Open surgical fusion of the tibiotalar (ankle) joint, performed through a direct incision to prepare joint surfaces and achieve bony union.

Verified May 8, 2026 · 7 sources ↓

Medicare: $927.88
Total RVUs: 27.78
Global, days: 90
Region: Foot & ankle

Drawn from CMSAAPCAetnaGuidelinesCgsmedicare

Documentation requirements

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

Source · Editorial brief grounded in 7 cited references ↓

Diagnosis driving fusion: specify type (post-traumatic arthritis, primary OA, inflammatory arthropathy, severe instability) with ICD-10 code
Failed conservative management: document duration, modalities tried (injections, bracing, PT), and patient response
Operative note must name the surgical approach (anteromedial, anterolateral, transfibular, posterior), hardware used, and bone graft source if applicable
Pre-op weight-bearing radiographs and/or advanced imaging (CT or MRI) confirming joint destruction or deformity
Laterality documented in both the op note and on the claim (LT or RT modifier)
Alignment achieved at time of fixation — neutral dorsiflexion, 5–10° external rotation, slight hindfoot valgus — stated explicitly in the operative note

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 7 cited references ↓

CPT 27870 covers open ankle arthrodesis — a procedure in which the surgeon makes a direct incision, removes the remaining cartilage from the tibiotalar joint surfaces, positions the talus in correct alignment beneath the tibia, and fixes the construct with internal hardware (screws, plates, or a combination) to achieve permanent bony fusion. The open approach distinguishes this code from arthroscopic ankle fusion techniques and gives the surgeon direct visualization for deformity correction, bone grafting, and hardware placement.

The 90-day global period means all routine postoperative care — wound checks, cast or boot changes, hardware interrogation visits, and physical therapy-related E&M — is bundled through day 90. Bill unrelated visits with modifier 79. If a staged procedure was planned at the time of the index surgery, use modifier 58 for the return trip; use modifier 78 only for an unplanned return to the OR for a related complication.

Precertification is routinely required by major commercial payers including Aetna and Carelon-managed plans. Document failure of conservative management (injections, bracing, PT) and the specific diagnosis driving the fusion — end-stage post-traumatic arthritis, primary osteoarthritis, inflammatory arthropathy, or severe instability — before submitting the auth request. Missing or thin conservative-care documentation is the leading prior-auth denial trigger for this code.

RVU & reimbursement

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

Source · CMS Physician Fee Schedule, RVU26A · January 2026

Work RVU	15.02
Practice expense RVU	10.07
Malpractice RVU	2.69
Total RVU	27.78
Medicare national rate	$927.88
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	$927.88
HOPD (APC 5115) Hospital outpatient department	$13,116.76
ASC (PI J8) Ambulatory surgical center (freestanding)	$9,693.82

Common denial reasons

The recurring reasons claims for CPT 27870 get rejected.

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

Prior authorization not obtained or obtained for wrong laterality — payers treating LT and RT as distinct auth requests
Insufficient conservative care documentation: no record of failed injections, bracing, or PT before surgery
Operative note lacks specificity on approach or hardware, triggering medical necessity review
ICD-10 mismatch: billing an arthritis code when the op note describes instability, or vice versa
Global period billing error: post-op E&M billed without modifier 24 when it is unrelated to the fusion

Frequently asked questions

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

01What is the global period for CPT 27870?

90 days. All routine postoperative care from the day of surgery through day 90 is bundled. Unrelated visits in that window require modifier 79; planned staged procedures require modifier 58.

02Does CPT 27870 require prior authorization?

Yes, for most commercial payers including Aetna and Carelon-managed plans. Submit documentation of the specific diagnosis and failed conservative management — plans routinely deny auth requests that lack a clear conservative-care trial on record.

03How does 27870 differ from arthroscopic ankle fusion?

27870 is the open approach only. Arthroscopic ankle arthrodesis is reported separately. If the surgeon converts from arthroscopic to open, bill 27870 with modifier 22 and document the reason for conversion in the operative note.

04Can 27870 be billed with adjacent subtalar or triple arthrodesis codes on the same day?

Yes, if the tibiotalar fusion is performed as a distinct component of a larger reconstructive procedure (e.g., pantalar arthrodesis). Use modifier 51 or 59 as appropriate and verify NCCI edits for the specific code combination using the CMS NCCI PTP lookup tool.

05Which modifiers indicate laterality for 27870?

LT for left ankle, RT for right ankle. Bill bilateral same-session fusions on two claim lines with modifiers LT and RT plus modifier 50; some payers want a single line with modifier 50 — confirm your payer's preference before submitting.

06Is bone grafting separately reportable with 27870?

Autograft harvested from a local site (e.g., distal tibia) is generally considered bundled. Structural allograft or iliac crest autograft may be separately reportable depending on payer policy — verify with NCCI edits and individual payer LCDs before billing a separate graft code.

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 surgical approach by name, hardware configuration, bone graft source and origin, tibiotalar alignment achieved at fixation, and laterality directly from the surgeon's dictation. That specificity prevents the operative-note vagueness that triggers post-payment audits and medical necessity reviews — the two most common denial pathways for 27870.

See how Mira captures CPT 27870 documentation