Bertolotti's syndrome refers to the association of back pain with lumbosacral 
transitional vertebrae. Such vertebrae were observed in 140 of 2,000 adults with 
back pain over a 4-year period of study. Each patient had radiographic 
evaluation of the lumbar spine by plain films as well as a sectional imaging 
modality (magnetic resonance [MR] or computed tomography [CT]). The overall 
incidence of structural pathology (eg, spinal stenosis and disc protrusion) 
detected by CT or MR was not apparently higher in patients with transitional 
vertebrae, but the distribution of these lesions was significantly different. 
Disc bulge or herniation, when it occurred, was nearly nine times more common at 
the interspace immediately above the transitional vertebra than at any other 
level. Spinal stenosis and nerve root canal stenosis were more common at or near 
the interspace above the transitional vertebra than at any other level. 
Degenerative change at the articulation between the transverse process of the 
transitional vertebra and the pelvis was an uncommon occurrence; when seen there 
was no significant correlation with the reported side of pain. It is postulated 
that hypermobility and altered stresses become concentrated in the spine at the 
level immediately above a lumbar transitional vertebra. Accelerated disc and 
facet joint degeneration at this level may then result.