S21.359A Open bite of unspecified front wall of thorax with penetration into thoracic cavity, initial encounter

Billable ICD-10-CM code, FY2026.

Built from S21.359 with 7th character A (initial encounter).

Applies from S21 Open wound of thorax

Excludes1 (never code together)

• traumatic amputation (partial) of thorax (S28.1)

Code also

• any associated injury, such as:
• injury of heart (S26.-)
• injury of intrathoracic organs (S27.-)
• rib fracture (S22.3-, S22.4-)
• spinal cord injury (S24.0-, S24.1-)
• traumatic hemopneumothorax (S27.3)
• traumatic hemothorax (S27.1)
• traumatic pneumothorax (S27.0)
• wound infection

7th character note

• The appropriate 7th character is to be added to each code from category S21

7th character required

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

Applies from S21.3 Open wound of front wall of thorax with penetration into thoracic cavity

Applicable to

• Open wound of chest with penetration into thoracic cavity

Applies from S21.35 Open bite of front wall of thorax with penetration into thoracic cavity

Excludes1 (never code together)

• superficial bite of front wall of thorax (S20.37)

Medicare Code Edits (MCE v43.1 (April 2026))

• Unspecified code (laterality): Unspecified codes for which a more specific code identifying laterality (right, left, bilateral) exists within the same code family.

Code annotations containing back-references to S21.359A

Back-references to S21

• Code Also: S23.1 Subluxation and dislocation of thoracic vertebra ("open wound of thorax (S21.-)")
• Code Also: S24 Injury of nerves and spinal cord at thorax level ("open wound of thorax (S21.-)")
• Code Also: S25 Injury of blood vessels of thorax ("any associated open wound (S21.-)")
• Code Also: S26 Injury of heart ("open wound of thorax (S21.-)")
• Code Also: S27 Injury of other and unspecified intrathoracic organs ("any associated open wound of thorax (S21.-)")
• Code Also: S29 Other and unspecified injuries of thorax ("any associated open wound (S21.-)")

Nearby codes

• S21.352 Open bite of left front wall of thorax with penetration into thoracic cavity
• S21.352A Open bite of left front wall of thorax with penetration into thoracic cavity, initial encounter
• S21.352D Open bite of left front wall of thorax with penetration into thoracic cavity, subsequent encounter
• S21.352S Open bite of left front wall of thorax with penetration into thoracic cavity, sequela
• S21.359 Open bite of unspecified front wall of thorax with penetration into thoracic cavity
• S21.359A Open bite of unspecified front wall of thorax with penetration into thoracic cavity, initial encounter (this code)
• S21.359D Open bite of unspecified front wall of thorax with penetration into thoracic cavity, subsequent encounter
• S21.359S Open bite of unspecified front wall of thorax with penetration into thoracic cavity, sequela
• S21.4 Open wound of back wall of thorax with penetration into thoracic cavity
• S21.40 Unspecified open wound of back wall of thorax with penetration into thoracic cavity
• S21.401 Unspecified open wound of right back wall of thorax with penetration into thoracic cavity