Patent Publication Number: US-2012029618-A1

Title: Stent Connector Bump Design

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
     This application claims the benefit of U.S. Provisional Application 61/368,447 filed Jul. 28, 2010, the entire contents of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION  
     A stent is a medical device which is introduced into a body lumen and is well known in the art. A stent is typically delivered in an unexpanded state to a desired location in a bodily lumen and then expanded by an internal radial force. 
     Stents, grafts, stent-grafts, vena cava filters, expandable frameworks, and similar implantable medical devices, are radially expandable endoprostheses, which are typically intravascular implants capable of being implanted transluminally and enlarged radially after being introduced percutaneously. Stents may be implanted in a variety of bodily lumens or vessels such as within the vascular system, urinary tracts, bile ducts, fallopian tubes, coronary vessels, secondary vessels, etc. Stents can be balloon-expandable, self-expanding or a combination of self-expanding and balloon-expandable (or “hybrid expandable”). 
     SUMMARY OF THE INVENTION  
     The invention is directed to an endoprosthesis comprising a plurality of serpentine bands including a first serpentine band and a second serpentine band. Each serpentine band comprises a plurality of interconnected struts forming peaks and troughs. Adjacent serpentine bands interconnected by one or more connectors. The first and second serpentine bands are connected via at least one connector. The connector has a first side facing one of the struts and a second side facing another of the struts. The connector extends from an inside of a trough of the first serpentine bands to the outside of a trough of the other serpentine band. The connector has a first bump extending from the first side and a second bump extending from the second side opposite the first. The first bump is located adjacent a first peak and the second bump located adjacent a second peak. 
     Desirably, the endosprosthesis is in the form of a stent. 
     Desirably, the stent will comprise a plurality of connectors. Typically, each of the connectors will extend from an inside of a trough of one of the serpentine bands to the outside of a trough of the other the other of the serpentine bands. Some, and desirably all, of the connectors will have a first bump extending from the first side and a second bump extending from the second side opposite the first. The first bump may be located adjacent a first trough and the second bump located adjacent a second trough. 
     The stent may comprise a plurality of the serpentine bands and, desirably, three or more of the serpentine bands where adjacent serpentine bands are connected by a plurality of said connectors, each of which has a said first bump and a said second bump extending therefrom. Each connector may extend from a trough connected to a first adjacent strut via a first curved portion of the trough and connected to a second adjacent strut via a second curved portion of the trough, the first curved portion characterized by a first radius of curvature and the second curved portion characterized by a second radius of curvature. For each connector, the first bump typically extends from the connector and is characterized by a width as measured in a circumferential direction about equal to the first radius of curvature and the second bump typically extends from the connector and is characterized by a width as measured in a circumferential direction about to the second radius of curvature. 
     The invention is also directed to a self-expanding endoprosthesis, desirably, in the form of a stent, comprising a plurality of serpentine bands. Each serpentine band comprises a plurality of struts interconnected by peaks and troughs. Connectors extend between and connect adjacent serpentine bands. Each connector has a first bump extending from a first side toward an end of an adjacent strut and a second bump extending from a second side toward an end of another adjacent strut. The first and second bumps each have a width which is approximately equal to the separation between the connector and the adjacent strut when the endoprosthesis is in a crimped state. 
     Typically, the struts will be straight and each of the bumps will have a flat edge facing an adjacent strut. The flat edge will extend parallel to the connector. In lieu of flat edges, some or all of the bumps may have a curved edge extending non-parallel to the connector. 
     The connectors may extend from a trough on one serpentine band to a trough on an adjacent serpentine band. 
     The invention is also directed to a self-expanding endoprosthesis, desirably, in the form of a stent, comprising a plurality of serpentine bands. Each serpentine band comprises a plurality of interconnected strut pairs. Each strut pair has a first strut and a second strut adjacent the first strut. The first strut is connected to the second strut to form a peak, and a first strut pair is connected to a second strut pair to form a trough. Each first strut of the strut pair has a bump extending from a first side of the first strut toward a second side of the second strut. The bump has a width which is approximately equal to a distance between the first strut and the second strut. One or more connectors extend between and connect adjacent serpentine bands. 
     Typically, the struts will be straight and each bump will have a flat edge facing the second side of the second strut. The flat edge extends parallel to the first strut. In lieu of flat edges, some or all of the bumps may have a curved edge extending non-parallel to the second strut. 
     The connectors may extend from a peak on one serpentine band to a trough on an adjacent serpentine band. In some embodiments, the peak is circumferentially and longitudinally offset from the trough. 
     The invention is also directed to a stent delivery system comprising: a delivery catheter and a stent disposed about the delivery catheter and deployed therefrom. The stent comprises a plurality of serpentine bands including a first serpentine band and a second serpentine band. Each serpentine band comprises a plurality of interconnected struts forming peaks and troughs. Adjacent serpentine bands are interconnected by one or more connectors. The first and second serpentine bands are connected via at least one connector. The connector has a first side facing one the struts and a second side facing another of the struts. The connector extends from an inside of a trough of the first serpentine bands to the outside of a trough of the other of the serpentine bands. The connector has a first bump extending from the first side and a second bump extending from the second side opposite the first. The first bump is located adjacent a first peak and the second bump located adjacent a second peak. The first bump contacts a first strut and the second bump contacts a second strut. 
     The angle between each pair of interconnected struts that is not associated with a connector may be constant. The stent may be configured such that when the stent is deployed, the angle between each pair of interconnected struts that is not associated with a connector is also constant. Typically, at least the first bump of the connector will be located towards an end of the connector. 
     In at least one embodiment of the invention, the stent comprises a plurality of serpentine bands each having alternating peaks and troughs connected by straight struts. Two of said serpentine bands are connected one to the other via straight connectors which extend parallel to the longitudinal axis of the stent. Each straight connector extends from a trough of one serpentine band to a trough of an adjacent serpentine band. Each straight connector includes a first side and a second side that each extend from an outer wall surface of the stent to an inner wall surface of the stent. Each connector has a bumped out region of greater width than the remainder of the connector. The bumped out region is located between two circumferentially adjacent peaks and one end of the bumped out region is substantially aligned with the two circumferentially adjacent peaks. The first and second sides of the connector each having a bump thereon in the bumped out region of the connector. In at least one embodiment, each serpentine band has twenty-four struts; each strut width is between about 0.0028 in. and 0.0052 in.; each connector width is between about 0.0029 in. and 0.0053 in.; and each bumped out region is between about 0.0104 in and 0.0128 in. wide. In at least one embodiment, each serpentine band has three evenly spaced connectors. In at least one embodiment, the outer diameter of the stent is about 0.196 in. In at least one embodiment, the strut width is about 0.0040 in., the connector width is about 0.0041 in, the bumped out region is 0.0116 in. wide, and the wall thickness is 0.0076 in. In at least one embodiment, the stent is sized to fit within a 6 French catheter having an inner diameter of about 0.070 in. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  shows a partial view of an embodiment of the stent of the present invention. 
         FIG. 2A  is a schematic showing of a stent similar to that of  FIG. 1  on a delivery catheter. 
         FIG. 2B  is a schematic showing the delivery system of  FIG. 2A  with the stent ready for deployment. 
         FIG. 2C  is a schematic showing of a stent similar to that of  FIG. 1  on a delivery catheter. 
         FIG. 2D  is a schematic showing the delivery system of  FIG. 2C  with the stent partially deployed. 
         FIGS. 3A-3B  show a prior art stent during expansion of the stent in the lumen. 
         FIGS. 4A-4B  show an embodiment of the stent of the present invention during expansion in the lumen. 
         FIG. 5  shows a partial view of an embodiment of the invention. 
         FIG. 6  shows a partial view of an embodiment of the invention. 
         FIG. 7  shows a partial view of an embodiment of the invention. 
         FIG. 8  shows a partial view of an embodiment of the invention. 
         FIG. 9  shows a flattened view of an embodiment of the stent of the present invention. 
     
    
    
     DESCRIPTION OF THE SPECIFIC EMBODIMENTS  
     While this invention may be embodied in many different forms, there are described in detail herein specific 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. 
     For the purposes of this invention, the term ‘inner surface’ shall refer to the surface of the stent or tubular member which faces the lumen of the stent or tubular member. The term ‘outer surface’ shall refer to the surface of the stent or tubular member which faces away from the lumen. The term ‘sidewall surface’ shall refer to the surface of the stent or tubular member which extends between the outer surface and the inner surface. 
       FIG. 1  shows a partial view of an endoprosthesis in the form of a stent, indicated generally at  100 , in the unexpanded state. Stent  100  may be any kind of expandable prostheses such as a stent, stent-graft or graft. Stent  100  is a frame work formed of one or more interconnected serpentine bands  120 . Stent  100  extends from a proximal end  105  to a distal end  106 . Individual serpentine bands  120  comprise a plurality of interconnected struts  124 . The serpentine band  120  of  FIG. 1  is depicted with 16 struts. It is within the scope of the invention for a serpentine band to have fewer or more struts. 
     As shown in  FIG. 1 , struts  124  are desirably straight. The struts may, however, include curvature. In the case where the struts include curvature, the struts may be fundamentally straight with curved sides or the struts may be fundamentally curved. Where the strut is fundamentally straight with curved sides, a straight midline extends along the length of the strut and the entirety of the midline lies on the strut midway between the sides of the strut. Where the strut is fundamentally curved, the strut does not have a straight midline which extends along the length of the strut, the entirety of which lies on the strut midway between the sides of the strut. 
     Adjacent struts  124  are connected one to the other via a plurality of turns of serpentine band  120 . For convenience, these turns may be referred to herein as peaks  128  and troughs  132 . For the purposes of this disclosure, peaks  128  are defined to be located at a distal end  106  of serpentine band  120 , while troughs  132  are defined to be located at a proximal end  105  of a serpentine band  120 . 
     Adjacent serpentine bands  120  are connected to one another via connectors  136 . As shown in  FIG. 1 , connector  136  extends from an inside portion  132   a  of a trough  132  to an outside portion  132   b  of another trough  132  of an adjacent serpentine band. Other arrangements of the connectors are also within the scope of the invention. For example, the connectors may extend from a peak of a serpentine band to a trough of an adjacent serpentine band. The connectors may also extend from locations along a serpentine band displaced from the peaks and troughs. To that end, the connectors may extend from locations along the serpentine band midway between a peak and a trough. They may extend from locations offset from the peak and trough as well as from the midway point between a peak and trough. 
     Typically, each connector  136  extends from trough  132  and connects to a first adjacent strut  124   a  via a first curved portion  132   c  of trough  132  and to a second adjacent strut  124   b  via a second curved portion  132   d  of trough  132 . The first curved portion of the trough may be characterized by a first radius of curvature and the second curved portion of the trough may be characterized by a second radius of curvature. 
     Connectors  136  may be straight or curved. The ends of the connectors may be longitudinally and circumferentially aligned with one another or the ends may be longitudinally and circumferentially offset from one another. Where the connectors include curvature, the curvature may be similar to the curvature discussed above for the struts. As such, curved connectors may be fundamentally straight with curved sides or they may be fundamentally curved. 
     Stent  100  of  FIG. 1  is shown with two connectors  136  between some serpentine bands  120  and one connector  136  between other serpentine bands  120 . It is within the scope of the invention, however, for the stent to be provided with more connectors or fewer connectors. Typically, at least one connector will be provided between adjacent serpentine bands. The invention does contemplate, however, the possibility of some adjacent serpentine bands being connected one to the other directly without a separate connector. 
     As further shown in  FIG. 1 , connector  136  has a first side  136   a  which faces one adjacent strut  124   a  and a second side  136   b  which faces another adjacent strut  124   b.  The first and second sides  136   a,    136   b  of connector  136  are opposite one another. Connector  136  has a first bump  140   a  extending from the first side  136   a  and a second bump  140   b  extending from the second side  136   b.  Bump  140   a  is desirably located adjacent a first peak and second bump  140   b  is desirably located adjacent a second peak. 
     Typically, bumps  140   a  and  140   b  will be of the same shape and size and will be mirror images of one another. It is also within the scope of the invention for the bumps on either side of a connector to be of different sizes and/or shapes. Desirably, the sidewall surface of the bumps will be complementary to the sidewall surface of the struts facing the bumps. Where the sidewall surface of the struts facing the bumps is straight, it is desirable for the sidewall surface of the bumps to include a straight portion which will contact the sidewall surface of the struts. 
     Also desirably, the first bump extending from the first side of a connector is characterized by a width, as measured in a circumferential direction, equal to the first radius of curvature of the first curved portion of the peak. The second bump extending from the second side of the connector is desirably characterized by a width, as measured in a circumferential direction, about equal to the second radius of curvature of the second curved portion of the peak. 
     Typically, the inventive stents will comprise a plurality of the serpentine bands. Adjacent serpentine bands will be connected by one or more of the connectors. Desirably at least one connector will include the above-described bumps. More desirably, all of the connectors will include the above-described bumps. 
     The invention is also directed to a stent or prosthesis comprising a plurality of serpentine bands, each of which comprises a plurality of struts interconnected by peaks and troughs. A plurality of connectors extends between and connects adjacent serpentine bands. Each connector has a first bump extending from a first side toward an end of an adjacent strut and a second bump extending from a second side toward an end of another adjacent strut. The first and second bumps each have a width which is approximately equal to the separation between the connector and the adjacent strut. Desirably, the struts are straight and each of the bumps has a flat edge facing an adjacent strut. The flat edge extends parallel to the connector. It is also within the scope of the invention for the struts to be straight and for each of the bumps to have a curved edge extending non-parallel to the connector. Typically, each connector extends from a peak on one serpentine band to a peak on an adjacent serpentine band. 
     The inventive stents disclosed herein may be provided in a balloon expandable form or in a self expanding form. They may also be provided in a hybrid form with both self expanding and the balloon expandable characteristics. The inventive stents, in many of the embodiments disclosed herein, may be deployed without the distortion that would result in the absence of the bumps or bumps disclosed herein. 
       FIG. 2A  shows an exemplary stent delivery system, which has stent  100  disposed about a delivery catheter  150 . Delivery catheter  150  in this embodiment has a retractable sheath  152  that allows for self-expansion of the stent  100  in the lumen and a balloon  152  for balloon expansion. As shown in  FIG. 2B , sheath  152  is retracted and balloon  154  can be expanded to deploy the stent in a bodily lumen. 
       FIG. 2C  shows another exemplary stent delivery system, in which stent  100  is a self expanding stent disposed within a sheath  152 . As shown in  FIG. 2D , when the sheath  152  is retracted at the position where the stent is desired to be deployed, the stent  100  expands. 
     The inventive nature of one embodiment of the stent may be seen with reference to  FIGS. 3A-3B  and  FIGS. 4A-4B , described further below. 
       FIGS. 3A-3B  show a stent in the absence of bumps in a loaded state and a deployed state. In  FIG. 3A , stent  200  is shown in a delivery catheter  204 . The stent comprises a plurality of serpentine circumferential bands  208 . Adjacent serpentine circumferential bands  208  are connected one to the other via straight connectors  236 . Connectors  236  extend from the outside of one trough to the inside of another trough on an adjacent serpentine circumferential band. Each serpentine band comprises a plurality of struts  242 . Some of the struts  242  are parallel to the longitudinal axis of stent  200 . Those struts forming strut pairs with a connector  236  extending from the outside of the associated peak, as well as other struts, are disposed at an oblique angle relative to the longitudinal axis of stent  200 . This distortion also results in other struts being disposed at oblique angles relative to the longitudinal axis of the stent. 
     When deployed, as shown in  FIG. 3B , stent  200  has distortions in the strut angles throughout each circumferential band  208 . The distortions are believed to result from axial force along connectors which results in differential openings of the turns and uneven expansion. Uneven expansion is believed to result from some struts, absent the bump, bending toward one another and others not bending. The stent will compress axially to a greater extent without bumps than with bumps. Reducing compression from both ends of the stent during delivery will affect deployed length. Compression may be reduced by providing one or more bumps which serve as a mechanical barrier to compression. The bumps take up the space that would have been filled by compression. 
     Rather than reducing the inner diameter of the sheath for the deployment mechanism, in the inventive stent shown in  FIG. 4A , a bump  140  was added to the connector. The bump  140  is situated such that it contacts adjacent struts  124  such that the struts are parallel to one other to provide improved column strength in a constrained condition. The bump  140  is sized without significantly increasing surface area for metal to lumen ratio and drug compatibility concerns. 
     The deployment of an inventive stent is shown in  FIGS. 4A-4B . In  FIG. 4A , an inventive stent  100  with bumps  140  is shown in catheter  104 . Circumferential bands  120  are shown prior to expansion. As shown in  FIG. 4A , stent  100  does not have any of the distortions present in the stent of  FIG. 3A . Stent  100  is shown deployed in  FIG. 4C . The stent  100  does not have any of the irregular strut angles that are present in the prior art stent of  FIGS. 3A-3B . 
     As shown in  FIG. 4A , bump  140  is provided toward an end of connector  136 . This location is particularly desirable in order to avoid the problem of “cowboy legging.” Specifically, if bump  140  is provided closer to a location midway between peak  128  and trough  132 , the adjacent struts  124  may bend around the bump  140  when the stent is crimped. This phenomenon will not occur when the bump is positioned closer to the distal end of the connector. Nevertheless, in other embodiments of the invention, as shown below, the bump may be provided at other locations as well. 
     In some embodiments, when stent  100  is loaded on the catheter  104 , bump  140  contacts adjacent struts  124 . An angle between each pair of interconnected struts that is not associated with a connector is constant. In at least one embodiment, the struts of each pair of struts are in a substantially parallel configuration. 
     In some embodiments, when the stent  100  is deployed, as shown in  FIG. 4B , the angle between each pair of interconnected struts that is not associated with a connector is constant. The stent  100  deploys evenly. 
       FIG. 5  shows a partial view of another embodiment of the invention in which the bump or bump  140   a,    140   b  is provided along a connector  136  approximately midway between a peak and trough. Two serpentine bands  120  are shown in the embodiment of  FIG. 5 . The stent may include additional serpentine bands beyond the two shown in  FIG. 5 . The serpentine bands are interconnected by two connectors  136 . Each connector  136  has at least one bump or bump  140  on a side of the connector. In the embodiment shown in  FIG. 5 , the bump or bump  140  has a trapezoidal shape with an outermost surface  141  of the bump being a flat surface. In the contracted (or loaded) state, bump  140  (particularly sidewall surface  141 ) abuts an adjacent strut  124  and is flush with the adjacent strut  124 . While  FIG. 5  shows a gap between bump  140 , desirably at least a portion of the bump  140  will contact the adjacent strut in the contracted state. In at least one embodiment, the entire sidewall surface  141  contacts the adjacent strut. The trapezoidal shape of the bump  140  shown in  FIG. 5  also allows for easy measurement of the width of the bump  140 . While  FIG. 5  shows the bump  140  having a trapezoidal shape, it is within the scope of the invention for the bumps  140  to have other configurations. 
       FIG. 6  shows a partial view of another embodiment of the invention in which bumps  142  are provided along struts  124   a  of a serpentine band in addition to bumps  140   a  and  140   b  along sides  136   a  and  136   b  of connectors  136 . The serpentine bands may also include struts  124   b  with bumps. 
     Desirably, as shown in  FIG. 6 , the bumps are provided approximately midway between a peak  128  and trough  132 . The connectors  136  between the adjacent serpentine bands  120  are shown extending axially relative to the longitudinal axis of the stent. It is within the scope of the invention for the connectors to be parallel to the longitudinal axis and/or for the connectors to include curvature. The stent may include additional serpentine  120  bands beyond the two shown in the figure. 
     In the serpentine bands  120  shown in  FIG. 6 , every other strut  124  includes a bump  142 . Thus, the serpentine band has an alternating pattern of straight struts including bumps (struts  124   a ) and straight struts lacking bumps (struts  124   b ). The serpentine band may include additional bumps. For example, each strut  124  may include a bump. Also, fewer struts may include bumps. For example, every third, fourth, fifth or sixth strut may include such a bump. 
     Where one or more struts of a serpentine band are provided with a bump, the connector connecting the serpentine band to an adjacent serpentine band may have a bump, as shown in  FIG. 6  or may lack a bump. Where the connector  136  is provided with a bump  140  and an adjacent strut  124  has a bump  142 , as shown in  FIG. 6 , bump  140  is slightly offset from bump  142 . It is within the scope of the invention for the bumps on the connector to be aligned with the bumps on the adjacent strut. 
     While  FIG. 6  shows a slight gap between bump  140   a,    140   b  and an adjacent strut  124  and a slight gap between bump  142  and an adjacent strut  124 , desirably at least a portion of the bumps  140 ,  142  abut the surface of the adjacent strut  124  in the contracted state. In at least one embodiment, the entire surface of the bump  140 ,  142  abuts the surface of the adjacent strut  124  in the contracted state. 
       FIG. 7  shows a partial view of another embodiment of the invention in which bumps  142  are provided only along some of the struts of the serpentine bands, and connectors  136  do not have bumps. As shown in  FIG. 7 , the bumps  142  are provided along the struts  124  approximately midway between a peak  128  and a trough  132 . Every other strut is provided with a bump. In the embodiment shown in  FIG. 7 , connectors  136  connect a peak  128  of a first serpentine band  120  with a longitudinally and circumferentially offset trough  132  of an adjacent serpentine band  120 . Connectors  136  extend at an oblique angle relative to the longitudinal axis of the stent. The stent may include additional serpentine bands beyond the two shown in the figure. The serpentine bands may be arranged such that the connectors extend between longitudinally aligned peaks and troughs. The connectors may be straight or may include curvature. 
     While  FIG. 7  shows a slight gap between each bump  142  and an adjacent strut  124 , desirably at least a portion of the bumps abut the surface of the adjacent strut in the contracted state. In at least one embodiment, the entire surface of the bump abuts the surface of the adjacent strut in the contracted state. 
       FIG. 8  shows a partial view of another embodiment of the invention, which has bump extensions between radiopaque marker housings at an end of the stent. At a first end  160  of the stent of this embodiment is first region  162 , which is connected to a second region  164 . 
     First region  162  comprises at least one serpentine band  165  (two serpentine bands are shown in  FIG. 8 ) having a plurality of interconnected strut pairs. Each strut pair has a first strut and a second strut adjacent the first strut. The first strut is connected to the second strut to form a peak  165   a  and a first strut pair is connected to a second strut pair to form a trough  165   b.  A serpentine band  165  is connected to an adjacent serpentine band  165  by a connector  166 . In some embodiments, the serpentine band  165  is connected to an adjacent serpentine band  165  by a connector  166  at trough  165   b.    
     At an end  160  of first region  162  are a plurality of radiopaque markers  168 . Each radiopaque marker  168  is attached to a peak  165   a  of the endmost serpentine band  165  and extends from the peak towards the end  160  of the stent. A bump extension  170  extends from each of a plurality of peaks  165   a  which are not associated with a radiopaque marker  168 . The bump extension  170  also extends from the peak towards the end  160  of the stent. In at least the embodiment shown, the bump extensions  170  are between radiopaque markers  168  along the circumference of the stent. 
     In at least the embodiment shown in  FIG. 8 , the bump portion  172  has a trapezoidal shape with a stub  174  protruding from the bump portion. A member  176  joins the bump portion  172  to the peak  165   a.  In other embodiments, the bump extension  170  can have a circular shape, does not have a stub, and may have other configurations. Using these bump extension  170  around radiopaque marker housings  168  ensures equal spacing of the markers  168  and provides extra strength or rigidity to the end of the stent when the stent is deployed. 
     Second region  164  of the embodiment shown in  FIG. 8  has a plurality of serpentine bands  120  as previously described herein. Each serpentine band is connected to an adjacent serpentine band in the second region  164  with a plurality of connectors  136  having bumps  140 . Second region  164  is connected to first region  162  by connectors  166 . In at least one embodiment connector  166  connects a trough  165   b  of the first region  162  with a confronting peak of an adjacent serpentine band  120  of the second region  164 . While in the embodiment shown in  FIG. 8 , the serpentine bands of the first region  162  are not the same as the serpentine bands of the second region  164 , it is within the scope of this invention that the serpentine bands of first region  162  are the same as the serpentine bands  120  the second region  164 . In some embodiments, the serpentine bands  165  of the first region  162  may also be connected to one another by connectors similar to connectors  136 . In some embodiments, these connectors can also have bumps similar to bumps  140 . 
     In some embodiments of the invention, the stent, or portion thereof, may be provided with a substance. The substance may be a coating or a portion of the stent constructed and arranged to deliver the substance to a location in a body lumen. The substance may be a drug, genetic material, cells, a non-genetic therapeutic agent, a polymer matrix having a therapeutic component or any other substance which it would desirable to deliver into a body lumen. In some embodiments the substance  18  may be a coating of SIBS (styrene isobutylene styrene); polycarboxylic acids; cellulosic polymers, including cellulose acetate and cellulose nitrate; gelatin, polyvinylpyrrolidone; cross-linked polyvinylpyrrolidone; polyanhydrides including maleic anhydride polymers; polyamides; polyvinyl alcohols; copolymers of vinyl monomers such as EVA; polyvinyl ethers; polyvinyl aromatics; polyethylene oxides; glycosaminoglycans; polysaccharides; polyesters including polyethylene terephthalate; polyacrylamides; polyethers; polyether sulfone; polycarbonate; polyalkylenes including polypropylene, polyethylene and high molecular weight polyethylene; halogenated polyalkylenes including polytetrafluoroethylene; polyurethanes; polyorthoesters; proteins; polypeptides; silicones; siloxane polymers; polylactic acid; polyglycolic acid; polycaprolactone; polyhydroxybutyrate valerate and blends and copolymers thereof; PLGA, coatings from polymer dispersions such as polyurethane dispersions (BAYHDROL.RTM., etc.); fibrin; collagen and derivatives thereof; polysaccharides such as celluloses, starches, dextrans, alginates and derivatives; hyaluronic acid; squalene emulsions; polyacrylic acid, available as HYDROPLUS™ from Boston Scientific Corporation, Natick, Mass., and described in U.S. Pat. No. 5,091,205, the entire contents of which are hereby incorporated herein by reference. 
     The substance may be disposed on any of the surfaces of the stent or within holes in the stent surface using any known technique for doing so. The bumps may be placed in any manner along a given connector or connectors and/or along any strut or struts. The individual bumps may be provided with a wide range of shapes, sizes, configurations, and compositions. Desirably, the side of the bump facing the adjacent strut (or connector) will have a shape which is complementary to that of the adjacent strut. 
     Bumps  140 ,  142  and bump extensions  170  may be constructed from any material desired and, desirably, of a biocompatible material or materials. Where the bump includes a non-biocompatible material in its construction, the bump preferably includes a biocompatible coating. More desirably, the bumper is constructed out of the same material as the connector or strut which the bump extends from. The bump may be an inherent part of the connector or strut, being merely a bump of connector or strut material, or it may be a separate component which is welded, adhered, or otherwise engaged to the connector or strut. 
     Depending on the flexibility of the stent as well as of the catheter, the bump in the various embodiments of the present invention may be provided with a wide range of heights or thicknesses relative to the connector or strut from which the bump extends. The bump may extend from about 0.0002 inches to about 0.015 inches from a given connector or strut. Preferably, the bump extends from a connector or strut by about 0.0002 to about 0.015 inches. In general, for a stent whose struts are from 0.002 inches to about 0.006 inches wide and connectors are from 0.002 inches to about 0.006 inches wide, the bump width will be approximately from 0.002 inches to about 0.006 inches wide. In other words, in at least one embodiment, the strut width will be the same as the connector width, and the connector width will be the same as the bump width. 
     The invention is also directed to a medical device delivery system here comprising a catheter and any the inventive stents disclosed herein. Where the stent is balloon expandable, the system will typically comprise a balloon catheter and a balloon expandable stent, as disclosed herein, disposed about the balloon catheter. In the case of a self-expanding stent, the system will typically include a catheter about which the self-expanding stent is disposed as well as a retractable sheath or cover disposed over the stent. Portions of the catheter may include any of the coatings disclosed herein. 
     The invention is also directed to a stent delivery system comprising a delivery catheter and a stent disposed about the delivery catheter and deployed therefrom. The stent comprises a plurality of serpentine bands including a first serpentine band and a second serpentine band. Each serpentine band comprises a plurality of interconnected struts forming peaks and troughs. Adjacent serpentine bands are interconnected by one or more connectors. The first and second serpentine bands are connected via at least one connector. The connector has a first side facing one the struts and a second side facing another of the struts. The connector extends from an inside of a trough of the first serpentine bands to the outside of a trough of the other of the serpentine bands. The connector has a first bump extending from the first side and a second bump extending from the second side opposite the first. The first bump is located adjacent a first peak and the second bump located adjacent a second peak. The first bump contacts a first strut and the second bump contacts a second strut. 
     The angle between each pair of interconnected struts that is not associated with a connector may be constant. The stent may be configured such that when the stent is deployed, the angle between each pair of interconnected struts that is not associated with a connector is also constant. Typically, at least the first bump of the connector will be located towards an end of the connector. 
       FIG. 9  shows a flat view of an embodiment of the present invention. As shown, the stent comprises a plurality of serpentine bands  120 , each serpentine band  120  having alternating peaks  128  and troughs  132  connected by struts  124 . The struts  124  are shown as straight struts in the embodiment, but other configurations are within the scope of the invention. Two of said serpentine bands are connected one to the other via straight connectors  136  which extend parallel to the longitudinal axis. Each connector  136  extends from a trough  132  of one serpentine band to a trough  132  of an adjacent serpentine band. Each straight connector has a first side  136   a  and a second side  136   b  that each extend from an outer wall surface  178  of the stent to an inner wall surface of the stent (not shown), forming the wall thickness of the stent. Each connector  136  has a bumped out region  180  of greater width than the remainder of the connector  136 , the first and second sides  136   a,    136   b  each having a bump  140  thereon in the bumped out region  180  of the connector  136 . The bumped out region is located between two circumferentially adjacent peaks  128  and one end of the bumped out region  140  is substantially aligned with the two circumferentially adjacent peaks  128 . 
     The stent in  FIG. 9  also has a pair of serpentine bands  181  at both the proximal end  104  and the distal end  105  of the stent. Each serpentine band  181  comprises a plurality of struts  182  forming alternating peaks  184  and troughs  186 . For the purposes of this disclosure, peaks  184  are defined to be located at a distal end  105  of serpentine band  120 , while troughs  186  are defined to be located at a proximal end  106  of a serpentine band  120 . The serpentine bands  181  are connected to each other where a peak  184  of the first serpentine band  181  confronts a trough  186  of the adjacent serpentine band  181 . In at least the embodiment shown, the first serpentine band  181  is connected to the adjacent serpentine band  181  at every peak  184  of the first serpentine band  181 . In the embodiment shown, serpentine band  181  is connected to some of the troughs  132  of an adjacent serpentine band  120 , but never at any of the troughs that are connected to connectors  136 . Other configurations are within the scope of the invention. 
     The embodiment shown in  FIG. 9  is for a stent having an outer diameter of 0.196 inches (5 mm) and is sized to fit within a 6 French catheter. 
     In this embodiment, each serpentine band  120  has twenty-four struts  124 . Each strut width is between about 0.0028 inches and 0.0052 inches. The width of each connector  136  is between about 0.0029 inches and 0.0053 inches. Each bumped out region  140  is between about 0.0104 inches and 0.0128 inches wide. The wall thickness of the stent between the outer surface and the inner surface is between about 0.0061 inches and 0.0091 inches. In a particular embodiment, the strut width is about 0.0040 inches, the connector width is about 0.0041 in, the bumped out region is 0.0116 inches wide, and the wall thickness is 0.0076 inches. 
     In some embodiments, each serpentine band  120  has at least two evenly spaced connectors  136 . In the embodiment shown in  FIG. 9 , each serpentine band  120  has three evenly spaced connectors  136 . 
     When the stent of  FIG. 9  is crimped, the struts  124  are parallel and the struts  124  touch the bumps  140 . The stent of  FIG. 9  may in some embodiments be self-expanding. The configuration of the bumps  140  on the connectors  136  allows the stent to expand more evenly from the crimped condition to the expanded condition. 
     In addition to being directed to the specific combinations of features claimed below, the invention is also directed to embodiments having other combinations of the dependent features claimed below and other combinations of the features described above. 
     In at least one embodiment, an endoprosthesis is self-expanding and comprises a plurality of serpentine bands, each band comprising a plurality of struts interconnected by peaks and troughs; and a plurality of connectors extending between and connecting adjacent serpentine bands, each connector having a first bump extending from a first side toward an end of an adjacent strut and a second bump extending from a second side toward an end of another adjacent strut. The first and second bumps each have a width which is approximately equal to the separation between the connector and the adjacent strut when the endoprosthesis is in a crimped state. In one embodiment, the endoprosthesis is a stent. The struts can be straight. At least one of the bumps has either a flat edge facing an adjacent strut and extending parallel to the connector or a curved edge extending non-parallel to the connector. In at least one embodiment, each connector extends from a trough on one serpentine band to a trough on an adjacent serpentine band. 
     In at least one embodiment, a stent delivery system is provided. The stent delivery system comprises a delivery catheter and a stent disposed about the delivery catheter and deployed therefrom. The stent comprises a plurality of serpentine bands including a first serpentine band and a second serpentine band, each serpentine band comprising a plurality of interconnected struts forming peaks and troughs, adjacent serpentine bands interconnected by one or more connectors, the first and second serpentine bands connected via at least one connector, the connector having a first side facing one the struts and a second side facing another of the struts, the connector extending from an inside of a trough of the first serpentine band to the outside of a trough of the second serpentine band, wherein the connector has a first bump extending from the first side and a second bump extending from the second side opposite the first, the first bump located adjacent a first peak and the second bump located adjacent a second peak, wherein the first bump contacts a first strut and the second bump contacts a second strut. In at least one embodiment, an angle between each pair of interconnected struts that is not associated with a connector is constant. In at least one embodiment, the stent is configured such that when the stent is deployed, the angle between each pair of interconnected struts that is not associated with a connector is constant. In at least one embodiment, the first bump of the connector is located towards an end of the connector. 
     In at least one embodiment, an endoprosthesis comprises a first region at a first end of the endoprosthesis, the first region comprising: one serpentine band comprising a plurality of interconnected strut pairs, each strut pair having a first strut and a second strut adjacent the first strut, the first strut connected to the second strut to form a peak, a first strut pair connected to a second strut pair to form a trough, and a plurality of extensions extending axially from peaks of the serpentine band towards the first end, wherein a first extension and a second extension comprise radiopaque markers and wherein extensions circumferentially between the first extension and the second extension comprise bumps. 
     In at least one embodiment, a self-expanding endoprosthesis comprises a plurality of serpentine bands, each band comprising a plurality of interconnected strut pairs, each strut pair having a first strut and a second strut adjacent the first strut, the first strut connected to the second strut to form a peak, a first strut pair connected to a second strut pair to form a trough, wherein each first strut has a bump extending from a first side of the first strut toward a second side of the second strut, wherein the bump has a width which is approximately equal to a distance between the first strut and the second strut; and at least one connector extending between and connecting adjacent serpentine bands. In at least one embodiment, the endoprosthesis is in the form of a stent. In at least one embodiment, the first and second struts of each strut pair are straight and the bump has a flat edge facing the second side of the second strut, the flat edge extending parallel to the second strut. In another embodiment, the struts are straight and each bump has a curved edge extending non-parallel to the second strut. In at least one embodiment, the endoprosthesis comprises a plurality of said connectors, wherein each connector extends from a peak on one serpentine band to a trough of an adjacent serpentine band. In at least one embodiment the peak is circumferentially and longitudinally offset from the trough. 
     The above disclosure is intended to be illustrative and not exhaustive. This 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 claims where the term “comprising” means “including, but not limited to”. 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. 
     Further, the particular features presented in the dependent claims can be combined with each other in other manners within the scope of the invention such that the invention should be recognized as also specifically directed to other embodiments having any other possible combination of the features of the dependent claims. For instance, for purposes of claim publication, any dependent claim which follows should be taken as alternatively written in a multiple dependent form from all prior claims which possess all antecedents referenced in such dependent claim if such multiple dependent format is an accepted format within the jurisdiction (e.g. each claim depending directly from claim  1  should be alternatively taken as depending from all previous claims). In jurisdictions where multiple dependent claim formats are restricted, the following dependent claims should each be also taken as alternatively written in each singly dependent claim format which creates a dependency from a prior antecedent-possessing claim other than the specific claim listed in such dependent claim below.