ICD-10 code S52.136N: Radial neck fracture nonunion

Key takeaways

S52.136N covers a nondisplaced fracture of the neck of an unspecified radius, seen again after an open type III injury failed to unite.

The 7th character N fits one situation only, a subsequent encounter for a Gustilo type IIIA, IIIB or IIIC fracture with documented nonunion.

Laterality is unspecified here, so use S52.134N for the right radius and S52.135N for the left.

Subcategory S52.136 has 16 valid 7th characters, and swapping N for M, R or J is the usual error.

Practice management software like Pabau checks the fields an insurer needs before you send, then files the claim through Claim.MD.

ICD-10 code S52.136N covers a nondisplaced fracture of the neck of an unspecified radius. You use it at a follow-up visit, after an open type IIIA, IIIB or IIIC fracture failed to unite. One fact decides it. N marks nonunion, and it fits only a Gustilo type III injury. Reach for M or R instead and the claim describes a different fracture, which is what payers and auditors pick up. So the reference below runs through all 16 seventh characters, the Gustilo criteria, the documentation a payer expects, and the ICD-9-CM mapping.

S52.136N describes one visit, not one injury

The long description reads nondisplaced fracture of neck of unspecified radius, subsequent encounter for open fracture type IIIA, IIIB, or IIIC with nonunion. It is a billable, specific code, valid for every HIPAA-covered transaction. The 2026 edition took effect October 1, 2025.

Billable is not the same as payable. Payer policy, medical necessity, and prior authorization rules all apply on top of a valid code.

S52.136N sits five levels down the injury chapter

Every level narrows the code, and skipping one is how coders end up under the wrong parent. Here is the full path.

• S00-T88: Injury, poisoning, and certain other consequences of external causes
• S50-S59: Injuries to the elbow and forearm
• S52: Fracture of forearm
• S52.1: Fracture of upper end of radius
• S52.13: Fracture of neck of radius
• S52.136: Nondisplaced fracture of neck of unspecified radius
• S52.136N: Subsequent encounter for open fracture type IIIA, IIIB, or IIIC with nonunion

That 6th character, the digit 6, is the only reason laterality is unspecified. Swap it for 4 and you have the right radius. Swap it for 5 and you have the left.

The 7th character does more work than the other six

Every code in subcategory S52.13 needs a 7th character, and 16 are valid, per the CMS ICD-10-CM guidelines. Three questions decide which one you use. Is this the first visit for the injury, or a later one? Was the fracture closed, or open and graded? And how is it healing now?

Laid out as a grid, the whole set is easier to hold onto than a list of letters.

N is correct only when all three answers line up. The encounter is subsequent, the original fracture was graded IIIA, IIIB or IIIC, and the bone has not united. If the original injury was type I or II, the nonunion character is M instead.

Delayed healing and nonunion are also separate characters, not two words for the same finding. A fracture that is healing slowly takes J, and the same split runs through the humerus codes like S42.332G.

Gustilo type III is three injuries, not one

Type III splits into IIIA, IIIB and IIIC, and what separates them is soft-tissue coverage and blood supply. The grading comes from Gustilo and Anderson’s 1976 paper in the Journal of Bone and Joint Surgery. For S52.136N, the surgeon has to have named the subtype at the time of the injury.

Coders do not assign a Gustilo type. It has to come from the operative report, the emergency note, or an orthopedic consult. When the record says only “open fracture”, query the clinician before you reach for a type III character.

Nonunion has to be written down, not inferred

The word has to be in the record. Nonunion means the fracture has stopped progressing toward healing, and only the treating physician can make that call.

No single timeframe defines it. Orthopedic literature generally treats 6 to 9 months without healing as nonunion, and the threshold shifts with the bone, the patient, and the surgery. Expected healing time is bone-specific, so the same characters on a tibial shaft code like S82.226G cover a different span of months.

• Atrophic nonunion: no callus forms, often with poor blood supply or infection
• Hypertrophic nonunion: callus forms but the fracture line persists, often after weak immobilization
• Oligotrophic nonunion: little callus, usually after inadequate reduction

None of those subtypes changes the code. S52.136N needs the word nonunion, or a clear equivalent such as “failure of fracture healing”, in the note for the visit you are coding.

Six checks before you assign the code

Work down the list in order. Each line is a separate question, and one wrong answer sends you to a different code.

1. Nondisplaced. The fragments have not shifted position. A displaced fracture belongs under a different 6th-character parent.
2. Neck of the radius. Not the head, not the shaft, not the distal end.
3. Gustilo type IIIA, IIIB or IIIC. Types I and II take their own characters, and so does a closed fracture.
4. Subsequent encounter. Active treatment is finished. The patient is back for follow-up, a cast change, a physical therapy referral, or nonunion management.
5. Nonunion documented. The physician or radiologist states in writing that the fracture has not united.
6. Laterality unspecified. If the record names a side, use S52.134N for the right radius or S52.135N for the left. Query the physician instead of defaulting to unspecified.

All six have to hold at the same time. Miss one and a different code applies, which is how a straightforward follow-up visit turns into denial management work.

Where a radial neck nonunion claim usually stalls

Take a patient who broke the radial neck in a bike crash in February, and who now sees a sports medicine practice for follow-up. The operative note from February grades the injury IIIB. Eight months on, imaging shows no union, and the surgeon writes nonunion in the office note. That visit codes to S52.136N.

From there the claim moves in a straight line. The coder assigns the diagnosis, the biller ties it to the service performed that day, and the claim leaves as an electronic CMS-1500. The payer adjudicates it and sends back a remittance.

Three failures break that line, and none of them is the code itself.

• The grade lives in an old note. February’s operative report holds the Gustilo type. Nobody looking at today’s office note can support the character.
• Only imaging says nonunion. The radiologist wrote it, the physician did not, so the strongest document in the chart is the wrong one.
• The authorization ran out. Approval covered the initial episode, and the follow-up visit gets denied on eligibility rather than coding.

Payers rarely spell out which of the three it was. The remittance carries a reason code instead, so reading denial codes against your own rejections is faster than guessing.

The record has to prove all six elements

A billable code carries no weight on its own. Every condition on the checklist needs a source document behind it, and an auditor will ask for each one by name.

Judging whether that record is strong enough stays a human review. What software checks is the claim form. Practice management software like Pabau runs a validation pass when you hit send. A missing membership number or authorization code holds the claim back, rather than the payer doing it later. That is the difference between a clean claim and a resubmission three weeks later.

Submission itself runs through the Claim.MD integration, which files electronically to thousands of US payers and brings the remittance back. Pabau’s claims management software also carries a searchable ICD-10 library of more than 20,000 codes. Treat that as a lookup for finding S52.136N quickly, not as a check on whether the chart supports it.

N, M, R and J are the four that get swapped

Subcategory S52.136 has 16 valid versions, one per 7th character. Four of them describe an open type III fracture at a later visit, and that is where errors cluster. F is routine healing, J is delayed healing, N is nonunion, and R is malunion.

Two mistakes account for most of the rework. The first uses N when the original fracture was type I or II, where M is correct. The second uses N for a malunion, where R is correct. Malunion characters behave the same way elsewhere in category S52, as S52.001P shows.

Physicians rarely write the code’s own words

Notes use clinical shorthand instead. All of these phrasings point to S52.136N when the rest of the record backs them up.

• Nondisplaced radial neck fracture with nonunion, open type IIIA, follow-up visit
• Non-displaced fracture of neck of radius, open grade IIIC with failure to heal
• Radius neck fracture, nondisplaced, open Gustilo type IIIB, nonunion, subsequent care
• Fracture nonunion, neck of radius, unspecified side, Gustilo III open fracture
• Open radial neck fracture type IIIA with nonunion on follow-up

A matching phrase does not make the code safe. Wording is what most medical billing compliance reviews turn on, so all six documentation elements still have to be in the chart.

Mapping back to ICD-9-CM takes two codes, not one

No single ICD-9-CM code matches S52.136N. ICD-9 never carried Gustilo type or healing status, so the closest reading pairs a fracture code with a nonunion code. Legacy audits and historical reconciliation are the only places you need it.

Watch the last digit. The radial head codes, 813.05 and 813.15, sit one digit away and cover a different part of the bone.

Treat any mapping as approximate rather than equivalent. CMS keeps its General Equivalence Mappings in the CMS GEM archive, and that is the reference to check a legacy conversion against. ICD-10-CM has been required since October 1, 2015, and S52.136N applies to any date of service in the 2026 coding year.

How Pabau keeps subsequent-encounter claims clean

In a lot of practices the diagnosis and the claim live in two systems. A coder picks S52.136N in the chart, and someone re-keys it into a billing tool. Nobody spots the missing authorization number until a rejection arrives weeks later.

Pabau keeps both in one record. The invoice, the diagnosis code, and the insurer details all come off the patient file, so nothing gets typed twice. Validation runs at the point of sending, and the claim waits until the fields the insurer needs are filled in.

From there it goes out electronically through the Claim.MD clearinghouse, with eligibility checks, claim status, and remittances in the same dashboard. For a practice billing a run of fracture follow-ups, that turns a week of chasing into a status you can read on a Monday morning.

Send fracture follow-up claims without re-keying

Pabau turns the invoice into an electronic claim, checks the fields the insurer needs, and files it through Claim.MD. You get fewer rejections on subsequent-encounter visits and a remittance you can track in one place.

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Conclusion

N is not a severity upgrade. It states two separate facts, the Gustilo grade from the original injury and the healing status today. Read both in the record before you type the character, and the rest of the code follows.

The trade-off worth remembering is specificity against speed. Unspecified laterality keeps a claim moving, but it also tells the payer that nobody checked. One query usually turns S52.136N into S52.134N or S52.135N, and that version survives review.

When the coding is right and the claim still comes back, the problem is usually the submission. Book a demo to see how Pabau moves a subsequent-encounter claim from invoice to remittance without a second system.

Continue your research

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Still on the initial encounter? S42.452A walks through the A character on a displaced humeral condyle fracture.

Billing a follow-up for a sprain rather than a fracture? S63.004D applies the same subsequent-encounter logic to the wrist.

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