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Superior rim of acetabulum

The superior rim of the acetabulum is the uppermost margin of the acetabular socket forming the superior boundary of the hip joint’s articular surface. It plays a critical role in load transmission across the hip and serves as an attachment site for the acetabular labrum, contributing to joint stability and congruency.

It is a key anatomical landmark in hip biomechanics, orthopedic surgery, sports medicine, and cross-sectional imaging of the hip joint.

Synonyms

  • Superior acetabular rim

  • Cranial acetabular margin

Location

  • Situated at the upper border of the acetabulum

  • Formed primarily by the ilium

  • Faces superolaterally and slightly anteriorly

  • Superior to the acetabular fossa

  • Inferior to the iliac wing

  • Encircles the superior aspect of the acetabular socket

Anatomical components

  • Osseous rim of the ilium

  • Acetabular labrum attachment zone

  • Articular cartilage margin

  • Capsular attachment along the rim

Relations

Superiorly:

  • Iliac wing

Inferiorly:

  • Acetabular cavity and lunate surface

Medially:

  • Pelvic cavity

Laterally:

  • Femoral head

Anteriorly:

  • Anterior acetabular rim and hip capsule

Posteriorly:

  • Posterior acetabular rim and labrum

X-ray appearance

Plain radiographs (AP pelvis and hip views):

  • Superior acetabular rim: Dense, curved cortical outline forming the superior margin of the acetabulum

  • Sourcil (acetabular roof): Appears as a sclerotic arc representing the weight-bearing zone

  • Joint congruency: Superior rim aligns with the femoral head contour

CT appearance (Pre-contrast)

Non-contrast CT:

  • Superior rim: Sharp cortical margin forming the superior boundary of the acetabulum

  • Subchondral bone: Uniform density beneath articular cartilage

  • Spatial definition: Excellent depiction of rim contour, thickness, and integrity

  • Relationship to femoral head: Clearly appreciated

MRI appearance

T1-weighted images:

  • Cortical bone: Low signal intensity

  • Subchondral marrow: High signal intensity

  • Labrum: Low-signal triangular structure attached to the rim

  • Cartilage margin: Intermediate signal at articular surface

T2-weighted images:

  • Joint fluid: High signal outlining the superior rim

  • Labrum: Low-signal structure against bright fluid

  • Cartilage: Intermediate-to-high signal depending on sequence

STIR:

  • Bone marrow: Fat-suppressed uniform signal

  • Joint fluid: Bright signal

  • Rim margins: Clearly delineated against suppressed marrow

Proton density fat-saturated (PD FS):

  • Labrum: Low signal, well contrasted against bright joint fluid

  • Articular cartilage: Well visualized

  • Rim contours: Sharply defined

CT VRT 3D image

Superior rim of acetabulum 3d

CT image

Superior rim of acetabulum ct coronal

MRI image

Superior rim of acetabulum mri anatomy labelled image-img-00000-00000