We can't tell for sure what exactly Itachi did to Sasuke there, there was a triggered amaterasu, but as we have seen amaterasu is available to Sasuke as if it was his own technique. There can be more surprises coming.Originally Posted by Archangel
As for the rib cage - does look like a mini susanoo, but I could use an explanation in, like, the next chapter as to why he has it at all. (like officially saying "itachi implanted more than just amaterasu on me").