Technique

A graft of temporalis fascia is harvested early in the procedure to allow time for the graft to dry (Fig. 3-1). Any muscle tissue adherent to the fascia is removed. We prefer to use the true temporalis fascia, rather than the areolar fascia. The areolar fascia has more of a trabecular structure, which occasionally results in the formation of small perforations. These small perforations sometimes appear months after primary healing.

The transcanal approach is appropriate for small posterior perforations where the entire margin can be seen through the ear canal (Fig. 3-2). Either local anesthesia (adults) or general anesthesia can be used. After sterile preparation and draping of the ear, local anesthetic with epinephrine is injected to supplement the general anesthetic and aid in he-mostasis. The graft is harvested and allowed to dry on a smooth, hard surface. The size of the fascial graft depends on the size of the perforation. The trimmed perforation should overlap the graft by at least 1 mm, and preferably by 2 mm or more, in all directions. Once harvested, the fascia is allowed to dry on a block of dense fluoroplastic.

Tympanic membrane perforations are fistulas between the ear canal and the middle ear space. They are stable because contact inhibition between the squamous epithelium of the lateral surface of the tympanic membrane and the mucous membrane of the medial surface prevents active growth of either epithelium. Consequently, it is necessary to disrupt the junction between the squamous and respiratory epithelia.23 The authors prefer to accomplish this step by removing a 1-mm rim of the perforation circumferentially (Fig. 3-2). This step is sometimes referred to as "freshening" the edges of the perforation.

Plaques of tympanosclerosis are patches of hyali-nized (calcified) scar that replace portions of the fibrous layers of the tympanic membrane following periods of inflammation from chronic otitis media. They probably interfere with healing by blocking vascularization of the graft. Tympanosclerosis can be removed from the medial surface of the tympanic membrane with an angled pick. It is also useful to score the medial surface of the tympanic membrane remnant to stimulate the respiratory epithelium to incorporate the graft.

Tympanic Membrane Scarring

FIGURE 3 — 1 Temporalis fascia may be harvested from the same postauricular incision used for exposure to the middle ear (incision A). If a transcanal approach is used, a smaller incision over the fascia may be used to obtain the graft (incision B). If fascia has already been harvested during a previous operation, it may be necessary to harvest fascia from a more superior position using a supplemental incision (incision C). Use of incision C requires shaving and sterile preparation of a larger area before starting the operation. It is important to be aware of the location of the temporalis muscle, because the true temporalis fascia makes a more suitable graft material than areolar fascia or the periosteum of the skull.

FIGURE 3 — 1 Temporalis fascia may be harvested from the same postauricular incision used for exposure to the middle ear (incision A). If a transcanal approach is used, a smaller incision over the fascia may be used to obtain the graft (incision B). If fascia has already been harvested during a previous operation, it may be necessary to harvest fascia from a more superior position using a supplemental incision (incision C). Use of incision C requires shaving and sterile preparation of a larger area before starting the operation. It is important to be aware of the location of the temporalis muscle, because the true temporalis fascia makes a more suitable graft material than areolar fascia or the periosteum of the skull.

A simple myringoplasty can be accomplished for small perforations without a tympanomeatal flap. In most cases, however, a tympanomeatal flap is raised to provide exposure to remove disease, reconstruct the ossicular chain, or facilitate placement of the graft.

The flap should be planned to expose at least the posterior half of the middle ear space. The flap should be folded anteriorly at the manubrium. Thus, incisions are made laterally from the annulus at the 6 and 12 o'clock positions, and directed posteriorly. The inferior incision may be placed more anteriorly if more anterior exposure is needed.

Three canal incisions are made to create the medially based flap (Fig. 3-3A). The two radial incisions are made first. Then they are connected by a third incision placed laterally. The flap should be long enough to accommodate curettage of the

Myringoplasty Underlay Technique

FIGURE 3-2 The transcanal approach is suitable for repair of a small posterior tympanic membrane perforation (A). A series of full-thickness punctures is made 1 mm from the edge of the perforation circumferentially using a sharp curved needle (B). The margin of the perforation is then stripped off using a cup forceps (C).

FIGURE 3-2 The transcanal approach is suitable for repair of a small posterior tympanic membrane perforation (A). A series of full-thickness punctures is made 1 mm from the edge of the perforation circumferentially using a sharp curved needle (B). The margin of the perforation is then stripped off using a cup forceps (C).

Myringoplasty Underlay

FIGURE 3-3 A tympanomeatal flap is raised to the annulus (A). Dividing the flap through the fibrous annulus to the perforation provides additional exposure (B). The graft is placed under the perforation allowing for generous overlapping of the tympanic membrane, and the tympanomeatal flap is returned to its normal position (C) prior to placement of absorbable packing lateral to the tympanic membrane.

FIGURE 3-3 A tympanomeatal flap is raised to the annulus (A). Dividing the flap through the fibrous annulus to the perforation provides additional exposure (B). The graft is placed under the perforation allowing for generous overlapping of the tympanic membrane, and the tympanomeatal flap is returned to its normal position (C) prior to placement of absorbable packing lateral to the tympanic membrane.

posterior scutum if needed for exposure. To avoid troublesome bleeding, the flap should not be extended more than necessary into the thicker poster-osuperior canal skin (the ''vascular strip''). Also, a large flap can obstruct exposure to the middle ear. In general the flap should extend two thirds of the distance from the annulus to the bony-cartilaginous junction of the external auditory canal, or about 7 mm from the annulus (Fig. 3-3A).

The flap is elevated until the fibrous annulus is identified. To avoid unnecessary trauma to the flap it should be elevated by gently scraping the skin from the bone, hugging the bone, advancing along a broad front. As much as possible the suction tip is applied only to the back of the elevator, not directly to the flap. Spherical pledgets of nonlinting, nonabsorbable sponge material (4-mm diameter) soaked in 1:5000 epinephrine solution are applied to the subcutaneous surface of the flap for several minutes to achieve hemostasis. Sometimes a speculum holder is brought into use while the epinephrine is applied.

After the epinephrine pledgets are removed, elevation of the tympanomeatal flap continues by elevation of the fibrous annulus from the sulcus of the bony annulus. An effort is made to keep the fibrous annulus intact. Care is taken not to injure the chorda tympani nerve, or to tear the flap off the annulus.

We usually make a fourth incision from the posterior midpoint of the flap medially through the flap, the annulus, and the tympanic membrane to the middle of the perforation (Fig. 3-3B). This incision creates two "wings" that can be separated, greatly enhancing exposure of the middle ear.

With maximum exposure thus achieved, we now lyse adhesions in the middle ear and remove inflammatory tissue. Care is taken to avoid trauma to any viable middle ear mucosa. If the promontory has been traumatized, it is important to retard the formation of adhesions to the newly grafted tympanic membrane. Either nonabsorbable (silicone sheeting of 0.16-mm thickness) or slowly absorbable sheeting may be used at the discretion of the surgeon.

If necessary, a postauricular incision is made and a mastoidectomy is performed. The ossicles are inspected for mobility and continuity. ossicular chain reconstruction is performed as indicated.25

pledgets of gelatin sponge are thoroughly moistened in normal saline, balanced salt solution, or an antibiotic solution, squeezed dry in a lint-free microwipe, and placed in the middle ear to support the graft. If the ossicles are absent, the epitympanum should also be packed so the packing will be stable. Enough packing material should be placed to fill the space but not to extend lateral to the tympanic membrane. if the packing starts to swell after it is placed, the surgeon can remove the excess packing or apply suction indirectly through a nonabsorbable 4-mm sponge to remove excess fluid and compress the packing material.

The temporalis fascia graft is trimmed so that the tympanic membrane remnant will overlap it by 2 mm or more circumferentially. The graft is grasped at the leading edge with a cup forceps and pushed under the remnant and lateral to the middle ear packing. it is spread out under the remnant so it is flat between the medial surface of the tympanic membrane and the gelatin sponge. The graft is extended posteriorly onto the bony portion of the external auditory canal to provide additional stability during healing (Fig. 3-3C).

After the graft is placed the external auditory canal is packed with absorbable gelatin sponges. The first few pieces are placed very carefully onto the grafted surface, beginning with the anterior sulcus of the external auditory canal, so the graft is not pulled out of position. A cotton ball saturated with baci-tracin ointment is placed in the ear canal. The incision for the graft donor site is closed with buried stitches of absorbable suture material.

Although there is little more than anecdotal supporting evidence, clinical experience teaches that anterior and large tympanic membrane perforations are less likely to heal than small or posterior perforations when underlay grafting techniques are used. Consequently, it is author Monsell's preference to use underlay grafting techniques only for small posterior tympanic membrane perforations.

Some authors have described techniques to supplement underlay techniques to improve results (Figs. 3-4 and 3-5). These include a postauricular skin incision and canal skin incisions to access the middle ear from a posterior approach for better exposure. When a postauricular approach is used, the fascia can be harvested from the same incision (Fig. 3-1). During closure the ear canal is packed with absorbable gel sponges. The postauricular incision is closed with absorbable suture. The remainder of the ear canal is packed with absorbable gel sponges, and a mastoid dressing is applied.

An anterior canaloplasty also enhances exposure (Fig. 3-4B). This can be performed through either the transcanal or the postauricular approach, though it is easier to accomplish through a postauricular approach. A medially based flap of anterior canal skin is elevated to the annulus. A graded series of diamond burs is used on the surgical drill with continuous suction-irrigation. A piece of metal foil from a suture package may be fitted over the canal skin flap to prevent the flap from catching in the bur during drilling. The anatomic goal is to be able to see the entire circumference of the annulus from a single position.

If adhesions form between the graft and the promontory, a conductive hearing loss will result. Adhesions can usually be prevented by placing silicone sheeting material in the middle ear whether or not the operation is staged.26,27

Oral analgesics are prescribed for postoperative pain. We do not routinely prescribe prophylactic antibiotics. The mastoid dressing can be removed 1 to 2 days after surgery. Dry ear precautions are maintained until the ear is healed, usually after 4 to 8 weeks, depending on the size of the perforation. Antibiotic eardrops are applied three times per day after surgery until healing is complete. The patient is advised not to blow forcefully through the nose, to avoid contact sports, and to avoid air travel for at least 2 weeks.

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