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Billing code 31040: Fossa explorationMedicare rate & RVUs

Operative exploration of the pterygomaxillary fossa behind the upper jaw, reported when the surgeon directly investigates this deep space.

CMS RVU26DEffective Oct 1, 2026109 payment localities144 Medicare services in 2024

Medicare pays $721.79 for 31040 nationally in a facility.

Medicare rate · 31040

Fossa exploration

Swap in your local Medicare rate.

Work RVUs
9.53
Total RVUs
21.61
Global days
090

National rate · 2026

$721.79

Facility setting, before claim adjustments.

See every locality for 31040 → · Billed by an NP, PA or therapist? →

Medicare allowed amount for participating (non-QP) physicians, before deductible, coinsurance and claim adjustments. Not a patient’s bill or a hospital charge.

On this page 10 sections
  1. Medicare rate
  2. What 31040 covers
  3. By payment locality
  4. Rate map
  5. How it’s calculated
  6. Payment rules
  7. Similar codes
  8. Related codes
  9. Billing questions
  10. Sources

What 31040 covers

This operation gives the surgeon access to and permits direct inspection of the pterygomaxillary fossa, a deep space behind the upper jaw. It is distinct from opening or irrigating a paranasal sinus. Otolaryngologists and oral and maxillofacial or head and neck surgeons may perform it in an operating room, generally in a facility setting. The operative report should identify the fossa as the target and describe the approach and exploration performed.

Report 31040 when the documented service is exploration of this space, rather than a maxillary or sphenoid sinus procedure. The 90-day global period includes the day-before preoperative visit and 90 days of related postoperative care. When multiple procedures occur in the same session, the highest-valued procedure is paid in full and other procedures are subject to the standard 50% reduction. Modifier 50 is paid at 150% for bilateral procedures. Medicare does not pay an assistant at surgery; co-surgeons require supporting documentation, and team surgery is not permitted.

This summary was written with AI assistance from CMS physician fee schedule data and checked against the CMS billing rules shown here. Rates on this page come directly from CMS files.

Where 31040 pays more and less

The same RVUs, adjusted for each area’s costs. Open a locality for its calculation, history and nearby areas.

109 of 109 payment localities

31040 office and facility rates by payment locality
Payment localityOfficeFacility
AlabamaUnavailable$656.60
Alaska*Unavailable$882.62
ArizonaUnavailable$703.89
ArkansasUnavailable$648.47
AtlantaUnavailable$738.04
AustinUnavailable$737.62
BakersfieldUnavailable$743.31
Baltimore/Surr. CntysUnavailable$764.17
BeaumontUnavailable$686.39
BrazoriaUnavailable$710.63

31040 rates by state

Office rate range in each state. Select a state to see its payment localities.

MEWIVTNHMTNDMNMINYMARIWAIDWYSDIAILINOHPANJCTORNVUTCONEMOKYWVVAMDDECAAZNMKSOKARTNNCSCDCTXLAMSALGAFLAKHI

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Local rates. Clear comparisons.

Hover or focus a tile to see its rate range. Select it to open the state’s fee schedule.

View every state and territory as a table
31040 office rate range by state
State / territoryOffice rate rangeLocalities
AKNo published base rate1
ALNo published base rate1
ARNo published base rate1
AZNo published base rate1
CANo published base rate29
CONo published base rate1
CTNo published base rate1
DCNo published base rate1
DENo published base rate1
FLNo published base rate3
GANo published base rate2
GUNo published base rate1
HINo published base rate1
IANo published base rate1
IDNo published base rate1
ILNo published base rate4
INNo published base rate1
KSNo published base rate1
KYNo published base rate1
LANo published base rate2
MANo published base rate2
MDNo published base rate3
MENo published base rate2
MINo published base rate2
MNNo published base rate1
MONo published base rate3
MSNo published base rate1
MTNo published base rate1
NCNo published base rate1
NDNo published base rate1
NENo published base rate1
NHNo published base rate1
NJNo published base rate2
NMNo published base rate1
NVNo published base rate1
NYNo published base rate5
OHNo published base rate1
OKNo published base rate1
ORNo published base rate2
PANo published base rate2
PRNo published base rate1
RINo published base rate1
SCNo published base rate1
SDNo published base rate1
TNNo published base rate1
TXNo published base rate8
UTNo published base rate1
VANo published base rate2
VINo published base rate1
VTNo published base rate1
WANo published base rate2
WINo published base rate1
WVNo published base rate1
WYNo published base rate1

How the 31040 rate is calculated

Each of 31040’s three RVUs is multiplied by a geographic index (GPCI) for the payment locality, added up, and multiplied by the conversion factor. Drag the indexes or enter a ZIP to see what moves the rate.

How the rate is built · 31040

RVUs × geographic indexes × conversion factor

Swap in your local Medicare rate.

Work 9.53Practice expense 10.65Malpractice 1.43

21.6100 adjusted RVUs×$33.4009 conversion factor=$721.79

All indexes start at 1.000 (the national rate). Enter a ZIP or drag a slider.

Payment rules and modifiers for 31040

31040 has a 90-day global period: related visits in that window are included in the surgery payment.

CMS payment indicators · 31040

Fossa exploration

RuleCMS valueWhat it means
Global period090Major surgery: the day before, the day of, and 90 days after are included.
Multiple procedures2Standard reduction: highest-valued procedure at 100%, others at 50%.
Bilateral (modifier 50)1Bilateral with modifier 50 pays 150% of the fee schedule amount.
Assistant at surgery (80/81/82/AS)1Not paid (statutory restriction).
Co-surgeons (62)1Permitted with supporting documentation.
Team surgery (66)0Not permitted.
Professional/technical0Physician service: no professional/technical split.
Split (54/55/56)0.10/0.76/0.14Share of the payment for pre-op, the procedure itself, and post-op care.

Global surgery period · 31040

Fossa exploration

90-day global period ends

Dec 30, 2026

Covers Sep 30, 2026 through Dec 30, 2026 (92 days, including the day before surgery).

Visit on Oct 31, 2026

Day 30 of the 90-day post-op period: related follow-up care is included in the surgical payment.

  • 24 Unrelated E/M visit by the same physician
  • 79 Unrelated procedure (starts its own global period)
  • 58 Staged, more extensive, or therapy procedure that was planned
  • 78 Unplanned return to the operating room for a related complication
SurgeryVisit
Sep 23, 2026Jan 10, 2027

Pre-op dayGlobal period

What modifiers do to the payment

Modifier 50 · payment effect

With and without the modifier

31040 without 50 · national facility

$721.79

Fossa exploration

31040-50 · Bilateral: 150%

$1,082.69

Both sides on one line with modifier 50 are paid at 150% of the fee schedule amount (subject to multiple-procedure rules with other procedures).

When to use modifier 50

31040 compared with similar codes

Compare codes

31040 vs 31020 vs 31030 vs 31050: national Medicare rates

Swap in your local Medicare rate.

  • 31040
    Fossa exploration · 9.53 wRVU
    —
  • 31020
    Maxillary sinusotomy · 2.99 wRVU
    $431.87
  • 31030
    Sinus exploration · 5.86 wRVU
    $652.32
  • 31050
    Sphenoid sinus surgery · 5.24 wRVU
    —

How to choose

31020Maxillary sinusotomy
Choose 31040 for exploration of the pterygomaxillary fossa behind the upper jaw. Code 31020 concerns a maxillary sinus procedure.
31030Sinus exploration
Code 31030 describes a radical maxillary sinus procedure; 31040 targets exploration of the adjacent pterygomaxillary fossa.
31050Sphenoid sinus surgery
Code 31050 targets the sphenoid sinus. Use 31040 when the operative exploration is of the pterygomaxillary fossa.

Codes related to 31040

Related codes aren’t interchangeable: bill the code that matches the service performed.

Codes related to 31040
CodeHow it relatesNational office range
Same family
31020Maxillary sinusotomyRelated sinus-surgery code, but it targets the maxillary sinus rather than the pterygomaxillary fossa.$380.81–$578.41
31030Sinus explorationMaxillary sinus surgery in the same broad procedural range; the operative target differs.$578.98–$852.06
31050Sphenoid sinus surgeryRelated sinus-surgery code targeting the sphenoid sinus, not the pterygomaxillary fossa.No office rate

31040 billing questions

How does 31040 differ from maxillary sinus surgery?

31040 targets the pterygomaxillary fossa behind the upper jaw. Codes for maxillary sinus procedures target the sinus itself.

What documentation supports 31040?

The operative report should identify the pterygomaxillary fossa as the site explored and describe the surgical access and exploration.

Does the 90-day global period include related postoperative care?

Yes. It includes the day-before preoperative visit and 90 days of related postoperative care.

How is a bilateral procedure reported?

Use modifier 50 for a bilateral procedure; CMS pays it at 150%.

Can an assistant or co-surgeon be paid?

Medicare does not pay an assistant at surgery for this code. Co-surgeons are paid only with supporting documentation.

What happens when other procedures are performed in the same session?

The highest-valued procedure is paid in full, and other procedures are subject to the standard multiple procedure reduction.

Where these rates come from

FeeBase calculates base physician payments from CMS work, practice-expense and malpractice RVUs, adjusted by each locality’s geographic indexes and the conversion factor. Services without a published rate are labeled, never given a made-up amount. Amounts are Medicare allowed amounts before claim adjustments: not a patient’s bill or a commercial rate.

CMS RVU26D · effective Oct 1, 2026 through the day before Jan 1, 2027

Show the CMS file lines behind this rate
RVUs for 31040PPRRVU2026_Oct_nonQPP.csv, line 3,499 (RVU26D)

Open CMS sourceHow we calculate rates

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