TRANSITIONAL SEGMENT

Transitional segment (transitional vertebral segment): a congenital anamoly of a vertebra in which it develops characteristics of the adjoining structure or region, e.g lumbosacral, cervicothoracic. The clinical significance of this lies in its aberrant motion characteristics; gross postural effects on the super incumbent spinal column or pseudoarthrosis between the enlarged transverse processes and either the sacrum or ilia.

Lumbarization:

a transitional segment in which the first sacral segment becomes like an additional lumbar vertebra articulating with the second sacral segment.

Sacralization:

1. Incomplete separation and differentiation of the fifth lumbar vertebra   (L5) such that it takes on characteristics of a sacral vertebra

2. When transverse processes of the fifth lumbar are atypically   Large,  causing pseudoarthrosis with the sacrum and/or ilia referred to as batwing deformity if bilateral.