In these more difficult cases, the stenosis is circumferential and overlies the posterior cricoid plate as well (Figure 25-3A). The mucosa is involved with inflammation and scar or it has been destroyed. Idiopathic stenoses are always circumferential, as are most postintubation stenoses from endotracheal tubes as well as those from certain miscellaneous causes such as Wegener's disease or trauma.9,14,15 Exposure, dissection, and initial tracheal division are performed exactly as described for anterolateral subglottic lesions. The anterior and lateral laryngeal division is also executed in an identical fashion. Most often, the tracheal specimen is initially resected by dividing posteriorly along the lower border of the posterior cricoid plate (see Figure 25-3A). Alternatively, the specimen remains attached posteriorly, and the final separation of the stenosis is commenced higher on the posterior cricoid plate, as described below.
We are left at this point with the anterior cricoid arch (and cricothyroid membrane) removed, the lateral cricoid laminae obliquely divided, and the stenotic distal tracheal segment removed, but with a ring of posterior shelf-like scar remaining on the anterior surface of the posterior cricoid plate. This stenosis is excised by making a transverse cut against the posterior plate of the cricoid cartilage inferior to the vocal cords and arytenoid cartilages, at a level dictated by the stenotic process (Figure 25-3B). The scarred mucosa and ridge of stenotic scar are excised sharply from the anterior surface of the posterior cricoid plate using a scalpel with a no. 15 blade or a small Beaver blade, leaving the denuded posterior plate of the cartilage as intact as possible. There is usually no reason to remove the posterior cricoid plate completely. Removal could endanger the recurrent nerves. Varying degrees of deformity and destruction of the posterior cartilage will be encountered, requiring surgical ingenuity. An absolute requirement is preservation of the posterior perichondrium.
The distal trachea is prepared differently from the case of anterior stenosis. The tracheal cartilage anteriorly and laterally is trimmed as before, sloping the line of division backward on either side over the width of only one ring. The membranous wall, however, is formed into a broad-based flap with the superior corners slightly curved. This full thickness flap of healthy tissue has excellent blood supply (see Figure 25-3B).
The anastomosis is more complicated, as might be expected. The goal is to resurface the bared posterior cricoid plate with the tracheal membranous wall flap, uniting it with the mucosa of the posterior larynx above (Figures 25-3C,D). The "prow" of cartilage will be sutured into the oblique defect in the anterior and lateral larynx, as previously described. To insure apposition of the membranous tracheal flap to the posterior plate of larynx, four nonabsorbable 4-0 sutures (usually Tevdek) are first placed from the inferior margin of the posterior cricoid plate to a line that runs across the back of the membranous wall from the lowest level of the flap on either side (Figures 25-4A,B). Two inner sutures are placed first, neatly dividing the posterior plate of cricoid into thirds. The two lateral sutures are next placed from the lateral corners of the posterior plate of cartilage to the lateral corners of the tissue just below the origin of the membranous wall flap, close to the cartilaginous junction of the trachea. These sutures do not penetrate the mucosa. The inner two Tevdek sutures are clipped to the drapes on either side, and the lateral sutures are clipped to the drapes caudad to the first. Since these are of different material, they are easily distinguishable from later anastomotic sutures of Vicryl. They will be tied in the same order as described for tracheal anastomosis, namely, the most lateral sutures will be tied first and the medial ones tied second (see Chapter 24, "Tracheal Reconstruction: Anterior Approach and Extended Resection").
A series of 4-0 Vicryl mucosal sutures are next placed from the posterior laryngeal mucosa and sub-mucosa to the membranous wall flap of trachea. These sutures are placed from within the larynx, although they are passed from the posterior wall of the laryngeal or tracheal mucosa into the lumen, and then from the lumen through the opposite mucosa to emerge posteriorly (see Figures 25-4B,C). The central suture is most conveniently placed first, then working laterally to either side. All sutures are clipped serially to the drapes over the patient's face. The endotracheal tube in the distal trachea is intermittently removed to facilitate placement and tying of sutures.
After placing the necessary number of sutures to anastomose the posterior flap to the mucosa within the larynx, the first of the "standard" anastomotic sutures are placed on either side, moving from posterior to anterior, and pausing at the level of the lateral traction sutures. This usually requires two or three sutures on each side. Each suture is passed through cartilage of the lateral laminae of cricoid or of the cut edge of the lateral lamina and edge of laryngeal mucosa above, and thence through the full thickness of mucosa and cartilage of the trachea below. These sutures are placed from posterior to anterior and tagged in the usual manner from cephalad (most posterior suture) to caudad (anterior sutures) on the drapes, usually above the Tevdek fixation sutures, which were initially placed. The next one or two sutures anterior to the traction sutures are also placed on each side at this time, since it will be more difficult to insert these after airway approximation.
figure 25-3 Circumferential stenosis involving subglottic larynx results from endotracheal tube injury, idiopathic stenosis, trauma, and other causes. A, The initial (dashed) line of inferior laryngeal resection is the same as for anterior stenosis. The line (dashed) of tracheal division is also the same anterolaterally, but posteriorly, a flap of membranous wall is preserved. If a longer posterior flap is necessary, then the line of cartilage division may be dropped one ring. The "prow" of tracheal cartilage is limited to one ring, even if the membranous flap is longer, in order to avoid flaccidity after anastomosis. The dotted lines indicate residual lumen and position of vocal cords. Note the circumferential involvement and extent of the stenosis over the anterior surface of the posterior cricoid plate. B, Internal view of the resection. Dashed lines show the level of the laryngeal and tracheal transection. Dotted line indicates the line of resection of the stenotic scar from the anterior surface of the cricoid plate. Irregular, damaged cartilage is also carved away, preserving a stable shell of cartilage with its posterior perichondrium. A posterior flap of membranous tracheal wall is preserved distally. Its corners are carefully rounded.
The inflatable "thyroid bag" beneath the patient's shoulders is deflated, the neck propped in partial flexion, and the lateral traction sutures are tied to remove tension from the anastomosis about to be commenced. The four posterior Tevdek sutures are next tied, to fix the membranous flap to the inferior margin of the cricoid cartilage plate posteriorly. The long ends of each suture are cut after tying. The internal sutures, which will anastomose the membranous flap to the posterior mucosa of the larynx below the arytenoids, are next tied with great care, to avoid tearing sutures out of the laryngeal mucosa. The tip of the finger may usually be inserted easily into the still open anterior larynx to tie these sutures. The endotracheal tube is removed when each suture is tied. If there is a gap or if one of the sutures should cut out of the mucosa of the larynx, because of inflammatory changes or excessive tension, another suture may be carefully placed. The integrity of this suture line is inspected directly before proceeding. Lateral anastomotic sutures posterior to the traction sutures are tied next. The one or two sutures already placed anterior to the traction sutures are not yet tied.
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