ICD-10 Code S65.301D: Right hand deep palmar arch injury
ICD-10 Code S65.301D is a billable diagnosis code for an unspecified injury of t...
Last Updated: August 17, 2026
Key takeaways
ICD-10 code S42.302K reports an unspecified fracture of the shaft of the left humerus at a follow-up visit with confirmed nonunion.
The code is billable for FY 2026 on CMS-1500 and UB-04 claims. S42.302 accepts seven valid seventh characters: A, B, D, G, K, P and S.
Imaging alone will not support the K. The physician has to write nonunion, failed union or pseudarthrosis in the note.
Nonunion repair pairs with CPT 24430 or 24435, not with 24515 and 24516, which treat acute fractures.
Practice management software like Pabau keeps the note, the imaging and the claim in one client record, so nothing is missing at submission.
ICD-10 code S42.302K reports an unspecified fracture of the shaft of the humerus in the left arm, at a subsequent encounter with nonunion. It is billable for FY 2026, effective October 1, 2025, and payers accept it on CMS-1500 and UB-04 claims.
Finding the code is the easy part. Holding on to it is where practices lose money. Three things have to line up before the K survives review. You need left-side laterality, a follow-up visit after active treatment, and a nonunion the physician has written down.
Chapter 19 of ICD-10-CM holds the code, inside block S40-S49 for injuries to the shoulder and upper arm. Here is what a billing team checks first.
S42.302K covers a left humerus shaft fracture that never healed
Every character in S42.302K tells the payer something
Read the code left to right and each segment narrows the picture. One wrong segment and the claim either denies at the clearinghouse or turns up in an audit sample later.
The word “unspecified” in .302 means the note never named the fracture pattern. When the physician does name it, a more specific subcategory takes over.
Greenstick fractures use S42.311, S42.312 and S42.319 for right, left and unspecified arm. Displaced transverse fractures use S42.321, S42.322 and S42.329. Oblique, spiral and comminuted patterns each have their own subcategory, split the same way by side. Coding to the pattern keeps medical necessity queries down.
Where S42.302K sits in the ICD-10-CM hierarchy
Knowing the ladder saves time when you are auditing a batch of claims or hunting for a sibling code.
- S00-T88: Injury, Poisoning and Certain Other Consequences of External Causes (Chapter 19)
- S40-S49: Injuries to the shoulder and upper arm
- S42: Fracture of shoulder and upper arm
- S42.3: Fracture of shaft of humerus
- S42.30: Unspecified fracture of shaft of humerus
- S42.302: Unspecified fracture of shaft of humerus, left arm
- S42.302K: Subsequent encounter for fracture with nonunion (billable leaf code)
S42.302 is a parent code, so it cannot go on a claim alone. It needs a seventh character. This family accepts seven of them: A, B, D, G, K, P and S. Submitting the parent code alone is a routine clearinghouse rejection.
B and G are the two that rarely make it onto a cheat sheet. B marks an initial encounter for an open fracture. G marks a subsequent encounter where healing is slow but nobody has called it a nonunion yet, as in S42.475G.
Excludes notes keep S42.302K off the wrong claim
Chapter 19 uses Excludes notes to fence codes off from one another. Two sit at the S42 category level and one sits at S42.3, directly above this code.
Excludes1 means never together. If the limb was traumatically amputated at that level, the S48.- codes take over, as in S48.922S. The fracture code does not ride along beside it.
Excludes2 works the other way. The conditions are different, but one patient can have both. A fracture around a shoulder implant is an M97.3- problem. A growth-plate injury in a skeletally immature patient goes to S49.0- or S49.1-, not the shaft subcategory.
What counts as nonunion in the humeral shaft
Nonunion means the fracture has stopped trying to heal. The humeral shaft runs from just below the surgical neck to the supracondylar ridge. Fractures there account for 1% to 5% of all fractures, according to StatPearls.
Most unite in 8 to 12 weeks in a functional brace. A meaningful share do not. Conservatively treated closed fractures carry a reported nonunion rate of 3% to 17.6%. That is why follow-up imaging matters even on a case that looks straightforward.
Six months is the usual working definition. Union that has not arrived by then is generally called nonunion, though the call stays clinical and radiographic rather than calendar-based. One early marker is worth knowing: no callus and persistent motion at the site six weeks after injury predicts nonunion almost every time.
Risk climbs sharply when any of the following are in play.
- Open fracture, or infection at the fracture site
- Inadequate immobilization, or distraction across the fracture
- Smoking, and poorly controlled blood glucose
- Regular NSAID use
- Osteoporosis
The type of nonunion matters for what comes next. Atrophic nonunion means the biology failed, so the surgeon usually adds graft. Hypertrophic nonunion means the fixation moved, so the answer is stability rather than biology. Neither changes the diagnosis code, but each changes the CPT code sitting beside it.
For coding, the word matters more than the picture. The physician has to write nonunion, failed union or pseudarthrosis. A radiologist’s impression does not carry the diagnosis unless the treating physician signs off on it. Orthopedic and sports medicine practices often run rehab alongside nonunion management, so the notes have to agree across providers.
Subsequent encounter means active treatment is over
A subsequent encounter is any visit after the patient has received active treatment for the fracture. That is the definition in the ICD-10-CM Official Guidelines, and it is narrower than “any follow-up appointment”.
One point trips people up. The same provider keeps using A for every active-treatment visit, even across several surgeries. The switch to D, G, K or P happens when active treatment ends and the patient moves into monitoring or aftercare.
The character follows the fracture’s phase, not your first look at the patient. Someone arriving with an established nonunion from another practice still gets K as the seventh character. So does the encounter where you operate to repair it. That surgery treats the failed healing rather than the original break.
Nonunion or malunion: The K and P split
Mixing up K and P is the costliest seventh-character error in humeral shaft coding. Both say something went wrong with healing, but they describe different problems with different surgeries behind them.
Never assign K and P for the same fracture. The bone either failed to unite or united badly. When the note reads both ways, query the physician before the claim goes out.
Sibling codes worth keeping on the shortlist
Coders working this part of S42 need the neighbours close at hand: same site, different encounter type, or same encounter type, different side.
The same seventh-character logic repeats across every S42 subcategory, including S42.242K and S42.256P.
For year-specific tabular browsing, the CDC ICD-10-CM web tool refreshes each October with the new fiscal year codes.
What the physician has to write before you can code K
Everything here turns on the physician’s words, not the coder’s reading of an imaging report. Miss one element and you are looking at a technical denial or a medical necessity appeal.
This is where patient record management earns its keep. A documentation checklist in front of the provider at the point of care catches most of these before the patient leaves.
- An explicit nonunion diagnosis. The physician writes “nonunion”, “failed union” or “pseudarthrosis”. A radiologist’s impression only counts once the treating physician co-signs it.
- Laterality in this note. “Left arm” or “left upper extremity” has to appear in the current encounter note, not only in the original injury record.
- Subsequent encounter context. The note has to read as follow-up care rather than a first evaluation of a fresh fracture.
- Radiographic evidence. Reference an X-ray, CT or MRI showing absent bridging callus or a persistent fracture line. Payers ask for it on review.
- Time since injury. An injury date or a phrase like “seven months post-injury” explains why nonunion is the right call.
Practices running high volumes of orthopedic follow-ups get there fastest with templated progress notes. Build the five elements into the template and the provider confirms them by exception, rather than remembering them from scratch at every visit.
Pro Tip
Audit your K claims monthly. Pull every claim submitted with seventh character K and read the matching note. Check that the word nonunion, or an accepted equivalent, appears in the assessment or impression. Claims where K was applied without that language are the most common trigger for a payer recoupment request in orthopedic practices.
How the claim moves, and where it stalls
A nonunion claim passes through four sets of hands before a payer sees it. The physician documents, the coder assigns S42.302K, the biller scrubs the claim, and the clearinghouse runs its edits. Most stalls happen at the last two steps, and nearly all of them trace back to the first.
Then come the payer-side rules that decide how the claim is read.
- Claim forms. S42.302K is valid on CMS-1500 for physician and outpatient billing, and on UB-04 for facility billing.
- Code ordering. Report S42.302K first when the nonunion is the reason for the visit. If the encounter addresses a complication such as infection or hardware failure, that code takes the principal position.
- External cause codes. Chapter 19 expects a code from V00-Y99 to explain how the original injury happened. Many payer contracts treat it as mandatory on trauma claims.
- Coverage. Grafting, revision surgery and electrical bone stimulation all turn on medical necessity and your MAC’s local policy. Blanket coverage is never safe to assume.
- Annual review. Code validity is fiscal-year specific, so re-check S42.302K each October 1 against the updated tabular list.
Payers often ask for the clinical rationale behind revision surgery. Sending a medical necessity letter up front beats working an appeal after the denial lands.
Before you submit: A seven-point check
- The note says nonunion, failed union or pseudarthrosis, in the physician’s own words.
- “Left” appears in this encounter’s note, not only in the original injury record.
- Active treatment of the original fracture is finished, so the visit really is subsequent.
- Imaging from this episode is referenced, with a date.
- The diagnosis line reads S42.302K, and the parent code appears nowhere on the form.
- Any procedure code on the claim describes nonunion treatment, not acute fracture care.
- An external cause code is attached if the payer’s contract calls for one.
CPT codes that pair with S42.302K
S42.302K rarely travels alone. It sits beside a procedure code describing what happened at the visit, and this pairing is where humeral shaft claims most often go wrong.
The two codes coders reach for out of habit, 24515 and 24516, treat acute humeral shaft fractures. They belong with seventh character A. Nonunion repair has its own pair. Use 24430 when no graft is taken, and 24435 when the surgeon harvests an iliac or other autograft.
24435 already includes obtaining the graft, so it never gets a separate harvest code beside it. The bone-graft harvest codes belong with 24430, where the graft was not built into the procedure.
A worked example, start to finish
Here is how that plays out. A patient comes back seven months after a left humeral shaft fracture treated in a brace. Imaging shows no bridging callus, and the surgeon documents an atrophic nonunion. She plates the humerus and takes an iliac crest graft in the same session.
That claim reads S42.302K with 24435, and nothing extra for the graft. Had she used 24430 instead, the harvest becomes separately reportable with 20900 or 20902, depending on its size.
When no procedure happens, the visit is an E/M service. A nonunion recheck with imaging review often lands at 99214, though the level follows the medical decision making rather than the diagnosis. Teams running post-surgical rehab on a physical therapy EMR report therapy codes against the same diagnosis instead.
Pairings are payer-specific either way. Confirm medical necessity linkage and your MAC’s local coverage determinations before you submit surgical codes with S42.302K.
Terms in the chart that map to S42.302K
Physicians describe this condition in half a dozen ways, and none of them is the tabular wording. Recognizing the variants saves a query on every second note.
- Humeral shaft fracture nonunion, left arm
- Left humerus diaphysis fracture with failed healing
- Broken left upper arm with nonunion
- Left arm pseudarthrosis following humeral shaft fracture
- Left humerus shaft fracture, failed union
- Nonunion of fracture of shaft of left humerus
- Left humeral diaphyseal fracture nonunion
Any of these supports S42.302K when the treating physician writes it, the visit is a subsequent encounter, and the left side is confirmed.
How Pabau keeps fracture claims clean
Most nonunion denials start in the chart, not on the claim form. The imaging sits in one system and the physician’s note in another. The claim then gets built from whichever screen the biller had open. By the time the denial arrives, nobody can find the sentence that would have supported the K.
Practice management software like Pabau keeps all of it in one client record. The encounter note, the uploaded imaging report and the injury date live in one place. The codes attached to the visit sit beside them, so a coder reads the evidence and the claim on the same screen.
From there, Pabau’s claims management software builds and submits the claim from that same record, then tracks what the payer sends back. Nothing gets retyped between the note and the form, which is where a seventh character usually goes astray.
For an orthopedic practice with a heavy load of fracture follow-ups, that changes the timing. You spot a thin note while the patient is still in the room, instead of chasing a denial six weeks later.
Keep coding evidence and claims in one record
Pabau brings the encounter note, imaging and claim together in one client record. Your coders can check the documentation behind a seventh character before the claim goes out.
Conclusion
S42.302K is a narrow code doing a specific job. It says the left humeral shaft never united, and it says the active treatment phase is behind you. Almost everything that decides whether it gets paid happens before the claim is built.
So the work sits upstream. Get the physician writing the word nonunion, keep the side in every follow-up note, and hold the imaging against the episode. Then look hard at the procedure code beside it, because pairing nonunion repair with an acute fracture code is the error that costs the most.
Specificity cuts both ways. A precise code is easier to defend on review, and harder to earn in the first place. Book a demo to see how Pabau keeps fracture documentation, coding and claims in one record.
Continue your research
Rehabbing the arm once the fracture unites? Brachial neuritis exercises sets out a phased upper-limb protocol you can slot into follow-up care.
Coding another fracture repair this week? 21452 walks through percutaneous fixation and the documentation payers expect behind it.
Need the open-treatment counterpart? 21465 covers open treatment of a mandibular condylar fracture, billing rules included.
Explaining a nonunion to a worried patient? Patient education collects the materials and tactics that make the conversation shorter.
Billing Medicare for the revision surgery? Medicare billing covers claiming channels and the compliance checks that hold claims up.
Frequently asked questions
Do CPT lines for S42.302K need the LT modifier?
Usually, yes. The diagnosis code carries laterality, but most payers still want the side on the procedure line. Append LT to the surgical line for a left humerus, unless the payer’s policy says otherwise.
Can a physical therapist report S42.302K?
Yes, when the physician’s documentation supports the nonunion. The therapist reports the same diagnosis alongside the treatment codes for that visit. A therapist cannot establish nonunion independently, so the referral or the surgeon’s note has to carry it.
Which code replaces S42.302K once the bone unites?
Follow-up visits during the rest of the healing move to S42.302D. Once healing is complete and the patient returns for a late effect, such as stiffness or chronic pain, use S42.302S instead.
How do you bill nonunion repair inside a global period?
Add a global surgery modifier. An unplanned return to the operating room for a related procedure is normally modifier 78. Check the payer’s policy first, because the right modifier depends on how that return is classified.
Does Medicare cover a bone growth stimulator for humeral nonunion?
Coverage exists, but it is conditional. Medicare expects radiographic evidence that the fracture has not united, usually serial films taken months apart. Your MAC’s policy article sets the exact interval and the records to keep on file.
