If a patient requires a second surgery while they are still in the 90-day global period of their first surgery, you must append a modifier to bypass the global edit. The choice between Modifier 78 and Modifier 79 dictates your payment.
Modifier 78: Related Complications
Use Modifier 78 when the patient returns to the OR for a complication related to the first surgery (e.g., stopping post-operative bleeding, treating an infected joint). Medicare pays the intraoperative portion of the fee, but it does NOT reset the global period. You do not get paid for pre-op or post-op care again.
Modifier 79: Unrelated Procedure
Use Modifier 79 when the patient requires a surgery completely unrelated to the first (e.g., patient had right knee replaced, but falls 30 days later and breaks their left arm). Modifier 79 pays at 100% and entirely resets the 90-day global period for the new procedure.
NCCI Edits
Ensure the ICD-10 diagnosis codes match the modifier. A 79 should almost always point to a completely different diagnosis code than the original surgery.