Holy cow, I feel for ya, Bigun. I had a second disk removed and two spaces fused in my lower back a couple of years ago. I was in pain 100% of the time and nothing relieved it totally. I was a basketcase. But mine was, thankfully, operable. I just don't know how I'd face it being inoperable. Now, everything's coming up roses!!
Truthfully, though? Walking was the only thing that made it bearable some days (when the meds didn't seem to work well)....so it's probably a good thing that you don't use those spaces unless you really have to.
Hubby is disabled veteran, retired. I kid you not, we had to assemble and mail a package of no less than 350 pages to have his disability status reviewed. Most of the records were written while he was in the service, but he still had to get them, copy them and send them in. Like they couldn't have taken a field trip within the Pentagon and gotten them themselves. What a debacle. We wonder if it will even be worth it the next time review comes up.
I truthfully don't know about civies, but his disability payments are subtracted from his retirement pay. The only thing is, his disability payments are not taxable income while his retirement pay is. It very well may be that Social Security is reduced by disability payments the same way.