The above figures reveal a lysis and anterolysthesis at L5-S1 level. However in addition there is formation of a pseudojoint between the L3 and L4 spinous processes due to these coming in contact. It is seen as synovial fluid between them with degenerative changes seen as irregularity of the cortical margins. This is known as Baastrup's disease.
Baastrup's "disease" or "Kissing Spine"; and other synonyms including: Arthrosis interspinosa, diarthrosis interspinosa, kissing osteophytes, kissing spinous disease, osteoarthrosis processus spinosi vertebrarum lumbalum, osteoarthrosis interspinalis are the same. It is characterized by;
-hypertrophy of spinous processes of adjacent vertebral bodies in close approximation or actual contact; i.e., arthritic joints between the spinous processes
-joints undergo reactive sclerosis/degenerative change, including formation of degenerative cysts as seen in this case
-etiology uncertain, may be related to excessive lordosis with degeneration of intervening ligaments
-can cause low back pain; originally described as "pain in the back when standing erect which is relieved by bending forward"
-can be associated with interspinous bursal fluid, which can extend into posterocentral epidural space and cause posterior compression of the thecal sac.
1. Hazlett J. Kissing spines. J Bone Joint Surg Br 1964: 46: 1368-1369 (Medline)
2. By waters EG , Evans S. The lumbar interspinous bursae and Baastrup's syndrome: an autopsy study. Rheumatol Int 1982; 2: 87-96.
Dr Muneesh Sharma, Goa