Well, I've had facet joints pointed to as part of my problem. Along with the severe DDD, herniations, etc. Had a double fusion L4-S1 over a year ago. The facet nerve block didn't help me either, and that was tried prior to the fusion.
I know I read somewhere while researching all my surgery that someone (maybe Cleveland Clinic, but not sure) was doing trials on facet joint replacement (as opposed to a disk replacement) but I think it's very new and highly experimental.
It's so hard to isolate where pain is coming from! If they can find the nerve causing is, maybe RF or something along those lines. But they've got to isolate it first, and that's often done with injections. I also have the nerve pain down the buttock, leg, and numbness in feet.
Oh, gosh, does it ever end? I do know when my SI joint is out of place the pain is worse, but even when my PT puts it back into place, the pain's still not totally gone, just reduced. And my SI joint won't stay put, even with exercises and a belt.
I hope someone else here can help more!