NL194778C - Method for making a woven synthetic vascular graft. - Google Patents

Description

1 194778

Method for making a woven synthetic vascular graft

The invention relates to a method for making a woven synthetic vascular graft comprising the step of forming a tubular fabric, wherein the step of forming comprises weaving a plurality of warp yarns with at least one filler yarn around a substrate to shape.

The British patent application 0.820.014 describes a method with a flat weaving machine that produces tubular fabrics in a flattened form wherein the tubular fabrics are for use as an artificial vein or for example as a fire hose. The tubular fabric provided by the method comprises a spiral coil of a composite fiber formed from a woven monofilament yarn of nylon or other artificial fibers by, for example, braids covered with a yarn of nylon or other artificial fiber and a second spiral coil of a finer woven yarn between the windings of the composite yarn, the spools being connected together by longitudinally arranged warp yarns.

According to the known method, the monofilament yarn and the finer yarn are woven in an alternating pattern along the length of the fabric to produce tubular fabrics that are capable of bending without kinking. The monofilament is therefore only included to form a kink-resistant tube and not for stiffening properties.

The known method has the disadvantage that it does not provide a self-supporting tubular structure (that is, a tubular structure that is normally open in a non-loaded state) without shrinking, and that it is not aimed at providing radial stiffness without resilience or compression resistance. . Namely, one of the intended uses for the resulting tubular structure obtained with the known method is that of a fire hose, wherein a fire hose must of course be able to be rolled up for storage in a flat condition. Of course, once the tube obtained with the known method is filled with liquid, it functions as a pressure vessel and remains open. Another disadvantage is that the fabric obtained with the known method was found to be able to fray.

It is an object of the invention to provide a method of the type mentioned in the preamble which improves on this.

To this end, the method of the type described above is characterized in that the filling yarn is provided with a reinforcing component, and the substrate comprises a meltable component with a lower melting temperature than the remaining yarns of the substrate, and that the method comprises the further steps of heating the fabric to a temperature higher than the melting temperature of the meltable component but lower than the melting temperature of the remaining yarns to connect the meltable component to neighboring yarns and heat curing the fabric in a substantially open lumen configuration wherein the reinforcement component has sufficient flexural stiffness to provide radial stiffness with resilience to the fabric without shrinking the fabric after heat curing of the fabric.

By fusing the fusible component with neighboring yarns, it has been found possible to make the fabric raffle-resistant. By using the reinforcement component, the obtained graft was found to be resistant to compression and to be self-supporting. The method according to the invention is suitable for providing tissue grafts in a wide variety of dimensions and diameters. Furthermore, the (tissue) graft obtained by the method was found to be: resistant to kinking without the need to bend the graft, to be suitable for peripheral use in small diameters of 6 mm or less, to be kink-resistant with a small diameter with a desirable 45 amount of longitudinal elongation without pleating, to be suitable to have an external velor surface to promote cell tissue eradication, to have a finely woven, low profile surface to promote the formation of smooth, thin pseudo intima. Single velor tissue graft obtained with the method was found to have improved kink resistance without creasing.

It is noted that French patent application 2,364,284 discloses a method for manufacturing a rigid, perforated cloth such as a filter element for filtering particulate matter from a liquid or gaseous medium when that fluid passes over the woven fabric filter element. The structure obtained with the method known from the French patent application is unsuitable for the construction of a vascular graft since a vascular graft must be both flexible and resilient. There is no suggestion in the French patent application directed to a method according to the invention for providing a vascular graft.

Preferably, the forming step includes weaving the substrate into a tube.

Advantageously, the step of heat curing includes placing a mold of the fabric in an elongated state at 194778 2 and heating the fabric to a predetermined temperature for a predetermined period of time.

In a preferred embodiment, the method further comprises the steps of weaving the substrate with a predetermined number of binding points per centimeter, placing the tubular fabric on a mold, compressing the tubular fabric longitudinally on the mold to bend the warp yarns and compressing the filler yarns without shrinking the tissue, and heating the tubular tissue to a predetermined temperature for a predetermined period of time to cure the warp yarns in a longitudinally-compressed state to provide a longitudinal strain on the resulting graft to give.

The invention also provides a method for making a woven vascular graft, comprising: weaving a number of warp yarns, with a fill yarn, characterized in that the fill yarn is provided with a yarn of low-meltable fibers, and the warp yarns include multi-fiber yarn; and wherein the method further comprises heat curing the fabric to connect the fusible fibers of the filler yarn to orthogonal warp yarns to make the fabric raffle-resistant.

Preferably, the method comprises weaving the graft into one tube.

Advantageously, the graft is woven into one tube and heat cured by placing the tube on a mold and heating it to connect the fusible fibers.

In a preferred embodiment, heat curing includes placing the graft on the mold in an elongated state and heating to connect the fusible fibers and compressing the graft longitudinally on the mold without bending the tissue and heating it around the tissue. curing yarns in a pleated state to give a longitudinal stretch to the graft.

For a more complete understanding of the invention, reference is made to the following description in conjunction with the accompanying drawings, in which: Figure 1 is a weaving diagram of a rafter-resistant woven synthetic vascular graft fabric made according to a preferred embodiment of the invention; Figure 2 is a schematic cross-sectional view in wire direction of a finished graft surface showing the intertwined threads and of the fill yarn of a graft fabric with the weave pattern of Figure 1; Figure 3 is an enlarged sectional view of the filler yarn of the graft substrate of Figure 1; Figure 4 is a cross-sectional view of a two-component fabric of the meltable component 35 of the filler yarn of Figure 3; Figure 5 is a perspective view of a tubular rafee-resistant woven single velor vascular graft made in accordance with the invention; and Figure 6 is a perspective view of a forked rafee-resistant woven single-velor vascular graft made in accordance with the invention.

40

The woven synthetic vascular grafts made according to the invention can be used for a wide range of diameters, containing the small 2 to 6 mm diameter range suitable for peripheral use as well as dimensions of up to 40 mm. Accordingly, grafts can be woven with inner diameters in the range of about 2 to about 40 mm that are resistant to fraying and are self-supporting and kink-resistant without being crimped.

In a preferred embodiment of the invention, the woven graft has a diameter of 6 mm or less. In another preferred embodiment, the woven graft has an outer surface with loops and a smooth inner surface. The grafts are refractory and self-supporting and kink-resistant without bending the tissue surface. The grafts have fray resistance by heat curing warp and filler yarns containing meltable two-component fibers with a core of polyester resin and a low-meltable copolyester or polyethylene shell. During heat curing, the fusible resin sheath in the yarn of the woven fabric is connected to any braid yarn in the fabric. The meltable yarn is made from Celbond type K54 two-component fibers from Hoechst Celanese. The fibers are available in 55 lengths of 4 to 8 cm and 2 denier. The yarns used are biologically compatible.

The reinforcement component in the filling yarn can be single-fiber. Selection will vary depending on the desired property of the tubular graft. The reinforcement component, however, should be sufficiently rigid to give dimensional stability and radial stiffness with resilience to the tube without crimping. The reinforcement component should have the following minimum physical properties:

Diameter> 50 <250 pm 5 Tensile strength:> 3 grams per denier (53,000 psi)

Initial modulus: £ 50 grams / denier (800,000 psi)

E1: £ 3.9 x 10'® Ib.in2

Where E1 is the calculated tube stiffness, E is the initial elasticity modulus and I is the moment of inertia, 10-¾).

The diameter can vary depending on the required properties, but would typically be in the range of 50 to 250 µm.

The grafts have longitudinal elasticity provided by heat curing when the graft is compressed longitudinally. This compresses the warp yarns to provide stretch without having to bend the fabric surface.

Preferably, the majority of yarns used in the woven graft are polyethylene terephthalate, such as Dacron polyester available from DuPont or polyester available from Teijin, Hoechst-Celanese and Toray Industries. Graft substrate is formed by weaving a number of warp yarns from multi-fiber yarn with a combined fill yarn from meltable yarn and stiffer single-fiber yarn that are folded or wound for weaving. The woven fabric is heat cured to connect the two-component fibers to orthogonal warp yarns to provide longitudinal flexibility that maintains the graft integrity. Joining the low-meltable sheath of the two-component fibers to the braid warp yarns provides rag resistance. The large number of connection sites makes it possible to cut the tubular graft at any angle and to retain fray resistance.

The single-fiber polyester used as a reinforcing component in the following example is a polyethylene terephthalate yarn of 127 µm. The yarn has the following physical properties: Diameter: 0.005 inch (5 mil or 0.127 mm)

Tensile strength: 6.2 grams per denier (110,000 psi)

Initial modulus: 112 grams per denier (1,980,000 psi) II4 I (moment of inertia) =

Calculated tube stiffness = E x I 40 E1 = 3.8 x KT® Ib.in2.

The fusible fiber, Celbond, is made up of a polyester core and a copolyester or polyethylene shell. It is the sheath of the fiber that provides the connection. The available sheath resins melt in the range of 110-200 ° C, while the core resin melts at about 260 ° C. The fiber can either be spun into a yarn itself and combined with the single fiber or it can be directly combined with the single fiber using the core spinning process. This produces a yarn with a single-fiber core involving the Celbond fibers. be wrapped around it to form a shell.

The meltable component can be a fiber that is entirely made up of meltable resin, where the entire fiber would melt, not just the sheath. It is also possible to use multi-fiber yarns, whether they are two-component or single, instead of staple yarn. The low-meltable resin can also be applied directly to the outside of the single-fiber component of the filler yarns by co-extrusion or post-coating processes. This would replace the use of the Celbond fiber in the example.

During the heat-cure process, when the tube is formed into a tubular vascular graft, the two-component Celbond fiber fuses with the orthogonal warp yarns. This means that the filling yarn and the warp yarns are melted together at each intersection. This fusion makes it possible for the finished graft to be cut at any angle without the yarn shifting, separating or fraying.

Stretch is built into the graft by weaving the fabric with 25 to 50% fewer stitches per centimeter than in the finished graft. During the finishing process, the tube on a forming mold is 25 to 50% longitudinally compressed, and cured under heat. Heat curing in this way causes the warp yarns to bend and bend, thereby building in the elongation. It is this strain that allows finished grafts to be longitudinally bendable without the need to bend the surface of the graft.

The stiffer single-fiber component of the fill yarn can be any compatible yarn, such as polyethylene terephthalate, polyurethane, polytetrafluoroethylene or silicone. It provides mechanical strength, dimensioned stability and radial stiffness with resilience which maintains an open lumen for normal blood flow and provides the necessary tear strength. The multi-fiber warp yarns provide the necessary texture and coverage for cell tissue adhesion and ingrowth on the external surface and assist in controlling the porosity of the graft. The velor loops are multi-fiber warp yarns that are only on the outer surface. In the preferred single velor construction, the outer velor surface promotes cell tissue adhesion and ingrowth. The inner surface has a fine, low profile that promotes the formation of smooth, thin neo-intima.

The specific choice of multi-fiber warp yarns together with the stiffer combined meltable yarn and single-fiber filler yarn provides a graft with improved kink resistance in a wide range of diameters. Thus, smaller bending radii can be achieved without closure.

Figure 1 shows the weave pattern of a woven vascular graft substrate 11 made according to a preferred embodiment of the invention. Substrate 11 is woven from a large number of warp yarns 12 and filler yarn 13. Figure 2 is a schematic representation of substrate 11 in section with a smooth inner surface 14 and a velor outer surface 16 with loops 17 of multi-fiber yarn protruding from the surface of the transplant 19.

Referring to Figure 1, warp yarns 12 include base warp threads of multi-fiber yarn 18. In the embodiment shown, the multi-fiber yarn 18 is a single-stranded 50 denier non-textured non-shrunk non-textured (flat) polyethylene terephthalate (Teijin) yarn (1/50/48) (single-stranded / 50 denier / 48 fibers) with a 5-z twist. The loop or pile component of warp yarns 12 is a multi-fiber yarn 19 that alternates with each thread of the base warp threads 18. In substrate 11, multi-fiber yarn 19 is a textured 2/50/48 (2 strand / 50 denier / 48 fiber) with 1.5 s rotation of poyethylene terephthalate (Teijin) yarn.

Filling yarn 13 is a combination of a single-fiber yarn component 21 combined with a fusible staple yarn component 22 as shown in detail in section in Figure 3. Fusible yarn 22 which is formed from two-component staple fibers 25 has a polyester core 23 with a low-meltable sheath of a copolyester resin 24 surrounding the core 23 as shown in the enlarged sectional view of a single fiber 25 in Figure 4. Meltable yarn 22 is 40 cc (English Cotton Count) Celbond Type K54, formed from 2 denier / 2 "staple fibers with a twist multiplier of 4 (about 25 turns per inch) with a wrap-around melting point of 110 ° C. The fill components are folded with or without turning for weaving .

Figure 5 is a perspective view of a tubular graft 31 made in accordance with the invention. Graft 31 has a smooth inner surface 32 and an externally raised tissue velor surface 33 with a plurality of outwardly extending loops 34. Analogously, Figure 6 shows a forked graft 41 with a main body segment 42 and two legs 43 and 44. Legs 43 and 44 are connected to the main body 42 at the location of the branch 46 which is generally reinforced by a row of stitches 47 to maintain the initial porosity of the graft as well as possible. Graft 41 has a smooth inner surface 48 and an outer surface 49 with loops 51. As clearly follows from the weave pattern of Figure 1, loops 34 and 51 of grafts 31 and 41 are respectively formed from multi-fiber yarn. In substrate 11, the yarns 19 are textured shrinked polyester yarns. After weaving the substrate 11 in the pattern as shown in Figure 1, the 50 tubular grafts 31 and 41 are cut, then cleaned and washed in a hot bath resulting in a shrinkage or relaxation in the order of about 10 to 30% . The tubes are then subjected to a first heat-curing step by placing on a straight mold of a certain size in a longitudinally stretched state and placed in a convection oven at 175 ° C for about 20 minutes to give the graft a round state and fusing the Celbond yarns with the yarns in contact therewith. The grafts are then subjected to a second heat-curing step on a mold of the same size, but approximately 25 to 50% compressed longitudinally. This two heat-curing step in the compressed state builds in a longitudinal elongation and structural integrity and kink resistance without the need to bend the graft wall. The grafts can also be heat cured in a non-straight state to form shaped grafts, such as an aortic arch, which does not need to be bent or shaped by the surgeon during implantation.

As shown in Figures 5 and 6, tubular woven vascular grafts 31 and 41 made in accordance with the invention are not folded to maintain an open lumen. This is due to the incorporation of the relatively stiffer single-fiber component 21 into filler yarn 13 and the fusing of two-component yarn 25 to orthogonal warp yarns 12.

The specifications of the yarns and substrate 11 used are set forth in the following example. This example is given for illustration purposes and is not intended to be limiting.

Example

Seven sizes of tubular grafts were woven with the following yarns in the pattern of Figure 1.

Tubular weaving structure:

Basic pattern for grid structure:

Lancéd wire chain pattern for loop or pole surface:

Hanepoot (lancé wires on external surfaces, see figure 2) alternates around the wire (see figure 1).

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Yarn construction:

Bottom chain: 1/50/48 (5z) flat un-textured unshrunk polyester (Teijin).

Lancéd wire chain: 2/50/48 (1.5s) textured non-shrunk polyester (Teijin).

Filling: 127 µm PET single fiber wound together with 40 c.c. Celbon K-54 25 polyester.

Density description:

Warp threads: 320 threads per inch (40 teeth per inch times 8 threads per tooth).

Wefts: 44 wefts per inch per layer (in tubular form 88 in total) inlaid, 46 30 relaxed (or languid).

Tube description:

Large internal diameters: 4.3, 5.3, 6.3, 7.3, 8.3, 9.3 and 10.3 mm. Ready internal diameters: 4, 5, 6, 7, 8, 9 and 10 mm.

The velor is formed by weaving each second warp thread in a cock-leg pattern, which allows the warp-forming chain to float above three wefts and below one weft. The remaining adjacent 40 transmitting wires form a flat pattern.

After weaving, the single velor graft materials of Example 1 were cut, cleaned at 80 ° C in water and detergent, and thoroughly rinsed, dried, and then rinsed in a hot water bath of about 70 ° C to remove trace chemicals and dried. The graft tubes shrunk about 10 to 20% in length.

The tubes were then placed on a straight mold of suitable size in a longitudinally stretched state and heat cured at 175 ° C for 20 minutes in a convection oven to provide a round shape and fuse the Celbond yarns. The tubes were then compressed longitudinally over 30 to 40% of the length and again heat cured on a mold of the same size at 175 ° C for 20 minutes in a convection oven. Preferably, the compression is approximately 50-50% in length.

The porosity of the grafts was estimated at 1000 ml / min / cm 2.

The longitudinal flexibility of a tubular vascular graft is a relative measure of the ability of the graft to stretch at a given force and is expressed as the percentage elongation per kilogram of force. The grafts made in the example were stretched 55 about 30% in length when the tensile force was increased from 0 to 1 kg. This allows the graft to bend easily without kinking. The meltable component did not affect feel or flexibility compared to conventional woven grafts.

Claims (8)

194778 6 After fusing into the heat-curing steps, the yarns could not be unraveled from the outer threads, even after cutting the graft threads at an angle. The characteristics and properties of the grafts woven in accordance with the invention can be varied if desired by selection and selection of the starting chain and filling yarns and the weaving pattern. In the illustrated examples, the base warp threads are multi-fiber unextruded unshrunk (or flat) polyester yarns, but may also be pre-shrunk or unshrunk in textured or un-textured or in combination of yarns alternating into desired weave patterns. The preferred thread forming the pole or loops is a multi-fiber textured polyester, but may also be pre-shrunk or uncrushed in textured or un-textured form. The only limiting aspect is that there must be sufficient multi-fiber yarns to achieve the desired end results. The fill yarn is a composite meltable two-component yarn combined with a single-fiber polyethylene terephthalate yarn. Thus, it will be apparent that the above-described objects, among those apparent from the foregoing description, have been efficiently achieved and, since certain changes to the said product can be made without departing from the spirit of the invention, it will be apparent The examples described in the foregoing description and shown in the accompanying drawings are to be construed as being illustrative and not limiting. Conclusions A method of making a woven synthetic vascular graft comprising the step of forming a tubular fabric, the step of forming comprising weaving a plurality of warp yarns with at least one filler yarn to form a substrate, characterized in that the filling yarn (13) is provided with a reinforcing component (21), and the substrate (11) contains a meltable component (22) with a lower melting temperature than the remaining yarns (12, 21) of the substrate (11) and that the method comprises the further steps of heating the fabric (11) to a temperature higher than the melting temperature of the fusible component (22) but lower than the melting temperature of the remaining yarns (12, 21) to fusible component (22) to adjacent yarns (12, 21) and heat-curing the fabric (11) in a substantially open lumen configuration, the reinforcement component (21) having sufficient bending stiffness to r provide adial stiffness with resilience to the fabric (11) without shrinking the fabric (11) after heat curing the fabric (11). 2. A method according to claim 1, characterized in that the forming step comprises weaving the substrate into a tube. Method according to claim 1 or 2, characterized in that the step of heat-curing comprises placing the fabric in a stretched state on a mold of the fabric and heating the fabric to a predetermined temperature for a predetermined period of time . A method according to claim 3, characterized in that the method further comprises the steps of weaving the substrate with a predetermined number of binding points per centimeter, placing the tubular tissue on a mold, compressing it longitudinally on the mold of the tubular fabric to crimp the warp yarns and compress the filler yarns without shrinking the fabric, and heating the tubular fabric to a predetermined period of time to extend the warp yarns in a longitudinally-compressed state curing to give 45 a longitudinal stretch to the resulting graft. Method for making a woven vascular graft, comprising: weaving a number of warp yarns, with a filler yarn, characterized in that the filler yarn (13) is provided with a yarn (22) of fibers that can be melted at a low temperature (24) and the warp yarns (12) include multi-fiber yarn (19); and wherein the method further comprises heat curing the fabric (11) to connect the 50 fusible fibers (24) of the filler yarn (13) to orthogonal warp yarns (12) to make the fabric (11) raffle-resistant. The method of claim 5, comprising weaving the graft into one tube. 7. Method according to claim 5 or 6, comprising weaving the graft into one tube and heat curing by placing the tube on a mold and heating it to connect the fusible fibers. A method according to claim 7, characterized in that heat curing placing the graft on the mold in an elongated state and heating it to connect the fusible fibers 7 194778 and compressing the graft longitudinally on the mold without folding the fabric and heating it to cure the yarns in a pleated state to impart a longitudinal stretch to the graft. Hereby 1 sheet drawing