Modified laser‐assisted stapedotomy

The evolution of modern stapes surgery, from stapedectomy through stapedotomy to step reordering, and more recently to the adjunctive use of laser has been driven by a desire to maximize technical success and minimize complications. The most serious operative complications of stapes surgery are sensorineural hearing loss (SNHL) or “dead ear,” most commonly from excessive footplate manipulation,1 and incus dislocation, which may occur during prosthesis placement.2 Prosthesis malfunction has been reported as the most common cause of delayed failure of primary stapedectomy.3, 4 Prosthesis-related failures can be corrected by a revision procedure; however, damage to the inner ear or the malleoincudal joint is often irreversible. This article presents a surgical method that aims to minimize operative trauma. The surgical technique combines a modification of the reverse order technique5, 6 with the adjunctive use of the argon beam laser and modified self-crimping prosthesis. In our experience, this technique provides better access to the footplate during fenestration than the reverse-order technique, while maintaining the advantage of better stability of the footplate and incus. Modification of the prosthesis facilitates placement without compromising hearing results.7 Laser-assisted fenestration minimizes cochlear damage enabling preservation of high-frequency hearing.7, 8 Middle ear exposure is gained through the standard endomeatal approach. Bone is curetted from the posterosuperior margin of the bony annulus to expose the pyramid. The ossicular chain is inspected and gently manipulated to ensure the diagnosis of stapes fixation is correct (Fig. 1). Middle ear exposure. LPI = long process of incus; CT = chorda tympani; ST= stapedial tendon. An argon laser (Lumenis Inc., Salt Lake City, UT) is used in conjunction with a 0.2 mm OtoProbe fiberoptic delivery system (Iridex Corp., Mountain View, CA). Beginning with an initial power setting of 2,000 mW and pulse duration of 0.2 seconds, the stapedius tendon and the posterior crus are vaporized. Removal of the posterior crus of the stapes provides the same access to the footplate as the conventional stapedotomy procedure, and retaining the anterior crus provides stability to the footplate and incus during the next two steps. The laser power is adjusted to 1,500 mW and the pulse duration reduced to 0.1 seconds. A laser pulse is then delivered to the posterosuperior quadrant of the stapes footplate and repeated until perilymph just begins to “sweat” through the laser burn (Fig. 2). This provides a set-hole for a series of hand perforators. The stapedotomy is gently widened, beginning with a 0.3-mm perforator and increasing in 0.1 mm steps to a 0.6-mm perforator, providing a final stapedotomy diameter of 0.5 mm (Fig. 3 and Fig. 4). Laser fenestration—creation of a set hole. SH = set-hole; FP = footplate. Manual fenestration with Halik graduated perforator. FP = footplate; HGP = Halik graduated perforator. Completed small fenestra stapedotomy. SF = small fenestra. A modified Causse Teflon (0.4-mm diameter) prosthesis (Medtronic Xomed, Jacksonville, FL) is employed in this technique. The prosthesis is modified by creating a notch at 3 o'clock, creating an easy click-on attachment to the long process of incus, which provides a tight hold without crimping (Fig. 5). This secure grip cannot always be achieved by the “memory” of the Teflon after the stretching of the prosthesis ring. The prosthesis is cut to an appropriate length, and is aligned with small middle ear alligator forceps while maintaining direct visualization of its distal and proximal ends. The prosthesis ring is maintained at a 90° angle to the long process of the incus to eliminate any distortion of the ring during application. The prosthesis is placed so that it simultaneously enters the footplate fenestra and engages the long process of incus (Fig. 6). This reduces the risk of incus subluxation and provides additional stabilization against the displacement of the footplate during down-fracture of the anterior crus. (A) Original and (B) modified Causse prosthesis. Prosthesis placement. LPI= long process of incus; MCP = modified Causse prosthesis; FP = footplate. The incudostapedial joint is separated using a small right angle hook, and the anterior crus is down-fractured toward the promontory. The superstructure is then gently removed, avoiding contact with the incus and prosthesis. Confirmation of restored mobility and continuity of the ossicular chain is achieved by gentle incus palpation, and if the prosthesis is not securely attached to the incus it can be corrected by an adjustment of the ring position. A secure position of the shaft within the fenestra is tested by gentle lateral pressure on the prosthesis with a small hook. Slight bending of the shaft ensures secure purchase within the fenestra. A precise fit of the fenestra to the diameter of the prosthesis reduces material used for the prevention of perilymph leak, and the natural blood clot around the shaft provides an adequate seal preventing postoperative fistula. The tympanomeatal flap is returned to its original position. The external auditory canal is lined with a strip of surgical rayon dressing and packed with a gauze ribbon soaked in Cortisporin ointment (neomycin sulphate 3.5 mg, polymyxin B sulphate 10.000 U, hydrocortisone acetate 5 mg; Alcon Ltd., Hünenberg Switzerland). External ear canal packing is removed on the next postoperative day. Reviews of intraoperative complications and findings at revision surgery have driven the evolution from the original stapedectomy technique.3, 4, 9-13 Footplate manipulation and prosthesis placement have been shown to occasion the most complications during surgery.2, 3, 14 Analysis of experience-based differences in surgical performance has led to a reduction in the surgeon's reliance on handheld instruments during precise manipulations.15-17 The employment of both laser-assisted fenestration18-21 and the development of self-crimping prostheses have reduced surgical trauma and technical difficulties relating to manual fenestration and prosthesis crimping, respectively.22-24 Recently, the advantage of reversed-order technique in reducing operative complications rate has also been demonstrated.25, 26 The procedure described in this article combines the strengths of a number of previously described techniques5, 6, 19, 24 and has emerged from practice-based learning of the senior author (J.H.). This technique involves a modification of the reverse–step-order technique, in which the prosthesis is placed before removal of the stapes crura. By removing the posterior crus and stapedius tendon, access to the footplate is similar to that obtained during conventional stapedotomy, and the retained anterior crus provides the same stability to the footplate and incus as provided by the reverse-order technique. In our experience, this appears to provide additional protection against inadvertent footplate fragmentation or incus mobilization. Initiating the fenestra with hand perforators or a microdrill can result in excessive pressure in the vertical plane, which may carry the risk of inadvertent footplate mobilization or fracture. Lasers offer an advantage in this step, as the fenestration can be created without pressure on the footplate. A number of different laser delivery methods are available—our own preference for the argon laser is that the laser energy is delivered via a handheld probe that has a similar feel to other middle ear instruments, such as the Rosen needle. Many surgeons perform laser-assisted stapedotomy with laser alone to fashion the stapedotomy; however, there have been concerns that this risks heating the perilymph or direct laser injury to structures of the membranous labyrinth.27-30 The use of lasers simply to attenuate the footplate, so perilymph just begins to seep through, reduces these risks to the labyrinth while providing a set-hole for the perforators. With this set-hole providing an initial key for the point of the perforator, the edges of the fenestration may be gently ground away with only minimal pressure in the vertical plane, avoiding the risk of overheating the vestibule or exposure of the inner ear structures to laser energy or vibration from a microdrill. Another advantage is preventing contamination of the vestibule with char or bone dust created by the laser beam applied to the rosette area or footplate drilling. This less traumatic opening of a vestibule has been shown to reduce the risk of inner ear trauma and subsequent SNHL.7, 8 The modification of the Causse Teflon prosthesis described in this article has provided reliable results and a low rate of piston-related failures. Normally, the ring of the piston is stretched to allow it to be placed over the long process of the incus, which relies on elastic recoil of the material to secure the attachment. This technique may be problematic if elastic recoil has drawn the ring closed before it can be placed upon the stapes or if the ring is overstretched and it remains loose or falls off. Cutting a small wedge from the ring, such that the entire inner circumference of the ring is maintained, provides means for the ring to key into the long process of the incus without prestretching, while still maintaining a circumferential hold on the long process of the incus. The length of the piston shaft has been another source of controversy. Some authors assert that measurements should be made, whereas others use a standard length, typically 4.5 mm. Our own use of a 5-mm prosthesis length was borne of advice given to the senior author from the late Gordon Smyth, who had switched to a 5-mm prosthesis later in his career, feeling that there may be a degree of late lateralization of the incus long process subsequent to division of the stapedius tendon (Gordon Smyth, personal communication). In our experience, this has not been associated with increased postoperative vertigo.7, 8 Traditionally, the results of stapes surgery were reported in relation to hearing thresholds at 0.5, 1, and 2 kHz, and more recently this has been extended to include 3 kHz. It is well recognized, though perhaps not well publicized, that hearing at higher frequencies (>4 kHz) may remain poor after stapes surgery. Anatomically, the basilar region of the cochlea, which provides high frequency hearing, is the closest to the operative site during stapedotomy and may be more susceptible to surgical trauma.1, 31-33 Thus, high-frequency sensorineural hearing loss following stapedotomy may provide a measure of operative trauma. Evaluation of hearing results using this technique has demonstrated good preservation of high-frequency hearing with a low complication rate.7, 8 Technical success measured by air-bone gap closure is equal or superior to other recently published series.6 The technique described in this article has been also proven useful in training of stapedotomy surgery, allowing the operation to be attempted in a series of controlled and increasingly difficult steps. The authors wish to thank John Rutka, MD, FRCS(C), and Ms. Maxine Armstrong, MSc, for their contributions in preparation of this article.

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