JP7722796B2 - stents - Google Patents

Description

The present invention relates to a stent.

Stents have been known for some time that are placed at lesions such as stenoses or obstructions in biological lumens, including blood vessels, esophagus, bile duct, trachea, and ureter, to expand the diameter of the lesion and maintain the patency of the biological lumen (see, for example, Patent Document 1).

Patent No. 4651943

The stents described in Patent Document 1 and elsewhere have a single, elongated structure in the axial direction. Therefore, in stent placement procedures, a stent with an axial length close to the axial length of the lesion in the biological lumen is selected and placed.

However, if a stent longer than necessary is placed relative to the axial length of the lesion, an excess stent portion will be present that does not directly function to treat the lesion, and this excess stent portion may interfere with the normal function of the biological lumen or may lead to complications such as perforation.
If the axial length of the stent is insufficient compared to the axial length of the lesion site, an additional stent must be placed.

The present invention was made in consideration of the above situation, and aims to provide a stent that can be placed with an axial length appropriate for the axial length of the lesion site.

One aspect of the present invention is a cylindrical stent to be placed in a biological lumen, comprising a plurality of stent sections that are expandable and contractable in a radial direction substantially perpendicular to the axial direction. The plurality of stent sections are placed in the biological lumen with their opposing axial ends overlapping each other. At least one of the plurality of stent sections has a restricting section in an area where it overlaps with the other stent section, which restricts relative axial displacement with respect to the other stent section. The end of one stent section, into which the end of the other stent section is inserted, is inclined so that its outer diameter decreases toward the distal end in the axial direction.
Another aspect of the present invention is a cylindrical stent to be placed in a biological lumen, comprising a plurality of stent sections that are expandable and contractable in a radial direction substantially perpendicular to the axial direction. The plurality of stent sections are placed in the biological lumen with their opposing axial ends overlapping each other. At least one of the plurality of stent sections has a restricting section in an area overlapping the other stent section that restricts relative axial displacement with respect to the other stent section. The end of the other stent section that is inserted into the end of the one stent section is inclined so that its outer diameter expands toward the distal end in the axial direction.

The present invention provides a stent that can be placed with an axial length appropriate for the axial length of the lesion site.

1A and 1B are diagrams showing an example of the configuration of a stent according to an embodiment of the present invention. FIG. 1B is a perspective view of FIG. FIG. 1 is a diagram schematically illustrating a state in which a stent is placed in a biological lumen. FIG. 2 is a diagram showing a reduced diameter portion and an expanded diameter portion. FIG. 1 is a diagram showing an example of a placement device used for placing a stent according to this embodiment. 10A and 10B are diagrams illustrating other examples of the restricting portion. 10A and 10B are diagrams illustrating other examples of the restricting portion.

Hereinafter, examples of the configuration of a stent according to an embodiment of the present invention will be described with reference to the drawings.
Here, the shapes, dimensions, etc. of each part in the drawings are shown schematically and do not represent the actual shapes, dimensions, etc. In the drawings, the axial direction Ax of the member is indicated by an arrow as needed. Also, the direction substantially perpendicular to the axial direction Ax is defined as the radial direction. In the drawings, one end side of the member is indicated by the symbol F as needed, and the other end side opposite to the one end side is indicated by the symbol B as needed.

Figures 1(a) and (b) are diagrams showing an example of the configuration of a stent 1 according to this embodiment. Figure 2 is a perspective view of Figure 1(b). Figure 3 is a diagram showing a schematic diagram of the stent 1 placed in a biological lumen. Figures 1 and 2 show a straight cylindrical stent 1, but the shape of the stent 1 may also be, for example, curved in an arched shape or twisted.

The stent 1 of this embodiment is placed at a lesion site, such as a narrowed or obstructed site, in a biological lumen such as a blood vessel, esophagus, bile duct, trachea, or ureter, and is used to expand the lesion site. Figure 3 shows an example of a biological lumen in which the stent 1 is placed at a lesion site 3a in the digestive tract 3 (e.g., the horizontal portion of the duodenum). Note that the stent 1 is not limited to being placed in the digestive tract 3, and may also be placed in other biological lumens.

As shown in FIG. 1(a), the stent 1 of this embodiment has a first stent section 11 arranged at one end and a second stent section 21 arranged at the other end. When the stent 1 is placed, as shown in FIGS. 1(b) and 2, the first stent section 11 and the second stent section 21 are aligned in the axial direction, with an overlapping area OA formed between the other end 11a of the first stent section 11 and the one end 21a of the second stent section 21. At this time, the one end 21a of the second stent section 21 is positioned inside the other end 11a of the first stent section 11. As a result, the first stent section 11 and the second stent section 21 are connected axially within the biological lumen to form the stent 1.

The first stent section 11 and the second stent section 21 each have a main body section that forms the framework of the stent 1. Hereinafter, the main body section of the first stent section 11 will also be referred to as the first main body section 12, and the main body section of the second stent section 21 will also be referred to as the second main body section 22. Furthermore, in describing parts common to the first main body section 12 and the second main body section 22, they may be collectively referred to as the first and second main body sections 12, 22.
A tubular coating (not shown) made of, for example, silicone resin, fluororesin, polyester resin, etc. may be attached to at least one of the inner and outer circumferential surfaces of the first and second main body portions 12, 22. In the following description, a bare stent configuration example without a coating on the circumferential surfaces of the first and second main body portions 12, 22 will be shown as an example of the stent 1.

The first and second main bodies 12, 22 are formed into cylindrical shapes with approximately the same overall diameter. In the first and second main bodies 12, 22, openings provided at both ends in the axial direction Ax communicate with each other, forming a flow path therein through which substances flowing through the digestive tract can pass when the stent 1 is placed in the digestive tract.
In addition, materials that pass through the digestive tract include, for example, food that has just been ingested and has not been digested at all, food that has been broken down as it passes through the digestive tract, and materials that have passed through the digestive tract but have not been digested (for example, feces), and the state of the material does not matter.

Furthermore, the first and second main body portions 12, 22 are expandable and contractible from a contracted state in which they contract radially inward to an expanded state in which they expand radially outward, and have a so-called self-expanding configuration in which the expanded shape is memorized.

Here, the first stent section 11 and the second stent section 21 are housed in a sheath 31 of the placement device 30 (described below) and introduced into the digestive tract 3 in a radially inward contracted state. After being delivered to the lesion site 3a of the digestive tract 3, the first stent section 11 and the second stent section 21 are released from the sheath 31 and expand radially outward. Note that the stent sections released from the placement device 30 may also be expanded radially outward by inflating and compressing a balloon (not shown) from the inside.

As an example, the first and second main body portions 12, 22 are constructed by weaving metal wires into a fence-like structure. Examples of materials for the wires of the first and second main body portions 12, 22 include well-known metals or metal alloys, such as Ni-Ti alloys, stainless steel, and titanium alloys. The first and second main body portions 12, 22 may also be formed from materials other than metals (such as ceramics or resins).

Furthermore, the wire material of the first and second main body portions 12, 22 may be made of an alloy material that is radiopaque, or a marker piece (not shown) made of an alloy material that is radiopaque may be attached to the wire material as appropriate. In these cases, the positions of the first stent portion 11 and the second stent portion 21 can be confirmed from outside the body.

When a Ni-Ti alloy is used as the material for the first and second body portions 12, 22, the first and second body portions 12, 22 can be adjusted to their expanded shape and then subjected to a specified heat treatment to allow the expanded shape to be memorized in the first and second body portions 12, 22.

The configuration of the first and second body portions 12, 22 is not limited to the above. For example, the first and second body portions 12, 22 may be formed by weaving metal wires in a lattice or spiral pattern using other weaving methods. Alternatively, the first and second body portions 12, 22 may be formed by laser cutting a thin-walled cylinder made of the above-mentioned metals, with the thin metal wires wound in a spiral pattern while being folded back in a zigzag pattern.

A first flared portion 13, which increases in diameter toward the one end, is formed at one end of the first main body portion 12. A second flared portion 23, which increases in diameter toward the other end, is formed at the other end of the second main body portion 22. The first flared portion 13 and the second flared portion 23 are both formed by braiding wire, for example, and serve to generate friction between the stent 1 and the inner wall of the digestive tract 3 when the stent 1 is placed, thereby suppressing displacement (migration) of the stent 1.
Although the first and second flared portions 13, 23 have been given as examples of mechanisms for suppressing displacement (migration) of the stent 1, these are merely examples and are not intended to be limiting. For example, the stent may be comprised of barbs (spikes, barbs) that pierce the inner wall of the digestive tract (biological lumen) 3.

In addition, a restricting portion 2 is provided on at least one of the other end of the first main body portion 12 and one end of the second main body portion 22 to restrict relative axial displacement with respect to the opposing stent portion. In this embodiment, as an example of the restricting portion 2, as shown in Figures 1(a) and 4(a), a reduced diameter portion 14 is formed on the other end of the first main body portion 12, and an expanded diameter portion 24 is formed on one end of the second main body portion 22.

The reduced diameter section 14 has a tapered shape, with the diameter narrowing toward the tip on the other end. The expanded diameter section 24 has a tapered shape, with the diameter widening toward the tip on one end. In Figures 1(a) and 4(a), for example, the inclination of the taper of the reduced diameter section 14 and the expanded diameter section 24 relative to a line extending in the axial direction Ax and the axial dimension are set to be approximately the same, but the inclination and axial dimension of the two may be different.

Figures 4(b) and (c) are diagrams showing examples of the positional relationship between the reduced diameter section 14 and the expanded diameter section 24 during stent placement. For simplicity, Figures 4(b) and (c) show the elements of the first stent section 11 and the second stent section 21 in diagrammatic form. Figure 4(b) shows a case where the reduced diameter section 14 of the first stent section 11 and the expanded diameter section 24 of the second stent section 21 are positioned to overlap in the axial direction Ax. Figure 4(c) shows a case where the expanded diameter section 24 of the second stent section 21 is positioned closer to one end than the reduced diameter section 14 of the first stent section 11 in the axial direction Ax.

Compared to FIG. 4(b), in FIG. 4(c), the axial length of the overlapping region OA of the first stent section 11 and the second stent section 21 is longer, thereby shortening the overall length of the stent 1. In other words, in this embodiment, the overall length of the stent 1 placed at the lesion site can be changed by adjusting the axial position of the second stent section 21 relative to the first stent section 11.

Furthermore, the stent 1 of this embodiment can maintain the overall length of the stent 1 placed at the lesion site using the restricting portion 2. This will be explained below with reference to Figures 4(b) and (c).

When the second stent section 21, which is in a contracted state in the position shown in Figure 4(b), expands, the enlarged diameter section 24 of the second stent section 21 abuts against the inside of the reduced diameter section 14 of the first stent section 11, which has been expanded in advance. The reduced diameter section 14 of the first stent section 11 is then biased radially outward from the inside by the expansion force of the enlarged diameter section 24. Meanwhile, because the first stent section 11 is supported by the inner wall of the digestive tract 3, a reaction force is exerted by the reduced diameter section 14 on the enlarged diameter section 24 of the second stent section 21, pushing it radially inward. As a result, in Figure 4(b), the reduced diameter section 14 of the first stent section 11 and the enlarged diameter section 24 of the second stent section 21 engage, mutually restricting axial displacement between the first stent section 11 and the second stent section 21, thereby maintaining the overall length of the stent 1.

In addition, in the position shown in Figure 4(c), the expanded diameter portion 24 of the second stent portion 21 faces the inner periphery of the first main body portion 12, and the reduced diameter portion 14 of the first stent portion 11 faces the outer periphery of the second main body portion 22. When the second stent portion 21 in its contracted state expands in this position, the first main body portion 12, supported by the inner wall of the digestive tract 3, is biased radially outward from the inside by the expansion force of the expanded diameter portion 24, while the expanded diameter portion 24 receives a reaction force from the first main body portion 12. Furthermore, the expanding second main body portion 22 is pressed from the outside by the radially inward force of the reduced diameter portion 14. As a result, even in Figure 4(c), the opposing second main body portion 22 is restrained at the position of the reduced diameter portion 14, and the opposing first main body portion 12 is restrained at the position of the expanded diameter portion 24. Therefore, axial displacement between the first stent portion 11 and the second stent portion 21 is restricted, and the overall length of the stent 1 is maintained.

4(b) and 4(c), when the stent 1 of this embodiment is placed, an overlapping region OA is generated between the first stent section 11 and the second stent section 21. In the region OA, the expansion forces of both the first stent section 11 and the second stent section 21 act, thereby enhancing the expansion force of the stent 1.
In addition, in region OA, the mesh of the skeleton is arranged with a shift in the axial and circumferential directions, making the mesh of the skeleton finer than in the region where the first stent section 11 and the second stent section 21 do not overlap.

In this embodiment, an example has been described in which a reduced diameter section 14 and an expanded diameter section 24 are provided as the restricting section 2 that restricts the axial displacement of the first stent section 11 and the second stent section 21. However, a configuration in which either the reduced diameter section 14 or the expanded diameter section 24 is provided and the other is omitted may also be used.

Alternatively, multiple types of products with different axial lengths may be prepared for either the first stent section 11 or the second stent section 21, and the length may be adjusted by changing the combination of stent sections to be placed in the biological lumen to match the lesion site. In this case, the length of the stent section is adjusted in advance to match the length of the lesion site, so that by engaging the reduced diameter section 14 and the expanded diameter section 24 and placing the stent section, a stent 1 with the appropriate overall length for the lesion site can be placed.

FIG. 5 is a diagram showing an example of a placement device 30 used when placing the first stent section 11 and the second stent section 21 at the lesion site.
The placement device 30 includes a sheath 31 and an axial member 32 that is disposed inside the sheath 31 and is capable of locking the first stent section 11 and the second stent section 21 .

The sheath 31 is a long, tubular member made of a flexible material such as a biocompatible synthetic resin. The sheath 31 can accommodate the first stent section 11 and the second stent section 21 in a contracted state.

The shaft-shaped member 32 is an elongated member configured to be movable inside the sheath 31 along the axial direction Ax of the sheath 31. For example, the shaft-shaped member 32 has an outer shaft portion 32a and an inner shaft portion 32b inserted into the outer shaft portion 32a.

The outer shaft portion 32a is a long tubular member having a substantially constant outer diameter. A second locked portion 34 to which the second stent portion 21 is locked is provided on the distal end side of the outer shaft portion 32a.
The inner shank 32b is coaxially inserted into the outer shank 32a so that their axes are substantially aligned, and one end of the inner shank 32b is exposed from the outer shank 32a. A distal tip 35 that closes the opening at one end of the sheath 31 is attached to one end of the inner shank 32b. A first locked portion 33 to which the first stent portion 11 is locked is provided on the inner shank 32b slightly toward the other end from the distal tip 35.

When the sheath 31 of the placement device 30 is displaced toward the other end along the axial direction Ax while the position of the axial member 32 is fixed, the first stent section 11 engaged with the first interlocking portion 33 of the inner shaft section 32b is released from inside the sheath 31 into the biological lumen. At this time, the second stent section 21 engaged with the second interlocking portion 34 of the outer shaft section 32a is restricted from moving in the axial direction Ax relative to the sheath 31, and the second stent section 21 moves integrally with the sheath 31 toward the other end in the axial direction Ax.

After the first stent section 11 is released, the second stent section 21 is released so that it overlaps the first stent section 11 from the inside, while its position is confirmed using an endoscope or X-ray. Specifically, after the first stent section 11 is released, the restriction on movement of the second stent section 21, which is engaged with the second interlocking portion 34 of the outer shaft section 32a, in the axial direction Ax relative to the sheath 31 is released. Then, when the sheath 31 is displaced toward the other end along the axial direction Ax with the position of the axial member 32 fixed, the second stent section 21, which is engaged with the second interlocking portion 34 of the outer shaft section 32a, is released from inside the sheath 31 into the biological lumen.

Means for switching between restricting and releasing the axial movement of the second stent section 21 relative to the sheath 31 include, for example, a configuration in which the outer shaft section 32a is pressed and clamped from the outer surface side by an operating section (not shown) provided at the other end of the placement device 30, or a configuration in which a predetermined portion of the outer shaft section 32a is engaged with a predetermined portion of the operating section.

In this way, the first stent section 11 and the second stent section 21 can be placed at the desired position within the biological lumen using a single placement device 30. The configuration of the placement device 30 is not limited to the above. For example, a cylindrical member may be placed between the housing section for the first stent section 11 and the housing section for the second stent section 21 within the sheath 31 to separate them, preventing the second stent section 21 from being released when the first stent section 11 is released.

The effects of the stent 1 of this embodiment will be described below.
The cylindrical stent 1 of this embodiment includes a first stent section 11 and a second stent section 21 that are expandable and contractable in a radial direction substantially perpendicular to the axial direction Ax. The first stent section 11 and the second stent section 21 are placed in a biological lumen (digestive tract 3) with their opposing axial end sections 11a, 21a overlapping each other. The first stent section 11 and the second stent section 21 also have restricting sections 2 (reduced diameter section 14, expanded diameter section 24) in an overlapping region OA that restricts relative axial displacement with respect to the other stent section.
According to this embodiment, the overall length of the stent 1 placed at the lesion site can be changed by adjusting the overlapping width of the stent sections or by changing the combination of the stent sections. Furthermore, since the restricting section 2 restricts the relative axial displacement between the first stent section 11 and the second stent section 21, the overall length of the stent 1 made up of multiple stent sections is maintained. Therefore, the stent 1 of this embodiment can be placed with an axial length appropriate for the axial length of the lesion site. In other words, this embodiment can reduce the portion of the stent 1 placed in healthy tissue beyond the lesion site, thereby reducing the possibility of damage to healthy tissue.

In the stent 1 of this embodiment, the expansion forces of both the first stent section 11 and the second stent section 21 act in the overlapping region OA of the first stent section 11 and the second stent section 21, thereby enhancing the expansion force of the stent 1, thereby making it possible to expand the lesion site more reliably.
In addition, in the overlapping region OA of the first stent section 11 and the second stent section 21, the mesh of the skeleton becomes finer and shifted, making it easier to suppress the phenomenon of cell tissue from the diseased area infiltrating into the stent 1 (ingrowth).

Furthermore, the restricting section 2 of this embodiment has an engagement structure that allows the opposing ends in the axial direction Ax to engage with each other via the reduced-diameter section 14 of the first stent section 11 and the expanded-diameter section 24 of the second stent section 21. Engaging the first stent section 11 and the second stent section 21 makes it easier to more reliably restrict relative axial displacement between the deployed first stent section 11 and second stent section 21.

The present invention is not limited to the above-described embodiments, and various improvements and design changes may be made without departing from the spirit of the present invention.

The configuration of the restricting portion 2 of the present invention is not limited to the shapes of the reduced diameter portion 14 and the expanded diameter portion 24 exemplified in the above embodiment, but can be modified as appropriate.
As an example, as shown in Fig. 6 , the second stent section 21 may have a plurality of tapered, enlarged diameter sections 24 formed in the same direction in the axial direction Ax. According to the configuration shown in Fig. 6 , the overall length of the stent 1 can be adjusted by engaging any of the plurality of enlarged diameter sections 24 with the reduced diameter section 14 of the first stent section 11. Furthermore, according to the configuration shown in Fig. 6 , the reduced diameter section 14 and the enlarged diameter section 24 can be engaged at a plurality of positions in the axial direction Ax, making it easier to reliably restrict axial displacement between the deployed stent sections. Although not shown, instead of forming a plurality of enlarged diameter sections 24 in the second stent section 21, the first stent section 11 may have a plurality of tapered, enlarged diameter sections 14 formed in the same direction in the axial direction Ax.

7 is a diagram showing another example of the configuration of the restricting portion 2. In the example shown in FIG. 7, annular slits 15, 25, in which no wire is woven, are provided as the restricting portion 2 in parts of the first and second main body portions 12, 22, respectively. As shown in FIG. 7( a), the unwoven wire is arranged so as to protrude in a zigzag pattern along the circumferential direction at the slits 15, 25. When the second stent portion 21 is expanded inside the first stent portion 11, as shown in FIG. 7( b), the wire protruding in a zigzag pattern at the slits 15, 25 hooks onto the framework of the other stent portion, thereby engaging the first stent portion 11 and the second stent portion 21. This allows for the restriction of axial displacement between the deployed stent portions.
The axial lengths of the slits 15, 25 and the lengths of the portions of the first and second body portions 12, 22 distal to the slits 15, 25 are merely examples and are not intended to be limiting and can be changed as appropriate. For example, the portion of the second body portion 22 distal to the slit 25 may be hooked onto the slit 15, or the portion of the first body portion 12 distal to the slit 15 may be hooked onto the slit 25.

Furthermore, although not shown in the figures, the first stent section 11 may have multiple slits 15 formed in the axial direction, and the second stent section 21 may have multiple slits 25 formed in the axial direction. This allows the first stent section 11 and the second stent section 21 to be engaged at multiple positions in the axial direction using multiple slits 15 or multiple slits 25, thereby more reliably restricting axial displacement between the deployed stent sections 11, 21.

As another example of the configuration of the restricting section 2 of the present invention, a locking pin (such as a barb) that hooks onto the framework of the other stent section may be provided on at least one of the inner periphery of the first stent section 11 or the outer periphery of the second stent section 21. In this case, the locking pin hooks onto the framework of the other stent section, engaging the first stent section 11 and the second stent section 12, thereby restricting axial displacement between the deployed stent sections.

As another example of the configuration of the restricting portion 2 of the present invention, when the stent 1 has a coating portion, the two coating portions may be bonded together to restrict axial displacement of the stent portions. For example, the coating portion may be formed using a biocompatible, soluble material, and the coating portions may be bonded together by dissolving the coating. In the above, the coating material may begin to dissolve at a temperature around body temperature, or may begin to dissolve upon contact with water or components of bodily fluids such as blood. Alternatively, a biocompatible adhesive layer made of a medical adhesive or the like may be formed on the surface of the coating portions to bond them together.

In addition, the embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

DESCRIPTION OF SYMBOLS 1... stent, 2... restricting portion, 3... digestive tract, 3a... lesion site, 11... first stent portion, 12... first main body portion, 14... reduced diameter portion, 21... second stent portion, 22... second main body portion, 24... expanded diameter portion, 30... placement device, 31... sheath

Claims (3)

A cylindrical stent to be placed in a biological lumen,
a plurality of stent sections that are expandable and contractable in a radial direction substantially perpendicular to the axial direction;
the plurality of stent sections are placed in the biological lumen with opposing axial end portions overlapping each other,
At least one of the plurality of stent sections has a restriction section in an area overlapping with the other stent section, which restricts relative displacement in the axial direction with respect to the other stent section,
The end of the one stent section into which the end of the other stent section is inserted is inclined so that the outer diameter decreases toward the tip side in the axial direction.
Stent. A cylindrical stent to be placed in a biological lumen,
a plurality of stent sections that are expandable and contractable in a radial direction substantially perpendicular to the axial direction;
the plurality of stent sections are placed in the biological lumen with opposing axial end portions overlapping each other,
At least one of the plurality of stent sections has a restriction section in an area overlapping with the other stent section, which restricts relative displacement in the axial direction with respect to the other stent section,
The end of the other stent section that is inserted into the end of the one stent section is inclined so that the outer diameter increases toward the tip side in the axial direction.
Stent. 3. The stent according to claim 1, wherein the restricting portion has an engaging structure that allows opposing axial ends of the plurality of stent portions to engage with each other.