ICD-10-CM > S00-T88 > S20-S29 > S21 > S21.4 > S21.45 S21.45 Open bite of back wall of thorax with penetration into thoracic cavity Non-Billable/Non-Specific Applicable To Bite of back wall of thorax NOS Type 1 Excludes superficial bite of back wall of thorax (S20.47) Codes S21.451Open bite of right back wall of thorax with penetration into thoracic cavityS21.451A..., initial encounterS21.451D..., subsequent encounterS21.451S..., sequelaS21.452Open bite of left back wall of thorax with penetration into thoracic cavityS21.452A..., initial encounterS21.452D..., subsequent encounterS21.452S..., sequelaS21.459Open bite of unspecified back wall of thorax with penetration into thoracic cavityS21.459A..., initial encounterS21.459D..., subsequent encounterS21.459S..., sequela