ICD code S52.541M – Smith's fracture of right radius with nonunion (open type I or II)

Key takeaways

S52.541M codes a follow-up visit for a right Smith’s fracture that was open at injury, graded Gustilo type I or II, and has not healed.

The 7th character M means nonunion after an open type I or II fracture. A malunion of the same fracture codes to S52.541Q instead.

The 7th character follows the original open fracture grade, so a closed injury with nonunion takes K and a type III injury takes N.

Before billing, the record needs a provider-documented nonunion, the right side, the Smith’s volar pattern, and the Gustilo grade from the injury.

Nonunion repair pairs with CPT 25400 or 25405, not the 25600-series acute fracture codes or the 25390-series osteoplasty codes.

ICD-10 Code S52.541M: Definition and billable status

ICD-10 Code S52.541M is the billable ICD-10-CM code for Smith’s fracture of right radius, subsequent encounter for open fracture type I or II with nonunion. It is used at a follow-up visit once the provider documents that the fracture has failed to heal.

Two facts recorded months apart decide the code. The injury was open and graded Gustilo type I or II at presentation, and the bone has not united since. If the fracture healed in a deformed position instead, the correct code is S52.541Q.

What S52.541M covers: Breaking down the code

A Smith’s fracture is a fracture of the distal radius in which the broken end tilts toward the palm. Clinicians call this volar angulation, and some call the injury a reverse Colles fracture.

A Colles fracture tilts the other way, toward the back of the hand. ICD-10-CM gives each pattern its own subcategory: S52.54- for Smith’s and S52.53- for Colles. The direction of tilt in the imaging report decides which one applies.

The usual mechanism is a fall onto a flexed wrist or a direct blow to the back of the hand. S52.541M applies only where that fracture also broke the skin and has since failed to heal.

Like every S52.5 subcategory, S52.54 has no displaced or nondisplaced split. The 6th character carries laterality only, so S52.541, S52.542 and S52.549 are the whole family.

Understanding the 7th character M: Open fracture type I or II with nonunion

The 7th character M means a subsequent encounter for an open fracture type I or II with nonunion. The patient is past the initial treatment, and the provider has diagnosed a fracture that has not united.

M does not mean malunion. Nonunion uses the letters K, M and N in the S52 extensions, while malunion uses P, Q and R instead. The letter within each set depends on whether the fracture was closed, open type I or II, or open type III.

The ICD-10-CM Official Guidelines, Section I.C.19.c.1, cover this directly. Care for nonunion and malunion is reported with the matching subsequent-encounter character, not with an aftercare Z code.

Gustilo-Anderson grade and why it decides M over K or N

ICD-10-CM bases its open fracture characters on the Gustilo-Anderson classification. The grade is set at the injury and stays with the fracture for the whole episode.

• Type I: a clean wound of 1 cm or less with minimal soft-tissue damage.
• Type II: a wound longer than 1 cm without extensive soft-tissue damage.
• Type IIIA, IIIB and IIIC: extensive soft-tissue damage, periosteal stripping needing flap coverage, or an arterial injury needing repair.

The skin wound may have closed long before the nonunion visit, but the code still reflects the open injury. A follow-up note that omits the open history is the usual reason S52.541K goes out in place of S52.541M.

The grid below crosses that injury grade with the healing status at follow-up. Each subsequent-encounter letter sits at exactly one crossing.

The tabular list gives S52.541 the full fracture extension set below. A fracture not documented as open or closed codes as closed, and an open fracture with no grade codes as type I or II.

Nonunion vs malunion: a nonunion has not healed, and imaging shows a persistent fracture line with no bridging bone. A malunion has healed, but in a deformed position. The two need different codes and usually different procedures.

Laterality and commonly confused codes

Most errors on S52.541M come from a neighbor that differs by one character. The table maps the usual mis-selections and the fact that rules each one out.

Includes, excludes, and official coding notes

The tabular notes at S52 and S52.5 decide when another code takes priority. Check them before assigning S52.541M.

What the code includes

• Smith’s fractures of the right distal radius, with the distal fragment tilted toward the palm
• Fractures that were open at presentation and graded Gustilo type I or II, or open with no grade documented
• Follow-up visits for a diagnosed nonunion, including the encounter for surgical repair

What the code excludes

• Excludes1 at S52: traumatic amputation of the forearm (S58.-) is never coded with S52.541M.
• Excludes2 at S52: fracture at wrist and hand level (S62.-) and periprosthetic fracture around an internal prosthetic elbow joint (M97.4). Either may be coded alongside S52.541M when both exist.
• Physeal fractures: growth plate fractures of the lower end of the radius code to S59.2- in skeletally immature patients.
• Pathological and stress fractures: these code to Chapter 13, such as M84.4- or M84.3-. S52 covers traumatic fractures.
• Other named patterns: a Colles fracture codes to S52.53- and a Barton’s fracture to S52.56-, each with its own 7th character.

Clinical documentation requirements for S52.541M

Coders assign S52.541M from provider documentation, not from their own reading of an imaging report. Five elements need to appear in the record before the code is safe to submit.

1. An explicit nonunion diagnosis. The provider writes “nonunion”, “ununited fracture”, or “failure of union”. A radiology finding counts only once the provider adopts it as a diagnosis.
2. The original open fracture grade. The record shows the injury was open and graded type I or II. The current note can cite the emergency or operative record from the injury.
3. The right side. The note, imaging, or operative report names the right wrist. If no side appears anywhere, S52.549M applies instead.
4. The Smith’s pattern. At least one document describes volar angulation or names a Smith’s fracture. A bare “distal radius fracture” supports only S52.50-.
5. Follow-up context. The note shows this visit follows the acute treatment phase. Time since injury and the prior treatment, such as plate fixation or casting, should both appear.

Open fractures carry a higher risk of infected nonunion. When the provider documents infection, code it as well, for example osteomyelitis from category M86. Where the record does not state nonunion, query the provider rather than inferring it from the films.

CPT codes commonly paired with S52.541M

A nonunion follow-up usually leads to monitoring, bone healing stimulation, or surgical repair. These CPT codes cover each path, with descriptors from the AMA CPT code set.

Two code families are often billed here by mistake. The 25600 to 25609 range describes treatment of an acute distal radius fracture, not repair of a nonunion.

The 25390 to 25393 range covers osteoplasty, meaning surgical shortening or lengthening of the radius or ulna. Report one only when the operative note documents that separate procedure, and check NCCI edits first.

Verify each pairing against the current AMA CPT codebook and the patient’s record before submission. Practices that track claims in claims management software can see which codes went out on each visit before a denial arrives.

Payer requirements and prior authorization

Payer rules for S52.541M vary by insurer and Medicare jurisdiction. The points below are common expectations rather than universal ones, so check each payer’s current policy.

• Serial imaging. Payers expect radiographs over time showing that healing has stopped. One film rarely supports a nonunion diagnosis on its own.
• Bone stimulator criteria. Medicare’s osteogenic stimulator policy (NCD 150.2) treats a long-bone nonunion as established once serial radiographs show healing has stopped for at least three months.
• Prior authorization for repair. Many commercial and Medicare Advantage plans require authorization for 25400 and 25405. Send the imaging, the functional assessment, and the planned procedure before scheduling.
• Open fracture history. Reviewers check that the claim’s open fracture grade matches the initial encounter record. Keep that record easy to retrieve.
• Medicare LCD review. Medicare Administrative Contractors publish jurisdiction-specific Local Coverage Determinations for fracture care. Check the one that applies before scheduling surgery.

Common claim denial reasons for S52.541M

Most S52.541M denials trace back to a character, side, or pairing error. Payers differ in the reason code they return, so treat the codes below as typical rather than fixed.

Practices with a structured denial management process catch these patterns before they repeat. Reviewing the denial codes alongside the claim history shows whether the cause was documentation or coding.

Sending clean claims from the outset is faster than appealing after adjudication.

How Pabau keeps S52.541M nonunion claims clean

An S52.541M claim draws on notes written at different stages of care. The Gustilo grade sits in the emergency or operative note from the injury. The nonunion diagnosis appears in a follow-up note, often written by a different provider.

Pabau, the practice management platform we build for private and specialty practices, keeps those notes on one patient record. The original open fracture grade stays visible at every later visit, so the coder can support M over K without a records request.

The invoice for the visit is raised from the same record that holds the note. Practices billing US payers can send claims electronically through Pabau’s Claim.MD integration. The coder still chooses the code, with the supporting notes in the same place.

A team that keeps the injury grade and the follow-up note together can answer a payer query in minutes. Here is how Pabau supports that.

Keep fracture nonunion evidence in one record

Pabau keeps injury notes, follow-up notes and invoices on one patient record. The Gustilo grade behind S52.541M is on hand when the claim goes out.

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Conclusion

S52.541M rests on three facts recorded at different times. They are the right side, an open type I or II grade at the injury, and a nonunion diagnosis at follow-up. Lose one and the claim drifts to K, N, Q, or the wrong side.

Practices that bill this code cleanly treat the original Gustilo grade as part of the diagnosis rather than a detail of the first visit. They also keep nonunion and malunion apart in every note and claim. To see how Pabau supports medical billing across a long fracture episode, book a demo.

Continue your research

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