WO2011132634A1

WO2011132634A1 - Stent

Info

Publication number: WO2011132634A1
Application number: PCT/JP2011/059517
Authority: WO
Inventors: 寛治井上
Original assignee: Inoue Kanji
Priority date: 2010-04-19
Filing date: 2011-04-18
Publication date: 2011-10-27
Also published as: JP2011224123A

Abstract

Disclosed is a stent which is mainly configured from a tubular member which forms a meshed tube having flexibility and elasticity, and a plurality of ring members which are arranged separated from one another in positions further inward than both end sections in the central axial direction of the tubular member. The tubular member is configured so that the vertical and horizontal linear sections which form the mesh of said tubular member are formed so as to all three-dimensionally intersect at a substantially equal angle in the central axial direction, and so that the flexible ring members which have a folding and bending restoring elastic force are attached further inward than both end opening sections in the central axial direction of the tubular member. Thus, the disclosed self-expanding stent can be applied to hollow organs such as those with weak inner walls or blood vessels which curve a great deal, to which conventional stents could not be applied due to problems such as durability, and the hardness of the end sections.

Description

Stent

The present invention relates to a stent which is a medical instrument used by being placed in a luminal organ.

Stents are used to expand strictures caused by lesions in digestive organs such as blood vessels, trachea, and bile ducts, and luminal organs such as esophagus, urinary organs, and reproductive organs. High nature. Recently, as a less invasive treatment instead of conventional surgery, a percutaneous transluminal tube, such as inserting and placing a stent in a lesion through a catheter introduced into the body from a blood vessel puncture part of an artery or vein, etc. Treatment has become the main treatment. The same applies to other luminal organs as well as blood vessels. The procedure for introducing a stent into a luminal organ is to reduce the diameter of a generally cylindrical stent, insert it into the catheter, transport it to the target affected area, and then release the stent from the catheter to expand the diameter. A general procedure is to dilate the stenosis of the luminal organ.

Stents are roughly classified into two types: a type that uses a balloon catheter to expand a reduced diameter stent, and a self-expanding type based on the structure of the stent itself. Although the present invention belongs to the self-expanding type, various types of stents have been proposed and used so far. As a typical stent (hereinafter referred to as a “stent” for only a self-expanding stent), a zigzag metal wire is formed in an annular shape, and a plurality of the annular members are connected. A plurality of arc-shaped parts in which metal wires are formed in a zigzag shape, such as those configured to be cylindrical as a whole, or those formed by knitting metal wires in a mesh shape, etc. Are connected to each other by a member made of a bioabsorbable material to form a cylindrical shape as a whole (Patent Document 1), and metal wires are arranged circumferentially and interlocked in a spiral with adjacent metal wires A cylindrical structure in which a large number of rhombus cells are formed by connecting and braiding (Patent Document 2), and an annular body in which both ends of a metal wire bent in a zigzag are connected in series. Various configurations such as a continuous configuration (Patent Document 3), a configuration in which metal wires are formed in a zigzag shape to form a spiral and each part is connected with a thread so as to form a cylindrical shape as a whole (Patent Document 4). Various configurations of stents have been proposed. These conventional stents have the common feature that any cylindrical frame portion is made of a metal member.

Special table 2009-522202 Special table 09-512460 JP 2002-291904 A JP 09-164209 A

Incidentally, the conventional metal stent as described above is minimally invasive and has a small burden on the patient, but the following problems have been pointed out. That is, the first problem is that almost the entire stent (at least the frame portion) is made of a metal material, and there is inevitably a limit in the flexibility in the longitudinal direction (cylindrical central axis direction). That is. For example, a blood vessel has a large number of curved portions and bent portions in a living body, and stenosis due to a lesion or the like is often observed at such a site. Therefore, when a metal stent is introduced into a curved part or a bent part of a luminal organ, the metal stent may break if it exceeds the limit of the bending performance. The second problem with metal stents is that they are not highly durable. When a metal stent is introduced into a luminal organ that repeats bending motion or a luminal organ that is repeatedly subjected to external compression, the metal stent itself eventually wears or breaks due to metal fatigue, and the luminal organ It causes further stenosis and damage to the luminal organs. Considering the application to blood vessels in particular, rupture of a metal stent can cause major bleeding, which can cause serious injury and life risk for the patient. In addition, the metal self-expanding stent has a drawback that the expansion force is insufficient, and a sufficient expansion force cannot be obtained in a hard stenosis. If the metal framework is stiff to increase this expansion force, the flexibility of the stent will be reduced and the bending performance will be reduced. The tendency of the stent to be easily broken by repeated bending and stretching movements of the hollow organ becomes strong.

The third problem with metal stents is that both ends of metal stents (both ends in the central axis direction) are hard metal stumps (some stents have rounded ends, but in any case Because the end is a hard metal), there is a risk of damaging the luminal organ even if the stent itself does not wear or break.

Because of these three major problems, when considering applying a metal stent to a blood vessel that bends at a large angle, such as a knee, for example, if it is bent so as to follow the blood vessel, the longitudinal direction (cylindrical shape) It may break in the direction of the central axis) and break or wear, causing new stenosis or causing fatal problems such as major bleeding or death due to damage to the blood vessel wall or the like. Therefore, among the metal stents currently available on the market, peripheral vascular stents used for diseases from the aortic bifurcation to downstream arteries are indicated for the iliac arterial region. It cannot be used for blood vessels downstream from the arterial region, particularly lower limb blood vessels below the ridge. In addition, when a commercially available metal stent is used for a lower limb blood vessel at present, the placed metal stent is not only in the vertical direction but also in the horizontal direction due to contraction from surrounding muscles and the shape and movement of the blood vessel itself. As a result of receiving an external force (in the direction of the cylindrical cross-sectional diameter), there is a possibility of wearing or breaking, and it is not always safe to say.

In addition, metal stents are inherently caused by the fact that the skeleton itself is made of metal, and the expansion and contraction properties in the direction of the diameter of the cylindrical cross section, particularly the expandability, are low. There is a problem that it is inferior to the following ability. Furthermore, even if a metal stent is a structure in which metal wires are connected or knitted, or a structure in which a plurality of annular members formed in a zigzag by laser cutting a metal tube are connected, the mesh becomes large. As a result, the thickened neointima infiltrates from the mesh and sticks out into the lumen of the stent, causing restenosis.

As described above, a commercially available metal stent has a particularly large angle in an actual medical field because of various problems including the danger described above, even if it has high bending performance. It is not applicable to bending or stretching luminal organs, thin luminal organs that are compressed by muscle contraction, or fragile inner wall luminal organs that are easily damaged by stump stumps. The development of applicable stents is strongly desired for patients such as patients who have lesions, their families, and medical workers.

The present invention solves such problems in conventional metal stents, and is flexible, tough, excellent in flexibility, easy to manufacture, and lumens for which conventional stents have been used so far. Of course, it can be applied to organs, especially luminal organs with bending movements that could not be used in the actual percutaneous transluminal stenting operation or deformed by external compression, The main object is to provide an excellent self-expanding stent that can be applied to fragile lumen organs on the inner wall.

The stent according to the present invention is a self-expanding stent that is inserted and indwelled in a luminal organ, has flexibility and elasticity, has a mesh shape through which bodily fluids can pass inside and outside, and has a central axis. It is composed mainly of a cylindrical member whose arbitrary cross section perpendicular to each other forms a substantially circular shape, and a plurality of ring members that are spaced apart from each other with their centers substantially coincident with the central axis of the cylindrical member. Further, the cylindrical member is formed so that both ends in the central axis direction are opened, and the vertical and horizontal linear portions constituting the mesh shape are three-dimensionally intersected at substantially the same angle with respect to the central axis, A plurality of ring members are disposed at least inward from both ends in the central axis direction of the cylindrical member, and an elastic restoring force that can be bent in both the radial direction and the central axis direction of the cylindrical member is provided. Consists of a flexible annular member having a cylinder It is characterized in that attached to the member.

The stent of the present invention can be applied to digestive organs such as blood vessels, trachea and bile ducts of animals including humans, human body such as esophagus, urinary organs, and reproductive organs, or almost any luminal organ of animals. The femur that can be applied to luminal organs that have been developed, and that is subjected to strong compression due to contraction of blood vessels and muscles that flex and stretch in a large angle range such as hip joints and knees, where conventional stents could not be applied. It can also be used by inserting and placing it in the blood vessels of the part.

That is, the stent of the present invention is flexible and elastic in itself (in other words, has a tension), and is a mesh-like cylinder (that is, a mesh shape through which blood or the like can pass) through which body fluid can pass in and out. A cylindrical member having a shape is intermittently supported by a plurality of flexible and elastic ring members. However, the cylindrical member does not necessarily have a cylindrical shape as long as both ends in the central axis direction are open. If the arbitrary cross section perpendicular to the central axis is substantially circular, the thickness may be different in each part. I do not care. In addition, it is necessary to arrange a plurality of ring members at least inward from the end in the central axis direction of the cylindrical member, and the ring members are provided at the end in the same central axis (both ends or one end). It is optional. Moreover, one part or all part ring member can also be attached to the inner surface side of a cylindrical member, and can also be attached to an outer surface side. Here, the ring member has one linear material formed in a substantially circular shape, one linear material wound in a plurality of turns into a substantially circular shape, and one linear material formed in a substantially circular shape Flexible, elastic, such as a bundle of a plurality of tubes, a cylindrical shape whose length in the long axis direction is very short compared to its diameter, and a conventional stent (eg, a Z-stent) that has a very short length in the long axis direction As long as it has a shape that can be regarded as an annular shape and has biocompatibility, the material and structure are not particularly limited, and it is also possible to employ a plurality of ring members having different configurations. .

Further, the mesh-shaped cylindrical member is a tubular member in which the vertical and horizontal linear portions constituting the mesh are not substantially parallel to the central axis of the cylindrical member or do not intersect three-dimensionally at a substantially right angle. The three-dimensional crossing is made at a substantially equal angle to the central axis. In the cylindrical member having such a structure, warps and wefts made of natural or synthetic resin fibers or metal fibers (which can be applied to either monofilaments or multifilaments) are knitted in a mesh shape, such as Adopting an appropriate configuration such as a mesh formed by welding or adhering warp and weft to each other, or a mesh formed by forming a large number of holes aligned in a synthetic resin sheet or cylindrical body be able to. In the case of a cylindrical member using warp and weft, the warp and weft yarns correspond to the vertical and horizontal linear portions constituting the mesh, and the cylindrical member is formed into a mesh by forming a large number of holes in the sheet or tubular body. In the case of, the linear part around the hole connecting each hole corresponds. The shape of the mesh formed by the vertical and horizontal linear portions of the cylindrical member is not limited to a specific shape. Note that a biocompatible material should be selected as the material used for the tubular member.

Since the stent of the present invention has a basic structure in which the mesh-shaped cylindrical member as described above is intermittently supported by a plurality of ring members, it maintains the flexibility in the central axis direction while maintaining the flexibility in the circumferential direction. It will be equipped with expansion power. The expansion force in the circumferential direction can be made stronger by increasing the expansion force in the circumferential direction of the ring member, and the flexibility of the entire stent in the central axis direction can be maintained. In addition, the stent according to the present invention does not buckle or wrinkle the tubular member even when the stent is reduced in diameter or expanded using the flexibility and elastic restoring force of each ring member. Even if this occurs, the degree is extremely small, and the mesh composed of vertical and horizontal linear portions expands and contracts while maintaining a basic shape such as a rhombus. For this reason, the cylindrical member itself in a reduced diameter state or the cylindrical member and the ring member hardly interfere with each other, and a stent having a reduced diameter using a catheter or the like is delivered to a stenosis portion of a luminal organ. In addition, it can be easily introduced into the affected area by spreading at the stenosis, and it can be introduced into a luminal organ such as a thin blood vessel or a narrow stenosis. It can easily follow the movement. In other words, the stent bends flexibly in both the central axis direction and the radial direction of the cylindrical shape, and can easily and flexibly follow its movement while in close contact with the inserted and indwelling luminal organ. it can. This differs from conventional metal stents in that the stent is subjected to external forces such as the movement of the luminal organ itself, such as the pulsation and bending of blood vessels, and compression from the muscles outside the luminal organ. However, this means that both the tubular member and the ring member can continue to function without being damaged or ruptured. For this reason, the stent has a very low possibility of damaging the luminal organ. It can be said that it is a good stent. For example, even when the stent of the present invention is introduced into a narrowed portion of a blood vessel that bends at a large angle such as a knee, the mesh structure of the cylindrical member supported by the elasticity of each ring member is maintained, and the entire stent is maintained. Since it bends following the blood vessel while maintaining the cylindrical shape, it can be continuously used for a long time without causing a positional shift. The overall shape of the stent of the present invention is defined by a simple structural member in which a plurality of ring members whose centers coincide with the central axis are attached to a mesh-like cylindrical member, so that the structure is simplified. Therefore, even a stent having a relatively small diameter can be easily produced. Therefore, it goes without saying that the stent of the present invention can be applied to a luminal organ to which various conventional stents have been applied while maintaining high safety and durability. It can also be applied to the blood vessels of the knee that repeatedly bend and stretch in a large angle range that could not be applied with a stent made of stent.

In addition, the stent of the present invention employs a structure in which a cylindrical member that can easily form a mesh size (mesh) is in close contact with a luminal organ. For this reason, the stent of the present invention has an advantage that intimal proliferation of the affected area hardly infiltrates into the stent, particularly when the mesh of the cylindrical member is set finely. Further, in the stent of the present invention, when the mesh of the cylindrical member is fine, the intima of the luminal organ is appropriately grown on the inner surface side of the stent and the stent is easily integrated with the body tissue, so that the thrombus is difficult to adhere. As described above, the stent of the present invention is suitable for insertion and placement in a hollow organ, which was difficult to apply with conventional stents, and therefore, treatment by percutaneous transluminal surgery has been greatly advanced. It can be said that it can be made to.

Further, as described above, in the stent of the present invention, a configuration in which the ring member is attached to the inner surface side of the cylindrical member or a configuration in which the ring member is attached to the outer surface side is possible. When attached to the side, the ring member does not contact the inner wall of the luminal organ, but only the flexible cylindrical member contacts, so the stimulation applied to the inner wall of the luminal organ over the entire stent is extremely small. Therefore, it can contribute to the progression of intimal proliferation and the prevention of the accompanying restenosis.

Further, as described above, in the stent of the present invention, a plurality of ring members arranged inward from the opening portions at both ends are arranged along the central axis of the tubular member, and the ring is formed at the opening portions at both ends of the tubular member. Although it is possible to employ a configuration in which a member is not provided, it is possible to arbitrarily provide a ring member in one or both of the both end openings of the cylindrical member. In the case of a stent having a ring member only on the inward side of the cylindrical member (here, “inward side of the cylindrical member” means “excluding openings at both ends in the central axis direction”), the central axis of the stent Only the cylindrical member comes into contact with the luminal organ at both ends in the direction, and the compression and stimulation applied to the inner wall of the luminal organ at that site can be reduced to prevent the progression of intimal proliferation and the accompanying restenosis There is an advantage. In addition, when the tubular member is sufficiently tensioned, sufficient shape retention is ensured even with a stent having no ring member at the opening at both ends, and the tube member is compressed before insertion into a luminal organ. Easier to fold when diameter is improved. On the other hand, when the ring member is provided at one end or both ends in addition to the inside of the tubular member, the shape retention of the entire stent can be improved. In particular, in the case where a ring member is provided only in one of the openings at both ends other than the inner ring member of the cylindrical member, the side on which the ring member is provided is upstream of the flow of body fluid such as blood flow. By placing this stent, the stability of the inner wall of the luminal organ is enhanced, and the end on the side where the ring member is not provided sufficiently functions as the stent of the present invention even when it is blown by a body fluid flow. can do. In the present invention, the inner ring member of the cylindrical member may be arranged on either the inner surface side or the outer surface side of the cylindrical member, but even when the ring member is provided on at least one of both end openings, You may arrange | position so that a ring member may not contact the inner wall of the hollow organ indwelled, and you may arrange | position so that it may expose to the outer surface side of a cylindrical member and may contact the inner wall of a hollow organ. When attaching the ring member arranged at the open end of the tubular member to the tubular member without contacting the inner wall of the luminal organ, for example, the end of the tubular member is folded back inward or outward to By adopting a configuration of attaching so as to be involved, it is possible to minimize irritation to the inner wall by contacting only the tubular member with the inner wall of the luminal organ. When the ring member is attached to the cylindrical member so as to contact the inner wall of the luminal organ, for example, a configuration in which the ring member is partially fixed at the end of the cylindrical member can be adopted. Compared with a conventional stent, it is possible to reduce the stimulation to the inner wall of the luminal organ as much as possible.

Here, in the stent of the present invention, as a ring member, a flexible metal wire material having a bendable elastic restoring force can be applied. In this case, strength and durability are ensured while ensuring flexibility of the stent. Can be improved.

In this case, the ring member may be formed by bundling a plurality of annular metal wires. As a ring member having such a configuration, for example, a structure in which one metal wire is formed into a ring member by annularly wrapping multiple metal rings, or a plurality of annular rings formed from metal wires are formed and bundled together. Such a metal ring member can increase the elastic restoring force while ensuring flexibility and is difficult to break and has high durability. It is possible to improve safety. Moreover, the elastic restoring force and durability of each ring member can be easily adjusted by adjusting the number of multiple windings of the metal wire or the number of rings to be bundled.

Generally, a stent is expanded at a position where it is inserted into a further narrow stenosis through a luminal organ such as a thin blood vessel. For this purpose, it is necessary to transport the stent via a thin catheter or sheath. The essential condition for the stent is to make the diameter at the time of diameter reduction as small as possible. In particular, in order to enable application to a luminal organ that could not be applied with a conventional stent, it is extremely important to reduce the diameter when the diameter is reduced. Therefore, the present invention adopts the basic configuration as described above, so that the compactness at the time of the diameter reduction of the stent, particularly the diameter can be made as small as possible. It is useful to fix them to the cylindrical member at four locations separated by approximately equal intervals. That is, when the diameter of the stent is reduced, if the tubular member is inserted into a thin tubular member such as a sheath while being stretched in the central axis direction, the four points at the intermediate portion of the four fixed portions of the ring member to the tubular member are alternately arranged. Although each ring member is greatly deformed as a result of being folded into a compact corrugated shape (a shape in which two tops and two bottoms of the corrugation are alternately formed) facing one end and the other end in the central axis direction of the cylindrical member, this ring The cylindrical member is not interfered with the deformation of the member, and only four points in the circumferential direction of the cylindrical member fixing the ring members approach in the central axis direction. Rarely occurs. Therefore, it becomes possible to efficiently insert a stent having a reduced diameter into a very thin catheter or the like and transport it to a stenosis of a luminal organ. Since the ring member has the elastic restoring force as described above, the ring member bent into the corrugated shape is restored to the original annular shape when released from the catheter or the like. In addition, since such a compact diameter reduction can be made based on the basic structure of the stent of the present invention, it is not limited to the case where each ring member is fixed to the cylindrical member at four locations in the circumferential direction. However, fixing each ring member to the cylindrical member at four locations is extremely useful because both the small diameter of the stent when the diameter is reduced and the simplicity of fixing the ring member to the cylindrical member are compatible. is there.

In the stent of the present invention, the elastic restoring force of each ring member can be made substantially constant, but the elastic restoring force can be made different for each ring member, for example, in the direction of the central axis of the cylindrical member The elastic restoring force of the ring member disposed in the vicinity of the center portion may be set larger than the elastic restoring force of the ring member disposed in the vicinity of the end portion in the same central axis direction. It is usual to place a stent so that the central portion in the central axis direction is located in a portion where the degree of stenosis is strong in a hollow organ. Therefore, by setting the elastic restoring force of the ring member near the central portion in the central axis direction of the stent to be larger, the stenosis of the luminal organ can be continuously and effectively spread by the stent having a large expansion force. It becomes possible.

Furthermore, in the stent of the present invention, the interval between adjacent ring members can be substantially constant, but the interval between adjacent ring members can be arbitrarily set, for example, a cylindrical member. The interval between the plurality of ring members arranged near the central portion in the central axis direction may be set to be narrower than the interval between the plurality of ring members arranged near the end portion in the central axis direction. In this case, for the same reason as described above, it is possible to continuously and effectively spread the narrowing of the luminal organ by the stent by narrowing the interval between the ring members in the central axial direction vicinity of the stent. Is possible.

Furthermore, in the stent of the present invention, the diameter of each ring member can be made substantially constant, but the diameter can also be made different for each ring member, for example, in the vicinity of one end in the central axis direction of the tubular member The diameter of the ring member disposed in the center may be set larger than the diameter of the ring member disposed in the vicinity of the other end in the same central axis direction. In this case, particularly when the luminal organ to be applied has a shape with a large upstream diameter and a small downstream diameter, the shape of the stent can accurately correspond to the shape of the placement site of the luminal organ. For example, the stent can be used in such a mode that the end portion having the larger diameter is disposed in the main flow portion of the artery and the end portion having the smaller diameter is disposed in the branch of the artery.

In particular, when the cylindrical member is made of a synthetic resin, there is a problem with the conventional stent using a metal material as a skeleton, that is, a metal caused by repeated bending or bending in a luminal organ. The problem of tearing due to fatigue does not occur, and a safer and more durable stent can be realized. In the stent of the present invention, since the cylindrical member made of synthetic resin is supported by a plurality of ring members, it is structurally stable and can continue to function in the luminal organ for a long time. In addition, a stent using a cylindrical member made of a synthetic resin can reduce irritation to a luminal organ, and can prevent intimal proliferation and accompanying restenosis. Furthermore, in the stent of the present invention, a drug can be applied to a cylindrical member or used as a drug-eluting stent. When a cylindrical member made of a synthetic resin is employed, the elution drug can be applied. It is easy to select a suitable synthetic resin material.

The stent of the present invention has a network structure that is flexible, elastic, excellent in flexibility, durable against bending, and has a cylindrical shape with a circular cross section, and is positioned inward from both ends of the central axial direction opening of the cylindrical member. It has a basic configuration in which a plurality of elastic ring members are arranged, and further, the vertical and horizontal linear portions constituting the mesh of the cylindrical member are three-dimensionally crossed at substantially equal angles with respect to the central axis of the cylindrical shape. It is composed. Because of such a structure, the stent of the present invention easily follows the movement of the luminal organ, and is easily maintained in a cylindrical shape even when bent at a large angle, is not easily broken, has high durability, and has a strong expansion force. A strong stenosis can also be expanded. Also, it functions in the structure that the stimulation to the luminal organ applied by insertion and placement is small, there is little infiltration of intimal proliferation into the stent, and moderate intimal proliferation on the inner surface side of the stent is easy. The above also has various excellent advantages. Therefore, the present invention is not only suitable for application to a luminal organ to which a conventional stent has been applied, but also to a luminal organ that bends and stretches in a large angle range that cannot be applied to a conventional stent. Therefore, it is possible to provide an extremely excellent stent that has an unprecedented safety, durability, and wide application range.

The schematic diagram which shows schematic structure of the stent which concerns on 1st Embodiment of this invention. The perspective view which shows the stent of the embodiment. The schematic diagram which shows an example of the bent state of the stent of the embodiment. The schematic diagram which expands and shows a part of stent of the embodiment. The schematic diagram which shows the state between the expansion state and diameter-reduction state of the stent of the embodiment. The schematic diagram which shows the state which diameter-reduced the stent of the embodiment. The schematic diagram which shows the other example of the state between the expansion state of the stent of the embodiment, and a diameter-reduced state. The schematic diagram which shows the state immediately after releasing the diameter of the stent of the same embodiment, conveying it to the stenosis part of a blood vessel, and discharging | emitting from a sheath etc. FIG. The schematic diagram which shows the state which expanded the stent of the embodiment in the constriction part of the blood vessel. The schematic diagram which shows the state which expanded the stent of the embodiment in the narrowed part of the curved blood vessel. The schematic diagram which shows schematic structure of the stent of 2nd Embodiment of this invention. The schematic diagram which shows the state between the expansion state and diameter-reduction state of the stent of the embodiment. The schematic diagram which shows schematic structure of the stent of 3rd Embodiment of this invention. The schematic diagram which shows schematic structure of the stent of 4th Embodiment of this invention. The schematic diagram which shows schematic structure of the stent of 5th Embodiment of this invention. The schematic diagram which shows schematic structure of the stent of 6th Embodiment of this invention.

Embodiments of the present invention will be described below with reference to the drawings.
First Embodiment A stent 1 according to this embodiment includes a lesion part of a luminal organ, particularly a stenosis part of a lower limb artery due to arteriosclerosis, a trachea or esophagus due to cancer, a stenosis part such as a duodenum, a biliary tract, and other blood vessels. In this embodiment, a stent 1 that is inserted and placed in a blood vessel will be described as an example. Even when applied to a luminal organ, the basic configuration is the same as that of the stent 1 described below, except that the size and the number of ring members are different.

The stent 1 of the present embodiment is a schematic diagram of the stent 1 in which the cylindrical portion 2 schematically representing the cylindrical shape in FIG. 1 and the ring member 31 viewed from an oblique direction are combined, and FIG. FIG. 3 is a perspective view showing the appearance of the stent, and FIG. 3 is a schematic diagram showing a state in which the stent 1 is bent, and a mesh-like cylindrical member 2 having a large number of aligned meshes forming a cylindrical shape, and the cylindrical shape A plurality of

ring members

31, 31... That are intermittently disposed inward from both end openings in the central axis direction of the member 2 are provided as a basic configuration. In the stent 1 of the present embodiment, the plurality of ring members 31 are arranged at regular intervals on the inner surface side of the cylindrical member, but depending on the type of the luminal organ to be applied, the position of the affected part, etc. It is also possible to vary the separation interval of the ring member 31 as appropriate. Hereinafter, each part of this stent 1 is explained in full detail.

The cylindrical member 2 is formed in a mesh shape (mesh shape) with a plurality of flexible warp yarns 21 and weft yarns 22 respectively, and is equivalent to the diameter of the applied luminal organ (blood vessel in this embodiment). It is a member having a cylindrical shape with a slightly thicker diameter (in this embodiment, a diameter of about 6 mm). The warp yarn 21 and the weft yarn 22 forming the network structure correspond to the vertical and horizontal linear portions of the cylindrical member 2 in the present invention. For example, a thread having a thickness of about 150 μm can be used for the warp 21 and the weft 22, and the thickness of the thread is preferably about 50 to 300 μm. The material of the yarn is natural fiber, synthetic resin fiber, metal fiber, composite fiber, etc. It has moderate strength, tension and flexibility, excellent flexibility, high durability against bending, and biocompatibility An appropriate material can be selected. As the warp yarn 21 and the weft yarn 22, appropriate ones such as one yarn, two or more plural yarns, and twisted yarn can be appropriately used depending on the application. Polyester, polyethylene, polypropylene, polytetrafluoroethylene, nylon and the like can be exemplified as materials that are particularly suitable for the synthetic resin fibers as the warp yarn 21 and the weft yarn 22. In this embodiment, polyester is used. Yes. Further, when the stent 1 of the present embodiment is used as a drug-eluting stent, the properties of the drug such as an antithrombotic agent, an intimal thickening preventive agent, and an anticancer agent are compatible with application to the warp yarn 21 and the weft yarn 22. Based on the above, appropriate materials for the warp yarn 21 and the weft yarn 22 may be selected. The size of the mesh composed of the plurality of warp yarns 21 and weft yarns 22 can also be set as appropriate. For example, the size is preferably in the range of 200 to 800 μm per side. In this embodiment, for example, an extremely fine mesh having a rhombus with a side of about 600 μm is used.

Here, a plurality of warp yarns 21 and weft yarns 22 constituting the cylindrical member 2 are shown by a one-dot chain line in FIG. The cylindrical member 2 is disposed so as to form a three-dimensional intersection with the central axis m at an equal angle θ with respect to the cylindrical central axis m. For example, in the state of the cylindrical member 2 alone before the ring member 31 is attached, the cylindrical member 2 is configured so that the warp yarn 21 and the weft yarn 22 intersect three-dimensionally at an angle of about 45 ° with respect to the central axis. Can do. Actually, the plurality of warp yarns 21 and weft yarns 22 form a curved circumferential surface of the mesh-like cylindrical member 2 on a curved line, but if the neighborhood of each mesh is viewed locally, The warp yarn 21 and the weft yarn 22 can be regarded as straight lines. Accordingly, one diagonal of one mesh forming a rhombus composed of two

warp yarns

21 and 21 and two

weft yarns

22 and 22 is substantially parallel to the central axis m, and the other diagonal is substantially perpendicular to the central axis m. A three-dimensional intersection will occur. In this embodiment, the cylindrical member 2 composed of the warp yarn 21 and the weft yarn 22 has a tensioned structure having both flexibility and elasticity. In addition, although the opening both ends 2a of the cylindrical member 2 are heat-welded so that the warp 21 and the weft 22 do not fall apart, the end 2a may be processed by sewing or the like. .

The plurality of ring members 31 (eight examples are shown in the drawings of this embodiment) are all circular ring-shaped members made of the same material and the same configuration. For each ring member 31, an appropriate linear material having appropriate strength, tension and flexibility and having biocompatibility can be selected from metals, synthetic resins, composite materials, etc. In the form, Nitinol wire which is a nickel titanium alloy is used. Further, each of the

ring members

31 and 32 is formed into a cylindrical shape by winding a nitinol wire a plurality of times (for example, 3 to 7 times) and fixing both ends thereof by adhesion or caulking to enhance elasticity and durability. The member 2 is formed in a circular shape having substantially the same diameter. However, depending on the elasticity and strength of the wire, a single ring may be applied, or a ring manufactured in advance in a circular shape may be used as the

ring members

31 and 32 of the present embodiment. In addition to such a linear material formed in an annular shape, a ring-shaped member obtained by bending a linear material in a zigzag manner or a cylindrical member that is extremely short in the long axis direction can be used as the ring member. In the stent 1 of the present embodiment, the plurality of ring members 31 as described above are arranged and attached at substantially equal intervals on the inner surface side of the tubular member 2.

Here, with respect to the attachment of the ring member 31 to the tubular member 2, each ring member 31 is disposed at each predetermined position inside the tubular member 2, and is rotated every 90 degrees around the central axis m. A ring member is attached to only one of the warp yarn 21 or the weft yarn 22 although the yarn 23 is tied and fixed to the intersecting portion of the warp yarn 21 and the weft yarn 22 constituting the mesh of the cylindrical member 2 at four locations (see FIG. 4). 31 may be attached. In the present embodiment, an example is shown in which the fixing points at the four points with respect to each ring member 31 are substantially matched on four straight lines parallel to the central axis of the cylindrical member 2 common to all the ring members 31. However, it is not necessary to match. In addition, the fixing method of each ring member 31 to the cylindrical member 2 is not limited to fixing with a thread, but can be performed with a biocompatible adhesive, and the fixing location is limited to four locations or the entire circumference. is not.

The stent 1 configured in this manner is in a state in which the central axis m of the tubular member 2 and the center of each ring member 31 are substantially aligned, as shown in each drawing. Therefore, the stent 1 as a whole has flexibility and elasticity both in the direction of the central axis m and in the radial direction (the radial direction of the tubular member 2 and the radial direction of the

ring members

31 and 32 corresponding thereto). As shown in FIG. 2, when the stent 1 is bent in the direction of the central axis m, it can be bent while maintaining the cylindrical shape. In addition, the rhomboid meshes are expanded and contracted in both diagonal directions by the warp yarn 21 and the weft yarn 22 which are maintained in a state of three-dimensionally intersecting with the central axis m of the cylindrical member 2 so that the cylindrical member 2 is centered. It bends and stretches flexibly in the direction of the axis m, so that the tubular member 2 does not buckle in the middle or a crease is formed on the tubular member 2, or buckling and crease are extremely unlikely to occur. Further, since such a cylindrical member 2 is used, the stent 1 can be expanded and contracted to a certain extent in the direction of the central axis m of the cylindrical member 2, and contracts in the diametrical direction when expanded and bulky when contracted. Will also be suppressed. Note that, as described above, FIG. 3 shows the bent state of the stent 1, but the case where the stent 1 is bent at an angle larger than that shown in the figure (for example, a U-turn of about 180 ° or more). Even so, the stent 1 can maintain a cylindrical shape.

Next, when the stent 1 of the present embodiment is introduced into a blood vessel percutaneously via a transluminal tube and placed to expand a stenosis, the stent 1 is not shown in advance before inserting the stent 1 into the blood vessel. The stent 1 is provided through a preload system in which the stent 1 is mounted on an appropriate delivery device and then released to expand the stent 1 or through a delivery device (catheter or sheath, etc.) that has been inserted to a target position in the blood vessel in advance. It is possible to adopt an afterload system that transports, discharges, and detains. In any of the introduction methods described above, the delivery / release method to the target site uses a method of pushing the rear end side of the stent 1 or pulling the distal end side (providing a suspension device at the distal end of a thin catheter). . However, even if it is a case where the stent 1 is detained in a stenosis part by any system, the balloon catheter is finally used as needed and expansion operation with respect to the stent 1 may be added.

The diameter of the stent 1 is reduced by, for example, inserting the stent 1 from the large diameter portion of the funnel-shaped device connected to the end of the tubular device such as a catheter toward the small diameter portion, and the elasticity of the ring member 31 and the cylindrical member. The stent 1 is automatically generated by the elasticity of 2, but the diameter of the stent 1 can be reduced by using an instrument such as a finger or tweezers. Further, by temporarily attaching a thread to the distal end portion of the stent 1, pulling the thread and introducing the thread into a sheath or a catheter through a funnel-like device, it is possible to reduce the diameter of the stent 1 as a result. is there. Specifically, the diameter reduction of the stent 1 is realized by bending each ring member 31 into an aligned waveform and the tubular member 2 extending in the central axis m direction and contracting in the radial direction. FIG. 5 shows a schematic diagram of the stent 1 in the process of the expanded state and the reduced diameter state, and FIG. 6 shows the stent 1 in the reduced state. First, the ring member 31 will be described. The wave form of each ring member 31 that is bent is alternately two along the circumference of the ring member 31 for each 90 ° angle phase around the center axis m of the wave. Each shape is formed. Here, for convenience of explanation, a portion facing the one opening end 2a side of the cylindrical member 2 is referred to as a corrugated

top portion

31a, 31c, and a portion facing the other opening end 2a side is referred to as a

corrugated bottom portion

31b, 31d. . The

top portions

31 a and 31 c and the

bottom portions

31 b and 31 d of these corrugations are formed at substantially intermediate positions of the four threads 23 that attach the ring members 31 to the tubular member 2. That is, all the ring members 31 are bent, and the corrugated top portion 31a, bottom portion 31b, top portion 31c, and bottom portion 31d respectively connect the central axis m of the cylindrical member 2 (that is, the circular center of each ring member 31). The line is aligned in parallel with the line segment. However, when the yarns 23 are not aligned in parallel with the central axis m, the waveform of the bent ring member 31 is not aligned. Further, the tubular member 2 extends in the direction of the central axis m following the wavy deformation of the ring member 31 and contracts in the radial direction. That is, as a result of the ring member 31 in the expanded state being bent into a wave shape, the fixing point of the ring member 31 by the yarn 23 of the warp yarn 21 and the weft yarn 22 approaches the central axis m, and as a result, the mesh of the cylindrical member 2 The rhombus shape extends in a diagonal direction parallel to the central axis m and contracts in the other diagonal direction. Therefore, in the present embodiment, when the diameter of the stent 1 is reduced, the

ring members

31 and 32 have the top part 31a and the top part 31c, the bottom part 31b and the bottom part 31d, and the top part with the central axis m of the cylindrical member 2 interposed therebetween. 32a and the top 32c, the bottom 32b and the bottom 32d are elastically bent so that they face each other or come close to each other, and the cylindrical member 2 that flexibly follows the shape change of each ring member 31 is maintained in the center while maintaining the rhombus network structure. While expanding in the direction of the axis m, the diameter is reduced toward the central axis m (in this embodiment, the diameter is reduced to about 2 mm) and contracted. 5 and 6, when the diameter of the stent 1 is reduced (the process of the expanded state and the reduced diameter state), all the ring members 31 are bent in a waveform in the same direction. FIG. 7 shows the

top portions

31a and 31c and the

bottom portions

31b and 31d of a part of the plurality of ring members 31 as shown in FIG. The bent state may be bent toward the opposite side in the direction of the central axis m. The same applies to other embodiments described below.

FIG. 8 shows a state immediately after the diameter-reduced stent 1 is released from the catheter (not shown) in the vicinity of the narrowed portion Aa of the blood vessel A. After the release, the expanded stent 1 is placed in the blood vessel A. FIG. 9 schematically shows the state in which the constricted portion Aa is pushed and expanded. That is, in the case of placement of the stent 1 in the case where the stenosis Aa develops in the linear portion of the blood vessel A, the tubular member 2 is expanded into a cylindrical shape by the elastic ring members 31 and the inner wall of the blood vessel A The stenosis Aa can be appropriately expanded by coming into contact with A1. Therefore, each ring member 31 and the cylindrical member 2 are elastic even when subjected to the pulsation of the blood vessel A itself, expansion and contraction associated therewith, or compression from the muscle outside the blood vessel A. The elasticity of 31 and 32 is transmitted also to the cylindrical member 2, and the stent 1 is bent in the radial direction as a whole or expanded and contracted in the direction of the central axis m by the expansion and contraction based on the elastic network structure of the cylindrical member 2. The state of following the movement of the blood vessel A and contacting the inner wall A1 is maintained. In addition, the cylindrical member 2 is expanded while maintaining the rhomboid mesh structure while the warp yarn 21 and the weft yarn 22 constituting the mesh structure are three-dimensionally intersecting at a substantially equal angle with respect to the central axis m of the stent 1. Therefore, even if the blood vessel A itself is subjected to pulsation, expansion and contraction, and external pressure, the mesh structure does not collapse.

The mesh-shaped cylindrical member 2 in which the warp yarn 21 and the weft yarn 22 are three-dimensionally intersected with the central axis m of the stent 1 at a substantially equal angle has a structure in which a plurality of ring members 31 are intermittently supported from the inner surface side. In particular, in the case of the stent 1 of the present embodiment, as shown in FIG. 10, even when the stenosis Ab is formed in the curved portion of the blood vessel A, the vessel A is placed in the linear stenosis Aa. In the same manner as described above, it is possible to push the stenosis Ab in contact with the inner wall A1 while curving corresponding to the curved shape. In this case, the mesh of the cylindrical member 2 is slightly narrowed on the inner side of the curved shape of the stent 1 and slightly expanded on the outer side to form a distorted rhombus shape. It stably abuts against the inner wall A1 of the blood vessel A with almost no wrinkles. For example, when the stenosis Ab is generated in the blood vessel A of the knee, the blood vessel A may be bent at a larger angle than the state shown in FIG. Since it has expandability in the circumferential direction while maintaining the curvature of m, it is possible to follow the curvature of the blood vessel A while maintaining the cylindrical shape while increasing the degree of curvature.

Furthermore, even if the stent 1 of this embodiment is applied to any of the narrowed portions Aa and Ab of the straight portion or the curved portion of the blood vessel A, the mesh of the cylindrical member 2 is formed as a very fine rhombus having a side of about 600 μm square. Furthermore, since the stimulation given to the inner wall A1 of the blood vessel A is minimized, the intimal proliferation of the inner wall A1 will remain at an appropriate proliferation even when reaching the inner surface side of the cylindrical member 2, Formation of a thrombus is suppressed. Therefore, the stent 1 of the present embodiment can be used by being placed in the stenosis portions Aa and Ab in the blood vessel A over a long period of time.

Furthermore, since there are no ring members at both ends 2a of the opening of the tubular member 2, the both ends 2a in the central axis m direction of the stent 1 are only the mesh-shaped tubular member 2, so that the inner wall A1 of the blood vessel A Can reduce the pressure applied. For the same reason, since the stent 1 does not have any metal parts that may come into contact with the inner wall A1 of the blood vessel A, the stimulation applied to the inner wall A1 of the blood vessel A can be extremely small. Therefore, if the stent 1 is used, the possibility of restenosis accompanying the proliferation of the intima from the inner wall A1 of the blood vessel A can be made extremely low.

As described in detail above, since the ring member 31 is intermittently attached to the inner surface side of the tubular member 2 having a mesh structure that expands and contracts in both the central axis m direction and the circumferential direction, the central axis The entire stent has a bend of m, bends in the central axis m direction and the radial direction, and expands in the circumferential direction. Therefore, the stent 1 of the present embodiment is excellent in durability and affinity to a living body (inner wall A1 of the blood vessel A), and also safe in that it does not break even if bent at a large angle. Is. Furthermore, since the stent 1 of the present embodiment has a simple structure as described above, if the cylindrical member 2 and each ring member 31 are formed in a small diameter, the thin stent 1 can be easily configured. . Because of these various features, the stent 1 of the present embodiment is suitable for blood vessels in the iliac artery region, which has been the subject of application of conventional stents for diseases from the aortic branch to the downstream artery, and other applications. In addition to providing many advantages by using it placed in a blood vessel, it can be applied to blood vessels below the siliceous part that could not be applied with conventional stents, especially knees that bend repeatedly at a large angle. Application to the blood vessels of the hip joint and the blood vessels of the thigh that are subjected to strong compression due to muscle contraction is also possible. In the above, the application example for pushing the stent 1 to expand the narrowed portions Aa and Ab of the blood vessel A has been described, but the stent 1 can also be applied to a luminal organ other than the blood vessel.

<Second Embodiment> The stent of the present invention is not limited to the configuration of the stent 1 of the above-described embodiment. For example, the stent 100 shown as the second embodiment in FIG. 11 has the same cylindrical member 2 as that applied to the stent 1 of the first embodiment and a larger diameter than the ring member 31 applied to the first embodiment. The ring member 32 is applied. That is, a plurality of ring members 32 are provided on the inner surface side of the mesh-like cylindrical member 2 made up of a plurality of warp yarns 21 and weft yarns 22 inwardly of the openings at both ends in the central axis m direction, as in the first embodiment. Are fixed at four locations. Therefore, when compared with the stent 1, in the stent 100, the mesh of the cylindrical member 2 is a rhombus that is shortened in the central axis m direction and extended in the circumferential direction.

The stent 100 having such a configuration can be reduced in diameter in the same manner as the stent 1. That is, as shown in FIG. 12, when the ring member 32 is bent into a wave shape, the middle portion of the four fixed portions by the thread 23 to the tubular member 2 has a wave-like top portion 32a and a bottom portion 32b in order in the circumferential direction. The top portion 32c and the bottom portion 32d are further reduced in flexure, so that the diameter of the stent 1 is as thin and compact as the stent 1 shown in FIG. The difference becomes larger.

<Third Embodiment> Further, the stent of the present invention may be as shown in FIG. 13 as the third embodiment. That is, the stent 200 shown in the figure is different from the cylindrical member 2 same as the stent 1 of the first embodiment, the ring member 31 used in the first embodiment, and the ring member 32 used in the second embodiment. A plurality of ring members each having a diameter are used. That is, a ring member 31 having a smaller diameter is attached to the inner surface side near the one opening end 2a in the central axis m direction of the cylindrical member 2, and a larger diameter ring is attached to the inner surface side near the other opening end 2a. A member 32 is attached. In the stent 200 having such a configuration, the rhombic shape of the mesh of the cylindrical member 2 is contracted in the direction parallel to the central axis m in the region where the ring member 32 is disposed, and in the circumferential direction, rather than the region where the ring member 31 is disposed. Becomes an elongated shape. The stent 200 can be reduced in diameter in the same manner as the stent 1 of the first embodiment and the stent 100 of the second embodiment.

Such a stent 200 having different diameters at both ends 2a in the direction of the central axis m is suitable for placement in, for example, a branch portion of a blood vessel, and the larger diameter side of the stent 200 is placed on the main flow side where the blood vessel is thick. The small diameter side of the stent 200 may be disposed on the side where the branch is thin. Further, the stent 200 of the present embodiment may be disposed at a location where the blood vessel is gradually narrowed according to the direction of blood flow. In the present embodiment, the

ring members

31 and 32 having two types of diameters are applied. However, as a modification of the present embodiment, ring members having three or more types of diameters may be used. As another modified example, a configuration in which a large-diameter member is applied to a ring member attached to a portion near the central portion in the central axis m direction of the cylindrical member can be exemplified. In the case of a stent having such a configuration, it is generally appropriate to arrange the stent so that the central portion in the central axis direction is positioned in a portion where the degree of stenosis is large in the luminal organ. A large site can be spread more strongly and continuously.

<Fourth Embodiment> Further, the stent of the present invention can be appropriately made different from the ring members 31 instead of being arranged at substantially equal intervals as in the stent 1 of the first embodiment. . The stent 300 shown as the fourth embodiment in FIG. 14 uses the same tubular member 2 and ring member 31 as the stent 1 of the first embodiment, but is arranged at the center in the direction of the central axis m. The interval between the ring members 31 is narrower than the interval between the ring members 31 arranged near the opening end 2a. That is, in the case of such a stent 300, it becomes possible to strongly and continuously push the stenosis by disposing more ring members 31 in the central portion where the degree of stenosis is large as described above.

<5th Embodiment, 6th Embodiment> Furthermore, the stent of this invention can be set as the structure which has arrange | positioned the ring member to one or the other of the opening both ends 2a of a cylindrical member. A stent 400 shown as a fifth embodiment in FIG. 15 includes a ring member 33 at one open end 2a in the central axis m direction in addition to the same cylindrical member 2 and a plurality of ring members 31 as in the first embodiment. The stent 500 shown as the sixth embodiment in FIG. 16 has a configuration in which the ring member 34 is also attached to the other open end 2a in addition to the configuration of the stent 400. In the stent 400 and the stent 500, the

ring members

33 and 34 attached to the open end 2a of the tubular member 2 are each ring member 31 attached closer to the inner side in the central axis m direction than the open end 2a of the tubular member 2. However, it is not always necessary to attach the

ring members

33 and 34 to the inner surface side of the tubular member 2. For example, the

ring members

33 and 34 may be attached to the outer surface side of the tubular member 2, or The opening end 2a of the shaped member 2 may be folded inward or outward to form a bag shape, and the

ring members

33 and 34 may be fixed inside the bag shape. Further, when the

ring members

33 and 34 are fixed to the cylindrical member 2, the

ring members

33 and 34 can be fixed to the cylindrical member 2 at four points similarly to the ring member 31, but at the open end 2 a of the cylindrical member 2, A thread may be wound around the circumference and sewn.

When the stent 400 is placed in the blood vessel so that the open end 2a on the side where the ring member 33 is provided is on the upstream side of the blood vessel, the other open end 2a without the ring member is in a so-called blowing state. Even so, since the cylindrical member 2 itself is also tensioned, it can be placed in a stable state in the blood vessel, and the function as a stent can be sufficiently exhibited. Further, regarding the stent 500, the

ring members

33 and 34 are provided at both ends 2a of the opening, thereby realizing more stable placement in the blood vessel.

In addition to the above, the stent of the present invention does not set the elastic restoring force of each ring member as the same, for example, the elastic restoring force of the ring member arranged at the central portion in the central axis direction of the cylindrical member. Can be set larger than the elastic restoring force and diameter of the ring member disposed at a position close to the opening end. In the case of such a stent, as described above, there is an advantage that a site where the degree of stenosis of the blood vessel is large can be more strongly and continuously pushed.

In addition, the stent of the present invention can appropriately set the shape of the tubular member and the diameter and width of the ring member in accordance with the shape of the luminal organ applied other than the blood vessel and the shape of the part. In addition, the configurations of the above-described embodiments can be appropriately combined.

In addition, the specific configuration of each part, such as the constituent material of the cylindrical member and the ring member, the number and configuration of the ring members, the size of the entire stent, and whether the ring member is fixed to the inner surface side or the outer surface side of the cylindrical member The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

As described above, the stent of the present invention is useful as a stent having a simple structure with high flexibility, safety, durability, and longitudinal and lateral elasticity. Not only the stenosis part of animal luminal organs, but also the stenosis part of the blood vessel downstream from the iliac artery area where conventional stents cannot be applied, and blood vessels that flex and stretch at large angles such as knees, etc. Applicable to luminal organs.

Claims

A stent inserted into a hollow organ and placed;
A cylindrical member having flexibility and elasticity, having a mesh shape through which body fluid can pass in and out, and an arbitrary cross section perpendicular to the central axis being substantially circular,
A plurality of ring members arranged to be spaced apart from each other with their centers substantially coincident with the central axis of the cylindrical member,
The cylindrical member is open at both ends in the central axis direction, and the vertical and horizontal linear portions constituting the mesh shape are formed so as to three-dimensionally intersect each other at a substantially equal angle with respect to the central axis. Which has been
The plurality of ring members are arranged at least inward from both ends of the cylindrical member in the central axis direction, and can be bent in both the radial direction and the central axis direction of the cylindrical member. A stent comprising: a flexible annular member having a structure attached to the tubular member.
The stent according to claim 1, wherein the ring member is attached to an inner surface side of the cylindrical member.
The stent according to any one of claims 1 and 2, wherein the ring member is not disposed in openings at both ends in the central axis direction of the cylindrical member.
The stent according to any one of claims 1 to 3, wherein the ring member is made of a flexible metal wire having a bendable elastic restoring force.
The stent according to claim 4, wherein the ring member is formed by bundling a plurality of the metal wires that are annular.
The stent according to any one of claims 1 to 5, wherein the ring members are fixed to the cylindrical member at four locations while being spaced apart at substantially equal intervals in the circumferential direction.
The elastic restoring force of the ring member arranged near the central portion in the central axis direction of the tubular member is set larger than the elastic restoring force of the ring member arranged near the central axial direction end portion. The stent according to any one of 6.
The interval between a plurality of ring members arranged near the central portion in the central axis direction of the cylindrical member is set to be narrower than the interval between the plurality of ring members arranged near an end portion in the central axis direction. The stent according to any one of 7.
The diameter of the ring member disposed near one end in the central axis direction of the cylindrical member is set larger than the diameter of the ring member disposed near the other end in the central axis direction. The stent according to crab.
The stent according to any one of claims 1 to 9, wherein the cylindrical member is made of synthetic resin.