ICD-10 Code S52.202H: Left ulna shaft fracture with malunion

Key Takeaways

S52.202H is a billable ICD-10-CM code for unspecified fracture of shaft of left ulna, subsequent encounter for open fracture type IIIA, IIIB, or IIIC with malunion

The 7th character H requires two conditions: the patient is in a subsequent (follow-up) encounter AND the fracture had open wound classified as Gustilo-Anderson Type IIIA, IIIB, or IIIC with documented malunion

Malunion (bone healed in misaligned position) uses 7th characters H, M, N, or R; nonunion (bone failed to heal) uses K, P, or Q – selecting the wrong suffix triggers claim denials

Pabau’s claims management software connects to the Claim.MD clearinghouse, supporting clean ICD-10-CM claim submission for fracture aftercare encounters

Open fracture aftercare is one of the most denial-prone areas in musculoskeletal coding. The Gustilo-Anderson classification adds clinical specificity that coders must translate precisely into 7th character selection, and the malunion/nonunion distinction trips up even experienced billers. ICD-10 Code S52.202H collapses several of these variables into a single billable code, and getting it right matters: a wrong 7th character on a subsequent encounter claim goes back unpaid, delaying reimbursement for a patient who may already be weeks into recovery. This reference covers the code’s full description, structure, 7th character logic, Gustilo classification context, and billing considerations for physical therapy practices and orthopaedic teams managing these complex fractures.

ICD-10 Code S52.202H: full description and billable status

ICD-10 Code S52.202H is a billable, specific ICD-10-CM diagnosis code. Its full official description is: Unspecified fracture of shaft of left ulna, subsequent encounter for open fracture type IIIA, IIIB, or IIIC with malunion. The 2026 edition of ICD-10-CM S52.202H became effective October 1, 2025, under the FY2026 update maintained by the Centers for Medicare and Medicaid Services (CMS) and the National Center for Health Statistics (NCHS).

Because this code carries a valid 7th character extension, it can be used directly on a claim without selecting a more specific child code. S52.202 without the 7th character is non-billable; the 7th character is mandatory for any claim submission.

What S52.202H means: breaking down the code structure

Every character in S52.202H carries clinical meaning. Misreading any segment leads to the wrong code selection.

The code hierarchy runs from the broad injury chapter (S00-T88) through the forearm fracture category (S52), down to the shaft of ulna subcategory (S52.2), and finally to the specific left-sided unspecified shaft fracture with the 7th character completing the clinical picture. The parent code S52.202 is non-billable on its own. As noted by the AAPC ICD-10-CM code reference, a 7th character extension must always be appended to complete the code.

Understanding the 7th character H: subsequent encounter for open fracture with malunion

The 7th character is where most coding errors on S52.202 occur. The character H encodes three simultaneous facts: the encounter type (subsequent), the original wound status (open), and the healing outcome (malunion). All three must be clinically accurate before assigning H.

The full table of 7th character options for S52.202 covers every combination of encounter type, wound status, and healing outcome. Use this table to locate the correct character when the clinical picture differs from the H scenario.

Gustilo-Anderson classification: types IIIA, IIIB, and IIIC explained

The Gustilo-Anderson classification system grades open fractures by wound size, degree of contamination, and soft tissue damage. For ICD-10 Code S52.202H, the clinician must have documented the original fracture as Grade IIIA, IIIB, or IIIC at the time of the initial injury encounter. Using 7th character H without that underlying documentation is a coding error, and payers may audit it as such.

The distinction between IIIA and IIIB turns on whether periosteal stripping has occurred; IIIC is defined entirely by arterial injury. When operative notes are ambiguous, the original treating surgeon should clarify the grade in an addendum before the coder assigns H (or any other Type III-specific 7th character) on a subsequent visit claim.

Malunion vs. nonunion: choosing the correct ICD-10 code

Malunion and nonunion are both complications of fracture healing, but they are clinically and radiologically distinct, and ICD-10-CM encodes them with completely different 7th characters. Assigning one when the other applies is among the most common fracture coding errors flagged in payer audits.

The clinical documentation must specifically state “malunion” or provide imaging findings consistent with malunion for code H to be valid. Terms like “delayed healing” or “slow to heal” do not support malunion and should instead point toward 7th character G (delayed healing, closed) or its open-fracture equivalents.

When to use a subsequent encounter code for fracture healing

Subsequent encounter coding applies once active treatment of the fracture is complete and the patient is receiving routine care during the healing or recovery phase. This is a concept embedded in the ICD-10-CM Official Guidelines and consistently misapplied when providers conflate “the first time the patient comes to our office” with “initial encounter.”

• Initial encounter (A, B, C): the patient is receiving active treatment for the fracture, regardless of which provider sees them. A second surgeon performing a corrective procedure on the same fracture is still using an initial encounter code.
• Subsequent encounter (D-R): active treatment is complete; the patient is receiving aftercare, monitoring, or management of a complication such as malunion. Routine follow-up visits, physical therapy encounters, and cast or hardware checks fall here.
• Sequela (S): used when the fracture itself has resolved but a late effect (such as chronic pain or limited range of motion directly caused by the old fracture) is the reason for the visit.

For S52.202H, the clinical scenario is: active treatment ended, the patient is being seen for management of a malunited left ulna shaft fracture that was originally open (IIIA/IIIB/IIIC), and the current visit is not re-initiating surgical or procedural treatment. If a corrective osteotomy is being performed to address the malunion, return to an initial encounter character for that procedure episode.

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Related ICD-10-CM codes for ulna and forearm fractures

Navigating the S52.202 sibling and adjacent codes prevents common laterality, wound-status, and healing-outcome errors. The table below covers the most frequently needed codes in this cluster, based on guidance from the ICD List reference database.

When the patient’s fracture was originally closed (not open), the correct malunion code at subsequent encounter is S52.202R, not S52.202H. Confirm the original wound type before selecting between these two. For guidance on denial management strategies when related fracture codes return on rejected claims, the Pabau blog covers common payer denial patterns in detail.

Approximate synonyms and clinical terminology

The ICD-10-CM index recognises several alternate clinical terms that map to S52.202H. Coders searching the index under these terms will be directed to this code or its parent category.

• Left ulnar shaft fracture, subsequent encounter with malunion (open grade IIIA/IIIB/IIIC)
• Malunited open fracture of the left ulna, follow-up care
• Open ulna shaft fracture with malunion, left, aftercare
• Fracture of the shaft of the left forearm bone (ulna), malunited, subsequent encounter
• Gustilo Type III open fracture of left ulnar shaft, healing with malunion

Clinical notes that use any of these descriptions should be mapped to S52.202H during chart abstraction, provided the wound was confirmed as Type IIIA, IIIB, or IIIC at initial encounter. Thorough medical billing compliance practices require that the coding audit trail links the subsequent encounter code back to the initial encounter documentation, including operative reports and emergency department notes.

Billing and reimbursement: using S52.202H for claims

S52.202H is a billable code and can be submitted on a CMS-1500 claim or 837P electronic transaction. Several documentation and payer considerations apply specifically to subsequent encounter open fracture claims. Understanding medical billing workflows for complex fracture aftercare helps reduce the risk of denial on what can be high-value orthopaedic encounters.

For US practices, Pabau integrates with electronic claims via Claim.MD, a clearinghouse connecting to over 4,000 US payers and supporting 837P claim submission, real-time eligibility checks, and electronic remittance advice. This is particularly useful when managing a fracture patient across multiple subsequent encounters. Sound revenue cycle management practices pair accurate code selection with clean electronic submission to reduce the administrative burden of fracture aftercare billing. Pabau’s claims management software handles the workflow from encounter documentation through to payer submission.

Key documentation requirements for S52.202H claims:

• Original operative note: confirms the fracture was open and the Gustilo-Anderson grade assigned at the time of initial injury or surgery
• Imaging report: current X-ray or CT confirming malunion (misaligned healed bone), not nonunion or delayed healing
• Encounter note: explicitly states this is a follow-up visit, not active surgical treatment
• Wound status: if the wound is closed at the time of the subsequent visit, the encounter is still coded with the original open fracture 7th character (per ICD-10-CM guidelines), but documentation of the original open status must be accessible

Pair S52.202H with the relevant CPT procedure code for the current visit (e.g. evaluation and management codes or manipulation codes if applicable). The clean claim submission process depends on the diagnosis code being specific, the encounter type being correct, and the procedure code pairing being medically appropriate. Reviewing insurance eligibility verification before the follow-up visit helps confirm the patient’s current coverage and any prior authorisation requirements for fracture aftercare. If claims return with a denial, consult superbill documentation practices and the clearinghouse submission process to identify whether the issue is at the code level or the claim format level. The electronic remittance advice returned by the payer will carry the specific denial reason code.

ICD-9 to ICD-10 crosswalk for S52.202H

Practices working with historical records or transitioning legacy documentation will need to map from ICD-9-CM to the ICD-10-CM equivalent. According to the ResDAC ICD coding resources for Medicare files, the General Equivalence Mapping (GEM) files provided by CMS facilitate bidirectional crosswalk lookups.

ICD-9-CM did not encode Gustilo-Anderson grades, laterality, or encounter type with the same granularity as ICD-10-CM. GEM forward maps for ulna fractures are typically one-to-many: a single ICD-9 code expands into multiple ICD-10-CM options. Clinical documentation from the original encounter is essential to determine which 7th character applies when migrating historical records.

Conclusion

Accurate use of ICD-10 Code S52.202H depends on three overlapping documentation anchors: the original Gustilo-Anderson Type IIIA, IIIB, or IIIC wound classification, a current imaging-supported diagnosis of malunion, and a clearly documented subsequent encounter status. Get any one of those wrong and the claim either goes to the wrong code or comes back denied.

Pabau’s integrated claims workflow supports orthopaedic and rehabilitation practices handling complex fracture aftercare billing, connecting clinical documentation directly to electronic claim submission through Claim.MD. To see how Pabau handles fracture aftercare coding workflows, book a demo with the team.

Continue your research

Need to understand how clearinghouse claims submission works? Medical claims clearinghouse guide explains the end-to-end submission process from practice to payer.

Looking for denial reason code definitions? Denial codes in medical billing breaks down common CARC reason codes and how to respond to them.

Want to understand how 837P electronic files are structured? 837 file guide covers the transaction set used for electronic claim submission.

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