S42.399P — Other fracture of shaft of unspecified humerus, subsequent encounter for fracture with malunion
Is S42.399P billable?
Yes, but S42.399P will trip a Medicare edit. S42.399P is a valid, billable ICD-10-CM code for encounters from October 1, 2026 through September 30, 2027. However, CMS lists S42.399P under Medicare Code Editor edit 20, “Unspecified code” — meaning a code specifying laterality (right, left or bilateral) exists in the same family. On an inpatient claim this triggers the edit, because CMS holds that there are very limited circumstances in which laterality cannot be documented.
S42.399P at a glance
| Code | S42.399P |
|---|---|
| Description | Other fracture of shaft of unspecified humerus, subsequent encounter for fracture with malunion |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
| 7th character "P" | subsequent encounter for fracture with malunion |
What does the 7th character "P" mean in S42.399P?
In S42.399P, the 7th character P means subsequent encounter for fracture with malunion. The 7th character is required for S42.399P to be a valid, complete code.
Same condition, different episode of care — switch the 7th character:
- Ainitial encounter for closed fractureS42.399A
- Binitial encounter for open fractureS42.399B
- Dsubsequent encounter for fracture with routine healingS42.399D
- Gsubsequent encounter for fracture with delayed healingS42.399G
- Ksubsequent encounter for fracture with nonunionS42.399K
- Psubsequent encounter for fracture with malunionS42.399P
- SsequelaS42.399S
What Medicare edits apply to S42.399P?
The Medicare Code Editor screens inpatient claims before they are grouped. These edits name S42.399P directly.
A code specifying laterality (right, left or bilateral) exists in the same family. CMS holds that there are very limited circumstances in which laterality cannot be documented.
Which MS-DRGs does S42.399P group to?
S42.399P sits in MDC 08 and helps define the logic of 3 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 564Other Musculoskeletal System and Connective Tissue Diagnoses with MCCmedical
- 565Other Musculoskeletal System and Connective Tissue Diagnoses with CCmedical
- 566Other Musculoskeletal System and Connective Tissue Diagnoses without CC/MCCmedical
As a secondary diagnosis, S42.399P is a complication or comorbidity (CC), which can move a stay into a higher-paying DRG.
How is S42.399P listed in the Alphabetic Index?
The Alphabetic Index lists these routes under S42.39, the nearest indexed parent of S42.399P. Use them to find the family, then select the specific code.
- Fracture, traumatic › humerus › shaft › specified NEC (abduction) (adduction) (separation)
Excludes1 — never code together — inherited from S42
The conditions below can never be reported together with S42.399P on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
- traumatic amputation of shoulder and upper arm (S48.-)
Use additional code — inherited from Chapter 19
Report an additional code alongside S42.399P to fully describe the condition. S42.399P is sequenced first.
- code to identify any retained foreign body, if applicable (Z18.-)
Excludes2 — not included here — inherited from Chapter 19
The conditions below are not part of S42.399P, but a patient may have both at the same time. When documentation supports it, S42.399P and the excluded code may both be reported.
Excludes2 — not included here — inherited from S40-S49
The conditions below are not part of S42.399P, but a patient may have both at the same time. When documentation supports it, S42.399P and the excluded code may both be reported.
Excludes2 — not included here — inherited from S42
The conditions below are not part of S42.399P, but a patient may have both at the same time. When documentation supports it, S42.399P and the excluded code may both be reported.
- periprosthetic fracture around internal prosthetic shoulder joint (M97.3)
Excludes2 — not included here — inherited from S42.3
The conditions below are not part of S42.399P, but a patient may have both at the same time. When documentation supports it, S42.399P and the excluded code may both be reported.
How long has S42.399P existed?
S42.399P has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.