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Myringoplasty
By
Dr. T. Balasubramanian M.S. D.L.O.
Synonyms: Myringoplasty,
Tympanoplasty.
Definition:
Myringoplasty is a procedure used to seal a perforated tympanic
membrane using a graft material.
Temporalis fascia is the commonly used graft material because:
1. It is an autograft with excellent chance of take
2. It is available close to the site of operation making its harvest
easier
3. It has a low basal metabolic rate, brightening its success rate
4. Its thickness is more or less similar to that of tympanic membrane
There are two available methods of performing myringoplasty:
Overlay technique
Under lay technique
Overlay technique: This is a
difficult technique to master. Here the graft material is
inserted under the squamous (skinlayer) of the ear drum. It is a
difficult task peeling only the skin layer away from the tympanic
membrane, placing the graft over the perforation and redraping the skin
layer.
Underlay technique: This is a
simpler and commonly used technique. Here the graft is placed
under the tympano meatal flap which has been elevated hence the name
under lay. The major advantage of this procedure is that it is
easy to perform with a good success rate.
Indications of Myringoplasty:
1. Central perforation which has been dry atleast for a period of 6
weeks.
2. As a follow up to mastoidectomy procedure to recreate the hearing
mechanism
Prerequisites for myringoplasty:
1. Central perforation which has been dry for atleast 6 weeks
2. Normal middle ear mucosa
3. Intact ossicular chain
4. Good cochlear reserve
Procedure: Firstly a temporalis
fascia of adequate site must be harvested and allowed to dry.
The surgery is performed under local anesthesia. Temporalis
fascia graft is harvested under local anesthesia conventionally and
allowed to dry. The external auditory canal is then
anesthetised using 2 % xylocaine mixed with 1 in 10,000
adrenaline injection. About 1/2 cc is infiltrated at 3 - o clock,
6 - o clock, 9 - o clock, and 12 - o clock positions about 3mm
from the annulus. The patient is premedicated with intramuscular
injections of 1 ampule fortwin and 1 ampule phenergan.
Step I: Freshening the margins of
perforation - In this step the margins of the perforation
is freshened using a sickle knife of an angled pick.
This step is very important because it breaks the adhesions formed
between the squamous margin of the ear drum (outer layer)
with that of the middle ear mucosa. These adhesions if left
undisturbed will hinder the take up of the neo tympanic graft.
This procedure will infact widen the already present perforation.
There is nothing to be alarmed about it.
Step II: This step is otherwise
known as elevation of tympano meatal flap. Using a drum knife a
curvilinear incision is made about 3 mm lateral to the annulus.
This incision ideally extends between the 12 - o clock, 3 - o clock,
and 6 - o clock positions in the left ear, and 12 - o clock, 9 - o
clock and 6 - o clock positions in the right ear. The skin is
slowly elevated away from the bone of the external canal.
Pressure should be applied to the bone while elevation. This
serves two purposes:
1. It prevents excessive bleeding
2. It prevents tearing of the flap
This step ends when the skin flap is raised up to the level
of the annulus.
Step III: Elevation of
the annulus and incising the middle ear mucosa. In this
step the annulus is gradually lifted from its rim. As soon as the
annulus is elevated a sickle knife is used to incise the middle ear
mucosal attachement with the tympano meatal flap. This is a very
important step because the inner layer of the remnant ear drum is
continuous with the middle ear mucosa. As soon as the middle ear
mucosa is raised, the flap is pushed anteriorly till the handle of the
malleus becomes visible.
Step IV: Freeing
the tympano meatal flap from the handle of malleus. In
this step the tymano meatal flap is freed from the handle of
malleus by sharp dissection of the middle ear mucosa. Sometimes
the handle of the malleus may be turned inwards hitching against
the promontory. In this scenario, an attempt is made
to lateralise the handle of the malleus. If it is not
possible to lateralise the handle of the malleus, the small deviated
tip portion of the handle can be clipped. The handle of the
malleus is freshened and stripped of its mucosal covering.
Step V: Placement of graft (underlay
technique). Now a properly dried temporalis fascia graft of
appropriate size is introduced through the ear canal. The graft
is gently pushed under the tympano meatal flap which has been
elevated. The graft is insinuated under the handle of
malleus. The tympano meatal flap is repositioned in such a way
that it covers the free edge of the graft which has been
introduced. Bits of gelfoam is placed around the edges of the
raised flap. One gel foam bit is placed over the sealed
perforation. This gelfoam has a specific role to play.
Due to the suction effect created it pulls the graft against the
edges of the perforation thus perventing medialisation of the graft
material.
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