Steering tool with enhanced flexibility and trackability

Abstract

To provide a steering tool with enhanced flexibility and trackability for use in a body cavity.SOLUTION: A steering tool includes an internal tube disposed inside an external tube. The internal and external tubes are arranged for longitudinal axial movement relative to one another. The distal portion of the internal tube is fixedly joined to the distal portion of the external tube. Either or both of the tubes is formed with a pattern of cuts made along a plurality of adjacent longitudinal stations along the length of the cut tube 10. The cutting pattern at a longitudinal station 12, 14, 16 is shifted with respect to a cutting pattern at a second longitudinal station and a cutting pattern at the second longitudinal station is shifted with respect to a cutting pattern at a third longitudinal station, so that a shift from one longitudinal station of cuts to the next adjacent longitudinal station of cuts is not repeated.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention generally relates to a steering tool for manipulating a medical device through a body cavity.

Background Art

[0002] U.S. Patents Nos. 8,684,953 and 9,138,566 by the present inventor describe a steering tool for manipulating a medical device through a body cavity. The steering tool has an inner tube disposed inside an outer tube. The inner tube and the outer tube are configured to move relative to each other in the longitudinal axis direction. The distal end of the inner tube is fixedly joined to the distal end of the outer tube. One or both of the inner tube and the outer tube are provided with slots near their distal ends. Due to the longitudinal movement, the distal end of the tube bends. The steering tool provides a distal tip having steerability, flexibility, and torque characteristics. This tool eliminates the need for a pull / push wire.

[0003] It is important that the tube has sufficient flexibility so that a steering tool (also called a steering catheter) can be pushed into a body cavity such as a blood vessel. However, it is also important that the distal end of the steering tool follows or tracks the movement of the operator's operation at the proximal end of the tool ("followability"). If the flexibility of the tool is too high, the distal end will not respond correctly to the operating movement and will not be able to follow or track the desired movement appropriately.

[0004] Although not limited to the mechanical properties of the tool material and the dimensions of the tool, such as elastic modulus, bending strength, shear strength, tube thickness, tube diameter, moment of inertia, etc., they determine the flexibility and followability of the tool. Representative materials for such tubes include stainless steel alloys and nitinol, which can have a thin wall thickness, but often these tubes are too strong to bend through the meandering bends in the body cavity.

[0005] When the tube is cut into various shapes, the flexibility and followability of the tool may be improved. However, there are also drawbacks and compromises. For example, when cutting the material, the tube may collapse prematurely before completely passing through the curved portion, thus reducing the ability to push the tube through various curved portions. Furthermore, when cutting the material, the elongation of the tube may increase, a harmful torque effect may occur, or local distortion may occur while pushing or pulling. For example, when the tube is cut into a shape like a spring, when pushing or pulling the tube, rotation or unexpected movement of the tip may occur.

[0006] Figures 1A and 1B illustrate one prior art cut pattern, namely, a homogeneous helical cut pattern (which is a kind of homogeneous spring shape). This pattern may function well when pulled, but the length may change while pushing, and undesirable random rotation may occur at the tip. Another drawback is that the helical cut transmits torque in one rotational direction (e.g., clockwise), but is restricted and stretched in the opposite rotational direction (e.g., counterclockwise).

[0007] As one solution, as shown in Figures 2A and 2B, it is conceivable to connect the helical members with a reinforcing material. This results in a configuration with high rigidity and little elongation in the pulling direction, thus being improved. However, the helical members between the connection parts act like short springs. As a result, in this configuration, it is still troubled by local rotation in each of the short springs, and large rotation may occur due to the accumulation of all the short springs. Another drawback is that this configuration also responds differently to clockwise rotation as opposed to counterclockwise rotation.

[0008] As another solution, as shown in FIGS. 3A, 3B, 4A, and 4B, it is conceivable to use orthogonal connections. The connections are perpendicular (orthogonal) to the connections in the previous row. The cut shape is repeated in any second row. Similar patterns can be used with a greater number of connections, but the overall rigidity of the catheter becomes greater.

[0009] Using orthogonal cuts can minimize the number and size of the connections and increase flexibility. The number of cuts is limited by the thickness and diameter of the tube, and the material properties of the tube. To achieve good flexibility of the tube in all directions, the cuts are shifted relative to each other. To maintain a one-to-one rotational movement from the proximal end to the distal end, the cuts generate the same moment of inertia throughout the circumference of the tube at any axial position of the tube.

[0010] However, this pattern itself is continuously repeated in a spiral-like manner along the axial direction of the tube, thereby causing an undesirable spring effect. This is shown by arrows 3 and 4 in FIGS. 3A and 4A, respectively. SUMMARY OF THE INVENTION

[0011] The present invention seeks to provide a steering tool (or catheter) with enhanced flexibility and followability for use within a body cavity, as described in more detail herein.

[0012] The steering tool is made from a tube having a pattern of incisions made along a plurality of longitudinal stations adjacent along the length of the tube. The incision pattern at the first longitudinal station is shifted relative to the incision pattern at the second longitudinal station. For the completed cylindrical tube, "shift" means shifting in the rotational direction (circumferential direction). Also, for the flattened incision pattern (when the tube is bent into tube shape after being made from a flat pattern), "shift" means shifting linearly. The incision pattern at the second longitudinal station is shifted relative to the incision pattern at the third longitudinal station, but the shift is different from the shift defined between the first longitudinal station and the second longitudinal station. In this way, the shift from one longitudinal station of an incision to the next adjacent longitudinal station of an incision is not repeated. This breaks the prior art spring effect caused by a monotonous repeating shape. The advantage is that the tube has excellent flexibility and, since there is no spring effect, the tube has excellent torque performance and followability in both the clockwise and counterclockwise directions.

[0013] Thus, according to one embodiment of the present invention, a steering tool is provided, the steering tool comprising an inner tube disposed inside an outer tube, the inner and outer tubes being configured to move relative to each other in the longitudinal axis direction, the distal portion of the inner tube being fixedly joined to the distal portion of the outer tube at a joining zone, and a cut pattern formed along a plurality of longitudinal stations adjacent to each other along the length direction of the cut tube, which is either the inner tube or the outer tube, the cut pattern at the first longitudinal station being shifted relative to the cut pattern at the second longitudinal station, and the cut pattern at the second longitudinal station being shifted relative to the cut pattern at the third longitudinal station, but the shift being different from the shift defined between the first and second longitudinal stations, whereby the shift from one longitudinal station of a cut to the next adjacent longitudinal station of a cut is not repeated.

[0014] According to one embodiment of the present invention, the shift from one longitudinal station of a cut to the next adjacent longitudinal station of a cut is a circumferential shift around the cut tube.

[0015] According to one embodiment of the present invention, at least one of the cuts has an elongated shape with a straight long side and rounded ends.

[0016] According to an embodiment of the present invention, at least one of the cuts has an elongated shape with a non - straight long side and rounded ends. The non - straight long side may gradually narrow towards the middle portion of at least one cut.

[0017] The steering tool has numerous applications in the delivery of tools or substances through body cavities, such as, for example, endovascular coiling for treating cerebral aneurysms, guiding a catheter from the aortic arch to the common carotid artery, and guiding a catheter from there to the carotid branches leading to the brain. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be more fully understood and recognized by reading the following detailed description in conjunction with the drawings.

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DETAILED DESCRIPTION OF THE INVENTION

[0019] Referring to FIGS. 5A and 5B, a tube 10 used to fabricate a steering tool (shown in FIG. 8 and described below with reference to that figure) according to a non-limiting embodiment of the present invention is shown.

[0020] The tube 10 has a cut pattern formed along a plurality of longitudinal stations adjacent to each other along the length direction of the tube. The cuts can be formed by any suitable method such as laser cutting, machining, and etching, but are not limited thereto. The cut pattern at the first longitudinal station 12 is shifted relative to the cut pattern at the second longitudinal station 14. For the completed cylindrical tube (FIG. 5A), "shift" means shifting in the rotational direction (circumferential direction). Also, for the flattened cut pattern (FIG. 5B; when the tube is bent into a tube shape after being made from a flat pattern), "shift" means shifting linearly. The cut pattern at the second longitudinal station 14 is shifted relative to the cut pattern at the third longitudinal station 16, but is different from the shift defined between the first longitudinal station 12 and the second longitudinal station 14. The cut pattern at the third longitudinal station 16 is shifted relative to the cut pattern at the fourth longitudinal station 18, but is different from the shift defined between the second longitudinal station 14 and the third longitudinal station 16. The same applies hereinafter.

[0021] In this way, the shift from the longitudinal station of one cut to the longitudinal station of the next adjacent cut is not repeated (this is confirmed by the non-repeating arrows in FIGS. 5B and 6B). This breaks the prior art spring effect generated by a monotonous repeating shape and generates a negative spring that compensates for the torque effect during extension. A "negative spring" means that any spring effect (springiness) in one direction (linear or rotational) of one column (longitudinal station) is at least partially cancelled out by the spring effect of an adjacent column in another direction (linear or rotational). The advantage is that the tube has excellent flexibility and, since there is no spring effect, the tube has excellent torque performance and followability in both the clockwise and counterclockwise directions.

[0022] The same also applies to the embodiments of FIGS. 6A and 6B. The difference between the embodiments of FIGS. 5A / 5B and FIGS. 6A / 6B is that in the embodiments of FIGS. 6A / 6B, the cut 26 has an elongated shape with a straight long side and rounded ends. In the embodiments of FIGS. 5A / 5B, the cut 25 has an elongated shape with a non-straight long side and rounded ends. The non-straight long side gradually narrows towards the middle part of the cut 25.

[0023] Referring to FIG. 7, one possible cut pattern is shown, where n lateral shift positions are called 1, 2, 3, 4... n. The pattern in FIG. 7 is the "1243" pattern. This is because the cut in the first longitudinal station 12 starts from the lateral position 1, the cut in the second longitudinal station 14 starts from the lateral position 2, the cut in the third longitudinal station 16 starts from the lateral position 4 (not 3 as in the prior art), and the cut in the fourth longitudinal station 18 starts from the lateral position 3 (not 4 as in the prior art). Other possible patterns include, but are not limited to, 1243, 1324, 1342, 12453, 153642, 124654, and many others.

[0024] Referring to FIG. 8, a steering tool 30 according to a non-limiting embodiment of the present invention is shown.

[0025] The steering tool 30 includes an inner tube 32 disposed inside an outer tube 34. The distal portion of the inner tube 32 is firmly joined to the distal portion of the outer tube 34 at a joining zone 36 (the term "joining" is defined below). The joining zone may be away from the distal tip of the tube or at the distal tip of the tube in any of the embodiments. The inner tube 32 and the outer tube 34 are configured to move relative to each other in the longitudinal axis direction (except for their joined distal portions). The tubes 32, 34 can additionally or alternatively rotate relative to each other to generate a phase shift at the incision. The combination of these two movements causes bending and / or twisting of the distal ends of the tubes 32, 34. One or both of the inner tube 32 and the outer tube 34 can be formed according to the incision pattern of FIGS. 5A / 5B, FIGS. 6A / 6B or FIG. 7.

[0026] The inner tube 32 and the outer tube 34 can be formed of any suitable flexible and medically safe material, such materials including, but not limited to, stainless steel (e.g., AISI 316), nitinol, cobalt-chromium alloy, nickel-titanium alloy, etc., glass fiber, plastic (e.g., nylon, polypropylene, PEBAX, etc.) or combinations thereof.

[0027] The term "joining" encompasses any method for attaching the materials of the tubes together, such methods including, but not limited to, welding, ultrasonic welding, thermal joining, adhesive joining, molding, etc.

Claims

1. 1. A steering tool comprising: the distal end of said inner tube (32) is fixedly joined to the distal end of said outer tube (34) at a joint zone (36); 1. A steering tool comprising: an inner tube (32) or an outer tube (34), referred to as a cut tube (10), formed with a pattern of cuts made along adjacent longitudinal stations along the length of the cut tube (10), the cut pattern at a first longitudinal station (12) being shifted relative to the cut pattern at a second longitudinal station (14) and the cut pattern at the second longitudinal station (14) being shifted relative to the cut pattern at a third longitudinal station (16), the shift being different from the shift defined between the first and second longitudinal stations (12, 14), such that the shift from one cut longitudinal station to the next adjacent cut longitudinal station is not repeated.

2. 2. The steering tool of claim 1, A steering tool, characterized in that the shift from the longitudinal station of one cut to the longitudinal station of the next adjacent cut is a circumferential shift around the circumference of said cut tube (10).

3. 2. The steering tool of claim 1, A steering tool, characterized in that at least one of the cutting edges (26) is elongated in shape with straight long sides and rounded ends.

4. 2. The steering tool of claim 1, A steering tool characterized in that at least one of the cut edges (25) is elongated in shape with non-linear long sides and rounded ends.

5. 5. The steering tool according to claim 4, A steering tool characterized in that the non-linear long side gradually narrows towards a central portion of at least one cut edge (25).

6. 2. The steering tool of claim 1, A steering tool, wherein the resiliency in one direction of one of the plurality of longitudinal stations is at least partially countered by the resiliency in another direction of an adjacent one of the plurality of longitudinal stations.

7. 2. The steering tool of claim 1, A steering tool characterized in that the shift settings of the kerf pattern include n lateral shift positions, designated 1, 2, 3, 4...n.

8. 8. A steering tool according to claim 7, 11. A steering tool, wherein the shift settings include a pattern of 1243 lateral shift positions.

9. 8. A steering tool according to claim 7, 11. A steering tool, wherein the shift settings include a pattern of 1,324 lateral shift positions.

10. 8. A steering tool according to claim 7, A steering tool, wherein the shift settings include a pattern of 1342 lateral shift positions.

11. 8. A steering tool according to claim 7, 11. A steering tool, wherein the shift settings include a pattern of 12453 lateral shift positions.

12. 8. A steering tool according to claim 7, 13. A steering tool, wherein the shift settings include a pattern of 153642 lateral shift positions.

13. 8. A steering tool according to claim 7, 13. A steering tool, wherein the shift settings include a pattern of 124654 lateral shift positions.

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