scb,
I had a similar experience. With my double fusion, anterior and posterior, I woke up in zero pain except for the incision pain if I moved around. They had me on a morphine pump for two days, but I never used it.
Then 6 months later I went back in for a refusion, one level didn't fuse and my doctor told me it would be a much more painful surgery because this time it would all be done from the back. With the first fusion surgery, I only had four tiny holes cut in my back to put in the hardware and those incisions never caused any pain at all, but the 6 inch incision in the back was off the wall painful, much more painful than and abdominal incision.
I came woke up from surgery on a morphine pump but I had enormous pain, if I did anything but blink it hurt. I was hitting that button every 5 mins and had zero pain relief. Finally, later the next day, my surgeon figured out that morphine doesn't work on me and they changed me to a Dilaudid pump and I had great relief right away.
I don't know about you, but I have made sure everyone in my family knows morphine doesn't work on me and it is written in my purse. God forbid I ever end up in the emergency room, unable to talk but in pain, and they are giving me morphine, which is the nuraber one pain med they give in the ER. You might want to do the same regarding the Dilaudid.
Isn't it really weird how pain meRAB in the same family can work so differently, one narcotic not working at all and another that does?