Medical use wire and guide wire

Abstract

To provide a medical use wire and a guide wire which are excellent in restoration ability.SOLUTION: There is provided a medical use wire formed of a stainless steel, wherein in the medical use wire, a cross sectional shape of the wire is a circle whose diameter is d mm. When hardness on the cross sectional shape of the wire is measured using a nano-indentation method, an average value of the hardness on an outer peripheral part which is formed of an outer peripheral edge and a circle whose distance from the outer peripheral edge is d / 17 mm, is 8.0 GPa or more.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a medical wire and a guidewire. [Background technology]

[0002] When treating stenosis in blood vessels surrounding the heart, such as the coronary arteries, or when treating areas where the blood vessel has become completely blocked due to the progression of calcification (such as chronic total occlusion (CTO)), a guidewire is inserted into the blood vessel prior to the treatment device, such as a balloon catheter, to guide the device.

[0003] For example, a guidewire made of SUS304 is proposed in Patent Document 1. Patent Document 2 discloses a wire for medical treatment instruments in which the average Vickers hardness at eight specific points on the cross section is 670 or more and 770 or less, with the aim of providing a wire for medical treatment instruments with excellent fatigue resistance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-172229 A [Patent Document 2] Patent No. 6596470 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, it is known that there is a correlation between the operability of the guidewire and its resistance to becoming habitual (resilience), but no guidewire with excellent resilience has been proposed.

[0006] An object of the present disclosure is to provide a medical wire and a guidewire that are excellent in resilience. [Means for solving the problem]

[0007] In order to solve the above problems, a medical wire according to one embodiment of the present disclosure is a medical wire made of stainless steel, the cross-sectional shape of the wire is a circle with a diameter of d mm, and when the hardness of the cross-sectional surface of the wire is measured by nanoindentation, the average hardness of the outer periphery formed by the area surrounded by the outer periphery and a circle at a distance of d / 17 mm from the outer periphery is 8.0 GPa or more.

[0008] The stainless steel has a temperature Md at which 50% of the deformation-induced martensite occurs when a 30% strain is applied, as given by Angel's formula. 30 It may be a stable austenitic stainless steel having a temperature of -50°C or lower.

[0009] The stable austenitic stainless steel may be a stainless steel conforming to ASTM F2581.

[0010] When the hardness of a cross section of the wire is measured by a nanoindentation method, the difference between the average hardness of the entire cross section of the wire and the average hardness of the outer periphery may be 0.7 GPa or less.

[0011] The wire may have an average hardness of 8.9 GPa or more over the entire cross section.

[0012] A guidewire according to one embodiment of the present disclosure includes the medical wire described above. Effect of the Invention

[0013] The present disclosure can provide a medical wire and a guidewire that are excellent in resilience and straightness. [Brief description of the drawings]

[0014] [Figure 1] 1 shows a schematic cross-sectional view of a guidewire according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a schematic diagram showing the results of measuring the cross section of a wire by a nanoindentation method. [Diagram 3]FIG. 2 is a schematic diagram of a jig used for evaluating restorability. [Figure 4] FIG. 13 is an explanatory diagram of a restorability evaluation. [Diagram 5] FIG. 4 is an explanatory diagram of a method for measuring a residual angle. [Figure 6] 3 is a diagram showing only the dots on the periphery among all the dots in the cross section of the wire shown in FIG. 2. FIG. [Figure 7] FIG. 1 is an explanatory diagram of wave height indicating straightness. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present inventors have intensively studied medical wire with excellent resilience and found that a medical wire with excellent resilience can be obtained by having a specific range of hardness of the outer periphery of the wire cross section. That is, the medical wire of the present disclosure is a medical wire made of stainless steel, the shape of the wire cross section is a circle with a diameter of d mm, and when the hardness of the wire cross section is measured by nanoindentation method, the average hardness of the outer periphery constituted by the region surrounded by the outer periphery and a circle at a distance of d / 17 mm from the outer periphery is 8.0 GPa or more. Although it is not clear why the above configuration improves resilience, when the wire is bent, the amount of distortion due to bending is greater at the outer periphery than at the inside of the wire. Therefore, even if the internal hardness is high, if the hardness of the outer periphery is low, the outer periphery, which has a larger amount of distortion, will be more likely to deform. However, it is speculated that the high hardness of the outer periphery makes it less likely to deform, thereby improving resilience.

[0016] The medical wire of the present disclosure has a cross-sectional shape of a circle with a diameter of d mm. The diameter d of the circle is not limited, but may be 0.02 to 2.00 mm, and is preferably 0.10 to 1.00 mm, and more preferably 0.20 to 0.50 mm, particularly when used in a guide wire described later. The cross-sectional shape does not need to be circular over the entire length of the wire. For example, it is sufficient that a part of the cross-sectional shape is circular, and the other part of the cross-sectional shape does not need to be circular. When a part of the cross-sectional shape is circular, it is sufficient that the average hardness of the outer periphery of the part of the cross-sectional shape is within the above range.

[0017] In the medical wire of the present disclosure, when the hardness of the cross section of the wire is measured by the nanoindentation method, the average hardness of the outer periphery formed by the outer periphery and a circle at a distance of d / 17 mm from the outer periphery is 8.0 GPa or more. From the viewpoint of further improving the restorability and rotational operability, the average hardness of the outer periphery is preferably 8.4 GPa or more, more preferably 8.9 GPa or more, and even more preferably 9.0 GPa or more. Although there is no upper limit, for example, from the viewpoint of brittleness, the average hardness of the entire cross section is preferably 12.0 GPa or less. An example of a specific method for calculating the average hardness of the outer periphery is shown below. In this specification, the hardness measurement by the nanoindentation method is a value obtained by performing the hardness measurement under the conditions of a maximum indentation load of 30 mN and a dot interval of 0.01 mm or more and less than 0.02 mm based on ISO 14577 "Instrumented Indentation Test". For example, the dot interval X can be determined by setting n so that [diameter of wire (mm) ÷ (17 × n)] is 0.01 mm or more and less than 0.02 mm. Specifically, when measuring a wire with a diameter of 0.34 mm, the dot interval by nanoindentation is set to 0.01 mm, and the hardness of the outer periphery is obtained by calculating the average value of the hardness of the outer two dots (0.02 mm) as shown in FIG. 6. That is, the hardness of the outer periphery in this case can be obtained as the average value of the outer two dots when the dot interval by nanoindentation is measured as [diameter of wire (mm) ÷ (17 × 2)].

[0018] In terms of resilience and brittleness, when the hardness of the cross section of the medical wire of the present disclosure is measured by nanoindentation, the difference between the average hardness of the entire cross section and the average hardness of the outer periphery formed by the outer periphery and a circle at a distance of d / 17 mm from the outer periphery is preferably 0.7 GPa or less. The difference is preferably 0.6 GPa or less, more preferably 0.5 GPa or less, and even more preferably 0.4 GPa or less.

[0019] In the medical wire of the present disclosure, the average hardness of the entire cross section is preferably 8.0 GPa or more. In order to further improve the restorability, the average hardness of the entire cross section is preferably 8.6 GPa or more, more preferably 8.9 GPa or more, and even more preferably 9.4 GPa or more. Although there is no upper limit, for example, in terms of brittleness, the average hardness of the entire cross section is preferably 12.0 GPa or less. The average hardness of the entire cross section may be higher than the average hardness of the outer periphery.

[0020] The residual angle of the medical wire of the present disclosure is preferably 12.0° or less, more preferably 9.5° or less, and particularly preferably 7.0° or less.

[0021] The medical wire of the present disclosure preferably has a wave height, which indicates straightness, of 1.0 mm or less, and more preferably 0.5 mm or less. The wave height can be determined by drawing a straight line from the valley of one wave of the wire to the valley and measuring the height of the crest from the line, as shown in Figure 7. When the wire has multiple waves, the wave height refers to the height of the largest wave.

[0022] The medical wire of the present disclosure has a tensile strength of 2800 N / mm 2 The tensile strength is preferably 2900N / mm or more, since this can further improve the restorability. 2 More preferably, it is 3000N / mm 2 More preferably, it is 3100N / mm 2 The upper limit of the tensile strength of the wire is not particularly limited, but is usually 3500 N / mm 2 The tensile strength of the wire can be measured by a normal tensile test for metal wire (for example, a tensile test conforming to JIS Z 2241 "Metallic Material Tensile Test Method").

[0023] The medical wire disclosed herein has a temperature Md at which 50% of deformation-induced martensite occurs when a 30% strain given by Angel's formula is applied. 30The wire can be manufactured by combining a specific straightening process with a wire drawing process performed on a steel material (base material) of a stable austenitic stainless steel having a hardness of -50°C or less. Generally, straightening processes include a process for straightening by plastic deformation such as a rotary straightener, a wire straightener, and a stretcher, and a process for straightening by applying heat such as tension annealing. However, as a result of intensive research by the present inventors, it was found that the hardness of the outer periphery of the stable austenitic stainless steel can be increased by straightening by heating after the straightening by plastic deformation, and thus a medical wire rod having excellent restorability can be obtained. It was also found that the difference between the average hardness of the cross section and the hardness of the outer periphery can be reduced by going through the above process, and that a wire rod having good straightness can be obtained. For example, even when the above-mentioned stable austenitic stainless steel is used, the recovery is poor if it is only straightened by plastic deformation as in Comparative Example 1 described later. It was found that by performing tension annealing by heat after straightening by plastic deformation, it is possible to achieve both recovery and recovery as in Examples 1 to 5 described later. In addition, it was found that, in terms of the material, metastable austenitic stainless steel such as SUS304 in which deformation-induced martensitic transformation occurs is not able to obtain excellent recovery even if tension annealing is performed after straightening by plastic deformation as in Comparative Example 2 described later. As described above, the medical wire of the present invention can only be obtained by using specific materials and carrying out specific processing.

[0024] The medical wire of the present disclosure is made of stainless steel, preferably made of stainless steel having a temperature Md at which 50% of deformation-induced martensite occurs when a 30% strain is applied, as given by the Angel formula below. 30 It is made of stable austenitic stainless steel with a temperature below -50°C. Md 30 =551-462×(C+N)-9.2×Si-8.1×Mn-13.7×Cr-×9.5Ni-18.5×Mo···Angel's formula Here, C, N, Si, Mn, Cr, Ni, Cu, and Mo are the amounts of each element (mass%). 30 The smaller the value, the more stable the austenite. The stainless steel is particularly preferably a high-nitrogen austenitic stainless steel having a nitrogen (N) content of 0.1% by mass or more, since this enhances the effects of solid solution strengthening and strain aging. The nitrogen content is more preferably 0.2% by mass or more, and even more preferably 0.4% by mass or more. The nitrogen content is preferably 1.0% by mass or less, and more preferably 0.8% by mass or less, since this enhances the breakage resistance. Examples of the stainless steel include stainless steels conforming to ASTM F2581 (C: 0.15 to 0.25 mass%, Mn: 9.50 to 12.50 mass%, P: 0.020 mass% max, S: 0.010 mass% max, Si: 0.20 to 0.60 mass%, Cr: 16.5 to 18.0 mass%, Ni: 0.05 mass% max, Mo: 2.70 to 3.70 mass%, N: 0.45 to 0.55 mass%, Cu: 0.25 mass% max, Fe: bal.), ASTM F138, F1314, F1586, and F2229. Of these, stainless steels conforming to ASTM F2581 are preferred because they provide a wire rod having particularly excellent restorability.

[0025] The wire drawing process is not particularly limited as long as it can continuously reduce the wire diameter of the steel material, and may be a process using a die or a process using a roll. The reduction in area of ​​the wire material during the process is preferably, for example, 80 to 97%. Here, the reduction in area is (1-r1 2 / r0 2 ) × 100, where r0 is the radius of the base material (wire material before processing) and r1 is the radius of the drawn wire (wire material after processing).

[0026] The straightening process for straightening the wire by plastic deformation is not particularly limited as long as it can straighten the wire, and examples thereof include a roller leveler, a wire strainer, a tension leveler, a stretcher, etc., which may be used alone or in combination. The straightening process for straightening the wire by plastic deformation may be performed at room temperature or at a temperature that does not significantly affect the metal, and is preferably performed at a temperature of, for example, 0°C to 100°C.

[0027] The tension annealing treatment is performed by heating the wire while applying tension (pulling) to the wire. The tension is preferably 10 to 40% of the tensile strength, and the heating temperature is preferably 300 to 700° C. The tension is more preferably 20 to 30%, and the heating temperature is more preferably 500 to 650° C.

[0028] Hereinafter, one embodiment of the guidewire of the present disclosure will be described with reference to the drawings, but the present disclosure is not limited to only the embodiment described in the drawings.

[0029] FIG. 1 is a schematic cross-sectional view of a guidewire 1 according to one embodiment of the present disclosure.

[0030] As shown in FIG. 1, the guidewire 1 includes a core shaft 10, a coil body 20, a distal joint portion 30, and a proximal fixing portion 40. The guidewire 1 includes a core shaft 10, a coil body 20, a distal joint portion 30, and a proximal fixing portion 40.

[0031] The core shaft 10 has a round bar shape that tapers from the base end to the tip end. A user performs rotation operation, etc. of the guide wire 1 at the end portion on the base end side.

[0032] The coil body 20 is formed into a hollow cylindrical shape by spirally winding a single metal wire 21 around the core shaft 10. As the material for the coil body 20, it is also possible to use X-ray opaque materials such as gold, platinum, tungsten, tantalum, or alloys containing these elements, or stainless steel, superelastic alloys, cobalt-based alloys, etc.

[0033] The tip joint 30 constitutes the tip of the guidewire 1 and has a substantially hemispherical shape. The material of the tip joint 30 is silver, gold, or an alloy containing these metals, lead-free solder, brazing material, adhesive, etc. Examples of the lead-free solder and brazing material that can be used include Sn-Ag based alloys, Sn-Ag-Cu based alloys, Au-Sn based alloys, Au-Ge based lead-free solders, silver brazing, gold brazing, etc.

[0034] The base end joint 40 fixes the base end of the coil body 20 to the core shaft 10. The material of the base end joint 40 is silver, gold, or an alloy containing these metals, lead-free solder, brazing material, adhesive, etc. Examples of the lead-free solder and brazing material that can be used include Sn-Ag based alloys, Sn-Ag-Cu based alloys, Au-Sn based alloys, Au-Ge based lead-free solders, silver brazing, gold brazing, etc.

[0035] The core shaft 10 is obtained by cutting the above-mentioned medical wire of the present disclosure and subjecting the end of the wire to tapering so that the outer diameter gradually becomes thinner toward the tip. By using the medical wire of the present disclosure, a guidewire with excellent restoring ability can be obtained. EXAMPLES

[0036] Next, the hardness measurement, tensile strength measurement, and recovery evaluation of the wire rod of the present disclosure will be described. The wire rods used in the evaluation are shown in Tables 1 and 2. Table 1 shows the composition, wire diameter, tensile strength, and straightness of the drawn wire rods used in Examples 1 to 5 and Comparative Examples 1 and 2. [Table 1]

[0037] The drawn wire material 1 used in Examples 1 to 5 and Comparative Example 1 shown in Table 1 is a wire material made of stainless steel conforming to ASTM F2581. The drawn wire material 2 used in Comparative Example 2 is a wire material made of SUS304 stainless steel.

[0038] Example 1 The drawn wire 1 was subjected to plastic processing at room temperature (25°C), and then tension annealing was performed by holding both ends of the wire and heating it to 500 to 650°C while applying a tension of 60 N to obtain a medical wire.

[0039] Example 2 A medical wire was obtained in the same manner as in Example 1, except that the heating temperature was changed to 450 to 600°C.

[0040] Example 3 A medical wire was obtained in the same manner as in Example 1, except that the heating temperature was changed to 400 to 550°C.

[0041] Example 4 A medical wire was obtained in the same manner as in Example 1, except that the heating temperature was changed to 550 to 700°C.

[0042] Example 5 A medical wire was obtained in the same manner as in Example 1, except that the conditions for the plastic working at room temperature (25° C.) were changed.

[0043] Comparative Example 1 A medical wire was obtained in the same manner as in Example 1, except that tension annealing was not performed.

[0044] Comparative Example 2 A medical wire was obtained in the same manner as in Example 1, except that the drawn wire 2 was used.

[0045] For the wires obtained in Examples 1 to 5 and Comparative Examples 1 and 2, the hardness and tensile strength were measured, and a restoration property was evaluated.

[0046] <Hardness measurement> The wires of Examples 1 to 5 and Comparative Examples 1 and 2 were embedded in resin, and polished so that the cross section of the wire was perpendicular to the measurement axis (indenter axis). The polished cross sections were subjected to nanoindentation hardness measurement using a KLA nanoindenter (iMicro) with a diamond Berkovich indenter under conditions of a maximum indentation load of 30 mN and a striking point spacing of 0.01 mm based on the nanoindentation method (ISO 14577 "Instrumented Indentation Test").

[0047] FIG. 2 is a schematic diagram showing the results of measuring the cross section of a wire by the nanoindentation method. The cross section in FIG. 2(a) is the measurement result of the wire of Example 1, and the cross section in FIG. 2(b) is the measurement result of the wire of Comparative Example 2. Each dot in each cross section is a square of 0.01 mm on each side, and corresponds to a measurement point. In addition, each dot is color-coded so that the harder the measured hardness, the lighter the color, and it can be seen that the wire of Example 1 is harder overall. In order to eliminate the influence of the resin used for embedding, measurement points with a hardness of less than 7.0 GPa were excluded.

[0048] <Tensile test> The tensile strength of the wires of Examples 1 to 5 and Comparative Examples 1 and 2 was measured by a tensile test of a metal wire (a tensile test conforming to JIS Z 2241 "Method of tensile test for metallic materials").

[0049] <Restorability evaluation> The wires of Examples 1 to 5 and Comparative Examples 1 and 2 were inserted into groove 3 of jig 2 shown in FIG. 3, and the residual angle of each wire was measured. FIG. 3 is a schematic diagram of a jig 2 used for evaluating the restorability.

[0050] The first jig 2 is made of resin (e.g., a transparent acrylic plate) and is composed of a first plate 2A having a groove 3 and a second plate 2B for covering the groove 3. The groove 3 of the first plate 2A is formed by a convex portion provided on the first plate 2A. The groove 3 has a pair of straight line portions 3a and a semicircular arc portion 3b. The width of the groove 3 is 1.0 mm, and the depth of the groove 3 is 1.0 mm. The length of the straight line portion 3a is 10 mm, and the radius R of the semicircular arc portion 3b is 10.0 mm. The second plate 2B abuts against the convex portion of the first plate 2A and covers the groove 3. The second plate 2B is fixed to the first plate 2A by four bolts 4.

[0051] FIG. 4 is an explanatory diagram of the restoration evaluation. With the bolt 4 (FIG. 3) loosened, the wire X cut to a predetermined length (for example, 100 mm) is inserted into the groove 3 as shown in FIG. 4(a), and the bolt 4 is tightened. As shown in FIG. 4(b), one end of the wire X is pushed into the very edge of the opening of the groove 3 of the first jig 2. As shown in FIG. 4(c), the other end of the wire X is pushed into the very edge of the opening of the groove 3 of the first jig 2. As shown in FIG. 4(d), one end of the wire X is pushed in, the center of the wire X is moved to the center of the groove 3, the bolt 4 is loosened, and the wire X is taken out. As a result, a strain (about 1.7) is applied to the entire wire X. The strain amount (%) is calculated by (R / (LR))×100. Here, R is the wire diameter of the wire X, and L is the diameter of the semicircular arc portion 3b of the groove 3 into which the wire X is inserted.

[0052] As shown in FIG. 5, tangents are drawn from both ends of wire X, and the angle at which the two tangents intersect (residual angle θ) is measured.

[0053] The results of the hardness measurement, tensile test, and recovery evaluation (residual angle) are shown in Table 3. [Table 2] Ave (whole) is the average hardness of all dots in the measured cross section. Ave (outer periphery) is the average hardness of the outer periphery dots (FIG. 6) among all dots in the measured cross section. FIG. 6 shows only the dots in the outer periphery C3 among all dots in the cross section of the wire shown in FIG. 2.

[0054] As in the wires of Examples 1 to 5, the average hardness of the outer periphery of the cross section is increased by performing straightening processing by plastic deformation on the drawn wire made of stable austenitic stainless steel, and then performing tension annealing, thereby making it possible to obtain a wire with a small residual angle. In addition, the average hardness of the entire cross section of the wire is increased, and the difference in hardness between the average hardness of the entire cross section of the wire and the average hardness of the outer periphery of the cross section of the wire is reduced.

[0055] On the other hand, the wire of Comparative Example 1 has a low average hardness over the entire cross section and a large residual angle because the drawn wire was not subjected to tension annealing. The wire of Comparative Example 2 is made of SUS304 drawn wire that has been subjected to plastic working and tension annealing, so that the average hardness over the entire cross section is equivalent to that of Example 5, but the hardness of the outer periphery is low, resulting in a large residual angle.

[0056] The present disclosure is not limited to the configurations of the above-described embodiments, but is intended to include all modifications within the meaning and scope of the claims, as defined by the claims.

[0057] For example, in the above embodiment, the medical wire was the core shaft 10 of the guidewire 1, but it may be the wire constituting the coil body 20, or the wire used in other medical instruments, such as the wire constituting a reinforcing body (e.g., a cylindrical braid, a coil body) used to reinforce a catheter. By forming the coil body 20 or the reinforcing body of a catheter using the medical wire of the above embodiment, it is possible to improve the restoring ability of the coil body 20 or the reinforcing body after bending. Furthermore, when a rotation operation is performed in a complex and intricate blood vessel, a medical member constituted by a coil or a hollow body manufactured using the wire can also exhibit excellent rotational followability, as described above. [Explanation of symbols]

[0058] 1 Guidewire 10 Core shaft 20 Coil body

Claims

1. A medical wire made of stainless steel, The cross-sectional shape of the wire is a circle with a diameter of d mm, When the hardness of a cross section of the wire is measured by a nanoindentation method, the average hardness of an outer periphery formed by a region surrounded by the outer periphery and a circle at a distance of d / 17 mm from the outer periphery is 8.0 GPa or more, The medical wire rod, wherein the stable austenitic stainless steel is a stainless steel conforming to ASTM F2581.

2. 2. The medical wire according to claim 1, wherein the stainless steel is a stable austenitic stainless steel having a temperature Md30 of −50° C. or lower at which 50% deformation-induced martensite occurs when a 30% strain given by Angel's formula is applied.

3. 3. The medical wire according to claim 1, wherein, when the hardness of a cross section of the wire is measured by a nanoindentation method, the difference between the average hardness of the entire cross section of the wire and the average hardness of the outer periphery is 0.7 GPa or less.

4. 4. The medical wire according to claim 1, wherein the average hardness of the entire cross section of the wire is 8.9 GPa or more.

5. A guide wire comprising the medical wire according to any one of claims 1 to 4.

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