Coccyx Lateral is a radiography positioning projection of the Pelvis. True lateral coccyx. SID 40". CR perpendicular to IR. The centering point is located 3 to 4 inches posterior and 2 inches inferior to the ASIS, at the coccyx. The central ray is perpendicular to the IR, vertical into the table Bucky, centered to the coccyx. Image-quality criteria include coccyx shown without rotation or forward angulation, all coccygeal segments visible. A sample technique is 85 kVp with DR 40 or CR 90 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- All coccygeal segments and their alignments.
- Articulation between coccyx and sacral apex.
- Coccygeal curvature and angulation.
- Anterior surface of coccyx.
Patient preparation
- Verify patient identity.
- Position patient in left or right lateral position.
- Align mid-sagittal plane parallel to IR.
- Flex hips and knees for patient comfort and stability.
- Place pillow or support under waist to prevent rotation.
- Remove radiopaque objects from perineal area.
- Suspend respiration during exposure.
Position & centering point
3 to 4 inches posterior and 2 inches inferior to the ASIS, at the coccyx.
Central ray
Perpendicular to the IR, vertical into the table Bucky, centered to the coccyx.
Exposure / technique
- kVp
- 85
- mAs
- DR 40 / CR 90
- SID
- 40" (102 cm)
- Notes
- Slightly lower mAs than sacral lateral due to thinner anatomy. Bontrager: a separate lateral coccyx needs lower kV and less mAs than the lateral sacrum, and one lateral can include both to decrease gonadal dose. As a separate view, this is not in the 2027 outline (from March 1, 2027), which lists only the combined lateral sacrum and coccyx. Sample technique: DR 40 / CR 90 mAs at 85 kVp, 40 in SID, for a 31 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
- Coccyx shown without rotation or forward angulation.
- All coccygeal segments visible.
- Bony margins and trabecular markings clear, with open segment interspaces if not fused.
- Coccyx centered on IR.
- Greater sciatic notches superimposed, showing no rotation.
Common errors
- 1 Patient rotation: the greater sciatic notches are not superimposed.
- 2 CR not centered to coccyx results in off-axis anatomy.
- 3 Too much scatter reaches the IR: use lead masking behind the patient, close collimation and suitable kV.
Clinical indications
- Suspected coccygeal fracture.
- Pathology of the coccyx.