Abstract:
Medical devices and methods for making and using a medical device are disclosed. An example medical device may include an implantable endoprosthesis. The implantable endoprosthesis may include a cylindrical body having a proximal end, a distal end, and an axial bonding region extending between the proximal end and the distal end. The cylindrical body may include one or more winding filaments and a plurality of discrete axial bonds disposed along the axial bonding region. The discrete axial bonds may secure together edge regions of the one or more winding filaments.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119 to U.S. Provisional Application Ser. No. 62/248,413, filed Oct. 30, 2015, the entirety of which is incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure pertains to medical devices, and methods for manufacturing medical devices. More particularly, the present disclosure pertains to implantable medical devices. 
       BACKGROUND 
       [0003]    A wide variety of intracorporeal medical devices have been developed for medical use, for example, intravascular use. Some of these devices include guidewires, catheters, stents, and the like. These devices are manufactured by any one of a variety of different manufacturing methods and may be used according to any one of a variety of methods. 
       SUMMARY 
       [0004]    This disclosure provides design, material, manufacturing method, and use alternatives for medical devices. An example medical device may include an implantable endoprosthesis comprising a cylindrical body having a proximal end, a distal end, and an axial bonding region extending between the proximal end and the distal end; wherein the cylindrical body includes one or more winding filaments; and a plurality of discrete axial bonds disposed along the axial bonding region, the discrete axial bonds securing together edge regions of the one or more winding filaments. 
         [0005]    Alternatively or additionally to any of the embodiments above, wherein the one or more winding filaments includes a braided portion, a knitted portion, or both. 
         [0006]    Alternatively or additionally to any of the embodiments above, wherein the one or more winding filaments includes a braided portion and a knitted portion, wherein the braided portion is interwoven with the knitted portion. 
         [0007]    Alternatively or additionally to any of the embodiments above, wherein the winding filaments includes a first filament having a first radial compression strength and a second filament having a second radial compression strength different from the first radial compression strength. 
         [0008]    Alternatively or additionally to any of the embodiments above, wherein the discrete axial bonds include a weld. 
         [0009]    Alternatively or additionally to any of the embodiments above, wherein the cylindrical body further comprises a bifurcated portion. 
         [0010]    Alternatively or additionally to any of the embodiments above, wherein the cylindrical body includes a second axial bonding region. 
         [0011]    Another example implantable endoprosthesis comprises a tubular scaffold including a proximal end, a distal end and a longitudinal axis, the tubular scaffold including at least a first filament including a first set of windings and a second set of windings; a bonding region extending along the tubular scaffold including a plurality of discrete bonds; wherein the one or more discrete bonds secure the first set of windings to the second set of windings. 
         [0012]    Alternatively or additionally to any of the embodiments above, further comprising a second filament, wherein the first filament includes a braided portion and the second filament includes a knitted portion. 
         [0013]    Alternatively or additionally to any of the embodiments above, wherein the braided portion and the knitted portion are interwoven. 
         [0014]    Alternatively or additionally to any of the embodiments above, further comprising a second filament, wherein the first filament includes a first material and the second filament includes a second material different from the first material. 
         [0015]    Alternatively or additionally to any of the embodiments above, wherein the tubular scaffold includes a bifurcated portion. 
         [0016]    Alternatively or additionally to any of the embodiments above, wherein the tubular scaffold includes a second bonding region including a plurality of discrete bonds along the bifurcated portion. 
         [0017]    An example method of making an implantable endoprosthesis comprises positioning at least one filament on along a planar surface of a base, the base including a plurality of projections extending away from the surface; wherein positioning the at least one filament on the planar surface of the base includes winding the at least one filament along the base by winding the filament about the plurality of projections to form a substantially planar stent structure, the planar stent structure including a first side and a second side and one or more interstices therebetween; removing the planar stent structure from the planar surface; positioning the planar stent structure around a shaping mandrel; and attaching the first side of the stent structure to the second side of the stent structure. 
         [0018]    Alternatively or additionally to any of the embodiments above, wherein attaching the first side of the stent structure to the second side of the stent structure further includes forming a bonding region. 
         [0019]    Alternatively or additionally to any of the embodiments above, wherein the bonding region includes at least one weld. 
         [0020]    Alternatively or additionally to any of the embodiments above, wherein positioning the at least one filament on a planar surface comprises both braiding and knitting the filament around the plurality of projections. 
         [0021]    Alternatively or additionally to any of the embodiments above, wherein positioning the planar stent structure around a shaping mandrel includes positioning the planar stent structure around a bifurcated mandrel. 
         [0022]    Alternatively or additionally to any of the embodiments above, wherein positioning the at least one filament between at least two of the plurality of projections to form a substantially planar stent structure includes forming a third side and a fourth side. 
         [0023]    Alternatively or additionally to any of the embodiments above, further comprising attaching the third side to the fourth side to form a second bonding region. 
         [0024]    The above summary of some embodiments is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The Figures, and Detailed Description, which follow, more particularly exemplify these embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    The disclosure may be more completely understood in consideration of the following detailed description in connection with the accompanying drawings, in which: 
           [0026]      FIG. 1  is a side view of an example implantable medical device; 
           [0027]      FIG. 2  illustrates a perspective view of an example base including outwardly extending projections; 
           [0028]      FIG. 3  illustrates a top view of an example base including outwardly extending projections; 
           [0029]      FIG. 4  illustrates an example base having at least one filament positioned thereon; 
           [0030]      FIG. 5  illustrates an example planar stent structure; 
           [0031]      FIG. 6  illustrates an example stent structure positioned on a mandrel; 
           [0032]      FIG. 7  illustrates an example stent structure being removed from a mandrel; 
           [0033]      FIG. 8  illustrates an example multi-filament stent pattern; 
           [0034]      FIG. 9  illustrates an example base having at least one filament positioned thereon; 
           [0035]      FIG. 10  illustrates an example mandrel; 
           [0036]      FIG. 11  illustrates an example bifurcated stent. 
       
    
    
       [0037]    While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the disclosure to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure. 
       DETAILED DESCRIPTION 
       [0038]    For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification. 
         [0039]    All numeric values are herein assumed to be modified by the term “about”, whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (e.g., having the same function or result). In many instances, the terms “about” may include numbers that are rounded to the nearest significant figure. 
         [0040]    The recitation of numerical ranges by endpoints includes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5). 
         [0041]    As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise. 
         [0042]    It is noted that references in the specification to “an embodiment”, “some embodiments”, “other embodiments”, etc., indicate that the embodiment described may include one or more particular features, structures, and/or characteristics. However, such recitations do not necessarily mean that all embodiments include the particular features, structures, and/or characteristics. Additionally, when particular features, structures, and/or characteristics are described in connection with one embodiment, it should be understood that such features, structures, and/or characteristics may also be used connection with other embodiments whether or not explicitly described unless clearly stated to the contrary. 
         [0043]    The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the disclosure. 
         [0044]      FIG. 1  illustrates an example implantable medical device  10 . Implantable medical device  10  may be configured to be positioned in a body lumen for a variety of medical applications. For example, implantable medical device  10  may be used to treat a stenosis in a blood vessel, used to maintain a fluid opening or pathway in the vascular, urinary, biliary, tracheobronchial, esophageal, or renal tracts, or position a device such as an artificial valve or filter within a body lumen, in some instances. In some instances, implantable medical device  10  may be a prosthetic graft, a stent-graft, or a stent (e.g., a vascular stent, tracheal stent, bronchial stent, esophageal stent, etc.), an aortic valve, filter, etc. Although illustrated as a stent, implantable medical device  10  may be any of a number of devices that may be introduced endoscopically, subcutaneously, percutaneously or surgically to be positioned within an organ, tissue, or lumen, such as a heart, artery, vein, urethra, esophagus, trachea, bronchus, bile duct, or the like. 
         [0045]    Implantable medical device  10  may include one or more different design configurations and/or components. For example, medical device  10  may have an expandable tubular framework with open ends and defining a lumen therethrough. In some instances medical device  10  may be a self-expanding stent. Self-expanding stent examples may include stents having one or more filaments  16  combined to form a rigid and/or semi-rigid stent structure. Further, wires  16  may be a solid member of a round or to non-round cross-section or may be tubular (e.g., with a round or non-round cross-sectional outer surface and/or round or non-round cross-sectional inner surface). 
         [0046]    Medical device (e.g., stent)  10  may be designed to shift between a first or “unexpanded” configuration and a second or “expanded” configuration. In at least some instances, stent  10  may be formed from a shape memory material (e.g., a nickel-titanium alloy such as nitinol) that can be constrained in the unexpanded configuration, such as within a delivery sheath, during delivery and that self-expands to the expanded configuration when unconstrained, such as when deployed from a delivery sheath and/or when exposed to a pre-determined temperature conditions to facilitate expansion. The precise material composition of stent  10  can vary, as desired, and may include the materials disclosed herein. 
         [0047]    In some circumstances, it may be desirable to customize medical device  10  to address particular medical applications. Further, in some instances it may be desirable to configure medical device  10  to include one or more filaments interwoven in a particular arrangement. For example, some implantable stents may include an open, mesh-like configuration. In some instances, the open, mesh-like configuration may resemble a braided, knitted and/or woven stent structure. In other words, one or more stent filaments  16  may be braided, intertwined, interwoven, weaved, knitted or the like to form the stent structure  10 . 
         [0048]    As stated above and will be discussed in greater detail below, the stent structure  10  may be constructed from one or more different braiding, weaving, knitting or similar techniques to form a single stent structure  10 . Furthermore, different portions of stent structure  10  may include varying mechanical properties corresponding to different stent structures (e.g., portions of stent  10  having differing design configurations). For example, a portion of stent  10  including a braided portion may exhibit different radial compression strength as compared to a portion of the stent  10  having a knitted or woven structure. For purposes of this disclosure, a “braided” stent structure may be defined as one or more interwoven wires that are weaved together such that the wires may be easily compressed, yet easily return (e.g., “spring back”) to a pre-compressed shape. In contrast, for purposes of this disclosure, a “knitted” stent structure may be defined as one or more interlocking wires that are combined into one or more interlocking loops that may be interdependent on one another. In other words, a “knitted” structure may include interlocking loops that work together to create a stent structure having greater compressive strength as compared a braided stent structure, for example. Further, it is contemplated that other mechanical and/or physical stent properties may be vary in accordance with different stent designs, materials and/or manufacturing techniques. 
         [0049]    Some stent structures are contemplated that include only braided filaments. Some stent structures are contemplated that only include knitted filaments. Furthermore some stent structures are contemplated that include one section with braided filaments and another section with knitted filaments. In such instances, the pattern and/or arrangement of the different sections can vary. For example, a stent structure may have braided filaments along a first portion (e.g., a first “half”) and may have a knitted filaments along a second portion (e.g., a second “half”). These are just examples. 
         [0050]    As will be discussed in greater detail below,  FIG. 1  shows stent  10  including a bonding region  18 . Bonding region  18  may extend along the longitudinal axis of stent  10 . Bonding region  18  may include one or more bonds  20 . In some instances, bonds  20  may be defined as the attachment and/or combination of one or more end regions  36  (shown in  FIG. 5 ) of wires  16 . While  FIG. 1  depicts bonds  20  as being longitudinally aligned along the longitudinal axis of stent  10 , it is contemplated that bonds  20  may be distributed along stent  10  in a variety of patterns and/or configurations. 
         [0051]    While the stent  10  shown in  FIG. 1  is depicted as being generally cylindrical in shape and including a substantially uniform pattern and/or distribution of filaments and/or wires  16 , it is contemplated that in some instances it may be desirable to construct stent  10  using more complicated or intricate stent patterns, configurations or structural geometries. For example, in some instances it may be desirable to utilize one or more assembly techniques (e.g., braiding and/or knitting) to construct a variety of different stent scaffolds. 
         [0052]    To that end,  FIG. 2  illustrates an example base member  22  having an outer surface  26 . Base member  22  may be defined as a substantially and/or at least partially planar (e.g., substantially flat) structure. While depicted as a square in  FIG. 2 , it is contemplated that base member  22  may be any shape. For example, base member may be circular, rectangular, ovular, triangular or the like. 
         [0053]      FIG. 2  show projections  24  extending away from surface  26  of base member  22 . In some instances, projections  24  may resemble pegs, pins, screws and/or rods extending away from base member  22 . However, this is not intended to be limiting. For example, it is contemplated that projections  24  may be a variety of shapes and extend away at any angle with respect to surface  26 . For example, in some examples slotted grooves may be utilized perform the methods disclosed herein. 
         [0054]    Further, while  FIG. 2  shows twenty-five projections  24  arranged in a grid-like pattern, it is contemplated that more or fewer projections  24  may be utilized in conjunction with base  22 . For example, base  22  may include 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 30, 40 50, 100 or more projections arranged in a variety of patterns and/or distributions along base  22 . In some instances, the arrangement of projections  24  may be determined by a particular stent geometry and/or design configuration. 
         [0055]    Base  22  (including projections  24 ) may be utilized to construct a planar (e.g., flat) stent structure. The planar stent structure may subsequently be formed into a variety of three-dimensional stent configurations (discussed below).  FIG. 3  shows a top view of the base  22  and projections  24  illustrated in  FIG. 2 . As discussed above, it can be appreciated that projections  24  may be configured in a variety of patterns, designs, arrangements, distributions, etc. along base  22 . 
         [0056]      FIG. 4  shows an example filament  16  positioned (e.g., wound, wrapped) around projections  24  of base  22  to form a planar stent structure  30  (shown in  FIG. 5  as removed from base  22  of  FIG. 4 ). The pattern illustrated in  FIG. 4  is merely an example. It is contemplated that filament  16  may be wound around projections  24  in a variety of different configurations. 
         [0057]    Furthermore, it is contemplated that more than one filament  16  may be utilized in the construction of planar stent structure  30 . For example, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 30, 40, 50 or more filaments  16  may be utilized to form stent structure  30 . Additionally, as described above, stent structure  30  may be constructed using one of more different techniques to combine wires  16 . For example, one or more portions of planar stent structure  30  may be formed by braiding one or more filaments  16 . Additionally, one or more portions of planar stent structure  30  may be formed by knitting one or more filaments  16 . While some planar stent structures  30  may be formed using a single technique (e.g., braiding, knitting, weaving, etc.), it is contemplated that more than one technique may be utilized together within the same planar stent structure  30 . For example, in some instances one or more wires  6  may be interlocked (via a knitting technique, for example) with one or more wire  16  which are interwoven together (via a braiding technique, for example). While the above examples discusses knitting and braiding as two construction techniques, it is contemplated that planar stent structure  30  may be formed using any stent construction techniques that interweave, interlock, combine, blend, twist, link, intertwine, etc. one or more stent filaments  16 . 
         [0058]    As stated above,  FIG. 5  shows the planar stent structure  30  after being removed from the base  22  shown in  FIG. 4 . As shown in  FIG. 5 , planar stent structure  30  may include a first set of stent windings  32  (illustrated in  FIG. 5  by a first dashed box) and a second set of windings  34  (illustrated in  FIG. 5  by a second dashed box). Further,  FIG. 5  illustrates that each set of windings  32 / 34  include edge regions  36  corresponding to various loops included in planar stent structure  30 . 
         [0059]    In some examples, prior to being removed from base member  22 , additional processing may be applied to stent structure  30  (while on base  22 ). For example, an annealing process may be applied to stent structure  30  while wound along projections  24  of base member  22  (shown in  FIG. 4 ). In some examples the annealing process may be a low-temperature anneal. The annealing process may “heat set” stent structure  30  such that when stent structure  30  is removed from base member  22 , stent structure  30  substantially retains its planar form. 
         [0060]    In some instances it may be desirable to transform the planar stent structure  30  shown in  FIG. 5  into a three-dimensional stent structure designed to treat a target area in the body.  FIG. 6  shows the planar stent structure  30  of  FIG. 5  positioned along (e.g., wrapped around) an example shaping mandrel  38 .  FIG. 6  illustrates the axial bonding region  18  (described above with respect to  FIG. 1 ) including bonds  20 . 
         [0061]    It can be appreciated the bonding region  18  shown in  FIG. 6  defines the combination and/or attachment of the first set of windings  32  with the second set of windings  34  shown in  FIG. 5 . Further, the detailed view of  FIG. 6  shows that in some examples, edge regions  36  (corresponding to the loop portions of stent structure  30 ) may be combined to attach the first set of windings  32  to the second set of windings  34 . 
         [0062]    The edge regions  36  of windings  32 / 34  may be combined using a variety of methodologies. For example, in some instances edge regions  36  may be attached to another via welding. However, this is just an example. It is contemplated that edge regions may be attached to one another using similar bonding techniques such as gluing, tacking, brazing, soldering, or the like. As stated above, the detailed view of  FIG. 6  shows edge regions  36  of example windings  32 / 34  being combined and/or attached. However, even though not shown in the detailed view, it is contemplated that the edge regions  36  may be combined (e.g., melted) together to form a singular structure (e.g., a monolithic stent filament and/or stent strut). 
         [0063]    It can be appreciated the positioning (e.g., wrapping) stent structure  30  around shaping mandrel  38  may form planar stent structure  30  into the shape of shaping mandrel  38 . Therefore, it can further be appreciated that a variety of different shaping mandrel designs may be utilized to construct three-dimensional stents having a variety of different shapes. For example, as will be discussed further below, shaping mandrel  38  may include one or more extensions or legs (e,g., a bifurcated shape) designed to treat particular vessel geometries in the body. 
         [0064]    The above discussion describes a stent manufacturing methodology that initially forms a planar stent structure  30  on a planar base member  22  and later shapes that planar stent structure  30  into a particular three-dimensional stent structure  10  using a shaped mandrel  38 . It should be appreciated that this methodology may be utilized to form stent configurations (e.g., self-expanding stent configurations) that are more intricate that those formed from existing manufacturing methods. For example, by winding filaments  16  along planar base  22  before forming the three-dimensional stent structure  10 , one or more different manufacturing techniques (such as braiding and knitting) may be combined to yield a single stent structure having a multitude of different arrangements, patterns, structures, and/or distributions that may otherwise be difficult to construct using existing methods. 
         [0065]    Furthermore, as stated above, the ability to utilize different manufacturing techniques (e.g., braiding, knitting, etc.) may allow stent  10  to be tailored to have different physical properties in different portions of the stent structure. For example, portions of the stent including a particular stent manufacturing method may have a radial strength that differs from another portion of the stent formed from a different manufacturing methodology. Other physical properties may be customized using similar techniques (e.g., combing braided with knitted portions within the same stent structure, etc.). 
         [0066]    Once planar stent structure  30  has been shaped into a three-dimensional stent design around shaping mandrel  38 , it may be removed from shaping mandrel  38  and thereafter resemble the stent structure illustrated in  FIG. 1 .  FIG. 7  illustrates the removal of the stent structure  30  from shaping mandrel  38 . For example,  FIG. 7  shows an arrow representing the removal of stent structure  30  from mandrel  38 . 
         [0067]    In some examples, stent structure  30  may undergo a second annealing process prior to the removal from the shaping mandrel  38 . For example, while on shaping mandrel  38 , stent  30  (shown in  FIG. 6 ), may be undergo a heat set. In some instances this heat set may be a high temperature heat set. Use of the higher temperature heat set may affect the shape memory attributes of the materials used to construct the stent. For example, in some instances, the higher heat set temperature may impart shape memory characteristics into the stent filaments. 
         [0068]    As stated, once removed from shaping mandrel  38 , stent  10  may resemble the example three-dimensional stent structure shown in  FIG. 1 . As shown in  FIG. 1 , the axial bonding region  18  may be defined as including a series of attachment points and/or combined edge regions  36  of the planar stent structure. In some examples, bonding region  18  may resemble that of a seam. In other words, the discrete bonding points may be longitudinally aligned such that they resembled a linear seam along the stent surface. However, in other examples, the discrete bonds  20  of bonding region  18  may not be longitudinally aligned. Rather, it is contemplated that stent  10  may be designed and/or configured such that any portion of filaments  16  may be attached (e.g., welded) to any other portion of filaments  16 , irrespective of their linear alignment. 
         [0069]    In some instances it may be desirable to utilize one or more different materials to construct the example stent structures disclosed herein. For example, in some instances it may be desirable to incorporate two or more filaments of differing materials when constructing the example stent structures disclosed herein.  FIG. 8  illustrates a planar stent structure  44  positioned on a base  22 . It can be appreciated that planar stent structure  44  may be formed similarly to the planar stent structure described above in relation to  FIG. 4 . 
         [0070]    However,  FIG. 8  further illustrates two different filament materials being utilized to construct structure  44 . For example, in some examples a first filament  40  (depicted as a solid line) may be combined (e.g., braided, weaved, knitted, wound, interwoven, etc.) with a second filament  42  (depicted as a dashed line) to form planar stent structure  44 . As shown in  FIG. 8 , filaments  42 / 44  may be positioned, wound, interwoven, etc. about projections  24 . Additionally, as described above with respect to  FIG. 4 , filaments  42 / 44  may be interwoven about projections  24  in any given arrangement, pattern and/or distribution. For example, filaments  42 / 44  may be arranged to form different shapes, spaces, interstices, etc. 
         [0071]    For purposes of this disclosure, it is further contemplated that stent structures disclosed herein may be constructed to have interstitial spaces of varying sizes. For example,  FIG. 8  shows planar stent structure  44  having an interstitial space  70  that is comparatively larger than interstitial space  72 . It can be appreciated that different size stent cells may be formed during the construction of planar stent structures. Further, these relative stent cell sizes may be maintained after an example planar stent structure is subsequently formed into a three-dimensional stent structure as disclosed herein. In some instances, different stent cell openings (e.g., interstitial spaces) may be incorporated into a particular stent design to customize the stent geometry to treat a particular body lumen. 
         [0072]    Additionally, different manufacturing methods may be used with a particular material and further combined with different materials and manufacturing methods. For example, in some examples, a first material may be braided and combined with a second material that is knitted. The first and second materials (having been braided and knitted, respectively), may be combined with one another to create a single stent structure. These are just examples. It is contemplated that many different materials may be combined with many different manufacturing methodologies to create both the planar, and subsequently, the three-dimensional stent structures disclosed herein. 
         [0073]    While the above example discloses using two different materials to create a planar stent structure, it is not intended to be limiting. For example, it is contemplated that more than two materials may be combined to form the stent structures described herein. For example 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20 or more different filament materials may be combined to form the stent structures described herein. 
         [0074]    As discussed above, the techniques described herein may be utilized to create varied, complex and/or intricate stent designs and/or configurations. For example,  FIG. 9  illustrates an example planar stent pattern  46  designed to form a stent having a bifurcated portion. As shown in  FIG. 9 , the planar stent pattern  46  may include a body portion  50 , a first leg portion  52  and a second leg portion  54 . The planar bifurcated stent pattern  46  may be constructed using any of the techniques disclosed herein. For example, the planar bifurcated stent pattern may include one or more filaments  16  positioned (e.g., wrapped, wound, etc.) around projections  24 . Filaments  16  may be one or more different materials and interwoven with one another using a variety of manufacturing techniques (e.g., braiding, weaving, knitting, interlocking, interweaving, etc.). 
         [0075]    In accordance with some example stent manufacturing methods disclosed herein, the planar bifurcated stent pattern  46  (shown in  FIG. 9 ) may be positioned on a bifurcated shaping mandrel  48  (shown in  FIG. 10 ). While the bifurcated stent pattern  46  is not shown wrapped around bifurcated mandrel  48 , it can be appreciated that planar stent  46  may be positioned on mandrel  48  in a similar manner as that described above with respect to  FIGS. 4-6 . 
         [0076]      FIG. 11  shows an example bifurcated stent  60  formed in accordance with the methods disclosed herein. For example, bifurcated stent  60  may be defined as the three-dimensional stent structure formed after planar bifurcated stent  46  has been positioned (e.g., wrapped) around shaping mandrel  48  and thereafter removed from shaping mandrel  48 . 
         [0077]    Additionally,  FIG. 11  shows bifurcated stent  60  including one or more axial bonding regions  62  including bonds  64 . It is noted that for the purposes of this disclosure, example stent structures formed according to methods disclose herein may include one or more axial bonding regions. For example, stent designs may include 2, 3, 4, 5, 6, 7, 8, 9, 10 or more axial bonding regions. The number and location of a particular axial bonding region within a given stent design may depend on the complexity of a given stent structure. 
         [0078]    The materials that can be used for the various components of implantable medical device  10  (and/or other devices disclosed herein) and the various tubular members disclosed herein may include those associated with medical devices. Implantable medical device  10 , and/or the components thereof, may be made from a metal, metal alloy, polymer (some examples of which are disclosed below), a metal-polymer composite, ceramics, combinations thereof, and the like, or other suitable material. Some examples of suitable polymers may include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM, for example, DELRIN® available from DuPont), polyether block ester, polyurethane (for example, Polyurethane  85 A), polypropylene (PP), polyvinylchloride (PVC), polyether-ester (for example, ARNITEL® available from DSM Engineering Plastics), ether or ester based copolymers (for example, butylene/poly(alkylene ether) phthalate and/or other polyester elastomers such as HYTREL® available from DuPont), polyamide (for example, DURETHAN® available from Bayer or CRISTAMID® available from Elf Atochem), elastomeric polyamides, block polyamide/ethers, polyether block amide (PEBA, for example available under the trade name PEBAX®), ethylene vinyl acetate copolymers (EVA), silicones, polyethylene (PE), Marlex high-density polyethylene, Marlex low-density polyethylene, linear low density polyethylene (for example REXELL®), polyester, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polytrimethylene terephthalate, polyethylene naphthalate (PEN), polyetheretherketone (PEEK), polyimide (PI), polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), poly paraphenylene terephthalamide (for example, KEVLAR®), polysulfone, nylon, nylon-12 (such as GRILAMID® available from EMS American Grilon), perfluoro(propyl vinyl ether) (PFA), ethylene vinyl alcohol, polyolefin, polystyrene, epoxy, polyvinylidene chloride (PVdC), poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS  50 A), polycarbonates, ionomers, biocompatible polymers, other suitable materials, or mixtures, combinations, copolymers thereof, polymer/metal composites, and the like. In some embodiments the sheath can be blended with a liquid crystal polymer (LCP). For example, the mixture can contain up to about 6 percent LCP. 
         [0079]    Some examples of suitable metals and metal alloys include stainless steel, such as 304V, 304L, and 316LV stainless steel; mild steel; nickel-titanium alloy such as linear-elastic and/or super-elastic nitinol; other nickel alloys such as nickel-chromium-molybdenum alloys (e.g., UNS: N06625 such as INCONEL® 625, UNS: N06022 such as HASTELLOY® C-22®, UNS: N10276 such as HASTELLOY® C276®, other HASTELLOY® alloys, and the like), nickel-copper alloys (e.g., UNS: N04400 such as MONEL® 400, NICKELVAC® 400, NICORROS® 400, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such as MP35-N® and the like), nickel-molybdenum alloys (e.g., UNS: N10665 such as HASTELLOY® ALLOY B2®), other nickel-chromium alloys, other nickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-iron alloys, other nickel-copper alloys, other nickel-tungsten or tungsten alloys, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like); platinum enriched stainless steel; titanium; combinations thereof; and the like; or any other suitable material. 
         [0080]    As alluded to herein, within the family of commercially available nickel-titanium or nitinol alloys, is a category designated “linear elastic” or “non-super-elastic” which, although may be similar in chemistry to conventional shape memory and super elastic varieties, may exhibit distinct and useful mechanical properties. Linear elastic and/or non-super-elastic nitinol may be distinguished from super elastic nitinol in that the linear elastic and/or non-super-elastic nitinol does not display a substantial “superelastic plateau” or “flag region” in its stress/strain curve like super elastic nitinol does. Instead, in the linear elastic and/or non-super-elastic nitinol, as recoverable strain increases, the stress continues to increase in a substantially linear, or a somewhat, but not necessarily entirely linear relationship until plastic deformation begins or at least in a relationship that is more linear that the super elastic plateau and/or flag region that may be seen with super elastic nitinol. Thus, for the purposes of this disclosure linear elastic and/or non-super-elastic nitinol may also be termed “substantially” linear elastic and/or non-super-elastic nitinol. 
         [0081]    In some cases, linear elastic and/or non-super-elastic nitinol may also be distinguishable from super elastic nitinol in that linear elastic and/or non-super-elastic nitinol may accept up to about 2-5% strain while remaining substantially elastic (e.g., before plastically deforming) whereas super elastic nitinol may accept up to about 8% strain before plastically deforming. Both of these materials can be distinguished from other linear elastic materials such as stainless steel (that can also can be distinguished based on its composition), which may accept only about 0.2 to 0.44 percent strain before plastically deforming. 
         [0082]    In some embodiments, the linear elastic and/or non-super-elastic nickel-titanium alloy is an alloy that does not show any martensite/austenite phase changes that are detectable by differential scanning calorimetry (DSC) and dynamic metal thermal analysis (DMTA) analysis over a large temperature range. For example, in some embodiments, there may be no martensite/austenite phase changes detectable by DSC and DMTA analysis in the range of about −60 degrees Celsius (° C.) to about 120° C. in the linear elastic and/or non-super-elastic nickel-titanium alloy. The mechanical bending properties of such material may therefore be generally inert to the effect of temperature over this very broad range of temperature. In some embodiments, the mechanical bending properties of the linear elastic and/or non-super-elastic nickel-titanium alloy at ambient or room temperature are substantially the same as the mechanical properties at body temperature, for example, in that they do not display a super-elastic plateau and/or flag region. In other words, across a broad temperature range, the linear elastic and/or non-super-elastic nickel-titanium alloy maintains its linear elastic and/or non-super-elastic characteristics and/or properties. 
         [0083]    In some embodiments, the linear elastic and/or non-super-elastic nickel-titanium alloy may be in the range of about 50 to about 60 weight percent nickel, with the remainder being essentially titanium. In some embodiments, the composition is in the range of about 54 to about 57 weight percent nickel. One example of a suitable nickel-titanium alloy is FHP-NT alloy commercially available from Furukawa Techno Material Co. of Kanagawa, Japan. Some examples of nickel titanium alloys are disclosed in U.S. Pat. Nos. 5,238,004 and 6,508,803, which are incorporated herein by reference. Other suitable materials may include ULTANIUM™ (available from Neo-Metrics) and GUM METAL™ (available from Toyota). In some other embodiments, a superelastic alloy, for example a superelastic nitinol can be used to achieve desired properties. 
         [0084]    In at least some embodiments, portions or all of device  10  may also be doped with, made of, or otherwise include a radiopaque material. Radiopaque materials are understood to be materials capable of producing a relatively bright image on a fluoroscopy screen or another imaging technique during a medical procedure. This relatively bright image aids the user of device  10  in determining its location. Some examples of radiopaque materials can include, but are not limited to, gold, platinum, palladium, tantalum, tungsten alloy, polymer material loaded with a radiopaque filler, and the like. Additionally, other radiopaque marker bands and/or coils may also be incorporated into the design of device  10  to achieve the same result. 
         [0085]    In some embodiments, a degree of Magnetic Resonance Imaging (Mill) compatibility is imparted into device  10 . For example, device  10 , or portions thereof, may be made of a material that does not substantially distort the image and create substantial artifacts (e.g., gaps in the image). Certain ferromagnetic materials, for example, may not be suitable because they may create artifacts in an MRI image. Device  10 , or portions thereof, may also be made from a material that the MRI machine can image. Some materials that exhibit these characteristics include, for example, tungsten, cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such as MP35-N® and the like), nitinol, and the like, and others. 
         [0086]    It should be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of steps without exceeding the scope of the disclosure. This may include, to the extent that it is appropriate, the use of any of the features of one example embodiment being used in other embodiments.