Abstract:
An improved hood provides for the attaching of endoluminal prosthesis within corporeal lumens. The hook is integrally formed with framing structure and is preset into an outward bend, but is resiliently flexible so as to form a substantially straight profile when compressed. The hook is capable of impinging upon the corporeal lumen and thereby securing the prosthesis. The hook may be configured for intraluminal delivery and deployment. A novel method of manufacturing said hook is also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of Ser. No. 11/609,222 filed Dec. 11, 2006, which is a continuation of Ser. No. 10/326,719 filed Dec. 19, 2002, now U.S. Pat. No. 7,147,662, which is a continuation of Ser. No. 09/547,822, filed Apr. 11, 2000, now U.S. Pat. No. 6,517,573, the contents of which are hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention relates to an attachment element for fixation to corporeal tissue and a method of manufacturing the same. Such an attachment element may be used to attach endoluminal prosthesis within arteries, veins and similar lumens. As such, the attachment element would be capable of intraluminal delivery. 
         [0003]    A variety of endoluminal prosthesis currently exist which require fixation within corporeal lumens. Examples of such are grafts and stents. Grafts are artificial lumens which replace the natural lumen or reside within the natural lumen and isolate the natural tissue from blood flow. 
         [0004]    Stents are semi-rigid tubular structures which may be used to maintain the patency of natural lumens or grafts. By providing scaffolding for the lumen, stents prevent collapse and occlusion. Stents are typically formed either by winding wire into a tubular structure or removing material from a solid tube. 
         [0005]    Prior art grafts and stents have described the use of hooks to improve fixation of the prosthesis. These hooks were typically formed of bent wire attached to the prosthesis. The prior art also teaches integrally formed hooks on the prosthesis. These integral hooks are formed to be axially aligned with the prosthesis prior to deployment and forced outwardly upon intraluminal deployment. 
         [0006]    What has not been taught by the prior art and was heretofore unknown is an integrally-formed, outwardly predisposed hook for attaching to a corporeal lumen. The present invention satisfies that need. 
       SUMMARY OF THE INVENTION 
       [0007]    Briefly and in general terms, the present invention embodies an attachment or anchoring element (i.e., protrusion, hook, barb) for fastening to corporeal tissues and a method of manufacturing the same. The attachment or anchoring element is formed as an integral portion of a metallic frame and has a preset outward bend or curve. The attachment or anchoring element is generally comprised of an elongated member and a pointed end. The pointed end is configured to impinge upon and possibly pierce corporeal tissue, plaque or other debris or disease. 
         [0008]    In general, the present invention provides an improved attachment or anchoring element (which will be referred to herein as a hook for convenience) for fixation of endoluminal prosthesis. As such, the hook is configured for intraluminal delivery within a catheter or capsule. The hook and endoluminal prosthesis may then be delivered to a diseased or damaged portion of a corporeal lumen such as an artery or vein. Once delivered the hook may be compressed into or pierce the interior surface of the lumen. When compressed in such a fashion, the hook and prosthesis are securely fastened to the corporeal lumen. 
         [0009]    There exists a variety of endoluminal prostheses which would benefit from the superior fixation provided by a hook which embodies the features of the present invention. Once such device, an abdominal aortic graft is used to treat abdominal aortic aneurysms. Such treatment requires the intraluminal delivery of the graft across the aneurysm. Once delivered the graft must be firmly attached to the surrounding tissue of the abdominal aorta. The present invention, in one possible embodiment, may be configured to provide secure leak-proof fixation for abdominal aortic grafts. 
         [0010]    The hook may be formed integrally with the endoluminal prosthesis to be secured. It may also be formed separately and attached to the prosthesis by a variety of well-known means. The hook is typically formed from a metallic frame. This frame could be separate from the host prosthesis or be a portion thereof. 
         [0011]    The hook is formed by cutting narrow incisions in the frame. These incisions define the elongated member and the pointed end. Laser-cutting is a well-known method of making such incisions. Once the hook is cut it can be bent outwardly such that the pointed end faces the direction in which the corporeal tissue will lie. This bend or curve in the hook may be permanently set by heating. Once set, the hook may be pressed back into the frame and the hook will spring back into the bent position when released due to its resilient nature. 
         [0012]    There are a variety of configurations for the hook which are embodied in the present invention. The elongated member may have a constant cross-section throughout its length. It may also have a reducing cross-section near the pointed end. The pointed end may include one or more barbs. One configuration includes a single barb on either side of the pointed end, forming an arrowhead configuration. The pointed end may also be sharpened to further ensure fixation. Multiple hooks may be formed within a single frame. It is possible to form multiple hooks from a single set of incisions. Multiple hooks in opposing directions may provide superior fixation. 
         [0013]    Other features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a perspective view of one embodiment of the hook and frame. 
           [0015]      FIG. 2  is a side view of the hook and frame piercing a corporeal lumen wall. 
           [0016]      FIG. 3  is a side view of the hook and frame with the hook compressed. 
           [0017]      FIG. 4  is a partial front view of multiple hook and frame combinations formed integrally with a typical endoluminal prosthesis. 
           [0018]      FIG. 5  is a perspective view of multiple hook and frame combinations attached to a typical endoluminal prosthesis. 
           [0019]      FIG. 6  is a perspective view of an endoprosthesis having medial hooks. 
           [0020]      FIG. 7A  is a front view of a first embodiment of the hook and frame. 
           [0021]      FIG. 7B  is a front view of a second embodiment of the hook and frame. 
           [0022]      FIG. 7C  is a front view of a third embodiment of the hook and frame. 
           [0023]      FIG. 7D  is a front view of a fourth embodiment of the hook and frame. 
           [0024]      FIG. 7E  is a front view of a fifth embodiment having multiple hooks on a single frame. 
           [0025]      FIG. 8  is a perspective view of a first embodiment of a mandrel assembly for bending the hook. 
           [0026]      FIG. 9  is a partial cross-sectional view of a second embodiment of the mandrel assembly and a hook and frame. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0027]    As shown in  FIGS. 1 and 2 , the invention may be embodied as a hook  20  formed integrally within a frame  22 . The hook  20  is comprised of an elongated member  24  and a pointed end  26 . The hook  20  may be bent or curved such that the pointed end  26  extends out of the frame  22 . 
         [0028]    The hook  20  and frame  22  are configured to secure themselves to corporeal tissue. The pointed end  26  may be compressed onto corporeal tissue such that it impinges into or possibly pierces the tissue. With the curve as shown in  FIG. 2 , force applied downward on the frame  22  causes the hook  20  to embed into the tissue. A preferred configuration is sized to be delivered intraluminally and attach to the inside of a blood vessel. Another possibility is to configure the hook  20  and frame  22  to attach to an artificial lumen such as an endoluminal graft. 
         [0029]    In the compressed configuration, as depicted in  FIG. 3 , the hook  20  is preferably compressed until the hook  20  is within the bounds or circumference of the frame  22 . In this manner, the combination of the hook  20  and frame  22  forms a nearly flat profile. Since the hook  20  has been deformed into a preset bend, the pointed end  26  may still extend a short distance out from the frame  22 . Furthermore, due to the preset bend, the elongated member  24  may extend a short distance out of the frame  22  in the opposite direction from the pointed end  26 . This compression of the hook  20  provides a very narrow cross section which facilitates loading the device into a catheter for delivery. 
         [0030]    The hook  20  and frame  22  may be attached to or formed as part of an intraluminal endoprosthesis  28 . This configuration is depicted in  FIG. 4 . When so attached, the function of the hook  20  and frame  22  is to secure the endoprosthesis  28  within a vascular lumen. This may be accomplished by forming or attaching the frame  22  on the endoprosthesis such that the hook  20  will embed itself into the lumen when the endoprosthesis  28  is deployed. It is to be recognized that although  FIG. 4  shows hooks  20  configured at a superior end of the endoprosthesis  28 , hooks  20  can also be incorporated into an inferior end of the device. 
         [0031]    The hook  20  and frame  22  may also form part of an attachment device  29  for a graft  30 . This configuration is shown in  FIG. 5 . Such an arrangement may be attached to a superior end as well as inferior ends (not shown) of the graft  30 . Additionally, the attachment device  29  may be affixed longitudinally separated from the graft  30  or may be attached to inside or outside surfaces thereof. The attachment device  29  expands the hook  20  into the vessel wall. The combined attachment forces of the imbedded hook  20  and the expanded attachment system  29  provide stable fixation of the endoluminal graft  30  within the vessel. 
         [0032]    There exists a variety of devices that fit within the definitions of an intraluminal endoprosthesis  28  and a graft  30 . Most of theses devices would benefit from the use of the securing devices defined herein. As shown, the same may form part of grafts which primarily replace the natural lumens or isolate them from the blood flow. Stents, which primarily ensure the patency of a lumen by resisting collapse and occlusion, can also benefit from the present invention as would implantable blood clot filters such as those often put in the vena cava. 
         [0033]    The addition of the frame  22  and hook  20  of the present invention to existing grafts, stents and filters would provide such devices with superior fixation capability. For grafts the present invention will provide the additional benefit of leak-proof sealing of the graft to the blood vessel. 
         [0034]    Endoluminal devices are typically collapsed for intraluminal delivery. Upon delivery to the desired location within the corporeal lumen, these devices are re-expanded. This re-expanding is accomplished in a number of ways. Balloon expansion requires the use of an angioplasty-type balloon catheter, which expands a device located about the balloon. Self-expansion uses the spring forces or super-elastic properties of the compressed device to expand outwardly once released. Shape memory metals have also been used in endoluminal devices to expand upon the addition of energy or chemicals. The expansion forces of any of these methods are sufficient to embed the appropriately placed hook  20  into a corporeal lumen. The frame  22  and hook  20  may be attached to the device such that the hook  20  is disposed radially outwardly from the device. As the device further expands radially outwardly the hook  20  is driven into the tissue of the corporeal lumen. Using several hook  20  and frame  22  combinations around the perimeter of the device ensures the most secure attachment. 
         [0035]    Another method of securing the hook  20  allows attachment without relying upon expansion forces. The hook  20  may be impinged into the corporeal lumen by translating the hook  20  and frame  22  axially. Since the elongated member  24  is bent outward as it extends toward the pointed end  26 , translating the hook  20  in the opposite direction of the elongated member&#39;s extension will force the pointed end  26  deeper into the corporeal lumen. Implanting the hook  20  and frame  22  in a position such that the axial forces of the blood flow are in this same direction will help secure the device over an extended period. 
         [0036]    The frame  22  may be a separate device or may be a portion of the endoluminal device to which the hook  20  and frame  22  are a part. The frame  22  may be a small flat plate. Additionally since many endoluminal devices are formed from tubes, the frame  22  may be a portion thereof, that is, the frame  22  may be curved. Within the Figures, the frame  22  is depicted as a small roughly rectangular element with a connection  36  at one end. However, the frame  22  may be of any size or shape, or the frame  22  may be indistinguishable from the components of the endoluminal device from which the frame  22  is formed. 
         [0037]    The hook  20  and frame  22  are typically formed of metal. Biocompatible stainless steel and Nitinol (Nickel Titanium Alloy) are particularly suited for this purpose. More exotic materials such as ceramics and plastics may also perform adequately. 
         [0038]    The hook  20  may be formed in the frame  22  by first cutting incisions  40  into the frame  22 . Preferably these incisions  40  are cut in such a manner as to remove the smallest amount of material from the frame  22  and hook  20 , while still allowing for stress relief and freedom of movement of the hook. This preferred method leaves the hook  20  bounded on three sides by a narrow incision  40 . This cutting forms the elongated member  24  and the pointed end  26 . Laser cutting is a process known in the art which is preferred for making these incisions. To relieve the stresses caused by bending, additional material may be removed at the end of the incisions  40  in the form of cut-outs  52  (shown in  FIG. 1 ). 
         [0039]    With reference to  FIG. 6 , it is to be noted that it is also contemplated that an endoprosthesis  28  of the present invention can embody hooks  20  that are located medial the ends  29 ,  31  of the endoprosthesis  28 . In such an arrangement, the hooks  20  can be positioned at a junction  33  between adjacent struts of adjacent cells  35  that define the endoprosthesis  28 . It is to be recognized that although  FIG. 9  shows a hook  20  positioned at each junction  33 , for certain applications, fewer hooks  20  may be desirable. 
         [0040]    Varying the configurations of the incisions  40  made in the frame  22  will provide a variety of configurations of the hook  20 . As depicted in  FIG. 7A  the simplest configuration may be to cut parallel incisions  40  with a pointed end  26  which forms a constant cross-section elongated member  24  with a simple point. 
         [0041]    Another configuration depicted in  FIG. 7B  has non-parallel incisions  40  which narrow towards the pointed end  26 . This produces an elongated member with a cross-section which reduces toward the pointed end  26 . The reduction in cross-section allows a decreasing bend radius near the pointed end  26 . In this manner the pointed end may be pointed outwardly more towards the perpendicular which aids in impinging the corporeal tissue. 
         [0042]    Another configuration, depicted in  FIG. 7C , includes barbs  38  on the pointed end  26 . With two such barbs  38  the pointed end has an arrowhead configuration. These barbs  38  may help secure the hook within the corporeal lumen. 
         [0043]    Combining configurations, as depicted in  FIG. 7D , produces a narrowing elongated member  24  with barbs  38 . Such a configuration could combine the advantages of a decreasing bend radius with that of a barbed pointed end  26 . 
         [0044]    Another configuration, depicted in  FIG. 7E , creates a plurality of hooks  20  from the same incisions  40 . This could form hooks  20  which project in opposing directions. Such a configuration would provide superior resistance to radial and axial loads from the corporeal lumen and blood flow. 
         [0045]    The pointed end  26  of each of these configurations may be sharpened to improve its ability to pierce the corporeal lumen. Material may be removed from either or both the lumen-facing or frame-facing sides of the pointed end  26  to produce a sharper point. 
         [0046]    The preferred method of manufacturing the hook  20  and frame  22  includes cutting the hook  20  out of the frame  22  using narrow incisions  40 . Several methods of making such incisions  40  in metal are well known. Possible examples are laser cutter, photo-etching and chemical etching. 
         [0047]    Once the hook  20  is cut into the frame  22 , it may be bent away from the frame  22 . This may be accomplished manually by using tweezers to force the pointed end  26  of the hook  20  away from the frame  22 . If the hook  20  and frame  22  are formed as part of an endoluminal device, the device may be mounted on a mandel  42  with pins  44  or similar means to force the pointed end  25  of the hook  20  away from the frame  22 . 
         [0048]    As depicted in  FIG. 8 , the mandrel  42  is preferably configured as a cylindrical shaft with pins  44  appropriately spaced about the circumference of the shaft. A frame  22  may be pressed against the shaft  46  such that a pin  44  forces the hook  20  outwardly. This configuration can be maintained while the hook  20  is heat sent to be permanently predisposed with an outward curve. Another preferred configuration for the mandrel, as depicted in  FIG. 9 , includes a cylindrical shaft  46 , a convex outer ring  48  and a concave outer ring  50 . A curved gap between the outer rings forces the hook  20  into a predetermined bend. This configuration of shaft and rings may be clamped together for heat setting. 
         [0049]    After bending, the hook  20  may be permanently deformed into the curved configuration by heat setting the material. For a Nitinol hook  20  and frame  22  combination heating at 550 degree. C. for ten minutes is sufficient. A ceramic or plastic hook  20  and frame  22  combination might be formed in a bent configuration. 
         [0050]    With a permanently deformed hook  20 , the hook  20  may still be compressed into alignment with the frame  22  without losing the preset curve. Thus, the hook  20  may be compressed into the frame for intraluminal low-profile delivery, and then deployed in the curved configuration by releasing. This is a significant advantage in producing a fixation device small enough to be delivered intraluminally. 
         [0051]    It will be apparent from the foregoing that, while particular forms of the invention have been illustrated and described, various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited, except as by the appended claims.