Modifiers · CPT modifier

Multiple procedures

Modifier 51 signals to a payer that the same provider performed two or more distinct procedures during a single operative session. It is appended to each secondary procedure code—never the primary—and typically triggers a 50% fee reduction on those additional services. It does not apply to E/M visits, add-on codes, or procedures flagged as modifier 51 exempt.

Verified May 8, 2026 · 8 sources ↓

Type: CPT
CPT codes use it: 1,468
Top regions: Foot & ankle, Hand, Other

Drawn from AMACMSNovitas SolutionsAmerican SocietyAAPC

When to use modifier 51

Source · Editorial brief grounded in 8 cited references ↓

Append modifier 51 to the second and any subsequent procedure codes when the same surgeon performs multiple distinct surgical services in one operative session. Always sequence the code with the highest relative value unit (RVU) first, unmodified, and attach modifier 51 to each lower-RVU code that follows. For example, if a surgeon performs a knee arthroscopy with meniscectomy and also repairs a separate soft-tissue structure during the same session, the arthroscopy carries the higher RVU and is listed first; modifier 51 is placed on the additional procedure. This ordering directly affects reimbursement, because payers reduce payment on every modified code.

Modifier 51 applies across three scenarios: different procedures performed in the same session, the same procedure performed at multiple distinct anatomic sites, or a single procedure repeated at the same site during one encounter. It is not used alongside E/M services, physical medicine and rehabilitation codes, or vaccine supply codes. Certain codes are permanently exempt—look for the circle-with-a-line symbol in the CPT codebook or consult Appendix E. Add-on codes (marked with a plus sign in CPT and listed in Appendix D) also never receive modifier 51; their parenthetical instructions already assume they are used with a primary code.

Medicare is an important exception: CMS instructs providers not to manually append modifier 51 on Medicare claims. Medicare's pricing system automatically identifies multiple procedures, ranks them by physician fee schedule amount, pays 100% for the highest-valued service, and applies a 50% reduction to the remaining procedures. Filing modifier 51 on a Medicare claim is not required and will not change how the claim prices. Commercial and Medicaid payers vary—some follow Medicare's auto-adjudication logic, others require the modifier to be present, and a few do not recognize it at all, making payer-specific verification essential before billing.

Orthopedic scenarios

Concrete situations in orthopedic practice that warrant modifier 51.

Source · Editorial brief grounded in AAOS coding guidance and cited references ↓

A surgeon performs a primary total knee arthroplasty (TKA, CPT 27447) and, during the same operative session, also repairs a quadriceps tendon rupture (CPT 27385). Code 27447 lists first (higher RVU, no modifier); 27385-51 is listed second, subject to the 50% multiple-procedure reduction.
During a single shoulder procedure, the surgeon performs an arthroscopic rotator cuff repair (CPT 29827) and an arthroscopic distal clavicle excision (CPT 29824). Report 29827 first unmodified, then 29824-51, because 29827 carries the higher RVU.
A surgeon performs open reduction and internal fixation of a distal radius fracture (CPT 25600 or 25607) and, in the same session, repairs an associated ulnar styloid fracture requiring separate fixation (CPT 25651). The ORIF of the radius is primary; 25651-51 reflects the secondary procedure.
Knee arthroscopy with medial meniscectomy (CPT 29881) is performed simultaneously with knee arthroscopy with chondroplasty of a separate compartment (CPT 29877). List 29881 first; append modifier 51 to 29877 because both are distinct arthroscopic services in the same session.
A surgeon performs a lumbar posterior arthrodesis at L4-L5 (CPT 22612) together with posterior instrumentation (CPT 22840, an add-on code). Modifier 51 is NOT appended to 22840 because it is a designated add-on code; it is simply listed in addition to 22612.
During a hip arthroplasty revision requiring both acetabular and femoral component removal and reimplantation, if a separate bursectomy (CPT 27060) is also performed in the same session, report the revision code first and append modifier 51 to 27060 as a secondary, lower-RVU service.

Common mistakes

Where coders most often go wrong with modifier 51.

Source · Editorial brief grounded in CMS NCCI Policy Manual and cited references ↓

Appending modifier 51 to the primary (highest-RVU) procedure code instead of reserving it exclusively for secondary and subsequent codes—this inverts the payment logic and typically causes the highest-value service to be reduced.
Adding modifier 51 to CPT add-on codes such as +20930 (allograft for spine surgery) or +22632 (additional interspace fusion)—these codes are inherently secondary and their parenthetical language already accounts for multiple-procedure context.
Using modifier 51 on codes listed in CPT Appendix E as modifier 51 exempt, such as 36620 (arterial catheterization for monitoring) or 31500 (emergency endotracheal intubation), which causes claim edits and potential denials.
Confusing modifier 51 with modifier 59 when NCCI edits bundle two procedures together—modifier 59 (or its X{EPSU} successors) addresses distinct procedural services that would otherwise be considered components of each other, while modifier 51 simply signals multiple unrelated procedures billed together.
Submitting modifier 51 on Medicare Part B professional claims when CMS explicitly instructs providers to omit it, resulting in a redundant modifier that can flag claims for manual review without adding any reimbursement benefit.
Failing to sequence codes by descending RVU before appending modifier 51, causing the lower-value code to price at 100% and the higher-value code to receive the 50% reduction—reversing intended payment.
Attaching modifier 51 to E/M service codes billed on the same date as a surgical procedure—E/M services are explicitly excluded from modifier 51 application and require modifier 25 when billed with a same-day procedure.

CPT codes that use modifier 51

1,468 orthopedic CPT codes in our reference list this modifier as applicable. Sorted by total RVU.

Source · Derived from per-code modifier guidance in our CPT reference

Showing top 12 of 1,468 by total RVU.

Where modifier 51 shows up

Body regions where this modifier most commonly appears in our orthopedic reference.

Foot & ankle 288 codes
Hand 196 codes
Other 190 codes
Wrist 147 codes

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 8 cited references ↓

01Which code gets modifier 51—the first procedure listed or the second?

Modifier 51 always goes on the second and any subsequent procedure codes, never on the primary. The primary code is the one with the highest RVU and is listed first without any modifier. Attaching modifier 51 to the primary code causes the highest-value service to be reimbursed at 50%, which is the opposite of the intended payment outcome.

02Do I append modifier 51 on Medicare claims?

No. CMS instructs providers to omit modifier 51 on Medicare Part B professional claims. Medicare's fee schedule system automatically ranks multiple procedures from highest to lowest physician fee schedule amount and applies the 50% reduction to secondary procedures without requiring the modifier on the claim form.

03Can modifier 51 be used with an E/M service billed the same day as surgery?

No. CPT explicitly excludes E/M services from modifier 51 application. When a significant, separately identifiable E/M service is documented on the same day as a procedure, modifier 25 is appended to the E/M code—not modifier 51.

04What is the difference between modifier 51 and modifier 59 in an orthopedic context?

Modifier 51 reports multiple distinct procedures performed together in one session and triggers a payment reduction on secondary codes. Modifier 59 (or its X-modifiers) overrides an NCCI bundling edit by demonstrating that two codes, which payers would normally consider components of each other, represent genuinely separate and distinct services. Use modifier 59 only when an NCCI edit exists and no other modifier more precisely describes the situation; modifier 51 is the appropriate choice when procedures are simply performed together without a bundling conflict.

05Are orthopedic add-on codes like +22840 (posterior instrumentation) subject to modifier 51?

No. Add-on codes are excluded from modifier 51. CPT add-on codes—identified by a plus sign and listed in Appendix D—are already priced as supplemental services and should never have modifier 51 appended. Doing so generates claim edits and can trigger denials.

06How does the 50% reduction work when three procedures are billed together?

Payers pay 100% of the fee schedule amount for the highest-RVU procedure, then reduce each additional procedure to 50% of its allowed amount. So if three procedures are billed, the first is paid at full value, and the second and third are each paid at 50%, with modifier 51 appended to both of the secondary codes.

07What codes are exempt from modifier 51 and where do I find them?

Modifier 51 exempt codes are listed in Appendix E of the CPT codebook and are marked with a specific symbol in the main code listings. Examples relevant to orthopedic-adjacent hospital settings include 36620 (arterial catheterization for monitoring) and 31500 (emergency endotracheal intubation). These codes must never receive modifier 51, regardless of what other procedures are performed in the same session.

Sources & references

Editorial content was developed using the following public sources. Last verified May 8, 2026.

01AMA CPT Professional Edition, Appendix D (Add-On Codes) and Appendix E (Modifier 51 Exempt Codes)
02CMS NCCI Medicare Coding Policy Manual, 2025 Edition — https://www.cms.gov/files/document/2025nccimedicarepolicymanualcompletepdf.pdf
03Novitas Solutions Medicare Jurisdiction H — Modifier 51 Fact Sheet — https://www.novitas-solutions.com/webcenter/portal/MedicareJH/pagebyid?contentId=00144532
04American Society of Anesthesiologists — Modifier 51 vs Modifier 59 — https://www.asahq.org/quality-and-practice-management/managing-your-practice/timely-topics-in-payment-and-practice-management/modifier-51-vs-modifier-59
05AAPC Knowledge Center — Get Paid Using Modifiers 50, 51, 59 — https://www.aapc.com/blog/24298-choose-a-surgical-modifier-50-51-or-59/
06Premera Blue Cross Payment Policy CP.PP.411.v1.1 — Modifier 51 Multiple Procedures — https://www.premera.com/portals/provider/paymentpolicies/cmi_171650.pdf
07Moda Health Reimbursement Policy RPM022 — Modifier 51 Multiple Procedure Fee Reductions — https://www.modahealth.com/-/media/modahealth/shared/Provider/Policies/RPM022.pdf
08Noridian Medicare JE Part B — Modifier 51 — https://med.noridianmedicare.com/web/jeb/topics/modifiers/51

Mira AI Scribe

When the operative note documents two or more distinct surgical procedures performed by the same surgeon in a single session, modifier 51 must be evaluated for each secondary procedure. Flag the highest-RVU code as primary (no modifier) and suggest appending -51 to each additional procedure code, listed in descending RVU order. Automatically exclude add-on codes (CPT Appendix D) and modifier 51 exempt codes (CPT Appendix E) from receiving this modifier. For Medicare claims, suppress modifier 51 per CMS policy. Surface a payer-check reminder for commercial plans, as adjudication rules differ. If the note documents a surgical procedure and a separately identifiable E/M service, route the E/M to modifier 25 logic rather than modifier 51.

See how Mira flags modifier 51 in dictation