ICD-10 code S82.61XN: Lateral malleolus fracture, right fibula

Key Takeaways

ICD-10 code S82.61XN describes a displaced fracture of the lateral malleolus of the right fibula, coded at a subsequent encounter for an open fracture type IIIA, IIIB, or IIIC with nonunion.

The code is billable and valid for fiscal year 2026; the 7th character N specifies subsequent encounter, open type IIIA/IIIB/IIIC, with nonunion.

Nonunion must be explicitly documented in the medical record (imaging or surgeon attestation) to support the N suffix; confusing it with malunion (suffix R) or with the type I/II nonunion suffix (M) is a common denial trigger.

Practice management software like Pabau keeps injury classification, encounter type, and healing status together in one patient record, so coders have consistent documentation for every follow-up visit.

ICD-10 code S82.61XN is a billable, specific diagnosis code for a displaced fracture of the lateral malleolus of the right fibula, at a subsequent encounter for an open fracture classified as Gustilo-Anderson type IIIA, IIIB, or IIIC, with nonunion. It’s valid for fiscal year 2026 and sits within the S82 category for lower leg fractures, including the ankle.

This page covers the code’s billable status, the 7th character breakdown, Gustilo-Anderson classification context, nonunion documentation requirements, sibling codes, and the coding errors that most often trip up orthopedic billing staff.

ICD-10 code S82.61XN: Definition and clinical description

Clinically, this code applies when a previously treated open fracture of the right fibula’s lateral malleolus has failed to unite by the time of a follow-up visit. The subsequent-encounter fracture codes in the S82 family track visit type, wound severity, and healing outcome together, which is why the 7th character carries as much weight as identifying the fracture itself.

The code is billable under CMS ICD-10-CM guidelines and valid for fiscal year 2026. It sits within the S82 category (fractures of lower leg, including ankle) and specifies right-side laterality, displaced fracture type, open wound classification, and healing complication in a single 7-character string.

Code details at a glance

Understanding the 7th character ‘N’ in fracture codes

The 7th character is where most fracture coding errors happen. For the S82 code family, each 7th character encodes the visit type, wound status, and healing outcome simultaneously. For S82.61XN, the character N specifies a subsequent encounter for an open fracture originally classified as Gustilo-Anderson type IIIA, IIIB, or IIIC, where the fracture has failed to unite.

To illustrate, the full 7-character breakdown for S82.61XN reads as follows: S82 identifies the lower leg/ankle fracture category; .61 specifies a displaced fracture of the lateral malleolus (right side, ‘1’ indicating right laterality per ICD-10-CM convention); X is a placeholder required to reach the 7th position; and N is the 7th character itself.

Note the critical three-way distinction for nonunion: K applies to a closed fracture, M applies to an open fracture originally classified as Gustilo-Anderson type I or II, and N applies to an open fracture originally classified as type IIIA, IIIB, or IIIC.

Mixing up M and N, or using K when the original fracture was open, is a common audit trigger. Keeping injury classification and encounter history in one clinical record, rather than scattered across paper charts, gives coders the documentation they need to apply the right suffix the first time.

Open fracture classification: Gustilo-Anderson

ICD-10 code S82.61XN is only appropriate when the original open fracture was classified as Gustilo-Anderson type IIIA, IIIB, or IIIC. By contrast, using N when the original fracture was type I or II is a coding error – the correct 7th character for that lower-severity injury with nonunion is M, not N.

The Gustilo-Anderson classification system, developed through peer-reviewed orthopedic research, grades open fractures by wound size, degree of soft-tissue injury, and level of contamination. Type I and II represent lower-severity open injuries and map to 7th characters B (initial), E (routine healing), H (delayed healing), M (nonunion), and Q (malunion) in the S82 family.

Type III grades carry significantly different clinical management implications and map to the distinct 7th character set C (initial), F (routine healing), J (delayed healing), N (nonunion), and R (malunion). Type IIIC injuries, which involve arterial damage requiring vascular repair, are typically billed alongside anesthesia codes such as 01500.

The operative report and emergency department notes must document the Gustilo-Anderson type at the time of injury. If the original classification is missing from the record, the coder cannot accurately assign the 7th character on subsequent visits. Type IIIB and IIIC wounds also often need staged wound care, such as A6010 collagen dressings, before definitive closure.

For orthopedic practices managing these patients long-term, digital intake and clinical forms that capture injury classification at first encounter keep this information from going missing months later at follow-up.

What is fracture nonunion and why does it matter for coding?

Nonunion occurs when a fracture fails to progress toward healing within the expected clinical timeframe. The orthopedic definition typically requires confirmation that healing has stalled, usually supported by serial imaging showing no callus formation or bridging across the fracture line.

There is no fixed statutory timeframe in the ICD-10-CM Official Guidelines for Coding and Reporting. Instead, the surgeon’s documented clinical judgment carries the coding weight.

For coding purposes, the distinction between nonunion, delayed union, and malunion matters because each maps to a different 7th character. Therefore, getting this wrong results in claim rejection.

• Nonunion (7th char K, M, or N): No healing progression; fracture fragments remain separated. Imaging shows persistent fracture line with absent or incomplete callus bridging. K applies to closed fractures, M to open type I/II, and N to open type IIIA/IIIB/IIIC.
• Delayed union (7th char G, H, or J): Healing is occurring but more slowly than expected. Some callus formation is present. G applies to closed fractures, H to open type I/II, and J to open type IIIA/IIIB/IIIC – there is a full open-fracture equivalent for delayed healing in S82, not just a closed-fracture option.
• Malunion (7th char P, Q, or R): Healing has occurred but with incorrect alignment. The fracture has united in a non-anatomical position. P applies to closed fractures, Q to open type I/II, and R to open type IIIA/IIIB/IIIC.

Documentation supporting the N suffix must come from the treating physician. A progress note stating “fracture remains ununited at 6 months per X-ray” combined with imaging reports is the minimum evidentiary standard most payers expect. Coders should not assign N based on time elapsed alone – the same evidentiary bar applies to S52.532N elsewhere in the fracture family.

Anatomy: The lateral malleolus and the fibula

The lateral malleolus is the distal end of the fibula, the smaller of the two lower-leg bones. It forms the lateral wall of the ankle mortise, the bony arch that cradles the talus and provides ankle joint stability.

A displaced fracture of the lateral malleolus disrupts this architecture and typically requires surgical fixation to restore ankle mortise congruity.

Laterality is explicit in this code family. Specifically, the digit ‘1’ in S82.61 encodes right-side laterality per ICD-10-CM convention. S82.62 is the left-side equivalent, and S82.63 is used when laterality is not documented. Even so, coders should never default to the unspecified code when the operative note or imaging report clearly states “right fibula.”

• Right fibula, lateral malleolus: S82.61 (displaced), S82.62 equivalent for left
• Displaced vs. nondisplaced: Displacement must be documented in the operative note or radiology report. When not specified, ICD-10-CM guidelines direct coders to assume displaced.
• Clinical significance: Displaced fractures are more likely to require open reduction and internal fixation (ORIF), which affects associated CPT code selection and may influence payer authorization requirements.

Orthopedic clinicians using the Ottawa Ankle Rules as a clinical decision tool for ankle fracture imaging will recognize the lateral malleolus as one of the key anatomical landmarks in that framework. Accurate laterality coding downstream starts with accurate documentation at the point of initial assessment.

Physical therapy practices managing post-fracture rehabilitation can also use physical therapy EMR software designed to track subsequent encounter coding across multi-visit episodes of care.

Code hierarchy: Where S82.61XN sits in ICD-10-CM

Understanding the parent code tree helps coders verify they are using the most specific applicable code and supports audit defense when payers question specificity. In particular, the full hierarchy for ICD-10 code S82.61XN is:

• Chapter 19: Injury, poisoning and certain other consequences of external causes (S00-T88)
• Block S80-S89: Injuries to the knee and lower leg
• Category S82: Fracture of lower leg, including ankle
• Subcategory S82.6: Fracture of lateral malleolus
• Code S82.61: Displaced fracture of lateral malleolus of right fibula
• Code S82.61X: With placeholder X (required for 7th character positioning)
• Code S82.61XN: Subsequent encounter, open fracture type IIIA, IIIB, or IIIC, with nonunion

The CDC/NCHS ICD-10-CM web tool allows coders to navigate this hierarchy interactively, confirming billable status and excludes notes at each level before finalizing a code selection. For sports medicine practices that frequently manage ankle fracture sequelae, sports medicine software with integrated coding support reduces the time spent cross-referencing the tabular list manually.

Excludes notes for S82.6 and S82

The ICD-10-CM Tabular List carries excludes notes at both the subcategory and category level, and these affect which code is correct when a record documents more than one injury.

• S82.6 (Fracture of lateral malleolus) Excludes1: pilon fracture of distal tibia (S82.87-)
• S82 (Fracture of lower leg, including ankle) Excludes1: traumatic amputation of lower leg (S88.-)
• S82 Excludes2: fracture of foot, except ankle (S92.-); periprosthetic fracture around internal prosthetic ankle joint (M97.2); periprosthetic fracture around internal prosthetic knee joint (M97.1-)

Related and sibling codes for lateral malleolus fractures

The S82.61X code family covers every permutation of displaced right lateral malleolus fractures across all encounter types and healing outcomes. For reference, the table below shows the full sibling set alongside the left-side and unspecified equivalents most relevant to coders billing fracture follow-up encounters.

Displaced vs. nondisplaced fracture coding differences

S82.61 (displaced) and S82.64 (nondisplaced) are not interchangeable. Accordingly, the displaced/nondisplaced distinction must be documented in the operative note or radiology report. Per ICD-10-CM guidelines, when displacement is not specified, coders default to displaced. However, this default applies at coding only; it does not substitute for missing documentation on audit.

Nondisplaced lateral malleolus fractures (S82.64) are more commonly managed conservatively, which affects associated CPT procedure code selection and may change whether prior authorization is required. Displacement documentation carries the same weight across the S82 family – S82.242N follows the identical displaced/nondisplaced logic.

For a broader lookup across the S82 family, the AAPC ICD-10-CM code search provides crosswalk and code-edit context alongside the official description.

Keep fracture follow-up documentation organized with Pabau

Pabau keeps injury classification, encounter type, and healing status attached to the patient record from the first visit through discharge, so orthopedic and physical therapy teams always have the documentation behind each subsequent-encounter claim.

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Clinical documentation requirements for S82.61XN

Every element encoded in ICD-10 code S82.61XN must be traceable to a specific entry in the medical record. Specifically, payers auditing this code will look for documentation supporting six distinct claims.

• Right laterality: The operative note, radiology report, or clinical documentation must specify “right fibula” or “right ankle.” A note stating “lateral malleolus fracture” without laterality does not support the 1 in S82.61.
• Displaced fracture: The imaging report or operative note must state displacement. Absent documentation defaults to displaced under ICD-10-CM guidelines, but the coder must be prepared to defend this on audit.
• Open fracture type IIIA, IIIB, or IIIC: The Gustilo-Anderson classification must appear in the initial emergency or operative note, including the wound size, soft-tissue findings (periosteal stripping or flap coverage for IIIB), and any arterial injury requiring repair (IIIC). If the original injury occurred at another facility, coders should request the transfer records documenting the wound classification.
• Subsequent encounter: Active treatment of the fracture itself is complete. The patient is attending for aftercare, monitoring of healing progress, or management of a complication. Initial encounter codes (A, B) are never appropriate for follow-up visits.
• Nonunion: The physician must explicitly state nonunion in the progress note, or the record must contain imaging evidence (X-ray, CT) showing absent healing across the fracture site. Time elapsed alone is not sufficient documentation.
• ICD-10-CM coding guidelines compliance: Per CMS ICD-10-CM Official Guidelines, code sequencing must follow injury coding conventions including the applicable 7th character for the healing phase.

In addition, practices managing fracture follow-up patients across multiple providers benefit from using clinical records software that centralizes documentation from the initial injury encounter through each subsequent visit, making the full audit trail available without cross-referencing paper charts.

Common coding errors and how to avoid them

Fracture codes with multiple 7th character options generate a predictable set of errors. Consequently, these are the most frequent mistakes seen on subsequent-visit claims for open lateral malleolus fractures.

• Using an initial encounter code on a follow-up visit: Assigning S82.61XA or S82.61XB at a post-operative check-up is the single most common error. Once active treatment ends, subsequent encounter codes (D, G, K, N, P, Q, R) are required for all follow-up visits. Initial encounter codes at follow-up visits are automatically flagged by most claim-editing software.
• Confusing nonunion (N) with malunion (R): Both are complications of an open type IIIA/IIIB/IIIC fracture, but they are clinically distinct. Malunion (R) means the fracture healed in the wrong position. Nonunion (N) means it has not healed at all. The physician note must clearly state which condition is present.
• Applying the wrong open fracture type suffix: Using M (open type I/II nonunion) when the original fracture was Gustilo-Anderson type IIIA/IIIB/IIIC (which requires N for nonunion) – or the reverse, applying N to a type I/II injury – constitutes a specificity error and may result in a medical necessity denial if the wound-size documentation contradicts the code.
• Omitting laterality: Defaulting to the unspecified code (S82.63) when the record documents right laterality is a specificity failure. Most payers require the most specific code available, and unspecified codes can trigger additional documentation requests.
• Skipping the placeholder X: S82.61N is not a valid code. The X placeholder in position 6 is required before the 7th character can be applied. Omitting it makes the code non-billable and it will reject on submission.

Billing teams that operate across multiple orthopedic providers can build the same coding checklist for other S82 codes – S82.871G follows a similar encounter and healing-status pattern for pilon fractures. The ICD List tool provides free ICD-10-CM lookup alongside code editing information for common error patterns in the S82 category.

Approximate synonyms and clinical terms

Operative notes and radiology reports use a variety of clinical descriptions that all map to ICD-10 code S82.61XN. Therefore, coders should recognize these alternate phrasings when reviewing records.

• Displaced fracture lateral malleolus right fibula with nonunion, subsequent encounter for open type IIIA, IIIB, or IIIC fracture
• Right lateral malleolus open fracture (Gustilo IIIA/IIIB/IIIC) nonunion, follow-up visit
• Right fibula distal fracture with persistent fracture gap, open injury, follow-up
• Subsequent encounter for right fibular lateral malleolus fracture nonunion following open reduction
• Right ankle lateral malleolus fracture with failed healing, open wound type IIIA, IIIB, or IIIC, subsequent visit
• Ununited displaced right lateral malleolus fracture, previously open, type IIIA, IIIB, or IIIC

All of the above describe the same clinical scenario and map to S82.61XN when all six documentation requirements above are met. Practices providing fracture management and physical therapy rehabilitation can benefit from keeping a reference list of these synonyms in their coding policy, particularly when processing notes from multiple referring providers.

For coding resources covering related musculoskeletal injury codes, the physical therapy return-to-running protocol provides clinical context on how post-fracture rehabilitation milestones are documented, which often appears in the same records being coded. The WHO ICD-10 browser also provides the international classification context from which the US ICD-10-CM adapts its injury code structure.

Conclusion

ICD-10 code S82.61XN is a precise, billable code that demands accurate documentation across five distinct clinical variables: right laterality, displaced fracture, open wound type IIIA, IIIB, or IIIC, subsequent encounter, and confirmed nonunion.

The most preventable errors involve misapplying the 7th character – particularly confusing K (closed fracture nonunion), M (open type I/II nonunion), and N (open type IIIA/IIIB/IIIC nonunion) with each other, or defaulting to an initial encounter code on a follow-up visit.

Practices managing complex fracture cases across multiple visits benefit from centralized clinical records that link the initial injury documentation to each subsequent encounter note. Pabau’s clinical records give orthopedic and physical therapy teams a single platform to track encounter types, injury classifications, and supporting documentation from first visit through discharge.

Book a demo to see how Pabau keeps fracture follow-up documentation organized.

Continue your research

Need anesthesia coding for ankle and lower leg procedures? CPT 01462 covers anesthesia for lower leg, ankle, and foot procedures often billed alongside subsequent-encounter fracture codes.

Billing wound care after a Gustilo type IIIB or IIIC injury? A6010 covers the collagen wound fillers frequently used before definitive closure.

Coding a Gustilo type IIIC injury with vascular involvement? CPT 01500 covers anesthesia for lower leg artery repair procedures that often accompany these higher-severity fractures.

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