dilator

Abstract

Provided is a dilator capable of preventing a helical protrusion from separating from a hollow shaft. The dilator (1) includes a hollow shaft (11) having a tapered portion (111) in which the outer diameter of the front end is smaller than the outer diameter of the base end, a front-end tip (21) having a base end located at the front end of the tapered portion (111) and extending toward the front end direction, and a helical protrusion (31) provided at least on the outer peripheral surface (11s) of the tapered portion (111), wherein the helical protrusion (31) is formed by winding a wire (31w), and has a gap (31g) between adjacent portions of the helical protrusion in the long axis direction of the hollow shaft (11), and the inner peripheral radius CIDmin of the portion of the helical protrusion (31) having the smallest inner peripheral radius is smaller than the outer peripheral radius TODmax of the portion of the front-end tip (21) having the largest outer peripheral radius.

Description

Technical Field

[0001] This invention relates to an expander. Background Technology

[0002] Dilatators are known to the public, for example, as devices for dilating openings formed on the body surface, organs, etc., or for dilating narrow sections formed in the bile duct, pancreatic duct, etc.

[0003] Since such expanders require strong propulsion when expanding, a type of expander is disclosed, for example, by providing a coil body on the outer circumferential surface of the tapered portion of the shaft used for expansion, thereby utilizing the thread action generated by rotation to supplement the propulsion force (see, for example, Patent Document 1).

[0004] The coil body described above is constructed, for example, by winding wire around the outer peripheral surface of the tapered portion, thereby making it easy to form a coil body.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: International Publication No. 2013 / 038720 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] However, the aforementioned existing expander is a structure in which the wire constituting the coil body is only wound around the outer circumference of the shaft. Therefore, the coil body may detach from the shaft due to resistance from the structure when expanding the hole or the tension when pulling.

[0010] The present invention was made based on the above circumstances, and its object is to provide an expander that can prevent the spiral protrusion from detaching from the hollow shaft.

[0011] Methods for solving problems

[0012] In some aspects of this disclosure,

[0013] (1) An expander, characterized in that the expander comprises: a hollow shaft having a tapered portion with an outer diameter at the front end smaller than the outer diameter at the base end;

[0014] A front tip, the base of which is located at the front end of the tapered portion, and the front tip extends toward the front end; and

[0015] A spiral-shaped protrusion is provided at least on the outer peripheral surface of the conical portion, wherein...

[0016] The spiral protrusions are formed by winding wire, and there are gaps between adjacent portions of the spiral protrusions in the long axis direction of the hollow shaft.

[0017] The inner radius of the portion with the smallest inner radius of the spiral protrusion is smaller than the outer radius of the portion with the largest outer radius of the tip.

[0018] (2) According to the expander described in (1) above, the outer circumferential radius of the portion with the largest outer circumferential radius of the spiral protrusion is greater than the outer circumferential radius of the portion with the largest outer circumferential radius of the front tip.

[0019] (3) According to the expander described in (2) above, in the portion of the spiral protrusion disposed on the outer peripheral surface of the conical portion, the outer peripheral radius of the portion with the largest outer peripheral radius is greater than the outer peripheral radius of the portion with the largest outer peripheral radius of the front tip.

[0020] (4) The expander according to (2) or (3) above, wherein the inner circumferential radius of the portion with the largest inner circumferential radius of the spiral protrusion is greater than the outer circumferential radius of the portion with the largest outer circumferential radius of the front tip.

[0021] (5) According to the expander described in (1) above, in the part with the smallest inner circumferential radius of the spiral protrusion, the distance between the long axis of the hollow shaft and the center of the wire is smaller than the outer circumferential radius of the part with the largest outer circumferential radius of the tip.

[0022] (6) The expander according to any one of (1) to (5) above, wherein the portion with the smallest inner circumferential radius of the spiral protrusion is located at the front end of the spiral protrusion.

[0023] (7) The expander according to any one of (1) to (6) above, wherein the spiral protrusion does not engage with the conical portion.

[0024] In this specification, "front end direction" refers to the direction along the long axis of the expander, indicating the direction in which the expander travels toward the portion being expanded. "Base end direction" refers to the direction along the long axis of the expander, indicating the direction opposite to the front end direction. Furthermore, "front end" refers to the end of any component or part in the front end direction, and "base end" refers to the end of any component or part in the base end direction. "Inner circumferential radius" refers to the distance between the long axis of the expander and the innermost circumference of the corresponding part, and "outer circumferential radius" refers to the distance between the long axis of the expander and the outermost circumference of the corresponding part.

[0025] Invention Effects

[0026] The present invention provides an expander that can prevent the spiral protrusion from detaching from the hollow shaft. Attached Figure Description

[0027] Figure 1 This is a schematic side view showing the first embodiment.

[0028] Figure 2 It is Figure 1 A partial enlarged view showing a rough side view.

[0029] Figure 3 This is a schematic side view showing the second embodiment.

[0030] Figure 4 This is a schematic side view showing the third embodiment.

[0031] Figure 5 This is a schematic side view showing the fourth embodiment. Detailed Implementation

[0032] The expander disclosed herein is characterized in that it comprises: a hollow shaft having a tapered portion with an outer diameter at the front end smaller than that at the base end; a front tip having its base end located at the front end of the tapered portion and extending toward the front end; and a helical protrusion having at least one portion disposed on the outer peripheral surface of the tapered portion, wherein the helical protrusion is formed by winding wire, and there is a gap between adjacent portions of the helical protrusion in the long axis direction of the hollow shaft, and the inner peripheral radius of the portion with the smallest inner peripheral radius of the helical protrusion is smaller than the outer peripheral radius of the portion with the largest outer peripheral radius of the front tip.

[0033] In addition, unless otherwise specified, "major axis direction" in this specification refers to the length direction of the expander.

[0034] The first to fourth embodiments of the present invention will now be described with reference to the accompanying drawings, but the present invention is not limited to the embodiments described in the drawings. Furthermore, the dimensions of the expanders shown in each drawing are for ease of understanding of the embodiments and do not correspond to actual dimensions.

[0035] [First Implementation Method]

[0036] Figure 1 This is a schematic side view showing the first embodiment. Figure 1 As shown, the expander 1 generally includes a hollow shaft 11, a front end tip 21, a spiral protrusion 31, and a base 41.

[0037] The hollow shaft 11 is a shaft with a hollow shape. The hollow shaft 11 has, for example, a tapered portion 111, a main body portion 112, and an inner cavity 11h.

[0038] The tapered portion 111 is the part where the outer diameter of the front end is smaller than the outer diameter of the base end. Specifically, the tapered portion 111 can be exemplified by, for example, having an outer diameter that increases linearly from the front end to the base end (see reference). Figure 1 Its surface expands in diameter in a convex or concave shape from the front end to the base end (not shown), etc.

[0039] The main body 112 is a portion whose front end is located at the base end of the tapered portion 111 and extends toward the base end. The main body 112 may, for example, be configured to have a certain outer diameter from its front end to its base end.

[0040] The inner cavity 11h is a through-hole through which a guide wire (not shown) or similar device is inserted and passes. The inner cavity 11h can, for example, be a continuous space extending along the long axis between the front end and the base end of the hollow shaft 11 (e.g., with...). Figure 1 It is composed of the part inside the common tangent line shown in the dashed diagram.

[0041] The tapered portion 111 and the main body portion 112 can be formed integrally or separately. Regarding the hollow shaft 11 of this embodiment, the tapered portion 111 and the main body portion 112 are integrally formed, and both are composed of a coil body 11C (hereinafter also referred to as "first coil body 11C"), which is formed by continuously and spirally winding a single wire 11w around the long axis Z of the expander. In this way, the hollow shaft 11 is formed by winding the wire 11w, thereby improving torque transmission (the reliability of the transmission when the rotational force applied to the base end of the expander 1 is transmitted to its front end).

[0042] As for the material constituting the hollow shaft 11, since the expander 1 is to be inserted into and penetrate the body cavity, it is preferable to have antithrombotic properties, flexibility, and biocompatibility. Examples of such materials include resins such as polyamide resin, polyolefin resin, polyester resin, polyurethane resin, silicone resin, and fluoropolymer resin; and metals such as stainless steel and superelastic alloys (nickel-titanium alloy). The materials constituting the conical portion 111 and the main body portion 112 can be the same material or different materials.

[0043] The tapered portion 111 and the main body 112 of the first coil body 11C can be integral or separate. Furthermore, the tapered portion 111 and the main body 112 can be formed of the same material or different materials. Additionally, the wire diameter of the coil body in the tapered portion 111 can be the same as or different from the wire diameter of the coil body in the main body 112. In this embodiment, the tapered portion 111 and the main body 112 of the first coil body 11C are formed by using a single wire of the same material and diameter as the wire 11w, and winding this wire 11w into a spiral shape.

[0044] In addition, the hollow shaft 11 may also have various coatings (not shown) on its outer peripheral surface 11s side. Examples of coatings include protective films (coatings, etc.) for protecting the surface of the hollow shaft 11, and base films for improving the adhesion between the hollow shaft 11 and the spiral protrusion 31 (described later).

[0045] The front tip 21 is a portion whose base is located at the front end of the tapered portion 111 and extends toward the front end. Specifically, the front tip 21 may be formed to taper toward the front end to facilitate the movement of the expander 1 within the body cavity.

[0046] The tip 21 may also have an inner cavity 21h. For example, the inner cavity 21h may be configured to extend from the tip of the tip 21 to the base end and connect to the inner cavity 11h of the hollow shaft 11.

[0047] Since the expander 1 needs to travel within the body cavity, a soft material is preferred as the material constituting the tip 21. Examples of resin materials constituting the tip 21 include polyurethane and polyurethane elastomers.

[0048] The spiral protrusion 31 is a portion provided at least on the outer peripheral surface of the conical portion 111. The spiral protrusion 31 is constituted by a coil body 31C (hereinafter also referred to as "second coil body 31C") formed by winding wire, and there is a gap 31g between adjacent portions of the spiral protrusion 31 in the long axis direction of the hollow shaft. Specifically, the spiral protrusion 31 can be formed, for example, by continuously or discontinuous single or multiple strands of wire 31w, which is spirally wound along the long axis direction of the hollow shaft 11 in a manner that contacts the outer peripheral surface 11s. In this embodiment, the spiral protrusion 31 is provided on the outer peripheral surface 11s of the conical portion 111 and the main body portion 112.

[0049] The wire 31w constituting the spiral-shaped protrusion 31 can be a single wire, a stranded wire, or a combination of single wires and stranded wires. A single wire refers to a single strand of wire, while a stranded wire refers to a bundle of wires formed by twisting multiple single wires together beforehand.

[0050] For example, the same material used to form the spiral protrusion 31 can be used as the material used to form the hollow shaft 11.

[0051] Here, as Figure 2 As shown, the spiral protrusion 31 and the front end tip 21 of the expander 1 are formed such that the inner circumferential radius (CIDmin) of the spiral protrusion 31 with the smallest inner circumferential radius is smaller than the outer circumferential radius (TODmax) of the front end tip 21 with the largest outer circumferential radius (CIDmin<TODmax).

[0052] Furthermore, in the portion with the smallest inner radius of the spiral protrusion 31, the distance (CMD, hereinafter also referred to as "center distance") between the major axis of the hollow shaft 11 and the center of the wire can also be formed to be smaller than the outer radius (TODmax) of the portion with the largest outer radius of the tip 21 (see reference). Figure 1 , Figure 2 Specifically, for example, by appropriately selecting the wire diameter of the second coil body 31C, the outer circumferential radius (TODmax) of the tip 21, and the outer circumferential radius of the tapered portion 111, the center distance (CMD) of the spiral protrusion 31 can be made smaller than the outer circumferential radius (TODmax) of the tip 21. This reliably prevents the spiral protrusion 31 from detaching from the hollow shaft 11.

[0053] Provided that the effect of the invention is not compromised, the portion of the spiral protrusion 31 with the smallest inner circumferential radius (the portion of the spiral protrusion that becomes the inner circumferential radius (CIDmin)) can also be located at any part of the spiral protrusion 31. For example, the portion of the spiral protrusion 31 that becomes the inner circumferential radius (CIDmin) can be located at the front end of the spiral protrusion 31 in the long axis direction (see reference). Figure 1 , Figure 2 It can also be located in the middle of the spiral protrusion 31 in the long axis direction (not shown).

[0054] In this embodiment, the portion of the spiral protrusion 31 that forms the inner circumferential radius (CIDmin) is positioned at the front end of the spiral protrusion 31. This prevents the spiral protrusion 31 from protruding further forward than the front end tip 21, thereby suppressing tissue damage caused by the second coil body 31C.

[0055] The spiral protrusion 31 and the tapered portion 111 may engage at least a portion of their contact points, or they may not engage (only contact).

[0056] In this embodiment, the spiral protrusion 31 does not engage with the conical portion 111, and the second spiral 31C is wound around the outer peripheral surface 11s of the hollow shaft 11 in a state of only contact. As a result, the reduction in flexibility of the portion of the expander 1 corresponding to the conical portion 111 can be suppressed.

[0057] The base 41 is the portion for the surgeon to operate the dilator 1. The base 41, for example, has an inner cavity 41h that communicates with the inner cavity 11h of the hollow shaft 11 and extends from the front end to the base end. The base 41 can be configured such that its front end is connected to the base end of the hollow shaft 11. During surgery, for example, a guide wire or similar device is inserted and passes through the inner cavity 41h. Furthermore, by rotating the base 41, the hollow shaft 11, the front tip 21, and the spiral protrusion 31 rotate together.

[0058] Next, the method of using the dilator 1 will be explained. Here, a procedure using the dilator 1 to dilate a portion of a lesion, such as a chronic total occlusion (CTO) formed within a blood vessel, will be described.

[0059] First, a hole is formed by puncturing the dilated portion using an insertion needle (not shown). Next, a guidewire (not shown) is inserted into the lumen of the insertion needle, and then the insertion needle is removed. Next, the base of the guidewire is inserted into the lumen 21h from the front end of the tip 21, and the hollow shaft 11 is advanced into the dilated portion. At this time, the front end of the dilator 1 travels while following the shape of the bent inserted portion (e.g., blood vessel, esophagus, stomach, bile duct, etc.).

[0060] Next, after inserting the front end of the expander 1 from the front tip 21 into the hole formed in the expanded portion, the hollow shaft 11 is rotated and advanced by operating the base 41, while the hole is expanded using the tapered portion 111. At this time, since the expander 1 is formed with an inner circumferential radius (CIDmin) smaller than the outer circumferential radius (TODmax), the expanded portion can be expanded smoothly without the second coil body 31C detaching from the hollow shaft 11.

[0061] As described above, since the expander 1 has the above structure, it is possible to prevent the spiral protrusion 31 from detaching from the hollow shaft 11 and to perform surgery smoothly.

[0062] [Second Implementation]

[0063] Figure 3 This is a schematic side view showing the second embodiment. Figure 3 As shown, the expander 2 generally includes a hollow shaft 12, a front end tip 21, a spiral protrusion 31, and a base 42. This expander 2 differs from the first embodiment in having a hollow shaft 12 and a base 42. However, the structure of the front end tip 21 and the spiral protrusion 31 is the same as in the first embodiment; therefore, the same reference numerals are used for the same parts, and detailed descriptions are omitted. Furthermore, since the structure, except for the hollow shaft 12 and the base 42 shown below, is the same as in the first embodiment, and the method of using the expander 2 is the same as in the first embodiment, detailed descriptions are omitted.

[0064] The hollow shaft 12 is a shaft with a hollow shape. The hollow shaft 12 has, for example, a tapered portion 121, a main body portion 122, and an inner cavity 12h.

[0065] The tapered portion 121 is a section where the outer diameter of the front end is smaller than the outer diameter of the base end. The main body portion 122 is a section where its front end is located at the base end of the tapered portion 121 and extends toward the base end. The inner cavity 12h is a through hole for inserting and passing through a guide wire (not shown).

[0066] The tapered portion 121 and the main body portion 122 can be integral or separate. Furthermore, the tapered portion 121 and the main body portion 122 can be formed from the same material or from different materials. Also, the wall thickness of the tapered portion 121 and the wall thickness of the main body portion 122 can be the same or different. In this embodiment, the tapered portion 121 and the main body portion 122 are made of the same material, formed integrally by casting or the like, and have different wall thicknesses (an inner cavity 12h with the same inner diameter from the front end to the base end of the hollow shaft 12).

[0067] The base 42 is the portion for the surgeon to operate the dilator 2. In this embodiment, the base 42 has an inner cavity 42h (see reference). Figure 3 The inner cavity 42h is connected to the inner cavity 12h of the hollow shaft 12, and extends from the front end to the base end, having the same inner diameter as the inner cavity 12h.

[0068] As described above, since the expander 2 has the above structure, it is possible to prevent the spiral protrusion 31 from detaching from the hollow shaft 12 and to perform surgery smoothly.

[0069] [Third Implementation Method]

[0070] Figure 4 This is a schematic side view showing the third embodiment. Figure 4 As shown, the expander 3 generally includes a hollow shaft 13, a front end tip 21, a spiral protrusion 33, and a base 41 (not shown). This expander 3 differs from the first embodiment in having a hollow shaft 13 and a spiral protrusion 33. Furthermore, since the structures of the front end tip 21 and the base 41 are the same as in the first embodiment, the same reference numerals are used for the same parts, and detailed descriptions are omitted. Additionally, since the structure, except for the hollow shaft 13 and the spiral protrusion 33 shown below, is the same as in the first embodiment, and the expander 3 is used in the same way as in the first embodiment, detailed descriptions are omitted.

[0071] The hollow shaft 13 is a shaft with a hollow shape. The hollow shaft 13 has, for example, a tapered portion 131, a main body portion 132, and an inner cavity 13h.

[0072] The tapered portion 131 is a section where the outer diameter of the front end is smaller than the outer diameter of the base end. The main body portion 132 is a section where its front end is located at the base end of the tapered portion 131 and extends toward the base end. The outer diameter of the main body portion 132 is the same as the outer diameter of the base end of the tapered portion 131. The inner cavity 13h is a through hole for inserting and passing through a guide wire (not shown).

[0073] The spiral protrusion 33 is a portion provided at least on the outer peripheral surface of the conical portion. The spiral protrusion 33 is composed of a coil body 33C (second coil body 33C) formed by winding wire 33w, and there is a gap 33g between adjacent portions of the spiral protrusion 33 in the long axis direction of the hollow shaft 13.

[0074] Furthermore, in this embodiment, the outer circumferential radius (CODmax) of the portion with the largest outer circumferential radius of the spiral protrusion 33 is formed to be larger than the outer circumferential radius (TODmax) of the portion with the largest outer circumferential radius of the tip 21. Specifically, for example, the outer diameter of the base end of the conical portion 131 of the hollow shaft 13 may also be formed to be larger than that of the conical portion 111 in the first embodiment (see reference). Figure 4 Alternatively, by appropriately adjusting the wire diameter of the second coil body 33C, the outer circumferential radius (CODmax) of the second coil body 33C can be made larger than the outer circumferential radius (TODmax) of the front end tip 21 (not shown). The portion of the spiral protrusion 33 that forms the outer circumferential radius (CODmax) can be a portion on the tapered portion 131 (not shown) or a portion on the main body portion 132 (see reference). Figure 4 ).

[0075] Furthermore, in the portion of the spiral protrusion 33 provided on the outer peripheral surface 13s of the conical portion 131, the outer peripheral radius (CODmax) of the portion with the largest outer peripheral radius can also be configured to be larger than the outer peripheral radius (TODmax) of the portion with the largest outer peripheral radius of the tip 21. This further enhances the propulsive force of the expander 3 generated by the thread action during tissue expansion (as the conical portion 131 passes through the expanded portion).

[0076] As described above, since the expander 3 has the above-described structure, it can benefit from the fact that the outer periphery of the spiral protrusion 33 protrudes from the front tip 21 in the front view (when the expander 3 is viewed from the front end side in the long axis direction toward the front tip 21), thereby correspondingly increasing the thrust of the expander 3 generated by the thread action.

[0077] [Fourth Implementation Method]

[0078] Figure 5 This is a schematic side view showing the fourth embodiment. (Example) Figure 5As shown, the expander 4 generally includes a hollow shaft 14, a front end tip 21, a spiral protrusion 34, and a base 41 (not shown). This expander 4 differs from the first embodiment in having a hollow shaft 14 and a spiral protrusion 34. Furthermore, since the structures of the hollow shaft 21 and the base 41 are the same as in the first embodiment, the same reference numerals are used for the same parts, and detailed descriptions are omitted. Moreover, since the structure, except for the hollow shaft 14 and the spiral protrusion 34 shown below, is the same as in the first embodiment, and the method of using the expander 4 is the same as in the first embodiment, detailed descriptions are omitted.

[0079] The hollow shaft 14 is a shaft with a hollow shape. The hollow shaft 14 has, for example, a tapered portion 141, a main body portion 142, and an inner cavity 14h.

[0080] The tapered portion 141 is a portion whose outer diameter at the front end is smaller than the outer diameter at the base end. The main body portion 142 is a portion whose front end is located at the base end of the tapered portion 141 and extends toward the base end. The outer diameter of the main body portion 142 is the same as the outer diameter of the base end of the tapered portion 141. The inner cavity 14h is a through hole for inserting and passing through a guide wire (not shown).

[0081] The spiral protrusion 34 is a portion provided at least on the outer peripheral surface of the conical portion 141. The spiral protrusion 34 is composed of a coil body 34C (second coil body 34C) formed by winding wire 34w, and there is a gap 34g between adjacent portions of the spiral protrusion 34 in the long axis direction of the hollow shaft 14.

[0082] Furthermore, in this embodiment, the inner radius (CIDmax) of the portion with the largest inner radius of the spiral protrusion 34 is formed to be larger than the outer radius (TODmax) of the portion with the largest outer radius of the tip 21. Specifically, for example, the outer diameter of the base of the tapered portion 141 of the hollow shaft 14 can be larger than that of the tapered portion 131 in the third embodiment (see reference). Figure 5 This results in the inner circumferential radius (CIDmax) of the second coil body 34C being larger than the outer circumferential radius (TODmax) of the front end tip 21 (not shown). The portion of the spiral protrusion 34 that forms the inner circumferential radius (CIDmax) can be a portion on the tapered portion 141 (not shown) or a portion on the main body portion 142 (see reference). Figure 5 ).

[0083] As shown above, since the expander 4 has the above-described structure, it can benefit from the outer periphery of the spiral protrusion 34 protruding from the front end tip 21 in the front view, thereby correspondingly increasing the propulsive force of the expander 4 generated by the thread action.

[0084] Furthermore, the present invention is not limited to the structure of the above-described embodiments, but is intended to include all changes within the meaning and scope of the claims as shown in the claims.

[0085] For example, in the first embodiment described above, the expander 1 at the front end of the spiral protrusion 31, where the inner circumferential radius (CIDmin) is located, was described. However, the location of the inner circumferential radius (CIDmin) can also be any part of the spiral protrusion in the long axis direction (e.g., the middle or base of the spiral protrusion in the long axis direction).

[0086] Furthermore, in the second embodiment, the hollow shaft 12 formed by the above-described casting process can also be applied to any other expander disclosed in this specification.

[0087] Furthermore, in the third embodiment described above, an expander 3 was explained in which the outer radius (CODmax) of the spiral protrusion 33 is made larger than the outer radius (TODmax) of the tip 21 by adjusting the outer diameter of the hollow shaft 13. However, this expander can also make the outer radius (CODmax) of the spiral protrusion larger than the outer radius (TODmax) of the tip by adjusting the wire diameter of the second coil body, or by adjusting both the outer diameter of the hollow shaft and the wire diameter of the second coil body.

[0088] Furthermore, in the above embodiment, the expanders 1 to 4 are described where the portion having the inner circumferential radius (CIDmin) exists only at one location of the spiral protrusions 31 to 34. However, the portion having the inner circumferential radius (CIDmin) may also be provided at two or more mutually separated locations of the spiral protrusions.

[0089] Furthermore, in the above embodiment, the expanders 1 to 4, which are provided only at specific locations within the spiral protrusions 31 to 34, are described for the inner circumferential radius (CIDmin), outer circumferential radius (CODmax), and center radius (CMD). However, these locations may also be provided at any location within the spiral protrusions along the long axis (the conical portion of the hollow shaft and / or any location on the main body).

[0090] Explanation of reference numerals in the attached figures

[0091] 1, 2, 3, 4 expanders

[0092] 11, 12, 13, 14 hollow shafts

[0093] 21 front tip

[0094] 31, 33, 34 spiral convex parts

[0095] 31C, 33C, 34C coil bodies (second coil body)

[0096] 31g, 33g, 34g interval

[0097] 111, 121, 131, 141 conical sections

Claims

1. An expander, characterized in that, The expander includes: A hollow shaft having a tapered portion whose outer diameter at the front end is smaller than the outer diameter at the base end; A front tip, the base of which is located at the front end of the tapered portion, and the front tip extends toward the front end; and A spiral-shaped protrusion, wherein the spiral-shaped protrusion is at least provided on the outer peripheral surface of the conical portion, wherein, The spiral protrusions are formed by winding wire, and there are gaps between adjacent portions of the spiral protrusions in the long axis direction of the hollow shaft. The inner radius of the portion with the smallest inner radius of the spiral protrusion is smaller than the outer radius of the portion with the largest outer radius of the tip. The outer radius of the portion with the largest outer circumference of the spiral protrusion is greater than the outer radius of the portion with the largest outer circumference of the tip. The outer radius of a portion of the spiral protrusion is smaller than the outer radius of the part with the largest outer radius of the tip.

2. The expander according to claim 1, wherein, In the portion of the spiral protrusion located on the outer circumferential surface of the conical portion, the outer circumferential radius of the portion with the largest outer circumferential radius is greater than the outer circumferential radius of the portion with the largest outer circumferential radius of the tip.

3. The expander according to claim 1, wherein, The inner radius of the portion with the largest inner radius of the spiral protrusion is greater than the outer radius of the portion with the largest outer radius of the tip.

4. The expander according to claim 2, wherein, The inner radius of the portion with the largest inner radius of the spiral protrusion is greater than the outer radius of the portion with the largest outer radius of the tip.

5. The expander according to claim 1, wherein, In the portion with the smallest inner circumferential radius of the spiral protrusion, the distance between the major axis of the hollow shaft and the center of the wire is smaller than the outer circumferential radius of the portion with the largest outer circumferential radius of the tip.

6. The expander according to any one of claims 1 to 5, wherein, The portion with the smallest inner circumferential radius of the spiral protrusion is located at the front end of the spiral protrusion.

7. The expander according to any one of claims 1 to 5, wherein, The spiral protrusions do not engage with the conical portion.

8. The expander according to claim 6, wherein, The spiral protrusions do not engage with the conical portion.

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