Pain and edema after posterior surgical fusion. Why? What will help?

I had a posterior cervical fusion about 12 weeks ago from C5-C7. It was after a previous ACDF failed to fuse. I am still having significant pain (started PT at 9 weeks). It’s a ripping pain in my neck and shoulder and pain into my shoulder blade. I’m also having some arm heaviness/numbness in recent weeks. My surgeon says my CT looks good (though the report mentions mild to moderate stenosis as well as osteophytes and moderate to severe bilateral uncovertebral joint disease at c6/c7) and an MRI showed a small paraspinal seroma and soft tissue edema. I’m unclear what’s causing my pain and what would help - ie an injection, more time, etc. Any advice or even comments on when you turned a positive corner after PCDF are welcome!