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Tympanoplasty: Staging and Use of Plastic
Acknowledgment
James Sheehy, MD (deceased), was the primary author for earlier versions of this chapter. His previous contributions to this work include the dominant surgical philosophy contained in the current version.
Elimination of the 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. However, the staging of the operation and the use of plastic in the middle ear require that the discussion consider both objectives. Staging the operation involves disease and function and is not technique-oriented; that is, the 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, as well as the techniques used in performing tympanoplasty in two stages. The controversies surrounding the procedure are discussed at the end of this chapter.
Postoperative Collapse of the 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, while 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 (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 the observation 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 remaining 6% developed collapse of the middle ear space. These results indicate that continued eustachian tube dysfunction is an uncommon cause of 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) permanently restoring hearing. , Whether one finds any indication for staging depends on how vigorously a good functional result is pursued in severely diseased ears.
The decision on whether to stage is made at the time of surgery. With experience, this judgment can usually be made before surgery, and the patient can be alerted 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 status of the ossicular chain, and (3) the certainty (or lack thereof) of removal of the cholesteatoma. Considering these three factors, we stage approximately 75% of tympanoplasty and mastoidectomy procedures, and approximately 15% of tympanoplasties not requiring mastoidectomy.
Mucosal disease factors
Frequently, large areas of diseased or absent mucosa are present in the chronically infected middle ear. Groundwork is necessary to promote the regrowth of the normal mucosa. The first step is the elimination of infection before surgery, if possible. The second step is the 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 the 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 the eventual formation of scar tissue or adhesions between the denuded surfaces. To prevent these adhesions from forming and to allow the 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 the 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. Therefore, a fixed stapes should not be removed during tympanic membrane grafting. In cases of otosclerosis, a two-stage procedure is usually 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 performed. At that time, an intact tympanic membrane allows for the removal of the fixed footplate in a sterile environment and the completion of the ossicular reconstruction.
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