Fig. 201. Delstanche’s Ring-knife.

Fig. 202. Removal of Malleus by Delstanche’s Ring-knife. A, Curette inserted round handle of malleus; B, Curette pushed upwards, in act of cutting through tendon of tensor tympani muscle.

Another method of extracting the malleus, and in my opinion the one to be preferred, is by Delstanche’s ring-knife (Fig. 201). This instrument differs from the ordinary ring-knife in that the upper border of its anterior part is especially sharpened so as to form a fine cutting surface. After the malleus has been freed from the membrane by means of the paracentesis knife, Delstanche’s ring-knife is made to encircle its handle. It is then pushed gradually upwards, keeping as close to the posterior border of the malleus as possible, until it cuts through the attachment of the tensor tympani. In doing this the instrument will embrace the neck of the malleus (Fig. 202). This permits of sufficient leverage to extract the malleus by gentle traction in a downward and outward direction without danger of fracturing its shaft. If much resistance be felt, probably the tensor tympani muscle has not been cut through, and another attempt should be made to do this before trying further extraction. The advantage of this instrument is, that once the knife has encircled the malleus it should be possible not only to cut through the tensor tympani, but to extract the bone itself without the use of any other instrument. If Schwartze’s tenotomy knife be used, two tenotomy knives are required, one for the right and one for the left ear. Delstanche’s ring-knife is equally good for either ear.

Extraction of the incus. Although it is frequently stated that extraction of the incus is more difficult than that of the malleus, in reality it is the easier part of the operation as, unlike the malleus, it has no firm attachments.

After removal of the malleus all hæmorrhage must be arrested and a view obtained of the inner wall of the tympanic cavity. If it be possible to see the long process of the incus and its articulation with the head of the stapes, the articulation should be cut through with a small sickle-shaped knife. The knife is inserted just in front of the long process of the incus and, keeping close to it posteriorly, is made to cut downwards and backwards, thus separating its connexion with the stapes. Frequently the long process cannot be seen, or it may indeed have already disappeared as a result of caries. Theoretically this delicate manœuvre is performed in order to prevent injury or dislodgment of the stapes during the act of removal of the incus. From a practical point of view, however, it does not appear to make any difference whether the incudo-stapedial articulation is cut through or not.

Fig. 203. Ludewig’s Incus Hook.    Fig. 204. Zeroni’s Incus Hook.

A variety of instruments have been described for the purpose of removal of the incus. Ludewig’s incus hook (named after Ludewig, who was one of the first to draw attention to this operation) is still recommended by many as being the best. It consists of a solid curved hook, having a length of 5 millimetres and a width of 2 millimetres, bent at right angles to its shaft (Fig. 203). A pair of these are necessary, one for each ear; also several sets of different sizes may be required owing to the variation in depth, height, and roof of the attic region. I, however, prefer Zeroni’s (Fig. 204). This hook, instead of being solid, consists of a steel eyelet having a backward curve similar to that of Ludewig’s.

  Fig. 205. Removal of Incus by Zeroni’s Hook. A, Diagrammatic section showing opening in tegmen tympani: b, processus cochleariformis; c, external semicircular canal; d, aditus and antrum. B, Diagrammatic section, through the auditory canal, just beyond the tympanic membrane: e, long process of incus; f, incudo-stapedial joint; g, tympanic ring; h, remains of the tympanic membrane; i, fenestra rotunda; above it is the promontory.