ICD-10-CM > S00-T88 > S20-S29 > S21 > S21.4 > S21.40 S21.40 Unspecified open wound of back wall of thorax with penetration into thoracic cavity Non-Billable/Non-Specific Codes S21.401Unspecified open wound of right back wall of thorax with penetration into thoracic cavityS21.401A..., initial encounterS21.401D..., subsequent encounterS21.401S..., sequelaS21.402Unspecified open wound of left back wall of thorax with penetration into thoracic cavityS21.402A..., initial encounterS21.402D..., subsequent encounterS21.402S..., sequelaS21.409Unspecified open wound of unspecified back wall of thorax with penetration into thoracic cavityS21.409A..., initial encounterS21.409D..., subsequent encounterS21.409S..., sequela