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Topic

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Iliac bone

The iliac bone (ilium) is the largest and superior-most component of the hip bone, forming the upper part of the pelvic girdle. It plays a major role in weight transmission from the axial skeleton to the lower limbs and provides extensive attachment for muscles of the trunk, abdomen, and lower extremity.

It is a key structure in pelvic anatomy, orthopedic surgery, trauma assessment, musculoskeletal imaging, and bone marrow evaluation.

Synonyms

  • Ilium

  • Iliac component of the hip bone

Location

  • Forms the superior and lateral portion of the hip bone

  • Articulates posteriorly with the sacrum at the sacroiliac joint

  • Contributes inferiorly to the acetabulum

  • Extends from the iliac crest superiorly to the acetabular region inferiorly

  • Lies lateral to the pelvic cavity and medial to the gluteal region

Anatomical components

  • Body of the ilium:

    • Forms the superior part of the acetabulum

  • Ala (wing) of the ilium:

    • Broad, fan-shaped superior portion

  • Iliac crest:

    • Superior curved border, palpable landmark

  • Anterior superior iliac spine (ASIS)

  • Anterior inferior iliac spine (AIIS)

  • Posterior superior iliac spine (PSIS)

  • Posterior inferior iliac spine (PIIS)

  • Iliac fossa (medial concavity)

  • Auricular surface for sacrum

Relations

Laterally:

  • Gluteal muscles (gluteus maximus, medius, minimus)

Medially:

  • Pelvic cavity

  • Iliacus muscle

  • Sacroiliac joint

Anteriorly:

  • Abdominal wall muscles

  • Inguinal region

Posteriorly:

  • Paraspinal muscles

  • Posterior sacroiliac ligaments

Inferiorly:

  • Acetabulum

  • Pubis and ischium (components of the hip bone)

Structures related to the iliac bone

  • Sacroiliac joint

  • Acetabulum

  • Iliac crest apophysis

  • Gluteal muscle origins

  • Iliacus muscle attachment

  • Pelvic brim contribution

X-ray appearance

Pelvic radiographs (AP pelvis / oblique views):

  • Iliac wings: Broad, symmetric bony plates

  • Iliac crest: Smooth curvilinear superior margin

  • Cortical bone: Dense outer margin

  • Trabecular pattern: Visible cancellous bone within the ilium

  • Sacroiliac joint: Clear joint space posteriorly

CT appearance

Pre-contrast CT:

  • Cortex: Hyperdense outer cortical shell

  • Cancellous bone: Lower density trabecular matrix

  • Iliac crest: Well-defined superior margin

  • Sacroiliac joint surface: Sharp cortical interfaces

  • Bone marrow cavity: Homogeneous density

MRI appearance

T1-weighted images:

  • Cortical bone: Low signal intensity

  • Bone marrow: High signal due to fatty marrow (age dependent)

  • Iliac crest and ala: Well-defined marrow signal pattern

T2-weighted images:

  • Cortical bone: Low signal

  • Normal marrow: Intermediate-to-high signal depending on fat content

  • Joint surfaces: Low-signal cortical margins

STIR:

  • Fat suppression: Normal marrow signal suppressed

  • Cortex: Persistently low signal

  • Soft tissues: High signal relative to suppressed marrow

CT image

Iliac bone ct anatomy Location and Imaging Appearance -img-00000-00000

CT image

Iliac bone ct anatomy Location and Imaging Appearance -img-00000-00000_00001

CT VRT 3D image

Iliac bone 3d image

X Ray image

X Ray Iliac bone