I don't recall reading about lower body sx on any of the sites- so far the only place I have heard about it spreading is the anecdotal stories here on the forum.
I did a very quick search on PubMed = TOS lower body sx ? but nothing related came up.

Maybe a search on articles by Roos, Sanders - I don't know if Brantigan or Annest have articles out on the subject. Does Ellis find that the spread can happen?

another option - email each of them and ask if they can point you to any studies or documentation relating to that.