Open surgical treatment of a depressed zygomatic arch fracture, involving direct incision, fracture reduction, and stabilization of the cheekbone prominence.

Verified May 8, 2026 · 6 sources ↓

Medicare: $593.20
Work RVU: 4.71
Global, days: 10
Region: Other

Drawn from CMSMedicalbillgurusMdclarity

Documentation requirements

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

Source · Editorial brief grounded in 6 cited references ↓

Specify fracture location as zygomatic arch — not simply 'malar' or 'ZMC' — to justify 21356 over adjacent codes
Document the surgical approach by name (e.g., temporal, coronal, preauricular, intraoral Gillies) — notes that say 'standard approach' draw audit flags
Confirm open reduction was performed, not percutaneous instrumentation, which maps to 21355
Describe the degree of depression and comminution to support medical necessity and any modifier 22 claim
Record whether internal fixation was placed; its absence distinguishes 21356 from higher-complexity ZMC codes
Include preoperative imaging (CT facial bones preferred) confirming isolated zygomatic arch fracture with depression
Document any concurrent procedures (e.g., orbital floor repair, soft tissue reconstruction) separately with their own CPT codes

Applicable modifiers

Modifiers commonly billed with this code.

Source · AMA CPT modifier descriptors · CMS NCCI Policy Manual

22 Increased complexity 51 Multiple procedures 58 Staged or related 59 Distinct service 76 Repeat, same physician 77 Repeat, another physician 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 6 cited references ↓

CPT 21356 covers open treatment of a depressed zygomatic arch fracture. The surgeon makes a direct incision to access the fractured arch, reduces the depressed segment, and stabilizes the repair. This is distinct from percutaneous approaches (21355) and from broader zygomaticomaxillary complex (ZMC) repairs (21360–21366), which involve additional bony structures, bone grafts, or orbital components. Selecting the wrong code in this family is a primary audit trigger — the operative note must clearly document that the zygomatic arch (not the full ZMC) was the target, and that the approach was open.

The global period is 10 days. That covers the day-of and routine post-op follow-up through day 10. Any unrelated E/M or procedure in that window needs modifier 24 or 79, respectively. If the patient returns to the OR for a complication related to the original repair — hardware irritation, malreduction, wound dehiscence — bill modifier 78. For an unrelated problem requiring OR intervention, use modifier 79.

This code appears in the maxillofacial fracture surgery family and is performed most often by oral-maxillofacial surgeons, plastic surgeons, and ENT/facial trauma specialists. When billed in an HOPD setting, the site-of-service differential versus the ASC is significant; see the payment comparison table on this page.

RVU & reimbursement

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

Source · CMS Physician Fee Schedule, RVU26A · January 2026

Work RVU vs. total RVU

The work RVU (4.71) is the surgeon's own effort — the figure physician pay and productivity targets are built on. The total RVU (17.76) adds practice overhead and malpractice, and is what drives the Medicare payment below.

Work RVU	4.71
Practice expense RVU	12.17
Malpractice RVU	0.88
Total RVU	17.76
Medicare national rate	$593.20
Global period	10 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	$593.20
HOPD (APC 5165) Hospital outpatient department	$6,048.05
ASC (PI A2) Ambulatory surgical center (freestanding)	$3,025.62

Common denial reasons

The recurring reasons claims for CPT 21356 get rejected.

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

Upcoding flag: operative note documents full ZMC involvement but only 21356 is billed — payers and auditors expect 21360–21366 when multiple ZMC buttresses are repaired
Undercoding caught in RAC audit: note describes internal fixation or bone graft but 21356 was submitted instead of a higher-complexity code
Insufficient documentation of open approach — notes referencing only an elevator or percutaneous instrument without a named incision may be reclassified to 21355
Missing or inadequate preoperative imaging documentation to establish medical necessity for open versus closed treatment
Global period billing conflict: E/M visit within 10-day global submitted without modifier 24, triggering automatic bundling denial

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 6 cited references ↓

01What separates 21356 from 21355 and 21360?

21355 is percutaneous treatment of the zygomatic arch — no open incision. 21356 is open treatment of the isolated zygomatic arch. 21360 steps up to open treatment of the full zygomaticomaxillary complex without bone graft. If your operative note documents incisions at multiple ZMC buttresses or orbital involvement, 21356 is the wrong code.

02Does 21356 include internal fixation?

No. 21356 describes open reduction without internal fixation of the isolated zygomatic arch. If plates and screws were placed, review whether the work maps to a higher-complexity ZMC code. Document fixation hardware explicitly so the code selection is defensible on audit.

03What is the global period for 21356?

Ten days. Routine post-op care through day 10 is bundled. Bill modifier 24 on an E/M for an unrelated problem during that window, modifier 78 if the patient returns to the OR for a related complication, and modifier 79 for an unrelated OR procedure.

04Can 21356 be billed with orbital floor repair (21385/21386) on the same day?

Yes, if both procedures were independently performed and documented. Use modifier 51 on the secondary procedure. The operative note must clearly describe both the zygomatic arch repair and the orbital floor work as distinct interventions — combined notes that don't delineate the procedures are a bundling denial risk.

05When is modifier 22 appropriate with 21356?

When the procedure required substantially more work than typical — severe comminution, prior surgical scarring, delayed presentation with callus formation, or unusually prolonged operative time. Attach a cover letter quantifying the additional work and time. Without that narrative, most payers deny modifier 22 as unsupported.

06Is prior authorization required for 21356 in the outpatient hospital setting?

21356 does not appear on CMS's outpatient department prior authorization list. However, commercial payers and Medicaid programs vary — verify with the specific payer before scheduling elective repair, particularly for delayed or reconstructive cases.

Sources & references

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

Mira Scribe

Mira's AI scribe captures the surgical approach by name, documents the specific anatomical target (zygomatic arch vs. full ZMC), records the presence or absence of internal fixation, and flags concurrent procedures for separate CPT assignment. This prevents the most common denial pattern for 21356: an operative note that describes the anatomy ambiguously enough that a payer's auditor reassigns the claim to 21355 or escalates it to a ZMC code requiring additional documentation.

See how Mira captures CPT 21356 documentation