Thank you for your question.
As per above scenario,
Co-surgeon is assisting another surgeon with a procedure, but is not another primary surgeon, we will append modifier 80 (Assistant Surgeon) to the CPT code. However, for another co-surgeon assistant we will use >81 (Minimum assistant surgeon).
Modifier -80 is the most commonly used of the three and describes the presence of a second physician in the operating room who acts as an extra pair of hands"" to assist the primary surgeon
Add Modifier AS for Certain Cases
Medicare will only pay for a surgical assistant when the procedure performed is authorized for an assistant, and the person performing the service is a physician, physician assistant (PA), nurse practitioner (NP), or a clinical nurse specialist (CNS).
When a PA, NP, or a CNS assists at surgery, attach modifier AS (Physician assistant, nurse practitioner, or clinical nurse specialist services for assistant at surgery) to the surgical code along with modifier 80.
Without modifier AS, modifiers 80, 81, and 82 indicate that a physician was the surgical assistant. Claims you submit that include modifier AS without modifier 80, 81, or 82 will be returned to you.
Caution: Many commercial insurers follow Medicare’s rules, but not all do. Be sure to query each of your payers to find out their policies on billing for surgical assistants. They may want only the modifier AS, or they may not recognize it at all.
Check the Fee Schedule for Guidelines
Before billing for an assistant at surgery, double check the ASST SURG column of the Medicare Physician Fee Schedule (MPFS) to verify that the procedure(s) allows an assistant.
Payers will not reimburse you for assistants at surgery in all cases, regardless of the modifier(s) you attach to the claim. For Medicare, assistant at surgery services are eligible for reimbursement only when national claims data indicates the procedure would require an assistant in at least 5 percent of the claims based on a national average, according to Medicare guidelines.