2026 ICD-10-CM Diagnosis Code M84.661APathological fracture in other disease, right tibia, initial encounter for fracture

ICD-10-CM Codes›M00–M99›M80-M85›M84

ICD-10-CM M84.661A
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M84.661A is a billable ICD-10-CM diagnosis code for pathological fracture in other disease, right tibia, initial encounter for fracture. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 542 through 544. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Pathological fracture, initial encounter.

Code Identity

ICD-10-CM Code
M84.661A
Billable Status
Yes — Valid for Submission
Code Describes
Pathological fracture in other disease, right tibia, initial encounter for fracture
Short Description
Pathological fracture in oth disease, right tibia, init
Parent Code
M84.661
Pathological fracture in other disease, right tibia

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM80-M85Disorders of bone density and structure
CategoryM84Disorder of continuity of bone
This CodeM84.661APathological fracture in other disease, right tibia, initial encounter for fracture

Clinical ClassificationClinical

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

CCSR MUS014
Pathological fracture, initial encounter
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Fractures

A fracture is a break in a bone. Fractures are usually caused by injuries. Since they can sometimes be serious, it's important to get medical care right away if you think you have a fracture.

The full article covers:

  • What is a fracture?
  • What are the different types of fractures?
  • What causes fractures?
  • What are the symptoms of a fracture?
  • How are fractures diagnosed?
  • What are the treatments for fractures?
  • Can fractures be prevented?

Read the full article at MedlinePlus

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

Convert M84.661A to ICD-9-CMHistory

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

ICD-9-CM
733.16 Path fx tibia fibula
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 M84.661AOverview

Is M84.661A (Pathological fracture in other disease, right tibia) a billable code?

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

What does the 7th character A in M84.661A mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for pathological fracture in other disease, right tibia, such as an emergency visit or first evaluation.

What MS-DRG does M84.661A group to?

When pathological fracture in other disease, right tibia, initial encounter for fracture is the principal diagnosis on an inpatient stay, it groups to MS-DRG 542, 543, 544, with relative weights from 0.7546 to 1.7665 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M84.661A?

Under the General Equivalence Mappings, pathological fracture in other disease, right tibia, initial encounter for fracture converts to ICD-9-CM 733.16 (path fx tibia fibula). 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.