Topics

Topic

design image
Mammillary process of vertebra

The mammillary process is a small bony projection located on the posterior aspect of the superior articular process of lumbar vertebrae. It is best developed in the lumbar region, where it serves as an attachment point for deep back muscles and ligaments. This structure contributes to spinal stability and acts as a landmark in both anatomy and spinal imaging.

Synonyms

  • Mammillary tubercle of vertebra

  • Posterior process of lumbar articular facet (descriptive term)

Location and Structure

  • Found exclusively in the lumbar vertebrae (L1–L5)

  • Situated on the posterior margin of the superior articular process

  • Appears as a small rounded projection or tubercle

  • Lies just posterior to the zygapophyseal (facet) joint articulation

Relations

  • Anteriorly: Superior articular facet of lumbar vertebrae

  • Posteriorly: Deep back muscles including multifidus

  • Superiorly: Lumbar lamina and spinous processes

  • Inferiorly: Accessory process of transverse process and pedicle

Function

  • Provides attachment for the multifidus muscle, an important stabilizer of the vertebral column

  • Serves as an anchoring point for small ligaments and connective tissue

  • Acts as a bony landmark in spinal anatomy and surgery

  • Contributes indirectly to lumbar stability and control of motion

Clinical Significance

  • Muscle attachment site: Injury or strain at the multifidus origin can lead to localized lumbar pain

  • Degeneration/arthropathy: Mammillary processes may become hypertrophic with facet joint osteoarthritis

  • Surgical relevance: Important landmark in spinal surgery and interventions (e.g., facet joint injections, nerve blocks)

  • Imaging relevance: Must be differentiated from accessory ossicles or osteophytes on CT/MRI

  • Fractures: Can rarely be involved in lumbar vertebral trauma

MRI Appearance

T1-weighted images:

  • Mammillary process appears as low signal intensity (cortical bone)

  • Surrounding fat appears bright, aiding identification

T2-weighted images:

  • Mammillary process shows very low signal intensity (cortical bone)

  • Adjacent facet joint fluid, if present, appears bright

STIR (Short Tau Inversion Recovery):

  • Mammillary process remains dark (no signal)

  • Pathology such as bone edema (fracture, inflammation) shows bright signal in adjacent marrow

T1 Fat-Sat Post-Contrast:

  • Normal cortical bone does not enhance

  • Pathologic conditions (osteomyelitis, metastasis, inflammatory changes) may show adjacent enhancement

3D T2 SPACE / CISS:

  • Mammillary process appears as a low-signal bony projection

  • Surrounded by bright CSF and fat, which provide contrast

  • Useful in defining facet anatomy and small bony details

CT Appearance

Non-Contrast CT:

  • Appears as a small, dense bony projection on posterior aspect of superior articular process

  • Clearly visible as high-density cortical bone

  • Hypertrophy, fracture, or degeneration can be evaluated precisely

Post-Contrast CT:

  • Mammillary process itself does not enhance

  • Adjacent soft tissue enhancement may indicate inflammatory or neoplastic involvement

MRI images

Mammillary process of vertebra mri axial image

CT images

Mammillary process of vertebra CT AXIAL anatomy image-img-00000-00000