ICD-10 code S52.001P: right ulna fracture, malunion

Key Takeaways

S52.001P is the billable ICD-10-CM code for an unspecified fracture of the upper end of the right ulna, healed with malunion. It took effect October 1, 2025 (FY2026).

The 7th character P marks a subsequent encounter where the closed fracture healed in an abnormal position. That is distinct from nonunion (character K) and routine healing (character D).

S52.0 is the ulna branch of the S52 forearm family. The upper end of the radius sits in S52.1, which makes S52.101P the radius equivalent of this code.

Documentation must confirm the site (upper end of the right ulna), closed fracture status, and malunion on imaging or in the notes. The record must also show a follow-up visit.

Pabau’s claims management software integrates with Claim.MD to submit S52.001P and related fracture codes directly to over 4,000 US payers. That cuts manual claim errors at the character-selection level.

Fracture coding errors cost orthopedic practices thousands of dollars in denied claims each year. Two mistakes dominate the S52 family: picking the wrong bone, and picking the wrong 7th character. ICD-10 code S52.001P covers a right ulna fracture at the upper end that healed in the wrong position, seen at a follow-up visit. S52.0 is the ulna branch of the forearm family, so a radius code will not stand in for it. This reference walks through every element of S52.001P that coders and sports medicine software users need to get right.

ICD-10 code S52.001P: definition and billable status

S52.001P is a billable ICD-10-CM diagnosis code, valid for HIPAA-covered electronic transactions. The full official description is: Unspecified fracture of upper end of right ulna, subsequent encounter for closed fracture with malunion. According to the CDC/NCHS ICD-10-CM web tool, this code became effective October 1, 2025, as part of the FY2026 edition of ICD-10-CM.

Breaking the code down by its components helps coders select it correctly every time.

“Unspecified” in the code title does not mean the fracture is undocumented – it means displacement status was not confirmed as displaced or nondisplaced. This is a legitimate coding choice when the clinical record does not specify displacement. The ICD-10-CM code structure uses this convention across many fracture categories.

Understanding the 7th character P in ICD-10 fracture codes

The 7th character is the most consequential element of any S52 fracture code. It tells payers which phase of care is being billed and what the fracture’s healing status is. Selecting the wrong character triggers claim denials that require appeals, rebilling, and documentation requests. The usual mix-up is P (malunion) with D (routine subsequent encounter) or K (nonunion).

The full set of valid 7th characters for S52.001 covers both closed and open fracture encounters. Only characters applicable to closed fractures apply to S52.001P specifically.

The ICD-10 injury chapter coding framework applies the same 7th character logic across all injury categories in S00-T88 – understanding this once means applying it everywhere. Per the CMS ICD-10-CM guidelines, the character must reflect the actual healing status documented at the time of the encounter, not the anticipated status.

What “subsequent encounter for closed fracture with malunion” means

Malunion means the fracture has healed – but in an abnormal position. The bone ends united, but they did not align correctly during the healing process. The patient is no longer in the acute fracture phase, which is why this is a subsequent encounter, not an initial one.

This is different from nonunion, where the fracture fails to heal at all. Both produce symptoms and may require intervention, but they represent different biological outcomes with different ICD-10-CM codes.

A patient may return to the practice reporting deformity, pain, or lost function after the fracture should have healed. Imaging that confirms abnormal bone union supports the malunion diagnosis. For a closed fracture at the upper end of the right ulna, S52.001P is the code for that visit.

S52.001P code hierarchy

Knowing where S52.001P sits in the ICD-10-CM documentation requirements hierarchy helps coders navigate the tabular list. It also confirms they have selected the most specific code available. The AAPC Codify ICD-10-CM lookup presents this hierarchy clearly for verification.

• S00-T88: Injury, poisoning, and certain other consequences of external causes
• S50-S59: Injuries to the elbow and forearm
• S52: Fracture of forearm
• S52.0: Fracture of upper end of ulna
• S52.00: Unspecified fracture of upper end of ulna
• S52.001: Unspecified fracture of upper end of right ulna
• S52.001P: Subsequent encounter for closed fracture with malunion (billable)

The S52 subcategories pair up by site and by bone. S52.0 is the upper end of the ulna, and S52.1 is the upper end of the radius. Both sit under the same category, so a coder reading the tabular list has to check the branch as well as the character.

S52.001 is not itself billable – it requires a 7th character to be complete. Submitting S52.001 without the character appended will result in an invalid code rejection at the clearinghouse level.

Laterality: coding right vs left ulna fractures

Laterality is confirmed at the S52.001 level – the sixth digit distinguishes right (1), left (2), and unspecified (9). This distinction is fixed in the code structure, so a coder cannot default to “unspecified” when the clinical record clearly documents right or left. Payers treat laterality omission as a documentation deficiency and may deny or downcode the claim.

For practices using physical therapy EMR systems that track rehabilitation after fracture repair, the laterality code also informs which limb’s functional metrics are being monitored. Consistent laterality documentation across clinical notes and billing records prevents downstream audit flags.

Documentation requirements for S52.001P

Using S52.001P on a claim without adequate clinical documentation creates audit exposure. The ICD-10-CM Official Guidelines for Coding and Reporting are maintained jointly by CMS and NCHS. They require that each element of the code be supported by the clinical record. Solid medical billing compliance means the record must confirm all of the following before this code is submitted.

• Fracture site: The notes or imaging report must place the fracture at the upper end of the ulna, near the elbow. The shaft and the lower end have their own codes.
• Laterality: The right side must be explicitly identified in the record. “Forearm fracture” alone is insufficient.
• Closed fracture status: The record must confirm the fracture is/was closed (no skin perforation). S52.001P cannot be used if the original fracture was open-type.
• Malunion confirmation: Imaging (X-ray or CT) must demonstrate healed bone in an abnormal position, or the clinician must document malunion in the assessment. A clinical note stating “fracture healed with deformity” or “malunion confirmed on imaging” is acceptable.
• Subsequent encounter: The visit must be a follow-up, not the initial treatment encounter. If this is the first time the patient is presenting for this fracture, character A applies, not P.
• No named structure: S52.001 covers an upper-end ulna fracture the record leaves unspecified. If the notes name the olecranon or the coronoid process, code S52.02x, S52.03x, or S52.04x instead.

The medical billing principle here is straightforward: every digit in S52.001P must have a corresponding documentation anchor in the clinical record. If any element is missing, the coder should query the provider before submitting.

S52.001P vs related codes: malunion, nonunion, and routine healing

The three subsequent-encounter characters that orthopedic coders confuse most often are D, K, and P. Each describes a different healing outcome. Submitting P when D is correct (or vice versa) misrepresents the clinical status and may trigger a post-payment audit. For claims submitted through a Claim.MD clearinghouse integration, the built-in ICD-10 catalogue flags codes in the S52 family for completeness before transmission.

The practical rule turns on where the bone is in its healing. If it is still healing and misaligned or not uniting, characters G and K apply. Once healing has finished, use D for a normal outcome or P for a malunion. After all treatment is concluded and only late effects remain, S applies. The clean claim requirement means the 7th character must match the documented clinical status precisely.

Approximate synonyms and clinical terms for S52.001P

Medical documentation rarely uses the exact ICD-10-CM phrasing. Coders need to recognize the clinical language that maps to S52.001P. The following terms in a provider’s note or imaging report should trigger consideration of this code (subject to all other documentation criteria being met).

• Right proximal ulna fracture with malunion, follow-up
• Upper end right ulna fracture, subsequent encounter, malunion
• Right forearm fracture (upper ulna), healed in malposition
• Right ulna fracture near the elbow, closed, healed with deformity
• Fracture of right ulna (proximal), malunion, closed
• Right ulnar fracture, post-acute encounter, bone healed in the wrong position

Two families of terms need care here. An olecranon fracture and a coronoid process fracture both sit at the upper end of the ulna. Each one has its own code in S52.02x through S52.04x. S52.001 applies only when the record leaves the exact structure unspecified. A radial head fracture points at the radius instead, which is coded in S52.1.

Common coding errors and how to avoid them

The ICD-10 code S52.001P is technically straightforward, but a short list of errors accounts for most claim denials in this code family. Each one below carries its claim consequence and the documentation fix.

Practices managing high volumes of orthopedic fracture claims benefit from automated edits that flag S52 codes without a valid 7th character before submission. Pabau’s claims management software validates coding completeness as part of the claim workflow, catching character omissions before they reach the payer. Reviewing denial codes in medical billing after any S52.001P denial provides a direct audit trail to the specific character-selection error.

Related ICD-10 codes for ulna and forearm fractures

S52.001P sits inside a larger family of forearm fracture codes. Coders handling ulna fractures across different sites, lateralities, and encounter types need to navigate the S52 category accurately. The ICD List lookup tool gives free access to the complete S52 code set with parent-code navigation. For the shaft equivalent one subcategory down, see ICD-10 code S52.209K, which covers ulna shaft fracture nonunion.

The radius equivalent is a separate code

S52.101P is the code for an unspecified fracture of the upper end of the right radius with malunion. It looks almost identical on the page, and it is the substitution that causes the most trouble in this part of the tabular list. If the imaging report names the radial head or the radial neck, the claim belongs in S52.1 rather than here.

Using the electronic remittance advice (ERA) system after submission shows how payers process each S52 code. It flags character-level rejections with the adjustment reason code, which points straight back to the documentation deficiency. The medical claims clearinghouse process validates these codes before they reach the payer, catching errors that ERA would only flag after the fact.

How Pabau supports accurate ulna fracture coding

Most S52 denials start in the notes rather than on the billing screen. If the imaging report records malunion and the treatment note does not, the coder has nothing to anchor character P to. The same goes for laterality, which often lives in one system while the claim is built in another.

Pabau keeps the clinical record and the claim in one place. When a coder builds the claim, the treatment note, the attached imaging, and the patient’s encounter history are one click away. Nobody has to switch between an EMR and a separate billing tool to confirm which bone, which side, or which healing status the record supports.

Claims go out electronically through our Claim.MD integration, and the remittance advice lands back on the same record. When a payer rejects an S52 code, the practice can see which claim, which code, and which reason code. The fix becomes a documentation query instead of a hunt through the ledger, so fewer fracture claims get rebilled twice.

Submit fracture codes with fewer denials

Pabau integrates with Claim.MD to submit ICD-10-CM codes like S52.001P directly to over 4,000 US payers. Built-in ICD-10 catalogues, real-time eligibility checks, and electronic remittance advice keep your orthopedic claims clean from submission through payment.

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Conclusion

Fracture claim denials in the S52 category almost always trace back to a handful of errors. The usual culprits are the wrong bone, the wrong encounter type, the wrong healing status, and open/closed confusion. ICD-10 code S52.001P is precise – it encodes six distinct clinical facts (injury type, site, laterality, fracture status, encounter phase, and healing complication) into seven characters. Every one has to match the record.

Pabau’s integration with Claim.MD validates ICD-10-CM codes like S52.001P against a live catalogue of 4,000+ US payers before the claim transmits. Character errors surface before denials do. To see how the workflow handles orthopedic and musculoskeletal billing end to end, book a demo.

Continue your research

Need to understand the broader fracture billing landscape? Revenue cycle management fundamentals covers how fracture claims fit into the end-to-end billing workflow from documentation to payment.

Getting denials on orthopedic claims? Denial management in healthcare explains how to analyze, appeal, and prevent the most common orthopedic claim rejections.

Want to verify coding before submission? Insurance eligibility verification outlines how to confirm coverage and coding requirements before billing S52 fracture codes.

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