Lumbar vertebrae

Bone: Lumbar vertebrae
A typical lumbar vertebra
Vertebral column.
Latin	vertebrae lumbales
Gray's	subject #23 104

The lumbar vertebrae are the largest segments of the movable part of the vertebral column, and are characterized by the absence of the foramen transversarium within the transverse process, and by the absence of facets on the sides of the body. They are designated L1 to L5, starting at the top.

Contents 1 General characteristics 1.1 Body 1.2 Arch 1.3 Processes 2 First to fifth lumbar vertebrae 3 Segmental movements 4 Additional images 5 See also 6 References 7 External links

General characteristics

These are the general characteristics of the first through fourth lumbar vertebrae. The fifth vertebra contains certain peculiarities, which are detailed below.

As with other vertebrae, each lumbar vertebra consists of a vertebral body and a vertebral arch. The vertebral arch, consisting of a pair of pedicles and a pair of laminae, encloses the vertebral foramen (opening) and supports seven processes.

Body

The vertebral body of each lumbar vertebra is large, wider from side to side than from front to back, and a little thicker in front than in back. It is flattened or slightly concave above and below, concave behind, and deeply constricted in front and at the sides.

Arch

The pedicles are very strong, directed backward from the upper part of the vertebral body; consequently, the inferior vertebral notches are of considerable depth. The pedicles change in morphology from the upper lumbar to the lower lumbar. They increase in sagittal width from 9 mm to up to 18 mm at L5. They increase in angulation in the axial plane from 10 degrees to 20 degrees by L5. The pedicle is sometimes used as a portal of entrance into the vertebral body for fixation with pedicle screws or for placement of bone cement as with kyphoplasty or vertebroplasty.

The laminae are broad, short, and strong. They form the posterior portion of the vertebral arch. In the upper lumbar region the lamina are taller than wide but in the lower lumbar vertebra the lamina are wider than tall. The lamina connect the spinous process to the pedicles.

The vertebral foramen within the arch is triangular, larger than in the thoracic vertebrae, but smaller than in the cervical vertebrae.

Processes

The spinous process is thick, broad, and somewhat quadrilateral; it projects backward and ends in a rough, uneven border, thickest below where it is occasionally notched.

The superior and inferior articular processes are well-defined, projecting respectively upward and downward from the junctions of pedicles and laminae. The facets on the superior processes are concave, and look backward and medialward; those on the inferior are convex, and are directed forward and lateralward. The former are wider apart than the latter, since in the articulated column the inferior articular processes are embraced by the superior processes of the subjacent vertebra.

The transverse processes are long and slender. They are horizontal in the upper three lumbar vertebrae and incline a little upward in the lower two. In the upper three vertebrae they arise from the junctions of the pedicles and laminae, but in the lower two they are set farther forward and spring from the pedicles and posterior parts of the vertebral bodies. They are situated in front of the articular processes instead of behind them as in the thoracic vertebrae, and are homologous with the ribs.

Of the three tubercles noticed in connection with the transverse processes of the lower lumbar vertebrae, the superior one is connected in the lumbar region with the back part of the superior articular process, and is named the mammillary process. The inferior is situated at the back part of the base of the transverse process, and is called the accessory process.

First to fifth lumbar vertebrae

Some individuals have four lumbar vertebrae, while others have six. Lumbar disorders that normally affect L5 will affect L4 or L6 in these individuals.

The first lumbar vertebra is level with the anterior end of the ninth rib. This level is also called the important transpyloric plane, since the pylorus of the stomach is at this level.

The fifth lumbar vertebra is characterized by its body being much deeper in front than behind, which accords with the prominence of the sacrovertebral articulation; by the smaller size of its spinous process; by the wide interval between the inferior articular processes, and by the thickness of its transverse processes, which spring from the body as well as from the pedicles.

The fifth lumbar vertebra is by far the most common site of spondylolysis and spondylolisthesis.^[1]

Segmental movements

The range of segmental movements in a single segment is difficult to measure clinically, not only because of variations between individuals, but also because it is age and gender dependent. Furthermore, flexion and extension in the lumbal spine is the product of a combination of rotation and translation in the sagittal plane between each vertebra.^[2]

Ranges of segmental movements in the lumbal spine (White and Panjabi, 1990) are (in degrees): ^[3]

	L1-L2	L2-L3	L3-L4	L4-L5	L5-S1
Flexion/ Extension	12	14	15	16	17
Lateral flexion	6	6	8	6	3
Axial rotation	2	2	2	2	1

Additional images

See also

• Sacralization of the l5
• Bertolotti's syndrome
• Lumbarization of the s1
• Spinal disc herniation
• Lumbar spinal stenosis

References

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.

External links

• "Lower back pain: Conditions and treatment". SpineUniverse. http://www.spineuniverse.com/displayarticle.php/article44.html. 
• "Cleveland Clinic videos". SpineUniverse. http://www.spineuniverse.com/displayarticle.php/article1948.html. 
• VIRTUAL Spine - Online Learning Resource

Bones of torso (TA A02.2,3, GA 2.96–128) Vertebra General structures body of vertebra, vertebral arch (pedicle, lamina, vertebral notch), foramina (vertebral, intervertebral), processes (transverse, articular/zygapophysis, spinous), spinal canal Cervical vertebrae Uncinate process of vertebra · Transverse foramen · Anterior tubercle · Carotid tubercle · Posterior tubercle C1 (lateral mass, anterior arch, posterior arch), C2 (dens), C3, C4, C5, C6, C7 Thoracic vertebrae T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12 costal facets (superior, inferior, transverse) · Uncinate process of vertebra Lumbar vertebrae L1, L2, L3, L4, L5, processes (accessory, mammillary) Sacrum Base: sacral promontory · ala of sacrum Lateral surface: sacral tuberosity · pelvic surface (anterior sacral foramina) Dorsal surface: posterior sacral foramina · median sacral crest · medial sacral crest · lateral sacral crest · sacral canal (sacral hiatus) Coccyx Coccygeal cornu Thoracic skeleton Rib specific ribs (1, 2, 9, 10, 11, 12, true – 1–7, false – 8–12, floating – 11–12) · parts (Angle, Tubercle, Costal groove, Neck, Head) Sternum Suprasternal notch, Manubrium, Sternal angle, Body of sternum, Xiphisternal joint, Xiphoid process Thoracic cage Superior thoracic aperture · Inferior thoracic aperture · Intercostal space · Costal margin · Infrasternal angle M: BON/CAR anat(c/f/k/f, u, t/p, l)/phys/devp/cell noco/cong/tumr, sysi/epon, injr proc, drug(M5)

Nerves: spinal nerves (TA A14.2, GA 9.916) Cervical (8) C1, C2, C3, C4, C5, C6, C7, C8 anterior (Cervical plexus, Brachial plexus) – posterior (Posterior branches of cervical nerves, Suboccipital – C1, Greater occipital – C2, Third occipital – C3) Thoracic (12) T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12 anterior (Intercostal, Intercostobrachial – T2, Thoraco-abdominal nerves – T7–T11, Subcostal – T12) – posterior (Posterior branches of thoracic nerves) Lumbar (5) L1, L2, L3, L4, L5 anterior (Lumbar plexus, Lumbosacral trunk) · posterior (Posterior branches of the lumbar nerves, Superior cluneal L1–L3) Sacral (5) S1, S2, S3, S4, S5 anterior (Sacral plexus) · posterior (Posterior branches of sacral nerves, Medial cluneal nerves) Coccygeal (1) anterior (Coccygeal plexus) · posterior (Posterior branch of coccygeal nerve) M: PNS anat(h/r/t/c/b/l/s/a)/phys(r)/devp/prot/nttr/nttm/ntrp noco/auto/cong/tumr, sysi/epon, injr proc, drug(N1B)