ICD code S82.299K – Other tibial shaft fracture nonunion, unspecified leg

Key takeaways

S82.299K codes a follow-up encounter for a closed tibial shaft fracture, leg not specified, where the provider has diagnosed nonunion rather than delayed healing.

The fifth character 9 means other fracture: a documented pattern with no dedicated tibial shaft code. If no pattern is documented at all, use S82.209K instead.

The K seventh character needs an explicit provider diagnosis of nonunion, backed by X-ray or CT. Coders cannot infer nonunion from elapsed time alone.

If the record documents the leg, use S82.291K (right) or S82.292K (left). S82.299K is only for records that omit laterality.

Pabau, the practice management platform we build, connects to the Claim.MD clearinghouse for electronic claims and real-time eligibility checks on these encounters.

ICD-10 Code S82.299K: Official description and quick reference

ICD-10 Code S82.299K is a full seven-character billable code effective for encounters coded under the current ICD-10-CM fiscal year. It codes a follow-up visit for a closed tibial shaft fracture that has failed to heal, when the record does not say which leg.

Its official descriptor is Other fracture of shaft of unspecified tibia, subsequent encounter for closed fracture with nonunion.

What S82.299K means: Tibial shaft nonunion in clinical context

The tibia, or shinbone, is the larger of the two lower-leg bones and carries most of the body’s weight. Its shaft (diaphysis) is the long tubular section between the proximal and distal metaphyses.

Tibial shaft fractures are the most common long-bone fracture. They usually follow a fall, a twisting sports injury, or high-energy trauma such as a motor vehicle collision.

The tibia is also one of the long bones most prone to nonunion. Its front inner surface sits just under the skin, so soft-tissue cover and blood supply are thin, especially in the lower third of the shaft.

High-energy injuries, open wounds, infection, and smoking all raise the risk further. Established tibial nonunion is often treated with exchange intramedullary nailing, bone grafting, or bone stimulation, so these encounters regularly carry procedure claims. Noninvasive low-intensity ultrasound bone stimulation, for example, is reported with CPT code 20979.

“Other fracture” in this code describes the fracture pattern. ICD-10-CM gives the tibial shaft dedicated codes for transverse, oblique, spiral, comminuted, and segmental fractures (S82.22- to S82.26-). S82.29- covers a documented pattern that fits none of those. If the record names no pattern at all, the unspecified code S82.209K applies instead.

Nonunion is a clinical diagnosis that belongs to the treating provider. It refers to a fracture that has failed to achieve bony union within the biologically expected window. Per ICD-10-CM Official Guidelines, nonunion must be documented by the treating provider and is typically supported by serial imaging showing absent or insufficient callus formation.

• Nonunion: Confirmed failure of bony union, with no bridging callus on imaging. The provider explicitly states “nonunion” (seventh character K for closed, M or N for open).
• Delayed healing: Union is progressing but slower than expected, and callus is present but immature (seventh character G, H, or J).
• Malunion: Fracture has healed but in an angulated or otherwise abnormal position (seventh character P, Q, or R).
• Routine healing: Normal healing trajectory, no complication (seventh character D, E, or F).

“Unspecified” laterality in S82.299K means the record does not document which leg is affected. If the provider documents left or right, the more specific code must be used.

A tibial shaft fracture often comes with a fibula fracture in the same leg. ICD-10-CM has no combination code for the pair, so a fibular shaft fracture is coded separately from S82.4-. For example, S82.409K covers an unspecified fibula shaft fracture that has also gone on to nonunion.

Breaking down the code: S82.299K character by character

Each of the seven characters in ICD-10-CM S82.299K carries a specific meaning. Understanding the structure prevents selection of an adjacent wrong code.

The seventh character K: When a nonunion follow-up qualifies

The seventh character K applies only when both of two conditions are met. The encounter is subsequent, so the patient is not presenting for the fracture for the first time. The provider has also documented nonunion as the healing status. Neither condition alone is sufficient.

The most common selection error is using G (delayed healing) when the provider has gone further and explicitly diagnosed nonunion. If the notes say “nonunion confirmed on CT,” K is correct. If the notes say “healing slowly” without a nonunion statement, G is correct. R, by contrast, codes malunion of an open type III fracture, so it never applies to a nonunion.

S82.299K vs similar nonunion codes

Several closely related codes share the same clinical territory as S82.299K. Each descriptor below is the official ICD-10-CM wording. Selecting the wrong one is a common cause of denials on these encounters.

Five documentation questions narrow the choice before you reach the table. Each answer either keeps you on S82.299K or points to the sibling code that fits better.

Included and excluded conditions under ICD-10 Code S82.299K

The ICD-10-CM Tabular List and Official Guidelines set out what S82.299K covers and what belongs elsewhere. Coders should review both lists before assigning the code.

What is included

• Fractures of the diaphysis (shaft) of the tibia with a documented “other” pattern, leg not specified
• Subsequent encounters (follow-up, continued management, definitive treatment planning)
• Established nonunion as the documented healing complication
• Closed fractures, including any fracture not documented as open or closed, which ICD-10-CM codes as closed (open-fracture nonunion uses M or N)

What is excluded

• Periprosthetic fractures: Use M97.1- (knee) or M97.2- (ankle) for a fracture around an internal prosthetic joint
• Pathological fractures: Use M84.4-, M84.5-, or M84.6- category codes (stress fractures use M84.3-)
• Traumatic amputation of the lower leg: Use S88.- category codes
• Fractures of the upper or lower end of the tibia: Use S82.1- (upper end) or S82.3- (lower end), not the shaft codes
• Fibula shaft fractures: Use S82.4- (for example, S82.409K for an unspecified fibula shaft nonunion)
• Fractures of the ankle or foot: Use S82.5- (medial malleolus), S82.6- (lateral malleolus), or S92.- (foot, except ankle)
• Fractures with sequela: Use S82.299S for late effects of the fracture

Documentation requirements for S82.299K

Payer audits for fracture nonunion codes concentrate on two questions. Did the provider diagnose nonunion, rather than slow healing? And does the record show a subsequent encounter rather than an initial one? A claim that cannot answer both questions from the medical record will not survive review.

The ICD-10-CM Official Guidelines, published through the Centers for Medicare and Medicaid Services (CMS), define a subsequent encounter. It is one where active treatment is complete and the patient receives routine care during healing or recovery, or treatment of complications. The following documentation elements are required to support S82.299K.

• Provider diagnosis statement: The word “nonunion” or an equivalent phrase must appear in the provider’s assessment or impression. Coders should not infer nonunion from imaging language alone.
• Imaging evidence: Radiology report (X-ray or CT) describing absent or insufficient callus formation, fibrous union, or pseudarthrosis. Serial imaging is stronger evidence than a single study.
• Encounter type documentation: Medical record must establish prior acute care (initial encounter) occurred for the same fracture. The subsequent encounter designation is only correct when the patient has already received active treatment.
• Laterality note: If the record is silent on laterality, S82.299K is appropriate. If one side is documented anywhere in the record, the coder should query the provider before defaulting to unspecified. That includes nursing notes, imaging, and physical therapy notes.
• Fracture pattern: The record should describe the tibial shaft fracture pattern. A transverse, oblique, spiral, comminuted, or segmental fracture has its own code (S82.22- to S82.26-), and no stated pattern means S82.209K.
• Fracture type (open vs closed): An open-fracture nonunion takes M (Gustilo type I or II) or N (type IIIA, IIIB, or IIIC). K is for closed-fracture nonunion.

Payer requirements and Medicare billing for S82.299K

Medicare coverage for fracture nonunion management is governed by Local Coverage Determinations (LCDs) issued by Medicare Administrative Contractors (MACs). These LCDs vary by region and are updated periodically. Coders should verify the applicable LCD for their MAC jurisdiction before billing.

Key payer considerations for S82.299K claims include the following points, though practices should confirm current requirements with their MAC or commercial payer directly.

• Prior authorization for associated procedures: Bone stimulators (electrical or ultrasonic) billed for nonunion treatment commonly require pre-authorization under Medicare Advantage and commercial plans. Authorization must reference the nonunion diagnosis code, making accurate ICD-10-CM selection critical.
• NCCI edits: The National Correct Coding Initiative (NCCI) maintains procedure-code-pair edits that may restrict specific CPT codes when billed alongside S82.299K. Quarterly NCCI updates can add or remove edits. Verify the current edit tables before submitting claims for fracture repair or bone stimulation.
• External cause code requirements: Many commercial payers and some MACs require an external cause code for traumatic fracture encounters. See the section below for sequencing rules.
• Medical necessity documentation: Medicare requires that the claim be supported by documentation establishing that the service is reasonable and necessary. For nonunion, this means the record must show the fracture has not healed despite appropriate treatment, and that ongoing management is clinically indicated.

When an authorization or coverage problem still turns into a denial, denial management guidance walks through the recovery workflow, from root cause to resubmission.

Common claim denial reasons for S82.299K and how to avoid them

Claims for S82.299K denials concentrate around a handful of predictable errors. Identifying the pattern for your practice is faster than chasing individual remittances.

• Wrong encounter type (A instead of K): Using the initial-encounter suffix A on a follow-up visit is the most frequent error. The claim tells the payer the patient is presenting for the fracture for the first time. That conflicts with other dates of service in the billing history. Confirm that active treatment has ended before replacing A with K.
• Missing nonunion imaging evidence: Payers requesting medical records on nonunion claims expect a radiology report describing failed healing. If the chart has no imaging to support the diagnosis, obtain an updated X-ray or CT before submitting.
• Unspecified laterality when a side is documented: Imaging or the provider note may say “right tibia” while the claim carries S82.299K instead of S82.291K. Payers may then deny for lack of specificity or flag the claim for audit. Query the provider before assigning unspecified laterality.
• Nonunion versus malunion suffix confusion: K (nonunion) and P (malunion) are clinically distinct. A claim for a corrective osteotomy of a malunion using S82.299K will mismatch the procedure’s medical necessity basis. Read the provider’s notes carefully and choose based on the documented diagnosis.
• Pattern documented but coded as other: If the radiology report calls the fracture spiral or oblique, S82.24- or S82.23- applies rather than S82.29-. Payers reviewing records will spot the mismatch.
• Missing or incorrectly sequenced external cause code: Some payers deny fracture claims that lack a mechanism-of-injury code. Review the payer’s submission guidelines and include the appropriate V/W/X/Y code as a secondary code when required.

Reviewing medical billing denial codes alongside your ERA (electronic remittance advice) helps isolate whether a denial is a coverage issue or a coding mismatch. Practices that use electronic remittance advice workflows can typically identify denial patterns across a batch of fracture claims in a single pass.

External cause and supplementary codes used with S82.299K

External cause codes (V00-Y99) document the circumstances that produced the original tibial shaft fracture. For subsequent encounters such as those coded with S82.299K, external cause codes are supplementary. The ICD-10-CM Official Guidelines never sequence them as the principal diagnosis.

S82.299K is sequenced first, and external cause codes follow it. Common supplementary codes used alongside S82.299K include the following:

• Mechanism of injury: Fall (W00-W19), transport accident (V00-V99), or sports-related force. Report the original injury mechanism with seventh character D for the subsequent encounter, not a new event.
• Place, activity, and status: Y92.- (place of occurrence), Y93.- (activity), and Y99.- (external cause status) are reported only once, at the initial encounter. They do not normally belong on an S82.299K claim.

Not all payers mandate external cause codes on subsequent fracture encounters. Check your MAC or commercial payer policy. When in doubt about the clean claim requirements for your payer mix, include the mechanism code. Removing it after a denial is simpler than appealing a code-not-applicable rejection.

How claims management software reduces denials for S82.299K

A nonunion follow-up often passes through three hands before it reaches a payer. The provider writes the assessment, a coder reads it for laterality and healing status, and someone keys the claim into a clearinghouse portal. Each handoff is a chance for an A to stay on a follow-up visit, or for a documented side to go uncoded.

In Pabau’s practice management software, the provider’s note, the diagnosis code and the claim sit on the same patient record. The claims software for practices connects to the Claim.MD clearinghouse. Eligibility checks run in real time, and 837P claims go out electronically.

The result is fewer surprises on remittance day. Coverage and authorization problems surface before submission, and posted ERAs make the quarterly suffix audit above far quicker to run.

Manage fracture care documentation and claims in one place

Pabau integrates with Claim.MD to support electronic claim submission, real-time eligibility verification, and ERA posting for fracture nonunion encounters and orthopedic billing workflows.

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Conclusion

S82.299K is a narrow code by design. It fits only when the chart confirms a follow-up, a provider-diagnosed nonunion, a closed fracture, an “other” pattern and no documented side.

That last condition is the one worth challenging on every claim. Before you submit, search the imaging report and therapy notes for a side. If one turns up, a one-line provider query moves the claim to S82.291K or S82.292K. The query takes minutes, while a specificity denial takes a resubmission.

Book a demo to see how Pabau keeps the provider’s note, the code and the claim on one record for your fracture follow-ups.

Continue your research

Submitting fracture claims electronically through a clearinghouse? 837 file format guide explains the EDI 837P structure used for professional claim submission.

Want to reduce eligibility denials before claims are submitted? Insurance eligibility verification walks through the pre-submission checks that catch coverage issues early.

Appealing a denied nonunion claim? Medical appeal form template gives you a ready structure for contesting a payer decision.

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