Cervical spine injury can cause catastrophic neurologic harm, so positioning must never take priority over spinal precautions. Radiographers should be able to produce diagnostic images of the seven cervical vertebrae, the upper-cervical joints, and the cervicothoracic junction when radiography is requested, while recognizing that CT is now the preferred initial examination for many adults with acute blunt trauma.
This guide reviews AP axial, lateral, open-mouth odontoid, oblique, swimmer's, and flexion-extension technique; image-evaluation principles; normal mimics; and safe participation in a clinician-led trauma pathway. Projection sets, receptor sizes, grids, SID, breathing instructions, and small CR adjustments vary by equipment and department; explicit protocol differences are labeled rather than blended.
POSITIONING CONVENTION: Angles below reflect common US radiography teaching and the cited accredited school procedure manual. They are not attributed to Clark's. Follow the current examination order, equipment chart, and departmental procedure manual. TRAUMA SAFETY: Do not remove immobilization, rotate the patient, depress the shoulders by traction, or extend the neck unless an authorized clinician and local protocol permit it.
The ABCS mnemonic is a useful framework for checking image coverage and recognizing findings that need escalation. It is not a validated clearance rule, and image interpretation and removal of spinal precautions remain the responsibility of appropriately credentialed clinicians.
Four parallel arcs: anterior and posterior vertebral body lines, spinolaminar line, and interspinous line. Any step-off or disruption must be explained.
Each vertebral body height, cortical margins, and pedicles. Check C1 lateral masses and the odontoid process integrity.
Review the atlanto-dental interval and every disc and interspinous space for unexpected asymmetry or widening; age and degeneration affect appearance.
Inspect the prevertebral contour for swelling. Numeric cutoffs depend on level, age, magnification, respiration, and whether they were derived from radiographs or CT.
On a technically adequate neutral lateral radiograph, four smooth alignment contours should be reviewed; they are not necessarily perfectly parallel at every level:
An unexplained break or step-off raises concern for malalignment, although positioning and degenerative change can mimic it. A requested lateral radiograph should show through C7–T1; if it does not, follow the ordered/local pathway for a repeat, supplemental swimmer's view, or CT. An incomplete radiograph cannot exclude injury, and the radiographer does not “clear” the spine.
The atlanto-dental interval (ADI) is measured between the posterior cortex of the anterior C1 arch and the anterior dens. Common radiographic teaching uses upper limits of 3 mm in adults and 5 mm in children. Widening can indicate C1–C2 instability or transverse-ligament injury, but a single radiographic measurement does not prove ligament rupture or determine treatment.
Rotation, non-neutral positioning, magnification, and age affect the measurement. Maintain precautions and communicate an unexpected abnormality immediately under local escalation policy; do not obtain motion views to “prove” instability.
For a routine non-trauma AP axial projection, align the midsagittal plane without rotation, elevate the chin enough to move the mandible off the upper cervical spine, and direct the CR 15–20° cephalad to C4 (thyroid-cartilage level). The cephalad angle parallels the lower cervical disc spaces. Collimate to include approximately C3 through T2, adjusted for anatomy and the examination request; the spinous processes should be near midline and the pedicles symmetric.
The cited Heritage Valley Health System School of Radiography manual specifies a 15° cephalad AP axial. Some departments use 15–20°, and a specifically ordered non-angled AP is a different projection. Do not invent a tube angle during trauma imaging; use the ordered departmental protocol.
The AP open mouth view is arguably the most technique-sensitive projection in the entire C-spine series. Its purpose is to evaluate the odontoid process (dens), the lateral masses of C1, and the atlanto-axial articulation. A non-diagnostic open mouth view is one of the most common reasons for repeat exposures in trauma radiography.
| Problem | Cause | Correction |
|---|---|---|
| Odontoid hidden behind incisors | Neck too flexed (chin down) | For a cleared, cooperative patient only, extend slightly; otherwise consult before any movement |
| Odontoid hidden behind skull base | Neck too extended (chin up) | For a cleared, cooperative patient only, flex slightly; otherwise consult before any movement |
| C1 lateral masses asymmetric | Rotation of head or CR not midline | Align midline to grid; ensure patient faces straight up |
| Dental hardware overlying odontoid | Fixed superimposition | Do not improvise tube angulation; consult the radiologist/local protocol about another projection or cross-sectional imaging |
| Cannot open mouth or cooperate | Patient condition | Do not force motion. In acute trauma, maintain precautions and escalate for the appropriate CT pathway |
The Fuchs (AP) and Judd (PA) methods project the dens within the foramen magnum and require substantial neck extension. In routine positioning teaching, the MML is placed approximately perpendicular to the receptor and the CR is parallel to the MML: the AP Fuchs is directed through the midline just inferior to the mandibular tip; the PA Judd is directed through the midline to exit just inferior to the mandibular tip. Both are contraindicated when fracture or instability is suspected and must not be attempted on an unconscious or uncleared trauma patient. Use only when specifically ordered and safe under the department's named protocol.
A diagnostic lateral radiograph should include C1 through the C7–T1 disc space, show the mandibular rami substantially superimposed, and demonstrate the posterior vertebral elements without marked rotation. For routine erect imaging, center a horizontal CR to C4 at thyroid-cartilage level; a long SID (commonly 60–72 inches/150–180 cm) reduces magnification. Exact SID is protocol- and equipment-dependent.
If a lateral radiograph is specifically ordered for an uncleared trauma patient, use a horizontal beam without moving the head or neck and retain immobilization unless the responsible clinical team directs otherwise. Current ACR adult blunt-trauma guidance generally favors CT when imaging is indicated. Technique factors must come from the validated local exposure chart:
The most common reason for a non-diagnostic lateral C-spine is inadequate visualization of C7–T1 due to shoulder superimposition. Every rad tech should have a systematic approach:
If the CT junction is still not visible, the image is incomplete. A supplemental swimmer's view, repeat lateral, or CT may be selected by the responsible protocol/clinician; no radiographic view by itself authorizes the radiographer to clear the spine.
The swimmer's view (Twining method/lateral cervicothoracic view) is a supplemental projection intended to separate the shoulders and show the C7–T1 region when it is obscured on a standard lateral. Whether it is included routinely, added only when needed, or replaced by CT is a local and indication-specific protocol decision.
Recumbent technique, only when movement is authorized: The arm closest to the IR is elevated alongside the head as far as safely possible; the opposite shoulder is depressed without traction. Maintain the head as directed by spinal precautions. Center to C7–T1, approximately 1 inch (2.5 cm) above the jugular notch. A perpendicular CR is standard; a slight 3–5° caudal angle may be used by protocols intended to separate the shoulders.
Alternative (erect): For non-trauma patients, place the patient lateral to the upright receptor. Raise the arm nearest the IR and depress the opposite shoulder; avoid rotation. Suspend respiration. A quiet-breathing technique is an equipment-specific alternative, not a universal instruction.
Traditional positioning questions often name the swimmer's view as the supplemental projection for an obscured C7–T1 junction. That educational convention must not be confused with current adult acute-trauma selection: ACR rates CT cervical spine without contrast as usually appropriate when CCR/NEXUS indicates imaging, and radiography as usually not appropriate.
Cervical obliques demonstrate the intervertebral foramina and pedicles. They may be used for degenerative foraminal assessment or selected follow-up indications, but they are not “critical” routine projections in modern acute adult blunt trauma, where CT is more sensitive and ACR-preferred when imaging is indicated.
For routine posterior obliques, rotate the cleared patient 45° into RPO and LPO, direct the CR 15–20° cephalad to C4, and suspend respiration. These AP axial oblique projections show the foramina farthest from the IR. For anterior obliques (RAO/LAO), use a 15–20° caudal angle to C4; these PA axial obliques show the foramina nearest the IR. Projection choice and the number of views are determined by the order and local protocol.
| Position | CR angle/centering | Projection family | Side demonstrated |
|---|---|---|---|
| RPO | 15–20° cephalad to C4 | AP axial oblique | Left foramina (farthest from IR) |
| LPO | 15–20° cephalad to C4 | AP axial oblique | Right foramina (farthest from IR) |
| RAO | 15–20° caudal to C4 | PA axial oblique | Right foramina (nearest IR) |
| LAO | 15–20° caudal to C4 | PA axial oblique | Left foramina (nearest IR) |
Do not overgeneralize: posterior/AP obliques demonstrate the foramina farthest from the IR; anterior/PA obliques demonstrate the foramina nearest the IR. Never rotate an uncleared trauma patient merely to create a named oblique position.
Flexion and extension lateral radiographs assess dynamic motion in selected patients, but they are not an initial acute-trauma examination and must never be performed simply because a plain-film series appears normal. A qualified clinician must first review the relevant examination and imaging, specifically order the views, and determine that active motion is safe. In current adult trauma pathways, CT is the preferred initial examination when imaging is indicated; MRI without contrast is usually appropriate when ligament, cord, or nerve-root injury is suspected.
Do not proceed with known or suspected instability, an uncleared acute injury, new neurologic symptoms, altered mental status, intoxication, inability to cooperate, or an order that lacks required clinical clearance. Alertness alone does not establish safety. Stop active motion if symptoms develop and follow local escalation policy. MRI is selected by the clinical team when ligamentous, spinal-cord, or nerve-root injury is suspected; it is not an automatic substitute in every scenario.
Several developmental and congenital variants of the cervical spine can appear suspicious on radiographs and lead to unnecessary CT scans or anxiety. Every rad tech should recognize these common mimics:
| Normal Variant | Appearance | How to Differentiate from Pathology |
|---|---|---|
| Os Odontoideum | Separate, rounded ossicle representing an unfused/separated odontoid above a hypoplastic dens base | Smooth corticated margins favor chronicity over an acute fracture, but C1–C2 instability may coexist and requires clinical assessment. |
| Persistent Ossiculum Terminale | Small ossicle at the tip of the odontoid | Well-corticated margins; normal alignment. Usually stable and incidental. |
| Congenital Block Vertebra | Congenital fusion with a narrowed or absent intervening disc and often a “wasp-waist” contour | Smooth remodeling and reduced combined vertebral height favor a developmental fusion; CT/MRI may be needed when trauma is suspected. |
| Klippel-Feil Syndrome | Congenital fusion of two or more cervical vertebrae | Congenital fusion with associated short neck, low hairline; no acute fracture line. |
| Limbus Vertebra | Anterior-superior corner defect of a vertebral body | Well-corticated triangular fragment; no acute fracture. Represents old herniation of disc material through the ring apophysis. |
| Pseudofracture of the Spinous Process (C6, C7, T1) | Lucency at the tip of the spinous process | This is the secondary ossification center (unfused apophysis) — smooth and well-corticated. True avulsion fractures have irregular margins. |
While radiographers do not provide final interpretations, recognizing classic fracture patterns allows you to (a) understand why additional projections may be ordered, (b) appreciate the clinical urgency, and (c) answer ARRT exam questions correctly. Here are the high-yield fractures:
| Fracture | Mechanism | Level | Best View | Key Radiographic Finding |
|---|---|---|---|---|
| Jefferson Fracture | Axial loading (e.g., diving) | C1 (atlas) | CT; open-mouth may suggest | C1 ring fractures; lateral-mass overhang relative to C2 may be seen, but overhang alone neither excludes nor proves transverse-ligament injury. |
| Odontoid (Dens) Fracture | Flexion or extension | C2 (dens) | CT; open-mouth/lateral may suggest | Type I (tip), Type II (base), Type III (into C2 body). Type II has an important nonunion risk. |
| Hangman's Fracture | Hyperextension with axial loading | C2 pars/pedicles | CT; lateral may suggest | Bilateral posterior-element fractures with variable C2–C3 translation or angulation. |
| Flexion teardrop fracture | Severe flexion-compression | Lower cervical, commonly C5 | CT; lateral may suggest | Anteroinferior fragment with posterior body displacement/kyphosis; highly unstable. Distinguish from the generally smaller extension-type avulsion injury. |
| Clay Shoveler's Fracture | Avulsion from forceful flexion | C6–T1 (spinous processes) | AP, lateral | Avulsion fracture of the spinous process tip, typically at C7 or T1. |
| Unilateral Facet Dislocation | Flexion-rotation | Subaxial cervical | CT; lateral/oblique may suggest | Typically less than 50% anterior translation, focal kyphosis/rotation, and a locked facet; exact translation varies. |
| Bilateral Facet Dislocation | Severe flexion | Subaxial cervical | CT; lateral may suggest | Often approximately 50% or greater anterior translation with severe instability and high cord-injury risk. |
| Projection | IR Size | CR/Centering | SID | Grid | Key Evaluation Criteria |
|---|---|---|---|---|---|
| AP axial | Commonly 10 × 12 | 15–20° cephalad to C4 (thyroid cartilage) | Commonly 40–44″ | Per protocol | Approximately C3–T2; disc spaces open; spinous processes near midline; symmetric pedicles |
| AP open mouth (odontoid) | Commonly 8 × 10 | Perpendicular through midline of open mouth | Commonly 40–44″ | Per protocol | Dens and C1 lateral masses without teeth/skull-base superimposition; symmetric C1–C2 joints |
| Lateral | Commonly 10 × 12 | Horizontal to C4 at thyroid-cartilage level | Commonly 60–72″ | Per protocol | C1 through C7–T1; minimal rotation; posterior elements and prevertebral contour included |
| Swimmer's (lateral CT junction) | Commonly 10 × 12 | C7–T1, about 1″ above jugular notch; perpendicular or protocol-specific 3–5° caudal | Protocol-specific | Per protocol | C7–T1 through separated shoulders with minimal rotation |
| Posterior obliques (RPO/LPO) | Commonly 10 × 12 | Patient 45°; 15–20° cephalad to C4 | Commonly 40–44″ | Per protocol | Foramina farthest from IR (RPO = left; LPO = right) |
| Anterior obliques (RAO/LAO) | Commonly 10 × 12 | Patient 45°; 15–20° caudal to C4 | Commonly 40–44″ | Per protocol | Foramina nearest IR (RAO = right; LAO = left) |
| Flexion/extension lateral | Commonly 10 × 12 | Horizontal to C4; active motion only after clinician clearance | Use lateral protocol | Per protocol | Ordered range included without avoidable rotation; interpretation by qualified clinician |
The radiographer acquires the ordered examination safely and escalates incomplete or unexpected images; the radiographer does not independently decide that imaging is unnecessary or remove precautions. For adults with acute blunt cervical trauma, current ACR guidance distinguishes clinical screening from imaging selection:
NEXUS: the original prospective study classified a blunt-trauma patient as low probability only when all five were absent: posterior midline cervical tenderness, focal neurologic deficit, abnormal alertness, intoxication, and painful distracting injury. It reported 99.0% sensitivity for cervical-spine injury and 99.6% for clinically significant injury in that cohort. CCR: for alert, stable trauma patients, imaging is mandated by any high-risk factor (age ≥65, dangerous mechanism, or extremity paresthesias); if a low-risk factor permits safe range-of-motion assessment, inability to actively rotate 45° left and right mandates imaging. Apply the full rule—not fragments—and only within its validated population and local clinical policy.
Patient contact shielding recommendations have changed. A shield placed at or near the cervical field can obscure anatomy, interfere with AEC, or trigger a repeat. Follow current facility policy and regulatory requirements:
Cervical spine injuries are terrifying for patients. Many arrive in the emergency department with a cervical collar, unsure of their condition. Communicate clearly: explain what you are doing, why you are positioning the X-ray tube a particular way, and how the patient can help (e.g., "I need you to keep your chin exactly where it is while I take this picture"). For the open mouth view, a clear instruction like "Open your mouth as wide as you can and say 'ah'" helps relax the tongue and palate for a better image.
Try these ARRT-style multiple choice questions based on this article. Click an option to check your answer — correct answers turn green, wrong ones turn red.