Me neither but, hey if he is that rotten, who knows how the parts will move and eventually fuse.
I do see how it looks like his shoulder though. I wish the picture encompassed the entire body in the shot for reference.
Shoulder???? Start at the fucked up spot and look.... UP. If it was a shoulder? A head and neck would be up there... NOT a back.
Sorry, but, THAT? in an ass... or... umm... was one.