ICD code S82.863Q – Displaced Maisonneuve fracture malunion

Key takeaways

S82.863Q codes a displaced Maisonneuve fracture of unspecified leg at a subsequent encounter, specifying open fracture type I or II with malunion.

The 7th character Q encodes three facts at once: subsequent encounter, Gustilo type I or II openness, and malunion rather than nonunion.

The nonunion code for the same open type I or II fracture is S82.863M. S82.863K covers a closed fracture with nonunion.

Use the unspecified leg code only when the record states no side. Use S82.861Q (right) or S82.862Q (left) when laterality is documented.

Pabau, the practice management platform we build, checks every claim for missing or invalid details before it reaches the payer.

ICD-10 Code S82.863Q: Definition and clinical overview

ICD-10 Code S82.863Q is the billable ICD-10-CM code for a displaced Maisonneuve’s fracture of an unspecified leg, seen at a subsequent encounter. It applies when an open type I or II fracture has healed out of alignment, which is malunion.

The code appears in the current CMS ICD-10 annual release. It sits in category S82 (fracture of lower leg, including ankle) and carries six qualifiers across its seven characters.

Breaking down the code anatomy of S82.863Q

Each character in S82.863Q carries a specific clinical meaning. Reading left to right, the code encodes the injury category, the anatomical subsite, the displacement status, the laterality, and the encounter-plus-complication bundle.

The 6th character in the S82.86 family carries displacement and laterality together. Displaced fractures use 1 (right), 2 (left) and 3 (unspecified leg). Nondisplaced fractures use 4, 5 and 6 in the same order. Use 3 only when the documentation states no side, never as a shortcut when laterality appears elsewhere in the chart.

What is a Maisonneuve fracture? Clinical context for coders

A Maisonneuve fracture is a proximal fibula fracture combined with disruption of the ankle syndesmosis, typically caused by a pronation-external rotation force at the ankle. The fibular fracture occurs at or near the fibular head, often with an associated medial malleolus fracture or deltoid ligament tear.

Coders need this clinical picture for two reasons. First, the fracture may not be immediately obvious on ankle X-rays because the fibular break is at the knee level. Second, displacement and laterality must come from the imaging, operative or ED note, not from inference. A displaced fracture codes to S82.863-, and a nondisplaced one to S82.866-.

• Mechanism: Pronation-external rotation at the ankle joint
• Anatomy: Proximal fibula fracture at or above the fibular neck, with syndesmotic disruption
• Associated injury: Medial malleolus fracture or deltoid ligament disruption
• Displaced vs nondisplaced: Determined by operative or imaging notes, not by fracture location alone
• Open vs closed: Determined by presence of a wound communicating with the fracture site, classified by Gustilo-Anderson criteria

Understanding the 7th character Q: Subsequent encounter, open fracture type I/II, malunion

The 7th character Q in ICD-10 Code S82.863Q encodes three clinical facts at once. The visit is a follow-up, so the encounter is subsequent. The fracture was open and graded Gustilo type I or II at injury. The fracture has also healed with malunion rather than nonunion. Change any one of those facts and the 7th character changes with it.

Coders most often confuse Q with M (nonunion, open type I or II) or with R (malunion, open type IIIA, IIIB or IIIC). The openness class and the complication type must both match the record. The grid below maps every subsequent-encounter character by those two facts.

The full 7th character table for category S82 follows, from the initial encounter through sequela.

Gustilo type I and II open fracture classification

Gustilo-Anderson type I describes an open fracture with a wound smaller than 1 cm and minimal contamination. It is typically a low-energy injury where the bone pierces the skin from inside.

Type II means a wound between 1 cm and 10 cm with moderate soft tissue damage. It lacks the extensive periosteal stripping seen in type IIIA or higher.

Type IIIA, IIIB, and IIIC injuries involve wounds larger than 10 cm, high-energy mechanisms, segmental fractures, or vascular compromise requiring repair. Q never applies to those cases. They use R for malunion or N for nonunion.

When the note records an open fracture but no Gustilo type, ICD-10-CM guidelines default to the type I or II characters. A wound described like a type III injury still needs a provider query rather than the default.

Subsequent encounter vs initial encounter vs sequela

The ICD-10-CM Official Guidelines define encounter type by the care being given, not by visit number. An initial encounter (7th character A, B, or C) applies while the patient receives active treatment for the fracture. That can span several visits, including surgery and early postoperative care.

A subsequent encounter (D through R) applies once the fracture is healing and the provider is managing that healing, including complications like malunion.

A routine follow-up for a closed displaced Maisonneuve fracture of unspecified leg, healing as expected, codes to S82.863D. Sequela (7th character S) applies when the fracture has healed but a residual condition from the injury is being treated.

• Initial encounter: Active fracture treatment, such as an ED visit, surgical reduction or intraoperative care
• Subsequent encounter: Follow-up care during healing, such as cast checks, implant removal planning, or malunion and nonunion management
• Sequela: Treating a late effect of a healed fracture, such as post-traumatic arthritis, stiffness or nerve damage from the original injury

Malunion is, by definition, a complication of the healing phase. That makes it a subsequent encounter complication, which is why 7th character Q carries both “subsequent encounter” and “malunion” in its descriptor. Coding malunion with an initial encounter 7th character is a contradiction, and payers routinely deny it.

Malunion vs nonunion in fracture coding

Malunion means the fracture has healed but in a poor anatomical position. Nonunion means the fracture has failed to heal within the expected timeframe. It is typically defined as no bridging callus on imaging after six months or longer, depending on the bone.

The key documentation for S82.863Q is the provider’s diagnosis of malunion, backed by imaging that shows healing with deformity or malalignment. Never assign Q from an impression the provider hasn’t documented.

Codes commonly confused with S82.863Q

ICD-10 Code S82.863Q is frequently confused with its sibling codes, which differ by only one or two characters. The table below isolates the exact variable in each case.

Verify the laterality digit first, then the 7th character. Confirm both the open fracture class and the complication type against the medical record before finalizing the code. The CDC/NCHS ICD-10-CM lookup tool lets you browse the full S82.86x family with official descriptors to cross-check each sibling code.

Documentation requirements for S82.863Q

A claim using S82.863Q must be supported by documentation covering all six qualifiers embedded in the code. Missing even one element creates an audit risk.

• Maisonneuve fracture pattern: Operative or imaging note must identify the fracture at the proximal fibula with associated syndesmotic disruption
• Displacement: Imaging or operative note should state “displaced.” A fracture not documented as displaced or nondisplaced defaults to displaced
• Laterality: Document which leg, or explicitly state laterality is unknown if that is the clinical reality
• Open fracture: ED or operative note must describe a wound communicating with the fracture site. A fracture not documented as open or closed defaults to closed
• Gustilo classification: Operative or ED note should state type I or II. An open fracture with no stated type defaults to type I or II
• Malunion: Follow-up imaging report must confirm callus formation with malalignment; clinical impression without imaging is insufficient
• Encounter type: Chart must make clear this is a subsequent visit, with active treatment concluded and the fracture in the healing phase

Orthopedic and physical therapy practices managing Maisonneuve fracture aftercare can build these elements into their follow-up note templates. A template that prompts for each one cuts the number of provider queries.

Payer requirements and claim submission considerations

Medicare and commercial payers treat malunion fracture claims as medically complex, particularly when surgical correction is planned. Some local coverage determinations (LCDs) require documented failure of conservative treatment before approving surgical malunion correction. Check the applicable LCD at the time of service, because these policies change.

Prior authorization is commonly triggered when the claim involves corrective osteotomy or hardware revision for malunion.

Payers may ask for the imaging report confirming malunion, the original operative note and the Gustilo class as part of the authorization package. Claims management software with eligibility checks and claim scrubbing catches missing details before the claim leaves the practice.

For Medicaid, malunion coding requirements vary by state. Don’t assume a federal Medicare rule applies to your state Medicaid plan without checking the state program manual. Some payers also require external cause codes (V00-Y99) as companion codes, so confirm the rule with each payer.

Common claim denial reasons and how to avoid them

Claims using S82.863Q are denied for a predictable set of reasons. Each one maps to a specific documentation or coding decision, so pre-bill review can catch it before an appeal is needed. Strong denial management in healthcare requires knowing which codes in a family carry the highest denial rates before claims go out.

Knowing the common denial codes in medical billing helps billers match each denial type above to its remittance reason code. That speeds up appeal preparation.

Coding example: S82.863Q in practice

This scenario shows where ICD-10 Code S82.863Q looks right but isn’t. A patient returns 14 weeks after surgical stabilization of a Gustilo type II Maisonneuve fracture of the right leg. Radiographs show callus with a 15-degree angular deformity at the fracture site.

The operative note from the original injury documents a proximal fibula fracture with syndesmotic disruption and a 3 cm wound (Gustilo type II). The follow-up note doesn’t restate which leg was injured, and the laterality field in the billing system is blank.

Code selection reasoning: The fracture has healed (callus present) but is malaligned, which confirms malunion rather than nonunion. The encounter is subsequent, and the original fracture was open Gustilo type II. The correct code is S82.861Q, because the original operative note documents the right leg. Defaulting to S82.863Q when the episode records a side is a coding error and an audit trigger.

Add an external cause code where the payer requires one. A place-of-occurrence code is reported only at the initial encounter, so it doesn’t belong on this follow-up claim.

For medical billing teams, the example shows why ICD-10 accuracy depends on reviewing the whole chart, not only the current visit note. The follow-up documentation has to be read alongside the initial injury record.

A pre-bill check against the standards for a clean claim catches this laterality error before the payer does.

How Pabau keeps malunion follow-up claims clean

A coder working a malunion follow-up often has the operative note, the imaging report and the claim form in three different systems. Matching the side, the Gustilo class and the healing status across all three is slow, manual work.

Pabau keeps the visit, the clinical notes and the claim on one patient record. Its claim validation scrubs each claim for missing or invalid details before it goes to the clearinghouse. Prior authorizations are stored as cases that follow the appointment through to the claim.

Your team fixes a wrong character or a missing authorization while the chart is still open. That means fewer rejected follow-up claims and less time spent on appeals.

Reduce coding errors on complex fracture claims

Pabau checks every claim for missing or invalid details before it reaches the payer, so complex fracture follow-ups go out right the first time.

Book a demo

Conclusion

S82.863Q is only right when three facts line up in the chart. The visit is a follow-up, the fracture was open type I or II, and imaging shows malunion. If one of them is missing, a neighboring code is the correct choice.

The habit that pays off is coding from the whole episode, not today’s note. Pull the original operative report for side and Gustilo class, and the latest imaging for healing status. That alone heads off the M-for-Q swap and the unspecified-leg denial.

Book a demo to see how Pabau stops an incomplete fracture claim before it reaches the payer.

Continue your research

Need to understand the broader fracture claim submission process? Claim.MD clearinghouse guide explains how electronic claim submission works from code entry to ERA receipt.

Handling a denied fracture claim? Electronic remittance advice covers how to read ERA files and match denial reason codes to the right appeal pathway.

Want to verify payer eligibility before the visit? Insurance eligibility verification outlines real-time eligibility checks that reduce claim rejections on complex orthopaedic encounters.

Frequently asked questions