How to differentiate the two causes?
1. Congenital block vertebra is equal to height of 2 bodies with the disc space height and so bigger in size than acquired block vertebra. 2. There is a "Wasp- waist sign " in the congenital form. 3. The AP diameter at the disc level is smaller in the congenital form.
There is a block vertebra. No intervertebral disc here. The sum of 2 vertebral bodies is equal to one big block vertebral body with disc space in measurement.