ICD-10 code S82.499Q: Fibula shaft fracture with malunion

Key takeaways

S82.499Q covers a fibula shaft fracture that healed crooked after an open type I or II injury, billed at a subsequent encounter

In S82.499, unspecified describes the side, not the bone. The fibula is named, but the left or right is not

The 7th character Q means open type I or II with malunion. Closed malunion takes P, and Gustilo type III malunion takes R

Use S82.499 only when the side is genuinely undocumented. Prefer S82.491Q for the right fibula and S82.492Q for the left

Practice management software like Pabau keeps the note, the code, and the claim on one patient record

ICD-10-CM code S82.499Q reports other fracture of the shaft of the unspecified fibula. The 7th character Q carries the rest. It marks a subsequent encounter for an open type I or II fracture that healed with malunion.

In plain terms, the fibula shaft broke, a small or moderate wound opened the skin, and the bone united out of position. The code is billable, so it can carry a claim on its own.

One word in that descriptor causes most of the errors. Unspecified points at the side of the body, not at the bone. S82.499 always names the fibula, whichever side is involved.

The tables below cover the official description, the code hierarchy, and the full 7th character set for S82.499. They also show which Gustilo types push you to R instead of Q, plus what the note must say before a claim goes out.

ICD-10 code S82.499Q: Definition and official description

ICD-10 Code S82.499Q is a valid, billable ICD-10-CM diagnosis code. According to the CMS ICD-10-CM code files, its full official description is:

The CDC/NCHS ICD-10-CM web tool confirms this code is active for the current fiscal year. Verify that annually, because CMS releases updated code files each October. The same category-to-7th-character path runs through neighboring lower-limb codes such as S72.309N.

Code hierarchy and parent codes

S82.499Q sits at the end of a precise hierarchical path within ICD-10-CM Chapter 19 (Injury, Poisoning and Certain Other Consequences of External Causes). Each level narrows the anatomical and clinical specificity.

The “other” designation at S82.49 means the fracture pattern is not one of the named patterns under S82.4. Those named options are transverse (S82.42), oblique (S82.43), spiral (S82.44), comminuted (S82.45), and segmental (S82.46). Work through them before you settle on S82.499Q.

A second trap sits nearby. S82.90 reads “unspecified fracture of unspecified lower leg”, and that code names no bone at all. Reach for it only when the record does not say which bone broke.

Platforms that build ICD-10-CM lookup into the note help here. A physical therapy EMR that searches by keyword surfaces the candidates side by side. The most specific code then wins before the claim leaves.

Understanding the 7th character Q

The 7th character is where most coding errors occur with fibula shaft fracture codes. For S82.499, 16 extensions apply. Each one encodes both the episode of care and the fracture’s healing status. The table below shows the complete set, as defined in the ICD-10-CM Official Guidelines for Coding and Reporting.

Three 7th character errors account for most denials in this code family:

• Using Q when the original fracture was closed. P applies instead.
• Using Q when the original fracture was Gustilo type IIIA, IIIB, or IIIC. R is correct.
• Using A or B on a return visit, after active treatment has ended.

The guidelines define a subsequent encounter narrowly. It is any encounter after active treatment is complete, while the patient receives routine care during healing or recovery. The same qualifier logic separates routine healing from a complication in codes like S72.036E.

Clinical context: When to use S82.499Q

Three conditions must all be true before S82.499Q is appropriate. Document each one clearly in the clinical note before submitting the claim.

• Open fracture, type I or II: The original injury broke through the skin. Type I and II sit at the low-energy, cleaner end of the Gustilo-Anderson scale, and the table below gives the wound sizes. Higher-energy type III fractures take different 7th characters.
• Malunion documented: Imaging or clinical examination confirms the fracture has healed in a non-anatomic position. Malunion is not the same as delayed healing (H) or nonunion (M/K). If the fracture has not yet healed, use the delayed healing or nonunion characters instead.
• Subsequent encounter: The patient has completed active fracture treatment and is presenting for follow-up care, rehabilitation, or management of the malunion complication. The treating provider is no longer managing an acute fracture.

Orthopedic and sports medicine software platforms that embed ICD-10-CM lookups can surface this code while the note is being written. That timing is what stops the wrong episode-of-care character reaching a repeat visit.

How the Gustilo type decides between Q and R

The Gustilo-Anderson system is the reference standard for open fracture classification in orthopedic coding. Wound size and contamination decide the type, and the type decides whether malunion takes Q or R.

Check how the original operative or emergency department note classified the fracture. If it was type IIIA, IIIB, or IIIC, a subsequent encounter with malunion takes S82.499R rather than S82.499Q. When the original Gustilo type is not documented, query the treating physician before selecting Q or R.

Coding guidelines and billing considerations

Several ICD-10-CM Official Guidelines sections directly affect how S82.499Q is reported. Skipping them is a frequent reason fracture claims get flagged on audit, and the wider rules on medical billing compliance apply on top.

Practice management software like Pabau records the diagnosis code on the encounter itself. The same record then carries through to the claim, so the note and the bill never drift apart.

Laterality: When “unspecified” applies

S82.499Q specifies an unspecified fibula, and that should be a last resort. Use it only when the provider’s documentation does not identify the left or right side. In practice, that is rare on a follow-up visit.

The specific alternatives are S82.491Q for the right fibula and S82.492Q for the left. Both accept the same 7th character extensions. Defaulting to unspecified when the side is documented is under-coding, and it weakens the record for any later audit.

Documentation requirements for malunion

Malunion must be explicitly documented by the treating clinician. Coders cannot infer malunion from imaging reports alone. The clinical note should state that the fracture has healed in a non-anatomic or malaligned position, or use equivalent clinical terminology.

Pabau’s digital clinical forms let practices build structured follow-up templates. Each template can prompt the provider for healing status, the Gustilo type from the original injury, and the side.

This reduces incomplete documentation before claims reach the payer. A medical chart audit tests the same three details, so a template that captures them holds up under review.

Sequencing and external cause codes

S82.499Q should be the principal diagnosis when malunion is the primary reason for the encounter. If the patient is admitted for a related procedure, such as corrective osteotomy, the procedure code drives the inpatient payment group. The malunion code still leads the diagnosis list.

An external cause code from the V, W, X, or Y categories is not required for subsequent encounters. Many payers and trauma registries still expect one for audit completeness. Check the place-of-service code too, since malunion follow-ups usually happen in an outpatient office rather than an inpatient setting.

Related and adjacent ICD-10 codes

S82.499Q has sibling and parent codes that coders meet in the same fracture management context. Picking the wrong one is a recurring audit finding on fibula shaft fracture claims. The AAPC ICD-10-CM lookup tool lets coders browse the full S82.499 family side by side before finalizing a claim.

Working through a code family this way is a habit worth keeping. Malunion coding turns on the same question in other regions of the body, as S49.109P shows.

The M versus Q distinction matters clinically as well as financially. Nonunion (M) means the bone ends never bridged. Malunion (Q) means the fracture did unite, but in a poor position. Each one leads to different management and different procedural codes if corrective surgery follows.

Templated follow-up notes cut the risk of mixing them up. Patient record documentation in Pabau can prompt the clinician to record healing status at every visit.

How Pabau keeps fibula fracture coding tied to the claim

Most practices split this work across two systems. The clinician writes the follow-up note in one place, and a biller re-keys the diagnosis into a claim somewhere else. Every re-key is a chance for the wrong 7th character to reach the payer.

Pabau keeps both halves on one patient record. The treatment note, the imaging that confirmed malunion, and the form that captured the side all sit on the same chart. Billing then works from what the clinician actually wrote.

Pabau’s claims management software runs validation checks each time you send a claim, so missing membership numbers or authorization codes surface before submission. US practices submit through Claim.MD and can run real-time eligibility checks. Every claim shows its live status, and payment is recorded against the right invoice in the same dashboard.

Documentation is the other half of the problem, because a coder can only work with what was written down. Pabau Scribe, our AI scribe, drafts the consultation note as the appointment happens. A malunion follow-up note has to confirm union, describe the malalignment, and name the side.

For an orthopedic or physical therapy practice, that means fewer claims returned for missing information. It also means a record that holds up when a payer asks how the malunion was confirmed.

Keep fibula fracture coding and claims in one record

Pabau holds the treatment note, the forms, and the claim on the same patient record. Validation checks run before every submission, so subsequent-encounter claims leave with the detail payers ask for.

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Conclusion

S82.499Q rewards the coder who reads the original injury note, not only the follow-up. The Gustilo type and the open-or-closed call were both made months earlier. Those two details decide whether this visit takes P, Q, or R.

Treat unspecified laterality as a prompt rather than a default. If the side appears anywhere in the chart, S82.491Q or S82.492Q makes the stronger claim. Payers read it the same way on review.

What holds all of this together is a record the biller can trust. Practice management software keeps the note, the imaging, and the claim on one chart. To see how your team could document a malunion follow-up and bill it from that record, book a demo.

Continue your research

Assessing a lower-limb injury before you code it? Pittsburgh Knee Rules gives the criteria and walk test that decide whether imaging is needed.

Documenting an orthopedic exam finding? Neer’s test sets out how to perform it and how to record the result.

Billing the surgery that follows a malunion? CPT code 20690 covers external fixation and what the operative note has to support.

Coding a late effect instead of active care? S72.124S shows how the sequela extension changes what the claim reports.

Losing revenue to fracture claim denials? Denial management explains how practices track, appeal, and prevent rejected claims.

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