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S66.21 ICD-10-CM Code: Strain of extensor muscle, fascia and tendon of thumb at wrist and hand level

Billing Status: NO. This is a clinician non-billable / parent hierarchy grouping in the ICD-10-CM system.

Official Registry Overview & Definition

Strain of extensor muscle, fascia and tendon of thumb at wrist and hand level is a non-billable ICD-10-CM category code (S66.21). A more specific billable subcode must be selected for claims submission.

Official Tabular Instructional Notes

Sequencing, inclusion, and exclusion notes published for S66.21 in the official ICD-10-CM tabular list.

Excludes2 — Not Included Here

Conditions not covered by this code, but which may be reported alongside it when both are present.

Code Also

Additional codes that may be required to fully describe the encounter.

  • any associated open wound (S61.-)

Frequently Compared Codes

The official Excludes notes on S66.21 name these codes. Each comparison page covers when the two can — or must not — be reported together.

Change history

No changes recorded for this code — unchanged since the FY2016 baseline of the change ledger.

Verify Before Coding

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim.

Relationships & Classification

Official ICD-10-CM tabular notes on other codes that name S66.21 or its code family.

3 Excludes2 notes: S56 (via S66.-), S63 (via S66.-), S66.3 (via S66.2.-).

Contextual Map

Every relationship of S66.21 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Hierarchy

  • S00-T88 — Chapter 19: Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88) (S00-T88) [Hierarchy]

Referenced by Excludes2 notes

  • S56 — Injury of muscle, fascia and tendon at forearm level [Excludes2](via S66.-): “injury of muscle, fascia and tendon at or below wrist (S66.-)” · check together
  • S63 — Dislocation and sprain of joints and ligaments at wrist and hand level [Excludes2](via S66.-): “strain of muscle, fascia and tendon of wrist and hand (S66.-)” · check together
  • S66.3 — Injury of extensor muscle, fascia and tendon of other and unspecified finger at wrist and hand level [Excludes2](via S66.2.-): “Injury of extensor muscle, fascia and tendon of thumb at wrist and hand level (S66.2-)” · check together

Nearest codes (40)

  • S66 — Injury of muscle, fascia and tendon at wrist and hand level [Sibling]
  • S66.198D — Other injury of flexor muscle, fascia and tendon of other finger at wrist and hand level, subsequent encounter [Sibling]
  • S66.198S — Other injury of flexor muscle, fascia and tendon of other finger at wrist and hand level, sequela [Sibling]
  • S66.199 — Other injury of flexor muscle, fascia and tendon of unspecified finger at wrist and hand level [Sibling]
  • S66.199A — Other injury of flexor muscle, fascia and tendon of unspecified finger at wrist and hand level, initial encounter [Sibling]
  • S66.199D — Other injury of flexor muscle, fascia and tendon of unspecified finger at wrist and hand level, subsequent encounter [Sibling]
  • S66.199S — Other injury of flexor muscle, fascia and tendon of unspecified finger at wrist and hand level, sequela [Sibling]
  • S66.2 — Injury of extensor muscle, fascia and tendon of thumb at wrist and hand level [Sibling]
  • and 32 more

Frequently Asked Questions (FAQ) & Clinical Guidance

Can S66.21 be billed directly?

No. S66.21 (Strain of extensor muscle, fascia and tendon of thumb at wrist and hand level) is a non-billable ICD-10-CM category code. A more specific billable subcode must be selected based on clinical documentation.

Does S66.21 require a 7th character?

Yes. The appropriate 7th character is to be added to each code from category S66.

Nearest Codes in This Family

Official ICD-10-CM classifications closest to S66.21 in its code family, with their registry titles.

  • S66.202S — Unspecified injury of extensor muscle, fascia and tendon of left thumb at wrist and hand level, sequela
  • S66.209 — Unspecified injury of extensor muscle, fascia and tendon of unspecified thumb at wrist and hand level
  • S66.209A — Unspecified injury of extensor muscle, fascia and tendon of unspecified thumb at wrist and hand level, initial encounter
  • S66.209D — Unspecified injury of extensor muscle, fascia and tendon of unspecified thumb at wrist and hand level, subsequent encounter
  • S66.209S — Unspecified injury of extensor muscle, fascia and tendon of unspecified thumb at wrist and hand level, sequela
  • S66.211 — Strain of extensor muscle, fascia and tendon of right thumb at wrist and hand level
  • S66.211A — Strain of extensor muscle, fascia and tendon of right thumb at wrist and hand level, initial encounter
  • S66.211D — Strain of extensor muscle, fascia and tendon of right thumb at wrist and hand level, subsequent encounter
  • S66.211S — Strain of extensor muscle, fascia and tendon of right thumb at wrist and hand level, sequela
  • S66.212 — Strain of extensor muscle, fascia and tendon of left thumb at wrist and hand level

View all codes in the S66 family