WO2014064181A1 - Braided stent and method for producing same - Google Patents

Abstract

The invention relates to a stent composed of a multiplicity of interwoven filaments (2, 3) which intersect one another, wherein filaments (2, 3) running in parallel maintain a respective predefined spacing. At at least one end of the stent, filaments (2, 3) are connected in pairs to sleeves (4), which have the shape of an eight, wherein filaments (2, 3) running in opposite directions are brought together in the sleeves (4), and the filament ends extend substantially in the same direction and terminate at the sleeve edge (5). The invention further relates to a method for producing such a stent.

Description

 The invention relates to a stent made of a plurality of intertwined filaments that intersect each other, parallel filaments being spaced a predetermined distance, and a method for producing such a stent and an endless braid from which such stents are obtained can. Stents or stents are used in medicine for a variety of purposes. Above all cardiovascular stents are known, which are used to keep arteries open in the cardiovascular area. In the meantime, however, stents are increasingly being used in the cerebral area and in the periphery, as well as for the support of hollow organs, for example in the trachea and in the intestinal area.

In the cardiovascular area, the placement of stents depends primarily on the radial force and less on the flexibility.

On the other hand, peripheral stents as well as stents in organs which are subject to constant movement and stents, which are introduced into strongly tortuous vessels, require a high degree of flexibility. Here are rigid stents, as they are usually placed on balloon catheter out of place. In many cases stents are used which consist of a wattle of individual filaments and in this way on the one hand have high flexibility and adaptability and on the other hand develop the necessary radial force. Materials suitable for this are in addition to spring steels so-called shape memory materials, in particular nickel titanium alloys. Preferred material for this is nitinol.

Braided stents are indicated in particular in the region of joints of the extremities and in the cerebral area. They can be used arterially and venously. Only braided stents provide the required mix of radial force and flexibility. In addition, from a certain stent length on the movement of the limb considerable stretching and compression forces occur, which must be compensated. The stent length should not change substantially. Such stents are known in a variety of embodiments and have proven themselves. One problem, however, is always the fixation of the filament ends. On the one hand, the filament ends must be converted atraumatically. On the other hand, it must be prevented that the weave of the stent loosens over loose ends over time or dissolves. Finally, a problem is also the x-ray marking of the stents, which alone allows precise placement. The treating physician must recognize during implantation whether the stent has found its right place and can also find the stent during check-ups.

The filament ends of the braided stents are fixed, for example, via welding points which simultaneously serve for the atraumatic transformation. Another method is the braiding of the filament ends in the stent body, but which usually leads to an undesirable stiffening of the body in the edge region.

The invention has for its object to provide a braided stent, which is made of a plurality of intersecting filaments and in which the filament ends are umgewnadad atraumatic and fixed radiopaque. Such a braiding stent should be simple and inexpensive to produce and at the same time be easily adaptable to the different circumstances, in particular as regards the braiding density and the radial force. These objects are achieved with a stent of the type mentioned in the beginning, in which filaments are connected in pairs to a cuff having the shape of an eight on at least one end of the stent, opposite filaments being brought together in the cuff, the filament ends being substantially rectilinear and end on the outer edge of the cuff (5).

The stents according to the invention can be used vascularly (venous and arterial), but also in other body products (trachea, intestine).

The stent according to the invention consists of a multiplicity of interwoven filaments. The filaments are usually made of wire, the thickness may for example be in the range of 0.10 to 0.30 mm. Preferably, the wire consists of a spring material, such as spring steel, but in particular of a shape memory material. Particularly suitable shape memory materials are nickel titanium alloys, for example nitinol.

The number of filaments is generally in the range of 8 to 32, but may well be higher. It is preferred that the number of filaments is even, so that they can be connected end to end in pairs. The interwoven filaments form the round stent body, with one half of the filaments running helically in a clockwise direction, the other half also helically but counterclockwise. The rectified filaments preferably maintain a substantially equal distance from each other in fully expanded, stress-free condition. Accordingly, the pitch angle of the filament, relative to the longitudinal axis of the stent, is constant.

According to another embodiment, the same directional filaments can comply with mutually varying distances, ie forming regions with denser and less dense braid. The distance between the parallel filaments to each other, for example, in the range of 0.5 to 4 mm. The pitch angle is, for example, between 50 and 75 °, wherein the pitch angle is the angle between the longitudinal axis of the stent and the course of the filament. The smaller the distance between parallel filaments to each other and the steeper the pitch angle, the stiffer the stent and the greater its radial force. At the same time, the degree of coverage of the vessel wall by the stent can be controlled via the distance and the pitch angle.

According to the invention, the filaments are connected in pairs to a cuff at least at one end of the stent, but preferably at both ends of the stent. In pairs means that two opposing filaments, ie a filament that runs in a clockwise direction and a filament that runs counterclockwise, are brought together at the stent end in such a way that they run a short distance in the same direction and almost parallel, and end in a cuff. The cuff itself has approximately the shape of an oval on the longitudinal sides on both sides impressed oval or the shape of an eight and surrounds the two filament ends positive and non-positive. The filaments themselves end at the outer edge of the cuff, which forms the frontal boundary of the stent. Preferably, the filament ends are crimped to the cuff. For this purpose, a sleeve tube is slipped over the filament ends and pressed together with a suitable pliers. Such crimp connections are known, for example, from electrical engineering and lead to positive and non-positive connection of the two filament ends. Cuff material can be any biocompatible metals, for example medical steel. However, the cuff preferably consists of a radiopaque material, such as tantalum, tungsten or a platinum metal or alloys of these metals. Preference is given to tantalum, which has good radiopacity in comparison with steel and is well tolerated by the body. When using a steel cuff, it is quite possible, the cuffs with the merged filaments with a To cover the welding spot from a radiopaque material. At the same time, this leads to atraumatic closure of the filaments.

When radiopaque cuffs are used, the atraumatic closure of the filaments is accomplished by remelting the filament ends and simultaneously welding them to the cuffs. For this purpose, lasers can be used.

The braided stents according to the invention are basically available in every length. Common lengths are, for example, for peripheral applications 20 to 250 mm. Standard lengths of 20 to 200 mm have been proven in 20-steps. The diameter of the corresponding stents amounts, in the expanded state, to 2 to 20 mm, with standard diameters in the core being 5 to 15 mm. Cerebral stents are generally shorter with significantly smaller diameters.

The placement of the stents according to the invention takes place in a manner known per se by means of a catheter through which the stent is pushed and / or pulled at its place of use. The braided structure causes the stent to elongate and tighten under tension, allowing or facilitating transport through the catheter and into narrow vessels.

The invention further relates to a method for producing a stent of the type described above, comprising the following steps:

Providing a plurality of suitable filaments,

Twisting each two opposing filaments and producing a plurality of twisted filament pairs, which form a connecting element, wherein a plurality of twisted connecting elements form a connecting segment,

Producing a woven segment of defined length from the filaments of the connecting segment, repeating the above-described steps several times, wherein each twisted-filament connecting segment merges into intertwined filament braid segments, and vice versa,

Cutting off individual braiding segments in the region of the connecting segments, connecting the twisted filaments at the transition from the braided segments to the connecting segments with sleeves in a positive and non-positive connection

blunt cutting of the filament ends extending beyond the front edge of the sleeves.

The inventive method allows the production of a starting material as a continuous braid. The endless braid consists of a sequence of connecting segments consisting of a plurality of twisted pairs of filaments, and braiding segments in which the filaments are interlaced with each other crossing each other. The connecting segments consist of a plurality of twisted or twisted filament pairs, which are arranged in a circle around a longitudinal axis. The twist ends in the transition region to the braid segments, in which the individual filaments of the connecting segments are intertwined crosswise to the actual stent element. At the end of the braiding segment, two opposing filaments are twisted together again to form the next connecting segment.

The method allows the production of braid segments of the desired length and the respective desired diameter, each separately connecting segments of a defined length.

To produce the stents according to the invention, the connecting elements are severed in the middle and the removed braid segments are provided with a sleeve in the region of the transition from the braiding segment into the connecting elements of filaments twisted together. The cuffs are positively and non-positively by two arranged opposite each other from the stent emerging filaments, preferably crimped. Following this, the twisted filaments projecting beyond the sleeve are cut off.

When using a good radiopaque cuff material, such. As tantalum, the cuffs with the filaments therein are terminally remelted, so they are atraumatic. When using less radiopaque material than cuff, such as medical grade steel, a more radiopaque material can be remotely fused onto the cuff; Tantalum has also proven itself in this case. Other materials include tungsten and platinum metals and their alloys.

It is understood that the atraumatic treatment of the filament ends with the sleeves is made at both ends of the braided stent, unless a different fixation of the filaments is made on one of the stent ends. Such a fixation can be done for example by the attachment of elements that allows the determination of the stent on a guide mechanism.

Finally, the invention also relates to an endless braid for the production of a stent of the aforementioned type, as can be seen from the method described above and can be further processed into the individual stents. Since the production of braids from a variety of nitinol wires requires special knowledge, it will be carried out regularly in specialized companies. The final production of the stents then takes place in specialist companies, who then process these endless braids into the corresponding braided stents.

The invention is explained in more detail by the accompanying drawings. In the drawings: an endless connecting segment and braiding segment according to the invention; Figure 2 associated with a cuff

 Filaments of a stent according to the invention and

FIG. 3 shows the connected filaments from FIG. 2 after the atraumatic deformation and remelting in the end region.

1 shows a "continuous braid" produced according to the invention and made of braiding segments A, B, C and connecting segments D and E. The connecting segments D are terminal and border only on a braiding segment, the connecting segments E are located between two braiding segments The braiding segments A, B and C. have different lengths, depending on the desired stent length, while the connecting segments D usually have a uniform length.

All connecting segments D and E consist of a plurality of mutually twisted filament pairs. These are pairs of filaments which emerge in opposite directions from a braiding segment and are combined by twisting and are broken down again into individual filaments at the transition to the next braiding segment. The co-extending filaments are designated by the reference numeral 2, and the opposing (crossing) filaments by the reference numeral 3. A plurality of filaments 2 and 3 are interlaced to form a stent member 1.

Typical stent lengths for peripheral purposes are, for example, 20 to 200 mm, whereby naturally also other stent lengths can be adapted to the individual patient.

In the braided segments of the endless braid (A, B, C), the filaments running in the same direction have a substantially equal distance from one another, for example in the range from 0.5 to 3 mm, in particular from approximately 1.4 to 1.8 mm. The same goes for the opposing filaments. It is true that with the decrease in the distance of the filament turns to each other, the radial force and stiffness of the stent increases, with expansion the distance corresponding to the radial force decreases and the flexibility increases. A rectified influence has the angle a, which forms between the course (slope) of the filaments and the longitudinal axis of the stent and which preferably lies in the range of 50 to 75 °. The larger the angle, the greater the radial force and rigidity, as the angle decreases a decreasing radial force follows with increasing flexibility.

According to the invention, winding distances of approximately 1.6 mm and angles of approximately 65 ° have proven successful.

The endless mesh of FIG. 1 is severed in the middle of the connecting segments E for conversion into a stent according to the invention, so that the twisted connecting elements formed from the filaments 2, 3 are divided between the adjacent braiding segments. At these connecting elements, the cuffs 4 are arranged, which limit the stent according to the invention. FIG. 2 shows two filaments 2 and 3 which emerge from a stent according to the invention at the end face, which emerge from turns running in opposite directions, are supplied to one another and are combined in a sleeve 4. The cuff 4 has the shape of an eight and summarizes the two filaments 2 and 3 a positive and non-positive. Such a cuff connection is formed for example by crimping a correspondingly shaped round or oval ring with a pair of pliers. After joining the filaments 2 and 3 of the sleeve 4, the filaments 2 and 3 at the front or outer edge 5 of the sleeve 4 are separated.

FIG. 3 shows the cuff connection of the filaments 2 and 3 after atraumatic deformation with a cap 6. Such a cap 6 can be formed from existing material by applying heat to a laser, but also by applied material. The first variant is useful if the cuff 4 consists of a good radiopaque material such as tantalum, the latter variant is appropriate if a good radiopaque material is applied to the cuff. In any case, the remelting process results in the formation of an atraumatic end of the filaments and an additional safeguard the connection of the two filaments 2 and 3.

 - Claims -

Claims

claims 1 . Stent comprising a plurality of interwoven filaments (2, 3) intersecting each other, parallel filaments (2, 3) each maintaining a predetermined spacing, characterized in that filaments (2, 3) are provided on at least one end of the stent (1) ) are connected in pairs with cuffs (4) having the shape of an eight, wherein opposing filaments (2, 3) in the sleeves (4) are merged, the filament ends are substantially rectilinear and end at the front edge of the cuff (5). 2. Stent according to claim 1, characterized in that the filament ends are crimped together with the sleeves (4). 3. Stent according to claim 1 or 2, characterized in that the filament ends and the sleeves (4) are provided with caps (6). 4. Stent according to claim 3, characterized in that the Material of the mansions (4) and / or the welded caps (6) is a radiopaque material. 5. Stent according to claim 3 or 4, characterized in that the sleeves (4) and / or caps made of tantalum, tungsten or a platinum metal. 6. Stent according to one of the preceding claims, characterized in that the stent on both sides via cuffs (4) connected filaments (2, 3). 7. Stent according to one of the preceding claims, characterized in that it consists of a shape memory material, preferably Nitinol exists. 8. Stent according to one of the preceding claims, characterized in that the filaments (2, 3) consist of wire of a thickness of 0.10 to 0.30 mm. 9. Stent according to one of the preceding claims, characterized by a diameter in the expanded state of 4 to 15 mm. 10. Stent according to one of the preceding claims, characterized in that it consists of 8 to 32 filaments (2, 3), preferably of 12 filaments (2, 3). 1 1. Method for producing a stent according to one of the preceding claims, comprising the steps: Providing a plurality of filaments (2, 3), - Twisting two filaments (2, 3) and producing a plurality of twisted filament pairs forming a connecting element, wherein a plurality of twisted connecting elements a Form connecting segment (D, E), Producing a braided segment (A, B, C) of defined length from the filaments (2, 3) of the connecting segment, repeating the above-described steps several times, each connecting segment (D, E) having twisted filaments (2, 3) in Weave segments (A, B, C) with intertwined filaments (2, 3) passes and vice versa, - Shortening individual braid segments (A, B, C) in the region of the connecting segments (D, E), - positively and non-positively connecting the twisted filaments (2, 3) on Transition from the braid segments to the connecting segments with sleeves (4), and - Blunt cutting of beyond the sleeves (4) outgoing filament ends (2, 3). 12. The method according to claim 1 1, characterized in that the Filaments (2, 3) are connected at the transition from the braid segments (A, B, C) to the connecting segments (D, E) with sleeves by crimping. 13. The method of claim 1 1 or 12, characterized in that the filament ends (2, 3) with the sleeves (4) are welded. 14. The method according to claim 13, characterized in that the sleeves (4) consist of a radiopaque material. 15. The method according to any one of claims 1 1 to 14, characterized in that the filament ends (2, 3) of the braid segments (A, B, C) are connected in pairs at both ends with sleeves (4). An endless braid for producing a stent according to any one of claims 1 to 10, wherein the stent consists of a plurality of interwoven filaments (2, 3) intersecting each other, and wherein parallel filaments (2, 3) each have a predetermined distance characterized in that a plurality of braid segments (A, B, C) having the features of the stent, by a plurality of Connection segments (D, E) is limited, which are connected in pairs by twisted together filaments (2, 3).  - Summary -