Abstract:
An implantable medical support frame ( 104 ) having a central longitudinally extending axis is expandable from a collapsed configuration having a first diameter to an expanded configuration having a second diameter. The frame also includes an anchoring mechanism with an elongate member ( 110 ). At least a portion of the elongate member is slidably disposed within a retaining structure when the frame is in the collapsed configuration. When the frame expands from the collapsed configuration to the expanded configuration, a portion of the elongate member is advanced out of the retaining structure such that the portion of the elongate member protrudes radially outward of the frame at an angle to the axis, thereby forming an anchor. A length of the protruding portion of the anchor increases as the frame expands from the collapsed configuration to the expanded configuration.

Description:
REFERENCE TO EARLIER FILED APPLICATIONS 
     This application is a 371 national phase of PCT/US2010/059680, filed Dec. 9, 2010, and claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/289,257, filed Dec. 22, 2009, the disclosures of which are incorporated, in their entirety, by this reference. 
    
    
     TECHNICAL FIELD 
     This invention relates to medical devices and, in particular, to prostheses for placement in a body lumen. 
     BACKGROUND ART 
     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 hemodynamic forces, an aneurysm can rupture. 
     Endoluminal 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. 
     One of the challenges of designing and using an endoluminal 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 endoluminal prosthesis is used, for example, to repair an aneurysm, migration of the device may result in endoleaks or inadequate exclusion of the aneurysm, and increased risk of aneurysm rupture. 
     Various devices have been proposed to address migration. For example, a prosthesis may comprise one or more anchor members, such as a barb or hook, that extends radially outward from the prosthesis and is configured to engage surrounding body tissue. Typically, such barbs or hooks may be attached to the prosthesis by, for example, sewing, gluing, wrapping, chemical bonding, welding, brazing, soldering, and the like. 
     DISCLOSURE OF THE INVENTION 
     Retractable anchor mechanisms are described which limit or prevent migration of a prosthesis and further facilitate insertion into a delivery system. The embodiments may include any of the following aspects in various combinations and may also include any other aspect described below in the written description or in the attached drawings. 
     In one aspect, an implantable medical support frame may include a frame having a central longitudinally extending axis. The frame may be expandable from a collapsed or compressed configuration having a first diameter to an expanded configuration having a second diameter, the second diameter being greater than the first diameter. An anchoring mechanism having an elongate member is also included. At least a portion of the elongate member is slidably disposed within a retaining structure when the frame is in the collapsed configuration. When the frame expands from the collapsed configuration to the expanded configuration, a portion of the elongate member is advanced out of the retaining structure such that the portion of the elongate member protrudes radially outward of the frame at an angle to the central axis and forms an anchor. A length of the protruding portion of the anchor increases as the frame expands from the collapsed configuration to the expanded configuration. 
     In another aspect, the elongate member may have first and second ends. The second end is coupled to the frame, and the first end is free of attachment to the frame. In one embodiment, the second end of the elongate member is fixedly attached to the frame. 
     The foregoing paragraphs have been provided by way of general introduction, and are not intended to limit the scope of the following claims. The described embodiments will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments may be more fully understood by reading the following description in conjunction with the drawings, in which: 
         FIG. 1(   a ) is a plan view of a portion of an embodiment of an implantable medical support frame having a retractable anchor member in a collapsed configuration; 
         FIG. 1(   b ) is a plan view of a portion of the embodiment of  FIG. 1(   a ) in a partially expanded configuration; 
         FIG. 1(   c ) is a plan view of a portion of the embodiment of  FIG. 1(   a ) in a fully expanded configuration; 
         FIG. 2(   a ) is a plan view of a portion of another embodiment of an implantable medical support frame having a retractable anchor member in a collapsed configuration; 
         FIG. 2(   b ) is a plan view of a portion of the embodiment of  FIG. 2(   a ) in a partially expanded configuration; 
         FIG. 2(   c ) is a plan view of a portion of the embodiment of  FIG. 2(   a ) in a fully expanded configuration; 
         FIG. 3(   a ) is a side view of an embodiment of an elongate anchor member; 
         FIG. 3(   b ) is a plan view of the elongate anchor member of  FIG. 3(   a ) attached to an implantable medical support frame; 
         FIG. 4(   a ) is a side view of an embodiment of an elongate anchor member; 
         FIG. 4(   b ) is a plan view of the elongate anchor member of  FIG. 4(   a ) attached to an implantable medical support frame; 
         FIG. 5(   a ) is a side view of an embodiment of an elongate anchor member; 
         FIG. 5(   b ) is a plan view of the elongate anchor member of  FIG. 5(   a ) attached to an implantable medical support frame; 
         FIG. 6(   a ) is a plan view of the medical support frame of  FIGS. 1(   a )-( c ) utilizing another embodiment of an elongate anchor member in a partially collapsed configuration; 
         FIG. 6(   b ) is a plan view of the elongate anchor member of  FIG. 6(   a ) in the partially collapsed configuration; 
         FIG. 7(   a ) is a plan view of the embodiment of  FIG. 6(   a ) in a fully expanded configuration; 
         FIG. 7(   b ) is a plan view of the elongate anchor member of  FIG. 7(   a ) in the fully expanded configuration; 
         FIG. 8(   a ) is a plan view of the medical support frame of  FIGS. 1(   a )-( c ) utilizing another embodiment of an elongate anchor member in a partially collapsed configuration; 
         FIG. 8(   b ) is a plan view of the elongate anchor member of  FIG. 8(   a ) in the partially collapsed configuration; 
         FIG. 9(   a ) is a plan view of the embodiment of  FIG. 8(   a ) in a fully expanded configuration; 
         FIG. 9(   b ) is a plan view of the elongate anchor member of  FIG. 9(   a ) in the fully expanded configuration; 
         FIGS. 10(   a ) and ( b ) illustrate another embodiment of the medical support frame having a retractable anchor member, with the support frame in a collapsed configuration; 
         FIGS. 11(   a ) and ( b ) illustrate another embodiment of a medical support frame having a retractable anchor member, with the support frame in a collapsed configuration; and 
         FIGS. 12(   a ) and ( b ) are a close-up side cross-sectional views of embodiments of the medical support frames shown in  FIGS. 11(   a ) and ( b ). 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the figures,  FIGS. 1(   a )-( c ) illustrate an embodiment of an endoluminal prosthesis  100  having a retractable anchor member. Throughout this description, like reference numbers refer to like elements in the Figures. As shown in  FIG. 1(   a ), the endoluminal prosthesis  100  includes a radially expandable frame  104  comprising a plurality of strut members  130  connected by bends in an undulating pattern to form a ring-like structure having a substantially cylindrical shape. Various designs may be used for the frame  104 . For example, the frame  104  may be made with undulating, serpentine rings interconnected with longitudinal structural members. The frame  104  may be fabricated from a cannula, as disclosed in U.S. Pat. Nos. 6,231,598, and 6,743,252, which are assigned to Cook Inc., the assignee of the present invention and are hereby incorporated by reference in their entirety. The strut members  130  may be made from elastic, super-elastic, or spring-metal alloys such as nitinol, stainless steel, cobalt chromium, nickel titanium, platinum, inconel, or any other suitable material, such that the strut members  130  can compress under force, and when unrestrained will tend to return to the expanded configuration in a spring-like manner. That is, in an embodiment, the frame  104  and the cells  102  are self-expanding. Alternatively, the strut members  130  may be made from a plastically deformable material such as stainless steel or the like that is expandable from a collapsed or compressed configuration to an expanded configuration by a balloon or the like. 
     The frame  104  also includes one or more anchor retaining structures. The retaining structures may include one or more cells  102 . In another embodiment, each cell  102  may be at least partially defined by two pairs of circumferentially adjacent strut members  130  connected by individual bends. More specifically, each cell may be formed from a left and a right upper strut member  130  and a left and a right lower strut member  130 . Each of the left and right upper and lower strut members  130  has an inner and an outer end. The outer ends of the left upper and lower strut members  130  are connected by a single bend disposed at a left longitudinal end of the cell  102 , such that the left upper and lower strut members  130  extend away from the bend and toward a center of the cell  102 . Similarly, the outer ends of the right upper and lower strut members  130  are connected by a single bend disposed at a right longitudinal end of the cell  102 , such that the right upper and lower strut members  130  extend away from the bend and toward a center of the cell  102 . The inner ends of the left and right upper strut members  130  are connected at an upper connecting member  150  and the inner ends of the left and right lower strut members  130  are connected at a lower connecting member  150 . Each cell  102  also includes an anchor attachment portion  140  attached to one of the bends, and an anchor deployment portion  120  attached to the other bend. 
     The strut members  130  of the frame  104  and the cells  102  are configured to flex between a collapsed configuration, depicted in  FIG. 1(   a ), and an expanded configuration, depicted in  FIG. 1(   c ). When the frame  104  and the cells  102  are the collapsed configuration, the left upper strut member  130  and the left lower strut member  130  are substantially adjacent to each other. For example, the left upper strut member  130  and the left lower strut member  130  may be substantially parallel or form an acute angle with one another. Similarly, the right upper strut member  130  and the right lower strut member  130  are substantially adjacent to each other such that the upper and lower right strut members  130  are substantially parallel or form an acute angle. 
     As shown in  FIG. 1(   b ), as the frame  104  and the cells  102  begin to expand in the radially outward direction, the upper and lower strut members  130  begin to flex away from each other such that the angle between the upper left and lower left, and the angle between the upper right and lower right strut members  130  increases. Because the strut members  130  have a fixed length that does not stretch during the expansion process, as the angle between the upper and lower struts  130  increases it causes a length of the cells  102  to increase in the circumferential direction and decrease in the axial/longitudinal direction. Note that the collapsed configuration need not correspond to a maximally collapsed configuration, and may refer to any intermediate configuration between the maximum collapsed and expanded states, provided that the outer diameter of the frame  104  is smaller in the collapsed configuration than in the expanded configuration. Similarly, the expanded configuration need not correspond to a maximally expanded configuration and may refer to any intermediate configuration between the maximum expanded and collapsed states, provided that the outer diameter of the frame  104  is larger in the expanded configuration than in the collapsed configuration. 
     It should be understood that while the strut members  130  are depicted as being straight, they are not limited thereto, and the strut members may have any curvilinear shape along their length to distribute bending forces and like during use. It should also be understood that while  FIG. 1(   a ) depicts the portion of the frame  104  corresponding to the cells  102 , in one embodiment the frame  104  may be wholly comprised of interconnected cells  102  that extend around a circumference of the frame  104 . In other embodiments, the frame  104  may contain some portions comprising cells  102  and other portions comprising strut members  130  arranged in other radially expandable patterns, for example and without limitation, zigzag, serpentine, and sinusoidal patterns. 
     An elongate anchor member  110  is attached to the anchor attachment portion  140  of the retaining structure at an anchor end  112 . The anchor attachment portion  140  may be formed as a lobe attached to a bend connecting the upper and lower right or left strut members  130 , and may include an aperture to receive the anchor end  112  of the elongate anchor member  110 . The elongate anchor member  110  also includes an engagement end  114  that is configured to extend through an anchor deployment portion  120 . The anchor deployment portion  120  may be shaped as a lobe and is attached to the bend opposite the bend connected to the anchor attachment portion  140 . 
     The engagement end  114  may be shaped to fixedly engage and penetrate into a wall of a body lumen or an inner surface of stent graft, such as a modular stent-graft endoluminal prosthesis, for example, the Zenith Endovascular Grafts sold by Cook Incorporated, the assignee of the present application. Exemplary shapes of the engagement end  114  include, but are not limited to, a conical point, a bevel, and a multi faced cutting surface or the like. The engagement end  114  may also be shaped to withstand repetitive loading experienced by anchor members in vivo, as described in U.S. Provisional Patent Application Ser. No. 61/138,355, which is assigned to Cook, Inc., the assignee of the present application, and incorporated herein in its entirety. 
     The anchor member  110  may extend from the anchor attachment portion  140  to the anchor deployment portion  120  along a radially inner surface of the cell  102 . In this way, the retaining structure prevents the portion of the anchor member  110  that is not designed to engage a vessel wall or endoluminal prosthesis from potentially interfering with the frame  104  and vessel wall/outer stent-graft interface. The anchor member  110  may be made from any elastic, super-elastic, or spring-metal alloys such as nitinol, stainless steel, cobalt chromium, nickel titanium, platinum, inconel, or any other material, such that the anchor member  110  will tend to return its predetermined shape when unrestrained. In one embodiment, the anchor member  110  may have a radially outwardly arching shape that biases the engagement end  114  in a radially outward direction, thereby increasing apposition and penetration in to the vessel wall or stent graft. In another embodiment, the anchor member  110  may be substantially straight along its length. In the substantially straight embodiment, the anchor deployment portion  120  may include a deflecting member  1151  that is designed to slidingly engage and deflect the engagement end  114  in the radially outward direction. The deflecting member may be a radially outward curved or angled surface (see also  FIGS. 10(   a ),  10 ( b ),  11 ( a ),  11 ( b ),  12 ( a ), and  12 ( b ) discussed below). 
     As shown in  FIG. 1(   a ), the anchor member  110  may have a length that is substantially equal to a distance between the anchor attachment portion  140  to the anchor deployment portion  120  when the cell  102  is in a fully collapsed configuration. In this way, when the cell  102  is in the fully collapsed configuration, the engagement end  114  of the anchor member  110  is disposed radially within the cell  102  and does not protrude beyond a radially external surface of the frame  104 . Thus, when each of the frame  104  and the cell  102  is in its completely collapsed configuration, the retaining structure prevents the engagement end  114  of the anchor member  110  from potentially engaging or interfering with a retention sheath of a delivery system during loading or deployment. 
     In one embodiment, the anchor end  114  of the elongate anchor member  110  may be fixedly attached to the anchor attachment portion  140  by welding, soldering, crimping, bonding, or any other suitable method. Alternatively, as shown in  FIGS. 3-5 , the anchor end  114  of the elongate anchor member  110  may be configured to mechanically couple to the anchor attachment portion  140  in a non-fixed manner to help reduce stress concentrations at the bond location between the elongate anchor member  110  and the anchor attachment portion  140 . The anchor end  114  may have a bifurcated shape designed to be inserted into an aperture disposed in the anchor attachment portion  140  and receive a surface thereof, as shown in  FIGS. 3(   a ) and ( b ). As shown in  FIGS. 4(   a )- 5 ( b ), the elongate anchor member  110  may be formed from a continuous piece of metallic wire that is inserted through an aperture in the anchor attachment portion  140  and looped around an outer surface thereof, thereby coupling the elongate anchor member  110  to the anchor attachment portion  140 . 
     In operation, as the strut members  130  of the frame  104  and the cells  102  expand from the collapsed configuration shown in  FIG. 1(   a ), to the fully expanded configuration shown in  FIG. 1(   c ), the anchor end  112  is held in place relative to the anchor attachment portion  140 . As the longitudinal distance between the anchor attachment portion  140  and the anchor deployment portion  120  decreases due to the expansion of the cell  102  in the circumferential direction, the engagement end  114  is forced outward through the anchor deployment portion  120 . Upon complete deployment, the deployment portion  120  of the elongate anchor member  110 , including the engagement end  114 , extends radially outward of the external surface of the retaining structure by a distance A. The distance A may be between about one to two or about one to four times the thickness of the elongate anchor member  110 . For example and without limitation, the elongate anchor member  110  may have a thickness of between about 0.2 mm and 0.6 mm. Accordingly, the distance A may be approximately 0.2 mm to approximately 2.4 mm. The distance A may be the same or different for each elongate anchor member  110  and each cell  102  to provide a desired tacking characteristic. Further, although the anchor attachment portions  140 , the anchor deployment portions  120 , and the elongate anchor members  110  are depicted with alternating orientation for each cell  102 , they are not limited thereto, and other configurations are contemplated. 
     It should be understood that the distance A may be greater or less than this range, so long as the portion of the elongate anchor member  110  is sufficiently long to provide adequate penetration into the surrounding vessel or stent-graft/desired structure and prevent migration of the endoluminal prosthesis  100 . Thus, as the frame  104  and the cells  102  are expanded, either through self-expansion or by a balloon, etc., the elongate anchor member  110  moves from a retracted position, in which the engagement end  114  of the anchor member  110  is disposed radially within the cell  102  and does not protrude beyond the external surface of the frame  104 , to a deployed position, in which the engagement end  114  is disposed radially outward of the external surface of the frame  104  to form an anchor or barb. Because the engagement end  104  is contained within the cells  102  when the frame  104  is in the initial collapsed state, the external surface of the endoluminal prosthesis  100  in the collapsed state is free of protrusions that may interfere with a retention sheath during loading or deployment. 
     This “barbless” profile in the collapsed configuration provides significant benefits over conventional barbed stents or stent grafts. For example, the endoluminal prosthesis  100  can be loaded into a delivery system in the same manner as a conventional barbless stent or stent-graft without potentially scarring or shaving the inner surface of a retention sheath or the like. The endoluminal prosthesis  100  can also be advanced through a modular prosthesis or a body lumen in an exposed, uncovered condition without the risk of inadvertent or unwanted snagging, scarring, or interference experienced with conventional barbed stents, stent-grafts and the like. Furthermore, because the barbs retract within the cells  102 , the endoluminal prosthesis  100  is capable of being “resheathed” during deployment. The resheathing process typically involves advancing a retention sheath of a delivery system in the distal direction over a partially deployed prosthesis. In conventional barbed prostheses, once the barbed portion is deployed, the barbs assume their outwardly protruding configuration, thus preventing the sheath from being advanced beyond the exposed/deployed barbs. In contrast, because the barb/anchor portion of the elongate anchor member  110  of this embodiment automatically retracts within the retaining structure as the frame  104  is collapsed, it is possible to resheath the prosthesis by advancing the retention sheath distally over the partially deployed endoluminal prosthesis  100  and compressing the frame  104 . 
       FIGS. 2(   a )-( c ) illustrate another embodiment of the endoluminal prosthesis  200 , in which the anchor attachment portion  140  and the anchor deployment portion  120  are attached to an inner surface of the bends connecting the upper and lower pairs of strut members  130 . The embodiment of  FIGS. 2(   a )-( c ) includes a radially expandable frame  204  comprising a plurality of strut members  230  connected by bends in an undulating pattern to form a ring-like structure having a substantially cylindrical shape. As with the embodiment of  FIGS. 1(   a )-( c ), various designs may be used for the frame  204 . For example, the frame  204  may be made of undulating, serpentine rings interconnected with longitudinal connecting members. The strut members  230  are made from elastic, super-elastic, or spring-metal alloys as described above in connection with embodiment of  FIGS. 1(   a )-( c ). The frame  204  may be self or balloon expandable. 
     The frame  204  also includes one or more retaining structures. The retaining structures may include one or more cells  202 . In one embodiment, each cell  202  may be at least partially defined by two pairs of circumferentially adjacent strut members  230  connected by individual bends. More specifically, each cell may be formed from a left and a right upper strut member  230  and a left and a right lower strut member  230 . Each of the left and right upper and lower strut members  230  has an inner and an outer end. The outer ends of the left upper and lower strut members  230  are connected by a single bend disposed at left longitudinal end of the cell  202 , such that the left upper and lower strut members  230  extend away from the bend and toward a center of the cell  202 . Similarly, the outer ends of the right upper and lower strut members  230  are connected by a single bend disposed at a right longitudinal end of the cell  202 , such that the right upper and lower strut members  230  extend away from the bend and toward a center of the cell  202 . The inner ends of the left and right upper strut members  230  are connected at an upper connecting member  250  and the inner ends of the left and right lower strut members are connected at a lower connecting member  250 . Each cell  202  also includes an anchor attachment portion  240  attached to an inner surface one of the bends, and an anchor deployment portion  220  attached to an external surface of the other bend. The anchor attachment portion  240  and the anchor deployment portion  220  extend from the respective bends toward a midpoint of the cell  202 . 
     It should be understood that while the strut members  230  are depicted as being straight, they are not limited thereto, and the strut members may have any curvilinear shape along their length to distribute bending forces and the like during use. The strut members may also have varied widths along their length. It should also be understood that while  FIGS. 2(   a )-( c ) depict the portion of the frame  204  corresponding to the cells  202 , in one embodiment, the frame  204  may be wholly comprised of interconnected cells  202  that extend around a circumference of the frame  204 . In other embodiments, the frame  204  may contain some portions utilizing the cells  202  and other portions utilizing strut members  230  arranged in other radially expandable patterns, for example and without limitation, zigzag, serpentine, and sinusoidal patterns. 
     An elongate anchor member  110  is attached to the anchor attachment portion  240  of the retaining structure at an anchor end  112 . The anchor attachment portion  240  may be formed as a lobe attached to a bend connecting the upper and lower right or left strut members  230 , and may include an aperture to receive the anchor end  112  of the elongate anchor member  110 . The elongate anchor member  110  also includes an engagement end  114  that is configured to extend through an anchor deployment portion  220 . The anchor deployment portion  220  may be shaped as the anchor deployment portion  120  described above in connection with embodiment of  FIGS. 1(   a )-( c ). As with embodiment of  FIGS. 1(   a )-( c ), the anchor member  110  extends from the anchor attachment portion  240  to the anchor deployment portion  220  along a radially inner surface of the cell  202 . The elongate anchor member  110  has a length that is substantially equal to a distance between the anchor attachment portion  240  to the anchor extruding portion  220  when the cell  202  is in a fully collapsed configuration. The anchor end  114  may be attached to the anchor attachment portion  240  in the manners described above in connection with embodiment of  FIGS. 1(   a )-( c ). 
     The frame  204 , the cells  202 , and the elongate anchor member  110  in the endoluminal prosthesis  200  function in substantially the same way as the embodiment of  FIGS. 1(   a )-( c ), and therefore their operation will not be described again. 
       FIGS. 6-12  illustrate alternative embodiments of the endoluminal prosthesis. As shown in  FIGS. 6(   a )- 7 ( b ), the frame may include cells  720  and  722  having anchor attachment portions  640  disposed at opposite longitudinal ends thereof. The cells  720 ,  722  may or may not be circumferentially adjacent one another. Each anchor attachment portion  640  includes an aperture  642 . An elongate anchor member  710  is threaded through the apertures  642  of the cells  720 ,  722  and bends around an outer edge of the respective anchor attachment portions  640 . In this way, the elongate anchor member  710  is fixed to each of the anchor attachment portions  640  and prevents the elongate anchor member  710  from moving relative to the anchor attachment portion  640  in the longitudinal direction as the frame  604  expands from the collapsed configuration ( FIG. 6(   a )) to the expanded configuration ( FIG. 7(   a )). 
     As shown in  FIG. 6(   b ), the elongate anchor member  710  has first and second portions  716 ,  718  that are configured substantially the same as the elongate member  110  described above in connection with the embodiments of  FIGS. 1(   a )-( c ) and  2 ( a )-( c ). The first and second portions  716 ,  718  are connected by a member  717  which is expandable along the circumferential direction of the prosthesis. Member  717  includes two straight portions connected at an angle by a bend disposed at a midsection thereof. As the cells  720 ,  722  expand from the collapsed to the expanded configuration ( FIGS. 6(   b ) and  7 ( b )), the expandable member  717  straightens, thereby expanding the elongate anchor member  710 . In operation, as the frame  104  is expanded, a distance between the anchor attachment portions  640  and the anchor deployment portions  620  decreases, thereby forcing the engagement ends  714  of the elongate anchor member  710  through the anchor deployment portions  620  in the radially outward direction, as described above in connection with  FIGS. 1(   a )- 2 ( c ). 
     As shown in  FIGS. 8(   a )- 9 ( b ), cells  920  and  922  have anchor attachment portions  840  disposed at the same longitudinal ends. The cells  920 ,  922  may or may not be circumferentially adjacent one another. Each anchor attachment portion  840  includes an aperture  842 . An elongate anchor member  810  includes a coupling member  816  that is inserted into the apertures  842  of the cells  920 ,  922  to attach the elongate anchor member  810  to each of the anchor attachment portions  840  and prevent the elongate anchor member  810  from moving relative to the anchor attachment portion  840  in the longitudinal direction as the frame  804  expands from the collapsed configuration ( FIG. 8(   a )) to the expanded configuration ( FIG. 9(   a )). 
     As shown in  FIG. 8(   b ), the elongate anchor member  810  has first and second portions  817 ,  818  that are configured substantially the same as the elongate member  110  described above in connection with the embodiments of  FIGS. 1(   a )-( c ) and  2 ( a )-( c ). The first and second portions  817 ,  818  are connected by a member  815  which is expandable in the circumferential direction of the prosthesis. Member  815  includes two straight portions connected at an angle by a bend disposed at a midsection thereof. As the cells  920 ,  922  expand from the collapsed to the expanded configuration ( FIGS. 8(   b ) and  9 ( b )), the expandable member  815  straightens, thereby expanding the elongate anchor member  810 . In operation, as the frame  804  is expanded, a distance between the anchor attachment portions  840  and the anchor deployment portions  820  decreases, thereby forcing the engagement ends  814  of the elongate anchor member  810  through the anchor deployment portions  820  in the radially outward direction, as described above in connection with  FIGS. 1(   a )- 2 ( c ). 
       FIGS. 10(   a ) and ( b ) illustrate an embodiment of an endoluminal prosthesis  1000  having an elongate member  110  that is integrally formed with the cells  1020  such that the cells  1020  and the elongate member  110  form a single monolithic structure. The elongate member  110  may be integrally formed with the cells  1020  by cutting a cannula or sheet using a laser, water jet, or the like. As shown in  FIG. 10(   a ), the elongate member  110  may be formed such that a first end  112  is integrally formed with a bend  1030  joining two circumferentially adjacent strut members  130 . The elongate member  110  extends across the cell  1020  in the longitudinal direction from the first end  112  toward the bend  1031  disposed at the opposite side of the cell  1020 . In this embodiment, the second end  111  of the elongate member  110  terminates somewhat short of the bend  1031  to allow access to the second end  111 . After the cell  1020  and the elongate member(s)  110  have been formed, a barb extension  1010  is attached to the second end  111  of the elongate member  110  in a secondary manufacturing process, as shown in  FIG. 10(   b ). The barb extension  1010  may include a receiving feature  1011  disposed at a first end  1013  in the form of a void or the like for receiving the second end  111  of the elongate member  110 . The barb extension  1010  may include an angled portion at a second end  1014  that, when attached to the elongate member  110 , protrudes in the radially outward direction. The barb extension  1010  may be fixedly attached to the elongate member  110  to prevent relative movement therebetween by, without limitation, press fitting, welding, soldering, adhesives, or the like. 
     In operation, the elongate member  110  of the endoluminal prosthesis  1000  functions in essentially the same manner as the embodiments described above. That is, as the distance between the bends  1030  and  1031  of the cell  1020  shrinks during radial expansion, the angled face of the barb extension  1010  contacts an inner surface of the bend  1031  and is deflected in a radially outward direction. As the cell  1020  continues to expand the elongate member  110  flexes along its length and extends further in the radially outward direction, thereby creating an anchoring feature. 
       FIGS. 11(   a ) and  11 ( b ) illustrates an alternative embodiment  1100  of the endoluminal prosthesis  1000  of  FIGS. 10(   a ) and ( b ), in which the elongate member  110  extends substantially across the entire width of the cell  1020 . However, unlike the prosthesis  1000 , a barb extension  1010  is not attached to the second end  111  of the elongate member  110 . Rather, a portion of the elongate member  110  including the second end  111  is bent in a radially outward direction in a secondary manufacturing process to create an angled portion  1122  similar to the angled portion of the barb extension  1010 . This angled portion  1122  of the elongate member  110  and the elongate member  110  itself operate in substantially the same manner as the embodiment  1000  described above, and therefore will not be described again. 
     In an alternative embodiment, the second end  111  of the elongate member  110  may not be bent to form an angled portion, as shown in  FIG. 12(   a ). Instead, a portion of the inner surface of the bend  1031  may be beveled through machining or the like to produce an angled surface  1130 . As the width of the cell  1020  decreases during expansion, the angled surface  1130  contacts the second end  111  of the elongate member  110 , thereby deflecting the second end  111  in a radially outward direction. Additionally, as shown in the embodiment of  FIG. 12(   b ), the second end  111  of the elongate member  110  may also be processed to have an angled face  1140  through machining or the like to help facilitate deflection and ensure the second end  111  of the elongate member  110  does not bind against the angled surface  1130  during expansion of the endoluminal prosthesis. It should be understood that the secondary processing of the bend  1031  illustrated in  FIG. 12  may also be applied to the embodiment  1000 . Because the embodiments  1000  and  1100  include integrally formed elongate members  110 , the overall profile of the resulting endoluminal prostheses may be reduced as compared to the embodiments of  FIGS. 1(   a )- 9 ( b ) having a separate elongate member. 
     While preferred embodiments have been described, it should be understood that the invention is not so limited, and modifications may be made without departing from the invention. The scope of the invention is defined by the appended claims, and all devices that come within the meaning of the claims, either literally or by equivalence, are intended to be embraced therein. Furthermore, the features described above are not necessarily the only features of the invention, and it is not necessarily expected that all of the described features will be achieved with every embodiment of the invention.