Patent Application
20050288775
The present invention is directed to an inventive yarn and prostheses therefrom. Additionally, a method for making the inventive yarn and prosthesis is also contemplated.
An intraluminal prosthesis is a medical device used in the treatment of diseased blood vessels. An intraluminal prosthesis is typically used to repair, replace, or otherwise correct a diseased or damaged blood vessel. An artery or vein may be diseased in a variety of different ways. The prosthesis may therefore be used to prevent or treat a wide variety of defects such as stenosis of the vessel, thrombosis, occlusion or an aneurysm.
One type of intraluminal prosthesis used in the repair of diseases in various body vessels is a graft. A graft is a commonly known type of intraluminal prosthesis which is used to repair and replace various body vessels. A graft provides a lumen through which blood may flow. Moreover, a graft is often configured to have porosity to permit the ingrowth of cells for stabilization of an implanted graft while also being generally impermeable to blood to inhibit substantial leakage of blood therethrough. Grafts are typically tubular devices which may be formed of a variety of materials, including textile and non-textile materials.
Grafts are typically flexible to provide compliance within a bodily lumen or within the bodily system. Such flexibility may result from the stretching of the textile yarns forming the graft. Such stretching, however, may effect the securement of the graft to the bodily lumen, which is typically secured by the use of sutures, as well as the dilation of the graft. Graft dilation is a common phenomenon following AAA repair. It is more pronounced in knitted grafts than in woven grafts. The knitted grafts can dilate as much as about 43% and woven grafts can dilate to about 26%. Graft dilation is affected by the textile structure, processing method and elongation of the yarn. Textile yarn can have a breaking point below the range of the dilation, such as with DuPont Dacron PET yarn which has a breaking elongation in a range of 30-50%. In other words, the graft flexibility may create undesirable stresses on the textile structure of the implanted graft and material failure.
Grafts are deployed in a vascular system by means of a catheter delivery system which passes the graft through the lumen of the blood vessel for deployment at the desired location. These standard delivery systems for delivering such prostheses intraluminally generally include catheters with the prosthesis removably mounted to the distal end of the catheter. Quite often a catheter, introducer sheath, or other similar retaining means, is disposed over the prosthesis to removably support the prosthesis on the catheter. Once the prosthesis is situated in the target site in the lumen, the catheter is removed by pulling the sheath or retaining means away from the prosthesis to allow the expansion.
Since catheter delivery is typically done under a fluoroscope or other similar x-ray type viewing mechanism, the movement of traditional textile vascular grafts during deployment cannot be fluoroscopically viewed. Further, as with traditional surgically implanted grafts, catheter implanted grafts must be longitudinally flexible to conform to the shape of the vessel which it is repairing. Also, such grafts should be capable of a certain degree of longitudinal expansion to conform to the length of the blood vessel which is to be replaced. Finally, the graft, once implanted by the catheter delivery system, must readily return to its open tubular shape and maintain that shape during use. This is particularly important where the graft is implanted by a catheter as the graft must be tightly compressed and packed so as to fit within the hollow lumen of the catheter.
Thus, there is a need for a prosthesis to optimize elasticity, flexibility, and radial expansion. Further, there is a need for a prosthesis having increased mechanical strength, abrasion resistance and a certain degree of radial structural integrity. Furthermore, there is a need for a prosthesis having radiopacity.
The present invention seeks to overcome the deficiencies of the currently available prostheses. More specifically, the present invention provides a fabric and a prostheses with improved mechanical properties including a metallic component.
One aspect of the present invention includes an implantable prosthesis including a biocompatible implantable fabric having a textile construction of metal fibers.
Another aspect of the present invention includes an implantable prosthesis including a biocompatible implantable fabric having a textile construction. The textile construction including a composite yarn and metal fibers. The prosthesis is a graft.
A further aspect of the present invention includes a composite yarn is a biocompatible, implantable yarn having a metallic component and a non-metallic component combined together by a twisting, co-spinning, wrapping and combinations thereof. The total denier of the yarn is about 20 to about 300.
Another aspect the present invention includes a implantable prosthesis including a biocompatible implantable fabric having a textile construction including a composite yarn. The composite yarn includes a combination of a metallic component and a non-metallic component. The components are combined by twisting, co-spinning, wrapping and combinations thereof.
A further aspect of the present invention includes a variation of the twisted, co-spun, and/or wrapped techniques using multiple strands, and at least one strand is a metallic component.
An additional aspect of the present invention includes an implantable prosthesis including a biocompatible fabric having a textile construction including a composite yarn. The composite yarn includes a co-spun yarn of a stainless steel fiber and a polymer. The stainless steel is present in amounts of about 5% to about 100% of the total composite yarn. The composite yarn has a total denier of about 20 to about 300.
Yet a further aspect of the invention includes a method for making a implantable prosthesis including the steps of providing a composite yarn including a combination of a metallic component and a non-metallic component. The composite yarn being a combined by twisting, co-spinning, wrapping, and combinations thereof. Forming the composite yarn into the implantable prosthesis using a selected textile construction. Various textile constructions include weaving, knitting, braiding, non-woven spinning and combinations thereof.
Further details regarding the present invention and variations thereof are further provided.
The present invention seeks to solve the deficiencies of the prior art by making prostheses having improved mechanical properties with a textile fabric made from a metallic component. A fabric or yarn made from the metallic component of the present invention provides a fabric having increased the durability of prostheses, thereby reducing the need for physicians to routinely remove, repair and replace vascular prostheses that have been implanted.
Further, the metallic component of the present invention provides a radiopaque guideline or marker for viewing the implanted prosthesis fluoroscopically. Radiopaque markers assist the surgeon to visualize the prosthesis both during and after implantation. The marker helps show the surgeon that the prosthesis is properly positioned. Also, it will indicate whether the prosthesis has dilated or collapsed after implantation.
Furthermore, the metallic component of the present invention provides strength, radial structural integrity, and abrasion resistance for the prosthesis or yarn made therefrom. Additionally, the metallic component provides controlled expansion and dilation of the prosthesis made therefrom. The properties of the metallic component provide the controlled expansion because of the rigidity and substantially inelasticity of the metallic properties.
The term “yarn” as used herein refers to a continuous strands, filaments, or materials in a form suitable for knitting, weaving, braiding, twisting, spinning, or otherwise intertwining to form a textile fabric. Yarn can occur in a variety of forms to include a spun yarn including staple fibers and strands usually bound together by twist, or multifilament yarn including many continuous filaments or strands. “Yarn” can also include manufactured fibers produced by, among other things, extrusion processes.
The term “component” herein refers to individual fibers, monofilament, multifilament, strands and materials in a form suitable for twisting, spinning, wrapping and otherwise intertwining to form the yarn of the present invention. Additionally, individual filaments which can make up the yarn may have any one of a variety of cross sections to include round, rectangular, serrated, bean-shaped or others. The individual components can be pre-twisted or spun prior to combining them to form the yarn of the present invention.
Inventive Yarn
One embodiment of the present invention is a yarn including a metallic component. The metallic component is constructed of any biocompatible metallic material as known in the art such as stainless steel, titanium, nitinol, and the like. The metallic component should have a total diameter of from about 0.05 mm to about 0.5 mm, and preferably from about 0.18 mm to about 0.38 mm. The metallic component may include monofilament and multiple metallic filaments, with the total diameters of the filaments being within these ranges.
Another embodiment of the present invention is a composite yarn including a combination of non-metallic component and metallic component. The composite yarn of the present invention provides the benefits of the non-metallic component being elasticity, flexibility and radial expansion as well as the benefits of the metallic component being strength, radial structural integrity, controlled expansion and abrasion resistance.
The non-metallic component of the composite yarn of the present invention is biocompatible. The non-metallic component may be constructed from one of a variety of available natural and man-made fibers. These materials include polyester, PTFE, polypropylene and combinations thereof. The man-made fibers in this group may be supplied in either continuous, multi-filament form or in spun form. The denier of these yarns may be between about 20 and 300 denier, with a denier between about 40 and 70 being preferred denier.
The composite yarn can be constructed of a metallic component or a portion thereof. Additionally, the yarn can include multiple components, any of which include metallic material. The metallic component is present in amounts of about 5% to about 100% of the total composite yarn. The ratio can be adjusted to optimize certain mechanical properties to provide the desired end product. For example, the more metallic material present in a composite yarn the more rigid, and non-elastic the composite yarn. This provides a greater mechanical strength yarn having greater burst and tensile strength. Additionally, increased metallic material in the composite yarn provides increased abrasion resistance, and increased radial expansion forces, if used to construct a tubular structure. Alternatively, the lower the percentage of metallic material present in the composite yarn provides for more flexibility and greater elasticity of the composite yarn.
In addition to choosing the materials of construction for the desired end product, the means of constructing the yarn are chosen to provide the desired properties for the end product; i.e. the thickness of the individual components used, the number and direction of twisting the components in forming the yarn, and the number of ply of the yarn. The heaviness, or weight, of the resulting yarn depends on the thickness of the individual components rather than the amount of plies in the yarn. For example, two fat components will result in a yarn much heavier than a 4-ply made of very fine ones. The number of strands, number of twists vary depending on the desired end use and desired properties, such as thickness, strength, flexibility, etc. For example, more twists which yield a stiffer, stronger yarn are typically desirable for a weaved textile fabric while less twists which yield a softer, flexible yarn is typically desirable for a knitted textile fabric.
The metallic component and the non-metallic component of the present invention are combined using various techniques such as twisting, co-spinning or over-wrapping. The twisting or co-spinning technique is performed manually and automatically. There are many different methods to spin fiber into twisted strands, but basically, the prepared material is drawn out and twisted using a spindle or other spinning device, such as a spinning wheel, or the industrial equivalent. The twist lends strength to the strand.
The composite yarn of the present invention is combined by twisting or co-spinning a metallic component with a non-metallic component(s). The twisting or co-spinning can be a “S twist” or “Z twist”. The “S twist” is formed by spinning counterclockwise, the resulting twist runs upwards and to the left, as shown in
Additionally, each component 2, 3 can be pre-twisted prior to combining them to form the composite yarn 1. The components 2, 3 can be pre-twisted as a 1-ply, 2-ply, 3-ply, etc. as well. For example, non-metallic component 3 can include two polymer strands twisted together forming a 2-ply component. The 2-ply component is combined with the metallic component 3 forming the composite yarn of the present invention. The additionally pre-twisted polymer strands provide for more flexibility and dilation, as opposed to the one strand polymer combination.
One embodiment, illustrated in
Additionally,
Further embodiments illustrated in
A large number of core/cover combinations can be contemplated depending on the yarn available, the characteristics desired in the finished product, and the processing equipment available. For example, any combination of number of strands used, material of construction of the strands, and varying sizes of the strands may be provided for the core yarns and/or the cover yarns. Additionally, any core yarn, cover yarn and combinations thereof may include a metallic component.
Further, various techniques as known in the art may be used to pretreat the materials prior to constructing the composite yarn of the present invention. For example, the non-metallic component may include the step of “drawing” the components. This treatment commonly includes longitudinally stretching the components beyond their point until complete plastic deformation (i.e., a region in which the component now exhibits loss of its elasticity and ability to change appreciably in length) is accomplished.
The force required to “draw” a component increases until the yield point is reached, at which point, the component enters a region of plastic deformation. Once the deformation point in a component has been reached through stretching, the material has substantially lost its elastic memory and is more or less “fixed”, neither being able to be further stretched or to return to its original length. Thus, these components retain their expanded circumferential length and now have a fixed diameter.
The composite yarn may also be stretched until a point at which the material fractures, i.e., the fracture point. The process of drawing the yarn to a point prior to the fracture point increases the tensile strength of the yarn and decreases the elongation to failure. As a result of drawing, the polymeric yarns become directionally aligned or oriented.
Inventive Prosthesis
Another embodiment of the present invention is a prosthesis made from a metallic component, metallic yarn, or metallic material. A further embodiment of the present invention is a composite prosthesis including a portion of the prosthesis being constructed of a metallic component, metallic yarn or metallic material. The below discussion pertains to both embodiments and herein referred to as “composite prosthesis” in general.
The yarns used to construct the various composite prostheses of the present invention, generally, can be flat, twisted, textured or combinations thereof, and may have high, low or moderate shrinkage properties. Additionally, the yarn type and yarn denier can be selected to meet specific properties desired for the prosthesis, such as porosity, flexibility and compliance, as above-discussed. The yarn denier represents the linear density of the yarn. Thus, yarn of small denier, e.g., 40-50 denier, would correspond to a very fine yarn whereas a yarn with a larger denier, e.g. 1,000, would correspond to a heavy yarn.
Yarns useful in the inventive composite prostheses have a denier range from about 20 to about 1500 and a filament count of about 10 to about 200, depending on the specific type of prosthesis and the use of the desired product. The yarns used with the present invention preferably have a denier from about 20 to about 300. A high filament count for the same overall linear density increases the yarns flexibility, reduces its stiffness and reduces permeability to viscous liquids, i.e. blood.
Further, the composite prosthesis of the present invention includes a yarn as above-discussed having at least a portion being metallic. The flexibility, durability, stiffness and strength can be adjusted by varying the percent ratio of metallic component in the composite prosthesis, as above-discussed.
The composite prosthesis of the present invention can have virtually any textile construction, including weaves, knits, braids, filament windings and the like.
A variety of textile constructions may be employed using the present invention. With respect to weaves, any known weave pattern in the art, including, simple weaves, basket weaves, twill weaves, velour weaves and the like may be used. Referring to the drawings and, in particular to
A composite prosthesis that is woven with undrawn or a combination of undrawn and partially drawn radial yarns is also contemplated. Such composite prostheses will be capable of circumferential expansion following manufacture of the product. For instance, if a balloon catheter (or similar device) is inserted into such a composite prosthesis and is thereafter expanded, the composite prosthesis will circumferentially expand a slight degree until the yield point is reached. At that point, the radial yarns, i.e. fill yarns, which were not drawn, will plastically deform, thereby allowing substantial circumferential expansion.
In addition to woven textile composite prostheses, knitted textile composite prostheses are provided. Knitting involves the interlooping or stitching of yarn into vertical columns (wales) and horizontal rows (courses) of loops to form the knitted fabric structure. Warp knitting is particularly useful with the knitted textile portions of the present invention. In warp knitting, the loops are formed along the textile length, i.e., in the wale or warp direction of the textile. As depicted in
Knitting patterns useful with the present invention include conventional warp-knitted patterns and high-stretch, warp-knitted patterns. Commonly used warp-knitted patterns include locknit (also referred to as tricot or jersey knits), reverse locknit, sharkskin, queenscord and velour knits. Useful high stretch, warp-knitted patterns include those with multiple patterns of diagonally shifting yarns, such as certain modified atlas knits which are described in U.S. Pat. No. 6,540,773, the contents of which are in incorporated herein by reference. Other useful high-stretch, warp knitted patterns include certain patterns with multiple needle underlap and one needle overlap, such as those patterns described in U.S. Pat. No. 6,554,855 and U.S. Patent Application Publication No. 2003/0204241 A1, the contents of which are incorporated herein by reference.
The knitted portion 92, as illustrated in
The knitted patterns 64, 90 and 92 are depicted as a single knitted layer in
Although weaving and knitting are among the most desirable constructions, braiding may also be used as shown in
An interlocking three-dimensional braid, as shown in
In
The next contiguous layer 43 is formed from segments of four yarns 54, 55, 56 and 58 inter-braided to form an inner layer in the multilayered structure. Layer 44 is formed in similar fashion, having three yarns 55, 57 and 58 which are interbraided.
A solid three-dimensional braided structure, may be used and is formed by continuous intertwining of the fibers. Solid three-dimensional braids are homogenous in that all yarns are present throughout the thickness of the braid. Typically, three-dimensional braiding machines used to form this type of solid braid include an array of fiber bobbins held in ring or track configurations. Circumferential motion of the array of the bobbins to form the braid is accomplished by shifting slotted rings containing the fiber holders. Fibers are directed through the thickness of the braid by shifting the holders between the rings. Reversal of the direction of ring and hold motions during the shift segment interlocks the fibers. Since every fiber undergoes a similar motion, all fibers become entwined in the balanced array.
Further, this invention contemplates a method for making a biocompatible, implantable prosthesis including the steps of providing a metallic component. Forming a metallic yarn. Selecting a textile construction and forming a prosthesis in accordance with the selected textile pattern. Various textile constructions may be used such as weaving, knitting, braiding, non-woven spinning and combinations thereof to construct a prosthesis having the desired properties.
Furthermore, this invention contemplates a method for making a biocompatible, implantable prosthesis including the steps of providing a composite yarn which includes a combination of a metallic component and non-metallic component. The combination of the components includes the steps of co-spinning, twisting, wrapping, and combinations thereof. Additional steps of this method include selecting a textile construction and forming a prosthesis in accordance with the selected textile pattern. Various textile constructions may be used such as weaving, knitting, braiding, non-woven spinning and combinations thereof to construct a prosthesis having the desired properties.
Virtually any type of implantable prosthesis can be made from the present invention due to the versatility of the metallic component of the present invention or composite yarn of the present invention. Particularly desirable applications include intraluminal prostheses, such as endovascular grafts, blood filters, stent-graft composites, balloon catheter, filter, mesh, valves, vascular patch, hernia plug, arterial-vascular access graft and the like. This invention may also be designed to repair or support a weakened or damaged lumen, such as a blood vessel in the vascular system.
Although the present invention has been described with preferred embodiments, it is to be understood that modifications and variations may be utilized without departing from the spirit and scope of this invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the appended claims and their equivalents.
