Operation. Preparation of the patient. The head should be shaved for a space of 2 inches around the mastoid region, twenty-four hours before the operation if possible. In women the hair in front of the ear, instead of being shaved off, should be combed forward and plastered down with carbolic soap. By doing this the hair can be arranged so as to cover the bald area during convalescence, a matter of great satisfaction to the patient.
Fig. 216. Diagram showing Position of Skin Incisions in Post-aural Operations. 1, For removal of foreign bodies or exostoses, or for excision of a stricture within auditory canal; 2, Usual incision for the mastoid operation; 3, Prolongation of incision upwards for exposure of temporo-sphenoidal lobe; 4, Extension of incision backwards, for exposure of lateral sinus or cerebellum.
The area of the operation and surrounding parts should be thoroughly washed with ethereal soap solution and afterwards protected with a compress of 1 in 2,000 solution of biniodide of mercury. After the patient has been anæsthetized, the cleansing process should be repeated, and the auditory canal syringed out with the lotion. The head is then covered with a sterilized towel drawn tightly over the ear and scalp, a portion of the towel being afterwards cut away so as to expose only the field of operation. The patient should be in the recumbent position, the head resting on some hard substance, such as a partially-filled sand-bag, and turned over to the opposite side, so that the affected ear is uppermost.
In addition to the ordinary instruments, those specially required for this operation are a well-balanced mallet and several gouges and chisels of varying size, one or two sharp spoons, a seeker, and a malleable blunt-pointed silver probe. They should be sterilized in the ordinary manner.
The incision. The surgeon stands at the side to be operated upon, facing the patient’s head. The auricle is pulled forward. An incision is made through the skin, beginning just above the pinna, and is carried downwards in a curved direction towards the tip of the mastoid process, lying about half an inch behind the insertion of the auricle (Fig. 216). Before making the incision, the tip of the mastoid process should be determined. Care must be taken not to let the knife slip at the end of the incision and so incise the neck tissues. The line of incision should correspond to what will afterwards be the middle of the wound cavity in the bone. If the incision be made too far forwards or too far backwards, one of the edges of the skin incision may afterwards tend to overlap the opening in the bone and in this way hinder the dressing and perhaps lead to the formation of a sinus. If there be much thickening of the soft tissues and periosteum, it may be necessary to make the incision longer than usual in order to expose the field of operation sufficiently.
In the upper angle of the incision the temporal fascia and the underlying temporal muscle will be exposed. Except in very muscular subjects, in whom the muscle comes low down into the wound and has to be cut through, it is better to push the lower border of the muscle upwards by means of a periosteal elevator. The incision is now carried right down to the bone throughout its length.
If there be an abscess over the mastoid process, its purulent contents should be allowed to drain away, the abscess cavity being then irrigated with a weak solution of biniodide of mercury (see [p. 389]).
Fig. 217. Schwartze’s Operation. Showing field of operation with anatomical landmarks and gouge in position for opening of antrum.