The Emergency Center assessment of the spine, whether for non-traumatic or traumatic indications, begins with the basic physical examination.  Similarly, imaging of the spine should begin with basic conventional radiography.  CT and MRI should be reserved for appropriate radiographic and/or clinical indications.  The point being, as every patient with spine complaints does not require imaging evaluation, so every patient whose signs and symptoms merit imaging does not require CT or MR.  As with the use of CT and MRI in imaging other parts of the body, the radiologist must approve all requests for CT and MR examinations of the spine. 

The primary emphasis of this section is the cervical spine. However, because the conventional radiographic examinations and anatomy of the cervical spine and the neck are similar, it seemed logical to consider them together.

The incidence of acute cervical spine injury due to blunt trauma in adult patients admitted to emergency centers ranges from 1.9 to 3.8% [16] [17].  In infants and children, the reported incidence of blunt cervical spine injury is <1% [18].  Even in multiply-injured patients, the incidence of cervical spine injury has been reported to be only 5.9% [19]. Concomitant cervical spine fractures are reported to occur in 10% of patients [20].

A nationwide, multi-center study based on 34,000 Emergency Center patients has shown that radiographic examination of the cervical spine is NOT indicated in patients with "no midline cervical tenderness, no focal neurologic deficit, normal alertness, no intoxication, and no painful, distracting injury" [21].

In most emergency centers, there is an inordinately high incidence of negative radiographic examinations of the cervical spine, most prompted by the complaint of “neck pain” and/or simply the presence of a cervical collar applied at the scene.  Commonly, the collar precludes even consideration of a physical examination of the cervical spine.

Therefore, and based on the above, it should be apparent that, as a member of the trauma team, the radiologist must participate in the decision to image the bluntly injured cervical spine in the interest of appropriate patient care and the conservation of institutional (patient transport, technologist, technical, clerical) and economic resources.

While diversity of opinion exists regarding what constitutes an “adequate” radiographic examination of the bluntly injured cervical spine, there is complete unanimity that the examination must include, on the lateral projection at least, from the cervicocranial junction through the cervicothoracic junction (C-T J).  It is generally held that the initial radiographic examination of the cervical spine should consist of AP, open-mouth (view of cervicocranium), and lateral projections – with the patient erect when possible. When the initial lateral examination is obtained with the patient supine, some authors advocate obtaining an erect lateral when possible to screen for ligamentous injury not recorded on the supine lateral.

At Memorial Hermann Hospital, a “contact” lateral is included in the routine examination of the cervical spine.  This radiograph is obtained with the cassette placed on top of the shoulder and the cassette in “contact” with the side of the patient’s face and head.  The central beam is entered at the angle of the mandible and the exposure made during forced inspiration when the patient is able to cooperate.  The “contact” lateral is designed to show the cervicocranial prevertebral soft tissue (ccpvst) shadow with the naso-oropharynx maximally distended.  An abnormal ccpvst shadow can indicate a subtle cervicocranial injury for which CT is required for further assessment.  A variant of the “contact” lateral is the “trumpet,” view which is obtained as the “contact,” but with the patient asked to forcefully exhale against closed lips.

On the AP radiograph of the cervical spine (Fig. csp02) structures to be recognized include the lower (C3 downward) cervical vertebral bodies; superior and inferior endplates; disk spaces; uncinate processes which, together with the inferolateral aspect of the supradjacent vertebral body, form the uncovertebral joint of Luschka; the superimposed lateral masses forming the radiographic optical illusion called the lateral column which normally has a smoothly undulating lateral margin said to resemble a column of bamboo; the spinous  processes; and the tracheal air column.  The AP projection does not reliably include the cervicocranium.

The open-mouth view (Fig. csp06) is optimally positioned so that, with the mouth maximally opened, the occlusal margins of the maxillary incisor teeth and the inferior margin of the occipital bone are superimposed on the same axial plane.  It is commonly believed that the open-mouth view is properly positioned and, therefore, diagnostic if the tip of the dens is recorded on the radiograph.  We believe the open-mouth projection is diagnostic only when it includes the inferior aspect of the occipital condyles in addition to the entire dens, the C1 lateral masses, the lateral atlanto-dental intervals, the axis body, and the lateral atlanto-axial articulations.  The C2 spinous process should be in the midline.  The coronal relationship of inferior facets of the C1 lateral masses to the superior facets of C2 (Fig. csp37) is particularly important to understanding the axial CT anatomy through these joints (Fig. csp38).  The biconvex occipital condyles nestled in the biconcave superior facets of C1 explain the bilateral lateral displacement of the lateral masses of C1 in the Jefferson bursting fracture.  Asymmetry of the lateral atlanto-dental interval is normally of no significance simply reflecting the normal variation of the configuration of the dens and the lateral masses of C1.  The C1-2 relationship on the open-mouth projection is normal when the lateral margins of the C1-2 facets are on essentially the same vertical plane.

The first observation regarding the lateral radiograph of the cervical spine (Fig. csp12) is the normal cervical lordotic curve.  (Physiologically, the cervical lordosis is straightened or reversed by flexing the neck (Fig. csp04), assuming the “military” position with the chin on the chest, recumbency, and the application of a cervical collar). Structures visible on the lateral cervical radiograph include the occipital condyles, C1 and the occipitoatlantal articulation, C2, including the dens, and lower cervical spine (C3-7) structures including vertebral body, disk space, u-shaped transverse process superimposed on the vertebral body, articular masses, adjacent facets and interfacetal joints, lamina, and spinous process.

From infancy through adolescence, the ring apophyses alter the appearance of the lower cervical vertebral bodies on the lateral radiograph. The anterior aspect of the vertebral bodies is rounded (Fig. csp11) due to the non-ossified apophyses in infants and young children. In older children and early adolescents, the ossified ring apophyses appear as wedge-shaped, separate structures typically located at the anterior inferior aspect of the vertebral body (Fig. csp01). The apophyses gradually fuse (Fig. csp18) with the vertebral bodies by early adulthood.

When the cervicothoracic junction is not visible on the initial lateral projections, a “pull-down” lateral is recommended, assuming the patient has no upper extremity injury and the body habitus provides reasonable assumption that applying traction to the shoulders will make the C-T J radiographically visible.  To obtain this view, the patient’s feet are against the puller’s abdomen while the puller applies traction to the patient’s wrists, pulling the shoulders down.  Counter-traction to the patient’s head must NOT be applied because of possible distraction of unrecognized ligamentous injury.  Only one attempt at the “pull-down” radiograph is recommended.  The advantage of the “pull-down” technique lies in demonstration of the 4 criteria for radiographically clearing the C-T J, namely (1) The C7-T1 apophyseal joints, (2) The superior end-plate of T1, (3) The anterosuperior aspect of the body of T1, (4) and the cervicothoracic prevertebral soft tissue shadow, defined by the posterior margin of the tracheal air shadow, paralleling the contour of the anterior cortex of the C-T vertebral bodies into the thoracic inlet (Fig. csp35).

A second method to visualize the C-T J is the “swimmer’s” view (Fig. csp08), so called because positioning of the arms is similar to that of the Australian freestyle swimming stroke position.  Disadvantages of the “swimmer’s” view include inability of the patient to cooperate for the required positioning for whatever reason (upper extremity injury, lack of consciousness), and/or superimposition of the clavicles, upper ribs, and shoulder joints upon the C-T J.  The osseous superimposition typically seriously obscures visualization of the middle and posterior columns of the C-T vertebrae.

A third method to demonstrate the C-T J is the use of supine, (“trauma”), oblique projections in which the cassette is placed as far as possible posterior to the shoulder, neck, and head without moving the supine patient.  The x-ray tube is placed to the opposite side, centered on the thyroid cartilage and angled 35 degrees.  The process is repeated for the contralateral side.  The resultant radiograph shows the same anatomy as the routine oblique projection only slightly distorted by magnification.  The advantages include:  useful in patients with short neck, requires no patient movement or cooperation, and demonstrates the posterolateral aspect of the C-T vertebrae.  The supine oblique projections, when mentally integrated with the AP radiograph, provide adequate basis for radiographically “clearing” the C-T J.

The C-T J is definitively imaged by CT which requires only patient movement onto the CT gurney.  Other than proximity to the Emergency Center and cost, CT has no disadvantages relative to visualization of the C-T J.

Some authors advocate a 5 film series, consisting of AP, lat, open mouth and each oblique projection as the initial examination of the acutely injured cervical spine. The oblique view (Fig. csp03) shows the posterolateral aspect of the vertebral body, pedicle, intervertebral foramen, and depending on patient positioning, either the articular masses and interfacetal joints or the laminae superimposed on the articular masses. With this degree of obliquity, the articular masses are not clearly recognizable. The laminae appear in the "shingles-on-a-roof" configuration (Fig. csp29) eg., the long axis of the lamina above when projected inferiorly lies posterior to the subjacent lamina. Because the lamina arises from the lateral mass, displacement of a lamina anterior to the subjacent lamina indicates articular mass dislocation and, therefore, unilateral interfacetal dislocation (UID) (Fig. csp29).

Finally, at least two Level I trauma centers, the Miami University and MIEMS, obtain only a "screening" lateral radiograph of the cervical spine in the trauma room, followed by CT of the entire cervical spine.

Normal skeletal anatomy seen on the lateral radiograph of the cervicocranium of a normal adult (Fig. csp07) includes the occipital condyles, anterior tubercle of C1, anterior atlantodental interval, dens, posterior aspect(s) of the lateral masses of C1, posterior arch of C1, the axis "ring" (composed of the anterior cortices of the axis "pedicles," the composite shadow formed by the cortex at the junction of the base of the dens and the superior facet of C2), the superior facet itself, and the posterior cortex of the axis body, pars interarticularis, inferior facet, lamina, and spinous process of C2, the axis body, and the C2-3 interfacetal joint.

The basion-axial interval (BAI) and basion-dental interval (BDI) are illustrated on Fig. csp13. Normally the basion lies within 12mm of the posterior axial line (PAL) which is the cephalad extension of the posterior cortex of the axis body (BAI). The distance between the basion and tip of the dens (BDI) normally should not exceed 12mm.

The cervicocranial prevertebral soft tissue (ccpvst) contour as seen on the "contact" lateral of a normal adult is shown in Fig. csp36. The ccpvst contour is normally concave above, convex anterior to, and concave below, the anterior tubercle of C1.

In infants and young children, the normal laxity of the cervical prevertebral soft tissues commonly appears as a "physiologic pseudomass" (Fig. csp14). In this instance, and when the cervical vertebrae are normally aligned, the lateral radiograph should be repeated during inspiration. Normally, the "physiologic pseudomass" will change contour (Fig. csp15) and may approach that seen in normal adults.

Representative axial CT anatomy of the lower cervical spine is shown in Figures csp09 and csp10 which extend from the mid-axial plane of one vertebra, through the subjacent disk space to the superior end-plate of the subjacent vertebra. It is important to remember that the articular mass of the suprajacent vertebra is situated above and behind the articular mass of the subjacent vertebra. Therefore, on axial CT images, the articular mass (and facet) of the vertebra above lies above and behind the articular mass (and facet) of the vertebra below (Fig. csp10). Thus the opposing articular masses are said to represent each half of a hamburger bun and the intervening interfacetal joint space, the hamburger meat (ie., the "hamburger sign").

Findings attributable to normal growth and development on the open-mouth radiograph (Fig. csp43) of infants and young children include the v-shaped tip of the dens representing the non-ossified terminal epiphysis and the neurocentral synchondroses.

The lateral radiograph of an infant or young child (Fig. csp05) shows the same skeletal anatomy as described for the adult except as modified by normal growth and development.  Because neither the occipital condyles nor the lateral masses of C1 are completely ossified, a radiographic lucency (“space”) between the condyles and lateral masses of C1 is physiologic.  For the same reason, the anterior tubercle of C1 appears to be partially above the tip of the dens.  The subchondral (subdental) synchondrosis is a horizontal lucency between the dens and the axis body.  The anterior atlantodental interval, while frequently wider than 3mm, which is normal for adults, does not normally exceed 6mm in width.  In infants and young children the atlantodental interval typically assumes a “V” configuration in physiologic flexion.

In older children to approximately age 8 years, the subchondral synchondrosis gradually fuses and may be represented by two thin transverse linear densities (Fig. csp42).  In approximately 25% of children to this age the axis body appears to lie anterior to that of C3 (physiologic pseudosubluxation of C2, eg. Fig. 40 and 41).  That this relationship is entirely normal is established by (1) normal C2-3 apophyseal joints and (2) the relationship of the spinolaminar line of C2 to the imaginary posterior spinal line drawn from the spinolaminar line of C1 to that of C2.  Normally, the spinolaminar line of C3 lies on, or 1mm anterior or posterior to, the posterior spinal line on the neutral lateral radiograph.

The vertebrae, and spine, are described as having three columns [22]; the anterior, which includes the anterior longitudinal ligament and the anterior 2/3 of the vertebral body; middle, the posterior 1/3 of the body and the posterior longitudinal ligament (PLL); and all structures posterior to the PLL, the posterior column (Fig. 3column ).

The radiographic examination of the cervical spine (and neck) for non-traumatic reasons should be determined by the clinical indications:

Classification of cervical spine injuries is: (1) Typically based on predominant mode of injury (MOI) or combinations of simultaneous mechanisms, eg., hyperflexion and rotation and; (2) the appearance of the injured cervical spine on both AP and lateral radiographs which reflect the MOI. (3) Table 1 illustrates a widely accepted MOI classification system.