The cervical spine is the most frequently imaged spinal segment in trauma, and it carries the highest stakes of any projection you will perform as a radiologic technologist. A missed cervical spine injury can result in catastrophic neurologic deficit or death. The ARRT examination devotes significant attention to C-spine positioning, evaluation criteria, and pathology recognition — and for good reason. Every rad tech must be able to produce diagnostic images of the seven cervical vertebrae, the atlanto-axial and atlanto-occipital joints, and the cervicothoracic junction, often under demanding trauma conditions.
This article picks up where the basics leave off. We assume you already know the fundamental positioning steps for the AP, lateral, open-mouth odontoid, oblique, and swimmer's views. Here, we focus on advanced evaluation criteria, the ABCS trauma clearance method, normal variants that masquerade as fractures, classic fracture patterns, and the critical role of the radiographer in cervical spine clearance protocols.
Cervical spine positioning and pathology consistently rank among the most heavily tested content areas on the ARRT Radiography Examination. According to the ARRT content specifications, approximately 8–12% of the exam covers vertebral column imaging, with C-spine pathology recognition appearing under both Image Production and Procedures domains. Master this material.
The single most important skill for any radiographer evaluating a trauma C-spine is the ability to assess the adequacy and diagnostic quality of the lateral view — because in many trauma protocols, the lateral is the first and sometimes only view obtained before spine clearance. The ABCS mnemonic provides a systematic framework:
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.
Predental space (ADI) ≤ 3 mm in adults. Intervertebral disc spaces should be uniform. Widening of interspinous distance suggests ligamentous injury.
Prevertebral soft tissue width: ≤ 7 mm at C3, ≤ 21 mm at C6 in adults. Widening = hematoma = occult fracture until proven otherwise.
On an adequate lateral C-spine radiograph, four continuous, parallel arcs should be identifiable from C1 through C7:
A break or step-off in any of these lines suggests malalignment from fracture, dislocation, or ligamentous injury. The cervicothoracic junction (C7–T1) must be visualized — if it isn't, a swimmer's view is required. Do not clear a C-spine when C7–T1 is obscured.
The atlanto-dental interval (ADI) — the distance between the anterior arch of C1 and the odontoid process of C2 — should measure no more than 3 mm in adults (5 mm in children) on a properly positioned lateral C-spine. An ADI > 3 mm indicates transverse ligament rupture with atlanto-axial instability. This is a surgical emergency. The patient must be kept immobilized, and the referring physician should be notified immediately.
False widening can occur if the lateral view is rotated — the spinous processes should be midline and the mandibular rami should overlap symmetrically.
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) | Extend neck slightly; tell patient to open wider |
| Odontoid hidden behind skull base | Neck too extended (chin up) | Flex neck slightly |
| C1 lateral masses asymmetric | Rotation of head or CR not midline | Align midline to grid; ensure patient faces straight up |
| Dental hardware overlying odontoid | Patient anatomy | Try Fuchs view (AP projection with chin extended); or use tube angulation to project teeth above odontoid |
| Can't open mouth (trauma, unconscious) | Patient condition | CT scan is indicated; or obtain Fuchs view as alternative |
When the patient cannot open the mouth (trismus, unconsciousness, facial trauma), the Fuchs view is an alternative: patient supine, neck extended so the mentomeatal line (MML) is perpendicular to the IR, CR directed to the tip of the chin, entering just below the mandibular symphysis. This projects the odontoid through the foramen magnum and is acceptable when the open mouth view cannot be obtained. Source: Clark's Pocket Handbook for Radiographers, 16th ed.
The lateral C-spine is the most important single view in the trauma series and is frequently the first image obtained in the emergency department. It must include all seven cervical vertebrae and the C7–T1 junction. The key difference between a passing and failing lateral C-spine often comes down to adequacy of shoulder depression.
For trauma patients, the lateral C-spine is typically performed with a horizontal beam (cross-table lateral) to avoid moving the patient. The patient remains supine on a spine board or backboard with a cervical collar in place. Key modifications:
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 after these measures, a swimmer's view is required before clearing the C-spine.
The swimmer's view (also called the Twining view or lateral cervicothoracic view) is a modified lateral projection designed to visualize the lower cervical and upper thoracic vertebrae (C4–T3) when the standard lateral view fails to show C7–T1. This is a mandatory second-line view — not an optional addition.
Supine trauma technique: The arm on the side closest to the IR (or closest to the image receptor) is elevated alongside the head as far as possible. The opposite arm remains at the patient's side, pulling downward on the shoulder. The head is maintained in neutral position without rotation. The CR is directed perpendicular (or 5° caudad) to the C7–T1 junction at the level of the jugular notch.
Alternative (erect): For non-trauma patients, the patient stands facing the upright Bucky in a lateral position. The arm closer to the IR is raised forward and upward (as if swimming a front crawl), while the opposite arm is pulled back and down. The patient suspends respiration and is instructed to depress both shoulders.
On the ARRT exam, you may be asked: "Which projection is required when the C7–T1 junction is not visualized on a standard lateral C-spine?" The answer is the swimmer's view (Twining view). Do NOT answer "oblique views" or "repeat the lateral with more shoulder depression." Once the standard lateral has been attempted and C7–T1 is still obscured, the swimmer's view is the protocol-mandated next step.
The C-spine oblique views provide visualization of the intervertebral foramina, pedicles, and the pars interarticularis — structures that are not well seen on the AP or lateral projections. These views are critical for detecting unilateral facet dislocations, pillar fractures, and foraminal stenosis.
For the trauma/recumbent technique, the patient is supine and the tube is rotated 45° lateral from the AP position (or the grid is rotated), centering to the midline at the level of C4–C5. A 15° cephalad angle is used to open the intervertebral foramina on the side opposite the tube. Two exposures (right posterior oblique and left posterior oblique) are required.
| Projection | Tube Angle | CR Direction | Side of Foramina Visualized |
|---|---|---|---|
| RPO (right posterior oblique) | 45° left of midline + 15° cephalad | Enters at C4–C5, exiting at left foramina | Left (side away from IR) |
| LPO (left posterior oblique) | 45° right of midline + 15° cephalad | Enters at C4–C5, exiting at right foramina | Right (side away from IR) |
ARRT rule of thumb: In the oblique position, the intervertebral foramina on the side farthest from the IR are demonstrated (the "open" side). This is a frequently tested concept.
Flexion and extension lateral views of the cervical spine are NOT performed in the acute trauma setting. They are obtained only after the standard trauma series has ruled out acute fracture or instability. Their purpose is to evaluate ligamentous integrity — abnormal motion between vertebral segments suggests ligamentous injury even when the bones appear intact.
Flexion-extension views are contraindicated in patients with known fracture, neurologic symptoms, altered mental status, or inability to cooperate. In these scenarios, MRI is the modality of choice for ligamentous injury evaluation. The radiographer must verify the patient is alert, oriented, and neurologically intact before performing these views.
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 | Round, ossified fragment at the tip of the odontoid with a well-corticated gap | Smooth, sclerotic margins vs. jagged, irregular margins of acute fracture. Often associated with C1–C2 instability. |
| Persistent Ossiculum Terminale | Small ossicle at the tip of the odontoid | Well-corticated margins; normal alignment. Usually stable and incidental. |
| Congenital Block Vertebra | Fused vertebral bodies with absent disc space | No fracture line; smooth anterior contour; associated with reduced height at the fused level. |
| 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) | AP open mouth | Lateral displacement of C1 lateral masses beyond C2 margins. Burst of the ring. |
| Odontoid (Dens) Fracture | Flexion or extension | C2 (dens) | AP open mouth, lateral | Type I (tip), Type II (base), Type III (body of C2). Type II is most common and prone to nonunion. |
| Hangman's Fracture | Hyperextension (e.g., MVA) | C2 (pars interarticularis) | Lateral | Fracture through the pars interarticularis of C2 with or without anterior subluxation of C2 on C3. |
| Teardrop Fracture | Severe flexion-compression | C5 (most common) | Lateral | Triangular fragment from anteroinferior corner of vertebral body; often associated with retropulsion into spinal canal. |
| 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 | Any level | Lateral, oblique | Vertebral body anteriorly displaced < 50% of width; on oblique, the "bow-tie" sign of a locked facet. |
| Bilateral Facet Dislocation | Severe flexion | Any level | Lateral | Vertebral body displaced > 50% of width; often catastrophic cord injury. |
| Projection | IR Size | CR/Centering | SID | Grid | Key Evaluation Criteria |
|---|---|---|---|---|---|
| AP C-Spine | 10 × 12 | Midsagittal plane at C4–C5 (level of thyroid cartilage) | 40″ | Yes | All 7 vertebrae visible; spinous processes midline; trachea centered; C3–T1 demonstrated |
| AP Open Mouth (Odontoid) | 8 × 10 | Midline through open mouth | 40″ | Yes | Odontoid between incisors and skull base; C1 lateral masses symmetric; ADI assessable |
| Lateral C-Spine | 10 × 12 | C4–C5, 2″ posterior to EAM | 72″ | Yes | C1–T1 all visible; 4 alignment arcs intact; spinous processes posterior; prevertebral soft tissues assessable |
| Swimmer's (Lateral CT Junction) | 10 × 12 | C7–T1 at jugular notch | 40″ | Yes | C4–T3 visualized; CT junction free of shoulder superimposition |
| Oblique (RPO/LPO) | 10 × 12 | C4–C5 midline; 45° + 15° cephalad | 40″ | Yes | Pedicles and intervertebral foramina of the side opposite the tube; foramina open without rotation |
| Flexion / Extension (Lateral) | 10 × 12 | C4–C5, true lateral, mid-coronal plane | 72″ | Yes | Range of motion documented; no angular step-off > 11°; interspinous widening < 1.5× adjacent levels |
The radiographer plays a critical role in the cervical spine clearance pathway. Understanding the protocol helps you anticipate the next steps and prioritize your workflow:
The NEXUS (National Emergency X-Radiography Utilization Study) Low-Risk Criteria state that cervical spine imaging is not required if the patient meets ALL five criteria: (1) No midline cervical tenderness, (2) No focal neurologic deficit, (3) Normal level of alertness, (4) No intoxication, (5) No painful distracting injury. The ARRT exam frequently tests these criteria as part of patient care and safety content.
The thyroid gland is one of the most radiosensitive organs in the body. For C-spine radiography:
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.