% were encountered in our diagnostic series.’ Two varieties may occur. The first is simple rotary luxation of C2. This may be diagnosed by the malalignment of the midline structures in the cervical regionthe internal occipital protuberance, the dens, and the spinous processesof C2 and C3 (Fig 8). A more serious injury is a rotary fixation of Cl on C2. This is a true dislocation of Cl on C2 with locking of the articular facets. This diagnosis may be suspected when a patient is encountered with gross rotation of the head to one side and inability to return the head to midline. Plain radiographs show the gross rotation. Confirmation may be made with either CT or tomograms (Fig 9). The “fingerprints” of rotary injuries include rotation and dislocation. The “fingerprints” of cervical vertebral injury are summarized in Table 3.

the plain radiographs as well as to delineate the full extent of injury. The author prefers a logical system of diagnosis that follows a mnemonic “ABC’S” where each letter represents an abnormality: A, alignment and anatomy; B, bony integrity; C, cartilage or joint spaces; S, soft tissues.

ABC’S of Radiological Interpretation For Cervical Vertebrul Trauma

Plain film radiography remains the single most important diagnostic modality that may be obtained for diagnosing vertebral injury. Other imaging studies such as CT, polydirectional tomography, or MRI should be directed toward confirming the initial diagnosis established from

Fig 6. Rotary luxation of CZ. There is malallgnment of the internal occipital protuberance, and spinous processes of C2 and C3 (vertical bars). These are all midllne structures. Were the patient simply rotated, there would be a gradual progression of the malalignment rather then the abrupt change at C2.

RICHARD

246

A knowledge of normal cervical vertebral anatomv is kev to understanding abnormalities of anatomy and alignment. An excellent illustrated discussion of normal radiographic anatomy of the cervical region may be found in a text by Daffner.5 For this reason, anatomy will not be included in this discussion. Abnormalities of alignment and anatomy include disruption of the anterior or posterior vertebral body lines, disruption of the spinolaminar line, jumped and locked facets, wide interspinous space, rotation of spinous processes, widening of the interpediculate distance, and the widening of the predental space. Three other abnormalities that are less specific include loss of lordosis, acute kyphotic angulation, and torticollis. Abnormalities of bony integrity include obvi,

d

Table 3. “Fingerprints”

of Cervical

Vertebral

H. DAFFNER

Injuries

Flexion Compression, fragmentation, burst of vertebral bodies “Teardrop”fragments Wide interspinous space Anterolisthesis Disrupted posterior vertebral body line Locked facets Narrowed disc space above involved vertebrae Extension Wide disc space Triangular avulsion fracture Retrolisthesis Neural arch fracture Anterolisthesis with normal interspinous space and spinolaminar line Rotary Rotation Dislocation Modified

and reprinted

with permission.7

CERVICAL

VERTEBRAL

TRAUMA

ous fractures, disruption of the ringlike structure of C2, widening of the body of C2, the so-called “fat” C2 sign, widening of the interpediculate distance, and disruption of the posterior vertebral body line. Quite often, abnormalities of alignment and bony integrity may be encountered with the same injury. You must carefully examine the radiographs to determine if any of the abnormalities present are subtle. Unlike the thoracic or lumbar region where fractures are often quite obvious, the abnormalities encountered in a patient with a cervical injury may be quite subtle. The patient with unilateral jumped locked facets serves as a perfect illustration. This is the most commonly missed abnormality for which malpractice suits are filed. Figure 10 illustrates the myriad of abnormalities that may be encountered with this injury. Note the anterolisthesis of C4 on C5, the widening of the interspinous space,s the

247

disruption of the spinolaminar line, the abrupt change in orientation of the facet images, and the “bow-tie” sign.9 Malalignment due to cervical spondylosis is a common occurrence. Minor degreesof anterolisthesis or retrolisthesis are often encountered. In most instances, the degree of offset is 2 mm or less. Flexion and extension radiographs often show the deformity to be fixed. In 1986, Lee et allo identified an important finding to allow confident differentiation of degenerative slippage from that of a traumatic etiology. They showed that malalignment due to spondylosis almost always had narrowed facet joints and disc spaces-the “grinding down” effect. Traumatic malalignment often had wide facets.‘O Two other subtle abnormalities may be encountered in fractures involving the body of C2. Harris et al” described disruption of the ringlike image in the body of C2 on lateral radio-

Fig 10. Unilateral jumped locked facets (C4 on C5) (same patient as Figure 16). (A) Lateral radiograph shows anterolisthesis of C4 on C5. Note the widening of the interspinous space (curved arrow). There is abrupt duplication of the facet images giving the appearance of a bow-tie (wide arrows). (B) Frontal radiograph shows rotation of the spinous process of C4 (arrow) to the right, the side of locking. Vertical bars denote the spinous processes of C4 through C7.

RICHARD

H. DAFFNER

Fig 11. Disruption of Harris’ ring. (A) Lateral radiograph of a cervical specimen show the components of Harris’ ring: (1) the upper arc represents the superior articular facet, (2) the posterior arc represents the posterior vertebral body line, (3) the inferior arc represents a portion of the foramen transversarium, (4) the anterior arc represents a portion of the anterior vertebral body. (B) Lateral radiograph shows a break in the inferior arc of Harris’ ring (arrow) in this patient with a C2 body fracture. There is slight anterolisthesis of the body of C2 on C3. (C) CT scan shows the fracture (arrow) through the posterior portion of the body of C2.

Fig 12. The “fat C2 sign.” [A) Lateral Note the break in the posterior vertebral

radiograph shows widening of the inferior portion of the body of C2 in comparison body line (arrow). (B) CT scan shows the fracture through the body of C2.

to C3.

CERVICAL

VERTEBRAL

TRAUMA

Fig 13. Ckcipltoatfantal dislocation. [A) Powers ratio measures 1.4. This should never exceed 1. (B) Lee method. Afthough the descending limb (D-D’) is within 5 mm of the dens, the ascending limb (A-A’) is nowhere near the spinolaminar line of Cl. The occiput is dislocated anteriorly.

Fig 14. Wide prevertebral area in an patient with a dens fracture. Lateral radiograph shows a subtle fracture of the base of the dens. Note the prevertebral soft tissue swelling (wide arrows). There is retro5sthesk of the dens and spinolaminar line of Cl on C2 (long arrows).

250

graphs. They were able to show that this “ring” was, in fact, a collection of images of overlying normal structures. The superior arc of the ring represents the superior articular facet; the posterior arc of the ring is the posterior vertebral body line; the inferior arc of the ring is part of the foramen transversarium; and the anterior arc of the ring is a portion of the anterior vertebral body (Fig 11A). The dens does not contribute to the ring. Harris et al” were able to show that subtle fractures of the body of C2 that do not separate disrupt one or more arcs of the ring (Figs 11B and C). The second subtle abnormality involving C2 was described by Smoker and Dolan12 in 1987. These authors were able to show that a shift of fracture fragments of the body of C2 produced apparent widening of that structure in relationship to the width of C3. They termed this the “fat C2 sign” (Fig 12). Abnormalities of the cartilage or joint space include widening of the predental space, abnormal intervertebral disc space, widening of the apophyseal or facet joints, “naked” facets, widening of the interspinous or interlaminar distance, and atlanto-occipital malalignment. The predental space between the anterior arch of the atlas and dens should never exceed 3 mm in an adult or 5 mm in a child. This space normally may be V-shaped. Widening of this joint is most commonly encountered in patients with rheumatoid arthritis and in children. Disc space abnormalities include narrowing or widening. The narrow disc space should not be taken as a sign of injury because it is most often encountered in patients with degenerative disease. However, as a rule, the disc space above a fracture due to a flexion mechanism is generally narrowed. However, more significantly, is widening of a disc space as may be seen in hyperextension injuries (Fig 7).13 Widening of facet joints or naked facets indicates severe posterior disruptive injury has occurred. This finding is almost always associated with widening of the interspinous or interlaminar distance (Fig 10). As a rule, facet joints and the interlaminar distance should not differ by more than 2 mm from level to level. However, one exception to this rule, is at C3-C4

RICHARD

H. DAFFNER

where a normal variant due to contouring of the inferior aspect of the spinous process of C3 may give the false appearance of an abnormal spinous space. When you encounter such a patient, look for other evidence of flexion injury such as widening of the facet joints, anterolisthesis, and disruption of the spinolaminar line. Occipitoatlantal dislocations are usually fatal injuries. However, a number of patients will survive the initial impact to arrive in the emergency department. Several methods of assessment have been devised to determine if an abnormality exists. The first of these is the Powers ratio4JJ4 which is determined by first drawing a line from the basion to the midpoint of the arch canal line on the posterior arch of the atlas (line B-C). A second line (line O-A) is drawn from the opisthion to the midpoint of the posterior surface of the anterior/arch of the atlas. Under normal circumstances, the ratio of B-C over O-A should be one or less (Fig 13A).4,5J4 Lee et a15J5devised an alternative method also using two lines. The first line, the descending limb, is drawn between the clivus or basion to the midpoint of the spinolaminar line of C2.

Fig 15. Tracheal deviation in a patient with hyperextension sprain at C6-C7 (same patient as Figure 76). Frontal radiograph shows displacement of the trachea to the right (long arrows). Note the widened disc space (wide arrow).

CERVICAL

VERTEBRAL

TRAUMA

251

Fig 16. Soft tissue swelling in a patient with aortic rupture. (A) Lateral radiograph shows massive prevertebral soft tissue swelling. The retropharyngeal space measures 17 mm; the retrotracheal space measures 30 mm. The vertebrae are normal. (6) Chest radiograph shows widening of the superior mediastinum (arrows). (C) Arch aortogram shows a lobular pseudoaneurysm (arrows) at the site of aortic rupture.

A second line, the ascending limb, is drawn from the posteroinferior corner of the body of C2 to the opisthion. Under normal circumstances, the descending limb should contact the dens or be within 5 mm of it, and the ascending limb should pass through the spinolaminar line of Cl (Fig 13B).5J5 Soft tissue abnormalities may provide important clues to the presence of underlying verte-

bra1 injury, particularly in the cervical region. They were once considered key to the diagnosis of many of these injuries.“j However, many of these changes were described at a time when plain-film radiography constituted the main means of imaging diagnosis of cervical injuries. These findings have become less important as a greater awareness of the subtle radiographic findings are now better appreciated, particu-

252

larly in the era of sophisticated multimodal imaging. Soft tissue abnormalities include widening of the retropharyngeal space, widening of the retrotracheal space, displacement of the pervertebral fat stripe, the presence of a soft tissue mass in the craniocervical junction, and deviation of the trachea or larynx. The retropharyngeal space is measured from the anteroinferior aspect of the body of C2 to the posterior aspect of the pharyngeal air column and should never exceed 7 mm in adult or children on a standard lateral beam radiograph (40-in focal film distance). The retrotracheal space is measured from the anteroinferior aspect of the body of C6 to the posterior tracheal wall (or image of an endotracheal tube). This space should never exceed 14 mm in children or 22 mm in adults on a standard 40-in radiograph. Both of these soft tissue spaces may be widened as the result of prevertebral soft tissue swelling. In most instances, there is other evidence of injury in the region. Occasionally, fractures of the dens or the anterior arch of Cl may produce soft tissue swelling anterior to Cl and C2 (Fig 14). However, the author has been surprised by the large number of casesin which soft tissue abnormalities were absent even in the presence of significant bony injury. The prevertebral fat stripe is a thin band of fatty tissue that parallels the anterior longitudinal ligament from C2 through C6. Displacement of this line from its normal location may indicate a subtle underlying injury.17 Tracheal or laryngeal deviation is a nonspecific abnormality that may occur with trauma or under a variety of circumstances other than trauma. The airway structures are not securely fixed in the neck, and thus, are subject to motion by any fluid collection in the region. Thus, this sign should not be relied upon as a sole basis of diagnosis of injury (Fig 15). Massive widening of the prevertebral soft tissues is usually the result of a condition other than cervical trauma. In the trauma setting, this may be encountered with patients with aortic injuries due dissection of blood from the thorax into the prevertebral region (Fig 16). Similarly, retropharyngeal abscessesmay produce massive prevertebral soft tissue swelling. The infant or small child who is crying will often have widen-

RICHARD

Table 4. ABC’S of Vertebral

H. DAFFNER

Trauma

Abnormalities of alignment or anatomy Disruption of anteroposterior vertebral body lines Disruption of spinolaminar line Jumped and locked facts Rotation of spinous processes Widening of interpediculate space Widening of predental space Loss of lordosis Kyphotic angulation Torticollis Abnormalities of bony integrity Obvious fracture Disruption of ring of C2 “Fat” C2 sign Widening of interpediculate space Disruption of posterior vertebral body line Abnormalities of cartilage joint space Widening of predental space Abnormal intervertebral disc space Widened facet joints “Naked” facets Widened interspinous or interlaminar distance Abnormal Powers ratio or Lee’s lines Abnormalities of soft tissues Widening of retropharyngeal space Widening of retrotracheal space Displacement of prevertebral fat stripe Soft tissue mass in craniocervical junction Tracheal or laryngeal deviation

ing of the soft tissues. In these patients, a repeat radiograph once the patient has quieted will be normal. Table 4 summarizes the ABCS of vertebral trauma. SUMMARY

The use of imaging studies on patients with suspected cervical vertebral injury should be restricted to those patients who fall into the high-risk category for injury. Once a decision is made to obtain radiographs, a minimum of five views is required to adequately rule in or rule out injury. Complex imaging studies such as CT, polydirectional tomography, and MRI may be performed to confirm the initial impression based on plain radiographic findings. The diagnosis of cervical injuries may be facilitated by following a logical pattern of analysis searching for abnormalities of alignment and anatomy, of bony integrity, of the cartilage or joint spaces, and of the soft tissues. This ABCS approach should simplify an intimidating subject and insure a confident radiological diagnosis.

CERVICAL

VERTEBRAL

253

TRAUMA

REFERENCES 1. Mirvis SE, Diaconis JN, Chirico PA, et al: Protocoldriven radiologic evaluation of suspected cervical injury: Efficacy study. Radiology 170:831-834,1989 2. Vandemark RM: Radiology of the cervical spine in trauma patients: Practice pitfalls and recommendations for improving efficiency and communication. AJR 155:465-472, 1990 3. American College of Surgeons Committee on Trauma: Advanced trauma life support course for physicians. Chicago, IL, American College of Surgeons, 1984; 256 4. Gehweiler JA Jr, Osborne RL Jr, Becker RF: The radiology vertebral trauma. Philadelphia, PA, Saunders, 1980 5. Daffner RH: Imaging of vertebral trauma. Rockville, MD. Aspen, 1988 6. Abel MS: The exaggerated supine oblique view of the cervical spine. Skeletal Radio1 8:213-219,1982 7. Daffner RH, Deeb ZL, Rothfus WE: “Fingerprints” of vertebral trauma-a unifying concept based on mechanisms. Skeletal Radio1 15:518-525,1986 8. Naidich JB, Naidich TP, Garfein C, et al: The widened interspinous distance: A useful sign of anterior cervical dislocation in the supine frontal projection. Radiology 123:113-116,1977 9. Young JWR, Resnik CS, DeCandido P, et al: The

laminar space in the diagnosis of rotational flexion injuries of the cervical spine. AJR 152:103-107,1989 10. Lee C, Woodring JH, Rogers LF, et al: The radiographic distinction of degenerative slippage (spondylolisthesis and retrolisthesis) from traumatic slippage of the cervical spine. Skeletal Radio1 15:439-443,1986 11. Harris JH Jr, Burke JT, Ray RD, et al: Low (type III) odontoid fracture: A new radiographic sign. Radiology 153:353-356,1984 12. Smoker WRK, Dolan KD: The “fat” C2: A sign of fracture. AJNR 8:33-38,1987 13. Cintron E, Gilula LA, Murphy WA, et al: The widened disc space: A sign of cervical hyperextension injury. Radiology 141:639-644,1981 14. Powers B, Miller MD, Kramer RS, et al: Traumatic anterior atlanto-occipital dislocation. Neurosurgery 4: 1217,1979 15. Lee C, Woodring JH, Goldstein SJ, et al: f%aluation of traumatic atlanto-occipital dislocations. AJNR X:19-26, 1987 16. Clark WM, Gehweiler JA Jr, Laib R: Twelve significant signs of cervical spine trauma. Skeletal Radio1 3:201205,1979 17. Whalen JP, Woodruff CL: The cervical prevertebral fat stripe. A new aid in evaluating the cervical prevertebral soft tissue space. AJR 109:445-451,1970