I used to be more bold in telling people to not have a back-up plan when they were very qualified but have had to change my tune over the last couple of years based on the increasingly competitive nature of Orthopaedic Surgery.
That being said, depending on the "other" factors (where you went to college, where you went to med school, extra-curriculars, etc...) you should be fine. However, I would certainly apply broadly (>40 programs for sure).
As for a back-up yes it's a good idea to be self-preservational - decide what you'd do if you don't in fact match and make sure you have an opportunity to do that specialty if possible. If you'd rather spend the year in the lab then that's an easier process typically.
Good luck ---
wnl