2026 ICD-10-CM Diagnosis Code M89.78Major osseous defect, other site

ICD-10-CM Codes›M00–M99›M86-M90›M89

ICD-10-CM M89.78
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M89.78 is a billable ICD-10-CM diagnosis code for major osseous defect, other site. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 553 through 554. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified bone disease and musculoskeletal deformities.

Code Identity

ICD-10-CM Code
M89.78
Billable Status
Yes — Valid for Submission
Code Describes
Major osseous defect, other site
Short Description
Major osseous defect, other site
Same as the full description in the CMS dataset.
Parent Code
M89.7
Major osseous defect

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM86-M90Other osteopathies
CategoryM89Other disorders of bone
This CodeM89.78Major osseous defect, other site

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Defect, defective
      • major osseous
        • specified NEC
    • Defect, defective
      • osseous, major
        • specified NEC

Clinical ClassificationClinical

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

CCSR MUS028
Other specified bone disease and musculoskeletal deformities
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Bone Diseases

Your bones help you move, give you shape and support your body. They are living tissues that rebuild constantly throughout your life. During childhood and your teens, your body adds new bone faster than it removes old bone. After about age 20, you can lose bone faster than you make bone.

Read the full article at MedlinePlus

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

Convert M89.78 to ICD-9-CMHistory

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

ICD-9-CM
731.3 Major osseous defects
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 M89.78Overview

Is M89.78 (Major osseous defect) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report major osseous defect, other site on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M89.78 group to?

When major osseous defect, other site is the principal diagnosis on an inpatient stay, it groups to MS-DRG 553, 554, with relative weights from 0.8301 to 1.2963 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M89.78?

Under the General Equivalence Mappings, major osseous defect, other site converts to ICD-9-CM 731.3 (major osseous defects). 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.