My ex wife had those injections. At first it worked for a few days. The second and third round she had were increasingly more painful and decreasingly effective. To be fair, she had a ruptured and leaking disc, which eventually required surgery. It doesn't sound like you've got anything as severe.
Oh. She had an artificial disc replacement. It was actually kind of cool. They went in through her abdomen, removed the disc, inserted two pieces of titanium and a piece of plastic between them. Three days post op, she was walking around the hospital and back at work within 6 weeks. She was part of the clinical trials for it here in the U.S. I believe she had the Cherite brand disc, but it might have been the Pro-Disc.