2027 ICD-10-CM Diagnosis Code S42.121PDisplaced fracture of acromial process, right shoulder, subsequent encounter for fracture with malunion

ICD-10-CM Codes›S00–T88›S40-S49›S42

ICD-10-CM S42.121P
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

S42.121P is a billable ICD-10-CM diagnosis code for displaced fracture of acromial process, right shoulder, subsequent encounter for fracture with malunion. The 7th character P means subsequent encounter for fracture with malunion. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 564 through 566. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 5,561 closely related codes. The code is exempt from POA reporting. Coders also document this condition as closed fracture of acromial process of right scapula. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Fracture of the upper limb, subsequent encounter.

Code Identity

ICD-10-CM Code
S42.121P
Billable Status
Yes — Valid for Submission
Code Describes
Displaced fracture of acromial process, right shoulder, subsequent encounter for fracture with malunion
Short Description
Disp fx of acromial process, r shldr, subs for fx w malunion
Parent Code
S42.121
Displaced fracture of acromial process, right shoulder

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionS40-S49Injuries to the shoulder and upper arm
CategoryS42Fracture of shoulder and upper arm
This CodeS42.121PDisplaced fracture of acromial process, right shoulder, subsequent encounter for fracture with malunion

Present on Admission (POA)Billing

S42.121P is exempt from POA reporting on inpatient claims to general acute care hospitals. Review the other POA exempt codes in Injuries to the shoulder and upper arm (S40-S49).

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Closed fracture of acromial process of right scapula
  • Closed fracture of acromial process of scapula
  • Closed fracture of right scapula
  • Closed fracture of right shoulder
  • Fracture of acromial process of scapula
  • Open fracture of acromial process of scapula
  • Open fracture of right acromion
  • Open fracture of right scapula

Coding GuidelinesGuidance

The principles of multiple coding of injuries should be followed in coding fractures. Fractures of specified sites are coded individually by site, to the level of detail furnished by medical record content.

A fracture not indicated as open or closed should be coded to closed. A fracture not indicated whether displaced or not displaced should be coded to displaced.

Initial vs. Subsequent Encounter for Fractures

Traumatic fractures are coded using the appropriate 7th character for initial encounter (A, B, C) while the patient is receiving active treatment for the fracture. The appropriate 7th character for initial encounter should also be assigned for a patient who delayed seeking treatment for the fracture or nonunion.

Fractures are coded using the appropriate 7th character for subsequent care for encounters after the patient has completed active treatment of the fracture and is receiving routine care for the fracture during the healing or recovery phase.

Care for complications of surgical treatment for fracture repairs during the healing or recovery phase should be coded with the appropriate complication codes.

Care of complications of fractures, such as malunion and nonunion, should be reported with the appropriate 7th character for subsequent care with nonunion (K, M, N) or subsequent care with malunion (P, Q, R).

The open fracture designations in the assignment of the 7th character for fractures of the forearm, femur and lower leg, including ankle are based on the Gustilo open fracture classification. When the Gustilo classification type is not specified for an open fracture, the 7th character for open fracture type I or II should be assigned (B, E, H, M, Q).

Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027, published by CMS and the National Center for Health Statistics.

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to S42.121P: its own notes plus those printed at S42, block S40-S49, and Chapter 19. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From Block S40-S49 Injuries to the shoulder and upper arm applies to 2,730 codes
  • injuries of axilla
  • injuries of scapular region

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From S42 Fracture of shoulder and upper arm applies to 1,398 codes
  • traumatic amputation of shoulder and upper arm (S48.-)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From S42 Fracture of shoulder and upper arm applies to 1,398 codes
  • periprosthetic fracture around internal prosthetic shoulder joint (M97.3)
From Block S40-S49 Injuries to the shoulder and upper arm applies to 2,730 codes
From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • code to identify any retained foreign body, if applicable (Z18.-)

Notes

General instructions on how these codes are used.

From S42 Fracture of shoulder and upper arm applies to 1,398 codes
  • A fracture not indicated as displaced or nondisplaced should be coded to displaced
  • A fracture not indicated as open or closed should be coded to closed
From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
  • The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.

7th Character

Every code in the category takes a 7th character from the listed values, with the placeholder X filling any empty positions before it.

From S42 Fracture of shoulder and upper arm applies to 1,398 codes
  • The appropriate 7th character is to be added to all codes from category S42
Values for category S42 Open or Closed Fracture Encounter
  • Ainitial encounter for closed fracture
  • Binitial encounter for open fracture
  • Dsubsequent encounter for fracture with routine healing
  • Gsubsequent encounter for fracture with delayed healing
  • Ksubsequent encounter for fracture with nonunion
  • Psubsequent encounter for fracture with malunion this code
  • Ssequela

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name S42.121P, its category, or a range that includes it.

Excludes1 2

These codes carry an Excludes1 note naming S42.121P: they are not reported together with it, unless the two conditions are unrelated.

  • M84.3 Stress fracture
    traumatic fracture (S12.-, S22.-, S32.-, S42.-, S52.-, S62.-, S72.-, S82.-, S92.-) names S42.-, which includes this code
  • M84.4 Pathological fracture, not elsewhere classified
    traumatic fracture (S12.-, S22.-, S32.-, S42.-, S52.-, S62.-, S72.-, S82.-, S92.-) names S42.-, which includes this code

Excludes2 2

These codes carry an Excludes2 note naming S42.121P: its condition is not part of those codes, and both may be reported when the patient has both.

  • S22 Fracture of rib(s), sternum and thoracic spine
    fracture of scapula (S42.1-) names S42.1-, which includes this code
  • S41 Open wound of shoulder and upper arm
    open fracture of shoulder and upper arm (S42.- with 7th character B or C) names S42.-, which includes this code

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INJ041
Fracture of the upper limb, subsequent encounter
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Fractures

A fracture is a break in a bone. Fractures are usually caused by injuries. Since they can sometimes be serious, it's important to get medical care right away if you think you have a fracture.

The full article covers:

  • What is a fracture?
  • What are the different types of fractures?
  • What causes fractures?
  • What are the symptoms of a fracture?
  • How are fractures diagnosed?
  • What are the treatments for fractures?
  • Can fractures be prevented?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert S42.121P to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
733.81 Malunion of fracture
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About S42.121POverview

Is S42.121P (Displaced fracture of acromial process, right shoulder) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report displaced fracture of acromial process, right shoulder, subsequent encounter for fracture with malunion on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What does the 7th character P in S42.121P mean?

The final character P reports a subsequent encounter where the displaced fracture of acromial process, right shoulder has healed in a faulty position, called a malunion. In this category the CMS Tabular List defines P as "subsequent encounter for fracture with malunion".

What MS-DRG does S42.121P group to?

When displaced fracture of acromial process, right shoulder, subsequent encounter for fracture with malunion is the principal diagnosis on an inpatient stay, it groups to MS-DRG 564, 566, 565, with relative weights from 0.7374 to 1.4909 depending on complications. Higher weights mean higher Medicare reimbursement.

Is S42.121P a CC or MCC?

CMS lists S42.121P as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 5,561 closely related codes in its exclusion list.

Is S42.121P exempt from POA reporting?

Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for displaced fracture of acromial process, right shoulder, subsequent encounter for fracture with malunion on inpatient claims. The code appears in the Injuries to the shoulder and upper arm (S40-S49) range of the CMS exempt list.