Topics

Topic

design image
Intermediate sacral crest

The intermediate sacral crest is a longitudinal bony ridge on the dorsal surface of the sacrum. It lies between the median sacral crest (midline) and the lateral sacral crests. It is formed by the fused articular processes of the sacral vertebrae (S1–S5). The intermediate crest extends vertically on each side of the median crest and is interrupted by the dorsal sacral foramina, through which the posterior rami of sacral spinal nerves emerge.

The intermediate sacral crest serves as a key anatomical landmark in radiology, anatomy, and surgical approaches to the sacrum and pelvis.

Synonyms

  • Medial sacral crest (older texts, but not correct)

  • Articular crest of sacrum

  • Sacral articular process ridge

Location and Formation

  • Location: On the dorsal surface of the sacrum, lateral to the median sacral crest and medial to the lateral sacral crest

  • Formation: Created by the fusion of superior and inferior articular processes of the sacral vertebrae (S1–S5)

  • Extent: Runs longitudinally from the base of the sacrum down toward the sacral hiatus, interrupted by the dorsal sacral foramina

Relations

  • Medially: Median sacral crest (formed by fused spinous processes)

  • Laterally: Lateral sacral crest (formed by fused transverse processes)

  • Anteriorly: Sacral canal, containing sacral nerve roots

  • Posteriorly: Covered by ligaments, muscles (erector spinae, multifidus), and fascia

Function / Importance

  • Represents the fused articular processes of the sacrum

  • Serves as a surface landmark for identifying sacral foramina and sacral canal

  • Important in anatomical orientation during lumbosacral surgery

  • Contributes to posterior sacral surface strength and rigidity

Clinical Significance

  • Used as a landmark in sacral laminectomy, sacral nerve blocks, and caudal epidural anesthesia

  • May be affected by congenital anomalies, fractures, or lytic lesions

  • Hypertrophy, sclerosis, or irregularity may be seen in degenerative disease or sacroiliitis

  • On imaging, helps distinguish the median sacral crest (spinous fusion) from the lateral sacral crest (transverse fusion)

MRI Appearance

T1-weighted images:

  • Crest appears as low signal intensity (dark) due to cortical bone

  • Adjacent marrow (if visible) shows high to intermediate signal

T2-weighted images:

  • Cortical bone of the crest appears low signal intensity (dark)

  • Adjacent sacral canal and foramina: bright signal from CSF

  • Fat around crest: intermediate to bright signal

STIR (Short Tau Inversion Recovery):

  • Crest remains low signal intensity

  • Edema, fracture, or inflammatory changes appear as bright hyperintensity adjacent to the crest

T1 Fat-Sat Post-Contrast:

  • Normal crest does not enhance

  • Pathologic changes (infection, tumor, inflammation) show enhancing marrow or soft tissue around the crest

3D T2 SPACE / CISS:

  • Crest itself is a dark, linear bony ridge

  • Dorsal sacral foramina and nerve roots are seen clearly adjacent, surrounded by bright CSF

CT Appearance

Non-Contrast CT:

  • Crest appears as a dense bony ridge lateral to the median sacral crest

  • Dorsal sacral foramina interrupt its course

  • Clear margins unless altered by pathology (fracture, erosion, sclerosis)

Post-Contrast CT:

  • Bone itself does not enhance

  • Surrounding soft tissue changes, inflammation, or tumors may show enhancement near the crest

MRI image

Intermediate sacral crest mri axial anatomy image-img-00000-00000

MRI image

Intermediate sacral crest mri coronal anatomy image-img-00000-00000

CT image

Intermediate sacral crest ct axial anatomy image-img-00000-00000