METHODS OF OPERATION
The actual method of carrying out this operation varies. For those who have not had great experience the best method is first to open the antrum, as in Schwartze’s operation, and then to remove the ‘bridge’ of bone between it and the tympanic cavity (Küster-Bergmann operation, sometimes called the Schwartze-Stacke operation). Instead of doing this, the upper posterior part of the auditory canal may be chiselled away simultaneously during the act of exposing the antrum (Wolf’s operation). On the other hand, the mastoid and antrum may be exposed from within outwards by removing the outer attic wall and working backwards (Stacke’s operation).
The Küster-Bergmann (or Schwartze-Stacke) operation. The preliminary preparation, the position of the patient, and the instruments required are the same as in opening the antrum.
Fig. 221. The ‘Radical’ Mastoid Operation. To show removal of the ‘bridge’ from above. The seeker, inserted into the aditus, acts as a protector to the underlying external semicircular canal and facial nerve.
The incision is begun just above the upper insertion of the pinna, and is carried downwards in a curved direction behind the auricle along the margin of the skin and scalp. Some authorities prefer to make the incision close behind or even along the post-auricular fold. In favour of the incision being placed far back is the concealment of the scar by the hair. Also, as it is situated on healthy bone somewhat posterior to the actual wound cavity, it should heal by primary union and with no after-displacement of the auricle. In addition, if it be necessary to expose the lateral sinus, this can usually be done by simple retraction of the soft parts.
The exposure of the field of operation is the same as in the simple opening of the antrum, excepting that the soft tissues should be separated a little further forwards and above the external bony meatus, as in this operation the upper posterior wall has to be removed.
The antrum is opened as already described (see [p. 382]).
The fibrous portion of the external meatus is separated carefully from the posterior wall of the bony meatus by means of a periosteal elevator, and is pulled forward by a retractor. The external portion of the posterior wall is now removed in a wedge-shaped fashion by alternate strokes of the chisel from above downwards (Fig. 221) and from below upwards. The upper level of the bone to be removed corresponds with the zygomatic ridge. After a small portion has been removed, a pair of forceps is passed into the auditory meatus and its point made to project into the wound posteriorly through the end of the now detached fibrous portion of the auditory canal. With the forceps a piece of gauze is drawn through the auditory meatus in the form of a loop. By its means the auricle and fibrous portion are pulled well forward, thus exposing to view the tympanic cavity. Two openings are now seen: one, the auditory canal and tympanic cavity, in front, and the other, the antrum and mastoid cavity, behind. Between them is the ‘bridge’; that is, the innermost portion of the posterior wall of the auditory canal.
Any granulations present are curetted away gently from the tympanic cavity. The seeker is next passed into the tympanic cavity, and its point directed upwards and backwards into the aditus, so that it rests on the floor of the latter, or its point may be inserted into the aditus through the mastoid wound. Beneath it lies the eminence of the external semicircular canal and the facial nerve. This is a most important landmark. Provided the seeker is kept in this position, all the bone lying superficially to it can be removed without injury to the semicircular canal or facial nerve.