My wife tried the injections, and they didn't help her. In fact, the injections seemed to increase pressure and discomfort. She eventually went to Laser Spine Institute for surgery a couple of years ago and achieved 100% relief.
I currently have a very close friend with similar back problems to you. He underwent the injections and they made a remarkable difference in his case. His pain went from a level 6-7 to a 1-2 and it lasted for several months.
I guess each case can be different. If it works for you, great. If not, at least it won't make it worse.