ICD-10-CM > S00-T88 > S60-S69 > S66 > S66.0 > S66.01 > S66.012 S66.012 Strain of long flexor muscle, fascia and tendon of left thumb at wrist and hand level Non-Billable/Non-Specific Codes S66.012A..., initial encounterS66.012D..., subsequent encounterS66.012S..., sequela