Reconstruction and advancement of the posterior tibial tendon combined with excision of an accessory tarsal navicular bone — the Kidner-type procedure.

Verified May 8, 2026 · 5 sources ↓

Medicare: $685.39
Work RVU: 7.76
Global, days: 90
Region: Foot & ankle

Drawn from CMSAAPCPodiatrymEmednyDol

Documentation requirements

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

Source · Editorial brief grounded in 5 cited references ↓

Confirm presence of an accessory tarsal navicular (os tibiale externum) — imaging and intraoperative findings must support this; a navicular exostosis alone does not satisfy the code.
Document posterior tibial tendon advancement explicitly — state that the tendon was detached, the accessory bone excised, and the tendon reattached or advanced to its new insertion site.
Record the operative side (left or right) in the operative report header and body; LT/RT modifier must match.
Include preoperative conservative treatment history — most payers require documented failure of non-surgical management (orthotics, physical therapy, immobilization) before approving elective reconstruction.
Specify the approach and layers entered in the operative note; avoid generic phrases like 'standard medial approach' — name the incision location and tissue planes.
Provide the ICD-10-CM diagnosis code tied to accessory navicular pathology (e.g., Q66.89 for congenital deformity or M89.37x for associated bony changes) along with any posterior tibial tendon disorder code.

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 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 5 cited references ↓

CPT 28238 covers the Kidner-type procedure: the surgeon excises the accessory tarsal navicular (os tibiale externum) on the medial foot and advances the posterior tibial tendon to restore its insertion and mechanical advantage. The code is specific — both components must be performed. Excising a navicular exostosis without a true accessory bone, or repairing the posterior tibial tendon without that excision, does not satisfy 28238 and requires separate coding (e.g., 28122 for the bony work, 28200 for tendon repair).

The 90-day global period covers the surgery, the day-before visit, and all routine post-op care through day 90. Separate E/M visits for related conditions within that window require modifier 24. New problems unrelated to the foot reconstruction require modifier 25 if billed same-day pre-op, or modifier 24 post-op.

Side matters: this procedure is performed unilaterally in the vast majority of cases, so append LT or RT to every claim. Bilateral Kidner procedures at a single session are rare but billable with modifier 50. Common places of service are ASC (POS 24) and on-campus outpatient hospital (POS 22); site of service affects payment significantly — see the Site of Service comparison table on this page.

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 (7.76) is the surgeon's own effort — the figure physician pay and productivity targets are built on. The total RVU (20.52) adds practice overhead and malpractice, and is what drives the Medicare payment below.

Work RVU	7.76
Practice expense RVU	11.81
Malpractice RVU	0.95
Total RVU	20.52
Medicare national rate	$685.39
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	$685.39
HOPD (APC 5114) Hospital outpatient department	$7,413.38
ASC (PI A2) Ambulatory surgical center (freestanding)	$3,695.53

Common denial reasons

The recurring reasons claims for CPT 28238 get rejected.

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

Medical necessity denied when operative note documents a navicular exostosis or prominence rather than a true accessory navicular bone — the code requires excision of an accessory tarsal navicular, not a bony spur.
Bundling or downcoding when a calcaneal osteotomy (28300) or other foot reconstruction is performed simultaneously and modifier 51 or 59 is missing from the secondary procedure.
Missing LT or RT modifier triggers claim rejection or suspended processing at most payers — always append a laterality modifier.
Global period violation when post-op E/M visits for wound checks or pain management are billed without modifier 24, causing automatic denial.
Prior authorization not obtained before surgery — many commercial payers require preauthorization for elective tendon reconstruction; lack of auth is a leading non-clinical denial reason.

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 5 cited references ↓

01Does 28238 apply when the patient has a navicular exostosis but no true accessory bone?

No. 28238 requires excision of an accessory tarsal navicular (os tibiale externum). When only a bony prominence is excised and the tendon is repaired, bill 28122 for the osseous work and 28200 for the tendon repair; confirm NCCI edits before appending modifier 59.

02Can 28238 and a calcaneal osteotomy (28300) be billed together on the same day?

Yes, when both are documented as distinct, separately indicated procedures. Append modifier 51 to the lower-value code. Confirm NCCI edits — the pair is not inherently bundled, but some payers apply their own edits.

03What is the global period for 28238 and what does it include?

28238 carries a 90-day global. It covers the day-before visit, the surgery, and all routine post-op care through day 90. Unrelated conditions billed in that window need modifier 24 (E/M) or 79 (procedure).

04Is modifier 50 appropriate if the Kidner procedure is performed bilaterally at the same session?

Yes. Bill a single line with modifier 50. Reimbursement is typically capped at 150% of the single-procedure rate. Bilateral accessory navicular pathology is uncommon — expect additional scrutiny and ensure both sides are documented in the operative report.

05Which ICD-10-CM codes support 28238?

Accessory navicular codes vary by presentation. Q66.89 covers congenital foot deformities including accessory ossicles; M89.37x addresses hypertrophy or bony changes at the ankle and foot. Posterior tibial tendon pathology is coded separately (e.g., M76.82x for insertional tendonitis). Use the most specific code supported by imaging and clinical notes.

06If the tendon repair breaks down and the patient returns to the OR within the global period, how is that coded?

An unplanned return to the OR for a complication related to the original procedure uses modifier 78. If the return surgery addresses a new, unrelated problem, use modifier 79. Do not invert these — wrong modifier assignment is an audit flag.

Sources & references

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

Mira Scribe

Mira's AI scribe captures the operative dictation cues that make or break 28238: presence of a true accessory tarsal navicular confirmed on imaging and intraoperatively, technique of tendon detachment and advancement, bony excision extent, and side of surgery. That documentation prevents the most common denial — the payer determining the excised structure was an exostosis rather than an accessory bone — and ensures LT/RT laterality is populated on the claim before it leaves the practice.

See how Mira captures CPT 28238 documentation