Having some experience in a med/surg unit would be helpful to working in an ortho unit but you can survive without it. You want to make good friends with a physical therapist to teach you some of the mobility information. You want to make friends with a pharmacist to teach you some of the pain management information. Find one of those old ortho nurses to teach you haw to poke the pillows just right for more comfort. Then you want to join the National Association of Orthopaedic Nurses so that you will have the best support system in the world behind you. They publish many references for orthopaedic nurses in all kinds of fields--home health, OR, office practice as well as the nurse on the unit. You can check them out at www.orthonurse.org
There is a certification in orthopaedics as well and you can get all the information about that at this site also. There are chapters all over the country where you can participate in workshops and educaitn sessions. We also have an annual conference on the national level that offers about 35 contact hours as well as lots of fun. Good luck with your job hunt. Hope you do get to do ortho. I've loved it for more than 20 years.