Adult laryngotracheal stenosis has numerous etiologies (Box 71-1). The pathophysiology of the specific cause plays a role in the timing of surgical management as well as the surgical procedure chosen.

The most common causes of laryngotracheal stenosis are external trauma to the neck and prolonged endotracheal intubation. Both may result in acute stenosis and chronic stenosis; which occur through different pathophysiologic processes. Anatomically, the larynx and trachea can be regarded as a semirigid tubular structure. When the laryngotracheal complex is injured by external trauma, disruption of the cartilaginous framework, hematoma in the laryngeal spaces, and mucosal disruption usually result. Resorption of the hematoma can cause cartilage loss and extensive deposition of collagen. Subsequent scar contracture leads to stenosis and loss of mobility. The location, mechanism, and severity of the laryngeal injury caused by external trauma vary.¹

In contrast, the injury from endotracheal intubation is usually initiated by ischemic necrosis of the mucosa from pressure of the cuff of the endotracheal tube or the endotracheal tube itself.² Mucosal ulceration in the presence of bacterial infection can lead to perichondritis and chondritis with subsequent cartilage resorption. Healing occurs by secondary intention with subsequent submucosal fibrosis and scar contraction. Injuries from endotracheal intubation occur primarily in the posterior glottis as a result of pressure exerted by the wall of the tube and the pressure of the cuff on the tube’s tip. The latter injury has been reduced significantly with low-pressure, high-volume cuffs. Other factors, including tube size and composition, duration of intubation, and laryngeal movement, contribute to the development of laryngotracheal stenosis. With the widespread acceptance and use of endotracheal intubation to provide ventilatory and airway support, efforts have been directed to modifying endotracheal tube design.³

Patient disease has also shown to be correlated with the development of subglottic and tracheal stenosis. Diabetes mellitus, congestive heart failure, and a history of stroke have been shown to be associated with a higher incidence of severe acute laryngeal injury from intubation. In some cases, this condition prompts early tracheotomy.⁴ Laryngopharyngeal reflux in the setting of gastroesophageal disease has also been demonstrated to be a causative agent and potentiator of laryngotracheal stenosis. Treatment with H₂ blockers and proton pump inhibitors in the perioperative and acute injury phases has been demonstrated to prevent scar formation and subsequent contracture.⁵

Classification of Stenosis

Multiple staging systems exist for airway stenosis; these are based on function or location of the stenotic section. As shown in Table 71-1, the most prevalent is the Cotton-Myers classification; however, the McCaffrey system and others also add to the diagnostic and therapeutic plan in providing not only size of stenosis but location and inclusion of multiple subsites, which are associated with a poorer prognosis following surgery.

Table 71-1 Classification and Staging Systems for Airway Stenosis

Myers-Cotton Classification: circumferential stenosis limited to subglottic region
Grade I	Obstruction of 0%-50% of the lumen
Grade II	Obstruction of 51%-70% of the lumen
Grade III	Obstruction of 71%-99% of the lumen
Grade IV	No detectable lumen; obstruction of 100% of the lumen
McCaffrey Classification: laryngotracheal stenosis based on the subsites and length of the stenosis
Stage I	Subglottic or tracheal lesions < 1 cm long
Stage II	Subglottic lesions > 1 cm long
Stage III	Subglottic/tracheal lesions not involving the glottis
Stage IV	Glottic lesions
Lano Classificaiton: based on number of subsites involved
Stage I	One subsite involved
Stage II	Two subsites involved
Stage III	Three subsites involved

Surgical Principles

Goals and Assessment

The goal of any surgical procedure addressing laryngotracheal stenosis is to establish a satisfactory airway, and eventually, to decannulate the patient. In addition, every effort should be made to preserve other important laryngeal functions—phonation, airway protection, and glottic closure. Surgical procedures designed to improve the airway often compromise other laryngeal functions. The anticipated overall function of the larynx should be carefully discussed with the patient so that expectations are reasonable.

Several factors should be considered, including the location, dimensions, and quality (soft vs. fibrous) of stenosis, associated vocal fold motion impairment, and extent of functional impairment. Initial evaluation should involve a thorough history that includes details of the degree of subjective impairment (perceived by the patient) along with objective measures (e.g., observing the patient walking 200 feet, climbing a flight of stairs, pulmonary function testing).⁶ Pulmonary function testing is helpful in delineating the site of obstruction and severity of airway compromise (Fig. 71-1).

Figure 71-1. Flow-volume loop for assessing adequacy of the upper airway. A, Normal result shows expiratory flow, indicated by positive deflection, and inspiratory flow, indicated by negative deflection. B, Loop from a patient with bilateral vocal fold motion impairment shows variable extrathoracic obstruction with a mid–vital capacity inspiratory flow rate (Vi₅₀) of less than 1.5 L per second. C, Loop from a patient with an infiltrative tumor and a fixed obstruction. BTPS, body temperature, pressure saturation.

Physical examination, including an indirect laryngeal examination followed by direct laryngoscopy and bronchoscopy, is essential (Fig. 71-2). High-resolution computed tomography of the larynx and trachea may be useful in assessing the level and extent of the stenosis. Three-dimensional computed tomography with volume rendering or virtual endoscopy has been employed to evaluate the extent or severity of the stenosis.^7,⁸

Figure 71-2. Endoscopic view of subglottic stenosis for preoperative staging and evaluation.

An important consideration is whether the site of stenosis requires reestablishment of structural support, usually by repositioning of existing cartilage or, more commonly, through the use of cartilage or bone grafts.⁹ Even with grafts, the preservation of existing mucosa and the judicious use of antibiotics, stents, skin or mucosal grafts are all adjunctive treatments intended to minimize formation of granulation tissue, and subsequent deposition of collagen.

Timing of Repair

A chronic laryngotracheal stenosis repair is generally elective, once the appropriate workup is completed. The onset of symptoms may be insidious, depending on the extent of scar formation and contracture, and in intubated patients, several attempts at extubation usually fail, requiring tracheotomy.¹³ Such patients subsequently cannot be decannulated or, after a brief decannulation, experience gradually progressive upper airway symptoms. Irreversible stenosis is usually diagnosed at this time, and repair can be performed electively after thorough evaluation. A key consideration is that patients with inflammatory or autoimmune diseases require stabilization of their underlying disease processes before surgical management of the stenosis.

Endoscopic versus Open Repair

Beginning in the 1940s, the literature describes the use of endoscopic division of webs and subsequent keel placement. These early endoscopic techniques included scar removal via instruments or lasers followed by application of mitomycin-C. The evolution of powered instrumentation such as better microlaryngeal instrumentation and refinements in laryngoscopes have both enhanced visualization and maneuvering and have led to an increase in the numbers of laryngeal lesions removed via endoscopic techniques that previously required open approaches. Duration of inpatient hospital stay and morbidity of procedures have both declined with endoscopic techniques; however, the skill and comfort level of the surgeon with these newer tools cannot be overemphasized.

The last few decades have seen the growing popularity of the carbon dioxide (CO₂) laser, which offers the advantages of delayed formation and maturation of collagen in wounds, thus allowing reepithelialization before scar formation as well as minimal deep tissue injury. The laser has enabled precise control of the areas removed and hemostasis with the aim of preserving existing mucosa that may be utilized for the repair. Limitations of the CO₂ laser include the risk of an airway fire, and the danger of the laser plume for the surgeon and hospital staff if they are working with infectious lesions.¹⁰ In addition, it is often difficult to control thermal injury, which may result in perioperative edema and postoperative scarring of the vocal folds.¹¹ “Due to these risks,” some authors advocate initial endoscopic management of chronic laryngotracheal stenosis, reserving open repair for patients whose stenosis does not resolve with endoscopic management.¹² The advantage of this approach is that an open surgical repair may be avoided in some instances; however, several endoscopic procedures may be required for long-term success. Current recommendations include treatment of mild stenosis (Cotton-Myer grades I and II) with endoscopic techniques. Failure of initial endoscopic technique is associated with previous surgery, circumferential scarring, loss of cartilaginous support, exposure of cartilage leading to chondritis, posterior inlet scarring with subsequent arytenoid fixation, postoperative bacterial infection, and initial poor choice of candidates, such as patients with combined laryngeal and tracheal stenosis or vertical scar length greater than 1 to 1.5 cm. With prudent choice of candidates and careful postoperative care and monitoring, success of decannulation at 1 year after endoscopic surgery for stenosis has risen from 60% to 65% to 80% to 85%.

Postoperative management should include antibiotics for 1 to 3 weeks, antireflux management, and subsequent wound reassessment in 6 weeks via endoscopy. Patients with more severe stenosis may be better served with an initial open technique, although this does not guarantee higher success rates in such difficult cases.

Microsurgical Débridement

Much like the impact of advanced instrumentation for endoscopic techniques in laryngeal surgery, the success of powered instrumentation in many arthroscopic procedures has led to the popularity of microsurgical debriders in airway surgery. This technique combines the use of flexible forceps and a microsurgical debrider with videoendoscopic control.¹⁴ The debrider has a powered rotating blade and suction so that soft tissue lesions are aspirated into the tip of the blade and cleanly cut. Use of this instrumentation in endoscopic sinus surgery provided for more efficient and precise tissue removal and reduced injury to normal mucosa. Development of a laryngeal microsurgical shaver in the 1990s allowed for removal of bulky, exophytic laryngeal papilloma in patients with recurrent respiratory papillomatosis, obstructing carcinoma, and Reinke’s edema.¹⁵^–¹⁷ In comparison with the carbon dioxide laser, the laryngeal microsurgical debrider eliminates the risk of airway fire because there is no laser plume and therefore a lower infectious risk for the operating room staff. Anecdotal data show that use of this instrument in patients with recurrent respiratory papillomatosis, which was previously treated with the laser, have less postoperative pain and a quicker return to a usable speaking voice. A decrease in operative time has also been observed, thus reducing both the patient’s exposure to a general anesthetic and overall operating room costs.¹⁸

We use the microdebrider for many laryngeal lesions (Box 71-2) by maneuvering the rigid telescope with the laryngeal shaver, thus promoting camera steadiness and good visualization of the blade tip relative to the lesion as it is removed. Subglottic and tracheal stenotic lesions are typically removed with a surgical microdebrider (4-mm) subglottic blade to excise the fibrous scar. Softer, bulky lesions, such as laryngeal and tracheal papilloma, are rapidly removed with the 4.0-mm round window (skimmer) blade. Papillomas and other lesions involving the true vocal folds are removed with the 3.5-mm round window (skimmer) laryngeal blade (Figs. 71-3 and 71-4).

Figure 71-3. Powered instrumentation. Microdebrider blade (upper inset), for use in larynx, subglottis, and trachea, and skimmer blade (lower inset), for removal of mucosal lesions.

Figure 71-4. Endoscopic view of endolaryngeal lesion removal using the round blade of a microdebrider.

Local Application of Mitomycin C

Topical mitomycin C may be useful for the treatment and prevention of subsequent re-stenosis and scar formation in the larynx and trachea. Mitomycin C is an antineoplastic antibiotic that acts as an alkylating agent by inhibiting DNA and protein synthesis. It can inhibit cell division, protein synthesis, and fibroblast proliferation.¹⁹

The use of topical mitomycin C remains controversial, with one study demonstrating that after 15 months of mitomycin application, all patients had clinical improvement of symptoms without evidence of recurrence.¹⁹ Another study performed on the pediatric airway found no statistical difference between a single topical dose of mitomycin and isotonic sodium chloride after laryngotracheal reconstruction.²⁰ Animal studies have shown a statistically significant reduction in the rate of restenosis after surgical lysis with the use of mitomycin C.²¹

Surgical Planning for Repair

The first consideration for successful repair of acute or chronic laryngotracheal stenosis is the establishment of an intact, reasonably shaped skeletal framework to provide a scaffold for the airway. Acute, blunt injuries to the larynx, in which cartilage is fractured and displaced, are generally best managed with open reduction and stabilization of the fragments. In contrast, chronic injuries often are devoid of cartilage as a result of resorption of devitalized segments or of chondritis and subsequent chondromalacia or necrosis. The cartilage has often been replaced by scar tissue, so cartilage or bone grafts are necessary to reestablish structural support and to provide luminal augmentation. There is no consensus as to the ideal graft materials, and the grafts described in the literature use rib, iliac crest, hyoid bone, epiglottis, thyroid cartilage, composite auricular cartilage, and nasal septal cartilage.

Each of these graft materials may be limited by size, lack of pliability, and variable resorption due to lack of blood supply. The rib or costal cartilage graft is most commonly used because of its size, strength, and relative ease of harvesting. Vascularized hyoid and thyroid cartilage grafts have shown considerable success ^22,²³ but are limited by the amount of cartilage available. Composite auricular and nasal septal cartilage has the advantage of providing simultaneous epithelial repair, but it generally lacks adequate size and rigidity for cases in which large grafts are required. Vascularized perichondrial grafts and periosteal grafts have been evaluated for their chondrogenic or osteogenic capabilities and show potential for providing a pliable, vascularized graft that generates viable rigid bone or cartilage. In a rabbit model, vascularized perichondrium was shown to form significantly more cartilage when placed in a subglottic defect, and it tolerated a 2-hour ischemia time²⁴; it has also been successfully maneuvered into tube form for reconstruction of a segmental tracheal defect.²⁵ The sternocleidomastoid myoperiosteal flap has been successfully used for subglottic and tracheal reconstruction, with a low incidence of bony overgrowth on long-term follow-up.²⁶