ICD-10 Code S52.261R: Segmental ulna fracture with malunion

Key takeaways

ICD-10 code S52.261R covers a displaced segmental fracture of the right ulna shaft, documented at a follow-up visit. The original wound was an open Gustilo Type III injury, and the bone healed malaligned.

The 7th character R is what carries the malunion meaning. S52.261E is a different scenario, covering an open type I or II wound with routine healing.

Malunion means the bone united in the wrong position. Nonunion means it never united, and that takes character N after an open Type III wound.

Practice management software like Pabau helps orthopedic teams track fracture encounter types, so S52 claims carry the right 7th character.

ICD-10 code S52.261R is the seven-character code for a displaced segmental fracture of the right ulna shaft at a follow-up visit. It applies when the original wound was an open Gustilo Type III injury and the bone has healed out of alignment. Both of those facts have to be in the chart before you can use it.

This guide breaks down every qualifier in the descriptor, the full 7th character table, and the documentation a payer will ask for. It also covers the letters most often confused with R, including S52.261E, which many coding references mislabel as the malunion code.

ICD-10 code S52.261R: Quick reference

S52.261R is a valid, billable ICD-10-CM diagnosis code for the FY2026 code set. According to the CDC/NCHS ICD-10-CM web tool, the code carries no age or sex exclusions. It is accepted in HIPAA-covered transactions.

What does S52.261R mean? Full code description

Here is the full official descriptor. Displaced segmental fracture of shaft of ulna, right arm, subsequent encounter for open fracture type IIIA, IIIB, or IIIC with malunion. Every word is a billable qualifier. Omitting any one of them in the chart creates a mismatch between the clinical record and the submitted code. Practice management software like Pabau adds claims management that flags these mismatches before submission.

Each segment of the descriptor carries a distinct clinical meaning. Coders who can read every qualifier are able to verify documentation before submission, rather than coding from memory.

• Displaced: The fracture fragments are separated or misaligned from their normal anatomical position. ICD-10-CM splits displaced from nondisplaced at every code level, so the operative or imaging report must state displacement explicitly.
• Segmental: Two separate fracture lines isolate a mid-shaft bone segment, leaving it free-floating. This is a higher-severity pattern than a simple transverse or oblique fracture.
• Shaft of ulna: The fracture sits in the diaphysis, the mid-section of the bone. Proximal and distal ulna fractures use different S52 sub-codes.
• Right arm: Laterality is required, and it is built into the 6th character. For segmental ulna shaft fractures, 1 is the right arm and 2 is the left.
• Subsequent encounter: Active treatment has already been delivered. Follow-up visits for healing assessment, hardware monitoring, or rehabilitation belong here.
• Open fracture type IIIA, IIIB, or IIIC: The skin was breached, and the wound met Gustilo-Anderson Grade III criteria. This qualifier is set at the initial encounter and carries through to every later visit.
• With malunion: The fracture has united, but in an anatomically abnormal position or alignment.

S52.261 7th character options: Full table

The 7th character is where S52 coding usually goes wrong, so it pays to work from the CMS ICD-10-CM coding guidance. S52.261 supports sixteen 7th characters. Each one combines an encounter type, a wound status, and a healing outcome. The alphabet is not continuous, because ICD-10-CM fracture extensions skip I, L, and O to avoid confusion with digits.

Read the table as three questions in sequence. Is this the initial encounter or a follow-up? Was the wound closed, open type I or II, or open type IIIA to IIIC? Did the bone heal routinely, heal slowly, fail to heal, or heal crooked? Answer all three and only one letter survives.

S52.261R vs S52.261E, S52.261F, and S52.261N

These four letters share the same base code and the same right ulna shaft anatomy. They differ only in wound grade and healing outcome. Published coding references get these four wrong often enough to be worth a check against the official tabular list.

One practical rule keeps R defensible. Use it only when the chart documents a follow-up visit, an original Gustilo Type III wound, and confirmed malunion. Miss any of the three and the code cannot be supported on audit. Practices handling complex orthopedic caseloads rely on structured clinical record documentation to tie each encounter to the right 7th character.

Gustilo-Anderson open fracture classification: Types IIIA, IIIB, and IIIC

The Gustilo-Anderson classification is the standard ICD-10-CM uses to grade open fracture severity. It was set out by Gustilo and Anderson in 1976, and extended by Gustilo and colleagues in 1984. Type III covers high-energy injuries with significant soft-tissue damage. The three sub-types differ in how much coverage the bone keeps, and whether the blood supply survived.

ICD-10-CM does not split IIIA, IIIB, and IIIC at the 7th character. All three share one letter for each combination of encounter and healing outcome. For this code that means C at the initial encounter, F for routine healing, J for delayed healing, N for nonunion, and R for malunion. The clinical distinction still matters for surgical planning, even though it does not narrow the code.

What is malunion? Malunion, nonunion, and delayed healing compared

Malunion is easy to misapply on S52 subsequent-encounter codes. Its clinical definition is narrow, and getting it right prevents both upcoding and downcoding. The same three-way split runs through every fracture family, from the ulna to S72.452Q at the femur.

• Malunion (7th character P, Q, or R): The fracture has united, so healing is complete. The result is angular deformity, rotational malalignment, or shortening. Closed fractures take P, open type I or II takes Q, and open type IIIA to IIIC takes R.
• Nonunion (7th character K, M, or N): The fracture has failed to heal in the expected timeframe. No bridging callus appears on imaging, and the bone ends stay mobile. Closed fractures take K, open type I or II takes M, and open type IIIA to IIIC takes N as the extension. The same logic sets S72.334N at the femoral shaft.
• Delayed healing (7th character G, H, or J): Healing is progressing, just more slowly than expected. It is neither complete nor failed. Closed fractures take G, open type I or II takes H, and open type IIIA to IIIC takes J.

For S52.261R the record must carry imaging evidence of malalignment, or an explicit physician statement of malunion. A note reading follow-up, fracture healing says nothing about alignment, so it cannot support the R extension. The correct choice there is F, which covers routine healing of an open Type III fracture.

Initial vs. subsequent vs. sequela: Encounter type guide for S52 fractures

The ICD-10-CM Official Guidelines define three encounter types for fractures. Choosing the wrong one is a frequent audit trigger in orthopedic coding, and the AAPC ICD-10-CM coding resources set out the distinctions. Practices using a physical therapy EMR meet this distinction constantly when billing rehab visits after surgical repair.

One point trips up coders repeatedly. A subsequent encounter is not simply the patient’s second or third visit in calendar order. It means active treatment has ended. A patient who has a second surgery at another facility is back at an initial encounter, because new active treatment is being delivered.

Documentation requirements for S52.261R

S52.261R needs seven separate facts in the chart. Capture each qualifier before the code is assigned, not after. Every element below has to be present and legible in the clinical record.

• Fracture pattern, segmental: The operative note or imaging report must describe two fracture lines isolating a free bone segment. Comminuted is not an equivalent term.
• Displacement: The record must state that the fracture is displaced. A bare reference to a fracture of the ulnar shaft does not confirm displacement.
• Anatomical site, shaft: Specify the diaphysis, or mid-shaft, location. Proximal and distal ulna fractures use different codes.
• Laterality, right arm: State it explicitly. It cannot be inferred from a single-limb X-ray order.
• Encounter type, subsequent: The note must show that active treatment happened at a prior encounter. A line such as patient returns for follow-up after open reduction meets the threshold.
• Open wound grade, Gustilo IIIA, IIIB, or IIIC: Carry the original Gustilo classification across from the operative report. If the follow-up note does not reference it, attach the operative note or add a short clinical summary.
• Healing outcome, malunion: Include a physician statement of malunion, or an imaging report noting angular deformity or malalignment of healed fragments.

Orthopedic practices with high trauma follow-up volumes use structured digital intake forms to pre-populate encounter type and fracture classification fields. Hand and forearm rehab teams on occupational therapy software record the same fields at every visit. Prompting for them at the point of care is what stops an omission from reaching the coder.

CPT codes commonly used with S52.261R

S52.261R pairs with different procedure codes depending on whether the visit is surgical or non-surgical. Malunion correction at the ulna shaft usually means a repair or osteotomy code, while a monitoring visit means an office visit code. Verify medical necessity pairing against payer policy before you submit.

Sequence S52.261R as the diagnosis that justifies the procedure. When a corrective osteotomy or revision repair is performed, the malunion is the medical necessity, so the diagnosis has to state it plainly.

Reimbursement and claim sequencing for S52.261R

S52.261R is accepted by Medicare, Medicaid, and most commercial payers for HIPAA-covered transactions, according to Check ICD-10. Payer rules still vary, so verify Local Coverage Determinations before submitting. Your compliance records should show which policy you checked.

• Primary or secondary diagnosis: S52.261R works as either. A visit focused on the malunion makes it the principal diagnosis. A visit where the malunion is incidental to another complaint places it as a secondary code.
• Sequencing with procedure codes: When revision fixation or corrective osteotomy is performed, the bone repair CPT codes sit alongside S52.261R as the justifying diagnosis.
• No Excludes 1 or Excludes 2 barrier: The code carries no exclusion note of its own. You can code it alongside soft-tissue injury, vascular repair, or infection codes from the same encounter.
• Workers’ compensation and liability: Most workers’ comp payers accept the code. Confirm with the specific payer, because open fracture with malunion often draws a request for extra clinical documentation.

Related ICD-10-CM codes for displaced segmental fracture of shaft of ulna

Coders working with S52.261R regularly need the adjacent letters, the opposite laterality, and the radius equivalent. The table below covers the codes requested most often. Clavicle malunion follows the same pattern under S42.012P.

ICD-10-CM coding guidelines for S52 forearm fractures

The ICD-10-CM Official Guidelines for Coding and Reporting set specific rules for the S52 category. Practices that write these rules into their internal protocol, and back them with clinical documentation software, see fewer code revisions mid-audit.

• The 7th character is mandatory: S52.261 on its own is not billable. Laterality lives in the 6th character, and the 7th character is what makes the code specific enough to submit.
• Multiple fracture sequencing: When the radius and ulna are both fractured, code each bone separately. The more severely injured bone is generally sequenced first, and official guidance defers to provider judgment when severity is equivalent.
• Open fracture grade carries forward: The Gustilo classification set at the initial encounter stays with the case. If the operative report documented Type IIIB, later encounters keep using the IIIA to IIIC letter group, whatever the wound looks like at follow-up.
• Traumatic and pathological fractures differ: S52 codes cover acute traumatic injury. Fractures caused by osteoporosis, malignancy, or another underlying condition use the M80 pathological fracture codes instead.

Approximate synonyms and clinical terminology for S52.261R

Physician notes rarely use the exact ICD-10-CM descriptor. The phrases below should prompt a coder to consider S52.261R, provided every other qualifier is also documented.

• Displaced segmental ulnar shaft fracture, right, follow-up, Gustilo III, malunited
• Right forearm ulna segmental fracture, open type III, subsequent visit, healed in malalignment
• Right ulna diaphysis segmental fracture, subsequent encounter, open grade III, malunion
• Right arm ulna shaft fracture, two fracture lines, open wound type IIIA to IIIC, follow-up care, malaligned healing
• Segmental fracture right ulna mid-shaft, contaminated wound Gustilo III, follow-up, bone united in abnormal position

How Pabau keeps fracture records claim-ready

In most orthopedic practices the 7th character is decided at the end of the process. A coder reads a follow-up note written days earlier. Then they hunt for the original Gustilo grade in a separate operative report, and guess the healing outcome from whatever the clinician wrote. That is how an S52.261R claim ends up submitted as S52.261E.

Practice management software like Pabau moves the decision to the point of care. Structured clinical forms prompt the clinician for encounter type, wound grade, and healing status while the patient is in the room. Every prior note, operative report, and image sits in one client record. The Gustilo grade from the initial encounter is one click away, not a phone call.

Claims then go out with the diagnosis and procedure codes already matched, and the supporting documentation attached. Your team spends less time reworking denials, and the codes you submit are the codes you can defend if a payer asks for the chart.

Streamline orthopedic billing from first encounter to follow-up

Pabau helps musculoskeletal and orthopedic practices track fracture encounter types, document Gustilo classifications, and submit cleaner S52 claims with fewer denials.

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Conclusion

Coding S52.261R well is a documentation habit more than a coding one. When the follow-up note names the Gustilo grade and states malunion outright, the letter picks itself. When it does not, F or N is usually the more honest answer.

So the letter worth guarding is R, not E. Both letters sit on the same base code. One keystroke turns an open Type III malunion into a lower-grade wound that healed on schedule. Prompt the clinician for both facts in the note and that substitution stops happening.

Practices that build encounter-type and fracture-classification prompts into their practice management workflows see fewer S52 denials. To see how Pabau supports trauma documentation and claims, book a demo.

Continue your research

Coding the same malunion after a lower-grade open wound? S72.452Q walks through the malunion extension on an open type I or II femur fracture.

Need the nonunion side of the decision? S72.334N covers what imaging has to show before you drop the routine-healing letter.

Coding malunion on a closed fracture instead? S42.012P shows how the same healing outcome works without an open wound qualifier.

Working across a shoulder fracture family too? S42.034P applies the malunion extension to a nondisplaced greater tuberosity fracture.

Want the extension tables in one place? The medical coding cheat sheet collects the tables coders reach for most often.

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