Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent structure
Reexamination Certificate
1999-05-25
2001-02-20
Millin, V. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent structure
Reexamination Certificate
active
06190405
ABSTRACT:
The invention relates to an expandable insert having the features of the preamble of claim
1
.
Such inserts, also called stents, are known from U.S. Pat. No. 5,102,417 and from U.S. Pat. No. 5,195,984.
The known inserts have three tubular sections or segments which are made of an implantable material. The three tubular segments are each connected to one another via bridge members which are intended to allow the segments to tilt or cross in relation to each other.
The individual segments are formed by cutting out rectangular blanks from the jacket of the tubular segments. Blanks adjacent to each other in the circumferential direction are offset in relation to one another. The rectangular blanks have axially parallel long sides and narrow sides running in the circumferential direction. The narrow sides at the ends are not interconnected, so that due to free spaces the end face of the tubular segment has a crenelated appearance. In the known inserts, the interconnected segments are oriented coaxial to one another in the state when the insert is not in use, and they are connected by bridges between the narrow sides at the ends. In U.S. Pat. No. 5,102,417, straight, parallel bridge members run obliquely from one end face of a segment in the direction toward the narrow side adjacent to the opposite narrow side in the circumferential direction. Each narrow side of a segment is connected to a narrow side of the adjacent section, so that the obliquely extending bridge members give the insert a twisted appearance.
U.S. Pat. No. 5,195,984 discloses an insert in which adjacent segments are in each case connected via a straight, axially parallel bridge between two exactly opposite narrow sides. Between each segment there is only one bridge member, so that the space between the segments remains essentially free.
In practice, these inserts, with small material thicknesses, are not sufficiently stiff with respect to compression in the radial direction.
The object of the invention is therefore to provide an expandable insert for use as a vessel support in blood vessels, in which, together with sufficient flexibility for adaptation to the curvatures of the vessels, there is a particularly high level of resistance (recoil) to forces exerted radially from the outside.
This object is achieved by means of an expandable insert having the features of claim
1
.
Because a first group of rings is provided whose strand length essentially corresponds to the circumference of the insert in the expanded state and a second group of rings is provided whose strand length is greater than the circumference of the insert in the expanded state, the rings of shorter strand length can efficiently take up compression forces, while the rings of greater strand length cover relatively uniformly the interspaces which arise between the rings of the first group. The rings of the second group additionally permit a flexibility of the insert under bending stresses within the necessary range.
It is advantageous if the strand length of the second group is 1.2 to 2.0 times as great as the strand length of the first group, in particular 1.3 to 1.5 times as great, because under these conditions a good relationship is obtained between expandability and shortening of length during expansion. Increased flexibility in relation to bending stresses is obtained if the strand length of the second group is 1.7 to 1.9 times as great as the strand length of the first group.
An arrangement with good coverage of the interspaces which arise is obtained if the meandering strands of the second group have length sections which in the nonexpanded state run parallel to the center axis of the main body. In addition, with regard to stability, it is advantageous if the meandering strands of the first group have circumferential sections which in the nonexpanded state run in the circumferential direction of the main body.
A particularly advantageous construction is obtained if the strands of the first group and the strands of the second group each intersect in the area of the length sections, in particular if the circumferential sections of the first group are connected centrally to the length sections of the second group.
A very uniform pattern of opening of the insert in the expanded state is obtained if the number of the periodically recurring meanderings of a strand of the first group is twice as great as the number of meanderings of a strand of the second group, for example if the meanderings of the first group have three or four periodic segments and the meanderings of the second group correspondingly have six or eight periodic segments.
REFERENCES:
patent: 5507771 (1996-04-01), Gianturco
patent: 5868781 (1999-02-01), Killion
patent: 5964798 (1999-10-01), Imran
patent: 6019789 (2000-02-01), Dinh et al.
patent: 6077296 (2000-06-01), Shokoohi et al.
Culombo Antonio
Heise Norbert
GFE Corporation for Research and Development Unlimited
Millin V.
Stewart Alvin
Woodbridge Richard C.
Woodbridge & Associates P.C.
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