go to
http://www.spine-health.com/Clinical-Trials.html
Look at what trials are active, see if you meet the criteria and then see which doctors/facilities are participating and make a consultation appointment letting them know you are interested in being a participant in their trial.
If you hear that there's a trial starting but it's not officially announced, you can sometimes contact the manufacturer to find out which dr to contact closest to where you live.
sometimes if you're lucky your regular treater is aware of an active trial and will refer you but that is not the only way to get in.