Abstract:
A stent is described and comprises an elongate strut having a first end and a second end, an aperture formed in the strut, and a barb having a base and a distal anchor. The barb base is attached to the strut and the barb extends distally from the base through the aperture. Other devices, systems, and methods are described.

Description:
RELATED APPLICATIONS 
       [0001]    This patent document claims the benefit of the filing date under 35 U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No. 60/956,534, filed Aug. 17, 2007 which is herein incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to medical devices and, in particular, to prostheses for placement in a body lumen. 
         [0004]    2. Description of Related Art 
         [0005]    The functional vessels of human and animal bodies such as the esophagus, bile duct, and blood vessels occasionally become damaged or diseased. For example, the aortic wall can weaken, resulting in an aneurysm. Upon further exposure to haemodynamic forces, an aneurysm can rupture. 
         [0006]    Intraluminal prostheses, such as stents and stent grafts, may be used for treating damaged or diseased functional vessels. For example, a stent graft may be used for repairing abdominal and thoracic aortic aneurysms. Such a stent graft is placed inside the vessel and provides some or all of the functionality of the original, healthy vessel. 
         [0007]    One of the challenges of designing and using an intraluminal prosthesis is preventing migration of the prosthesis once it is placed in a body lumen. This challenge is particularly great when the environment in which the prosthesis is placed is subject to a continuous strain, such as by the pulsatile force of blood flow in the vasculature. When an intraluminal prosthesis is used, for example, to repair an aneurysm, migration of the device may result in inadequate exclusion of the aneurysm, and increased risk of aneurysm rupture. 
         [0008]    Various devices have been proposed to address migration. For example, a prosthesis may comprise one or more barbs or hooks that extend outwardly from the prosthesis and are configured to engage surrounding body tissue. Typically, such barbs or hooks may be attached to the prosthesis, for example, by sewing, gluing, wrapping, chemical bonding, welding, brazing, soldering, and the like. 
         [0009]    Although each of these attachment methods may create a strong bond between the barb and the prosthesis, these bonds have been known to break when the device is placed in situ. One possible explanation is that the attachment is particularly prone to the mechanical and chemical hazards of the intraluminal environment. For example, cardiovascular pulsatile forces may be concentrated at the junction between the barb and the stent, which may also be the site of a weld, solder, or the like. In addition, the saline, oxygen-rich, and acidic physiological environment of the body may tend to weaken and corrode the stent-barb attachment. 
         [0010]    One solution to address barb detachment was disclosed in U.S. Pat. No. 5,720,776 to Chuter et al. The barb includes both a mechanical attachment, as well as the traditional solder bond. The mechanical attachment comprises a helical winding of the base of the barb around a strut of the stent. This mechanical attachment supplements the traditional solder bond to help protect the solder joint from breaking. In addition, the barb is made laterally flexible to help accommodate forces acting at the anchor point. These improvements help ensure that the barb does not readily separate from the stent due to a failure of the solder joint alone. While the combination of both solder and a mechanical means to affix the barb to the stent has proved effective in most respects, this area of the barb remains most subject to stresses, such as from cyclic load resulting from the pulsatile action of the implant vessel. 
       SUMMARY 
       [0011]    Various devices, systems, and methods are disclosed throughout the specification and in the drawings. In one example, a stent may be provided and comprise an elongate strut having a first end and a second end, an aperture formed in the strut, and a barb having a base and a distal anchor. The barb base is attached to the strut and the barb extends distally from the base through the aperture. 
         [0012]    The aperture may be formed at a strut end or between the first and second ends of the strut. In examples where the stent comprises a first strut and a second strut joined at an apex, the aperture may be formed in the apex. 
         [0013]    The aperture may comprise any suitable configuration or structure. In one example, the aperture comprises a winding. In another example, the aperture is forged in the strut. The aperture may define a cavity having any suitable contour. For example, the aperture may comprise a generally cylindrical cavity or a generally frustoconical cavity. Other shapes and contours are contemplated and are within the scope of the present invention. The cavity may extend at an oblique angle or at a generally transverse angle with respect to a longitudinal axis of the strut. 
         [0014]    In some examples, the barb base may have a diameter that is less than or equal to the diameter of the aperture. In other examples, the barb base may have a diameter that is greater than a diameter of the aperture. In these cases, it may not be possible to pass the barb base through the aperture. The barb base may be attached to the strut so that it is spaced apart from the aperture along the strut. Alternatively, the barb base may be disposed adjacent the aperture or at least partially within the aperture. 
         [0015]    The aperture may have any dimension that is suitable for the particular application. For example, the aperture may have an inner diameter that is less than or equal to 0.030 inches, less than or equal to 0.020 inches, or less than or equal to 0.010 inches. 
         [0016]    In another example, a stent may be provided and comprise an elongate strut having a first end and a second end, and a barb having a base and a distal anchor, where the barb base is attached to the strut. The barb base may extend distally from the base and pass through the strut. The stent may comprise one or more additional features as described above. 
         [0017]    In another example, a method of attaching a barb to a stent strut comprises the steps of forming an aperture in a strut, passing a barb through the aperture, and fixing the barb to the strut so that at least a portion of the barb is disposed within the aperture. Additional features may be provided as described throughout the specification and figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a side schematic view of an intraluminal prosthesis comprising a stent and a barb; 
           [0019]      FIG. 2  is a schematic view of a zigzag stent comprising multiple barbs; 
           [0020]      FIGS. 3A-3E  are schematic views of portions of stents and depict apertures of various configurations; 
           [0021]      FIGS. 4A-4C  are side schematic views of various intraluminal prostheses comprising a stent and a barb; 
           [0022]      FIGS. 5A and 5B  are side and front perspective views, respectively, of another intraluminal prosthesis comprising a stent and a barb; and 
           [0023]      FIG. 6  is a side perspective view of another intraluminal prosthesis comprising a stent and a barb. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]    Throughout the specification, when referring to a barb or a portion thereof, the terms “distal” and “distally” shall denote a position, direction, or orientation along the barb that is generally towards or in the direction of the anchor, whereas the terms “proximal” and “proximally” shall denote a position, direction, or orientation along the barb that is generally away from or in the opposite direction of the anchor. 
         [0025]    The term “prosthesis” means any device, object, or structure that supports, repairs, or replaces, or is configured to support, repair, or replace a body part or a function of that body part. It can also mean a device that enhances or adds functionality to a physiological system. 
         [0026]    The term “stent” means any device or structure that provides or is configured to provide rigidity, expansion force, or support to a body part, for example, a diseased, damaged, or otherwise compromised body lumen. A stent may comprise any suitable material, including, but not limited to, biocompatible metals and plastics. Examples of suitable materials include metals such as stainless steel and NITINOL, and plastics such as polyethylene terephthalate (“PET”), polytetrafluoroethylene (“PTFE”) and polyurethane. 
         [0027]    A stent may be “expandable,” that is, it may be capable of being expanded to a larger-dimension configuration. A stent may be self-expanding and expand by virtue of its own resilience, pressure-expandable and expand only upon the application of an external force, or may have both self-expanding and pressure-expandable features. In one example, a stent may have one or more self-expanding portions and one or more balloon-expandable portions. An example of a suitable self-expanding stent includes Z-STENTS®, which are available from Cook Incorporated, Bloomington, Ind., USA. 
         [0028]    The term “lumen” describes a cavity or channel within a tube or a tubular body, such as vessel. The term “intraluminal” means within a lumen, and can refer to objects that are found or that can be placed within a lumen, or methods or processes that occur within a lumen. An “intraluminal prosthesis” is thus a prosthesis that is found or that can be placed within a lumen. Examples of intraluminal prostheses include, but are not limited to, stents, grafts, stent grafts, venous or aortal valves, and vena cava filters. An intraluminal prosthesis may be generally tubular and comprise one or more lumens. Examples of tubular prostheses include straight, branched, and bifurcated prostheses. 
         [0029]      FIG. 1  depicts an intraluminal prosthesis comprising a stent  10  and at least one barb  12 . The barb  12  comprises a base  18 , a distal anchor  20 , and a body  22  extending along the barb between the base  18  and the anchor  20 . The barb  12  may attach to the prosthesis via the base  18 . The anchor  20  is configured to extend outwardly from the prosthesis so that, in use, it may engage tissue and prevent movement between the prosthesis and the vessel in which the prosthesis is placed. 
         [0030]    The barb may comprise a suitable biocompatible material, such as a biocompatible metal or plastic. Suitable biocompatible materials include the stent materials described above. Where the stent comprises a metal, the barb  12  and the stent  10  may comprise the same or a similar material. For example, the materials may have similar electromotive forces. Such a construction may minimize corrosion at the junction between the barb and the stent. 
         [0031]    As shown in  FIGS. 1 and 2 , the anchor  20  may extend outwardly from the prosthesis and may be disposed at an angle relative to an axis A of the stent  10 . As shown in  FIG. 1 , the anchor  20  may extend at an angle of approximately 90° to the stent axis A. Alternatively, as shown in  FIG. 2 , the anchor  20  may extend at an oblique angle, or at an angle that is less than or greater than 90° to the stent axis A. 
         [0032]    The stent  10  may comprise at least one strut  14 . For example, the stent  10  may comprise a plurality of struts  14  that are arranged in a pattern, such as the alternating zig-zag pattern depicted in  FIG. 2 . In this example, the struts  14  are joined by one or more apices  16  that define alternating “peaks” and “valleys.” 
         [0033]    A barb may be secured to a prosthesis by any suitable means known in the art. As shown in  FIGS. 1 and 2 , the barb  12  may attach to the stent  10  via a fixing element  24 , such as a weld, solder, adhesive, or the like. Additionally, or alternatively, a barb  12  may attach to a stent by crimping, wrapping, or otherwise mechanically securing the barb around a strut  14 . If the prosthesis includes a graft, the barb  12  may additionally or alternatively attach to the graft, for example by suturing, gluing, interweaving, or the like. 
         [0034]    As shown in various examples depicted throughout the specification and in the figures, a barb may be secured to a prosthesis by fitting the barb through a hole or aperture in the strut.  FIG. 1  depicts a stent  10  comprising a strut  14  and an aperture  30  formed in the strut. At least a portion of the barb  12  is disposed within a cavity defined by the aperture  30 . The barb  12  may engage the cavity and, in some examples, this engagement may be sufficient to form an attachment between the barb  12  and the strut  14 . A fixing element  24 , such as a weld, may optionally be provided to further secure the barb  12  to the strut  14 . In the event that the fixing element  24  weakens, or is otherwise compromised, the aperture  30  may retain the barb  12  and prevent the barb  12  from detaching from the strut  14 . Further, external forces that may contribute to or cause breakage of the barb at a point of attachment to the stent  10  are transferred to the aperture, thus reducing the possibility of fracture at the point of attachment. 
         [0035]    In the example shown in  FIG. 1 , the barb  12  is attached to the inner radial surface of the stent  10  via fixing element  24 , the barb body  22  extends distally from the base  18  through the aperture  30 , and the anchor  12  extends radially outwardly from the outer radial surface of the stent  10 . When a force is applied to the anchor  20 , a resulting stress will be transmitted towards and focused at the barb-stent junction  25  at the outer radial surface of the stent  10 . Because the weld  24  is spaced apart from the barb-stent junction  25 , unlike in the prior art where the weld is disposed at the barb-stent junction, the force will not be focused at the weld. Accordingly, the weld may be less susceptible to weakening during use. 
         [0036]    The weld  24  may be spaced apart from the barb-stent junction  25  by a distance that is approximately equal to the distance between opposing openings of the aperture. Alternatively, the weld  24  may be spaced apart from the junction  25  by a greater distance. For example, the weld  24  may be disposed along the strut  14  and spaced from the aperture  30  along a longitudinal axis of the stent. 
         [0037]    The aperture  30  has an inner dimension that may be equal to or greater than a corresponding outer dimension of the barb portion that is disposed within the aperture. In one example, the barb  12  may have a diameter of 0.020 inches, and the aperture  30  may have an inner diameter that is 0.020 inches or greater. In another example, the barb  12  may have a diameter of 0.010 inches, and the aperture  30  may have an inner diameter that is 0.010 inches or greater. In other examples, the aperture  30  may have an inner diameter that is less than or equal to 0.030 inches, less than or equal to 0.020 inches, or less than or equal to 0.010 inches. 
         [0038]    As used herein, the term “diameter” refers generally to an inner or outer radial dimension of an aperture or barb, respectively. The use of the term is not limited to barbs and/or apertures having a circular cross-section and includes barbs and/or apertures having non-circular cross-sections (for example, elliptical and polygonal cross-sections). 
         [0039]    The aperture  30  may have an inner contour that corresponds with or conforms to an outer contour of the barb  12 . For example, the aperture  30  may have an inner diameter that is generally equal to, or not substantially greater than, an outer diameter of the barb  12 . Accordingly, the barb  12  may frictionally and/or mechanically engage the stent  10  within the aperture  30 . One advantage of this feature is that it may increase the area of surface contact between the stent  10  and the barb  12 , and increase the bond between the stent and the barb. In some examples, the barb  12  may be attached to the stent  10  via a fixing element  24 , such as a weld. In other examples, the engagement between the stent  10  and the barb  12  within the aperture  30  may be sufficient so that a fixing element is not necessary. 
         [0040]      FIG. 2  depicts a stent  10  that comprises a plurality of barbs  12 , each having an anchor  20  that extends outwardly at an oblique angle to the stent axis A. The barbs  12  may be retractable and have a retracted configuration and an extended configuration. In the extended configuration (shown in  FIG. 2 ), the anchors  20  extend outwardly from the prosthesis at an angle that allows the anchors  20  to engage a surrounding vessel. For example, the anchors  20  may be disposed at an angle of about 20-50° with respect to the axis A. In the retracted configuration, the anchors  20  extend at an angle that limits or prevents the anchors from engaging a surrounding vessel. For example, the barbs  12  may be disposed at an angle of about 0-20° with respect to the axis A. As in  FIG. 1 , each of the barbs  12  may pass through the stent  10 . 
         [0041]      FIGS. 3A-3E  depict additional exemplary stents  110 . The stents  110  comprise at least two struts  114  joined by at least one apex  116 . In each of the figures, an aperture  130  is shown and is formed in at least one of the struts  114 . Each aperture  130  defines a cavity or passageway  136  having a length. In  FIG. 3A , the aperture  130  is provided at a medial location along the length of the strut  114 . The aperture  130  may be provided, for example, by drilling, machining, or otherwise removing material from the stent  110 . Examples of such processes include laser drilling, electrochemical erosion, and electrical discharge machining (“EDM”). Alternatively, the aperture  130  could be bent, molded, or forged in the stent  110 . Such an aperture  130  may occupy a volume and constitute a void within the strut  114 , and accordingly, the size of the aperture  130  may be limited by the dimensions of the strut. In general, as the size of the aperture  130  increases in relation to the size of the strut  114 , the stent may become weaker and more susceptible to wear. Accordingly, larger apertures  130  may be provided, simply by increasing the overall thickness of the strut  114 . 
         [0042]    As shown in  FIG. 3B , a strut  114  may be provided having a generally uniform outer contour over a majority of its length and a region of increased thickness corresponding with the location of the aperture  130 . Thus, in the example shown in  FIG. 3B , the majority of the strut  114  may have a relatively low thickness so that the overall stiffness of the stent is not adversely affected. The aperture  130  may be provided, for example, by any of the means described above. 
         [0043]    In  FIG. 3C , an aperture  130  is provided and comprises a winding  134 . The winding  134  may be provided, for example, by bending or plastically deforming the wire comprising the strut  114 .  FIG. 3D  depicts an aperture  130  that is disposed at an apex  116  of the stent  110 . The aperture  130  may be provided by any of the means previously described. 
         [0044]    In  FIG. 3E , the stent  110  comprises a plate  140  that is affixed to a strut  114 . In one example, the strut  114  may comprise two wire ends and the plate  140  may comprise a cannula sleeve that covers the wire ends to form the strut  114 . The plate  140  has an outer dimension that is generally greater than the corresponding outer dimension of the strut  114 . The aperture  130  is formed in the plate  140 . The aperture  130  may be provided by any of the means previously described. 
         [0045]      FIGS. 4A-4C  illustrate additional exemplary stents, each comprising at least one strut  214  having an aperture  230 . In each example, a barb  212  is provided and comprises a base  218 , a distal anchor  220 , and a barb body  222  extending therebetween. At least a portion of the barb  212  is disposed within the aperture  230  and at least the anchor  220  extends from the aperture  230  and away from the strut  214 . 
         [0046]    In  FIG. 4A , the aperture  230  forms a passageway or cavity  236  that extends through the strut  214  at a generally transverse angle with respect to the axis A of the strut  214 . The portion of the barb  212  that is disposed within the cavity  230  has an outer contour that corresponds with the contour of the cavity  236 . For example, the barb  212  may have a diameter that is equal to or slightly smaller than the diameter of the cavity  236 . The barb base  218  may have a diameter that is larger than the diameter of the cavity  236 . This may prevent the base  218  from sliding distally through the aperture  230  and may increase the total area of surface contact between the stent  210  and the barb  212 . The barb  212  may be further secured to the strut  214 , for example, by a weld (not shown). The anchor  220  extends distally from the stent  210  at an oblique angle with respect to the axis A of the strut  214 . Accordingly, a bend  240  may be provided in the barb body  222  to orient the anchor  220  at the oblique angle. 
         [0047]    In  FIG. 4B , the strut  214  comprises an aperture  230  having a cavity  236  that extends through the stent at a generally oblique angle with respect to the axis A of the strut  214 . A barb  212  is provided and passes through the aperture  230 . The barb  212  may have an outer contour that corresponds with the inner contour of the cavity  236 , as described above. The anchor  220  extends distally from the stent  210  at an oblique angle with respect to the strut axis A. In the example shown in  FIG. 4B , the cavity  236  is aligned so that a bend may not be required to properly orient the anchor  220 . 
         [0048]    In the examples depicted in  FIGS. 4A and 4B , the aperture  230  comprises a cavity  236  with a generally cylindrical inner contour. In other examples, the cavity  236  may have a non-cylindrical inner contour. For example, in  FIG. 4C , the cavity  230  comprises a generally frustoconical inner contour. 
         [0049]    The cavity  236  may have an inner contour that conforms to an outer contour of the barb  212  at a point of engagement. For example, in  FIG. 4C , the cavity  236  conforms to a generally frustoconical outer contour of the barb  212 . In this example, the barb base  218  has a diameter that is less than, or equal to, the corresponding diameter of the cavity  236 . When the barb  212  is placed within the aperture  220 , the frustoconical base  218  may engage the frustoconical cavity  236  to limit movement between the barb  212  and the stent  210 . The frustoconical contours provide a greater area of surface contact than a cylindrical contour, thus increasing the integrity and strength of the attachment between the stent  210  and the barb  212 . 
         [0050]      FIGS. 5A and 5B  depict another exemplary intraluminal prosthesis. A stent  310  comprises at least one strut  314  and a barb  312  passing through an aperture  330  in the strut  314 . At least a portion of the barb  312  is disposed within the aperture  330  and at least the anchor (not shown) extends from the aperture  330  and away from the strut  314 . 
         [0051]    In these examples, an attachment structure  350  is provided for attaching the barb  312  to the strut  314 . As shown in  FIGS. 5A and 5B , the attachment structure  350  may comprise a cannula  358  that extends at least partially about the strut  314 . The cannula  358  may extend more than 90° about the strut  314  so that the attachment structure  350  may attach to the strut  314  by crimping or “snapping” the cannula  358  to the strut. In some examples, this attachment may be sufficient such that a fixing element, such as a weld, may not be necessary. In other examples, a fixing element (not shown) may be provided in addition to the attachment structure  350 . The cannula  358  may comprise one or more fenestrations  354  for providing an increased bonding area for gluing, soldering, or welding the cannula  358  to the strut  314 . In some examples, the cannula  358  may comprise a winding, such as a barb winding, that extends at least partially about the strut  314 . 
         [0052]    The attachment structure  350  may be integrally formed with the barb  312 . In these examples, the barb  312  and the attachment structure  350  may comprise a unitary or monolithic structure. In other examples, the attachment structure  350  may be provided as a separate structure from the barb  312 . For example, a stent  210  and a barb  212  may be provided, as shown in  FIGS. 4A-4C . After the barb  212  is placed within the aperture  230  and the barb base  218  is seated, a separate cannula  358  may be provided and crimped, snapped, or otherwise secured over the strut  214  to constrain the base  218 . As described above, the engagement between the barb  212  and the aperture  230  prevents the barb from sliding distally through the passageway  236 . Further, the attachment structure  350  may prevent the barb  212  from sliding proximally through the passageway  236 . Thus, the barb  212  may attach to the stent  210  without placing a weld or other such bond between the barb and the stent. The cannula  358  may optionally be welded to the strut  214  to increase the attachment between the cannula  358  and the stent  210 , and to prevent detachment therebetween. 
         [0053]      FIG. 6  depicts another exemplary intraluminal prosthesis that comprises a stent  410  and a barb  412 . The barb  412  passes through an aperture  430  in a strut  414 . The barb base  418  may be attached to the strut  414  by a fixing element  424 , such as a weld. Alternatively, or additionally, an attachment structure (not shown) may be provided for attaching the barb  412  to the strut  414 . The barb body  422  extends distally from the base  418  towards the aperture  430  and distally from the aperture  430  towards the anchor  420  and away from the strut  414 . In the example shown in  FIG. 6 , the base  418  and the weld  424  are spaced apart from the aperture  430 , thus increasing the distance between the weld and the high-stress barb-stent junction  425 . Accordingly, in use, any stress on the anchor  420  will be transmitted to and focused at a region of the prosthesis that is spaced apart from the weld  424 . 
         [0054]    Throughout this specification various indications have been given as to preferred and alternative embodiments of the invention. However, it should be understood that the invention is not limited to any one of these. It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the appended claims, including all equivalents, that are intended to define the spirit and scope of this invention.