Composite compliant vascular graft

Abstract

The present invention provides a composite compliant vascular graft for implantation in a host, the graft comprising a tubular body having a lumen and a tubular wall surrounding the lumen made of a composite material adapted to permit expansion of the tubular body from a natural state to an expanded state, the composite material includes a mechanical member adapted to limit the expanded state and a compliant member adapted to biased return of the tubular body to the natural state, and then return to the natural state in response to a pressure change in the lumen.

Description

Technical Field

[0001] The present invention relates to a composite compliant vascular graft material used in surgical vascular grafts and endovascular grafts for treating compliant blood vessels. Background Art

[0002] Existing surgical vascular grafts and endovascular grafts are primarily designed to treat vascular diseases by providing structures such as a generally tubular body, a tapered or conical body, a bifurcated body, a tubular body with fenestrations, and / or a body with side branches. These structures serve as artificial blood vessels, replacing or eliminating affected blood vessels. The specific function of surgical or endovascular vascular grafts in treating vascular diseases dictates their specific form.

[0003] Graft bodies employed in aortic surgery and endovascular grafts are typically constructed of a matrix of woven or knitted fabrics using a suitable plastic material like polyethylene terephthalate (PET) or polytetrafluoroethylene (PTFE) spun fibers.

[0004] Due to the woven or knitted matrix nature of the body, the described grafts are non-compliant in both radial and longitudinal directions.

[0005] Typical surgical grafts of tubular and / or conical shape are crimped or pleated to provide cylindrical stability and flexibility when placed in a curved position. These grafts have proximal and distal ends that are anastomosed end-to-end to bridge a removed segment of a patient's diseased vessel or to be placed within a patient's diseased vessel. These surgical vascular devices are radially non-compliant.

[0006] Typical endovascular grafts commonly used to treat aneurysms consist of proximal and distal anchoring segments with multiple circumferentially expandable stent elements attached to the wall of a tubular body. These stent elements are longitudinally spaced apart, terminated at proximal and distal ends, and adapted to anchor in healthy aortic tissue proximal to the aneurysm (referred to as the "proximal landing zone") and distal to the aneurysm (referred to as the "distal landing zone"). This placement allows the vascular graft to form a seal within the aorta, with the inner portion of the vascular graft bridging the aneurysm and excluding it from the circulating blood flow.

[0007] Each stent element is typically a nitinol ring that allows for circumferential expansion and compression. However, the oversized nature of the tubular graft body and each stent element relative to the diameter of the aorta imparts significant radial forces on the aorta and causes folding or buckling of the tubular graft body upon implantation.

[0008] To achieve effective sealing, oversizing of the vascular graft relative to the aortic diameter at the proximal and distal landing zones is required, with typical oversizing factors of 10%-20% being selected for aneurysms.

[0009] These vascular grafts are also used to treat aortic dissections, but physiological differences from aneurysms present challenges. Dissections are caused by tears in the aorta's intimal layer, which leak blood and create a "false lumen" separated from the "true lumen." Endovascular treatments aim to plug the entry tear and prevent blood from flowing into the wall between the layers of the vessel wall.

[0010] However, the inherent rigidity of these grafts reduces the "Weidecksel function" of the aorta, potentially inducing left ventricular hypertrophy, increasing pulse wave velocity, and leading to arterial hypertension and higher blood pressure.

[0011] Furthermore, lack of compliance can lead to mechanical complications such as retroperitoneal dissection or distal graft-induced new rupture (dSINE), requiring open surgery or secondary graft placement.

[0012] The present invention at least partially solves the problem. Summary of the Invention

[0013] The present invention provides a composite compliant vascular graft for implantation in a host, the graft comprising a tubular body having a lumen and a tubular wall surrounding the lumen made of a composite material, the composite material being adapted to permit the tubular body to expand from a natural state to an expanded state and then return to the natural state in response to pressure changes in the lumen, the composite material comprising a mechanical member adapted to limit the expanded state and a compliant member adapted to bias the tubular body back to the natural state.

[0014] The mechanical member may be adapted to limit an increase in the radial dimension of the expanded state.

[0015] The mechanical member may be adapted to limit a reduction in the longitudinal dimension of the expanded state.

[0016] The mechanical member may be adapted to accommodate an increase in longitudinal dimension in the expanded state.

[0017] The mechanical structure may comprise a framework of filamentary elements.

[0018] The filamentary elements may be yarns comprising elastic yarns, inelastic yarns, or a combination of elastic and inelastic yarns (composite yarns).

[0019] The yarns may have a linear density from 10 dtex to 80 dtex.

[0020] The elastic yarns may be made from filaments of thermoplastic polyurethane or polyurethane-polyurea copolymer materials, and the inelastic yarns from filaments of polyester or nylon.

[0021] The yarn may be adapted (by shaping or by construction) to elongate under load to an elongation limit.

[0022] The composite yarn may include an elastic yarn with a non-elastic yarn twisted around the elastic yarn.

[0023] The non-elastic yarn may be twisted around the elastic yarn at a twist density of 25 to 1500 twists per meter.

[0024] The yarn may be formed with crimps, or the yarn may be textured to release the constituent filaments into small bundles.

[0025] The frame may be a matrix of yarns entangled in a knitted or woven structure.

[0026] The woven structure may include weft yarns and warp yarns adapted to adjust the degree of radial expansion or the longitudinal dimension of the expanded state.

[0027] The weft yarns may be composite yarns.

[0028] Alternatively, the weft yarn elements and the warp yarn elements may be composite yarns.

[0029] The twist density of the weft yarns may be different from the twist density of the warp yarns.

[0030] The knitted structure is either warp knit or weft knit.

[0031] The warp knitted fabric may include a plurality of wales and a plurality of connecting elements, each connecting element connecting a pair of wales.

[0032] Each wale may include a stitching post formed from the first set of warp yarns, and each connecting element is the first set of inlay yarns.

[0033] Alternatively, the knit structure may be produced with a warp knit seam pattern in which each wale includes stitches formed alternately by a first set of warp yarns and a second set of warp yarns, and the connecting elements are crosslinks created by each warp yarn as it extends between a pair of wales.

[0034] The first set of inlaid yarns may adopt a sinusoidal pattern as they traverse between and connect pairs of adjacent wales.

[0035] The warp knit may include a second set of inlay yarns.

[0036] The first set of inlaid yarns and the second set of inlaid yarns both employ a sinusoidal pattern as they interweave with the wales from opposite directions, are connected in pairs, and wherein the first set of inlaid yarns and the second set of inlaid yarns both extend in opposite directions such that the peaks of the first set of yarns are aligned with the valleys of the second set of yarns.

[0037] Pairs of wales connected by the inlaid yarn may be adjacent to each other or separated by one or more intervening wales.

[0038] The first set of inlaid yarns and the second set of inlaid yarns may extend in phase, with the peaks of the first set of yarns aligned with the peaks of the second set of yarns.

[0039] The first set of inlaid yarns and the second set of inlaid yarns may extend out of phase with the peaks of the first set of yarns aligned with the valleys of the second set of yarns.

[0040] The first set of inlay yarns and the second set of inlay yarns can be non-elastic yarns.

[0041] Furthermore, alternatively, the warp knit structure may form a symmetrical mesh wherein each wale is alternately entangled with the adjacent wale on one side and the adjacent wale on the opposite side to provide entangled sections, and wherein there are gaps between these sections where the wales are not entangled.

[0042] The gaps may provide hexagonal shaped mesh openings.

[0043] The mesh openings may be dog-bone shaped by one or more of: longitudinal compression and heat setting.

[0044] Warp knits may have a weft knit density of 3 to 50 wales per centimeter.

[0045] Warp knits may have a longitudinal knit density of 6 to 50 passes per centimeter.

[0046] The compliant member may include at least a first layer of tubular wall that is joined to an underlying layer of the mechanical member or encapsulates the mechanical member.

[0047] The compliant member may include an adhesive layer of a tubular wall joined to a bottom layer as a first layer or mechanical member.

[0048] The compliant member may include at least a second layer of tubular wall joined to a bottom layer that is either the first layer, an adhesive layer, or a mechanical member.

[0049] The first layer or the second layer may be made of polycarbonate thermoplastic polyurethane (polycarbonate TPU) or thermoplastic polyurethane-silicone copolymer (TPU-silicone).

[0050] The adhesive layer can be made of polyester or polyether thermoplastic polyurethane or aliphatic or aromatic diisocyanate thermoplastic polyurethane.

[0051] The TPU-silicone may include silicone in a concentration of 5% to 50% (wt / wt).

[0052] The polycarbonate TPU or TPU-silicone may have a Shore hardness of from 65A to 95A.

[0053] The polyester or polyether thermoplastic polyurethane, the aliphatic diisocyanate thermoplastic polyurethane, or the aromatic diisocyanate thermoplastic polyurethane may have a Shore hardness of from 42A to 70A.

[0054] The first or second layer may include longitudinal regions of varying stiffness.

[0055] The longitudinal region may include a proximal region and a distal region and an intermediate region between the proximal region and the distal region.

[0056] The polycarbonate TPU or TPU-silicone of the proximal and distal regions may have a Shore hardness of from 85A to 95A, and the polycarbonate TPU or TPU-silicone of the middle region may have a Shore hardness of from 65A to 85A.

[0057] The compliant member may be a preform that is joined to the base layer as a first layer, a second layer, or an adhesive layer.

[0058] Alternatively, the compliant member may be applied directly to the base layer as a first layer, a second layer, or an adhesive layer to cover or encapsulate the base layer.

[0059] The compliant member may be a laminar layer or a filamentous layer.

[0060] The filamentous layer may include an inner or outer layer composed of filaments oriented in multiple directions, as well as an outer or inner layer composed of filaments oriented in a single direction.

[0061] The filaments of the outer or inner layer may be oriented in a circumferential direction or in an axial direction of the tubular body.

[0062] The composite compliant vascular graft may include a stent coupled to the exterior of the tubular body and adapted to constrain the radial dimension of the expanded state.

[0063] The stent may include at least one yarn that is inelastic, or a combination of elastic and inelastic yarns wrapped around the tubular body.

[0064] A stent may be a tubular frame made of an elastic polymer material or a superelastic metal alloy such as, for example, Nitinol.

[0065] The stent may include a plurality of rings, each ring being made of a superelastic metal alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The present invention will be further described by way of example with reference to the accompanying drawings, in which: Figure 1 isometrically showing a composite compliant vascular graft according to the present invention, Figure 2 is a cross-sectional view of a composite compliant vascular graft according to a first embodiment of the present invention, Figure 3 is a cross-sectional view of a composite compliant vascular graft according to a second embodiment of the present invention, Figure 4 is a cross-sectional view of a composite compliant vascular graft according to a third embodiment of the present invention, Figure 5A is a cross-sectional view of a composite compliant vascular graft according to a fourth embodiment of the present invention, Figure 5B yes Figure 5A Isometric longitudinal cross-section of a vascular graft. Figure 6 is a cross-sectional view of a composite compliant vascular graft according to a fifth embodiment of the present invention, Figure 7A is a graphic representation of the relationship between pressure within a vascular graft and the increase in its diameter, Figure 7B is a graphic representation of the correlation between stress and strain experienced by a vascular graft, Figure 8A schematically illustrating composite yarns used in some examples of vascular grafts in an unstretched configuration, Figure 8B Schematically illustrating composite yarns used in some examples of vascular grafts in a stretched configuration, Figure 9 shows textured yarns used in some examples of vascular grafts, Figure 10 presents an isometric plan view of a column stitch knit pattern of a knitted fabric used in some examples of vascular grafts, Figure 11A and 11B All present Figure 10 isometric oblique views of a column stitch knit pattern of a knitted fabric in a relaxed configuration and in a stretched configuration, Figure 12 Yes Figure 10 、 11A The overlap diagram of the knitting pattern of 11B, Figure 13 、 14 and 15 are overlap diagrams showing various alternative inlay patterns incorporated into a warp knit pattern of a knit fabric used in some examples of vascular grafts, Figure 16 is a diagram showing a tiling pattern of a warp knit pattern incorporated into a knit fabric used in some examples of vascular grafts, Figure 17A 、 17B and 17c both show Figure 16 Isometric plan view of a warp knitting pattern for a knitted fabric, Figure 18A and 18B All present Figure 16 and 17 are isometric plan views of the warp knit pattern of the knitted fabric in a relaxed configuration and in a stretched configuration, respectively, Figure 19 presenting an isometric plan view of a stretched knit pattern of a knitted fabric used in some examples of vascular grafts, Figure 20 yes Figure 19 Lap diagram of stretch knitting pattern of knitted fabric, Figure 21 yes Figure 19 Isometric plan views of variations of the stretch knitting pattern of the knitted fabric shown in, Figure 22A and 22B schematically illustrates the weave patterns of woven fabrics used in some examples of vascular grafts in relaxed and stretched configurations, respectively, Figure 23 Schematically shown Figure 10 Variations in the inlay pattern of the column needle of the knitted fabric, Figure 24 and 25 Schematically shown Figure 22A and 22B Changes in weaving fabrics, Figure 26 isometrically showing a composite compliant vascular graft according to a sixth embodiment of the present invention, Figure 27 isometrically showing a composite compliant vascular graft according to a seventh embodiment of the present invention, Figure 28A and 28B Provide composition Figure 27 A schematic diagram of the fibrous layer of the outer sublayer of a vascular graft is depicted in FIG, and Figures 29A to 29E Isometric views depicting vascular grafts according to the present invention, each showing variations in the composition, configuration or pattern of the exostent. DETAILED DESCRIPTION

[0067] In the attached figure Figure 1 A composite compliant vascular graft 10 is shown according to a first embodiment of the present invention for use in surgical grafts and endovascular grafts for treating compliant blood vessels.

[0068] Treatment may be surgery or endovascular aortic or peripheral vascular repair.

[0069] The vascular graft 10 has a tubular body 12 having a tubular wall 14 made of a composite material surrounding and defining a lumen 16. In a longitudinal direction, the body extends between a proximal end 18 and a distal end 20.

[0070] Reference Figure 2 , wall 14 of vascular graft body 12 is composite, as it comprises a mechanical component 22 and a compliant component 24. In this example 10.1, the mechanical component (the fabric frame) is embedded within the compliant component. In this example, the compliant component is layered, comprising a first layer 26 and a second layer 28 overlying the first layer.

[0071] The tubular body is designed to contract and expand in a coordinated manner within or across a vessel, synchronized with pressure fluctuations within the lumen. This pressure varies between a natural state observed during minimal diastole and an expanded state noted during maximum contraction. The complex composition of the tubular body allows for permissive and compliant movement between these two states, maintaining the vessel's Weideksha function.

[0072] To be functionally relevant, the tubular body is adapted to expand 5% to 30% of its diameter in a natural state.In a preferred embodiment, this radial compliance is integrated with the longitudinal compliance, allowing the tubular body to withstand longitudinal strains of up to 32%. Figure 7B The graph shows the stress-strain relationship in radial compliance and the inherent limitation on elasticity due to the present invention.

[0073] The compliant member is designed to impart compliance to the tubular body, enable the expansion, and facilitate biasing return from the expanded state to the natural state. Simultaneously, the mechanical member is configured to constrain the expanded state while preferably preventing the tubular body from shortening in the longitudinal direction during radial expansion. Figure 7A The graph shows the relationship between pressure and diameter expansion of the graft before reaching the constraint limit. This limit can be important in preventing the graft from exceeding a high blood pressure limit, which can exceed the elastic range of the compliant member.

[0074] The mechanical member is a framework of filamentary elements, more precisely a fabric, which may be knitted or woven, comprising elastic, inelastic or composite yarns.

[0075] The first layer 26 of the compliant member is an elastic polymer material. The second layer 28 also includes an elastic polymer material. The composition of the elastic polymer material of the first and second layers can be different, wherein the first layer provides properties that indicate device compliance, while the second layer is primarily formulated to maintain the shape of the stent, provide erosion resistance, and / or other beneficial properties.

[0076] In order to maintain the tubular form of the tubular body, the graft 10.2 may include a stent 30, such as, for example, a corrugated stent made of a superelastic material such as Nitinol. Figure 3 , where the corrugated support is shown encapsulated within the second layer 28 .

[0077] The polymer material of the first or second layer may be polyurethane, a class of materials chosen for their elastomeric, fluid-tight properties, achieving radial compliance while limiting the permeability of the tubular wall to blood that would flow across the wall due to any porosity in the underlying layer.

[0078] exist Figure 4 In another example of a vascular graft 10.3 shown in FIG, the wall 14 has only a single layer 26 of compliant member 24, with the mechanical member 22 embedded within this layer.

[0079] exist Figure 5A and 5B In the example depicted in FIG, the wall of vascular graft 10.4 comprises a first, inner, compliant layer 26 and a second, outer, compliant layer 28. Mechanical member 22 is represented by discrete layers sandwiched between the inner and outer layers. The layers are laminated to one another, i.e., bonded together to form a single composite structure, by any suitable process, such as, for example, adhesive bonding, heat, pressure, or a combination of these processes.

[0080] The iterative process continues, e.g. Figure 6 As shown in Figure 6

[00106] Here, another example is presented. In this case, a vascular graft 10.5 maintains a mechanical member 22 positioned between an inner layer and an outer layer (26, 28). Notably, in this embodiment, the outer layer of the compliant member is composed of two sublayers (28.1 and 28.2), making it different from the previously described examples. The layers may differ in their relative adhesive properties, wherein layer 28.1 is a layer having relative adhesive properties that adheres to and around the mechanical member, referred to as an adhesive layer, and layer 28.2 may be laminated to this adhesive layer. Alternatively, the layers may differ in their construction, wherein both layers are filamentous compliant layers (see Figures 28, 29A, and 29B), but wherein layer 28.1 has randomly laid filaments, whereas the filaments of layer 28.2 are aligned and laid, as will be described more fully below.

[0081] Several key attributes (either independently or in combination) configure the mechanical aspects to enable at least radial expansion while imposing strain-enhancing constraints as the expanded state approaches its operational limit (see Figure 7). These attributes (referred to as "locking" features) include fabric type (such as whether it is knitted or woven), fabric pattern (arrangement within a knitted or woven fabric), yarn type (whether it is elastic, inelastic, or composite), and yarn structure (whether it is composed of straight filaments or shaped filaments, or is it textured). In essence, the mechanical component undergoes a conformational change as it approaches its limiting diameter, which provides resistance to further expansion. yarn

[0082] As mentioned, the fabric (mechanical component) can be knitted or woven. The yarns constituting the fabric can be elastic, inelastic or composite.

[0083] In the following examples, the elastic yarn is made of TPU or polyurethane-polyurea copolymer, and the non-elastic yarn is made of PET or nylon 6,6.

[0084] Reference Figure 8A and 8B , the composite yarn 32.1 comprises an elastic core yarn 34 wrapped with at least one inelastic cover yarn 36. The composite yarn (referred to herein as the "cover yarn") can be adapted to achieve a desired elongation or strain before the inelastic cover yarns are engaged, varying the cover angle α to limit further elongation. Modifying this angle affects the twist per meter, affects the amount of cover yarn applied over the core and determines the slack generated in the yarn. A reduced cover angle (resulting in more twist per meter) will result in greater elongation before engagement. This locking feature is shown in a stretched configuration of the yarn ( Figure 8B ).

[0085] Composite yarns can be tailored to meet specific functional requirements by modifying one or more of the following parameters: the materials of the elastic core yarn and the inelastic cover yarn, the number of core and cover yarns in the composite yarn, the linear density of the core and cover yarns, the twist density, and the inherent structure or texture of the yarn.

[0086] The twist density is the number of times the cover yarns of each composite yarn are twisted around the core yarn per meter. In the context of the present invention, the range is 25 to 1500 twists per meter.

[0087] With respect to its inherent structure or texture, the yarn (preferably a non-elastic yarn) may be subjected to processes such as knitting and de-knitting, or heat-set to provide a crimped yarn 32.2 (see Figures 23 to 25 ), or air texturizing to provide textured yarn 32.3. Figure 9 The deformation result of the air deformation on the yarn 32 . 3 is shown, revealing a number of “released” filaments 33 .

[0088] The crimped yarn 32.2 can be introduced into a knitted fabric, such as Figure 23 In the knitted fabric shown in FIG, the coiled yarn is a cover yarn that covers the core yarn 34 to provide an alternative to the standard composite yarn (32.1) described above. The coiling of the coiled yarn enables the composite yarn to have additional inherent stretching ability before locking.

[0089] Figure 23 The introduction of a crimped yarn 32.2 into the knitted fabric as a component of a composite inlay yarn is shown. Figure 24 and 25 The crimped yarn 32.2 is shown as a component of the composite inlay yarn in the weft direction ( Figure 24 ) and along the longitude and latitude directions ( Figure 25 ) is introduced into the woven fabric. knitwear

[0090] While the fabric can be manufactured using both warp and weft knitting techniques, the invention is not limited to these methods. However, a preference is shown for warp knitted fabrics over weft knitted fabrics because the warp yarn pattern provides greater customization for fine-tuning the functionality of a mechanical component.

[0091] In the following examples of warp knitted fabrics, a common feature is that the wales are connected to each other by connecting elements, which allows the fabric to expand radially. However, the differences between them lie in the composition, configuration or origin of these connecting elements.

[0092] Column gap: in Figure 10 In the first example of a knitted fabric 40.1 shown in FIG, the knitting pattern is a column stitch pattern. In this pattern, each warp yarn element is a yarn 32 stitched into a series of loops or stitches (loops designated 42.1, 42.2, ... 42.N), called a wale, which is formed in the longitudinal direction of the tubular body 12. The wales are designated 44.1, 44.2, 44.3, and 44.4, respectively. A series of courses, each consisting of a row of loops (one course is highlighted with a dotted outline and designated 45), extend in the radial direction. The wales are connected by a plurality of connecting elements (designated 46.1, 46.2, 46.3, respectively).

[0093] There are various options for the way in which the connecting elements establish the connection between the wales. In one alternative (see Figure 10 ), adjacent pairs of wales (such as 44.1 and 44.2) are connected by a connecting element (46.1). Using inlay technology, the connecting element adopts a wavy pattern, passes through the upper or lower lap of the adjacent wales, and is captured by it.

[0094] Each connecting element 46 can be a non-elastic yarn or a composite yarn. In an example, including a composite yarn can provide a variety of radial expansion options for the graft. This is in addition to the radial expansion achieved by selecting a knitted structure.

[0095] The benefit of using a column gap filled with connecting elements is that it results in a stent structure with a large allowable radial expansion range before reaching the limit diameter. Figure 11A The relaxed configuration of the knitted fabric shown in Figure 11B The disadvantage is that this large radial expansion range can lead to significant longitudinal shortening.

[0096] Figure 12 is a lap diagram showing Figure 10 、 11A and the structure of the knitted fabric 40.1 already described and shown in FIG. 11B.

[0097] Warp knitting :exist Figure 17A 、 17B In the second example of a knitted fabric 40.2 shown in FIG17C , the knit pattern is a warp-stitched pattern. The wales ( 44.1 , 44.2 , etc. ) are created using a single yarn system, with guides crossing between adjacent wales, resulting in stitches along each wale. These stitches are formed alternately with warp yarns 32.1 from the first group and warp yarns 32.2 from the second group, thereby creating interconnected wales. In this case, the connecting element consists of the crosslinks 49 created by each warp yarn as it passes between a pair of wales.

[0098] The warp knitted seam creates a stable structure without the need for additional connecting elements. However, for additional stability and the desired limit diameter, additional connecting elements in the form of inlay yarns 46 can be introduced.

[0099] Introducing these inlay elements 46.1, 46.2 and 46.3 (see Figure 18A and 18B An advantage of the present invention is that it allows for overall diameter constraint without significantly changing the angle (α) between successive passes, compared to the considerable reduction in this angle (α) observed in the post-slit embodiment. This is achieved by the forces exerted by the connecting elements (as the stent expands radially toward the ultimate diameter) and offset by the structure of the connecting base pattern, which presents a significant advantage in terms of diameter constraint and limited foreshortening.

[0100] Figure 16 is a lap diagram showing Figure 17A 、 17B , 17C, 18A and 18B have already described and shown the structure of the knitted fabric 40.2.

[0101] and Figure 10 Similar to the column seam embodiment 40.1 shown in FIG, each connecting element (46.1, 46.2, 46.3) (e.g., a composite yarn) adopts a sinusoidal pattern as it is interwoven and connected with the paired wales. In this example, the connecting elements are positioned radially spaced and phase-aligned. They are stretched between the paired wales (44) separated by a single intervening wale.

[0102] Figure 13 Another alternative is shown in which each connecting element (46.1, 46.2, ...) is configured to bridge and interconnect non-consecutive wales (44.1, 44.2) separated by three intervening wales.

[0103] Figure 14 A third alternative is shown wherein a second plurality of connecting elements (48.1, 48.2, ...) is introduced with respect to a third yarn system, allowing the first plurality of connecting elements (46) and the second plurality of connecting elements (48) to extend in opposite directions in an alternating mirror image configuration.

[0104] In the final example, the first plurality of connecting elements (46.1, 46.2, etc.) and the second plurality of connecting elements (48.1, 48.2, etc.) also extend in opposite directions, with peaks and valleys of the first and second pluralities. This example differs in the separation of the respective pairs of wales connected by the first and second pluralities of connecting elements. The first plurality of connecting elements connects adjacent wales, while the second plurality of connecting elements connects wales separated by three intervening wales (see Figure 15 ).

[0105] The various connecting element inlay configurations outlined in the context of warp knitted fabric 40.2 can be applied to column knitted fabric 40.1. Although due to the more stable structure resulting, Figures 13 to 16 The inlay configuration depicted in is better suited for incorporation into warp knitwear rather than column knitwear.

[0106] For the sake of completeness, connecting elements (46, 48) can be added using weft insertion as an alternative to the inlay technique, wherein the connecting elements are added perpendicular to the production direction.

[0107] Auxetic net : In the case of a specified value of 40.3 and Figure 19 In the third example shown in FIG, the knitting pattern adopts a mesh structure, such as Figure 19. This mesh structure is created by forming wales (44.1, 44.2, ...) of warp yarn elements 32. In this configuration, wales on opposite sides of a central wale (44.2) (such as 44.3 and 44.1 in this example) are interwoven with it along alternating interweaving sections (46.1, 46.2). Specifically, wale 44.1 is interconnected with wale 44.2 along section 46.1, while wale 44.3 is interconnected with wale 44.2 along section 46.2.

[0108] In this mesh structure, when the underlap is crossed, the wales are pulled together to form mesh posts 46 (the interwoven sections described above). Conversely, when the underlap is not crossed, the wales remain separate, creating mesh openings (50.1, 50.2, 50.3, ...) (see Figure 20 ).

[0109] In the case of a specified value of 40.4 and Figure 21 In a variation of the embodiment depicted in FIG, the mesh opening geometry is modified with the goal of reducing the longitudinal distance between consecutive mesh posts 46. This modification transforms the mesh opening 50 from a hexagonal shape to a dog-bone or bow tie shape. Such geometric changes are achieved during production by a) manipulating the connection pattern or b) incorporating elastic warp yarn elements that span the mesh opening in the longitudinal or production direction.

[0110] Alternatively, achieving the desired mesh opening geometry may involve post-processing steps. For example, the knitted surface may be subjected to longitudinal compression and subsequent heat setting to fix the modified opening shape. The dog-bone shape of the mesh openings is configured to impart auxetic properties to the scaffold, where radial expansion also promotes longitudinal expansion.

[0111] These auxetic mesh embodiments (40.3, 40.4) are beneficial in that they eliminate shortening issues, allow for longitudinal compliance, and more closely resemble the behavior of native tissue. overall

[0112] The yarns constituting the warp elements and the connecting elements may have a linear density of from 20 dtex to 80 dtex.

[0113] The yarns of the weft or connecting elements may be the same as the warp elements, or may be of a different linear density, material, spin or construction (including composite cover yarns) to give the desired ultimate diameter.

[0114] In the preceding embodiments, the total number of wales per centimeter is between 3 and 50. In case a wale is a row of stitches in the production (functionally longitudinal) direction, the number of wales per centimeter is a measure of the weft knitting density.

[0115] The knitted structure may be formed with a route density of 6 to 50 routes per centimeter. Where a route is a row of stitches perpendicular to the production direction, the number of routes per centimeter is a measure of the longitudinal knit density.

[0116] The warp yarns and connecting elements may be configured to allow unconstrained radial expansion within a range while restricting radial expansion under a second strain. Weaving

[0117] As an alternative to knitted fabrics (40.1, 40.2, 40.3, 40.4), a fabric may be formed using a basic weave pattern. This weave pattern fabric is designated 40.5 and is Figure 22A and 22B In one variation, the weft yarns (designated 46.1, 46.2, 46.3, 46.4, respectively) are composite yarns 32.1 that are introduced to allow radial compliance before the inelastic element is engaged.

[0118] As mentioned above, the composite yarn 32.1 can be produced with a twist count of the cover yarn 36 of 25-1500 twists per meter.

[0119] When configured with weft yarn elements that are cover yarns, the woven fabric 40.5 will have an allowable degree of radial expansion (where only the elastic core is under strain), and a target radial expansion at which the inelastic cover yarns are engaged, thereby limiting radial compliance beyond a certain radial strain.

[0120] In another embodiment (not shown), the warp elements (44.1, 44.2, 44.3, 44.4) of the woven fabric 40.5 are also composed of composite cover yarns. The structure of the first (weft) cover yarn and the second (warp) cover yarn can be different to impart different degrees of radial and longitudinal expansion.

[0121] Woven fabrics can be constructed in a basic weave structure as shown, or in a Reynolds weave structure (a technique in which pairs of warp yarns are twisted around weft yarns to create a more open and softer fabric), with cover yarns in the weft and / or warp direction. Compliant components

[0122] While the mechanical components play a vital role in constraining the expanded state, the compliance components must allow the tubular body to expand while also facilitating the biased return from the expanded state to the natural state. Optimal function of the vascular graft 10, and the anticipated benefits of controlled compliance, rely on the interaction between compliance and the mechanical components.

[0123] Similar to mechanical components, various basic characteristics (whether alone or in combination) configure the compliant component to meet its functional purpose of compliance and recoil. These attributes include the layered configuration (referring to the number of layers in the compliant component) as described earlier, the manufacturing materials (including the materials comprising the compliant component), and the application and attachment method (how the compliant component is applied to the implant). Manufacturing materials : The compliant member comprises an elastic biocompatible synthetic polymer material. Figures 2 to 6 As shown in , the vascular graft exists in various iterations, having multiple layered configurations, and with the elastic polymer material composition varying between the first and second layers.

[0124] The compliant member is made of thermoplastic polyurethane (TPU) or thermoplastic polyurethane-silicone copolymer (TPU-silicone), a material selected primarily for its elasticity, impermeability, biostability, and mechanical and tensile strength (sufficient to provide erosion resistance and retain the embedded stent).

[0125] All layers within the compliant member (26 and 28 or 28.1 and 28.2) are functionally compliant, regardless of their position in the layered structure. However, only certain layers (the adhesive layers) do not require recoil functionality and only need to possess low tensile strength so as not to hinder the compliance of the graft and the adhesive properties of adhesion to the mechanical member.

[0126] TPU or TPU-silicone is produced: By synthesizing polycarbonate diols and aliphatic or aromatic diisocyanates, referred to herein as "polycarbonate TPU", or from thermoplastic silicone polyurethane copolymers, which involve crosslinking silicone and TPU, where these copolymers are synthesized using diisocyanates from the diisocyanate family and hydroxyl-terminated siloxanes, or Utilize polyester or polyether polyols or aliphatic or aromatic diisocyanates.

[0127] Polycarbonate TPU and TPU-silicone are highly conformable and elastic.

[0128] Aliphatic or aromatic polycarbonate TPUs or TPU-silicone exhibit a Shore A hardness of 65A to 95A. They possess ultimate tensile strengths ranging from 27 MPa to 60 MPa, ultimate elongations ranging from 300% to 1200%, and tensile strengths at 100% elongation of 2 MPa to 7 MPa. Furthermore, these TPUs have flexural moduli ranging from 6 MPa to 22 MPa.

[0129] To enhance biostability and increase elasticity, the TPU-silicone may suitably include silicone (along the polymer backbone or as covalently bonded end groups) in a concentration of 5% to 50% (wt / wt).

[0130] Polyester or polyether polyol or aliphatic or aromatic diisocyanate TPUs are compliant, have good adhesive / cohesive properties, but are relatively soft, with a Shore hardness ranging from 42A to 70A, an ultimate tensile strength in the range of 6MPa to 20MPa, a tensile strength at 100% elongation falling between 1MPa and 3MPa, and an ultimate elongation varying from 500% to 900%.

[0131] The layers of the compliant member, such as the first layer 26, may include longitudinal regions (52.1, 52.2, 52.3) of varying stiffness along the length of the graft body 12 (see Figure 26 ), achieved by using different materials in each longitudinal region. This configuration establishes specific longitudinal compliance regions to accommodate varying radial compliance requirements along the length of the device. For example, the proximal and distal regions (52.1, 52.3) exhibit greater stability, increased stiffness, and enhanced sutureability, with a stiffness range of 85-95A. Meanwhile, the stiffness of the intermediate region falls within the range of 65-85A. Application method The elastic polymer material of the conformable member may be applied to a base layer, such as the mechanical knit layer 22, to cover, bond or encapsulate (in the case of a solid) that layer.

[0132] The compliant member may be a solid preform made by electrospinning (providing a filamentous tubular structure) or by extrusion, dip molding or spray molding (providing a uniform sheet or layered tubular structure).The solid preform is then applied or bonded to a substrate.

[0133] Alternatively, the compliant member may be electrospun directly onto the substrate. Additionally, alternatively, if the substrate is a mechanical member, the compliant member may be dipped or spray molded directly onto the substrate to penetrate the substrate to encapsulate the mechanical member.

[0134] The choice of application method depends largely on the structure of the mechanical member - if the mechanical member has elastic yarns, dip molding is not preferred - and the type of polymer material comprising the compliant member - if the polymer material is not solution grade, extrusion (melt) is preferred.

[0135] The elastic polymer material of the compliant member has a thickness of from 30 μm to 400 μm when applied to the base layer as a solid preform.

[0136] With the selected polycarbonate TPU or TPU-silicone in the thickness range mentioned above, the solid preform will have the properties required for elastic recoil, namely: 500% to 1200% ultimate elongation, 2MPa to 20MPa tensile strength, and • Elastic modulus of 0.2 MPa to 3 MPa at strains up to 200%.

[0137] The elastic polymer material of the compliant member may be electrospun onto the underlying layer (in this example, the mechanical member 22) in a first layer (28.1) and a second layer (28.2). The first layer may have a thickness from 30 μm to 400 μm, and the second layer may have a thickness of 10 μm-400 μm.

[0138] The fiber diameter of the electrospun filaments will range from 0.9 μm to 4 μm.

[0139] exist Figure 27 、 28A In the example shown in FIG. 28B , the electrospun fibers of the first layer 28.1 are laid in a random mesh configuration, while the fibers of the second layer 28.2 are laid in a unidirectional manner. The fibers are placed unidirectionally in the circumferential direction of the tubular body 12 (see FIG. 28A ). Figure 27 and 28A ) will complement the mechanical structure and constrain expansion. Conversely, orienting the fibers longitudinally will limit longitudinal compliance while increasing radial elasticity. Orienting the fibers at an angle (see Figure 28B ) will produce performance between these extremes, with specific characteristics being influenced by the selected tilt angle. In this way, the second layer will help prevent excessive expansion in the compliant member (a function not found in sheet / layered tubular compliant members). External bracket

[0140] To limit the degree of radial compliance, the graft 10 of any of the embodiments described above may include a stent 50. Figure 29A In the example of the stent, the stent is a helical filament 50.1 that is helically wrapped or wound around and bonded to the outer surface of the tubular body 12. The helical filament may be a composite or non-elastic yarn (32).

[0141] In another example, the stent is a frame made of the same elastic polymer material that makes up the compliant member. However, rather than being applied as a sheet or layer, it is printed directly onto the base layer (22 or 28) by inkjet printing, or is pre-printed and then applied. Inkjet printing allows for Figure 29B 、 29C and 29D and designated as 50.2, 50.3 and 50.4 respectively to create a complex pattern. As an alternative, Figure 29D and 29E In the embodiment of the present invention, the frames 50.4 and 50.5 (in this example a series of struts or corrugated rings) can be made of a superelastic metal alloy such as, for example, Nitinol.

[0142] These latter examples incorporate mechanical elements that are part of the compliant member when the stent is made from an elastic polymer material. The advantage here is that the locking properties associated with the mechanical member are introduced by the compliant material, despite the presence of deviations.

Claims

1. A composite compliant vascular graft for implantation in a host, the graft comprising a tubular body having a lumen and a tubular wall surrounding the lumen made of a composite material, the composite material being adapted to permit the tubular body to expand from a natural state to an expanded state and then return to the natural state in response to pressure changes in the lumen, the composite material comprising a mechanical member adapted to limit the expanded state and a compliant member adapted to bias the tubular body back to the natural state.

2. The composite compliant vascular graft according to claim 1, wherein: The mechanical member is adapted to limit an increase in the radial dimension of the expanded state.

3. The composite compliant vascular graft according to claim 1 or 2, wherein: The mechanical member is adapted to limit a reduction in the longitudinal dimension of the expanded state.

4. The composite compliant vascular graft according to any one of claims 1 to 3, wherein: The mechanical member is adapted to accommodate an increase in the longitudinal dimension of the expanded state.

5. The composite compliant vascular graft according to any one of claims 1 to 4, wherein: The mechanical structure comprises a frame of filamentary elements.

6. The composite compliant vascular graft according to claim 5, wherein: The filamentary elements are yarns comprising elastic yarns, inelastic yarns, or a combination of elastic yarns and inelastic yarns (composite yarns).

7. The composite compliant vascular graft according to claim 6, wherein: The yarn has a linear density of from 10 dtex to 80 dtex.

8. The composite compliant vascular graft according to claim 6 or 7, wherein: The elastic yarns are made of filaments of thermoplastic polyurethane or polyurethane-polyurea copolymer material, and the non-elastic yarns are made of filaments of polyester or nylon.

9. The composite compliant vascular graft according to any one of claims 6 to 8, wherein: The yarn is adapted (by shaping or by construction) to elongate under load to a limit of elongation.

10. The composite compliant vascular graft according to claim 9, wherein: The yarn is a composite yarn including an elastic yarn and a non-elastic yarn twisted around the elastic yarn.

11. The composite compliant vascular graft according to claim 10, wherein: The non-elastic yarn is twisted around the elastic yarn at a twist density of 25 to 1500 twists per meter.

12. The composite compliant vascular graft according to claim 9, wherein: The yarn is formed with crimps, or the yarn is textured to release the constituent filaments into small bundles.

13. The composite compliant vascular graft according to any one of claims 6 to 12, wherein: The frame is composed of yarns entangled in a knitted or woven structure.

14. The composite compliant vascular graft according to claim 13, wherein: The woven structure includes weft yarns and warp yarns adapted to adjust the degree of radial expansion or the longitudinal dimension of the expanded state.

15. The composite compliant vascular graft according to claim 14, wherein: The weft yarns are composite yarns.

16. The composite compliant vascular graft according to claim 14, wherein: The weft yarn elements and the warp yarn elements are composite yarns.

17. The composite compliant vascular graft according to claim 16, wherein: The twist density of the weft yarns is different from the twist density of the warp yarns.

18. The composite compliant vascular graft according to claim 13, wherein: The knitted structure is a warp knitted fabric or a weft knitted fabric.

19. The composite compliant vascular graft according to claim 18, wherein: The warp knitted fabric includes a plurality of wales and a plurality of connecting elements, each connecting element connecting a pair of wales.

20. The composite compliant vascular graft according to claim 19, wherein Each wale includes a stitching post formed from the first set of warp yarns, and each connecting element is the first set of inlay yarns.

21. The composite compliant vascular graft according to claim 20, wherein: The warp knit fabric includes a second set of inlay yarns.

22. The composite compliant vascular graft according to claim 21, wherein The first group of inlaid yarns and the second group of inlaid yarns both employ a sinusoidal pattern as they interweave with the wales from opposite directions, connecting in pairs, and wherein the first group of inlaid yarns and the second group of inlaid yarns both extend in opposite directions such that the peaks of the first group of yarns are aligned with the valleys of the second group of yarns.

23. The composite compliant vascular graft according to claim 19, wherein: The warp knit structure produces a warp knit seam pattern in which each wale includes stitches formed alternately by a first set of warp yarns and a second set of warp yarns, and the connecting elements are crosslinks created by each warp yarn as it extends between a pair of wales.

24. The composite compliant vascular graft according to claim 23, wherein: The warp knitted fabric includes a plurality of inlaid yarns, each inlaid yarn exhibiting a sinusoidal shape when connecting a pair of wales.

25. The composite conformable vascular graft of any one of claims 20 to 24, wherein the inlay yarn is a non-elastic yarn.

26. The composite compliant vascular graft of claim 19, wherein: The warp knit structure forms a symmetrical mesh in which each wale is alternately entangled with an adjacent wale on one side and an adjacent wale on an opposite side to provide entangled sections, and in which there are gaps between these sections in which the wales are not entangled.

27. The composite compliant vascular graft according to claim 26, wherein: The gaps provide hexagonal shaped mesh openings.

28. The composite compliant vascular graft according to claim 27, wherein: The mesh openings are dog-bone shaped by one or more of: longitudinal compression and heat setting.

29. The composite compliant vascular graft according to claims 19 to 28, wherein: The warp knitted fabric has a weft knitting density of 3 to 50 wales per centimeter.

30. The composite compliant vascular graft according to claims 19 to 29, wherein: The warp knitted fabric has a longitudinal knitting density of 6 to 50 routes per centimeter.

31. The composite compliant vascular graft according to any one of claims 1 to 30, wherein: The compliant member includes at least a first layer of the tubular wall, the at least first layer being joined to an underlying layer of the mechanical member or encapsulating the mechanical member.

32. The composite compliant vascular graft of claim 31, wherein: The compliant member includes an adhesive layer to the tubular wall, the adhesive layer being bonded to a bottom layer which is the first layer or the mechanical member.

33. The composite compliant vascular graft according to claim 31 or 32, wherein: The compliant member includes at least a second layer of the tubular wall, the at least second layer being joined to a bottom layer that is either the first layer, the adhesive layer, or the mechanical member.

34. The composite compliant vascular graft of claim 33, wherein: The first layer or the second layer is made of polycarbonate thermoplastic polyurethane or thermoplastic polyurethane-silicone copolymer, and the adhesive layer is made of polyester or polyether thermoplastic polyurethane or aliphatic or aromatic diisocyanate thermoplastic polyester.

35. The composite compliant vascular graft of claim 34, wherein: The TPU-silicone includes silicone at a concentration of 5% to 50% (wt / wt).

36. The composite compliant vascular graft according to claim 34 or 35, wherein: The polycarbonate TPU or TPU-silicone has a Shore hardness of from 65A to 95A, and the polyester or polyether thermoplastic polyurethane or the aliphatic or aromatic diisocyanate thermoplastic polyurethane has a Shore hardness of from 42A to 70A.

37. The composite compliant vascular graft of claim 36, wherein: The first layer or the second layer includes longitudinal regions of varying hardness.

38. The composite vascular graft according to claim 37, wherein: The longitudinal region includes a proximal region and a distal region and an intermediate region between the proximal region and the distal region, and wherein the polycarbonate TPU or TPU-silicone in the proximal region and the distal region has a Shore hardness from 85A to 95A, and the polycarbonate TPU or TPU-silicone in the intermediate region has a Shore hardness from 65A to 85A.

39. The composite compliant vascular graft according to any one of claims 33 to 38, wherein: The compliant member is a preform that is joined to the base layer as the first, second, or adhesive layer, or the compliant member is applied directly to the base layer as the second, third, or adhesive layer to cover or encapsulate the base layer.

40. The composite compliant vascular graft of claim 39, wherein: The compliant member is a lamellar layer or a filamentous layer.

41. The composite compliant vascular graft of claim 40, wherein: The filamentous layer includes an inner layer composed of filaments oriented in multiple directions and an outer layer composed of filaments oriented in a single direction.

42. The composite compliant vascular graft of claim 41, wherein: The filaments of the outer layer are oriented in a circumferential direction or an axial direction of the tubular body.

43. The composite compliant vascular graft of any one of claims 1 to 42, comprising a stent engaging an exterior of the tubular body and adapted to limit the radial dimension of the expanded state.

44. The composite compliant vascular graft of claim 43, wherein: The stent comprises at least one yarn that is inelastic, or a combination of elastic and inelastic yarns wrapped around the tubular body.

45. The composite compliant vascular graft of claim 43, wherein: The stent is a frame made of elastic polymer material or superelastic metal alloy.

46. ​​The composite compliant vascular graft of claim 43, wherein: The stent includes a plurality of rings, each ring being made of a superelastic metal alloy.

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