CPT Modifier 51 exempt codes

Modifier 51 exempt codes are typically adjunctive or reported with other procedures. The amount of pre- and postservice time associated with these codes is minimal, and use of modifier 51 to signify a value reduction would be inappropriate. For information on service time and work relative values, please refer to the AMA publication Medicare RBRVS: The Physicians’ Guide. Multiple codes [eg, 20660, Application of cranial tongs, caliper, or stereotac- tic frame, including removal (separate procedure)] were
removed from the list of modifier 51 exempt codes found in Appendix E of CPT 2008.

The bone graft for spinal surgery codes 20930, 20931, and 20936-20938 have been removed from the modifier 51 exemption list (Appendix E), assigned add-on code status, and relocated to the add-on code list (Appendix D of the CPT codebook).

The CPT Editorial Panel supported the AMA’s RVS Update Committee (RUC) finding that codes 20930-20938 include more characteristics associated with add-on codes rather than modifier 51 exempt codes.
Add-on codes are always performed with a defined base code or codes, whereas modifier 51 exempt codes are not always adjunctive; and the base codes associated with modifier 51 exempt codes are either too extensive to list or not easily defined. Both add-on and modifier 51 exempt codes are similar in that neither should be subject to mul-tiple procedure reductions.