The Medicare Carriers Manual, section 4828, states, "If surgeons of different specialties are each performing a different procedure (with specific CPT-4 codes [e.g., "sequential" surgery]), neither co-surgery nor multiple-surgery rules apply (even if the procedures are performed through the same incision). If one of the surgeons performs multiple procedures, the multiple-procedure rules apply to that surgeon's services."
For example, a patient who was in a motor-vehicle accident requires emergency surgery for serious internal injuries of the chest and abdomen, as well as subdural cranial hematoma. In this case, a general surgeon, an orthopedic surgeon and a neurosurgeon may all attend to the same patient during the same operative session, but as long as each performs his portion without explicit aid from the others, each should report his or her portion of the overall surgery independently, with no modifiers appended.
If the orthopedic surgeon performs multiple procedures, however, the standard multiple-procedures rules apply.