S66.409Unspecified injury of intrinsic muscle, fascia and tendon of unspecified thumb at wrist and hand level

S66.409 is the ICD-10-CM diagnosis code for unspecified injury of intrinsic muscle, fascia and tendon of unspecified thumb at wrist and hand level. It belongs to category S66 (injury of muscle, fascia and tendon at wrist and hand level), block S60-S69 (injuries to the wrist, hand and fingers) and chapter 19 (injury, poisoning and certain other consequences of external causes). It is a header code, so it can't be reported by itself; one of its 3 subcodes must be used instead.

Within S66.40, choose S66.409 (unspecified thumb at wrist and hand level) only when documentation doesn't support a more specific option: right thumb at wrist and hand level (S66.401) and left thumb at wrist and hand level (S66.402).

Codes in this range require a 7th character: A for initial encounter, D for subsequent encounter and S for sequela. Use placeholder "X" characters to fill any empty positions before the 7th character.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.