In the article, it’s also mentioned that Hippocrates recommended using gold, and many of his teachings were still followed in Byzantine times.
So what’s your next theory? Gold sounds fairly plausible to me.
https://en.wikipedia.org/wiki/Catgut_suture#History:
> Gut strings were being used as medical sutures as early as the 3rd century AD as Galen, a prominent Greek physician from the Roman Empire, is known to have used them.[4]
It couldn't be an organic suture, unless it was supposed to last very little (on wiki it says 90 days). Also only something study like a metal could hold a bone in place reliably, I imagine.
The assumption that it had to last X amount of time is questionable.
The other point I'm less certain of is that the discovery was based on dental calculus... I suspect that this wouldn't have been so pronounced if the thread was replaced frequently.