JP3697261B2 - Stent - Google Patents

Description

[Technical field]
The present invention relates to a stent for expanding and maintaining a blood vessel in an open state, having a radially contracted state for introduction into a blood vessel and an expanded state after introduction into the blood vessel. .
[Background technology]
Stents of the above type that can be inserted into body cavities, blood vessels, etc., or implantable catheters can be made of plastic or of an inert metal such as steel or nickel-titanium alloy. Such stents are also called endovascular stents or internal luminal stents or endoprostheses. The stent is used, for example, to dilate the prostatic ureter in benign prostatic hypertrophy (BPH), or to dilate the vessel in a calcified blood vessel and keep it open. The stent has material regions and a gap between the material regions. Thereby, the peripheral surface of the stent is covered by the growth of the wall tissue of the organ maintained in an open state. Stents can be configured as spirals or wound wounds in vines. The stent can be made of woven or knitted wire or plastic material. Such stents can have shape memory properties such as found in certain nickel-titanium alloys (Nitinol).
[Disclosure of the Invention]
The object of the present invention is to ensure a secure anchoring of such a stent in the blood vessel to be expanded.
The constituent means of the present invention for solving the above-mentioned problem in the stent of the type described at the beginning is characterized in that the stent has ribs and gaps remaining between the ribs, and is at least one of them in a radially expanded state. The end face of the stent has a larger radial extent than the remaining main body of the stent, and the ribs in the region of the end face of at least one end of the stent are larger than the corresponding ribs of the main body of the stent. Has a large length.
In an advantageous configuration of the invention, the length of the ribs in the end face side end region is 120-190% of the length of the ribs in the main body region of the stent.
In another advantageous configuration of the invention, the ribs in the end face side region extend radially outwardly wider than the ribs in the main body area of the stent, and the ribs in the end face side region are in the main axis of the stent. Is at an acute angle.
The voids can be formed in a rhombus shape or a honeycomb shape. Advantageously, the stent is self-expanding not only by its elastic properties and by being inserted in a radially constricted state, but also by being made of a shape memory alloy.
In order to obtain a relatively large bending capacity and flexibility of the stent, another advantageous configuration is that there are gaps in part between the axially arranged ribs and partly in the coupling area. Is present. With this configuration, higher flexibility can be obtained than in the case of a stent in which ribs that continue in the axial direction are fixedly connected to each other in the connection region. In addition, when a force perpendicular to the axial direction acts and bends, deformation of the cross section does not occur.
By forming the stent in a single layer, a high bending ability can be obtained. In this case, the intersection of the metal wires does not cause a large material thickness as seen in a knitted fabric or a braid. Also, the fixation of the stent of the present invention in the body tissue is improved. Furthermore, the risk of thrombus formation, particularly in the vascular region, is significantly reduced or virtually eliminated.
In a particularly advantageous configuration in this case, the coupling zones are offset from one another in the circumferential direction. This achieves and maintains the desired axial strength (in short, upset resistance and axial tensile resistance) with bending strength perpendicular to the axis.
In a further advantageous configuration, the stent is made from a flat sheet of metal that has been slit to form a void, in which case the flat sheet of metal is bent together into a cylindrical profile and then along each side edge region. Joined, in particular welded, and the voids are formed by slits after the heat treatment.
[Brief description of the drawings]
FIG. 1 shows an advantageous stent of the present invention in a radially contracted cold state or introduced state.
FIG. 2 is a diagram showing the stent of the present invention in a radially expanded state or in use.
FIG. 3 is a schematic view of the stent portion showing the configuration of the end portion on the end face side.
[Best Mode for Carrying Out the Invention]
Next, embodiments of the present invention will be described in detail with reference to the drawings.
The stent 1 according to the present invention has a cylindrical shape or outer contour as shown in FIG. 1 in a radially contracted state for insertion into a blood vessel to be expanded. In the expanded state, the stent 1 of the present invention also has a cylindrical outer profile over the length of its main body 1a, ie over its maximum length. The stent of the present invention is of course expanded over the radial dimension, i.e. over the diameter D of the main body 1a, in the region of both end surfaces 1b, 1c, so that the stent 1 can be expanded radially. It can be fixed to the blood vessel wall by the end portions 1b and 1c.
As can be seen in particular in FIG. 2, the stent 1 according to the present invention comprises a number of meandering webs, i. It consists of meandering webs in the form of ribs 2, 2a, 2b which are joined together in a mountain shape at 3a, 3'a, 3b. When viewed in the circumferential direction, the meandering webs or ribs 2, 2a, 2b are respectively connected to the meandering webs or ribs 2, 2a, 2b arranged in parallel and facing each other adjacent to each other. 'A and 3b are arranged so as to be aligned in the direction of the vertical axis.
As can also be seen from FIG. 2, the meandering webs successively formed in the direction of the longitudinal axis and formed by the ribs 2, 2a, 2b, respectively, A plurality of transition parts 4 to 4d of the two meandering webs formed by the ribs 2 and 2a are not coupled to each other by the transition parts 4, 4a, 4b, 4c and 4d and viewed in the circumferential direction. Gaps 5, 5 ', 5a, 5b, 5b' and the like are arranged. Both the transition portions 4 to 4d and the gaps 5 to 5b 'are also called nodes.
In other words, the stent of the present invention is constituted by ribs 2, 2a, 2b and voids 6, 6a formed between the ribs. In this case, the voids 6, 6a are not illustrated in the illustrated embodiment. It may basically have a rhombus profile, ie, limited by four rib areas, and in principle may have a honeycomb shape limited by six rib areas. According to the above view, the nodal region partially remains as a coupling portion (transitional portion 4 to 4d), while other regions are cut open by gaps 5 to 5b '. The coupling parts or transition parts 4 to 4d are not aligned in the longitudinal direction but are angled with respect to each other, that is, shifted in the circumferential direction.
High flexibility is obtained in the stent of the present invention by the gaps 5 to 5b '. When bent perpendicular to the longitudinal axis A, therefore, even if the longitudinal axis itself bends, the stent 1 will not bend in the central region of the stent, so that the stent substantially loses its circular cross-sectional profile. The central portion of the stent is pressed flat in the direction in which the force is applied and is not undesirably widened in the direction perpendicular to the direction in which the force is applied in the approximate center of the stent longitudinal dimension. Such an inconvenient situation is that all the coupling areas or peak areas 3, 3a,... Of meander windings extending parallel to each other in the longitudinal direction are fixed by the coupling areas or transition parts 4, 4a. This is often the case with conventional stents that are bonded together. .. Are integrally formed with the other parts of the stent, in particular with the ribs 2, 2 a.
As can be seen from FIG. 1, the substantially rhombic void formed between the ribs 2, 2a ... of the meandering web in a high temperature state (FIG. 2) is reduced to form a slit in the low temperature state or the insertion position, And the ribs 2 of the meandering web extend substantially parallel to each other.
In particular, as can be seen from FIG. 3, the length of the rib 2 in the meandering region on the outer side or on the end surface is significantly larger than the ribs 2a, 2b in the main body 1a of the stent 1 of the present invention. The length of the rib 2 at the end portion on the end surface side can be 120 to 200% of the ribs 2a to 2c of the main body 1a. The length ratio is selectable and is determined by the allowable elongation, the required stent length, and the desired radial extent of the end faces 1b, 1c of the stent 1 relative to the main body 1a.
The stent 1 of the present invention is made of a nickel-titanium alloy such as Nitinol. In order to produce the stent, the metal sheet is first etched to a desired sheet thickness with high accuracy, ie within a tolerance range of 0.001 mm. The portion forming the stent is then cut from the large sheet. In these thin plate portions, slits or slits are cut so that the slits adjacent in the circumferential direction are shifted in the axial direction by half the length thereof. The slit cutting is performed by a laser. Since the slit has an extension in the central area of each slit, the material that restricts the extension in the circumferential direction is substantially reduced to the width of the material remaining between the slits. If these sections are left as they are, the coupling areas 4 and 4a will be formed later. If the sections are removed, gaps or gaps 5 and 5a are formed in these areas. . After the slit is cut, the cut portion is stripped and the slit thin film is removed. Next, since the slit thin plate is curved and formed into one cylindrical body, both side edges of the slit thin plate are in contact with each other. Next, a slit thin plate is welded to the joining plate or the attachment portion, and thereby a low temperature stent corresponding to FIG. 1 is generated. The stent thus formed is then heat treated to provide shape memory characteristics, so that the stent is heated to a temperature above a predetermined ambient temperature that is significantly lower than the body temperature of the human body, In this case, the temperature reaches 35 ° C. at most.
After the stent has been manufactured in this way and subjected to heat treatment, the bridging strip is then removed as desired, so that the connecting zone or web 4, 4a or gap 5, 5 ', 5a as described above. Is formed. It is then ground and polished on a rotating drum machine. The stent is inspected for size, function and adjustment. Finally, the stent is first cleaned with soap solution, then with distilled water and finally with alcohol in an ultrasonic bath.

Claims (12)

In a stent for expanding and maintaining an open state of a blood vessel, having a radially contracted state for introduction into the blood vessel and an expanded state after introduction into the blood vessel,
The stent has ribs (2, 2a, 2b, 2c) and gaps (6, 6a) remaining between the ribs , and at least one end face side end (1b, 1c) has a larger radial extent than the remaining main body (1a) of the stent (1) and ribs in the region of at least one end face side end (1b, 1c) of the stent (1) Stent, characterized in that (2) has a length greater than the corresponding rib (2a, 2b, 2c) of the main body (1a) of the stent (1) . End surface side end portion (1b, 1c) the length of the ribs (2) in the region of a 120 to 190% of the main body (1a) of the rib region length of the stent (1), according to claim 1, wherein Stent. The stent according to claim 1 or 2 , wherein the rib in the end surface side end region extends radially outwardly wider than the rib in the main body region of the stent. End surface side end portion (1b, 1c) rib areas (2), forms an acute angle with the main axis of the stent (1) (A), any one of claims 2 to 3 Stent. The stent according to any one of claims 2 to 4 , wherein the gap (6, 6a) is configured in a diamond shape. The stent according to any one of claims 2 to 5 , wherein the gap is configured in a honeycomb shape. The stent according to any one of claims 1 to 6 , wherein the stent is self-expanding. The stent according to any one of claims 1 to 7 , wherein the stent is made of a shape memory alloy. Between longitudinal axis disposed one behind as viewed in the direction ribs, in part gaps (5, ...) it is also engaging zones partially (4, ...) are provided, according to claim 1 The stent according to any one of 1 to 8 . 10. Stent according to claim 9 , wherein the coupling zones (4, ...) are offset from one another in the circumferential direction. The stent is manufactured from a flat metal sheet, and a slit is cut out in the flat metal sheet to form a gap (6, 6a), and the flat metal sheet is curved and formed into one cylindrical body 11. A stent according to any one of the preceding claims, which is subsequently joined together, in particular welded, along both side edges. The stent according to any one of claims 1 to 11, wherein the gap (6, 6a) is formed by a slit after heat treatment.

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