ICD-10-CM > S00-T88 > S60-S69 > S66 > S66.4 > S66.40 S66.40 Unspecified injury of intrinsic muscle, fascia and tendon of thumb at wrist and hand level Non-Billable/Non-Specific Codes S66.401Unspecified injury of intrinsic muscle, fascia and tendon of right thumb at wrist and hand levelS66.401A..., initial encounterS66.401D..., subsequent encounterS66.401S..., sequelaS66.402Unspecified injury of intrinsic muscle, fascia and tendon of left thumb at wrist and hand levelS66.402A..., initial encounterS66.402D..., subsequent encounterS66.402S..., sequelaS66.409Unspecified injury of intrinsic muscle, fascia and tendon of unspecified thumb at wrist and hand levelS66.409A..., initial encounterS66.409D..., subsequent encounterS66.409S..., sequela