Operating Room Setup and Preparation

Stapedectomy surgery requires great finesse for good results. Thorough preoperative preparation results in smoother intraoperative execution and consistently good results. A surgical team that is familiar with the procedure and setup is of paramount importance. A scrub nurse who is knowledgeable about otologic instruments and can anticipate what is needed for the next step of the procedure is crucial. A microscope mounted closed circuit television camera with monitor allows the scrub nurse to see what the surgeon is doing and anticipate the next instrument that is needed. In a difficult case, with unfavorable anatomy or bleeding or both, the surgeon must have the right instrument in a short amount of time to complete the operation effectively. A scrub nurse who is not trained to assist in a stapes surgery is unable to perform adequately in these situations.

The anesthesiologist or local monitoring nurse is positioned at the foot of the table. The scrub nurse is positioned directly across the table from the surgeon. This positioning allows the nurse to hand instruments to both of the surgeon’s hands, greatly improving the efficiency. The microscope is positioned at the head of the table. Proper patient positioning can greatly facilitate the ease of this procedure. The patient’s head is turned away from the surgeon with the chin tucked toward the opposite shoulder. This maneuver aligns the external auditory canal with the view of the surgeon sitting in a neutral position. Failure to tuck the chin can result in the surgeon leaning over the patient’s chest and much less effective visualization of the field. The operating table is positioned in slight Trendelenburg. This head-down position counteracts the normal inferior angulation of the external auditory canal and results in improved visualization. Generally, the patient is positioned so the plane of the tympanic membrane is parallel with the plane of the floor in the operating room.

A support bar (Fig. 22-1) is attached to the operating table to keep the drapes off the patient’s face. By attaching the bar directly to the table, the bar moves in conjunction with the table. Using a floor-mounted device, such as a Mayo stand, does not allow the coordination of movement between the two items and can result in limitations of table movement. The operative site is prepared by surrounding the ear with a plastic drape (1030; 3M) that keeps the hair out of the operative field. The ear and a margin of the plastic drape are prepared with povidone-iodine (Betadine) solution, and the povidone-iodine solution is allowed to fill the ear canal. Intravenous midazolam (Versed) is used for sedation. This medication is given in 0.5 mg increments until the patient is sleepy and relaxed. Typically, the patient requires 4 to 5 mg. Intravenous meperidine (Demerol), given in 12.5 mg increments, can be used to supplement the midazolam. An antiemetic such as ondansetron (Zofran) is also administered during surgery. The amount of sedation is titrated to the point that the patient is somnolent, yet appropriately responsive. At this point, 3 mL of blood is drawn and transferred to the scrub nurse.

FIGURE 22-1 Drape support bar is attached directly to operating table.

A local field block is performed with 1% lidocaine with 1:100,000 epinephrine. A four quadrant block is performed in the meatus, and an additional injection is administered to the vascular strip and posteroinferiorly in the canal. Blanching of the canal skin is important for good hemostasis. Also important for good hemostasis is a snugly fitting speculum. The pressure provided by the speculum helps tamponade the vessels supplying the ear canal from the meatus. If one encounters troublesome bleeding during the procedure, a different speculum size can be tried, which typically results in improved hemostasis.

Surgical Technique

A tympanomeatal flap is incised using disposable tympanoplasty blades (7200 and 7210 BD Beaver). These disposable blades result in a sharp incision and rapid healing of the ear canal. Two incisions are made tangential to the annulus, one beginning adjacent to the short process of the malleus and following the tympanosquamous suture line. The second is adjacent to the tympanic annulus starting at approximately the 6 o’clock position and extending posterosuperiorly in the canal. These two incisions (Fig. 22-2) are connected with a transverse incision approximately 5 mm posterior to the tympanic annulus. The flap length is approximately the width of two Sheehy weapons (3 mm round knife). An excessively long flap would result in more bleeding, and can be difficult to fold forward in a narrow ear canal because of the bulk of the flap.

FIGURE 22-2 Canal incisions are outlined for the tympanomeatal flap.

The flap is elevated with a Sheehy weapon to the edge of the bony tympanic annulus. During this elevation process, the tip of the weapon is kept in contact with the ear canal bone. A No. 3 Baron suction is used behind the weapon, avoiding suction on the skin flap. A Rosen needle is used to enter the middle ear in a posterosuperior location. The tip of the instrument is placed through the middle ear mucosa, and the mucosa is divided. It is imperative not to place the instrument too deeply into the middle ear during this maneuver, or incus dislocation can occur. When the middle ear space is identified, the dissection is carried inferiorly, and the tympanic annulus is directly visualized. The annulus is elevated with the Rosen needle out of its sulcus. A House annulus elevator is also useful at this point. The annulus elevator is a blunt instrument, and if used posterosuperiorly, it too can result in incus dislocation.

The flap is elevated inferiorly to allow visualization of the round window (Fig. 22-3). It is elevated superiorly until the neck of the malleus is visualized. The chorda tympani nerve is adherent to the posterosuperior bony tympanic annulus. It is separated from this bone, and separated from the undersurface of the malleus. Separating the chorda tympani allows mobilization of the nerve inferiorly for good visualization of the stapes, and prevents injury during curetting.

FIGURE 22-3 Tympanomeatal flap is elevated exposing the neck of the malleus and the round window.

Posterior external auditory canal bone is removed with a curette to visualize the oval window. Initial curetting occurs several millimeters posterior to the edge of the tympanic annulus (Fig. 22-4). Initial curetting on the edge can result in displacement of the curette into the middle ear with dislocation of the incus. The posterior curetting allows for the bone to be weakened by creating a trough in this area. When the bone is weakened, the edge of the bone can be cracked off with the curette and little force is needed. The bone should be removed posteriorly to allow visualization of the stapedial tendon and pyramidal process (Fig. 22-5). For a right-handed surgeon working on a right ear, the bone should be removed superiorly so that half of the diameter of the horizontal fallopian canal can be visualized. For a right-handed surgeon working on a left ear, more curetting is necessary to introduce instruments in the middle ear, and bone should be removed so that the entire diameter of the horizontal fallopian canal can be visualized. At the conclusion of the curetting, all of the resultant bone chips should be removed from the ear canal to prevent postoperative healing problems.

FIGURE 22-4 Initial curetting begins posterior to the edge of the scutum.

FIGURE 22-5 Completed curetting exposes stapedial tendon, pyramidal process, and horizontal fallopian canal.

The incudostapedial joint is separated with a joint knife (Fig. 22-6). The joint is typically 1 mm medial to the undersurface of the incus and can be identified by pushing the incus slightly forward and laterally. The joint is separated with a side-to-side motion by the knife. When the joint is separated, the malleus mobility is tested to rule out idiopathic malleus head fixation. The stapes is tested for motion, and the anterior oval window is inspected visually for evidence of otosclerosis. Otosclerosis can reliably be seen in this area and appears to be bright white bone with prominent vessels on it. The adjacent normal otic capsule bone looks slightly gray compared with the otosclerotic bone. If otosclerosis is not visualized, one must be quite confident that the stapes is not mobile before proceeding (see the section on pitfalls).

FIGURE 22-6 Incudostapedial joint is separated with joint knife.

FIGURE 22-7. Stapedial tendon divided with laser.

FIGURE 22-8. Posterior crus of stapes is now exposed.

In some cases, patients experience pain during manipulation of the middle ear structures. The local anesthesia can be supplemented by topical application of 1% lidocaine with 1:100,000 epinephrine. The solution can be squirted into the middle ear. It is important to remove the solution quickly, however, so that it does not diffuse through the round window and result in postoperative severe vertigo.

Using the laser, the stapedial tendon and posterior crus are removed (Figs. 22-7 through 22-12). A typical setting for the KTP or argon laser is 1.5 W, at of a second duration. The author prefers a fiberoptic probe for delivery of the laser. Any mucosal adhesions in the oval window area are also removed with the laser to prevent bleeding from the mucosa. Care should be taken not to use the laser directly on the tympanic facial nerve, particularly if dehiscent. In some cases, the posterior stapes crus has a three-dimensional shape like the letter C. It is important to char not only the posterior aspects of the crus, but also the superior and inferior aspects. The charred area is picked through with a Rosen needle (see Fig. 22-10), and the superstructure is down fractured toward the promontory with a Rosen needle (see Fig. 22-12A). A quick sharp jerk on the superstructure is important to fracture the anterior crus (see Fig. 22-12B). A slow down fracture movement may result in mobilization of the footplate.

FIGURE 22-9 Posterior crus is vaporized with laser.

FIGURE 22-10. Charred posterior crus is picked away.

FIGURE 22-11. Posterior crus is now divided.

FIGURE 22-12 A, Stapedial superstructure is down-fractured toward the promontory. B, A quick sharp motion toward the promontory results in fracture of the anterior crus.

The distance between the surface of the footplate and the lateral aspect of the incus is measured (Fig. 22-13). In most cases, this measurement is 4.5 mm. If it is shorter, one should suspect a thick footplate. Measurements can also be routinely taken to the undersurface of the incus. The surgeon should always measure in a consistent fashion, however, and know how the prosthesis he or she uses is sized to determine the correct prosthesis length (Fig. 22-14). Optimally, the prosthesis should extend 0.5 mm into the vestibule.⁸ The fenestra in the footplate is usually placed in the middle or posterior half.

FIGURE 22-13 Measurement is taken between the surface of the footplate and the lateral aspect of the incus.

FIGURE 22-14 Piston prostheses are typically sized to the bottom of the shepherd’s crook.

Using the laser, a footplate vessel is the initial target. With a visible wavelength laser, the energy is absorbed by pigment. The white footplate is a poor absorber of this energy; however, if an initial char is developed by using a laser on a red vessel, the char can be overlapped with each subsequent laser blast (Fig. 22-15) creating a rosette of chars. Perilymph seeps through the charred footplate and can be aspirated with a 24 gauge suction tip (Fig. 22-16). The charred area is created larger than the intended fenestra (Fig. 22-17). It is easier to remove charred footplate than normal footplate if the fenestra needs to be enlarged.

FIGURE 22-15 Char is created on the footplate with the laser. Subsequent chars overlap creating a rosette.

FIGURE 22-16 Perilymph seepage is removed with a 24 gauge suction tip.

FIGURE 22-17 Char on the footplate is created larger than desired opening.

When a char of sufficient size has been fashioned, a sizing instrument “disk on a stick” (N1685-spec; Storz Instruments) is used to create the fenestra. The disk is 0.6 mm in diameter and creates a fenestra the same size as a 0.6 mm diameter piston. The disk is gently pushed through the char (Fig. 22-18) to create the hole. It can be used to rasp the hole, resulting in a hole slightly larger than the disk. When the fenestra is open, it is important to avoid suctioning directly into the oval window. A No. 24 suction is used at the margins of the oval window with the surgeon’s finger off the control hole. If a blood clot accumulates in the oval window obscuring the view, it can be lifted out using a Rosen needle rather than suction.

FIGURE 22-18 “Disk-on-a-stick” is used to make the opening in footplate.

As an alternative to the laser, a small fenestra can be easily created using a microdrill. To make a footplate opening, a 0.7 mm diamond burr is used, which allows sufficient clearance for a 0.6 mm piston prosthesis. After the superstructure has been removed, the burr is lightly placed on the footplate (Fig. 22-19). Pressure is not exerted against the footplate, and a light touch is used. The drill motor is activated, and when the fenestra is completed, the surgeon senses a subtle resistance change at his or her fingertips. The drilling can be quite noisy and can startle a patient who is under local anesthesia. In these cases, it is helpful to place the drill against the promontory and activate it, alerting the patient to the noise of the drill and avoiding unexpected patient movement. The microdrill provides a uniformly sized footplate opening.

FIGURE 22-19 Microdrill is used to make the small fenestra in the footplate.

The prosthesis is introduced into the oval window using nonserrated alligator forceps. After placement in the oval window, the prosthesis is maneuvered into position with a strut guide. If using a platinum wire prosthesis, the wire is quite malleable, and care must be taken not to bend the wire using excessive force while manipulating the prosthesis into position. In some cases, the diameter of the incus is wider than the opening of the shepherd’s crook. Gentle downward pressure on the shoulder of the piston, pushing it into the open fenestra, allows the crook opening to enlarge and slip over the incus. When the piston is in the fenestra, and the wire is around the incus, it is crimped with crimping forceps. Allowing both jaws of the forceps to contact the prosthesis simultaneously prevents displacement during this maneuver. The crimp should be firm and not oval in shape. An oval crimp can lead to excessive movement of the wire on the incus and ultimately lead to incus necrosis. The prosthesis is crimped over the narrowest portion of the incus (Fig. 22-20), and then slid inferiorly toward the lenticular process. The incus typically widens at this point, and this results in a very snug connection.

FIGURE 22-20 A, Wire is crimped around the incus at its narrowest portion. B, Piston protrudes slightly into vestibule.

The new nitinol-polytef (Teflon) piston (SMart; Gyrus Medical) allows heat-activated crimping of the wire. The argon or KTP laser is set at 0.75 W, and the wire is lasered resulting in self-crimping of the prosthesis. In some cases, the wire is bent slightly when removing it from the packaging. The shaft of the prosthesis can also be lasered to straighten the wire into its native shape. The heat-activated crimping results in a very tight crimp. The length of the SMart piston may shorten on crimping, resulting in a shorter effective length than a manually crimped prosthesis. To correct for this, a longer prosthesis size is used, adding 0.25 mm to the usual length. In the author’s practice, the most common prosthesis length for the SMart piston is 4.5 mm compared with 4.25 mm for a manually crimped prosthesis design.

Autologous venous blood is applied to the oval window to seal it. This is usually placed in a 3 mL syringe with a 20 gauge suction tip. Enough blood is applied to fill the oval window. The tympanic membrane is returned to its anatomic location, and the ear canal is filled with an inert ointment packing (Kos-House Otic Cream; Otomed Inc). A cotton ball is placed in the ear canal, and a Band-Aid is placed over the cotton ball.

Overhanging Facial Nerve

The facial nerve may be dehiscent over the oval window, and in some cases prolapse inferiorly to obscure the view of the oval window. Obliterative otosclerosis on the promontory side can narrow the oval window and lead to a similar appearance as an overhanging facial nerve, and so this possibility must also be evaluated. The otosclerotic bone is very vascular and can be differentiated from the normal promontory When faced with a significantly overhanging facial nerve intraoperatively, the most conservative way to manage this situation is to close the ear and have the patient evaluated for a hearing aid. For an experienced stapes surgeon, however, it is usually possible to complete the operation in this situation. Typically, the facial nerve can be retracted superiorly with a No. 24 suction allowing creation of a fenestra in the footplate either with a fiberoptic laser probe or with a microdrill. Contact of the prosthesis with the facial nerve causes no facial nerve dysfunction. In some cases, removing part of the promontory bone with a microdrill allows additional access. Creating the fenestra on the inferior edge of the footplate can allow for a better angle of the prosthesis past the facial nerve. Bending the wire of the prosthesis around the facial nerve is generally unsuccessful.

Obliterative Otosclerosis

These cases have a thickened footplate, sometimes with loss of the normal oval window landmarks. A shallow measurement from the footplate to the incus may be the first clue that one is dealing with an obliterative case. Rather than seeing a thin blue footplate, an opaque white footplate is visible.

It is possible to create a fenestra through an obliterative footplate with a laser; however, this is a slow and tedious process. The author prefers to use the laser initially to char the footplate to prevent bleeding of the otosclerotic bone. Next, a microdrill is used to create the fenestra. The fenestra is created gradually by excavating the footplate in layers. The goal is a funnel-shaped opening, with the opening wider on the surface. This allows a wider angle of approach by the prosthesis into the fenestra, and prevents binding of the prosthesis against the edges of the footplate. When drilling the fenestra, serial measurements to the incus can be taken with a measuring device to monitor the progress toward the vestibule.

Floating Footplate

In some instances, the footplate mobilizes during down fracture of the stapes superstructure. With the laser technique, it is possible to complete the operation with little difficulty. The fenestra in the footplate is created as previously described. Care in opening the fenestra should be observed to avoid fracture of the footplate and a resultant large opening. A large opening can be managed with a large-diameter prosthesis (0.8 mm). Also, the force used to place the prosthesis in the fenestra in a mobile footplate should be reduced.

Tympanic Membrane Perforation

Perforation of the tympanic membrane may occur during elevation of the tympanomeatal flap. Most commonly, this occurs in a posteroinferior location and results from failure to elevate the annulus in this location. It is possible to elevate the skin of the ear canal and tympanic membrane lateral to the fibrous layer of the drum, which results in perforation. Direct visualization of the annulus to allow its elevation is the best way to avoid this complication. If this complication occurs, the operation can be completed, and the perforation can be closed at the end of the procedure. A small piece of fat is harvested from the lobule, and a fat patch myringoplasty is performed by placing the fat through the perforation in a dumbbell fashion.

Dislocated Incus

The incus can be dislocated while entering the middle ear when raising the tympanomeatal flap or during the curetting process (see earlier). Typically, the incus remains in near-normal anatomic location, and the incudomalleal joint can heal and result in an intact ossicular chain. During the healing process, however, the incus tends to lateralize. In this situation, a slightly longer prosthesis is placed, 0.25 mm longer than would be used in the usual situation.

Chorda Tympani Nerve Injury

Care should be taken to preserve the chorda tympani nerve, if possible. The nerve is particularly vulnerable to injury during curetting. In some cases, it is necessary to mobilize the nerve out of its bony canal in the posterior ear canal. Curetting directly over the course of the nerve unroofs the canal and allows the nerve to be moved. If the nerve is partially injured or stretched, the nerve should be completely transected in a sharp fashion with microscissors. Sharp transection leads to fewer postoperative symptoms of dysgeusia than does partial injury or stretching. The nerve can also be desiccated by the intense light of the microscope. Saline can be installed into the middle ear to rehydrate the nerve.

Success Rate

Small fenestra stapedectomy provides reliable hearing improvement for most patients. Reported closure of the air-bone gap to within 10 dB (when measured by comparing the postoperative bone conduction with the postoperative air conduction) ranges from 56% to 94%.^9–12 Some authors have found an advantage of small fenestra stapedectomy performed with a laser compared with procedures done with a nonlaser technique; others have not found a difference. Sedgwick and coworkers¹³ compared small fenestra hearing results done by drill or laser, and found no difference for the closure of the air-bone gap within 10 dB or postoperative sensorineural hearing loss. When comparing small fenestra techniques with partial or total stapedectomy, there was better preservation of the high-frequency sensorineural hearing with a small fenestra technique, but the difference was small.

Several prosthesis materials have been introduced more recently. Titanium has been advocated as a superior prosthesis material because of its light weight and ease of crimping. Some authors have reported better results¹⁴ with this prosthesis material, whereas others have found no advantage of it over a platinum and Teflon prosthesis.¹⁵

Nitinol is a bimetallic wire (nickel and titanium) that reforms to a preset shape on heating.¹⁶ It has been incorporated into a piston prosthesis (SMart) that allows for heat-activated crimping of the shepherd’s crook around the incus. Heat can be provided by laser or cautery. Early reports are encouraging, showing results comparable or superior to manually crimped prosthesis.^17–19 The author has analyzed his own outcomes comparing the SMart piston with platinum-Teflon piston. Closure of the postoperative four-frequency air-bone gap to within 10 db occurred in 96% of the SMart prosthesis cases compared with 86% of the platinum-Teflon group. The SMart piston is now the author’s preferred prosthesis.

Postoperative Complications

The management of the stapedectomy patient with postoperative dizziness or sensorineural hearing loss is controversial. Some surgeons believe that these symptoms represent either a perilymphatic fistula or a reparative granuloma and advocate immediate surgical re-exploration.²⁰ Other surgeons believe that these symptoms are caused by postoperative serous labyrinthitis, and no surgical intervention is needed. Blood entering the vestibule during surgery can irritate the labyrinth, particularly during its metabolism and degradation. These surgeons believe that early surgical exploration may be more harmful than helpful. Some authors have observed a transient decrease in the sensorineural hearing level after stapes surgery as a routine occurrence during the postoperative period.²¹

Reparative granuloma was a phenomenon that was encountered on the East Coast in the 1960s, but was rarely seen on the West Coast. Some have explained the observed geographic variation as due to differences in the composition of Gelfoam in various parts of the United States at that time (Linthicum FH, personal communication, 2006). It is theorized that ethylene oxide, used during sterilization, was retained by the lot of Gelfoam used on the East Coast for the Gelfoam-wire prosthesis technique, and this led to the cases of reparative granulomas. Many surgeons believe that reparative granuloma have historical significance only and does not occur with modern stapes prostheses.

The author’s approach to postoperative dizziness is to examine the patient in the office to rule out evidence of infection. An audiogram is obtained, and if the sensorineural level has worsened compared with the preoperative levels, the patient is placed on a course of oral steroids for presumed serous labyrinthitis. This treatment has been extremely successful in managing these patients. Early postoperative exploration has not been needed.

Patient Selection Pitfalls

Most patients with a conductive hearing loss and a normal tympanic membrane have otosclerosis. The term inner ear conductive hearing loss has been used to describe patients who had either a normal ossicular chain at the time of stapedectomy or a persistent conductive hearing loss after an uncomplicated stapedectomy.²² More recently, superior semicircular canal dehiscence²³ and intralabyrinthine neuromas²⁴ have been identified as possible causes of inner ear conductive hearing loss. In the case of an unchanged postoperative conductive loss after an uneventful stapedectomy, one should consider both entities, and further imaging may be indicated. Superior semicircular canal dehiscence typically has very good to supranormal bone thresholds and can be diagnosed on coronal CT scan. Intralabyrinthine neuromas have a mixed hearing loss and can be diagnosed on high-resolution MRI.

One must approach otosclerosis patients who have coexisting dizziness with caution. Most patients with otosclerotic inner ear syndrome²⁵ have improvement in vertigo after stapedectomy, whereas patients with Meniere’s disease may have a profound postoperative sensorineural hearing loss. The dilated saccule caused by endolymphatic hydrops can be damaged during stapedectomy and lead to the sensorineural hearing loss. Issa and coworkers²⁶ found stapedectomy to be safe in patients with Meniere’s disease if the bone conduction threshold at 500 Hz was 35 dB or better, and there was no high-frequency sensorineural hearing loss.