Histology of injected autologous fascia in the paralyzed canine vocal fold.

ABSTRACT

OBJECTIVE: To evaluate the histology of minced and injected autologous fascia graft in the augmentation of unilateral vocal fold paralysis. STUDY DESIGN: Prospective study using a canine model. METHODS: Nine dogs were operated. At first, a piece of fascia was harvested from fascia lata and minced into tiny chips with a scalpel. Cutting off a section of the recurrent nerve paralyzed the right vocal fold. The minced fascia-paste (0.1 mL) was injected using a pressure syringe into the paralyzed thyroarytenoid muscle under direct laryngoscopy. Two animals were killed at 3 days, one at 10 days, three at 6 months, and three at 12 months postinjection. Each dog underwent laryngectomy and serial coronal sections of paraffin blocks from the posterior part of the vocal folds were made. RESULTS: The dogs experienced no complications perioperatively or during follow-up. Under microscopy, muscle of the paralyzed vocal fold was atrophied in comparison to the contralateral control. There was an acute inflammatory reaction induced by the graft. This did not exist in the specimens taken at 6 and 12 months. No extensive edema, areas of necrosis, or formation of granulomas was seen at any time. Maturation of the graft was characterized by active collagen remodeling up to 12 months. At that time the graft consisted of firm, condensed fibrous tissue. Scar formation around the graft was moderate, and the subepithelial layer of the vocal fold remained undisturbed. Each graft consisted of singular foreign bodies from the polyamide mincing plate. We cannot exclude that their presence would have had an impact on the final architecture of the graft. CONCLUSION: In a canine vocal fold, the free fascia graft is well tolerated and after 12 months a well-organized, collagen rich tissue is seen on histological sections. The findings are in accordance with clinical studies applying free fascia grafts.