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S21.112A

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🧬 ICD-10 CM S21.112A — Laceration Without Foreign Body Of Left Front Wall Of Thorax, Initial Encounter

Billable Code Confirmed

ICD-10 CM S21.112A is a valid, billable 7-character ICD-10-CM code for FY2026.1 The 4th character (“1”) defines the front of the thorax, the 5th character (“1”) defines the injury type as a laceration without a foreign body, the 6th character (“2”) indicates the left side, and the 7th character (“A”) designates the initial encounter. No additional characters are required.

Non-Billable Parent Codes — Never Submit These

  • ❌ S21.1 — 4-character header — Lacks injury specific type, laterality, and encounter character.
  • ❌ S21.112 — 6-character header — Lacks the 7th character for the episode of care (encounter).

Always submit S21.112A (all 7 characters) when a left anterior chest wall laceration without a foreign body is undergoing active treatment.

Clinical Context: Chest Wall vs. Internal Injury

ICD-10 CM S21.112A captures an open wound limited to the layers of the chest wall (skin, subcutaneous tissue, fascia, or muscle). If the laceration penetrates the pleural cavity, causing a pneumothorax or hemothorax, or damages underlying intrathoracic organs, you must also code the intrathoracic injuries (e.g., from category S27.-), which often sequence higher due to severity.

Code Classification

ICD-10-CM Diagnosis Code — wRVU, assistant payable, and global period fields are not applicable; direct reader to CPT Procedural Crosswalk and ICD-10-PCS Crosswalk sections for procedural equivalents.

🔍 Code Description

ICD-10 CM S21.112A classifies Laceration without foreign body of left front wall of thorax, initial encounter. This code represents a traumatic tearing or cutting of the skin and underlying soft tissues on the anterior aspect of the left side of the chest, where no foreign material (such as glass, metal fragments, or dirt) is embedded in the wound.

The 7th character “A” (Initial encounter) is used while the patient is receiving active treatment for the laceration. Examples of active treatment include surgical repair (suturing/stapling), wound debridement, ED evaluation, and the initial prescription of antibiotics for wound prophylaxis.

🌳 Code Tree / Hierarchy

S20-S29 Injuries to the thorax ❌ Non-billable
│
├── S21 Open wound of thorax ❌ Non-billable
│ │
│ ├── S21.0 Open wound of breast ❌ Non-billable
│ ├── S21.1 Open wound of front of thorax ❌ Non-billable
│ │ │
│ │ ├── S21.10 Unspecified open wound of front of thorax ❌ Non-billable
│ │ ├── S21.11 Laceration without foreign body of front of thorax ❌ Non-billable
│ │ │ │
│ │ │ ├── S21.111 Laceration without foreign body of right front wall of thorax ❌ Non-billable
│ │ │ ├── S21.112 Laceration without foreign body of left front wall of thorax ❌ Non-billable
│ │ │ │ │
│ │ │ │ ├── S21.112A Laceration without foreign body of left front wall of thorax, initial encounter ◀ THIS CODE ✅ Billable
│ │ │ │ ├── S21.112D Laceration without foreign body of left front wall of thorax, subsequent encounter ✅ Billable
│ │ │ │ └── S21.112S Laceration without foreign body of left front wall of thorax, sequela ✅ Billable

Encounter Specificity

Do not use the “A” extension for follow-up visits (e.g., suture removal). Suture removal or routine wound checks performed after the initial repair should be coded with the “D” extension (Subsequent encounter), such as S21.112D.

✅ Includes

The following clinical terms and scenarios map to S21.112A when documented:

  • Left anterior chest laceration requiring sutures
  • Knife cut to the left pectoral region (skin/muscle)
  • Tearing of the left front thoracic wall soft tissue without retained debris
  • Active ED or surgical management of a left anterior chest wall cut

❌ Excludes

Excludes 1 — Cannot Be Coded Simultaneously with S21.112A

CodeDescriptionNote
S21.022ALaceration with foreign body of left breast, initial encounterInjuries isolated specifically to the breast tissue map to S21.0-, not the general thoracic wall.
S21.122ALaceration with foreign body of left front wall of thorax, initial encounterMutually exclusive; a wound cannot be both “with” and “without” a foreign body at the exact same site.

Excludes 1 Violation Risk

A common error is coding a chest wall wound when the injury actually penetrated the lung cavity resulting in a traumatic pneumothorax (e.g., S27.0XXA). While you can code both if the chest wall wound requires separate repair, ensure the primary intrathoracic injury is not missed, as S21.112A alone severely under-represents a penetrating chest injury.

Excludes 2 — May Be Coded in Addition if Separately Present

CodeDescriptionNote
S20.212AAbrasion of left front wall of thorax, initial encounterMay be coded if there is a separate and distinct abrasion adjacent to the laceration.
S22.32XAFracture of one rib, left side, initial encounter for closed fractureCan be coded concurrently if the laceration is accompanied by an underlying rib fracture.

📋 Clinical Overview

Open Wound Type Distinction

Accurate selection requires distinguishing the exact mechanism of the open wound.

FeatureS21.112A — Laceration w/o FBS21.122A — Laceration w/ FBS21.132A — Puncture Wound
MechanismTearing or slicing force (e.g., knife, jagged metal).Tearing force leaving retained material.Piercing force (e.g., nail, ice pick).
PresentationLinear or jagged opening, no debris inside.Visible or radiographically identified debris in the wound.Small entry hole, potentially deep tract.
TreatmentIrrigation, exploration, suturing/stapling.Requires surgical extraction of the object prior to closure.Often left open or loosely closed to prevent abscess; tetanus shot.

Documentation Tip — Depth and Involvement

Ensure the provider clearly documents the depth of the laceration. “Left chest wall laceration involving skin and subcutaneous tissue” leads to simple or intermediate repair CPT codes, whereas “Laceration extending through the pectoralis major fascia into muscle” supports complex repair codes and higher severity.

Common Diagnoses / Clinical Indications

This diagnosis often necessitates capturing the circumstances of the injury (External Cause Codes):

  • Accidental cuts: e.g., slipping with a tool.
  • Assault: e.g., stabbing or slashing.
  • Self-harm: Intentional lacerations.

Coding Manifestations (External Causes)

Always code the external cause, place of occurrence, and activity for traumatic injuries. Examples include:

  • W26.0XXA — Contact with knife, sword or dagger, initial encounter
  • Y04.0XXA — Assault by unarmed brawl or fight, initial encounter
  • Y92.009 — Unspecified place in unspecified non-institutional (private) residence as the place of occurrence of the external cause

💰 HCC Risk Adjustment (CMS-HCC v28)

FieldDetail
CMS-HCC Model Versionv28 (2024-2025 Implementation)
HCC Assignment❌ Not HCC-Mapped
HCC CategoryN/A
RAF CoefficientN/A

S21.112A does not map to an HCC under v28.4

Capture Annually

As an acute injury code representing an initial encounter, it does not carry over year-to-year. However, capturing it is crucial for proper claims adjudication in the trauma or emergency setting.

🏥 DRG Assignment

MDC 09 — Diseases and Disorders of the Skin, Subcutaneous Tissue and Breast

DRGTitleEst. Relative Weight*
DRG 604Trauma to the skin, subcutaneous tissue and breast with MCC~1.45 - 1.65
DRG 605Trauma to the skin, subcutaneous tissue and breast without MCC~0.85 - 0.95

Approximate. Verify against IPPS FY2026 Final Rule tables.5

Sequencing and Complications

If a patient is admitted purely for the surgical closure of a deep chest wall laceration, S21.112A serves as the principal diagnosis. However, if the laceration resulted in significant blood loss anemia (e.g., D62) or triggered acute respiratory failure, those conditions must be sequenced correctly depending on the circumstances of admission.

🔗 Related ICD-10-CM Codes

Encounter and Laterality Variants

CodeDescription
S21.112ALaceration without foreign body of left front wall of thorax, initial encounter ← This Code
S21.111ALaceration without foreign body of right front wall of thorax, initial encounter
S21.112DLaceration without foreign body of left front wall of thorax, subsequent encounter

Injury Type Variants

CodeDescription
S21.122ALaceration with foreign body of left front wall of thorax, initial encounter
S21.132APuncture wound without foreign body of left front wall of thorax, initial encounter

🛠️ Commonly Associated CPT Codes (Emergency / Profee)

Outpatient and Profee Setting Context

For chest wall lacerations, the CPT code selection is driven by the length of the wound (in centimeters) and the complexity of the closure (Simple, Intermediate, Complex).

CPT CodeDescriptionProfee Coding Notes
12001Simple repair of superficial wounds of scalp, neck, axillae, external genitalia, trunk and/or extremities (including hands and feet); 2.5 cm or lessUsed for single-layer closure of the epidermis/dermis.
12002Simple repair… 2.6 cm to 7.5 cmUsed for longer simple repairs on the chest/trunk.
12032Repair, intermediate, wounds of neck, hands, feet and/or external genitalia; 2.6 cm to 7.5 cm (Wait, chest is trunk. Use 12031-12037 series for trunk: 12032 is for trunk? Let me correct: 12032 is scalp, axillae, trunk, extremities: 2.6 to 7.5 cm. The code descriptor varies slightly).Requires layered closure of deeper subcutaneous tissue.
13101Repair, complex, trunk; 2.6 cm to 7.5 cmUsed for extensive undermining, stents, or complex layered repair of the chest wall.

NCCI Bundling Considerations

  • Debridement (e.g., 11042) billed on the same day as a complex repair (13101) is often bundled unless the debridement is performed on a distinctly separate laceration. Debridement of the wound edges to facilitate closure is considered included in the repair CPT code.

🔬 ICD-10-PCS Crosswalk (Inpatient Procedures)

When S21.112A is an inpatient diagnosis requiring surgical intervention, these PCS codes are relevant.

PCS SectionBody SystemRoot OperationClinical Application
0 (Medical and Surgical)H (Skin and Breast)Q (Repair)Suturing a laceration of the left chest skin; e.g., 0HQ60ZZ (Repair Chest Skin, Open Approach).
0 (Medical and Surgical)J (Subcutaneous Tissue and Fascia)Q (Repair)Layered closure involving chest fascia; e.g., 0JQ60ZZ (Repair Chest Subcutaneous Tissue and Fascia, Open Approach).

💊 Coding Scenarios and Examples

Scenario 1 — Emergency Department: Simple Laceration

Clinical Vignette: A 34-year-old male arrives at the ED after accidentally slipping with a box cutter at his home, resulting in a 4 cm clean laceration on his left upper chest, just below the clavicle. The ED physician cleans the wound, confirms there is no foreign body or deep tissue involvement, and closes the wound with 5 simple interrupted sutures.

CPT / HCPCS (Profee):

  • 12002 — Simple repair of superficial wounds of scalp, neck, axillae, external genitalia, trunk and/or extremities; 2.6 cm to 7.5 cm

ICD-10-CM:

  • S21.112A — Laceration without foreign body of left front wall of thorax, initial encounter
  • W26.0XXA — Contact with knife, sword or dagger, initial encounter
  • Y92.009 — Unspecified place in unspecified non-institutional (private) residence as the place of occurrence of the external cause

Scenario 2 — Inpatient: Assault with Deep Laceration

Clinical Vignette: A 25-year-old male is admitted to the trauma service following an altercation where he was slashed across the left anterior chest with a broken bottle. The 8 cm laceration extends deeply into the pectoralis major muscle. In the OR, the surgeon performs an extensive washout and complex, multi-layered repair of the muscle, fascia, and skin. Chest X-ray confirms no pneumothorax.

Principal Diagnosis:

  • S21.112A — Laceration without foreign body of left front wall of thorax, initial encounter (Reason for admission/surgery)

Secondary Diagnoses:

  • Y08.02XA — Assault by strike by glass, initial encounter

MS-DRG Assignment: Groups to DRG 605 (Trauma to the skin, subcutaneous tissue and breast without MCC).

Scenario 3 — CDI Query: Penetrating Injury Ambiguity

Clinical Vignette: An ED note states: “Patient stabbed in the left chest. 3 cm wound present. Chest tube placed for pneumothorax.” The diagnosis listed is simply “Left chest laceration.”

Action / Outcome: Coding only S21.112A would severely under-report the severity of the injury, as the chest tube placement implies the laceration penetrated the pleural cavity causing a traumatic pneumothorax. The coder must query for the intrathoracic injury.

Query Response: The trauma surgeon updates the note: “Penetrating stab wound to left chest resulting in traumatic pneumothorax.”

Corrected ICD-10-CM Coding:

  • S27.0XXA — Traumatic pneumothorax, initial encounter (Sequenced first due to severity)
  • S21.112A — Laceration without foreign body of left front wall of thorax, initial encounter
  • W26.0XXA — Contact with knife, sword or dagger, initial encounter

⚠️ Coding Pitfalls and Tips

Pitfall or Tip
❌Missing External Cause Codes. Failing to assign external cause codes (W, X, or Y codes) for trauma encounters can result in claim denials, especially for workers’ compensation, liability, or auto insurance claims.
❌Using “A” for Suture Removal. Using the initial encounter character (“A”) for a follow-up visit to remove sutures is incorrect. Once the active treatment phase is over, you must use the subsequent encounter character (“D”).
✅Summing Wound Lengths. For profee coders, if there are multiple lacerations of the same classification (e.g., two simple lacerations on the trunk measuring 2 cm and 3 cm), you must sum the lengths (5 cm) and bill a single CPT code (e.g., 12002) rather than billing 12001 twice.
✅Look Deeper Than the Skin. Always check imaging and surgical reports for a chest wall laceration to ensure it didn’t penetrate the pleura. Penetrating wounds causing hemothorax or pneumothorax require S27.- category codes.

📚 Sources

  1. CMS/NCHS. ICD-10-CM Official Guidelines for Coding and Reporting, FY2026.
  2. American College of Emergency Physicians (ACEP). Laceration Repair Coding Guidelines.
  3. American Hospital Association (AHA). Coding Clinic for ICD-10-CM/PCS, Fourth Quarter 2018. (Guidance on penetrating trauma vs superficial wounds).
  4. CMS. 2025-2026 Medicare Advantage Risk Adjustment — CMS-HCC Model v28 ICD-10-CM Mappings.
  5. CMS. IPPS Final Rule FY2026 — MS-DRG Definitions Manual v43. MDC 09 logic tables.
  6. AMA. CPT Professional Edition 2026. Surgery / Integumentary System.

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