Hi Judy Allen,
to NT
Degenerative Disc Disease is caused by osteoarthritis in the spine. You didn't mention your age, but this hits many of us in middle age - it's a part of the aging process, and part of the tradeoff we pay for walking upright. Thing is, some people get it much worse than others. Scoliosis complicates things because you're starting out with a physical defect. It's possible (I do not know this) that your discs have begun deteriorating, causing your spine to shift further, and the procedure halted that progression (kind of what
ger was getting at).
If the doctor doesn't know why, perhaps there's somebody he can send you to who may know why, or can find out(?) Has any mention been made of a follow-up MRI to see what's going on in there?
Doc