Avoidance and Management of Complications of Otosclerosis Surgery

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Chapter 26 Avoidance and Management of Complications of Otosclerosis Surgery

Joseph B. Roberson, Jr.

image Videos corresponding to this chapter are available online at www.expertconsult.com.

Otosclerosis surgery is one of the most exciting and rewarding procedures an otologic surgeon performs. The physical demands of the operation are among the most refined of the surgical disciplines, and includes an extremely small tolerance for error even when the case goes along well with perfect equipment and perfect performance of support personnel. Small deviations from the surgical techniques illustrated in the remainder of this text regularly prove necessary to avoid complication. The knowledge base and technical skills needed to handle these deviations add difficulty to an already challenging undertaking seen with routine cases. With this difficulty comes a large reward, however, as patients experience improvement of their hearing with a successful outcome—frequently to the normal range.

As with other difficult procedures, the learning curve for otosclerosis surgery is not steep. Complete preparedness for each potential surgical obstacle or complication is necessary to achieve results approaching those of experienced surgeons in centers of excellence located throughout the world. The atmosphere in the operating room is usually one of excitement and potentially slight tension with this procedure, especially for surgeons just beginning their careers. Thorough knowledge of and ability to deal with potential complications and surgical deviations help reduce anxiety and allow the operating surgeon to focus on and complete the job at hand.

Reliable correction of otosclerotic conductive hearing impairment requires discipline, precision, knowledge, preparation of the operating facility, and judgment. Cognitive preparation should be complete before undertaking stapes surgery as the primary surgeon. Expert training and steady experience provide mastery of technical skill and development of operative judgment. Only then can the fullest potential as a stapes surgeon be reached. This chapter provides knowledge based on my own experience and that of other contributors to the field who have courteously shared their experience as colleagues, professors, mentors, and authors. The focus is on the preoperative, operative, postoperative, and reoperative situations a surgeon faces when he or she seeks to prevent or rectify complications.

PREOPERATIVE EVALUATION

Medical Conditions

A written or mental checklist is useful to avoid overlooking an important medical feature during preoperative evaluation. It is helpful (and recommended) to have any and all family members in the office present in the examination room during the interview. A useful practice is to write the names of the individuals present on the chart during the interview. In addition to a complete history and physical examination with attention to medical conditions germane to any surgical procedure, the prudent surgeon attempts to identify the following conditions.

Fluctuating hearing loss, episodic vertigo, and low-frequency sensorineural hearing loss (SNHL) may indicate endolymphatic hydrops. Care must be taken to avoid confusing the early conductive hearing loss of prior audiograms (which may falsely appear as SNHL) with endolymphatic hydrops. Patients with endolymphatic hydrops who undergo stapes surgery have a higher rate of SNHL (presumably from dilation of the saccule that contacts the stapes footplate where it is at risk during stapedectomy or stapedotomy) and chronic dizziness. This condition may be a contraindication to surgery.1

Surgeons should insist that acoustic reflex testing be performed and reviewed before entering the operating room because superior semicircular canal dehiscence manifests with conductive hearing impairment, which may be confused with impairment caused by otosclerosis on pure tone audiometry. This practice helps avoid the situation where a mobile and normal stapes is found intraoperatively after entering the middle ear. Clinical history also is very helpful if the patient has symptoms of vertigo with loud sounds. Diagnosis is established or refuted with a computed tomography (CT) scan in the plane of the superior semicircular canal. Patient symptoms such as vertigo with impulse noise may also alert the operating surgeon to the presence of this otosclerosis look-alike.

A history of multiple fractures or blue sclera may allow the diagnosis of osteogenesis imperfecta to be made preoperatively.2

Lifelong hearing loss in one ear should alert the surgeon to the possibility of congenital footplate fixation. Congenital footplate fixation carries a higher than usual risk of gusher and SNHL.3 A CT scan should be performed preoperatively in patients with suspected congenital footplate fixation to look for abnormal cerebrospinal fluid (CSF)–perilymph connections that predispose to gusher. If a high risk of a gusher is found, amplification is recommended. A genetic pedigree focused on hearing loss is helpful in identifying patients with X-linked progressive mixed deafness. Patients with this disorder are rare and unique in that a conductive hearing loss is seen on the audiogram with intact stapedial reflexes.4,5 During surgery, a stapes gusher is encountered with the attendant risk of SNHL. Although males are typically affected, heterozygous females may exhibit milder audiologic abnormalities.6

Imbalance may occur after otosclerosis surgery despite a well-done surgical procedure and an excellent hearing result. Professional athletes, high-rise steelworkers, and painters might be best advised to avoid surgery until the completion of their careers. In similar fashion, patients who depend on their sense of taste for employment (e.g., workers in the wine industry, coffee tasters, and professional chefs) may choose to avoid surgery. Changes in chorda tympani function considered minor to most patients may be a source of disability in such professions. Commercial airline pilots usually are allowed to have stapes surgery without affecting their employability, but the operating surgeon or patient should secure written documentation of the patient’s employer’s policy before undertaking surgery. Military personnel who fly aircraft should consult with a flight surgeon.

A history of or exhibited characteristics of severe anxiety, neuropsychiatric disease, claustrophobia, restless legs syndrome, and other conditions that would make the procedure difficult under sedation with an awake patient should be sought. When such patients have surgery, it should be performed under general anesthesia.

Physical Examination

Various findings have an impact on upcoming surgery, including the following:

• Otitis externa must be completely treated for at least 1 month before undertaking surgery.
• Serous otitis media contains bacteria in approximately 50% of patients. Entrance into the vestibule in this situation puts the patient at risk for bacterial labyrinthitis, SNHL, and meningitis.7–9
• Tympanic membrane perforation or chronic otitis media must be repaired with a separate procedure before stapes surgery to reduce the bacteria present within the operative field as much as possible. Six to 12 months should pass after the first-stage repair for eustachian tube function to manifest, and for the hyperemia attendant with the primary procedure to fade.
• Exostosis, common in cold water swimmers, should be corrected and allowed to heal before attempting stapes surgery. Occasionally, small exostoses or osteomas may be removed at the same time as stapes surgery.
• A small or unusually angled ear canal should be noted in the clinic preoperatively. In extreme circumstances, enlargement may be necessary. More commonly, the case is simply made more difficult.
• Limited neck rotation or obesity may require rotation of the surgical table to allow correct positioning of the ear for the procedure. If this rotation is more than about 15 degrees, patients having surgery under local anesthesia with sedation are concerned about sliding on the operating room table. Such situations are better handled with general anesthesia so that the patient can be positioned more securely on the table.
• Congenital auricular or periauricular anomalies may indicate congenital malformation of the middle ear structures.
• Abnormalities of the ossicles or of the chorda tympani nerve noted at otomicroscopy are markers for congenital abnormalities.
• Severe myringosclerosis or an area of bimeric tympanic membrane (where the fibrous layer of the eardrum is missing, leaving only a mucosal lining and an epithelial surface) increases the chance of tympanic membrane perforation occurring as a result of tympanomeatal flap elevation. Note to the patient should be made of the finding with an explanation of the procedure for correction intraoperatively or during a second procedure. Myringosclerosis may be an indicator of tympanosclerosis involving the stapes footplate (see later for tympanosclerosis management).
• Tuning forks should confirm a conductive hearing loss with Weber or Rinne testing consistent with the audiogram. Overestimation of the conductive hearing loss using some audiologic techniques occurs. Lack of a “flipped tuning fork” may not be a contraindication to surgery when bilateral disease is present.10
• Careful examination may reveal evidence of prior otologic surgery not mentioned by the patient.

Informed Consent

Medicolegal situations over complications that are expected to occur in a small percentage of patients are avoided by obtaining written informed consent before the procedure. The reader is referred to other chapters for more information on the subject.

OPERATING ROOM

Surgical Technique Prerequisites for Residents

When surgeons are in training, much effort is put toward using proper methodology in the operating room. The technical difficulty associated with stapes surgery requires the surgeon to be facile with several key techniques. Residents and fellows should enter the operating room with previously demonstrated abilities in several areas. Preparation becomes more of an issue as the number of cases of surgically correctable otosclerosis decreases in most training programs.11 Limitation of hospital privileges may become more of an issue in the future if case availability precludes ascent to an acceptable level on an individual’s own learning curve. The following list is put forth for surgeons in training to use as preparation for successful performance of stapes surgery, while minimizing the risk of complications for the patient.

• Parfocal setup of the operating microscope: This allows the surgeon to change magnification without losing focus in the operative field. Safety, accuracy, and speed all are improved.
• Appropriate microscope triangulation intraoperatively to allow depth of field perspective: To achieve depth of field information, the plane of view must be off-axis from the surgical instrument by several degrees. Movement of the microscope off-axis establishes a virtual triangle with its apex at the point of surgical interest (usually the tip of an instrument or an anatomic structure). The two points of the base of the triangle are formed by the microscope lens and the intersection of an imaginary line drawn perpendicular to the line of vision from the microscope where it intersects another imaginary line extending from the handle of the instrument (Fig. 26-1). Very small movements of the microscope can mean the difference between success and failure with delicate manipulations mandatory with stapedotomy.
• Appropriate use of magnification balancing depth of field with surgical detail: Increasing magnification decreases depth of field and vice versa. The surgeon must balance the need for high magnification (e.g., needed with footplate work) with the need for depth of field (e.g., needed when securing the tympanomeatal flap with absorbable gelatin sponge [Gelfoam]).
• Laser safety, use, beam sizing, and focus coincident with parfocal microscope: Delivery of laser energy is a function of laser wavelength, generated power from the laser base unit, and power density as determined by the size of the working spot size in the operative field. If the laser is scope mounted, it should remain focused precisely with the vision at the working magnifications in which it would be needed. The surgeon should also be familiar with beam defocusing. This technique can be useful with measures such as stopping bleeding and shrinking tissue. Hand-held lasers diverge from the fiberoptic tip. In this instance, laser power can be manipulated by moving the probe tip to or away from the intended target.
• Two-handed technique: It is crucial that the operative surgeon be able to use two hands to perform surgical maneuvers. This skill is learned and starts with the use of two hands for otologic procedures beginning with tympanostomy tubes. Likewise, vision with two eyes is necessary to allow depth perception. Instruments must be grasped and used in a way that neither the right nor the left eye’s visual pathway from the microscope is obstructed. Observer side arms are monocular, and the surgeon in training may not realize when binocular vision is missing when using the binocular microscope unless instructed. Professors of otologic surgery can ensure binocular vision while looking through the monocular side arm by watching the video monitor and the side arm in succession. Typically, the side arm is what the operating surgeon sees through one eye, while the video shows what is seen through the other eye.
• Lack of significant tremor: Although many fine surgeons have rhythmic variation in fine muscle control, delicate otologic surgery and significant tremor are mutually exclusive. Nervousness and anxiety make tremor worse. The surgeon and the professor of surgery should attempt to create and maintain an atmosphere of relaxed concentration and focus. Responsible surgeons would determine if caffeine avoidance on the morning of surgery is prudent.
• Canal injection for hemostasis: Local anesthetic provides anesthesia for the patient under sedation and is crucial to procedure success. The mucosa of the middle ear receives innervation from deeper nerves and is not affected by the canal injection. A drop or two of local anesthesia instilled into the middle ear provides nearly instant relief. Anesthetic should be promptly removed from the middle ear to prevent absorption into the inner ear, avoiding the coincident severe vertigo, nausea, and vomiting. A high percentage of epinephrine in the canal injection (e.g., 1:20,000) provides a maximal amount of vasoconstriction with a minimum of volume of injection. Turning the needle such that the bevel is against the bone allows delicate instillation of solution under thin skin. Most innervation proceeds down the canal, but small nerves traverse the fissures of Santorini in the anteroinferior canal adjacent to the annulus. These nerves are more of an issue when dissection is carried out in this area, but they may also need to be surrounded with local anesthetic to provide a comfortable patient under sedation. Use of identical syringes for each procedure allows the surgeon to develop the feel necessary to perform excellent injections (we suggest a glass dental-type syringe holding 3 mL of solution). A perfect injection is an art that comes only with practice. Surgeons in training should perform and demonstrate proficiency with injections in cases where it is not as critical to the outcome of the procedure (e.g., tympanoplasty) before being allowed to inject for stapedotomy. Creation of large blebs cannot be rectified easily, and markedly increases case difficulty.
• Tympanomeatal flap design and elevation: A recurring mistake of inexperienced surgeons occurs when the tympanomeatal flap is too short to reach anatomic position after curetting to expose the oval window niche (Fig. 26-2). One should avoid suctioning the elevated skin to prevent flap tears. Positioning the suction behind the round knife during flap elevation keeps the field dry and prevents inadvertent suctioning of the elevated skin. The vertical incisions of the flap should be kept 1 to 2 mm lateral to the annulus to reduce the likelihood of tearing the tympanic membrane.
• Chorda tympani nerve identification and preservation: Surgeons should be able to identify and mobilize this nerve at the iter chordae posterius and from the posterior surface of the malleus to maximize the chance of its preservation.
• Curetting: Proficiency must be shown in removing the posterosuperior canal wall to expose the facial nerve and pyramidal process, while preserving the chorda tympani nerve.
• Incudostapedial joint identification and division: Correct identification of the joint is necessary to prevent removal of the lenticular process of the incus. This becomes more of an issue when a bucket handle prosthesis is used. Slight anterior pressure on the incus while focusing on the joint under high power allows correct identification of this plane.
• Prosthesis sizing: Understanding of the measurements used (Fig. 26-3) improves results. Measurement from the lateral surface of the footplate to the medial side of the incus is taken. To this figure is added 0.5 mm and an amount equal to the thickness of the stapes footplate. Footplate thickness may vary from 0.2 mm to several millimeters. The prosthesis should extend 0.5 mm beyond the medial surface of the footplate into the vestibule (Figs. 26-4 and 26-5).
• Suction sizing to usage and risk: Proper two-handed technique turns the suction into an instrument. Suction size must be scaled to use. Damage to middle and inner ear structures may occur with use of too large a suction or with improper use of any suction. Intraoperative electronystagmographic studies performed on stapedectomy patients in the prelaser era implicate suctioning over the vestibule, drilling near the oval and round windows, and manipulation of the stapes footplate as the great offenders for vestibular and presumably for cochlear damage.12
• Crus division and stapes superstructure removal: Fracture of the stapes superstructure with both crura intact and a fixed footplate is frequently possible. Division of the posterior crus before fracture decreases the chance of stapes footplate fracture, mobilization, and transmission of potentially damaging energy to the inner ear. Various methods are available for division of the posterior crus. Our preferred method is laser vaporization, which carries with it a much reduced risk for the inner ear. Although some techniques advocate laser vaporization of the anterior crus, there is no indication that fracture of a single crus with a fixed footplate carries any risk of footplate mobilization.
• Prosthesis preparation and loading: For surgeons using a vein-clad technique, vein preparation, sizing, and vein-clad prosthesis preparation are steps in which small variations can produce postoperative conductive hearing loss. The stapedotomy, prosthesis, and attached vein should be approximately 0.9 mm, 0.6 mm, and 0.2 mm. Variations in the thickness of the attached vein may cause the surgeon to vary the size of the stapedotomy. For this reason, the vein-clad prosthesis should be prepared before creation of the stapedotomy. In situations in which a vein is not attached to the prosthesis, the stapedotomy should exceed the size of the prosthesis by 0.2 to 0.3 mm. Bucket handle prostheses should be inserted with the bail inferior to the incus to allow it to be swung superiorly and secured with small pieces of tissue. Shepherd’s crook pistons should be grasped with smooth forceps in a way that the open end of the wire hook can be placed directly over the incus.
• Footplate removal: The surgeon must be able to create a round and concentrically located stapedotomy by melding multiple round individual laser bursts. The tiny movements used to move the laser are more reliably produced by moving the microscope with pressure from a hand or nose than with the joystick, although both methods work. Vaporization of the footplate with a laser leaves a small meshwork of char. This char does not need to be removed before prosthesis placement. Large fragments of footplate that enter the vestibule can give patients symptoms of positional vertigo. For this reason, all bony fragments within the stapedotomy that may mobilize with prosthesis placement should be vaporized. One should never attempt to “fish out” a fragment that has entered the vestibule. Use of a microdrill creates a round stapedotomy. Significant pressure on the footplate must be avoided to prevent drill overinsertion in the vestibule.
• Prosthesis placement: Resident surgeons should practice crimping techniques in the laboratory before undertaking the maneuver on a patient. Likewise, placement of a bucket handle prosthesis should be performed in the temporal bone laboratory setting first. Excess vein from operative procedures can be taken to the laboratory to create a realistic practice model.
• Prosthesis removal: Frequently with revision surgery, a prior prosthesis must be removed. It is also sometimes necessary, especially early in one’s career, to remove a prosthesis that is the wrong size during primary surgery. This is best accomplished for a prosthesis attached to the incus with a wire by inserting a right angle hook and rotating the hook to open the wire loop. In this way, traction forces on the incus are avoided. Laser ablation of the tissue surrounding the oval window segment of the prosthesis is a first step before removal to avoid traction damage of structures within the vestibule.
image

FIGURE 26-1

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FIGURE 26-3

Surgeons who have performed stapes surgery frequently understand that each individual step of the procedure itself must be performed to perfection, or the ill effects become additive. (For example, an imperfect injection makes every remaining portion of the procedure more difficult if blood continues to enter the operative field. Likewise, inadequate curetting limits exposure of the footplate.) A small amount of compromise in each step of the procedure quickly adds up to overall failure. This “law of additive inadequacy” has proven useful as a teaching concept. Viewing the procedure in this way emphasizes the need for perfection in each step before moving forward in the operation.

Similar to a preflight checklist, every skill must be checked off before allowing performance of a stapedotomy. Surgeons who never master the listed techniques probably should not perform stapes surgery as part of their surgical practice—just as not every otolaryngologist is able to perform procedures such as blepharoplasty, partial laryngectomy, and laryngotracheal reconstruction.

Attending physicians are reticent to allow significant participation of residents and fellows if this means that several inadequacies have already summed to put the senior surgeon in a tough spot while completing the procedure. Residents and fellows gain the confidence of their attending surgeons as these skills are mastered allowing greater and greater participation. It is the duty of those of us who teach surgical technique to deliver to the next generation a cadre of well-trained individuals suited to stapes surgery without sacrificing success and safety for our current patients.

Surgical Equipment, Decisions, and Techniques

Prosthesis Type, Size, and Availability

Three general prosthesis types exist: piston/wire, bucket handle, and polytef (Teflon) varieties. Few comparative data exist to compare the different types, but bucket handle prostheses may have a smaller incidence of incus necrosis in long-term follow-up. Piston/wire and Teflon varieties are probably easier to place. Self-crimping prostheses offer a new option in design, which may reduce the need for manual crimping.13 Long-term results with attention to incus necrosis would be of interest because the metal nitinol used in these prostheses contains a small percentage of nickel—a known cause of hypersensitivity reactions in other uses in humans such as jewelry.

Prostheses come in several different diameters, ranging from 0.3 to 0.8 mm most commonly. Experienced surgeons have indicated that 0.6 mm gives optimal results.14 Several studies have looked at alternative sizes, and there seems to be no degradation of results in the speech range down to 0.4 mm piston diameter.15 Prostheses measuring 0.3 mm show worse hearing results compared with prostheses measuring 0.4 mm.16 Lighter prostheses perform better in higher frequencies in situ in temporal bone studies.

Prosthesis length varies from patient to patient. Availability of the correct prosthesis is crucial to successful outcome. We prefer to use nonferromagnetic materials, in particular titanium bucket handle prostheses. Table 26-1 outlines the prostheses stocked in our operating suite. Note the inclusion of the incus replacement prosthesis (see the later discussion on incus necrosis).

TABLE 26-1 Prosthesis Type and Size Stocked in Operating Suite

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Laser Stapedotomy versus Drill Stapedotomy

It is generally agreed among most surgeons that use of the laser reduces the risk of mechanical transmission of vibratory energy to the inner ear, making it a safer technique. Comparative data from primary stapedotomy question this tenet, viewing both techniques as effective and safe.17 Use of a laser does improve results in revision cases.18 In all cases, proper use of the laser reduces bleeding associated with tissue ablation, which is an advantage. Both techniques are accepted within the standard of care.

Stapedectomy versus Stapedotomy

For most otologists, the procedure of choice for otosclerosis has become stapedotomy. Compared with stapedectomy, the limited fenestra improves results in the high frequencies, and most authors report a reduction in SNHL as a result of the procedure.19–21 Stapedotomy carries a smaller rate of postoperative vestibular complaints. Stapedectomy remains a valuable alternative in the experience of some surgeons. Occasionally, a stapedotomy needs to be converted to a complete stapedectomy.

Stapedotomy Site

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