Patent Application
20100249902
The present invention relates to a stent inserted into a tubular organ of a human body, such as a blood vessel, a ureter, a bile duct, or a trachea, to keep a lumen of the tubular organ open, and also relates to a tubular-organ treatment device using the same.
In recent years, when a lumen of a tubular organ of a human body, such as a blood vessel, is blocked, in order to expand and reopen the lumen or reinforce the weakened lumen, a treatment in which a catheter is passed through the tubular organ to insert and position a stent in a lesion is performed. For example, as an approach to treat aortic aneurysm, a treatment method in which a treatment device, i.e., a stent having the outer peripheral surface covered with a graft, is inserted into a lesion and the stent is expanded in a blood vessel to attach the graft to the inner peripheral surface of the blood vessel has been studied.
In a treatment method employing such a stent, although insertion and positioning can be easily performed at a straight tubular portion of a tubular organ of a human body, insertion and positioning of the stent is difficult at a curved portion. Thus, various improvements have been made.
For example, Patent Document 1 discloses a stent formed of an elastic wire deformed in a zigzag manner and spirally wound, anchoring portions of bent portions being tied with thread, so as to be formed into a curved cylinder shape. Patent Document 2 discloses a stent formed of a first wire and second wire composed of a super-elastic shape memory alloy material, the first and second wires being bent in a zigzag manner in a longitudinal direction and entangled with each other at bent portions so as to be formed into a mesh structure. Patent Document 3 discloses a stent formed of a metal wire woven into a tubular shape, the stent having a woven structure in which U-shaped bent portions of the metal wire are entangled with cross portions. Patent Document 4 discloses that Z-stents are attached to the inner peripheral surfaces on both sides of a tube made of a graft material, a Z-stent is disposed on the outer peripheral surface of the middle portion, and both ends of an elastic material are attached to the tube so that the length is contracted.
In Patent Document 1, although the stent can be formed into a curved shape, flexible deformation according to the shape of a tubular organ is difficult. Further, because the curve of an installation site needs to be measured in advance, it is difficult to cope with an urgent case.
In Patent Documents 2 and 3, the bent portions of the metal wires are entangled. When the stent is curved, the entangled portions are shifted, allowing the stent to easily deform into a curved shape. However, because a long metal wire extending over the entire length of the stent is used in a bent state, the metal wire accommodated in a catheter is in an elongated state. When such an elongated metal wire is released in a blood vessel, the entire stent is contracted in the longitudinal direction. This makes handling difficult.
In Patent Document 4, a plurality of Z-stents are arranged in the longitudinal direction. However, because the adjacent Z-stents are not connected, they are susceptible to deformation in the longitudinal direction. Thus, handling during insertion by a catheter is difficult.
Therefore, an object of the present invention is to provide a stent which can flexibly deform with respect to a curved portion of a tubular organ, contracts less in the longitudinal direction during insertion, and is easy to handle, and to provide a tubular-organ treatment device using the same.
A stent according to the present invention is a stent formed into a tubular form, including a plurality of tubular unit bodies arranged in an axial direction, the plurality of tubular unit bodies each being composed of a wire formed into a closed loop and bent in a zigzag manner in a peripheral direction to form a plurality of bent portions spaced apart from one another on both sides, the bent portions each having an anchoring portion, the anchoring portions of the adjacent tubular unit bodies, facing each other, being connected by a connecting filament. At least some of the tubular unit bodies are connected to the adjacent tubular unit bodies only at the anchoring portions of some of the bent portions of a bent portion group on at least one side so as to be rockably retained. In addition, the bent portions connected to retain rockably are projected in the axial direction compared to the other bent portions. In addition, there is provided an elastic shape-retaining member that is attached to the plurality of tubular unit bodies including the rockably retained tubular unit bodies and allows the tubular unit bodies to rock to maintain them in a curved state. In addition, the shape-retaining member is formed of a curved elastic wire having both ends fixed to the tubular unit bodies, the shape-retaining member being retained by the connecting filament stretched in the peripheral direction so as to conform to the external shape of the stent in the axial direction. In addition, a pair of the shape-retaining members are fixed at one end to the tubular unit body so as to be spaced apart from each other, crossed over each other, and fixed at the other end to the tubular unit body so as to be spaced apart from each other. In addition, the shape-retaining member is composed of a shape memory alloy material.
A tubular organ treatment device of the present invention includes the above-described stent and a tubular cover that covers an inner peripheral surface and/or outer peripheral surface of the stent.
In the present invention, because of the above-described structure, since at least some of the tubular unit bodies are connected to and rockably retained by the tubular unit bodies adjacent thereto only at the anchoring portions of some of the bent portions of at least one of the bent portion groups, by inserting and positioning the rockably retained tubular unit bodies into a curved portion of a tubular organ, the tubular unit bodies rock so as to conform to the curved portion and can easily deform into a curved shape. Because the tubular unit bodies rock and deform, even when the curve of the tubular organ differs from person to person, it is possible to flexibly cope with it and easily deform into a curved shape. It also becomes easy to prepare the stent in advance and cope with an urgent treatment.
Furthermore, because the plurality of tubular unit bodies, each composed of a wire formed into a closed loop and bent in a zigzag manner in the peripheral direction to form a plurality of bent portions on both sides, the bent portions each having an anchoring portion, are arranged in the axial direction, the tubular unit bodies can expand and contract from the center in the radial direction, and, when they deform from a contracted state to an expanded state, the length in the axial direction does not significantly change. This enables easy handling during insertion by a catheter. In addition, because each tubular unit body is connected to the adjacent tubular unit body by the connecting filament, they have sufficient durability against deformation in the axial direction and are maintained in a stable shape when inserted and positioned in a tubular organ.
In addition, to retain rockably, by forming the connected bent portions so as to be projected in the axial direction compared to the other bent portions, the rocking range of the tubular unit bodies can be increased. Thus, it is possible to sufficiently cope with a sharp curve.
Furthermore, by providing the elastic shape-retaining member that is attached to the plurality of tubular unit bodies including the rockably retained tubular unit bodies and allows the tubular unit bodies to rock to maintain them in a curved state, the curve of the stent can be stably maintained. Because the shape-retaining member has elasticity, during insertion of the stent, deformation into a straight tubular form can be easily performed. Thus, convenience of handling improves.
Furthermore, by forming the shape-retaining member of a curved elastic wire, fixing both ends thereof to the tubular unit bodies, and retaining the shape-retaining member by the connecting filament stretched in the peripheral direction so as to conform to the external shape of the stent in the axial direction, both ends of the shape-retaining member are fixed to the tubular unit bodies so as not to be displaced easily, and by holding the middle portion, without fixing it, by the connecting filament stretched in the peripheral direction so as to conform to the external shape of the stent, when the entire stent is deformed into a straight tubular form, the shape-retaining member is sifted and easily deformed into a straight shape.
Furthermore, by fixing a pair of the shape-retaining members, spaced apart from each other, at one end to the tubular unit body, crossing them over each other, and fixing them, at the other end, to the tubular unit body so as to be spaced apart from each other, resistance to deformation, such as twist of the stent, is increased, the curve can be more stably maintained, and the strength of the entire stent can be improved.
Furthermore, by using a shape memory alloy material as the shape-retaining member, when positioned in a tubular organ, a desirable curve can be formed.
Embodiments of the present invention will be described in detail below. Although the embodiments described below include various technical limitations since they are preferable examples for embodying the present invention, the present invention is not limited to such embodiments unless the following description specifies that the present invention is limited.
Each tubular unit is formed into a closed loop by cutting a metal wire to a predetermined length, bending it in a zigzag manner in the peripheral direction, and securely connecting both ends.
The tubular unit bodies U1 to U3 are used in a straight tubular portion.
At each bent portion, an anchoring portion, to which the connecting filament F is anchored, is formed. For example, as shown in
When the wire T, having the bent portions n1 to n10, is connected at the connection portion S into a closed loop, each tubular unit body has the bent portions arranged at the vertices of a pentagon on both sides in the axial direction. A bent portion group, in which five bent portions, n2, n4, n6, n8 and n10, are arranged, is defined on one side, and a bent portion group, in which five bent portions, n1, n3, n5, n7 and n9, are arranged, is defined on the other side. The bent portions on both sides are arranged in a plane perpendicular to the axial direction.
The tubular unit bodies V and W are used in a curved portion.
The tubular unit body V is formed of the metal wire T cut to a predetermined length and bent in a zigzag manner to have a width d1 or d2, and has ten bent portions k1 to k10. The width d2 is set to have a greater width than d1, and the metal wire T is bent to have a greater length at the bent portions k3 and k7, that is, bent such that the width is d2. Similarly to the tubular unit bodies U1 to U3, an anchoring portion, to which the connecting filament F is anchored, is formed at each bent portion. Similarly to the tubular unit bodies U1 to U3, the tubular unit body V is formed of the wire T, both ends thereof being securely connected at the connection portion S to be formed into a closed loop, and has, on both sides in the axial direction, a bent portion group, in which five bent portions, k2, k4, ks, k8 and k10, are arranged at the vertices of a pentagon, on one side, and a bent portion group, in which five bent portions, k1, k3, k5, k7 and k9, are arranged at the vertices of a pentagon, on the other side. Although the bent portions are arranged in a plane perpendicular to the axial direction on one side, the bent portions k3 and k7 are projected in the axial direction compared to the other bent portions on the other side.
The tubular unit body W is formed of the metal wire T cut to a predetermined length and bent in a zigzag manner to have a width d1, d2, or d3, and has ten bent portions m1 to m10. The width d2 is set to have a greater width than d1, and the width d3 is set to have a smaller width than d1. The metal wire T is bent to have a greater length at the bent portions m3 and m7, that is, bent such that the width is d2, and is bent to have a smaller length at the bent portions m1, m9 and m10, that is, bent such that the width is d3. Similarly to the tubular unit bodies U1 to U3, an anchoring portion, to which the connecting filament F is anchored, is formed at each bent portion. Similarly to the tubular unit bodies U1 to U3, the tubular unit body W has the wire T, both ends thereof being securely connected at the connection portion S to be formed into a closed loop, and has, on both sides in the axial direction, a bent portion group, in which five bent portions, m2, m4, m6, m8, and m10, are arranged at the vertices of a pentagon, on one side, and a bent portion group, in which five bent portions, m1, m3, ms, m7 and m9, are arranged at the vertices of a pentagon, on the other side. The bent portions m2, m4, m6 and m8 are arranged in a plane perpendicular to the axial direction and the bent portion m10 is provided at a position inward of the plane on one side. On the other side, with respect to the plane perpendicular to the axial direction extending through the bent portions m5, the bent portions m3 and m7 are provided so as to be projected in the axial direction, and the bent portions m1 and m9 are provided at positions inward of the plane.
The connecting filament F is stretched in the peripheral direction while being anchored to the bent portions on both sides of the tubular unit bodies and is connected at both ends into a closed loop. The tubular unit bodies can be deformed so as to contract toward the center by bending the bent portions, and are automatically returned from a contracted state to an expanded state by elasticity exerted by the torsion springs of the bent portions. Therefore, the tubular unit bodies can be maintained in an expanded state having a predetermined size by adjusting the length of the connecting filament F anchored to both sides thereof. Accordingly, it becomes possible to preliminarily determine the size to which the tubular units are expanded when the stent is inserted into a tubular organ by a catheter.
In this embodiment, the connecting filament F is stretched in the peripheral direction over the bent portion groups on both sides of the tubular unit bodies U1 and W. The bent portions m3 and m7, projecting in the axial direction of the tubular unit body W, are further connected to the connecting filament F anchored to the tubular unit body U1. As shown in
In the tubular unit body V, the connecting filament F is stretched in the peripheral direction over the bent portion group on the tubular unit body W side. The bent portions k3 and k7, projecting in the axial direction of the tubular unit body V, are connected to the connecting filament F anchored to the tubular unit body W. The bent portions k3 of the tubular unit body V is connected by being entangled with the connecting filament F between the bent portions m2 and m4 of the tubular unit body W, and the bent portions k7 is connected by being entangled with the connecting filament F between the bent portions m6 and m8. Thus, the tubular unit body V is retained rockably by the tubular unit body W, using the bent portions k3 and k7 as the fulcrum. Because the bent portions k3 and k7 of the tubular unit body V are projected and the bent portions m10 of the tubular unit body W is provided at an inward position, when the tubular unit body V rocks, a wide rocking range, to the extent that the bent portions m1 and m9 come into contact with the tubular unit body W, can be provided. Thus, a sharp curve can be formed.
As shown in
The wire used for the tubular unit bodies is preferably composed of an elastic material that is harmless to the human body and has excellent workability, such as stainless or an alloy of titanium and nickel. Alternatively, a resin material processed in a zigzag manner and formed into a closed loop may be used.
As the connecting filament F, a thread composed of a synthetic fiber, such as polypropylene, may be used.
Although the above-described tubular unit bodies are those having the bent portions arranged at the vertices of a pentagon on both sides, tubular unit bodies having the bent portions arranged at the vertices of another polygon may also be used. For example, if the number of vertices increases, like an octagon, the shape of the tubular unit bodies becomes cylindrical. This increases the entire strength and can further equalize the strength of the respective portions. In the tubular unit bodies constituting the curved portion, the position and number of the bent portions projecting in the axial direction may be appropriately determined according to the curved shape of the stent, and the length of projection can be appropriately determined according to the curvature of the curve. In addition, the width and size of the tubular unit bodies in the axial direction may be individually and appropriately determined, and they can be designed according to the shape of the tubular organ in which the tubular unit bodies are positioned.
By attaching an elastic shape-retaining member for retaining the curve to the above-described stent 1, the curved shape as shown in
Because the shape-retaining members can deform elastically, the stent can easily deform into a straight tubular form. Thus, easy handling during mounting of the stent on a catheter becomes possible.
As has been described, by attaching the shape-retaining members, the stent can be maintained in a predetermined curved state, and the strength of the stent with respect to torsion and the strength with respect to deformation in the axial direction can be increased. In particular, although the strength is low at the curved portion because the tubular unit bodies are rockably connected, by providing two shape-retaining members in a crossed manner, the strength of the curved portion can be increased.
As a shape-retaining member, a single elastic wire may be used. Besides wires, a resin material, such as silicon rubber, may be used and attached to the inside of the curved shape to maintain the shape. Alternatively, the shape-retaining member may be attached to the inside of the stent to keep the shape.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-040035 | Feb 2007 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2008/050749 | 1/22/2008 | WO | 00 | 2/4/2009 |
