Histologic findings of silastic medialization in the canine model.

OBJECTIVES

Examine the long-term histological effects of Silastic medialization using a canine model.

STUDY

DESIGN

Prospective study evaluating the effects of Silastic medialization in six canine larynges.

METHODS

Two subject groups were evaluated. The first group of four dogs underwent recurrent laryngeal section followed by Silastic medialization on the paralyzed side and placement of a smaller implant on the mobile side. Two of the dogs were sacrificed at 9 months and two at 2 years. The second subject group consisted of two additional dogs who underwent Silastic medialization followed by removal of the implants at 7 months and were sacrificed 18 months later. The larynges were then processed, sectioned in the axial plane, and examined microscopically.

RESULTS

Histological findings of both the mobile and paralyzed sides showed a thin (< 0.5 mm) fibrous capsule surrounding the implant and minimal inflammatory response. Vocal fold mobility was maintained in all cases in which the recurrent laryngeal nerve was left intact. Capsule formation and inflammatory response were similar in all cases.

CONCLUSIONS

Minimal tissue reactivity over a prolonged period of time suggests that long-term results of Silastic medialization remain stable in paralyzed and mobile vocal folds for up to 2 years. Similar tissue response in the subjects in which the Silastic block was removed also suggests that Silastic medialization is a reversible procedure.