Anna N. Miller
Timothy S. Achor

Bony Anatomy

The acetabulum is a hemispherical portion of the bony pelvis. The pelvis itself is made up of the sacrum and two innominate bones, joined at the sacroiliac joints and symphysis pubis.
Each innominate bone consists of the iliac wing, from the posterior superior iliac spine posteriorly to the anterior superior iliac spine anteriorly, and extending inferiorly to the greater sciatic notch.
Anterior to the greater sciatic notch and inferoposterior to the anterior inferior iliac spine is the acetabulum, bounded medially by the quadrilateral surface.
The ischial tuberosity extends distal below the acetabulum.
The acetabulum has various degrees of tilt and retroversion depending on the patient’s bony anatomy and possible dysplasia (Figs. 15-1 and 15-2).

Radiographic Anatomy

The commonly assessed views for the acetabulum are AP and Judet views.
A good AP view should have the spinous processes in line with the symphysis pubis. The coccyx should be at the level of the superior portion of the symphysis pubis (Fig. 15-3).

Judet views consist of tilting the patient to the right or left (or digitally manipulating the image instead) such that the AP view is rotated to the point where the coccyx overlaps with the femoral head.
The two Judet views are “obturator oblique” and “iliac oblique.”
On the obturator oblique view, the obturator foramen of the side of interest is tilted anteriorly, and the anterior column and posterior wall of the acetabulum are more visible (Fig. 15-4).

On the iliac oblique view, the greater and lesser sciatic notches and ischial spine of the side of interest are visible as the obturator foramen is tilted posteriorly. This view is better for evaluating the posterior column (Fig. 15-5).

The six lines of Judet and Letournel are the anterior wall (red), posterior wall (white), ilioischial line (posterior column; orange), iliopectineal line (anterior column; blue), sourcil (dome; yellow), and teardrop (medial wall; light green) (Fig. 15-6).

Advanced imaging (CT) is recommended for further delineation of fracture pattern, including articular fragments and marginal impaction.

For both anterior and posterior approaches to the acetabulum, intraoperative views are similar to those discussed above (AP and Judet).
The obturator oblique outlet view is also helpful specifically to delineate the superior pubic ramus for interosseous screw fixation from a prone or supine position (Fig. 15-7).