I matched ortho at my top choice program in the DO match this year. I was a competitive applicant, but did fewer auditions than most due to family obligations. Because of this, I was a little worried about not matching. With a family, I knew I had to keep the ball rolling and not matching at all would not have been good for us. Therefore, I applied to a backup specialty.
I wanted the backup to be EM, but I learned that EM is too competitive for a backup. To get a SLOE, I would have had to use a valuable ortho audition month to do an EM rotation, which would have negatively affected my ortho chances. It seems that with EM nowadays, you have to go all in for that specialty.
In the end I chose FM as my backup. Aside from writing a second personal statement and getting LORs from third year FM & IM preceptors, it seems to take minimal effort for an ortho applicant to match FM. I knew I could do a FM sports fellowship or work in a rural ED or something, which would not have been a terrible career.
I interviewed at four FM programs, both DO and MD. Further into interview season after ortho interviews as I was getting more confident in matching ortho, I cancelled a lot of FM interviews. Nobody mentioned anything about my ortho intentions (even though my dean's letter mentioned it) during FM interviews. I was heavily courted by these programs, lots of emails, phone calls etc after interview, them letting me know they wanted me in their programs. Ortho programs never knew about it or mentioned it either. If I was asked what I would do if I didn't match ortho, I was planning on just being honest about it, but thankfully nobody asked me.
In the end, I may have wasted time and money on FM interviews. However, given my circumstances being married with kids, I'm happy I did it. It made the whole process less stressful knowing that worst case scenario was matching FM in a nice program and good location. While it would have sucked super hard not matching ortho, I always kept a good attitude and knew that being a FM doc is still much better than most jobs in the world. With that said, I am SO happy and relieved that I matched ortho!!
I know you've got a different situation going through the MD ortho match, but hopefully this helps. Good luck!