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Vertebrae

A vertebra is the fundamental structural and functional unit of the vertebral column. Each vertebra consists of a vertebral body, vertebral arch, and various processes that together protect the spinal cord, provide structural support, and allow flexibility of the spine.

Vertebrae vary in morphology depending on region (cervical, thoracic, lumbar, sacral, coccygeal), but share a common structural pattern. They form a strong, flexible column that supports the head, trunk, and transmits loads to the pelvis and lower limbs.

Synonyms

  • Spinal bone

  • Segment of the vertebral column

  • Vertebral unit

Structure

  • Vertebral body:

    • Large, anterior, weight-bearing component

    • Composed of cancellous bone with cortical shell

  • Vertebral arch:

    • Posterior part formed by pedicles and laminae, enclosing the vertebral foramen

  • Processes:

    • Spinous process: posterior projection, attachment for muscles/ligaments

    • Transverse processes: lateral projections, articulation with ribs (thoracic)

    • Articular processes: superior and inferior facets forming facet joints

  • Vertebral foramen:

    • Encloses spinal cord and meninges

  • Intervertebral foramina:

    • Openings between adjacent vertebrae for spinal nerve roots

Relations

  • Anteriorly: Major vessels (aorta, vena cava), retroperitoneal and mediastinal structures

  • Posteriorly: Paraspinal muscles and ligaments

  • Laterally: Nerve roots exiting through intervertebral foramina

  • Superiorly and inferiorly: Intervertebral discs and adjacent vertebrae

Function

  • Provides support for head and trunk

  • Protects spinal cord and cauda equina

  • Acts as a weight-bearing column, transmitting load to pelvis

  • Allows controlled flexibility and motion of spine

  • Serves as an attachment site for muscles and ligaments

Clinical Significance

  • Fractures: Common in trauma, osteoporosis, and metastatic disease

  • Degenerative changes: Osteophytes, sclerosis, and collapse in spondylosis

  • Tumors: Primary or secondary (metastases) often involve vertebral bodies

  • Infections: Spondylodiscitis and vertebral osteomyelitis

  • Congenital anomalies: Hemivertebra, block vertebra, transitional vertebra

  • Surgical relevance: Landmarks for spinal instrumentation and anesthesia

MRI Appearance

T1-weighted images:

  • Vertebral body marrow: intermediate signal (bright in fatty marrow, darker in red marrow)

  • Cortical bone: uniformly dark (low signal)

  • Pathology: metastatic or infectious infiltration → low T1 signal

T2-weighted images:

  • Vertebral body marrow: intermediate to bright (varies with fat/water content)

  • Intervertebral discs: bright nucleus pulposus

  • Cortical bone: low signal

  • Pathology: edema, inflammation, or tumor infiltration → bright signal

STIR (Short Tau Inversion Recovery):

  • Normal fatty marrow: suppressed and dark

  • Edema, fracture, infection, or tumor: bright hyperintensity

  • Excellent for detecting early bone marrow edema

T1 Fat-Sat Post-Contrast:

  • Normal marrow: mild diffuse enhancement

  • Pathology: focal, heterogeneous, or rim enhancement in infection/tumor

  • Scar tissue: may enhance uniformly, while necrosis remains non-enhancing

CT Appearance

Non-Contrast CT:

  • Vertebral body: trabecular bone with cortical outline

  • Cortical bone: dense, high attenuation

  • Pathology: fractures, osteophytes, lytic/sclerotic lesions, calcifications easily detected

Post-Contrast CT:

  • Normal bone: minimal enhancement

  • Pathology: tumors or infection → enhancing soft tissue masses or marrow infiltration

  • Epidural or paravertebral extension well visualized

MRI image

vertebrae MRI SAGITTAL IMAGE

CT image

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CT image

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