Stent struts and articulations: their impact on balloon-expandable stents' hoop strength, pushability, and radiopacity in an experimental setting.
OBJECTIVE
To evaluate the hoop strength, the pushability, and the radiopacity of endovascular stents depending on their design.


METHODS
The Palmaz Medium (rectangular stent struts, no articulation = RE-NA), the Palmaz-Schatz Long-Medium (rectangular stent struts, central articulations = RE-CA), and the 39 mm and 29 mm version of the Palmaz Corinthian Stent (arch-like stent struts, omega hinges = AR-OH 1 and AR-OH 2) were included in the study. Hoop strength, pushability, and radiopacity were assessed in-vitro. A radiopacity score (RS)-ranging from 0 = invisible, 1 = poor, 2 = average, 3 = good, and 4 = very good-was used.


RESULTS
Mass adjusted hoop strength was nearly the same for the AR-OH 1 and the AR-OH 2 (AR-OH 1: 159.2 N/g*cm; AR-OH 2: 156.5 N/g*cm). Their hoop strengths per unit mass significantly exceeded that of a RE-NA (125 N/g*cm) and that of a RE-CA (75.3 N/g*cm). The most pushable stent was the AR-OH 2 (0.54 1/N) followed by the AR-OH 1 (0.47 1/N) and the RE-CA (0.169 1/N). Because of multiple stent dislocations, the RE-NA was considered nonflexible. At spotfilm mode the RE-NA was the most visible stent (RS 3.5) followed by the AR-OH 1 (RS 3.25), the RE-CA (RS 3.12), and the AR-OH 2 (RS 1.9). At continuous fluoroscopy the AR-OH 1 (RS 1.8) was better than the RE-CA (RS 1.125), the RE-NA (RS 1.0), and the AR-OH 2 (RS 0.6). At 7.5 pulses per second the RE-NA (RS 1.3) performed slightly better than the AR-OH 1 (RS 1.25), and clearly better than the RE-CA (RS 0.8), and the AR-OH 2 (RS 0.3).


CONCLUSIONS
Overall, the ideal stent-having high hoop strength, a low profile, a good pushability, and a good radiopacity-still does not exist. However, by changing strut design (from rectangular to arch-like struts) and by inserting articulations, hoop strength and pushability can be improved without reducing radiopacity.
Wiskirchen
Jakub
J
Department of Diagnostic Radiology, University Hospital Tübingen, Germany. jakub.wiskirchen@uni-tuebingen.de
Pusich
Benjamin
B
Kramer
Ulrich
U
König
Claudius
C
Trübenbach
Jochen
J
Tepe
Gunnar
G
Claussen
Claus D
CD
Duda
Stephan D
SD
D000800:Angioplasty, Balloon / Q000295:instrumentation / Q000379:methods*; D004867:Equipment Design; D005471:Fluoroscopy; D015607:Stents