2026 ICD-10-CM Diagnosis Code M84.531KPathological fracture in neoplastic disease, right ulna, subsequent encounter for fracture with nonunion

ICD-10-CM Codes›M00–M99›M80-M85›M84

ICD-10-CM M84.531K
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M84.531K is a billable ICD-10-CM diagnosis code for pathological fracture in neoplastic disease, right ulna, subsequent encounter for fracture with nonunion. The 7th character K reports a subsequent encounter for a fracture that has failed to heal, called a nonunion. 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. Coders also document this condition as neoplasm of right ulna. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Pathological fracture, subsequent encounter.

Code Identity

ICD-10-CM Code
M84.531K
Billable Status
Yes — Valid for Submission
Code Describes
Pathological fracture in neoplastic disease, right ulna, subsequent encounter for fracture with nonunion
Short Description
Path fx in neopltc disease, r ulna, subs for fx w nonunion
Parent Code
M84.531
Pathological fracture in neoplastic disease, right ulna

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM80-M85Disorders of bone density and structure
CategoryM84Disorder of continuity of bone
This CodeM84.531KPathological fracture in neoplastic disease, right ulna, subsequent encounter for fracture with nonunion

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Neoplasm of right ulna
  • Pathologic fracture of ulna at site of neoplasm
  • Pathological fracture of right ulna
  • Pathological fracture of right ulna at site of neoplasm
  • Pathological fracture of ulna

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 M84.531K to ICD-9-CMHistory

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

ICD-9-CM
733.82 Nonunion 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 M84.531KOverview

Is M84.531K (Pathological fracture in neoplastic disease, right ulna) a billable code?

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

What does the 7th character K in M84.531K mean?

The final character K reports a subsequent encounter where the pathological fracture in neoplastic disease, right ulna has failed to heal, called a nonunion.

What MS-DRG does M84.531K group to?

When pathological fracture in neoplastic disease, right ulna, subsequent encounter for fracture with nonunion 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 M84.531K?

Under the General Equivalence Mappings, pathological fracture in neoplastic disease, right ulna, subsequent encounter for fracture with nonunion converts to ICD-9-CM 733.82 (nonunion of fracture). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.