Method for attaching x-ray marker to stent

Abstract

To provide an implant that is connected to an X-ray marker in a simple and reliable manner such that potential contact corrosion is avoided from the outset.SOLUTION: An implant comprises a receptacle for an X-ray marker in a base body of the implant, and a plastically deformable X-ray marker. The X-ray marker is fixed in a press-fit manner in the receptacle together with a flexible film such that the X-ray marker does not contact the base-body.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a method for connecting an X-ray marker to the substrate of an implant, in particular a stent. The invention is mainly described on the basis of the example of an X-ray marker on a stent, but is not limited thereto. The invention can be used to connect a marker to any implant, in particular a biodegradable one, such as a stent, an occluder, a filter, a heart valve prosthesis (in particular a stent-based aortic valve prosthesis), or other vascular support device. [Background technology]

[0002] In such methods, the X-ray markers were originally connected to the stent, for example by gluing or pressing.

[0003] In the case of gluing, problems arise that on the one hand it is difficult to accurately meter out the relatively small amounts of adhesive, and on the other hand the exact placement of the adhesive amount presents another challenge. In principle, a further problem with gluing is that the processing time (pot life) is limited. Moreover, when using solvent-based adhesives, it is necessary to ensure that these do not have a negative effect on the implant or stent.

[0004] Furthermore, a problem with pressing is that the X-ray markers made of precious metals (gold or platinum, etc.) are frequently used, which in combination with the substrate of the stent made of base metals create contact corrosion. Especially in biodegradable stents, this can lead to an undesirable acceleration of degradation. It is also necessary to prevent direct contact between the X-ray marker and the substrate, since the X-ray marker can break out of the stent. This applies to all joining methods with direct contact (joining by screws, riveting, etc.).

[0005] US Pat. No. 5,399,633 discloses a method of pressing an X-ray marker into a stent, which allows the space between the X-ray marker and the stent to be filled with polymer as the stent is coated. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] US Patent Application Publication No. 2016 / 0228267 Summary of the Invention [Problem to be solved by the invention]

[0007] Proceeding from this, the object of the present invention is to connect X-ray markers to implants, in particular to stents, in a simple and reliable manner, in which potential contact corrosion can be avoided from the outset, in particular adhesive bonding can be dispensed with in this process. [Means for solving the problem]

[0008] This objective is achieved in the following manner:

[0009] According to the present invention, a method for connecting an X-ray marker to a base of an implant, in particular a stent, is disclosed, comprising the steps of: providing a base of the implant comprising a receptacle, in particular a through opening, for receiving the X-ray marker; providing a flexible membrane and the X-ray marker, such that at least one section of the membrane is positioned between the receptacle, in particular the base comprising the through opening, and the X-ray marker; and pressing the X-ray marker into the receptacle, in particular the through opening, of the base, with the membrane interposed, such that the X-ray marker plastically deforms and is fixed together with the membrane in the receptacle, in particular the through opening, in a press-fit manner, the membrane preventing contact between the X-ray marker and the base.

[0010] The connection between the X-ray marker thus implemented and the base of the implant is sufficiently elastic in the process so as to be able to compensate for small deformations of the base of the implant.Furthermore, the pressing operation can be advantageously configured such that the wall thickness of the base is not increased by the pressed in X-ray marker.

[0011] The receptacle is preferably designed as a cavity or, particularly preferably, as a through-opening.

[0012] The substrate may comprise a plurality of interconnected struts forming a circumferential lattice structure. Such a substrate may be provided by cutting out individual regions from a tubular blank, for example by means of a laser. According to a particularly preferred embodiment, the substrate is made of a magnesium alloy, in particular an Mg-Zn-Ca, Mg-Zn-Al or Mg-Al alloy.

[0013] According to one embodiment of the method, it is provided that the X-ray marker is pressed into the cavity or through-opening with the membrane interposed therebetween so that the X-ray marker is in contact with the membrane on the circumferential outside, and then a circumferential section of the membrane is supported on the circumferential inside of the cavity or through-opening so that it is positioned between the X-ray marker and the substrate.

[0014] Within the scope of this application, a cavity should be understood to mean an opening on at least one side in the base of the implant.

[0015] According to an embodiment of the method, it is further provided that the X-ray marker, after being pressed into the cavity / through opening, has a surface that is covered by a section of the membrane, which extends along the opening surface of the cavity / through opening and is connected to the circumferential section of the membrane that is pressed into the through opening. Thus, in other words, the X-ray marker, after being pressed, is embedded in the membrane and only a further surface of the X-ray marker facing away from the surface covered by the membrane is exposed.

[0016] According to one embodiment of the method, it is further provided that the section of the membrane protruding from the cavity / through opening is cut such that a circumferential section of the membrane terminates on one side of the substrate, preferably flush with or is located flush with the surface of the substrate.

[0017] According to another embodiment of the method, it is provided that the protruding section of the membrane is removed or cut off by a stamping action during the pressing operation. According to an alternative embodiment of the method, it is provided that the protruding section of the membrane is subsequently removed or cut off for the pressing operation, for example by trimming.

[0018] According to an alternative embodiment of the method according to the invention, it is provided that the membrane is dimensioned such that after the X-ray marker has been pressed into the substrate, the membrane does not protrude from the cavity / through opening on one side of the substrate.

[0019] According to an embodiment of the method, it is further provided that the X-ray marker is spherical or cylindrical before being forced into the through-opening. According to an embodiment of the method, it is further provided that the X-ray marker is designed such that after being forced into the cavity / through-opening, as a result of its plastic deformation, it assumes a half-shell / disk shape with its two surfaces facing away from each other, preferably flush with the adjacent surfaces of the base body.

[0020] The X-ray marker together with the membrane is placed between press jaws, which are moved towards each other in order to press the X-ray marker and the membrane into the cavity / through opening, so that the at least one X-ray marker is plastically deformed by the press jaws engaging on both sides and is fixed in the cavity / through opening in a press-fit manner in the process. According to one embodiment, the movement of the press jaws towards each other can be controlled (see above) in such a way that the final thickness in the press direction of the at least one X-ray marker corresponds to the wall thickness of the base body.

[0021] The membrane used is preferably designed to be elastically or plastically deformable so that it can absorb the forces occurring when the X-ray marker is pressed in without tearing.

[0022] According to one embodiment of the method, it is provided that the membrane comprises or is made of one of the following materials: a plastic material, a polymer, a polyurethane, an electrospun plastic, an electrospun polyurethane, PTFE, or a silicone.

[0023] According to one embodiment of the present invention, it is further provided that the X-ray marker is made of a metallic material that is more noble (inert) than the metallic material of which the substrate is made. According to one embodiment, the X-ray marker may be made of or may include one of the following materials: radiopaque metallic material, gold, gold alloy, platinum, or platinum alloy.

[0024] According to another embodiment of the method, it is provided that after the at least one X-ray marker is pressed in, the membrane is fused, for example to round off the cut edge of the membrane or to distribute the membrane material evenly in the annular gap around the at least one X-ray marker.

[0025] According to one embodiment of the invention, it is further provided that the membrane is fused to the at least one X-ray marker, the membrane being pressed into the cavity / through opening. For this purpose, for example, the press jaws can be heated, by which the at least one X-ray marker and the membrane are pressed into the through opening by the press jaws.

[0026] According to another embodiment of the method, it is provided that the X-ray marker or the plurality of X-ray markers and the membrane are pre-manufactured.

[0027] According to one embodiment of the method, in this regard, it is provided that a flexible membrane and an X-ray marker are provided such that the X-ray marker, together with the other X-ray markers, are placed on the membrane and suitably fixed thereto before being pressed in. Thereafter, the individual X-ray markers can be pressed in.

[0028] According to one embodiment, in this regard, it is provided that the flexible membrane and X-ray marker are provided in such a way that before being pressed, the membrane is placed on a perforated plate comprising a plurality of holes, and the X-ray marker and other X-ray markers are placed on and fixed to the respective membrane sections covering the holes, such that a curvature is formed (given a curvature) to the respective membrane sections as a result of the holes of the perforated plate placed below, and such that the curvature of the membrane section including the X-ray marker fixed above is positioned within at least one of the through openings before the X-ray marker is pressed into the cavity / through opening of the base.

[0029] According to another alternative embodiment of the method, it is provided that the flexible membrane and the X-ray marker are provided such that before being pressed together, the X-ray marker and the other X-ray marker are arranged side by side and coated with a plastic material, preferably polyurethane, using an electrospinning process to form the membrane.

[0030] Electrospinning should be understood to mean the creation of thin plastic or polymer fibers from a plastic or polymer solution in an electric field. The solution can be accelerated for this purpose between an electrode and a counter electrode, the solution being processed in a complex process into fine fibers that are finally deposited on the counter electrode, and the X-ray marker can act as the counter electrode during the process so that these can be directly coated with a membrane material using electrospinning.

[0031] According to another alternative embodiment of the method, a flexible membrane and an X-ray marker are provided such that before being pressed in, the X-ray marker and other X-ray markers are placed between two layers of the membrane forming the membrane and fixed to the membrane.

[0032] Another aspect of the invention relates to an implant, in particular a stent, comprising a substrate and an X-ray marker arranged in a receptacle, in particular a through opening, of the substrate and connected to the substrate by the method according to the invention.

[0033] Embodiments of the invention as well as further configurations and advantages are explained below with reference to the figures. [Brief description of the drawings]

[0034] [Figure 1A] A schematic cross-sectional view of a cross section of a base of a stent is shown, including a through opening, a spherical X-ray marker positioned above the through opening, and a membrane positioned between the marker and the base that is pressed into the through opening together with the marker. [Figure 1B] 1B shows a schematic cross-sectional view of the X-ray marker according to FIG. 1A, which is arranged in a through-opening of a substrate together with a section of a membrane. [Diagram 2] 1 shows a schematic cross-sectional view of an X-ray marker, a membrane and a substrate, in which two press jaws are displaced towards each other to press the X-ray marker together with the membrane into the through opening. [Diagram 3] 3 shows the plastic deformation of the X-ray marker according to FIG. 2 by the press jaws. [Figure 4] 3 shows the plastic deformation of the X-ray marker according to FIG. 2 by the press jaws. [Diagram 5] 1 shows an X-ray marker pressed into a through opening in a substrate, with a portion of the membrane protruding from the through opening after pressing. [Figure 6] 1 shows a schematic cross-sectional view of the X-ray marker, membrane, and substrate after the X-ray marker has been pressed into the through opening in the substrate, with the portion of the membrane protruding from the through opening removed. [Figure 7A] 1 shows an SEM image of an indented X-ray marker made of gold in a membrane made of electrospun polyurethane. [Figure 7B] 1 shows an SEM image of an X-ray marker pressed into molten polyurethane as viewed from the outside of the substrate. [Figure 7C] 1 shows an SEM image of an X-ray marker pressed into molten polyurethane as viewed from the inside of the substrate. [Figure 8A] FIG. 1 shows a schematic cross-sectional view of the pre-attachment of X-ray markers to a membrane on a perforated plate. [Figure 8B] FIG. 1 shows a schematic cross-sectional view of the pre-attachment of X-ray markers to a membrane on a perforated plate. [Figure 8C] FIG. 1 shows a schematic cross-sectional view of the pre-attachment of X-ray markers to a membrane on a perforated plate. [Figure 9A] 8A-8C show schematic insertions of the X-ray markers into through openings in a base. [Figure 9B] 8A-8C show schematic insertions of the X-ray markers into through openings in a base. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] 1A and 1B, in conjunction with FIGS. 2 to 6, show an embodiment of a method according to the present invention for connecting an X-ray marker 1 to a base 20 of a stent 2, in which a base 20 of a stent 2 is provided, the base 20 including a through opening 21 for receiving the X-ray marker 1, a flexible membrane and an X-ray marker 1 are provided, such that at least one section 30 of the membrane 3 is disposed between the base 20 including the through opening 21 and the X-ray marker 1, and finally, the X-ray marker 1 is pressed into the through opening 21 of the base 20 with the membrane 3 interposed therebetween, such that the X-ray marker 1 is plastically deformed and, together with the membrane 3, is fixed in the through opening 21 in a press-fit manner, and the membrane 3 prevents contact between the X-ray marker 1 and the base 20, thereby preventing contact corrosion.

[0036] The present invention therefore describes an alternative mounting option for X-ray markers 1 on a stent 2. Traditionally, these are glued using adhesive application. On the other hand, the present invention makes it possible to establish a plastic or polymeric connection between the marker 1 and the substrate 20 without the application of an adhesive.

[0037] The membrane 3 used is therefore preferably designed to be elastically deformable and able to absorb the forces occurring when the marker 1 is being pressed in without tearing. For example, electrospun polyurethane is one membrane material that has these properties. In principle any electrospinnable plastic material could be used, or single or multi-layered PTFE or silicone membranes.

[0038] According to FIG. 1A, such a membrane 3 is placed on the base 20 of the stent 2. The base 20, in particular the one or more preformed through-openings 21, also called marker holes or eyelets, are aligned in such a way that the marker 1 can be placed in a blind manner from above, meaning that the relevant through-opening 21 does not have to be visible through the membrane 3. Membranes made of electrospun polyurethane are generally not very transparent. Alternatively, for example, a light source can be placed below the through-openings 21. The position of a particular through-opening 21 then becomes visible from the corresponding shadow cast. Furthermore, a counter plunger can be pressed into the particular through-opening, which then guides the marker 1 during the pressing operation. FIG. 1B shows the X-ray marker 1 placed in the through-opening 21 together with the membrane 3 before the pressing operation shown in FIGS. 2-4.

[0039] Then, the X-ray marker 1, which is initially spherical and can be made for example of gold (or another highly radiopaque and soft metal such as platinum), is pressed together with the membrane 3 by the pressing jaws 4 into the through opening 21. Using a displacement-controlled movement of the clamping jaws, a control is performed to ensure that the final thickness D of the marker disc 1 matches the wall thickness W of the substrate 20 of the stent 2. In this way, it can be ensured that the substrate is not damaged by the pressing action and that the X-ray marker or markers 1 do not protrude beyond the edge of the substrate.

[0040] The membrane 3 may have a suitable size so that there are no protruding membrane sections 33 after the pressing operation. Otherwise, the protruding remainders 33 of the membrane 3 are removed. This may be achieved, for example, by cutting off the protruding sections 33 of the membrane 3 by a stamping operation during pressing or after the pressing operation (see figures 5 and 6).

[0041] According to FIG. 6 , the X-ray marker 1 is brought into contact with the membrane 3 by its circumferential outer side 1a, which is then supported by the circumferential inner side 21a of the through opening 21, so that a circumferential section 31 of the membrane is positioned between the X-ray marker 1 and the base 20, or is eventually preferably pressed into the through opening 21, with the membrane 3 interposed, so as to fill the corresponding annular gap between the marker 1 and the base 20.

[0042] According to Figure 6 it is further provided that after being pressed into the through opening 21, the X-ray marker 1 has a surface 1b which extends along the opening surface of the through opening 21 and is covered by a section 32 of the membrane 3 connected to a circumferential section 31 of the membrane 3 which is pressed into the through opening 21.

[0043] Furthermore, the pressed membrane 3 can also be melted afterwards. This is done, for example, to round off the cut edges of the membrane 3 or to distribute the membrane material (such as polyurethane) evenly in the annular gap. The melting can be integrated into the pressing operation, for example by using heatable pressing jaws 4.

[0044] For example, flat nose pliers can be used as press jaws that have a mechanically limited pressing action, so that it is not possible to press through the thickness of the stent wall.

[0045] The pressing operation can also be integrated into the existing process step of crimping. Within the scope of this application, crimping should be understood to mean the process step in which a stent is placed around an expansion means (e.g. an expandable balloon of a balloon catheter) and the diameter of the stent is reduced to a diameter for insertion into the body. The stent is compressed onto the balloon.

[0046] In an alternative embodiment shown by way of example in Figures 8A to 9, for example, the assembly is made prior to the actual mounting step or step of pressing the marker 1 into the associated through opening 21 of the base 20, with the marker 1 being pre-positioned on the membrane 3 and in particular fixed thereto.

[0047] For example, a number of X-ray markers 1 are pre-attached to a membrane 3, for example in the form of a membrane strip 3, on a perforated plate (for example in the form of a perforated metal sheet) (see Figure 8A), with each X-ray marker 1 being placed on a membrane section 34 covering one hole 50 of the perforated plate 5 and pressed into the same, whereby a curved portion 35 of the membrane 3 is brought about in each case to accommodate the marker 1 (see Figures 8B and 8C).

[0048] These bends 35 can then be particularly easily positioned in the associated through-openings 21 of the base body 20 with the respective X-ray markers 1 arranged therein according to Figures 9A and 9B. A pressing operation can then be carried out, for example, according to Figures 2 to 6 (see above).

[0049] Moreover, it is possible to create such an assembly comprising markers 1 and membrane 3 by directly coating the multiple X-ray markers 1 with a suitable plastic material / polymer (such as polyurethane) by electrospinning. As an alternative there is the option to cover the multiple X-ray markers 1 on both sides with a membrane layer (such as polyurethane), so that the markers 1 are encased in a membrane 3 consisting of at least two membrane layers.

[0050] 7A-7C show SEM images of X-ray markers imprinted into an illustrated stent using the present invention.

[0051] The advantages of the present invention are that the administration of adhesive (with its attendant disadvantages, see above) can be omitted completely; since no tight tolerances are required, cost-effective X-ray markers can be used in their original (spherical) form; the mounting step can be further integrated into the crimping process.

Claims

1. An implant, a receptacle for an X-ray marker in a base of the implant; A plastically deformable X-ray marker and Equipped with The x-ray marker is press-fit into the receptacle with a flexible membrane such that the x-ray marker does not contact the substrate.

2. The implant of claim 1 , wherein the substrate comprises a magnesium alloy, a Mg—Zn—Ca alloy, a Mg—Zn—Al alloy, or a Mg—Al alloy.

3. 3. An implant according to claim 1 or claim 2, wherein the X-ray marker is half-shell or disc-shaped.

4. 4. The implant of claim 1, wherein the flexible membrane comprises a plastic material, a polymer, a polyurethane, an electrospun plastic, an electrospun polyurethane, PTFE, or a silicone.

5. 5. An implant according to claim 1, wherein the X-ray marker is made of a metallic material which is more noble than the metallic material from which the substrate is made.

6. 6. The implant of claim 1, wherein the X-ray marker comprises a radiopaque metallic material, gold, a gold alloy, platinum, or a platinum alloy.

Images