Medical wire rod

Abstract

To provide a medical wire rod having high slipperiness.SOLUTION: A medical wire rod 10 is made from a titanium nickel alloy and includes a base part 12 and a reduced diameter part 14 of which diameter is reduced from the base part 12. An oxide film is formed at a surface of the base part 12 with heating treatment to provide high slipperiness of the medical wire rod 10.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a medical wire, and more particularly to a medical wire used as a delivery wire or guide wire for an embolization coil. [Background technology]

[0002] In the treatment of cerebral arteries, multiple embolic coils are filled into an aneurysm to block blood flow and prevent the aneurysm from rupturing, or when administering an anticancer drug or the like, an embolic coil is placed in one of two branched blood vessels to block the blood flow and allow the anticancer drug or the like to flow more easily into the other blood vessel. Patent Document 1 discloses an embolic coil pusher (embolic coil delivery wire) for pushing an embolic coil out from the tip of a catheter.

[0003] In coil embolization, a guidewire is first moved to a predetermined position inside the body, and a catheter is then advanced along the guidewire. When the distal end of the catheter reaches the desired location, the guidewire is removed from the catheter, an embolic coil is placed inside the catheter, and a pusher is inserted from the proximal end of the catheter. The pushing part at the distal end of the pusher pushes the embolic coil, moving it toward the distal end of the catheter and finally pushing it out from the distal end of the catheter and leaving it in the desired position. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-70866 Summary of the Invention [Problem to be solved by the invention]

[0005] In coil embolization, a pusher slides inside a catheter, so the pusher must have high slidability relative to the catheter. Conventionally, to reduce sliding resistance, the core wire of the pusher has been coated with fluororesin or urethane resin. However, because coating is costly, it is desirable to inexpensively achieve high slidability for the pusher without coating. Similar issues exist for guidewires that slide inside catheters, and it is desirable to inexpensively achieve high slidability for guidewires. [Means for solving the problem]

[0006] The medical wire of one embodiment of the present invention is made of a titanium-nickel alloy and has a base portion and a tapered portion that is tapered from the base portion. An oxide coating is formed on the surface of the base portion by heat treatment, and this oxide coating provides the medical wire with high slip resistance. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 10 is a diagram showing an example of a cross section of an embolic coil pusher. [Figure 2] 10A and 10B are diagrams for explaining how to use the embolic coil pusher. [Figure 3] FIG. 10 is a diagram illustrating the state in which an embolic coil is placed inside the body. [Figure 4] 1A and 1B are diagrams illustrating an example of the external configuration of an embolic coil pusher. [Figure 5] FIG. 1 is a diagram for explaining an outline of a method for measuring surface characteristics of a wire. [Figure 6] FIG. 10 is a diagram showing the measurement results of wire surface properties. [Figure 7] FIG. 10 is a graph showing the measurement results of wire surface properties. [Figure 8] FIG. 10 is a graph showing the measurement results of wire surface properties. [Figure 9] FIG. 10 is a photograph of a marker formed by laser processing. DETAILED DESCRIPTION OF THE INVENTION

[0008] Figure 1 shows an example of a cross section of an embolic coil pusher constructed using a medical wire according to an embodiment. The embolic coil pusher 1 is a medical device used to push an embolic coil placed inside a catheter out of the catheter. The embolic coil pusher 1 includes a medical wire 10, which is an elongated member with a large diameter at the base end and a small diameter at the tip end, and a pressing part 20 attached to the tip of the medical wire 10 to press the embolic coil.

[0009] In the embodiment, medical wire 10 is made of a titanium-nickel (Ti-Ni) alloy and constitutes the core wire of embolic coil pusher 1. Medical wire 10 has a large-diameter base portion 12 and a reduced-diameter portion 14 that is smaller in diameter than base portion 12. Medical wire 10 is produced by cutting a titanium-nickel wire to a predetermined length and then reducing the diameter of one end (tip) of the wire using a taper processing machine. In the example shown in FIG. 1 , the taper angle of reduced-diameter portion 14 is shown as being constant, but the taper angle of reduced-diameter portion 14 may change stepwise in the axial direction, and the taper angle at the most distal end of reduced-diameter portion 14 may be zero.

[0010] The pressing unit 20 has a coil portion formed by winding a metal wire. In the embodiment, the coil portion has an X-ray transparent region formed by winding a wire of an X-ray transparent material and an X-ray opaque region formed by winding a wire of an X-ray opaque material. The X-ray transparent region may be formed from a wire made of an Fe-based alloy such as stainless steel or piano wire, copper, aluminum, chromium, nickel, titanium, or an alloy thereof. The X-ray opaque region may also be formed from a wire made of W, Pt, Ti, Pd, Rh, Au, Ag, Bi, Ta, or an alloy thereof. The coil portion may have a structure in which the X-ray opaque region is sandwiched between two X-ray transparent regions on either side.

[0011] The pressing portion 20 is fixed to the tip side of the reduced diameter portion 14 of the medical wire 10. The pressing portion 20 may be soldered to the reduced diameter portion 14 at its front and rear ends.

[0012] FIG. 2 is a diagram for explaining how the embolic coil pusher is used. In coil embolization, an embolic coil 32 is placed inside a catheter 30 whose tip is located at a desired position inside the body, and the embolic coil pusher 1 is inserted from the proximal end 30b of the catheter 30, so that the front end of the pressing part 20 comes into contact with the rear end of the embolic coil 32. The user (operator) pushes the medical wire 10 into the catheter 30, and moves the embolic coil 32 toward the tip of the catheter 30. The embolic coil 32 may be formed by winding a wire made of a radiopaque material such as W, Pt, Ti, Pd, Rh, Au, Ag, Bi, Ta, or an alloy thereof.

[0013] FIG. 3 is a diagram for explaining a state in which an embolization coil is placed at a desired position inside the body. When the embolic coil 32 reaches the vicinity of the distal end 30a of the catheter 30, X-ray imaging of the affected area begins. By not performing X-ray imaging until the embolic coil 32 reaches the vicinity of the distal end 30a, the amount of X-ray exposure to the user and the patient can be reduced. The user recognizes that the embolic coil 32 has reached the vicinity of the distal end 30a by checking the position of a marker, which will be described later. Once X-ray imaging begins, the user pushes the embolic coil 32 out of the distal end 30a of the catheter 30 while viewing the angiographic image displayed on the display, and places it in the desired position (for example, within an aneurysm). Figure 3 shows a state in which multiple embolic coils 32 have been placed within an aneurysm.

[0014] FIG. 4 shows an example of the external configuration of an embolic coil pusher according to an embodiment. The embolic coil pusher 1 may have a total length of approximately 1,800 mm. The coil portion of the pressing unit 20 has, from the distal end to the proximal end, an X-ray transparent region 22a, an X-ray opaque region 24, and an X-ray transparent region 22b. The coil portion may have a length of approximately 450 to 470 mm, and the X-ray opaque region 24 may be located, for example, 30 mm from the distal end of the coil portion. By positioning the X-ray opaque region 24 away from the distal end, the user can easily distinguish between the embolic coil 32 and the X-ray opaque region 24 in an angiographic image displayed on the display, allowing the user to place the embolic coil 32 in the affected area while checking the position of the X-ray opaque region 24.

[0015] In the embodiment, an oxide film is formed on the surface of the base 12, which is made of a titanium-nickel alloy, by heat treatment. In the manufacturing process of titanium-nickel wire, a bus wire is cold-drawn to a desired diameter, and then straightened by heat treatment. Therefore, an oxide film is formed on the surface of the titanium-nickel wire that has been straightened by heat treatment.

[0016] Conventional pushers for embolic coils use a core wire in which the oxide coating of a titanium-nickel wire is removed and the surface from which the oxide coating has been removed is coated with a fluororesin or urethane resin. The inventors focused on the sliding properties of the oxide coating formed by heat treatment of the titanium-nickel wire and measured the surface properties of the oxide coating using a surface property measuring device.

[0017] Figure 5 is a diagram outlining the method for measuring the surface properties of wire. The surface property measuring instrument measures the static friction coefficient, dynamic friction coefficient, static friction force, and dynamic friction force when a wire is slid against the wire under load. In this measurement, the loads were set to 50 gf, 100 gf, and 200 gf, and the surface properties of the following four types of wire were measured. Note that the measurements were carried out under wet conditions to match the actual usage environment. (1) Titanium-nickel wire Diameter 0.42mm, no oxide film (2) Titanium-nickel wire Diameter 0.42mm, with oxide coating (3) Titanium-nickel wire (commercially available) Diameter 0.42mm, fluorine resin coated (4) Stainless steel wire (commercially available) Diameter 0.40mm, fluororesin coated

[0018] Figure 6 shows the measurement results of the wire surface properties. The results shown are the average values ​​of five measurements of the static friction coefficient (μS), dynamic friction coefficient (μK), static friction force (Fs), and dynamic friction force (Fk). 7 and 8 show graphs of the measurement results of the wire surface characteristics.

[0019] When comparing titanium-nickel wires with and without an oxide coating, the static friction coefficient, dynamic friction coefficient, static friction force, and dynamic friction force (hereinafter simply referred to as "friction coefficient and friction force") of titanium-nickel wire with an oxide coating were less than half those of titanium-nickel wire without an oxide coating. This confirmed that titanium-nickel wire with an oxide coating has better surface sliding properties than titanium-nickel wire without an oxide coating. Furthermore, the friction coefficient and friction force of titanium-nickel wire with an oxide coating hardly changed with load, and it was also confirmed that the surface condition did not deteriorate with load.

[0020] When comparing titanium-nickel wire with an oxide coating and titanium-nickel wire with a fluororesin coating (commercially available), the coefficient of friction and frictional force of the titanium-nickel wire with an oxide coating were lower than those of the titanium-nickel wire with a fluororesin coating. This confirmed that the titanium-nickel wire with an oxide coating has better surface slipperiness than the titanium-nickel wire with a fluororesin coating. It was also observed that the coating of the titanium-nickel wire with a fluororesin coating peeled off at a load of 100 gf, leaving the titanium-nickel wire exposed.

[0021] When comparing titanium-nickel wire with an oxide coating and stainless steel wire with a fluororesin coating (commercially available), the coefficient of friction and frictional force of the titanium-nickel wire with an oxide coating were lower than those of the stainless steel wire with a fluororesin coating. This confirmed that titanium-nickel wire with an oxide coating has better surface slipperiness than stainless steel wire with a fluororesin coating. It was also observed that the coating of the fluororesin-coated stainless steel wire peeled off at a load of 200 gf, exposing the stainless steel wire.

[0022] The above measurement results confirmed that the surface condition of fluororesin-coated wire can deteriorate under load, and that the friction coefficient and friction force of titanium-nickel wire with an oxide film are lower than those of fluororesin-coated wire. As mentioned above, the oxide film on titanium-nickel wire is formed during the straightening process, and no additional processing is required to form the oxide film. Therefore, it has been proven that by using titanium-nickel wire with an oxide film for the core wire of the embolization coil pusher 1, it is possible to reduce the manufacturing cost of the core wire while maintaining high slip properties.

[0023] 4, a marker 16 that is directly visible by the user is provided on the base portion 12 of the medical wire 10. Here, "directly visible" means that the user can see the marker 16 by directing their gaze toward the marker 16, rather than by viewing it in an X-ray image displayed on a display. The marker 16 is provided on the base portion 12 so as to be located near the base end 30b of the catheter 30 immediately before the embolic coil 32 is pushed out from the distal end 30a of the catheter 30. For example, if the total length of the catheter 30 is 1000 mm, the marker 16 may be provided 990 mm from the distal end of the pressing portion 20.

[0024] The user does not take X-rays until he or she confirms that the marker 16 has moved near the base end 30b. When the user visually recognizes the marker 16 near the base end 30b, he or she determines that the embolic coil 32 has reached the vicinity of the distal end 30a and starts X-rays. By providing the marker 16 at a predetermined position on the base 12 in this manner, X-rays do not need to be taken until just before the embolic coil 32 is pushed out from the distal end 30a of the catheter 30, thereby minimizing the X-ray exposure of the user and patient. The marker 16 may be formed by removing the oxide coating on the base 12 from the entire circumference.

[0025] Figure 9 shows a photograph of a marker formed by removing the oxide layer from a titanium-nickel wire. In this example, the oxide layer was removed by laser processing, and the areas where the oxide layer remains are black, while the titanium-nickel wire is exposed in the areas where the oxide layer was removed. In this example, the marker can be formed simply by removing the oxide layer, making the marker formation process easier than, for example, forming a marker by applying paint. The method for removing the oxide layer is not limited to laser processing; the oxide layer can also be removed by mechanical polishing or etching.

[0026] In the base 12, it is preferable that the surface roughness of the region where the oxide film is provided differs from the surface roughness of the region where the marker 16 is formed. Specifically, the region where the oxide film has been removed is made to have large irregularities, thereby increasing the surface roughness of the marker region. By making the surface roughness different in this way, a user who is operating the base 12 with their fingers can confirm the presence of the marker 16 by the difference in tactile sensation when they touch the marker 16.

[0027] A plurality of markers 16 may be provided at intervals on the base 12. In this case, by making the interval between the markers shorter than the marker length, the user can more clearly recognize the difference in tactile sensation. For example, the length of the markers 16 may be set to 10 mm and the interval between the markers may be set to 5 mm, so that the user can simultaneously touch an area where a marker 16 is formed and an area where no marker 16 is formed. For this reason, the interval between the markers is preferably shorter than the length of the base 12 that is pinched with the fingers, and may be set to, for example, 3 mm or more and less than 10 mm.

[0028] The present invention is not limited to the above-described embodiments, and various design modifications can be made to the embodiments based on the knowledge of those skilled in the art. Embodiments incorporating such modifications are also within the scope of the present invention. In the embodiments, the medical wire 10 is used as the core of an embolic coil delivery wire that pushes out the embolic coil 32, which is a separate component. However, the medical wire 10 may also be used as the core of an embolic coil delivery wire in which the embolic coil 32 is physically connected to the tip. The medical wire 10 may also be used as the core of a guidewire. In this manner, the medical wire 10 of the embodiments may be used as the core of a medical device for minimally invasive treatment. [Explanation of symbols]

[0029] 1···Pusher for embolic coil, 10···Medical wire, 12···Base portion, 14···Reduced diameter portion, 16···Marker, 20···Pressing portion, 22a, 22b···X-ray transparent region, 24···X-ray opaque region, 30···Catheter, 30a···Tip portion, 30b···Base end portion, 32···Emblic coil.

Claims

1. A medical wire made of a titanium-nickel alloy, A base portion and a reduced diameter portion having a diameter reduced from the base portion, an oxide film formed on the surface of the base by heat treatment; A medical wire characterized by:

2. A marker formed by removing the oxide film is provided on the base.

2. The medical wire according to claim 1.

3. The marker is provided so as to be directly visible by a user.

3. The medical wire according to claim 2.

4. the surface roughness of the region where the oxide coating is provided is different from the surface roughness of the region where the marker is formed; 3. The medical wire according to claim 2.

5. The medical wire is used as a delivery wire or guide wire for an embolization coil.

5. The medical wire according to claim 1.

Images