Utility and Safety of Commercially Available Injection Laryngoplasty Materials in a Rabbit Model

Abstract

Objective. To demonstrate foreign body and chronic inflammatory reaction of commercially available injection materials using the rabbit vocal fold paralysis model. Study Design. Animal study. Methods. The left recurrent laryngeal nerve was identified and divided at the tracheoesophageal groove. Amounts (100 mu L) of phosphate-buffered saline (PBS), polyacrylamide hydrogel (Aquamid; Ferrosan A/S, Soborg, Denmark), calcium hydroxyapatite (Radiesse; BioForm Medical Inc., San Mateo, CA), or hyaluronic acid derivative (Rofilan; Rofil Medical International, Breda, Netherlands) were injected into the left vocalis muscle. Six months later, the larynx was harvested. Hematoxylin/eosin and Masson trichrome staining were performed to compare inflammatory and foreign body reactions, granuloma development, and relative vocal fold areas among groups. Results. Compared with the PBS (control) group, the Aquamid, Radiesse, and Rofilan groups exhibited only mild chronic inflammatory reactions that did not significantly differ among groups, or from controls (P > 0.05). However, the Aquamid and Radiesse groups exhibited moderate foreign body reactions that were significantly greater than those of controls (P < 0.05). No foreign body granuloma formed in any group. All test groups exhibited significant increases in vocal fold areas at 6 months (P < 0.05). Conclusions. Although commercially available injection materials induced more foreign body reactions than a control injection of PBS, no foreign body granuloma developed and the augmented vocal fold area was maintained until 6 months after injection.