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Lateral sacral crest

The lateral sacral crest is a bony ridge located on the posterior surface of the sacrum. It represents the fused transverse processes of the sacral vertebrae (S1–S5). There are two lateral sacral crests, one on each side of the sacrum, running vertically and parallel to the midline. These crests serve as attachment points for ligaments and muscles that stabilize the pelvis and sacroiliac joint.

Anatomically, the lateral sacral crest forms part of the posterior sacral surface landmarks, alongside the median and intermediate sacral crests.

Synonyms

  • Lateral crest of the sacrum

  • Transverse sacral crest (posterior)

  • Sacral transverse fusion ridge

Location and Structure

  • Found on the posterior aspect of the sacrum, lateral to the intermediate sacral crest

  • Extends vertically from the ala of the sacrum superiorly to the inferior lateral angle of the sacrum

  • Represents the fused transverse processes of sacral vertebrae

  • Lies adjacent to the sacral foramina

Relations

  • Medial: Intermediate sacral crest and dorsal sacral foramina

  • Lateral: Sacral ala and auricular surface for articulation with the ilium

  • Superior: Continuous with sacral ala near L5 vertebra

  • Inferior: Approaches the coccyx and sacrococcygeal junction

Function

  • Provides attachment for posterior sacroiliac ligaments

  • Contributes to stability of the sacroiliac joint and posterior pelvis

  • Serves as a bony landmark for surgical and radiologic orientation

Clinical Significance

  • Important surface landmark in spinal and pelvic surgery

  • Can be involved in trauma (sacral fractures)

  • Degenerative changes may affect the sacroiliac ligament insertions at this crest

  • Seen clearly on radiographs, CT, and MRI, aiding in anatomical localization

  • May show bony overgrowth, sclerosis, or irregularity in arthropathies (e.g., ankylosing spondylitis, osteitis condensans ilii)

MRI Appearance

T1-weighted images:

  • Lateral sacral crest appears as very low signal intensity (dark) due to cortical bone

  • Adjacent fat planes and marrow within sacrum show bright signal

T2-weighted images:

  • Crest remains dark signal (cortical bone)

  • Adjacent marrow shows higher signal intensity

  • In pathology (edema, fracture), adjacent bone marrow becomes bright

STIR (Short Tau Inversion Recovery):

  • Crest itself remains dark

  • Edema, inflammation, or fracture adjacent to crest shows bright hyperintensity

T1 Fat-Sat Post-Contrast:

  • Crest does not enhance (cortical bone)

  • Adjacent soft tissue inflammation, infection, or tumor shows contrast enhancement

3D T2 SPACE / CISS:

  • Crest appears as a dark, sharply defined linear ridge

  • Excellent delineation of its relation to sacral foramina and nerve roots

CT Appearance

Non-Contrast CT:

  • Crest visualized as a dense bony ridge lateral to sacral foramina

  • Clearly shows cortical definition and any fractures or irregularities

Post-Contrast CT:

  • Bone itself does not enhance

  • Enhancement may be seen in surrounding soft tissues in cases of infection, tumor infiltration, or vascular structures nearby

MRI image

Lateral sacral crest MRI axial image

CT image

Lateral sacral crest CT AXIAL anatomy image-img-00000-00000