Tympanoplasty-Staging and Use of Plastic

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Chapter 18 Tympanoplasty—Staging and Use of Plastic

James L. Sheehy, Clough Shelton∗

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

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