Base Of The Sacrum, Anterior View

Description

Sacral promontory and the body of S1 dominate the superior anterior margin of the sacrum, forming the projecting lip that faces anteroinferiorly toward the pelvic cavity. Lateral to the midline, the sacral alae flare laterally and blend with the superior aspect of the pelvic (anterior) surface, where the shallow transverse ridges begin below the base. The anterior opening of the sacral canal sits posterior to the promontory at the center of the base, aligned with the lumbosacral junction where L5 will articulate. Orientation is fixed to an anterior viewpoint. This region matters because the L5 to S1 articulation bears high shear forces, and the anterior contour of the promontory is a key landmark when discussing spondylolisthesis, lumbosacral transitional vertebrae, and alignment parameters such as pelvic incidence. Obstetric teaching also returns to this anatomy: a prominent promontory can contribute to a contracted pelvic inlet (classically the android pelvis), and its relationship to the pelvic brim guides interpretation of pelvic inlet dimensions. Lighting and surface relief help separate the smooth pelvic surface from the sharper superior rim. Landmarks read quickly. Use this illustration in gross anatomy courses covering the pelvis and perineum, spine modules focused on the lumbosacral junction, and radiology or orthopaedics publications that need a clean reference for the sacral base and promontory in anterior orientation. It also supports patient education materials explaining low back pain related to L5-S1 degeneration and the bony anatomy that frames surgical corridors for anterior lumbar interbody fusion. Anatomical accuracy verified by SciePro's Medical Advisory Board.