The October "Coding Corner" article states that if a procedure is done arthroscopically but no code exists in that section (only an open code), you should write your insurance carrier and tell them that you will bill the open code for a procedure done arthroscopically, with a modifier -22 or -52. According to AMA guidelines, this is incorrect. If there is no code for the procedure in the arthroscopic section of the CPT, you must use the unlisted arthroscopic code 29909. You may attach a note to the insurance carrier stating that the work is similar to the open code (for payment purposes). The AAOS CPT and ICD Coding Committee agrees with the AMA guidelines.