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L1-L5 Vertebrae (Lumbar)

vertebrae lumbales (L1-L5)

The five lumbar vertebrae have the largest bodies of the spinal column (accepting the highest axial loads), kidney-shaped bodies, and sagittally-oriented facet joints that permit flexion-extension while restricting rotation. The pedicle dimensions are the largest in the spine, accommodating the widest pedicle screws for spinal instrumentation. The cauda equina occupies the lumbar spinal canal below the conus medullaris at L1-L2.

Anatomical Data

Structure & Landmarks

Articulations	Adjacent vertebrae at intervertebral discs and facet joints Sacrum at the lumbosacral junction (L5-S1)
Landmarks	L4 spinous process (at the level of the iliac crests, used as a landmark for lumbar puncture) L5 transverse processes (the largest, iliolumbar ligament attachment) Pedicles (the strongest structural column, pedicle screw fixation site)
Ossification	Three primary centres (body and two neural arches) fuse in early childhood. The ring epiphyses fuse at skeletal maturity. Lumbarisation of S1 and sacralisation of L5 are common transitional vertebral variants.

Clinical Relevance

Clinical Notes

L4 is identified by palpation at the supracrestal line (the line connecting the highest points of the iliac crests). Lumbar puncture is performed at L3-L4 or L4-L5 to avoid the conus (which ends at L1-L2 in adults). Transforaminal lumbar interbody fusion (TLIF) and posterior lumbar interbody fusion (PLIF) are the most common surgical techniques for lumbar fusion using pedicle screw fixation.

Pathology

Common Injuries & Conditions

Lumbar Disc Herniation

Usually at L4-L5 or L5-S1, causing sciatica in the distribution of the compressed nerve root.

Spondylolysis and Spondylolisthesis

Pars stress fractures, usually at L5, can allow the vertebra to slip forward.

Lumbar Compression Fracture

Anterior wedge fractures from osteoporosis or trauma, most often at L1.

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