Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent structure
Reexamination Certificate
2000-09-27
2002-02-05
Thaler, Michael H. (Department: 3731)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent structure
C623S001170, C623S901000, C029S896600
Reexamination Certificate
active
06344055
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an expandable stent and to a method for production of same.
BACKGROUND ART
Stents are generally known. Indeed, the term “stent” has been used interchangeably with terms such as “intraluminal vascular graft” and “expansible prosthesis”. As used throughout this specification the term “stent” is intended to have a broad meaning and encompasses any expandable prosthetic device for implantation in a body passageway (e.g. a lumen or artery).
In the past six to eight years, the use of stents has attracted an increasing amount of attention due the potential of these devices to be used, in certain cases, as an alternative to surgery. Generally, a stent is used to obtain and maintain the patency of the body passageway while maintaining the integrity of the passageway. As used in this specification, the term “body passageway” is intended to have a broad meaning and encompasses any duct (e.g. natural or iatrogenic) within the human body and can include a member selected from the group comprising: blood vessels, respiratory ducts, gastrointestinal ducts and the like.
Stent development has evolved to the point where the vast majority of currently available stents rely on controlled plastic deformation of the entire structure of the stent at the target body passageway so that only sufficient force to maintain the patency of the body passageway is applied during expansion of the stent.
Generally, in many of these systems, a stent, in association with a balloon, is delivered to the target area of the body passageway by a catheter system. Once the stent has been properly located (for example, for intravascular implantation the target area of the vessel can be filled with a contrast medium to facilitate visualization during fluoroscopy), the balloon is expanded thereby plastically deforming the entire structure of the stent so that the latter is urged in place against the body passageway. As indicated above, the amount of force applied is at least that necessary to expand the stent (i.e., the applied the force exceeds the minimum force above which the stent material will undergo plastic deformation) while maintaining the patency of the body passageway. At this point, the balloon is deflated and withdrawn within the catheter, and is subsequently removed. Ideally, the stent will remain in place and maintain the target area of the body passageway substantially free of blockage (or narrowing).
See, for example, any of the following patents:
U.S. Pat. No. 4,733,665 (Palmaz),
U.S. Pat. No. 4,739,762 (Palmaz),
U.S. Pat. No. 4,800,882 (Gianturco),
U.S. Pat. No. 4,907,336 (Gianturco),
U.S. Pat. No. 5,035,706 (Gianturco et al.),
U.S. Pat. No. 5,037,392 (Hillstead),
U.S. Pat. No. 5,041,126 (Gianturco),
U.S. Pat. No. 5,102,417 (Palmaz),
U.S. Pat. No. 5,147,385 (Beck et al.),
U.S. Pat. No. 5,282,824 (Gianturco),
U.S. Pat. No. 5,316,023 (Palmaz et al.),
Canadian patent 1,239,755 (Wallsten), and
Canadian patent 1,245,527 (Gianturco et al.),
the contents of each of which are hereby incorporated by reference, for a discussion on previous stent designs and deployment systems.
While prior stents which are reliant on plastic deformation of the entire stent structure for deployment have achieved a certain degree of success, they do suffer from some disadvantages. One particular disadvantage is that the stent structure is susceptible to the occurrence of “micro-cracks”—i.e., cracks of relatively small width and depth—especially in curved regions of the stent structure. Also, plastic deformation can lead to the occurrence of uneven thinning of the stent material. The occurrence of such cracks and/or uneven thinning can lead to weakened radial rigidity of the stent which, in turn, can lead to devastating consequences for the patient. Additionally, the many of the prior art stents are time consuming and expensive to produce.
Published International patent application WO 95/26695 [Lau et al. (Lau)] teaches a self-expandable, foldable stent which may be delivered using a catheter or other technique. The purported point of novelty in Lau relates to a stent which may be folded along its longitudinal axis. The folding is accomplished by conferring bending and twisting stresses to the stent, which stresses, for the material used to produce the stent, do not exceed that minimum stresses above which plastic deformation of the stent will occur—i.e., application of these stresses to the stent results in the storage of mechanical energy in the stent but does not result in the occurrence of any plastic deformation. The stent disclosed by Lau is disadvantageous since a relatively complicated folding protocol is needed. Specifically, in the illustrated embodiments, Lau teaches that the stent is folded into “a loose-C configuration” (FIGS. 33A and 33B), “a rolled configuration” (FIGS. 33C and 33D) or “a triple lobed configuration” (FIGS. 33E and 33F). The stent taught by Lau is also disadvantageous since, after it is folded (and thus contains the bending/twisting stresses described above), the stent must be restrained mechanically from spontaneous expansion—see, for example, FIGS. 35A, 35B, 36A, 36B, 39 and 40 of Lau which illustrate complicated tethering systems for mechanically restraining the folded stent from spontaneous expansion.
Published European patent application 0,669,114A [Fischell et al. (Fischell)] teaches a stent having a multiplicity of closed circular structures connected by a series of longitudinals. The stent is initially produced in a pre-deployment form comprising ovals connected by the longitudinals (see FIGS.
4
and
5
). The pre-deployment form of the stent is than placed on the end of a balloon stent delivery catheter and the ovals are folded about their minor axis by securing the ovals at each end of the structure and translating a pair of opposed longitudinals (see FIG.
6
). A disadvantage of this approach is that, during the folding step, plastic deformation of the stent structure unavoidable since folding is accomplished by securing selected portions of the stent while translating other portions of the stent. As discussed above, while this is disadvantageous during expansion of the stent, the disadvantages are heightened if the stent undergoes plastic deformation during adaption of the unexpanded stent to a delivery system prior to expansion. A further disadvantage of this approach is the need have distinct unfolded pre-deployment (i.e., post-production
o balloon), folded pre-deployment (i.e., on balloon) and post-deployment forms of the stent.
Accordingly, it would be desirable to have an improved stent which overcomes these disadvantages. It would be further desirable if the improved stent could be manufactured readily.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide a novel expandable stent which obviates or mitigates at least one of the above-mentioned disadvantages of the prior art.
It is another object of the present invention to provide a novel method for manufacturing an expandable stent.
Accordingly, in one of its aspects, the present invention provides an expandable stent comprising a proximal end and a distal end in communication with one another, a tubular wall disposed between the proximal end and the distal end, the tubular wall having a longitudinal axis and a porous surface defined by a plurality of interconnecting struts, a series of the struts connected to one another at an interconnection point, the struts being reversibly hingable at the interconnection point between a first, contracted position and a second, expanded position, the stent being unrestrained in and expandable from the first position to the second position upon the application of a radially outward force on the stent.
In another of its aspects, the present invention provides an expandable stent comprising a proximal end and a distal end in communication with one another, a tubular wall disposed between the proximal end and the distal end, the tubular wall having a longitudinal axis and a porous surface defined by a pluralit
Katten Muchin & Zavis
Novo RPS ULC
Thaler Michael H.
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