Lumbar spine
The lumbar spine consists of five adjacent vertebrae of the lower vertebral column. They participate in the lumbar lordosis, a natural curve in the spine, that is convex anteriorly.
Articulations of the facet (zygapophyseal) joints permit flexion/extension and abduction movements. Rotation is greatly limited, and may occur only slightly at the lumbosacral joints.
For a basic anatomic description of the structure a generic vertebra, see vertebrae.
On this page:
Images:
Gross anatomy
Similar to other vertebrae, the osteology of each lumbar vertebrae can be subdivided anteriorly to posteriorly:
- body: kidney shaped, convex anteriorly, flattened posteriorly; resulting vertebral canal is triangular in cross-section
- pedicles: project directly posteriorly, attached to the upper half of the body
- transverse processes: spatulate, project laterally on both sides; L3 most often has the longest transverse processes of the lumbar spine, a fact that can be used to number the vertebrae
- lamina: broad, thick, overlap minimally
- articular processes (superior and inferior): lie at the lateral angle of the laminae (junction with pedicle), connected via the pars interarticularis
- spinous process: single, short, thick, roughly horizontal, hatchet-shaped (upper border is straight, lower border curves down)
L1 to L4 are considered typical lumbar vertebrae, whereas due to various and distinctive differences the fifth lumbar vertebra is considered atypical.
Articulations
Vertebrae articulate with one another via:
- intervertebral discs (superior and inferior): wedge shaped (taller anterior, shorter posterior), and contribute most to the lumbar lordosis
-
facet (zygapophyseal) joints: obliquely oriented, cylindrically-shaped articular surfaces
- superior articular facets are concave and face posteromedially
- inferior articular facets are convex, and face anteriorly
Inferior articular process of the vertebrae above always lies posterior to the superior articular process of the vertebrae below.
Attachments
A large number of attachments occur at the transverse process. On its anterior surface, a vertical ridge serves as an important landmark.
- medial to ridge: psoas muscle
- at the ridge: psoas fascia, anterior layer of the lumbar fascia, medial and lateral arcuate ligaments (at L1)
- lateral to ridge: quadratus lumborum partially inserts
- transverse process tip: middle layer of lumbar fascia
Posterior surface receives attachments of erector spinae. Back muscles (multifidus, longissimus) attach to the mamillary process and accessory tubercle:
- mamillary process: located on the superior articular process, behind the margin of the articular facet, projects posteriorly
- accessory tubercle: located at the root of the transverse process, projects posteriorly
Relations and/or boundaries
Can be superimposed onto the three-column concept.
Anterior column
- anterior longitudinal ligament: anterior to vertebral body
Middle column
- posterior longitudinal ligament: lies posterior to vertebral body
- centrally
- vertebral foramen
- cauda equina
- basivertebral veins and internal vertebral venous plexus
- laterally
- Iliolumbar ligament
- lumbar fascia
- quadratus lumborum muscle
- intertransverse ligaments
- regional/segmental lumbar arteries and veins
Posterior column
- ligamentum flavum
- interspinous ligament
- supraspinous ligament
- erector spinae muscles
- external vertebral venous plexus (lying within muscle)
Blood supply
Arterial supply comes from regional/segmental lumbar arteries.
Venous drainage is complex. Lumbar vertebral bodies are posteriorly perforated by a pair of basivertebral veins that drain into the internal vertebral venous plexus. Regional/segmental lumbar veins also contribute.
Variant anatomy
Transitional vertebrae of the lumbar spine are possible at multiple levels in the lumbar spine.
Limbus vertebrae represent herniation of the disk nucleous pulposus through the superior endplate and can simulate a fracture.
Development
Transverse processes are actually fused ribs. Mamillary process and the accessory tubercle are the remnants of the true transverse process, typically seen on thoracic vertebrae.
Related Radiopaedia articles
Anatomy: abdominopelvic
- skeleton of the abdomen and pelvis
- muscles of the abdomen and pelvis
- spaces of the abdomen and pelvis
- anterior abdominal wall
- posterior abdominal wall
-
abdominal cavity
-
peritoneum
- peritoneal ligaments
- mesentery
-
peritoneal spaces
-
supramesocolic space
-
right supramesocolic space
- right subphrenic space
-
right subhepatic space
- anterior right subhepatic space
- posterior right subhepatic space (Morison pouch)
-
lesser sac
- epiploic foramen (of Winslow)
- left supramesocolic space (left perihepatic space)
-
right supramesocolic space
- inframesocolic space
-
supramesocolic space
- inguinal canal (mnemonic)
- Hesselbach triangle
- scrotal sac
- retroperitoneum
-
peritoneum
- pelvic cavity
- perineum
- abdominal and pelvic viscera
- gastrointestinal tract
- spleen
- hepatobiliary system
-
endocrine system
-
adrenal gland
- adrenal vessels
- chromaffin cells
- variants
- pancreas
- organs of Zuckerkandl
-
adrenal gland
-
urinary system
-
kidney
- renal pelvis
- renal sinus
- avascular plane of Brodel
-
variants
- number
- fusion
- location
- shape
- ureter
- urinary bladder
- urethra
- embryology
-
kidney
- male reproductive system
-
female reproductive system
- vulva
- vagina
- uterus
- uterine tubes
- ovaries
- broad ligament (mnemonic)
- variant anatomy
- embryology
- blood supply of the abdomen and pelvis
- arteries
-
abdominal aorta
- inferior phrenic artery
- celiac artery
- superior mesenteric artery
- middle suprarenal artery
- renal artery (variant anatomy)
- gonadal artery (ovarian artery | testicular artery)
- inferior mesenteric artery
- lumbar arteries
- median sacral artery
-
common iliac artery
- external iliac artery
-
internal iliac artery (mnemonic)
- anterior division
- posterior division (mnemonic)
- variant anatomy
-
abdominal aorta
- portal venous system
- veins
- anastomoses
- arterio-arterial anastomoses
- portal-systemic venous collateral pathways
- watershed areas
- arteries
- lymphatics
- innervation of the abdomen and pelvis
- lumbar plexus
-
sacral plexus
- lumbosacral trunk
- sciatic nerve
- superior gluteal nerve
- inferior gluteal nerve
- nerve to piriformis
- perforating cutaneous nerve
- posterior femoral cutaneous nerve
- parasympathetic pelvic splanchnic nerves
- pudendal nerve
- nerve to quadratus femoris and inferior gemellus
- nerve to internal obturator and superior gemellus
Anatomy: Spine
-
osteology
- vertebrae
- spinal canal
- cervical spine
- thoracic spine
- lumbar spine
- sacrum
- coccyx
-
anatomical variants
- vertebral body
- neural arch
- transitional vertebrae
- ossicles
- ossification centers
- intervertebral disk
- articulations
- ligaments
- musculature of the vertebral column
- muscles of the neck
- muscles of the back
-
suboccipital muscle group
- rectus capitis posterior major muscle
- rectus capitis posterior minor muscle
- obliquus capitis superior muscle
- obliquus capitis inferior muscle
- splenius capitis muscle
- splenius cervicis muscle
- erector spinae group
- transversospinalis group
- quadratus lumborum
-
suboccipital muscle group
-
spinal cord
- gross anatomy
-
white matter tracts (white matter)
- anterolateral columns
- lateral columns
-
dorsal columns
- fasiculus gracilis (column of Goll)
- fasiculus cuneatus (column of Burdach)
- grey matter
- nerve root
- spinal meninges and spaces
- functional anatomy
- spinal cord blood supply
- sympathetic chain