Clinical experience with injectable collagen for vocal fold augmentation.

Injectable collagen appears to be safe and effective in treating glottic insufficiency. Fifty-four patients received vocal-fold injections of Zyderm Collagen Implant and their responses were followed for as long as 2 years. Videostroboscopy affords the best assessment of glottic function and correlates well with vocal quality. Maximum phonation time and transglottic airflow are the most sensitive measures of glottic efficiency; follow-up studies indicate that responses to treatment vary at 1 week, tend to stabilize by 3 months, and show only slight decrement over 1 year. One patient experienced a delayed hypersensitivity reaction, but it did not adversely affect his result. The use of cross-linked preparations of collagen should decrease the incidence of such responses. Treated patients were divided into diagnostic groups. Patients with bilaterally scarred vocal folds did not appear to respond optimally to collagen injection. Vocal rehabilitation was better if patients had at least one normal vocal fold. The best results occurred in patients with unilateral vocal fold paralysis and pre-existent bowing or atrophy did not affect these results. Collagen should be injected in the plane of the vocal ligament for best results; if the injection is too deep the implant is resorbed, and if too superficial, vocal-fold vibration is impaired.