There are multiple topics on this forum that address this question one way or another. Most spots become available by either people dropping out during their first year, programs expanding the number of positions, or somebody wanting to transfer to another program for some personal reason. Programs that interview applicants for PGY2 spots that do become available usually do not fill through the Match. Most openings altogether are usually independent of Match Day. I can imagine as the year gets longer, more people will quit, however most residents realize how hard these spots are to acquire. What makes it harder is that there is a huge pool of nondesignated PGY1s who are willing to sell off their first born for an ortho spot and have probably been looking to do so for a year straight. A switch is not an easy thing by any means. Good luck to you.