S66.49 vs S66.491A
S66.49 (Other specified injury of intrinsic muscle, fascia and tendon of thumb at wrist and hand level) compared with S66.491A (Other specified injury of intrinsic muscle, fascia and tendon of right thumb at wrist and hand level, initial encounter), from the official CMS tabular data.
Summary
These codes represent different levels of the same hierarchy: S66.49 is the non-billable header that contains S66.491A, so only S66.491A (or a sibling) is reported.
Registry fact- What is different?
Title wording and billing status.The titles share “Other specified injury of intrinsic muscle, fascia and tendon of”; S66.49 says “thumb at wrist and hand level” where S66.491A says “right thumb at wrist and hand level, initial encounter”. S66.49 is a non-billable header; S66.491A is billable.
Registry fact
- Can these codes be reported together?
Not as a pair.S66.49 is the non-billable header that contains S66.491A. A header is not reported on a claim, so the choice is S66.491A or a sibling that matches the documentation.
Registry fact
- Is there an Excludes1 relationship?
None.Neither entry carries an Excludes1 note that names the other code.
Official rule
- Is there an Excludes2 relationship?
None.Neither entry carries an Excludes2 note that names the other code. S66.49 carries 4 Excludes2 notes and S66.491A carries 4 Excludes2 notes covering other codes; the side-by-side table quotes them.
Official rule
- Is one more specific?
Yes.S66.491A is a subdivision of S66.49 in the tabular hierarchy, so it is the more specific of the two.
Registry fact
- Is one a parent or header code?
Yes.S66.49 is the non-billable header that contains S66.491A. A header stands for the whole family beneath it and is not reported on a claim.
Registry fact
- Are there sequencing instructions?
None.Neither entry carries a Code First or Use Additional Code note that names the other.
Official rule
- Are there other coding relationships?
None found.No laterality, encounter-phase, Table of Neoplasms, Table of Drugs and Chemicals, or history-versus-active-disease relationship links these codes.
MedCoder-derived
Official rule: a tabular instructional note or a section of the ICD-10-CM Official Guidelines, quoted as published. Registry fact: the codes’ own published attributes (titles, billable status, position in the hierarchy, code set). MedCoder-derived: a reading MedCoder computes from those facts; it is not itself a rule. How to read the labels
Can these codes be reported together?
Not as a pair — S66.49 is not reportable. S66.49 is the non-billable category that contains S66.491A.
A header stands for the whole family of codes beneath it and is not reported on a claim, so the choice is S66.491A or a sibling that matches the documentation. No Excludes1/Excludes2 relationship exists between these codes in the official tabular list.
Official guidance behind these answers
Section I.B.2 — Level of Detail in Coding · applies to: S66.49 and S66.491A
Diagnosis codes are to be used and reported at their highest number of characters available and to the highest level of specificity documented in the medical record. ICD-10-CM diagnosis codes are composed of codes with 3, 4, 5, 6 or 7 characters. Codes with three characters are included in ICD-10-CM as the heading of a category of codes that may be further subdivided by the use of fourth and/or fifth characters and/or sixth characters, which provide greater detail. A three-character code is to be used only if it is not further subdivided. A code is invalid if it has not been coded to the full number of characters required for that code, including the 7th character, if applicable.
ICD-10-CM Official Guidelines FY2026
Quoted from the ICD-10-CM Official Guidelines for Coding and Reporting in effect for the release shown. The tabular notes above are the code-level instruction; these sections are the convention that says how such a note is applied. Source document (CMS PDF) · Release and checksum
Side by side
| S66.49Other specified injury of intrinsic muscle, fascia and tendon of thumb at wrist and hand level | S66.491AOther specified injury of intrinsic muscle, fascia and tendon of right thumb at wrist and hand level, initial encounter | |
|---|---|---|
| Billing status | Non-billable header Report instead: S66.491A, S66.491D, S66.491S, S66.492A, S66.492D | Billable |
| Classification | S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88) | S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88) |
| Definition | Other specified injury of intrinsic muscle, fascia and tendon of thumb at wrist and hand level is a non-billable ICD-10-CM category code (S66.49). | Other specified injury of intrinsic muscle, fascia and tendon of right thumb at wrist and hand level, initial encounter is a billable ICD-10-CM diagnosis code (S66.491A). |
| 7th character | The appropriate 7th character is to be added to each code from category S66 | The appropriate 7th character is to be added to each code from category S66 |
| Excludes2 | sprain of joints and ligaments of wrist and hand (S63.-) burns and corrosions (T20-T32) frostbite (T33-T34) insect bite or sting, venomous (T63.4) | sprain of joints and ligaments of wrist and hand (S63.-) burns and corrosions (T20-T32) frostbite (T33-T34) insect bite or sting, venomous (T63.4) |
| Code also | any associated open wound (S61.-) | any associated open wound (S61.-) |
Notes are the code’s own tabular entry, quoted as published. A note that names the other code is the one the verdict above rests on.
Derived from the official CMS ICD-10-CM tabular data (FY2026). A coding-rule comparison, not billing advice: payer-specific edits and medical-necessity policy are outside its scope. All data sources