Medialization Thyroplasty

Historic Aspects

The predominant focus of phonosurgical procedures has been rehabilitation of the paralyzed larynx. With a few exceptions, primary repair by end-to-end anastomosis after injury to the recurrent laryngeal nerve has been universally unsuccessful. Failure of primary repair is ascribed to a random process of axonal regeneration at the site of injury that results in the simultaneous contraction of antagonistic muscle groups, otherwise known as synkinesis . Alternative methods of reinnervation using ansa hypoglossus nerve–muscle pedicle implants into the posterior cricoarytenoid muscle and phrenic nerve–recurrent laryngeal nerve anastomosis for bilateral vocal fold paralysis have been explored. Ansa hypoglossus nerve–nerve anastomosis and nerve-muscle implant techniques have also been applied to unilateral vocal fold paralysis. Despite significant efforts to establish appropriate reinnervation and function after injury to the recurrent laryngeal nerve, debate continues about the efficacy of these procedures. Reinnervation procedures applied to laryngeal rehabilitation are covered in greater detail in Chapter 64 .

Vocal Fold Medialization

The first report of a phonosurgical procedure appeared when Brunings introduced the concept of vocal fold medialization by injection of paraffin within the body of the paralyzed fold. This was followed by Payr's description of an external approach for medialization that used a posterior vertical incision through the thyroid lamina, whereby the anterior flap was collapsed inward, which resulted in limited medialization. Neither approach gained acceptance.

Almost four decades later, Meurman reported a series of patients with vocal cord paralysis in whom external medialization procedures were performed with use of a vertical parasagittal incision in the anterior thyroid cartilage and autologous rib cartilage grafts placed between the thyroid ala and the inner perichondrium. Meurman's procedure resulted in a high incidence of complications, probably as a result of perichondrial and mucosal perforations that occur with the anterior midline approach.

In the 1960s, Arnold reintroduced vocal fold injection but with use of an alloplastic material, polytetrafluoroethylene (PTFE). Over the ensuing years, experience with this material has demonstrated a rising frequency of problems related to granuloma formation. Subsequently, an absorbable material (absorbable gelatin sponge [Gelfoam]) was applied, which allowed temporary vocal fold medialization by injection. Autologous fat has also been used to attempt permanent medialization. However, the long-term effectiveness of autologous fat has been shown to be unpredictable, with an overall success rate of 62% at 12 months. Hydroxyapatite (Radiesse) has been shown to have similar response to fat injections relative to voice quality and duration of effect. Reports of the use of bovine collagen injections for medialization were initially promising; however, soft tissue response led to variable results with respect to phonatory function. At the beginning of this century, micronized alloderm regenerative tissue matrix (Cymetra) was applied for vocal fold injection, and early reports indicate improvements in soft tissue response, tissue compliance, and overall phonatory function. Like bovine collagen, Cymetra may last 3 to 9 months and can be used for temporary medialization in patients for whom recovery is likely to occur after recurrent laryngeal nerve injury.

Although numerous modifications of external approaches have been reported, Isshiki and associates were the first to introduce the concept of alloplastic implant material for medialization. Using an external approach with a Silastic implant, these investigators are credited with the ultimate success and popularity of type I medialization thyroplasty. We are proponents of prefabricated implants with sizing systems. Two systems, VoCoM hydroxyapatite implants (Gyrus ACMI, Southborough, MA) and Montgomery Silastic implants (Boston Medical Products Inc, Westborough, MA), are currently available. The Netterville implant system provides instrumentation for sizing and carving preformed implants. Gore-Tex strips (WL Gore, Flagstaff, AZ) are also used to maintain vocal fold medialization with and without arytenoid adduction.

Although type I medialization procedures result in dramatic improvement in glottal efficiency and sound production, a small group of patients continue to have difficulty during phonation as a result of a large posterior glottal chink or vocal folds at unequal levels. To address this specific problem, Isshiki and associates introduced the arytenoid adduction procedure for unilateral vocal cord paralysis. Placement of a suture around the muscular process of the arytenoid with traction in the direction of the lateral cricoarytenoid and thyroarytenoid muscles results in medial rotation of the arytenoid and downward displacement of the vocal process. The posterior gap is reduced, and the paralyzed vocal folds are placed at equal levels. Two recent studies have demonstrated significant closure of the posterior gap in patients undergoing medialization thyroplasty with arytenoid adduction when compared to medialization thyroplasty alone. Improvement in vocal handicap index (VHI-10) was observed in one of these studies and no difference was observed in the other. Arytenoid adduction and related procedures are covered in greater detail in Chapter 63 .

The advantages of an external approach to modify vocal fold tension and position without altering the structural components (mucosal fold and underlying muscle body) have expanded the role of laryngeal framework surgery. Isshiki and associates and Koufman have reported their experience with medialization and tensioning procedures for the management of vocal fold bowing and dysphonia as a result of sulcus vocalis and soft tissue deficits.