Surgical · Knee

Proximal tibial osteotomy with fibular excision or osteotomy for correction of genu varus or genu valgus, performed before epiphyseal closure.

Verified May 8, 2026 · 6 sources ↓

Medicare: $892.81
Total RVUs: 26.73
Global, days: 90
Region: Knee

Drawn from CMSAAPCNIHAbosEmedny

Documentation requirements

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

Source · Editorial brief grounded in 6 cited references ↓

Radiographic confirmation of open physes (growth plates not closed) — this is what separates 27455 from 27457 and must be explicit in the operative record
Standing alignment X-rays (AP long-leg or full-limb) documenting degree of angular deformity (genu varus or genu valgus) with measured mechanical axis deviation
Operative note specifying whether fibular excision or fibular osteotomy was performed, the level of the tibial cut, fixation method used, and correction achieved
Patient age and skeletal maturity assessment documented in the pre-op note or imaging interpretation, confirming pre-epiphyseal closure status
Diagnosis linked to ICD-10 code consistent with angular deformity (e.g., M21.161/M21.162 for varus knee, M21.061/M21.062 for valgus knee) — payers flag mismatched CPT-ICD pairs
Documentation of failed or contraindicated conservative management when required by payer prior authorization criteria

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 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 27455 covers a proximal tibial realignment osteotomy — including fibular excision or osteotomy as needed — performed specifically in skeletally immature patients, before the growth plates (epiphyses) have closed. The operative goal is correction of angular deformity: genu varus (bowleg) or genu valgus (knock-knee). The timing relative to epiphyseal closure is the critical distinguishing element between 27455 (open physes) and its paired code 27457 (closed physes). Bill the wrong one and you have a mismatched diagnosis-to-code relationship that will trigger denial.

The 90-day global period means the surgery date plus all related post-op management through day 90 are bundled. Separate E/M visits in that window require modifier 24 (unrelated problem) or 25 (significant, separately identifiable service same day as a procedure). Hardware removal, if planned and staged, bills with modifier 58; unplanned returns to the OR for a related complication use modifier 78.

Site of service matters here: HOPD and ASC payment rates differ substantially — see the Site of Service comparison table. The procedure carries a high complexity designation; payers will scrutinize medical necessity documentation, particularly confirmation that conservative management was exhausted and that the patient's skeletal maturity status supports this specific code over 27457.

RVU & reimbursement

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

Source · CMS Physician Fee Schedule, RVU26A · January 2026

Work RVU	13.03
Practice expense RVU	10.93
Malpractice RVU	2.77
Total RVU	26.73
Medicare national rate	$892.81
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	$892.81
HOPD (APC 5114) Hospital outpatient department	$7,413.38
ASC (PI G2) Ambulatory surgical center (freestanding)	$3,695.53

Common denial reasons

The recurring reasons claims for CPT 27455 get rejected.

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

Wrong code selected — 27457 billed instead of 27455 (or vice versa) when skeletal maturity status is not clearly documented, causing CPT-diagnosis mismatch
Missing or inadequate laterality modifier — payers require LT or RT on unilateral knee procedures; absent laterality triggers technical denial on many commercial and Medicare Advantage plans
Medical necessity denial when pre-op documentation lacks standing alignment films or quantified deformity measurements supporting surgical correction
Global period violation — related post-op E/M visits billed without modifier 24 or 25 during the 90-day global window
Prior authorization not obtained or obtained for 27457 rather than 27455, triggering authorization mismatch denial on commercial plans

Frequently asked questions

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

01What is the difference between CPT 27455 and CPT 27457?

The only procedural difference is patient skeletal maturity. CPT 27455 is used when the patient's growth plates are still open (before epiphyseal closure). CPT 27457 covers the same proximal tibial osteotomy in a skeletally mature patient. Billing the wrong code relative to documented skeletal maturity is a direct path to denial or audit.

02Does CPT 27455 require laterality modifiers?

Yes. Append LT or RT for a unilateral procedure. If the deformity is corrected bilaterally in the same session, use modifier 50. Most payers — including Medicare and Medicare Advantage plans — require laterality on knee procedure codes.

03Can 27455 be billed with fibular osteotomy codes separately?

No. The fibular excision or osteotomy is bundled into 27455 per the code descriptor. Billing a separate fibular code on the same side same session will be denied as unbundling under NCCI edits.

04What global period applies to 27455, and what does it include?

CPT 27455 carries a 90-day global period. That includes the day-before pre-op visit, the procedure itself, and all routine post-op management through day 90. Unrelated E/M visits in the window need modifier 24; a staged return to the OR needs modifier 58; an unplanned return for a related complication needs modifier 78.

05Can 27455 be billed with modifier 22 for increased complexity?

Yes, if the work was substantially greater than typical — for example, severe multiplanar deformity requiring extended operative time with documented complexity. The operative note must explicitly describe what made the case extraordinary. Modifier 22 without supporting documentation is a common audit trigger.

06Is 27455 typically performed in an ASC or hospital outpatient setting?

Both are used. The procedure is commonly performed in on-campus outpatient hospital (POS 22) and ASC (POS 24) settings. HOPD and ASC facility payments differ — see the Site of Service comparison table on this page. The surgeon's professional fee is the same regardless of site; only the facility payment varies.

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 patient's skeletal maturity status from dictation — open versus closed physes — along with the specific deformity type (genu varus or genu valgus), the tibial cut level, whether fibular excision or osteotomy was performed, fixation details, and laterality. This prevents the most common audit flag on 27455: an operative note that fails to document pre-epiphyseal closure, which is the sole clinical justification for this code over 27457.

See how Mira captures CPT 27455 documentation