I had spinal fusion surgery at L5-S1 (the lowest part of your back) in Jan '07 and went to IOA/US in Jan '08.
I went on most everything, except Dr. Doom (but mostly b/c I'm not the hugest fan of that ride). The Mummy was a little jerky, but I still went on it 3 times, and didn't feel any effects. I also don't really like water rides, so we skipped the 3 at IOA. But Dueling Dragons, Hulk, Spiderman, MIB..all of the fun ones were just fine.
Incidently, we were also there a month before my surgery (which was to fix a fracture in my spine) and I didn't really have too many problems either. More than anything, the walking around all day was the hard part, not so much the riding of rides.
I don't know if you're planning to go to any of the Disney parks, but I can tell you to stay far far away from Dinosaur and the Primeval Whirl at Animal Kingdom. Those are NOT good for back issues.