Surgical · Other

LeFort I midface reconstruction split into two segments, moved in any direction, with bone grafts obtained at the same operative session — the classic approach for ungrafted unilateral alveolar clefts.

Verified May 8, 2026 · 5 sources ↓

Medicare: $1,452.94
Total RVUs: 43.5
Global, days: 90
Region: Other

Drawn from CMSEmednyAaomsHca

Documentation requirements

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

Source · Editorial brief grounded in 5 cited references ↓

Operative note must specify the exact number of maxillary segments created and the direction of each segment's movement to distinguish 21146 from 21145 or 21147
Document the autograft harvest site (e.g., iliac crest, cranial calvarium, rib) and confirm harvesting was performed — not use of freeze-dried or synthetic substitute
Confirm and document the underlying diagnosis (e.g., ungrafted unilateral alveolar cleft, malocclusion class, craniofacial syndrome) with a matching ICD-10 code
Pre-operative cephalometric radiographs, dental models or intraoral scans, and facial photographs are required by most payers and Medicaid programs as part of the prior authorization record
If prior authorization was obtained, attach the authorization number to the claim; document that the surgical plan matched the authorized procedure
Note whether the case was performed inpatient (POS 21) or on-campus outpatient hospital (POS 22), as site of service affects facility payment rates significantly

Applicable modifiers

Modifiers commonly billed with this code.

Source · AMA CPT modifier descriptors · CMS NCCI Policy Manual

22 Increased complexity 52 Reduced services 58 Staged or related 78 Unplanned return — related 79 Unrelated during global 80 Assistant surgeon AS PA/NP/CNS assistant

What this code covers

Source · Editorial summary grounded in 5 cited references ↓

CPT 21146 covers a LeFort I osteotomy in which the maxilla is divided into two separate pieces, each repositioned in any direction (advancement, impaction, widening, or combination), with autogenous bone grafts harvested and placed during the same surgery. The parenthetical example — ungrafted unilateral alveolar cleft — signals the typical patient: someone with a persistent bony gap in one side of the alveolar arch that requires simultaneous skeletal mobilization and graft fill. Because graft harvesting is included in the code, do not separately report 21210 (nasal/maxillary graft) when the harvest is part of this procedure.

This code sits in a logical family: 21145 handles the single-piece grafted LeFort I; 21146 handles two pieces; 21147 handles three or more pieces. Choosing the wrong code in the series is the most common coding error — the operative note must explicitly state the number of osteotomy cuts and the resulting segments. A note that just says 'LeFort I with graft' without specifying segment count will not support 21146 over 21145 on audit.

The 90-day global period means all routine post-op visits, splint adjustments, and wire management through day 90 are bundled. Unrelated procedures in that window need modifier 79; a return to the OR for a related complication (e.g., hardware failure requiring revision) needs modifier 78. Many payers — and most state Medicaid programs — require prior authorization for orthognathic surgery. Confirm PA status before scheduling; retroactive denials on a procedure this complex are difficult to overturn.

RVU & reimbursement

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

Source · CMS Physician Fee Schedule, RVU26A · January 2026

Work RVU	24.25
Practice expense RVU	15.74
Malpractice RVU	3.51
Total RVU	43.5
Medicare national rate	$1,452.94
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	$1,452.94
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 21146 get rejected.

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

Wrong code in the LeFort I series — billing 21146 when the operative note supports only a single-piece osteotomy (21145) or does not state segment count
Missing or expired prior authorization — most payers and Medicaid programs require PA for all LeFort orthognathic procedures before the date of service
Cosmetic vs. reconstructive determination — payers deny claims lacking documentation that the procedure addresses a functional or congenital condition rather than purely aesthetic correction
Separate billing of bone graft harvest (e.g., 21210) that is already bundled into 21146 when autografts are obtained at the same session
ICD-10 diagnosis mismatch — filing with a diagnosis code that the payer's LCD or coverage policy does not recognize as a covered indication for LeFort I reconstruction

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 5 cited references ↓

01What is the difference between 21145, 21146, and 21147?

The entire distinction is segment count. 21145 = one-piece grafted LeFort I. 21146 = two pieces with grafts. 21147 = three or more pieces with grafts. The operative note must state the number of segments explicitly; 'LeFort I with graft' alone won't hold up under audit.

02Is bone graft harvesting separately billable with 21146?

No. When autografts are obtained at the same operative session, harvest is included in 21146. Separately billing 21210 or 21215 for the harvest will trigger a bundling edit and likely a denial or takebacks on audit.

03Can I use modifier 52 if a synthetic bone substitute was used instead of autograft?

Yes. If a freeze-dried or synthetic substitute was placed and no surgical harvest was performed, modifier 52 is appropriate because part of the procedure — the harvesting component — was not performed. Reduce the fee accordingly and document the material used.

04Does 21146 require prior authorization?

Most commercial payers and Medicaid programs require PA for all LeFort orthognathic procedures. Washington Apple Health (Medicaid) specifically lists 21146 under EPA #870001539 with required cephalometric x-rays, intraoral scans, and a surgical treatment plan. Confirm with each payer before scheduling.

05What modifiers apply when an assistant surgeon helps with a 21146?

Use modifier 80 for a physician assistant surgeon or modifier AS when the assistant is a non-physician practitioner (PA, NP, CNS). Confirm that the payer and CMS indicator for 21146 allow assistant surgeon billing before submission, as this varies by MAC and commercial contract.

06If the patient returns to the OR during the 90-day global for a related complication, how do I bill?

Bill the return procedure with modifier 78 — unplanned return to the OR for a complication related to the original surgery. If the return procedure is completely unrelated to the LeFort reconstruction, use modifier 79 instead. Do not invert these two modifiers.

07What ICD-10 codes are typically accepted for 21146?

Commonly accepted diagnoses include M26.220 (open bite, unspecified), M26.03 (mandibular excess), M26.02 (maxillary excess), and M26.213 (malocclusion, Angle's class III). Payer LCDs and coverage policies vary — verify the accepted diagnosis list with each payer before billing.

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 number of maxillary osteotomy segments, direction of movement for each piece, graft harvest site and type, and the underlying diagnosis from dictation — the four details auditors check first on a 21146 claim. Locking those specifics into the operative note at dictation time prevents downcoding to 21145 and blocks bundling disputes over separately billed graft codes.

See how Mira captures CPT 21146 documentation