Clinical UM Guideline

This document addresses use of an assistant during surgical procedures. An assistant at surgery refers to a licensed professional who actively participates with the operating surgeon who is performing a surgical procedure. This document does not address use of a co-surgeon or team of surgeons.

Note: For a high-level overview of this document, please see “Summary for Members and Families” below. 

Medically Necessary:

Use of one assistant surgeon during a surgical procedure may be considered medically necessary when the following criteria are met:

1. The American College of Surgeons (ACS) has designated a procedure as “always” requiring an assistant surgeon; or
2. ACS has designated a procedure as “sometimes” requiring an assistant surgeon and the Centers for Medicare and Medicaid Services (CMS) have designated the procedure as “always” requiring an assistant surgeon; or
3. There is documented evidence that the procedure requires assistance due to the complexity of the procedure or health status of the individual and both the ACS and CMS have designated a procedure as “sometimes” requiring an assistant surgeon.

Not Medically Necessary:

The use of an assistant surgeon during surgery is considered not medically necessary for the following:

1. The surgical procedure is designated as “never” requiring an assistant surgeon by the ACS;
2. ACS has designated the procedure as “sometimes” requiring an assistant surgeon and CMS has designated the procedure as “never” requiring an assistant surgeon;
3. The procedure could be assisted by a surgical technician and there is no documented need for an assistant surgeon’s level of training and expertise.

This document describes when use of an assistant during surgical procedures may be appropriate. The following summary does not replace the medical necessity criteria or other information in this document. The summary may not contain all of the relevant criteria or information. This summary is not medical advice. Please check with your healthcare provider for any advice about your health.

Key Information

An assistant at surgery is a trained health professional who helps the main surgeon during an operation. This person may be a doctor or another licensed professional, such as a nurse practitioner (NP) or physician assistant (PA). They help with tasks like holding tools, controlling bleeding, and improving visibility. Whether an assistant is needed depends on how complex the surgery is and the person’s health. National groups like the American College of Surgeons (ACS) and the Centers for Medicare and Medicaid Services (CMS) review procedures and classify them as always, sometimes, or never needing an assistant. These classifications help guide when using an assistant is appropriate. Using an assistant when not needed may not improve outcomes and may expose people to added risks from having more providers involved in care.

What the Studies Show

Expert groups such as the ACS have reviewed many types of surgeries to decide when an assistant is needed. They looked at procedure codes and rated how often an assistant is required based on complexity and technical needs. CMS also reviewed real world data on how often assistants are used and created similar categories. These ratings help guide safe and effective care.

Having an assistant may help the surgeon complete complex procedures more safely and efficiently. For example, assistants can help control bleeding or improve the view of the surgical area while the primary surgeon is focused on other aspects of a procedure. However, if a procedure is simple, a highly trained assistant surgeon may not be needed, and a surgical technician may be enough. Using an assistant when not needed does not improve health outcomes. It may also increase the chance of confusion in the operating room or lead to care that does not add benefit.

When is an Assistant at Surgery Clinically Appropriate?

An assistant at surgery may be appropriate in these situations:

• The ACS classifies the procedure as always needing an assistant; or
• The ACS says the procedure sometimes needs an assistant and CMS says it always needs one; or
• The procedure is complex or the person has health issues that make surgery more difficult, and both ACS and CMS say the procedure sometimes needs an assistant.

When is this not Clinically Appropriate?

An assistant at surgery is not clinically appropriate in these situations:

• The ACS classifies the procedure as never needing an assistant. Studies reviewed by the ACS show these procedures can be safely done without one.
• The ACS says the procedure sometimes needs an assistant and CMS says it never does. Data from CMS show assistants are not needed to complete these procedures safely.
• A surgical technician can assist, and there is no clear medical need for a higher level of training. Studies and expert reviews show that using a more highly trained assistant in these cases does not improve health outcomes.

An assistant at surgery is not clinically appropriate in scenarios other than those listed above. Using assistants when they are not needed can lead to care that does not help and may expose people to unnecessary risks.

(Return to Description)

The American College of Surgeons (ACS, 2013) has defined an assistant surgeon as someone “who is able to participate in and actively assist the surgeon in completing the operation safely and expeditiously by helping to provide exposure, maintain hemostasis, and serve other technical functions.” An assistant surgeon generally refers to a medical doctor (MD), Doctor of Podiatric Medicine (D.P.M.), Doctor of Dental Surgery (D.D.S.), or Doctor of Osteopathy (D.O.). ACS indicates that at times, it may also be appropriate to use other licensed allied health professionals such as a physician assistant (PA), clinical nurse specialist (CNS), nurse practitioner (NP), or registered nurse first assistant (RNFA).

ACS has determined that assistant surgeon services are required for the successful completion of certain surgical procedures that have been identified as sufficiently complex or intensive in the sixth edition of their study, Physicians as Assistants at Surgery (2023*), which was developed in collaboration with 15 other specialty societies. The study was undertaken by examining all of the codes listed in the American Medical Associations (AMA) Current Procedural Terminology (CPT) 2020. The organizations, in collaboration with the ACS, were asked to review each code and indicate if surgical procedures required the use of an assistant surgeon “almost always,” “almost never,” or “sometimes.”

Similar to the ACS,  the Centers for Medicare and Medicaid Services (CMS) designates surgical procedures as “always,” “sometimes,” or “never” requiring a surgical assistant based on utilization patterns reflected in the Medicare Physician Fee Schedule (MPFS) Relative Value File. These designations are operationalized through specific assistant-at-surgery payment indicators within the MPFS and include multiple values that specify whether assistant-at-surgery services are payable under defined circumstances, as outlined below. These indicators apply to assistant-at-surgery services, including those performed by MDs, PAs and NPs.

0 = Payment restriction for assistants at surgery applies to this procedure unless supporting documentation is submitted to establish medical necessity.
1 = Statutory payment restriction for assistants at surgery applies to this procedure. Assistants at surgery may not be paid.
2 = Payment restriction for assistants at surgery don’t apply to this procedure. Assistants at surgery may be paid.
9 = Concept does not apply [e.g., procedures during which use of an assist surgeon would not be considered].

These indicators provide a code-level representation of CMS policy and are used in conjunction with ACS classifications to inform when assistant-at-surgery services may be appropriate.

*If there is a more recent version available of the ACS Physicians as Assistants at Surgery publication, it supersedes the version and link listed in the Reference section of this document.

Assistant surgeon: A practitioner who actively assists the operating surgeon. An assistant may be necessary because of the complex nature of the procedure(s) or the individual’s condition. The assistant surgeon is usually trained in the same specialty.

Co-surgeons: Two or more surgeons, where the skills of both surgeons are necessary to perform distinct parts of a specific operative procedure.

Team of surgeons: More than two surgeons, usually of different specialties, where the skills of each are necessary to perform distinct parts of a specific operative procedure.

Peer Reviewed Publications:

1. Deery SE, O'Donnell TFX, Zettervall SL, et al. Use of an assistant surgeon does not mitigate the effect of lead surgeon volume on outcomes following open repair of intact abdominal aortic aneurysms. Eur J Vasc Endovasc Surg. 2018; 55(5):714-719.
2. Kajiwara M, Ishii F, Sasaki T, et al. Crucial roles of the assistant surgeon during laparoscopic left hemihepatectomy. Cureus. 2022; 14(4):e24050.

Government Agency, Medical Society, and Other Authoritative Publications:

1. American College of Surgeons. Physicians as assistants at surgery: 2023 study. Available at: https://www.facs.org/media/gp3ny4ps/2023-update-physicians-as-assistants-at-surgery.pdf. Accessed on March 18, 2026.
2. Centers for Medicare and Medicaid Services. Physician Fee Schedule (PFS) Relative Value Files. February 25, 2026. Available at: http://www.cms.gov/Medicare/Medicare-Fee-for-Service-Payment/PhysicianFeeSched/PFS-Relative-Value-Files.html. Accessed on March 18, 2026.

Federal and State law, as well as contract language, and Medical Policy take precedence over Clinical UM Guidelines. We reserve the right to review and update Clinical UM Guidelines periodically. Clinical guidelines approved by the Medical Policy & Technology Assessment Committee are available for general adoption by plans or lines of business for consistent review of the medical necessity of services related to the clinical guideline when the plan performs utilization review for the subject. Due to variances in utilization patterns, each plan may choose whether to adopt a particular Clinical UM Guideline. To determine if review is required for this Clinical UM Guideline, please contact the customer service number on the member's card.

Alternatively, commercial or FEP plans or lines of business which determine there is not a need to adopt the guideline to review services generally across all providers delivering services to Plan’s or line of business’s members may instead use the clinical guideline for provider education and/or to review the medical necessity of services for any provider who has been notified that his/her/its claims will be reviewed for medical necessity due to billing practices or claims that are not consistent with other providers, in terms of frequency or in some other manner.

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