Presentation
Patient presented with a history of chronic lower back pain.
Patient Data
A fracture of the pars interarticularis of the L5 vertebral body is seen, with resultant grade 1 anterolisthesis of the L5 on S1 vertebra and reduced L5-S1 intervertebral disc space.
Although the Scottie Dog sign is (strictly speaking) reserved for oblique radiographic projection, it is clearly seen here on the lateral radiographs, with a defect at the neck of the Scottie Dog which is the portion of the lamina between the superior and inferior articular facets.
Case Discussion
Pars interarticularis fractures or defects are a common cause of lower back pain. This is commonly seen in adolescents, especially young athletes. The defect may be a unilateral or bilateral fracture, and it occurs almost exclusively in the lower lumbar region, most often at L5.
A pars interarticularis fracture/defect is also known as spondylosis and may progress to spondylolisthesis (as seen in this case).
The most accepted theory for the etiology of this defect is repetitive mechanical stress, specifically lumbar extension and rotation, which results in overuse or stress fracture to the pars interarticularis 1.
Treatment of these defects ranges from conservative strategies to surgical intervention, depending on the presence and degree of spondylolisthesis, as well as the response to conservative measures.
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