Liza Jane,
I'm not too well versed in this area at all- but do have a son who 7 mos ago had a burst fracture at C-5 and had to have an anterior and posterior osteo surgery by a surgeon skilled in spinal cord injuries.
Sadly, he's now a quadriplegic, but in therapy with the doc who treated Chris Reeves and is progressing, somewhat slowly.
True, his case is SCI replated, but my thought is that of the surgeon and the type of 360 surgery that was performed.
You are having problems with regrowth of bone and stabilization of the area.
The screws & plates aren't helping.
Possibly you may find that searching in the area of a surgeon who deals with spinal cored injury (SCI), may give you further insight into the methodology as to what would be best in your situation. I don't know if there is an SCI trauma center near you, but that probably would be a starting point.
I don't know if this would be helpful, but it was just a thought.