I agree with Pixiangelj. She should have her autoimmune, immune, endocrin workup. Also, recent studies have shown that people with metabolic disorder (diabetes and high cholesterol/triglycerides) tend to have denser bones sometimes and less arthritis and conversely those with low cholesterols and low blood sugars develop more arthritis and possibly disk problems. Therefore even her thyroid and parathyroid, etcetera can play a role. Arthritis can cause disk damage and visa-versa.
On a positive note, they have started using the new artificial disks in certain areas of the back. I am unsure of the thoracic area; but I am hearing promising results in some areas of the back from doctors that I know. A small number of patients are even having two artificial disks inserted at a time. I do not know if your wife would be a candidate, but I sure would look into it as it sounds like a more promising option than some of the procedures being routinely used now. Good luck!
Eddie, I am sorry to hear about your wife's situation. Have you posted in the dr. moderated forum. I would suggest that. Also getting multiple drs. opinions and a copy of your records can be a big help. There is constant research that is always evolving, specifically I'm not sure. Are there any kinds of medications that can help slow with disc degeneration? It sounds like almost an autoimmune, or some type of other problem. Does she have any other symptoms. Let me know, until then, I wish you guys the best.