(iii) Adhesion of the edge of a perforation to the inner wall. If the middle-ear suppuration has only recently ceased, it may be sufficient to divide the adhesion with a small knife curved on the flat and afterwards force the tympanic membrane outwards by means of inflation through the Eustachian tube, and by rarefaction of the air within the external meatus. In the majority of cases, however, it is necessary to excise the adhesion, especially in the more chronic conditions. This is done by cutting through the movable part of the membrane just beyond the adherent portion (vide supra).
Fig. 195. Division of Intratympanic Adhesion with Excision of Handle of Malleus. A, Surface view; B, vertical section. a, Remains of malleus (handle already excised); c, Free edge of membrane; d, Scar tissue on promontory, at which point malleus and membrane were previously adherent.
(iv) Adhesions surrounding the articulation between the incus and stapes, and the stapes itself. These adhesions can only be observed if a large perforation involves the upper posterior quadrant. Even then it may be anatomically impossible to see the stapes. The operation should only be performed if definite bands of adhesions can be seen. Sometimes, although rarely, it happens that such adhesions are present. If the incudo-stapedial joint be fixed to the inner wall of the tympanic cavity, the adhesions are separated from it by passing the knife between the joint and the inner wall. In order to cut through adhesions surrounding the base of the stapes, a small horizontal incision should be made along its upper margin, and also along the lower, if this is in view. This operation, however, is seldom of any value.
TENOTOMY OF THE TENSOR TYMPANI
Indication. The chief indication for this operation is marked retraction of the tympanic membrane, in a case of middle-ear deafness, in which there are no adhesions between the membrane and the inner wall of the middle ear, and in which it is assumed that the retraction is due to shortening of the tensor tympani muscle.
Fig. 196. Schwartze’s Tenotomy Knife.
Operation. The first step of the operation is to incise the tympanic membrane with a paracentesis knife in a vertical direction just behind the margin of the malleus. At the same time the posterior fold can be cut through, if required, by continuing the incision upwards. Through the incision thus made Schwartze’s tenotomy knife (a very fine blunt-pointed instrument curved on the flat (Fig. 196)) is inserted, its point being directed upwards. The knife is pushed upwards until its shaft is on a level with the processus brevis. The handle is then rotated in a forward direction so that the sharp edge of the knife, which is kept close to the posterior border of the neck of the malleus, makes a circular movement forwards and downwards and thus cuts through the tendon of the muscle. If the knife has been too deeply inserted, the attempt to rotate the shaft forwards will be resisted by the projecting processus cochleariformis. To overcome this difficulty the shaft of the instrument is rotated backwards so as to raise the point of the tenotomy knife and thus free it; the instrument is then withdrawn slightly and the shaft again rotated forwards. The division of the tendon can be distinctly felt, and may be accompanied by a slight crackling noise; after this has been effected, the knife is rotated backwards and withdrawn through the incision in the tympanic membrane.