Surgical transfer of the external oblique abdominal muscle to the greater trochanter to restore hip abductor function lost to paralysis.

Verified May 8, 2026 · 6 sources ↓

Medicare: $778.24
Work RVU: 11.07
Global, days: 90
Region: Hip

Drawn from CMSAAPCFastrvuFindacodeEmedny

Documentation requirements

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

Source · Editorial brief grounded in 6 cited references ↓

Documented diagnosis of hip abductor paralysis with etiology (e.g., poliomyelitis sequela, neurologic injury) supporting medical necessity for muscle transfer
Operative note naming the donor muscle (external oblique) and the recipient attachment site (greater trochanter) explicitly — do not use generic language like 'muscle transfer performed'
Description of the surgical approach, dissection planes, and method of fixation at the greater trochanter
Preoperative assessment confirming paralysis or severe insufficiency of native hip abductors, distinguishing this from tendon repair or reinforcement
Documentation of failed or non-applicable conservative management prior to surgical intervention
Laterality clearly stated (left, right) in both the operative report and the diagnosis coding

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 50 Bilateral procedure 51 Multiple procedures 52 Reduced services 58 Staged or related 59 Distinct service 62 Co-surgeons 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 6 cited references ↓

CPT 27100 describes a reconstructive procedure in which the external oblique muscle — the largest and most superficial muscle of the anterolateral abdominal wall — is detached and rerouted to the greater trochanter of the femur. The purpose is to substitute for paralyzed hip abductor musculature, restoring the active abduction strength needed for stable gait. This is a salvage-level reconstruction, not a routine hip procedure, and its indication must be clearly documented.

The code carries a 90-day global period. All routine follow-up within that window — wound checks, suture removal, therapy coordination visits — is bundled. Any visit for a separate, unrelated condition during the global requires modifier 24. An unrelated surgical procedure in the same window requires modifier 79; a related return to the OR requires modifier 78.

Site of service matters here. The HOPD and ASC facility payments differ substantially — see the Site of Service comparison table. The physician professional fee is the same regardless of site, but where you schedule the case affects total episode cost and patient liability.

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 (11.07) is the surgeon's own effort — the figure physician pay and productivity targets are built on. The total RVU (23.3) adds practice overhead and malpractice, and is what drives the Medicare payment below.

Work RVU	11.07
Practice expense RVU	9.87
Malpractice RVU	2.36
Total RVU	23.3
Medicare national rate	$778.24
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	$778.24
HOPD (APC 5114) Hospital outpatient department	$7,413.38
ASC (PI J8) Ambulatory surgical center (freestanding)	$4,754.22

Common denial reasons

The recurring reasons claims for CPT 27100 get rejected.

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

Medical necessity not established — payer requires documented neurologic or paralytic diagnosis; a general 'hip weakness' notation is insufficient
Operative report fails to name the specific donor muscle and recipient site, causing the claim to be down-coded or denied for incomplete documentation
Modifier 24 or 79 missing when the case is billed during another surgeon's or the same surgeon's global period for a prior hip procedure
Incorrect ICD-10 linkage — sequela coding for polio or neurologic conditions requires the correct seventh character or sequela code suffix; mismatch triggers automatic denial
Bilateral modifier 50 applied without payer authorization — this procedure is rarely performed bilaterally and payers may require clinical justification before processing a bilateral claim

Frequently asked questions

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

01What ICD-10 codes typically support medical necessity for CPT 27100?

Sequela of poliomyelitis (B91), late effects of other paralytic conditions, and traumatic or surgical nerve injuries affecting the superior gluteal nerve are the most common supporting diagnoses. The diagnosis must reflect paralysis or severe functional loss of the hip abductors — not just weakness — and sequela codes require correct coding convention with the 'S' seventh character or separate sequela code.

02Is CPT 27100 ever billed with other hip reconstruction codes on the same day?

It can be, but modifier 51 is required on the secondary procedure. If a concurrent bony procedure or total hip arthroplasty is performed, document each procedure's distinct purpose. NCCI edits may bundle certain pelvic/hip codes — check the NCCI table before submitting the pair, and use modifier 59 or XS only when the edits are genuinely bypassable.

03Does the 90-day global period affect post-op PT orders billed under the surgeon's NPI?

Therapy billed under the surgeon's NPI is bundled in the global. Therapy billed independently by a physical therapist under their own NPI is not. If your practice employs the therapist and bills incident-to, the bundling analysis changes — confirm with your payer.

04When should modifier 22 be used with 27100?

Modifier 22 applies when the procedure is substantially more complex than typical — for example, a patient with prior pelvic surgery, significant scarring, or altered anatomy requiring extended dissection time. You need documentation of the increased complexity in the operative note and a cover letter explaining the additional work when submitting the claim.

05How does site of service affect reimbursement for CPT 27100?

The surgeon's professional fee is site-neutral. Facility reimbursement differs — HOPD pays the hospital more than the ASC rate. For patients with high cost-sharing, the ASC setting typically reduces out-of-pocket exposure. Factor site of service into pre-authorization conversations, as some payers require ASC-first for elective reconstructive cases.

06Is prior authorization typically required for CPT 27100?

Yes — this is a high-RVU reconstructive procedure with a narrow clinical indication. Most commercial payers and Medicare Advantage plans require prior authorization. Submit the neurologic diagnosis, functional assessment, and operative plan with the auth request. Approval without documented paralytic etiology is rare.

Sources & references

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

Mira Scribe

Mira's AI scribe captures the donor muscle name, recipient attachment site, surgical approach, and the underlying paralytic diagnosis from dictation — the four elements auditors check first on muscle transfer notes. That prevents the most common down-code trigger: an operative report that says 'abdominal muscle transferred to hip' without specifying the external oblique-to-greater-trochanter construct or linking it to a documented neurologic indication.

See how Mira captures CPT 27100 documentation