Evaluation of a Bioabsorbable Self-Expandable Vein Stent-Base Made of Poly(L-lactide) In Vitro and In Vivo.
OBJECTIVE
This study was designed to evaluate performance and tissue response to a self-expandable bioabsorbable vein stent-base cut from a tube with enhanced stiffness and strength in vitro and in vivo.


METHODS
A diamond-shaped stent-base was cut from a sequential biaxially strained poly(L-lactide) (PLLA) tube for optimized performance. The performance of the stent-base was evaluated in a finite element analysis model, and validation was attempted in vitro through a cyclic flat-plate compression and radial force measurement. The performance of the stent-base was tested in vivo using 3 sheep with 2 implants each for 2 and 3½ weeks, respectively.


RESULTS
In vitro the stent-base showed an elliptical deformation but no fractures. In vivo the stent-base showed adequate radial force and no migration. All implanted stent-bases showed multiple fractures not only at the predicted stress zones but at all connecting points. Fragments of the caudal stent-base stayed in the vein wall indicating sufficient tissue coverage to avoid embolization of the fractured stent pieces, whereas fragments from the cranial device remaining were few. Neointima formation was confirmed histologically at 2 and 3½ weeks.


CONCLUSIONS
A bioabsorbable self-expandable stent-base made from PLLA for large veins seems feasible, but over time, the PLLA used in this study appears too stiff and lacks the sufficient flexibility to move with the vena cava, causing multiple fractures.
Department of Micro- and Nanotechnology, Technical University of Denmark, Ørsteds Plads, 345E, 2800, Kongens Lyngby, Denmark. alvlo@nanotech.dtu.dk.
Alexandra Liv Vest
AL
Løvdal
Weldon School of Biomedical Engineering, Purdue University, 206 S. Martin Jischke Drive, West Lafayette, IN, 47907-2032, USA.
Sarah
S
Calve
Cook Research Incorporated, 1 Geddes Way, West Lafayette, IN, 47906, USA.
Shuo
S
Yang
Cook Research Incorporated, 1 Geddes Way, West Lafayette, IN, 47906, USA.
William
W
Van Alstine
Kantonsspital Winterthur, Institut für Radiologie, Brauerstrasse 15, Winterthur, 8401, Switzerland.
Christoph A
CA
Binkert
William Cook Europe, Sandet 6, 4632, Bjæverskov, Denmark.
Kasper
K
Klausen
D020341:Absorbable Implants; D000818:Animals; D004867:Equipment Design; D020342:Finite Element Analysis; D066298:In Vitro Techniques / Q000379:methods; D023421:Models, Animal; D011091:Polyesters; D015203:Reproducibility of Results; D012756:Sheep; D015607:Stents
D011091:Polyesters; C033616:poly(lactide)
Bioabsorbable; PLLA; Poly-(L-lactide); Self-expandable; Vein stent