ICD-10-CM > S00-T88 > S50-S59 > S56 > S56.0 > S56.01 > S56.012 S56.012 Strain of flexor muscle, fascia and tendon of left thumb at forearm level Non-Billable/Non-Specific Codes S56.012A..., initial encounterS56.012D..., subsequent encounterS56.012S..., sequela