Reinforced graft and method of deployment Number:7,520,890 from the United States Patent and Trademark Office (PTO) owispatent A graft is provided with a flexible sheet (10) of graft material to which is sewn a reinforcing wire (12), preferably of shape-memory alloy. Sewing of the wire (12) is carried out while the sheet (10) is substantially planar, thus by conventional embroidery machines. The sheet (10) is subsequently rolled into a tubular shape.<H deployment, Reinforced, Reinforced, graf, 7520890.html, Patent, pto, 7520890

Title: Reinforced graft and method of deployment

Abstract: A graft is provided with a flexible sheet (10) of graft material to which is sewn a reinforcing wire (12), preferably of shape-memory alloy. Sewing of the wire (12) is carried out while the sheet (10) is substantially planar, thus by conventional embroidery machines. The sheet (10) is subsequently rolled into a tubular shape.

Patent Number: 7,520,890 Issued on 04/21/2009 to Phillips

Inventors: Phillips; Peter W. (Didcot, Oxfordshire OX11 7HJ, GB)
Appl. No.: 11/051,614

Filed: February 4, 2005

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
09601023		6899728
PCT/GB99/00261	Jan., 1999

Foreign Application Priority Data


Jan 26, 1998 [GB]			9801660.3
Jan 31, 1998 [GB]			9802060.5

Current U.S. Class: 623/1.13 ; 623/1.35

Current International Class: A61F 2/06 (20060101)

Field of Search: 623/1.11,1.13,1.35,903 606/191-195

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Primary Examiner: Stewart; Alvin J.
Attorney, Agent or Firm: Fieschko, Esq.; Craig A. DeWitt Ross & Stevens S.C.

Parent Case Text

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part under 35 USC .sctn.120 of U.S. patent application Ser. No. 09/601,023 filed 26 Jul. 2000 (now U.S. Pat. No. 6,899,728), which in turn claims the priority under 35 USC .sctn.371 of International (PCT) Patent application PCT/GB99/00261 filed 26 Jan. 1999, which in turn claims priority to GB 9802060.5 filed 31 Jan. 1998 and GB 9801660.3 filed 26 Jan. 1998. In addition, this application claims the benefit under 35 USC .sctn.119 of GB 0402499.8 filed 4 Feb. 2004. All of these prior applications are incorporated by reference herein.

Claims

What is claimed is:

1. A method of deploying a stent graft between proximal and distal landing sites axially spaced along the lumen of a patient, the method comprising the following steps: a. selecting a flexible stent graft having spaced proximal and distal ends, the proximal and distal ends being spaced further apart than the proximal and distal landing sites, b. situating the stent graft within a deployment sheath, c introducing the proximal end of the stent graft into the lumen of the patient, with the distal end trailing, while the stent graft is within the deployment sheath, d. situating: (1) the proximal end of the stent graft at the proximal landing site, the proximal end being ejected from the deployment sheath, and (2) the distal end of the stent graft away from the distal landing site within the deployment sheath, such that the distal landing site is between the proximal landing site and the distal end of the stent graft; and e. subsequently moving the distal end of the stent graft by moving the deployment sheath toward the proximal end until the distal end is situated at the distal landing site, thereby compressing the stent graft along at least a portion of its length, while maintaining the diameter of the stent graft at least substantially unchanged at the compressed portion of the stent graft length, and f. ejecting the distal end of the stent graft at the distal landing site.

2. The method of claim 1 wherein the distance between the proximal and distal ends of the stent graft is at least 15% greater than the distance between the proximal and distal landing sites.

3. The method of claim 1 wherein the stent graft is formed of: a. flexible sheet material which defines a tubular shape; and b. resiliently flexible supports spaced along the axial length of the tubular shape, wherein: (1) the supports bias the tubular shape from a radially compacted form to a radially expanded form; and (2) the supports are spaced by distances less than one-third of the diameter of the tubular shape.

4. The method of claim 3 wherein the spacing of the supports varies along the axial length of the tubular shape, thereby forming regions of varying axial extensibility of the tubular shape.

5. The method of claim 1 wherein the stent graft is furcated.

6. The method of claim 1: a. wherein the stent graft includes: (1) an interior axial passage extending between its proximal and distal ends, and (2) a side aperture opening onto the interior axial passage between the proximal and distal ends; b. further comprising the step of rotating the stent graft to align the side aperture with a lumen branch extending from the patient's lumen.

7. The method of claim 1 wherein: the step of situating the proximal end of the stent graft at the proximal landing site includes the substeps of: (1) holding the proximal end of the stent graft at the proximal landing site; and (2) simultaneously withdrawing the deployment sheath from the proximal end.

8. The method of claim 7 wherein the proximal end of the stent graft is restrained at the proximal landing site by a pushing member extending along the lumen.

9. The method of claim 7 wherein the proximal end of the stent graft is restrained at the proximal landing site by a pushing member which extends through a wall of the stent graft.

10. The method of claim 1 wherein: (1) the stent graft may be situated within the deployment sheath with the stent graft being radially compressed, the stent graft radially expanding when released from the deployment sheath; (2) the stent graft is provided in combination with proximal attachment means for releasably engaging the proximal end of the stent graft, the distal attachment means extending along the deployment sheath; (3) the stent graft is provided in combination with distal attachment means for releasably engaging the distal end of the stent graft, the distal attachment means extending along the deployment sheath; wherein: a. the proximal end of the stent graft is situated at the proximal landing site by the proximal attachment means; and b. the distal end of the stent graft is situated at the distal landing site by the distal attachment means.

11. The method of claim 10 wherein the step of situating the proximal end of the stent graft at the proximal landing site includes withdrawing the deployment sheath from the proximal end of the stent graft while the proximal attachment means maintains the proximal end of the stent graft at the proximal landing site.

12. The method of claim 11 wherein the step of situating the distal end of the stent graft at the distal landing site includes withdrawing the deployment sheath from the distal end of the stent graft while the distal attachment means maintains the distal end of the stent graft at the distal landing site.

13. The method of claim 10 wherein the proximal attachment means includes: a. a first elongated member terminating in a pocket, and b. a second elongated member adapted to extend alongside the first elongated member, the second elongated member terminating in an end sized to be received within the pocket of the first elongated member.

14. The method of claim 10 wherein: a. the stent graft has an at least substantially tubular sidewall extending between its proximal and distal ends; and b. at least a portion of the proximal attachment means extends through the sidewall when the proximal end of the stent graft is situated at the proximal landing site.

15. The method of claim 1 wherein the step of moving the distal end of the stent graft toward the proximal end until it is situated at the distal landing site is followed by the steps of: a. continuing the motion of the distal end of the stent graft toward the proximal end until it is situated past the distal landing site; and b. reversing the motion of the distal end of the stent graft until it is situated at the distal landing site.

16. A method of deploying a stent graft between proximal and distal landing sites axially spaced along the lumen of a patient, wherein the stent graft: (1) has spaced proximal and distal ends, the proximal and distal ends being spaced further apart than the proximal and distal landing sites, and (2) is axially compressible to allow the proximal and distal ends to be more closely spaced,and wherein the diameter of the stent graft is at least substantially constant during such compression, the method comprising the following steps: a. firstly introducing the proximal end of the stent graft into the lumen of a patient, with the distal end trailing behind, while the stent graft is whithin a deployment sheath; b. secondly situating the proximal end of the stent graft at the proximal landing site; c. thirdly advancing the distal end of the stent graft by moving the deployment sheath toward the proximal landing site, with the distal end being within the deployment sheath, until the distal end is situated at the distal landing site, with such advancing axially compressing the stent graft; and d. fourthly releasing the distal end of the stent graft from the deployment sheath at the distal landing site.

17. A method of deploying a stent graft between proximal and distal landing sites axially spaced along the lumen of a patient, wherein the stent graft: I. has spaced proximal and distal ends, the proximal and distal ends being spaced further apart than the proximal and distal landing sites; II. is axially compressible to allow the proximal and distal ends to be more closely spaced; and III. is provided in combination with: i. a deployment sheath wherein the stent graft may be situated with the stent graft being radially compressed, the stent graft radially expanding when released from the deployment sheath; ii. proximal attachment means for releasably engaging the proximal end of the stent graft, the proximal attachment means extending along the deployment sheath; iii. distal attachment means for releasably engaging the distal end of the stent graft, the distal attachment means extending along the deployment sheath; the method comprising the following steps: a. introducing the deployment sheath into the lumen of a patient with: (1) the deployment sheath having the stent graft therein, and (2) the proximal end of the stent graft leading the distal end; b. locating the deployment sheath within the lumen such that the proximal end of the stent graft is situated at the proximal landing site; c. withdrawing the deployment sheath from the proximal end of the stent graft while the proximal attachment means maintains the proximal end of the stent graft at the proximal landing site; d. axially compressing at least a portion of the stent graft to move the distal end of the stent graft by moving the deployment sheath toward the proximal end, with the distal end being within the deployment sheath, and with the compressed portion having at least substantially the same diameter before and after compression; and e. withdrawing the deployment sheath from the distal end of the stent graft while the distal attachment means maintains the distal end of the stent graft at the distal landing site.

18. The method of claim 17 further comprising the steps of: a. moving the distal end of the stent graft toward the proximal landing site to axially compress the length of the stent graft; b. continuing such motion until the distal end of the stent graft is situated at the distal landing site; and c. releasing the distal end of the stent graft to remain at the distal landing site.

19. The method of claim 17 further comprising the steps of: a. after withdrawing the deployment sheath from the proximal end of the stent graft, engaging the distal end of the stent graft with the distal attachment means; and b. moving the distal attachment means toward the proximal landing site to axially compress the length of the stent graft.

20. The method of claim 19 wherein the step of moving the distal attachment means toward the proximal landing site is followed by the step of releasing the distal attachment means from the distal end of the stent graft when the distal end of the stent graft is at the distal landing site.

Description

FIELD OF THE INVENTION

This invention relates to a reinforced graft and to a method of producing such a graft which may be used for the treatment of lesions in vessels, e.g., aneurysms in the aorta or lesions in the esophagus or trachea, by an endoluminal technique, which is minimally invasive and which can therefore be used on many patients who are too old or frail to be able to withstand conventional surgery.

BACKGROUND OF THE INVENTION

Conventional vascular grafts commonly consist of a textile or polymer tube which is implanted into a patient in a major open surgical procedure. grafts which have been implanted endoluminally, that is from within the vessel, consist of grafts which are combined with stents. Such grafts are very time-consuming to produce and this causes particular problems when a bespoke graft is required to be produced at short notice.

Additionally, one of the major problems of existing vascular grafts for endoluminal surgery is that, because of the tortuous bends commonly encountered between the aorta and iliac arteries of patients with aneurysms, there is a tendency for existing tubular grafts to collapse at least partially. This is because, when the tube is curved for any reason, the external diameter of the curve is necessarily longer than the internal, and the excess graft material on the internal diameter of the curve kinks into the lumen, thereby narrowing or even closing it completely. This problem also arises in vascular grafts for repair of, for example, the popliteal artery because of the extreme bending movements which are imparted to this artery during knee flexion.

Furthermore once a graft has been introduced into an artery by the surgeon and located at the correct position, it is necessary to ensure that it is reliably held at such position.

Some devices in use to date are based upon the combination of a stent with a graft, a stent being a relatively rigid metallic cylinder with highly fenestrated walls. This produces a strong implant but one which is relatively inflexible. Some prior graft stents comprise a woven fabric tube which is supported by a series of wire rings which are stitched to the outer or inner surfaces of the implant. Usually these rings are made in the form of a `Z` stent (as with the ZENITH graft manufactured by Cook Inc., or the TALENT graft manufactured by Medtronic Inc.). The `Z` stent, as well as other graft stents, is known to be relatively inflexible and for this reason, graft stents manufactured using such supports are not easily bent around curved vessels. (A frequent complication of arterial disease is the development of highly tortuous vessels through which it is very difficult to pass substantially rigid graft stents.) Moreover the graft stents are difficult to compress axially and this requires that the length of the patient's vessels must be measured accurately so that the selected graft stent is a good fit. Estimating the length of graft stent required to fit a patient can be surprisingly difficult because the presence of the graft stent itself modifies the anatomy of the patient, straightening tortuous vessels and taking unpredictable paths through aneurysmal voids.

Once measured, another problem for the practitioner is to place the graft stent in the same position as was planned; generally the top or proximal end of the implant is deployed first and the rest of the implant follows. If the top is incorrectly placed, then it follows that the bottom of the implant will also be incorrectly placed because the implants cannot be significantly compressed along their axes.

Most graft stents require the inflation of a balloon inside them to expand the graft to fit within the blood vessel although self expanding designs have been recently introduced.

Most existing designs involve the use of a preformed stent which usually involves expensive construction techniques such as laser cutting and plasma welding.

In attaching the preformed stent to the graft, current devices usually involve multiple individual stitches around the stent and attached to the graft. These stitches are necessarily attached by hand in a costly and time consuming process.

A further problem with the current designs, arising from the substantial stent components, is the difficulty in designing bifurcated grafts which can be used at, for instance, the aorto-iliac bifurcation.

A further problem associated with long graft stents, particularly in the arteries of the lower limb, is irritation of the arteries arising from trauma of insertion and the longer term presence of the synthetic material.

SUMMARY OF THE INVENTION

The present invention seeks to provide an improved reinforced graft and method of making such a graft.

According to an aspect of the present invention, there is provided a graft including a sheet of flexible material, a plurality of reinforcement elements extending transversely relative to a longitudinal direction of the sheet of material, the reinforcement elements being spaced from one another in the longitudinal direction, wherein at least some of the plurality of reinforcement elements are formed from a continuous wire.

Advantageously, the sheet of material is formed as a tube with the reinforcement elements extending annularly around the tube.

The reinforcement elements are preferably compressible radially relative to the tube.

When the graft is formed into its in-use shape, the reinforcing elements are preferably pre-stressed. This enables the use of reinforcement elements which are more deformable than prior art devices.

According to another aspect of the present invention, there is provided a graft including at least one radio-opaque marker embroidered onto the graft. Advantageously, the marker provides an indication of the part of the graft to which the marker is embroidered. For example, the marker could denote an "L", "R", "A" or "P" denoting, respectively, left, right, anterior and posterior. A plurality of opaque markers could be provided on the graft.

It will be apparent that an embroidered marker could also be provided on a stent by providing embroiderable material on the stent.

According to another aspect of the present invention there is provided a graft or stent including at one extremity thereof a plurality of flexible members extending in a longitudinal direction of the graft or stent from an annular perimeter thereof, an annulus being provided at a free extremity of the flexible members, the flexible members being deformable substantially to a point to provide a flexible neck about which the annulus can rotate. This structure can provide a front guide to the graft or stent considerably facilitating insertion of the graft or stent into, for example, an artery, and greatly improving fixation in highly tortuous vessels.

Preferably, the elongate members provide a flow path into the graft or stent.

In the preferred embodiment, the elongate members are provided with barbs at their extremities remote from the graft or stent, for fixing the graft or stent into, for example, an artery.

Alternatively, separate barbs may be provided on the annulus.

According to another aspect of the present invention, there is provided a method of forming a reinforced graft, including providing a sheet of material, a plurality of reinforcement elements in substantially flat configuration, sewing the reinforced elements to the fabric, forming the fabric into a substantially tubular shape.

This method enables the graft to be produced by conventional sewing machines.

Preferably, the method includes a step of sewing guides over the reinforcement elements, moving the reinforcement elements into their correct position on the sheet of material, and then sewing the reinforcement elements into substantially fixed positions on the sheet of material.

Advantageously, the reinforcement elements are sewn loosely onto the sheet of material. For example, spaced stitches could be used to enable slight buckling of the material between stitches during compression of the graft. Alternatively, stitches which have a stitch width of 2 to 9 times the width of the reinforcement elements could be used.

Advantageously, a reduced friction coated yarn is used to enable some movement of the reinforcement elements relative to the sheet of material, particularly on compression of the finished graft.

In the preferred embodiment, the reinforcement elements are provided by a single wire sewn into a ladder of substantially straight portions connected by substantially U-shaped connecting portions. The connecting portions may be round or substantially square in shape.

Advantageously, the graft is formed so that connecting portions overlap. In the preferred embodiment overlapping connection portions are sewn to one another.

According to another aspect of the present invention, there is a provided a method of forming a reinforced graft or stent in which reinforcement elements are connected to a flexible fabric sheet by means of a lock-stitch or chain-link.

According to another aspect of the present invention, there is provided a reinforced graft including a sheet of flexible material and a plurality of reinforcement elements, the reinforcement elements being substantially parallel to the weft or warp of the fabric or substantially at 450 to the weft or warp of the fabric. Providing reinforcement elements substantially parallel to the weft or warp of the fabric to provide a stable and substantially inelastic structure. On the other hand, providing reinforcement elements at substantially 450 to the weft or warp provides a more elastic device.

The preferred embodiment can provide a reinforced graft which is sufficiently flexible to allow it to be drawn through tortuous vessels and which has sufficient radial stiffness to resist kinking and subsequent collapse which would occlude the flow of blood through the graft. It can be used for endovascular implantation in diseased arteries such as the aorta, carotid, iliac, femoral and popliteal arteries. Other applications of the device exist in vessels in the body such as veins, bile ducts, oesophagus, trachea etc.

Preferably, the reinforced graft is self expanding to the extent that it does not require a balloon for inflation.

Advantageously, the reinforced graft does not involve the separate manufacture and attachment of a stent and can be manufactured simply and relatively quickly. The simplicity of the preferred construction is intended to assist in the production of bifurcated, tapered and connecting grafts.

It is preferred that the graft is sufficiently supple that it can be everted so that when initially inserted, the proximal part of the graft can be held and the distant part pulled through the proximal part so that finally, the graft is everted end to end. This possibility reduces the trauma of implanting long lengths of graft.

An example of a method of producing a reinforced graft comprises the steps of attaching filamentary reinforcing material to a sheet of flexible graft material having opposite side edges so that the reinforcing material extends laterally over the sheet with respect to the opposite side edges and is preferably attached along substantially the whole of its length to the sheet; forming the sheet into a tube having a longitudinal seam; and preferably securing together the reinforcing material on opposite sides of the longitudinal seam.

In this example, the reinforcing material can be very accurately and conveniently attached at the required places to the sheet when the latter is laid out flat and before the sheet is formed into a tube, thus avoiding the complication of attaching the reinforcing material to a pre-formed tube of graft material.

Preferably, the filamentary reinforcing material is attached to the sheet of flexible graft material so as to define a sinuous pattern of the reinforcing material in which a multiplicity of substantially linear regions extending laterally with respect to the sheet are joined by bends, and the bends at one side of the sinuous pattern are secured to corresponding regions of the reinforcing material at the other side. In this way, spaced hoops of filamentary reinforcing material are provided which are secured to the tube, the hoops being spaced apart in the longitudinal direction of extent of the tube. It will be understood that these hoops can be appropriately spaced apart so as to permit the required flexibility of the tube to enable it to be bent around tortuous bends commonly encountered in the arteries of patients whilst still supporting the tube in such a way as to prevent kinking thereof exclusively in a localized region. Thus, when the tube is bent, it is constrained to bend in a series of small kinks between the reinforcing hoops, and thereby able to follow curvatures encountered in practice without significant stenosis of the lumen.

In a particularly preferred embodiment, the bends are secured using ties which are not passed through the wall of the tube.

This may be effected simply by passing the ties solely around the part of the filamentary material to be joined together and knotting them.

The seam in the tube is preferably formed by securing the sheet along the side edges and then folding the portion of the tube in the region of the seam so that the fold is disposed on the outside of the tube.

Another example of a method of producing a reinforced graft comprises the steps of securing filamentary anchor material to flexible graft material by attaching it to the graft material over a plurality of spaced bends in the filamentary anchor material; and cutting the filamentary material at regions between the bends so as to form a multiplicity of bristles or barbs of the filamentary material which project from the flexible graft material.

The bristles or barbs (hereinafter generally referred to simply as bristles) act as effective anchors which retain the graft in place in use and may even be longer than the thickness of the wall of the artery or other organ into which the graft is to be fitted.

Preferably, the flexible graft material is in the form of a sheet, and this method includes the step of forming the sheet into a tube so that the filamentary anchor material is disposed on the outer surface of the tube. The cutting step may be performed before the tube is formed but is preferably performed after.

Preferably, the bends are formed so that, although they may all face in the same general direction relative to the direction of extent of the tube, some of the bristles extend from the bends at different angles relative to others in the direction of extent of the tube. This may be achieved by making some of the bends tighter than others.

The sheet of flexible graft material may be a woven or nonwoven fabric formed e.g. of a suitable bio-compatible polymer such as a bio-compatible polyester. A woven polyester microfibre (typically, 6-7 Fm diameter fibre) fabric is particularly preferred, which may be coated for example with gelatine or other material to enhance tissue in-growth or reduce thrombogenicity or permeability.

The filamentary material may be attached to one surface of the sheet by gluing or welding. However, it is preferred to effect the attachment by stitching, preferably using a computer controlled embroidery machine. Stitching may be effected over substantially the whole of the length of the filamentary reinforcing material which is fully secured to the sheet of flexible graft material and thus incapable of being displaced relative to the sheet.

The filamentary material is preferably a material having superelastic and/or shape-memory properties, e.g. a super-elastic, shape-memory alloy such as a nickel-titanium alloy (e.g. Nitinol -50 Ni/50 Ti), and is preferably also in the form of a wire. The wire may have a diameter of about 0.2 mm. However, it is within the scope of the present invention for the reinforcing material to be any suitable bio-compatible material suitable for implantation, for example nylon, polyester, silk, polyglycolic acid, polyactic acid, metal or alloy or any combination thereof.

The preferred embodiment includes a combination of the features and methods described herein. Thus, it is preferred for portions of the filamentary reinforcing material used in the first method described above to define the plurality of bends provided in the second method described above. In such a case, the filamentary reinforcing material is chosen to be sufficiently rigid to impart the required anchor properties of the bristles formed from the bends.

A spring structure may be provided at one or both ends of the tubular graft so as to assist in retention of the tubular graft against the wall of the artery in which the graft is in use located.

An example of reinforced graft comprises a tubular body formed of flexible graft material, and a filamentary reinforcing material secured to the graft material in a pattern such that the filamentary reinforcing material extends around the tube and longitudinally thereof to allow the thus-reinforced tubular body to bend, wherein the pattern is defined whilst the filamentary reinforcing material is being secured to the graft material. This can be achieved before the tubular body is formed from a sheet of the graft material as described above, or it may be achieved by securing the filamentary reinforcing material to the pre-formed tubular body. The pattern may be a helical arrangement of the filamentary reinforcing material around the tubular body, or it may be a sinuous arrangement as described above. A sinuous arrangement where opposed bends are overlapped and interdigitated (see below) can assist in imparting columnar strength to the tubular body.

Typically in the embodiments described herein the reinforcement does not constitute a stand-alone stent.

Another aspect of the present invention comprises a graft which is sufficiently axially compressible that once the proximal part is deployed, the distal part can be repositioned prior to its deployment. The position of the distal part can be positioned independently of the position of the proximal part, provided that the distance separating the landing sites of the proximal and distal parts does not exceed the length of the implant.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present invention are described below, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a first embodiment of reinforced graft prior to rolling into a tubular shape;

FIG. 2 is a schematic diagram of a second embodiment of reinforced graft prior to rolling into a frusto-conical shape;

FIG. 3a is a schematic diagram of part of the graft of FIG. 1 or FIG. 2 when rolled into a tubular or frusto-conical shape;

FIG. 3b is a schematic diagram similar to FIG. 3a, showing interdigitation of adjacent rung ends;

FIG. 4 is a schematic diagram of another embodiment of reinforced graft prior to rolling into a frusto-conical shape;

FIG. 5 is a schematic diagram of another embodiment of reinforced graft prior to rolling into a frusto-conical shape;

FIGS. 6a and 6b show two different methods of joining a reinforced graft into tubular form with both ends of a reinforcement rung opposing one another;

FIG. 7 is a schematic diagram showing a method of stitching a reinforcement ladder lattice;

FIG. 8 is a schematic diagram showing the embodiment of reinforced graft of FIG. 1 in a flexed condition;

FIG. 9 is a schematic diagram of another embodiment of reinforced gr