A surgeon told a friend of mine that it can take a few months to essentially get all the chemical effects of surgery out of one's system. Disturbed sleep can be one symptom. That said, I didn't have fusion surgery, but a diskectomy (l4/l5) It was a solid month before I could sleep through the night, just dealing with assorted little pains. It was 3 months before I could say I felt normal.

Good luck to you,

Kay