ICD-10 Code S92.403K: Displaced left lesser toe fracture, nonunion

Key Takeaways

ICD-10 Code S92.403K describes a displaced unspecified fracture of the left lesser toe(s), subsequent encounter for fracture with nonunion – a billable ICD-10-CM code valid for HIPAA-covered claims.

The 7th character K signals a subsequent encounter where the fracture has failed to heal (nonunion), distinguishing it from routine follow-up (D) or initial treatment (A/B).

Documentation must confirm laterality (left), displacement status, toe involvement (lesser toes 2-5), and radiographic or clinical evidence of nonunion to support this code.

Pabau’s claims management software integrates with the Claim.MD clearinghouse, supporting accurate ICD-10-CM code submission and real-time eligibility checks for fracture cases.

Nonunion fractures of the lesser toes are more common than most coders expect, and the 7th character K is where documentation gaps most often trigger claim denials. Without clear radiographic or clinical confirmation of failed healing, a payer audit can reclassify the encounter, leaving the practice exposed.

ICD-10 Code S92.403K is a billable, HIPAA-valid diagnosis code used when a patient returns for ongoing care of a displaced unspecified fracture of the left lesser toe(s) that has not healed as expected. This reference page covers the full code description, hierarchy, 7th character logic, sibling codes, documentation requirements, and the encounter-type decision matrix coders need to select the correct suffix every time.

ICD-10 Code S92.403K: full description and billable status

S92.403K is a billable, specific ICD-10-CM diagnosis code. Its full official description is: Displaced unspecified fracture of left lesser toe(s), subsequent encounter for fracture with nonunion. The code is valid for submission on HIPAA-compliant claims submission across all payer types, including Medicare, Medicaid, and commercial insurers.

It is active for the current fiscal year ICD-10-CM edition and has no age or sex exclusions. Verify against the CDC/NCHS ICD-10-CM web tool at the start of each fiscal year to confirm continued validity.

What S92.403K means: breaking down each component

Each character in ICD-10 Code S92.403K carries a specific clinical meaning. Misreading any one of them produces the wrong code. Here is the character-by-character breakdown.

Lesser toes covered: The S92.40x subcategory applies to toes 2 through 5 of the specified foot. It does not include the great toe (hallux), which is coded separately under S92.1x. When the chart specifies which lesser toe is fractured (e.g. the third toe), check whether a more specific code exists before defaulting to the unspecified subcategory.

Displaced vs nondisplaced: Displacement means the fractured bone fragments have moved out of anatomical alignment. This distinction is established by the treating clinician or radiologist, not inferred by the coder. The chart must state “displaced” explicitly, or the coder must query the provider. Defaulting to “displaced” without documentation support is a coding error.

Understanding the 7th character K: subsequent encounter for fracture with nonunion

The 7th character is the single most consequential part of fracture coding and the place where ICD-10 Code S92.403K gets most frequently miscoded. The K suffix has a precise clinical meaning: the patient is presenting for active management of a fracture that has failed to unite (nonunion), not for routine healing follow-up.

Per CMS ICD-10-CM Official Guidelines Section I.C.19.a, the 7th character reflects the type of encounter the patient is receiving, not the age of the original injury. Nonunion is defined as failure of a fracture to heal within the expected timeframe, confirmed by clinical examination or imaging. It is distinct from delayed union (fracture healing slower than expected but still progressing) and malunion (fracture healed in an abnormal position). Using K for delayed union or malunion is incorrect. The review of subsequent encounter coding for anxiety illustrates how the same 7th character logic applies across ICD-10-CM fracture and injury categories.

S92.403K code hierarchy and parent codes

S92.403K sits within the ICD-10-CM injury code hierarchy under five levels of parent categories, each narrowing from chapter to individual code. Coders moving between related codes should understand this structure to avoid selecting a non-billable header code.

S92.403K sibling and related codes

The S92.403 family shares the same base description (displaced unspecified fracture of left lesser toe(s)) but differs only by 7th character. For the broader S92.40x group, laterality changes the digit before the suffix. Understanding the full family prevents coding the wrong laterality or the wrong encounter type. Refer to the ICD-10-CM diagnostic code reference framework for how code families are structured across all chapters.

S92.403 family (left lesser toe, displaced, unspecified)

Laterality siblings (displaced, unspecified, subsequent nonunion)

• S92.401K – Displaced unspecified fracture of right lesser toe(s), subsequent encounter for fracture with nonunion
• S92.402K – Displaced unspecified fracture of unspecified lesser toe(s), subsequent encounter for fracture with nonunion
• S92.403K – Displaced unspecified fracture of left lesser toe(s), subsequent encounter for fracture with nonunion (this code)

Clinical documentation requirements for S92.403K

Every character in S92.403K must be supported by the clinical record. Missing even one element can result in a denied or downcoded claim. Denial management strategies for orthopedic practices consistently identify incomplete fracture documentation as a leading root cause of avoidable rejections. The checklist below reflects what payers expect to see before accepting a K-suffix fracture claim.

Documentation checklist for K suffix nonunion claims

• Laterality confirmed (left): The note must state “left foot” or “left lesser toe.” A note that says “lesser toe fracture” without laterality requires a provider query before coding.
• Displacement confirmed: Radiologist or treating clinician must explicitly document “displaced fracture.” Do not infer displacement from imaging reports alone without physician characterisation.
• Nonunion confirmed: The record must include evidence of failed healing, typically via X-ray or CT scan showing absence of callus formation or continued fracture line. Document the imaging date and findings.
• Toe specification: If the specific lesser toe (2nd through 5th) is identified in the chart, confirm whether a more precise subcategory exists. The unspecified code applies only when the documentation does not specify which lesser toe is involved.
• Encounter type confirmed: Confirm this is a subsequent encounter for active nonunion management, not an initial encounter or a routine healing follow-up. The type of care being rendered determines the 7th character, not the patient’s visit number.
• No new injury: If the patient sustained a new injury at the same visit, sequence the new injury code first per ICD-10-CM sequencing guidelines.

Practices using physical therapy practice management platforms for post-fracture rehabilitation should ensure the rehab encounter notes carry the same laterality and healing-status documentation to maintain coding consistency across the episode of care.

Commonly associated diagnosis and procedure codes

Nonunion of a lesser toe fracture typically involves extended management including imaging, possible surgical intervention, and ancillary support. The codes below are commonly paired with S92.403K in the same claim, though procedure coding always depends on what was actually performed and documented. Supporting your medical billing compliance framework includes verifying that every associated code reflects a service rendered during that encounter.

Associated CPT codes

The medical billing workflow for nonunion fracture cases often spans multiple encounters and provider types. A well-structured superbill documentation system that carries forward the ICD-10-CM code with the correct 7th character across all visits reduces the risk of encounter-type errors between the initial orthopaedic assessment and subsequent rehabilitation claims.

Co-diagnosis codes

• M85.872 – Other specified disorders of bone density and structure, left ankle and foot (relevant if osteoporosis is a contributing factor)
• M80.872 – Age-related osteoporosis with current pathological fracture, left ankle and foot (when osteoporosis underlies the fracture)
• Z87.39 – Personal history of other musculoskeletal disorders (past fracture history, if relevant to current nonunion management)
• W19.XXXA / subsequent – Unspecified fall (external cause code, if applicable to original injury mechanism)

Submitting claims through Pabau’s Claim.MD clearinghouse integration supports real-time eligibility verification and electronic remittance processing for complex multi-code fracture claims. The integration covers over 4,000 US payers, handling both CMS-1500 and 837P formats. For practices managing electronic remittance advice for nonunion cases, automated ERA posting reduces manual reconciliation across extended care episodes.

Streamline fracture coding and claims management

Pabau integrates with Claim.MD to support accurate ICD-10-CM code submission, real-time eligibility checks, and electronic remittance advice for orthopedic and musculoskeletal practices.

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Billing and claims submission for S92.403K

S92.403K is valid for submission on CMS-1500 claims forms and 837P electronic transactions. Payers will expect this code to appear as the primary diagnosis on claims for nonunion management visits. When the visit also includes an E/M service, ensure the E/M level is supported by the complexity and medical decision-making documented for the nonunion assessment.

Practices can use the claims management software inside Pabau to route fracture nonunion claims through the Claim.MD clearinghouse. Built-in CPT and ICD-10-CM catalogues within the clearinghouse pipeline help flag coding mismatches before submission, reducing first-pass denial rates. The medical claims clearinghouse also supports secondary claims and corrected claims with CARC denial reason codes, which is particularly relevant for nonunion cases that span multiple payer adjudications.

For additional coding context, the AAPC Codify ICD-10-CM lookup provides crosswalk data linking S92.403K to related CPT codes and Medicare coverage policies. The ICD List tool offers free ICD-10-CM/PCS browsing with DRG grouper integration for hospital coders. For bidirectional procedure-to-diagnosis crosswalk verification, CrossCoder supports LCD/LCA policy lookups relevant to fracture nonunion treatment.

Conclusion

Nonunion fracture coding fails most often when the 7th character is selected without adequate documentation support. ICD-10 Code S92.403K is precise: it requires confirmed nonunion, confirmed left laterality, confirmed displacement, and a subsequent encounter for active management, not routine follow-up. Get any one of those elements wrong in the chart, and the claim is vulnerable.

Pabau’s integrated revenue cycle management workflows, combined with the Claim.MD clearinghouse, help musculoskeletal practices submit these complex multi-visit claims accurately and track their status through to payment. To see how Pabau handles fracture billing workflows end to end, book a demo.

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