Division of the scalenus anticus muscle at the neck to relieve nerve and vascular compression caused by scalenus anticus syndrome, performed without resection of a cervical rib.

Verified May 8, 2026 · 5 sources ↓

Medicare: $332.34
Work RVU: 6.15
Global, days: 90
Region: Other

Drawn from CMSEmednyAAPC

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 name the scalenus anticus (anterior scalene) muscle explicitly as the structure divided — generic 'neck muscle revision' is insufficient.
Document the surgical approach by name (supraclavicular, anterior cervical) and confirm no cervical rib resection was performed, distinguishing 21700 from 21705.
Preoperative clinical findings establishing scalenus anticus syndrome: arm pain, paresthesias, vascular symptoms, and provocative test results (Adson, elevated-arm stress test).
Record failure or inadequacy of conservative management (physical therapy, activity modification) prior to surgical intervention to satisfy medical necessity requirements.
Anesthesia type, patient positioning, and intraoperative findings including degree of muscle tension and neurovascular involvement.
Postoperative neurovascular status documented in the recovery note to establish baseline for the 90-day global period.

Applicable modifiers

Modifiers commonly billed with this code.

Source · AMA CPT modifier descriptors · CMS NCCI Policy Manual

22 Increased complexity 24 Unrelated E/M during global 51 Multiple procedures 57 Decision for surgery 58 Staged or related 59 Distinct service 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 5 cited references ↓

CPT 21700 describes open division of the scalenus anticus muscle — the procedure of choice when this anterior scalene muscle compresses the brachial plexus or subclavian vessels, producing the clinical picture of scalenus anticus syndrome. The surgeon divides the muscle at its insertion on the first rib through a supraclavicular or anterior cervical approach. No cervical rib resection is performed; if that step is added, bill 21705 instead.

The 90-day global period means all routine follow-up through day 90 is bundled. Separate E/M visits during the global window require modifier 24 (unrelated) or modifier 79 (unrelated surgical procedure). A new, distinct problem presenting postoperatively is the threshold — not patient inconvenience or routine wound checks.

Scalenus anticus syndrome overlaps diagnostically with thoracic outlet syndrome (TOS). ICD-10 specificity matters here: payers scrutinize the clinical distinction between neurogenic TOS and vascular TOS, and some require documented failure of conservative treatment before authorizing surgical intervention. Make sure the diagnosis code on the claim matches the documented pathology driving the division.

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 (6.15) is the surgeon's own effort — the figure physician pay and productivity targets are built on. The total RVU (9.95) adds practice overhead and malpractice, and is what drives the Medicare payment below.

Work RVU	6.15
Practice expense RVU	2.23
Malpractice RVU	1.57
Total RVU	9.95
Medicare national rate	$332.34
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	$332.34
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 21700 get rejected.

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

Medical necessity denial when documentation lacks objective findings or imaging correlating with scalenus anticus syndrome and does not show prior conservative treatment failure.
Upcoding/wrong-code denial when cervical rib resection is documented intraoperatively but 21700 is billed instead of 21705.
Separate E/M visit billed during the 90-day global period without modifier 24, causing automatic bundling denial.
Diagnosis-procedure mismatch when a thoracic outlet or cervical radiculopathy ICD-10 code is used without specificity linking it to anterior scalene pathology.
Prior authorization missing or expired at time of service, particularly for commercial and managed care payers requiring documented conservative-treatment step therapy.

Frequently asked questions

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

01What is the difference between CPT 21700 and 21705?

21700 is division of the scalenus anticus muscle alone. 21705 adds resection of a cervical rib at the same operation. If you perform both, bill 21705 — not 21700 with an add-on.

02Can I bill a same-day E/M with 21700?

Yes, if the decision for surgery is made at that visit. Append modifier 57 to the E/M when it represents the decision-making encounter for a procedure with a 90-day global.

03What ICD-10 codes support medical necessity for 21700?

Scalenus anticus syndrome maps most directly to thoracic outlet syndrome codes (G54.2 for neurogenic TOS, vascular TOS under I77-range). Confirm the documented clinical diagnosis and use the most specific code available. Payer LCDs may enumerate required diagnoses — check the applicable MAC.

04Is 21700 performed bilaterally? How do I bill that?

Bilateral scalenus anticus division is uncommon but possible. If performed at the same session through separate incisions, append modifier 50. Some payers prefer LT/RT on separate lines — verify the payer's bilateral billing preference before submitting.

05What happens if a return to the OR is needed within the 90-day global?

Use modifier 78 for an unplanned return to the OR for a complication related to 21700 (e.g., hematoma evacuation at the same neck site). Use modifier 79 for an unrelated surgical procedure during the global period.

06Does modifier 22 apply if the procedure is unusually complex?

Yes, but documentation must explicitly describe what made the work substantially greater than typical — dense adhesions, aberrant anatomy, prolonged operative time with explanation. Without that narrative, payers routinely reject modifier 22 claims.

Sources & references

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

Mira Scribe

Mira's AI scribe captures the muscle name (scalenus anticus), surgical approach, absence of cervical rib resection, and preoperative neurovascular findings directly from dictation — preventing the most common audit flag on 21700, which is an operative note that documents 'neck muscle division' without confirming the specific structure and ruling out 21705-level work.

See how Mira captures CPT 21700 documentation