The lumbar spine is composed of five vertebrae (L1–L5) that are the largest of the vertebral column, adapted for weight-bearing and mobility. It has characteristic lordotic curve, which develops after infancy as a secondary curvature when the child begins standing and walking. Normal lumbar lordosis ranged from 40° to 65°. Each lumbar vertebra is consists of:
Vertebral Body
- Shape: Large, kidney-shaped in axial view.
- Function: Bears the majority of axial load.
- Surface: Superior and inferior surfaces are flat, articulating with intervertebral discs.
Pedicles
- Short and stout, projecting posteriorly from the vertebral body.
- Oriented in a sagittal plane, forming the lateral walls of the vertebral foramen.
- Surgical importance: Pedicles serve as anchor points for pedicle screws in spinal instrumentation.
Laminae
- Flattened plates connecting pedicles to the spinous process.
- Form the posterior wall of the vertebral canal.
- Surgical landmark: Site for laminectomy in decompression procedures.
Spinous Process
- Short, broad, and quadrangular.
- Projects horizontally backward, providing attachment for muscles (multifidus, erector spinae).
- Easily palpable through the skin, used for surgical level identification.
Transverse Processes
- Long, thin, and laterally directed.
- Represent embryological remnants of ribs.
- Provide attachment for psoas major and quadratus lumborum muscles, as well as ligaments (intertransverse ligaments).
Superior Articular Process & Surface
- Surface: Faces posteromedially in the lumbar spine.
- Function: Articulates with the inferior articular surface of the vertebra above to form the zygapophyseal (facet) joint.
Inferior Articular Process & Surface
- Project downward from the vertebral arch.
- Surface: Faces anterolaterally to articulate with the superior articular surface of the vertebra below.
- Helps stabilize movement while permitting flexion/extension.
Vertebral Foramen
- Triangular in lumbar region.
- Houses the cauda equina (spinal cord typically ends at L1–L2).
- Clinical relevance: Narrowing from disc herniation, hypertrophied ligamentum flavum, or facet joint hypertrophy leads to lumbar canal stenosis.
Intervertebral Foramen (formed with adjacent vertebrae)
- Located laterally between pedicles.
- Passage for lumbar spinal nerves, radicular arteries, and veins.
- Clinical importance: Site of nerve root compression from disc herniation or spondylolisthesis.
Pars Interarticularis
- Segment of bone between superior and inferior articular processes.
Image
Figure: This is a lumbar vertebra (posterior and axial views). 1. Superior articular surface. 2. Pars articularis. 3. Spinous process. 4. Transverse process. 5. Spinal canal
