ICD-10 code S52.355J: Nondisplaced comminuted fracture of shaft of radius

Key Takeaways

ICD-10 code S52.355J describes a nondisplaced comminuted fracture of the shaft of the radius (unspecified arm), subsequent encounter for an open fracture type IIIA, IIIB, or IIIC with malunion

The 7th character J is the key billing signal: it encodes three simultaneous facts – subsequent encounter, open fracture Gustilo type III subclass, and malunion healing complication

Unspecified arm laterality should only be coded when clinical documentation genuinely does not identify left or right – auditors routinely flag incorrect use

Pabau’s claims management software and digital forms help orthopaedic and musculoskeletal practices document displacement status, Gustilo subtype, and encounter type accurately at every visit

According to CMS ICD-10-CM guidance, S52.355J is a valid, billable diagnosis code for fiscal year 2026, effective October 1, 2025, and is accepted for HIPAA-covered transaction submission.

ICD-10 Code S52.355J: quick reference

S52.355J is a specific, billable ICD-10-CM code. The table below captures every detail a coder needs at a glance before reviewing supporting sections.

Full code description and clinical meaning

Each word in the ICD-10 Code S52.355J description carries a billing consequence. Misreading any component leads to the wrong code selection.

• Nondisplaced: The fracture fragments remain in anatomic alignment. No separation of bone ends has occurred. This is the opposite of a displaced fracture, where fragments shift out of position.
• Comminuted: The bone has shattered into three or more fragments at the fracture site. Comminuted fractures are associated with higher-energy mechanisms (motor vehicle accidents, falls from height).
• Shaft of radius: The fracture is located in the diaphysis (mid-section) of the radius, not the distal end (Colles/Smith-type) or radial head. Anatomical specificity is required.
• Unspecified arm: Laterality is not documented. Use this only when the medical record genuinely does not identify left or right – payer auditors flag incorrect use of “unspecified” as a documentation deficiency.
• Subsequent encounter: The patient is receiving active care after the initial treatment phase has concluded. Routine follow-up visits, wound checks, and physical therapy consultations following definitive treatment fall under subsequent encounter.
• Open fracture type IIIA, IIIB, or IIIC: The fracture was open (skin breached, bone exposed), graded as Gustilo-Anderson Type III – the most severe open fracture category. ICD-10-CM does not distinguish between IIIA, IIIB, and IIIC within this 7th character; the code applies to all three subtypes.
• With malunion: The fracture has healed, but in a non-anatomic position. This healing complication is the reason the encounter is taking place.

For practices documenting complex musculoskeletal cases, digital intake forms that capture displacement status and encounter type at the point of care significantly reduce post-visit documentation gaps.

Understanding the 7th character J in fracture coding

The 7th character is the most consequential element of any S52-range fracture code. Without it, the code is invalid and unpayable. For S52.355, there are 18 valid 7th character options covering initial encounters, subsequent encounters, and sequela across closed and open fracture types.

Note that characters L, I, and O are not used in this range – ICD-10-CM avoids letters that visually resemble numbers 1 and 0. For reference on how ICD-10-CM diagnosis code reference structures apply across clinical specialties, the coding logic follows the same 7th character framework throughout the tabular list.

Gustilo classification for open fractures: types IIIA, IIIB, and IIIC

The Gustilo-Anderson classification is the standard system for grading open fracture severity. Developed in peer-reviewed orthopaedic literature, it bases grading on wound size, degree of soft tissue injury, and vascular involvement. For ICD-10 Code S52.355J, the medical record must document that the original fracture was a Gustilo Type III injury – the subtype (IIIA, IIIB, or IIIC) determines surgical management, but all three map to the same 7th character J for this subsequent encounter with malunion. For practices managing these patients, a physical therapy EMR can help structure follow-up care documentation across the full rehabilitation episode.

When the operative note or discharge summary specifies the Gustilo subtype, coders should record it in the documentation even though ICD-10-CM groups IIIA, IIIB, and IIIC under the same 7th character. This supports medical necessity and protects against audit queries.

Malunion vs. nonunion vs. delayed union: What each means for coding

These three healing complications are frequently confused, and coding them incorrectly changes the 7th character entirely. The table below shows how each maps to a different character in the S52.355 family. Refer to the ICD-10 hemorrhage diagnosis codes article for a parallel example of how healing and complication qualifiers operate across different injury categories in ICD-10-CM.

The critical distinction: malunion means the bone has healed, just incorrectly. Nonunion means the bone has not healed at all. Submitting S52.355J (malunion) when the patient actually has a nonunion is a material coding error with potential fraud and abuse implications.

ICD-10-CM hierarchy and parent codes for S52.355J

Understanding the classification tree helps coders verify that S52.355J is the most specific code available, and supports chart audits. For additional context on how ICD-10 documentation workflows apply across specialties using the same hierarchical logic, the coding structure follows identically throughout the tabular list.

Related codes: the S52.355 family

S52.355J sits within a family of sibling codes that cover the same base fracture (nondisplaced comminuted fracture of shaft of radius, unspecified arm) across every encounter type and healing outcome. Selecting the correct sibling is the primary coding decision. Practices managing sports-related forearm injuries may find that a sports medicine practice management platform with built-in coding workflows reduces selection errors across this code family.

Use the AAPC Codify ICD-10-CM lookup to verify the full S52.355 sibling list and confirm which 7th characters are valid for a given fiscal year before submission.

Documentation requirements for coding ICD-10 Code S52.355J

Every element of the 7th character J must appear explicitly in the medical record. Coders cannot infer these details from context – payer audits specifically look for documented support for each qualifier. This is particularly important for open fracture type IIIA, IIIB, or IIIC ICD-10 coding, where Gustilo subtype documentation is the most commonly missing element. Clinics managing complex trauma patients should review compliance requirements for musculoskeletal clinics for broader documentation standards applicable to this patient population.

• Displacement status: The operative report or clinical note must state “nondisplaced.” If displacement status is not documented, do not assume – query the provider.
• Fracture type: The record must confirm the fracture was “open” and record the wound description or surgical findings that support this classification.
• Gustilo subtype: The orthopaedic note or operative report must specify Type IIIA, IIIB, or IIIC. “Open fracture Type III” without the subtype is insufficient documentation for coding purposes, though ICD-10-CM groups them under the same 7th character.
• Encounter type: The visit must be a follow-up visit, not the initial treatment episode. A patient presenting for the first time after sustaining this fracture uses S52.355C (initial encounter, open type IIIA/IIIB/IIIC), not S52.355J.
• Laterality: If the record identifies left or right, use S52.351 (right) or S52.352 (left) rather than S52.355 (unspecified). Unspecified is only appropriate when laterality is genuinely absent from the record.
• Healing complication: The treating clinician must document malunion specifically – radiographic findings, clinical examination findings, or both – in the note for the visit being coded.

Practices using digital intake forms can build encounter-type and healing-status checkboxes into follow-up templates, prompting providers to capture all required ICD-10 qualifier fields at the point of care rather than during retrospective chart review.

Common coding errors and how to avoid them

S52.355J is a code where most errors occur at the 7th character selection stage, not the base code. The clinical descriptions are granular enough that coders who work quickly through high-volume orthopaedic encounters frequently apply the wrong qualifier. Implementing features that streamline clinical documentation helps reduce the retrospective coding burden that increases error rates.

• Confusing malunion (J) with nonunion (N): These are the two most commonly swapped 7th characters for open Type III fractures. Malunion = healed incorrectly. Nonunion = not healed. The clinical note must state which complication is present.
• Using the initial encounter code on a follow-up visit: S52.355C is the initial encounter equivalent of S52.355J. A patient attending a six-week post-op review should never have S52.355C on the claim. The ICD-10-CM Official Guidelines for Coding and Reporting define initial, subsequent, and sequela encounter types precisely.
• Ignoring laterality when it is documented: If the record says “left radius,” the coder must use the left-side sibling code (S52.352J), not S52.355J. Using “unspecified” when laterality is available in the chart is a documentation deficiency that auditors flag.
• Missing Gustilo subtype in the source document query: If the original Gustilo subtype is not in the record being coded, the coder should query the provider rather than defaulting to a lower-grade open fracture code. Incorrect downgrading affects case mix reporting and DRG assignment for inpatient claims.
• Applying S52.355J to a closed fracture with malunion: The J 7th character specifically encodes an open Type IIIA/IIIB/IIIC fracture with malunion. A closed fracture with malunion uses S52.355P, not S52.355J.

The CDC/NCHS ICD-10-CM web tool allows coders to look up codes by description and verify the 7th character table directly from the official tabular list before submission. The ICD List also provides a free search tool mirroring CMS and NCHS data for rapid code verification.

Approximate synonyms and clinical terms for S52.355J

Operative notes, discharge summaries, and referral letters use varied clinical language. Coders who encounter any of these terms should consider S52.355J as a candidate code – then verify all qualifying conditions are met. For HIPAA-compliant patient data workflows governing how clinical records are stored and transmitted, practitioners should ensure diagnostic codes are logged against each encounter in the patient record.

• Nondisplaced comminuted radial shaft fracture, open type III, with malunion
• Malunited open comminuted fracture of the radius shaft, unspecified side
• Radius shaft comminuted fracture, Gustilo III, healed in malposition
• Subsequent care: nondisplaced open comminuted fracture of the radius with malunion
• Comminuted radial diaphysis fracture with malunion, open wound, type IIIA/IIIB/IIIC

None of these synonyms should replace a direct code lookup. They serve as pattern-recognition triggers – when a coder encounters this language, it signals the S52.355 family is the correct starting point, with the 7th character then selected based on full documentation review.

How Pabau supports accurate fracture coding workflows

Orthopaedic and musculoskeletal practices dealing with complex open fractures face a documentation challenge: ensuring that every follow-up encounter captures the qualifier details ICD-10 Code S52.355J requires. Missing a single element – laterality, Gustilo subtype, healing status – changes the valid code or makes the claim unpayable.

Pabau’s claims management software gives practice teams a structured environment for linking diagnosis codes to each encounter, reviewing documentation completeness before submission, and tracking claim status after submission. Combined with the platform’s appointment and encounter management tools, it helps practices distinguish between initial and subsequent encounter visits at the scheduling level – reducing the risk of applying the wrong 7th character before the claim is ever generated. Book a demo to see how Pabau handles musculoskeletal billing workflows.

Conclusion

ICD-10 Code S52.355J is a billable, FY2026-valid diagnosis code encoding a highly specific clinical scenario: a nondisplaced comminuted fracture of the radial shaft (unspecified arm), documented at a subsequent encounter following an open Gustilo Type IIIA/IIIB/IIIC injury, where the fracture has healed in a non-anatomic position (malunion). Every component of that description must appear in the supporting medical record.

The most common errors – confusing malunion with nonunion, applying initial encounter codes at follow-up visits, and ignoring laterality – are preventable with a structured documentation checklist at the point of care. Pabau’s clinical documentation and claims management tools help orthopaedic practices build that checklist into every follow-up encounter template.

Continue your research

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