Pott's spine is commonest in the spine -
Maheshwari has mentioned that Dorsolumbar region is the most common site of spinal tuberculosis. Which is absolutely correct. However, It is worth noting that dorsolumbar region refers to combination of lower dorsal and upper lumbar.
The exact frequency for each segment is as follows (Published on the site of AIIMS as well as given in Ebnezar) : -
Cevical
Thoracic
Lumbar
Sacral