I've also found that each person is different...some can tolerate rides that others cannot.
I've had 2 spinal surgeries, my lower spine is fused and I have screws in it, also currently have another herniated disc, and I rode Matterhorn, Indiana Jones, and Big Thunder Mountain last week. I cannot ride Space Mountain (it being totally in the dark does not allow me to anticipate and brace for upcoming turns).
If you are afraid, don't ride it! I was super cautious after my first back surgery. By being careful, I was able to determine which rides I could still ride.