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.