ICD-10 code S42.012P: Anterior displaced left clavicle fracture with malunion

Key takeaways

S42.012P describes an anterior displaced fracture of the sternal end of the left clavicle. It applies at a follow-up visit, after the bone healed out of position.

The 7th character P means malunion. Nonunion is a different finding and takes K, so the two are never interchangeable.

The note must state four things: left side, sternal end, anterior displacement, and malunion at a subsequent encounter.

Malunion must come from the treating provider. A coder cannot read it off an imaging report alone.

Practice management software like Pabau keeps records, coding, and claims in one system. That makes follow-up billing quicker to check and submit.

ICD-10 code S42.012P describes an anterior displaced fracture of the sternal end of the left clavicle. You report it at a subsequent encounter, once that fracture has healed in the wrong position.

Malunion is where these claims come unstuck. Payers want the word itself in the provider’s note, not a hint of it buried in the imaging. A report that reads “healed with angulation” will not carry the P character on its own.

The rest of the code is mechanical. Side, site, displacement direction, and encounter type all sit in the descriptor. Each one has to appear somewhere in the chart.

S42.012P is billable for the FY2026 code set

Yes, S42.012P is a billable and specific ICD-10-CM code. It is valid for the FY2026 code set, which took effect on October 1, 2025.

Practices can report it on Medicare, Medicaid, and commercial claims. The CMS ICD-10 codes page carries the current release files.

What each part of the descriptor actually means

The descriptor packs five separate clinical facts into eight characters. Read them one at a time and the code stops looking arbitrary.

• Anterior displaced: the broken fragment has shifted forward. “Displaced” rules out the nondisplaced codes, and “anterior” fixes the direction.
• Sternal end: the inner end of the collarbone, nearest the breastbone. Some surgeons call it the medial or sternoclavicular end.
• Left clavicle: laterality lives in the 6th character. The digit 2 in S42.012 carries both the anterior displacement and the left side.
• Subsequent encounter: definitive treatment is done. The patient is now in the healing or recovery phase.
• Malunion: the bone knitted back together, but crooked. Healing finished, alignment did not.

Charts rarely use that exact wording. You will see “malunited left medial clavicle fracture” or “healed left sternoclavicular fracture in malposition” instead. Either phrasing works, as long as the four coded facts are all there.

The 7th character is where clavicle claims go wrong

The 7th character tells the payer where the patient sits in the healing process. It has nothing to do with how many times the provider has seen them.

Category S42 uses the plain closed and open pair at the start. A covers a closed fracture on first treatment, and B covers an open one, as in S42.009B.

You will never see Q or R in the shoulder chapter, though. Those extra malunion characters follow the Gustilo open fracture classification. It applies to the forearm, femur, and lower leg only. S72.452Q is one of them, and it is a useful contrast when you work across body regions.

Malunion healed crooked, nonunion never healed at all

Both characters describe a fracture that did not end well, but they are not interchangeable. Nonunion means the bone gave up on healing, and it takes the K character.

Malunion means it healed badly instead, which is what the P character records. That difference drives both the code and the treatment plan.

Radiology often sits on the fence. Reports describing “abnormal healing” or “residual angulation” support neither character by themselves.

Query the provider before you pick one, because assigning P without the word malunion is exactly what auditors look for. The shoulder girdle carries its own nonunion codes too, such as S42.131K.

Where S42.012P sits in the S42 family

Parent codes carry instructional notes, so it pays to know the branch you are standing on. The path runs like this:

• S00-T88: injury, poisoning, and certain other consequences of external causes
• S40-S49: injuries to the shoulder and upper arm
• S42: fracture of shoulder and upper arm
• S42.0: fracture of clavicle
• S42.01: fracture of sternal end of clavicle
• S42.012: anterior displaced fracture of sternal end of left clavicle
• S42.012P: subsequent encounter for fracture with malunion

Sibling codes you switch between as the patient heals

One fracture can move through four or five codes before the file closes. The base code stays put and the 7th character does the work.

Move to a different part of the collarbone and the base code changes with it. A late effect at the outer end, for instance, belongs to S42.032S. Site, side, and healing status each shift the code independently.

Four details your provider note must state

A seven-character trauma code fails on one missing detail. For S42.012P, four things need to be explicit in the note before you assign it.

• Laterality: the note names the left clavicle. “Clavicle fracture” on its own is not enough.
• Anatomical site: the medial or sternal end. Mid-shaft and lateral end fractures map to other S42.0 codes.
• Displacement direction: anterior. Posterior and unspecified displacement have their own codes.
• Encounter and healing status: active treatment is finished, and the provider has documented malunion rather than nonunion or routine healing.

Those four facts are usually scattered across the operative note, the follow-up note, and the imaging report. Pulling them together is far quicker when patient records and imaging sit in one system rather than three.

Initial or subsequent? Three questions settle it

Work through them in order and the character picks itself.

1. Is the patient still under active treatment for this fracture? If so, use A or B, however many visits have gone by.
2. Has the provider described how it healed? Routine healing takes D, and slow union takes G.
3. Does the note say malunion? Only then does P apply.

Two traps hide inside that sequence. First, a patient who put off care still gets the initial encounter character, even if the injury happened months ago. Second, a fresh face in your practice does not reset anything. Treatment phase decides the character, not the relationship with the provider.

Other injuries treated at the same visit keep their own characters. A bruised upper arm coded as S40.022A can sit happily on the same claim as a malunion code.

How a malunion claim moves from note to payment

Coding is one stop on a longer trip. Knowing the whole route tells you where a clavicle claim tends to stall.

1. The provider signs the note. Nothing downstream can be fixed if the malunion wording never lands here.
2. Charge entry. The coder pairs S42.012P with the office visit or procedure code performed that day.
3. Claim scrubbing. Your billing system checks the code is valid for the date of service and complete to seven characters.
4. Clearinghouse edits. Front-end rejections land here, usually within a day, with a reason code attached.
5. Payer adjudication. The payer weighs the diagnosis against the service billed, then pays, adjusts, or denies.

A rejection at step four never reaches a claims examiner, so it is cheap and fast to correct. Denials at step five cost far more, because they usually need records attached and a written appeal.

In smaller musculoskeletal teams, such as an osteopathy practice, the same person often codes the visit and chases the rework.

Run this check before you submit

Five quick checks catch most of what comes back. Work through them at charge entry, not after the denial arrives.

1. The date of service falls inside the fiscal year this code is valid for. Code sets refresh every October 1.
2. The diagnosis pointer links S42.012P to the right service line on the claim.
3. Laterality on the claim matches the note. Left in the chart, left in the code.
4. The malunion wording is signed off, not sitting in an open provider query.
5. No unspecified code has crept in where the chart documents something specific.

Mistakes that send this claim back

Four errors account for most rework on healed fracture claims.

• Coding P from the radiology report. Imaging describes the bone, not the diagnosis. The finding has to come from the treating provider.
• Using P during active treatment. While definitive care is still under way, the encounter is initial, so A or B applies.
• Swapping P and K. The clinical difference is real and payers track it, since nonunion often triggers surgery.
• Billing a late effect as malunion. Once treatment is finished and you are coding a residual problem, the sequela character applies, as in S82.036S.

What the official guidelines actually require

Fracture coding rules live in Section I.C.19 of the FY2026 ICD-10-CM Official Guidelines. Four of them shape how you use S42.012P.

• Active treatment sets the character. Assignment turns on whether the patient is still receiving active treatment, not on whether the provider has seen them before.
• Healing complications have their own characters. For malunion the guidelines allow P, Q, or R characters, while nonunion uses K, M, or N characters. Clavicle codes only need K and P.
• Delayed care still counts as initial. A patient who put off treatment for the fracture takes the initial encounter character.
• Surgical complications are coded separately. Problems caused by fracture repair surgery during healing get the appropriate complication code.

One more rule sits outside Section I.C.19 and matters just as much. Code assignment follows the provider’s documentation, so malunion is never something a coder infers.

Rehab teams feel this constantly. A therapist, or a clinician in a chiropractic practice, can document lost range of motion in a healed shoulder. That note supports the therapy claim, but it cannot establish the malunion behind it.

How Pabau keeps orthopedic follow-up claims clean

Most of the rework on a code like this is admin, not clinical. The follow-up note lives in one system, the coder works in another, and the claim leaves through a third. Every handoff is a chance for the malunion wording to go missing.

Practice management software like Pabau closes that distance. Patient records, treatment notes, and billing sit in the same platform. The coder reads the signed follow-up note without exporting anything, and nobody rekeys data between the chart and the charge.

From there, our claims management software submits the claim and tracks its progress. It also validates the insurer details before the claim leaves your practice. When something does bounce, the reason code and the note sit side by side. Your biller can correct and resubmit the same day.

Keep follow-up claims moving

Pabau brings patient records, treatment notes, and billing into one platform. Claims management then submits each claim, tracks its progress, and validates the insurer details before it leaves your practice.

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Conclusion

S42.012P asks for three anatomical facts and one clinical judgment. Those facts are almost always in the chart already. The judgment, malunion, is the single thing a coder can never supply.

So the fix sits upstream of billing. Agree with your surgeons on the word they will use when a fracture heals crooked. Query the ones who reach for something vaguer. Do that once and this code becomes data entry.

Book a demo to see how Pabau keeps notes, coding, and claims for follow-up visits in one system.

Continue your research

Coding a clavicle procedure at the same visit? CPT code 23146 covers excision of a bone cyst from the clavicle or scapula with an allograft.

Billing surgery after a shoulder injury? CPT code 23670 covers open treatment of a shoulder dislocation with a greater tuberosity fracture.

Need the nonunion code near the elbow? S42.442K covers a displaced medial epicondyle fracture that failed to join.

Working with open fracture healing characters? S72.334N shows how the nonunion characters work once Gustilo typing applies.

Assessing shoulder pain at a follow-up visit? Arm squeeze test walks through performing and scoring a test that separates neck pain from shoulder pain.

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