Does Dr say what he believes is possibly pinching the artery in your case? anything specific?
extra cervical rib, scalenes, ligaments, or large bands, etc.

There are special MRIs {3D?} that can be done to get more specific details
info- http://rsirescue.com/articles/collins.htm

What is your avg daily pain level?

Oh what were the broken bones you had or where? collarbone?

Have you found our useful sticky thread- tons of medical links and info-
http://neurotalk.psychcentral.com/showthread.php?t=84
also we have a Drs & PT listing -
http://neurotalk.psychcentral.com/showthread.php?t=135