S29.021A ICD-10-CM Code: Laceration of muscle and tendon of front wall of thorax, initial encounter

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for S29.021A in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Notes without a marker are published on S29.021A itself; “inherited from” names the category or block whose note applies here.

7th Character Guide

"The appropriate 7th character is to be added to each code from category S29"

• A — initial encounter (this page’s code)
• D — subsequent encounter
• S — sequela

How the encounter character is assigned. “Initial encounter” means the patient is receiving active treatment for the condition — it is not limited to the first visit, and a different or new provider giving active treatment still assigns it. “Subsequent encounter” covers care during the healing or recovery phase after active treatment. “Sequela” is for complications or conditions that arise as a direct result of the original condition.

ICD-10-CM Official Guidelines for Coding and Reporting, Section I.C.19.a (paraphrased by MedCoder).

Variant codes in this family

S29.021A, S29.021D, S29.021S

Character meanings are CMS's official 7th-character extensions for this family, as carried in each variant code's official description; variant codes are registry rows. The explanation of how the encounter character is assigned is MedCoder editorial, distinct from the official content above it.

Coder workflow for S29.021A

MedCoder structured workflow — derived from this code’s own official record

Before you code S29.021A

1. A 7th character is required in this family. Confirm the documented encounter: initial (active treatment), subsequent (healing or recovery phase), or sequela. This page’s code carries “A”. “Initial” means active treatment, not the first visit (Guidelines I.C.19.a).

   See the 7th Character Guide · Guide: 7th characters: initial, subsequent, sequela →

2. Confirm the injury type, the anatomical site at the most specific level documented, laterality where the family codes it, and the encounter for the 7th character. Each injury is coded separately unless the classification provides a combination code, and a superficial injury is not coded when a more severe injury of the same site is documented. Injury chapter guidelines (Guidelines I.C.19.b, I.C.19.b.1).

   Guide: 7th characters: initial, subsequent, sequela →

Choose the right path

1. Is the encounter phase documented — active treatment, healing or recovery, or a sequela?
   Yes → Assign the matching 7th character; the variant codes are in the 7th Character Guide.
   No → The code is invalid without its 7th character — query for the missing element.

Consider S29.021A. Then review the Code Also note, and confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement

Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).

Anatomical site

At the most specific level the record states; a site the classification separates cannot be assumed from a procedure or a measurement.

Encounter type

Active treatment, healing or recovery phase, or sequela — the basis of the 7th character (Guidelines I.C.19.a).

External cause, place and activity

For the external cause codes reported with the injury or poisoning, where documented (Guidelines I.C.20.a).

Official instructions as workflow

• Excludes2 — not part of S29.021A(11 notes)

  Coding workflow: The conditions named in this note are not included in S29.021A. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

  CompareT17.5, T18.1, T17.8, T17.4, T63.4

  See the official tabular notes · Guidelines I.A.12.b

• Code Also — related condition(1 note)

  Coding workflow: Review the related condition when both are documented and the instruction applies. A Code Also note does not fix sequencing; the order follows the circumstances of the encounter.

  ReviewS21

  See the official tabular notes · Guidelines I.A.17

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Indexed Clinical Terms (1)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

• Injury, muscle (and fascia) (and tendon), thorax (level), laceration, front wall

Don’t confuse S29.021A with…

MedCoder analysis — pairs from this code’s official notes, distinctions written by MedCoder

The codes most likely to be picked instead of S29.021A — named in its own official notes, or sharing its laterality or encounter family — with what separates them and which documentation moves the case. Each links to the full comparison.

• S29.021D— Encounter relationship (Review)

  Same underlying diagnosis, different encounter phase.

  The same diagnosis at a different phase of care; one encounter takes one 7th character.

  What moves you there: Documentation of a subsequent encounter moves the case to S29.021D.

  Full comparison: S29.021A vs S29.021D →

• S29.021S— Encounter relationship (Review)

  Same underlying diagnosis, different encounter phase.

  The same diagnosis at a different phase of care; one encounter takes one 7th character.

  What moves you there: Documentation of a sequela moves the case to S29.021S.

  Full comparison: S29.021A vs S29.021S →

• T20— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of burns and corrosions adds T20; it is not part of this code and both may be reported when both are documented.

  Full comparison: S29.021A vs T20 →

• T32— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of burns and corrosions adds T32; it is not part of this code and both may be reported when both are documented.

  Full comparison: S29.021A vs T32 →

• T17.5— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of effects of foreign body in bronchus adds T17.5; it is not part of this code and both may be reported when both are documented.

  Full comparison: S29.021A vs T17.5 →

• T18.1— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of effects of foreign body in esophagus adds T18.1; it is not part of this code and both may be reported when both are documented.

  Full comparison: S29.021A vs T18.1 →

Relationships are read from this code's own official notes, its laterality siblings and its encounter family; the wording of each distinction is MedCoder editorial, and the documentation named in each “what moves you there” line is the official note phrase or sibling title itself. Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a.

Decision Points

The directives on this code's own record, as a pre-claim checklist.

1. A 7th character applies in this family. Confirm the documented encounter matches the character assigned. See the official 7th-character definitions and this code’s variants
2. 1 Code Also note — a second code may apply; the guidelines leave its sequencing to the circumstances of the encounter. See the Code Also notes
3. 11 Excludes2 entries — those conditions are not part of this code and may be reported additionally when documented. See the Excludes2 notes

Checklist rows are derived from this code's own official directives; the wording of each check is MedCoder editorial. The official notes themselves are in the sections each row links to.

Verify Before Coding

• CC as a secondary diagnosis (FY2026). Can raise the stay's MS-DRG severity tier.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

MS-DRG Grouper Relationships (FY2026)

Potential MS-DRG participation — not a DRG assignment.

FY2026 MS-DRG: CC — Complication or Comorbidity. Reported as a secondary diagnosis, this code raises the stay's MS-DRG severity tier — except when the principal diagnosis is one of 95 clinically related codes on its CMS exclusion list.

Named in the grouper logic of 5 MS-DRGs: DRG 604 (MDC 09), DRG 605 (MDC 09), DRG 963 (MDC 24), DRG 964 (MDC 24), DRG 965 (MDC 24).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):INJ013 — Open wounds of trunk, initial encounter (default).

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same clinical process (MS-DRG)

Acts as CC — raises the severity of other admissions. CMS groups these diagnoses into one MS-DRG principal-diagnosis exclusion process — a CC/MCC on this list never raises severity when the principal diagnosis is also on it.

S27.59XA — Other injury of thoracic trachea, initial encounter, S27.60XA — Unspecified injury of pleura, initial encounter, S27.63XA — Laceration of pleura, initial encounter, S27.69XA — Other injury of pleura, initial encounter, S27.892A — Contusion of other specified intrathoracic organs, initial encounter, S27.893A — Laceration of other specified intrathoracic organs, initial encounter, S27.898A — Other injury of other specified intrathoracic organs, initial encounter, S27.899A — Unspecified injury of other specified intrathoracic organs, initial encounter, S27.9XXA — Injury of unspecified intrathoracic organ, initial encounter, S28.1XXA — Traumatic amputation (partial) of part of thorax, except breast, initial encounter, S29.029A — Laceration of muscle and tendon of unspecified wall of thorax, initial encounter, S38.3XXA — Transection (partial) of abdomen, initial encounter, T07.XXXA — Unspecified multiple injuries, initial encounter, T14.8XXA — Other injury of unspecified body region, initial encounter, T14.90XA — Injury, unspecified, initial encounter, T14.91XA — Suicide attempt, initial encounter, T79.7XXA — Traumatic subcutaneous emphysema, initial encounter, T79.8XXA — Other early complications of trauma, initial encounter, T79.9XXA — Unspecified early complication of trauma, initial encounter, T79.A0XA — Compartment syndrome, unspecified, initial encounter, +74 more

Same injury, other encounter phase

Same injury, coded at a different phase of treatment via the 7th character.

S29.021D — Laceration of muscle and tendon of front wall of thorax, subsequent encounterCompare S29.021A vs S29.021D →, S29.021S — Laceration of muscle and tendon of front wall of thorax, sequelaCompare S29.021A vs S29.021S →

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Open wounds of trunk, initial encounter).

S21.449A — Puncture wound with foreign body of unspecified back wall of thorax with penetration into thoracic cavity, initial encounter, S21.451A — Open bite of right back wall of thorax with penetration into thoracic cavity, initial encounter, S21.452A — Open bite of left back wall of thorax with penetration into thoracic cavity, initial encounter, S21.459A — Open bite of unspecified back wall of thorax with penetration into thoracic cavity, initial encounter, S21.90XA — Unspecified open wound of unspecified part of thorax, initial encounter, S21.91XA — Laceration without foreign body of unspecified part of thorax, initial encounter, S21.92XA — Laceration with foreign body of unspecified part of thorax, initial encounter, S21.93XA — Puncture wound without foreign body of unspecified part of thorax, initial encounter, S21.94XA — Puncture wound with foreign body of unspecified part of thorax, initial encounter, S21.95XA — Open bite of unspecified part of thorax, initial encounter, S29.022A — Laceration of muscle and tendon of back wall of thorax, initial encounter, S29.029A — Laceration of muscle and tendon of unspecified wall of thorax, initial encounter, S31.000A — Unspecified open wound of lower back and pelvis without penetration into retroperitoneum, initial encounter, S31.001A — Unspecified open wound of lower back and pelvis with penetration into retroperitoneum, initial encounter, S31.010A — Laceration without foreign body of lower back and pelvis without penetration into retroperitoneum, initial encounter, S31.011A — Laceration without foreign body of lower back and pelvis with penetration into retroperitoneum, initial encounter, S31.020A — Laceration with foreign body of lower back and pelvis without penetration into retroperitoneum, initial encounter, S31.021A — Laceration with foreign body of lower back and pelvis with penetration into retroperitoneum, initial encounter, S31.030A — Puncture wound without foreign body of lower back and pelvis without penetration into retroperitoneum, initial encounter, S31.031A — Puncture wound without foreign body of lower back and pelvis with penetration into retroperitoneum, initial encounter, +267 more

Contextual Map

Every relationship of S29.021A in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Hierarchy

• S00-T88 — Chapter 19: Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88) (S00-T88)[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S20-S29 — Injuries to the thorax[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

Clinical classification (CCSR)

• INJ013 — Open wounds of trunk, initial encounter[CCSR]— AHRQ CCSR for ICD-10-CM Diagnoses (HCUP)

MS-DRG Grouper

• CC — Complication or Comorbidity [MS-DRG severity]: “As a secondary diagnosis this code can raise the stay's MS-DRG severity tier (CC).”— CMS MS-DRG Definitions Manual (Appendix C) · FY2026
• DRG 604 — TRAUMA TO THE SKIN, SUBCUTANEOUS TISSUE AND BREAST WITH MCC[MS-DRG]: “TRAUMA TO THE SKIN, SUBCUTANEOUS TISSUE AND BREAST WITH MCC (MDC 09)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026
• DRG 605 — TRAUMA TO THE SKIN, SUBCUTANEOUS TISSUE AND BREAST WITHOUT MCC[MS-DRG]: “TRAUMA TO THE SKIN, SUBCUTANEOUS TISSUE AND BREAST WITHOUT MCC (MDC 09)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026
• DRG 963 — OTHER MULTIPLE SIGNIFICANT TRAUMA WITH MCC[MS-DRG]: “OTHER MULTIPLE SIGNIFICANT TRAUMA WITH MCC (MDC 24)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026
• DRG 964 — OTHER MULTIPLE SIGNIFICANT TRAUMA WITH CC[MS-DRG]: “OTHER MULTIPLE SIGNIFICANT TRAUMA WITH CC (MDC 24)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026
• DRG 965 — OTHER MULTIPLE SIGNIFICANT TRAUMA WITHOUT CC/MCC[MS-DRG]: “OTHER MULTIPLE SIGNIFICANT TRAUMA WITHOUT CC/MCC (MDC 24)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026

MDC crossing

• MDC 09 — Diseases and Disorders of the Skin, Subcutaneous Tissue and Breast[MDC crossing]: “Diseases and Disorders of the Skin, Subcutaneous Tissue and Breast — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 7,376 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026
• MDC 24 — Multiple Significant Trauma[MDC crossing]: “Multiple Significant Trauma — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 22,957 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026

Index entries

• Injury, muscle (and fascia) (and tendon), thorax (level), laceration, front wall[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026

Nearest codes (40)

• S29 — Other and unspecified injuries of thorax[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S29.002S — Unspecified injury of muscle and tendon of back wall of thorax, sequela[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S29.009 — Unspecified injury of muscle and tendon of unspecified wall of thorax[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S29.009A — Unspecified injury of muscle and tendon of unspecified wall of thorax, initial encounter[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S29.009D — Unspecified injury of muscle and tendon of unspecified wall of thorax, subsequent encounter[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S29.009S — Unspecified injury of muscle and tendon of unspecified wall of thorax, sequela[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S29.01 — Strain of muscle and tendon of thorax[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S29.011 — Strain of muscle and tendon of front wall of thorax[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• and 32 more

Change history

• FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Common coding questions

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data

CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page

Claim edits Official source data

CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page

Inpatient payment groups Official source data

CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v43 Release, file and checksum · Publisher’s page

Change history and date-of-service validity Official source data

CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page

Comparisons, relationships and the contextual map MedCoder structured relationship

Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears

Summary and FAQ answers MedCoder explanation

Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Nearest Codes in This Family

Official ICD-10-CM classifications closest to S29.021A in its code family, with their registry titles.

• S29.019A — Strain of muscle and tendon of unspecified wall of thorax, initial encounter
• S29.019D — Strain of muscle and tendon of unspecified wall of thorax, subsequent encounter
• S29.019S — Strain of muscle and tendon of unspecified wall of thorax, sequela
• S29.02 — Laceration of muscle and tendon of thorax
• S29.021 — Laceration of muscle and tendon of front wall of thorax
• S29.021D — Laceration of muscle and tendon of front wall of thorax, subsequent encounter
• S29.021S — Laceration of muscle and tendon of front wall of thorax, sequela
• S29.022 — Laceration of muscle and tendon of back wall of thorax
• S29.022A — Laceration of muscle and tendon of back wall of thorax, initial encounter
• S29.022D — Laceration of muscle and tendon of back wall of thorax, subsequent encounter

View all codes in the S29 family