T79.A21A (Traumatic compartment syndrome of right lower extremity, initial encounter) compared with T79.A21S (Traumatic compartment syndrome of right lower extremity, sequela), from the official CMS tabular data. T79.A21A and T79.A21S code the same injury at a different phase of treatment.
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
Same injury, other encounter phase. T79.A21A and T79.A21S 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.
| T79.A21ATraumatic compartment syndrome of right lower extremity, initial encounter | T79.A21STraumatic compartment syndrome of right lower extremity, sequela | |
|---|---|---|
| Billing status | Billable | Billable |
| Classification | S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88) | S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88) |
| Definition | Traumatic compartment syndrome of right lower extremity, initial encounter is a billable ICD-10-CM diagnosis code (T79.A21A). | Traumatic compartment syndrome of right lower extremity, sequela is a billable ICD-10-CM diagnosis code (T79.A21S). |
| 7th character | The appropriate 7th character is to be added to each code from category T79 | The appropriate 7th character is to be added to each code from category T79 |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources