X Ray Coccyx AP View

Patient lies supine with knees flexed to relax abdominal muscles. Align the midsagittal plane to the table and center the image receptor over the coccyx (approximately 2 inches superior to the pubic symphysis). Direct the central ray 10° caudad for males and 15° caudad for females for an AP axial coccyx. Suspend respiration during exposure.

The best plain-film view for the coccyx is the lateral view, which typically most clearly shows alignment, angulation, subluxation and fractures. AP views are of limited value. If radiographs are inconclusive or the injury is complex, cross-sectional imaging (CT for bony detail, MRI for soft tissues and occult fractures) is recommended.

Identify PA vs AP by patient position and image signs: PA is upright with shoulders rolled forward so scapulae lie outside the lung fields, clavicles symmetric, good inspiration and true heart size. AP (portable/supine) often shows scapulae projected over lungs, apparent cardiomegaly from magnification, higher/asymmetric clavicles and shallower inspiration. Always confirm with the radiographic marker when present.

There are four coccyx types (Postacchini classification): Type I — slight forward curve with apex pointing downward; Type II — more pronounced anterior curvature; Type III — sharply angulated anteriorly; Type IV — subluxation or dislocation at sacrococcygeal or intercoccygeal joints (mobile or malaligned segment). These variations can influence risk of coccydynia.

The AP (anteroposterior) position is an X‑ray projection where the beam enters the front (anterior) of the body and exits through the back (posterior) to the detector. The patient faces the detector or lies supine with the X‑ray tube in front. AP views are used for portable, trauma, or bedridden patients and can magnify the heart and slightly reduce image quality compared with PA projections.

The best positions reduce pressure on the tailbone: when sitting, sit on a firm chair, lean slightly forward, or use a coccyx/donut cushion with a cut-out at the back so the tailbone is suspended; avoid slumping and prolonged hard-seat sitting. For rest, lie on your side with a pillow between knees or on your back with a small pillow under knees to relieve spinal pressure.