What is the "Scotty Dog"?

If the picture below was your first inclination I’ll go ahead and say you’re halfway there.

Week 3 expanded our knowledge of Spondylolysis and Spondylolisthesis.  The pictures below provide a light and quick explanation of the conditions.  The pars interarticularis is the region of the lamina between the superior and inferior articulating processes.  A fracture of the pars interarticularis (spondylolysis) is usually caused by repetitive loading and unloading of this region of the vertebrae from physical activity.  It can also result from age related degenerative disease.

Spondylolisthesis is the anterior slippage of one vertebra in relation to the other.  In this case (as in many) the L5 in relation to the S1.

When diagnosing a possible fracture of the pars interarticularis, the doctor will commonly order a low back x-ray.  An oblique view is used to check for a fractured pars.  The doctor will then trace around the vertebral body and bony ring on the X-ray film. The outline normally forms an image that looks like a small dog.  However, when the pars interarticularis has fractured, the dog will appear to have a collar around it’s neck.  This is referred to as the Scotty Dog sign and it confirms a diagnosis of spondylolysis.

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