S23.421A (Sprain of chondrosternal joint, initial encounter) compared with S23.421D (Sprain of chondrosternal joint, subsequent encounter), from the official CMS tabular data. S23.421A and S23.421D 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. S23.421A and S23.421D 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.
| S23.421ASprain of chondrosternal joint, initial encounter | S23.421DSprain of chondrosternal joint, subsequent encounter | |
|---|---|---|
| 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 | Sprain of chondrosternal joint, initial encounter is a billable ICD-10-CM diagnosis code (S23.421A). | Sprain of chondrosternal joint, subsequent encounter is a billable ICD-10-CM diagnosis code (S23.421D). |
| 7th character | The appropriate 7th character is to be added to each code from category S23 | The appropriate 7th character is to be added to each code from category S23 |
| Includes | avulsion of joint or ligament of thorax laceration of cartilage, joint or ligament of thorax sprain of cartilage, joint or ligament of thorax traumatic hemarthrosis of joint or ligament of thorax | avulsion of joint or ligament of thorax laceration of cartilage, joint or ligament of thorax sprain of cartilage, joint or ligament of thorax traumatic hemarthrosis of joint or ligament of thorax |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources