All AS listings are contacted on which structure?

• A. Inferior PSIS
• B. Medial PSIS
• C. Lateral PSIS
• D. Acetabular ridge

Answer: (D)

The main idea here is that AS listings require a stable, precise contact point on the pelvis to deliver the correct directional force. An anterior–superior orientation of the sacrum relative to the ilium is best addressed from a robust bony landmark that can tolerate the thrust without slipping or causing soft tissue trouble. The acetabular ridge on the ilium provides that solid, predictable contact surface, making it the optimal point for applying the adjustment in AS listings.

Landmarks like the inferior, medial, or lateral PSIS sit further back on the pelvis and are more variable in shape and softness, which can make delivering a clean, controlled vector harder. They are not the preferred contact for this particular listing, whereas the acetabular ridge offers a stable, reliable surface for the intended anterior–superior correction.