Total Stapedectomy

Published on 13/06/2015 by admin

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Chapter 21 Total Stapedectomy

The goal of stapes surgery is to re-establish sound transmission through an ossicular chain stiffened because of otosclerosis. Various techniques have been used to accomplish this goal, including stapes mobilization, fragmentation, small fenestration, and partial and total stapes footplate removal.

The history of surgery for otosclerosis began in the latter part of the 19th century. A group of pioneering surgeons, including Kessel,¹ Boucheron,² Miot,³ Faraci,⁴ and Passow,⁵ began to mobilize the stapes. At about this time, Jack⁶ reported on a series of cases in which he removed the stapes entirely. The unacceptably high rate of inner ear injury and infection led to the abandonment of stapes surgery. As stated by Goodhill,⁷ “it was probably Siebenmann⁸ along with Moure⁹ who closed the door on further stapes surgery at the turn of the century.”

Surgery for otosclerosis was reactivated in 1923, when Holmgren ¹⁰ bypassed the stapes area by creating a fenestra in the horizontal canal to stimulate inner ear fluids in response to sound, and the fenestration operation was reborn. In 1937, Sourdille¹¹ presented a series of fenestration cases before the New York Academy of Medicine. In 1938, Lempert¹² introduced his unique one-stage fenestration technique using his endaural approach and a dental drill to create the fenestra. Surgeons throughout the world clamored to learn his technique, which became the standard. Lempert will forever be known as the father of otosclerosis surgery.

In 1952, Rosen ¹³ reintroduced stapes mobilization for otosclerosis. For a brief time, this technique was widely used and threatened to replace the Lempert procedure. It was soon realized, however, that refixation of the footplate often occurred. Shea¹⁴ introduced his technique of total stapedectomy. After removing the total stapes, he covered the oval window with a vein graft and introduced an artificial stapes made of polytef (Teflon) by Treace to make the connection with the incus. This reactivation of stapedectomy by Shea replaced Lempert’s fenestration procedure and Rosen’s mobilization operation, and, with modification, is now used universally throughout the world. We are greatly indebted to Shea for his tremendous contribution to otosclerosis surgery.

PATIENT COUNSELING

All patients should be told that even though their hearing loss is hereditary, their children or grandchildren will not necessarily have a similar problem. They should be assured they are not going to become totally deaf. The mechanics of the hearing loss should also be explained in detail, preferably by use of a suitable illustration.

Patients who are suitable for stapes surgery should be told that they have the option of wearing hearing aids, and if there is any doubt about the decision to have surgery, they should be encouraged to have a trial period with hearing aids unless they are already wearing them. The expected hearing result and all possible risks, such as further or total hearing loss, taste disturbance, dizziness, the effect on tinnitus (if present), and the very remote possibility of a partial or total facial paralysis, should be clearly understood. Hearing improvement is in direct proportion to the preoperative bone conduction level, and the patient must understand the degree of improvement to be expected.

SELECTION OF PATIENTS FOR STAPES SURGERY

All patients who are suitable for stapes surgery should be thoroughly informed of the advantages and the possible complications of the operation. For some patients, serviceable hearing can be restored with no need for a hearing aid. In others, the hearing can be improved so that they may need a hearing aid only for distant conversation. In still other patients, the hearing can be improved, and they may be able to convert their postauricular aid to an all-in-the-ear hearing aid or from an all-in-the-ear aid to an intracanal aid.

Occasionally, patients have a totally blank audiogram and are still suitable for stapes surgery. This situation occurs when the bone conduction level exceeds the capability of the audiometer. There may be a 75 or 80 dB bone conduction level, but a 40 to 50 dB air-bone gap. Typically, when the patient is initially evaluated, he or she is hearing surprisingly well with a powerful hearing aid and possesses excellent speech quality. On examination, one may note a positive Schwartze’s sign, but the 512 Hz tuning fork is not helpful. After surgery, these patients are grateful because they can now wear less powerful hearing aids with fewer feedback problems.

Indications for Stapes Surgery

The patient should understand the details of the operation, including the operative procedure itself, and all admission and discharge procedures. The following principles also apply:

1. The patient should be in reasonably good health, especially if general anesthesia is contemplated.

2. The age of the patient is not a factor in the decision to perform surgery. The youngest in our series was 7 years old, and the oldest was 98.

3. The poorer hearing ear, based on the patient’s statement and not on the audiogram, should be chosen for surgery. In children, the poorer hearing ear should be operated on so that the hearing aid can be eliminated before they enter school. Surgery for the second ear should be delayed until they are old enough to make their own decision.

4. Tuning forks should be used to confirm the audiometric findings. If bone conduction is heard louder than air conduction with a 512 or a 1024 Hz tuning fork, with proper masking of the better hearing ear, the individual is a suitable candidate for surgery. If one reverses the 2048 Hz fork, he or she is an excellent candidate. The minimum air-bone gap should be 15 dB, as averaged in speech frequencies.

5. Speech discrimination is not a major factor in determining stapes suitability. If the patient understands sentences and answers questions correctly using a speaking tube while masking the opposite ear with a Bárány apparatus, he or she is suitable, provided that the earlier criteria are met. The improvement the patient receives with a cochlear implant substantiates the value of any sound that helps patients hear and react better to their environment.

6. Indications for stapes surgery are essentially the same whether the hearing loss is unilateral or bilateral. Surgery in the opposite ear can occur 6 months later, provided that it is then the poorer hearing ear.

Contraindications of Stapes Surgery

Stapes surgery is contraindicated in patients (1) in poor physical health; (2) with a current balance problem, such as active Meniere’s disease or a fluctuating type of hearing loss; (3) with pre-existing tympanic membrane perforation; (4) with active external or middle ear infection; and (5) with an inadequate air-bone gap confirmed by an audiogram and the 512 Hz tuning fork.

SURGICAL TECHNIQUE

Step 1

Stapes surgery may be performed with a local or a general anesthetic. We prefer local anesthesia with adequate sedation that may be supplemented during the procedure with intravenous midazolam (Versed) or diazepam (Valium), if necessary. We prefer local anesthesia because there is less bleeding, and the surgeon is alerted if any vertigo occurs while working on the footplate, inserting the prosthesis, or removing the prosthesis, in a revision case.

Step 2

During surgery, the patient’s vital signs are monitored by electrocardiography, blood pressure, and oxygen saturation. The auricle and the surrounding area are cleaned with povidone-iodine (Betadine) solution, and plastic drapes and folded towels are applied. A final head drape with an opening exposing the ear is placed over the head and rested on a metal support to help prevent the feeling of claustrophobia.

Step 3

The operating table is placed slightly in Trendelenburg’s position and rotated toward the surgeon so that he or she can see directly down the ear canal from the sitting position.

Step 4

The ear canal is washed with warm saline solution to remove the povidone-iodine, and local anesthesia containing 2% lidocaine in epinephrine 1:100,000 is infiltrated. The initial injections are made with a 30 gauge needle around the periphery of the entrance to the ear canal. Approximately 2.5 to 3 mL of this solution is injected, and 1 or 2 drops are placed in the vascular strip just external to the tympanic membrane. This helps reduce the bleeding at the time of the incision. The tissue to be used, whether vein, fascia, perichondrium, or fat, may be obtained before or after the canal surgery is started.

Several sizes of oval and round specula should be on the tray, and the largest one that can be seated into the canal is used. The shafts of the instruments entering the speculum are in firm contact with the middle finger, which is stabilized against the speculum, and the speculum is stabilized by the other fingers against the head. A fixed speculum holder is not used. The advantage of not using a fixed speculum holder is flexibility of the speculum for viewing purposes and for allowing the patient to move his or her head, if desired. The specula and all instruments should be plain metal because black specula and instruments absorb much-needed light. The shafts of the needles and hooks should be malleable so that they can be bent slightly to reach difficult areas.

The inferior and superior vertical incisions are made at the 6:30 and 11:30 o’clock positions (Fig. 21-1). The point of the sickle knife is started 1 mm from the edge of the tympanic membrane to prevent a possible tear. It is extended externally approximately 8 mm, and this distance can be confirmed when the curve of the incision knife strikes the edge of the properly inserted speculum. If one extends the incisions further externally, the skin becomes thicker, and more bleeding occurs. Several sweeps are made to ensure that one cuts through the periosteum.

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