ICD-10-CM > S00-T88 > S50-S59 > S56 > S56.3 > S56.39 > S56.399 S56.399 Other injury of extensor or abductor muscles, fascia and tendons of unspecified thumb at forearm level Non-Billable/Non-Specific Codes S56.399A..., initial encounterS56.399D..., subsequent encounterS56.399S..., sequela