The neocartilaginous formation with hydroxyl-apatite in injection laryngoplasty: an experimental study on rabbit model

Adductor paralysis or the pathologies occurring after laryngeal surgery such as scarring or atrophy of the vocal cords cause glottic insufficiency during phonation. Injection laryngoplasty has been a widely accepted technique due to lower morbidity of the procedure and the applicability via endoscope in the treatment of these pathologies. Various materials have been used in injection laryngoplasty. The primary expectations in these techniques are the persistence of injected material long enough, without resorbtion or any cause of serious tissue response and having beneficial effects in reinforcing the glottic tissue. In the present study, we used large molecular-sized calcium hydroxyl-apatite (CaHA) particles in injection laryngoplasty to observe the effects of the material in the laryngeal tissues under the light microscopic examination. The study was performed on 12 rabbits in four groups. After injecting Ca₁₀ (PO4)₆(OH)₂ (Coaptite^®) into their vocal folds, the rabbits were killed at certain intervals, in the 1st week (group 1) in the 1st month (group 2) in the 3rd month (group 3) and in the 6th month (group 4). Larynges were removed and processed for light microscopic observations. Our observations revealed that this material induced the new cartilage formation without a serious tissue response in the larynges. Formation of a new cartilage tissue was the most significant, but an unexpected outcome of the study. The injected material inducing a neocartilage formation without any tissue reaction persisted long enough in the laryngeal tissues. Although neocartilage formation may interfere the vocal fold vibrations, providing glottic closure in the phonation with a durable material will be an important gain.