Arthrodesis of the thumb carpometacarpal joint using an autogenous bone graft, with or without internal fixation; graft harvest is included in the code.

Verified May 8, 2026 · 6 sources ↓

Medicare: $815.98
Total RVUs: 24.43
Global, days: 90
Region: Hand

Drawn from CMSFastrvuEmednyEatonhandMdclarity

Documentation requirements

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

Source · Editorial brief grounded in 6 cited references ↓

Specify the diagnosis driving fusion (e.g., primary osteoarthritis, post-traumatic arthritis, instability) with a supporting ICD-10 code
Confirm autograft was harvested and document the donor site location (e.g., distal radius, iliac crest)
Describe internal fixation method if used (e.g., K-wires, screw, plate) — absence does not change the code but absence of documentation invites queries
Document failed conservative treatment (splinting, corticosteroid injections) to establish medical necessity
Record the surgical approach and joint preparation technique — operative notes that reference only 'standard approach' are audit flags
Note intraoperative fluoroscopy or imaging if used to confirm hardware position

Applicable modifiers

Modifiers commonly billed with this code.

Source · AMA CPT modifier descriptors · CMS NCCI Policy Manual

22 Increased complexity 50 Bilateral procedure 51 Multiple procedures 58 Staged or related 59 Distinct service 78 Unplanned return — related 79 Unrelated during global 80 Assistant surgeon LT Left side RT Right side

What this code covers

Source · Editorial summary grounded in 6 cited references ↓

CPT 26842 covers surgical fusion of the thumb's carpometacarpal (CMC) joint — where the first metacarpal meets the trapezium — using bone harvested from the patient's own body. The autograft harvest is bundled into 26842; don't bill a separate graft procurement code (e.g., 20900-series). Internal fixation, when used, is also included and not separately reportable.

The procedure is performed primarily for advanced basal joint arthritis or post-traumatic instability where conservative measures have failed. The goal is permanent elimination of painful CMC motion. The 90-day global period means all routine post-op care through day 90 — splint checks, suture removal, routine radiographs interpreted by the operating surgeon, and standard fusion monitoring — is bundled. Services outside the global for unrelated conditions require modifier 24; related staged work requires modifier 58.

Compare to the parent code 26841, which covers CMC thumb arthrodesis without autograft. If the surgeon uses allograft or synthetic graft material instead of autograft, 26841 is the correct code. Billing 26842 when no autograft was harvested is a common audit trigger.

RVU & reimbursement

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

Source · CMS Physician Fee Schedule, RVU26A · January 2026

Work RVU	8.28
Practice expense RVU	14.39
Malpractice RVU	1.76
Total RVU	24.43
Medicare national rate	$815.98
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	$815.98
HOPD (APC 5114) Hospital outpatient department	$7,413.38
ASC (PI A2) Ambulatory surgical center (freestanding)	$3,695.53

Common denial reasons

The recurring reasons claims for CPT 26842 get rejected.

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

Billing 26842 when autograft harvest is not documented — payers default to 26841 and adjust payment accordingly
Separate billing of bone graft procurement codes (20900-20924) alongside 26842 — graft harvest is bundled by code definition per NCCI policy
Missing or inadequate medical necessity documentation; no evidence of failed conservative care prior to surgery
Unbundling internal fixation or fluoroscopy as separate line items when performed as part of the fusion
Modifier absent when billing during another surgeon's global period for an unrelated procedure (modifier 79 required)

Frequently asked questions

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

01What is the difference between CPT 26841 and 26842?

26841 is CMC thumb arthrodesis without autograft. 26842 adds autograft harvest from the patient's own body. If you used allograft or no graft at all, bill 26841.

02Can I separately bill for bone graft harvest when billing 26842?

No. The autograft harvest is included in the 26842 descriptor and is not separately reportable. Billing 20900 or similar graft procurement codes alongside 26842 violates NCCI bundling rules.

03What global period applies to 26842, and what does it include?

26842 carries a 90-day global. The day before surgery, the surgery itself, and all routine post-op visits, splint checks, suture removal, and related radiograph interpretations by the operating surgeon through day 90 are bundled. Use modifier 24 for unrelated E/M visits and modifier 79 for unrelated procedures during that window.

04When is modifier 22 appropriate with 26842?

Use modifier 22 when the procedure required substantially more work than typical — for example, severely deformed anatomy, prior hardware removal complicating the fusion, or an exceptionally difficult graft harvest. Attach a letter of medical necessity explaining the increased complexity; without documentation, payers routinely ignore modifier 22.

05Can 26842 be billed bilaterally?

Yes. Use modifier 50 if both CMC thumb joints are fused in the same operative session. Some payers want LT and RT on separate lines instead of modifier 50 — verify payer preference before submitting.

06Is 26842 performed in ASC or HOPD settings, and does the site affect payment?

26842 is performed in both settings. ASC and HOPD facility payments differ — see the Site of Service comparison on this page. Physician RVU-based reimbursement is the same regardless of facility site.

07What ICD-10 codes most commonly support 26842 medical necessity?

Primary osteoarthritis of the first CMC joint (M18.11/M18.12 for unilateral), post-traumatic arthritis (M19.211/M19.212), and instability or chronic subluxation of the CMC joint are the primary drivers. Payers expect the diagnosis to reflect failure of non-surgical management.

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 autograft donor site, joint preparation detail, fixation method, and intraoperative imaging from dictation — the exact elements payers audit when distinguishing 26842 from 26841. Documenting the donor site by name prevents downcoding to the no-graft parent code and defends against graft-harvest unbundling denials.

See how Mira captures CPT 26842 documentation