ICD code S52.201B – Right ulna shaft fracture

Key takeaways

S52.201B is a billable ICD-10-CM code for an open type I or II fracture of the right ulna shaft, initial encounter.

The 7th character B denotes an initial encounter for open fracture type I or II, unlike A (closed) and C (type III open).

Documentation must state laterality (right), fracture site (shaft/diaphysis), open fracture type, and that the visit is active treatment.

Practice management software like Pabau checks the fields insurers require before a fracture claim goes out, then tracks it to payment.

ICD-10 Code S52.201B: Quick-reference summary

ICD-10 code S52.201B reports an unspecified fracture of the right ulna shaft at an initial encounter for open fracture type I or II.

The table below gives the code’s core facts at a glance. The sections after it cover the 7th character, adjacent codes, documentation, and CPT pairings.

What S52.201B covers: Code definition and clinical meaning

Each word in the descriptor carries a coding implication. Reading them together is what keeps laterality and fracture type from being assigned on assumption.

• Unspecified: The fracture pattern (transverse, oblique, comminuted, spiral) is not documented in the clinical record. This is acceptable under ICD-10-CM guidelines but may invite payer scrutiny. If the operative or radiology report names the pattern, use a more specific code in the S52.2 series.
• Shaft: The fracture involves the diaphysis of the ulna, not the proximal head, olecranon, or distal styloid process. Coders sometimes confuse proximal ulna fractures (S52.0xx) with shaft fractures; anatomical review of the radiology report is essential.
• Right ulna: Laterality is explicit and non-negotiable. S52.201B applies to the right forearm only. Left-side injuries require S52.202B.
• Initial encounter: The patient is actively receiving treatment for the fracture. This includes surgical repair, casting, splinting, and any visit where the fracture is under active management.
• Open fracture type I or II: Skin is broken at the fracture site. Type I involves a wound of 1 cm or less with minimal contamination and a simple fracture pattern. Type II involves a wound larger than 1 cm with moderate soft tissue damage. These correspond to Gustilo-Anderson classification grades.

When the surgeon’s operative report does not specify a Gustilo-Anderson grade, ICD-10-CM guidelines default the open fracture to type I or II. B is then the correct 7th character. Per the CMS ICD-10 coding guidance, coders should not assign type IIIA/B/C (character C) without explicit documentation of that severity level.

Understanding the 7th character: What B means in ICD-10-CM fracture codes

The 7th character in S52 codes defines both the fracture type (open vs. closed) and the encounter phase (initial vs. subsequent vs. sequela). It is the highest-risk element in the code string. Assign A when the chart documents an open wound, or D while the patient is still in active treatment, and the claim is denied. Clearing that denial takes a resubmission and corrected documentation.

The B vs. A distinction is the most common coding error on ulna shaft fractures. A claim carrying 7th character A alongside a CPT code for open surgical repair is an automatic mismatch denial. Always confirm the wound description in the emergency or operative note before selecting the character. Three questions settle the choice, and the record answers all three.

S52.201B vs adjacent ulna and radius codes

Five codes sit close enough to S52.201B to cause assignment errors in busy orthopedic and urgent care practices. The decision logic below covers laterality, fracture type, and the related radius code.

When both the radius and ulna are fractured (a both-bone forearm fracture), assign separate codes for each. Reporting S52.201B alone when the radius is also fractured is undercoding. Validate laterality against the radiologist’s report, not the clinical note, since side is sometimes transcribed inconsistently. ICD-10-CM requires laterality specificity across the injury chapters, and forearm codes are no exception.

Excludes notes and code-first instructions

Category S52 carries several tabular instructions that affect how S52.201B is reported. Missing an excludes note is one of the quieter denial triggers coders encounter.

• Excludes1 (cannot code together): S52 codes exclude traumatic amputation of the forearm (S58.-). If the patient presents with a forearm amputation, code from S58 rather than S52.
• Excludes2 (code both if applicable): Pathological fractures of the ulna (M84.4-) are excluded from S52. If the fracture occurs through diseased bone (metastatic lesion, osteoporotic bone), code M84.4- instead. If a traumatic fracture complicates a pathological one, clinical judgment and documentation govern which takes priority.
• Use additional code for external cause: Assign a code from Chapter 20 (V00-Y99) to identify the mechanism of injury. Workers’ compensation payers and many commercial insurers require this. Fall from height typically uses W17.- codes; motor vehicle trauma uses V codes.
• Use additional code for associated wound: If a wound is present beyond what is inherent to the open fracture classification, code it separately.

Read the tabular list at the category level, not only at the individual code. The S52 instructions apply to every code in the category, S52.201B included.

Documentation the chart must contain

Four elements must appear in the clinical record to support S52.201B without triggering a documentation-related denial or audit flag.

• Explicit laterality (right): The emergency note, operative report, or attending physician’s note must state “right” forearm or “right ulna.” Radiology reports that say only “the fractured forearm” without laterality cannot support a laterality-specific code.
• Fracture site confirmation (shaft/diaphysis): The note must confirm the fracture involves the shaft, not the olecranon (proximal) or styloid (distal). Phrases such as “mid-shaft ulna fracture,” “diaphyseal ulna fracture,” or “ulnar shaft” satisfy this requirement.
• Open fracture classification: Documentation of an open wound at the fracture site is required. A Gustilo-Anderson grade of I or II, documented by the surgeon, directly supports the B character. Where the record says only “open fracture” with no grade, ICD-10-CM guidelines let the coder default to B as well. Do not apply that default if the operative note describes severe soft tissue damage, vascular injury, or bone loss. Those findings point to type III severity, which is character C.
• Encounter type (initial, active treatment): The visit must represent active treatment. That covers the initial surgical procedure, casting, external fixation, and any encounter where the fracture is actively managed. Routine follow-up after healing begins uses subsequent encounter codes (E, G, H, J, K, M, N, P, Q, R).

According to the CDC/NCHS ICD-10-CM coding tool, the official tabular list is the authoritative source for all S52 documentation instructions. Coders should consult the current fiscal year’s guidelines rather than relying on prior-year memorization, since 7th character assignments are occasionally revised.

CPT codes commonly paired with S52.201B

Procedure code selection depends on what the surgeon did, not on the diagnosis alone. The table below maps the most common CPT codes to their clinical scenarios. Verify the CPT against the operative note first, then read it back against the ICD-10 code before the claim is submitted.

A common billing error pairs S52.201B with CPT 25535 (closed treatment with manipulation). An open-fracture ICD-10 code paired with a closed-treatment CPT is a clinical impossibility on paper. Payers flag it as a medical necessity mismatch. When the surgeon converts from attempted closed management to open repair, update the CPT accordingly. Debridement carried out at the fracture site has its own code family. CPT 11011 covers debridement performed at the site of an open fracture.

Most payer systems apply their clinical edits after the claim arrives, so the open-closed pairing is worth checking while the claim is still editable. A short review step, with the operative note open beside the claim, catches the mismatch that clinical edits would otherwise return days later.

Common claim denial reasons

S52.201B denials cluster around six predictable patterns. Each one is avoidable with a pre-submission checklist, and naming the pattern is what shortens the rework when a claim does come back.

1. Wrong 7th character (A instead of B): The chart documents an open wound but the coder assigns A (closed fracture). This is the most frequent S52.201B denial. Confirm the wound description in the emergency or operative note before selecting the character.
2. Laterality mismatch: The claim states right ulna (S52.201B) but the operative report or radiology note references the left forearm. Always cross-reference the claim against the radiology report’s laterality statement.
3. CPT/ICD-10 open-closed mismatch: Billing a closed-treatment CPT (25535) alongside an open-fracture diagnosis (S52.201B). Payer clinical edits automatically reject this combination. Use CPT 25545 for open treatment of the ulnar shaft fracture.
4. Missing external cause code: Workers’ compensation payers require a V, W, X, or Y chapter code identifying injury mechanism. Some commercial payers do too. Adding W codes for fall from height or V codes for vehicle trauma prevents this denial category entirely.
5. Subsequent encounter code on active treatment visit: Using D or E on a visit that is still managing the acute fracture. Per ICD-10-CM Section I.C.19 guidelines, “subsequent encounter” applies only after active treatment has concluded and the patient is in the healing/monitoring phase.
6. Unbundling wound debridement: Separately billing CPT 97597 or 97598 for wound debridement already included in the fracture repair CPT. Review NCCI bundling edits before adding a debridement code.

Three denial codes appear most often on S52.201B rejections. They are CO-4 (inconsistent modifier or procedure), CO-11 (diagnosis inconsistent with procedure), and CO-97 (payment included in another service). Knowing which CARC code landed on the EOB narrows the appeal strategy immediately.

Payer-specific considerations and pre-authorization

Requirements vary by payer and change annually. Treat the points below as a starting-point checklist, not a definitive payer policy statement.

• Medicare: NCCI edits apply to CPT codes billed alongside S52.201B, particularly around debridement and fixation hardware. Verify current NCCI tables before submitting a multi-procedure claim. The CMS Physician Fee Schedule lookup tool confirms RVU values and modifier requirements for each CPT code paired with the diagnosis.
• Workers’ compensation: Most workers’ comp payers require the external cause code from the W/V/X/Y chapter alongside the injury diagnosis. Many also require a statement of work-relatedness in the clinical note. Submit S52.201B with the appropriate mechanism code from the outset rather than waiting for a denial and resubmitting.
• Commercial payers: Prior authorization may be required for open reduction internal fixation (ORIF) procedures. The CPT code (typically 25545) triggers the auth requirement, not the ICD-10 code itself. Confirm auth requirements before the surgical date using your payer’s online portal or the eligibility verification workflow.
• Medicaid: State Medicaid programs vary widely. Some require the NPI of the supervising orthopedic surgeon when the procedure is performed by a resident or PA. Others require place-of-service codes that distinguish inpatient surgery from outpatient or ED settings.

Getting paid on the first pass means mapping each payer’s authorization triggers against the CPT codes billed with S52.201B. Building that into a pre-authorization routine for orthopedic surgical codes removes most of the rework. Review the AAPC’s ICD-10-CM code reference for crosswalk data, and ICD List for DRG grouper lookups when the admission context affects the reimbursement level.

How Pabau supports fracture claim submission and tracking

Once the coder has settled on S52.201B and the matching CPT, the claim usually moves into a separate portal. Someone rekeys it, and the status of that claim then lives somewhere nobody looks at daily. A rejection can sit unread for a week before anyone starts the appeal.

Practice management software like Pabau keeps that step in the same system as the patient record. Its claims management software runs validation checks each time you send a claim, confirming that the details insurers ask for are present. Membership numbers and authorization codes are the two that most often hold a fracture claim up.

From there, claims go to Claim.MD without leaving Pabau, or by email where an insurer is not connected. Every claim carries a live status of pending, submitted, processing, paid, or error, filterable by date, insurer, or invoice ID. When payment arrives, you record it against the right invoice from the same dashboard.

Choosing between A, B, and C on the 7th character stays a coding judgment, made from the operative note. What changes is the time between a fracture claim being rejected and someone noticing.

Submit and track fracture claims in one place

Pabau validates the details insurers need on every claim, sends it without rekeying, and shows a live status for each one. See how it works for orthopedic and urgent care practices.

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Conclusion

S52.201B is a straightforward code when the documentation is right, and a persistent denial source when it is not. The 7th character assignment, laterality, and CPT alignment account for most claim rejections on right ulna shaft fractures.

Almost none of that is a software problem. It is a documentation discipline, built into the few seconds between reading the operative note and choosing the character. Software earns its place afterward, by validating the fields insurers require and showing where each claim stands. Book a demo to see how Pabau handles fracture claims for orthopedic and urgent care teams.

Continue your research

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