Iliac Crest's Intermediate Zone, Posterior View

Description

Iliac crest intermediate zone is centered along the thickened superior border of the ilium between the outer and inner lips, and in this posterior perspective it tracks medially toward the posterior superior iliac spine (PSIS) at the dorsal margin of the hip bone. The iliac ala (wing) fans inferiorly and laterally from the crest, while the posterior iliac tuberosity and adjacent roughened surface lie inferior to the crest and approach the auricular region for the sacroiliac joint. Bony contour dominates the field. Subtle changes in curvature mark where the crest transitions from its broad intermediate segment into the more irregular posterior third. Palpation and surgical planning often hinge on this segment of the iliac crest because it provides a reliable surface landmark for the PSIS, a reference point used when estimating the L4 level for neuraxial procedures, and it frames the posterior approach corridor for posterior iliac crest bone graft harvest. Enthesopathic change along the iliac crest, including traction spurs and periosteal reaction, is frequently discussed alongside pelvic apophyseal injury in adolescent athletes, while in adults the same region can be a pain generator after iliac crest harvest or repetitive loading through the thoracolumbar fascia. The fixed posterior orientation supports teaching of laterality and depth cues around the sacroiliac region, where the iliac tuberosity sits posteromedial to the broader iliac wing and just lateral to the sacral attachment sites of posterior sacroiliac ligaments. Use this illustration in gross anatomy labs when introducing surface landmarks of the pelvis, in orthopedic and spine surgery texts describing posterior pelvic exposure and graft donor site anatomy, or in radiology teaching files that correlate iliac crest contour with pelvic radiographs and CT. Anatomical accuracy verified by SciePro's Medical Advisory Board.