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Topic

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Posterior acetabular wall

The posterior acetabular wall is the posterolateral bony margin of the acetabulum that contributes to the acetabular socket, supporting and stabilizing the posterior aspect of the femoral head. It is formed primarily by the ischium, and extends from the superior acetabular margin down toward the acetabular notch.

The posterior wall is thicker than the anterior wall and provides substantial stability to the hip joint. The posterior labrum attaches along its edge, enhancing depth and stability of the socket.

Biomechanically, the posterior wall is critical during hip flexion and axial loading, making it a key load-bearing structure. Fractures of the posterior acetabular wall are common in high-energy trauma, particularly in dashboard injuries, and may cause posterior hip dislocation. Morphological abnormalities such as posterior wall deficiency or retroversion predispose to instability and arthritis.

Synonyms

  • Posterior acetabular rim

  • Posterior wall of acetabulum

Function

  • Contributes to the posterolateral stability of the hip joint

  • Provides attachment for the posterior acetabular labrum and capsule

  • Serves as a buttress preventing posterior femoral head displacement

  • Critical for hip stability in weight-bearing, gait, and seated postures

MRI Appearance (Bone + Soft Tissue)

T1-weighted images:

  • Bone cortex: uniformly hypointense

  • Bone marrow: intermediate signal (yellow marrow hyperintense in adults; red marrow more intermediate)

  • Labrum: hypointense triangular structure attached to posterior wall

  • Useful for assessing fractures, marrow infiltration, and bone alignment

T2-weighted images:

  • Bone cortex: hypointense outline

  • Bone marrow: intermediate; edema appears hyperintense

  • Labrum: dark hypointense; tears show bright hyperintense clefts

  • Useful for cartilage loss, marrow edema, subchondral cysts, and labral pathology

PD Fat-Saturated (Proton Density with Fat Suppression):

  • Bone cortex: remains hypointense

  • Bone marrow: edema highlighted as bright hyperintense against suppressed fat

  • Excellent for detecting subtle bone marrow edema, osteochondral injuries, and posterior labral tears

STIR:

  • Bone cortex: hypointense

  • Bone marrow: edema and inflammatory changes hyperintense

  • Highly sensitive for occult fractures, posterior wall contusions, and early arthritis

T1 Fat-Saturated Post-Gadolinium (MR Arthrography):

  • Bone marrow: mild enhancement if hyperemic or infiltrated

  • Posterior labrum: contrast outlines and fills tears, detachments, or cysts

  • Detects labral tears, synovitis, capsular lesions, and chondral pathology

3D T2-weighted Imaging:

  • Bone cortex: hypointense, outlining acetabular contour

  • Bone marrow: intermediate

  • Provides isotropic imaging with reconstructions in any plane

  • Essential for evaluating posterior wall thickness, version, retroversion, and labral-chondral integrity

  • Widely used for arthroscopic planning and femoroacetabular impingement assessment

CT Appearance (Bone Focused)

Non-contrast CT:

  • Bone cortex: hyperdense, sharply defined posterior wall

  • Bone marrow: less dense than cortex

  • Gold standard for detecting posterior acetabular wall fractures, comminution, bone loss, retroversion, and pincer-type impingement

  • 3D reconstructions are invaluable in surgical planning for acetabular fracture fixation

CT Post-Contrast (CT Arthrography):

  • Bone cortex: unchanged, hyperdense

  • Bone marrow: may enhance subtly with vascularity or infiltration

  • Labrum and cartilage: intra-articular contrast outlines posterior labral tears and chondral defects

  • Alternative when MR arthrography is contraindicated

CT VRT 3D image

posterior acetabular wall 3d ct image

CT image

posterior acetabular wall ct axial image

MRI image

posterior acetabular wall MRI axial anatomy image-img-00000-00000