2026 ICD-10-CM Diagnosis Code T79.A19ATraumatic compartment syndrome of unspecified upper extremity, initial encounter

ICD-10-CM Codes›S00–T88›T79›T79

ICD-10-CM T79.A19A
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

T79.A19A is a billable ICD-10-CM diagnosis code for traumatic compartment syndrome of unspecified upper extremity, initial encounter. 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 922 through 923, 963 through 965. The code is flagged as an unspecified code, since codes identifying laterality exist in the same family. Coders also document this condition as compartment syndrome of forearm. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified injury.

Code Identity

ICD-10-CM Code
T79.A19A
Billable Status
Yes — Valid for Submission
Code Describes
Traumatic compartment syndrome of unspecified upper extremity, initial encounter
Short Description
Traumatic compartment syndrome of unsp upper extremity, init
Parent Code
T79.A19
Traumatic compartment syndrome of unspecified upper extremity

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionT79Certain early complications of trauma
CategoryT79Certain early complications of trauma, not elsewhere classified
This CodeT79.A19ATraumatic compartment syndrome of unspecified upper extremity, initial encounter

Code EditsBilling

Medicare Code Editor checks that affect claim validity for T79.A19A.

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.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Compartment syndrome of forearm
  • Compartment syndrome of forearm due to traumatic injury
  • Compartment syndrome of hand due to traumatic injury
  • Compartment syndrome of lower leg due to traumatic injury
  • Compartment syndrome of upper arm due to traumatic injury
  • Compartment syndrome of upper limb due to traumatic injury
  • Extensor compartment syndrome of forearm due to traumatic injury
  • Triceps surae compartment syndrome due to traumatic injury

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Certain early complications of trauma, not elsewhere classified (T79). Use the following options for the applicable episode of care:

  • A - initial encounter
  • D - subsequent encounter
  • S - sequela

Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026, published by CMS and the National Center for Health Statistics.

Clinical ClassificationClinical

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

CCSR INJ026
Other specified injury
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

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Read the full article at MedlinePlus

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

Convert T79.A19A to ICD-9-CMHistory

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

ICD-9-CM
958.91 Trauma comp synd up ext
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 T79.A19AOverview

Is T79.A19A a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report traumatic compartment syndrome of unspecified upper extremity, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character A in T79.A19A mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for traumatic compartment syndrome of unspecified upper extremity, such as an emergency visit or first evaluation.

What MS-DRG does T79.A19A group to?

When traumatic compartment syndrome of unspecified upper extremity, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 922, 923, 963, 964, 965, with relative weights from 0.9405 to 2.7338 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of T79.A19A?

Under the General Equivalence Mappings, traumatic compartment syndrome of unspecified upper extremity, initial encounter converts to ICD-9-CM 958.91 (trauma comp synd up ext). 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.