Surgical Approach

''Nowhere is the laser more appropriate than in revision stapes surgery.''22

in preparing to approach a failed stapes surgery, the availability of a laser is extremely important. A large meta-analysis demonstrated the significant benefit to outcome with the use of lasers as compared to conventional techniques in revision surgery. Wiet et al35 showed that a successful (<10 dB) result occurred in 69% of cases treated with a laser, whereas only 51% attained the same result when conventional techniques were used (p = 0.002).35 Of the available lasers, the fiberoptic handpiece probes are uniquely advantageous compared to the micromanipulator controls found with CO2 lasers. Horn et al36 and Nissen37 extolled the virtues of the argon laser for these cases.

Although some patients may not prefer local anesthesia with sedation, performing revision stapes surgery in this manner affords greater assurance and safety. Patients under general anesthesia cannot react to vestibular irritation nor can they be queried intraoperatively about hearing acuity. unless there are extenuating circumstances, or significant patient concerns, the surgeon should plan to do the cases under local anesthesia with sedation.

Fisch et al38 proposed that all revision cases be performed via an endaural approach. in their experience, the view, orientation, and greater ability to assess the ossicular mobility dictate this approach. Farrior and Temple9 also cited the advantage of this approach if the prosthesis must be attached to the malleus instead of the incus. There is indeed an advantage to placement of the prosthesis via the endaural approach. But with an adequate external auditory canal that can accommodate at least a 6mm surgical ear speculum and visualization of the tympanic annulus and tympanic membrane anterior to the short process of the malleus, it is not essential. Nevertheless, the endaural approach should be within the armamentarium of the surgeon, as it is invaluable in the most difficult cases and when performing a malleostapedotomy.

After the patient has been given medication for sedation, along with intravenous steroids, an antibiotic, and an antiemetic, a periauricular block is performed. The ear canal is then injected in quadratic fashion until light blanching of the tympanic membrane occurs.

After the ear is prepped, the ear canal is suctioned of any residual fluids. After examining the meatus and ear canal, the largest speculum to be accommodated just medial to the hair-bearing line in the canal is chosen. A wide apex is positioned posterior to the scutum, and a generous triangular-shaped tympanomeatal flap is incised and raised. The incision must extend anterior and lateral to the short process of the malleus, so when the flap is raised the anterior malleal process and ligament are visualized as well as the posterosuperior quadrant (Fig. 16-3). Often the tympanomeatal flap is quite thick. it may be thinned sharply on its medial surface to facilitate mobilizing and reflecting the flap forward. Quite commonly there are multiple adhesions in the posterosuperior quadrant, so the tympanum is

Tympanomeauil

Tympanomeauil

Surgical Changes Tympanic Membrane

Suction

FIGURE 16-3 Raising the tympanomeatal flap. A generous triangularly shaped flap should be elevated. The incision, as indicated by the arrow, must extend anterior and lateral to the short process of the malleus.

Suction

FIGURE 16-3 Raising the tympanomeatal flap. A generous triangularly shaped flap should be elevated. The incision, as indicated by the arrow, must extend anterior and lateral to the short process of the malleus.

entered inferiorly and the drum elevated from there. All adhesions not encasing the prosthesis are lysed using the laser with 1 to 2 W of power and a 0.1-second-duration pulse.

It is imperative in revision stapes surgery to palpate and determine the mobility of the lateral ossicular chain. Fisch et al noted3 that although ''complete fixation of the incus and malleus is easily detected ... partial fixation of these ossicles may defy years of experience.'' Incus-malleus fixation or ankylosis is more frequent in ears with otosclerosis and represents a significant cause of revision stapes surgery. This type of ossicular fixation may be evident in between 3 and 13.5% of revision stapes surgeries.39 To correctly assess and correct malleus ankylosis, it is important to both visualize and directly inspect the anterior malleal process and ligament38 (for cases of malleal ankylosis, see below).

The fallopian canal is inspected to determine any areas of bony dehiscence or prolapse of the nerve itself. Then the promontory is followed posteriorly to the round window. The lip and niche of the round window are inspected. If there is obliterative involvement by otosclerosis, then the surgery is terminated and the patient should be fitted with a hearing aid.

Horn et al36 stated, ''The most difficult problem of revision stapedectomy is management of the soft tissue and prosthesis in the oval window.'' Understandably, if there does not appear to be lateral ossicular fixation, if the facial nerve does not obscure the well of the oval window, and there is no obvious obliteration of the round window, the surgeon must now deal with the likely pathology extending from or involving the incus to the oval window.

The incus is examined first, and in particular the attachment of the prosthesis to the long process. Adhesions may be easily lysed, with the laser exposing the wire or ribbon loops or the handle of the Robinson prosthesis. Then the laser is used to undress the prosthesis of its investing bands or adhesions down to the lip of the fossa ovalis (Fig. 16-4).

One must explore the oval window neomembrane; otherwise the depth to the fenestration cannot be ascertained, nor can one determine the presence of obstructing footplate parts or otosclerotic re-growth.22 This is most easily accomplished with a 20- or 24-gauge suction stabilizing the prosthesis and working with the laser probe to dissect the adhesions of the neomembrane away.

Usually it is difficult to ascertain the depth of the prosthesis and whether it is positioned favorably within the fenestration or oval window. Therefore, as advocated by Prasad and Kamerer40 and Langman and Lindeman,27 the prosthesis should be removed. (Even in cases where the findings point to a loose prosthesis, the prosthesis should be removed because it has often been displaced outside of the oval window fenestration.) To remove it, the prosthesis must be released from its attachment to the incus. The incus is stabilized either with a suction or alligator. Then the loop or bucket handle can be

Mild tension (Right angled hook)

Mild tension (Right angled hook)

laser

FIGURE 16—4 Dissection within the fossa ovalis. Dissection around the prosthesis and incus may be facilitated with gentle distraction using a right-angle pick. The laser allows safe vaporization of adhesive tissue and scar engulfing the incus and prosthesis.

laser

FIGURE 16—4 Dissection within the fossa ovalis. Dissection around the prosthesis and incus may be facilitated with gentle distraction using a right-angle pick. The laser allows safe vaporization of adhesive tissue and scar engulfing the incus and prosthesis.

lifted away using a 1-mm right-angle pick, and, without suctioning within the oval window, the prosthesis may be gently removed from the middle ear.

Although an initial response would be to replace the prosthesis with one measured against the one removed, further exploration and removal of scar and adhesions must be performed within the oval window. once the footplate or fenestration is visualized, a new prosthesis may be placed. A measurement from the undersurface of the long process to the footplate or annulus is made, adding 0.2 mm of length to allow for the thickness of the footplate and sufficient penetration into the vestibule. A custom piston prosthesis is made from a 6-mm-long Fisch Teflon piston-platinum wire prosthesis (Smith-Nephew Richards, Memphis, TN).

Utilizing the 1-mm-long, right-angle pick to center and place the prosthesis, high field magnification ensures placement into the oval window. proper crimping around the long process may be accentuated with a pressed piece of fibroareolar material applied over the wire and around the incus at that point. promontory mucosa may be gently scraped to prompt a bit of bleeding that, along with a single drop of fibrin glue, acts as the sealant.

if, during the elevation of the tympanomeatal flap, ossification of the anterior malleal ligament and process is recognized, there are two paths one can follow to address this problem. if the ligament and process are not too rigidly fixed, then one can proceed with either mechanical or laser separation in this area, protecting the underlying chorda tympani nerve. When the region anterior to the lateral process is narrowed, however, it is common to find the ligament and process more densely ossified and the fixation to be greater. These cases are better addressed with resection of the head of the malleus and attached process and ligament followed by the malleostapedotomy (see below).

When there is not sufficient incus length, or there is lateral ossicular fixation or severe subluxation and disassociation at the incudomalleal joint, then a malleostapedotomy may be performed. originally described as an incus-replacement prosthesis by Shuknecht,41 the ability to circumvent an incus deficiency or attic ossicular fixation has gone through various iterations. Fisch38 presents a simple and compelling approach to this problem. (An alternative to the malleostapedotomy for a deficient incus has been detailed. Tange42 describes using ionomeric cement to lengthen the long process to accept placement of a new prosthesis.)

The incus is removed when performing a mal-leostapedotomy. once this is complete, if the tym panic membrane has not been released from the short process of the malleus, this is done. As the malleus is stabilized with the suction, a sickle knife can lift the cartilaginous cap and then be dragged along the superior surface of the malleus, dividing the plica mallearis.

The head of the malleus is removed, either with a malleus nipper or high-speed otology drill, just superior to the attachment of the tensor tympani tendon. The malleus is notched and this is contoured to accept a secure crimping of a wire loop (Fig. 16-5). A Fisch Teflon piston-platinum wire prosthesis is obtained and the wire loop carefully opened. This may be done by hanging it on the tapered end of the right-angled pick and carefully moving along toward the wider portion with a jeweler's forceps. Then, in a similar fashion to work with an intact incus, the ribbon wire loop may be secured to the neck of the malleus just below the offshoot of the short process. Typically the length of the prosthesis is between 5.5 and 6.0 mm.

When the wire ribbon loop has been secured and a blood-fibrin glue patch applied to seal the oval window, the tympanomeatal flap may be reflected back into position. A whisper into the operative ear is done to confirm audition. Finally, moistened and pressed pieces of Gelfoam are placed to secure the edges of the flap, and the medial canal is filled with antibiotic ointment.

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