Objectives: Examine the long-term histological effects of Silastic medializ
ation using a canine model. Study Design: Prospective study evaluating the
effects of Silastic medialization in six canine larynges, Methods: Two subj
ect 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 wer
e sacrificed at 9 months and two at 2 years. The second subject group consi
sted of two additional dogs who underwent Silastic medialization followed b
y removal of the implants at 7 months and were sacrificed 18 months later.
The larynges were then processed, sectioned in the axial plane, and examine
d microscopically. Results: Histological findings of both the mobile and pa
ralyzed sides showed a thin (<0.5 mm) fibrous capsule surrounding the impla
nt 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 lo
ng-term results of Silastic medialization remain stable in paralyzed and mo
bile vocal folds for up to 2 years. Similar tissue response in the subjects
in which the Silastic block was removed also suggests that Silastic medial
ization is a reversible procedure.