ICD code S82.402R – Left fibula shaft fracture with malunion

Key takeaways

S82.402R is the billable ICD-10-CM code for an unspecified fracture of the shaft of the left fibula. The 7th character R means a subsequent encounter for open fracture type IIIA, IIIB, or IIIC with malunion.

R applies only to open fractures graded Gustilo type IIIA, IIIB, or IIIC. A closed fibula shaft fracture that healed crooked takes P instead, and an open type I or II takes Q.

Use R only after active fracture treatment has ended and imaging confirms the bone healed in a faulty position.

The note must carry four facts: left laterality, shaft location, the Gustilo open-fracture type from the original injury, and malunion confirmed on imaging.

Pabau’s claims management software helps orthopedic and physical therapy practices submit S82.402R claims with the correct 7th character and supporting documentation attached.

ICD-10 Code S82.402R: Definition and clinical meaning

ICD-10 Code S82.402R describes a fracture of the shaft of the left fibula.

The injury was open at the time it happened, and graded Gustilo type IIIA, IIIB, or IIIC. The patient is now at a subsequent encounter, and the bone has consolidated in a faulty position. Each element of that descriptor carries a billing consequence.

The fibula shaft runs from below the knee joint to above the ankle mortise. Shaft fractures in this zone follow high-energy trauma, which is also what produces grade III open wounds. When such a fracture consolidates with angular deformity, R is the correct 7th character. A fracture of the same type that never unites at all is nonunion, which codes to N.

Breaking down the code structure

Every character in S82.402R encodes a specific anatomical or encounter-status fact. Misreading a single position is the most common source of incorrect code selection on orthopedic claims.

Category S82 covers all fractures of the lower leg including the ankle. The subcategory .4 isolates the fibula shaft. That separates these injuries from tibial shaft fractures (S82.2x) and from fibular head or malleolus fractures coded elsewhere in S82. Within .4, the fifth character records the fracture pattern, and 0 is the group used when that pattern is not documented.

Walking the hierarchy from the top makes the code assemble itself:

• S00-T88: Injury, poisoning and certain other consequences of external causes
• S80-S89: Injuries to the knee and lower leg
• S82: Fracture of lower leg, including ankle
• S82.4: Fracture of shaft of fibula
• S82.40: Unspecified fracture of shaft of fibula
• S82.402: Unspecified fracture of shaft of left fibula
• S82.402R: Subsequent encounter, open type IIIA, IIIB, or IIIC, malunion

7th character R: Open fracture type IIIA, IIIB, or IIIC with malunion

The 7th character is where most S82.402 coding errors occur. “Subsequent encounter” does not mean the second visit. It means the active treatment phase has ended and the patient is now receiving follow-up care, physical therapy, or evaluation of complications.

Malunion means the fracture has consolidated but the bone healed in an anatomically incorrect position, producing deformity, pain, or functional limitation. Malunion is confirmed radiographically. A clinical suspicion without supporting imaging is not sufficient documentation for R.

R carries a second fact alongside the healing outcome. It states that the original injury was an open fracture graded Gustilo type IIIA, IIIB, or IIIC. Closed fractures and lower-grade open fractures take different characters, even when the healing outcome is identical.

Read the table in two directions. Across the malunion row group, P, Q, and R differ only by the fracture type recorded at the injury. Down the open type III column, F, J, N, and R differ only by how the bone healed. The grid below sets both readings side by side.

Nonunion (N) means bone healing never completed. Malunion (R) means healing completed but in a faulty position. Imaging that shows bony bridging with angular deformity indicates malunion. Imaging that shows a persistent fracture gap without bridging indicates nonunion.

Gustilo-Anderson type III and why it decides the R character

ICD-10-CM ties the open fracture 7th characters to the Gustilo-Anderson classification, the orthopedic grading system for open fracture severity. The surgeon assigns the grade at the time of the original injury, usually in the operative note from the initial debridement. That grade then follows the patient through every subsequent encounter code.

The official ICD-10-CM guidelines settle what happens when the grade is missing. When the record documents an open fracture but does not designate the type, coders assign the type I or II classification. At a malunion follow-up, that means using Q rather than the R character. Grade III is never assumed from the severity of the injury description alone.

Complete list of S82.402 7th character variants

All sixteen variants share the same base code, S82.402 (unspecified fracture of shaft of left fibula). They differ by encounter status, fracture type, and healing outcome. Every one of them is billable.

P, Q, and R all describe malunion, and only the fracture type separates them. S82.402P is the closed fracture that healed crooked. S82.402R is the open type IIIA, IIIB, or IIIC fracture that healed crooked. Choosing P for a grade III open injury, or R for a closed one, puts the claim at odds with the operative record. See the CDC/NCHS ICD-10-CM web tool to confirm current-year validity for each variant.

Related and adjacent ICD-10 codes

Several codes are routinely confused with S82.402R. Selecting the wrong fracture type, laterality, or healing outcome is the fastest path to a denial. The table below maps the alternatives coders reach for most often, and what separates each one from S82.402R.

Includes, excludes, and official coding notes

ICD-10-CM places important instructions at the S82 category level that govern how S82.402R can be used. Reviewing them prevents claim edits before submission. Per CMS ICD-10 guidance, coders must read category-level notes alongside the specific code.

• Includes note (S82): Fractures of the lower leg including the ankle. The category intentionally encompasses fibula, tibia, and ankle fractures together.
• Open fracture designations (S82): The category carries a note tying the open fracture 7th characters to the Gustilo classification. Those characters are B, C, E, F, H, J, M, N, Q, and R.
• Undesignated open fracture type: Sometimes an open fracture is documented without a Gustilo type. The official guidelines then direct coders to assign the type I or II classification.
• Excludes1 (S82): Pathological fractures (M84.4-, M84.5-, M84.6-) and stress fractures (M84.3-). You cannot code S82.402R and a pathological fracture code simultaneously for the same site.
• Excludes2 (S82): Periprosthetic fracture of prosthetic implant of knee (M97.1-). If the patient has a knee prosthesis, separate guidelines apply.
• Use additional code: An external cause code from Chapter 20 (V-Y) should accompany S82.402R when the injury mechanism is known. For subsequent encounters, CMS treats these as optional, but many commercial payers expect them.
• Code also: Physical therapy delivered at the visit is captured by a CPT code on the same claim. It does not take an additional ICD-10 code.

One Excludes1 pairing at the S82 level deserves a second look. A patient with metastatic disease who sustains what looks like a traumatic fibula fracture may have a pathological fracture instead. That belongs in M84.464 (pathological fracture, left fibula) or M84.364 (stress fracture, left fibula), not S82, and both need their own 7th character.

Review the mechanism of injury and bone quality documentation before assigning S82.402R. The wider ICD-10-CM code set applies the same category-level instructions to every musculoskeletal chapter.

Clinical documentation requirements

S82.402R requires five documentation elements to support a clean claim. Any one of them missing is a predictable denial trigger. Documentation must sit in the provider’s note at the time of service, not be reconstructed after a payer request.

• Laterality confirmed as left: The treating provider’s note must explicitly state “left fibula” or document the left lower leg as the site. Imaging reports alone, without provider confirmation in the encounter note, may not satisfy payer auditors.
• Shaft location: The provider note should reference the shaft (diaphysis) or mid-fibula. A fracture documented only as “fibula fracture” without a location falls into a different subcategory within S82.
• Open fracture type from the original injury: The record must carry the Gustilo grade, IIIA, IIIB, or IIIC. An open fracture with no grade recorded defaults to type I or II. That moves the code to Q, and a closed injury moves it to P.
• Subsequent encounter status: The record must establish that active fracture treatment has ended. This can be implicit, such as a note referencing cast removal or completed fixation, or explicit, such as “patient presents for follow-up fracture care”.
• Malunion confirmed on imaging: An X-ray or CT report must document deformity, angular malposition, or healing in a non-anatomical alignment. The radiologist’s or treating provider’s wording, such as “malunion” or “healed with deformity”, is the standard of evidence. Physical exam alone is insufficient for R.

For practices managing fracture rehabilitation across multiple visits, consistent notation at each encounter reduces the risk of 7th character errors.

The word “unspecified” in the descriptor refers to the fracture pattern, not to the wound. Coders do not need to query the provider about whether the break was transverse, oblique, or spiral. They do need the open fracture type, because that single fact separates R from Q and P.

Common CPT codes billed with S82.402R

The CPT codes paired with S82.402R reflect the encounter type. Because R denotes a subsequent encounter, the accompanying procedure codes are follow-up, rehabilitation, or corrective surgery codes, not initial fracture treatment codes.

Practices submitting electronic claims work from a built-in CPT and ICD-10 catalog. That catalog flags mismatched code pairs before the claim reaches the payer.

CPT code selection must match the encounter type. Billing a corrective repair code such as 27726 with S82.402R is appropriate only when that surgery was performed. Using it for a routine evaluation visit will trigger a medical necessity denial.

Systems that link the diagnosis and the procedure code at the point of service let staff catch these mismatches before submission. The check costs nothing at the visit and saves a rework cycle afterward.

Common claim denial reasons and how to avoid them

Denial patterns for S82.402R cluster around a handful of specific errors. Fixing them requires changes to documentation workflow, not just coding behavior. Practices that treat denial management as a proactive process catch these patterns before they become write-offs.

Built-in edit checks surface the same errors at the point of claim building, well before payer adjudication.

• Wrong fracture type (most common): S82.402P, the closed-fracture malunion code, billed for a patient whose original injury was an open grade III fracture. The reverse error is just as common. The fix is carrying the Gustilo grade forward in the problem list.
• Wrong healing outcome: Using S82.402C (initial encounter) for a follow-up visit, or S82.402F (routine healing) when imaging shows malunion. A provider query template that captures healing status at every fracture follow-up resolves this.
• Fracture type that contradicts the initial claim: If the initial encounter was billed as S82.402A (closed), a later S82.402R claim contradicts it. Payers compare codes across the episode of care.
• Missing laterality in the provider note: Imaging reports often state “left fibula”. If the treating provider’s note does not confirm it, payers may reject on laterality grounds. The coder cannot self-assign laterality from a radiology report without provider attestation.
• Malunion not documented at the time of service: Submitting S82.402R against an imaging report from a prior encounter leaves the current visit unsupported. The current visit’s note must reference or confirm the malunion diagnosis.
• CPT-diagnosis mismatch: Billing a corrective surgery CPT such as 27726 against S82.402R for an evaluation-only encounter triggers an edit. So does billing a routine E/M code when a surgical procedure was performed. The CPT code must match the service rendered.
• Missing external cause code: Some commercial payers and Medicare Advantage plans flag S82.402R claims filed without a V, W, X, or Y code. That applies when the injury mechanism is known. Check individual payer policies.

How Pabau keeps the 7th character tied to the record behind it

In most practices the Gustilo grade lives in one place and the follow-up claim is built in another. A surgeon records the open fracture type in an operative note at the initial encounter. Six months later a coder working from a brief follow-up note picks the malunion character that looks right, and nobody reconciles the two. That is how an open type III injury ends up billed as S82.402P.

Pabau is practice management software for orthopedic, physical therapy, and multi-specialty practices. It keeps the diagnosis, the supporting imaging, and the procedure codes on one patient timeline. The fracture type recorded at the injury stays visible at every later visit.

Our claims management software links diagnosis codes to procedure codes at the point of service. It also runs edit checks before the claim is released.

Claims go out electronically through Claim.MD to more than 4,000 US payers, and remittance advice comes back into the same record. A fracture-heavy caseload sees fewer 7th character corrections, fewer resubmissions, and faster payment.

Reduce claim denials on fracture codes

Pabau’s claims management software links diagnosis codes to procedure codes at the point of service and flags 7th character mismatches. Claims go out electronically through Claim.MD across 4,000+ US payers.

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Conclusion

S82.402R claims are denied over the record far more often than over the code. The code itself is straightforward once four clinical facts are confirmed.

Those facts are the left fibula shaft, an open fracture graded IIIA, IIIB, or IIIC at the injury, a follow-up visit, and imaging-confirmed malunion. Capturing them consistently across an episode of care that may span months and several providers is the harder part.

Pabau’s claims management software connects diagnosis and procedure codes at the point of service. It submits orthopedic fracture claims electronically through Claim.MD across more than 4,000 US payers. Book a demo to see how it handles 7th character validation on fracture claims.

Continue your research

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Managing ERA responses after S82.402R claims? Electronic remittance advice (ERA) guide walks through reading 835 remittance files to identify denial reason codes on musculoskeletal claims.

Frequently asked questions about ICD-10 Code S82.402R