Mark,
I've had injections in my back and really should have surgery on my low back and also my neck. I've refused surgery on my low back because I know what I'm dealing with, but never know what I'll end up with!!! The neck is a different matter with the head aches that I may have to someday. (Right now my lawyer is fighting with the workers comp insurance to get injections in my neck. It's pretty bad when I took future medical in 1982 over money and now have to fight with the insurance because of Arnold Schwarzenegger!) I've taken pain meds for 29 years, use a portable tens unit, an inversion table, chiropractic, etc. As you see I'm kinda dealing with the same issues as you.
I guess you’re mainly looking at tadpole trikes. I've only seen pictures of them. Other than ones like the Rover with the high seat, I think I'd have a heck of a time getting out of it! Judging from what you've said, I'd think that might be an issue for you also?
Have you thought at all about a delta recumbent trike with over seat steering? With my Sun X3-SX it doesn't set too low or too high. I feel like I'm sitting "in" it, instead of something like a Rover where I'd feel like I'm sitting on top of girder on a high-rise being built. I have no problem getting up from it, and if I did then I could use the ape hanger handle bars to help. Talk about ape hangers, I changed the stock ones to the Rans 3-way chopper bars...best thing I ever did to that trike!!!
Have you thought about trying out one of those recumbent stationary exercise bikes? I've never been on one, but I'd think that should give you some type of feel what a road recumbent would be like.
Bob