Spondylolisthesis, anterior and posterior disc herniation at L4-L5 level. Note inter-spinous bursal fluid collection at the same level (yellow arrows). Note also flattening of the spinous processes.

Also called kissing spines, Baastrup disease results from adjacent spinous processes in the lumbar spine rubbing against each other. This results in hypertrophy and sclerosis with focal midline pain and tenderness. It may lead to epidural cyst formation and canal stenosis. Commonly seen with spondylolisthesis. Bursogram is valuable in detecting epidural cysts. Relief of symptoms is by bursal injection of steroids.