@bspurgeon: I've had three spinal surgeries and am now fused from L2-S1. First was a laminectmy at L2, then a fusion L2-L3, and finally a fusion L3-S1, at which time the hardware was removed from the previous fusion. The last surgery was done in 2016. In about 2018 I was diagnosed w/ Idiopathic PN. Legs are starting to go numb, feet don't respond like they used to, and it is very difficult to walk because of pain in lower back. Between an excellent neurosurgeon and a very good DO who does the injections, I've managed with injections at L5-S1 and/ or the R S-I. I'm now to the point where it is difficult to walk and the injections no longer have any effect. No longer being able to walk, due to pain, more than 100 yards, has been bad for my weight and overall strength and conditioning. I am working with a great PT using a treadmill and exercycle, the treatmill is weightbearing but the exercycle not. Up to about 2 years ago, I was able to ride a recumbent tricycle - what a blast. I'm very thankful for the PTist who is very encouraging and is helping me keep moving. I still live alone.

If I were in your shoes, and I'm obviously not, I'd find a very good physical therapist, who is a good diagnostician, to find out how much movement you will retain after the proposed fusion. When injections failed to give me pain relief, and my spine doc was suggesting a fusion the
R S-I joint, he prediccted it wouldn't affect my walking very much and my pain would be reduced (a bone scan as indicated very active arthritis at the R C-I). My PT, however, took me through quite a few moves and concluded that I still had a significant amount of movement in my R S-I, which I would lose if it were fused. That would affect my gait and could make walking even more difficult. I've postponed any surgery on the R S-I indefinitely.