2026 ICD-10-CM Diagnosis Code S21.109DUnspecified open wound of unspecified front wall of thorax without penetration into thoracic cavity, subsequent encounter

ICD-10-CM Codes›S00–T88›S20-S29›S21

ICD-10-CM S21.109D
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

S21.109D is a billable ICD-10-CM diagnosis code for unspecified open wound of unspecified front wall of thorax without penetration into thoracic cavity, subsequent encounter. The 7th character D marks it as a subsequent encounter code, used during routine care in the healing or recovery phase. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 949 through 950. The code is exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Open wounds of trunk, subsequent encounter.

Code Identity

ICD-10-CM Code
S21.109D
Billable Status
Yes — Valid for Submission
Code Describes
Unspecified open wound of unspecified front wall of thorax without penetration into thoracic cavity, subsequent encounter
Short Description
Unsp opn wnd unsp frnt wall of thrx w/o penet thor cav, subs
Parent Code
S21.109
Unspecified open wound of unspecified front wall of thorax without penetration into thoracic cavity

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionS20-S29Injuries to the thorax
CategoryS21Open wound of thorax
This CodeS21.109DUnspecified open wound of unspecified front wall of thorax without penetration into thoracic cavity, subsequent encounter

Present on Admission (POA)Billing

S21.109D is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Cut of chest
  • Open division, chondrocostal joint ligament
  • Open division, chondrosternal ligament
  • Open division, rib ligament
  • Open division, sternal ligament
  • Open division, xiphoid cartilage ligament
  • Open fracture dislocation of sternum
  • Open fracture of sternum
  • Open fracture subluxation of sternum
  • Open traumatic dislocation of sternum
  • Open traumatic subluxation of sternum
  • Open wound of chest wall
  • Open wound of front wall of thorax
  • Sucking chest wound
  • Wound of sternal region

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Open wound of thorax (S21). Use the following options for the applicable episode of care:

  • A - initial encounter
  • D - subsequent encounter
  • S - sequela

Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026, published by CMS and the National Center for Health Statistics.

Clinical ClassificationClinical

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

CCSR INJ050
Open wounds of trunk, subsequent encounter
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Chest Injuries and Disorders

The chest is the part of your body between your neck and your abdomen (belly). The medical term for your chest is thorax.

The full article covers:

  • What is the chest?
  • What are chest injuries and disorders?
  • How are chest injuries and disorders diagnosed?

Read the full article at MedlinePlus

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

Convert S21.109D to ICD-9-CMHistory

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

ICD-9-CM
V58.89 Other specfied aftercare
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 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About S21.109DOverview

Is S21.109D a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report unspecified open wound of unspecified front wall of thorax without penetration into thoracic cavity, subsequent encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character D in S21.109D mean?

The final character D marks a subsequent encounter: use it for routine care while the unspecified open wound of unspecified front wall of thorax without penetration into thoracic cavity is healing, after active treatment has ended.

What MS-DRG does S21.109D group to?

When unspecified open wound of unspecified front wall of thorax without penetration into thoracic cavity, subsequent encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 949, 950, with relative weights from 0.6277 to 1.1897 depending on complications. Higher weights mean higher Medicare reimbursement.

Is S21.109D 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 unspecified open wound of unspecified front wall of thorax without penetration into thoracic cavity, subsequent encounter on inpatient claims.

What is the ICD-9 equivalent of S21.109D?

Under the General Equivalence Mappings, unspecified open wound of unspecified front wall of thorax without penetration into thoracic cavity, subsequent encounter converts to ICD-9-CM V58.89 (other specfied aftercare). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.