Arthroscopic surgery on the subtalar joint with removal of a loose or foreign body

Verified May 8, 2026 · 6 sources ↓

Medicare: $602.22
Total RVUs: 18.03
Global, days: 90
Region: Foot & ankle

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Documentation requirements

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

Source · Editorial brief grounded in 6 cited references ↓

Specify that the operative site is the subtalar joint, not the tibiotalar (ankle) joint — these are distinct spaces with different codes
Describe the loose body or foreign body by type, size, and location within the joint at time of arthroscopy
Document portal placement sites and instruments used to confirm subtalar — not ankle — joint entry
Record pre-operative imaging (X-ray, CT, or MRI) identifying the loose or foreign body and correlating with operative findings
Note laterality explicitly (left, right, or bilateral) in both the operative note and on the claim
Confirm that removal was accomplished arthroscopically and document technique used to extract the body

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 52 Reduced services 58 Staged or related 59 Distinct service 62 Co-surgeons 73 Discontinued pre-anesthesia 74 Discontinued post-anesthesia 76 Repeat, same physician 77 Repeat, another physician 78 Unplanned return — related 79 Unrelated during global 80 Assistant surgeon AS PA/NP/CNS assistant LT Left side RT Right side XS Separate structure

What this code covers

Source · Editorial summary grounded in 6 cited references ↓

CPT 29904 covers subtalar joint arthroscopy performed specifically to remove a loose body or foreign body from within the joint. The subtalar joint sits below the ankle joint (tibiotalar) between the talus and calcaneus — a distinct anatomical space requiring its own portal placement and instrumentation. This is a surgical arthroscopy code, not diagnostic; the removal is the defining service.

The 090 global period means the 90-day post-op window applies. All routine follow-up care, wound checks, and related E/M visits are bundled through day 90. Use modifier 24 for unrelated E/M services during global, modifier 78 for an unplanned return to the OR for a complication related to the index procedure, and modifier 79 for an unrelated surgical procedure performed during the global period.

The subtalar arthroscopy family (29904–29907) is organized by the additional surgical service performed — loose/foreign body removal (29904), synovectomy (29905), debridement (29906), and arthrodesis (29907). Bill the single code that best describes the highest-complexity service performed. If a diagnostic scope is converted to surgical, bill only the surgical 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	8.43
Practice expense RVU	7.82
Malpractice RVU	1.78
Total RVU	18.03
Medicare national rate	$602.22
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	$602.22
HOPD (APC 5113) Hospital outpatient department	$3,342.87
ASC (PI G2) Ambulatory surgical center (freestanding)	$1,644.87

Common denial reasons

The recurring reasons claims for CPT 29904 get rejected.

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

Laterality modifier missing — RT or LT required by most payers; claims without it reject on edit
Confusion between subtalar joint (29904) and ankle joint (29894) — coders or auditors flag when imaging references the tibiotalar joint but 29904 is billed
Insufficient operative documentation of the loose or foreign body — if the note doesn't describe what was removed, payers downcode or deny
Global period conflict — E/M or injection billed within 90-day post-op window without modifier 24 or 25
Medical necessity not established — missing pre-op imaging or clinical documentation showing a discrete loose or foreign body in the subtalar joint

Frequently asked questions

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

01What's the difference between 29894 and 29904 for loose body removal?

29894 is loose/foreign body removal from the ankle joint (tibiotalar and fibulotalar joints). 29904 is the same service performed in the subtalar joint, which sits below the ankle between the talus and calcaneus. These are anatomically distinct spaces — bill the code that matches where the scope actually entered and the body was removed.

02Do I need a laterality modifier for 29904?

Yes. Append RT or LT on every 29904 claim. Most Medicare contractors and commercial payers reject or suspend claims without a laterality modifier for unilateral foot and ankle procedures. If performed bilaterally in the same session, use modifier 50 instead.

03Can I bill 29904 and 29906 together if debridement was also performed?

Bill the single code that represents the highest-complexity or dominant service. 29904 (loose body removal) and 29906 (debridement) are in the same surgical arthroscopy family for the subtalar joint. Billing both together will trigger a bundling edit. If the removal was the primary service and debridement was incidental, 29904 is correct.

04What modifiers apply if I need to return to the OR during the 90-day global period?

Use modifier 78 if the return is for an unplanned complication related to the original 29904 procedure. Use modifier 79 if the return is for a completely unrelated surgical problem. Never invert these — misapplying 78 and 79 is a common audit finding.

05Is a pre-operative imaging report required for medical necessity?

Most payers require documented evidence of a loose or foreign body prior to surgery — typically X-ray, CT, or MRI. The operative note should correlate the imaging finding with what was observed and removed arthroscopically. Claims denied for medical necessity almost always lack this pre-op imaging documentation or show a mismatch between imaging and operative findings.

06What global period applies and what's bundled into it?

29904 carries a 90-day global period. The surgery day, the day-before pre-op visit, and all routine post-op E/M visits, wound checks, and stitch removals through day 90 are bundled. Bill unrelated E/M services during global with modifier 24; bill a new and distinct procedure in the global with modifier 79.

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 joint name (subtalar, not tibiotalar), laterality, a description of the loose or foreign body removed, portal placement details, and the correlation between pre-op imaging and intraoperative findings — directly from dictation. This prevents the two most common audit flags on 29904: operative notes that omit what was removed and notes that ambiguously reference the ankle joint rather than the subtalar joint, both of which trigger downcoding or medical necessity denials.

See how Mira captures CPT 29904 documentation