Lumbar spine


Of normal subjects 24% have an abnormal myelogram, 36% have an abnormal CT scan, 38% an abnormal discogram and 30% an abnormal MRI.

Symptoms of lumbosacral radiculopathy develop in 64% of patients with asymptomatic lumbar disc herniations followed for three years.

MRI scans of the lumbar spine does not predict the development or duration of low-back pain.

Evidence of disc abnormalities on MRI imaging is very common in the general population and unrelated to symptoms.

Composed of five vertebrae.

The prevalence of lumbosacral transitional vertebrae ranges from 7-30%.

Lumbar vertebrae transverse processes may be broad and elongated which can lead to complete sacral fusion.

The lumbar vertebral canal is roughly triangular in shape and is narrowest in its anteroposterior diameter in the axial plane.

The average anteroposterior diameter of the lumbar canal in adults, ranges from 15 to 23 mm.

The canal is bounded anteriorly by the posterior edge of the vertebral body including the posterior longitudinal ligament, which is closely apposed to the posterior vertebral body surface, laterally by the pedicles, posterolaterally by the facet joints and articular capsules, and posteriorly by the lamina and ligamenta flava.

L5vertebra assimilation into the sacrum is termed sacralization of L5.

The first sacral vertebrae, S1, may form articulations with the S2 vertebral body and even have lumbar type facet joints and the lumbar-sized intervertebral disc.

Lumbarization refers to an S1 vertebrae that has features of a lumbar vertebra.

It is important to identify the presence of lumbosacral transitional vertebrae to avoid surgical and procedural errors attributed to inaccurate vertebral body enumeration and to ensure accurate correlation of clinical symptoms.

The lumbar intravertebral disc is approximately 4 cm in diameter and 7-10 mm in thickness, and is composed of an outer annulus fibrosus and an inner nuclear pulposus.

Entrapment of the cauda equina roots, which pass within the dural sac, can occur as a result of progressive hypertrophy of any of the osseocartilaginous and ligamentous elements surrounding the spinal canal.

Lumbar facet joints are true synovial joints formed by the superior and inferior articulating processes of two adjacent vertebrae.

Lumbar facet joints are zygapophysial joints.

The inferior aspect of each lumbar facet joint is invaded by the medial branch of the posterior primary rami at the same level of the facet joint, and the superior aspect is innervated by the medial branch from one level above.

The two innervation of the facets is important when considering interventional therapies for lumbar facet pain.

The two facet joints and the intravertebral disc at each spinal level are inter-dependent and form a motion segment, termed the three joint complex.

The intravertebral disc is the principal weight or load bearing structure of each motion segment, and the facet joints help to limit torsion and resist forward displacement of the vertebral segment.

When degeneration of the disc occurs and the disc space narrowing occurs, the total load transmitted to the facet joint increases and can exceed 50% of the total load placed on the vertebral segment.

Osteoarthritis changes involving the lumbar spine facet joints are common and include joint space narrowing due to degenerative thinning of the cartilage, presence of inflammatory cells and mediators, increased vascularization, subchondral bone remodeling and osteophyte formation, which can contribute to axial low back pain and spinal stenosis.

Osteoarthritic changes, particularly osteophyte formation can contribute to neuroforaminal stenosis and compression of exiting nerve roots which can lead to radicular pain.

The ligamentum flavum extends along the posterior vertebral column and connects the laminae of adjacent vertebrae.

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