ICD-10-CM > S00-T88 > S60-S69 > S66 > S66.2 > S66.21 > S66.212 S66.212 Strain of extensor muscle, fascia and tendon of left thumb at wrist and hand level Non-Billable/Non-Specific Codes S66.212A..., initial encounterS66.212D..., subsequent encounterS66.212S..., sequela