Sten Retriever

Abstract

To provide a stent retriever with a novel structure which can flexibly permit deformation like bending in an extended state while obtaining the excellent expansion / contraction deformability.SOLUTION: A stent retriever 10 includes a cylindrical peripheral wall part 18 which is constituted by a self-expanding type linear skeleton 12 that becomes a mesh structure in an expanded state. The linear skeleton 12 includes a peripheral direction separation part 20 which extends so as to be continuous to the cylindrical peripheral wall part 18 over the entire length in the retriever length direction. The cylindrical peripheral wall part 18 is configured to be expandable on both sides in the peripheral direction in the peripheral direction separation part 20. The peripheral direction separation part 20 extends in the retriever length direction while being inclined in the retriever peripheral direction in the cylindrical peripheral wall part 18. The peripheral direction separation part 20 in the cylindrical peripheral wall part 18 extends by a length equal to or greater than the peripheral direction size of a unit cell 22 constituting the mesh structure of the linear skeleton 12 in the retriever peripheral direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a stent retriever used in thrombus retrieval therapy for retrieving thrombus in blood vessels.

Background Art

[0002] Conventionally, as a method for removing thrombus formed in blood vessels such as the brain, thrombus retrieval therapy using a catheter has been proposed. Thrombus retrieval therapy is a treatment method for restoring blood flow by delivering a stent retriever to the thrombus through a catheter inserted percutaneously into the blood vessel, entangling and retrieving the thrombus with the stent retriever, and then withdrawing it into the catheter.

[0003] The stent retriever has, for example, a self-expanding linear skeleton that forms a mesh structure in the expanded state, like the device for restoring blood flow disclosed in Japanese Patent Publication No. 2:2011-512900 (Patent Document 1). Then, the stent retriever expands at the part where the thrombus is formed in the blood vessel, and the linear skeleton with the mesh structure entangles the thrombus and is drawn into the catheter, thereby retrieving the thrombus.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, conventional stent retrievers generally have a linear skeleton that is endless in the circumferential direction, resulting in a continuous tubular mesh structure around the entire circumference. On the other hand, Figures 13 to 15 of Patent Document 1 propose a stent retriever that is expandable in the circumferential direction. It is believed that a stent retriever with a linear skeleton and a mesh structure that is expandable in the circumferential direction has better expandability and deformability compared to conventional stent retrievers that are endlessly tubular in the circumferential direction, and can be adapted to a wider range of blood vessel sizes, for example.

[0006] However, the inventors have found that conventional circumferentially deployable stent retrievers, such as those described in Patent Document 1, do not yet have sufficient deformation characteristics. In particular, they tend to have high deformation stiffness against bending deformation, making it difficult to ensure flexibility. Therefore, it has been found that they have new problems, such as the risk of excessive tensile resistance of the stent retriever when it is pulled proximal to a curved portion of the blood vessel during a procedure, an increased risk of bleeding due to the linear deformation of the blood vessel during stent retriever insertion, and the risk of the stent retriever locally bending in the curved portion of the blood vessel, causing the entangled thrombus to detach from the stent retriever.

[0007] The problem to be solved by the present invention is to provide a novel stent retriever structure that can flexibly tolerate deformation such as bending in an expanded state while achieving good expandability and contraction. [Means for solving the problem]

[0008] The following describes preferred embodiments for understanding the present invention. However, each embodiment described below is illustrative and can be combined with others as appropriate. Furthermore, the multiple components described in each embodiment can be recognized and adopted as independently as possible, and can be combined with any component described in another embodiment as appropriate. Thus, the present invention is not limited to the embodiments described below, and various other embodiments can be realized.

[0009] The first embodiment is a stent retriever having a cylindrical circumferential wall portion composed of a self-expanding linear skeleton that forms a mesh structure when expanded, wherein the linear skeleton has a circumferential separation portion that extends continuously over the entire length of the cylindrical circumferential wall portion in the length direction of the retriever, the cylindrical circumferential wall portion is expandable on both sides in the circumferential direction at the circumferential separation portion, and the circumferential separation portion in the cylindrical circumferential wall portion extends in the length direction of the retriever while being inclined in the circumferential direction of the retriever, and the circumferential separation portion in the cylindrical circumferential wall portion is a stent retriever In the circumferential direction, the linear skeleton extends for a length greater than or equal to the circumferential size of the unit cell constituting the mesh structure of the linear skeleton, and the base portion of the linear skeleton has a connecting line that extends linearly toward the operating wire, and in the unfolded and laid-flat state when unfolded on both sides in the circumferential direction at the circumferential separation portion, the circumferential ends of the linear skeleton constituting the circumferential separation portion extend linearly in a direction inclined with respect to the connecting line, and in the expanded state, the circumferential ends of the linear skeleton extend parallel to each other in the circumferential direction at the cylindrical circumferential wall portion. Furthermore, a widened portion is formed on only one of the circumferential edges of the linear skeleton. They exist.

[0010] In a stent retriever with a structure according to this embodiment, the circumferential separation portion is continuously provided along the entire length of the tubular circumferential wall portion of the retriever. Compared to a circumferentially endless tubular structure that is continuously unable to expand in the circumferential direction, the expandability and contraction deformability are better, and for example, it can be easily adapted to a wider range of blood vessel sizes.

[0011] The circumferential separation portion extends with a circumferential length greater than or equal to the circumferential size of the unit cells constituting the mesh structure of the cylindrical circumferential wall portion, and is inclined in the circumferential direction. This reduces the bending deformation rigidity of the cylindrical circumferential wall portion, improving, for example, its ability to follow the curvature of blood vessels, thereby preventing localized bending, the resulting detachment of captured thrombi, and excessive pressure against the inner surface of blood vessels. In particular, as described in Figures 13 to 15 of Patent Document 1, if the circumferential separation portion in the cylindrical circumferential wall portion extends in a manner as close to a straight line as possible in the longitudinal direction, strain and stress during bending deformation are not easily distributed in the circumferential direction, and as a result, deformation states in which localized bending in the longitudinal direction are likely to occur. In contrast, in this embodiment, because the circumferential separation portion in the cylindrical circumferential wall portion extends with a circumferential inclination, strain and stress during bending deformation are easily distributed over a wide area including the circumferential direction, localized bending is avoided, and a deformation state in which the overall curve is easily achieved. Furthermore, in a stent retriever with a structure according to this embodiment, when the cylindrical peripheral wall portion is rolled up to form a cylindrical mesh structure extending in the longitudinal direction of the connecting line, the circumferential separation portion is provided extending in a spiral shape, allowing for flexible expansion and contraction deformation characteristics and bending deformation characteristics to be set.

[0012] A second embodiment is the stent retriever described in the first embodiment, wherein, in the expanded state of the linear skeleton, the circumferential separation portion extends in a spiral shape.

[0013] According to the stent retriever structured in this embodiment, the expanded cylindrical peripheral wall portion is provided with a spirally arranged circumferential separation portion, thereby making both the expansion / contraction deformation characteristics and the bending deformation characteristics flexible.

[0014] A third embodiment is a stent retriever as described in the first or second embodiment, wherein, in the expanded state of the linear skeleton, the circumferential separation portion in the cylindrical peripheral wall portion extends for a length of half a circumference or more in the circumferential direction of the retriever.

[0015] According to the stent retriever structured in this embodiment, for example, the bending deformation rigidity of the cylindrical circumferential wall portion can be effectively reduced by providing a circumferential separation portion. [Effects of the Invention]

[0018] According to the present invention, in a stent retriever, while obtaining good expansion and contraction deformability due to a mesh structure that can be expanded in the circumferential direction, it is possible to flexibly allow deformation such as bending in the expanded state.

Brief Description of the Drawings

[0019] [Figure 1] Perspective view showing a stent retriever as a first embodiment of the present invention [Figure 2] Plan view of the expanded and flattened state in which the stent retriever shown in FIG. 1 is expanded to both sides in the circumferential direction at the circumferential separation part and laid flat [Figure 3] View showing an enlarged view of the III-III cross section of FIG. 2 [Figure 4] Perspective view showing a stent retriever as a second embodiment of the present invention [Figure 5] Plan view of the expanded and flattened state in which the stent retriever shown in FIG. 4 is expanded to both sides in the circumferential direction at the circumferential separation part and laid flat [Figure 6] Perspective view showing a stent retriever as a third embodiment of the present invention [Figure 7] Plan view of the expanded and flattened state in which the stent retriever shown in FIG. 6 is expanded to both sides in the circumferential direction at the circumferential separation part and laid flat [Figure 8] Perspective view showing a stent retriever as a fourth embodiment of the present invention [Figure 9] Plan view of the expanded and flattened state in which the stent retriever shown in FIG. 8 is expanded to both sides in the circumferential direction at the circumferential separation part and laid flat [Figure 10] Perspective view showing a stent retriever as a fifth embodiment of the present invention [Figure 11] Plan view of the expanded and flattened state in which the stent retriever shown in FIG. 10 is expanded to both sides in the circumferential direction at the circumferential separation part and laid flat [Figure 12] Perspective view showing a stent retriever as a sixth embodiment of the present invention [Figure 13] Plan view of the expanded and flattened state in which the stent retriever shown in FIG. 12 is expanded to both sides in the circumferential direction at the circumferential separation part and laid flat [Modes for carrying out the invention]

[0020] Embodiments of the present invention will be described below with reference to the drawings.

[0021] Figure 1 shows a stent retriever 10 as a first embodiment of the present invention. The stent retriever 10 is equipped with a linear skeleton 12 provided on the tip side of the operating wire A. Figure 1 shows the stent retriever 10 in an expanded state.

[0022] The linear skeleton 12 is formed of, for example, a medical-grade metal, preferably a shape memory alloy such as a Ni-Ti alloy. The linear skeleton 12 integrally comprises a connecting wire 14 connected to the operating wire A and a mesh-like portion 16 provided at the tip end (distal end during the procedure) of the connecting wire 14.

[0023] The connecting wire 14 is a flat plate with a width dimension greater than its thickness dimension, and extends in the direction of the retriever's length. One connecting wire 14 is provided that extends linearly from the base end of the mesh section 16 toward the operating wire A, connecting the operating wire A and the mesh section 16.

[0024] The mesh portion 16 is cylindrical in shape when expanded. The base end of the mesh portion 16 is a curved wall portion 17 with a large opening in the circumferential direction when expanded, and is not cylindrical. The base end (curved wall portion 17) of the mesh portion 16 tapers toward the base end when expanded, and is connected to a single connecting wire 14 at the base end.

[0025] The portion of the mesh portion 16 closer to the tip than the curved wall portion 17 is a cylindrical circumferential wall portion 18. The cylindrical circumferential wall portion 18 is generally cylindrical in shape and has a circumferential separation portion 20 in a part of its circumferential direction. The circumferential separation portion 20 extends continuously along the entire length of the cylindrical circumferential wall portion 18 in the retriever length direction, and the cylindrical circumferential wall portion 18 is divided in the circumferential direction by the circumferential separation portion 20 in a part of its circumferential direction. As a result, the mesh portion 16, including the cylindrical circumferential wall portion 18, can be unfolded on both sides of the circumferential separation portion 20.

[0026] Figure 2 shows the linear skeleton 12 in an unfolded and laid-down state, with the mesh portion 16 unfolded on both sides in the circumferential direction at the circumferential separation portion 20 and laid flat. In Figure 2, the left-right direction is the retriever length direction, and the up-down direction is the retriever circumferential direction. The retriever length direction is the axial direction of the cylindrical circumferential wall portion 18 in the expanded state shown in Figure 1, and the retriever circumferential direction is the circumferential direction of the cylindrical circumferential wall portion 18 in the expanded state.

[0027] As shown in Figure 2, the mesh portion 16 is the unfolded shape of a linear skeleton 12 that branches out from the tip of the connecting line 14 in the circumferential direction of the retriever, spreading out in a mesh-like manner toward the tip (to the right in Figure 2), reaching a predetermined number of meshes, and then extending with a substantially constant width. Furthermore, the linear skeleton 12 in the mesh portion 16 is provided with multiple linear bodies 21 that can be perceived as a wave shape continuous in the retriever length direction with the circumferential direction of the retriever as the amplitude direction, and adjacent linear bodies 21, 21 in the circumferential direction of the retriever are integrally continuous in the adjacent portions of the wave. As a result, the expanded linear skeleton 12 in the mesh portion 16 is a mesh structure consisting of multiple unit cells 22 that are connected to each other in the retriever length direction and the retriever circumferential direction.

[0028] The multiple unit cells 22 constituting the mesh structure of the mesh portion 16 may have substantially a single shape and size, or may include different shapes and sizes as needed. In this embodiment, the unit cells 22 are formed with substantially a constant size overall, but more precisely, the mesh structure of the mesh portion 16 is composed of multiple unit cells 22a arranged in the length direction and circumferential direction of the retriever, and unit cells 22b arranged between adjacent unit cells 22a, 22a and having a different shape from the unit cells 22a. The mesh structure of the mesh portion 16 is deformable into a contracted state described later by the action of an external force, and is self-expanding, so that its shape is restored from the contracted state to the expanded state based on superelasticity when the external force is released.

[0029] The circumferential separation section 20 is formed between the circumferential edge portions 23, 23 on both sides of the linear skeleton 12 (network portion 16). The circumferential edge portions 23 of the linear skeleton 12 extend linearly in the retriever length direction while inclined in the circumferential direction of the retriever when the linear skeleton 12 is laid flat and unfolded. The circumferential end edges 23, 23 of the linear skeleton 12 that constitute the circumferential separation section 20 extend substantially parallel to each other. Therefore, in the expanded state of the linear skeleton 12 shown in Figure 1, the circumferential separation section 20 is spiral in shape, extending in the retriever length direction while inclined in the circumferential direction of the retriever.

[0030] The circumferential separation section 20 has an amplitude in the circumferential direction of the retriever that is equal to or greater than the circumferential size (Wa, Wb) of the unit cell 22, and preferably greater than the circumferential size of the unit cell 22. The amplitude of the circumferential separation section 20 in the circumferential direction of the retriever is preferably twice or more the circumferential size of the unit cell 22, and more preferably three times or more the circumferential size of the unit cell 22. Here, the unit cell 22 refers to those that constitute the cylindrical circumferential wall portion 18. Therefore, for example, a unit cell 22 located on the base end side of the retriever and provided in a portion (curved wall portion 17) that constitutes an arc-shaped circumferential wall portion that is less than one full turn in the expanded state is excluded. Furthermore, the circumferential separation portion 20 of this embodiment extends spirally in the circumferential direction of the cylindrical circumferential wall portion 18 for a length of more than half a circumference (more than 180 degrees around the central axis), and the amplitude in the circumferential direction is more than half a circumference of the cylindrical circumferential wall portion 18 (more than half the circumference of the cylindrical circumferential wall portion 18).

[0031] In the extended state of the retriever, the circumferential size (Wa, Wb) of the unit cell 22 is, for example, 2.5 to 5.5 mm, more preferably 3 to 4 mm. In this embodiment, the circumferential size Wa of unit cell 22a is approximately 3.4 mm, and the circumferential size Wb of unit cell 22b is approximately 3.4 mm (both approximately 5 to 15 degrees around the central axis), and the circumferential separation portion 20 extends in the circumferential direction for a length of more than half a turn. As a result, the angle at which the circumferential separation portion 20 extends in the circumferential direction around the central axis of the retriever is greater than or equal to the circumferential angle of the unit cell 22. Furthermore, if the mesh structure of the mesh portion 16 is composed of multiple types of unit cells 22 with different circumferential width dimensions, the circumferential size of the unit cell 22 may be the minimum value (the smaller of Wa and Wb in this embodiment), preferably the average value ((Wa + Wb) / 2 in this embodiment), and more preferably the maximum value (the larger of Wa and Wb in this embodiment).

[0032] The linear skeleton 12 is provided with a widened section 24 that is partially widened. The widened section 24 is a part of the linear skeleton 12 whose width is larger than many other parts. In this embodiment, the widened section 24 of the linear skeleton 12 is composed of a base widened section 24a set on the connecting line 14, an intermediate widened section 24b as an edge widened section provided on one circumferential edge 23 of the mesh section 16 that extends from the connecting line 14 to the tip of the mesh section 16, and tip widened sections 24c provided at each tip of the mesh section 16 located at multiple locations in the circumferential direction.

[0033] The base widening portion 24a is provided by the fact that the connecting line 14 is in the shape of a flat rectangular plate. The intermediate widening portion 24b is wider than the other circumferential edge portion 23 of the mesh portion 16 in the linear skeleton 12, and in the expanded state of the linear skeleton 12, it is arranged on a line that extends spirally in the retriever length direction along the circumferential separation portion 20. In a free state where no external force is applied, the intermediate widening portion 24b is expanded into a substantially cylindrical shape by superelasticity and is continuous over more than half the circumference of the cylindrical circumferential wall portion 18 in the circumferential direction of the retriever, and in this embodiment, it extends continuously over substantially the entire circumference.

[0034] The widened tip portion 24c is located at the tip of each striatum 21 that constitutes the multiple cells of the mesh, and is provided at the intersection where the tip sides of each cell in adjacent striatum 21 in the circumferential direction are closed. That is, each of these intersection portions is widened by being roughly disc-shaped, and by making the intersection portions located at the tip of the mesh portion 16 a wide, roughly curved surface, problems such as damaging blood vessels or getting caught in the microcatheter described later are prevented.

[0035] In this embodiment, one of the base widening portion 24a, the intermediate widening portion 24b, and the tip widening portion 24c is continuous in the retriever length direction, and these widening portions 24a, 24b, and 24c constitute a continuous widening portion that extends continuously along the entire length of the linear skeleton 12 in the retriever length direction.

[0036] As shown in Figure 3, the widened portion 24 has a plating layer 26 formed on both the inner and outer circumferential surfaces of the expanded linear skeleton 12. The plating layer 26 is made of a material that is easily distinguishable from body tissues such as blood vessels by the difference in brightness under X-ray fluoroscopy, and is made of, for example, an X-ray opaque material. As the material for forming the plating layer 26, a metal material that is harmless to the human body is used, such as gold, platinum, palladium, or various alloys thereof, and in this embodiment, the plating layer 26 is gold plated. The plating layer 26 may be provided on both sides of the widened portion 24, only on both sides of the widened portion 24, or on the entire surface including the sides of the widened portion 24 as shown in Figure 3. The plating layer 26 is not provided on the linear body 21, etc., outside the widened portion 24, but is provided only on the widened portion 24. Because the plating layer 26 is formed on both sides of the widened portion 24, the marker visible under X-ray fluoroscopy is composed of the widened portion 24 equipped with the plating layer 26.

[0037] The thickness t of the plating layer 26 formed on one side of the widened portion 24 is preferably 0.007 to 0.015 mm, for example, 0.01 mm. The thickness t of the plating layer 26 may differ between the inner and outer surfaces of the retriever, but in this embodiment, they are the same thickness. The width w of the widened portion 24 on which the plating layer 26 is formed is preferably 0.1 to 0.3 mm, more preferably 0.15 to 0.25 mm, for example, 0.2 mm. On the other hand, the width w of the filament body 21 outside the widened portion 24 is smaller than the width w of the widened portion 24, preferably 0.05 to 0.1 mm, for example, 0.07 mm. The thickness h of the widened portion 24 is preferably 0.05 to 0.1 mm, for example, 0.07 mm. In this embodiment, the thickness dimension of the linear skeleton 12, excluding the plating layer 26, is approximately constant throughout. However, the thickness may vary in parts, for example, by making the base end portion, including the connecting line 14, thicker than other parts.

[0038] The specific manufacturing method for the stent retriever 10 is not limited to known methods and can be applied. For example, the linear skeleton 12 can be manufactured by cutting a Ni-Ti alloy metal material into a predetermined shape using a laser. The plating layer 26 can be formed in any part and of any size by, for example, applying masking and then plating. The thickness of the plating layer 26 can be controlled by adjusting the plating conditions, such as the plating time.

[0039] A stent retriever 10 with such a structure is used, for example, when performing thrombectomy in the event of cerebral blood vessel embolism. First, the stent retriever 10 is inserted into a microcatheter (not shown) in a contracted state in which the mesh portion 16 has a smaller diameter than its expanded state. The tubular circumferential wall portion 18 of the stent retriever 10 has a linear mesh structure, and can be efficiently reduced in diameter by extending in the axial direction. In addition, in this embodiment, the tubular circumferential wall portion 18 is structured to be expandable on both sides in the circumferential direction at the circumferential separation portion 20. By winding the tubular circumferential wall portion 18 in a double-overlapped state in at least a part of the circumferential direction, the mesh portion 16 including the tubular circumferential wall portion 18 can be more efficiently reduced in diameter.

[0040] Furthermore, since the intermediate widened portion 24b on which the plating layer 26 is formed tends to have high sliding resistance to the microcatheter, it is desirable that when the mesh portion 16 is contracted, one side in the circumferential direction of the circumferential separation portion 20 on which the intermediate widened portion 24b is formed is wound in such a way that it is positioned on the inner side relative to the other side in the circumferential direction where the intermediate widened portion 24b is absent, thereby reducing the sliding resistance to the microcatheter.

[0041] Next, the microcatheter containing the stent retriever 10 is inserted to the vicinity of the thromboembolic lesion in the cerebral blood vessel, and the stent retriever 10 is pushed distally from the microcatheter. As the stent retriever 10 is pushed distally from the microcatheter, the mesh portion 16 of the stent retriever 10 recovers its shape from a contracted state to an expanded state due to its superelastic properties. The tubular peripheral wall portion 18 of the mesh portion 16, which becomes a mesh structure in the expanded state, bites into the thrombus and entangles it.

[0042] The stent retriever 10, which has entangled the thrombus, is then retrieved by the operator by pulling the operating wire A proximal to a guiding catheter, for example, inserted into the carotid artery. This allows the thrombus in the blood vessel to be collected and removed, resolving the thrombus-induced thrombus blockage in the cerebral blood vessel and rapidly restoring blood flow to the cerebral blood vessel. The thrombus entangled by the stent retriever 10 may also be removed by aspirate using a suction catheter if necessary.

[0043] In the stent retriever 10 of this embodiment, the circumferential separation portion 20, which extends continuously along the entire length of the retriever, extends in the circumferential direction of the retriever while being inclined in the circumferential direction. As a result, for example, when the cylindrical circumferential wall portion 18 of the stent retriever 10 is located in a curved portion of a blood vessel, the circumferential ends of the cylindrical circumferential wall portion 18 located on both sides of the circumferential separation portion 20 are relatively displaced, making it easier to allow for curvature deformation of the cylindrical circumferential wall portion 18. Therefore, the ability of the stent retriever 10 to follow the curvature of the blood vessel is improved, and buckling deformation in the mesh portion 16 can be prevented. As a result, for example, when the stent retriever 10 passes through a curved portion of a blood vessel at low speed, problems such as the stent retriever 10 being strongly pressed against the blood vessel wall or the thrombus detaching from the buckled cylindrical circumferential wall portion 18 can be avoided, and the thrombus can be safely and efficiently retrieved.

[0044] If the amplitude of the circumferential separation portion 20 is too small, the circumferential ends of the cylindrical circumferential wall portion 18 will interlock in a zigzag structure, which may restrict the relative displacement of the circumferential ends of the cylindrical circumferential wall portion 18 during bending deformation, potentially resulting in stiffer deformation characteristics. For this reason, in conventional stent retrievers where the wave-shaped circumferential separation portion extending in the length direction of the retriever while reciprocating in the circumferential direction of the retriever is smaller than the circumferential size of the unit cells constituting the mesh structure of the cylindrical circumferential wall portion, it is expected that the cylindrical circumferential wall portion will buckle and bend when a bending moment is applied to the cylindrical circumferential wall portion to bend it.

[0045] Therefore, by making the amplitude of the circumferential separation portion 20 in the retriever circumferential direction greater than or equal to the circumferential size of the unit cell 22 in the cylindrical circumferential wall portion 18, relative displacement of both ends of the cylindrical circumferential wall portion 18 located on both sides of the circumferential separation portion 20 is more easily tolerated. Thus, the relative displacement of both ends of the cylindrical circumferential wall portion 18 in the circumferential direction makes it possible to obtain a cylindrical circumferential wall portion 18 that has good conformability to the curved shape of the blood vessel.

[0046] In particular, in this embodiment, since the circumferential amplitude of the circumferential separation portion 20 is set to be greater than half the circumference of the cylindrical circumferential wall portion 18, flexible bending deformation characteristics are set for the cylindrical circumferential wall portion 18 equipped with the circumferential separation portion 20, thereby further improving the ability of the cylindrical circumferential wall portion 18 to follow the curvature of blood vessels.

[0047] In the expanded state of the mesh portion 16, the circumferential separation portion 20 extends in a spiral shape, so the cylindrical circumferential wall portion 18 equipped with the circumferential separation portion 20 has a structure that is more tolerant of bending deformation, and excellent conformability to the curvature of blood vessels is achieved. The circumferential separation portion 20, which becomes spiral in the expanded state, can be easily formed by arranging the circumferential end edges 23, 23 of the mesh portion 16, which extends linearly in the unfolded and laid-flat state, at an angle with respect to the connecting line 14 that extends in the length direction of the retriever.

[0048] Furthermore, the linear skeleton 12 is provided with a partially widened section 24, and a plating layer 26 is formed on both sides of the widened section 24, thereby creating an X-ray opaque marker. As a result, the stent retriever 10 has good visibility under X-ray fluoroscopy, making it easy to grasp the relative position of the stent retriever 10 with respect to a microcatheter, as well as the position and shape of the stent retriever 10 within a blood vessel. In particular, the stent retriever 10 of this embodiment has a proximal widened section 24a provided at the proximal end of the linear skeleton 12, an intermediate widened section 24b that is continuous along the entire length of the mesh section 16, and a tip widened section 24c provided at the tip of the linear skeleton 12, making it easy to grasp the entire stent retriever 10 under X-ray fluoroscopy.

[0049] Furthermore, the marker, which is visible under X-ray fluoroscopy, is formed by forming a plating layer 26 on a widened portion 24 provided on the linear skeleton 12, and the marker is integrally provided with the linear skeleton 12. Therefore, even if the marker gets caught on the inner surface of the microcatheter or the blood vessel wall, for example, it is less likely for the marker to detach from the linear skeleton 12 compared to when a separate marker is attached to the linear skeleton, thus achieving a higher level of safety. In addition, there is no need to prepare the marker as a separate component from the linear skeleton 12, which reduces the number of parts.

[0050] Figure 4 shows a stent retriever 30 as a second embodiment of the present invention. In the following description, components and parts that are substantially the same as those in the first embodiment may be denoted by the same reference numerals in the figures and their descriptions may be omitted.

[0051] As shown in the unfolded view of Figure 5, the stent retriever 30 does not have an intermediate widening section 24b along the circumferential separation section 20. The stent retriever 30 also has multiple intermediate widening sections 24d in the middle of the retriever length direction in the mesh section 16. The intermediate widening sections 24d are inter-cell widening sections provided on the linear body 21 extending between adjacent unit cells 22, 22. The intermediate widening sections 24d have a longitudinal shape shorter than the portion of the linear body 21 extending between the unit cells 22, 22, and are arranged on a spirally extending line in the expanded mesh section 16. The intermediate widening sections 24d are not continuous along the entire length of the retriever, but are divided widening sections provided in a divided state at multiple locations in the retriever length direction.

[0052] According to the stent retriever 30 of this embodiment, the multiple intermediate widening sections 24d ensure good visibility of the mesh section 16 under X-ray fluoroscopy. Since the multiple intermediate widening sections 24d are arranged in a spiral shape inclined with respect to the length direction of the retriever, it is easy to grasp the shape of the mesh section 16 in its expanded state.

[0053] In this embodiment, since multiple intermediate widening sections 24d are intermittently arranged in the length direction of the retriever, the influence of the intermediate widening sections 24d on the deformation rigidity of the mesh section 16 can be suppressed compared to the case where they are continuous along the entire length of the retriever. Therefore, a stent retriever 30 with excellent conformability to the curved shape of blood vessels can be obtained. In particular, because a band-shaped intermediate widening section 24b is not provided at the circumferential edge 23 of the cylindrical circumferential wall section 18 along the circumferential separation section 20, relative displacement of both circumferential sides of the cylindrical circumferential wall section 18 is more easily tolerated, and more flexible curvature deformation characteristics can be set for the cylindrical circumferential wall section 18.

[0054] In this embodiment, an example of the arrangement of the intermediate widening section 24d is shown as being arranged on a spirally extending line. However, the intermediate widening section 24d can be provided in any portion of the linear body 21 that extends between unit cells 22, 22, allowing for a large degree of freedom in the arrangement of the intermediate widening section 24d.

[0055] Furthermore, as shown in Figures 6 and 7, the stent retriever 40 as a third embodiment may be equipped with both the intermediate widening portion 24b shown in the first embodiment and the intermediate widening portion 24d shown in the second embodiment. This makes it possible to obtain the flexible deformation characteristics required for the cylindrical peripheral wall portion 18 while achieving better visibility under X-ray fluoroscopy.

[0056] Figures 8 and 9 show a stent retriever 50 as a fourth embodiment. The stent retriever 50 has a widened section 24 which includes a base widened section 24a connected by a connecting wire 14 and a tip widened section 24c provided at the tip of the mesh section 16. The middle portion of the mesh section 16 does not have a widened section.

[0057] According to the stent retriever 50 of this embodiment, the absence of widened portions in the linear skeleton 12 other than the base and tip allows for more effective realization of the flexible deformation characteristics of the cylindrical peripheral wall portion 18. Furthermore, visibility is ensured by the widened portions 24a and 24c at the base and tip of the stent retriever 50, where visibility under X-ray fluoroscopy is particularly required.

[0058] Figure 10 shows a stent retriever 60 as a fifth embodiment. The stent retriever 60 has two circumferential separation sections 20, 20 extending in a double helix shape. That is, as shown in the unfolded view of Figure 11, the mesh section 16 is composed of a first cell group 62 and a second cell group 64, each consisting of a plurality of unit cells 22.

[0059] The first cell group 62 and the second cell group 64 each have circumferential edges 23 that extend linearly and are inclined with respect to the retriever length direction, and the circumferential edges 23 are substantially parallel to each other. One circumferential edge 23 of the first cell group 62 and the other circumferential edge 23 of the second cell group 64 are spaced apart from each other but close together, and one circumferential separation portion 20 is formed between the one circumferential edge 23 of the first cell group 62 and the other circumferential edge 23 of the second cell group 64. Furthermore, the other circumferential edge 23 of the first cell group 62 and the one circumferential edge 23 of the second cell group 64 are positioned close together and separated from each other in the expanded state in which the mesh portion 16 is cylindrical, and the other circumferential separation portion 20 is formed between the other circumferential edge 23 of the first cell group 62 and the one circumferential edge 23 of the second cell group 64 (see Figure 10).

[0060] In both of the two circumferential separation sections 20, 20, the amplitude in the circumferential direction of the retriever is greater than the circumferential size of the unit cell 22. Furthermore, each circumferential separation section 20 extends continuously for more than half the circumference in the circumferential direction of the retriever, and its circumferential phase is shifted by approximately 180 degrees. As a result, the two circumferential separation sections 20, 20 are arranged around the entire circumference of the mesh section 16.

[0061] The provision of these two circumferential separation sections 20, 20 allows relative displacement to be more easily tolerated at the circumferential edges 23 of the first and second cell groups 62, 64 located on both sides of the circumferential separation sections 20, 20. This relative displacement of the circumferential edges 23 of the first and second cell groups 62, 64 results in soft deformation characteristics of the cylindrical circumferential wall portion 18 in relation to curvature. In particular, the fact that both circumferential separation sections 20, 20 are provided extending in a double helix shape while being inclined with respect to the length direction of the retriever further enhances the soft curvature characteristics of the cylindrical circumferential wall portion 18.

[0062] Furthermore, the two circumferential separation sections 20, 20 allow for a larger expansion and contraction deformation amount of the cylindrical circumferential wall portion 18, making it possible to accommodate a wider range of blood vessel sizes.

[0063] Furthermore, the two circumferential separation sections 20, 20 do not need to have the same circumferential amplitude; they may be formed with different amplitudes. Also, there may be three or more circumferential separation sections 20.

[0064] Furthermore, in this embodiment, only the tip widening portion 24c is provided as a marker for the first and second cell groups 62 and 64 constituting the mesh portion 16. However, for example, intermediate widening portions 24b extending along the circumferential separation portion 20 and / or intermediate widening portions 24d arranged between adjacent unit cells 22 and 22 can also be provided. In addition, if intermediate widening portions 24b are provided, for example, two intermediate widening portions 24b, 24b can be provided along two circumferential separation portions 20 and 20, which improves the visibility of the mesh portion 16 under X-ray fluoroscopy by using a double helix-shaped marker.

[0065] Figure 12 shows a stent retriever 70 as a sixth embodiment. As shown in the unfolded view in Figure 13, the stent retriever 70 has circumferential edges 71, 71 on both sides of the mesh portion 16 that are not linear in shape. As a result, the circumferential separation portion 72 shown in Figure 12, formed between the circumferential edges 71, 71 of the mesh portion 16, has a width dimension in the circumferential direction of the retriever that changes in the length direction of the retriever, and as a whole, it does not extend in a spiral shape but is wavy in a reciprocating manner in the circumferential direction.

[0066] The circumferential separation portion 72 extends in the length direction of the retriever while being inclined in the circumferential direction of the retriever. The amplitude of the circumferential separation portion 72 in the circumferential direction of the retriever is made larger than the circumferential size of the unit cell 22 in the cylindrical circumferential wall portion 18. In this embodiment, the circumferential amplitude of the circumferential separation portion 72 is less than half the circumference of the cylindrical circumferential wall portion 18.

[0067] As shown in Figure 13, the mesh portion 16 has a mesh structure in which unit cells 22c and 22d, each having a different width dimension (circumferential size) in the circumferential direction of the retriever, are arranged alternately in the length direction of the retriever, and unit cells 22e are provided adjacent to the sides of adjacent unit cells 22c and 22d in the length direction of the retriever. The base end (curved wall portion 17) of the mesh portion 16 connected to the connecting line 14 is composed of three elongated unit cells 22f that are longitudinal in the length direction of the retriever. The circumferential amplitude of the circumferential separation portion 72 is made larger than, for example, the circumferential size Wc of unit cell 22c, the circumferential size Wd of unit cell 22d, and the circumferential size We of unit cell 22e.

[0068] Even with a stent retriever 70 equipped with a wavy circumferential separation section 72 that reciprocates in the circumferential direction, as shown in this embodiment, the bending deformation characteristics of the stent retriever 70 can be made softer, thereby improving its ability to follow the curved portion of the blood vessel. Furthermore, by changing the circumferential width dimension of the circumferential separation section 72 instead of keeping it constant, the bending deformation characteristics of the cylindrical circumferential wall portion 18 can also be adjusted.

[0069] Furthermore, as shown in this embodiment, the specific shape and size of the unit cells 22 constituting the mesh structure of the cylindrical peripheral wall portion 18 are determined based on the required deformation characteristics, accommodation characteristics, friction characteristics, etc. of the cylindrical peripheral wall portion 18, and are not particularly limited.

[0070] In addition, in the stent retriever 70 shown in Figures 12 and 13, a marker may be formed by providing an intermediate widening section 24b extending along the circumferential separation section 72, or a marker may be formed by providing an intermediate widening section 24d between adjacent unit cells 22, 22.

[0071] Although embodiments of the present invention have been described in detail above, the present invention is not limited by its specific description. For example, the amplitude of the circumferential separation portion 20 does not need to be constant over the entire length of the retriever, but may change continuously or in steps. In this case, the minimum value of the amplitude of the circumferential separation portion 20 is set to be greater than or equal to the circumferential size of the unit cell.

[0072] The inclination angle of the circumferential separation section 20 in the circumferential direction of the retriever does not need to be constant over its entire length, and may change continuously or in steps.

[0073] The markers integrally provided on the linear frame 12 by forming a plating layer 26 on both sides of the widened portion 24 are not essential. For example, separate markers can also be attached to the linear frame.

[0074] In the above embodiment, a unit cell 22 was formed by arranging multiple linear bodies 21 that can grasp a wave shape extending in the length direction of the retriever while curving in a wave-like manner in the circumferential direction of the retriever, in the direction of the amplitude of the wave, and by shifting the phases of adjacent linear bodies 21, 21 relative to each other in the length direction of the wave, so that the approximate peaks of the waves that are close to each other become connection points. However, the shape of the unit cell 22 is not particularly limited and is designed appropriately according to the required deformation characteristics and thrombus capture performance. For example, a unit cell can also be formed by arranging linear zigzag-shaped linear bodies instead of wave-shaped linear bodies. Furthermore, in the proximal end portion (curved wall portion 17) of the mesh portion 16, which has little effect on the thrombus capture performance, the deformation characteristics of the mesh portion 16 can be adjusted by, for example, arranging larger unit cells. Thus, the size of the unit cells constituting the mesh structure does not need to be approximately constant in shape and size throughout, and it is possible to use cells of different shapes and sizes in parts, and the width dimension of the linear skeleton in a particular cell component may be different from that of other parts. Furthermore, the present invention originally includes all of the inventions described in (i) to (iv) below, and its structure and effects are noted below. The present invention (i) A stent retriever having a cylindrical circumferential wall portion composed of a self-expanding linear skeleton that forms a mesh structure when expanded, wherein the linear skeleton has a circumferential separation portion that extends continuously over the entire length of the circumferential wall portion in the length direction of the retriever, the cylindrical circumferential wall portion is expandable on both sides in the circumferential direction at the circumferential separation portion, the circumferential separation portion extends in the length direction of the retriever while being inclined in the circumferential direction of the retriever, and the circumferential separation portion in the cylindrical circumferential wall portion extends for a length in the circumferential direction of the retriever that is greater than or equal to the circumferential size of the unit cell constituting the mesh structure of the linear skeleton, (ii) The stent retriever according to (i), wherein in the expanded state of the linear skeleton, the circumferential separation portion extends in a spiral shape, (iii) In the expanded state of the linear skeleton, the circumferential separation portion in the cylindrical peripheral wall portion extends for a length of half a circumference or more in the circumferential direction of the retriever, as described in (i) or (ii), (iv) The base portion of the linear skeleton has a connecting wire extending linearly toward the operating wire, and in the unfolded and laid-down state where the linear skeleton is unfolded on both sides in the circumferential direction in the circumferential separation portion, both circumferential edges of the linear skeleton constituting the circumferential separation portion extend linearly in a direction inclined with respect to the connecting wire, as described in any one of (i) to (iii). This includes inventions relating to the present invention. In the invention described in (i) above, since the circumferential separation portion is continuously provided along the entire length of the tubular circumferential wall portion in the retriever length direction, the expandability and contraction deformability is better compared to a circumferentially endless tubular structure that is continuously unable to expand in the circumferential direction over the entire circumference, and for example, it is possible to easily adapt to a wider range of blood vessel sizes. The circumferential separation portion extends with a circumferential length greater than or equal to the circumferential size of the unit cells constituting the mesh structure of the tubular circumferential wall portion, and is inclined in the circumferential direction. As a result, the bending deformation rigidity of the tubular circumferential wall portion is reduced, and for example, the ability to follow the curvature of blood vessels is improved, preventing localized bending, the resulting detachment of captured thrombi, and excessive pressure on the inner surface of the blood vessel. In particular, as shown in Figures 13 to 15 of Patent Document 1, if the circumferential separation portion in the tubular circumferential wall portion extends in a manner that is as close to a straight line as possible in the length direction, the strain and stress during bending deformation are not easily distributed in the circumferential direction, and as a result, it is easy for deformation to occur in a state where it bends locally in the length direction. In contrast, in this embodiment, the circumferential separation portion in the cylindrical peripheral wall extends while inclined in the circumferential direction, which makes it easier to distribute strain and stress during bending deformation over a wide area including the circumferential direction, thus avoiding localized bending and making it easier to achieve a smoothly curved deformation state overall. In the invention described in (ii) above, the expanded cylindrical peripheral wall portion is provided with a spirally arranged circumferential separation portion, thereby making both the expansion / contraction deformation characteristics and the bending deformation characteristics flexible. In the invention described in (iii) above, for example, the bending deformation rigidity of the cylindrical peripheral wall portion is effectively reduced by providing a circumferential separation portion. In the invention described in (iv) above, when the cylindrical peripheral wall portion is rolled up to form a cylindrical mesh structure that extends in the longitudinal direction of the connecting line, the circumferential separation portion is provided extending in a spiral shape, thereby enabling flexible expansion and contraction deformation characteristics and bending deformation characteristics. [Explanation of Symbols]

[0075] 10. Stent retriever (first embodiment) 12 Linear skeleton 14 Connecting lines 16 Reticulated part 17 Curved wall section 18 Cylindrical peripheral wall part 20 Circumferential separation part 21. Striatum 22 unit cells 22a Unit Cell 22b unit cell 22c unit cell 22d unit cell 22e unit cell 22f unit cell 23 Circumferential edge 24 Widening section 24a Base widening section 24b Intermediate widening section 24c Widening section at the tip 24d Intermediate widening section (inter-cell widening section, segmented widening section) 26 Plating layer 30 Stent Retriever (Second Embodiment) 40 Stent Retriever (Third Embodiment) 50 Stent Retriever (Fourth Embodiment) 60 Stent Retriever (Fifth Embodiment) 62 Cell Group 1 64 Cell Group 2 70 Stent Retriever (Sixth Embodiment) 71 Circumferential edge 72 Circumferential separation part 1. Sten Retriever (Conventional Product) 2 Linear skeleton 3 Cylindrical peripheral wall part 4 Circumferential separation part 5 unit cells A Operating wire

Claims

1. A stent retriever having a cylindrical peripheral wall portion composed of a self-expanding linear skeleton that forms a mesh structure when expanded, The linear skeleton has a circumferential separation portion that extends continuously over the entire length in the retriever direction along the cylindrical circumferential wall portion, and the cylindrical circumferential wall portion is expandable on both sides in the circumferential direction at the circumferential separation portion, In the cylindrical peripheral wall portion, the circumferential separation portion extends in the length direction of the retriever while being inclined in the circumferential direction of the retriever. The circumferential separation portion in the cylindrical peripheral wall extends in the circumferential direction of the retriever with a length greater than or equal to the circumferential size of the unit cell constituting the mesh structure of the linear skeleton, The base portion of the linear skeleton has a connecting wire that extends linearly toward the operating wire, and in the unfolded and laid-down state where it is spread out on both sides in the circumferential direction at the circumferential separation portion, the circumferential edges of both ends of the linear skeleton constituting the circumferential separation portion extend linearly in a direction inclined with respect to the connecting wire. In the expanded state, the circumferential edges of the linear skeleton extend parallel to each other in the circumferential direction within the cylindrical circumferential wall portion. A stent retriever in which a widened portion is formed on only one of the circumferential edges of the linear skeleton.

2. The stent retriever according to claim 1, wherein in the expanded state of the linear skeleton, the circumferential separation portion extends in a spiral shape.

3. The stent retriever according to claim 1 or 2, wherein, in the expanded state of the linear skeleton, the circumferential separation portion in the cylindrical peripheral wall portion extends for a length of half a circumference or more in the circumferential direction of the retriever.

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