Stapedectomy and Stapedotomy - technical
Synonyms are: Small fenestra stapedotomy; Stapes operation; Stapes surgery
Stapedectomy: Removal of the stapes (crurae and footplate). Total stapedectomy involves the removal of the entire stapes footplate and crurae such that all of the oval window margins are visualized. Partial stapedectomy involves removal of a portion of the footplate. Performed in conjunction with placement of a stapes prosthesis connected to the incus and/or soft tissue or vein graft to seal the oval window. Performed to correct conductive hearing loss in cases of otosclerosis.
Stapedotomy: Creation of a fenestration within the stapes footplate, usually a limited central perforation. Performed in conjunction with placement of a stapes prosthesis connected to the incus. Performed to correct conductive hearing loss in cases of otosclerosis.
The purpose of stapedectomy and stapedotomy is to correct or bypass the ossification and fixation of the stapes footplate seen in otosclerosis. In so doing, the conductive hearing loss and air-bone gap can be corrected or greatly improved.
The fixation of the stapes footplate seen in otosclerosis reduces or prevents the mechanical transmission of sound to the cochlea. By removing the footplate or by creating a fenestra in the footplate and placing a prosthesis, the fixation of the footplate is either corrected or bypassed.
- Good overall health of the patient
- No active middle or external ear disease or infection
- Minimum air-bone gap of 15–20 dB averaged over the speech frequencies (500, 1,000, and 2,000 Hz)
- Bone conduction greater than air conduction with a 512 Hz or a 1,024 Hz tuning fork
- The poorer hearing ear, per the patient’s report
- The patient completely understands all of the risks and benefits of the surgery
- Preserved speech discrimination, unless patient has extremely degraded sensorineural function by bone conduction suggesting far-advanced otosclerosis
- Poor physical health of the patient
- Preexisting tympanic membrane perforation
- Active middle or external ear disease, infection, or cholesteatoma
- Inadequate air-bone gap on audiometry or tuning fork evaluation
- Extremely poor speech discrimination suggesting poor cochlear reserve
Stapes surgery can be performed under local or general anesthesia or under conscious sedation. The advantages of local anesthesia include the ability of the patient to inform the surgeon of any vertigo, shorter operating room times, and the ability to converse with the patient to ensure improved hearing at the end of the procedure. Additionally, local anesthesia avoids coughing or valsalva on emergence from general anesthesia. Local anesthesia containing 1% lidocaine with 1:100,000 epinephrine is infiltrated around the external meatus in four quadrants just under the skin. It is then injected into the vascular strip down to bone. Lidocaine can be buffered with a bicarbonate solution to lessen the pain associated with the injection.
The largest ear speculum that can be seated into the canal should be used. Inferior and superior incisions are made with a sickle knife approximately 1 mm from the edge of the tympanic membrane and extended approximately 4–6 mm laterally (Fig. 1). These incisions are then connected with a House canal knife and then used to elevate the tympanomeatal flap. Once the annulus is approached, it is elevated with an annulus elevator (gimmick) to the level of the malleus superiorly and to the level of the round window inferiorly (Fig. 2). Care is taken to avoid injury to the chorda tympani and a Rosen needle can be used alternatively to assist in the careful elevation of the tympanic membrane adjacent to the chorda tympani. The entire tympanomeatal flap is then elevated anteriorly.
The superior overhang of bone from the scutum usually limits completely visualization of the stapes footplate and is therefore removed in order to allow visualization of the facial nerve superiorly and the pyramidal prominence posteriorly. This can be performed with a curette or a microdrill with a diamond burr. Care must be taken when removing the scutum with a curette to avoid inadvertently plunging the instrument into the middle ear space and causing potential injury.
Adequate visualization is achieved once the following structures are visible: the round window inferiorly, the lower half of the fallopian canal superiorly, the stapedial tendon pyramidal eminence and posterior crus posteriorly, and the malleus anteriorly (Fig. 3).
Once adequate exposure is obtained, the ossicular chain must be palpated to ensure mobility.
A small, round right angle knife or joint knife is then used to disarticulate the incudostapedial joint (Fig. 4). The stapedial tendon is cut sharply and the stapes superstructure is then sharply fractured toward the promontory with a Rosen needle placed against the superior side of the stapes arch near the neck.
The distance from the top of the incus to the stapes footplate is then measured (Fig. 5). This is often approximately 4.5 mm. A distance of 0.25 mm is subtracted from this measurement since most prostheses are measured from medial surface of the incus.
The footplate is then removed using right angle hooks, starting with the posterior and then the anterior portion of the footplate (Fig. 6). If blood or bone chips enter the vestibule during removal, these are left undisturbed.
The tissue graft of choice (vein, fat, or fascia) should measure 5 x 5 mm and is placed over the oval window. A vein graft can be harvested from the dorsum of the hand and thinned to remove as much adventitia as possible (Fig. 7).
The single-wire loop prosthesis is then placed over the lenticular process of the incus and into the center of the oval window. The prosthesis is then crimped to secure its position (Fig. 8).
The tympanomeatal flap is then placed back into its normal position and a small piece of gelfoam is placed on the flap. A gauze wick may also be used. A small piece of cotton is then placed at the meatus and a Band- Aid applied.
Partial Stapedectomy and Stapedotomy (Fenestration) Procedure
While the approach and exposure of the middle ear has remained largely unchanged over the years, some authors have opted for partial footplate removal and small fenestration of the footplate as opposed to total removal of the stapes footplate as less invasive alternatives to total stapedectomy (Bailey et al. 1983; Rizer and Lippy 1993; Perkins 1980). These approaches present less potential trauma to the inner ear and less risk of sensorineural hearing loss (House and Cunningham 2005; Shelton 2010). Partial stapes footplate removal, such as procedures that involved the shattered footplate procedure and subluxated footplate procedure, has largely been abandoned secondary to the associated sensorineural hearing loss (Robinson 2010).
Various techniques have been employed that include the use of a manual pick, hand drill, microdrill (Fig. 9), and a laser (Fisch and May 1994; House 1993; Shelton 2010; Bailey et al. 1983; Rizer and Lippy 1993; Perkins 1980). Great care must be taken when employing a drill to not push against the footplate. Patients under local anesthesia must also be warned prior to any manipulation of the stapes as they should expect loud noise.
The choice of a prosthesis has also evolved. Shea described the first stapedectomy procedure using a polyethylene strut prosthesis (Shea 1958). Subsequent prostheses included the wire and fat prosthesis (Schuknecht 1960), the single-loop wire prosthesis with absorbable gelatin sponge (House and Greenfield 1969), and the piston prosthesis (Robinson 1962).
The piston prosthesis did not require removal of the entire footplate and consequently reduced the risk of injury to the inner ear.
The crimping mechanism has also evolved from one of a manual crimp to a prosthesis that is able to “self-crimp” in response to the application of heat, such as that applied via bipolar cautery or laser.
Lasers and Stapes Surgery
A laser technique was described in the early 1980s by Perkins (Perkins 1980). Microscope mounted and more recently, handheld laser fibers have been used in stapes surgery. Multiple lasers, including argon, KTP, and CO2, have all been employed (Shelton 2010). Lasers are available can be mounted on the microscope as well as be operated via the use of a handheld probe. The rationale behind employing lasers is to introduce less mechanical trauma to the middle and inner ear, theoretically reducing risk of sensorineural hearing loss.
The preoperative preparation, operating room setup, and surgical approaches are all the same. Techniques similar to those described above are employed to elevate a tympanomeatal flap and achieve adequate visualization of the stapes footplate.
The laser can be employed in the division of the stapedial tendon and posterior crus of the stapes (Figs. 10, 11, and 12).
The fenestration can also be created with the use of a laser. As some lasers are usually absorbed by pigment, the target should be a red vessel along the footplate in these cases. Once an initial char is created, a series of “rosettes” can be created with subsequent laser chars to weaken the footplate (Figs. 13, 14). This is less of an issue with CO2 lasers as their primary targets are water. Once the footplate has been weakened by the laser, the fenestration can subsequently be created with a microdrill using a 0.7 mm diamond burr or a disk can be used to make a fenestration.
The remaining portions of the surgery are completed as previously described.
Pitfalls and Complications
Intraoperative vertigo can occur if the tissue graft or prosthesis is placed too deeply within the vestibule (House and Kwartler 2010). Dizziness is common for a few hours immediately after surgery and usually resolves spontaneously. Sheehy et al. (1979) reported 0.4% of their patients experienced dizziness beyond four postoperative months and they found an association with the use of Gelfoam® seals.
A displaced prosthesis is the most common cause of failure (Wiet et al. 1993; Sheehy and House 1962; Battista et al. 2006). Prosthesis migration out of the oval window has been thought to occur secondary to contracture of the neomembrane causing the prosthesis to lift out of the fenestration or a too short prosthesis (Battista et al. 2006). Displacement of the prosthesis at the incus can occur secondary to incus necrosis or loose crimping. Revision surgery is usually required to correct these complications.
Chorda Tympani Nerve Injury
The position of the chorda tympani nerve can at times impede access or visualization. It can be carefully moved superiorly or inferiorly but is at risk for tearing and stretching. If partially torn, it is advised to completely sever the nerve rather than leave a partially functioning nerve (House and Kwartler 2010). Symptoms include dry mouth, soreness of the tongue, and a metallic taste, which usually resolve within 3–4 months (Wiet et al. 1993).
Tympanic Membrane Perforation
Small perforations usually heal without further intervention or with placement of a paper patch. Larger perforations should be repaired using an underlay technique (Wiet et al. 1993). In cases of large perforation recognized prior to the opening of the oval window, consideration should be given to terminating the procedure.
Malleus fixation can mimic the clinical and audiometric findings of otosclerosis and must be ruled out prior to performing a stapedectomy. It is thought to result from ossification of superior and anterior suspensory ligaments of the head of the malleus (Goodhill 1966; Moon and Hahn 1981). If the diagnosis cannot be made prior to surgery, it can be made at the time of surgery by palpating the ossicular chain. This disorder requires a different surgical treatment and stapdectomy should not be performed in these cases.
Facial Nerve Injury
In some cases, the facial nerve may be dehiscent in its tympanic segment. It may also prolapse inferiorly and partially or completely obscure the oval window. Some authors have described carefully moving the facial nerve superiorly to allow access to the footplate (House and Kwartler 2010) if it is only partially obscuring the oval window. The facial nerve can be gently retracted with a small microsuction while the fenestration is created. Contact of the prosthesis with the facial nerve does not cause facial nerve dysfunction (House and Kwartler 2010; Shelton 2010). It is not advisable to bend the prosthesis around the nerve. If this cannot be performed safely, the safest course of action would be to abort the procedure and have the patient evaluated for a hearing aid.
Accidental dislocation or subluxation of the incus can occur during scutum bone removal and/or prosthesis placement. In some cases, the incus can be returned to a near normal position and the surgery can proceed that day or delayed to allow healing. In other cases, the incus is removed and an incus bypass procedure is performed (Wiet et al. 1993).
If a significant amount of perilymph is encountered once the footplate is perforated, one can proceed by creating a small fenestration (not remove the footplate), elevate the patient’s head, and place a large tissue graft prior to prosthesis insertion (House and Kwartler 2010; Wiet et al. 1993). Other authors have advocated for immediate packing of the middle ear and aborting the procedure or placing a lumbar drain at the conclusion of surgery (Wiet et al. 1993).
Sensorineural Hearing Loss
Serous labyrinthitis is thought to cause a transient and slight decrease in hearing above 2,000 Hz that is associated with vertigo. These symptoms usually resolve within days to weeks.
The more dreaded complication of total and permanent sensorineural hearing loss after stapedectomy has an incidence that ranges from 0.6% to 3% in the literature (Wiet et al. 1993) and varies depending on patient age, previous procedures, and type of stapdectomy/ stapedotomy.
The cause of this is often unknown but some authors have opined that it is caused by excessive drilling, surgical instrument trauma, slippage of the prosthesis into the vestibule, hemorrhage, and prior traumatic mobilization (Sheehy and House 1962; Wiet et al. 1993). Reparative granuloma is a known cause and is discussed below. Extensive cochlear otosclerosis may also predispose a patient to spontaneous rupture of the basilar membrane (Wiet et al. 1993). The use of Gelfoam® as a tissue graft has been associated with a higher chance of sensorineural hearing loss following stapedectomy (Sheehy et al. 1979). Other mechanisms proposed by Causse (1980) include increased negative pressure in the middle ear that forced the prosthesis into the vestibule, impaired cochlear blood flow secondary to neck torsion during surgery, perilymphatic gusher, and sudden release of active enzymes from the otosclerotic focus into the inner ear.
The incidence of reparative granuloma has been reported to be 1.3% in previous series (Wiet et al. 1993). Patients typically present with a gradual or sudden sensorineural or mixed hearing loss and vertigo 1–6 weeks after stapedectomy, usually after having experienced immediate improvement in hearing. Physical exam can demonstrate reddish discoloration of the tympanic membrane. Operative exploration demonstrates granulation tissue involving the prosthesis and the oval window (Seicshnaydre et al. 1994).
It is unclear why reparative granulomas develop. Seicshnaydre et al. (1994) reported that while reparative granulomas can occur in patients who undergo both stapedectomy and stapedotomy, it appeared more common in those who underwent stapedectomy. There were also a higher number of cases associated with the use of Gelfoam® as a grafting material in stapedectomy. The statistical significance of these findings is unclear, however.
Many advocate immediate recognition and surgical management of reparative granulomas (Wiet et al. 1993; Seicshnaydre et al. 1994). Complete replacement of the prosthesis and graft and/or removal of the granulation tissue have been reported as improving the long-term hearing outcomes, particularly if performed with 2 weeks of symptom onset (Wiet et al. 1993).
The stapes footplate can become mobilized during the downward fracture of the stapes superstructure. This has been described as “the most difficult complication in otosclerosis surgery” (House and Kwartler 2010). If this occurs, the footplate must be carefully secured during its manipulation or instrumentation in creating a fenestration. In creating the fenestration, care must be taken to not fracture the footplate.
- High rate of success in closure of air-bone gap to within 10 dB
- Can be performed under local or general anesthesia
- Can eliminate the need for hearing aid use
- Can enable the use of hearing aids in cases of mixed hearing loss
- Overall well-tolerated postoperative recovery
Potential risks including total hearing loss, facial nerve injury, vertigo, need for revision.
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