Iliac

Iliac is an anatomical adjective relating to the ilium, the broad, upper part of the hip bone. The ilium, together with the ischium and pubis, forms the pelvic bone that constitutes the pelvic girdle.

In the mature skeleton the ilium fuses with the ischium and pubis at the acetabulum to form the os coxae. The iliac crest runs along the superior border of the bone and is palpable across the flanks. The anterior superior iliac spine (ASIS) and posterior superior iliac spine (PSIS) are important landmarks used in clinical examination and imaging.

The ilium features several landmarks and surfaces. The auricular surface forms part of the sacroiliac joint with the sacrum, and the iliac crest marks the top edge. The inner surface contains the iliac fossa, a large concave area for the iliacus muscle; the outer surface bears the gluteal surface for gluteal muscles and related attachments.

Vascular and neural relations are clinically important. The common iliac arteries bifurcate into the internal and external iliac arteries; the external iliac artery continues as the femoral artery, while the internal iliac supplies pelvic organs, pelvic walls, and the gluteal region. Venous drainage parallels the arteries, with internal and external iliac veins joining to form the common iliac veins, which drain into the inferior vena cava. Lymphatic drainage trends to pelvic iliac nodes.

Clinical relevance includes iliac crest fractures and other pelvic injuries, which can affect stability and gait. The ilium’s landmarks aid in radiographic assessment, surgical planning, and regional anesthesia approaches.