[Experimental studies on the therapy of epiglottis hypoplasia in horses--transendoscopic injection of collagen and polytetrafluoroethylene].

Epiglottic augmentation by transendoscopic injection of an implant material was performed on ten clinically healthy horses. In six cases bovine collagen (Zyplast) was used, in the remaining four horses the injection was done with polytetrafluorethylene (PTFE-Paste). The results of the surgery were observed endoscopically and by contrast radiography. Using the radiographs, epiglottic length and thickness were measured. For necropsy and histologic assessment the horses, three and two animals of the two groups, were euthanized at three and 12 weeks after surgery. The data obtained from the measurements at necropsy were correlated with those from the radiographs. The minimal invasive technique was very easy to perform with the bovine collagen while PTFE was less suitable for the transendoscopic injection. The data concerning the epiglottic length as well as its thickness measured on the radiographs correlated well to those obtained from the measurements at necropsy. After injection of collagen as well as PTFE an organisation of the implant was noticed histologically, which increased in accordance with the increasing time after injection. As far as the collagen implant is concerned, there was fibrous granulation tissue accompanied by an inflammatory reaction consisting mainly of lymphocytes and histiocytes. In contrast the injection of PTFE led to the development of a foreign body granuloma. In addition, some cases showed ulcers. Both implant materials led to an increase in epiglottic thickness, so that one can expect an improvement in its stability which could be of benefit to the therapy of epiglottic hypoplasia. But this increase in thickness had its maximum level directly after injection and declined over the period observed. Still, especially in the case of the collagen used here, the development of a fibrous granulation tissue and the immigration of fibroblasts and fibrocytes into the implant indicates that there is a stabilisation to some extent. Bovine collagen was proven to be highly suitable for transendoscopic injection. Although there is report about good clinical results using PTFE via laryngotomy, this material seems to be unsuitable for the transendoscopic technique due to the circumstances that lead to a higher number of complications.