As a final step the gauze which has been inserted into the meatus is removed, and the cavity again packed evenly and lightly from the bottom of the wound with a fresh strip. The ear and surrounding parts are protected with a pad of sterilized gauze covered with cotton-wool and kept in position with a bandage.
The posterior wound should be left open under the following circumstances:—
1. If there be an abscess over the mastoid process. Although it may be possible to excise the whole of the lining membrane of the abscess cavity, it is wiser to leave the wound open for the first few days. The innermost portion of the wound cavity is packed through the external meatus, only the superficial part being packed through the posterior wound incision. As healthy granulations appear, the posterior packing is diminished, so that the edges of the incision gradually come together. If necessary, the edges of the wound can also be freshened and brought together by silkworm-gut sutures under cocaine anæsthesia.
2. If there be extensive disease of the bone, especially if the dura mater and lateral sinus are covered with septic granulations.
3. If there be bone disease of the anterior and inferior parts of the tympanic cavity. The after-treatment of packing or the curetting away of granulations can be carried out more easily through the posterior wound than through the external meatus, as it gives a better view of these regions.
4. In young children it is frequently advisable to leave the posterior wound open owing to the difficulty of packing the wound cavity through the small external meatus.
SKIN-GRAFTING AFTER THE MASTOID OPERATION
In order to shorten the duration of healing, a large Thiersch’s skin graft may be transplanted into the wound cavity. If this procedure be adopted it may be carried out in several ways. The skin may be transplanted in one large piece or in several small portions, and it may be introduced into the wound cavity either immediately after the completion of the mastoid operation or from seven to ten days later.
There is considerable diversity of opinion as to whether skin-grafting should be employed or not, and also when it should be done.