2026 ICD-10-CM Diagnosis Code S66.592AOther injury of intrinsic muscle, fascia and tendon of right middle finger at wrist and hand level, initial encounter
S66.592A is a billable ICD-10-CM diagnosis code for other injury of intrinsic muscle, fascia and tendon of right middle finger at wrist and hand level, 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 913 through 914, 963 through 965. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Injury to nerves, muscles and tendons, initial encounter.
Code Identity
Code Classification
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.
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 S66.592A to ICD-9-CMHistory
Code HistoryHistory
Questions About S66.592AOverview
Is S66.592A a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report other injury of intrinsic muscle, fascia and tendon of right middle finger at wrist and hand level, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in S66.592A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for other injury of intrinsic muscle, fascia and tendon of right middle finger at wrist and hand level, such as an emergency visit or first evaluation.
What MS-DRG does S66.592A group to?
When other injury of intrinsic muscle, fascia and tendon of right middle finger at wrist and hand level, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 913, 914, 963, 964, 965, with relative weights from 0.8855 to 2.7338 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of S66.592A?
Under the General Equivalence Mappings, other injury of intrinsic muscle, fascia and tendon of right middle finger at wrist and hand level, initial encounter converts to ICD-9-CM 959.3 (elb/forearm/wrst inj NOS) and 959.4 (hand injury NOS). 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.
