A fundamental study of injectable collagen in vocal rehabilitation

Abstract

Vocal fold augmentation therapy has been accepted as a choice of treatment for glottic insufficiency due to unilateral recurrent nerve paralysis, vocal fold atrophy and sulcus vocalis. Various injectable materials have so far been investigated and clinically utilized. Although silicone and teflon are materials most widely used currently, our clinical experiences have indicated that they are not totally dependable because of such problems as tissue rection and instability of the volume.Recently, atelocollagen extracted from young calf skin has been reported to be an excellent injectable material and its application to phonosurgery has been described by Ford without investigating its long-termed safety and histocompatibility, and its effect on the vocal fold vibrations after the injection.This lack of investigation on the injection therapy of atelocollagen has prompted the animal experiments to study histological attitude of collagen in the vocal fold and the vocal fold vibration after the injection. The collagen at a concentration of 35, 20 and 10mg/ml were injected into canine vocal folds. The follow up period ranged from 3 days to 9 months after the injection. It was revealed that the most suitable concentration of the collagen for maintenance of the contour of the vocal fold was 35mg/ml, although the volume of the vocal fold tended to decrease very slightly during three days after the injection. Histological studies confirmed no inflammatory reaction in the surrounding tissue after the injection and no migration of collagen during the following-up period. Vibrations of the injected vocal folds during phonation were photographed with an ultra-high speed motion camera and frame-by-frame analyses were done. Mucosal wave-like movements were satisfactority preserved even when the collagen stayed in the submucosal superficial layer of the vocal fold. The result indicates that atelocollagen can be injected into any layers of the vocal fold without specific technical care. Owing to this advantage, use of the atelocollagen will expand indication of augmentation therapy.