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Spondylolisthesis

http://www.learningradiology.com/archives06/COW%20204-

Spondolytic%20Spondylolisthesis/spondylocorrect.htm

Normally the inferior articulating fact of each lumbar vertebral body lies posterior to thesuperior articulating facet of the body below it

If the bony connection between the inferior and superior articulating facets (pars

interarticularis) is defective, the weight of the body may cause the upper vertebra, including all of

the vertebral bodies above it, to slip forward for varying amounts on the body below

(spondylolisthesis)

The defect in the pars interarticularis is called spondylolysis

Spondylolysis is not present at birth but increases in frequency with increasing age

When symptomatic, pain is the most frequent symptom of either spondylolysis or

spondylolisthesis

There are several different etiologies for spondylolisthesis

o Spondylolytic spondylolisthesis

Is the most common type and results from bilateral defects in the pars interarticularis

Has a 2:1 male to female predominance and is more common in Caucasians than African-

Americans

With bilateral spondylolysis, the posterior aspect of vertebral body separates from the

anterior body

Posterior body remains fixed in position while the anterior part is free to slip forward

Cause of spondylolysis appears to be a combination of a dysplastic pars at birth coupled with

the long-term stresses of upright posture

Certain athletic endeavors (e.g., football, weight-lifting, tennis and wrestling) appear to

increase these stresses

Fractures of the pars may heal with a pseudarthrosis or fibrous ankylosis

o Degenerative spondylolisthesis

More common in African American women than in Caucasian women

Most frequent at the L4-L5 level

Is not the result of a pars defect but a complex interaction between the disk, facets joints and

the ligamentous structures

There is usually narrowing, sclerosis of the facet joints from osteoarthritis

http://www.learningradiology.com/archives06/COW%20204-Spondolytic%20Spondylolisthesis/spondylocorrect.htmhttp://www.learningradiology.com/archives06/COW%20204-Spondolytic%20Spondylolisthesis/spondylocorrect.htmhttp://www.learningradiology.com/archives06/COW%20204-Spondolytic%20Spondylolisthesis/spondylocorrect.htmhttp://www.learningradiology.com/archives06/COW%20204-Spondolytic%20Spondylolisthesis/spondylocorrect.htmhttp://www.learningradiology.com/archives06/COW%20204-Spondolytic%20Spondylolisthesis/spondylocorrect.htm

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There is less forward slippage (spondylolisthesis) in this group than in spondylolytic group

Retrolisthesis (backward slippage of a vertebral body on the body below it) may occur with

osteoarthritis of the facets joints

o Dysplastic spondylolisthesis

Results from congenital abnormalities of the body and/or facets in the lumbar region such

that the alignment of the facets allows spondylolisthesis to occur

The pars may or may not be intact

Females are more apt to have this type than males (2:1)

Symptoms usually develop during the adolescent growth period

o Traumatic spondylolisthesis

Trauma can lead to an acute fracture through a normal pars interarticularis

Results in a diastatic defect that may lead to a spondylolisthesis

Imaging findings

o Conventional radiography in the anteroposterior, lateral and both oblique projections is usually

adequate to demonstrate both spondylolysis and spondylolisthesis

o Spondylolysis appears as a break in the neck of the ScottieDog on the oblique view

o Bilateral spondylolysis is visible on the lateral view

o Forward slippage of one vertebral body on the other is observed and graded on the lateral view

o Spondylolisthesis is graded in this manner

Grade 1-vertebral body above subtends of the AP diameter of the vertebral body below

Grade 2- vertebral body above subtends 1/2 of the AP diameter of the vertebral body below

Grade 3- vertebral body above subtends 3/4 of the AP diameter of the vertebral body below

Grade 4- vertebral body above subtends the full AP diameter of the vertebral body below

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Spondylolytic Spondylolisthesis. Lateral view of the lumbar spine demonstrates

a bilateral break in the pars interarticularis or spondylolysis (lucency shown by black arrow)

that allows the L5 vertebral body (red arrow) to slip forward on the S1 vertebral body (blue arrow).

The forward slippage is called spondylolisthesis. The normal pars interarticularis is shown by the

white arrow.

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the degree of forward slippage is equal to about 1/4 to 1/2 of the AP diameter of S1

so this is a Grade1-Grade 2 spondylolisthesis.