When the frontal (nasal) portion of the maxilla is broken, the lachrymal sac and nasal duct may be damaged and the flow of the tears obstructed. In such cases emphysema is also liable to develop. Fractures of the facial portion are frequently complicated by hæmorrhage from the infra-orbital vessels, and anæsthesia of the area supplied by the infra-orbital nerve. Suppuration may occur in the maxillary sinus. In some cases the maxilla is driven in as a whole, and in others the fracture radiates to the base of the skull and cerebral symptoms develop.
The treatment consists in reducing any deformity that may be present, ensuring efficient drainage, and keeping the mouth as aseptic as possible. Union takes place rapidly, and owing to the vascularity of the parts necrosis is rare, even when suppuration ensues. When the alveolar portion is comminuted, the fragments may be kept in position by fixing the mandible against the maxilla by means of a four-tailed bandage ([Fig. 255]), or by adjusting a moulded lead or gutta-percha splint to the alveolus and palate.
The zygomatic (malar) bone is sometimes fractured by direct violence, along with the adjacent portion of the maxilla. It may be possible to manipulate the displaced fragments into position with the fingers introduced between the cheek and the gum; if this fails, a small incision should be made in the mucous membrane anterior to the masseter, and the bone levered into position with an elevator.
The zygomatic arch is occasionally fractured by a direct blow. As the depressed fragments are liable to interfere with the movement of the mandible, they should be elevated either by manipulation or through an incision.
Fractures of the Mandible.—The most common situation for fracture of the mandible is through the body of the bone in the vicinity of the canine tooth ([Fig. 254]). The depth of the socket of this tooth, and the comparative narrowness of the jaw at this level, render it the weakest part of the arch. The fracture is usually due to direct violence, such as a blow with the fist, the kick of a horse, or a fall from a height. It is sometimes bilateral, the bone giving way at the canine fossa on one side and just in front of the masseter on the other; or both fractures may be at the canine fossæ. The fracture is usually oblique from above downwards and outwards, and is nearly always rendered compound by tearing of the mucous membrane of the mouth.
Fig. 254.—Multiple Fracture of Mandible.
(From Sir Patrick Heron Watson's collection.)
When only one side is broken, the smaller fragment is usually displaced outwards and forwards by the masseter and temporal muscles, so that it overlaps the larger fragment. In bilateral fractures the central loose segment is driven downwards and backwards towards the hyoid bone by the force causing the fracture, and is held in this position by the muscles attached to the chin, while both lateral fragments are tilted outwards and forwards by the masseters and temporals. The amount of displacement is best recognised by observing the degree of irregularity in the line of the teeth. Abnormal mobility and crepitus are readily elicited, and there is severe pain, particularly if the inferior dental nerve is stretched or crushed. The patient's attitude is characteristic; he supports the broken jaw with his hands, and keeps it as steady as possible when he attempts to speak or swallow. Saliva dribbles from the open mouth, and the speech is indistinct.
In adults, the bone may be broken at the symphysis as a result of lateral compression of the jaw—for example, pressing together of the angles. The general characters of the fracture are the same as those of fracture of the body, but the displacement is inconsiderable.