Introduction to Stapes Surgery
Many otologists would describe stapes surgery as among the most satisfying of all ear operations. The procedure is elegant, technically sophisticated, and most patients are highly appreciative for their improved hearing. It is also among the most perilous. For such a miniscule area, the number of variations and anomalies the otologist might encounter are numerous and can tax even the most experienced ear microsurgeon. When a tympanoplasty fails, it can usually be successfully redone. When stapes surgery goes wrong, it can result in irremediable consequences such as deafness, vertigo, and even facial paralysis. Success in surgery is less about technical virtuosity than it is about mental preparedness, the exercise of sound judgment, and knowing one’s limits. The better prepared a surgeon is, the more likely to achieve success and avoid preventable complications.
One important goal in creating these illustrations was to help the novice surgeon gain competence, efficiency, and finesse with the routine aspects of stapes surgery. During training, the learning curve for stapes procedures is steeper than for most ear procedures. Stapes procedures require the surgeon to have a clear plan of the technical maneuvers which, in turn, have to occur in specific sequence. Our illustrations are intended to guide the inexperienced surgeon to learn the principles of obtaining adequate exposure by designing and raising a tympanomeatal flap of the proper size and shape as well as avoiding flap tears or disruption of the tympanic membrane. The fledgling surgeon must master hand positions that afford high levels of stability and also master the skill of two-handed surgery. Beginning surgeons rapidly become facile with their dominant hand, but development of nondominant hand skill takes time and practice. Many of the maneuvers in stapes surgery are completed most effectively when exposure is adequate for binocular viewing. The methods of obtaining adequate exposure of the oval window and incus are central to making the procedure go smoothly. We have made an effort to show a diversity of technical options for opening the footplate (small and large fenestra, microdrill, laser, and pick) as well as illustrating some of the most commonly used stapes prostheses.
The second major goal of these illustrations was to provide stapes surgeons with the intellectual framework to be prepared for the myriad uncommon variants and technical challenges which inevitably arise from time to time. The majority of these (e.g., overhanging facial nerve, narrow niche, deficient incus, thick footplate) are usually not knowable preoperatively by the surgeon. Chances are that when surgeons first encounter a stapes gusher or biscuit footplate, for example, they will be on their own, never having faced these challenges during training. The only way to prepare is through mental preparedness and formulation of a plan, much as an airline pilot does in anticipation of rare emergencies. Illustrations are one means of helping surgeons to recognize and deal with uncommon variants and technical challenges.
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4.2 Overview of Stapes Surgery
Fig. 4.1 Schematic coronal view of the middle and inner ear showing a fixed stapes due to an otosclerotic plaque at the anterior margin of the oval window.
Fig. 4.2 Schematic illustrating small fenestra stapedotomy with a Teflon-wire prosthesis.
Fig. 4.3 Otosclerosis is a disease of the otic capsule. In its active phase, known as otospongiosis, highly vascular lesions resorb bone surrounding the inner ear, most often in a patchy pattern. The active lesions mature into calcified otosclerotic plaques which are responsible for stapes fixation.
Fig. 4.4 Schematic view of the middle and inner ear displayed via a perspective looking upward from the hypotympanum. This projection was chosen as a means of introducing the concepts of stapes surgery in a perspective which enables simultaneous viewing of the ear canal, middle ear, stapes, vestibule, utricle (blue), and saccule (green).
Fig. 4.5 The tympanomeatal flap (canal skin and eardrum) has been raised and reflected anteriorly to expose the posterior half of the middle ear. To aid in selection of the proper length prosthesis, the distance from the lateral surface of the incus to the footplate is being measured.
Fig. 4.6 Division of the joint between the incus and stapes using an incudostapedial joint knife.
Fig. 4.7 After division of the joint, mobility of the lateral ossicles (malleus and incus) is tested.
Fig. 4.8 Section of the stapedius muscle with microscissors.
Fig. 4.9 Removal of the stapes superstructure using a curved needle.
Fig. 4.10 Creation of a small fenestra stapedotomy with a microdrill.
Fig. 4.11 Placement of a stapedotomy piston.
Fig. 4.12 Positioning of the shepherd’s crook on the incus with a notched chisel (strut guide) and closing the wire with a crimper.
Fig. 4.13 Completed placement of the stapes piston through the stapes fenestra into the vestibule.
Fig. 4.14 Sealing around the prosthesis with blood.
Fig. 4.15 Placement of the surgeon’s hands during transcanal stapes microsurgery. The third and fourth fingers of each hand stabilize the speculum. Note that the microinstrument (right hand) and suction (left hand) are held in a manner to both optimize stability and to enable binocular viewing. Some surgeons use a speculum holder to enhance stability.
Fig. 4.16 Injection of lidocaine with epinephrine into the ear canal has two purposes: anesthesia and vasoconstriction. Using the speculum to offset the cartilaginous canal, circumferential injections are placed around the bony cartilaginous junction. To avoid transient postoperative facial paralysis, a smaller volume of anesthetic is injected anteriorly. It is usually best to avoid injection in the bony canal, other than raising a bleb under the vascular strip, to avoid narrowing the lumen and hindering exposure.
Fig. 4.17 Injection of lidocaine with epinephrine via a 27-gauge needle in the posterior-superior ear canal resulting in vasoconstriction of the “vascular strip.”
Fig. 4.18 During vascular strip injection, the bevel of the needle must face the bone.
Fig. 4.19 Operative view of the ear canal and ear drum as seen in a transcanal approach. Dotted line represents the canal incision of a tympanomeatal flap. The flap is longer superiorly to cover the scutectomy defect. Note that the optimal incision is not “12 to 6” but rather more like 1 o’clock to 7 o’clock on an imaginary clock face in which the malleus sits at 12 noon. For the flap to properly fold on itself exposing the posterior superior quadrant, it is best to carry the incision slightly beyond the malleus.
Fig. 4.20 The incision line is first crushed with a round stapes knife. This maneuver squeezes closed blood vessels and thereby reduces bleeding. It also helps minimize flap tearing during incision.
Fig. 4.21 Using a twisting motion, the incision is created with a stapes knife.
Fig. 4.22 The incision is carried inferiorly. As the stapes exposure is in the superior quadrant, the inferior portion of the flap can be kept quite short.
Fig. 4.23 Using either a stapes knife or annulus elevator, a tunnel is created under the so-called vascular strip, the portion of the flap most likely to bleed.
Fig. 4.24 Cutting the vascular strip with scissors squeezes vessels closed and thereby reduces bleeding. It also creates a neatly designed flap without irregular edges. Some surgeons prefer to cut the entire flap with a stapes knife.
Fig. 4.25 The flap is raised to the level of the tympanic annulus. Care must be taken to avoid traumatizing the flap by aspirating it with the suction. The suction is best kept above the stapes knife blade.
Fig. 4.26 To avoid potential disturbance to the ossicles, the middle ear is first entered inferiorly. The stapes knife lifts the tympanic annulus out of its bony groove. With gentle downward and inward pressure, the knife can then safely fall over the margin into the posterior tympanic space.
Fig. 4.27 A bony prominence is often encountered slightly lateral to the tympanic membrane level.
Fig. 4.28 To avoid tearing of the flap or tympanic membrane, it is necessary to maintain continuous pressure with the stapes knife against the bony canal. Allowing the stapes knife to disengage from the canal wall risks tearing the flap. EAC, external auditory canal.
Fig. 4.29 The tympanic mucosa is lysed with a curved needle. When done under local, lidocaine is infused into the middle ear to anesthetize the tympanic mucosa. To avoid anesthetizing the labyrinth with resultant postoperative vertigo, lidocaine should be promptly suctioned from the middle ear, especially from the round window niche where it tends to accumulate.
Fig. 4.30 Elevation of the tympanic annulus inferiorly using an annulus elevator. To avoid tearing, it is important to maintain firm pressure against the bone. Elevation is with the side of the shaft, not the tip of the instrument. When under local, this maneuver is often incompletely anesthetized.
Fig. 4.31 Bleeding from the inferior edge is common after this maneuver. Application of a small cube of epinephrine-soaked absorbable gelatin sponge readily controls.
Fig. 4.32 It is important to have the middle ear exposure remain adequately open throughout the surgery. Using the back of the annulus elevator, the flap can be pushed against the anterior canal wall where surface tension will adhere to it.
Fig. 4.33 Elevation of the annulus superiorly is done with a curved needle. The chorda tympani nerve is identified and dissected free.
Fig. 4.34 Elevation needs to be carried superiorly until the flap is free from the notch of Rivinus. This ensures that the flap will fold over the malleus handle and thus give sufficient exposure of the incus long process to enable crimping.
Fig. 4.35 Completed flap elevation. Note that flap is folded on the umbo and that a space is available anterior to the incus. If the flap does readily retain this position, further elevation superiorly or inferiorly is needed.
Fig. 4.36 When the flap sags and limits the tympanotomy exposure, sometimes a blood clot may have formed under the flap. Its evacuation restores adequate exposure.
Fig. 4.37 When the flap sags and limits the tympanotomy exposure, sometimes a blood clot may have formed under the flap. Its evacuation restores adequate exposure.
Fig. 4.38 Most commonly the scutum (posterior ear canal overhang) allows at least a partial view of the stapes superstructure. It must be removed to provide full access to the oval window. Scutum removal may be done with either a curette or microdrill or a combination of the two.
Fig. 4.39 A long scutum may fully obscure the stapes and require a greater degree of bone removal. Curettage of such a thick scutum can require considerable effort.
Fig. 4.40 Combined technique in which the scutum is first thinned with a drill (e.g., 2.3-mm diamond) and then a curette removes the last shell. A diamond burr is slightly slower compared to a cutting burr, but is less likely to injure the chorda tympani, flap, or tympanic membrane.
Fig. 4.41 Use of a stapes curette to remove the scutum. The curette is firmly braced against the speculum to create a fulcrum effect. The motion is rotational and outward, never inward. A sudden release of inwardly directed force could lead to incus dislocation. Effective use of the curette takes practice and may be challenging for the novice. Considerable force is needed to fracture pieces of bone. When chipping away bone, it is important to prevent the curette from lurching outward where it can tear the canal skin and trigger bleeding.
Fig. 4.42 Curetting outward and away from the incus. Sometimes, the scutum breaks away in a single piece. More commonly, it is nibbled away in a series of small bone fragments.
Fig. 4.43 Removal of the last ridge needed for adequate exposure of the stapes. Curetting is complete when the facial nerve is in full view superiorly and the junction of the stapes tendon and pyramid are visible posteriorly.
Fig. 4.44 A bony prominence often exists under the entry of the chorda tympani. When the bone hinders exposure of the posterior aspect of the footplate, it must be removed. This must be done carefully to reduce the risk of injury to the chorda tympani.
Fig. 4.45 The chorda tympani sometimes traverses a bony prominence.
Fig. 4.46 A 1-mm diamond burr is used to partially remove the prominence.
Fig. 4.47 A curette is used to remove the remaining shell.
Fig. 4.48 Exposure for stapes surgery is adequate when both the facial nerve and the junction of the stapes tendon with the pyramid are visible. It is important not merely to be able to see the stapes, but to have sufficient room to bring instruments into action from superior, posterior, and inferior directions. Mesenteries (often erroneously called “adhesions” when the mucosal folds are actually embryological remnants) often need to be lysed between the incus long process and the malleus. Establishing exposure anterior to the incus is essential for later placement of the prosthesis.
Fig. 4.49 Palpation of the stapes superstructure to confirm fixation. This should be done gently, as excessive force could mobilize a lightly fixed footplate.
Fig. 4.50 The so-called adhesions are common in the middle ear. During stapes surgery, they are most commonly embryological remnants. To enable later placement of the prosthesis on the incus, the intraosseous ligament needs to be lysed.
Fig. 4.51 Mucosal folds often overlie the footplate. If visible at this point (sometimes they are obscured by the superstructure), then these should be lysed with a needle or hook.
Fig. 4.52 Small fenestra technique.
Fig. 4.53 The large fenestra operation requires placement of a membrane across the oval window, most commonly tragal perichondrium, temporalis fascia, or vein harvested from the dorsum of the hand.