Tympanoplasty-Staging and Use of Plastic

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Chapter 18 Tympanoplasty—Staging and Use of Plastic

Elimination of disease and restoration of function are the two aims of tympanoplasty. In most teaching situations, one can separate the two aims, limiting the discussion to one or the other. The staging of the operation and the use of plastic in the middle ear require, however, that the discussion consider both objectives. Staging the operation involves disease and function, and it is not technique oriented; that is, staging does not vary significantly with the technique of tympanic membrane grafting or of restoring the sound pressure transfer mechanism, or even the management of the mastoid. This chapter discusses the indications for staging tympanoplasty and mastoidectomy, and techniques used in performing tympanoplasty in two stages. The controversies surrounding the procedure are discussed at the end of the chapter.

POSTOPERATIVE COLLAPSE OF TYMPANIC MEMBRANE

Retraction and collapse of the tympanic membrane is a well-recognized postoperative problem. Many authors blame the collapse on continued poor eustachian tube function.¹ Others blame the collapse on fibrous adhesions between the denuded middle ear surfaces and the tympanic membrane graft (see later). The introduction of a barrier material, such as silicone elastomer (Silastic) sheeting, between these two raw surfaces prevents the formation of fibrous adhesions, with subsequent retraction and collapse of the tympanic membrane. This alternative explanation is supported by observations of healing after staging. In a review of 400 planned two-stage tympanoplasty operations, 89% of patients achieved an aerated middle ear, 5% required the placement of a ventilation tube, and the remainder developed collapse of the middle ear space.² These results would indicate that continued eustachian tube dysfunction is an uncommon cause for postoperative tympanic membrane retraction.

INDICATIONS FOR STAGING

There are two reasons for staging the operation in tympanoplasty: (1) obtaining a permanently disease-free ear and (2) obtaining permanent restoration of hearing.^3,⁴ Whether one finds any indication for staging depends on how vigorously a good functional result is pursued in badly diseased ears.

The decision whether or not to stage is made at the time of surgery. With experience, one usually can make this judgment preoperatively and alert the patient to the possible necessity of a two-stage procedure. The decision is based on three factors: (1) the extent of the mucous membrane problem, (2) the certainty (or lack thereof) of removal of cholesteatoma, and (3) the status of the ossicular chain. Taking these three factors into account, we stage about 75% of tympanoplasty and mastoidectomy procedures and about 15% of tympanoplasties not requiring mastoidectomy.

Mucosal Disease Factors

There are frequently large areas of diseased or absent mucosa in the chronically infected middle ear. Groundwork is necessary to promote regrowth of normal mucosa. The first step is elimination of infection before surgery, if possible. The second step is removal of all squamous epithelium, granulations, and irreversibly diseased mucosa at the time of surgery. The middle ear is sealed with a graft to prevent squamous epithelium from migrating back into the middle ear. This sealed middle ear space fills with a blood clot, and this clot supports fibroblastic invasion with eventual formation of scar tissue or adhesions between the denuded surfaces. To prevent these adhesions from forming, and to allow mucosa to migrate in, plastic sheeting is used over the denuded areas.

A two-stage operation is indicated to obtain the best hearing results, and to prevent recurrence of cholesteatoma (retraction pocket) in patients with extensive mucous membrane destruction. The objective of the two-stage procedure is to obtain a well-healed ear with a mucosa-lined pneumatized middle ear cleft so that ossicular reconstruction may be performed later under ideal circumstances.

Ossicular Chain Factors

An increase in the incidence of sensorineural hearing impairment has been observed in patients in whom the inner ear has been opened in the presence of actual or potential infection. Because of this result, a fixed stapes should not be removed at the time of tympanic membrane grafting. In cases of otosclerosis, a two-stage procedure is almost always indicated. When the fixation is due to tympanosclerosis, it may be possible to mobilize the stapes, depending on the area of fixation. In diffusely involved cases, a laser can be useful to remove the suprastructure and to char the tympanosclerosis, allowing its removal and resulting in a mobile footplate. If it is impossible to mobilize the footplate, a second stage procedure should be carried out. At that time, the tympanic membrane would be intact, and the middle ear would be without infection, allowing for removal of the fixed footplate in a sterile environment and completion of ossicular reconstruction.

Residual Cholesteatoma Factor

It may seem illogical to leave behind epithelial disease, removing it at a planned second stage procedure, but this is exactly what is done under certain circumstances. Removal of cholesteatoma in the middle ear may be questionable sometimes in an acutely inflamed ear, in which differentiating between granulation tissue and matrix is difficult. Differentiating becomes a particular problem when granulations fill the oval and round windows. Excessive manipulation in these areas could result in an inner ear complication.

Removal of matrix involving a mobile stapes with an intact suprastructure can be challenging. Sometimes it is impossible to be certain that every shred of cholesteatoma has been removed. In such cases, a laser can be used at the second stage to cut the crura off the mobile footplate and facilitate removal of residual disease.

The surgeon may have torn the matrix when removing it from the tympanic recess and may be uncertain of complete removal, which presents a considerable problem under the pyramidal process, an area hidden from view regardless of the technique of surgery, whether it is an open or closed cavity technique. Removal of the pyramidal process with a diamond burr may or may not resolve the problem. One third of patients with middle ear cholesteatoma at the first operation have residual disease at the second stage.²

It is much easier to be certain of cholesteatoma removal from the mastoid, especially in a small apneumatic one. Extensive cholesteatoma in a pneumatized mastoid poses a problem. In using the intact canal wall procedure, one should usually revise the mastoid in such cases within 1 to 2 years to be certain not to leave disease behind.

The mastoid and epitympanum are often re-explored in patients in whom excessive bleeding occurred at surgery. Unexpected residual disease in the epitympanum has been noted in some cases of this type in the past.

Timing the Second Stage

The second-stage operation may be performed in 6 to 9 months if the primary indication for staging was an ossicular or a mucous membrane problem. The middle ear should be well healed by that time. If the primary reason for staging is reinspection of the mastoid and epitympanum for possible residual cholesteatoma, it is best to wait 9 to 18 months. The delay allows time for any residual disease to have grown to a 1 or 2 mm cyst so that it may be identified with greater ease. The only exception to this rule is if this disorder occurs in a child, or if serous otitis media develops; a residuum may grow faster under these circumstances.

What is the best strategy for managing a patient with bilateral cholesteatomas who needs staged procedures on both ears? The decision here is based on disease activity and hearing level. After the first stage, it is common for the ear to have a maximal conductive hearing loss until the second operation. This ear would not provide the patient with functionally useful hearing without a hearing aid.

If only one ear has active disease or poor hearing, that ear is operated initially. After the second stage is completed, surgery begins on the second ear. If both ears have active disease, after healing has occurred from the first stage on the initial ear, the second ear can be operated. The patient typically requires a hearing aid on the first ear until the ossicular reconstruction is performed at the second stage. Fitting a behind-the-ear hearing aid provides the capability to switch the aid easily to the opposite ear as needed.

Patients with chronic otitis media present the surgeon with many management complexities. Bilateral disease is common, and each ear may require two surgeries. It is helpful to record the plan for the second stage at the time the first stage is completed; this can be done through a handwritten chart note, a customized surgical data sheet, or prominent placement in the dictated operative report. Common included items are timing of the next stage, approach (transcanal or postauricular), type of prosthesis, location of possible residual cholesteatoma, need for special equipment (laser, facial nerve monitor), and areas of special caution (exposed dura, dehiscent facial nerve or jugular bulb). These details are best documented at the time of the first operation, and provide a clear basis for the planning of the second stage.

PREOPERATIVE EVALUATION AND COUNSELING

The ability to predict the need for staging the operation depends on one’s experience and philosophy regarding the badly diseased ear. We discuss the possibility of needing a planned two-stage operation with the patient at the initial consultation and include it in printed patient educational materials. In some cases, it is clear at the initial evaluation that two stages are required; in others, the need for staging can be determined only intraoperatively. Typically, when the rationale for staging is explained to the patient, it is readily understood and accepted.

PLASTIC IN THE MIDDLE EAR

The most common middle ear indication for staging the operation is a mucous membrane problem. To avoid confusion, the following discussion is limited to that problem. The techniques are the same when there are other indications.⁶

Plastic Sheeting

Silicone sheeting is referred to here as “thin” and “thick.” The thin sheeting is 0.005 inch; the thick sheeting is 0.040 inch. Silicone sheeting is distributed by Invotec International, Inc., Jacksonville, Florida. An alternative to thin silicone sheeting is absorbable gelatin film (Gelfilm).

Thin silicone sheeting is malleable. It adapts easily to the middle ear space and does not tend to curl when exposed to body temperature. Thick silicone sheeting is stiff and is not deformed by fibrous tissue that may develop in the middle ear. Although stiff, it is malleable enough to be withdrawn from the mastoid and middle ear through a tympanotomy exposure.

Supramid Extra is the trade name for a medical-grade nylon 6. The sheeting thickness of Supramid Extra Foil is 0.3 mm. Because it is thinner than thick silicone sheeting, it is easier to insert. It is not malleable, however, and this quality prevents it from being extracted from the mastoid without a mastoid re-exploration. Most cases can be managed with Gelfilm for minimal mucosal disease and thick silicone sheeting for severe disease. Gelfilm is used for cases not requiring a second stage, and thick silicone sheeting is used for cases that are to be staged.

Mucous Membrane Indications

When the mucous membrane problem is limited, there is no need for staging (Fig. 18-1). Adhesions form between denuded bone of the middle ear and the tympanic membrane graft, but usually do not pose a long-term problem. Nonetheless, Gelfilm is frequently placed over the denuded areas to prevent adhesions (Fig. 18-2). Alternatively, one may use thin silicone sheeting, if desired. The silicone sheeting may be left in place indefinitely.

FIGURE 18-1 Absence of mucosa over promontory.

FIGURE 18-2. Silicone sheeting has prevented adhesions between tympanic membrane graft and denuded promontory.

FIGURE 18-3. More extensive mucous membrane destruction and absence of the stapes. Good mucosa remains in the recesses and the epitympanum.

FIGURE 18-4. Stiff plastic sheeting holds its position and prevents adhesions between the tympanic membrane graft and the raw areas of bone.

FIGURE 18-5. Mucous membrane destruction is extensive. Note a few islands here and there of mucosa and some in the tubotympanum.

FIGURE 18-6. Thick silicone or Supramid sheeting is not displaced by fibrous tissue. Mucosa should regrow over all denuded bone and the undersurface of the graft.

In more diseased ears, one may find that normal mucosa remains only in the tubotympanum, facial recess, and epitympanum (Fig. 18-3). Reconstruction of this ear without regard to the mucous membrane problem usually results in a fibrosed middle ear.

When thin silicone sheeting was used in such cases in the early 1960s, the results were frequently disappointing. The silicone sheeting was rolled up or deformed by advancing fibrous tissue. If the silicone sheeting contacted the tympanic membrane, extrusion often occurred. To obtain the best hearing results in such cases, it was necessary to perform the reconstruction in two stages. At the initial operation, the tympanic membrane was grafted over a piece of thick silicone sheeting that filled the middle ear (Fig. 18-4). Six months later, the thick silicone sheeting was removed, and a suitable prosthesis was inserted.

In badly infected ears, there may be no mucosa remaining in the middle ear cleft except for the tubotympanum (Fig. 18-5). Some physicians believe that nothing can be done to reconstruct such an ear; radical mastoidectomy has been advised. Ears of this type can be reconstructed by staging the tympanoplasty, as long as some mucosa remains in the tubotympanum, and the plastic sheeting can reach the area to prevent eustachian tube closure.

In cases of extensive or total mucous membrane destruction, it may be wise to perform an intact canal wall mastoidectomy even though there may not be other indications for a mastoid exploration. The mastoid is opened into the middle ear through the facial recess for insertion of a sheet of Supramid or thick silicone sheeting (Fig. 18-6). This process ensures that the plastic would not roll up—hence, no fibrous tissue. During revision, the plastic is removed, and a suitable prosthesis may be placed between the stapes capitulum or footplate and the mobile tympanic membrane in a well-healed normal middle ear.

Canal Wall Down Procedures

The principles and indications involved in staging the operation in canal wall down procedures are the same as in canal wall up procedures, but the technique is different. Many physicians who use both techniques in tympanoplasty have stated that their hearing results are less satisfactory in canal wall down cases. The probable reason for these results is the narrowing of the middle ear space, which should not be allowed to occur in canal wall down procedures. In staging the operation in canal wall down procedures, a wide middle ear space is obtained by extending the thick silicone sheeting onto the fallopian canal. It is important to bevel the superior edge of the plastic to help delay extrusion; the graft rests on that edge.

Plastic Extrusion

There is no question that plastic material placed in the middle ear may extrude if an edge of the plastic comes in contact with the tympanic membrane. It is our experience, however, that extrusion occurs in less than 0.5% of the cases. Surgeons who have reported a major problem with extrusion are probably using thin silicone sheeting in situations in which they should have used thick plastic and staged the operation.

CONTROVERSY

There is considerable difference of opinion among experienced otologists in regard to staging the operation.⁵ The major difference occurs over more diseased ears, usually with cholesteatoma, and is related not to the management of the mastoid (canal wall up or canal wall down), but instead to the surgeon’s philosophy.⁷ Staging proponents believe that the great divergence of opinion on staging that one encounters is related to two factors. How hard does the individual pursue a good functional result in the most severely diseased ear? What does one accept as a satisfactory functional result? In an ear with no remaining mucosa except in the tubotympanum, it is our experience that unless the operation is staged, one cannot usually obtain a satisfactory functional result.