Surgical Algorithms

The surgical algorithm for primary stapedectomy in either routine or problem cases is essentially the same. Our technique has been described elsewhere as have techniques for specific problems encountered at both primary and revision stapedectomy.20-29 Six general principles in our partial stapedectomy technique have served the senior author successfully for more than 38 years in more than 15,000 stapedectomies: the use of local anesthesia, vein graft for OW coverage, partial stapedectomy technique, Robinson prosthesis, intraoperative audiome-try, and laser assistance when necessary.

Stapedectomy under local anesthesia has been widely acknowledged as having the added safety and benefit of active feedback from the patient. This is most important during manipulation of the OW-footplate interface and in positioning the prosthesis to monitor for any vestibular symptoms and to allow audiologic testing at the end of the procedure.

A tissue graft is a key element to the success of the technique for protection of the vestibule and prevention of fistulae and also for the mechanical advantage of this self-centering and self-height-adjusting Robinson prosthesis. Causse et al.10 have argued in favor of "reconstructing the acoustic impedance of the annular ligament" with a vein graft, a tissue of similar thickness, resistance, and elasticity. Causse and colleagues eloquently explain biophysically what many have noted clinically. A tissue graft can and should be used with any technique or prosthesis and is easily accessible above the wrist. We prefer the vein for its texture, thickness, translucency, elasticity, and lack of memory.

The size of the footplate fenestra or amount of footplate removed during stapedectomy for optimal performance and minimal complication has been evaluated by several studies.29-33 The general consensus is that there are probably no significant differences for overall performance in speech frequencies between stapedectomy and stapedotomy (fenestra size), but there may be a lower incidence of SNHL with stapedotomy.30 Review of our own cases varying only fenestra size demonstrated no significant differences for hearing (including 4 kHz). However there was a significant difference for overclosure with a medium to large vs. small fenestra (80% vs 64%; P =0.0018).29 Causse et al.10 reason in favor of a medium sized fenestra, suggesting that a fenestra of medium size, located posteriorly with a vein graft gives a "more balanced response from low to high frequencies," simulating best the natural acoustic impedance transfer of the ossicular chain. We recommend removing the portion of the footplate that comes most easily, usually the posterior third to half. A stout, short, footplate hook (Lippy) is useful for this maneuver.

Prosthesis choices are numerous, each having individual nuances, technical benefits, and difficulties. Our selection of the Robinson prosthesis for use in stapedectomy for the past 38 years is based on a combination of sensible mechanics, ease of use, and reproducibility of results. The mechanical advantages are that the prosthesis is self-centering in the fenestra and self-adjusting for height. A large-well, 0.4-diameter shaft, 4-mm-length prosthesis is used in more than 98% of cases. The distance from the incus to the OW is not measured. The position of the prosthesis is determined by an equalization of forces from the natural tension of the incudal ligaments levering the incus long process down on the prosthesis and the elastic resistance of the vein graft covering the OW. The piston end of the prosthesis naturally migrates to the center of the fenestra, whereas the cup end is held in place by the lenticular process. The Robinson prosthesis has several advantages in dealing with special problems encountered during stapedectomy and revisions.20-29

The use of intraoperative audiometry (IOA) in the operating room offers several advantages: (1) it can provide instant, quantifiable, objective feedback to the surgeon; (2) improvement in hearing defines the endpoint of surgery; (3) it dictates attempts in repositioning the prosthesis to maximize hearing gains; and (4) in difficult revision cases, it permits testing with different reconstructive solutions to determine the best option for optimal hearing results. Preoperative air level is tested at either 500 or 1000 Hz, wherever the gap is wider. Improvement of the same test frequency to within 10 to 15 dB of the preoperative bone threshold is considered a satisfactory end result. Further improvement is seen postoperatively. If test performance does not fall within the expected range, the prosthesis is reexamined, and adjustments are made until retesting determines that the best possible result has been obtained. If a satisfactory result is not achieved in the primary procedure, a revision procedure is not indicated. In revision cases, IOA has become especially invaluable.34

The final principle is the use of laser assistance, when necessary. For example, in primary cases in which a "blue" footplate is mobilized, the laser is used to safely fenestrate or incise the footplate and allow completion of the procedure. If a laser is unavailable, successful results in 94% of cases can be achieved by placing a Robinson vein graft over the mobile footplate.28 In revision cases, a laser allows us to atraumatically ablate soft tissue at the OW membrane-prosthesis interface to verify or re-create patency of the fenestra and also facilitate removal of the failed prosthesis. We prefer the argon laser for its hemostatic qualities and method of delivery, a hand-held "otoprobe" that gives the surgeon control to manipulate and defocus the beam easily as needed.10

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