Thank you very much for your response. Now its just a matter of knowing which commercial carriers don't recognize the XP.The X modifiers were created by CMS to give them more specific information why procedures don't bundle such as a different provider, anatomical structure/surgical approach and so forth. So for CMS you would always use the X modifiers. I would use -59 for commercial as a general rule. Some commercial payers may process claims with the X modifiers, but I would use modifier -59 first. Let's hope that someone can respond with a list of any commercial that does process with the X modifier