However small or large the opening may be, all rough corners must be removed, so that at the end of the operation a smooth funnel-shaped cavity exists. To obtain this a burr may be used, worked either by the electric motor or, if a portable one, by an assistant. The burrs are of various sizes and of the cross-cut variety recommended by Ballance. Some operators perform the operation by burring throughout. Personally, during the earlier stages of the operation, I prefer to use the gouge and mallet. If the operator has not had much experience in the use of the burr there is always a slight risk, if it be not kept sufficiently under control, and especially if too great pressure be used, of it being driven through the dura mater above or into the lateral sinus posteriorly, or of it injuring the contents of the tympanic cavity. As a means of finishing the operation no instrument could be better. In private practice, however, few surgeons keep one. For this reason it is advisable to become accustomed to the chisel and gouge.
Removal of part of the posterior wall of the auditory canal. This may be necessary if the anterior wall of the antrum and mastoid process be affected. The fibrous portion of the auditory canal is partially separated from the bony portion and held forward by means of a retractor. The upper posterior portion of the bony meatus can now be removed either by means of punch-forceps or by the chisel, to what extent does not matter so long as its innermost portion, ‘the bridge,’ is not interfered with, that is, so long as the tympanic cavity and aditus are not encroached upon.
Exposure of the dura mater and lateral sinus. This may have already occurred before the operation, as a result of extension of the bone disease, or it may be necessary to do so during the course of the operation. Owing to the fact that an extra-dural abscess is a frequent complication of acute inflammation of the mastoid process, Victor Horsley and Körner advocate the exposure of the dura mater and the lateral sinus in every case, especially if a tract of carious bone leads in their direction. No harm is done in exposing these structures, and it precludes missing an extra-dural abscess.
It is better to expose the dura mater than to leave it covered with infected bone and septic granulations.
Final step of the operation. In order to make certain that a free opening exists between the antrum and the tympanic cavity, some warm boric lotion should be syringed through the opening of the aditus. A small syringe is used, having a fine piece of india-rubber tubing fixed on to its point. The end of the tubing is pushed into the entrance of the aditus. The fluid is then syringed through and should emerge from the external meatus. This is also beneficial in order to cleanse the tympanic cavity of its purulent secretion. To expel all the fluid from the middle ear the syringe is emptied and the piston withdrawn to its full extent. Its point is again placed within the entrance of the aditus and the piston pressed home, so that air is forced through and so drives out any remaining fluid from the tympanic cavity into the external meatus, which in its turn should be carefully dried. If there be no perforation, or if it be very small, the membrane should be freely incised before fluid is syringed through the aditus.
Immediate treatment of the wound cavity. The wound cavity is lightly packed with sterilized ribbon gauze, half an inch in width. Care must be taken to introduce the gauze right down to the aditus and to pack the cavity evenly.
The wound should be left open for a few days until the acute inflammation of the soft tissues has subsided, after which the upper and lower angles of the wound can be partially closed by sutures. A strip of gauze is also inserted into the auditory canal and a light dressing of plain sterilized gauze and a pad of cotton-wool covers the ear and surrounding parts. The bandage should be passed round the head and not beneath the chin, as the latter method is often a source of great discomfort to the patient during the stage of vomiting following the anæsthetic.
Blake of America has suggested that the wound should be allowed to fill with blood-clot on the supposition that the subsequent organization of the clot will result in a rapid closure of the wound. This method cannot be considered seriously owing to the impossibility of keeping the wound sterile.
After-treatment. There is seldom any shock, but there may be considerable pain during the next twenty-four hours.
If there has been no subperiosteal abscess, the dressing need not be removed for forty-eight hours. If an abscess has been present the dry dressing should be removed after twenty-four hours, and if there is much œdema and inflammation of the surrounding region, a compress of wet boric lint, kept in position by a few turns of a bandage, should be substituted, and changed every four hours.