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S66.419A vs S66.419D

S66.419A (Strain of intrinsic muscle, fascia and tendon of unspecified thumb at wrist and hand level, initial encounter) compared with S66.419D (Strain of intrinsic muscle, fascia and tendon of unspecified thumb at wrist and hand level, subsequent encounter), from the official CMS tabular data. S66.419A and S66.419D code the same injury at a different phase of treatment.

Relationship

Review

Encounter relationship

S66.419A
Initial encounter
Strain of intrinsic muscle, fascia and tendon of unspecified thumb at wrist and hand level, initial encounter
S66.419D
Subsequent encounter
Strain of intrinsic muscle, fascia and tendon of unspecified thumb at wrist and hand level, subsequent encounter

Same underlying diagnosis, different encounter phase.

The 7th character records the phase of care for the encounter being coded, so a single encounter takes one of these characters, not several. Review whether both phases belong on the same episode of care.

Source: ICD-10-CM Official Guidelines, Section I.C.19.a

Can these codes be reported together?

Same injury, other encounter phase. S66.419A and S66.419D code the same injury at a different phase of treatment, set by the 7th character.

The 7th character records the type of care given at the encounter being coded (ICD-10-CM Official Guidelines, Section I.C.19.a), so one encounter takes one of these, not both.

Side by side

S66.419AStrain of intrinsic muscle, fascia and tendon of unspecified thumb at wrist and hand level, initial encounterS66.419DStrain of intrinsic muscle, fascia and tendon of unspecified thumb at wrist and hand level, subsequent encounter
Billing statusBillableBillable
ClassificationS00-T88 — Injury, poisoning and certain other consequences of external causesS00-T88 — Injury, poisoning and certain other consequences of external causes
DefinitionStrain of intrinsic muscle, fascia and tendon of unspecified thumb at wrist and hand level, initial encounter is a billable ICD-10-CM diagnosis code (S66.419A).Strain of intrinsic muscle, fascia and tendon of unspecified thumb at wrist and hand level, subsequent encounter is a billable ICD-10-CM diagnosis code (S66.419D).
7th characterThe appropriate 7th character is to be added to each code from category S66The appropriate 7th character is to be added to each code from category S66

Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources