MXPA96005485A - Compound implant recubie - Google Patents

Abstract

The present invention relates to a compatible body device comprising: an elongate filament substantially uniform in lateral cross section over its length and including an elongated core (24) and an elongated cover (26) surrounding the core (24); wherein the cover (26) is constructed of a cover material having an elastic limit of at least 7,000 kg / cm2 (100,000 psi) (0.2% remaining deformation), and the core (24) is constructed of a core material comprising at least one of the following constituents: tantalum, an alloy with tantalum base, platinum, a platinum-based alloy, tungsten and an alloy with wolframi base

Description

COATED COMPOUND IMPLANT BACKGROUND OF THE INVENTION The present invention relates to medical devices in the body, and more particularly to implants and prostheses configured for high opacity to radiation, in addition to favorable characteristics. Recently, several prostheses have been developed, usually lattice construction or open structure for a series of medical applications, e.g. mtravascular implants for the treatment of stenosis, prostheses for the maintenance of the orifices of the urinary tracts, biliary prostheses, esophageal implants, renal implants and filters for the vena cava to overcome thrombosis. A particularly well-accepted device is a self-expanding mesh implant described in U.S. Patent No. 4,655,771 (Wallsten). The implant is an elastic tubular braided structure formed by fiber elements can be constructed of a biologically compatible metal or plastic, e.g. certain stainless steels, polypropylene, polyesters and polyethylene. Alternatively, polyesters and other prostheses may be extensible by plastic deformation, typically by the extension of a dilatation balloon surrounded by the prosthesis. For example, the Patent of the United States No.

No. 733,665 (Palmaz) describes a stainless steel graft constructed in stainless steel, either entangled or welded at its intersections with silver. U.S. Patent No. 4,886,062 (U? L? 'Tor) presents an extensive balloon implant constructed of stainless steel, an alloy of copper, tatam or gold. Without thinking about whether the prosthesis is self-extending or stretches plastic, the safe placement of the prosthesis is critical for its efficient operation. Accordingly, there is a need to perceive the visual form of the prosthesis when it is being placed inside a blood vessel or other body cavity, Rdernas, it is advantageous and sometimes necessary to visually locate and inspect a previously deployed prosthesis. Fluorocopy is the predominant technique for visualization, and this requires the radiological opacity of the materials to be visualized. The preferred structural materials for the construction of prostheses, e.g. Stainless steels and alloys with cobalt base, are not highly radiopaque. Therefore, prostheses constructed with these materials do not allow us a good fluoroscopic visualization. Some techniques have been proposed, in the evident recognition of this difficulty. For example, U.S. Patent No. 4,681,110 (Uiktor) discloses a coating of a self-extending blood vessel formed by braided plastic webs radially compressed for distribution within a conduit. A metallic ring around the conduct is radiopaque. Similarly, U.S. Patent No. 4,830,0003 (Uolff) describes the confinement of a radially self-extending implant within a distribution conduit and that provides markers. radiopaque on the distribution conduit. This technique facilitates visualization only during initial deployment and placement. To allow fluroscopic visualization after placement, the implant itself must be radiopaque. The Uol patent indicates that the implant can be formed by platinum or an alloy of platinum-iridium to substantially increase its radiological opacity. Such an implant, however, lacks the necessary elasticity, and would show a poor resistance to fatigue. Uiktor Patent 110 describes the joining of metal staples to their blood vessel coating to increase radiological opacity. However, for many applications (e.g., in blood vessels), the implant is so small that such staples would be too small to provide useful fluroscopic visualization or would adversely affect the efficacy and safety of the deployment of the implant or other prostheses. This Uiktor patent also indicates the infusion of your plastic fibers with a suitable filler material, e.g. gold or barium sulfate to enhance radiological opacity. Uiktor does not provide scripts of how this could be done. In addition, given the small size of the prostheses intended for placement on blood vessels, it is unlikely that this technique will increase the material form the radiological opacity, due to an insufficient amount and density of gold or barium sulfate. Therefore, it is an object of the present invention to provide an implant or other prosthesis with a substantially increased radiological opacity, without a substantial reduction in the favorable mechanical properties of the prosthesis. Another object is to provide an elastic composite filament insertable into the body having a high degree of radiological opacity and favorable structural characteristics, even for implants employing filaments of a relatively small diameter. A further object is to provide a method for the manufacture of a composite filament consisting essentially of a structural material to impart the desired mechanical characteristics in combination with a radiopaque material to substantially enhance the fluoroscopic visualization of the filament. Yet another object is to provide a composite prosthesis with a cover in which a highly radiopaque material and a structural material cooperate to provide mechanical stability and improve fluroscopic visualization and are additionally selectively associated for crystal structure compatibility and coefficients. thermal expansion and tempering temperatures.

BRIEF DESCRIPTION OF THE INVENTION To achieve these and other objects, a method is provided for the production of an elastic msertable body composite filament. The procedure includes the following stages: a. the arrangement of an elongated cylindrical core substantially uniform in the lateral cross-section and having an internal diameter and a tubular elongate sheath or substantially uniform cover in the lateral cross-section and having an inner diameter of the shell, in which the core or the cover is formed by a radiopaque material and the other is formed by an elastic material having a plastic modulus (remaining deformation of 0.2%) of at least 10500 kg / crn2 (150,000 psi), in which the diameter of the core is less than the inner diameter of the tire and the lateral cross-sectional area of the core and the tire is at most ten times the area of the lateral cross-section of the core; b. inserting the core into the shell to form an elongated composite filament in which the shell surrounds the core; c. The cold treatment of the composite filament will reduce the cross-sectional area of the composite filament by at least 15%, so that the composite filament has a selected diameter smaller than the initial external diameter of the composite filament before the cold fixation; d. the tempering of the filament composed after the cold treatment, to substantially eliminate any hardening by deformation and other tensions Induced by the cold treatment stage; and. the mechanical molding of the tempered composite filament in a predetermined form; and f. after the cold and tempering treatment stages, and while the composite filament maintains in a predetermined manner, the maturation hardening of the composite material. In a preferred embodiment of the method, the radiopaque material has a linear attenuation coefficient at 100 keV of at least 25 c -1. The radiopaque material forms the core and is at least as ductile as the cover. The external diameter of the composite filament, before the cold treatment, is preferably at least about six millimeters (about 0.25 inches). The cold treatment step may include a stretching of the filament composed in series through several rows, the plastic filament deforming each row in plastic form to reduce the outer diameter. Whenever a step including one or more cold tiers has reduced the cross-sectional area by at least 25%, a hardening step should be carried out before any further treatment. During each tempering step, the composite filament is heated to a temperature in the range of approximately 1038-1260 ° C (1900-230 ° F) for a period that depends on the diameter of the filament, usually in the range of several seconds to several. minutes The core material and the coating materials (cover) are preferably selected to have overlapping tempering temperature ranges and similar thermal expansion coefficients. The materials of the core and the cover can be selectively joined in addition by their crystalline structure and metallurgical compatibility. In an alternative version of the procedure, the initial external diameter of the composite structure (initial rnatepal piece) is at least fifty millimeters (about two inches) in diameter. Then, before the cold treatment, the composite filament is subjected to temperatures in the tempering range, since the external diameter is substantially reduced, either by compression or by stripping, with successive increases until the outer diameter is at least of 6 millimeters (0.25 inches). The resulting filament is processed as before, in alternative stages of cold and tempering treatment.

Furthermore, according to the process, the composite filament can be separated into a large number of fibers. Then, the fibers are arranged in two parallel helical coil-directed opposite groups, approximately in cylindrical form, with the fibers entangled in a braided configuration to form multiple intersections. Then, while the fibers are held at a predetermined uniform tension, they are heated to a temperature in the range of about 371-649 ° C (700-1200 ° F), more preferably 482-538 ° C (900-1000 °). F), for a sufficient time to harden by maturation the helical windings. The result of this procedure is a body implantable elastic prosthesis. The prosthesis has a large number of elastic fibers, helically wound in two groups directed in an opposite manner of separate and parallel fibers, wound internally between them in a coagulated pattern. Each of the fibers includes an elongated core and an elongated tubular shell surrounding the core. A cross-sectional area of the core is at least ten percent of the cross-sectional area of the fiber. The core is constructed of a first material that has a linear attenuation coefficient of at least 25 crn-i at 100 KeV. The cover is constructed of a second elastic material, less ductile than the first material. More generally, the method can be combined to mold a compatible body device comprising an elongated filament and an elongated tubular shell surrounding the core. The core or shell is consisted of a first material that has an elastic limit (remaining deformation of 0.2%) of at least twice that of the second material. The other core and shell are constructed of a second material that is radiopaque and at least as ductile as the first material. In a fundamentally preferred embodiment of the invention, the core was constructed of tantalum for radiological opacity and the shell is constructed of a cobalt base alloy, e.g. as the one available under the "Elgiloy", "Phynox" and "Mp35N" brands. The "Elgiloy" and "Phynox" alloys contain cobalt, chromium, nickel and molybdenum, together with iron. Which of these alloys joins well with tantalum, in terms of overlapping tempering temperature ranges, coefficients of thermal expansion and crystalline structure. The tantalum core and the alloy shell can be contiguous with each other, practically without interneal formation. When on the other hand, compatible core and shell materials present the risk of interneuric formation, an intermediate layer can be formed, e.g. of tantalum, niobium or platinum between the core and the shell to provide a barrier against inter-nettal formation. In addition, if the cover itself is not biologically compatible, a biologically compatible coating or film may surround the cover. For this purpose you can use tantalum, platinum, iridium and its alloys or stainless steels. Although they have been described herein in connection with radially self-expanding implants, the composite filaments can be employed in the construction of other implantable medical devices, e.g. vena cava filters, blood filters and deviations for thrombosis. Thus, according to the present invention, elastic compatible body prostheses are provided, which, despite being small enough for placement within the blood vessels and body cavities within the blood vessels and similar body cavities, have an opacity sufficient radiological for fluoroscopic visualization based on the same materials of the pro? is.

DESCRIPTION OF THE FIGURES For a further understanding of the above - and other features and advantages, reference is made to the following detailed description and to the figures, in which: Figure 1 is a side elevation of a self-extending implant constructed in accordance with the present invention; Figure 2 is a view in elevation from one end; Figure 3 is an enlarged partial view of one of "JS composite filaments forming the implant; Figure 4 is an enlarged cross-section taken along the line 4-4"Figure 3; Figures 5-9 illustrate schematically a procedure for manufacturing the implant; Figure 10 schematically illustrates a step of compressing an alternative procedure for the manufacture of the implant; Figure 11 is an end elevation view of a filament of the alternative embodiment; Figure 12 is an elevational view of several components of an alternative composite filament constructed in accordance with the present invention; Figure 13 is an end elevational view of the composite filament formed by the components shown in Figure 12; and Figure 14 is an end elevation view of another filament composed of another alternative embodiment.

DETAILED DESCRIPTION OF THE PREFERRED MODALITY Turning now to the figures, Figures 1 and 2 show a plantable body prosthesis 16, which is frequently referred to as an implant. The implant 16 is of an open or braided mesh construction, being composed of two groups of fibers wound s-Helicoidal in an opposite direction, par-allele and spaced 18 and 20, respectively. The groups of fibers are wound between them in a braided configuration up and down to form multiple intersections, one of which is indicated at? 2. The implant 16 is illustrated in its relaxed state, that is, in the configuration it adopts when it is not subjected to external stress. The filaments or fibers of the implant 16 are elastic, allowing a radial compression of the implant in a reduced radius, they have the configuration of extensive length suitable for the transluminal release of the implant in the intended place of placement. As a typical example, an implant 16 can have a diameter of approximately ten millimeters in a relaxed state and is compressed elastically to a diameter of approximately 2 millimeters (0.08 inches) in an axial length of approximately two times the length axial of the relaxed implant. However, different applications need different diameters. Additionally, previously determining the degree of axial elongation for a given radial compression is well known for the selective control of the angle between the helical fibers directed in an opposite manner. Non-elastic open braided prostheses, extendable for example by expansion balloons, provide an alternative to elastic prostheses. Elastic or self-expanding prostheses are often preferred, since they can be deployed without expansion balloons or other means of implant removal, the self-expanding implants can be pre-selected according to the diameter of the blood vessel or other location of the implant. intended fixation. Although its use and experience in the placement of implants, such deployment or requires additional experience in the careful dilatation of balloons to extend plastically the prosthesis to the appropriate diameter. In addition, the self-expanding implant remains at least slightly elastic compressed after fixation and, thus, has a restoring force that facilitates strong fixation. On the contrary, a plastically extended implant must rely on the restoring force of the deformed tissue or on hooks, tongues or other independent fixation elements. According to this, the materials that form the fibers for the filaments must be strong and elastic, biologically compatible and resistant to fatigue and corrosion. In addition, vascular applications require hernocornpatibilidad. Various materials meet these needs, which include the stainless steels "sticos" and certain alloys that include cobalt, chromium, iron, nickel and oli deno sold under the trademarks of "Elgiloy" (available from Carpenter Technology Corporation of Reading, Pennsí lvania ) and "Phynox" (available from Metal Tmphy of Tinphy, France), respectively. Another suitable cobalt-chromium alloy is available under the trademark "MP35N" from Carpenter Technology Corporation of Readin, Pennsylvania.

In addition, it is advantageous to form a prosthesis with substantial open space to promote the embedding of the implant in the tissue and the growth of fibers through the implant wall to improve long-term fixation. A more open construction also allows substantial radial compression of the prosthesis for deployment. In a typical construction suitable for translucent implantation, the filaments may have a diameter of approximately U. 1 millimeters (0.004 inches), with adjacent parallax filaments separated from each other by approximately 1-2 millimeters (0.04-0.08 inches)., with adjacent parallel filaments separated from each other by approximately 1-2 millimeters (0.04-0.08 inches) when the implant is in a relaxed state. Fluorescent oscillating visualization of a conventional open braided prosthesis is extremely difficult. Due to their minimal diameters and the involved rnatepals, the filaments show a relatively poor contrast with the body tissue for the purposes of fl ocoscopic visualization. The filaments also require a high degree of spatial resolution in the visualization equipment involved. Thus, an implant recognizable in X-ray film may be indistinguishable for real-time visualization, due to the relatively poor spatial resolution of the video monitor compared to the X-ray film. However, according to the present invention, the prosthesis 16 is substantially easier to visualize fluoroscopically, due to the construction of the fibers 18 and 20. In particular, the fibers help to present a sufficiently radiopaque handle on the tangents of the device 16 (parallel to the rays X) for satisfactory visualization in real time. As seen in Figures 3 and 4, a filament 18a of the prosthesis is of composite construction, with a radiopaque core 24 surrounded by a concentric annular elastic cover 26. The core 24 is highly X-ray absorbent, preferably having a linear attenuation coefficient of at least 25 (and more preferably at least 40) cm ia 100 KeV. Materials with atomic numbers and relatively high densities tend to have the necessary attenuation coefficients. More particularly, it has been found that those materials with an atomic number (elements) or "effective" atomic number (based on the means of weight of the elements in alloys or compounds) of at least fifty, and densities of at least 13.84 g / crn3 (0.5 lb / m3), show the capacity required to absorb the x-rays. Finally, the core 24 is preferably a ductile material so that it can easily acquire the shape in the shell. In contrast, the cover 26 is formed of a highly elastic material, preferably with a high yield strength (remaining strain of 0.2%) of at least 10,500 (kg / crn 2) (150,000 psi). More preferably, the limit <; r > Last? co is at least 21,000 kg / crn2 (300,000 psi). Accordingly, the mechanical behavior of the composite filament 18a in terms of elastic deformation as a response to external stresses is, fundamentally, the behavior of the cover 26. In addition to the individual characteristics of the core and the cover, it is desirable to selectively adapt the core materials and cover over certain Common characteristics The core and shell materials should have the same or substantially the same linear coefficients of thermal expansion.A similarity of the core and shell materials in their crystalline structure is also an advantage. The core and the cover should have an overlap in their tempering temperature ranges, to facilitate the preparation of the filaments according to the method explained In a highly preferred embodiment, the core 24 is formed by tantalum and the cover 26 is formed by Cobalt base alloy, more particularly Elgiloy alloy (brand) Tantalum is a ductile metal that has an atomic number of 73 and a density of approximately 20.27 g / cm3 (0.6 pounds per cubic inch). linear attenuation is 69.7 cin-1 to 100 KeV.Elgiloy alloy mainly includes cobalt and chromium, and has an atomic number The effective alloy is less than thirty-one density substantially less than 16.9 g / crn3 (0.5 lb /? n3) "However, the alloy is compatible with the body, hernocornpatible and highly elastic with a limit of the elastic (residual deformation of the 0.2%) of at least 24,500 kg / crn (350,000 psi), after cold treatment and hardening by maturation. The cover 26 and the core 24 thus help to provide a prosthesis that can be visualized m live and in real time .. Of course, the amount of core material in relation to the amount of material of the cover should be sufficient to ensure radiological opacity while maintaining the favorable mechanical characteristics of the implant 16. It has been discovered from the surface of the core 24, turned along a transverse or lateral plane as illustrated in Figure 4, should be within the range of approximately ten percent at the quarter and six percent of the lateral cross-sectional area of the filament, that is, the area of the roof and the combined core. Tantalum and Elgiloy alloy adapt well, since the materials have similar linear coefficients of thermal expansion (3.6 x 10-6 or F grade and 8.4 x 10 ~ 6 per F grade, respectively), similar crystalline structures and tempering temperatures in the range of 1038-1260 ° C (1900-2300 ° F). In addition, there is virtually no tendency for the formation of metathermal compounds along the interface of the tantalum / Elgiloy alloy.

Platinum and platinum alloys (eg platinum) are also suitable as materials for the core 24. The atomic number of platinum is 78 and its density is 26.18 g / crn3 (0.775 pounds per cubic inch) . Its linear attenuation coefficient is 105 <; m_1 to 100 MeV. The coefficient of linear thermal expansion for platinum is approximately 4.9 x 10_6 per degree F. Thus, when compared to tantalum, the plate is structurally more compatible with the Elgiloy alloy and more efficiently absorbs X-rays. to this, platinum is particularly well suited for use in prostheses formed by small diameter filaments. The first disadvantage of platinum with respect to tantalum is its higher cost. Other materials suitable for the radiopaque nucleus 24 includes gold, wolfram, iridium, rowing, ru + enio and depleted uranium. Other materials suitable for cover 26 include other cobalt base alloys, e.g. the alloys of the brand Phynox and MP35N. Cobalt-chromium and cobalt-chrome-rnolibdenum alloys of the orthopedic type can also be used, in addition to the titanium-aluminum-vanadium alloys. The HP35N alloy is widely available, and has a potential for the best fatigue strength due to improved manufacturing techniques, particularly in the vacuum melting process. The aluminum-titanium-vanadium alloys are highly biologically compatible and have a more moderate stress / strain response, that is, better elastic modulus. Composite filaments such as filament lna are manufactured by a stretched-fill tube (DFT) process illustrated schematically in Figures 7-9. The DFT procedure can be carried out for example, Dick Fort Uayne Metals Research Products Corporation of Ft. Uayne, Indiana The process begins with the insertion of a solid cylinder or thread 28 of the core material into a central opening 30 of tube 32 of the material of the shell. The core thread 28 and the tube 32 are substantially uniform in the transverse or lateral sections, ie the sections taken perpendicular to the longitudinal or axial dimension. For example, the tube 32 may have an external diameter of approximately 2.6 nm (0.102 inches) and an internal diameter of 2 (aperture diameter 30) of approximately 1.42 nm (0.056 inches). The core or wire 28 has an external diameter d3 slightly smaller than the internal diameter of the tube, e.g. 1.17 mm (0.046 inches). In general, the outer diameter of the wire is sufficiently close to the inner diameter of the tube to ensure that the thread or thread 28, once it has been inserted into the opening 30, is substantially centered in the radial position within the tube. At the same time, the inner diameter of the tube must exceed the outer diameter of the core sufficiently to facilitate the insertion of the wire over a long length of the wire and tube, e.g. at least 6.10 meters (twenty feet). The values of the inner diameter of the tube and the external diameter of the core go with the materials involved. For example, platinum when compared to tantalum has an exterior-smoother finish when molded into an elongated core or thread. As a result, the outer diameter of the platinum wire can be closer to the inner diameter of the tube. In this way, it will be appreciated that the optimum diameters values vary with the materials involved and the expected length of the opposite filament. In any case, the insertion of the core into the tube forms a composite filament 34, which is then directed through a series of alternate cold treatment and annealing steps, as indicated schematically in Figure 6. More particularly, the composite filament 3i is stretched through three rows, indicated at 36, 38 and 40, respectively. In each row, the composite filament 34 is cold treated in a radial compression, causing the cover tube 32 and tantalum core yarn 28 to flow cold in a way that lengthens the filament while reducing its diameter. Initially, the tube of the cover 32 is elongated and radially reduced to a greater degree than the core thread 28, due to the minimum radial hole that allows the insertion of the core in the tube. However, the radial? P-Lc? Closes rapidly when the filament is stretched through row 36, with the back pressure inside row 36 and the cold treatments of the remaining rows both of the core and of the cover together, as if these were a single solid filament. In fact, once the radial orifice is closed, the cold treatment inside all the rows produces a pressure union along the whole interface of the core and the cover , to form a union between the core material and the cover. As the composite filament 34 is stretched through each row, the cold treatment induces maturation hardening and other stresses within the filament. According to this, the respective stages of heating are arranged, that is to say, the ovens 42, 44 and 46, a heating step that follows each stage of cold treatment. At each tempering stage, the composite filament 34 is heated to a temperature in the range of about 1038 to about 1260 ° C (1900-2300 QF), or more preferably 1093-1177 ° C (2000-2150QF). At each tempering stage, all the tensions of the cover and the core are substantially eliminated, to allow subsequent cold treatment. Each tempering stage is carried out in a short time, e.g. in as little as one to fifteen seconds at the tempering temperature, depending on the size of the composite filament 34. Although Figure 6 illustrates a cold treatment step and a tempering step, it will be understood that the number 70 suitable stage is selected with orme to the final size of the filament, the desired degree of reduction of the transverse section during the final stage of cold treatment and the initial size of the filament before the cold treatment: Fn ratio with the composite filament 34 , a reduction of the lateral cross-sectional area in the range of about forty percent to eighty percent, and a range of about forty percent to sixty percent is preferred. The successive stages of cold and tempering treatment lead to the necessity of adapting to the core and cover mates, particularly as regards their coefficients of thermal expansion, elastic moduli to the tension, tempering temperature intervals, capacity of Total elongation and also in its crystalline structure. A good adaptation of the modules of elasticity, elongation and coefficients of thermal expansion minimizes the tendency to any rupture or discontinuity along the core / shell interface when the composite filament is treated. The crystalline structures should be considered in the adaptation of the core and shell materials. The Elgiloy alloy and other materials used to form the cover tube 32, commonly undergo a transformation between the cold treatment and maturation stages, from a cubic crystal structure centered on the faces to a hexagonal closed packaged crystalline structure. Elgiloy alloy undergoes contraction when it undergoes this transformation. Accordingly, the core material should undergo a similar reduction or be sufficiently hard to adapt to the reduction of the shell. There is no tempering after the final stage of cold treatment. At this point, the composite filament 34 is molded in the manner intended for the device incorporating the filament. In Figure 8, several filaments or fibers 34a-e are helically wound around a cylindrical shape 48 and held at their opposite ends by groups of coils 50a-e and 52a-e. The fibers 34a-e can be treated individually or the individual segments of a cold-treated, tempered composite filament cut after the final stage of cold treatment. In any case, the filaments help to form one of the two opposite directed groups of separate and parallel filaments forming a device such as an implant 16. Although only one group of filaments is shown, it will be understood that a corresponding group is formed of filaments, wound helically and intertwined around 48 in the opposite direction, are held by corresponding coils at the ends of opposite filaments. A useful prosthesis depends in part, on a correct fastening of the filaments. The filaments are kept in tension and it is important to select the appropriate tension force and apply the tension force evenly to all the filaments. An insufficient tensile force can allow melting or lifting effects which cause the individual filaments to deviate from their helioidal configuration when they are released from the coils and the braided structure of the implant can become entangled. Figure 9 illustrates two filaments 34a and 54a, each of the groups of opposed wound filaments, held by the respective coils 50a / 52a and 56a / 58a in a furnace 60 for curing by maturing in an empty or protective atmosphere. Hardening by ripening is carried out at temperatures substantially less than that of tempering, e.g. in the range of about 371-649 ° C (700 - 1200OF), more preferably 482-538 ° C (900-1000QF). The filaments overlap each other to form several intersections, one of which is indicated at 62. When the filaments are adequately taut, slight traces are formed on the filament that overlap at each intersection. These tracks or chairs tend to block the position of the filaments one in relation to the other at the intersections, maintaining the configuration of the prosthesis without the need for welding or other union of the filaments at their intersections. Although only two filaments are illustrated in opposite directions as a matter of convenience, it will be appreciated that the maturation hardening step is carried out after the winding and tensioning of all the filaments, ie, both groups directed oppositely. According to this, during the endui eciiento by maturation, the filaments are locked one in relation to the other at multiple intersections. The preferred time for hardening by maturation is about 1-5 hours. This stage d? Hardening by maturation is critical for the formation of a satisfactory self-expanding prosthesis, since it substantially increases the elasticity, yield strength and tensile strength. Normally, the elastic modulus increases by at least 10% and the elastic limit (remaining deformation of 0.02%) and the resistance to the attraction each increase by at least 20%. As an alternative to the procedure just explained, a substantially longer and shorter composite filament 65 (eg, 15, 24 crn (6 inches) in length with a diameter of approximately ten crn) can be subjected to a series of stages of elongation / diameter reduction. Figure 10 illustrates schematically two rows of reduction of the diameter 66 and 68, which can be used in the course of a process of reducing the hot-treated initial material. Of course, any suitable number of diameter reduction rows can be used. Alternatively, the diameter reduction can be carried out by injection molding / stripping at each stage. When a sufficient number of diameter reduction steps have reduced the diameter of the composite structure to approximately 6 millimeters (0.25 inches). The composite structure or filament can be further processed by spinning and quenching, as illustrated in Figure 6 for the procedure described above As before, the composite filament is ready for selective molding and maturation hardening after the final stage of cold treatment.When compared to the procedure depicted in Figures 5-7, diameter reduction techniques or "Pull-out involves a substantial increase in cold and hot treatment of the composite structure or filament, and the initial assembly of the core in the shell or shell tube is easier, given the size of the initial composite structure is much larger , the structure is subjected to tempering temperatures for a substantially longer time, eg from half an hour to an hour, as opposed to the times of one to fifteen seconds of annealing associated with the process depicted in Figure 6. Accordingly, Special care should be taken to avoid combinations of core and shell materials with tendencies to the formation of intermetallics along the core / shell interface.In addition, the required hot treatment of the larger initial material may not provide the same degree of refining of metallurgical grain In general, the preferred composite filaments have: (1) sufficient capacity for radiation p to allow visualization m alive; (2) the preferred mechanical properties; and (3) a sufficiently low cost. The interrelation between these factors requires that all three be taken into account in the determination of filament size, the ratio of core 24 to cover 26 both in size as the materials selected for the core and shell. In particular, the core 24 will be at least 0.0038 cm (0.0015 inches) in diameter, if an implant constructed of such a filament is visible using conventional radiographic visualization equipment. At the same time, the structural requirements (particularly the elasticity for a self-extending implant) require a minimum ratio of the material of the cover with respect to the core material. Thus, the requirement of effective visibility imposes a minimum diameter for the cover 26 in addition to the core 24. Of course, proper selection of the core and cover materials can reduce the minimum diameters required. However, potential substitute materials will be considered in view of their impact or cost-not only the cost of the material per se, but also the impact of such substitution on production costs. Some composite filament structures are especially preferred in terms of compliance with the above requirements. In the first of these structures, the core material is tantalum, and the shell is constructed of cobalt-based alloy of Elgiloy fibers. The maximum external iarnetro of the composite filament is approximately 0.150 inrn or ap or immeasurably 0.006 inches. Elgiloy filaments of this diameter or greater may be sufficiently radiopaque without a core of tantalum or other additional radiopaque material. However, even such diameters, radiation opacity is enhanced with a tantalum core, and likewise with an alloy core with tantalum base, platinum, platinum-based alloy, wol ramium and alloy with tungsten base or combinations of these constituents. It has been found that the preferred core size, relative to the size of the composite fiber, varies with the diameter of the filament. In particular, for larger filaments (diameter of 0.10-0.15 mrn or 0.004-0.006 inches) sufficient radiation opacity occurs when the area of the transverse section of the core 24 is approximately one quarter of the cross-sectional area of the core. full fiber. For smaller diameters (eg 0.07-0.10 mm or 0.00276-0.0039 inches such as those of the type often used in coronary implant implants), the core will contribute at least about one third of the cross-sectional area of the composite filament. The increase in core percentage above 33% of the cross-sectional area of the filament undesirably affects the mechanical properties of the yarn and the elasticity of the implant, reducing the capacity of an implant constructed from the filament to "- < ut oext enderse completely after its release from the release device. The filaments composed of this structure have core diameters in the range of 0. 0037-0.05 rnm (0.0015-0.002 inches), with filament diameters up to approximately 0.135 mm or approximately 0. 0055 inches. In a second filament structure, the core is formed of 10% platinum-nickel alloy, ie, > 90% platinum and 10% nickel, by weight. Although the preferred proportion of nickel is 10%, satisfactory results can be obtained with nickel ranging from about 5% to about 15% of the alloy. The cover is constructed of Elgiloy alloy. The platinum-nickel alloy, when compared to pure tantalum, has superior radiographic and structural properties. More particularly, the alloy has a higher density, combined with a higher atomic number factor (z) for an improvement in radiation opacity of 1-20%. In addition, when compared to tantalum, the alloy is more resistant to fatigue and thus better resists the procedures for the manufacture of implants and other devices. Due to its better mechanical properties, a core formed by alloy of platinum-nickel can constitute up to 40% of the cross-sectional area of the total filament. Accordingly, the alloy adapts particularly well to the construction of extremely fine filaments. This composite filament structure is suitable for the construction of implants having diameters (without tension) in the range of about 3.5-6 nm. As for all composite filament structures, the purity of the elements and alloys is important. Accordingly, high purity production techniques, e.g. custom fusion (triple fusion and electron beam refinement techniques) to provide seamless tubes of high purity Elgiloy alloys. A third filament structure involves a cover of Elgiloy and a core formed by a tantalum-tungsten shaft alloy at 10%, although the percentage of Tungsten can range between approximately 5% and approximately 20%. The tantalum / Uol ramie alloy is superior to tantalum in terms of mechanical strength and visibility and lower costs than the platinum-nickel alloy. According to a fourth filament structure, the cover 26 is formed by Elgiloy alloy, and the core 24 is formed by an alloy of platinum-yrilo of 20 to 30%. The platinum-iplo alloy may include between about 50% of the amount. When compared to the platinum-nickel alloy, the pla-inoidium alloy may show better resistance to fatigue. This is partly due to the segregation that can occur during the cooling of an alloy containing 30% (by weight) or more of iridium, due to the relatively high melting point of the indium.

In addition, hot treatment may be required if the alloy contains more than 25% indium, so that the final cold reduction of the difficult compound is made. A fifth filament structure employs a cover of Elgiloy alloy and a core of platinum-tungsten alloy having Tungsten in the range of about 5-15% and more preferably 8%. the opacity to the radiation of this alloy is superior- to the alloy it platinum- nor that! and this maintains the favorable mechanical characteristics. In a sixth filament structure, the cover 26 is constructed of an alloy with a titanium base. More particularly, the alloy can be an alloy known as "grade 10" or "beta 3" alloy, containing titanium together with 11.5% rnolibdenum, 6% zirconium and 4.5% tin. Alternatively, the titanium-based alloy may include about 11% niobium, and about 13% zirconium. The core 24 can be formed by tantalum. Most preferably, the core is formed of 10% platinum-nickel alloy. In this case, a barrier must be formed between the core and the cover, as described in relation to Figures 12 and 13. The alloy cover with titanium axis base is advantageous, particularly for patients exhibiting sensitivity to nickel in The Elgiloy alloy can also be beneficial since it does not contain cobalt or chromium.

Due to the low modulus of elasticity of the titanium-based alloy (compared to Elgiloy), implants or other devices using titanium-based alloy show a moderate elastic response once they are released from a deployment catheter or another device. This may tend to reduce neointimal vascular hyperplasia and consequently stenosis. On the contrary, the smaller elastic modulus produces a less favorable adaptation of the cover and core in the elasticity. In filaments using the titanium-based alloy shell, the ratio of core material to shell material should be reduced. As a result, this construction is suitable for filaments having diameters in the range of 0.10-0.30 mm. Finally, according to a seventh filament structure, the core 24 is constructed in a Wolfram-based alloy including 5-40 weight percent oar. More preferably, the alloy includes rowing at about 25 weight percent. Additional preferred materials for core 24 include alloys of about 85-95 weight percent platinum and approximately 5-15 weight percent nickel core; alloys which include about 50-95 weight percent platinum and about 5-50 weight percent iridium; alloys including at least 80 percent by weight of tantalum and at m20 percent by weight of tungsten; and alloys that include at least 60 percent by weight of tungsten and as much as 40 percent in that (rowing.) The msuitable roofing materials are alloys that include approximately 30-55 percent by weight of cobalt, 15-25 weight percent chromium, up to 40 weight percent nickel, 5-15 weight percent rnolybdenum, up to 5 weight percent manganese and up to 25 percent In weight of iron, the material should preferably have an elastic limit of at least 10,500 kg / crn2 (150,000 psi) (remaining deformation of 0.2%). Although less preferred, the material of the shell may have an elastic limit of less 7,000 kg / cm2 (100,000 psi) (0.2% residual strain) Figure 11 is an end elevation of a composite filament 74 that includes a central core 76 of a structural material such as the Elgiloy alloy, surrounded by a covered shell radioopaca 70 that, in this way inverts the function respective core and shell when compared to the composite filament 34. The composite filament 74, when compared to the filament 34 has a higher refractory radiopaque profile - and smaller for a composite filament diameter ciado. The composite filament 74, however, is more difficult to manufacture than filaments that use the structural material as a cover. Figures 12 and 13 show a further alternative composite filament, as it consists of a radio-opaque core 82, an outer annular shell 84 and an annular-intermediate layer 86 between the core and the shell. Intermediate layer 86 provides a barrier between the shell and the core and is particularly useful in composite filaments employing core and shell materials which would be incompatible if contiguous, e.g. due to a tendency to form inter-metallic. Suitable materials for the barrier layer 86 include tantalum, niobium and platinum. As shown in Figure 12, the core, the barrier layer and the cover can be arranged as a cylinder and two tubes, inserted one into the other for the manufacture of the composite filament as explained above. Figure 14 illustrates another alternative embodiment of the composite filament 88 having a central radiopaque core 90, a structural shell 92 and a thin annular outer protective layer 94. The composite filament 88 is particularly useful when the selected mechanical structure lacks biocompatibility., hemo-compatibility or both sati factories. Suitable materials for the protective layer 94 include tantalum, platinum, iridium, niobium, titanium and stainless steel. The composite filament may be manufactured as described above, beginning with the insertion of the radiopaque core into the structural cover and, instead, inserting the cover into a tube formed of the protective material. Alternatively, the protective layer 94 can be applied by a vacuum deposition process, co or a thin layer .e. from ten to a few hundred microns) which is what is needed. The following examples illustrate the formation of composite finishes according to the above described procedures.

EXAMPLE 1 An elongated tantalum core was introduced to give you a diameter of 1.17 cm (0.46 inches) in an Elgiloy alloy casing that had an external diameter of 2.6 mm (0.102 inches) and an internal diameter of 1.42 mn (0.056 inches). Accordingly, the cross-sectional area of the tantalum core was approximately 25% of the lateral cross-sectional area of the composite filament. The composite filaments thus constructed were subjected to 5-6 alternative stages of cold and tempering treatment, to reduce the external diameters of the composite filaments to values within the range of 0.010-0.017 cm (0.004-0.0067 inches). The diameters of the tantalum core were reduced to values in the range of 0.05-0.0086 c (0.002-0.0034 inches). The composite filaments were molded into an implant suitable for biliary applications and hardened by maturation for up to five hours, at temperatures in the range of 482-538 ° C (900-1000 QF).

EXAMPLE 2 Elongated nuclei of alloy "Je plat ino-iridium" (20% by weight iridium) were inserted with external core diameters of 0.22 cin (0.088 inches) in Elgiloy covers with external diameters of 0.25 cm (0.098 inches) and diameters. internal 011 crn (0.044 inches). The resultant composite filaments were treated through six cycles of cold and tempering treatment as in the first example, to reduce the diameter of the inner filament to values within the range of 0.007-0.010 cm (0.00276-0.0039 inches) and reduce it. outer diameter of the core to values in the range of 0.004-0.006 (0.0018-0.0026 inches). Thus, the core consisted of 43% of the lateral cross-sectional area. The resulting filaments were molded into a small vessel implant, and hardened by maturation for approximately three hours.

EXAMPLE 3 Composite filaments were constructed and substantially treated as in Example 2, except that the core was formed of platinum-nickel alloy with 10% by weight of nickel.

EXAMPLE 4 The composite filaments were constructed and treated as in Examples 2 and 3, except that the core was formed by a core, and the shell was formed of MP35N alloy and the cold treatment steps reduced the external diameter of the filament to values in the interval of 0.007- 0.012 cm (0.00276-0.0047 inches). In the case of all the previous examples, the resulting implants showed satisfactory elasticity and were visualized fluoroscopically in a simple way in real time. In other embodiments, the device has an additional layer that protects the cover. Possible materials for the additional layer include tantalum, gold, titanium and platinum. The The additional layer preferably has a thickness in the range of about 0.005-5.0 microns, and can be applied by procedures such as overlapping joint deposition of a thin shell, electromechanical deposition of the metal after manufacture of the composite filament , ion implantation (such as physical vapor deposition or ion beam deposition) and cathodic sputtering. Preferably, the additional layer is a metal having an electronegative surface such as tantalum. Each of the above-described composite filaments combines structural stability and elasticity, with radiation opacity that permits visualization of the device, formed by the filaments, during deployment and after fixation of the device. This result is achieved by a stretch-filled UoB process that cold-treats a central core and its surrounding sheath, to join the core and shell together as possible, such that the composite filament behaves like a solid structure. and continues. The realization of the filament and the resultant device are further increased by a selective adaptation of the core and shell materials, the coefficient of thermal expansion, the tempering temperature, the moduli of elasticity and the crystalline structure.

Claims (26)

NOVELTY OF THE INVENTION CLAIMS

1. - A compatible body device comprising: an elongate filament substantially uniform in lateral cross section over its length and including an elongated core (24) and an elongated cover (26) surrounding the core (24); wherein the cover (26) is constructed of a roofing material having an elastic boundary axis of at least 7,000 g / crn2 (100,000 psi) (remaining deformation of 0.2%), and the core (24) is constructed in a core material comprising at least one of the following constLtuyent.es: tantalum, an alloy with tantalum base, platinum, an alloy with platinum base, tungsten and an alloy with base / - * of wolramio.

2. The device of claim 1, wherein: said tantalum alloy comprises tungsten from about 5 to about 20% by weight.

3. The device of claim 2, wherein: said tantalum alloy includes tungsten at about 10%.

4. The device of claim 2, wherein: said cover material comprises an alloy with cobalt base.

5. The device of claim 2, wherein: This roof material comprises an alloy with titanium base.

6. The device of claim 5 further comprising: an intermediate layer (86) that forms a barrier between the core (24) and the cover (26).

7. The device of claim 1, wherein said platinum-axis alloy includes at least one of the following constituents: nickel of about 5 to fifteen%; Lpdio of approximately 5 to 50% and tungsten of approximately 5 to 15%.

8. The device of claim 1, wherein: said platinum alloy includes at least one of the following constituents: nickel at about 10%; iridium at approximately 20-30% and tungsten at approximately 8%.

9. The device of claim 1, wherein: said tungsten-based alloy comprises 5-40 weight percent rowing.

The device of claim 9, wherein: said base alloy tungsten comprises blunt to about 25% by weight.

11. The device of claim 1, wherein the cover (26) and the core (24) are contiguous.

12. An elastic implantable body prosthesis that includes a plurality of elongated filaments as defined in claim 1, wherein: said long filaments are heliocoidally wound in at least two groups in opposite directions of separate filaments, said groups of filaments intertwined with each other in a braided configuration.

13. A compatible body device comprising: an elongate filament substantially uniform in lateral cross section over its length and includes an elongated core (24) and an elongated cover (26) surrounding the core (24); wherein the core (24) is constructed in a core material having a linear attenuation coefficient of at least 25 crn-i at 100 KeV and the cover (26) is constructed in a covering material, said material being core more ductile and more radiopaque than the material of the cover, and in which the material of the cover comprises an alloy with titanium base.

14. The device according to claim 13, wherein said alloy with a titanium base includes niobium of approximately 10 to 15% and zirconium of approximately 10 to 15%.

15. The device of claim 14, wherein: said alloy with titanium base includes about 13% niobium and about 13% zirconium.

16. The device of claim 13, wherein: said alloy with titanium base includes aßjemás molybdenum, zirconium and tin.

17. The device of claim 16, wherein: said titanium based alloy includes rnolybdenum at about 11.5%, zirconium at about 6% and tin at about 4%.,5%.

18. The device of claim 13, wherein: said core material comprises one of the following constituents: tantalum, an alloy with tantalum base and a platinum-based alloy.

19. The device of claim 18, wherein: said core material comprises a platinum-based alloy.

20. The device of claim 19, further including: an intermediate layer (86) that forms a barrier between the core (24) and the cover (26).

21. An elastic implantable body prosthesis that includes a plurality of elongated filaments as defined in claim 13, wherein: said elongated filaments are wound heliocoidally in at least two groups of separate filaments in opposite directions, said groups of filaments intertwined with each other in a braided configuration.

22. A compatible body device comprising: an elongate filament substantially uniform in lateral cross section over its length and including an elongated core (24) and an elongated cover (26) surrounding the core (24); wherein the core (24) is formed of a core material comprising substantially unalloyed tantalum and the shell (26) is formed of a shell material comprising approximately 30-55 weight percent cobalt, approximately 15-25 weight percent chromium, about 0-40 weight percent nickel, about 5-15 weight percent nickel, about 0-5 weight percent manganese, and about 15 weight percent 0-25 percent by weight of merro.

23. A compatible body device comprising: an elongated filament substantially uniform in lateral cross section over its length and including an elongated core (24) and an elongated cover (26) surrounding the core (24); wherein the core material comprises from about 85-95 weight percent platinum and about 5-15 weight percent nickel, and the The cover (26) is formed by a cover material < It comprises approximately 30-55 weight percent cobalt, about 15-25 weight percent chromium axis, about 0-40 weight percent nickel axis, about 5-15 weight percent molybdenum, approximately 0-5 weight percent magnesium axis and approximately 0-25 weight percent iron.

24. A compatible body device comprising: an elongated filament substantially uniform in lateral cross section over its length and including an elongated core (24) and an elongated cover (26) surrounding the nucleus (24); wherein the core (24) is formed of a core material comprising from about 50-95 percent by weight "Je platinum and about 5-50 percent by weight of indium, and the shell (26) it is formed by a roofing material comprising approximately 30-55 weight percent cobalt, approximately 15-25 weight percent chromium, approximately 0-40 weight percent nickel, approximately 5- 15 percent by weight of rnolibdene, approximately 0-5 percent by weight of manganese and approximately 0-25 percent by weight of iron.

25. A compatible body device comprising: an elongated filament substantially uniform in lateral cross section over its length and including an elongated core (24) and an elongated cover (26) surrounding the core (24); wherein the core (24) is formed of a core material comprising approximately 80-100 weight percent tantalum and approximately 0-20 weight percent tungsten, and the cover (26) is formed by a cover material comprising approximately 30-55 weight percent cobalt, about 15-25 weight percent chromium, about 0-40 weight percent nickel, about 15 percent by weight. -25 weight percent of molibejeno about 0-5 weight percent manganese and about 0-25 weight percent iron.

26. - A compatible body device comprising: an elongated filament substantially uniform in lateral cross section over its length and including an elongated core (24) and an elongated cover (269 surrounding the core (24)) in which the core ( 24) is formed of a core material comprising approximately 60-100 weight percent tungsten and approximately 0-40 weight percent rowing. SUMMARY OF THE INVENTION A compatible body implant is formed by multiple filaments arranged in two groups of heliocoidal coils directed in an opposite manner interlaced with one another in a braided configuration; each of the filaments is a composite material that includes a central core (24) and a cover (26) surrounding the core (24); in the most preferred version, the core is formed of radiopaque and relatively ductile material, e.g. tantalize or platinum. The outer cover (26) is formed by a relatively elastic material, e.g. alloys with cobalt / chromium base; the favorable mechanical characteristics of the implant are determined by the cover (26), while the core (24) allows the in vivo visualization of the implant: The composite filaments are molded by a stretch-filled tube method, in which the core (24) is inserted into a tubular cover (26) of a diameter substantially greater than the diameter of the intended final filament; the composite filament is cold treated in vain stages to reduce its diameter and in successive stages tempered axis and cold treatment; after the cold treatment end stage, the composite filament is molded into the desired shape and hardened by maturation. The alternative composite filaments employ an intermediate barrier layer (86) between the cover (26) and the core (24), an iocompatible protective layer surrounding the cover (26) and a radiopaque cover (26) surrounding a structural core. (24) P96 / 738F PF / ieoh * yhc