Spondylolysis is a unilateral or bilateral defect in the pars interarticularis portion of the vertebrae.
It is a stress fracture mostly seen in the lumbar vertebrae, and most commonly L5.
Pain is relieved with rest and worsened by lateral bending or extension (NOTE: most back pain is worsened by flexion).
If neurologic symptoms and/or radiculopathy are present, an alternative diagnosis should be considered, because they are rarely associated with spondylolysis.
Diagnostic imaging should start with plain radiographs with added oblique views.
Classically, oblique views show the Scotty dog sign with a crack on the dog’s neck/collar, the pars.
The Scotty dog’s head (superior articular facet), nose (transverse process), eye (pedicle), neck (pars interarticularis), and body (lamina) should be easily identified on the oblique radiograph.
