Patent Publication Number: US-2010114297-A1

Title: Stent

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to stents that are implanted into a body vessel. More specifically, the present invention relates to an expandable stent having a tubular flexible body with a wall formed of a web structure. 
     2. Background Information 
     Very different types of stents are already known from the prior art. For example, there are coronary stents such as balloon expanded stents or self-expandable stents. The stent forms a vascular prosthesis made from a physically compatible material. The stent or stent prosthesis is used for expanding blood vessels, or also other body orifices, and for keeping the vessels or orifices in an expanded state. To this end, the stent is normally positioned in a non-expanded state in a patient&#39;s body, usually with the help of a balloon catheter onto which the stent is crimped, and is then expanded. During expansion the individual stent portions of the stent are deformed, so that the stent remains in its expanded form in a permanent way. 
     A stent of the type indicated is disclosed in German Utility Model Patent Publication DE-U-297 08 689.8. In this stent, several S-shaped connection elements are provided as connectors between the web patterns of the web structure of the stent wall. Although these connection elements in the non-expanded state result in a very flexible stent construction and, in the expanded state, in a stent construction with a high radial force or radial-force absorbing capacity, improvements are nevertheless possible as it cannot be ruled out all the time that during expansion the connection elements bulge outwards or inwards from the wall plane, whereby the surrounding tissue is slightly injured and the formation of thromboses or restenoses is promoted. 
     In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved stent. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure. 
     SUMMARY OF THE INVENTION 
     It is therefore the object of the present invention to provide a stent, which in the non-expanded state is very flexible and in the case of which it can be prevented during expansion that the connection elements can move out of the wall surface of the stent. 
     This object is achieved by the features of a stent comprising a tubular flexible body with a wall having a web structure that can be transformed from a non-expanded state into an expanded state. The web structure comprises a plurality of neighboring web patterns which include webs arranged side by side, and adjacent pairs of the web patterns being interconnected by at least one connection element. Each of the connection elements comprises three connection webs arranged at an angle relative to one another and interconnected via a pair of hinges. 
     The stent according to the invention yields a very flexible structure during bending and compression. It is possible in a particularly advantageous manner to prevent a situation where upon expansion of the stent the connection elements impair the tissue in the expanded state of the stent, and where the lumen of the stent interior is reduced. 
     The reason for such an advantageous effect must above all be seen in the fact that the connection elements become shorter both during bending (e.g., when the stent is placed in a curved vessel) and during expansion (e.g., during expansion by means of the balloon), which is achieved by the special arrangement of the connection webs of the connection elements with the hinges or joints provided for. 
     The connection webs of the connection elements in the non-expanded or compressed state of the web structure are arranged relative to one another at least approximately, preferably exactly, at a right angle. 
     It is thus possible to make the width of each of the connection webs equal or, in order to achieve an enhanced flexibility, to make the width of the central connection web slightly smaller than the width of the connection webs joining the central web. 
     The connection webs which are connected to the neighboring webs of the web structure are mounted in a particularly preferred embodiment also via hinges. 
     Film hinges are provided as a particularly preferred and particularly simple embodiment for the hinges. 
     Preferably, the stent consists of a biocompatible material which in a particularly preferred embodiment is a nickel-titanium alloy or special steel. 
     These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the attached drawings which form a part of this original disclosure: 
         FIG. 1  is a diagrammatically very simplified schematic illustration of the basic shape of the stent according to the present invention; 
         FIG. 2  is an enlarged, partial elevational view of a part of the web structure of the wall of the stent in the non-expanded state according to the present invention; 
         FIG. 3  is a schematic illustration of the connection elements according to the invention for explaining the function of the connection elements; 
         FIG. 4A  is a partial diagrammatically illustration, corresponding to  FIG. 2 , of the arrangement of the stent according to the present invention in a non-expanded state after being inserted into a curved vessel; 
         FIG. 4B  is an illustration corresponding to  FIG. 2  of the arrangement of the stent according to the present invention in an expanded state within a curved vessel; and 
         FIG. 5  is an enlarged, partial elevational view of a part of a modified connection element that can be used in place of the connection elements of the stent in  FIG. 2  according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Selected embodiments of the present invention will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments of the present invention are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. 
     Referring initially to  FIG. 1 , a stent  1  is diagrammatically illustrated in a very simplified schematic illustration to show the overall general shape of the stent in accordance with a first embodiment of the present invention.  FIG. 1  is a front perspective view of the stent  1 . The stent  1  basically comprises a flexible tubular body  2  with a tubular wall  3  with a longitudinal direction L and a circumferential direction C. The stent  1  according to the present invention can be designed as a balloon-expandable or self-expandable stent. 
       FIG. 2  shows the basic construction of the wall  3  of the body  2  of the stent  1  according to the present invention. The wall  3  of the body  2  of the stent  1  has a stent web structure  4  which can be transformed from a non-expanded state (compressed) into an expanded state. To this end the stent web structure  4  comprises a plurality of neighboring web patterns, of which only portions of web patterns  5  and  6  are illustrated in  FIG. 2  by way of example. The web patterns  5  and  6  are continuous circumferentially extending rings that are axially interconnected by at least one connection element  7 , preferably by a plurality of the connection elements  7  as shown. While only two web patterns  5  and  6  are shown, it will be apparent to those skilled in the art from this disclosure that there exists a plurality of web patterns  5  and  6  arranged in an alternating manner with at least one connection element  7  (preferably several connection elements  7 ) connecting adjacent pairs of the web patterns  5  and  6 . In  FIG. 2 , the web pattern  5  is an end web pattern with the connection elements  7  coupled to only one of its axial sides, while the web pattern  6  is an inner web pattern with the connection elements  7  coupled to both of its axial sides. The right axial side of the web pattern  6  is coupled to a circumferential web pattern (not shown) that is identical to the web pattern  5 , except the left axial side of this web pattern (not shown) is interconnected to the web pattern  6  by the connection elements  7 . 
     As seen in  FIG. 2 , the web pattern  5  is formed of a plurality of first webs  8  and a plurality of second webs  9  that are arranged in an alternating manner. Each end the first webs  8  is connected to a corresponding end of one of the second webs  9  by a bend or curved section  12 . Likewise, the web pattern  6  is formed of a plurality of first webs  10  and a plurality of second webs  11  that are arranged in an alternating manner. Each end the first webs  10  is connected to a corresponding end of one of the second webs  11  by a bend or curved section  13 . Preferably, the web patterns of the wall  3  of the body  2  of the stent  1  alternate with the web patterns  5  and  6  such that every other web pattern look like the web pattern  5  with the web pattern  6  located therebetween and coupled together by the connection elements  7  as shown in  FIG. 2 . 
     The connection element  7  comprises three connection webs, i.e., a first outer connection web  14 , a central connection web  15  and a second outer connection web  16  that are arranged at an angle relative to one another and interconnected via a pair of inner hinges  17  and  18 . In particular, the connection elements  14  and  15  are interconnected via the hinge  17 , and the connection webs  15  and  16  are interconnected the hinge  18 . The outer connection web  14  is further connected via an outer hinge  19  to one of the bends  12 , and the second outer connection web  16  via an outer hinge  20  to one of the bends  13 , in accordance with the web patterns  5  and  6 , respectively. 
     In the particularly preferred embodiment in  FIG. 2 , the connection webs  14 ,  15  and  16  are arranged at right angles relative to one another. The hinges  17 ,  18 ,  19  and  20  are designed as film hinges which are formed by providing approximately semicircular openings  24 ,  25 ,  23  and  26 , respectively, in the respective connection webs  14 ,  15  and  16 . 
     Preferably, the central connection web  15  has a length that is smaller than the lengths of the connection webs  14  and  16  as seen in  FIG. 2 . However, as seen in the alternate embodiment of  FIG. 5 , it is possible to make, the lengths of the webs  14 ,  15  and  16  all equal. 
     Furthermore, in the particularly preferred embodiment shown in  FIG. 2 , the width B 1  is equal to the width B 2  and the width, in turn, is equal to width B 3  of the connection webs  14 ,  15  and  16 , respectively. However, as seen in the alternate embodiment of  FIG. 5 , it is possible to make the width B 2  of the connection web  15  smaller than the width B 1  and the width B 3  for increasing flexibility of the connection element  7 . 
       FIG. 3  illustrates the mode of operation of the connection element  7  according to the invention within the stent web structure  4 . The arrangement  7   1  shows the configuration of the connection element  7  according to  FIG. 2  in a schematically simplified view. This results in a distance A of the length of the central connection web  15 . 
     The state  7   2  of the connection element  7  illustrates the positions of the webs  14 ,  15  and  16  in their compressed or unexpanded states, which are symbolized by the two arrows K. This yields a distance at between the hinges  17  and  18  that is smaller than the distance A. 
     The state  7   3 , which corresponds to an expanded state, also yields a distance a 2  that is also smaller than the distance A. 
     This means that the connection element  7  is shortened both in the compressed (unexpanded) and the expanded state so that the connection elements  7  cannot protrude from the wall plane of the web structure, whereby in particular in the implanted state the surrounding tissue of the respective volume cannot be injured. Furthermore, this has the advantage that the connection elements  7  in curved vessels yield a uniform wall cover through the web patterns  5  and  6  as well as flexibility of the whole stent construction. 
     Reference is here made to  FIG. 4A and 4B , each showing a section of the stent web structure  4  arranged in a curved vessel.  FIG. 4A  shows the compressed (unexpanded) state of the connection element  7  with its connection webs  14  to  16 , whereas  FIG. 4B  shows and illustrates the stretched (expanded) state of a corresponding connection element  7  with its connection webs  14  to  16 . 
     The terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. For example, these terms can be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies. 
     This application claims priority to European Patent Application No. 01122285.8. The entire disclosure of European Patent Application No. 01122285.8 is hereby incorporated herein by reference. 
     While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. Furthermore, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. Thus, the scope of the invention is not limited to the disclosed embodiments.