Surgical reshaping or realignment of the anterior tibial tubercle to correct patellofemoral malalignment and relieve kneecap degeneration (Maquet-type or similar osteotomy procedure).

Verified May 8, 2026 · 7 sources ↓

Medicare: $763.21
Total RVUs: 22.85
Global, days: 90
Region: Knee

Drawn from CMSNIHMdclarityAAPCAAOS

Documentation requirements

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

Source · Editorial brief grounded in 7 cited references ↓

Operative note must name the specific technique performed (e.g., Maquet, Fulkerson anteromedialization, straight anteriorization).
Document the degree of tubercle displacement or elevation achieved and the direction of correction.
Specify fixation method: screw type, count, size, and placement relative to the osteotomy site.
Pre-op imaging (X-ray, MRI, or CT) demonstrating patellofemoral malalignment, chondral degeneration, or elevated TT-TG distance should be referenced in the note.
If concurrent procedures were performed (e.g., MPFL reconstruction, lateral release), document each as a distinct, separately described surgical step.
Note the surgical approach by name and any intraoperative findings that altered the planned technique.

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 25 Significant separate E/M 50 Bilateral procedure 51 Multiple procedures 57 Decision for surgery 58 Staged or related 59 Distinct service 62 Co-surgeons 78 Unplanned return — related 79 Unrelated during global 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 27418 describes an anterior tibial tubercleplasty — an open surgical procedure that repositions the tibial tubercle to offload the patellofemoral joint and address degenerative or malalignment-related kneecap pathology. The Maquet procedure (anterior elevation) and the Fulkerson osteotomy (anteromedialization) are the most commonly performed variants; operative notes must name the specific technique. The bone cut is fixed with hardware, and the approach, fixation method, and degree of correction must be documented in detail.

This code carries a 90-day global period. All routine post-op visits, wound checks, and hardware-site care through day 90 are bundled. Bill unrelated E/M visits in that window with modifier 24; a separate significant decision-making visit on the day of surgery needs modifier 57 if the decision to operate occurred that day. When a tibial tubercleplasty is performed alongside MPFL reconstruction (27427) or other ligamentous work at the same encounter, modifier 59 or XS is required to unbundle the separately identifiable procedures — NCCI edits apply.

Site-of-service matters here: HOPD and ASC payments differ substantially (see the Site of Service comparison table). Most payers follow Medicare's global surgery rules, but verify commercial plan policies for bilateral reporting — Medicare requires a single-line claim with modifier 50 for bilateral cases billed to the physician fee schedule, while ASCs report two lines with LT and RT.

RVU & reimbursement

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

Source · CMS Physician Fee Schedule, RVU26A · January 2026

Work RVU	11.31
Practice expense RVU	9.28
Malpractice RVU	2.26
Total RVU	22.85
Medicare national rate	$763.21
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	$763.21
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 27418 get rejected.

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

Operative note describes only 'tibial tubercle osteotomy' without identifying the specific technique, triggering a medical necessity review.
Missing or insufficient pre-op imaging documentation to support patellofemoral malalignment diagnosis — payers deny without objective alignment data.
Concurrent procedures (e.g., 27427) billed same-day without modifier 59 or XS, triggering NCCI bundling denial.
Routine post-op visit billed within the 90-day global without modifier 24, resulting in automatic denial.
ICD-10 diagnosis code doesn't specify laterality or align with the documented pathology (malalignment vs. chondrosis vs. instability), causing claim rejection.

Frequently asked questions

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

01What is the global period for CPT 27418?

90 days. The day-before visit, the surgery day, and all routine post-op care through day 90 are included. Use modifier 24 for unrelated E/M visits and modifier 78 if you return to the OR for a related complication during that window.

02Can I bill 27418 and 27427 (MPFL reconstruction) together on the same claim?

Yes, but modifier 59 or XS is required on the secondary code to bypass NCCI bundling edits. Both procedures must be documented as distinct surgical steps in the operative note — a single narrative that blends them together won't survive audit.

03Which diagnosis codes support 27418?

Patellofemoral syndrome (M22.2x), chondromalacia patellae (M22.4x), recurrent patellar dislocation (M22.0x), and patellar malalignment codes are the primary ICD-10 drivers. Laterality must be specified — unspecified-side codes draw payer scrutiny.

04How do I report 27418 if the procedure is performed bilaterally?

On the Medicare Physician Fee Schedule, report one line with modifier 50. At an ASC, report two separate claim lines — one with modifier LT and one with RT. Commercial payers vary; confirm their bilateral billing policy before submission.

05Is modifier 22 ever appropriate for 27418?

Yes, when the procedure is substantially more complex than typical — for example, revision after a prior tubercle osteotomy with hardware removal, or severe deformity requiring additional fixation. Documentation must quantify the added work (operative time, complexity of dissection) and a cover letter should accompany the claim.

06What ICD-10 TT-TG distance or imaging threshold do payers require for medical necessity?

Most commercial policies cite a TT-TG distance greater than 15–20 mm on CT or MRI as a threshold, but specific cutoffs vary by payer. Check individual payer LCDs or coverage policies before surgery when the TT-TG is borderline, and document the measured value explicitly in the pre-op note.

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 technique name (Maquet, Fulkerson, or variant), direction and magnitude of tubercle displacement, fixation hardware details, and intraoperative alignment assessment from surgeon dictation. It also flags when concurrent procedures are dictated so the coder is prompted to apply modifier 59 or XS — preventing same-day NCCI bundling denials before the claim is submitted.

See how Mira captures CPT 27418 documentation