Stent configurations

Improved stent configurations exhibiting limited recoil, resistance to compression and improved longitudinal flexibility.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to stents of improved configuration. 
2. Brief Description of the Prior Art 
Stents are radially expandable endoprosthesis which are typically 
intravascular implants capable of being implanted transluminally and 
enlarged radially after being introduced percutaneously. They have also 
been implanted in urinary tracts and bile ducts. They are used to 
reinforce body vessels and to prevent restenosis following angioplasty in 
the vascular system. They may be self-expanding or expanded by an internal 
radial force, such as when mounted on a balloon. 
In the past, stents have been generally tubular but have been composed of 
many configurations and have been made of many materials, including metals 
and plastic. Ordinary metals such as stainless steel have been used as 
have shape memory metals such as Nitinol and the like. Stents have also 
been made of biodegradable plastic materials. Such stents have been formed 
from wire, tube stock, etc. 
SUMMARY OF THE INVENTION 
This invention provides new configurations of the cells making up stents 
which may be adapted to all of the various types of prior art stents 
described above and/or known previously in the art. There are numerous 
advantages to the new configurations. The configurations of the invention 
limit recoil and add resistance to compression for an expanded stent, 
among other things. Other configurations than cylindrical are 
contemplated, e.g., square, triangular octagonal, etc. The stents of this 
invention are longitudinally flexible and expandable.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A preferred embodiment of a generally cylindrical stent 10 according to the 
invention is illustrated in FIGS. 1-4. It comprises a metal tube as shown 
in FIGS. 2 and 4, such as nitinol or stainless steel preferably, which has 
been etched or preferably laser cut to the configuration shown in the flat 
plan view of FIG. 1. An enlarged detail of FIG. 1 is shown in FIG. 3. The 
configuration is made up of a series of curvilinear expansion cell 
elements generally indicated at 12 (see darkened example in FIG. 3 for 
clarity) having relatively wide end portions 14 joined by relatively 
narrow center portions 16. Cells 12 are arranged longitudinally as shown 
in FIG. 1 end to end with respect to the longitudinal axis of the stent 10 
and in substantially parallel rows as also shown in FIG. 1. A plurality of 
longitudinally extending elongate support members 18 are included, one 
each being disposed between adjacent rows of cells 12. Also, a plurality 
of circumferentially extending support members 19, preferably 
substantially normal to support members 18 are also positioned between the 
rows of cells 12 to intersect portions of the support members 18 and to 
interconnect them to the narrow center portions 16 of cells 12. As can be 
seen in FIG. 1a, cells 12 may also be arranged in a staggered arrangement. 
FIGS. 1b and 1c demonstrate different arrangements and interconnections 
for cells 12. 
When the stent is expanded, as shown in FIG. 4, on a balloon 20 the cells 
12 take on a new configuration as shown, the members making up the stent 
being indicated by the same numbers as used in FIG. 1 and FIG. 3. Again, 
one cell is shown darkened for clarity. 
Referring now to FIGS. 5-7, another stent embodiment generally indicated at 
22 of the invention is shown. In this embodiment, as seen in FIGS. 5 and 
6, expansion cells 24, best seen in the detail of FIG. 6 and indicated by 
darkened portion, have relatively wide end portions 26, best seen in FIG. 
6, and narrow center portions 28 and are arranged end to end in 
longitudinal rows as described with respect to the first embodiment. 
Adjacent end portions 26 are interconnected by pairs of longitudinal 
support members in the form of segments 30 which have curved end portions 
32. Circumferential extending segments 34 extend between rows of cells 24 
to interconnect the narrow center portions 28. 
Upon radial expansion of the stent, as on a balloon 20 for example, its 
configuration changes by deformation force in the directions shown by the 
arrows in FIG. 6 to that configuration shown in FIG. 7. The elements 
indicated in FIG. 7 are identified by the same numbers indicated for 
similar elements in FIGS. 5 and 6. 
FIGS. 20 and 21 show a configuration somewhat similar to that of FIGS. 5-7 
but without interconnecting elements 28. 
Referring now to FIGS. 8-10, another stent embodiment of the invention is 
shown and generally indicated at 40. Again, as seen in FIGS. 8 and 9, 
expansion cells 42 (example darkened for clarity) have relatively wide end 
portions 44 and narrow center portions 46. The end portions include 
inwardly extending loop portions 48. Cells 42 are arranged end to end in 
longitudinal rows as in the preceding embodiments. Adjacent end portions 
44 are interconnected by pairs of longitudinal support member segments 50 
which have curved end portions 52. Circumferentially extending segments 54 
extend between rows of cells 42 to interconnect the narrow center portions 
46 of the cells. FIG. 8a shows a variation in shape for cells 42. 
Upon radial expansion of the stent upon a balloon 20, the configuration 
changes to that shown in FIG. 10. The arrows show the direction of force 
of deformation upon expansion. 
Referring now to FIGS. 11 and 12, still another embodiment of a stent 60 is 
shown. Again, as shown in FIGS. 11 and 12, expansion cells 62 (example 
darkened for clarity) have relatively wide end portions 64 having a slight 
inward bend 65 to them and narrow center portions 66. Cells 62 are 
arranged end to end in longitudinal rows as in the preceding embodiments. 
Adjacent end portions 64 are interconnected by pairs of longitudinal 
support member segments 68 which have curved end portions 70. 
Circumferentially extending segments 72 extend between rows of cells 62 to 
interconnect the narrow center portions 66 of the cells. 
Reference to FIG. 13 will show the inherent flexibility of the stents of 
this invention. 
Upon radial expansion of the stent upon a balloon 20, the configuration 
changes to that shown in FIG. 14. 
Referring now to FIGS. 15 and 16, yet another embodiment of a stent 80 is 
shown in a configuration quite similar to that of FIGS. 11-14 but with an 
added circumferentially extending structural element 81. Again, as best 
seen in FIG. 16, expansion cells 82 (examples darkened for clarity) have 
relatively wide end portions 84 having a slight inward bend 85 to them and 
narrow center portions 86. Cells 82 are arranged end to end in 
longitudinal rows as in the preceding embodiments. Adjacent end portions 
84 are interconnected by pairs of longitudinal support member segments 88 
which have curved end portions 90. Circumferentially extending segments 92 
extend between rows of cells 82 to interconnect the narrow center portions 
86 of the cells. Circumferentially extending segments 81 interconnect 
pairs of support member segments 88. 
Upon radial expansion of the stent on a balloon 20, the configuration 
changes to that shown in FIG. 17. 
Referring now to FIGS. 18 and 19, still another embodiment of a stent 
configuration 100 is shown. As before this embodiment is similar to that 
of FIGS. 11-12 except that the circumferentially extending segments 101 
are arranged differently than those identified in FIGS. 11-12 as 72. In 
this embodiment the circumferentially extending members 101 extend between 
the adjacent ends of adjacent cells 103 (examples darkened for clarity) to 
interconnect the top of one end to the bottom of the adjacent end and the 
members 101 have a slight curve or bend 105 in their length. The other 
members are all similarly numbered as in the preceding Figures. 
FIG. 22 shows yet another embodiment of a stent comprised of cells 120 
having interconnecting circumferential extending members 122. The cells 
have common sides or end members 124 and are arranged in groups to form 
bands 126 which are interconnected by joined cells 128. 
While this invention may be embodied in many different forms, there are 
described in detail herein specific preferred embodiments of the 
invention. This description is an exemplification of the principles of the 
invention and is not intended to limit the invention to the particular 
embodiments illustrated. 
The above Examples and disclosure are intended to be illustrative and not 
exhaustive. These examples and description will suggest many variations 
and alternatives to one of ordinary skill in this art. All these 
alternatives and variations are intended to be included within the scope 
of the attached claims. Those familiar with the art may recognize other 
equivalents to the specific embodiments described herein which equivalents 
are also intended to be encompassed by the claims attached hereto.