ICD code S92.135K – Nondisplaced fracture of posterior process of left talus

Key takeaways

S92.135K is a billable ICD-10-CM code for a nondisplaced fracture of the posterior process of the left talus, subsequent encounter for fracture with nonunion.

Laterality sits in the 6th character. For a nondisplaced posterior process fracture, 4 is right, 5 is left, and 6 is unspecified.

The 7th character K covers subsequent encounters where the fracture has failed to heal. Nonunion must be confirmed by the treating provider, not assumed.

Coders commonly confuse K (nonunion) with D (routine healing) or G (delayed healing). The wrong suffix triggers payer denials and audit flags.

Practice management software like Pabau validates ICD-10 claims before submission and tracks denial patterns for orthopedic and podiatric practices.

ICD-10 Code S92.135K: Code details at a glance

What does S92.135K mean? Breaking down the code

Each segment of S92.135K carries precise clinical and coding information. Misreading any component, particularly laterality or the 7th character, produces an incorrect code that payers will reject. Here is what each alphanumeric position means.

The 6th character carries displacement and laterality together, which is where most laterality errors on this code start. For a displaced posterior process fracture, 1 is right, 2 is left, and 3 is unspecified. For a nondisplaced fracture, 4 is right, 5 is left, and 6 is unspecified.

So S92.135K is the left-sided code, S92.134K is its right-sided counterpart, and S92.136K covers a documented nondisplaced fracture where the side was never recorded. Bilateral injuries are uncommon with this fracture pattern. When they do occur, code each side separately rather than reaching for the unspecified option.

The 7th character is where most billing errors occur, so the section below covers it in detail. For the official tabular list and index, the CDC/NCHS ICD-10-CM web tool is the primary source.

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

The 7th character in ICD-10-CM fracture codes is not optional or interchangeable. Each value defines the stage of care, and the wrong selection changes the clinical meaning of the code entirely.

Per the ICD-10-CM Official Guidelines for Coding and Reporting, maintained by CMS and NCHS, the provider’s documentation must support whichever character is assigned.

Critical distinction: K (nonunion) and P (malunion) are not the same. Nonunion means the fracture has not healed at all. Malunion means it healed in the wrong position. Payers audit these closely.

K also differs from G (delayed healing), because G implies active, ongoing healing with a positive prognosis. K is assigned only when the provider explicitly documents that union has failed, usually backed by radiographic evidence.

Those two characters get read off the note in a fixed order, which the diagram below traces.

Clinical description: Posterior process talus fracture

The posterior process of the talus is a small bony projection at the back of the talar body. It serves as an attachment point for the posterior talofibular ligament and the flexor hallucis longus tendon. Fractures here are often missed on initial X-ray, which is one reason nonunion develops more frequently than with other talus fractures.

• Mechanism of injury: Forced plantarflexion, such as an impact landing, or avulsion from ligament traction. It is also associated with os trigonum syndrome, where an accessory bone sits at the posterior talus.
• Nondisplaced vs. displaced: In a nondisplaced fracture, the bone fragments remain in anatomical alignment. Treatment is typically conservative with cast or boot immobilization. Surgical fixation is sometimes needed when the fragment is large or symptomatic.
• Why nonunion occurs: Poor vascular supply to the posterior process, late diagnosis, and inadequate immobilization are the primary factors. Athletes and active patients who return to weight-bearing too quickly are at elevated risk.
• Laterality confirmation: S92.135K specifies the left talus. If the imaging and clinical notes document the right side, S92.134K applies instead. If the record never states a side, the unspecified code S92.136K is the only accurate option.

Documentation requirements for S92.135K

S92.135K is a specificity-heavy code. Every element in its description must be supported by the clinical record before it can be assigned. Missing or ambiguous documentation is the most common reason this code triggers a denial.

• Laterality: The record must explicitly state the left talus. Bilateral or unspecified laterality does not support S92.135K.
• Displacement status: The treating provider or radiologist must document nondisplaced. A fracture described only as a talus fracture, with no displacement status, is insufficient.
• Encounter type: The visit must be a subsequent encounter, meaning the patient has been seen before for this fracture. Initial encounters use the A or B suffix, not K.
• Nonunion confirmation: The provider must explicitly document that the fracture has not united. Radiographic evidence from X-ray or CT is the standard, and imaging dates and findings belong in the clinical note.
• Anatomical site: The note must specify the posterior process, not just the talus broadly. A bare talus fracture maps to a less specific parent code.

Related ICD-10-CM codes

S92.135K sits within the S92 family of foot fracture codes. Coders working with talus fractures meet several sibling and parent codes, and the table below maps the closest ones.

Sibling codes for other injury sites sit in the same ICD-10-CM code library. For broader code navigation, the AAPC Codify ICD-10-CM lookup provides a searchable database.

Coding guidelines and billing considerations for S92.135K

Coding S92.135K correctly is the first step. Getting the claim paid also takes clean submission practices and a process for the denials that nonunion codes attract. The CMS ICD-10 codes page holds the official guidelines and the annual FY code update files.

Running submissions through validation-first claims management catches a wrong 6th character before the claim leaves the practice. For US practices, practice management software like Pabau connects to Claim.MD for electronic claims. That link covers thousands of US payers, with real-time eligibility checks and ERA processing.

• ICD-10-CM guideline: fracture sequencing. Per the official guidelines, the fracture code is sequenced as the principal diagnosis unless a different condition prompted the encounter. When S92.135K is assigned, the nonunion is usually the reason for the visit, so it sequences first.
• External cause codes. An external cause code from the V00-Y99 range may be appended when the mechanism of the original injury is documented, such as a fall. This is not required for subsequent encounters, but it can support medical necessity.
• Common denial pattern: K vs. D confusion. Payers flag claims where K is used without supporting documentation of nonunion. If the chart note says healing is progressing normally but the code is K, the claim will deny. Use claim denial management workflows to track and resolve these systematically.
• Laterality mismatch. A claim carrying S92.135K against a note that documents the right talus will not survive review. Match the 6th character to the imaging report every time, and choose S92.136K only when the side is genuinely absent from the record.
• Clean claim requirements. S92.135K must be paired with a valid CPT procedure code for the visit type. That is usually 99213-99215 for an evaluation and management encounter, or a surgical CPT when operative intervention is planned. The diagnosis and the procedure must be consistent with the documented encounter.
• Payer policies vary. Some payers publish local coverage determinations (LCDs) for nonunion fracture management. Always verify coverage before scheduling surgical intervention for nonunion.

How Pabau supports accurate nonunion fracture coding

In an orthopedic or podiatric practice, the laterality and encounter-type checks on a code like S92.135K usually happen in someone’s head. A biller reads the note and picks the 6th character from memory. The mistake then surfaces weeks later as a remittance line.

Rework costs staff time twice. Someone hunts down the original note, then resubmits the claim. Pabau moves those checks upstream instead. Structured note templates capture the side, the displacement status, and the nonunion finding as discrete fields.

The coder then reads data instead of interpreting prose. Claims pass through validation before they go out to Claim.MD, and denials come back into one queue with the reason codes attached.

The outcome is a shorter cash cycle and fewer K-suffix write-offs. Your team sees which payers reject nonunion claims and why, so the same denial does not repeat across a quarter of follow-up visits.

Simplify ICD-10 billing for orthopedic and podiatric practices

Pabau’s claims management tools integrate with Claim.MD to validate ICD-10 codes before submission, track denial patterns, and process ERAs. Your billing team spends less time on rework and more time on patient care.

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Conclusion

S92.135K is a narrow code, and the narrowness is the point. It is only correct when the note states the left talus, a nondisplaced posterior process fracture, a subsequent encounter, and a failed union. Change any one of those and the code changes with it.

The trade-off worth remembering is that specificity cuts both ways. A note that never records the side leaves you with S92.136K, the least specific option available. Chasing the provider for one word costs less than reworking the claim twice.

Validating the code at the point of submission is what stops a K-suffix denial from becoming a month of rework. Book a demo to see how Pabau fits your orthopedic billing workflow.

Continue your research

Looking for guidance on clean claim submission for ICD-10 codes? Submitting clean claims outlines the pre-submission checks that prevent the most common billing errors.

Want to understand how clearinghouse integration works for orthopedic practices? Medical claims clearinghouse explains how electronic claim routing connects practices to payers.

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