I had fusion at L5-S1 done in 2005 by an ortho surgeon who does a lot of spinal surgeries and is very well regarded in the community. I had almost complete loss of the joint space and bone spurs, with constant low back pain. The procedure was anterior (about a 4" horizontal slice just above my pubic bone) with cadaver bone implant, plate, and big ol’ screw. I had asked about an artificial disc, and the surgeon said “We do artificial discs on bad discs, but not horrible discs like yours.”
My recovery from the surgery was amazingly quick. I was in the hospital for 2 nights, but more than eager to leave after one. I was walking several hours after the surgery, walked a few times a day once I got home, and gradually increased the distance. I was feeling pretty darn good within a couple of weeks, and was released to drive after 3 weeks. I didn’t have a horse at the time, so didn’t have a time frame for getting in the saddle.
The problem I have had is that the discs above the fusion level have had more stress on them, and my spine has become unstable, with resulting persistent low back pain. I had a slip and fall several months after the surgery, which might have triggered the problem. I was pretty much pain free from about 3-6 months after the surgery, then things went downhill.
As far as riding, I asked my doc about it about a year after surgery. He said that since the fusion was solid I wouldn’t damage it, though all the other sorts of horse-related spinal injuries remained possible. I did get back to riding without too much trouble, though riding consecutive days was too much. The problem I had was that my horse lived about a 45-minute drive from me, and the car trip was difficult (sitting is the worst position for me). And mounting was more of a challenge, because I’d lost some flexibility. Once I was on the horse, things were pretty good.
Best of luck to you! My surgeon had given me an 80% chance of significant improvement from the fusion, and for a while that seemed as though it would happen. Then I ended up on the wrong side of that estimate. I’m not sorry I had the fusion done, because I had to give it a go, but I am disappointed not to have had lasting relief from LBP.