Modifiers · CPT modifier

Unrelated procedure during postop

Modifier 79 tells a payer that the same provider performed a completely separate, unrelated surgical procedure while the patient was still inside the global period of a prior operation. It prevents the new procedure from being bundled into the original surgery's global package, triggers a fresh global period for the new procedure, and protects full reimbursement.

Verified May 8, 2026 · 10 sources ↓

Type: CPT
CPT codes use it: 1,557
Top regions: Foot & ankle, Other, Hand

Drawn from AMACMSNovitas SolutionsFirst CoastPalmetto GBA

When to use modifier 79

Source · Editorial brief grounded in 10 cited references ↓

Append modifier 79 to a surgery code when three conditions are all true: the original procedure carries a 10-day or 90-day global period, the same physician (or a physician of the same specialty within the same billing group) is performing the new procedure, and the new procedure is genuinely unrelated to the original surgery—typically tied to a different diagnosis and a different body region or organ system. Place modifier 79 in the first modifier position because it is a pricing modifier that directly affects how the claim adjudicates.

A practical orthopaedic example: a patient is 45 days into the 90-day global period following a right total knee arthroplasty (TKA) when she falls and sustains a displaced distal radius fracture on the opposite limb. The same orthopaedic surgeon performs open reduction and internal fixation (ORIF) of the radius. Because the ORIF is anatomically and diagnostically unrelated to the TKA, the surgeon appends modifier 79 to the ORIF code. The TKA global period continues to run independently; simultaneously, a brand-new global period begins for the ORIF.

Do not use modifier 79 for procedures performed during the same operative session as the original surgery—the global period does not start until that session ends, so modifier 79 is simply inapplicable intraoperatively. Also avoid modifier 79 on procedure codes assigned a global-days indicator of 000 or XXX in the Medicare Physician Fee Schedule; those codes sit outside the global surgery framework entirely.

Orthopedic scenarios

Concrete situations in orthopedic practice that warrant modifier 79.

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

Patient is 60 days post right TKA (90-day global). She sustains a femoral neck fracture on the left side after a fall. The same orthopaedic surgeon performs a left hip hemiarthroplasty. Bill the hemiarthroplasty with modifier 79 appended; the fracture diagnosis is unrelated to the arthroplasty global period.
Surgeon performs a right shoulder arthroscopic rotator cuff repair (90-day global) on March 1. On April 15, the same patient presents with a locked left knee; the surgeon performs a left knee diagnostic and therapeutic arthroscopy with meniscectomy. Append modifier 79 to the knee arthroscopy code—different limb, different diagnosis, same surgeon, still inside the shoulder global period.
Patient had an ORIF of a left tibial plateau fracture 30 days ago (90-day global). The patient is now seen for a displaced fifth metacarpal fracture of the right hand unrelated to the lower-extremity injury. The same surgeon performs closed reduction and percutaneous pinning of the metacarpal. Report the pinning code with modifier 79.
Spine surgeon performs an L4-L5 posterior lumbar interbody fusion (90-day global) on January 10. On February 20, the same patient suffers a traumatic right clavicle fracture in a car accident. The same spine surgeon—also credentialed in shoulder and upper extremity—performs ORIF of the clavicle. Bill the ORIF with modifier 79 because the clavicle fracture is anatomically and diagnostically unrelated to the lumbar fusion.
Orthopaedic surgeon performs bilateral staged cataract surgeries—wait, wrong specialty. Correct example: surgeon performs arthroscopic ACL reconstruction on the right knee (90-day global). Six weeks later, the same patient tears the left ACL in a separate athletic incident. The surgeon reconstructs the left ACL during the right knee global period. Append modifier 79 to the left-knee ACL reconstruction code; document the separate injury event and distinct diagnosis code.

Common mistakes

Where coders most often go wrong with modifier 79.

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

Using modifier 79 instead of modifier 78 when the second surgery is a complication or direct consequence of the first—modifier 78 is required for related return-to-OR procedures, and misapplying 79 can trigger overpayment audits.
Appending modifier 79 to E&M codes during a global period—modifier 24 governs unrelated E&M visits in the postoperative period; modifier 79 is valid only on surgical procedure codes.
Placing modifier 79 on codes with a global-days indicator of 000 or XXX (e.g., most injections and infusions)—those codes are never subject to global period bundling, making the modifier not just unnecessary but a billing error.
Applying modifier 79 to a staged or pre-planned procedure—if the second surgery was prospectively planned at the time of the original operation, modifier 58 is the correct choice, not 79.
Failing to document that the two procedures are unrelated in the medical record—payers can and do request records to confirm the diagnoses are distinct; absence of supporting documentation leads to denial or recoupment.
Billing both modifier 79 and modifier 78 on the same procedure code—these modifiers are mutually exclusive; only one global-period modifier applies to any single line item.
Assuming modifier 79 overrides multiple-procedure payment reductions—modifier 79 protects against global bundling but does not bypass bilateral fee adjustments, MPPR, or assistant-surgeon fee reductions.

CPT codes that use modifier 79

1,557 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 1,557 by total RVU.

Where modifier 79 shows up

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

Foot & ankle 312 codes
Other 212 codes
Hand 190 codes
Wrist 162 codes

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 10 cited references ↓

01Does modifier 79 reset the global period for the original surgery?

No. The original surgery's global period continues to run on its own schedule. Modifier 79 starts a brand-new, independent global period only for the second (unrelated) procedure. Both global periods run simultaneously after the second procedure is performed.

02How is modifier 79 different from modifier 78?

Modifier 78 signals a return to the OR for a procedure that IS related to—or caused by—the original surgery. Modifier 79 signals a procedure that is completely UNRELATED. The reimbursement consequence differs materially: modifier 78 typically reimburses only the intraoperative component (roughly 70% of the global fee), whereas modifier 79 should reimburse at 100% of the allowed amount for the new procedure.

03Can modifier 79 be used for E&M visits during the global period?

No. Modifier 79 applies exclusively to surgical procedure codes. For an unrelated evaluation and management visit performed during the postoperative period, append modifier 24 to the E&M code instead.

04Is additional documentation required on the claim itself?

Generally no separate attachment is required at the time of submission, but supporting documentation confirming the unrelated nature of the procedures must exist in the patient's medical record and be available on request. Absence of that documentation is the leading cause of recoupment on modifier 79 claims.

05Can modifier 79 be used when both procedures occur on the same calendar day?

Not if they occur in the same operative session—the global period begins only after the session ends, making modifier 79 inapplicable intraoperatively. If a genuinely separate, unrelated procedure is performed later the same day (different operative session, different diagnosis), modifier 79 may be appropriate, though payers will scrutinize same-day claims closely.

06Does modifier 79 bypass multiple-procedure payment reductions?

No. Modifier 79 protects against global-period bundling, but it does not override standard multiple-procedure payment reductions, bilateral fee adjustments, or assistant-surgeon fee adjustments. All other applicable payment rules still apply alongside modifier 79.

07What global-period indicators make modifier 79 valid?

Modifier 79 is valid only when the original surgery carries a global-days indicator of 010 (minor, 10-day global) or 090 (major, 90-day global) in the Medicare Physician Fee Schedule. Procedures coded 000, XXX, or YYY are outside the global surgery framework, and appending modifier 79 to them constitutes a billing error.

Sources & references

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

01AMA CPT Appendix A (Modifiers) — modifier 79 descriptor and usage note
02CMS Medicare NCCI Policy Manual (2025), Chapter 1, Section C — https://www.cms.gov/files/document/2025nccimedicarepolicymanualcompletepdf.pdf
03CMS IOM Pub. 100-04 Medicare Claims Processing Manual, Chapter 12, Sections 40.1 and 40.2
04Novitas Solutions Modifier 79 Fact Sheet — https://www.novitas-solutions.com/webcenter/portal/MedicareJL/pagebyid?contentId=00107559
05First Coast Service Options (FCSO) Medicare — Billing Modifier 79 — https://medicare.fcso.com/coding/billing-modifier-79
06Palmetto GBA Railroad Providers CPT Modifier 79 — https://dominoapps.palmettogba.com/palmetto/rr.nsf/DIDC/8EELFH8311~Claims~Modifier%20Lookup
07AAPC Knowledge Center — When to Use Post-Op Modifiers 58, 78, 79 — https://www.aapc.com/blog/24234-choose-which-modifier-58-78-or-79/
08California Medical Association Coding Corner: How to Apply CPT Modifier 79 — https://www.cmadocs.org/newsroom/news/view/ArticleId/27229/Coding-Corner-How-to-apply-CPT-174-modifier-79
09Premera Blue Cross Payment Policy CP.PP.147 Modifier 79 — https://www.premera.com/portals/provider/paymentpolicies/CMI_051729.pdf
10Providence Health Plan Coding Policy CP72 Modifiers 58, 78, and 79 — https://www.providencehealthplan.com/-/media/providence/website/pdfs/providers/medical-policy-and-provider-information/billing-payment-and-coding-policies/php_coding_72.pdf

Mira AI Scribe

DOCUMENTATION TIP FOR AI SCRIBES — Modifier 79 (Unrelated Procedure During Postoperative Period): For modifier 79 to survive payer audit, the clinical note for the second procedure must clearly establish (1) the new diagnosis is distinct from the diagnosis driving the original surgery, (2) the anatomical site or organ system involved is separate, and (3) the decision to perform the second procedure was not anticipated at the time of the original operation. Capture the mechanism of new injury or new clinical presentation, confirm the treating provider identity matches or falls within the same specialty group, and record that the original postoperative wound or surgical site was not the source of the current complaint. Payers may request records to substantiate the unrelated nature of the service; a note that simply states 'unrelated procedure' without clinical detail is insufficient.

See how Mira flags modifier 79 in dictation