NL9900012A - Woven synthetic vascular implants - Google Patents

Abstract

Woven synthetic vascular implants comprise a series of warp fibres woven with a weft yarn and contain a component (I) with a low m.pt. The implants are woven as hoses with a lattice structure comprising a series of multifilament warp fibres forming a velour-type outer surface and a smooth inner surface. The structure is reinforced by a monofilament weft yarn to make it self-supporting. The weft fibres are a combination of structured (19) and unstructured (18) non-shrunk polyester fibres. The warp monofilaments (13) are made of polyethylene terephthalate and are coated with a low-melting, heat-curable material, e.g. 'Celbond K-54'.

Description

Frayed slide. self-supporting woven vascular graft.

This invention relates to synthetic vascular grafts, and in particular to synthetic woven vascular grafts that are fray resistant due to the incorporation of a fusible component and self-supporting due to the incorporation of a firming component.

Synthetic material vascular grafts are commonly used to replace parts of human blood vessels. Synthetic vascular grafts have a wide variety of configurations and are made from a wide variety of materials. Among the accepted and successful vascular grafts are those formed from a biocompatible tubular material that maintain an open lumen to allow blood to flow normally through the graft after implantation. The biocompatible materials include thermoplastic materials such as polyester, polytetrafluoroethylene (PTFE), silicone and polyurethanes. The most commonly used are polyester fibers and PTFE. The polyester fibers, usually Dacron, can be knitted or woven and can be made of a single-fiber, or multi-fiber, or staple yarn, or a combination of any.

A wide variety of synthetic vascular grafts are used today. An important factor in the selection of a specific graft is the porosity of the substrate from which the graft is formed, the resilience of the tubular construction, and the strength requirements for the graft. Porosity is important as it tends to bleed during and controls after implantation and influences ingrowth of cellular tissue in the wall of the graft.

Synthetically manufactured vascular grafts can be of a woven knitted construction with or without velor. A synthetic vascular graft with a knitted chain construction is described by William J. Liebig in US-A-3,945,052. Another graft with a double velor knitted warp construction is described by Liebig and German Rodriquez in US-A-4,047,252. William J. Liebig and Dennis Cummings describe a synthetic woven double velor graft in US-A-4,517,687; the velor loops being formed from warp yarns which are braided pre-shrunk multi-fiber yarns. These three U.S. synthetic vascular graft patents are issued by the applicant for this application.

US-A-4,892,539 issued to Durraus Koch describes a synthetically fabricated woven single graft graft on the exterior surface. The graft is described as being woven from multi-fiber polyester yarns, particularly described as being braided, the single outer velor being formed from filler yarn with each velor loop extending beyond a number of warp yarns.

After knitting or weaving multi-fiber yarn into a tubular graft, the graft is compressed by a method as described in US-A-3,853,462 to Ray E. Smith and US-A-3,986,828 to Harmcn Hoffman and Jacob Tolsma. in the name of the applicant for this application. Compression results in a pleat of the yarn in the fabric and generally reduces the overall porosity of the fabric substrate. After compression, these tubular grafts generally have a diameter of about 6mm to 40mm.

Following compression, synthetic tubular tissue grafts are pleated. The pleating involves the formation of ridges in the wall of the grafts to avoid the risk of kinking or collapsing of the tube when it is bent and resulting in uniform, regular, circular undulations that have uniform strength over the entire surface of the tube. maintain graft tube. This applies to both woven and knitted vascular tissue grafts. Examples are shown by L.S. Sauvage in US-A-3,878,565 which describes a synthetic fiber tubular fiber prosthesis having a body with a number of fiber loops extending outward. In Figure 2a, the graft body is pleated in irregular, peripheral undulations. The degree of protection afforded by the irregular undulations varies along the length of the pipe and may fall below the required level of protection in specific areas. The knitted warp and woven grafts described above in US-A-3,945,052, US-A-4,047,252 and US-A-4,517,687 are circularly pleated. The graft in US-A-4,892,539 is spirally pleated. Pleated or corrugated walls can disrupt blood flow and form areas where a lot of cellular tissue builds up, due to the profile.

S. Polansky in US-A-3,304,557 avoids pleating in vascular prostheses by forming a tube with repetitive annular reinforcement portions. These annular reinforcement portions contain reinforcement weft threads adjacent to the outer surface only. He suggests that the rings can be in the form of a spiral, alternating rings and spiral loops. The latter suggestions are analogous to the tubular prostheses of I.B. Medell in US-A-3,479,670 wherein an open mesh tube is wrapped with two polypropylene single fiber right hand and left hand coils and fused to partially penetrate the outer wall of the tube. In US-A-3,272,204 to C. Artandi and L.E. Bechtol is a Dacron fabric sewn to Teflon rings or spiral to prevent an absorbable collagen-reinforced graft tube from collapsing.

The selection of a specific type of graft substrate by a vascular surgeon depends on several factors. Among the factors is the specific location of the implant. This also determines the size of the graft to maintain a sufficiently small or large lumen to provide normal blood flow in the implantation area. The fundamental strength requirements and blood pressure in the area of implantation also influence selection. Generally, the woven grafts provide greater strength and reduced porosity, but are generally considered to be difficult to handle and sew and tend to fray when cut, especially at an oblique angle. Velor is often preferred as clear velor surfaces promote the growth of cellular tissue in the loops extending from the surface of the velor fabric. The knitted grafts are generally softer and easier to sew, but are generally more porous. Depending on the implant site and the coagulation condition of the patient, synthetic tissue grafts should generally be clotted with the patient's blood prior to implantation. Pre-solidification is not necessary for woven grafts, but is generally recommended.

Tubular grafts of smaller diameter, for example 6 mm or less, are often used: peripheral areas of the body and appendages. Today, PTFE grafts of the material described by Robert W. Gore in US-A-4,187,390 and US-A-3,953,566 are most successful. These grafts are formed by extrusion of the PTFE material. While accepted for use in smaller diameter applications, PTFE grafts often require surgical replacement within relatively short periods of time compared to larger diameter vascular tissue grafts as described above.

Accordingly, it is desirable to provide a synthetic vascular tissue graft suitable for a wide variety of dimensions and diameters that provides the benefits of a woven graft, but which does not fray when cut and which does not require pleating and which is self-supporting and maintains open lumen.

Generally speaking, according to the invention, a fray-resistant, self-supporting woven synthetic vascular graft is provided with improved kink resistance and containing fusible components in the fabric. A number of multi-fiber warp and fill yarns are woven in tubular form and contain a fusible component to prevent fraying. The filler yarn may contain a reinforcing component to prevent collapse and provide a tubular graft with improved radial resilience. The warp yarns can be the same or contain flat and braided textured yarns. A fill of stiffer single fiber yarn and fusible components provides radial tear strength, dimensional stability and resilient radial stiffness to keep the lumen of the tubular structure open and to provide a sufficient degree of fraying resistance. The graft surfaces can be smooth or can be single or double velor.

In a preferred embodiment of the invention, the fusible component of the filler yarn is formed of two-component fiber with a polyester core surrounded by a low-temperature fusible polymer jacket designed to join adjacent yarns to form a solid joint ra exposure to heat. In another preferred embodiment, the finished fray-resistant, sail-bearing woven vascular graft has an external surface similar to velor. The internal surface features a fine, textured ribbed surface to promote the formation of smooth, thin psuedo intima. The loops on the external surface are formed by multi-fiber warp yarns which provide the necessary fabric cover for cellular tissue adhesion and ingrowth. The density of the multi-fiber warp yarns also controls blood porosity.

The woven grafts made in accordance with the invention are particularly suitable for 2-6 mm diameter peripheral vascular prostheses, but are also suitable for larger dimensions up to about 40 mm. Kink resistance is provided without the need to fold the vascular graft.

Accordingly, it is an object of the invention to provide an improved woven synthetic vascular graft.

Another object of the invention is to provide a self-supporting woven synthetic vascular graft that is fray resistant.

A further object of the invention is to provide a synthetic woven vascular graft that is resistant to kinking without the need to fold the graft.

A further object of the invention is to provide a woven synthetic vascular tissue graft suitable for peripheral use in small diameters of 6 mm or less.

Yet a further object of the invention is to provide a woven synthetic vascular tissue graft with a small diameter that is kink resistant and provides a desirable amount of longitudinal stretch without crimping.

Yet a further object of the invention is to provide a fray-resistant woven synthetic vascular tissue graft containing an external velor surface to promote cell tissue growth.

Yet a further object of the invention is to provide a self-supporting woven synthetic vascular graft with a fine, low profile woven surface to promote the formation of smooth, thin pseudo intima.

Yet a further object of the invention is to provide a fray-resistant woven synthetic single velor vascular tissue graft with improved kink resistance without wrinkling.

Yet a further object of the invention is to provide a method of making an improved fray-resistant woven synthetic vascular tissue graft according to the invention.

Further objects and advantages of the invention follow from the description.

Accordingly, the invention includes several steps and the relationship between one or more such steps relative to each of the others, the device embodying the features of construction, combination and arrangement of parts adapted to effect such steps, and the product Containing the properties, features, and relationship of builder members will be described in detail below, by way of example, and the scope of the invention will be set out in the claims.

For a more complete understanding of the invention, reference is made to the following description in conjunction with the accompanying drawing, in which: Figure 1 is a weave diagram of a fray-resistant woven synthetic vascular graft fabric made in accordance with a preferred embodiment of the invention; FIG. 2 is a schematic cross-sectional view of a finished graft surface showing the intertwined threads and of the fill yarn of a graft fabric with the weave of FIG. 1; Figure 3 is an enlarged cross-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 fusible component of the filler yarn of Figure 3; Figure 5 is a perspective view of a tubular fray-resistant woven single velor vascular graft made in accordance with the invention; and Figure 6 is a perspective view of a forked, fray-resistant woven single-velor vascular graft made in accordance with the invention.

The woven synthetic vascular grafts made according to the invention are applicable 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 ranging from about 2 to about 40 nm that are fray resistant, 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 external looped surface and a smooth internal surface. The grafts are fray resistant, self-supporting and kink resistant without wrinkling the tissue surface. The grafts exhibit fraying resistance by heat-curing warp and filler yarns containing two-component fusible fibers with a polyester resin core and a low-temperature fusible copolyester or polyethylene shell. During heat curing, the fusible resin jacket in the woven fabric yarn is bonded to each braid yarn in the fabric. The fusible yarn is constructed from Celbond type K54 two-component fibers from Hoechst Celanese. The fibers are available in lengths from 4 to 8 cm and 2 15 denier. The yarns used are biologically compatible.

The reinforcing component in the filler yarn can be monofilament. Selection will vary depending on the desired property of the tubular graft. The stiffening component, however, should be sufficiently rigid to provide dimensional stability and radial stiffness to the pipe without bending. The stiffening component should have the following minimum physical properties:

Diameter:> 50 <250 μπι

Tensile strength:>. 3 grams per denier (53,000 psi)

Initial modulus:> 50 grams / denier (800,000 psi) EI:> 3.9 x 10 "8 lb.in2

Where EI is the calculated tube stiffness, E is the initial elasticity modulus and I is the moment of inertia,

is.

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

The grafts have longitudinal elasticity provided by the heat curing when the graft is longitudinally compressed. 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 of polyethylene terephthalate, such as Dacron polyester are available from DuPont or polyester are available from Teijin, Hoechst-Celanese and Toray Industries. Graft substrate is formed by weaving a number of multi-filament warp yarns with a combined fill yarn of fusible yarn and stiffer monofiber yarn which are folded or wound before weaving. The woven fabric is heat cured to bond the two-component fibers to orthogonal warp yarns to provide longitudinal flexibility that maintains the integrity of the graft. Connecting the low temperature fusible sheath of the two-component fibers to the braid warp yarns provides fray resistance. The large number of connection points makes it possible to cut the tubular graft at any angle and maintain fray resistance.

The single-fiber polyester used as a reinforcement component in the following example is a 127 μτη polyethylene terephthalate yarn. 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)

Calculated tube stiffness = E x I EI = 3.8 x 10'6 lb.in2.

The fusible fiber, Celbond, consists of a core of polyester and a sheath of copolyester or polyethylene. It is the shell 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 in 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 single fiber core yarn with the Celbond fibers twisted around it to form a sheath.

The fusible component can be a fiber built entirely of fusible 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-temperature fusible resin can also be applied directly to the outside of the monofilament 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-curing 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 filler yarn and warp yarns are fused together at every crossing. This fusion allows 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% less stitches per centimeter than the finished graft. During the finishing process, the tube is compressed longitudinally on a molding mold 25 to 50%, and cured under heat. Heat curing in this way causes the warp yarns to fold and bend, thereby building in stretch. It is this stretch that allows finished grafts to be longitudinally bendable without the need to bend the surface of the graft.

The stiffer monofilament component of the filler yarn can be any compatible yarn, such as polyethylene terephthalate, polyurethane, polytetrafluoroethylene or silicone. It provides mechanical strength, dimensional 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 cellular tissue adhesion and ingrowth on the exterior surface and assist in controlling the porosity of the graft. The velor loops are multi-fiber warp yarns that are located only on the external surface. In the preferred single velor construction, the exterior velor surface promotes cellular tissue adhesion and ingrowth. The internal 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 fusible yarn and single-fiber filling yarn provides a graft moth with improved kink resistance over a wide range of diameters. Thus, smaller bend radii can be achieved without occlusion.

Figure 1 shows the weave of a woven vascular graft substrate 11 made in accordance with 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 mst loops 17 of multi-fiber yarn protruding from the surface of the graft 19.

Referring to Figure 1, warp yarns 12 contain coiled threads of multi-fiber yarn 18. In the embodiment shown, the multi-fiber yarn 18 is single stranded 50 denier unexturized unshrunk unstretched (flat) polyethylene terephthalate (Teijin) garsn (1/50/48) (single strand / 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 strand of the warp threads 18. In substrate 11, multi-fiber yarn 19 is a textured 2/50/48 (2 skein / 50 denier / 48 fibers) with 1.5 s rotation of polyethylene 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 core 23 of polyester with a low temperature fusible 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. Fusible yarn 22 is 40 cc (English Cotton Count) Celbond Type K54, formed from 2 de-kidney / 2 "staple fibers with a rotary multiplier of 4 (approximately 25 turns per inch) with a casing melting point of 110 ° C. The filling components are folded together with or without twisting 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. Similarly, 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 branch 46 which is generally reinforced by a row of stitches 47 in order to maintain as much as possible the initial porosity of the graft . Graft 41 has a smooth inner surface 48 and an outer surface 49 with loops 51. As clearly follows from the weaving pattern of Figure 1, loops 34 and 51 of grafts 31 and 41 are formed of multi-fiber yarn, respectively. In substrate 11, the yarns 19 are textured unshrunk polyester yarns. After weaving the substrate. 11 in the pattern as shown in Figure 1, the tubular grafts 31 and 41 are cut, then cleaned and washed in a hot bath resulting in a shrinkage or relaxation of the order of about 10 to 30%. The tubes are then subjected to a first heat-curing step by placing on a straight gauge 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 compressed about 25 to 50% longitudinally. This two heat-cured step in the compressed state builds in a longitudinal stretch and structural integrity and kink resistance without the need to bend the graft wall. The grafts may also be heat cured in a non-straight state to form shaped grafts, such as an aortic arch, which need not be bent or formed by the surgeon during implantation.

As shown in Figures 5 and 6, tubular woven vascular grafts 31 and 41 made according to the invention are not pleated to maintain an open lumen. This is due to the inclusion of the relatively stiffer single-fiber component 21 in filler yarn 13 and the fusion 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 illustrative 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 weave construction:

Ground pattern for grid structure:

Lance wire chain pattern for loop or pole surface:

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

Yarn construction:

Soil chain: 1/50/48 (5z) flat unexturized unshrunk polyester (Teijin). Lancé wire chain: 2/50/48 (1.5s) textured unshrunk polyester (Teijin).

Filling: 127 μτη PET single fiber wound together with 40 c.c. Celbon K-54 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 (88 in total in tubular form) inlaid, 46 relaxed (or loom).

Tube description:

Large internal diameters: 4.3, 5.3, 6.3, 7.3, 8.3, 9.3 and 10.3 mm

Finished internal diameters: 4, 5, 6, 7, 8, 9 and 10 mm.

The velor is formed by weaving every second warp thread into a cuff pattern, allowing the warp forming the loop thread to float above three wefts and under one weft. The remaining adjacent 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 rinsed thoroughly, dried, then rinsed in a hot water bath at about 70 ° C to remove trace chemicals and dried. The graft tubes shrank about 10 to 20% in length.

The tubes were then placed on an appropriately sized straight mold 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 longitudinally compressed over 30 to 40% of the length and re-cured on the same sized mold at 175 ° C for 20 minutes in a convection oven. Preferably, the compression is about 25-50%: n length.

Graft porosity was estimated at 1000ml / min / cm2.

The longitudinal flexibility of a tubular vascular graft is a relative measure of the graft's ability to stretch at a given force and is expressed in percent safety length per kilogram of force. The grafts made in the example were stretched 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 fusible component did not affect the feel or flexibility compared to conventional woven grafts.

After fusing in the heat-curing steps, the yarns could not be unraveled from the outer threads even after cutting the graft threads at an angle.

The features 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 filler yarns and the weave. In the illustrated examples, the ground warp threads are multi-fiber unexturized unshrunk (or flat) polyester yarns, but may also be pre-shrunk or unshrunk in textured or unexturized or in combination of yarns alternately in desired weaves. The preferred thread forming the pile or loops is a multi-fiber textured polyester, but it may also be pre-shrunk or un-shrunk in textured or non-textured form.

The only limiting aspect is that sufficient multi-fiber yarns must be present to achieve the desired end results. The filler yarn is a composite two-component fusible yarn combined with a one-fiber polyethylene terephthalate yarn.

Thus, it will be understood that the above-described objectives amid those set forth in the foregoing description have been efficiently achieved and, since certain changes may be made to the said product without departing from the spirit of the invention, it will be apparent that the examples described in the foregoing description and shown in the accompanying drawings are to be construed as illustrative and not limiting.

Claims (8)

A method for making a fray-resistant self-supporting woven synthetic vascular graft comprising the steps of: forming a tubular fabric, the step of forming comprising weaving a plurality of warp yarns with at least one filler yarn to to form a substrate, wherein the filler yarn is provided with a reinforcing component, and wherein the substrate contains a fusible component having a lower melting temperature than the remaining yarns of the substrate, and comprising the further steps of heating the fabric to a temperature which higher: _s than the melting temperature of the fusible component but lower than the melting temperature of the remaining yarns to bond the fusible component to neighboring yarns to make the fabric fray and heat cure the fabric in a substantially open lumen configuration the stiffening component having sufficient bending stiffness to withstand radial stiffness provide strength to the fabric making the resulting graft resistant to compression and self-supporting without shrinking the fabric after heat-curing the fabric. 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 condition on a mold and heating the fabric to a predetermined temperature for a predetermined period of time. | | The method according to claim 3, characterized in that the method further comprises the steps of weaving the substrate with a predetermined number of bonding points per centimeter, placing the tubular fabric on a mold, compressing it longitudinally on the mold the tubular fabric to crimp the warp yarns and compress the fill 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 harden to give a longitudinal stretch to the resulting graft. A method for making a fray-resistant self-supporting woven vascular graft, comprising: weaving a plurality of warp yarns containing multi-fiber yarn with a fill yarn provided with a low-temperature fusible fiber yarn; and heat-curing the fabric to bond the fusible fibers of the fill yarn to orthogonal warp yarns. The method of claim 5 comprising weaving the graft into one tube. A 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 bond the fusible fibers. A method according to claim 7, characterized in that heat curing placing the graft on the mold in a stretched state and heating to bond the fusible fibers and compressing the graft longitudinally on the mold without the tissue pleating and heating to harden the yarns in a pleated condition to impart a longitudinal stretch to the graft.