margaretisabel,
There are two excellent medications you might consider. One is Evenity. It builds the heaviest bone more quickly than the other medications. Original Medicare part b pays for 80% If you have a secondary it will pay the remaining 20%. It is covered by Medicare because it has to be given in clinic. It is two injections every month.
You might consider Evenity because it adds the most bone in the first three months. You seem not to want to wait for the surgery and it would be the quickest path.
Without telling any stories, you shouldn't take Evenity if you have cardiac issues.
The second medication is Forteo, which I'm partial to. It builds a more careful bone, more slowly. But it focuses on the vertebrae and would help to integrate the hardware from your surgery into the bone.
I'm sure I would choose Forteo, or try to get Evenity for 3 months and then switch to Forteo.
I've never taken Evenity and think that it causes joint aches for most patients. I'm on Forteo and have every good thing to say about the drug. I don't know what your insurance covers, but I guess you have until Dec 7 to find the best coverage. If you are low income you might call RX Advocates. I think they can tell you on the phone if you would qualify. https://therxadvocates.com/
Your endocrinologist may have the best advice but you could ask about these two drugs.
I'm assuming your surgery will be fusion, but wonder if you have looked a artificial discs.
Mostly I'm very excited for you with this surgery. It is going to be a different world.