Patent Publication Number: US-2010131047-A1

Title: Stent Cell Configurations

Description:
This application is a continuation of U.S. application Ser. No. 10/131,772 filed Apr. 23, 2002, which is a continuation of U.S. application Ser. No. 09/261,687 filed May 7, 1999 and which issued as U.S. Pat. No. 6,231,599, which is a continuation-in-part of U.S. application Ser. No. 09/036,665 filed Mar. 4, 1998, the contents of all of which are incorporated herein in its entirety by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to stents of improved cell configuration. 
     2. Brief Description of the Prior Art 
     Stents are radially expandable endoprostheses 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 cell 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, and the like. 
     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. In general, as will be seen from the embodiments described hereinafter, the improved cell configurations are generally trichotomous, i.e., divided into three parts. More particularly, the cells are of a triskelion-like or trifurcate configuration, i.e., composed of three parts with axes of each part radiating from a common center. There are numerous advantages to the new configurations. For example, the configurations of the invention limit recoil and add resistance to compression for an expanded stent and provides increased side branch access, among other things. Also, the stents of this invention are longitudinally flexible. 
     The invention is also directed to a stent of generally cylindrical shape composed of at least one multibonate cell structure and desirably of a plurality of interconnected multibonate cell structures, as defined below. The multibonate structures may be interlocking and may be regularly arranged. 
     The invention contemplates stents having only one type of multibonate cell structure present as well as stents having a plurality of different multibonate cell structures present. Stents comprised of a plurality of multibonate cell structures of different order are also contemplated. 
     The invention is also directed to a stent comprised of a plurality of interlocking cell structures selected from the group consisting of bonate cell structures oriented at an oblique angle relative to the longitudinal axis of the stent, multibonate cell structures and combinations thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a flat plan view of an embodiment of a stent configuration of the invention in the unexpanded condition in which the cells share common elements; 
         FIG. 2  is an end view of a tubular stent of  FIG. 1  according to the invention in its normal unexpanded condition; 
         FIG. 3  is a detail view of a portion of  FIG. 1 , as indicated; 
         FIG. 4  is a view of the stent of  FIGS. 1 and 2  showing the expanded condition; 
         FIG. 5  is another embodiment of the invention, similar in view to that of  FIG. 1 , showing the flat plan of the stent in the unexpanded condition; 
         FIG. 6  is a detail view of a portion of  FIG. 5 , as indicated; 
         FIG. 7  is a flat plan view of another cell configuration according to the invention; 
         FIG. 8  is a schematic showing of yet another cell configuration; 
         FIG. 9  is a flat plan view showing a form of interconnection between cells; 
         FIG. 10  is a flat plan view showing another form of interconnection between cells; 
         FIG. 11  is a flat plan view showing yet another embodiment of the invention; 
         FIG. 12  is a flat plan view showing a bonate cell structure; 
         FIG. 13  is a flat plan view showing a multibonate (tribonate) cell structure; 
         FIG. 14   a  is a flat plan view showing yet another tribonate embodiment of the invention; 
         FIG. 14   b  is a flat plan view showing the rotational axis of symmetry of the multibonate cells of  FIG. 14   a;    
         FIG. 14   c  is a flat plan view showing the planes of reflectional symmetry of the multibonate cells of  FIG. 14   a;    
         FIG. 15   a  is a flat plan view showing yet another tribonate embodiment of the invention; 
         FIG. 15   b  is a flat plan view showing the plane of reflectional symmetry of the multibonate cells of  FIG. 15   b;    
         FIG. 16   a  is a flat plan view showing yet another tribonate embodiment of the invention; 
         FIG. 16   b  is a side elevational view of the stent of  FIG. 16   a;    
         FIG. 16   c  is a three dimensional isometric view of the stent of  FIG. 16   a;    
         FIG. 16   d  is a magnified view of an end portion of the stent as shown in  FIG. 16   d;    
         FIG. 16   e  is a three dimensional isometric view of a stent similar to that of  FIG. 16   c , but shorter; 
         FIG. 17  is a flat plan view showing yet another embodiment of the invention which includes tribonate and bonate structures; 
         FIG. 18  is a flat plan view showing yet another embodiment of the invention which includes tribonate and bonate structures; 
         FIG. 19  is a flat plan view showing a quadribonate embodiment of the invention; 
         FIG. 20   a  is a flat plan view showing yet another quadribonate embodiment of the invention; 
         FIG. 20   b  is an enlarged portion of  FIG. 20   a  showing the various planes of symmetry; 
         FIG. 21   a  is a flat plan view showing yet another tribonate embodiment of the invention; 
         FIG. 21   b  is an enlarged portion of  FIG. 21   a  showing the various planes of symmetry; 
         FIG. 22   a  is a flat plan view showing yet an embodiment of the invention which includes tribonate and quadribonate cells; 
         FIG. 22   b  is an enlarged portion of  FIG. 22   a ; and 
         FIG. 23  is a flat plan view showing an embodiment of the invention including obliquely oriented bonate cells. 
     
    
    
     DETAILED DESCRIPTION 
     An 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 the  FIG. 2  end view, such as Nitinol, or stainless steel preferably, which has been etched or more preferably laser cut to the configuration shown in the flat plan view of  FIG. 1 . The configuration may be formed in flat sheet, rolled into a cylinder and welded or the like, or the configuration may be formed directly from a small tube such as a hypotube. An enlarged detail of  FIG. 1  is shown in  FIG. 3 . This configuration is made up of a series of generally triangular-like expansion cell elements generally indicated at  11  (see darkened cell in the Figures for clarity) having relatively straight segments  13 ,  15  and  17 , relatively straight segments  12 ,  14  and  16  and curvilinear segments  18 - 23 . Segments  12 ,  14  and  16  comprise a first set of three segments arranged relative to each other in triangular spaced positions as shown in  FIG. 3 . Segments  13 ,  15  and  17  are placed in triangular spaced positions also but are outwardly positioned with respect to inwardly positioned segments  12 ,  14  and  16  and are placed opposite paired ends of  12 / 16 ,  16 / 14  and  12 / 14  as shown. In this embodiment these segments  12 - 17  are all straight. Curvilinear segments  18 ,  19 ,  20 ,  21 ,  22  and  23  interconnect segments  12 / 13 ,  13 / 16 ,  16 / 17 ,  14 / 17 ,  14 / 15  and  12 / 15  as shown. Preferably the segments are curvilinear, more preferably they are S-shaped as shown, although they can be made up of one or more straight sections. The resultant cell exhibits the triskelion configuration, having the three part axis  25  radiating from a common center. Cells  11  in this embodiment are arranged in an internested arrangement or network as shown in the Figures with adjacent cells sharing common sides or segments. 
     Finally, the longitudinal axis of the stent is indicated by reference numeral  270  in the above figures and in all of the remaining figures of the application. 
     When the stent of  FIGS. 1 and 2  is expanded, as shown in  FIG. 4 , on a balloon for example (not shown), the cells  11  take on a new configuration as shown, the segments making up the stent being indicated by the same numbers as used in  FIGS. 1 and 3 . 
     Referring now to  FIGS. 5-6 , another internested stent embodiment is shown. In this embodiment, as seen in  FIGS. 5 and 6 , expansion cells  11 , best seen in the detail of  FIG. 6  (again a cell is indicated by darkening) are shaped the same as cells  11  in  FIGS. 1-3 . However, they are skewed with respect to the longitudinal axis  270  of the stent rather than being arranged in parallel longitudinal lines in which the cells are positioned perpendicular to the longitudinal axis of the stent as in  FIGS. 1-4 . 
     Referring now to  FIG. 7 , another cell configuration is shown to demonstrate that elements or segments  12 ,  14  and  16  need not be straight but may be arcuate as shown, either inwardly as shown in the Figure or outwardly. 
     The cell configuration shown in  FIG. 8  is a three-lobed configuration preferably used in an interconnected cellular arrangement with individual connecting members as discussed in  FIGS. 9 and 10 . In this embodiment three sections,  12   a / 12   bm    14   a / 14   bm  and  16   a / 16   b , radiate from a common center to terminate in enlarged end portions  13 ,  15  and  17 , respectively. However,  FIGS. 9 and 10  make use of cell configurations similar to those shown in  FIGS. 1-6 . 
     In  FIG. 9 , a series of sets of cells, each set consisting of six cells  11  arranged in a circular pattern  28 , repeated throughout the stent body. Each cell  11  is connected to three adjacent cells  11  by three connector segments  30  in a repeating pattern through the stent body. In this particular arrangement, the connector members  30  extend from an inner segment on one cell to an inner segment on an adjacent cell, as shown. The connector members may be straight or curved and may be in various shapes such as zig-zag or S-shaped, etc. 
     In  FIG. 10  the connector members  30  extend from an inner segment on one cell to an outer segment on the adjacent cell as shown. Cells  11  are arranged in vertical rows in this embodiment but are staggered longitudinally as can be seen in the Figures. 
       FIG. 11  is illustrative of an internested stent configuration in which all segments of each cell are straight as opposed to curvilinear. 
     For the purposes of this disclosure, the term ‘bonate’ refers to a structure which has relatively wide end portions joined by a connecting portion which is, at least in part, relatively narrow. A bonate cell structure is illustrated generally at  100  in  FIG. 12 . Bonate cell structure  100  has a first relatively wide end portion  104  of the cell and a second relatively wide end portion  108  of the cell and a relatively narrow connecting portion  112  of the cell and resembles a dog bone. Connecting portion  112  may also be relatively narrow in only a portion thereof. Stents having bonate cell structures have been disclosed in commonly assigned U.S. application Ser. No. 08/947,620 filed Oct. 9, 1997, the contents of which are incorporated herein in their entirety by reference. 
     The term ‘multibonate’, for the purposes of this disclosure, refers to a structure which has three or more relatively wide end portions each of which is joined to a common portion via a relatively narrow connecting portion. Further, each of the end portions radiates from at least one common point in the common portion, desirably in the center of the common portion. The relatively wide end portions of a multibonate structure may be lobe shaped. Also desirably, each of the end portions emanates from a vertex region of the common portion. One such multibonate cell structure is shown generally at  120  in  FIG. 13 . Multibonate structure  120  consists of three relatively wide end portions  124  of the cell each of which is joined to a common portion  128  of the cell via relatively narrow connecting portions  132  of the cell. It is noted that each of end portions  124  extends from a common point  129 . It is also noted that each of end portions  124  extends from a vertex  131  of common portion  128 . The multibonate structure of  FIG. 13  is also termed a tribonate structure because of the presence of the three end portions. Multibonate structures with four relatively wide end portions would similarly be termed ‘quadribonate’ and multibonate structures with five, six, seven and eight relatively wide end portions would be termed ‘pentibonate’, ‘hexibonate’, ‘heptabonate’ and ‘octabonate’, respectively. A multibonate structure with ‘n’ end portions is referred to as an ‘n th  order’ multibonate structure. 
     The present invention is directed generally to stents formed of multibonate cell structures. In one embodiment, the invention is directed to a stent of generally cylindrical shape comprised of at least one multibonate cell structure and desirably of a plurality of interconnected multibonate cell structures. The multibonate cell structures may optionally be regularly arranged. One such stent is shown in the flat in  FIG. 14   a . Stent  200  consists of a plurality of interconnected tribonate cell structures  120 . Tribonate cell structures are arranged in interconnected longitudinal rows  204 . Tribonate cell structures within a row are seen to be tessellated or interlocking with adjacent cell structures having at least one member  124   a  in common. Member  124  simultaneously serves as an end portion of a cell structure and as a portion of the central portion of a cell structure. Tribonate cell structures  120  in adjacent rows  204  are also seen to share a member  124   b  in common. Member  124   b , similarly, serves as an end portion in one cell structure and as a portion of the central portion of a cell in an adjacent row. All of the tribonate structures  120  in adjacent rows  204  of multibonate structures are identically oriented relative to the longitudinal axis of the stent. 
     It is further noted that tribonate cells  120  of  FIG. 14   a  have a common portion  128  which is substantially triangular and moreover formed substantially in an equilateral triangle. Each tribonate cell  120  has a threefold rotational axis of symmetry (C 3  axis of symmetry)  121  in the flat, through the center of the cell, as shown in  FIG. 14   b . Each tribonate structure further is characterized by three planes of reflectional symmetry (σ v )  123   a - c , as shown in  FIG. 14   c . To that end, first, second and third end portions  124   a - c , respectively, are the same shape. Moreover, all three connecting portions  132   a - c  are substantially the same shape, width and length. 
     The invention further contemplates variations on the multibonate structure in general and the tribonate structure in particular. One such variation is shown in stent  200  in  FIG. 15   a . Tribonate cell structure  120  is not seen to possess the threefold rotational symmetry of the tribonate cell structure of  FIG. 14   a . Moreover, cells  120  are seen to possess only a single plane of reflectional symmetry (σ v )  123 , as shown in  FIG. 15   b . The cell structure is also seen to vary in that second and third end portions  124   b,c  are a reflection of one another while end portion  124   a  differs in shape. End portion  124   a  is substantially triangular in shape. Its boundaries are defined by two convex side portions  136   a,b . End portions  124   b,c  are each seen to be mushroom shaped. Each of end portions  124   a - c  extend from connecting portions  132   a - c , respectively, which in turn, extend from common portion  128 . End portions  124   a - c  are seen to be mushroom shaped. 
     Another embodiment of the invention is shown generally at  200  in  FIGS. 16   a - e . As in  FIG. 15 , tribonate cell structure  120  does not possess the threefold rotational symmetry of the tribonate cell structure of  FIG. 13 . Moreover, cells  120  are seen to possess only a single plane of reflectional symmetry (σ v ). The cell structure is also seen to vary in that second and third end portions  124   b,c  are a reflection of one another while end portion  124   a  differs in shape. End portion  124   a  is substantially triangular in shape. Its boundaries are defined by two substantially straight side portions  136   a,b . End portions  124   b,c  are each slot shaped. 
     In another embodiment, the invention is directed to a stent, as shown generally at  200  in  FIG. 17 . Stent  200  is composed of a plurality of connected tribonate cell structures  120  arranged in longitudinal rows  204 . The stent further comprises a plurality of bonate cell structures  140  arranged in longitudinal rows  208  and extending between adjacent rows  204  of tribonate cells  120 . Bonate cell structures  140  serve as connectors between adjacent rows of multibonate cells. Bonate cell structures  140  are disposed at an oblique angle relative to the longitudinal axis of the stent. Adjacent rows of bonate cell structures  140  are disposed at equal but opposite angles relative to the longitudinal axis  270  of the stent  200 . Bonate cell structures  140  and multibonate cell structures  120  are seen to interlock with one another. End portions  104  of bonate structures  140  form a portion of the side of common portion  128  of tribonate cell structures  120 . Similarly, end portions  124   b,c  of tribonate cell structures  120  form a portion of narrow connecting portion  112  of bonate cell structures  140 . Within a longitudinal row  204  of tribonate structures, adjacent tribonate cell structures interlock as well with end portion  124   a  of a cell forming a part of common portion  128  of an adjacent cell. 
     The stent of  FIG. 17  also differs from the previously shown stents in that tribonate cell structures in adjacent row  204  of tribonate cell structures are oppositely oriented—the cell structures in adjacent rows are rotated by 180° relative to one another. For example, end portions  124   a  of cell structures in row  204   a  is directed in an opposite direction relative to end portions  124   a  of cell structures in row  204   b.    
     Another embodiment of the stent is shown generally at  200  in  FIG. 18 . Stent  200  is formed of a plurality of multibonate (tribonate) cells  120  and bonate cells  140 . The stent of  FIG. 18  is similar to that of  FIG. 17  differing in the shape of end portions  124   a . End portion  124   a  is substantially triangular. 
     In the embodiments of  FIGS. 14 and 17 , tribonate cell structures include an end portion  124   a  which is oriented perpendicular to the longitudinal axis of the stent. The invention also contemplates stents in which multibonate cells include an end portion which is parallel to the longitudinal axis of the stent. Such a stent is shown generally at  10  in  FIG. 1 . End portions  124   b  are aligned parallel to the longitudinal axis  270  of the stent. 
     Yet another embodiment of the invention is shown generally at  200  in  FIG. 19 . Stent  200  is comprised of a series of interconnected, internested quadribonate cells  120  including first quadribonate cells  120   a  and second quadribonate cells  120   b . First and second quadribonate cell  120   a,b  are differently shaped. End portions  124   a  of first quadribonate cells  120   a  also serve as side portions of adjacent second quadribonate cells  120   b . First quadribonate cells  120   a  are joined together by connecting members  154  which also serve as end portions  124   b  for quadribonate cells  120   b . End portions  124   a  of first quadribonate cell structures  120   a  are oriented at oblique angles relative to longitudinal axis  270 . End portions  124   b  of second quadribonate cell structures  120   b  are oriented parallel or perpendicular to longitudinal axis  270  of stent  200 . The stent of  FIG. 19  is an example of a multibonate stent which consists of at least two different types of multibonate cells of the same order. 
     Another quadribonate stent is shown generally at  200  in  FIG. 20   a . Stent  200  is formed of a series of interconnected, internested quadribonate cells  120  including first quadribonate  120   a  and second quadribonate cells  120   b . End portions  124   a  of first quadribonate cell structures  120   a  are oriented at oblique angles relative to longitudinal axis  270 . End portions  124   b  of second quadribonate cell structures  120   b  are oriented parallel or perpendicular to longitudinal axis  270  of stent  200 . Stent  200  further includes bonate cell structures  140  oriented at oblique angles relative to the longitudinal axis  270  of the stent. The stent of  FIG. 20   a  is an example of a multibonate stent which consists of at least two different types of multibonate cells of the same order and further contains bonate cells. 
     The quadribonate cells of  FIGS. 19 and 20  have a four-fold axis of rotational symmetry.  FIG. 20   b  shows this axis  121  for one quadribonate cell  120   b  of  FIG. 20   a . The quadribonate cells also are characterized by four planes of reflectional symmetry  123   a - d.    
     The invention is also directed to a stent, shown generally at  200  in  FIG. 21   a , which includes elongated tribonate cell structures  120  as well as a row of bonate cell structures  140  at one end of the stent. Tribonate cells  120  include a relatively long, but relatively narrow connecting portion  132   a  and relatively short and relatively narrow connecting portions  132   b . Tribonate cells  120  have a plane of reflectional symmetry  123   a  as shown in  FIG. 21   b.    
     Another embodiment of the inventive stent is shown generally at  200  in  FIG. 22   a . The pattern of  FIG. 22   a  is magnified in  FIG. 22   b . Stent  200  is formed of interconnected tribonate cells  120   a  and interconnected quadribonate cells  120   b . Tribonate cells  120   a  are formed of three relatively wide end portions  124   a , each of which is joined to a common portion  128   a  of the cell via relatively narrow connecting portions  132   a . Quadribonate cells  120   b  are formed of a four relatively wide end portions  124   b  each of which is joined to a common portion  128   b  of the cell via relatively narrow connecting portions  132   b.    
     The stent of  FIG. 22   a  also consists of a plurality of interconnected five member spirals  160   a , four member spirals  160   b  and three member spirals  160   c . Five member spirals  160   a  each have five members  163   a  spiraling about a center portion  165   a , four member spirals  160   b  each have four members  163   b  spiraling about a center portion  165   b  and three member spirals  160   c  each have three members  163   c  spiraling about a center portion  165   c.    
     Stents having spiral members have also been disclosed in copending, commonly assigned U.S. application Ser. No. 08/846,164, filed Apr. 25, 1997 and incorporated herein in its entirety by reference. 
     More generally, the invention is directed to stents having multibonate cell structures which include at least one end portion disposed parallel to the longitudinal axis of the stent as well as multibonate cell structures which include at least one end portion disposed perpendicular to the longitudinal axis of the stent. 
     The invention further contemplates stents which comprise multibonate cell structure in which none of the end portions are perpendicular or parallel to the longitudinal axis of the stent. Such a stent is shown generally at  200  in  FIG. 22   a . Each of end portions  124   a - c  are obliquely oriented relative to the longitudinal axis of the stent. 
     The invention is also directed more generally to stents comprising any order of multibonate structure. A stent comprising sixth order multibonate cell structures is shown generally at  10  in  FIG. 9 . Hexabonate cell structure  150  consists of six end portions  154  emanating from connector portions  162  which in turn emanate from a common portion  166 . The invention contemplates stents in which adjacent multibonate structures have at least one side in common, as shown in  FIG. 9 , as well as stent in which adjacent multibonate structures do not have at least one side in common. 
     The invention is also directed to stents comprising at least one multibonate structure of n th  order and at least one bonate structure or multibonate structure of m th  order where n and m are integers, n and m are greater than 2 and n≠m. These stents comprise at least one multibonate structure of a desired order and one bonate structure or multibonate structure of a different order. 
     The stent of  FIG. 9  comprises sixth order multibonate structures (hexabonate)  150  as well as third order (tribonate) structures  120 . The different order multibonate structures may be interlocking, having parts in common. Tribonate structures  120  in  FIG. 9  are interconnected by connecting segments  154  which also serve as end portions of hexabonate cell structures  150 . The different order multibonate structures may also be separate from one another and interconnected via connecting members. 
     The invention also contemplates stents formed of at least two different types of multibonate cell structures of the same order. For example, the two different types of multibonate cells may have different dimensions or different shapes. This is illustrated in  FIG. 10 . The stent, shown in the flat, includes first tribonate cells  120   a  and second tribonate cells  120   b . The shape of first tribonate cells  120   a  differs from that of second tribonate cells  120   b .  FIG. 19  similarly includes two different types of quadribonate cells  120   a,b.    
     The invention is also directed to a stent comprised of at least one cell structure selected from the group consisting of bonate cell structures oriented at an oblique angle relative to the longitudinal axis of the stent, multibonate cell structures and combinations thereof. Desirably, the stent will be composed comprised of a plurality of cell structures selected from the group consisting of bonate cell structures oriented at an oblique angle relative to the longitudinal axis of the stent, multibonate cell structures and combinations thereof. Optionally, the cell structures will be interlocking. 
     The invention is further directed to a stent comprising one or more bonate structures oriented at an oblique angle relative to the longitudinal axis of the stent. As shown in the flat in  FIG. 23 , stent  200  consists of interconnected bonate cell structures  140 . The stent includes first bonate cell structures  140   a  which are oriented at a first oblique angle relative to the longitudinal axis of the stent  270  and second bonate cell structures  140   b  which are oriented at a second oblique angle relative to the longitudinal axis of the stent. 
     The second oblique angle is equal but opposite to the first oblique angle. The stent of  FIG. 23  consists of alternating rows  280   a  and  280   b  of first bonate cell structures  140   a  and second bonate cell structures  140   b , respectively, disposed about the circumference of the stent. 
     All of the configurations shown in the Figures may be utilized uniformly throughout a stent or they may be mixed as a means of tailoring a variety of different characteristics throughout various regions of a stent. Other cell configurations may also be used in the practice of the invention. 
     It is understood that the invention contemplates substituting straight sections of the cell structure for curved structures and vice versa as long as the multibonate structure of the cells is maintained. 
     It is also understood that the term stent, as used in this application, is directed to stents, stent-grafts, grafts and other endoluminal and intraluminal prostheses. For example, the configurations disclosed herein may be used as a framework for grafts. 
     It will be also appreciated that, while the specific shapes depicted in the figures hereof contain many functional features, those functional features can all readily be obtained in other embodiments which have an overall appearance which is quite different. Therefore, the article of the figures is considered to have a novel and non-obvious ornamental appearance independent of the functional features described herein. 
     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. 
     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.