COVERED STENT MANUFACTURING METHOD AND COVERED STENT

Provided is a covered stent manufacturing method including: disposing an inner cover inside a stent body having a mesh structure formed by knitting wires, the stent body having engagement portions, each of which is formed by hooking two bent portions of the wires with each other; disposing an outer cover outside the stent body; forming a slack portion that expands in a radial direction of the stent body in at least one of the covers, the slack portion creating slack that allows movements of the two bent portions in a longitudinal direction and the radial direction of the stent body in at least one of the covers; and joining the covers with each other in regions on an inner side of the mesh of the mesh structure.

TECHNICAL FIELD

The present invention relates to a covered stent manufacturing method and a covered stent.

BACKGROUND ART

In the related art, there is a known covered stent that is disposed in a constricted portion of a lumen in order to release the constriction (for example, see Patent Literatures 1 and 2). A covered stent includes a cover that covers at least one of inside or outside of a tubular stent body. The cover prevents tissue from infiltrating into the interior of the stent placed in a lumen.

In the covered stent of Patent Literature 1, an inner cover and an outer cover are bonded to each other in mesh portions of a mesh-like stent body. Accordingly, the covers are prevented from being twisted when the stent body is expanded, and the inner and outer covers can be bent together with the stent body.

In the covered stent of Patent Literature 2, a plurality of bonding portions in which an inner cover and an outer cover are bonded to each other are formed with spacings between each other and pockets that allow a stent body to move are formed between the bonding portions adjacent to each other.

Accordingly, the covered stent can be compressed in a radial direction with a small force.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

An aspect of the present invention is a covered stent manufacturing method including: disposing an inner cover inside a stent body having a mesh structure formed by knitting wires, the stent body having engagement portions, each of which is formed by hooking two bent portions of the wires with each other; disposing an outer cover outside the stent body; forming a slack portion that expands in a radial direction of the stent body in at least one of the inner cover or the outer cover, the slack portion creating slack that allows movements of the two bent portions in a longitudinal direction and the radial direction of the stent body in at least one of the inner cover or the outer cover; and joining the inner cover and the outer cover with each other in regions on an inner side of the mesh of the mesh structure.

Another aspect of the present invention is a covered stent including: a stent body that has a mesh structure formed by knitting wires and that has engagement portions, each of which is formed by hooking two bent portions of the wires with each other; an inner cover that covers an inside of the stent body; and an outer cover that covers an outside of the stent body, wherein at least one of the inner cover or the outer cover has a slack portion that expands in a radial direction of the stent body, the slack portion creating slack that allows movements of the two bent portions in a longitudinal direction and the radial direction of the stent body in at least one of the inner cover or the outer cover, and the inner cover and the outer cover are joined with each other in regions on an inner side of the mesh of the mesh structure.

Another aspect of the present invention is a covered stent manufacturing method including: disposing, at least inside or outside a stent body, a cover made of an ePTFE in an orientation in which a stretching direction of the ePTFE is aligned with a stretching direction of the stent body when the stent body is contracted in a radial direction; partially connecting the cover with the stent body; and creating slack in the cover by contracting the stent body in the radial direction and stretching the cover.

Another aspect of the present invention is a covered stent including: a stent body; and a cover that is made of an ePTFE, that covers at least one of inside or outside of the stent body, and that is partially connected to the stent body, wherein the cover is disposed in an orientation in which a stretching direction of the ePTFE is aligned with a stretching direction of the stent body when the stent body is contracted in a radial direction, and the cover has slack in a longitudinal direction of the stent body in a state in which the stent body is expanded in the radial direction.

DESCRIPTION OF EMBODIMENTS

First Embodiment

A covered stent manufacturing method and a covered stent according to a first embodiment of the present invention will be described with reference to the drawings.

As shown inFIG.1, a covered stent1according to this embodiment includes a tubular stent body2, a tubular inner cover3that covers the inside of the stent body2, and a tubular outer cover4that covers the outside of the stent body2.

The stent body2is formed by knitting one or more wires2awhile the wires2aare bent in a zigzag manner and wound about a center axis and has a mesh structure in which numerous rhombus meshes are arrayed in a circumferential direction and a longitudinal direction. The stent body2can be contracted in a radial direction. The covered stent1is mounted on a delivery system in a contracted state, is transported into a body cavity by means of the delivery system, and is expanded in the radial direction in the body cavity.

As shown inFIG.2A, the stent body2has engagement portions2b, each of which consists of two bent portions2c,2dof the wires2ahooked on each other in the longitudinal direction of the stent body2. The bent portions2care peak portions that are bent toward one end of the stent body2and protrude toward the other end thereof. The bent portions2dare valley portions that are bent toward the other end of the stent body2and protrude toward the one end thereof. The zigzagging wires2ahave the peak portions2cand the valley portions2dthat are arrayed in the circumferential direction in an alternating manner. The engagement portions2bare formed by hooking the peak portions2cin one column with the valley portions2din another column adjacent thereto.

Accordingly, the two bent portions2c,2dare linked with each other so as to be freely displaced in the longitudinal direction and the radial direction. As a result of the three-dimensional displacement of the bent portions2c,2din the engagement portions2b, the stent body2can be easily bent by generating nearly or entirely no axial force.

The inner cover3and the outer cover4are sheets made of an expanded polytetrafluoroethylene (ePTFE). The material of the covers3,4may be other materials that have biocompatibility and flexibility and that are generally used in stents, for example, silicone. The inner cover3and the outer cover4are joined with each other in joining portions5, which are portions of regions on an inner side of the mesh, and are separated from each other in portions other than the joining portions5.

As shown inFIG.2B, the inner cover3has a plurality of slack portions6that are arrayed in the longitudinal direction with spacings therebetween. Each of the slack portions6consists of a depression that extends over the entire circumference of the inner cover3and expands radially inward, and is, for example, a U-shaped groove having a rectangular cross-sectional shape in a longitudinal cross section in the longitudinal direction. Some of the engagement portions2bare disposed between the slack portions6and the outer cover4.

The slack portions6form spaces between the inner cover3and the outer cover4and, in addition, create slack in the inner cover3. The inner cover3having slack can freely deform in accordance with an external force and allows movements of the pair of bent portions2c,2d, forming each of the engagement portions2b, in the longitudinal direction and the radial direction. Therefore, the movable ranges of the bent portions2c,2din the engagement portions2bincrease and the covers3,4are prevented from hindering the three-dimensional displacements of the bent portions2c,2dwhen the covered stent1is bent. Accordingly, a low axial force and high flexibility are realized in the covered stent1.

FIGS.3and4describe the relationship between the displacement of the bent portions2c,2ddue to bending of the covered stent1and the deformation of the covers3,4having slack. InFIGS.3and4, the left diagram is a diagram in which the stent body2inside a bend is viewed from the front, the center diagram is a schematic diagram of the cover3inside the bend and the cover4outside the bend, and the right diagram is a schematic diagram of the wires2ainside and outside the bend. InFIGS.3and4, the inner cover3and the outer cover4both have slack.

When the covered stent1is bent from the straight shape inFIG.3to the bent shape inFIG.4, apexes of the two bent portions2c,2din each of the engagement portions2bare displaced in opposite directions with respect to each other in the longitudinal direction inside and outside the bend and displaced radially inward. At this time, the covers3,4having slack are deformed in accordance with the longitudinal direction and radially inward displacements of the bent portions2c,2d. Therefore, when the covered stent1is bent, the two bent portions2c,2dcan be displaced in the same manner as in the case in which the covers3,4are not present, and thus, it is possible to realize a low axial force.

Next, the covered stent manufacturing method according to this embodiment will be described.

As shown inFIG.5, the covered stent manufacturing method includes: step SA1of disposing the inner cover3on a first jig20; step SA2of forming the slack portions6in the inner cover3; step SA3of disposing the inner cover3inside the stent body2; step SA4of disposing the outer cover4outside the stent body2; step SA5of joining the inner cover3and the outer cover4with each other; and SA6of removing the covered stent1from the jig20.

As shown inFIG.6, the jig20is a columnar core rod and, on an outer surface of the core rod20, a plurality of depressions20athat are arrayed in the longitudinal direction with spacings therebetween are formed. The plurality of depressions20aare structures for forming the slack portions6. Each of the depressions20aextends over the entire circumference and is depressed radially inward. Protrusions20bare formed between the depressions20aadjacent to each other.

As shown inFIG.7, the inner cover3is disposed on the outer surface of the core rod20(step SA1). The form of the inner cover3is selected from a tube, a tape, and a sheet. In the case of a tape shape or a sheet shape, the inner cover3is disposed on the core rod20after being molded and joined into a tube shape in advance or is wound around the core rod20without any gap.

Next, the slack portions6are formed by pushing the inner cover3into the depressions20aby using push tools30(step SA2). The push tools30are, for example, rod-shaped or ring-shaped members. As a result of the inner cover3being deformed along inner surfaces of the depressions20a, the slack portions6having dimensions and shapes corresponding to the dimensions and the shapes of the depressions20aare formed. In order to reliably cause the inner cover3to be deformed along the inner surfaces of the depressions20a, a distal-end portion of each of the push tools30may have an outer surface shape that is complementary to the inner surface shape of each of the depressions20a.

Next, the stent body2is disposed on an outer surface of the inner cover3by inserting the core rod20into the stent body2(step SA3). The stent body2and the inner cover3are aligned with respect to each other at positions at which the engagement portions2bare disposed at the slack portions6.

Next, the outer cover4is disposed on the stent body2and the stent body2is covered with the outer cover4(step SA4). As in the inner cover3, the form of the outer cover4is selected from a tube, a tape, and a sheet. In the case of a tube shape, the core rod20on which the inner cover3and the stent body2are disposed is inserted into the outer cover4. In the case of a tape shape or a sheet shape, the core rod20is inserted into the outer cover4molded into a tube shape in advance or the outer cover4is wound around the core rod20over the entire circumference thereof.

Next, in some regions on an inner side of the mesh of the stent body2, the inner cover3and the outer cover4are joined by using a joining tool40by means of a method such as thermocompression bonding, and the joining portions5are consequently formed (step SAS). The regions to be joined are regions on the inner side of the mesh on the protrusions20b, and each of the joining portions5is formed between the two engagement portions2bdisposed at the two slack portions6adjacent to each other (seeFIG.2A).

Next, by removing the core rod20from inside the inner cover3, the covered stent1having the slack portions6is manufactured (step SA6).

Accordingly, with the manufacturing method of this embodiment, it is possible to manufacture the covered stent1with a low axial force and high flexibility, in which the inner cover3has slack due to the slack portions6and the covers3,4do not hinder bending of the stent body2.

In addition, the movable ranges of the bent portions2c,2ddepend on the dimensions of the slack portions6. In step SA2, the slack portions6having the dimensions equivalent to those of the depressions20aare formed by pushing the inner cover3into the depressions20aof the core rod20.

Accordingly, it is possible to form the slack portions6having desired dimensions by easily and accurately controlling the dimensions of the slack portions6, such as the depths and the widths thereof, and it is possible to reliably achieve desired bending properties in the covered stent1. In addition, by varying the dimensions, the shapes, etc. of the depressions20aat different positions, it is possible to easily form the slack portions6having different sizes and shapes at different positions.

Excessive slack in the inner cover3causes the diameter of the covered stent1in the contracted state to increase, and, consequently, a sliding resistance of the covered stent1with respect to the delivery system increases when the covered stent1is released from the delivery system, and thus, a large operating force is required. In addition, excessive slack in the inner cover3could decrease the volume of a hollow portion inside the covered stent1through which a substance passes in the body cavity. Therefore, it is important to control the dimensions of the slack portions6to be desired dimensions. With this embodiment, as described above, as a result of using the core rod20having the depressions20a, it is possible to easily and accurately control the dimensions of the slack portions6.

In addition, of the covers3,4forming a double structure, only the inner cover3has the slack portions6and the outer cover4does not have the slack portions. Therefore, it is possible to decrease the sliding resistance exerted when the covered stent1is released from the delivery system.

In this embodiment, the slack portions6are U-shaped grooves having flat bottom walls; however, the shapes of the slack portions6are not limited thereto and can be changed, as appropriate.

FIGS.8A and9Ashow other examples of the longitudinal cross-sectional shape of the slack portions6. A slack portion6inFIG.8Ahas a substantially M-shape and has two side walls that are parallel to each other in the radial direction and a bent bottom wall that protrudes radially outward. A slack portion6inFIG.9Ahas a substantially V-shape having two side walls that form an angle between each other, wherein one of the side walls is parallel to the radial direction and the other side wall is inclined with respect to the radial direction. Such slack portions6are formed by pushing the inner cover3into substantially M-shaped or substantially V-shaped depressions20a. The distal-end portion of each of the push tools30may have a shape corresponding to the shape of each of the depressions20a.

FIGS.8B and9Bshow the slack portions6folded in the radial direction with a compression force.

In the case of the substantially M-shaped slack portions6, the two side walls are folded outward and stacked on portions of the inner cover3constituting the slack portions6in the radial direction outside openings of the slack portions6. In the case of the substantially V-shaped slack portions6, the two side walls are folded outward in the same direction and stacked on the portions of the inner cover3constituting the slack portions6in the radial direction outside openings of the slack portions6.

As described above, the substantially M-shaped and substantially V-shaped slack portions6are deformed into the prescribed folded shapes due to a compression force in the radial direction. Therefore, when the covered stent1is mounted on the delivery system, it is possible to fold the slack portions6into the prescribed shapes simply by compressing the covered stent1in the radial direction.

The thickness increases in the portions in which the portions of the inner cover3are stacked in the radial direction due to folding of the slack portions6(see the areas indicated by arrows inFIGS.8B and9B). Such thick portions are preferably disposed at positions displaced from the engagement portions2bin which the two portions2c,2dof the wires2aare stacked in the radial direction. With the slack portions6inFIGS.8A to9B, it is possible to control the folded shapes of the slack portions6so that the thick portions are disposed in regions in which interference with the engagement portions2bdoes not occur.

Second Embodiment

Next, a covered stent manufacturing method and a covered stent according to a second embodiment of the present invention will be described.

In this embodiment, configurations that are different from those of the first embodiment will be described and configurations that are the same as those of the first embodiment will be given the same reference signs, and the descriptions thereof will be omitted.

The covered stent according to this embodiment includes the stent body2, the inner cover3, and the outer cover4. The covered stent of this embodiment differs from the covered stent1of the first embodiment in that the inner cover3has slack portions6and the outer cover4has slack portions7(seeFIG.11).

The outer cover4has the plurality of slack portions7that are arrayed in the longitudinal direction of the outer cover4with spacings therebetween and that are formed at the same positions as the slack portions6. As in the slack portions6, each of the slack portions7consists of a depression that extends over the entire circumference of the outer cover4and expands radially inward, and is, for example, a U-shaped groove having a rectangular cross-sectional shape in a longitudinal cross section in the longitudinal direction. Some of the engagement portions2bare disposed between the slack portions6and the slack portions7.

As in the inner cover3, the outer cover4in which slack is created by the slack portions7can freely deform in accordance with an external force and allows movements of the pair of bent portions2c,2d, forming each of the engagement portions2b, in the longitudinal direction and the radial direction. Therefore, the covers3,4are prevented from hindering the three-dimensional displacements of the bent portions2c,2dwhen the covered stent is bent. Accordingly, a low axial force and high flexibility are realized in the covered stent.

As shown inFIG.10, the covered stent manufacturing method according to this embodiment includes: step SB1of disposing the inner cover3on the jig20; step SB2of disposing the inner cover3inside the stent body2; step SB3of disposing the outer cover4outside the stent body2; step SB41of forming the slack portions6in the inner cover3; step SB42of forming the slack portions7in the outer cover4; step SB5of joining the inner cover3and the outer cover4with each other; and step SB6of removing the covered stent from the jig20.

The steps of forming the slack portions6and7include: step SB41of forming the slack portions6in the inner cover3before step SB3; and step SB42of forming the slack portions7in the outer cover4after step SB3.

As shown inFIG.11, as in step SA1, the inner cover3is disposed on the outer surface of the core rod20(step SB1).

Next, as in step SA2, the slack portions6are formed by pushing the inner cover3into the depressions20aby using the push tools30(step SB41).

Next, as in step SA3, the stent body2is disposed on the outer surface of the inner cover3by inserting the core rod20into the stent body2(step SB2).

Next, as in step SA4, the outer cover4is disposed on the stent body2and the stent body2is covered with the outer cover4(step SB3).

Next, the slack portions7are formed by pushing the outer cover4into the depressions20aby using the push tools30(step SB42).

Next, in some regions on the inner side of the mesh of the stent body2, the inner cover3and the outer cover4are joined by using the joining tool40by means of a method such as thermocompression bonding, and the joining portions5are consequently formed (step SB5). As shown inFIG.12A, the regions to be joined are regions between the two engagement portions2badjacent to each other disposed in the same slack portions6,7, and the joining portions5are formed in the slack portions6,7. The regions to be joined may be the same as the joining portions5in the first embodiment. In addition, as shown inFIG.12B, joining portions5having large areas may be formed in wide slack portions6,7.

Next, by removing the core rod20from inside the inner cover3, the covered stent having the slack portions6and7is manufactured (step SB6).

Accordingly, with the manufacturing method of this embodiment, it is possible to manufacture the covered stent with a low axial force and high flexibility, in which the inner covers3,4both have slack due to the slack portions6,7and the covers3,4do not hinder bending of the stent body2.

In addition, the slack portions6,7having the dimensions equivalent to those of the depressions20aare formed by pushing the inner covers3,4into the depressions20aof the core rod20. Accordingly, it is possible to form the slack portions6,7having desired dimensions by easily and accurately controlling the dimensions of the slack portions6,7.

In this embodiment, the slack portions6,7may have shapes that deform into prescribed folded shapes, as shown inFIGS.8A and9A, as in the first embodiment.

In this embodiment, the slack portions6and the slack portions7are formed in different steps SB41and SB42; however, alternatively, the slack portions6and7may be simultaneously formed in single step SB4.

FIGS.13and14describe a first modification of the manufacturing method of the second embodiment. In this modification, step SB4of forming the slack portions6and7is performed by simultaneously pushing the inner cover3and the outer cover4into the depressions20aby using the push tools30after step SB3. With this modification, it is possible to decrease the number of steps.

The formation of the slack portions6and7and the joining of the covers3,4may simultaneously be performed in the single step SB45.

FIGS.15and16describe a second modification of the manufacturing method of the second embodiment. In this modification, step SB45is performed by joining the covers3,4with each other by means of a joining tool40, such as a pressurizing or heating pin, while the covers3,4are simultaneously being pushed into the depressions20aby using the joining tool40, after step SB3. With this modification, it is possible to further decrease the number of steps.

In this embodiment, the slack portions6are formed and the covers3,4are subsequently joined with each other; however, alternatively, the covers3,4may be joined with each other (step SB5) and the slack portions6,7may subsequently be formed (step SB4).

FIGS.17and18describe a third modification of the manufacturing method of the second embodiment. In this modification, the inner cover3and the outer cover4are joined with each other in the regions on the inner side of the mesh on the protrusions20band the joining portions5are formed (step SB5), as in the joining portions5in the first embodiment (seeFIG.2A). Subsequently, the covers3,4are pushed into the depressions20a, and the slack portions6,7are formed as a result of the stretching of the covers3,4(step SB4).

Third Embodiment

Next, a covered stent manufacturing method and a covered stent according to a third embodiment of the present invention will be described.

In this embodiment, configurations that are different from those of the first embodiment will be described and configurations that are the same as those of the first embodiment will be given the same reference signs, and the descriptions thereof will be omitted.

The covered stent according to this embodiment includes the stent body2, the inner cover3, and the outer cover4. The covered stent of this embodiment differs from the covered stent1of the first embodiment in that the stent body2is disposed at the slack portions6of the inner cover3(seeFIG.21).

The inner cover3has, in addition to the plurality of slack portions6that extend in the circumferential direction and that are arrayed in the longitudinal direction, a plurality of slack portions6that extend in the longitudinal direction and that are arrayed in the circumferential direction. the slack portions6are continuous with each other and form, as a whole, grid-like depressions in the inner cover3. The wires2aof the stent body2are disposed inside the slack portions6.

As shown inFIG.19, the covered stent manufacturing method according to this embodiment includes: step SC1of disposing the inner cover3on a first jig21; step SC2of forming the slack portions6by disposing the stent body2outside the inner cover3; step SC3of disposing the outer cover4outside the stent body2; step SC4of joining the inner cover3and the outer cover4with each other; and step SC5of removing the covered stent from the jig21.

As shown inFIG.20, the jig21has a plurality of protrusions21bthat are arrayed in the longitudinal direction and the circumferential direction with spacings therebetween. The protrusions21bare columnar protrusions that protrude radially outward from an outer circumferential surface of the jig21. Between the protrusions21b, depressions21athat extend in the circumferential direction and depressions21athat extend in the longitudinal direction are formed, and the depressions21aare continuous with each other.

As shown inFIG.21, the inner cover3is disposed on the protrusions21bof the core rod20(step SC1).

Next, the stent body2is disposed on the outer surface of the inner cover3so that the protrusions21bare positioned on the inner side of the mesh. Accordingly, the inner cover3is depressed radially inward in the regions of the depressions21aand the slack portions6are formed in the depressions21a(step SC2).

Next, the outer cover4is disposed outside the inner cover3and the stent body2is covered with the outer cover4(step SC3).

Next, the joining portions5are formed by joining the inner cover3and the outer cover4with each other in the regions of the protrusions21b(step SC4).

Next, by removing the core rod21from inside the inner cover3, the covered stent having the slack portions6is manufactured (step SC5).

Accordingly, with the manufacturing method of this embodiment, the slack portions6are formed by disposing the stent body2on the inner cover3; therefore, special push tools30are not required. In addition, the entire inner cover3is uniformly pressed radially inward by the stent body2; therefore, it is possible to form the slack portions6having desired dimensions by easily and accurately controlling the dimensions of the slack portions6even if the push tools30are not used.

In addition, only the inner cover3has the slack portions6and the outer cover4does not have slack portions; therefore, it is possible to decrease the sliding resistance exerted when the covered stent is released from the delivery system.

In this embodiment, the plurality of depressions21ain the circumferential direction and the longitudinal direction are continuous with each other; however, alternatively, the depressions21ain the two directions may be independent of each other, as in the depressions20ain the first embodiment.

Fourth Embodiment

Next, a covered stent manufacturing method and a covered stent according to a fourth embodiment of the present invention will be described.

In this embodiment, configurations that are different from those of the first embodiment will be described and configurations that are the same as those of the first embodiment will be given the same reference signs, and the descriptions thereof will be omitted.

The covered stent according to this embodiment includes the stent body2, the inner cover3, and the outer cover4. The covered stent of this embodiment differs from the covered stent1of the first embodiment in that the inner cover3does not have slack portions6and the outer cover4has the slack portions7that expand radially outward.

The outer cover4has the plurality of slack portions7that are arrayed in the longitudinal direction with spacings therebetween. Each of the slack portions7consists of a depression that extends over the entire circumference of the outer cover4and expands radially outward. Some of the engagement portions2bare disposed between the inner cover3and the slack portions7. The slack portions7form spaces between the inner cover3and the outer cover4, and, in addition, create slack in the outer cover4. Therefore, as in the inner cover3of the first embodiment, the outer cover4allows movements of the pair of bent portions2c,2d, forming each of the engagement portions2b, in the longitudinal direction and the radial direction, and thus, the covers3,4are prevented from hindering the three-dimensional displacements of the bent portions2c,2dwhen the covered stent is bent. Accordingly, a low axial force and high flexibility are realized in the covered stent.

As shown inFIG.22, the covered stent manufacturing method according to this embodiment includes: step SD1of disposing the inner cover3on a first jig22; step SD2of disposing the inner cover3inside the stent body2; step SD3of disposing the outer cover4on a second jig23; step SD4of forming the slack portions7in the outer cover4; step SD5of disposing the outer cover4outside the inner cover3; step SD6of joining the inner cover3and the outer cover4with each other; and step SD7of removing the covered stent from the jigs22and23.

FIGS.23A to23Cshow the jigs22and23used in this embodiment.

The first jig22is a columnar core rod and an outer surface of the core rod22is a cylindrical surface without unevenness.

The second jig23is a cylindrical member and, on a cylindrical inner surface (mounting surface)23aof the second jig23, a plurality of depressions23bthat are arrayed in the longitudinal direction with spacings therebetween are formed. The plurality of depressions23bare structures for forming the slack portions7. Each of the depressions23bextends over the entire circumference and are depressed radially outward. As shown inFIGS.23B and23C, in order to make it possible to expose the inner surface23a, the second jig23may consist of two half bodies231and232that are semi-cylindrical. The two half bodies231and232may be separated from each other (seeFIG.23B) or may be connected so as to allow opening/closing thereof (seeFIG.23C).

As shown inFIG.24, the inner cover3is disposed on the outer surface of the core rod22(step SD1), as in step SA1. Next, the stent body2is disposed on the outer surface of the inner cover3(step SD2), as in step SA3.

Next, the outer cover4is disposed on the inner surface23aof the second jig23(step SD3).

Next, the slack portions7are formed by pushing the outer cover4into the depressions23bby using the push tools30(not shown) (step SD4).

Next, the outer cover4is disposed outside the stent body2by inserting the core rod22into the second jig23(step SD5). Here, the outer cover4is aligned with respect to the stent body2at a position at which a joining mechanism (not shown) provided in the second jig23is disposed at a center of the mesh of the stent body2. The joining mechanism is for the joining of the covers3,4. For example, the joining mechanism is a pin that protrudes from the inner surface23aof the second jig23and pressurizes or heats the covers3,4or is a through-hole through which a separate joining tool passes from outside to inside the second jig23.

Next, the covers3,4are joined with each other in some regions on the inner side of the mesh by utilizing the joining mechanism, and the joining portions5are consequently formed (step SD6).

Next, by removing the core rod22from inside the inner cover3, the covered stent having the slack portions7is manufactured (step SD7).

Accordingly, with the manufacturing method of this embodiment, it is possible to manufacture the covered stent with a low axial force and high flexibility, in which the outer cover4has slack due to the slack portions7and the covers3,4do not hinder bending of the stent body2.

In addition, the slack portions7having the dimensions equivalent to those of the depressions23bare formed by pushing the outer cover4into the depressions23bof the second jig23. Accordingly, it is possible to form the slack portions7having desired dimensions by easily and accurately controlling the dimensions of the slack portions7.

In addition, of the covers3,4forming a double structure, only the outer cover4has the slack portions7and the inner cover3does not have slack portions. Therefore, the inner surface of the covered stent is a smooth surface without unevenness and a substance in the body can smoothly flow in the hollow portion inside the covered stent.

In this embodiment, the inner cover3does not have slack portions; however, alternatively, the inner cover3may have the slack portions6described in the first to third embodiments.

In this case, instead of the first jig22, a first jig having depressions, such as the core rod20,21of the first to third embodiments, is used in combination with the second jig23. Accordingly, it is possible to manufacture the covered stent in which the inner cover3has the radial slack portions6that expand radially inward and the outer cover4has the slack portions7that expand radially outward. Furthermore, it is possible to vary the dimensions and the shapes of the slack portions6and the slack portions7with respect to each other.

Fifth Embodiment

Next, a covered stent manufacturing method and a covered stent according to a fifth embodiment of the present invention will be described.

This embodiment is a modification of the fourth embodiment and differs from the fourth embodiment in terms of the covered stent manufacturing method. In this embodiment, configurations that are different from those of the first and fourth embodiments will be described and configurations that are the same as those of the first and fourth embodiments will be given the same reference signs, and the descriptions thereof will be omitted.

The covered stent according to this embodiment includes the stent body2, the inner cover3, and the outer cover4, and the outer cover4has the slack portions7that expand radially outward.

The covered stent manufacturing method according to this embodiment includes steps SD1, SD2, SD3, SD4, SD5, SD6, and SD7described in the fourth embodiment.

FIG.25Ashows a second jig24used in this embodiment. The second jig24is a flat member having a rectangular flat mounting surface24aand a plurality of depressions24bthat are arrayed in the longitudinal direction with spacings therebetween are formed on the mounting surface24a. The depressions24bare structures for forming the slack portions7. Each of the depressions24bconsists of a groove that extends over the entire width of the mounting surface24a. The second jig24may be formed from a hard material or may be formed from a flexible material, for example, silicone.

In this embodiment, the outer cover4is disposed on the mounting surface24aof the second jig24(step SD3).

Next, the slack portions7are formed by pushing the outer cover4into the depressions24bby using the push tools30(step SD4).

Next, as shown inFIG.26A, the outer cover4is disposed on the stent body2by winding the outer cover4around the core rod21by rotating the mounting surface24aabout the core rod22(step SD5). After the outer cover4is disposed, the second jig24is removed. InFIGS.26A and26B, the illustrations of the stent body2and the inner cover3are omitted.

In the case in which the second jig24possesses flexibility, as shown inFIG.26B, the outer cover4may be disposed on the stent body2by winding the second jig24around the core rod22. In this case, the inner cover3and the outer cover4may be joined with each other (step SD6) by using the joining mechanism or the like described in the fourth embodiment while the state in which the second jig24is wound around the core rod22is maintained, and the second jig24may subsequently be removed.

Accordingly, with the manufacturing method of this embodiment, the second jig24has a simple shape in which the depressions24bare machined on the flat mounting surface24a. Therefore, it is possible to form the depressions24bhaving various shapes and dimensions in a highly precise manner and it is possible to manufacture a covered stent having the slack portions7having various shapes and dimensions.

FIG.25Bshows another example of the second jig24. Accordingly, it is possible to easily form the depressions24bin an inclined direction. The second jig24inFIG.26Bis used in combination with the stent body2that is formed by knitting the wires2awhile winding the wires in a spiraling manner and in which the engagement portions2bare arrayed in a spiraling manner.

In this embodiment, the covered stent in which the inner cover3has the slack portions6and the outer cover4has the slack portions7may be manufactured, as in the fourth embodiment, by using the first jig having the depressions and the second jig24in combination.

In this embodiment, the slack portions6,7may have the shapes that deform into the prescribed folded shapes shown inFIGS.8A and9A, as in the first embodiment.FIGS.27A and27Bshow other examples of the shapes of the slack portions6,7that are deformed into the prescribed folded shapes due to the compression in the radial direction. Accordingly, the shapes of the slack portions6,7can be changed in various manners.

In the above-described first, second, fourth, and fifth embodiments, the push tools30are used as means for pushing the covers3,4into the depressions20a,23b,24b; however, alternatively, other means may be used.

For example, suction holes may be provided in inner surfaces of the depressions20a,23b,24band the covers3,4may be sucked into the depressions20a,23b,24bby means of suction. By employing such a means also, it is possible to push the covers3,4into the depressions20a,23b,24band to cause deformations thereof along the inner surfaces of the depressions20a,23b,24b.

Sixth Embodiment

Next, a covered stent manufacturing method and a covered stent according to a sixth embodiment of the present invention will be described.

In this embodiment, configurations that are different from those of the first embodiment will be described and configurations that are the same as those of the first embodiment will be given the same reference signs, and the descriptions thereof will be omitted.

As shown inFIG.28A, a covered stent10according to this embodiment includes: the stent body2; a tubular outer cover41that covers the outside of the stent body2; and securing covers8that are disposed inside the stent body2at two end portions thereof.

The stent body2can be deformed into a contracted state from an expanded state due to contraction in the radial direction and is mounted on a delivery system in the contracted state. As shown inFIG.28B, the stent body2stretches in the longitudinal direction due to the contraction in the radial direction and a length L2of the stent body2in the contracted state increases by, for example, about 20% to 50%, as compared with a length L1of the stent body2in the expanded state.

The securing covers8are formed from an ePTFE and are disposed inside the stent body2over the entire circumference at the two end portions thereof. Two end portions of the outer cover41are joined with the securing covers8and the outer cover41is consequently connected to the stent body2at the two end portions.

The outer cover41is formed from an ePTFE and includes a stretching direction A in which high ductility is exhibited. Specifically, the outer cover41easily stretches in the stretching direction A and does not easily stretch in a direction orthogonal to the stretching direction. The stretching properties of such an outer cover41result from an ePTFE manufacturing method. The ePTFE manufacturing method includes a step of stretching PTFE and a step of sintering the stretched PTFE. Stretching the PTFE forms nodes that are distributed in an island-like manner and fibrils that extend in the stretching direction between the nodes, and the ePTFE exhibits high ductility in the stretching direction A in which the fibrils are oriented.

The outer cover41is disposed in the orientation in which the stretching direction A is aligned with the longitudinal direction of the stent body2. In addition, in the expanded state, the outer cover41has slack in the longitudinal direction. In other words, the total length of the outer cover41corresponds to the length in which an extra length is added to the length L1of the stent body2in the expanded state. Such an outer cover41is freely deformed in accordance with an external force in the expanded state and allows movements of the pair of bent portions2c,2d, forming each of the engagement portions2b, in the longitudinal direction and the radial direction. Therefore, the outer cover41is prevented from hindering the three-dimensional displacements of the bent portions2c,2dwhen the covered stent10is bent and a low axial force and high flexibility are realized in the covered stent10.

Furthermore, the stretching direction A of the outer cover41is aligned with the stretching direction of the stent body2when being contracted; therefore, the outer cover41is prevented from being broken or peeled off from the stent body2due to the stretching of the stent body2. In the case in which the ductility of the outer cover is low in the stretching direction of the stent body, breakage, such as the outer cover being broken or being peeled off from the stent body, could occur due to the contraction of the covered stent.

Next, the covered stent manufacturing method according to this embodiment will be described.

As shown inFIG.29, the covered stent manufacturing method includes: step SE1of preparing the outer cover41and the securing covers8; step SE2of disposing the securing covers8on the jig22; step SE3of disposing the securing covers8inside the stent body2; step SE4of disposing the outer cover41outside the stent body2; step SE5of partially connecting the outer cover41with the stent body2; and step SE6of stretching the outer cover41by contracting the stent body2in the radial direction.

As shown inFIG.30, the rectangular outer cover41and the band-like securing covers8out cut out from ePTFE sheets in consideration of the stretching direction A of the ePTFE (step SE1). The outer cover41includes a length direction and a width direction that respectively correspond to the longitudinal direction and the circumferential direction of the stent body2. The outer cover41is cut out from the sheet so that the length direction of the outer cover41is aligned with the stretching direction A of the ePTFE.

Next, as shown inFIG.31, the securing covers8are wound around two sites in the jig22(step SE2). The jig22is a core rod having a cylindrical outer surface without unevenness.

Next, the securing covers8are disposed inside the stent body2at the two end portions thereof by inserting the core rod22into the stent body2(step SE3).

Next, the outer cover41is disposed outside the stent body2by aligning the length direction of the outer cover41with the longitudinal direction of the stent body2and winding the outer cover41around the core rod22over the entire circumference thereof (step SE4).

Next, the outer cover41is connected to the stent body2by joining the two end portions of the outer cover41with the securing covers8by means of an arbitrary joining method, such as thermocompression bonding or an adhesive (step SE5). In step SE5, the outer cover41is formed into a tubular shape by also joining end portions of the outer cover41in the width direction with other portions of the outer cover41over the entire length thereof. By removing the core rod22from inside the stent body2after the joining, an assembly of the stent body2, the outer cover41, and the securing covers8is removed from the core rod22.

Next, the outer cover41is stretched in the longitudinal direction together with the stent body2by contracting the stent body2in the radial direction (step SE6). Step SE6may be performed by inserting the assembly into a tube50having an inner diameter that is smaller than the diameter of the assembly in the expanded state. Accordingly, the length of the outer cover41increases and slack is formed in the outer cover41with respect to the length of the stent body2in the expanded state.

Accordingly, with the manufacturing method of this embodiment, slack for allowing the three-dimensional displacements of the bent portions2c,2dwhen the stent body2is bent is formed in the outer cover41simply by contracting the stent body2, to which the outer cover41is partially connected, in the radial direction. Accordingly, it is possible to easily manufacture the covered stent10with a low axial force and high flexibility.

Furthermore, the stretching direction A of the outer cover41is aligned with the stretching direction of the stent body2when being contracted; therefore, it is possible to easily manufacture the covered stent10in which breakage is less likely to occur and that is highly reliable.

In this embodiment, the outer cover41is connected to the stent body2at the two end portions thereof; however, the number and the positions of connecting portions of the outer cover41with respect to the stent body2can be changed, as appropriate. For example, the outer cover41may be connected to the stent body2at a center portion in addition to the two end portions in order to increase the securing force of the outer cover41with respect to the stent body2.

In the connecting portions joined by means of thermocompression bonding or the like, the ductility of the ePTFE deteriorates because the node and fibril structures are broken. Therefore, the number of the connecting portions is preferably small.

In this embodiment, the outer cover41is stretched by inserting the assembly into the tube50; however, alternatively, the outer cover41may be stretched by mounting the assembly on a delivery system.

The delivery system has a tubular sheath to be inserted into a body cavity and the covered stent10is mounted on a distal-end portion of the sheath. After step SE5, by inserting the assembly into the sheath, it is possible to stretch the outer cover41by contracting the stent body2at the same time as the mounting on the delivery system.

In this embodiment, the manufacturing method includes step SE6of stretching the outer cover41; however, step SE6may not be included. In this case, the covered stent10is provided in a state in which the outer cover41is not stretched.

The unstretched outer cover41is stretched by, for example, a user himself/herself mounting the covered stent10on the delivery system. Accordingly, it is possible to form slack in the outer cover41and realize a low axial force in the covered stent10.

Seventh Embodiment

Next, a covered stent manufacturing method and a covered stent according to a seventh embodiment of the present invention will be described.

In this embodiment, configurations that are different from those of the first and sixth embodiments will be described and configurations that are the same as those of the first and sixth embodiments will be given the same reference signs, and the descriptions thereof will be omitted.

As shown inFIG.32, a covered stent11according to this embodiment differs from the covered stent10of the sixth embodiment in that the covered stent11additionally includes a tubular inner cover31that covers the inside of the stent body2in addition to the stent body2and the outer cover41.

The covers31,41are partially joined with each other and are consequently partially connected to the stent body2. For example, the covers31,41are joined with each other in the joining portions5, which are some regions on the inner side of the mesh of the stent body2, and are separated from each other in the portions other than the joining portions5.

The inner cover31is formed from an ePTFE, includes the stretching direction A in which high ductility is exhibited, and is disposed in the orientation in which the stretching direction A is aligned with the longitudinal direction of the stent body2, as in the outer cover41. In addition, in the expanded state, the inner cover31has slack in the longitudinal direction. In other words, the total length of the inner cover31corresponds to the length in which an extra length is added to the length L1of the stent body2in the expanded state.

Such an inner cover31allows the movements of the pair of bent portions2c,2d, forming each of the engagement portions2b, in the longitudinal direction and the radial direction, as in the outer cover41. Therefore, the covers31,41are prevented from hindering the three-dimensional displacements of the bent portions2c,2dwhen the covered stent11is bent, and a low axial force and high flexibility are realized in the covered stent11.

Furthermore, the stretching directions A of the covers31,41are aligned with the stretching direction of the stent body2when being contracted; therefore, the covers31,41are prevented from being broken or being peeled off from the stent body2due to the stretching of the stent body2.

Next, the covered stent manufacturing method according to this embodiment will be described.

As shown inFIG.33, the covered stent manufacturing method includes: step SF1of preparing the inner cover31and the outer cover41; step SF2of disposing the inner cover31on the jig22; step SF3of disposing the inner cover31inside the stent body2; step SF4of disposing the outer cover41outside the stent body2; step SF5of partially connecting the inner cover31and the outer cover41to the stent body2; and step SF6of stretching the inner cover31and the outer cover41by contracting the stent body2in the radial direction.

As in step SE1, the rectangular outer cover41and the rectangular inner cover31are cut out from ePTFE sheets in consideration of the stretching direction A of the ePTFE so that the length directions of the covers31,41are aligned with the stretching direction A (step SF1).

Next, as shown inFIG.34, the inner cover31is disposed on the outer surface of the core rod22by aligning the length direction of the inner cover31with the longitudinal direction of the core rod22and winding the inner cover31around the core rod22over the entire circumference thereof (step SF2). In step SF2, the inner cover31is formed into a tubular shape by joining end portions of the inner cover31in the width direction with other portions of the inner cover31over the entire length thereof.

Next, the stent body2is disposed outside the inner cover31by inserting the core rod22into the stent body2(step SF3).

Next, the outer cover41is disposed outside the stent body2by aligning the length direction of the outer cover41with the longitudinal direction of the stent body2and winding the outer cover41around the core rod22over the entire circumference thereof (step SF4). In step SF4, the outer cover41is formed into a tubular shape by joining end portions of the outer cover41in the width direction with other portions of the outer cover41over the entire length thereof.

Next, the covers31,41are connected to the stent body2by forming the joining portions5by joining the outer cover41and the inner cover31with each other by means of an arbitrary joining method, such as thermocompression bonding or an adhesive, in some regions on the inner side of the mesh (step SF5). By removing the core rod22from the inner cover31after the joining, an assembly of the stent body2and the covers31,41is removed from the core rod22.

Next, as in step SE6, the covers31,41are stretched in the longitudinal direction together with the stent body2by contracting the stent body2in the radial direction (step SF6). Accordingly, the length of each of the covers31,41increases and slack is formed in each of the covers31,41with respect to the length of the stent body2in the expanded state.

Accordingly, with the manufacturing method of this embodiment, slack for allowing the three-dimensional displacements of the bent portions2c,2dwhen the stent body2is bent is simultaneously formed in the covers31,41simply by contracting the stent body2, to which the covers31,41forming the double structure are partially connected, in the radial direction. Accordingly, it is possible to easily manufacture the covered stent11with a low axial force and high flexibility. Furthermore, the stretching directions A of the covers31,41are aligned with the stretching direction of the stent body2when being contracted; therefore, it is possible to easily manufacture the covered stent11in which breakage of the covers31,41is less likely to occur and that is highly reliable.

In step SF6of this embodiment, as in the sixth embodiment, the covers31,41may be stretched by mounting the assembly on the delivery system instead of the tube50.

In this embodiment, as in the sixth embodiment, the manufacturing method may not include step SF6and the covered stent11may be provided in a state in which the covers31,41are not stretched.

In the sixth and seventh embodiments, the stretching directions A of the covers31,41are aligned with the longitudinal direction of the stent body2; however, in the case in which the wires2aare wound around the stent body2in a spiraling manner, the stretching direction A may be aligned with the stretching directions of the wires2awhen the stent body2is contracted.

As shown inFIG.35, the stent body2formed by knitting the wires2awhile winding the wires in a spiraling manner stretches when the diameter thereof decreases in the radial direction, while being rotated in a direction in which twist thereof is released. Therefore, as a result of aligning the stretching direction A with the stretching directions of the wires2a, it is possible to effectively stretch the covers31,41. In this case, in step SE1, SF1, the covers31,41are cut out from ePTFE sheets so that the length directions of the covers31,41are inclined with respect to the stretching direction A by an angle according to the angle of the wires2ain the stretching directions.

In the sixth and seventh embodiments, the stent body2is not limited to a stent body having the engagement portions2b, and a stent body having other structures in which the stent body stretches in the longitudinal direction due to the contraction in the radial direction may be employed. In addition, although examples in which the covers31,41are disposed over the entire length of the stent body2have been described, the same effects are also afforded in the case in which the covers are disposed in a portion of the stent body2.

Furthermore, in the first to fifth embodiments also, the covers made of the ePTFE and the stent body can be disposed so that the stretching directions of the covers31,41are aligned with the stretching direction of the stent body2.

As above, although the embodiments and modifications of the present invention have been described in detail with reference to the drawings, the specific configurations are not limited to the above-described embodiments and design alterations, etc. within the range that does not depart from the scope of the present invention are also encompassed. In addition, the constituent elements indicated in the above-described embodiments and modifications can be configured in combination, as appropriate.

REFERENCE SIGNS LIST