Progression of congenital scoliosis is least likely in which of the following vertebral anomalies -
Congenital vertebral anomalies causing scoliosis are :


Hemivertebrae
Wedge vertebra
Unsegmented bar
Block vertebra
Combination : unsegmented bar with hemivertebrae


Amongst these minimum chances of progression are with block vertebrae and maximum with the combination of unsegmented bar & hemivertebrae.
Unsegmented bar - with hemivertebra > unsegmented bar > hemivertebra > wedge vertebra > block vertebra
Fully segmented Hemivertebra
Wedge vertebra
Block vertebra
Unilateral unsegmented bar with Hemivertebra