2027 ICD-10-CM Diagnosis Code S44.00XAInjury of ulnar nerve at upper arm level, unspecified arm, initial encounter

ICD-10-CM Codes›S00–T88›S40-S49›S44

ICD-10-CM S44.00XA
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

S44.00XA is a billable ICD-10-CM diagnosis code for injury of ulnar nerve at upper arm level, unspecified arm, 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 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 73 through 74, 963 through 965. Coders also document this condition as injury of ulnar nerve. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Injury to nerves, muscles and tendons, initial encounter.

Code Identity

ICD-10-CM Code
S44.00XA
Billable Status
Yes — Valid for Submission
Code Describes
Injury of ulnar nerve at upper arm level, unspecified arm, initial encounter
Short Description
Injury of ulnar nerve at upper arm level, unsp arm, init
Parent Code
S44.00
Injury of ulnar nerve at upper arm level, unspecified arm

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionS40-S49Injuries to the shoulder and upper arm
CategoryS44Injury of nerves at shoulder and upper arm level
This CodeS44.00XAInjury of ulnar nerve at upper arm level, unspecified arm, initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Injury of ulnar nerve
  • Injury of ulnar nerve at upper arm level

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Injury of nerves at shoulder and upper arm level (S44). 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 2027, published by CMS and the National Center for Health Statistics.

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to S44.00XA: its own notes plus those printed at S44.0, S44, block S40-S49, and Chapter 19. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From Block S40-S49 Injuries to the shoulder and upper arm applies to 2,730 codes
  • injuries of axilla
  • injuries of scapular region

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From S44.0 Injury of ulnar nerve at upper arm level applies to 9 codes

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From S44 Injury of nerves at shoulder and upper arm level applies to 72 codes
  • injury of brachial plexus (S14.3-)
From Block S40-S49 Injuries to the shoulder and upper arm applies to 2,730 codes
From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • code to identify any retained foreign body, if applicable (Z18.-)

Code Also

A second code may be needed to fully describe the condition; the note gives no sequencing direction.

From S44 Injury of nerves at shoulder and upper arm level applies to 72 codes
  • any associated open wound (S41.-)

Notes

General instructions on how these codes are used.

From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
  • The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.

7th Character

Every code in the category takes a 7th character from the listed values, with the placeholder X filling any empty positions before it.

From S44 Injury of nerves at shoulder and upper arm level applies to 72 codes
  • The appropriate 7th character is to be added to each code from category S44
Values for category S44 Encounter: Initial, Subsequent, Sequela
  • Ainitial encounter this code
  • Dsubsequent encounter
  • Ssequela

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Clinical ClassificationClinical

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

CCSR INJ025
Injury to nerves, muscles and tendons, initial encounter
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Peripheral Nerve Disorders

Nerves are like wires that carry messages back and forth between your brain and your body. Your peripheral nerves branch off from your brain and spinal cord and connect to all parts of your body, including your muscles and organs.

The full article covers:

  • What are peripheral nerves?
  • What are peripheral nerve disorders?
  • What causes peripheral nerve disorders?
  • What are the symptoms of peripheral nerve disorders?
  • How are peripheral nerve disorders diagnosed?
  • What are the treatments for peripheral nerve disorders?
  • Can peripheral nerve disorders be prevented?

Read the full article at MedlinePlus

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

Convert S44.00XA to ICD-9-CMHistory

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

ICD-9-CM
955.2 Injury ulnar nerve
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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About S44.00XAOverview

Is S44.00XA (Injury of ulnar nerve at upper arm level, unspecified arm) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report injury of ulnar nerve at upper arm level, unspecified arm, initial encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What does the 7th character A in S44.00XA mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for injury of ulnar nerve at upper arm level, unspecified arm, such as an emergency visit or first evaluation.

What MS-DRG does S44.00XA group to?

When injury of ulnar nerve at upper arm level, unspecified arm, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 964, 965, 74, 73, 963, with relative weights from 1.0054 to 2.6361 depending on complications. Higher weights mean higher Medicare reimbursement.

Can S44.00XA be reported with S54.0?

Not as a rule. The Excludes1 note at S44.0, which applies to S44.00XA, lists "ulnar nerve NOS (S54.0)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).

What is the ICD-9 equivalent of S44.00XA?

Under the General Equivalence Mappings, injury of ulnar nerve at upper arm level, unspecified arm, initial encounter converts to ICD-9-CM 955.2 (injury ulnar nerve). The mapping is approximate, so confirm the match fits the documentation.