Study objectives: To assess the usefulness of an animal
model for testing new tracheobronchial stents.
Setting: Animal laboratory of a university hospital.
Animals and interventions: In a series with 12 mini-pigs,
we induced a stable fibromalacic tracheal stenosis that was 50% to
70% of the normal tracheal diameter. After dilation we inserted a
16 × 40-mm self-expandable silicone stent into the stenotic part of
the trachea in 10 of the mini-pigs. Five of the stents had a
smooth outer surface, and five had additional silicone retaining
spikes. Because of a long stenosis in two of the mini-pigs, two
overlapping stents (one smooth and one with spikes) were inserted.
Measurements and results: Stent deployment was successful
and resulted in the disappearance of the slight to moderate stridor in
all of the mini-pigs. Over a mean (± SD) observation period of 24 days
(range, 10 to 41 days), all of the mini-pigs redeveloped stridor. Three
of them died unexpectedly of suffocation: in all three a smooth stent
had migrated, leading to total obstruction of the stenosis. In total,
five of the six smooth stents migrated, and only one of the six spiked
stents migrated. There was considerable granulation tissue formation at
the ends of all of the stents. In the two control mini-pigs, a
12 × 35-mm Dumon stent was inserted. Both Dumon stents migrated, and
one of them had considerable granuloma formation at its ends. At the
end of the observation period, all stents were removed endoscopically
and were found not to have deteriorated over time.
Conclusions: Our model proved to be suitable for the
evaluation of the technical aspects of the Polyflex stent. Spikes on
the outer stent surface are more effective in preventing migration than
smooth-surface stents. Long-term compatibility, however, seems to be
difficult to test with our model because both the Polyflex and the
Dumon stents had excessive granulation tissue formation at both ends, a
factor which—in the case of the Dumon stent—does not occur to such a
degree in benign human airway stenoses. Our results indicate a need for
prospective long-term studies in benign human airway