Anterior glottic webs can be acquired or congenital. Surgery is indicated for airway restriction or symptomatic dysphonia. Comorbidities should be addressed before intervention. Approaches include open or endoscopic approaches. The current review focuses on two common endoscopic approaches, the endoscopic flap and endoscopic keel placement. These procedures generally have high success rates; many of the associated postoperative complications can be avoided simply with close attention to detail during the initial procedure, although a small percentage of patients are likely predisposed to web reformation and development of granulation tissue despite excellent surgical technique.
An anterior glottic web (Figure 1) may be congenital or acquired. A congenital anterior glottic web is rare, and the symptoms are usually identified at birth or at a young age if the web is large and causes stridor. Smaller congenital webs are often identified later in life and are associated with exercise restriction and/or dysphonia. Acquired anterior glottic webs are the most common type of glottic web; these typically occur from a traumatic injury to the larynx, including external trauma and iatrogenic injuries such as intubation or surgery. Anterior glottic webs range in size from extremely small microwebs to very large webs that encompass the entire length of the membranous vocal folds. The associated symptoms, severity, and indicated surgical procedure will vary significantly based on the etiology and size of the web.
Anterior glottic webs should be evaluated in 2 specific planes: an anterior-posterior dimension and a superior-inferior plane. The latter can often reveal web formation from the glottis to the supraglottis and/or web formation from the glottis into the subglottis.
A variety of conditions are associated with anterior glottic web. Vocal fold scar is frequently associated with an anterior glottic web because of the traumatic etiology of most of these cases. Laryngopharyngeal reflux (LPR) can also be associated with anterior glottic web formation. Stenoses at other levels including the supraglottis, subglottis, or trachea should be sought as well. These conditions can result from the same underlying traumatic injury or associated intubation, or they can result from unrelated etiologies such as chemoradiation therapy, congenital cricoid or tracheal cartilage deformities, or tracheomalacia.
Differential diagnosis for an anterior glottic web includes Wegener's granulomatosis, sarcoidosis, and amyloidosis. These conditions should be worked up in the absence of another obvious etiology.
Indications for surgical treatment of anterior glottic webs include airway restriction, abnormally elevated phonatory pitch, or other dysphonia that is concerning to the patient. Contraindications include uncontrolled LPR, active recurrent respiratory papillomatosis (RRP) not causing airway restriction, or the lack of functional voice limitations or dyspnea.
The procedure is performed under general anesthesia with rigid laryngoscopy. The patient is intubated with the smallest tube possible, using a laser-safe tube if indicated. Perioperative antibiotics and steroids are administered. Necessary surgical equipment includes:
- •Standard phonomicrosurgery and laser microlaryngoscopy sets.
- •Silastic sheet or premade laryngeal keel.
- •Endo-extralaryngeal needle passer (Richard Wolf Medical) or 18-gauge angiocatheter/2.5-cm-long, 18-gauge needle (Figure 2) .
- •A 0 prolene suture.
- •Mitomycin C (optional).
- •Silicone surgical button(s).
Two approaches are used most often for the release and removal of an anterior glottic web: endoscopic flap or endoscopic placement of a keel. The endoscopic flap approach is best used for smaller anterior glottic webs and involves the asymmetric division of the web with use of the mucosa associated with the web for mucosal coverage of one side of the anterior commissure. It should be emphasized that this operation involves delicate surgical handling of involved mucosa. Elevation and preservation of the anterior glottic web mucosa is performed; then the flap is sutured over one side of the anterior commissure.
For larger anterior glottic webs and for patients who do not have adequate tissue for an endoscopic flap, release of the anterior glottic web and endoscopic placement of a keel are required. Patients undergoing this procedure should be informed of the need for 2 surgical procedures (placement of keel and removal of keel); they should also be prepared for moderate pain and discomfort as well as globus sensation for the 7-10-day period that the keel is in position.
Other less-frequently used procedures include lysis of the web without keel placement (more commonly performed in children with small webs) or open approaches with laryngofissure for large stenoses involving multiple levels of the airway.
The endoscopic flap is performed by first obtaining rigid laryngoscopic exposure of the anterior glottic web and anterior commissure region with suspension laryngoscopy. The optimal head and neck position for exposure of the endolarynx with the laryngoscope is neck flexion on the body and head extension on the neck. A shoulder roll typically places the patient in a suboptimal position (ie, neck extension), and thus it should not be used. Dental and alveolar ridge protection before insertion of the laryngoscope is important. For patients who are edentulous at the maxilla, the best way to protect the mucosa and underlying alveolar ridge is to place a small high-density foam pad between the laryngoscope and the alveolar ridge. As the laryngoscope is placed into the oral cavity, the lips and tongue should be retracted with the nondominant hand. The laryngoscope is then slid along the ventral surface of the tongue and advanced down toward the base of the tongue and posterior pharyngeal wall. The laryngoscope is placed under the epiglottis without folding or traumatizing it. The optimal position of the laryngoscope for this procedure is immediately superior to the web, using the laryngoscope to retract the false vocal fold tissues. Care should be taken to avoid contacting the superior surface of the vocal fold, given that this will significantly alter the anatomic orientation of the vocal fold and often distort the appearance of the pathologic region. External counterpressure can be applied if necessary using silk tape over gauze.
After appropriate positioning, the superior and inferior depth of the anterior glottic web is evaluated with both 0-degree and angled telescopes (Figure 3) . Photodocumentation is obtained. The operating microscope is then brought into the field for further evaluation. Minor but important adjustments of the position of the microscope and laryngoscope will bring the viewing access of the microscope perfectly coaxial with the longitudinal aspect of the laryngoscope; binocular vision at high-power magnification is thus achieved for the remainder of the procedure.
The anterior glottic web is now incised in an asymmetric fashion at either the free edge or even the superior surface of the vocal fold; this mucosa is elevated and preserved for incorporation into the flap (Figure 4) . The flap is grasped and retracted laterally, and the remaining anterior glottis web is released all the way to the thyroid cartilage at the anterior commissure using cold steel instrumentation or the CO2 laser (Figure 5) . The endoscopic flap can now be draped down over the infraglottis and secured in place with a single 5-0 or 6-0 absorbable suture (Figure 6, Figure 7) . It is rare that the endoscopic flap does not need suturing to stay in the proper location. Tissue glue does not appear to be adequate to secure the endoscopic flap. Application of mitomycin C onto the demucosalized portion of the contralateral vocal fold and anterior commissure is optional.
Endoscopic keel placement
Keel placement is another option after release of the anterior glottic web. Laryngoscopic exposure with suspension and angled telescopic evaluation are obtained as noted above. There should again be adequate false vocal fold retraction and complete exposure of the anterior glottic web and anterior commissure; there should also be enough room above the vocal folds to account for the superior position of the planned keel, approximately 3-4 mm above the level of the web. It is emphasized that evaluation of the superior-inferior extent of the web is crucial, as it will dictate the minimum length of the planned keel.
Release or excision of the web can be done with a CO2 laser (smallest spot size and low power), up-cutting scissors, or a sickle knife (Figure 8) . When incising the anterior glottic web, it is important to put tension on the vocal folds with lateral retraction and to stay in the midline between the vocal folds to minimize any lamina propria damage. Cold steel excision is preferable to minimize surgery-related scar formation. After release of the anterior glottic web up to the anterior commissure, the CO2 laser can be used to make a 1-mm-deep groove in the inner aspect of the thyroid cartilage, extending 3-4 mm above the anterior commissure and 4-5 mm below (Figure 9) . This groove will be used to place the keel as far anteriorly as possible.
30-degree and 70-degree telescopes can then be used to visualize the superior and inferior extent of the anterior glottic web release and to determine the length of the intended keel. When visualizing this area with a 30-degree or 70-degree telescope, the telescope should be passed to the superior-most location to which the keel will need to be secured, and then the telescope shaft can be marked at the location of the junction of the shaft and the proximal laryngoscope. The telescope is then advanced to the inferior limit of the planned keel location, and another mark is made on the telescope. The distance between the two marks is measured and used to determine the superior-inferior length of the keel (Figure 10) . The necessary width of the keel is determined by the degree to which the vocal fold is involved in an anterior-posterior direction.
After trimming the keel to the required length and width, the keel is placed with a heavy cup forceps into the larynx to evaluate the fit. The eventual placement of the suture through the keel will ultimately determine the exact location of the keel in the larynx. Thus, it is helpful to place the keel in the appropriate location and obtain endoscopic visualization with the 70-degree telescope to determine where the fixation sutures should be placed in the keel.
A 0 prolene suture with needles on both ends is then passed from the subglottis to the anterior neck with the Lichtenberger endo-extralaryngeal needle passer. This is done with the operating microscope or with a 30-degree telescope. A clamp is placed on the free end of the suture penetrating the anterior neck (Figure 11) .
An alternative method that does not rely on the endo-extralaryngeal needle passer is to have an assistant pass an 18-gauge angiocatheter or a 2.5-cm-long, 18-gauge needle from the anterior neck to the desired location in the anterior subglottis during simultaneous microlaryngoscopy or telescopic visualization of the larynx. Once the needle is in the proper location in the subglottis, a 0 prolene suture is passed without a needle passer through the hollow tip of needle or angiocatheter and out through the neck where it is secured with a clamp.
Now that one end of the prolene suture has been placed at the inferior or subglottic position, the other end is brought out through the laryngoscope. The suture is passed through the spine of the keel twice, first inferiorly (starting at the convex side) and then superiorly (coming back from the concave side to the convex side). The suture is then loaded into the endo-extralaryngeal needle passer and placed down the laryngoscope. It is passed from the region superior to the anterior commissure out through the anterior neck (Figure 11). If an endo-extralaryngeal needle passer is not available, the method described earlier can also be used to pass the suture out through the neck.
The keel is guided into position in the endolarynx as an assistant applies moderate but equal tension to the sutures coming out of the anterior neck. The proper location of the keel is confirmed using 30-degree and 70-degree telescopic visualization. If the keel is not in the proper location, the placement of the sutures through the keel should be adjusted and repeated. Once the appropriate position is obtained, the keel is secured in place by tying the sutures over a surgical button (or over two buttons, if the sutures have been placed widely apart). The keel should remain in endoscopic or microscopic visualization while the suture is tied (Figure 12) .
Keel removal is performed 7-10 days later, preferably with apneic anesthesia. Endotracheal intubation can complicate endoscopic keel removal and injure the operative site. Direct laryngoscopy is performed, and an assistant uses a 0-degree telescope to visualize the superior portion of the keel. A large cup forceps is used to grasp the keel. Once the endoscopist is confident that he or she has a firm grasp of the keel, the anterior neck sutures are cut and the keel is removed through the laryngoscope.
The patient is mask ventilated; once adequate oxygenation is achieved, repeat direct laryngoscopy and endoscopic visualization of the operative site are performed. If there is severe granulation tissue or reformation of the web, the endoscopic glottic web procedure is repeated. Mitomycin C can also be applied at this point. These decisions are made based on the amount of mucosalization that has occurred at the anterior glottis.
Postoperative care includes reflux treatment, pain control, postoperative steroid taper, cough suppression, and possible overnight observation in the hospital. Patients are reevaluated in approximately 8-10 days in the office, with flexible laryngoscopy or indirect laryngoscopy to determine the amount of mucosalization that has occurred underneath the keel.
Complications include reformation of the anterior glottic web, dislodgement of keel, scar or erosion of the vocal fold from poor keel position, granulation at the keel suture location, and subcutaneous emphysema. Reformation of the web may be prevented by ensuring adequate anterior extension of the cut with a sufficiently deep and wide cut into the thyroid cartilage. Too deep a cut, however, must be avoided to prevent the development of subcutaneous air.
Prevention of vocal fold erosion and keel dislodgement is crucial; close attention to the tying of a secure knot and correct placement of sutures during the initial procedure, with adjustment of suture position in the neck and in the keel as necessary, will help avoid these complications. Granulation tissue and reformation of the anterior glottic web may be reduced with application of mitomycin C, although this is controversial.
Anterior glottic web is most commonly an acquired condition from iatrogenic injury such as intubation or surgery for pathology at the anterior commissure, although congenital glottic webs are encountered. Surgery is indicated for airway restriction or symptomatic dysphonia. Comorbidities such as active RRP or LPR should be addressed before intervention. Approaches include open or endoscopic approaches. Although open approaches such as laryngofissure may have offered more control of pathology at the anterior commissure in the past, the comfort and skill level that many current-day laryngologists have with endoscopic procedures as well as the improved instrumentation available have made an endoscopic approach a reasonable choice for the majority of cases. Endoscopic approaches are advisable when good exposure can be obtained and webs are small, although even larger webs can be treated endoscopically when keel placement is used. Both asymmetric release of the web with flap coverage and web release with endoscopic keel placement are discussed in detail here, and these procedures generally have high success rates. Many of the postoperative complications can be avoided simply with close attention to detail during the initial procedure, although a small percentage of patients are likely predisposed to web reformation and development of granulation tissue despite excellent surgical technique.
© 2012 Elsevier Inc. Published by Elsevier Inc. All rights reserved.