Hi Lauderdale,
I'm no expert on lumbar stuff (or anything else for that matter) because I'm a cervie. But, I can tell you that when they went in through your stomach, they used retractors to get all the guts out of the way to get to your spine. They did that with me when they slit my throat to get to my cervical spine and that was the worst pain of the whole ordeal...the swelling resulting from the retraction of the guts. It hurt way down below my throat. So, I don't think it's anything unusual to be in pain especially if your doctor isn't concerned.
Now I'm sure someone else will come along that has more experience in this area than me, but I'm not sure if they will word things quite as eloquently as I do
DebbieMc