JP2003062086A - Stent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stent which doesn't interfere with each other if they are made to continue in the longitudinal direction when indwelt in a curved lesion site, and can be stably indwelt in such a manner that the distances between lower apexes as well as those between upper apexes are made roughly equal with each other when they are indwelt in the lesion site. SOLUTION: A stent A is so constituted that the upper apexes 2a and the lower apexes 2b are formed by folding the stent material 1 in the zigzag form, and both ends of the stent material 1 are joined. Especially, the zigzag form has a following constitutional property: the distances between the abutting upper apexes 2a and the lower apexes 2b are changed so as to adjust to the curve form of the lesion site; according to the distances, the distances between the lower apexes as well as those between the upper apexes are changed; when the stent is indwelt in the lesion site, the distances between the lower apexes as well as those between the upper apexes are roughly made equal.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zigzag stent used for treating a tubular tissue in a body represented by a blood vessel, for example, for treating an aneurysm. . 2. Description of the Related Art There are many tubular tissues such as blood vessels, bile ducts, ureters and esophagus in the body, and there is a possibility that specific diseases such as stenosis and obstruction may occur. For example, in the case of blood vessels, stenosis and occlusion,
Diseases such as aneurysms and varices may occur. In particular, an aneurysm is a serious disease that causes major bleeding when ruptured, and it is necessary to treat it promptly. Therefore, various devices for effective treatment have been developed. [0003] Recently, a metal cylindrical device called a stent has been often used for treating a stenosis or an aneurysm of a blood vessel. For example, when treating an aneurysm, a stent graft in which the stent is coated with an artificial blood vessel is used, and the stent graft is placed inside the aneurysm so that blood pressure does not act on the aneurysm. When a stent is to be placed in an affected area, the stent is reduced in diameter and inserted into a delivery kit having a long cylindrical shape and a guide wire inserted therein, and the blood vessel is placed along the guide wire from the base of the foot. It is performed by removing the delivery kit and releasing the restraint to the stent when the patient reaches the affected part by conducting into the patient and reaches the affected part. Then, the stent released from the restraint expands on its own, and is placed in the affected part in this state to exhibit the function of protecting the blood vessel. [0005] As described above, the stent placed at the affected site expands by itself and comes into close contact with the inner wall surface of the tubular tissue. At this time, if the expansion force is small, a gap is formed between the inner wall of the tissue and the stent graft, the original effect as the stent graft cannot be exhibited, and the stent graft may be detached from the affected part. For this reason, the released stent does not return to its initial free state,
The expansion force is exerted by being constrained by the inner wall of the tubular tissue, and thereby closely adheres to the inner wall of the tissue. In experience,
Stent grafts with too large an expansion force cannot be manufactured. [0006] Several types of stents are provided. Among them, a metal wire is bent in a zigzag to form a curved top, and both ends of the wire are joined to form a cylinder. There is something. In particular, the material constituting the stent must not have a risk of adversely affecting the living body. For this reason, metal materials that can be used at this stage include stainless steel or Ni-T
2. Description of the Related Art Shape memory alloys made of an i-alloy are known. In particular, recently, Ni-Ti alloys having good biocompatibility have been increasingly used. Also, since the thickness and shape of the affected part in the tubular tissue of a living body vary from individual to individual, the shape information of the affected part is obtained in advance, and an optimum diameter (a cylindrically shaped stent) is obtained based on this shape information. In general, a stent having a length (diameter of a cylindrical portion, a diameter of a stent) and a length is formed. In particular, when the diseased part is long and curved, a single stent cannot cope with it. Therefore, a plurality of stents are arranged in the longitudinal direction, and the stent is bent along the curvature of the diseased part. To form a composite stent connected by the same. In the above conventional stent, when the stent material is bent in a zigzag manner, the distance between the top formed on the upper side of the zigzag and the top formed on the lower side of the zigzag is: Equal, and the distance between adjacent tops formed on the upper and lower sides is also equal. That is, all the triangles that constitute the zigzag and are formed of three adjacent vertices are formed to have substantially the same shape. Accordingly, the formed stent is a straight tubular cylinder obtained by cutting the cylinder in a direction perpendicular to the axis of the cylinder. When the stent is placed in a diseased part having a straight tubular shape, it can be effectively protected by contacting the inner wall of the diseased part with a substantially uniform force. However, when placed in a curved affected part, a zigzag part that contacts the inside of the curve tends to be larger than a zigzag part that contacts the outside of the curve, and as a result, a large force acts on the affected part inside the curve, In addition, there is a problem that a small force acts on the affected part outside the curve, and it becomes difficult to effectively protect the affected part. In particular, when the affected part is curved and the site to be placed is long and cannot be protected by one stent, as shown in the figure, the plurality of straight tubular stents 51 and 52 are moved in the longitudinal direction. The composite stent 54 is arranged and connected by struts 53 so as to correspond to the curved shape of the diseased part, and is used. When the composite stent 54 is placed in the diseased part, the upper top of the stent 51 is inside the curve. There is a problem that the side and the lower top side of the stent 52 cannot interfere with each other to achieve good expansion. In addition, if the distance between the top and the bottom of the stent is not uniform even at portions other than the inside and outside of the curve, the pressure acting on the tissue inner wall becomes uneven, and the stent is stably applied to the tissue inner wall. There is a problem that they cannot adhere to each other and cannot effectively protect the affected part. It is an object of the present invention to provide a medical device which does not interfere with each other even when it is placed in a curved affected part in the longitudinal direction, and that when placed in an affected part, the distance between the top part and the lower part An object of the present invention is to provide a stent in which the distance between the tops is substantially equal and can be stably placed. [0013] In order to solve the above problems, a stent according to the present invention is formed by bending a stent material zigzag to form an upper top portion and a lower top portion, and joining both end portions of the stent material. Wherein the zigzag changes the distance between the adjacent upper and lower apexes in accordance with the curved shape of the affected area and responds to the change in the distance between the upper and lower apexes. It has a shape in which the distance between the adjacent upper vertices and the distance between the adjacent lower vertices are changed, and when placed in the affected part, the distance between the upper vertices and the distance between the lower vertices are substantially equal. It is. In the above-mentioned stent, when the stent material is bent in a zigzag manner, the upper apex (the apex formed on the upper side of the zigzag) and the lower apex (the lower side of the zigzag) correspond to a predetermined curved shape of the affected part. Formed top)
By changing the distance between them (the height of the stent), when both ends of the stent material are connected, it is possible to obtain a stent having a shape in which both ends of the cylinder are cut obliquely. For this reason, the lower side is the inside of the curve,
By setting the high side outside the curve, even when a plurality of stents are connected in the longitudinal direction to form a composite stent, the stents constituting the composite stent do not partially interfere with each other. Also, by changing the distance between the adjacent upper vertices and the distance between the lower vertices in accordance with the change in the height of the stent, that is, the distance between the adjacent upper vertices at a high height portion. By increasing the distance between the lower apexes and decreasing the distance between the adjacent upper apexes and the distance between the lower apexes at low heights, when the stent is placed in a curved diseased area, the stent is staggered. Despite the different heights, the distance between the upper ridges and the distance between the lower ridges can be made substantially equal over the entire circumference, and can be placed in a stable state. Hereinafter, preferred embodiments of a stent according to the present invention will be described. The stent according to the present invention is applied to a curved portion in a tubular tissue such as a blood vessel, a bile duct, a ureter or an esophagus in a living body,
When these diseases occur such as stenosis or occlusion, especially when the tubular tissue is a blood vessel, when an aneurysm or varicose vein occurs, it has the function of placing it in the affected area and reinforcing the tubular tissue It is. The stent according to the present invention is made of a stainless steel wire rod having elasticity and flexibility and having no adverse effect on living tissue, a round rod shape memory alloy wire made of Ni--Ti alloy, or a biological material. Using a wire (stent material) selected from synthetic resin wires or the like which can generate an expanding force due to having appropriate elasticity without adversely affecting the tissue, the stent material is bent in a zigzag manner. The upper and lower apexes are formed, and the distance between the adjacent upper and lower apexes is changed in accordance with the curvature of the affected area. With this change, the distance between the adjacent upper apex,
It is formed in a cylindrical shape by changing the distance between the lower apexes and joining both ends of the stent material. With this stent, when placed on a curved affected part, the distance between the upper apexes and the distance between the lower apexes are substantially equal, and a moderate force can be applied to the affected part to maintain a stable indwelling state. In the above-mentioned stent, a plurality of tops (upper tops) are formed on one side (upper side) by bending the stent material in a zigzag shape, and a plurality of tops (lower tops) are also formed on the other side (lower side). And changing the distance between adjacent upper and lower vertices according to the curvature of the affected area, and changing the distance between adjacent upper and lower vertices in accordance with this change. Therefore, when the stent is placed in a curved diseased part, the stent does not partially interfere with each other, and can maintain a stable placement state. That is, at a portion where the distance between the adjacent upper and lower ridges corresponding to the outside of the curve is large, the distance between the adjacent upper ridges and the distance between the lower ridges are increased.
In addition, at a site where the distance between the adjacent upper and lower ridges corresponding to the inside of the curve is small, the distance between the adjacent upper ridges and the distance between the lower ridges are also reduced, so that a plurality of stents are arranged in the longitudinal direction. When the composite stent is connected by struts and has a shape corresponding to the curvature of the affected part, the stents arranged in the longitudinal direction do not interfere with each other, and each stent is in good condition. The distance between the upper top and the lower top is substantially equal, and a stable indwelling state can be maintained. In the above-mentioned stent, it is preferable that the top and the bottom of the zigzag are formed in a loop, respectively, and a constricted portion where the stent material is in contact with each other is provided at a portion of the loop facing the top. preferable. In this way, by forming a loop and forming a constricted portion at each apex, even when a stent material having a small longitudinal elastic modulus is used, it is possible to exert a high expansion force,
It is possible to increase the choice of materials for the stent material. Further, when a stent material having a large longitudinal elastic modulus is used, the thickness of the material can be reduced. In the present embodiment described below, it is possible to use a stent material made of a Ni-Ti alloy to exert an expanding force comparable to that of a stent material made of stainless steel. It is possible to reliably restore and apply an appropriate force to the affected part to stably maintain the indwelling position. Stents are prepared in advance for each patient by X-ray, ultrasonic tomographic image (US), and computed tomographic image (C
T), three-dimensional shape information of the affected part is obtained by means such as magnetic resonance imaging (MRI), and a surrounding model including the affected part is created by a machine tool or the like controlled based on the shape information. Using this model, it is processed into an optimal shape corresponding to the target diseased part. For this reason, the obtained stent is not compatible with each other, and is formed as a dedicated stent applied only to a specific patient. Therefore, when the indwelling part is placed in the affected part, it substantially matches the curved shape of the affected part, and it is possible to come into contact with the inner surface of the tubular tissue in the affected part with a suitable expanding force, and to be placed in a stable state. Maintain position. Next, a preferred embodiment of the stent will be described with reference to the drawings. FIG. 1 is a diagram illustrating the configuration of a stent. FIG. 2 is a view for explaining a stent material bent in a zigzag shape when forming a stent. FIG. 3 is a diagram illustrating a composite stent formed by connecting a plurality of stents in the longitudinal direction. As shown in FIGS. 1 and 2, the stent A is formed by bending the stent material 1 zigzag to form an upper top 2a and a lower top 2b, and joining both ends of the stent material 1 by means such as welding. Thereby, both ends are formed in a cylindrical shape formed obliquely with respect to the axis. The stent A has a shape corresponding to the curved shape of the diseased part to be placed, and is formed such that the outer height H of the curve is larger than the inner height h. The values of the heights H and h of the stent A are set in accordance with the curved shape of the diseased part where the stent A is to be placed. It is a numerical value set for each stent A. That is, when configuring the target stent A, necessary numerical values are set in advance based on shape information including the curved shape, thickness, and length of the diseased part. However, since the dimensions of the stent A itself are not large, in this embodiment, as shown in FIG.
When bending the stent material 1 zigzag,
a and 2b are respectively formed, and the distance in the height direction between the adjacent upper apex 2a and the lower apex 2b is D1 to D10, and the circumferential distance between the adjacent upper apex 2a and the lower apex 2b is L.
1 to L10, D1 corresponds to H, D10 corresponds to h, and the difference between H and h is almost equally distributed. For example, when the height H of the stent A is 26
When mm and h are set to 22 mm, D1 = 26 mm,
D2 = 25.5 mm, D3 = 25 mm ... D9 = 22 mm,
It is set to be. The stent A is configured to change the distance between the adjacent upper ridges 2a and the distance between the lower ridges 2b (circumferential distances, L1 to L10) in accordance with changes in the heights H and h. ing. That is, when the values of the heights H and h increase, the distance in the circumferential direction also increases, and when the values of the heights H and h decrease, the distance in the circumferential direction also decreases. It is possible to make the distance and the distance between the lower tops 2b substantially equal. Next, the procedure for manufacturing the stent A will be briefly described. In this embodiment, the stent material 1
N is composed of 56.06% by weight of Ni and the balance of Ti
A wire having a diameter of 0.5 mm is used as a shape memory alloy of an i-Ti alloy. As shown in FIG. 2, a jig for bending the stent material 1 in a zigzag manner in a plane is provided in advance, and the jig positions the tops 2a and 2b, the shape of the loop 3, and the constriction. The shape and the like of the part 4 are set. That is, the jig is provided with a plurality of pins for forming the tops 2a and 2b, and the position of each pin is D1 to D1 in the vertical direction.
D1 and L1 to L10 in the width direction.
Is set corresponding to. The pin has a size twice as large as the diameter of the stent material 1, and a forming member for forming a narrowed portion 4 at a position spaced from the center of the pin by three times the diameter of the stent material 1. After the stent material 1 is engaged with the forming member, the pin is turned around and engaged with the forming member again, whereby the egg-shaped or drop-shaped loop 3 can be formed. The ends of the stent material 1 formed as described above are joined by means of welding or the like, wound around a metal cylinder and subjected to memory processing, thereby forming an initial shape of a predetermined cylindrical section. It is possible to obtain a finished intermediate material. When performing the shape memory processing on the intermediate material, it is possible to prepare a master in accordance with the three-dimensional shape information of the affected part obtained in advance, and attach the intermediate material to the master for processing. . Further, when forming the stent material A, the master can be used as a jig other than using the jig as described above. As described above, the stent material 1 is wound around the master, and a memory process is performed by maintaining this state and performing a heat treatment. The memory treatment is a heat treatment performed by holding the semiconductor wafer in a vacuum heat treatment furnace set at a temperature in the range of 400 ° C. to 550 ° C. for a predetermined time and then cooling it. In this embodiment, the degree of vacuum of the vacuum heat treatment furnace is set to 10
^-2 to 10 ^-3 Pa and the temperature is 400 ℃, 450 ℃, 500 ℃
C., 550.degree. C., the processing time was 30 minutes and 60 minutes, and the above conditions were combined to perform the memory processing. The stent A constructed as described above is folded in the circumferential direction, reduced in diameter, inserted into a delivery kit, introduced into a diseased part through a blood vessel, and then expanded when taken out of the delivery kit at the diseased part. At this time, it is possible to make close contact with the tubular tissue constituting the affected part, and no gap is generated between the stent A and the inner wall surface of the affected part. Further, the stent A maintains a state in which the opposed stent materials 1 are in contact with each other in the constricted portion 4 and exerts an expanding force with the contact portion as a fulcrum. It is possible to make contact. In particular, when the affected area is long and cannot be reinforced by one stent A, as shown in FIG. 3, a plurality of stents A are arranged in the longitudinal direction and connected by struts 5 to limit the length. It is possible to construct a composite stent B without. In the stent B, each stent A has a shape corresponding to the curved shape of the affected part, that is, the height is low at the portion corresponding to the inside of the curve and high at the portion corresponding to the outside of the curve. Therefore, even when a plurality of stents A are arranged in the longitudinal direction and connected by struts 5, a part of each stent A does not interfere, and when the restraint is released at the affected part, the distance between the top apexes 2a is reduced. And the distance between the lower apex 2b and the lower apex 2b are substantially equal, and it is possible to place the device in a stable state. Even with the stent B configured as described above, when placed in the diseased part, the individual stents A adhere to each other in a curved state corresponding to the curvature of the diseased part, and each stent A and the inner wall of the diseased part are brought into close contact. No gap is formed between them. As described in detail above, in the stent according to the present invention, when the stent material is formed in a zigzag shape, the distance between the upper apex and the lower apex is adjusted according to the curved shape of the affected part. By changing the distance between the adjacent upper apexes and the distance between the lower apexes in accordance with the change, when connecting both ends of the stent material, it is possible to cut both ends of the cylinder obliquely. A stent having a shape can be obtained, and the distance between the upper apexes and the distance between the lower apexes can be made substantially equal when the stent is placed in an affected area. For this reason, even if a plurality of stents are connected in the longitudinal direction to form a composite stent, the lower side is the inside of the curve and the higher side is the outside of the curve. The stents constituting the composite stent do not partially interfere with each other, and when the stent is placed in a curved diseased area, the distance between the top apexes over the entire circumference, despite the different zigzag height of the stent. And the distance between the top and the lower part can be made substantially equal, and can be placed in a stable state.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating a configuration of a stent. FIG. 2 is a diagram illustrating a stent material bent in a zigzag shape when forming a stent. FIG. 3 is a view for explaining a composite stent formed by connecting a plurality of stents in the longitudinal direction. FIG. 4 is a view for explaining a problem when a conventional stent is connected in a longitudinal direction. [Description of Signs] A Stent B Composite stent D1 to D10 Height distance L1 to L10 Circumferential distance 1 Stent material 2a Upper top 2b Lower top 3 Loop 4 Narrowing part 5 Strut

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Claims (1)

Claims: 1. A stent formed by bending a stent material in a zigzag manner to form upper and lower apexes and joining both ends of the stent material, wherein the zigzag is a curved shape of an affected part. The distance between the adjacent upper and lower tops is changed according to the distance between the adjacent upper and lower tops, and the distance between the adjacent upper and lower tops is changed in accordance with the change in the distance between the upper and lower tops. Wherein the distance between the upper apexes and the distance between the lower apexes are substantially equal when the stent is placed in an affected area.