Skeletal Trauma

Spondylolysis

Spondylolysis

Spondylolysis is a bony defect of the pars interarticularis.
It happens most often in adolescent athletes and at the L5 vertebrae.
The defect results in formation of a "collar" around the Scotty Dog Model of the lumbar vertebrae.

The Scotty Dog Model of the lumbar spine

Spondylolysis

Spondylolisthesis is the anterior slippage of the vertebral column relative to an adjacent inferior vertebra.
Spondylolisthesis is usually a result of bilateral spondylolysis and most commonly occurs at the L4-5 or L5-S1 level.
Look carefully at the location of the spinous process step off to assess for spondylolisthesis.

Spondylolisthesis