I've been out to ORS/AAOS a few times as a medical student. I can say that unless you are presenting some research, it would be a big waste of time, energy, money to go there. The level of material was largely over my head, and only now that I have done some ortho rotations I am finally understanding what they were talking about. I've never seen a residency fair, and attendings/program directors are much too busy to talk with their friends, let alone a medical student they've never met.
Of course, if you are presenting, you should definitely go, as that is a great thing to talk about on interviews.