Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Having built-in reinforcement
Reexamination Certificate
1999-11-16
2003-08-26
Isabella, David J. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Having built-in reinforcement
C623S001160, C623S001350, C606S194000
Reexamination Certificate
active
06610087
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to endoluminal grafts or prostheses and, more specifically, to a prosthesis having regions of different stiffness.
BACKGROUND OF THE INVENTION
A stent is an elongated device used to support an intraluminal wall. In the case of stenosis, a stent provides an unobstructed conduit for blood in the area of the stenosis. Such a stent may also have a prosthetic graft layer of fabric or covering lining the inside or outside thereof, such a covered stent being commonly referred to in the art as an intraluminal prosthesis, an endoluminal or endovascular graft (EVG), or a stent-graft.
A prosthesis may be used, for example, to treat a vascular aneurysm by removing the pressure on a weakened part of an artery so as to reduce the risk of rupture. Typically, a prosthesis is implanted in a blood vessel at the site of a stenosis or aneurysm endoluminally, i.e. by so-called “minimally invasive techniques” in which the prosthesis, maintained in a radially compressed configuration by a sheath or catheter, is delivered by a deployment system or “introducer” to the site where it is required. The introducer may enter the body through the patient's skin, or by a “cut down” technique in which the entry blood vessel is exposed by minor surgical means. When the introducer has been advanced into the body lumen to the prosthesis deployment location, the introducer is manipulated to cause the prosthesis to be deployed from the surrounding sheath or catheter in which it is maintained (or alternatively the surrounding sheath or catheter is retracted from the prosthesis), whereupon the prosthesis expands to a predetermined diameter at the deployment location, and the introducer is withdrawn. Stent expansion may be effected by spring elasticity, balloon expansion, or by the self-expansion of a thermally or stress-induced return of a memory material to a pre-conditioned expanded configuration.
Various types of stent architectures are known in the art, including many that comprise multiple regions, each region having a different stiffness, radial strength, and/or kink resistance. For example, referring now to
FIG. 1
, one configuration of a bifurcated modular stent
10
adapted to treat abdominal aortic aneurysms (AAA) comprises two components: a bifurcated component
12
comprising a trunk section
14
with an attached or unibody fixed ipsilateral iliac leg (IIL)
16
and a socket
18
, and a second component
20
that comprises the adjoining contralateral iliac leg (CIL). When CIL
20
is connected into socket
18
as shown in
FIG. 1
, interface section
19
between the CIL and the socket is stiffer than interface section
15
between IlL
16
and trunk section
14
. The mismatched stiffness between interfaces
15
and
19
arises in part because interface
19
comprises an overlap between the structure of leg
20
and the structure of socket
18
, whereas interface
15
has no such overlapping structure.
The resulting different properties of interfaces
15
and
19
may predispose the stent to unwanted in vivo behavior such as local kinking, occlusion, or bending. Because the lumen itself into which stent
10
is placed may vary in stiffness and/or geometry, may require the stent to conform to tortuous anatomy, and/or may require the stent to accommodate bending or longitudinal or transverse deformations, it is desirable that the stent mimic the lumen and respond coherently to applied deformation or loading. Thus, it is desirable to provide a stent design that does not have local regions of mismatched stiffness such as interfaces
15
and
19
as shown in FIG.
1
.
The interfaces between adjacent stent regions of different stiffness may also cause kinking, occlusion, or bending at the interface due to the drastic change in properties from one region to another. Thus, it is also desirable to minimize problems caused by abrupt stiffness interfaces between adjacent stent regions.
SUMMARY OF THE INVENTION
One aspect of the invention comprises a modular elongated stent for holding open a body lumen and for assembly in situ, the stent comprising at least a first component and a second component, the stent having an assembled configuration comprising the first component and the second component assembled together. The stent comprises an overlap region of the first component adapted to receive a portion of the second component in the assembled configuration, the overlap region having a first set of manipulation properties in the assembled configuration. One or more flexible stent regions are attached to the overlap region. Each flexible region has a second set of manipulation properties that differs from the first set of manipulation properties. The second set of manipulation properties includes greater flexibility, greater kink resistance, and/or less radial strength than the first set of manipulation properties. A mimic region is attached to the flexible region, the mimic region having a third set of manipulation properties that is essentially equivalent to the first set of manipulation properties.
The different manipulation properties may be achieved by the flexible regions and mimic region having different metallurgical properties, such as a different annealing history, by each region having structural elements of differing cross-sectional areas, or by the mimic region having reinforcing material attached thereto. The reinforcing material may comprise an overlapping stent or one or more stiffening filaments.
The modular stent may be a bifurcated modular stent in which the first component comprises a bifurcated component comprising a trunk section, a bifurcated section attached to the trunk section and having a first branch comprising a socket and a second branch comprising a fixed leg interface, and a fixed leg section depending from the fixed leg interface. In such case, the second component comprises a modular leg component adapted for insertion into the socket, the overlap region comprises the socket, the assembled configuration comprises the modular leg component inserted in the socket, and the mimic region comprises the fixed leg interface. The flexible regions comprise the trunk section and the fixed leg section.
The mimic region may comprise a region of different stent architecture relative to the flexible region, such as different element heights, different numbers of elements in each hoop, different ratios of connected to unconnected elements, or a combination thereof.
The invention also comprises a method for providing an elongated stent to hold open a designated portion of a body lumen having one or more curved regions. The method comprises first designing and fabricating the stent comprising one or more relatively stiff regions and one or more relatively flexible regions positioned to align with one of the curved regions of the body lumen when the stent is deployed within the body lumen. The relatively flexible regions have a stiffness less than the stiffness of the relatively stiff regions. Next, the stent is compressed, loaded within an introducer, and introduced into the body lumen. Finally, the stent is deployed from the introducer into the body lumen with each of the relatively flexible regions positioned in alignment with one of the curved regions of the body lumen.
Any of the stents of this invention may comprise at least one transition region between the stiff region and the flexible region having an intermediate set of manipulation properties, such as a gradient of manipulation properties, between the first set of manipulation properties and the second set of manipulation properties. The invention also comprises such a transition region between two regions having different manipulation properties wherein the transition region comprises a bridging material attached to the stent. The bridging material may comprise one or more filaments attached to the stent, such as wires welded to the stent.
The invention also comprises an elongated stent for holding open a body lumen, the stent comprising at least a first longitudinal region having firs
Hijlkema Lukas J.
Moskowitz Ari
Quigley Fergus P.
Zarbatany David J.
Chattopadhyay Urmi
Isabella David J.
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