LARYNGOTRACHEAL TRAUMA 193 Over the age of 40 the thyroid cartilage has lost much of its elasticity because of ossification of the cartilage. This means that as the larynx is forced back on to the cervical vertebrae the compressing force will shatter it, and when this force is removed the shattered, inelastic larynx will not recoil. The effect of this is to disorganize the cords and the base of the epiglottis, to Fig. 96. Seat-belt injury. To illustrate the extent of injury in the older patient in whom the thyroid cartilage has ossified. The initial impact shatters the cartilage which cannot recoil. The neck is flattened and the airway reduced. damage the arytenoids, to narrow or close the airway and to cause a flattening of the neck (Fig. 96). Minor degrees of external trauma and other injuring factors such as burns and scalds will cause only internal soft tissue damage with no skeletal disrup- tion. This can take the form of bruising, haemorrhage or laryngeal oedema. The type of injury often sustained in karate or basketball is a fractured hyoid. This presents as exquisite pain over the fracture site on swallowing and also on 'springing' the hyoid by palpation. DIAGNOSIS. As indicated in the introduction to this chapter a laryngeal fracture is easy to miss as the associated injuries mask it. It is vital to be aware of this condition and to suspect it in any multiple injury. Bruising and other soft-tissue injury is not always dramatically obvious and indeed a major laryngeal fracture can exist in the absence of bruising. If the laryngeal lumen has been opened there will be surgical emphysema. This is diagnosed by palpating the neck and feeling the very typical crepitus. If, however, the forces applied to the larynx were sufficient to cause severe internal soft-tissue derangement without tearing the perichondrium surgical emphysema will be absent. In the older patient with an ossified thyroid cartilage the neck will be flattened (Fig. 97) and in the young patient a linear fracture may be palpated down the line of the thyroid prominence.