Articulated Shaft of a Catheter System Capable of Operation and Manufacturing Method

Abstract

To provide a method for fabricating an articulating shaft for a steerable catheter system, which may be usable in minimally invasive procedures employing an intravascular treatment system, by using 3D printing to achieve mechanisms required to allow articulation while maintaining a sealed lumen.SOLUTION: A shaft 100 includes a tubular body and a plurality of wire support elements 110 to support at least one actuating wire. The tubular body has a longitudinal central axis and at least one sealed lumen 106 with a distal opening and a proximal opening. Each of the wire support elements includes at least one through opening 112 to receive the actuating wire. Two adjacent wire support elements are separated from each other in an axial direction by a slot 118. The body and the wire support elements are integrally formed from a single piece.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an articulating shaft of an operable catheter system that may be usable in minimally invasive procedures, for example, using an endovascular treatment system. The present invention also relates to a method of making such a shaft.

Background Art

[0002] Endovascular medical procedures enable the performance of treatments at various locations within a patient's body, requiring only relatively small access incisions. Endovascular procedures can, for example, obviate the need for open-heart surgery, reduce the risks associated with open-heart procedures, and reduce costs and time. In addition, endovascular procedures can accelerate recovery time and reduce the associated costs and risks of complications. Examples of endovascular procedures that significantly reduce treatment time, recovery time, and costs compared to conventional open-heart surgery include heart valve replacement or repair procedures in which an artificial valve or valve repair device is guided through a patient's vasculature to the heart. For example, a catheter is inserted into a patient's vasculature and guided into the inferior vena cava. Thereafter, by applying a longitudinal force to the catheter, the catheter is passed through the inferior vena cava and sent to the heart. When the catheter enters the heart from the inferior vena cava, it enters the right atrium. One or more deflection mechanisms enabled by an extension cable, or other mechanisms located within the catheter, can deflect the distal end of the catheter. Precise control of the distal end of the catheter enables more reliable and rapid positioning of medical devices and / or grafts, as well as other improvements in procedures. Catheters are also used in minimally invasive procedures such as endoscopic procedures, such as neurovascular procedures, coronary artery procedures, structural heart procedures, peripheral vascular procedures, or gastrointestinal applications, apart from structural heart applications.

[0003] It is necessary to accurately position an intravascular delivery device so that the correct positioning of the medical device is ensured. This is essential for the functionality of the medical device as it can be difficult to change the position of the medical device after it has been fully deployed from the delivery system. In addition, the catheter must be able to change the orientation of the distal end of the catheter or rotate the distal end by movement of the proximal portion or an equivalent of the catheter handle. This is achieved by torque transmission along the length of the shaft. For example, anatomical difficulties can be overcome with a single operation. At the same time, a portion of the catheter must be able to move independently of the remainder of the catheter. The design of the catheter shaft is an important factor in determining the formation of curvature, the angle of deflection, and the level of operability. The choice of material determines the levels of pushability, torque, and flexibility, and the catheter can be manipulated by various means along its length to achieve the desired results.

[0004] It is necessary to accurately position the catheter shaft so that the correct positioning of the medical device is ensured. A plurality of lumens can be formed within the catheter for passing a guidewire, catheter, fluid, and gas. The number of lumens is determined by the material and cross-sectional area. The lumens can be formed to meet the requirements of the user. A reinforcing rod (or wire) and a pull wire can be inserted into the lumens. Usually, a core lumen is provided to receive the catheter containing the medical device. Such a core lumen needs to be sealed to protect the medical device.

[0005] It is known to use a single lumen shaft or multiple lumen shafts and arrange layers such as a braided layer and a coil layer thereon to enhance torque performance and deflection. Reinforcing rods and pull wires can be placed in situ during the braiding process. Since the braided reinforcement layer becomes asymmetric due to the change in the thickness of the wire height, the torque performance is not optimal and often decreases over the length of the catheter shaft. In addition, problems associated with incorporating reinforcing wires or pull wires into the lumen may occur during fabrication, and furthermore, a complex braiding machine has to be installed to assemble additional braided layers, increasing the fabrication cost.

Summary of the Invention

Problems to be Solved by the Invention

[0006] There is still a need for an articulating shaft that has improved mechanical properties, enables sealing of the core lumen, and at the same time improves the manufacturing process to reduce manufacturing costs.

Means for Solving the Problems

[0007] This object is solved by the subject matter of the independent claims. Advantageous embodiments of the invention are the subject matter of the dependent claims.

[0008] The present invention is based on the idea of making the articulating shaft of an operable catheter as an integral part, so that the central lumen for inserting the catheter is completely sealed along the entire length of the shaft. The central lumen can also be referred to as the "main lumen" or "core lumen". To enable the operation of the shaft, at least one operating wire (hereinafter also referred to as "pull wire" or "actuating wire") can be inserted into an operating wire lumen formed by a plurality of aligned openings provided in a wire support element. These wire support elements are separated from each other by slots so that the shaft can be easily bent. These slots can also be referred to as "notches". By including such notches in the outer wall of the shaft, the shaft can be shrunk and bent on this side.

[0009] In particular, the present invention provides an articulating shaft of an operable catheter system, comprising a tubular body having a longitudinal central axis and at least one sealed, i.e., radially closed, lumen having a distal opening and a proximal opening, and a plurality of wire support elements for supporting at least one actuating wire. Each of the wire support elements includes at least one through-opening for receiving the actuating wire, two adjacent wire support elements are axially separated from each other by a slot, and the body and the wire support elements are integrally formed from a single part.

[0010] The advantage of this solution can be seen from the fact that the sealing of the core lumen can be easily achieved without an additional cover or sheath. Furthermore, the integral design of the shaft simplifies the assembly process.

[0011] According to an advantageous embodiment of the invention, the slot extends radially around the body by at least 45°. Thus, a sufficiently large portion of the shaft has sufficient flexibility to facilitate the operating process. For example, each slot can be provided to extend along approximately half of the circumference of the shaft. Each slot may have a depth that gradually decreases radially towards the peripheral region of the slot along the circumference of the shaft. This design enables an optimal force distribution when bending the shaft.

[0012] To further enhance the flexibility of the shaft for the bending caused by the actuating wire, each wire support member can be formed to include at least one bracket separated from the body by a gap, and the through-opening is arranged in this bracket. The bracket is advantageously formed symmetrically with respect to a mirror plane intersecting at right angles to the cross-section of the shaft and the central longitudinal axis. In particular, the through-opening is advantageously arranged at the center of the bracket.

[0013] To enable the use of a two-direction operating system, i.e., the use of two pull wires that pull the shaft in two different directions, preferably opposite directions, the shaft can comprise a first row and a second row of wire support elements that extend axially along the longitudinal axis and each have a first through-opening and a second through-opening, the first row and the second row being arranged radially opposite to each other, and the first through-opening being aligned on the opposite side of the second through-opening. Again, the wire support member can be configured as a bracket having a gap between the through-opening and the body.

[0014] According to an advantageous example, the shaft has a circular radial outer shape. Such a design is compatible with existing operating systems and enables an optimal force distribution.

[0015] In the case of a two-direction operating shaft, it is advantageous to concentrically arrange a closed main lumen within the outer shape of the shaft.

[0016] On the one hand, in the case of a joint shaft that must be bent in only one direction, by arranging the main lumen offset from the central axis, the central axis of the closed lumen is separated from the longitudinal central axis of the shaft, and it is advantageous to arrange the closed lumen within the outer shape of the shaft. In this case, most of the cross-section of the shaft can be used for the wire support element.

[0017] According to an advantageous example, the shaft is made of a 3D printed biocompatible material. 3D printing has become an increasingly cost-effective and accurate technology for producing medical materials. 3D printing is defined as an additive manufacturing (AM) process that joins materials, usually layer by layer on top of each other, to form an object from 3D model data, in contrast to subtractive manufacturing methods such as conventional machining. 3D printing can form very intricate and complex geometric parts that require no post-processing, from custom and composite materials, with little waste of material, and is applicable to a variety of materials including shape memory polymers and other smart materials or biocompatible materials. Therefore, 3D printing is a technology that allows designers and engineers to create unique products that can be manufactured in small quantities in a cost-effective manner. In the field of medical engineering, 3D printing can also be used to produce custom shafts adapted to specific patients.

[0018] According to an even more advantageous example, the shaft further comprises at least one reinforcing lumen for receiving a reinforcing wire. The reinforcing wire incorporated into these lumens can be formed from steel or nitinol or other suitable material having some elastic properties. The reinforcing wire can also be called a "neutral axis support wire".

[0019] When the actuating wire is attached to the distal end of the assembly and a tensile load is applied, the wire shortens. As a result, the notch closes and the assembly bends in the direction of the notch. Similarly, the neutral axis support wire, which is also attached to the distal end, bends, allowing the assembly to be bent. Also, the neutral axis support wire bears some of the load in the articulation axis direction. The wire prevents separation of the segments by aligning the segments and maintaining them in a fixed position and also maintaining the tension applied to the assembly.

[0020] To facilitate bending, the reinforcement lumen can be divided by the peripheral region of the slot.

[0021] Furthermore, other lumens, such as for electrical cables, may be provided in the shaft according to the present invention. Such lumens can be attached to the inner surface of the non-sealed outer wall or to the outer surface of the sealed inner wall.

[0022] The present invention further relates to a method of fabricating a shaft of an operable catheter system that uses 3D printing to realize the mechanisms necessary to enable articulation while maintaining a sealed lumen, the method including providing a longitudinal central axis to a tubular body having at least one closed lumen with a distal opening and a proximal opening, and fabricating a plurality of wire support elements for supporting at least one actuating wire, each of the wire support elements including at least one through opening for receiving the actuating wire, two adjacent wire support elements being axially separated from each other by a slot, and the body and the wire support elements being integrally formed from a single component.

[0023] As described above, sealing of the core lumen can be easily achieved without an additional cover or sheath. Furthermore, the integrated design of the shaft simplifies the assembly process.

[0024] As described above, when the shaft is manufactured by a 3D printing process, a particularly high degree of design freedom can be achieved at low cost. However, the shaft may also be manufactured by an extrusion process or an injection molding process. These processes are advantageous for mass production at low cost.

[0025] According to an advantageous embodiment, the shaft is made of a polymer material having a durometer in the range of Shore A 30 to Shore A 70. It is particularly advantageous to manufacture the shaft from a polymer material having a durometer in the range of Shore A 35 to Shore A 40. For example, a possible material is polyamide. However, the shaft may be made of any other suitable material. A relatively soft material is desirable when a weak tensile force and a soft surface are required, and a harder material is advantageous when it is necessary to increase rigidity.

[0026] To illustrate some embodiments of the present invention, the accompanying drawings are incorporated herein and form a part of this specification. These drawings serve to explain the principles of the present invention together with this specification. The drawings are only for showing preferred and alternative examples of ways in which the present invention can be formed and used, and should not be construed as limiting the present invention to only the illustrated and described embodiments. Furthermore, some aspects of the embodiments can form solutions according to the present invention individually or in different combinations. Therefore, the embodiments described below can be considered alone or in any combination. Further features and advantages will become apparent from the following more detailed description of various embodiments of the present invention shown in the accompanying drawings. In the figures, the same reference numerals denote the same elements.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, the present invention will be described in more detail with reference to the drawings. First, refer to FIGS. 1 and 2.

[0029] FIG. 1 is a schematic perspective view of an articulating shaft 100 according to a first example of the present invention, and FIG. 2 is an enlarged view of the distal end 102 of the shaft 100. The shaft 100 has a distal end 102 with a distal opening and a proximal end 104 with a proximal opening. As used herein, the terms "proximal" and "distal" should be understood as relative to the user using the disclosed delivery device. "Proximal" is understood to be relatively close to the user, and "distal" is understood to be relatively far from the user.

[0030] The main lumen 106 extends along the entire length of the shaft 100. According to the present invention, the main lumen is defined by a closed inner wall along the length of the shaft 100. Thus, the main lumen can be sealed by connecting the distal end 102 and the proximal end 104 to a sealed fixture or connector (not shown), respectively.

[0031] According to the example shown in FIG. 1, the joint shaft 100 includes a wire support element 110 having a through opening 112. The through opening is linearly arranged in the longitudinal direction of the shaft 100 so as to form a divided lumen for the operating wire. It should be noted that the operating wires and other elements inserted into the various lumens are not shown. Each of the wire support elements 110 is formed as a bracket separated from the main body 114 of the shaft 100 by a gap 116.

[0032] Slots 118 separate each of the brackets 110 from the adjacent brackets 110. These slots 118 facilitate bending of the shaft 100 when a pull wire is inserted into the row of through openings 112 to apply a bending force to the joint shaft 100. The presence of the gap 116 further enhances the flexibility and softness of the shaft 100.

[0033] The shaft 100 according to the first example further includes a reinforcement lumen 120 for receiving a reinforcement bar or reinforcement wire (not shown). Such a reinforcement wire can be formed, for example, from steel, nitinol, or other suitable materials having some elastic properties. The reinforcement wire can also be called a neutral axis support wire because it aligns and stabilizes the segments formed by the slots 118 in a fixed position. When a tensile load is applied, the actuating wire shortens and the notch 118 closes, so the assembly bends in the direction of the notch 118. The neutral axis support wire disposed in the reinforcement lumen 120 also bends and can move the assembly. Further, the reinforcement wire bears some of the joint axis direction load and prevents separation of the segments by maintaining the tension applied to the assembly.

[0034] In the illustrated embodiment, two reinforcement lumens 120 are provided. However, it will be apparent to those skilled in the art that any other number of lumens may be provided. Further, additional lumens for electrical cables or fluid channels may be provided.

[0035] As shown in FIG. 1, a fluid connector 122 can be provided at the proximal end 104 for sealing connection to, for example, a rigid portion of a catheter or a handle (not shown). Of course, a similar fluid connector can also be provided at the distal end 102. Thereby, complete sealing of the main lumen 106 can be achieved. If the shaft is intended to include an electrical cable, the connector 122 can also be provided with means for forming an electrical connection.

[0036] In the illustrated example, the shaft 100 has an essentially circular outer shape. However, any other cross-sectional outer shape, such as an oval or polygonal outer shape, may be selected. As shown in this specification, all the openings forming the lumen also have a circular cross-section. It is not necessarily limited to this, and any other suitable cross-section, such as an oval or polygon, may be used.

[0037] According to an advantageous aspect of the invention, the articulating shaft 100 is formed as a 3D printed part in which parts are additionally deposited along the longitudinal axis of the shaft 100.

[0038] Further views of the articulating shaft according to the examples shown in FIGS. 1 and 2 are shown in FIGS. 3 to 8.

[0039] As can be seen from the front view of FIG. 3, the main lumen 106 has a center 128 that is offset with respect to the center 126 through which the longitudinal axis 130 of the shaft passes. Therefore, more space can be provided for the bracket 110 including the through opening 112, and the flexibility of the shaft 100 is increased.

[0040] The first lumen 120 and the second lumen 120 for the neutral axis support wire are disposed in the body 114 diametrically opposite to each other along a diameter passing through the center 126 of the shaft 100.

[0041] Figures 4 and 6 show that the slots 118 that separate the plurality of segments formed by the wire support element 110 extend around the center 126 of the shaft 100 and cover a relatively large angle α, for example 270°. Only the wall 132 that forms the main lumen 106 remains continuously closed along the entire length of the shaft 100, providing a sealed inner lumen 106.

[0042] When the shaft is bent in the direction of the through-opening 112 side, the notch 118 closes, but since the bracket 110 formed by the gap 116 can be deformed as needed, the distance between the through-opening 112 and the wall 132 becomes shorter.

[0043] Figure 9 shows a second example of an articulating shaft 200 according to the present invention. The shaft 200 has a distal end 202 with a distal opening and a proximal end (not shown in Figure 9) with a proximal opening.

[0044] The main lumen 206 extends along the entire length of the shaft 200. According to the present invention, the main lumen 206 is defined by an inner wall 208 that is closed along the length of the shaft 200. Therefore, the main lumen 206 can be sealed by connecting the distal end and the proximal end to a sealed fixture or connector (not shown), respectively.

[0045] According to the example shown in Figure 9, the articulating shaft 200 includes a first wire support element 210 having a first through-opening 212 and a second wire support element 211 having a second through-opening 213. The through-openings 212, 213 are linearly arranged in the longitudinal direction of the shaft 200 so as to form two divided lumens for two operating wires. Therefore, using the shaft 200 shown in Figure 9, a catheter that can be operated in two directions can be provided.

[0046] Note that here too, the operating wires and other elements inserted into the various lumens are not shown. Each of the wire support elements 210 is formed as a bracket separated from the body 214 of the shaft 200 by a gap 216.

[0047] Slots 218 separate each of the brackets 210 from adjacent brackets 210. These slots 218 facilitate bending of the shaft 200 when a pull wire is inserted into the rows of through openings 212, 213 to apply a bending force to the articulating shaft 200. The presence of the gap 216 further enhances the flexibility and pliability of the shaft 200.

[0048] The design of the shaft 200 is further different from the design of the shaft 100 in that the cross-section is symmetric, in other words, the center of the main lumen 106 is coaxial with the central axis of the shaft 200.

[0049] When the shaft 200 is bent in the direction of one side of the row of through openings 212, the notch 218 closes, but the brackets 210 formed by the gap 216 can also be deformed as needed, so that the distance between the through opening 212 and the wall 232 is reduced.

[0050] Furthermore, each of the slots 218 extends along less than 180° of the outer periphery of the shaft 200, leaving two backbone portions 234 for stabilizing the shaft 200. In the illustrated example, the backbone portions 234 themselves stabilize the neutral axis. However, it will be apparent to those skilled in the art that one or more additional reinforcing lumens (similar to those shown with respect to the first example of shaft 100) may be embedded within the backbone portions 234 to receive a neutral axis support wire for the rod. Such a reinforcing wire can be formed from, for example, steel, nitinol, or other suitable material having some elastic properties. The reinforcing wire can also be referred to as a neutral axis support wire because it aligns and stabilizes the segments formed by the slots 218 in a fixed position. When a tensile load is applied, the actuator wires on each side shorten and the notches 218 on the actuator wire side close, causing the assembly to bend in the direction of the notches 218. The neutral axis support wire disposed within the reinforcing lumen can also bend to move the assembly. Further, the reinforcing wire carries some of the axial load of the joint and prevents separation of the segments by maintaining the tension applied to the assembly.

[0051] Furthermore, additional lumens for electrical cables or fluid channels may be provided.

[0052] Although not visible in FIG. 9, a fluid connector for sealingly connecting, for example, to a rigid portion of a catheter or a handle (not shown) can be provided at the proximal end of the shaft 200. Of course, a similar fluid connector can also be provided at the distal end 202. Thereby, complete sealing of the main lumen 206 can be achieved. If the shaft is intended to include an electrical cable, the connector can also be provided with means for forming an electrical connection.

[0053] In the illustrated example, the shaft 200 has an essentially circular outer shape. However, any other cross-sectional outer shape, such as an oval or polygonal outer shape, may be selected. As shown herein, all openings that form the lumen also have a circular cross-section. Not necessarily limited to this, any other suitable cross-section, such as an oval or polygon, may be used.

[0054] According to an advantageous aspect of the invention, the articulating shaft 200 is formed as a 3D printed part that additionally deposits parts along the longitudinal axis of the shaft 200. However, it is clear that other techniques for manufacturing the shaft 200 may be used. It is preferred to use 3D printing to realize the mechanisms necessary to enable articulation while maintaining a sealed lumen.

[0055] In summary, the present invention can provide an articulating shaft design based on a 3D printed low durometer biocompatible material that includes a sealed main lumen. The 3D printed articulating design can include one or more lumens for wires or cables, and the sealed lumen can be arranged concentrically with respect to the outer diameter or offset from the central axis. By including notches in the outer wall, the shaft can be shrunk and bent on this side.

[0056] Furthermore, a wire lumen or cable lumen can be attached to the inner surface of the unsealed outer wall or to the outer surface of the sealed inner wall. Additional wires may be incorporated into such lumens. Such wires can be formed from steel or nitinol or other suitable materials having some elastic properties. Such wires can also be called neutral axis support wires.

[0057] These wires are attached to the distal end of the assembly. When a tensile load is applied, the wires (cables) shorten. This causes the notch to close and the assembly to bend in the direction of the notch. By bending the neutral axis support wires, the assembly can be bent. Also, such wires carry some of the load in the joint axis direction. The wires align the segments and hold them in place. Further, the wires prevent separation of the segments by maintaining the tension applied to the assembly.

[0058] The notch may be configured in multiple directions to allow one - way and two - way operation.

Description of Reference Numerals

[0059] 100, 200 Joint shafts 102, 202 Distal ends 104, 204 Proximal ends 106, 206 Main lumens 108, 208 Inner walls of the main lumen 110, 210 Wire support elements 211 Second wire support element 112, 212 Through - openings 213 Second through - opening 114, 214 Bodies 116, 216 Gaps 118, 218 Slots 120 Reinforcement lumen 122 Connector 126 Center of the shaft 128 Center of the main lumen 130 Longitudinal axis 132, 232 Walls 234 Backbone

Claims

1. An articulating shaft (100, 200) of an operable catheter system, wherein the articulating shaft (100, 200) comprises: - a tubular body (114, 214) having a longitudinal central axis (130) and at least one closed lumen (106, 206) with a distal opening and a proximal opening; - a plurality of wire support elements (110, 210) for supporting at least one actuating wire, each of the plurality of wire support elements (110, 210) includes at least one through - opening (112, 212) for receiving the actuating wire, two adjacent ones of the wire support elements (110, 210) are axially separated from each other by a slot (118, 218), and the tubular body (114, 214) and the wire support elements (110, 210) are integrally formed from a single piece; each of the wire support elements (110, 210) includes at least one bracket separated from the tubular body (114, 214) by a gap (116, 216), and the through - opening (112, 212) is disposed in the bracket, An articulating shaft.

2. The slot (118, 218) extends radially around the tubular body (114, 214) by at least 45°. The articulating shaft according to claim 1.

3. Each of the wire support elements (110, 210) includes one bracket separated from the tubular body (114, 214) by one of the gaps (116, 216), and one of the through - openings (112, 212) is disposed in one of the brackets. The articulating shaft according to claim 1 or 2.

4. The articulating shaft (200) further comprises: A first row of the wire support elements (210, 211) that extends axially along the longitudinal axis and has a first through-opening (212), A second row of the wire support elements (210, 211) that extends axially along the longitudinal axis and has a second through-opening (213), and The first row and the second row are arranged radially opposite to each other, and the first through-opening (212) is aligned on the opposite side of the second through-opening (213). The articulating shaft according to any one of claims 1 to 3.

5. The articulating shaft (100, 200) has a circular radial outer shape, The articulating shaft according to any one of claims 1 to 4.

6. The closed lumen (206) is concentrically arranged within the circular radial outer shape of the articulating shaft (200). The articulating shaft according to claim 5.

7. The closed lumen (106) is arranged within the circular radial outer shape of the articulating shaft (100) with its central axis (128) spaced from the longitudinal central axis (130) of the shaft (100). The articulating shaft according to claim 5.

8. The articulating shaft (100, 200) is made of a 3D printed biocompatible material, The articulating shaft according to any one of claims 1 to 7.

9. The articulating shaft (100, 200) further comprises at least one Reinforcing lumen (120) for receiving reinforcing wires, The articulating shaft according to any one of claims 1 to 8.

10. The reinforcing lumen (120) is divided by a peripheral region of the slot, The joint shaft according to claim 9. **Claim 11** A method of fabricating a shaft (100, 200) of an operable catheter system, comprising: providing a longitudinal central axis (130) to a tubular body (114, 214) having at least one closed lumen (106, 206) with a distal opening and a proximal opening; fabricating a plurality of wire support elements (110, 210) for supporting at least one actuating wire; each of the plurality of wire support elements (110, 210) includes at least one through-opening (112, 212) for receiving the actuating wire, two adjacent wire support elements (110, 210) are axially separated from each other by a slot (118, 218), and the tubular body (114, 214) and the wire support elements (110, 210) are integrally formed from a single piece; each of the wire support elements (110, 210) includes at least one bracket separated from the tubular body (114, 214) by a gap (116, 216), and the through-opening (112, 212) is disposed in the bracket; A method. **Claim 12** The shaft (100, 200) is fabricated by a 3D printing process. The method according to claim 11. **Claim 13** The shaft (100, 200) is fabricated by an extrusion process. The method according to claim 11 or 12. **Claim 14** The shaft (100, 200) is 3D printed from a material having a durometer in the range of Shore A30 to Shore A70. The method according to any one of claims 11 to 13. **Claim 15** The shaft (100, 200) is 3D printed from a polymer material having a durometer in the range of Shore A 35 to Shore A 40. The method according to claim 14.

Images