13.1 Cervical, Thoracic & Lumbar Spine Radiography & Trauma Adaptations

13.1 Cervical, Thoracic & Lumbar Spine Radiography & Trauma Adaptations

Spinal radiography requires meticulous anatomical understanding, precise central ray angulation, and strict adherence to trauma safety protocols. The vertebral column consists of 33 vertebrae during early development, which fuse into 26 distinct presacral and sacrococcygeal segments in adults: 7 cervical, 12 thoracic, 5 lumbar, 1 sacrum (5 fused segments), and 1 coccyx (4 fused segments). Anatomical curvatures play a critical role in positioning: the cervical and lumbar regions exhibit anteriorly convex lordotic curves, whereas the thoracic and sacral regions display anteriorly concave kyphotic curves.

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Cervical Spine Radiography & Trauma Adaptations

1. AP Axial Cervical Spine (C3–C7)

• Central Ray (CR): Angled 15° to 20° cephalad, entering at the level of C4 (lower margin of thyroid cartilage / upper margin of spinous process).
• Positioning Purpose: The cephalad angulation opens the intervertebral disk spaces (C3 through C7) and demonstrates the vertebral bodies, uncinate processes (joints of Luschka), and intervertebral disk spaces without foreshortening caused by normal lordosis.
• Respiration: Suspended expiration to prevent chest movement.

2. AP Open Mouth (Fuchs & Judd Methods for C1–C2 Dens/Odontoid)

• AP Open Mouth (Atlas & Axis): Patient's mouth is opened as wide as possible. Adjust head position so that a line from the lower margin of the upper incisors to the base of the skull (mastoid tip) is perpendicular to the image receptor (IR).
• CR: Perpendicular to IR, directed through the center of the open mouth.
• Demonstrated Structures: Dens (odontoid process) of C2, body of C2, lateral masses of C1 (atlas), atlantoaxial joints, and zygapophyseal joints between C1 and C2.
• Fuchs Method (AP) / Judd Method (PA): Used when the upper incisors superimpose the dens or when the patient cannot open their mouth. In the Fuchs method, the chin is extended so the mentomeatal line (MML) is perpendicular to the IR; CR is perpendicular, entering at the inferior tip of the mandible.

3. Lateral Cervical Spine (C1–T1)

• SID: Extended to 72 inches (180 cm) to minimize magnification and distortion caused by the increased object-to-image distance (OID) across the shoulders.
• Positioning: Patient erect (seated or standing) with shoulders depressed as low as possible (holding sandbags in hands). Chin slightly elevated to prevent mandible from superimposing upper cervical vertebrae.
• CR: Perpendicular to C4 (level of thyroid cartilage).
• Demonstrated Structures: C1 through C7 vertebral bodies, spinous processes, intervertebral disk spaces, articular pillars, and zygapophyseal joints (which are in true profile on a lateral view).

4. Cervical Intervertebral Foramina: AP vs. PA Obliques

Cervical intervertebral foramina lie at a 45° anterior angle from the mid-sagittal plane and a 15° inferior angle.

• AP Obliques (RPO and LPO): Patient rotated 45° body oblique. CR angled 15° to 20° cephalad entering C4. Demonstrates the intervertebral foramina and pedicles on the UPSIDE (side farthest from the IR). E.g., RPO shows left foramina; LPO shows right foramina.
• PA Obliques (RAO and LAO): Patient rotated 45° body oblique. CR angled 15° to 20° caudal entering C4. Demonstrates the intervertebral foramina and pedicles on the DOWNSIDE (side closest to the IR). E.g., RAO shows right foramina; LAO shows left foramina.

5. Swimmer's View (Twining Method / Pawlow Method)

• Indication: Required when the shoulders obscure the C7–T1 interspace on the standard lateral cervical spine radiograph.
• Positioning: Patient in lateral position (erect or recumbent). Arm closest to IR elevated above head; opposite arm and shoulder depressed maximally.
• CR: Perpendicular to C7–T1 interspace (centered 1 inch above jugular notch). A slight caudal angle of 3° to 5° may be applied if the depressed shoulder cannot be sufficiently separated from C7–T1.

6. Cervical Spine Trauma Protocol

• Trauma Golden Rule: In cases of head or neck trauma, a horizontal beam cross-table lateral radiograph MUST be taken first without moving the patient's head or neck.
• Immobilization: The patient MUST remain immobilized in a hard cervical collar on a trauma board. DO NOT move the patient, remove the collar, or perform flex/ext views until the cross-table lateral is reviewed and cleared by an emergency physician or radiologist.
• Inclusion Requirement: All 7 cervical vertebrae and the C7–T1 junction MUST be clearly visualized on the initial lateral trauma radiograph. If C7–T1 is obscured by shoulders, a trauma Swimmer's view (with horizontal beam) must be performed.

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Thoracic Spine Radiography

1. AP Thoracic Spine

• Positioning: Patient supine with knees and hips flexed (reduces thoracic curvature and flattens spine against IR).
• CR: Perpendicular to T7 (centered 3 to 4 inches inferior to jugular notch or midway between xiphoid process and jugular notch).
• Anode Heel Effect: Utilize the anode heel effect by placing the patient's head at the anode end of the X-ray tube and the thicker lower thoracic region at the cathode end. This yields uniform radiographic density across the length of the T-spine.

2. Lateral Thoracic Spine

• Positioning: Patient recumbent in left lateral position (reduces cardiac magnification) with knees flexed for stability. Arms elevated 90° in front of body.
• CR: Perpendicular to T7 (entering posterior edge of mid-axillary line).
• Breathing Technique vs. Scatter Reduction:
  • Orthostatic Breathing Technique: Low mA (25–50 mA) and long exposure time (3 to 4 seconds) while patient breathes gently. Blurs out overlying lung vascular markings and rib structures while keeping T-spine sharply detailed.
  • Lead Rubber Block: Place a lead rubber sheet/block on the tabletop behind the patient's back. This absorbs secondary scatter radiation emitted from the patient, dramatically improving image contrast and preventing automatic exposure control (AEC) pre-termination.

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Lumbar Spine Radiography & The "Scotty Dog"

1. AP / PA Lumbar Spine

• Positioning: Patient supine or prone. Flexing hips and knees in AP flattens the lumbar lordotic curve and opens intervertebral disk spaces.
• PA Projection Advantage: Performing PA lumbar spine reduces gonad dose to female patients significantly compared to AP.
• CR: Perpendicular to L4–L5 (level of iliac crests) for entire lumbar/sacral examination, or L3 (1.5 inches above iliac crest) for lumbar spine only.

2. Lateral Lumbar Spine & L5–S1 Spot Lateral

• Lateral Lumbar: Patient in true lateral position. CR perpendicular to iliac crest (L4) or 1.5 inches above crest (L3). Demonstrates intervertebral foramina L1–L4, intervertebral disk spaces, spinous processes, and vertebral bodies.
• L5–S1 Spot Lateral Projection: CR angled 5° caudal for males and 8° caudal for females (compensating for broader female pelvis). CR centered 1.5 inches inferior to iliac crest and 2 inches posterior to anterior superior iliac spine (ASIS). Opens the L5–S1 intervertebral disk space and demonstrates the L5–S1 junction.

3. AP Oblique Lumbar Spine (RPO / LPO) & Scotty Dog Anatomy

• Positioning: Patient rotated 45° from supine (30° rotation for L5–S1 joint). CR perpendicular entering 2 inches medial to elevated ASIS and 1.5 inches above iliac crest.
• Demonstrated Joint: AP Obliques (RPO and LPO) demonstrate the zygapophyseal joints on the DOWNSIDE (side closest to the IR). E.g., RPO demonstrates right zygapophyseal joints; LPO demonstrates left zygapophyseal joints. (PA obliques RAO/LAO show upside).
• The "Scotty Dog" Anatomic Landmarks: In a properly rotated 45° oblique lumbar radiograph, the posterior elements align to create the classic "Scotty Dog" appearance:
  • Ear: Superior articular process
  • Eye: Pedicle
  • Nose: Transverse process
  • Neck: Pars interarticularis
  • Front Leg: Inferior articular process
  • Body: Lamina
  • Back Leg: Opposite inferior articular process
• Pathology Correlation: A translucent break or fracture line across the neck of the Scotty dog represents spondylolysis (defect of the pars interarticularis). If the vertebra slips anteriorly, it is termed spondylolisthesis.

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Spine Positioning & Anatomy Summary Table