Laser Stapedotomy

Patient Counseling

Before surgery, the patient is educated regarding the anatomy and physiology of the ear and the effect of otosclerosis on hearing. The expected outcomes of the procedure are described, including the limitations of hearing improvement that might be imposed by a preexisting sensorineural component of the hearing loss. The possible risks and complications of the procedure include poorer hearing or total hearing loss, aggravated tinnitus, dizziness, taste disturbance, and facial paralysis. These risks are outlined in a patient education booklet given to the patient during the initial office visit.

I perform stapedectomy with the patient under local anesthesia. The recovery appears easier and there is less intraoperative bleeding. Symptoms of disturbance of the inner ear related to footplate manipulation, such as dizziness, are also apparent intraoperatively. As part of the preparation of the patient for a procedure performed under local anesthesia, an explanation of what is to be expected in the operating room appears to alleviate patient anxiety and results in a calmer and more cooperative patient during the procedure. The preparation steps up to the beginning of surgery are described in detail to the patient, including the expectations regarding the level of sedation. During the procedure, the patient is sedated to the point of somnolence, but is still conscious and able to respond to questions appropriately. If the sedation is too deep, the patient may become disinhibited and thus much less cooperative.

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 paramount. The presence of 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 a monitor allows the scrub nurse to see what the surgeon is doing and anticipate the next instrument that is needed. In a difficult procedure, with unfavorable patient anatomy, bleeding, or both, the surgeon must have the correct instrument immediately to complete the operation effectively. A scrub nurse who is not trained to assist in 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 may cause the surgeon to lean over the patient’s chest and limit visualization of the surgical field. The operating table is placed in a slight Trendelenburg position. 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 that 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 solution is allowed to fill the ear canal. Intravenous midazolam (Versed) or fentanyl (Sublimaze) is used for sedation. This medication is administered in small increments until the patient is sleepy and relaxed. 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.

A local field block is performed with 1% lidocaine with 1:100,000 epinephrine. Propofol can be administered at this point to reduce the discomfort of the administration of the block, but not for the remainder of the operation. The disinhibited behavior that can result from propofol can lead to troublesome patient movement during critical portions of the procedure. 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, as is a snugly fitting speculum. The pressure provided by the speculum helps to tamponade the vessels supplying the ear canal from the meatus. If one encounters troublesome bleeding during the procedure, a different speculum size can be attempted, 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 begins 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 double the width of a Sheehy weapon (3-mm round knife). An excessively long flap results in more bleeding, and it can be difficult to fold forward in a narrow ear canal because of the bulk of the 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 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 directly visualized. The annulus is elevated out of its sulcus with a Rosen needle. 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 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.

The posterior external auditory canal bone is removed with a curette to visualize the oval window. The initial curetting occurs several millimeters posterior to the edge of the tympanic annulus ( Fig. 22.4 ). Initial curetting on the edge can result in the 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.

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 it 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 Patient Selection Pitfalls section).

Some 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 severe postoperative vertigo. The instillation of saline into the middle ear and removal with suction can facilitate removal of the lidocaine and prevent dizziness.

Using the laser, the stapedial tendon and posterior crus are removed ( Figs. 22.7–22.12 ). A typical setting for the KTP or argon laser is 1.5 W, at a 0.10-second duration. I prefer 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 ( Fig. 22.10 ), and the superstructure is down-fractured toward the promontory with a Rosen needle ( Fig. 22.12A ). A quick, sharp jerk on the superstructure is important to fracture the anterior crus ( Fig. 22.12B ). A slow-down fracture movement may result in the mobilization of the footplate.

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 taken to the undersurface of the incus routinely. However, the surgeon should always measure consistently, 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. The fenestra in the footplate is usually placed in the middle or posterior half.

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 black 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 a charred than a normal footplate if the fenestra must be enlarged.

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 it 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 with a Rosen needle rather than suction.

As an alternative to the laser, a small fenestra can be created using a microdrill. To create 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 under local anesthesia. In these cases, it is helpful to first place the drill against the promontory and activate it, alerting the patient to the noise of the drill and avoiding unexpected patient movement when drilling on the footplate. The microdrill provides a uniformly sized footplate opening.

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 patients, 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 leads 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.

The nitinol-polytef (Teflon) piston allows heat-activated crimping of the wire. The argon or KTP laser is set at 0.75 W, and the wire is heated with the laser, resulting in the self-crimping of the prosthesis. Occasionally, the wire is bent slightly when removing it from the packaging. The shaft of the prosthesis can also be heated with the laser to straighten the wire into its native shape. The heat-activated crimping results in a very tight crimp. The length of the nitinol 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 my practice, the most common prosthesis length for the nitinol 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 anatomical location and the ear canal filled with powdered Gelfoam and saline packing. A cotton ball is placed in the ear canal and a bandage placed over the cotton ball.