Fig. 3 Pelvis and Hip Anatomy Hank Grebe/

The pelvis is a ring structure made up of 3 bones:

  • 2 X innominate bones (Each innominate bone is formed by fusion of the 3 ossification centres named ILIUM, ISCHIUM and PUBIS at the Triradiate cartilage, which closes at around 15-17 years old to form a cup-shaped socket known as the acetabulum.)
  • 1 X sacrum. Joined anteriorly at the symphysis and posteriorly at the paired sacroiliac joints.

Learning bite

The acetabulum is made up of all 3 parts of ilium, ischium and pubis. It is important to consider an acetabulum fracture as a potential complex pelvic fracture.