Resection and Reconstruction Anterior Subglottic Stenosis

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Basic dissection is entirely similar to anterior upper tracheal resection (see Chapter 24, "Tracheal Reconstruction: Anterior Approach and Extended Resection"). Often, little pretracheal mobilization is necessary. This approach is applicable where the entire extent of the anterior cricoid is involved and, also, where there may be circumferential damage in the proximal trachea, but where the posterior cricoid plate is not significantly involved (Figures 25-2A,B). If only the lower border of the anterior cricoid cartilage is involved, then this technique is not needed. In such a case, a simple segmental resection of the upper tracheal stenosis is accomplished, additionally bevelling off a portion of the lower margin of the anterior cricoid cartilage (see Figure 25-1B). If the full vertical length of the anterior cricoid is involved (see Figure 25-1C), then it is resected. The cricothyroid muscle on either side is elevated sharply with a scalpel, carrying the dissection sufficiently posterior for division of lateral cricoid laminae. The proximal line of resection encompasses the anterior arch of the cricoid cartilage, including as much as is necessary of the cricothyroid membrane, usually more rather than less (see Figures 25-2A,B), thus bringing the resection nearly to the level of the thyroid cartilage. The resection line bevels laterally through the lateral laminae of the cricoid cartilage, usually more than halfway to a midlateral line. The balance of the line of resection posteriorly is at the level of the inferior margin of the cricoid cartilage (see Figures 25-2B,C). The surface of the vocal cords may be seen just a few millimeters above the anterior inferior midline border of the thyroid cartilage. If there is any question about the extent of resection of the anterior cricoid arch that will be needed, the initial proximal line of resection can be made just beneath the cricoid circumferentially. The arcuate excision is then made under direct vision from below.

The distal line of resection of the lesion is placed below the level of stenosis, just above the first unin-volved tracheal ring or a ring that has good cartilaginous structure, even if slightly involved by inflammation or scar. This ring is bevelled backward from a high point in the anterior midline to the lower margin of that ring posteriorly on either side (see Figures 25-2A-D). The membranous wall is cut straight across. Only one ring is bevelled in this way, even though the inverted "U" of the superior anterior laryngeal resection line may seem to be a much sharper angle than that below. This avoids creating a floppy flap of cartilage anteriorly, which might occur if two rings were so trimmed. As a consequence, the trachea may arch forward slightly in the subsequent anastomosis. This may provide a better lumen at the anastomotic level.

Initial dissection is similar to that described in the anterior approach to the trachea (see Chapter 24, "Tracheal Reconstruction: Anterior Approach and Extended Resection"). The upper incisional flap must be elevated higher on the surface of the thyroid cartilage, usually to the superior notch of the thyroid cartilage. Dissection of the anterior surface of the airway is superficial to the cricothyroid muscle and cricothyroid membrane. The thyroid isthmus or its remnant is divided and retracted laterally. The pyramidal lobe of the thyroid is divided or removed if it lies in the way. It is necessary to detach the often scarred medial attachments of the upper poles of the thyroid gland from the cricothyroid muscle. Dissection is not, however, carried any further laterally than is necessary to expose the midportion of the lateral laminae of the cricoid cartilage. Pretracheal dissection down to the carina is often done, but may be omitted in those patients in figure 25-2 Anterolateral stenosis involving the subglottic larynx most often results from high or erosive tracheostomy or from crico-thyroidostomy. A, The anterior cricoid arch and cricothyroid membrane, which overlies the stenosis, is excised with the stenosis in an arcuate line. The first intact cartilage below the stenosis is trimmed in similar contour. B, Lateral lines of resection. The posterior plate of the cricoid and its posterior perichondrium is preserved. The recurrent inferior laryngeal nerves (illustrated) are not dissected, but allowed to fall laterally. Only the inferior rim of the posterior cricoid cartilage is dissected. C, D, Stay sutures (2-0 Vicryl) are placed laterally in the substance of the remaining lateral laminae of cricoid, but do not penetrate the laryngeal mucosa. Corresponding tracheal stay sutures encircle a ring at least one cartilage distal to the most proximal complete ring, and do include mucosa. Cricoid and tracheal stay sutures are located at corresponding points in the circumference of the airway. Dotted lines outline vocal cords. For clarity, surrounding tissues are not illustrated, but minimal trachea is dissected circumferentially in order to preserve blood supply. Often, only a small space is opened in the lateral attachments of the trachea in order to place the stay sutures.

Anterior Laryngeal ReconstructionAnterior Laryngeal Reconstruction

figure 25-2 (continued) E, F, Completed anastomosis. Anastomotic sutures are placed as described in Chapter 24, "Tracheal Reconstruction: Anterior Approach and Extended Resection," for tracheotracheal anastomosis. Posteriorly, because of the thickness of the cricoid plate, sutures often traverse only part of the cartilage's thickness, but enter the airway lumen through full thickness of mucous membrane. Stay sutures are approximated first, as described in Chapter 24, "Tracheal Reconstruction: Anterior Approach and Extended Resection." They are omitted in the illustration for clarity. Some overriding of the cut edges of lateral cricoid laminae and trachea often occurs. G, The anastomosis is usually covered with reapproxi-mated thyroid isthmus or strap muscles, which are sutured together over it and to the larynx and trachea above and below the anastomosis. The right sternohyoid muscle may be sutured to the trachea over the brachiocephalic artery, as shown, for its protection. The site of a potential tracheostomy in the triangle between the covered anastomosis and the artery will be marked with a single fine suture.

figure 25-2 (continued) E, F, Completed anastomosis. Anastomotic sutures are placed as described in Chapter 24, "Tracheal Reconstruction: Anterior Approach and Extended Resection," for tracheotracheal anastomosis. Posteriorly, because of the thickness of the cricoid plate, sutures often traverse only part of the cartilage's thickness, but enter the airway lumen through full thickness of mucous membrane. Stay sutures are approximated first, as described in Chapter 24, "Tracheal Reconstruction: Anterior Approach and Extended Resection." They are omitted in the illustration for clarity. Some overriding of the cut edges of lateral cricoid laminae and trachea often occurs. G, The anastomosis is usually covered with reapproxi-mated thyroid isthmus or strap muscles, which are sutured together over it and to the larynx and trachea above and below the anastomosis. The right sternohyoid muscle may be sutured to the trachea over the brachiocephalic artery, as shown, for its protection. The site of a potential tracheostomy in the triangle between the covered anastomosis and the artery will be marked with a single fine suture.

whom only a short length of resection is required. Where a longer segment is to be resected, the surgeon must remember that nearly a centimeter of trachea will be needed to repair the defect in the anterior larynx, in addition to the length of trachea resected. Infrequently, a laryngeal release may be required, with its potential attendant difficulties.

Circumferential dissection is effected just below the lesion in the usual manner and tracheal transec-tion is performed. The trachea is initially divided transversely, with oblique bevelling of the cartilage done later. Midlateral traction sutures of 2-0 Vicryl are placed in the distal segment and the distal trachea is then intubated (see Figures 25-2C, D).

The stenotic segment is grasped laterally with two Allis forceps, as in upper tracheal resection (see Figure 24-8A in Chapter 24, "Tracheal Reconstruction: Anterior Approach and Extended Resection"), and the trachea is carefully dissected cephalad to the inferior margin of the cricoid cartilage laterally and posteriorly. This dissection must be done painstakingly, adjacent to the specimen. The surgical scissors will be working within millimeters of the recurrent laryngeal nerves. No attempt should be made to identify or dissect out the nerves. If the principles of dissection described are rigorously followed, damage to recurrent laryngeal nerves will be very rare and is usually transient if it should occur. It is important during dissection to palpate frequently and not carry posterior dissection above the lower border of the posterior cricoid plate. Such dissection could endanger the recurrent laryngeal nerves at their point of entry into the larynx posteriorly.

In commencing the anterior cricoid resection, the cricothyroid muscles are dissected off their attachment to the anterior and lateral cricoid cartilage. The line of resection of the lower larynx commences in the midline anteriorly, usually just below the thyroid cartilage. It sweeps laterally beneath the border of the thyroid cartilage, through the cricothyroid membrane obliquely inferiorly and posteriorly, dividing the lateral laminae of the cricoid cartilage (see Figures 25-2C,D). If the lateral laminae of the cricoid cartilage are severely deformed by the pathological process, the division will be more posterior, closer to the posterior cricoid plate. Great care is necessary at this point, because of the proximity of the recurrent laryngeal nerves. The posterior line of division of the larynx is at the inferior margin of the posterior cricoid plate.

Should the proximal airway appear smaller than expected, a small right-angle clamp is inserted into the residual lower larynx beneath the vocal cords and the tip drawn downward along the anterior wall of the larynx to discover whether a "shelf" is present. At times, a very small amount of additional excision of a rim of anterior tissue will very much enlarge the airway, at what will become the anastomotic level. Lateral midline traction sutures (2-0 Vicryl) are placed in the larynx, being certain that these pass through cartilage substantially, so that they will not pull out during approximation of the airway (see Figures 25-2C,D). The sutures usually lie in the residual lateral cricoid laminae just behind the line of their transection, but they may sometimes be partly in the thyroid cartilage. They do not enter the laryngeal lumen (see Figure 24-9 in Chapter 24, "Tracheal Reconstruction: Anterior Approach and Extended Resection"). In placing these sutures, it must be noted that the direction of the needle cannot be changed once it enters the cartilage. Therefore, the angle of placement must be carefully directed initially.

The distal trachea is tailored next, as previously described, preparing an anterior "prow" of tracheal cartilage, which will be drawn into the laryngeal defect to restore this portion of the airway wall (see Figures 25-2A-D). In case of a lengthy resection, it may be necessary to accept some slight degree of scarring or inflammation in the midline of the tracheal ring, which will be shaped for anastomosis, but its cartilaginous structure must be acceptably intact. Preparation of the trachea for anastomosis is deferred until after laryngeal division, in order to establish with certainty that a posterior flap of membranous trachea will not be needed to resurface the posterior cricoid plate.

Tentative approximation of the airway (see Chapter 24, "Tracheal Reconstruction: Anterior Approach and Extended Resection") demonstrates the degree of tension that will be placed on the anastomosis. The anastomosis is done with great care, using the basic technique described in Chapter 24, "Tracheal Reconstruction: Anterior Approach and Extended Resection" and the same 4-0 Vicryl sutures. All sutures are placed before any are tied. Since both laryngeal and tracheal ends are obliquely divided and disparate in size, sutures must be placed proportionately, using the midlateral sutures as guide points as well as anterior and posterior midpoints. Since mucosal approximation is sought, sutures may in some cases pass through a partial thickness of laryngeal cartilage above, but it must always pass through mucosa of the larynx, into or from the lumen, in order to assure approximation with tracheal mucosa. The purchase on cartilage must be secure, however. In the presence of dense scarring or calcification, one or more anterior "keystone" sutures of heavier Vicryl (usually 3-0 and rarely 2-0) may help the anastomotic approximation. Dense calcification is dealt with as described in Chapter 24, "Tracheal Reconstruction: Anterior Approach and Extended Resection," and may necessitate use of a fine dental drill. In placing the anterior sutures, it helps to place the midline suture first, halfway between the lateral traction sutures. This makes it easier to space the remaining anterior sutures proportionally on each side.

After placement of all sutures and prior to final flexion of the neck, a catheter is passed from the operative field into the pharynx. It is retrieved by the anesthetist, who draws it out through the mouth and sutures to it an endotracheal tube of a caliber that will pass atraumatically through the smaller than normal airway (see Figure 24-11 in Chapter 24, "Tracheal Reconstruction: Anterior Approach and Extended Resection"). This tube is pulled into the field and passed into the distal trachea where it replaces the cross-field tube. The patient's neck is placed in flexion, the lateral traction sutures are tied, followed by the anastomotic sutures (Figures 25-2E,F). Because of the disparity in tissues and, frequently, their rigidity, the anterior sutures are often best tied by starting first with the most lateral sutures on either side, and then gradually working toward the center where the greatest tension is. The use of heavier central sutures helps in such cases. The posterior line of sutures is tied last, with half being tied from one side and half from the other side (see Figure 24-15 in Chapter 24, "Tracheal Reconstruction: Anterior Approach and Extended Resection").

Since some of these patients have, at best, 50% of normal subglottic laryngeal cross-sectional area just below the vocal cords, and since some intraoperative laryngeal trauma is unavoidable, the possibility of early postoperative laryngeal edema is real. Initially, I routinely placed a small tracheostomy tube distal to the anastomosis, but it became clear that few patients required this.9 The anastomosis is covered with tissue to seal it from a potential later tracheostomy. The thyroid isthmus may serve this purpose in some cases. More often, the strap muscles are sutured together in the midline and to the airway above and below the anastomosis, sealing it off. Since the trachea is much shortened in many patients, the site of a potential tra-cheostomy, which should be placed at least two rings below the laryngotracheal anastomosis, might lie dangerously close to the brachiocephalic artery below. The brachiocephalic artery is therefore compartmentalized, by suturing the right sternothyroid muscle obliquely across the trachea, placing the sutures just behind the artery to the tracheal wall. The muscle will conform appropriately without being pedicled. This leaves a triangle of anterior tracheal wall (Figure 25-2G), which lies below the protected anastomosis and above the obliquity of the course of the protected brachiocephalic artery. A 4-0 silk suture is placed to mark the point of election for tracheostomy, should it become necessary later.

The endotracheal tube is removed in the operating room as the patient awakens. If the airway appears adequate, the patient is returned to the intensive care unit breathing spontaneously. If the patient is stri-dorous, the glottis is examined directly, using either a rigid laryngoscope (without extending the neck) or a flexible bronchoscope. The glottis can usually be examined quite satisfactorily without extending the neck, even by laryngoscopy. If vocal cord paralysis is seen (a rare occurrence unless present preoperatively), or if laryngeal edema is present, a small bore endotracheal tube, usually uncuffed, is passed, either nasotracheally or orotracheally. The nasotracheal route is preferable, if it can be done without excessive extension and traction on the suture line (most easily over a pediatric flexible bronchoscope). Patients are informed preoperatively of this possibility. The tube is removed 4 or 5 days later in the operating room under general anesthesia, and if the airway is still not adequate, a small sized tracheostomy tube is inserted at the premarked site. Tissue planes over the anastomosis and artery are well sealed by this time. The possibility of damage to either of these critical areas is minimized.

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