S66.099A – Other specified injury of long flexor muscle, fascia and tendon of unspecified thumb at wrist and hand level, initial encounter

ICD-10-CM 2027 diagnosis code · Injuries to the wrist, hand and fingers

Billable code

ICD-10-CM code S66.099A

Code: S66.099A (claims format: S66099A)
Description: Other specified injury of long flexor muscle, fascia and tendon of unspecified thumb at wrist and hand level, initial encounter
Short description: Inj long flexor musc/fasc/tend thmb at wrs/hnd lv, init
Billable: Yes – valid for HIPAA-covered transactions
Valid for: Dates of service October 1, 2026 – September 30, 2027 (FY2027)
Chapter: 19. Injury, poisoning and certain other consequences of external causes (S00-T88)
Block: S60-S69 Injuries to the wrist, hand and fingers
Parent codes: S66 › S66.0 › S66.09 › S66.099

7th character values

Codes in this category need a 7th character to describe the encounter or episode of care.

Character	Meaning
`A`	initial encounter
`D`	subsequent encounter
`S`	sequela

Notes inherited from parent codes

Instructional notes at a category or block level apply to every code below it.

S66 – Injury of muscle, fascia and tendon at wrist and hand level

Excludes2 (not included here):

sprain of joints and ligaments of wrist and hand (S63.-)

Code also:

any associated open wound (S61.-)

7th character note:

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

Block S60-S69

Excludes2 (not included here):

burns and corrosions (T20-T32)
frostbite (T33-T34)
insect bite or sting, venomous (T63.4)

Related codes in S66.099

Frequently asked questions

What is ICD-10 code S66.099A?

S66.099A is the ICD-10-CM code for other specified injury of long flexor muscle, fascia and tendon of unspecified thumb at wrist and hand level, initial encounter, in the block S60-S69 (Injuries to the wrist, hand and fingers).

Is S66.099A a billable code?

Yes. S66.099A is a billable/specific code that can be used to indicate a diagnosis for reimbursement purposes.

What category does S66.099A belong to?

It belongs to category S66 – Injury of muscle, fascia and tendon at wrist and hand level.

Source: CDC/NCHS ICD-10-CM FY2027 code files, tabular list and index. Reference only – code assignment must follow the official ICD-10-CM guidelines and documentation in the medical record.