Medical device shaft and medical device

Abstract

If the diameter of a medical device shaft, which is the minimum length in a cross-section orthogonal to the axial direction, is defined as the minimum diameter, the diameter in a cross-section in the direction orthogonal to the direction of the minimum diameter is defined as the orthogonal diameter, and a value obtained by dividing the difference between the minimum diameter and the orthogonal diameter by the orthogonal diameter is defined as an oblateness ratio, the medical shaft has a specific portion in which the oblateness ratio is 2% to 6%, inclusive.

Description

Shaft for medical device and medical device

[0001] The technology disclosed herein relates to a shaft for a medical device and a medical device.

[0002] For example, methods using catheters are widely used to treat or examine stenosis or occlusions (hereinafter referred to as "lesions") in blood vessels. A guidewire is used to guide the catheter to the lesion in the blood vessel. The guidewire includes a core shaft.

[0003] A guidewire is required to have rotational followability such that when the proximal end portion held by an operator such as a doctor is rotated, the distal end portion rotates smoothly in response to the rotation.

[0004] In order to improve the blood vessel selectivity of the guide wire, the operator performs a procedure called "shaping" in which the tip of the guide wire is bent at a predetermined angle in advance.

[0005] A known guidewire has a portion at the distal end of the core shaft with a flattening ratio of 7% to 35% in order to ensure good rotational followability while facilitating shaping of the distal end (see, for example, Patent Document 1). The flattening ratio of the core shaft is a percentage obtained by dividing the difference between the minimum diameter and the minimum diameter in a cross section perpendicular to the axial direction of the core shaft, where the minimum diameter is the diameter with the smallest length in the cross section perpendicular to the axial direction of the core shaft and the orthogonal diameter is the diameter in the cross section perpendicular to the direction of the minimum diameter, by the orthogonal diameter.

[0006] International Publication No. 2021 / 131019

[0007] The above-described conventional techniques have a problem in that it is difficult to suppress three-dimensional deformation when shaping the distal end of a guidewire while ensuring good rotational tracking of the guidewire. It is preferable that the guidewire does not undergo three-dimensional deformation even when shaped. The absence of three-dimensional deformation in a guidewire means that the silhouette obtained by projecting the shaped guidewire onto a certain plane is a shape that is close to a straight line. This problem is not limited to guidewires having a core shaft, but is a common problem in medical devices having a medical device shaft.

[0008] This specification discloses a technique that can solve the above-mentioned problems.

[0009] The technology disclosed in this specification can be realized, for example, in the following forms.

[0010] (1) The shaft for a medical device disclosed in this specification has a specific portion in which the flattening ratio is 2% or more and 6% or less, where the minimum diameter is the diameter with the shortest length in a cross section perpendicular to the axial direction, the orthogonal diameter is the diameter in the cross section perpendicular to the direction of the minimum diameter, and the difference between the orthogonal diameter and the minimum diameter divided by the orthogonal diameter is the flattening ratio.

[0011] The rotational compliance of a medical device improves as the cross-sectional shape of the medical device shaft approaches a circle. If the cross-sectional shape of a medical device shaft approaches a circle, variations in the shaping direction may occur during shaping, resulting in three-dimensional deformation of the medical device. This medical device shaft has a specific portion with a flattening ratio of 2% or more and 6% or less. Although the cross-sectional shape of the specific portion is close to a circle, it is flattened to a certain extent, which can prevent variations in the shaping direction. Therefore, this medical device shaft can prevent three-dimensional deformation during shaping while ensuring good rotational compliance.

[0012] (2) The shaft for a medical device may have a distal end specific portion located distally of the specific portion and having a flattening ratio of 7% or more. With this configuration, it is possible to effectively suppress variations in the direction of shaping in the distal end specific portion, and it is possible to effectively suppress three-dimensional deformation during shaping.

[0013] (3) In the above-described medical device shaft, the tip specified portion may have a curved portion that is curved around an axis parallel to the orthogonal diameter of the tip specified portion. With this configuration, it is possible to more effectively suppress variations in the direction of shaping in the tip specified portion, and it is possible to more effectively suppress three-dimensional deformation during shaping.

[0014] (4) In the above-described medical device shaft, the direction of the minimum diameter of the specific portion may be parallel to the direction of the minimum diameter of the tip specific portion. With this configuration, it is possible to effectively suppress variations in the shaping direction of the specific portion and the tip specific portion, and it is possible to effectively suppress three-dimensional deformation during shaping.

[0015] (5) In the shaft for a medical device, the flatness of the specific portion may be 4% or more and 6% or less. With this configuration, it is possible to effectively suppress variations in the shaping direction and effectively suppress three-dimensional deformation during shaping.

[0016] The techniques disclosed in this specification can be realized in various forms, such as shafts for medical devices, medical devices, and methods for manufacturing the same.

[0017] 1. FIG. 1 is a cross-sectional view of the core shaft taken along the line II-II in FIG. 1. FIG. 1 is a cross-sectional view of the core shaft taken along the line III-III in FIG. 1. FIG. 2 is an explanatory diagram showing an example of a method for shaping the guide wire. FIG. 2 is a cross-sectional view of the guide wire taken along the line III-III in FIG. 1. FIG. 3 is a cross-sectional view of the core shaft taken along the line III-III in FIG. 1. FIG. 4 is an explanatory diagram showing an example of a method for shaping the guide wire. FIG. 4 is a cross-sectional view of the guide wire taken along the line III-III in FIG. 1. FIG. 5 is a cross-sectional view of the core shaft taken along the line III-III in FIG.

[0018] A. First Embodiment: A-1. Configuration of Guidewire 100: FIG. 1 is an explanatory diagram schematically illustrating a side view of guidewire 100 in the first embodiment. In FIG. 1, mutually orthogonal X, Y, and Z axes for specifying directions are shown, and a side view of guidewire 100 as viewed in the X-axis direction is shown. The positive Z-axis direction is the tip end (distal side) that is inserted into the body, and the negative Z-axis direction is the base end (proximal side) that is manipulated by a surgeon such as a doctor. These points also apply to FIG. 2 and subsequent figures. In FIG. 1, a cross section (specifically, a YZ cross section) of a coil body 20, which will be described later, is shown. Although FIG. 1 illustrates a state in which guidewire 100 as a whole is linear and substantially parallel to the Z-axis direction, guidewire 100 has a flexibility sufficient to allow it to be bent. In this specification, the distal end of the guidewire 100 and each of its constituent parts is referred to as the "tip," the distal end and its vicinity are referred to as the "tip portion," the proximal end is referred to as the "proximal end," and the proximal end and its vicinity are referred to as the "proximal end portion."

[0019] The guidewire 100 is a medical device. The guidewire 100 is inserted into a blood vessel to guide another medical device (not shown), such as a catheter, to a lesion in the blood vessel. The guidewire 100 includes a core shaft 10. The guidewire 100 includes a coil body 20. The guidewire 100 includes a distal joint 30. The guidewire 100 includes a proximal joint 40.

[0020] The core shaft 10 is an elongated member. The core shaft 10 has a first portion 11, a second portion 12, a third portion 13, a fourth portion 14, a fifth portion 15, a sixth portion 16, and a seventh portion 17. The first portion 11, the second portion 12, the third portion 13, the fourth portion 14, the fifth portion 15, the sixth portion 16, and the seventh portion 17 are arranged in order from the distal end toward the proximal end. The core shaft 10 is an example of a shaft for a medical device.

[0021] In this embodiment, the first portion 11, the third portion 13, the fifth portion 15, and the seventh portion 17 have a constant cross-sectional shape at each position along the axial direction. The cross-sectional area of ​​the third portion 13 is larger than that of the first portion 11. The cross-sectional area of ​​the fifth portion 15 is larger than that of the third portion 13. The cross-sectional area of ​​the seventh portion 17 is larger than that of the fifth portion 15. The second portion 12, the fourth portion 14, and the sixth portion 16 smoothly connect the cross-sectional shapes of other portions adjacent to each other along the axial direction. The second portion 12, the fourth portion 14, and the sixth portion 16 are tapered portions whose cross-sectional areas gradually increase from the distal end toward the proximal end.

[0022] Examples of materials for forming the core shaft 10 include metal materials, more specifically, stainless steel (SUS302, SUS304, SUS316, etc.), Ni-Ti alloys, piano wire, nickel-chromium alloys, cobalt alloys, tungsten, etc. The configuration of the core shaft 10 will be described in detail later.

[0023] The coil body 20 is a hollow cylindrical member formed by spirally winding a wire. The coil body 20 is disposed so as to surround the outer periphery of the tip end of the core shaft 10.

[0024] Examples of materials for forming the coil body 20 include metal materials, more specifically, radiolucent alloys such as stainless steel (SUS302, SUS304, SUS316, etc.), Ni-Ti alloys, piano wire, nickel-chromium alloys, or cobalt alloys, and radiopaque alloys such as gold, platinum, tungsten, or alloys containing these elements (e.g., platinum-nickel alloys).

[0025] The distal joint portion 30 joins the distal end of the core shaft 10 to the distal end of the coil body 20. The outer peripheral surface on the distal side of the distal joint portion 30 is a smooth surface (e.g., a substantially hemispherical surface). The proximal joint portion 40 joins the core shaft 10 to the proximal end of the coil body 20. Examples of materials for forming the distal joint portion 30 and the proximal joint portion 40 include metal solders such as silver solder, gold solder, zinc, Sn—Ag alloy, and Au—Sn alloy, and adhesives such as epoxy adhesives.

[0026] A-2. Detailed configuration of the core shaft 10: Fig. 2 is a diagram showing a cross section of the core shaft 10 taken along line II-II in Fig. 1. Fig. 3 is a diagram showing a cross section of the core shaft 10 taken along line III-III in Fig. 1. In this specification, in a cross section (XY cross section) perpendicular to the axial direction (Z-axis direction) of each part of the core shaft 10, the diameter with the smallest length is defined as the minimum diameter Dmin, and the diameter in the direction perpendicular to the direction of the minimum diameter Dmin is defined as the orthogonal diameter Do. The flattening ratio F of each part of the core shaft 10 is defined as a percentage obtained by dividing the difference between the orthogonal diameter Do and the minimum diameter Dmin by the orthogonal diameter Do. That is, the flattening ratio F of each part of the core shaft 10 is defined by the following formula (1): F = ((Do - Dmin) / Do) × 100 ... (1)

[0027] As shown in FIG. 2 , the cross section of the first portion 11 of the core shaft 10 has a relatively flat shape. The cross section of the first portion 11 is, for example, substantially elliptical. The flatness F of the first portion 11 is 7% or more. The flatness F of the first portion 11 may be 10% or more and 70% or less, 20% or more and 60% or less, or 30% or more and 50% or less. The direction of the minimum diameter Dmin of the first portion 11 is the Y-axis direction, and the direction of the orthogonal diameter Do of the first portion 11 is the X-axis direction. The length of the first portion 11 may be, for example, approximately 1 mm to 10 mm. The first portion 11 of the core shaft 10 is an example of a tip specific portion.

[0028] As shown in FIG. 3 , the cross section of the third portion 13 of the core shaft 10 has a shape that is relatively close to a circle. The flatness F of the third portion 13 is 2% or more and 6% or less. The flatness F of the third portion 13 may be 4% or more. The direction of the minimum diameter Dmin of the third portion 13 is the Y-axis direction, and the direction of the orthogonal diameter Do of the third portion 13 is the X-axis direction. That is, the direction of the minimum diameter Dmin of the third portion 13 and the direction of the minimum diameter Dmin of the first portion 11 are parallel to each other, and the direction of the orthogonal diameter Do of the third portion 13 and the direction of the orthogonal diameter Do of the first portion 11 are parallel to each other. The tip of the third portion 13 may be located, for example, approximately 5 mm to 10 mm from the tip of the core shaft 10, and the length of the third portion 13 may be, for example, approximately 3 mm to 15 mm. The third portion 13 of the core shaft 10 is an example of a specific portion.

[0029] The flatness F of the second portion 12 of the core shaft 10 is close to the flatness F of the first portion 11, and is, for example, 7% or more. The flatness F of the second portion 12 may be 10% or more, 20% or more, 30% or more, 70% or less, 60% or less, or 50% or less. The cross sections of the fourth portion 14 of the core shaft 10 and the portions proximal thereto are substantially circular. The flatness F of these portions is, for example, less than 2%.

[0030] The core shaft 10 can be manufactured, for example, by preparing a member having a circular cross section at each portion, and then performing flattening processing such as press working in accordance with the flattening ratio set for each portion.

[0031] A-3. Method of Shaping Guidewire 100: Fig. 4 is an explanatory diagram showing an example of a method of shaping guidewire 100. Fig. 4 shows a method of performing a procedure called "shaping," in which the distal end of guidewire 100 is bent at a predetermined angle to improve blood vessel selectivity when the operator uses guidewire 100.

[0032] As shown in FIG. 4 , the operator aligns the shaping needle 200 along the distal end of the guidewire 100 and shapes it in one direction. At this time, the operator bends the guidewire 100 around an axis (X-axis) parallel to the orthogonal diameter Do of the first and third portions 11 and 13 of the core shaft 10. In other words, the operator bends the guidewire 100 along the direction of the minimum diameter Dmin of the first and third portions 11 and 13 of the core shaft 10 (Y-axis direction). The operator then inserts the guidewire 100 into a blood vessel for use. For example, when selecting a blood vessel, the operator rotates the proximal end of the guidewire 100 around the Z-axis to rotate the distal end of the guidewire 100.

[0033] A-4. Advantages of this embodiment: As described above, the core shaft 10 for the guide wire 100 of this embodiment has the third portion 13 with a flattening ratio F of 2% or more and 6% or less.

[0034] The rotational compliance of the guidewire 100 improves as the cross-sectional shape of the core shaft 10 approaches a circle. If the cross-sectional shape of the core shaft 10 approaches a circle, variations in the shaping direction may occur, which may result in three-dimensional deformation of the guidewire 100. In this embodiment, the flattening ratio F of the third portion 13 of the core shaft 10 is 2% or more and 6% or less. Although the cross-sectional shape of the third portion 13 is close to a circle, it is flattened to a certain extent, which can suppress variations in the shaping direction. Therefore, the guidewire 100 of this embodiment can suppress three-dimensional deformation due to shaping while ensuring good rotational compliance.

[0035] The flattening ratio F of the third portion 13 of the core shaft 10 may be 4% or more and 6% or less. In this way, it is possible to effectively suppress the occurrence of variations in the shaping direction, and it is possible to effectively suppress three-dimensional deformation due to shaping.

[0036] The core shaft 10 for the guide wire 100 of this embodiment has a first portion 11 that is located distally of the third portion 13 and has a flattening ratio F of 7% or more. Therefore, according to the core shaft 10 of this embodiment, it is possible to effectively suppress the occurrence of variations in the shaping direction in the first portion 11, and it is also possible to effectively suppress three-dimensional deformation due to shaping.

[0037] In the core shaft 10 for the guide wire 100 of this embodiment, the direction of the minimum diameter Dmin of the third portion 13 is parallel to the direction of the minimum diameter Dmin of the first portion 11. Therefore, according to the core shaft 10 of this embodiment, it is possible to effectively suppress variations in the shaping directions of the first portion 11 and the third portion 13, and it is possible to effectively suppress three-dimensional deformation during shaping.

[0038] B. Second Embodiment: Fig. 5 is an explanatory diagram schematically illustrating a side view of a guidewire 100A according to a second embodiment. In the following, among the configuration of the guidewire 100A of the second embodiment, the same configuration as that of the guidewire 100 of the first embodiment described above will be denoted by the same reference numerals, and description thereof will be omitted as appropriate.

[0039] In the core shaft 10A of the guidewire 100A of the second embodiment, the first portion 11 has a curved portion 11a. The curved portion 11a is a portion that is pre-bent around an axis (X-axis) parallel to the orthogonal diameter Do (see FIG. 2) of the first portion 11. Due to the presence of the curved portion 11a in the core shaft 10A, the guidewire 100A, in which the coil body 20 (FIG. 1) is joined to the core shaft 10A, is also curved at the position of the curved portion 11a. The bending angle of the curved portion 11a may be, for example, 10 degrees or more and 70 degrees or less, 20 degrees or more and 60 degrees or less, or 30 degrees or more and 50 degrees or less. The position of the curved portion 11a may be, for example, approximately 0.5 mm to 5 mm from the tip of the core shaft 10.

[0040] The guide wire 100A of the second embodiment can be manufactured by joining the coil body 20 to the core shaft 10A and then performing a bending process to form the curved portion 11a.

[0041] In the core shaft 10A for the guide wire 100A of the second embodiment, the first portion 11 has a curved portion 11a, which makes it possible to more effectively suppress variation in the shaping direction in the first portion 11, and more effectively suppress three-dimensional deformation due to shaping.

[0042] C. Performance Evaluation: The core shaft for the guidewire was evaluated for its resistance to three-dimensional deformation during repeated shaping and its rotational followability.

[0043] FIG. 6 is an explanatory diagram showing the results of a performance evaluation of the resistance to three-dimensional deformation when shaping is repeated. In actual surgery, shaping is usually performed only once. In this performance evaluation, shaping and reshaping were repeated to evaluate three-dimensional deformation. As shown in FIG. 6, for this performance evaluation, multiple core shafts 10 with different flattening ratios F of the distal end (the third portion 13 in the above-described embodiment) were prepared. Samples of guidewires 100 including the core shafts 10 were fabricated. Samples S1-S4 include core shafts 10 without a curved portion 11a (corresponding to the first embodiment described above). Samples S5-S8 include core shafts 10 with a curved portion 11a (corresponding to the second embodiment described above). For each sample, the guidewire 100 was shaped from an initial state in which it was straight to a height of 5 mm, and then reshaped to a height of 1 mm or less. This process was repeated the number of times shown in FIG. 6. The shape of the guidewire 100 after the repeated process is shown in FIG. 6. 6 represents the silhouette obtained by projecting the guidewire 100 onto the ZX plane. The silhouette is a straight line before shaping. After shaping and reshaping, if no three-dimensional deformation occurs, the silhouette is a straight line.

[0044] As shown in Figure 6, for both the samples (S1-S4) without curved portions 11a and the samples (S5-S8) with curved portions 11a, the samples (S2-S4, S6-S8) with a flatness F of 2% or more and 6% or less showed relatively good suppression of three-dimensional deformation during repeated shaping. In particular, the samples (S3-S4, S7-S8) with a flatness F of 4% or more and 6% or less showed even better suppression of three-dimensional deformation during repeated shaping. Furthermore, when comparing samples with the same flatness F, the samples (S6-S8) with curved portions 11a showed better suppression of three-dimensional deformation during repeated shaping than the samples (S2-S4) without curved portions 11a.

[0045] 7 is an explanatory diagram showing the results of a performance evaluation of rotational tracking ability. As shown in FIG. 7, this performance evaluation evaluated the relationship between the angle at which the proximal end of the guidewire 100 was rotated (input rotation angle) and the corresponding angle at which the distal end of the guidewire 100 was rotated (output rotation angle). The closer the input rotation angle and the output rotation angle are to the line (the "ideal" line in FIG. 7), the higher the rotational tracking ability. This performance evaluation was performed using a sample having a curved portion 11a.

[0046] As shown in Fig. 7, the larger the flatness F of the tip end of the core shaft 10, the lower the rotational followability. In the sample in which the flatness F of the tip end of the core shaft 10 was 8%, the input rotational torque accumulated as strain, and then a whip occurred, in which the tip end rotated suddenly. Since the presence or absence of the curved portion 11a is thought to have almost no effect on the rotational followability, it is thought that the same result would be obtained even with a core shaft 10 that does not have the curved portion 11a.

[0047] In view of the above performance evaluation results, if the core shaft 10 for the guidewire 100 has a third portion 13 with a flattening ratio F of 2% or more and 6% or less, it can ensure good rotational followability while suppressing three-dimensional deformation during shaping. It can be said that if the flattening ratio F of the third portion 13 of the core shaft 10 is 4% or more and 6% or less, it can effectively suppress three-dimensional deformation during shaping. Furthermore, it can be said that if the first portion 11 of the core shaft 10 has a curved portion 11a, it can even more effectively suppress three-dimensional deformation due to shaping.

[0048] D. Modifications: The technology disclosed in this specification is not limited to the above-described embodiment, and can be modified in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0049] The configuration of the guide wire 100 in the above embodiment is merely an example, and various modifications are possible. For example, the core shaft 10 does not need to have a portion with a flattening ratio of 7% or more distally of the third portion 13.

[0050] The core shaft 10 may not have at least one of the first portion 11 to the seventh portion 17, as long as it has the third portion 13 whose flatness ratio is 2% or more and 6% or less.

[0051] The direction of the minimum diameter Dmin of the third portion 13 of the core shaft 10 and the direction of the minimum diameter Dmin of the first portion 11 may be non-parallel.

[0052] The technology disclosed in this specification is not limited to the core shaft 10 for the guidewire 100, but is generally applicable to shafts for medical devices.

[0053] 10: Core shaft 11: First portion 11a: Curved portion 12: Second portion 13: Third portion 14: Fourth portion 15: Fifth portion 16: Sixth portion 17: Seventh portion 20: Coil body 30: Distal-end joint portion 40: Proximal-end joint portion 100: Guidewire 200: Shape needle Dmin: Minimum diameter Do: Orthogonal diameter

Claims

1. A shaft for a medical device, having a specific portion in which the flattening ratio is 2% or more and 6% or less, where the minimum diameter is the diameter with the shortest length in a cross section perpendicular to the axial direction, the orthogonal diameter is the diameter in the cross section perpendicular to the direction of the minimum diameter, and the flattening ratio is the difference between the orthogonal diameter and the minimum diameter divided by the orthogonal diameter.

2. A shaft for a medical device as described in claim 1, which has a tip specific portion located on the tip side of the specific portion and has a flattening ratio of 7% or more.

3. A shaft for a medical device according to claim 2, wherein the tip specific portion has a curved portion curved about an axis parallel to the perpendicular diameter of the tip specific portion.

4. A shaft for a medical device according to claim 2 or 3, wherein the direction of the minimum diameter of the specific portion is parallel to the direction of the minimum diameter of the tip specific portion.

5. A shaft for a medical device according to any one of claims 1 to 4, wherein the flattening ratio of the specific portion is 4% or more and 6% or less.

6. A medical device comprising a shaft for a medical device according to any one of claims 1 to 5.

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