ICD-10 Code S42.131K: Displaced coracoid fracture, nonunion

Key takeaways

ICD-10 Code S42.131K covers a displaced fracture of the coracoid process of the right shoulder at a subsequent encounter with nonunion.

S42.131K is a fully billable ICD-10-CM code for fiscal year 2026. Its parent code S42.131 is not billable without a 7th character.

The K character means nonunion has been confirmed, so it is not the routine follow-up that D covers.

Seven 7th characters attach to S42.131, including B for an initial encounter with an open fracture.

Practice management software like Pabau flags a missing 7th character before a fracture claim leaves the practice.

ICD-10 Code S42.131K is a billable code for a displaced fracture of the coracoid process of the right shoulder. The K character marks a subsequent encounter where nonunion has been confirmed.

This reference covers the code breakdown, the seven 7th character options, the hierarchy, related codes, documentation requirements, and the errors that trigger rejections.

Orthopedic and sports medicine practices bill these codes at every post-acute shoulder follow-up. Claims management software can flag a missing 7th character before the claim leaves the practice, which is where most of these denials start.

ICD-10 Code S42.131K: Quick reference and billable status

ICD-10 Code S42.131K is a billable, specific ICD-10-CM code valid for fiscal year 2026. It covers a displaced fracture of the coracoid process of the right shoulder at a subsequent encounter with confirmed nonunion. The table below is the at-a-glance summary for quick clinical lookup.

What does S42.131K mean? Breaking down the code

Each segment of ICD-10 Code S42.131K carries a specific clinical meaning. Reading it from left to right tells the full clinical story of the encounter.

The parent code S42.131 identifies the displaced coracoid fracture of the right shoulder, but it is not billable on its own. Adding the 7th character K specifies a follow-up visit where nonunion is confirmed, which completes the code. Practices carrying sports medicine and orthopedic caseloads meet this pattern at post-acute follow-ups where healing has stalled.

Anatomy: Why the coracoid process fractures

The coracoid process is a hook-shaped projection of the scapula, or shoulder blade. It curves forward and downward from the upper part of the bone. It anchors several muscles and ligaments, including the short head of the biceps brachii, the coracobrachialis, the pectoralis minor, and the coracoclavicular ligament complex.

Coracoid fractures are uncommon, and they tend to happen through three mechanisms. Physical therapy practices managing post-fracture rehabilitation meet this code at follow-up visits when consolidation imaging shows incomplete union.

• Direct trauma: a fall or blow directly to the anterior shoulder
• Avulsion: forceful muscle contraction pulling the process away from the scapular body
• Indirect force: acromioclavicular dislocation transmitting stress through the coracoclavicular ligament

Displacement, as specified in S42.131K, means the fragments have shifted out of anatomical alignment. Displaced coracoid fractures progress to nonunion more often than non-displaced ones, which is why the K character matters so much at this site.

What the 7th character K means

The K character is one of seven options applied to the parent code S42.131. Each option signals a different clinical phase of the fracture encounter. Choosing the wrong one is the most common coding error on fracture follow-up visits. It is also the most frequent reason payers reject these claims.

The CMS ICD-10 codes page confirms that a 7th character is required before a fracture code reaches billable specificity.

All seven 7th characters for S42.131

K vs. D: the critical distinction. D applies when a fracture is healing normally at a follow-up visit. K applies only when imaging or clinical assessment confirms the fracture has failed to unite.

Using D when nonunion is documented undercodes the encounter. Using K without documented nonunion is a compliance risk. The same test applies at every fracture site, including S32.432D at the acetabulum.

Where S42.131K sits in the ICD-10-CM hierarchy

Knowing where the code sits in the hierarchy helps coders navigate related codes and confirm they have the most specific option. The CDC ICD-10-CM web tool publishes the official hierarchical tree for all current codes.

Sibling and related shoulder fracture codes

S42.131K sits alongside laterality variants and encounter-type siblings under the same parent code. The table below covers the related codes most often referenced for coracoid process fractures. The AAPC ICD-10-CM lookup holds the full searchable list for this code family.

The same 7th character logic runs through the rest of the S42 family. S42.223G marks delayed healing in the humerus, and S42.253S covers the sequela of a greater tuberosity fracture.

Documentation requirements for S42.131K

ICD-10 Code S42.131K will be denied if the documentation does not confirm each element the code claims. Five documentation elements have to appear in the record for K to hold up on audit. Structured digital clinical forms that prompt these fields at each follow-up cut down on retrospective claim adjustments.

• Nonunion confirmed: imaging or clinical assessment must explicitly document failure of bone union. Wording such as “fracture not healed” or “no callus formation on imaging” supports K. Delayed healing without confirmed nonunion supports G instead.
• Laterality documented: the note must specify the right shoulder, and that laterality has to match the code submitted.
• Displacement status confirmed: the record must show the fracture is displaced, or that it remains displaced from its original state. If it has been reduced, displacement status needs reassessment.
• Encounter type as subsequent: the note must show that active treatment has already started. This is a follow-up visit, not a new injury presentation.
• Site specificity: the coracoid process must be identifiable from the note, the imaging report, or the referral. “Shoulder fracture” alone does not support this level of specificity.

Practices with strong patient record management workflows make this audit-ready from the first follow-up visit. A payer reviewer should be able to verify every element of the code without requesting extra records. Standardized clinical documentation practices across the orthopedic team are what keep that consistent.

Payers run targeted audits on nonunion codes, because they carry higher clinical acuity and higher treatment costs. A routine medical chart audit inside the practice catches thin documentation before an external reviewer does.

Common coding errors with S42.131K

Coracoid fracture nonunion codes generate a predictable set of errors. Each one below maps to a specific denial pattern on shoulder fracture submissions.

• Submitting S42.131 with no 7th character: the parent code is not billable. Claims carrying it are rejected for lack of specificity, so always append the right 7th character first.
• Confusing K with D: D is for routine subsequent encounters where healing is progressing. K is only correct once nonunion is confirmed by imaging or clinical assessment.
• Missing laterality: S42.132K is the left shoulder variant, and S42.139K covers unspecified laterality. The wrong laterality is a common automated edit trigger.
• Using G when K applies: delayed healing is not the same as nonunion. G fits a fracture that is progressing slowly, and K takes over once nonunion is confirmed.
• Switching back to A at a follow-up: A applies only at the first active treatment visit. Using it later misrepresents the encounter type.
• Coding the wrong scapular structure: the coracoid process is one specific projection of the scapula. Confusing it with the glenoid cavity, the acromion, or the scapular body produces a code-level error.

Practices that route shoulder fracture follow-ups through an automated documentation workflow catch most of these before the claim goes out. Building the 7th character check into the visit note template beats a coder review after the fact.

ICD-10-CM fracture coding guidelines from CMS

The official ICD-10-CM fracture coding guidelines, maintained by CMS and NCHS, govern how S42.131K is applied. They cover every fracture code, not only coracoid process fractures. Learning them prevents systematic errors across a whole practice’s fracture billing.

The guidelines split encounter types into two groups. Initial encounter (A) means the patient is receiving active treatment, whoever provides it. A patient transferred between providers for active treatment still uses A.

Subsequent encounter (D, G, K, P, S) means active treatment has already happened and the patient is in follow-up care. That covers cast changes, removal of fixation devices, medication adjustment, and recuperation.

• Nonunion definition: the guidelines describe nonunion as failure of the fracture to heal within the expected timeframe. No fixed number of weeks is given. The attending clinician’s judgment, supported by imaging, establishes it.
• Sequencing: when nonunion is the primary reason for the visit, S42.131K is sequenced as the principal diagnosis. Where the visit addresses several conditions, standard principal diagnosis rules apply.
• 7th character required: fracture codes in the S00-T14 range need a 7th character to reach billable specificity. Claims without one are rejected as invalid codes.
• Code the condition, not the procedure: S42.131K describes the patient’s condition and implies no particular treatment. Procedures and supplies from the visit carry their own CPT or HCPCS codes, such as HCPCS code E0218 for a cold therapy unit.

How Pabau keeps 7th character errors off fracture claims

Most practices catch 7th character errors after the fact. A coder reads the note, sees that K was assigned with no confirmed nonunion, and sends it back to the provider. That round trip adds days to a claim that was clinically correct all along.

Practice management software like Pabau moves the check into the visit itself. A fracture follow-up template can require the imaging finding, the laterality, and the encounter type before the note is filed. Every subscription includes those clinical forms and the billing tools that read from them, so nothing here sits behind a higher tier.

The outcome is a shorter path from visit to payment. Everything that supports S42.131K is captured while the patient is still in the room, so fewer claims come back for rework. Medical compliance workflows hold that standard steady across every provider in the group.

Reduce claim denials on fracture follow-up visits

Pabau's documentation workflows catch 7th character errors and laterality mismatches before a claim is submitted. See how orthopedic and sports medicine practices use Pabau to keep fracture coding clean.

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Conclusion

Nonunion coding rewards precision. S42.131K holds up only when the record confirms nonunion, names the right shoulder, and shows the encounter as a follow-up. Miss one of those three and a legitimate visit turns into a denial or an audit finding.

Put the check in the template rather than in the review. A follow-up note that asks for the imaging finding by name costs the provider seconds and saves the practice a resubmission. Book a demo to see how Pabau supports fracture coding accuracy across a multi-provider practice.

Continue your research

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Documenting a musculoskeletal exam? The reverse pivot shift test guide shows what to record so the finding still stands up months later.

Recovering revenue after a denial? Patient collections covers how to lift your collection rate without straining the patient relationship.

Planning a move to a new system? Switching EHR systems maps out the migration steps that keep clinical records intact.

Taking payments on the fracture episode? HIPAA compliant payment processing explains what the payment flow around a claim has to protect.

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