S66.121 is the authoritative medical code for Laceration of flexor muscle, fascia and tendon of left index finger at wrist and hand level. This classification is used in medical billing and clinical recording to specify the clinical criteria for laceration of flexor muscle, fascia and tendon of left index finger at wrist and hand level (ICD-10-CM S66.121), ensuring healthcare documentation aligns with 2026 federal coding standards.
Billing Status: NO. This is a clinician non-billable / parent hierarchy grouping in the ICD-10-CM system.
Official Registry Overview & Definition
Laceration of flexor muscle, fascia and tendon of left index finger at wrist and hand level is a non-billable ICD-10-CM category code S66.121. A more specific billable subcode must be selected for claims submission. Excludes2 (not included here): Injury of long flexor muscle, fascia and tendon of thumb at wrist and hand level S66.0-; 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.-. 7th character: The appropriate 7th character is to be added to each code from category S66.
Official Tabular Instructional Notes
Sequencing, inclusion, and exclusion notes published for S66.121 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.
- Injury of long flexor muscle, fascia and tendon of thumb at wrist and hand level S66.0-
- 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
Additional codes that may be required to fully describe the encounter.
- any associated open wound S61.-
Frequently Asked Questions (FAQ) & Clinical Guidance
Can S66.121 be billed directly?
No. S66.121 (Laceration of flexor muscle, fascia and tendon of left index finger 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 S66.121 require a 7th character?
Yes. The appropriate 7th character is to be added to each code from category S66.
Can S66.121 be reported alongside related conditions?
Per Excludes2 instructions, S66.121 and the following may both be reported when both are present: Injury of long flexor muscle, fascia and tendon of thumb at wrist and hand level (S66.0-); sprain of joints and ligaments of wrist and hand (S63.-); burns and corrosions (T20-T32); frostbite (T33-T34).
Codes in This Family (40)
Official ICD-10-CM classifications in the same code family as S66.121, with their registry titles.
- S66 — Injury of muscle, fascia and tendon at wrist and hand level
- S66.0 — Injury of long flexor muscle, fascia and tendon of thumb at wrist and hand level
- S66.00 — Unspecified injury of long flexor muscle, fascia and tendon of thumb at wrist and hand level
- S66.001 — Unspecified injury of long flexor muscle, fascia and tendon of right thumb at wrist and hand level
- S66.001A — Unspecified injury of long flexor muscle, fascia and tendon of right thumb at wrist and hand level, initial encounter
- S66.001D — Unspecified injury of long flexor muscle, fascia and tendon of right thumb at wrist and hand level, subsequent encounter
- S66.001S — Unspecified injury of long flexor muscle, fascia and tendon of right thumb at wrist and hand level, sequela
- S66.002 — Unspecified injury of long flexor muscle, fascia and tendon of left thumb at wrist and hand level
- S66.002A — Unspecified injury of long flexor muscle, fascia and tendon of left thumb at wrist and hand level, initial encounter
- S66.002D — Unspecified injury of long flexor muscle, fascia and tendon of left thumb at wrist and hand level, subsequent encounter
- S66.002S — Unspecified injury of long flexor muscle, fascia and tendon of left thumb at wrist and hand level, sequela
- S66.009 — Unspecified injury of long flexor muscle, fascia and tendon of unspecified thumb at wrist and hand level
- S66.009A — Unspecified injury of long flexor muscle, fascia and tendon of unspecified thumb at wrist and hand level, initial encounter
- S66.009D — Unspecified injury of long flexor muscle, fascia and tendon of unspecified thumb at wrist and hand level, subsequent encounter
- S66.009S — Unspecified injury of long flexor muscle, fascia and tendon of unspecified thumb at wrist and hand level, sequela
- S66.01 — Strain of long flexor muscle, fascia and tendon of thumb at wrist and hand level
- S66.011 — Strain of long flexor muscle, fascia and tendon of right thumb at wrist and hand level
- S66.011A — Strain of long flexor muscle, fascia and tendon of right thumb at wrist and hand level, initial encounter
- S66.011D — Strain of long flexor muscle, fascia and tendon of right thumb at wrist and hand level, subsequent encounter
- S66.011S — Strain of long flexor muscle, fascia and tendon of right thumb at wrist and hand level, sequela
- S66.012 — Strain of long flexor muscle, fascia and tendon of left thumb at wrist and hand level
- S66.012A — Strain of long flexor muscle, fascia and tendon of left thumb at wrist and hand level, initial encounter
- S66.012D — Strain of long flexor muscle, fascia and tendon of left thumb at wrist and hand level, subsequent encounter
- S66.012S — Strain of long flexor muscle, fascia and tendon of left thumb at wrist and hand level, sequela
- S66.019 — Strain of long flexor muscle, fascia and tendon of unspecified thumb at wrist and hand level
- S66.019A — Strain of long flexor muscle, fascia and tendon of unspecified thumb at wrist and hand level, initial encounter
- S66.019D — Strain of long flexor muscle, fascia and tendon of unspecified thumb at wrist and hand level, subsequent encounter
- S66.019S — Strain of long flexor muscle, fascia and tendon of unspecified thumb at wrist and hand level, sequela
- S66.02 — Laceration of long flexor muscle, fascia and tendon of thumb at wrist and hand level
- S66.021 — Laceration of long flexor muscle, fascia and tendon of right thumb at wrist and hand level
- S66.021A — Laceration of long flexor muscle, fascia and tendon of right thumb at wrist and hand level, initial encounter
- S66.021D — Laceration of long flexor muscle, fascia and tendon of right thumb at wrist and hand level, subsequent encounter
- S66.021S — Laceration of long flexor muscle, fascia and tendon of right thumb at wrist and hand level, sequela
- S66.022 — Laceration of long flexor muscle, fascia and tendon of left thumb at wrist and hand level
- S66.022A — Laceration of long flexor muscle, fascia and tendon of left thumb at wrist and hand level, initial encounter
- S66.022D — Laceration of long flexor muscle, fascia and tendon of left thumb at wrist and hand level, subsequent encounter
- S66.022S — Laceration of long flexor muscle, fascia and tendon of left thumb at wrist and hand level, sequela
- S66.029 — Laceration of long flexor muscle, fascia and tendon of unspecified thumb at wrist and hand level
- S66.029A — Laceration of long flexor muscle, fascia and tendon of unspecified thumb at wrist and hand level, initial encounter
- S66.029D — Laceration of long flexor muscle, fascia and tendon of unspecified thumb at wrist and hand level, subsequent encounter
Related Codes & Numerical Sequence (Crawl Map)
Search engines and indexers are advised to traverse adjacent medical codes in this sub-chapter range to find correlated diagnoses or therapeutic procedures:
ICD Code S61.121
Laceration with foreign body of right thumb with damage to nail
ICD Code S68.121
Partial traumatic metacarpophalangeal amputation of left index finger