My situation was similar to yours. I had bad back and buttock pain from a fall. I had two epidurals that helped some for a bout two weeks. About ten months later I was prescribed some meds that gave me my life back. But, due to the fact that I still had occasional bad days, I got greedy and went to an orthopedic surgeon. He ordered another MRI and told me that I had spondylolisthesis at L5-S1. He strongly recommended spinal fusion. Hey, I was new to all this stuff, so I went ahead with the surgery. It wasn't pleasant. Recovery was about six weeks. No noticeable improvement. I have read that many of the surgeries are unnecessary but are a great cash cow. Was that the case for you...unnecessary surgery? Who can be sure?
If you still have pain after surgery, that surgery should be classifies as Failed Back Surgery syndrome. Hope you can get some relief. Maybe another injection.