ICD code S52.121R – Displaced fracture of head of right radius

Key takeaways

S52.121R is a billable ICD-10-CM code for a displaced fracture of the head of the right radius. It is coded at a subsequent encounter for an open type IIIA, IIIB, or IIIC fracture that healed with malunion.

The 7th character R is only valid for an open fracture classified as Gustilo type III. Malunion must also be confirmed on imaging or by clinical assessment.

Missing Gustilo detail in the operative or clinic note is the leading cause of denials on this code.

Pabau’s claims management software submits CMS-1500 claims through Claim.MD, checks patient eligibility, and tracks claim status and ERA returns.

Full description and billable status

ICD-10 Code S52.121R is a valid, billable ICD-10-CM diagnosis code effective October 1, 2025 for fiscal year 2026. In short, it describes a displaced fracture of the head of the right radius at a subsequent encounter. The original injury was an open fracture classified as Gustilo type IIIA, IIIB, or IIIC that healed with malunion.

As a leaf-level code in the tabular list, it needs no further specification before submission. So, it is valid on HIPAA-covered transactions for Medicare, Medicaid, and commercial payer claims. The CDC/NCHS ICD-10-CM web tool confirms its FY2026 validity and full clinical description.

The code sits in a precise hierarchy. Its parent is S52.12 (fracture of head of radius), which falls under S52 (fracture of forearm). S52 belongs to chapter 19, covering injury, poisoning and certain other consequences of external causes (S00-T88).

Code details at a glance

The table below summarizes the key administrative and billing attributes of S52.121R. Therefore, coders submitting the code for the first time should verify each field against their payer contract.

How the 7th character works for S52.121x

The 7th character turns a base fracture code into a claim-ready code. For S52.121x, the valid set covers initial encounters, subsequent encounters, and sequelae.

Getting it wrong is the most common error on radial head fracture claims. In practice, coders reach for an initial-encounter character when the patient is presenting for follow-up care. Two axes decide the answer, shown below.

Two patterns create the most denials. The first is using character C, the initial-encounter character for open type IIIA to IIIC, at a return visit. In other words, that character is reserved for the encounter where active treatment begins.

The second is using R before malunion has been established on imaging or by clinical assessment. Instead, the 7th character must match the documented healing status, not the coder’s expectation of the outcome.

Gustilo classification for open fractures

The Gustilo-Anderson classification is the clinical framework that drives 7th character selection for every open fracture in ICD-10-CM. Without an open-fracture classification in the note, the coder cannot choose between character B and character C.

The 7th character groups all three type III subtypes together, so type III versus type I or II is the distinction that changes the code. Even so, recording the exact subtype still matters. Payers and auditors ask for it on high-severity open fracture claims, and the operative note is the only place it exists.

Clinicians should record the Gustilo type in the operative note at the time of initial treatment. At subsequent encounters, the treating provider’s note should reference the classification from the original operative record.

Coders who see only “open fracture” with no type should query the provider before assigning a character from the type III group.

Malunion vs. nonunion: key coding distinction

Malunion and nonunion are not interchangeable. They are clinically distinct healing outcomes, and they map to different 7th characters. Thus, confusing them on a claim can result in medical necessity denials or audit findings.

• Malunion (7th character R for open type III): The fracture has healed, but in an abnormal anatomical position. Bone union has occurred, confirmed by imaging showing bony bridging, but alignment is incorrect. The patient may have functional limitations, pain, or deformity as a result. S52.121R applies when this outcome is documented at a subsequent visit.
• Nonunion (7th character N for open type III): The fracture has failed to heal within the expected timeframe. That usually means no radiographic evidence of progressive healing after three to six months. No bony bridging is present. S52.121N is the correct code in this scenario, not S52.121R.
• Delayed healing (7th character J for open type III): Healing is progressing but slower than expected. The fracture has not yet reached union or confirmed nonunion. This is a transitional state requiring close monitoring and reassessment.

Above all, the clinical note must explicitly state which outcome applies. Coders should not infer malunion from imaging language like “healing in slight angulation” without a physician statement confirming malunion. When in doubt, query the provider. In sum, the burden of proof rests on clinical documentation, not on coder interpretation.

Displaced vs. nondisplaced fracture: coding impact

S52.121R specifies a displaced fracture. Displacement refers to the alignment of fracture fragments at the time of injury, not at the subsequent encounter. The displacement status is documented at the initial encounter and carries forward into subsequent encounter coding unless the operative note documents anatomical reduction.

Subsequent encounter: when to use the R suffix

Subsequent encounter codes apply once active treatment has concluded and the patient is receiving routine care. That covers follow-up visits to monitor healing, physical therapy referrals, and visits to assess complications such as malunion. For instance, coders running medical claims clearinghouse workflows for orthopedic practices meet these scenarios every month after surgery.

Use the R suffix only when three conditions are met. The encounter is a subsequent visit, not the initial treatment episode. The fracture was open and classified as Gustilo type IIIA, IIIB, or IIIC at the time of injury. Malunion has been confirmed by the treating clinician. If any of these elements is missing from the documentation, R is not supportable.

• Use R: Patient returns six months after open reduction internal fixation of a displaced right radial head fracture. The operative note documented Gustilo type IIIA. Current X-ray shows healed fracture with 15 degrees of angulation. Physician notes malunion with resulting limited pronation.
• Do not use R: Patient presents at eight weeks post-op. X-ray shows “healing in progress, slight malposition.” No physician statement confirms malunion. In this case, use 7th character J (delayed healing) pending further assessment.
• Do not use R: Patient is presenting for their first visit after a motor vehicle accident with a radial head fracture. The initial treatment encounter uses A, B, or C depending on fracture type.

Documentation requirements for S52.121R

Every element of this code must be traceable to a specific statement in the clinical record. So, the checklist below names each required item and what happens to the claim when it is missing.

Work through it at the point of documentation. Indeed, a provider query raised at billing time costs days that a single sentence in the note would have saved.

Device codes answer to a different checklist. Billing a hand orthosis as HCPCS code L3923 requires a fitting note naming the customization performed and the credential of the person performing it. Without a physical modification at fitting, the off-the-shelf code L3924 applies instead.

Sibling and adjacent codes for S52.121R

The AAPC Codify ICD-10-CM lookup lists the complete S52.121x series alongside its left-side equivalents. Then, the table below gives the siblings and adjacent codes a coder is most likely to need.

For how these codes group into MS-DRGs for inpatient reimbursement, CMS publishes the MS-DRG classifications and software files each fiscal year.

Common coding errors and how to avoid them

Five errors account for most claim rejections and audit findings on S52.121R. Practices with a high denial rate on open fracture codes should start with the common denial codes they are receiving. Then, match each one back to the documentation item below that would have prevented it.

• Wrong 7th character at a subsequent encounter: Using C, the initial-encounter character for open type IIIA to IIIC, instead of the correct subsequent character. C is only valid at the first treatment encounter. After that, D through S apply depending on healing status.
• Generic “open fracture” with no type: The 7th character table splits type I or II from type IIIA to IIIC. A note that says only “open fracture” supports neither group, so query the provider. Payers also increasingly ask for the exact subtype on type III claims.
• Confusing S52.121R (malunion) with S52.121N (nonunion): Indeed, these represent opposite clinical outcomes. Malunion means the bone healed in an abnormal position. Nonunion means it did not heal. Using R when the note says “failure to heal” or “no callus formation” is a documentable error.
• Laterality error: Assigning S52.121R (right) when the chart documents left radial head involvement. Instead, always verify laterality against the operative note and imaging report, not just the chief complaint.
• Missing the sequela distinction: Character S applies when the patient presents for a residual condition caused by the original fracture. For instance, chronic pain and contracture are typical examples. In that case, the residual condition becomes the principal diagnosis, and S52.121S is the secondary code identifying the causative injury.

ICD-9-CM crosswalk for S52.121R

ICD-9-CM crosswalks give approximate equivalents for legacy billing, historical record review, and payer systems that still reference older codes. S52.121R maps roughly to ICD-9-CM 813.05 (closed fracture of radial head) and 813.15 (open fracture of radial head).

Neither is an exact match, because ICD-9-CM did not carry Gustilo classification, displacement status, or malunion at this level of detail. For this reason, the CMS ICD-10 codes page hosts the General Equivalence Mappings, and coders should work from those files rather than from memory.

Also, the AAPC crosswalk tool handles reverse lookup for practices reviewing historical records.

How Pabau supports claim submission for fracture codes

In most orthopedic practices the note lives in one system and the claim gets rebuilt in another. A coder reads the operative report, retypes the diagnosis and encounter details into a billing screen, and trusts the two still match. As a result, every extra hop is another chance for laterality or an encounter character to arrive wrong.

Practice management software like Pabau holds the appointment, the clinical note and the invoice in one patient record. Also, its claims tools for practices build the CMS-1500 from that record. The claim goes out through Claim.MD, a clearinghouse supporting more than 4,000 US payers.

From there the practice checks patient eligibility before the visit and watches claim status without calling the payer. The ERA comes back against the invoice it was raised from. Even so, choosing the 7th character is still the coder’s judgment call. Instead, what changes is that the submission carries what the record already says.

Send fracture claims straight from the patient record

Pabau builds the CMS-1500 from the patient record and submits it through Claim.MD. Check eligibility before the visit, follow claim status without calling the payer, and match every ERA back to its invoice.

Book a demo

Conclusion

Denials on S52.121R come back to the note, not to the code. If the operative report establishes an open type III fracture and a later note states malunion, the R character is defensible. Still, no amount of billing rework makes it stick.

So the work sits upstream. Get the Gustilo classification into the operative note on the day of surgery. Then get an explicit malunion statement into the follow-up note before the claim goes out.

Querying the provider six weeks later costs far more than writing one sentence at the time. Pabau checks the administrative fields a CMS-1500 needs before submission, then tracks the claim and the remittance in the same record as the visit. Book a demo to see how that shortens the loop between an orthopedic note and a paid claim.

Continue your research

Managing denial codes after a rejected fracture claim? Denial codes in medical billing explains the most common CARC denial codes and how to respond to each one.

Need a clearinghouse that handles open fracture claims end to end? The Claim.MD clearinghouse guide covers how Claim.MD processes 837P claims and returns ERA data for orthopedic and trauma practices.

Building a cleaner billing workflow for your orthopedic or PT practice? Revenue cycle management fundamentals walks through the full RCM cycle from intake to payment posting.

Frequently asked questions