2026 ICD-10-CM Diagnosis Code M84.639PPathological fracture in other disease, unspecified ulna and radius, subsequent encounter for fracture with malunion

ICD-10-CM Codes›M00–M99›M80-M85›M84

ICD-10-CM M84.639P
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M84.639P is a billable ICD-10-CM diagnosis code for pathological fracture in other disease, unspecified ulna and radius, subsequent encounter for fracture with malunion. The 7th character P reports a subsequent encounter for a fracture that has healed in a faulty position, called a malunion. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 564 through 566. The code is flagged as an unspecified code, since codes identifying laterality exist in the same family. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Pathological fracture, subsequent encounter.

Code Identity

ICD-10-CM Code
M84.639P
Billable Status
Yes — Valid for Submission
Code Describes
Pathological fracture in other disease, unspecified ulna and radius, subsequent encounter for fracture with malunion
Short Description
Path fx in oth dis, unsp ulna & rad, subs for fx w malunion
Parent Code
M84.639
Pathological fracture in other disease, unspecified ulna and radius

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM80-M85Disorders of bone density and structure
CategoryM84Disorder of continuity of bone
This CodeM84.639PPathological fracture in other disease, unspecified ulna and radius, subsequent encounter for fracture with malunion

Code EditsBilling

Medicare Code Editor checks that affect claim validity for M84.639P.

Unspecified codes
Unspecified codes exist in the ICD-10-CM classification for circumstances when documentation in the medical record does not provide the level of detail needed to support reporting a more specific code. However, in the inpatient setting, there should generally be very limited and rare circumstances for which the laterality (right, left, bilateral) of a condition is unable to be documented and reported. The following pages contain the list of unspecified ICD-10-CM diagnosis codes for which there is a more specific code to identify laterality (right, left, bilateral) within that code family.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR MUS015
Pathological fracture, subsequent encounter
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Arm Injuries and Disorders

Of the 206 bones in your body, three of them are in your arm: the humerus, radius, and ulna. Your arms are also made up of muscles, joints, tendons, and other connective tissue. Injuries to any of these parts of the arm can occur during sports, a fall, or an accident.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert M84.639P to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
733.81 Malunion of fracture
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About M84.639POverview

Is M84.639P a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report pathological fracture in other disease, unspecified ulna and radius, subsequent encounter for fracture with malunion on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character P in M84.639P mean?

The final character P reports a subsequent encounter where the pathological fracture in other disease, unspecified ulna and radius has healed in a faulty position, called a malunion.

What MS-DRG does M84.639P group to?

When pathological fracture in other disease, unspecified ulna and radius, subsequent encounter for fracture with malunion is the principal diagnosis on an inpatient stay, it groups to MS-DRG 564, 565, 566, with relative weights from 0.7493 to 1.5436 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M84.639P?

Under the General Equivalence Mappings, pathological fracture in other disease, unspecified ulna and radius, subsequent encounter for fracture with malunion converts to ICD-9-CM 733.81 (malunion of fracture). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.