the reason that I’m posting here is that I’m wondering if maybe I’m missing metastasis in her spine. The thought did occur to me but none of the doctors have even brought this up without me asking.  Neither said that they think that it is related to her osteosarcoma but now I’m worried that we are all missing something. 

I know it's easy to think the worst when you see cases like Ellie's, and I'm hoping that Whitney will see this and chime in. I sure miss her presence here.

Mets in the spine is a relatively rare situation overall, but yes, it happens. Since our community is so small, we tend to see it here more than most vets ever will in the course of their career.

Most times though, it's just a guess that spinal mets are the actual cause when a dog like Ellie goes downhill so quickly. There just isn't time to do those diagnostics, and few if any options to do anything even if mets are discovered. Thankfully you are getting this possibility looked at when Ophelia has the PET/CT scan at CSU in a few weeks (ironically where Ellie also received care at first). It's literally the best machine on the planet, so IF there's anything there, they'll find it. My gut instinct says from what you describe of Ophelia's pain issues, that this is not what's going on, and my heart really hopes that is the case.