ABSTRACT
The pelvis is formed by the sacrum and two innominate bones. The acetabulum lies
within the innominate bone and forms the “socket” that allows articulation with the
femoral head. It is formed by the three ossification centers of the innominate bone-the
ilium, the ischium, and the pubis-and is divided into anterior and posterior columns (8).
The posterior column is composed superiorly by the ilium and inferiorly by the ischium
and extends from an area just below the greater sciatic notch past the ischial tuberosity.
In cross-section it is triangular in shape and contains the posterior half of the joint, the
posterior rim, the ischial spine, and all of the ischial tuberosity. The anterior column
consists of the anterior half of the ilium and extends to the pubic symphysis. It contains
the anterior border of the iliac wing, the pelvic brim (superior pubic rami), and the
anterior half of the acetabulum. The columns unite at an area above the level of the
