ICD code S12.591B – Nondisplaced sixth cervical vertebra fracture, open

Key takeaways

S12.591B codes an open, nondisplaced C6 fracture of the “other” type while the patient is in active treatment, unlike the closed-fracture code S12.591A.

The 9 in S12.591B marks an “other” fracture type, excluding the specifically named C6 types, such as traumatic spondylolisthesis (S12.53-S12.55) and unspecified fracture (S12.50-).

Reusing suffix B on follow-up visits after active treatment ends can lead to denials or audit queries. Switch to suffix D for routine healing-phase care.

Pabau’s claims management software generates CMS-1500 claims from invoices, submits them through Claim.MD and flags denied claims for rework.

ICD-10 code S12.591B: Definition and billable status

ICD-10 code S12.591B is the billable ICD-10-CM code for an other nondisplaced fracture of the sixth cervical vertebra, initial encounter for open fracture. It is valid in the FY2026 and FY2027 ICD-10-CM code sets, as the CDC/NCHS ICD-10-CM web tool confirms.

The code sits in category S12 (fracture of cervical vertebra and other parts of neck), within subcategory S12.59 for other fractures of C6. Use it when the record documents an open C6 fracture of a type with no code of its own, with no displacement, during active treatment.

The official full descriptor is: Other nondisplaced fracture of sixth cervical vertebra, initial encounter for open fracture. Each part of that descriptor maps to one character of the code, as the next section shows.

Code descriptor breakdown: What each segment of S12.591B means

Reading the ICD-10-CM code structure character by character stops most S12.591B errors before the claim reaches the payer. Each character carries a specific clinical meaning.

The 9 marks an “other” fracture type, excluding the specifically named C6 types, such as traumatic spondylolisthesis (S12.53-S12.55) and unspecified fracture (S12.50-). Use it when the record describes a C6 fracture type that has no code of its own. If the record identifies traumatic spondylolisthesis, code to S12.53-S12.55 instead. If it gives no fracture type at all, S12.50- applies.

Clinical anatomy: The sixth cervical vertebra (C6) in trauma coding

C6 sits in the lower cervical spine, just above the cervicothoracic junction. That position makes it vulnerable in high-energy flexion-compression injuries, such as diving accidents, motor vehicle collisions and falls from height. A nondisplaced fracture at this level means the bone is broken but the fragments have not shifted out of alignment.

Open fractures at C6 are uncommon but clinically urgent. An open wound at the fracture site raises the infection risk and often needs prompt surgical debridement. It also needs explicit documentation to support suffix B, because payers may review open-fracture claims more closely than the closed equivalent.

• Common injury mechanisms at C6: Axial loading with flexion (diving), high-speed motor vehicle collisions and direct penetrating trauma
• Nondisplaced confirmation: The CT or plain radiograph report must state “nondisplaced” or “no displacement” for the nondisplaced character to hold up on audit
• Open fracture confirmation: An operative note, wound care note or emergency physician note that describes the fracture as open

Open vs closed fracture: When to use suffix A vs B

Suffix A means initial encounter for a closed fracture, and suffix B means initial encounter for an open fracture. Section I.C.19 of the ICD-10-CM Official Guidelines for Coding and Reporting lists the terms that classify a fracture as open. They include compound, infected, with foreign body and puncture wound with foreign body. A fracture not specified as open or closed is coded as closed.

When the medical record is silent on wound status, assign suffix A (closed), as Section I.C.19 directs. Assigning suffix B without documentation of an open fracture is a coding error that payers can recover on audit.

S12.591B vs neighboring codes: How to choose correctly

ICD-10 code S12.591B sits in a tight group of C6 fracture codes from the ICD-10-CM tabular list. Choosing the right one depends on three facts in the record: The fracture type, whether it is displaced, and whether it is open or closed. The comparison below covers the codes most often confused with S12.591B.

Displacement is the only difference between S12.591B and S12.590B. Both code an open “other” C6 fracture at the initial encounter, but S12.590B applies when imaging shows the fragments have shifted. When the radiologist describes a “nondisplaced fracture of C6” without naming a type, S12.501B is the accurate open-fracture code.

The four checks in the diagram below lead to S12.591B, and each other answer points to the code that fits instead.

Encounter type selection: Initial, subsequent, and sequela

The 7th character for S12.591B follows the standard trauma encounter rules in Section I.C.19 of the ICD-10-CM Official Guidelines published by CMS and NCHS.

• Suffix B (initial encounter, open): Use for every visit while the patient is receiving active treatment for the fracture, whichever provider performs it. A patient who sees a specialist two weeks after the emergency department visit is still “initial” if active treatment continues
• Suffix D (subsequent encounter): Use once active treatment is complete and the patient is receiving routine care during healing or recovery. Examples include brace changes, imaging to check healing and medication adjustments
• Suffix S (sequela): Use when the visit treats a condition that results directly from the fracture, such as chronic pain attributable to the old injury

Reusing suffix B after the active treatment phase ends can lead to denials or audit queries. Switch to suffix D as soon as the documentation shows routine follow-up care rather than active fracture management.

Documentation requirements to support S12.591B

A complete medical record for S12.591B contains each of the five elements below. Missing any one of them creates a denial or audit risk. Confirm all five before the claim goes out to give yourself the best chance of a clean claim on the first pass.

• Anatomical specificity: The record must name “sixth cervical vertebra”, “C6” or an equivalent notation. “Cervical fracture” without a level does not support S12.591B
• Nondisplaced status: The CT or plain film report must confirm no displacement. Accept “nondisplaced”, “non-displaced”, “in alignment” or a statement that the fragments have not shifted
• Open fracture documentation: An operative, emergency department or wound care note must describe the fracture as open. A neck laceration alone is not enough, so the provider must link the wound to the fracture site
• Encounter type confirmation: The note must show the patient is still in active treatment for the fracture, not attending routine follow-up
• Physician attestation: If the open classification followed a clinical documentation integrity (CDI) query, the physician’s written response must be in the record before submission

CPT codes commonly paired with S12.591B

The procedure codes below are the ones most often billed alongside S12.591B, from fusion at C6 to imaging and emergency evaluation. Anterior fusion below C2 is reported with 22551, and the first CT of the cervical spine with 72125. Each row notes the review trigger to flag before submission.

Bundling edits can apply when several radiology codes are submitted for the same session. Check the Medicare MAC’s LCD or the payer’s medical policy before submitting both 72125 and 72141 for the same encounter.

Payer requirements and pre-authorization

Payer policies differ by plan and plan year, so the guidance below reflects general industry practice. Verify current requirements with each payer before submitting. Insurance eligibility verification before the encounter surfaces prior-authorization requirements ahead of the procedure.

• Medicare: The S12.591B diagnosis code does not trigger pre-authorization under traditional fee-for-service Medicare. Surgical CPT codes paired with it (such as 22551 and 22600) may need prior authorization under Medicare Advantage plans. Check the LCD for cervical spine surgery in your MAC jurisdiction
• Commercial insurance: Most commercial payers require prior authorization for elective or semi-elective cervical fusion. Open fractures treated as surgical emergencies may have expedited or post-service authorization pathways, so confirm with the specific plan
• Medicaid: Prior authorization for cervical spine surgery under Medicaid varies by state. The CPT procedure code drives the review, not the diagnosis code alone

For practices handling many trauma claims, tying revenue cycle management to real-time eligibility checks gets urgent fracture claims submitted sooner.

Common claim denial reasons and how to avoid them

Two documentation points commonly cause problems on this code: Suffix selection (A vs B) and open-wound documentation. A structured denial management workflow catches both before submission. When a claim is denied anyway, the remittance advice states the reason using standard denial codes in medical billing.

For a denied claim, record the CARC reason code from the remittance advice before you start an appeal. Denial patterns across a code family, such as all S12.5- codes, are easier to fix at the policy level than claim by claim.

How claims management software speeds up S12.591B billing

Many practices still code the encounter in one place, re-key it into a billing system and upload the claim through a separate clearinghouse portal. Each hand-off is a chance for suffix B to become A, or for a denial to sit unnoticed in a payer portal.

Pabau, the practice management platform we build, keeps those steps in one system. Its claims management software generates CMS-1500 claims from invoices and submits them through Claim.MD. It also checks eligibility in real time, matches ERAs to claims and flags denied claims for rework.

The result is less re-keying between the chart and the claim. A denied trauma claim also reaches your team for rework instead of waiting to be found.

Submit and rework trauma claims faster

Pabau generates CMS-1500 claims from invoices, submits them through Claim.MD and checks eligibility in real time. Matched ERAs and flagged denials help your team rework a rejected S12.591B claim quickly.

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Conclusion

Treat S12.591B as a documentation code first. Before you assign it, confirm three facts in the record: The fracture is open, it is nondisplaced, and the patient is still in active treatment. If one is missing, query the physician or code the closed, displaced or subsequent-encounter alternative instead.

A query delays the claim, but a suffix B claim without open-fracture documentation can be denied or recovered after payment. The extra step up front is the cheaper of the two.

To spend less time re-keying and reworking trauma claims, book a demo and see how Pabau submits CMS-1500 claims through Claim.MD.

Continue your research

Need to read the denial codes on a rejected S12.591B claim? Medical billing denial codes covers the CARC and RARC codes that appear on fracture claim rejections.

Want to streamline trauma claim submission across a multi-provider practice? Claim.MD clearinghouse guide explains how Pabau generates and submits CMS-1500 claims, checks eligibility in real time and matches ERAs.

Coding a named C6 fracture type instead? ICD-10 code S12.54XA covers type III traumatic spondylolisthesis of the sixth cervical vertebra, initial encounter for closed fracture.

Want to see where diagnosis coding fits in the billing cycle? Revenue cycle management guide explains how coding, claim submission and denial resolution connect across patient billing.

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