Lateral Cervical (Extension) is a radiography positioning projection of the Spine. Erect lateral, head extended backward, CR to C4. The centering point is located C4 vertebra with head extended backward. The central ray is perpendicular to IR at C4 level. Image-quality criteria include cervical vertebrae aligned in extended position, intervertebral disk spaces and zygapophyseal joints shown. A sample technique is 85 kVp with DR 7.1 or CR 18 mAs, at an SID of 72 inches (183 cm).
Anatomy demonstrated
- Cervical vertebrae C1-C7 in extension.
- Intervertebral disk spaces in extension.
- Spinous process approximation in extension.
- Cervical zygapophyseal joints, C2-C3 through C6-C7, in extension.
Patient preparation
- Trauma: never attempt until a physician has reviewed the horizontal-beam lateral or CT (Bontrager). Merrill's: do not attempt until cervical spine pathology or fracture has been ruled out.
- Verify patient identity using two identifiers.
- Remove neck jewelry and radiopaque objects.
- Erect lateral posture with shoulders relaxed.
- Raise the chin and tilt the head back as much as possible; do not hold longer than necessary.
Position & centering point
C4 vertebra with head extended backward.
Central ray
Perpendicular to IR at C4 level.
Exposure / technique
- kVp
- 85
- mAs
- DR 7.1 / CR 18
- SID
- 72" (183 cm)
- Notes
- Extension position. Bontrager gives SID 60 to 72 inches and warns not to hold the position longer than necessary. Sample technique: DR 7.1 / CR 18 mAs at 85 kVp, 72 in SID, for an 11 cm part (Merrill's sample chart). Adjust for your equipment.
kVp and mAs are sample values. Use caution when applying them in your department.
Image-quality criteria
- Cervical vertebrae aligned in extended position.
- Intervertebral disk spaces and zygapophyseal joints shown.
- Spinous processes close together (extension).
- C1-C7 included, although C7 may not be fully seen on some patients.
- Soft tissue outline visible.
Common errors
- 1 Patient moves backward, so part of the cervical spine leaves the IR.
- 2 Insufficient extension: spinous processes not in close proximity.
- 3 Rotation or lateral flexion prevents accurate assessment.
- 4 CR not at C4, the level of the upper margin of the thyroid cartilage.
Clinical indications
- Evaluation of cervical range of motion.
- Assessment of segmental instability and alignment in extension.
- Rule out whiplash-type injury, or follow up after spinal fusion surgery.