20956

Bone graft harvested from the iliac crest and transferred to a recipient site using microvascular anastomosis to restore the graft's blood supply.

Verified May 8, 2026 · 7 sources ↓

Medicare: $2,355.43
Total RVUs: 70.52
Global, days: 90
Region: General

Drawn from CMSAAPCFindacodePayerpriceEmedny

Documentation requirements

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

Source · Editorial brief grounded in 7 cited references ↓

Identify the donor site explicitly as the iliac crest — generic language like 'pelvic bone graft' is insufficient for site-specific code selection.
Document use of an operative microscope and the microvascular anastomosis technique, including the vessels connected at the recipient site.
Describe the recipient site pathology justifying vascularized graft over conventional autograft (e.g., avascular necrosis, segmental defect size, irradiated bed).
If co-surgeons billed under modifier 62, each surgeon must submit a separate operative note detailing their distinct intraoperative role.
Record estimated blood loss, graft dimensions, ischemia time, and any intraoperative Doppler or fluorescein perfusion checks.
Document donor-site closure and any harvest-site complications separately — these are within the global but must appear in the note.

Applicable modifiers

Modifiers commonly billed with this code.

Source · AMA CPT modifier descriptors · CMS NCCI Policy Manual

22 Increased complexity 51 Multiple procedures 59 Distinct service 62 Co-surgeons 80 Assistant surgeon LT Left side RT Right side XS Separate structure

What this code covers

Source · Editorial summary grounded in 7 cited references ↓

CPT 20956 describes harvesting a vascularized bone graft from the iliac crest and transferring it to a deficient or damaged skeletal site, with operative-microscope-assisted reconnection of the graft's feeding vessels at the recipient bed. Maintaining an intact vascular pedicle — rather than using a conventional avascular graft — dramatically improves graft viability and healing potential, which is why this code is reserved for cases where a standard bone graft is insufficient: large segmental defects, avascular necrosis, failed prior grafts, or heavily irradiated tissue beds.

The procedure carries a 90-day global period. That window covers the harvest and transplant, all routine post-op visits, and donor-site wound management. Unrelated E/M visits or procedures during the global need modifier 24 or 79, respectively. Because the complexity routinely involves a reconstructive microsurgeon and an orthopedic or hand surgeon working simultaneously, co-surgeon billing under modifier 62 is common and should be supported by two separate operative notes documenting each surgeon's distinct contribution.

Within the microvascular bone graft family, 20956 is specific to the iliac crest donor site. For fibula grafts use 20955; for metatarsal, 20957; for all other donor sites, 20962. Billing the wrong site-specific code when the operative note clearly names the iliac crest is a straightforward audit target.

RVU & reimbursement

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

Source · CMS Physician Fee Schedule, RVU26A · January 2026

Work RVU	40.15
Practice expense RVU	21.79
Malpractice RVU	8.58
Total RVU	70.52
Medicare national rate	$2,355.43
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	$2,355.43
HOPD (APC 5114) Hospital outpatient department	$7,413.38
ASC (PI J8) Ambulatory surgical center (freestanding)	$4,682.29

Common denial reasons

The recurring reasons claims for CPT 20956 get rejected.

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

Wrong microvascular graft code selected — payers deny 20956 when the operative note identifies the fibula or metatarsal as the donor site instead of the iliac crest.
Missing microvascular anastomosis documentation — if the note describes a conventional non-vascularized iliac graft, the claim downcodes or denies outright.
Co-surgeon modifier 62 denied for lack of a second operative note establishing the assistant surgeon's distinct and necessary role.
Routine post-operative services billed separately within the 90-day global without modifier 24 (unrelated E/M) or 79 (unrelated procedure).
Site-of-service mismatch — this procedure almost exclusively occurs in an inpatient or on-campus outpatient hospital setting; claims submitted under an incorrect place-of-service code trigger automated edits.

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 7 cited references ↓

01How does 20956 differ from 20955 and 20962?

Donor site is the only distinction within this family. 20955 = fibula, 20956 = iliac crest, 20957 = metatarsal, 20962 = any other donor site. All four require microvascular anastomosis; the operative note must name the harvest site to support the correct code.

02Can two surgeons each bill 20956 when they work together on the same case?

Yes — modifier 62 (co-surgeons) applies when a microsurgeon handles the vessel anastomosis and an orthopedic surgeon manages the recipient site preparation, and each must submit a separate operative note documenting their distinct contribution. Both bills are subject to a payment split per payer contract.

03What is the global period for 20956 and what does it include?

The global period is 90 days. It covers the surgery itself, the day-before visit, and all routine post-op care through day 90 — including donor-site wound checks and stitch removal. Unrelated procedures or E/M visits during that window require modifier 79 or 24, respectively.

04Is modifier 22 ever appropriate for 20956?

Yes, when the operative complexity is substantially greater than typical — for example, a failed prior graft requiring extensive recipient bed preparation, or vessel anastomosis complicated by prior radiation or scarring. Attach a letter of medical necessity explaining the added work; payers routinely request this before approving the upward adjustment.

05Can 20956 and the recipient-site reconstruction code be billed together on the same date?

Generally yes, because the harvest and the recipient-site procedure are distinct services. Use modifier 59 or XS on the lower-valued code if an NCCI edit pairs them. Confirm the specific edit is modifier-bypassable (indicator 1) before submitting.

06Does 20956 require inpatient admission or can it be performed in an ASC?

CMS data shows the procedure is billed almost exclusively from inpatient hospital (POS 21) and on-campus outpatient hospital (POS 22) settings. ASC payment rates exist but the prolonged operative time and post-anastomosis monitoring requirements make true outpatient ASC performance uncommon; verify your payer's site-of-service policy before scheduling.

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 donor site by name (iliac crest), documents operative microscope use, names the vessels anastomosed at the recipient bed, and records the clinical rationale for choosing a vascularized graft over a conventional autograft. That documentation locks in the correct site-specific code — 20956 versus 20955 or 20962 — and satisfies the key audit trigger that causes microvascular graft claims to downcode or deny.

See how Mira captures CPT 20956 documentation