Trauma X-ray - Axial skeleton
Sacrum and Pelvis

Anatomy

The bony pelvis comprises the two hemi-pelvis bones which are bound anteriorly at the pubic symphysis and posteriorly at the sacroiliac joints.

As with other anatomical bone rings if a fracture is seen in one place a careful check should be made for a second fracture, or for disruption of the pubic symphysis or sacroiliac joints.

Pubic ramus fracture

Fractures seen in the superior or inferior pubic ramus are usually accompanied by another fracture of the other ramus on the same side. These are very common fractures in the elderly.

Pelvic fractures

Fractures to the pelvis are highly variable in appearance depending on the mechanism and force of injury. Careful examination of the cortical surfaces of the bony rings will reveal most fractures.

The extent of injury is often underestimated on plain radiographs.

Pelvis diastasis

High force injury to the bony pelvis may result in "diastasis" (separation) at the pubic symphysis or a sacroiliac joint.

Avulsion injuries

In young athletically active individuals avulsion injuries may occur, most frequently at the ASIS, and occasionally at the AIIS.

Sacral injuries

Fractures of the sacrum may be isolated or accompany pelvis fractures. They are easily missed unless a specific check of the arcuate lines is made on every pelvic X-ray.