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Median sacral crest

The median sacral crest is a prominent longitudinal ridge on the dorsal (posterior) surface of the sacrum, formed by the fusion of the spinous processes of the first through fourth (and often fifth) sacral vertebrae. It runs vertically in the midline, beginning just below the sacral base and tapering inferiorly toward the sacral hiatus.

Flanking the median sacral crest are the intermediate sacral crests (from fused articular processes) and the lateral sacral crests (from fused transverse processes). Together, these bony ridges mark the posterior surface of the sacrum and serve as important attachment points for ligaments that stabilize the pelvis and spine.

The crest contributes to the posterior wall of the sacral canal and is an important anatomical landmark in spinal imaging, anesthesia (caudal epidural block), and surgical procedures involving the sacrum.

Synonyms

  • Sacral median crest

  • Posterior sacral crest

  • Midline sacral ridge

Function

  • Represents the fused spinous processes of sacral vertebrae

  • Provides attachment for the supraspinous ligament and interspinous ligaments

  • Contributes to posterior sacral wall strength and stability

  • Serves as a palpable and imaging landmark in spinal and pelvic procedures

MRI Appearance

T1-weighted images:

  • Appears as a low signal intensity bony ridge in the midline posterior sacrum

  • Surrounded by intermediate signal marrow and high signal fat planes

T2-weighted images:

  • Shows as very low signal intensity (cortical bone)

  • Adjacent sacral canal and marrow provide intermediate to bright contrast

STIR:

  • Crest remains hypointense due to cortical bone

  • Highlights edema, fractures, or inflammation adjacent to the crest if pathology present

T1 Fat-Saturated (Pre-contrast):

  • Crest appears as very low signal intensity against suppressed fat background

  • Improves visualization of marrow pathology around the crest

T1 Fat-Saturated Post-Contrast (Gadolinium):

  • Crest itself does not enhance

  • Enhancement may be seen in adjacent soft tissues or marrow lesions (infection, tumor, inflammatory changes)

MRI Non-Contrast 3D Imaging:

  • Provides detailed reconstruction of sacral anatomy, clearly showing the median crest with surrounding foramina and canal

  • Useful in pre-surgical and interventional planning

CT Appearance

CT Pre-Contrast:

  • Crest appears as a dense bony ridge in midline of posterior sacrum

  • Excellent visualization of cortical detail and fused sacral spines

  • Useful for detecting fractures, malformations, or congenital variants

CT Post-Contrast:

  • Bone itself does not enhance

  • Post-contrast studies may highlight adjacent vascular structures, soft-tissue pathology, or mass effect

CT image

median sacral crest ct axial image

CT image

median sacral crest ct sag image

CT VRT 3D image

median sacral crest cr 3d vrt image

MRI image

median sacral crest MRI axial anatomy image -img-00000-00000