ICD code S82.236K – Nondisplaced oblique tibial shaft fracture nonunion

Key takeaways

S82.236K codes a nondisplaced oblique tibial shaft fracture, unspecified leg, at a subsequent encounter where nonunion is documented.

Seventh character K requires the provider to document nonunion explicitly. Imaging findings alone don’t support it without a clinician statement.

Unspecified laterality (.236) is valid only when documentation genuinely omits left or right. Payers may deny or downcode when laterality can be inferred from the record.

Open fractures with nonunion take M or N instead of K, based on the Gustilo type the treating surgeon documented.

Pabau, the practice management and billing platform we build, puts ICD-10-CM code search inside the clinical workflow and flags CPT-ICD mismatches before claim submission.

ICD-10 Code S82.236K: Official description and code hierarchy

ICD-10 Code S82.236K carries the full official descriptor: “Nondisplaced oblique fracture of shaft of unspecified tibia, subsequent encounter for closed fracture with nonunion.” Each character encodes a distinct clinical fact, so one wrong character produces a different code that the documentation doesn’t support.

Per the CMS ICD-10-CM coding updates, all codes in the S82 category cover fractures of the lower leg. The S82.2 subcategory restricts this further to the tibial shaft (diaphysis), excluding the proximal plateau and distal epiphysis.

The sixth character encodes displacement and laterality together. For nondisplaced oblique fractures, .234 is right leg, .235 is left leg, and .236 is unspecified leg. Codes .231 to .233 are the displaced oblique codes.

Decoding the seventh character K: Subsequent encounter with nonunion

Seventh character K means the patient is at a follow-up visit (subsequent encounter) for a closed fracture that has failed to achieve bony union. Section I.C.19.a of the ICD-10-CM Official Guidelines governs how seventh characters are applied. The CDC ICD-10-CM code tool lists six seventh characters for closed fractures of the tibial shaft: A, D, G, K, P, and S.

There is no single clinical cutoff for nonunion. The most widely cited definition comes from the FDA, as summarized in StatPearls. It requires at least nine months since injury and no visible progress toward healing over three consecutive months. StatPearls calls this a loose definition, because bones heal at different rates.

Medicare’s NCD 150.2 applies its own, shorter test for bone stimulator coverage, and the ICD-10-CM guidelines set no time cutoff at all.

What distinguishes K from G (delayed healing) is the provider’s clinical judgment, documented explicitly in the note. A radiograph showing persistent fracture lucency is necessary evidence, but it isn’t enough on its own to justify K on the claim. The provider must state that nonunion is present.

Full S82.236 code family: All seventh-character variants

S82.236 without a seventh character is not a billable code. Every encounter must append one of the following seventh characters. The table covers closed-fracture variants.

Open-fracture seventh characters apply when the Gustilo classification is documented by the treating surgeon. B (open type I or II) and C (open type IIIA, IIIB, or IIIC) cover the initial encounter. E, F, H, J, M, N, Q, and R cover subsequent encounters.

The code S82.236A is appropriate for every visit during the active treatment phase, regardless of how many visits that entails. Once active treatment ends and the patient moves to monitoring, the coder switches to D, G, K, or P based on the progress note. Switching back from K to D is not appropriate unless documentation explicitly describes new healing activity.

Clinical criteria: When to use S82.236K vs adjacent codes

Choosing S82.236K means confirming four documented facts in order. They are the fracture pattern and site, displacement, laterality, and healing status. The chart below shows where the code goes when the note says something else at any step.

Laterality in S82.236: Why “unspecified leg” matters

Unspecified laterality (.236) is valid when the documentation genuinely does not specify left or right leg. ICD-10-CM Official Guidelines Section I.B.13 instructs coders to assign the unspecified code only when the information is not available. Laterality must be queried from the provider if it can be determined from the record and was merely omitted from the note.

Many payers, including Medicare Advantage plans, flag unspecified laterality on musculoskeletal claims for additional review or deny outright, so resolving it upfront saves appeals.

• S82.234K — right leg. Use when the operative or clinical note states the right tibia.
• S82.235K — left leg. Use when the note states the left tibia.
• S82.236K — unspecified leg. Use only when laterality is undocumented and can’t be inferred.

Nonunion vs malunion: Coding the difference in ICD-10-CM

Nonunion (seventh character K) and malunion (seventh character P) are not interchangeable. Nonunion means the fracture has failed to heal. The fracture gap persists on imaging, and the provider confirms there is no bridging callus. Malunion means healing has occurred but the bone has consolidated in an angulated, rotated, or shortened position.

Assigning K when the provider documents malunion, or P when nonunion is stated, constitutes a coding error that can trigger a medical necessity denial. The two conditions need separate clinical and radiographic documentation, and neither can be assumed from the other.

Documentation requirements for S82.236K

A tibial shaft fracture nonunion claim that carries S82.236K must be supported by progress notes and imaging that establish five elements. Missing any one of them gives an auditor grounds to downcode or deny.

• Fracture morphology: The note must identify the fracture as oblique. “Tibial shaft fracture” alone is insufficient. Without the morphology, the coder cannot reach S82.23x and must use the less specific S82.20x (unspecified fracture of shaft of tibia).
• Displacement status: Documentation must confirm nondisplaced. If displacement is not addressed, Guidelines Section I.C.19.c defaults the fracture to displaced. That would push the code to the S82.231 to S82.233 range (displaced oblique).
• Affected bone segment: The note must confirm the shaft (diaphysis). Proximal or distal tibial fractures map to different S82 subcategories.
• Healing complication: The provider must explicitly state nonunion. Imaging findings such as persistent fracture line or absence of callus on X-ray or CT are supporting evidence, not a substitute for the clinical statement.
• Laterality: Left, right, or a documented reason why laterality cannot be specified.

Open fracture addenda: When to add a seventh character for open type

S82.236K assumes a closed fracture. If the original fracture was open, alternate seventh characters apply based on the Gustilo-Anderson classification documented by the treating surgeon. Open tibial shaft fractures with nonunion use the following seventh characters instead of K.

Gustilo classification must be documented by the surgeon who treated the open wound. Coders must not infer the Gustilo type from soft tissue description alone. If open fracture type is not documented, assign the closed-fracture seventh character (K) per the default-to-closed rule in ICD-10-CM Guidelines Section I.C.19.c.

Payer requirements and CPT companion codes for S82.236K

Claims carrying S82.236K often go through medical necessity review, because nonunion treatment tends to involve surgery or durable medical equipment. A clearinghouse that validates CPT-ICD pairings before transmission catches a mismatch before the payer does.

CPT and HCPCS codes commonly billed with S82.236K

The CPT and HCPCS codes most frequently paired with S82.236K reflect the clinical interventions for tibial shaft fracture nonunion. Medical necessity for each pairing must be individually established in the documentation.

A visit that only monitors the nonunion is billed with an established-patient office visit code, such as 99213. The E/M level follows the medical decision-making or total time documented for that visit.

For bone stimulator claims (E0747), Medicare and most commercial payers require a Local Coverage Determination (LCD)-compliant note. It must show failure of conservative treatment and physician attestation of nonunion. It must also show at least 3 months without healing, documented on serial radiographs at least 90 days apart (Medicare NCD 150.2).

Verify the applicable LCD by Medicare Administrative Contractor (MAC) jurisdiction, as policies vary across regions.

Common S82.236K claim denials and how to avoid them

S82.236K denials cluster around six root causes. Each one traces back to a specific weakness in the record, so coders can fix it before submission instead of after.

Good denial management workflows start at coding, not at remittance. Every claim should also pass as a clean claim before it leaves the practice. That means no missing fields, correct modifiers, and matched CPT-ICD pairs.

When one of these slips through, the remittance carries a claim adjustment reason code that names the failure. Our list of common medical billing denial codes explains what each one means and how to correct it.

ICD-10-CM coding guidelines: Section I.C.19 injury and fracture rules

Section I.C.19 of the ICD-10-CM Official Guidelines governs all injury and fracture coding. CMS and the National Center for Health Statistics (NCHS) at the CDC publish the guidelines each year. ResDAC explains how these diagnosis codes appear in Medicare claims files.

Staying current with medical billing compliance requirements means reviewing these guidelines with each annual ICD-10-CM update. The rules most relevant to S82.236K are summarized below.

• Default to closed and displaced (I.C.19.c): When documentation does not specify open or closed, assign the closed-fracture code. A fracture not documented as displaced or nondisplaced is coded as displaced.
• Subsequent vs initial encounter (I.C.19.a): Use initial encounter (A) for visits providing active treatment. Once care transitions to monitoring or routine follow-up, use the appropriate subsequent-encounter character (D, G, K, or P).
• Multiple fractures (I.C.19.c.2): Sequence the most severe fracture first when multiple fractures are coded in the same encounter.
• Laterality defaults (I.B.13): Assign the most specific laterality available. Unspecified codes require querying if laterality can reasonably be determined.
• External cause codes: A secondary code from the V/W/X/Y block describes what caused the original fracture, such as a fall or a motor vehicle collision.
• Aftercare vs subsequent encounter (I.C.19.a): Aftercare Z codes are not used for injuries. For any subsequent encounter, including routine healing, assign the injury code with the matching seventh character (D, G, K, or P).

How Pabau catches S82.236K coding errors before submission

Without a coding check at the point of care, a nonunion claim usually gets reviewed after the visit. A biller compares the note with the codes, then chases the provider for a missing laterality or nonunion statement. By then, the patient has left and the details are harder to recall.

Pabau moves that check into the visit. Clinicians search ICD-10-CM codes from inside the patient record, and each diagnosis links straight to its invoice and procedure line. Pabau’s claims management software then flags a CPT-ICD mismatch, such as E0747 billed without S82.236K, before the claim goes out.

Clean claims go out through Pabau’s Claim.MD clearinghouse integration, which connects to thousands of US payers and runs real-time eligibility checks. Your team fixes a weak note while the provider still remembers the visit, instead of after the denial arrives.

Reduce S82.236K claim denials before they happen

Pabau links ICD-10 diagnosis codes directly to invoices and procedure lines, flags CPT-ICD mismatches at entry, and submits clean claims through the Claim.MD clearinghouse. See how it fits your orthopedic or multi-specialty workflow.

Book a demo

Conclusion

S82.236K comes down to one habit. Read the note for an explicit nonunion statement before you choose the seventh character, and query the provider if it isn’t there. Inferring K from an X-ray is how these claims get denied.

Apply the same discipline to laterality. An unspecified leg is valid only when the record doesn’t say which tibia is affected, so check earlier encounters before you settle for .236.

Building these checks into the visit means fewer claims come back for rework or appeal. Book a demo to see how Pabau links each nonunion diagnosis to its claim before it leaves your practice.

Continue your research

Need to understand how clearinghouse validation reduces denials? Claim.MD clearinghouse overview explains how real-time claim scrubbing catches ICD-CPT mismatches before payer submission.

Looking to understand the full 837 claim submission workflow? 837 file guide covers the EDI transaction format used to submit ICD-10-coded claims electronically.

Want to verify insurance eligibility before a follow-up fracture encounter? Insurance eligibility verification guide outlines the process for confirming coverage before a subsequent-encounter visit.

Frequently asked questions