Which of the following is used to define penetrating neck injury?

Neck Injuries Most severe neck injuries are caused by penetrating wounds and may present an immediate threat to life as a result of airway compromise or hemorrhage. Major vascular & aerodigestive structures in the neck are located in anterior triangle, & all are deep to platysma. Platysma & SCM are useful anatomic boundaries. Injuries that donot penetrate the platysma can be considered superficial, and no fuher investigations is needed. Wounds that penetrate the platysma must be fuher evaluated. Injuries that are anterior to SCM present a high likelihood of significant injury, whereas those that track posterior to SCM are unlikely to involve major vascular or aerodigestive structures. Penetrating injuries to the posterior triangle should raise concern about trauma to cervical spinal cord. Neck is divided into Three Horizontal Zones on Craniocaudal location Zone I At thoracic inlet Extends from sternal notch to cricoid cailage Injuries in this zone carry the highest moality beacuse of the presence of great vessels & difficult surgical approach Zone II Mid-poion of the neck Extends from cricoid cailage to angle of mandible Zone III Extends from angle of mandible to base of skull Ref: Sabiston 20th edition Pgno: 423