ICD-10-CM > S00-T88 > S50-S59 > S56 > S56.3 > S56.31 > S56.312 S56.312 Strain of extensor or abductor muscles, fascia and tendons of left thumb at forearm level Non-Billable/Non-Specific Codes S56.312A..., initial encounterS56.312D..., subsequent encounterS56.312S..., sequela