2026 ICD-10-CM Diagnosis Code S66.500DUnspecified injury of intrinsic muscle, fascia and tendon of right index finger at wrist and hand level, subsequent encounter

ICD-10-CM Codes›S00–T88›S60-S69›S66

ICD-10-CM S66.500D
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

S66.500D is a billable ICD-10-CM diagnosis code for unspecified injury of intrinsic muscle, fascia and tendon of right index finger at wrist and hand level, subsequent encounter. The 7th character D marks it as a subsequent encounter code, used during routine care in the healing or recovery phase. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 949 through 950. The code is exempt from POA reporting. Coders also document this condition as injury of intrinsic muscle of index finger. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Injury to nerves, muscles and tendons, subsequent encounter.

Code Identity

ICD-10-CM Code
S66.500D
Billable Status
Yes — Valid for Submission
Code Describes
Unspecified injury of intrinsic muscle, fascia and tendon of right index finger at wrist and hand level, subsequent encounter
Short Description
Unsp inj intrns musc/fasc/tend r idx fngr at wrs/hnd lv,subs
Parent Code
S66.500
Unspecified injury of intrinsic muscle, fascia and tendon of right index finger at wrist and hand level

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionS60-S69Injuries to the wrist, hand and fingers
CategoryS66Injury of muscle, fascia and tendon at wrist and hand level
This CodeS66.500DUnspecified injury of intrinsic muscle, fascia and tendon of right index finger at wrist and hand level, subsequent encounter

Present on Admission (POA)Billing

S66.500D is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Injury of intrinsic muscle of index finger
  • Right index finger intrinsic muscle injury

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Injury of muscle, fascia and tendon at wrist and hand level (S66). 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 INJ062
Injury to nerves, muscles and tendons, subsequent encounter
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Hand Injuries and Disorders

No matter how old you are or what you do for a living, you are always using your hands. When there is something wrong with them, you may not be able to do your regular activities.

Read the full article at MedlinePlus

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

Convert S66.500D to ICD-9-CMHistory

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

ICD-9-CM
V58.89 Other specfied aftercare
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 S66.500DOverview

Is S66.500D a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report unspecified injury of intrinsic muscle, fascia and tendon of right index finger at wrist and hand level, subsequent encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character D in S66.500D mean?

The final character D marks a subsequent encounter: use it for routine care while the unspecified injury of intrinsic muscle, fascia and tendon of right index finger at wrist and hand level is healing, after active treatment has ended.

What MS-DRG does S66.500D group to?

When unspecified injury of intrinsic muscle, fascia and tendon of right index finger at wrist and hand level, subsequent encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 949, 950, with relative weights from 0.6277 to 1.1897 depending on complications. Higher weights mean higher Medicare reimbursement.

Is S66.500D exempt from POA reporting?

Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for unspecified injury of intrinsic muscle, fascia and tendon of right index finger at wrist and hand level, subsequent encounter on inpatient claims.

What is the ICD-9 equivalent of S66.500D?

Under the General Equivalence Mappings, unspecified injury of intrinsic muscle, fascia and tendon of right index finger at wrist and hand level, subsequent encounter converts to ICD-9-CM V58.89 (other specfied aftercare). 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.