(c) If the exostoses spring from the anterior wall, it is necessary to make a T-shaped incision through the posterior membranous portion of the auditory canal in order to bring them into view clearly. This is done with a tenotomy knife, the flaps being held apart by means of forceps. The growths can now be removed by means of the gouge and mallet.
(d) If the obstruction is due to multiple small exostoses forming an annular stricture within the bony canal, it is better to separate the membranous portion completely from the bony meatus. In doing so the skin over the exostoses tears through, so that the membranous portion can be reflected outwards as a finger-like process. To give greater room for the operation, the auricle and fibrous portion are pulled well forward by means of a loop of gauze passed through the lumen of the cartilaginous meatus.
If necessary, reflected light should now be used. To reach the exostoses it may be necessary, as in the previous case, to remove part of the posterior bony wall. With the gouge and mallet the exostoses are carefully chiselled away. They frequently abut on the tympanic membrane, so that their removal without injuring it may be well-nigh impossible. It is of the utmost importance that the field of operation should be kept dry, if necessary by repeatedly mopping out the canal with pledgets of cotton-wool soaked in adrenalin solution. The chief difficulty is to determine the situation of the tympanic membrane. A fine probe is used to discover any existing chink between the growths; this will be a guide to show the direction in which to work. As soon as a small passage has been made, sufficient to allow of a view of the deeper-lying parts, the ear should be syringed out and dried, and a thorough inspection made. The tympanic membrane can usually be seen as a greyish-blue membrane; at other times it can be recognized by touching it with a probe. After making certain of the position of the membrane, the rest of the operation is easy. A small seeker ([Fig. 219]), such as is used in the mastoid operation, is passed through the opening already made, and with it the deeper limits of the exostoses can be felt. The opening is gradually enlarged by removing the growths piecemeal with the chisel or gouge.
Although the burr is contra-indicated when operating through the external meatus, it is frequently of great service in these cases in rendering the walls of the canal smooth. The disadvantages of using a burr are, that it is less easy to control (unless the surgeon has had considerable experience in using it), and that it destroys all the epithelial lining of the auditory canal with which it comes in contact. It should, therefore, only be used in those cases in which there is a complete ring of exostoses, but should be avoided if the exostoses are limited and if it is still possible to leave untouched a portion of the epithelial lining of the auditory canal.
When the surgeon considers he has successfully removed the obstruction, he should verify this fact by syringing out and drying the ear, and again obtaining a clear view of the tympanic membrane.
The fibrous portion is now replaced by inserting a finger into the cartilaginous meatus and pressing it back into the bony canal, the auricle being meanwhile pulled back into its normal position. The edges of the posterior wound are sutured together and the auditory canal is gently packed with gauze which should be inserted right down to the tympanic membrane. It is not necessary to make special meatal skin flaps, as careful packing of the auditory canal should be sufficient to keep the parts in apposition.
When middle-ear suppuration is present. In acute middle-ear suppuration the chief difficulty is to decide what operation to perform. As operation is only indicated if there is retention of pus, it is wiser to open the mastoid antrum; the exostosis, if superficial and pedunculated, can also be removed at the same time. If, however, the obstruction is due to multiple and deeply placed exostoses, this part of the operation should be deferred to a later date, that is, after the acute symptoms have subsided.
In chronic middle-ear suppuration the only operation to be recommended is the complete mastoid operation (see [p. 392]).
After-treatment. The after-treatment is practically the same whatever operation has been performed. The first dressing need not be done until the third day. The gauze plugging is then withdrawn and the auditory canal is syringed out and dried. If only a single exostosis has been removed the wound surface is small, and it is usually sufficient to puff in some boracic powder and again insert a piece of gauze. This may be repeated every second day, healing usually taking place within two or three weeks. In the case of deeply situated multiple exostoses, especially if removed from the anterior wall, considerable swelling of the soft parts lining the auditory canal may occur as a result of the manipulations. In such cases, after syringing out any existing blood-clots, some cocaine and adrenalin solution should be instilled into the meatus. An aural speculum is then gradually worked into the auditory canal, which is gently mopped out with small pledgets of cotton-wool, and the deeper parts are carefully inspected. Sometimes the torn ends of the fibrous portion, instead of covering the bony walls, are found to project into the auditory canal and to cause considerable narrowing of its lumen. By careful manipulations with the probe or by stroking the edges with tiny pledgets of cotton-wool, these rough surfaces may be smoothed down. It is very important, in the early days of the after-treatment, to prevent any narrowing at the site of the operation. This is one of the chief causes of subsequent failure. The gauze should always be reinserted right down to the tympanic membrane, and if there is not much secretion it should be packed firmly against the posterior and outer portion of the canal in order to prevent subsequent stenosis from the tendency of the cartilage to prolapse forward owing to the soft parts having been separated from the bony canal at the time of the operation.
The wound behind the ear heals very quickly and the stitches can generally be removed on the third or fourth day. Subsequent treatment consists in preventing the formation of granulations over the wound area. This is best accomplished by keeping the auditory canal aseptic and dry. If granulations occur they should be touched from time to time with a saturated solution of trichloracetic acid. If healing has not taken place within two weeks, it will frequently be advantageous to discontinue the gauze packing and, in its stead, to instil drops of pure rectified spirit.