Radiology Corner – Pseudo-spondylolisthesis

By: Terry R. Yochum, DC, DACBR, Fellow, ACCR, and Chad J. Maola, DC

Case History

This 50-year-old female patient presents with localized lumbosacral pain of six months’ duration. Radiographs of the lumbar spine reveal a striking abnormality. What is it?

Figure 1. What abnormality is revealed here?

Figure 1. What abnormality is revealed here?

Diagnosis

Note the extensive reactive sclerosis affecting the facet structures bilaterally at the L5/S1 level. There is an anterolisthesis of L5 upon the sacrum without pars defects. The anterolisthesis is approximately 10% slippage and represents a pseudo- or degenerative spondylolisthesis.

Discussion

Degenerative spondylolisthesis (type III), with an intact neural arch, has been referred to by Junghans as “pseudospondylolisthesis” to differentiate it from those with a neural arch defect. Macnab prefers the phrase “spondylolisthesis with an intact neural arch,” which is a more accurate description. Thus, degenerative spondylolisthesis is another type of non-spondylolytic spondylolisthesis. Degenerative spondylolisthesis is approximately 10 times more common at L4 than at the L3 or L5 vertebra, and no greater than 25% anterior displacement of the L4 vertebral body occurs, with the majority involving only 10 to 15% displacement.

Figure 2. Can you spot the abnormality here?

Figure 2. Can you spot the abnormality here?

Distribution of degenerative spondylolisthesis varies among populations. It is six times more common in females 60 years of age or older, compared with males of the same age and is rare in individuals under 50 years of age. Degenerative spondylolisthesis is three times more common in blacks than whites with no adequate explanations for these sexual and racial disparities. Degenerative spondylolisthesis is four times more likely to be found in association with a sacralized fifth lumbar vertebra.

The mechanisms of displacement are thought to involve a combination of zygapophyseal joint arthrosis, disc degeneration and remodeling of the articular processes and pars. An increase of the “pedicle-facet angle” has been noted in the degenerative type of spondylolisthesis. This angle, formed by the long axis of the pedicle (or vertebral root) at its intersection with the long axis of the articular pillar, indicates the more horizontal alignment of the degenerative zygapophyseal joints, as seen on the lateral radiograph, and demonstrates the overriding of the articular surfaces.

Several explanations have been proposed for degenerative spondylolisthesis occurring with such great frequency at the L4 level. Allbrook has stated that the greater mobility of L4 due to the sagittal orientation of the facets at the L4–L5 level may explain the unusual frequency of degenerative spondylolisthesis at the L4 level. Additionally, the firmly attached, normal lumbosacral joint may place increased stress on the L4–L5 intervertebral joints, ultimately leading to hypermobility and degeneration of the articular triad.

The “3 Fs” of degenerative spondylolisthesis are:

  • Female
  • Fourth lumbar vertebra
  • Forty years or older

Pain associated with degenerative spondylolisthesis is usually secondary to arthritic changes and foraminal compromise. Degenerative facet arthropathy causing lateral recess stenosis and neurologic signs and symptoms is possible. Degenerative spondylolistheses should be suspected in any patient presenting with symptoms of intermittent neurogenic claudication.

Reference

Yochum TR, Rowe LJ. Essentials of Skeletal Radiology, 3rd ed. Baltimore: Williams & Wilkins, 2005:513.