Surgical · Other

Reconstruction of the orbital walls, rims, forehead, and nasoethmoid complex after intra- and extracranial excision of a benign cranial bone tumor, using multiple autografts with a total bone-graft area exceeding 80 square centimeters — graft harvesting is included.

Verified May 8, 2026 · 7 sources ↓

Medicare: $2,154.36
Total RVUs: 64.5
Global, days: 90
Region: Other

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Documentation requirements

What must appear in the operative or office note to support the claim.

Source · Editorial brief grounded in 7 cited references ↓

Measured total autograft surface area explicitly documented as greater than 80 sq cm to distinguish 21184 from 21183 and 21182
Operative note confirming both intracranial and extracranial tumor excision preceded the reconstruction
Identification of the benign tumor type (e.g., fibrous dysplasia) with pathology or preoperative imaging correlation
Anatomic structures reconstructed named specifically: orbital walls, rims, forehead, nasoethmoid complex — or subset thereof
Graft donor site documented, including harvest technique and confirmation that procurement is not billed separately
Number and configuration of autografts used to support 'multiple autografts' descriptor in the code

Applicable modifiers

Modifiers commonly billed with this code.

Source · AMA CPT modifier descriptors · CMS NCCI Policy Manual

22 Increased complexity 51 Multiple procedures 52 Reduced services 58 Staged or related 59 Distinct service 62 Co-surgeons 74 Discontinued post-anesthesia 78 Unplanned return — related 79 Unrelated during global 80 Assistant surgeon AS PA/NP/CNS assistant LT Left side RT Right side

What this code covers

Source · Editorial summary grounded in 7 cited references ↓

CPT 21184 covers the most extensive tier of cranial bone reconstruction following excision of a benign skull tumor such as fibrous dysplasia. The procedure addresses the orbital walls and rims, forehead, and nasoethmoid complex after both intracranial and extracranial tumor removal, and requires multiple autografts totaling more than 80 sq cm. Graft harvesting is bundled into the code — do not separately report bone graft procurement.

The 21182–21184 family is tiered strictly by total autograft surface area: 21182 for less than 40 sq cm, 21183 for 40–80 sq cm, and 21184 for greater than 80 sq cm. The operative note must document the measured graft area to justify 21184 over the lower-tier codes. Choosing the wrong tier based on vague or absent measurements is a top audit trigger for this code family.

21184 carries a 90-day global period. All routine follow-up through day 90 is included. Return visits for complications related to the original reconstruction require modifier 78. Unrelated procedures in the global window need modifier 79. The NCCI edit table for 21184 is extensive — over 1,000 PTP edit pairs — so scrub co-billed codes carefully before submission, particularly any separately reported graft harvesting or bone contouring codes.

RVU & reimbursement

Component RVUs and Medicare national rate. Actual payment varies by GPCI locality.

Source · CMS Physician Fee Schedule, RVU26A · January 2026

Work RVU	37.65
Practice expense RVU	19.84
Malpractice RVU	7.01
Total RVU	64.5
Medicare national rate	$2,154.36
Global period	90 days

Payment by site of service

Medicare pays different rates by setting. HOPD typically pays substantially more than ASC for the same procedure.

Source · CMS OPPS Addendum B·ASC HCPCS payment rates·2026

Setting	Medicare rate (national)
Office (PFS non-facility) Procedure performed in physician's office	$2,154.36
HOPD (APC 5165) Hospital outpatient department	$6,048.05
ASC (PI J8) Ambulatory surgical center (freestanding)	$3,833.49

Common denial reasons

The recurring reasons claims for CPT 21184 get rejected.

Source · Editorial brief grounded in CMS NCCI edits, AAOS coding appeals, and cited references ↓

Graft area not documented or not measured — payer downcodes to 21183 or 21182
Bone graft harvesting billed as a separate code when it is already included in 21184
Missing documentation of both intracranial and extracranial components of tumor excision, causing payer to reject the reconstruction claim
Co-billed codes triggering NCCI PTP bundling edits without a valid modifier to bypass the edit
Routine post-op visits billed within the 90-day global period without modifier 24 for unrelated E/M services

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 7 cited references ↓

01What separates 21184 from 21183 and 21182?

Total autograft surface area is the only differentiator. 21182 applies when the graft area is less than 40 sq cm, 21183 for 40–80 sq cm, and 21184 for greater than 80 sq cm. The surgeon must measure and document the area in the operative note — estimated or undocumented area defaults to the lower-tier code on audit.

02Is bone graft harvesting separately billable with 21184?

No. The code descriptor explicitly includes obtaining the autografts. Billing a separate graft procurement code alongside 21184 will trigger a bundling denial under NCCI PTP edits.

03Can 21184 be billed with modifier 22 for unusual procedural complexity?

Yes, if the reconstruction involved documented complexity beyond the typical procedure — for example, unusually extensive tumor involvement requiring additional operative time. The operative note must quantify the extra work; a generic statement of complexity will not support modifier 22 on audit.

04What global period applies and how does it affect post-op billing?

21184 carries a 90-day global period. All routine post-op care through day 90 is bundled. Use modifier 78 for an unplanned return to the OR for a related complication. Use modifier 79 for an unrelated procedure in the global window. Use modifier 24 on E/M visits that are clearly unrelated to the original reconstruction.

05Does 21184 require a specific diagnosis code to support medical necessity?

Payers expect an ICD-10 code corresponding to a benign cranial bone tumor — fibrous dysplasia (M85.0x) is the most common. Malignant tumor diagnoses do not map to this code, which is defined for benign tumors. Confirm the pathology report aligns with the diagnosis before billing.

06How should a co-surgeon arrangement be billed for 21184?

When two surgeons of different specialties each perform a distinct portion of the procedure, both may bill 21184 with modifier 62. Each surgeon's operative note must describe their specific contribution. If one surgeon assists without performing a distinct part, modifier 80 or AS applies instead.

Sources & references

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

Mira AI Scribe

Mira's AI scribe captures the total measured autograft surface area, the specific anatomic structures reconstructed (orbital walls, rims, forehead, nasoethmoid complex), confirmation of both intracranial and extracranial tumor excision, and the graft donor site from surgeon dictation. This prevents downcoding to 21183 or 21182 due to missing area measurements and eliminates the audit flag that fires when the operative note omits the intracranial excision component.

See how Mira captures CPT 21184 documentation