NL2035502B1

NL2035502B1 - Bendable tube with path length compensation of steering wires

Info

Publication number: NL2035502B1
Application number: NL2035502A
Authority: NL
Inventors: Hendrik Louis Thissen Mattheus
Original assignee: Fortimedix Assets Ii B V
Priority date: 2023-07-28
Filing date: 2023-07-28
Publication date: 2025-02-11
Also published as: WO2025026670A1; AU2024316847A1

Abstract

A deﬂectable tube (312) has a deﬂectable tip section (301) and a bendable body section (3 09). The deﬂectable tube has one or more steering wires (16(i)) spiraling in the body section (309) in order to compensate path length differences occurring in the body section (309) when the body section (3 O9) bends. To isolate axial loads in the body section (309) the deﬂectable tube (312) is provided with one or more longitudinal force isolation elements (322(k)) in the body section (309), which are running in parallel to the one or more steering wires (16(i)). The force 10 isolation elements (322(k)) are attached at both ends to an outer tube (340) or inner tube (330) or to both. |Fig. 5A|

Description

BENDABLE TUBE WITH PATH LENGTH COMPENSATION OF

STEERING WIRES

FIELD OF THE INVENTION

[01] The invention relates to a bendable tube with path length compensation of steering wires. The invention also relates to a bendable tube with an improved elastic hinge. The invention also relates to an invasive instrument such as an endoscope comprising such a bendable tube.

BACKGROUND OF THE INVENTION

[02] Transformation of surgical interventions that require large incisions for exposing a target area into minimal invasive surgical interventions, i.e. requiring only natural orifices or small incisions for establishing access to the target area, is a well-known and ongoing process. In performing minimal invasive surgical interventions, an operator such as a physician, requires an access device that is arranged for introducing and guiding invasive instruments into the human or animal body via an access port of that body. In order to reduce scar tissue formation and pain to a human or animal patient, the access port is preferably provided by a single small incision in the skin and underlying tissue. In some applications, a natural orifice of the body can be used as an entrance. Furthermore, the access device preferably enables the operator to control one or more degrees of freedom that the invasive instruments offer. In this way, the operator can perform required actions at the target area in the human or animal body in an ergonomic and accurate manner with a reduced risk of clashing of the instruments used.

[03] Surgical invasive instruments and endoscopes are well-known in the art.

Both the invasive instruments and endoscopes can comprise a steerable tube that enhances its navigation and steering capabilities. Such a steerable tube may comprise a proximal end part including at least one flexible zone, a distal end part including at least one flexible zone, and an intermediate part, wherein the steerable tube further comprises a steering arrangement that is adapted for translating a deflection of at least a part of the proximal end part relative to the intermediate part into a related deflection of at least a part of the distal end part.

Alternatively, the distal flexible zone may be steered by a robotic system arranged at the proximal end of the steerable instrument.

[04] Steerable invasive instruments may comprise a handle that is arranged at the proximal end part of the steerable tube for steering the tube and/or for manipulating a tool that is arranged at the distal end part of the steerable tube.

Such a tool can for example be a camera, a manual manipulator, e.g. a pair of scissors, forceps, or manipulators using an energy source, e.g. an electrical, ultrasonic or optical energy source.

[05] Furthermore, such a steerable tube may comprise a number of co-axially arranged cylindrical elements including an outer cylindrical element, an inner cylindrical element and one or more intermediate cylindrical elements depending on the number of flexible zones in the proximal and distal end parts of the tube and the desired implementation of the steering members of the steering arrangement, i.e. all steering members can be arranged in a single intermediate cylindrical element or the steering members are divided in different sets and each set of steering members is arranged, at least in part, in a different or the same intermediate cylindrical element. In most prior art devices, the steering arrangement comprises conventional steering cables with, for instance, sub 1 mm diameters as steering members, wherein the steering cables are arranged between related flexible zones at the proximal and distal end parts of the tube. Other steering units at the proximal end, like ball shaped steering units or robot driven steering units, may be applied instead.

[06] However, as steering cables have many well-known disadvantages, for some applications one may want to avoid them and to implement the steering members by one or more sets of steering wires that form integral parts of the one or more intermediate cylindrical elements. Each of the intermediate cylindrical elements including the steering wires can be fabricated either by using a suitable material addition technique, such as injection molding or plating, or by starting from a tube and then using a suitable material removal technique, such as laser cutting, photochemical etching, deep pressing, conventional chipping techniques such as drilling or milling or high-pressure water jet cutting systems. Steering wires manufactured in that way are, then, implemented as longitudinal strips resulting from the tube material, and can be used as pulling/pushing wires. Of the aforementioned material removal techniques, laser cutting is very advantageous as it allows a very accurate and clean removal of material under reasonable economic conditions.

[07] The inner and outer cylindrical elements may be manufactured from tubes too. These tubes should be flexible at locations where the distal end, and possibly the proximal end too, of the instrument is bendable. Also at other locations where the instrument should be flexible, the inner and outer cylindrical elements should be flexible. This can be implemented by providing the inner and outer cylindrical elements with hinges at these flexible locations.

Such hinges may result from (laser) cutting predetermined patterns in the tube.

Many different patterns are known from the prior art. Which pattern to use depends on design requirements at the location concerned including but not limited to the required bending angle, bending flexibility, longitudinal stiffness, and radial stiffness.

[08] As is known from for example a flexible endoscopic instrument with a steerable tip, flexible invasive steerable instruments can show performance flaws with respect to steerable tip control. When such a flexible instrument is inserted into a body through a curved channel, either an endoscope or a natural body lumen, bending of the instrument causes displacement of the longitudinal tip steering elements. Because in conventionally built instruments the steering elements, e.g. wires, are fixed to a steering device, like a handle, at the proximal side and to the steerable tip at the distal side, movement of the steering wires will result in deflection of the steering device and or deflection of the steerable tip. This causes the problem that when the instrument is advanced through a narrow curved channel, and when one holds the steering device in a fixed position, the tip will deflect uncontrollable during advancement and can either lock up in, for example, a narrow endoscope working channel or it can damage tissue in for example a soft tissue natural body lumen like the lung bronchi or the esophagus.

[09] Another problem is that when the instrument passed the entrance channel and the instrument tip reached the targeted operation site, the tip deflection does not match the steering device deflection anymore. So a neutral position of the steering device does not result in a neutral position of the steerable tip. This offset does adversely affect eye-hand coordination of the user.

[10] Yet another problem with flexible steerable instruments is that when the tip is steered with the steering elements, also the body will be steered by the steering elements because the whole body, mechanically, behaves like a steerable tip. The ratio of deflection between the body and tip deflection merely depends on the bending stiffness of the body and the tip. The stiffer the body 1s with respect to the stiffness of the tip, the more the tip will be steered. In practice, the tip is more flexible than the body, but still there is a tendency that steering the tip will result also in body deflection which on its turn will result in side forces on the surrounding channel that tends to keep the instrument body in a certain curvature. If the surrounding channel exists of soft body tissue, this is a strongly unwanted instrument behavior, since the side forces might damage the surrounding tissue. Also body movement might disturb the positioning of the steerable tip at the target site and makes accurate and predictable tip steering more difficult.

[11] Such problems are caused by the portions of the different steering wires inside the flexible body part of the instrument obtaining different lengths inside the body due the bending. Thus will be explained with reference to figures 1A and 1B.

[12] Figure 1A shows a body of a tube shaped instrument 1 having a first steering wire 16(1) running from one end to the opposing end on one side of the body in a straight fashion, as well as a second steering wire 16(2) running from one end to the opposing end on the other side, i.e. 180 degrees rotated locations, of the body in a straight fashion. Steering wires are running in parallel. The tube 1 has a central axis of symmetry 29. The body of tube 1 has a length L. In the unbent status of figure 1A, both steering wires 16(1) and 16(2) also have a length L inside the body.

[13] Figure 1B shows tube 1 in a bent position, here in a 180 degrees curve.

In this condition, the length of axis 29 inside the body remains the same.

However, a portion of steering wire 16(1) located at the inner side of the curve now extends from the body by an offset of +AL whereas a portion of steering wire 16(2) located at the outer side of the curve now extends inside the body by an offset of -AL. In other words, steering wire 16(1) is pushed outside the body and steering wire 16(2) is pulled inside the body. Since steering wires 16(1), 16(2) are attached to the tip of the instrument, this causes one or more of the above mentioned problems, e.g., undesired deflection of the tip. 5 [14] As known from the prior art this undesired effect can be compensated for by spiraling steering wires 16(1), 16(2) about the body by 180 degrees, as schematically shown in figure 2A. In Figure 2A, the spiraling of steering wires 16(1), 16(2) 180 degrees is implemented in a central section of the body. When the body of figure 2A is bent in a curve of 180 degrees as shown in figure 2B, both steering wires 16(1), 16(2) have half of their length located at the inside of the bent body and half at the outside of the bent body. So, both have a portion of less length at the inside and a portion of more length at the outside of the bent body than in the condition of figure 2A, thus compensating path length differences due to bending of the body.

[15] One prior art solution based on the technique of figure 2B is known from US4,745,908. This patent shows an invasive instrument with a deflectable tip. Deflection is caused by a cable located inside a conduit. Both the cable and the conduit run from the proximal end to the tip at the distal end. The path of the conduit is spiraled about the core longitudinal axis.

[16] Because of a substantially constant overall length of the conduit created by the non-straight conduit path, the length of the cable and the length of the conduit remain relatively equal even when the shaft of the instrument is bent or is located in a bending channel path and twisted or torqued in order to rotationally move an objective head. Since the length of the cable and the length of the conduit remain relatively equal there is no involuntary or uncontrolled deflection of the distal end of the instrument.

[17] This known technique is sometimes called Bowden cable technique.

Another term used in the art is “coil pipe”. Other prior art can be found in, e.g,

US20110004157 Al, US20080300462 A1, WO2009048796A2,

KR101312071B1, WO2015084174, WO2016063348A 1, US2018055589A1,

WO2020016577A1, and WO2022260518.

SUMMARY OF THE INVENTION

[18] In a first aspect, it is an object of the invention to provide a steerable instrument for endoscopic and/or invasive type of applications where at least one of the above mentioned problems are solved or at least reduced.

[19] This is achieved by a steerable instrument as claimed in the attached independent claim 1.

[20] The force isolation elements are isolating axial loads of the invasive instrument from the bendable body portion which axial loads are caused by pulling/pushing the steering wires in order to deflect the deflectable tip portion.

Because the steering wires are spiraling in at least a part of the body section, they can compensate at least some of the path length differences when the body section bends. Moreover, because the longitudinal force isolation elements are running through the body portion in a parallel fashion to the steering wires, they are spiraling as well, resulting in at least some path length compensation for the longitudinal force isolation elements in the body portion themselves too.

[21] Embodiments of the first aspect of the invention are claimed in claims dependent on claim 1.

[22] In a second aspect, the invention relates to an improved hinge structure as claimed in independent claim 17.

[23] Embodiments of the second aspect of the invention are claimed in claims dependent on claim 17.

BRIEF DESCRIPTION OF THE DRAWINGS

[24] Further features and advantages of the invention will become apparent from the description of the invention by way of non-limiting and non-exclusive embodiments. These embodiments are not to be construed as limiting the scope of protection. The person skilled in the art will realize that other alternatives and equivalent embodiments of the invention can be conceived and reduced to practice without departing from the scope of the present invention. Moreover, separate features of different embodiments can be combined, even if not explicitly shown in the drawings or explained in the specification, unless such combination is physically impossible. The scope of the present invention is only limited by the claims and their technical equivalents. Embodiments of the invention will be described with reference to the figures of the accompanying drawings, in which like or same reference symbols denote like, same or corresponding parts, and in which:

[25] Figures 1A and 1B show schematic drawings to introduce some of the problems dealt with by a first aspect of the invention.

[26] Figures 2A and 2B show a schematic solution of the prior art to the problem shown in figures 1A, 1B.

[27] Figures 3A and 3B show prior art tubes of a steerable instrument having steering wires made from a tube wall.

[28] Figure 4 shows a schematic perspective view of a tube having steering wires made from a tube wall.

[29] Figure SA shows a schematic perspective view of an alternative tube having steering wires made from a tube wall.

[30] Figure 5B shows an enlarged view of a distal portion of the tube shown in figure SA.

[31] Figure 5C shows a schematic cross sectional view of some components of a proximal portion of the steerable instrument.

[32] Figure 6 shows an example of an inner tube which can be used inside the tube shown in figures 4, SA, 5B and 5C.

[33] Figure 7 shows an example of a tip and body portion of an outer tube which can be used outside the tube shown in figures 4, SA, 5B and 5C.

[34] Figure 8 shows a hinge structure according to the prior art.

[35] Figures 9-12C show portions of hinge structure embodiments according to a second aspect of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[36] The present invention is, in an embodiment, implemented with tubes provided with suitable cutting patterns, also called “cylindrical elements” hereinafter. The basic technology of such tubes is, e.g., described in EP 2 273 911

B1. Figure 3A shows an exploded view of three cylindrical members forming an instrument according to EP 2 273 911 Bl. The instrument 202 is composed of three coaxial cylindrical members: an inner member 204, an intermediate member 206 and an outer member 208. The inner cylindrical member 204 is composed of a first rigid, steerable end part 210, which is the part normally used at an operating location which may be difficult to reach, e.g., inside the human body, a first flexible part 212, an intermediate rigid part 214, a second flexible part 216 and a second, steering rigid end part 218. The steerable end part 210 is located at a distal end of the instrument. The steering rigid end part is located at a proximal end of the instrument.

[37] The outer cylindrical member 208 is in the same way composed of a first, steerable rigid part 201, a flexible part 203, an intermediate rigid part 205, a second flexible part 207 and a second, steering rigid part 209. The flexible parts of cylindrical members 204, 208 are also called “hinges” in the art. The length of the different parts of the cylindrical members 208 and 212 are substantially the same so that when the cylindrical member 204 is inserted into the cylindrical member 208, steerable end parts 210 and 201, flexible parts 212 and 203, rigid parts 214 and 205, flexible parts 216 and 207, and rigid steering end parts 218 and 209 are aligned with each other, respectively.

[38] The intermediate cylindrical member 206 also has a first, steerable rigid end part 240 and a second, steering rigid end part 242 which in the assembled condition are located between the corresponding rigid steerable end parts 210, 201 and the rigid steering end parts 218, 209, respectively, of the two other cylindrical members 204, 208.

[39] Components 216, 218, 242, 207, 209 and the portion of 211 that is axially aligned with components 216 and 207 together form a steering unit 244 of the steerable instrument. Components 210, 212, 240, 201, 203 and the portion of 211 that is axially aligned with components 212 and 203 together form a steerable — or deflectable - portion 248 of the steerable instrument. The portion in between steering unit 244 and steerable portion 248 is a body portion 246.

[40] The intermediate cylindrical member 206 has an intermediate part 211 which is formed by one or more, e.g. three, separate longitudinal elements 16(1) (i = 1,2, ...., D) which can have different forms and shapes. These longitudinal elements are made from the wall material of the intermediate cylindrical member 206 and, therefore, have the form of longitudinal strips. Since they act as steering wires, hereinafter, they will be referred as “steering wires”. After assembly of the three cylindrical members after which the cylindrical member 204 is inside the cylindrical member 206 and the two combined cylindrical members 204, 206 are inside the cylindrical member 208, the rigid steering end parts 218, 242, 209 of the three cylindrical members may be attached to each other. Moreover, the steerable end parts 210, 240, 201 may be attached to one another. The steering end parts 218, 242, 209 are located at a proximal end of the invasive instrument whereas the steerable end parts 210, 240, 201 are located at a distal end of the invasive instrument.

[41] All three cylindrical members 204, 206, 208 are shown in a straight fashion extending in an axial (or longitudinal) direction. By bending the steering end parts 218, 242, 209 of the assembled instrument away from the axial direction, the steerable end parts 210, 240, 201 will be forced to bend away from the axial direction too because some of the steering wires 16(1) will develop a pulling force whereas other steering wires 16(1) will develop a pushing force, as will be evident to a person skilled in the art.

[42] Figure 3B, which is also known from EP 2 273 911 B1, shows an unrolled view of a part of an alternative embodiment of the intermediate cylindrical member of the instrument of figure 3A. The intermediate cylindrical member of figure 3B is formed by a number of steering wires 16(1) wherein each steering wire 16(1) is composed of three portions 222, 224 and 226, co-existing with the first flexible portion, the intermediate rigid portion and the second flexible portion, respectively.

In the portion 224 coinciding with the intermediate rigid portion, each pair of adjacent longitudinal elements 220 is very close to each other in the tangential direction so that in fact only a narrow gap is present there between just sufficient to allow independent movement of each longitudinal element.

[43] In the other two portions 222 and 226 each longitudinal element consists of a relatively small and flexible strip 228, 230 as seen in circumferential direction, so that there is a substantial gap between each pair of adjacent strips, and each strip 228, 230 is provided with a number of cams 232, extending in circumferential direction and almost bridging completely the gap to the next strip.

[44] The examples of the cylindrical elements shown in figures 3A, 3B can be manufactured entirely by cutting suitable cutting patterns in tubes, e.g., by laser cutting. Thus, the steering wires 16(i) are strips manufactured from the wall of cylindrical element 206.

[45] They show the basic technology used in the cylindrical elements of the present invention too. Other examples of — steerable invasive -instruments manufactured by (laser) cutting suitable patterns in cylindrical elements can, e.g., be derived from W02009112060, WO2009127236, WO2012128618,

WO2012173478, WO2014011049, WO2015084174, WO2016089202,

WO2017010883, WO2017014624, WO2017082720, WO2017213491,

WO2018067004, WO2019009710, WO2020080938, WO2020214027,

WO2020218920, WO2020218921, WO2022260518, WO2023287286, and

WO2023287289. Such other examples may relate to instruments having more than one steerable end part and/or having a flexible, instead of a rigid intermediate part.

Path length compensation

[46] Figure 4 shows an example of a tube 306 implementing the solution of figures 3A, 3B. The figure shows a distal portion at the distal end of tube 306.

The shown implementation has a ring-shaped end portion 300. Proximal to the ring-shaped end portion 300, tube 306 has one or more steering wires 16(1) (i = 1, 2, ...1). Here, I = 4 but I may have any other suitable value. The four steering wires 16(1) are equidistantly divided over the circumference of tube 306. All steering wires 16(1) are attached to ring-shaped end portion 300, e.g., by cutting them from the same wall of tube 306 as ring-shaped end portion 300.

[47] The distal portion has a deflectable tip section 301 that can be deflected by suitable longitudinal movements of the four steering wires 16(1). In the deflectable tip section 301, adjacent steering wires 16(1) are separated by spacers 304(1), respectively. Spacer 304(1) is located between steering wires 16(1) and 16(1+1) as seen in the circumferential direction. Each spacer 304(1) may be made from the wall of tube 306 by providing the wall material between adjacent steering wires 16(1) with a suitable cutting pattern such that the resulting spacers 304(1) keep adjacent steering wires 16(1) at a desired tangential distance and at the same time have enough flexibility to allow deflection of the deflectable tip section 301. The flexibility depends on the used cutting pattern. A cutting pattern that may be used is explained hereinafter with reference number 316(1) (cf. figure 5B).

[48] Proximal to deflectable tip section 301 tube 306 has a body section 309 with three sub body sections 303, 305, 307. In sub body section 303, adjacent to deflectable tip section 301, all steering wires 16(1) are straight and running in parallel to one another and to central axis 29. In the next sub body section 305, adjacent to sub body section 303, all steering wires 16(1) are spiraling 180 degrees about central axis 29 in a parallel fashion. Sub body section 307 extends proximally from sub body section 305. In sub body section 307 all steering wires 16(1) are straight and running in parallel to one another and to central axis 29.

[49] In all sections 301, 303, 305, 307 of tube 306 all steering wires 16(1) may have an equal thickness and width. However, depending on the design thicknesses and/or widths of all steering wires 16(1) may differ per section 301, 303, 305, 307, provided they are flexible along the entire tip and body section length.

[50] Spacers 302(1) (1 = 1, 2, … I) are, respectively, located between adjacent steering wires 16(1) in body section 309. Spacers 302(1) are designed to keep adjacent steering wires at a predetermined distance from one another and still allow bending of the body section 303, 305, 307. Spacers 302(1) may be made from the wall of tube 306 by providing the wall with a suitable cutting pattern 310.

[51] The position of sub body section 305 in which steering wires 16(1) are spiraling 180 degrees can be selected in dependence on the application of tube 306, i.e., knowledge of a curved channel in which tube 306 will be inserted. If the body section 309 is bent due to inserting tube 306 in a curved channel path length differences of wires 16(1) in sub body sections 303, 305, 307 caused by the bending are compensated due to the spiraling in sub body portion 305, as explained with reference to figures 2A, 2B.

[52] The tube 306 shown in figure 4 may have more than one sub body section 305 in which steering wires 16(1) are spiraling 180 degrees. They may be consecutive to one another or may be divided by sub body sections in which steering wires 16(1) are running straight in parallel to central axis 29 like in sub body section 307. The size of the pitch of the 180 degrees spiral depends on the application. In an alternative embodiment, steering wires 16(1) are spiraling in the entire body section 309, 1.e., sub body sections 303, 307 are absent. To compensate path length differences between steering wires 16(1) inside body section 309 due to body section bending as much as possible, the total spiraling in body section 309 between the distal end and the proximal end is an integer number of times 180 degrees.

[53] At its proximal end, body section 309 is connected or attached to a steering section - shown in figure 5C with reference number 354. Such a steering section 354 is configured to move steering wires 16(i) in the longitudinal direction of the instrument such that together they may deflect deflectable tip section 301. To that end, steering section 354 may be equipped with a bendable portion configured to translate a bending action into such movement of steering wires 16(1), as is known in the art, e.g. as shown in figures 3A, 3B. Alternatively, longitudinal movement of steering wires 16(i) may be controlled by directly controlling the longitudinal movement of steering wires 16(1) on an individual level, e.g. by means of a robotic steering section, as is also known in the art.

[54] Figures 5A, 5B, 5C, SD, 6 and 7 show an embodiment of a first aspect of the invention. Figure 5A shows an inner tube 330 coaxially surrounded by an intermediate tube 312. An outer tube 340 — of which an example of the distal end and body section is shown in figure 7 - may be provided coaxially arranged with inner tube 330 and intermediate tube 312. Figure 5B shows an enlarged view of an example of the distal end and body section of intermediate tube 312.

Figure 5C shows some components at the proximal end of the instrument in a cross sectional view. Figure 6 shows an enlarged view of an example of the distal end and body section of inner tube 330.

[55] Intermediate tube 312 of the embodiment of figure 5A again has a deflectable tip section 301 and a flexible body section 309 proximally from deflectable tip section 301.

[56] The shown implementation of figure 5A has a ring-shaped end portion 314. Proximal to the ring-shaped end portion 314, intermediate tube 312 has one or more steering wires 16(1) (1 = 1, 2, ...1). Here, I = 4 but I may have any other suitable value. The four steering wires 16(1) are equidistantly divided over the circumference of intermediate tube 312. All steering wires 16(1) are attached to ring-shaped end portion 314, e.g., by cutting them from the same wall of tube 312 as ring-shaped end portion 314.

[57] The deflectable tip section 301 can be deflected by the four steering wires 16(1) in all directions in 3D space. In the deflectable tip section 301, adjacent steering wires 16(1) are separated by spacers 316(1), respectively.

Spacer 316(1) is located between steering wires 16(i) and 16(i+1) as seen in the circumferential direction. Each spacer 316(i) may be made from the wall of intermediate tube 312 by providing the wall material between adjacent steering wires 16(1) with a suitable cutting pattern such that the resulting spacers 316(1) keep adjacent steering wires 16(1) at a desired tangential distance and at the same time have enough flexibility to allow deflection of the deflectable tip section 301. The flexibility depends on the used cutting pattern. A cutting pattern of spacers 316(1) that may be used ts explained hereinafter with reference to figure 5B.

[58] As shown in figure 5B, spacers 316(1) have a spring shape design. In the tangential direction of tube 312 each spacer 316(i) extends from one steering wire 16(1) to adjacent steering wire 16(i+1) and has a tangential cross section equal to the tangential cross section of tube 312. In an embodiment, spacers 316(i) are not attached to steering wires 16(1). In the axial direction of tube 312 spacers 316(1) have a regular repetitive pattern like a block wave pattern, as shown. At its distal end, each spacer 316(1) may be attached to ring-shaped end portion 314. However, the repetitive pattern may be different, and more like a sinus wave pattern. Such a repetitive pattern can be easily made by providing the wall of tube 312 with a suitable cutting pattern. Such spacers 316(1) with a block wave pattern have the advantage of providing tip section 301 with a high flexibility in all directions and, at the same time, a high rigidity against torque because they fill up a lot of space between adjacent steering wires 16(i).

[59] In body section 309, adjacent to deflectable tip section 301, all steering wires 16(1) are running in parallel to one another in a continuous spiraling fashion. In this embodiment, along the total length of body section 309, steering wires 16(1) are spiraling an integer number of times 180 degrees in order to compensate path length differences between them inside body section 309 once body section 309 bends. However, the total amount of spiraling depends on the design requirements: e.g., one may wish to have another amount of spiraling in order to deflect the tip section in a certain plane different from a plane of bending a steering section at the proximal end. Then, the spiraling may not fully compensate path length differences in the body section due to bending of the body section. However, that may be compensated by e.g. a Bowden cable arrangement at the proximal end of the instrument.

[60] In all sections 301, 309 of tube 312 all steering wires 16(1) may have an equal thickness and width. However, depending on the design thicknesses and/or widths of all steering wires 16(1) may differ per section 301, 309 provided they are flexible along the entire body section length.

[61] Proximally from deflectable tip section 301, in an embodiment, tube 312 is provided with solid fill spacers 318(1) of which, in an embodiment, the distal end is attached to one of the spacers 316(1). Each solid fill spacer 318(1) is located between adjacent steering wires 16(i) and 16(i+1) and is, in an embodiment, attached to spacer 316(1) inside deflectable tip section 301. Solid fill spacer 318(1) is designed to keep adjacent steering wires 16(1), 16(1+1) apart from one another in body section 309 at a desired tangential distance. Reference number 319(1) refers to a location on solid fill spacer 318(i) where a portion 350(1) of an outer tube 340 and/or of inner tube 330 is attached to solid fill spacer 318(1) (cf. hereinafter with reference to figure 7).

[62] Between each pair of adjacent steering wires 16(1), 16(1+1) a pair of spacers 320a(1), 320b(1) extends in the body section 309 from solid fill spacer 318(1) in the proximal direction of tube 312. Note that in the present document, the notation “16(1), 16(i+1)” includes the adjacent pair “16(1), 16(1)”. Each pair of spacers 320a(1), 320b(1) is separated by a longitudinal force isolation element 322(k), k=1, 2, ... K. K may be but need not be equal to I. Each longitudinal force isolation element 322(k) is, at its distal end, attached to solid fill spacer 318(1). As shown, longitudinal force isolation element 322(k) may extend into solid fill spacer 318(1) by providing solid fill spacer 318(1) with two longitudinal slits. This provides body section 309 with more flexibility in the area of solid fill spacers 318(1).

[63] Here, an embodiment is shown having the same number of longitudinal force isolation elements as the number of steering wires 16(1). However, that is not strictly necessary. E.g., there may be more or less than one longitudinal force isolation element 322(k) between two adjacent steering wires 16(i). Each longitudinal force isolation element 322(k) is shown to have equal tangential distances to adjacently located steering wires 16(1), 16(i+1). This is not strictly necessary.

[64] Spacer pairs 320a(1), 320b(1) are designed to keep adjacent steering wires at a predetermined distance from one another together with the material of longitudinal force isolation element 322(k) and still allow bending of body section 309. Spacer pairs 320a(1), 320b(1) may be made from the wall of tube 306 by providing the wall with a suitable cutting pattern 310. For instance, cutting pattern 310 may comprise a plurality of slit sets in which each slit set comprises a few parallel slits extending tangentially from a first side of one spacer of the spacer pair 320a(1), 320b(1) towards but not entirely until a second side of that one spacer, as well as a few more parallel slits extending tangentially from the second side of the one spacer of the spacer pair 320a(1), 320b(1) towards but not entirely until the first side of that one spacer. This is, however, only an example of a cutting pattern 310. The flexibility of body section 309 may be less than the flexibility of deflectable tip section 301.

[65] To provide tube 306 with more rigidity against torque spacer pairs 320(1) may be provided with one or more through holes 324, each one designed to receive a radially bent lip from inner tube 330 and/or from outer tube 340.

Figure 7 shows such lips 352 in outer tube 340. Once a lip 352 is bent into through hole 324 spacer pairs 320a(1), 320b(1) will have less room for tangential and axial movement relative to inner tube 330 or outer tube 340 from which lip 352 extends. It is preferred that tangential movement of spacer pairs 320a(1), 320b(1) relative to inner tube 330 and/or outer tube 340 is blocked as much as possible by these lips 352, whereas axial movement of spacer pairs 320a(i), 320b(1) relative to inner tube 330 and outer tube 340 is allowed until a certain maximum amount.

[66] At their longitudinal sides the longitudinal force isolation elements 322(k) are not attached to adjacent spacer pairs 320a(i), 320b(1) which are also not attached to adjacent steering wires 16(i). Depending on design requirements, longitudinal force isolation elements 322(k) may have an equal thickness and width as steering wires 16(1). Together with steering wires 16(1) and spacer pairs 320a(1), 320b(1) they should provide body section 309 with the required flexibility in order to allow inserting into a curved channel.

[67] Each longitudinal force isolation element 322(k) has a proximal end located at the proximal end of the body section 309. Proximal ends of longitudinal force isolation elements 322(k) are each attached to at least one of a proximal portion of outer tube 340 or a proximal portion of inner tube 330.

This is shown in figure 5C which shows a schematic longitudinal cross section of the proximal end of a bendable body portion 356 of the invasive instrument.

The invasive instrument comprises inner tube 330, intermediate tube 312 and outer tube 340. The cross section of figure 5C shows two opposite longitudinal force isolation elements 322(1), 322(3), respectively. They are attached to at least one of inner tube 330 or outer tube 340 by means of an attachment 326(1), 326(3), respectively, at or near the proximal end of body portion 356. The attachments 326(k) for all longitudinal force isolation elements 322(k) may be made by (laser) melting or any other suitable method.

[68] Steering wires 16(1) are extending proximally from the proximal end of body portion 356 to a steering unit 354 of the invasive instrument, which steering unit 354 is schematically indicated as a box in figure 5C. Such a steering unit 354 may be implemented as a proximal bendable unit, like the steering unit 244 schematically shown in figure 3A or as a robotic instrument.

The steering wires 16(1) may be configured such that they can be easily coupled with or decoupled from a suitable driving mechanism of a manually operable steering handle or a robotic instrument, e.g., one as shown in WO2020218920,

WO2020218921 or NL2030160B1. Steering unit 354 may be configured to translate a bending action or longitudinal action of one or more driving mechanisms into longitudinal movement of steering wires 16(1).

[69] Figure 6 shows a portion of inner tube 330 at the distal side of the instrument. Inner tube 330 has a ring-shaped end section 332, a flexible tip section 334 proximal from ring-shaped end section 332, a rigid, ring-shaped section 336 proximal from flexible tip section 334 and a bendable body section 338 proximal from ring-shaped section 336. Once inner tube 330 is inserted in intermediate tube 312 at a desired axial location, ring-shaped end section 332 is axially aligned with ring-shaped end portion 314, flexible tip section 334 is axially aligned with deflectable tip section 301, rigid, ring-shaped section 336 is axially aligned with solid fill spacers 318(1) and bendable body section 338 is axially aligned with flexible spacer pairs 320a(i), 320b(i). The flexibility of flexible tip section 334 may be higher than the flexibility of bendable body section 338.

[70] Flexible tip section 334 is provided with a desired flexibility by making a suitable cutting pattern in inner tube 330. This may be any cutting pattern known in the art or still to be developed. An example may be the cutting pattern as shown with reference number 360 in figure 7 and as explained in detail with reference to hinges 407(j), j= 1, 2, ... J, in figures 9-12C.

[71] Bendable body section 338 is provided with a desired flexibility by making a suitable cutting pattern in inner tube 330. This may be any cutting pattern known in the art or still to be developed. An example may be the cutting pattern as shown with reference number 360 in figure 7 and as explained in detail with reference to hinges 407(j) in figures 9-12C.

[72] Rigid, ring-shaped section 336 may be attached to all solid fill spacers 318(1) in intermediate tube 312.

[73] Figure 7 shows a portion 358 of the invasive instrument with coaxially arranged inner tube 330, intermediate tube 312 and outer tube 340. The figure shows details of outer tube 340. The figure also shows tip portion 358 and body portion 356. The body portion 356, at its proximal end, is connected or attached to steering unit 354 (cf. figure 5C) or configured to be coupled to steering unit 354.

[74] Outer tube 340 has a ring-shaped end section 342, a flexible tip section 344 proximal from ring-shaped end section 342, a rigid, ring-shaped section 346 proximal from flexible tip section 344 and a bendable body section 348 proximal from ring-shaped section 346. Once inner tube 330 and intermediate tube 312 are inserted in outer tube 340 at a desired axial location, ring-shaped end section 342 is axially aligned with ring-shaped end sections 314 and 332, flexible tip section 344 is axially aligned with flexible tip section 334 and deflectable tip section 301, rigid, ring-shaped section 346 is axially aligned with ring-shape section 336 and solid fill spacers 318(1), and bendable body section

348 is axially aligned with bendable body section 338 and flexible spacer pairs 320a(1), 320b(1). The flexibility of flexible tip section 344 may be higher than the flexibility of bendable body section 348.

[75] Flexible tip section 344 is provided with a desired flexibility by making a suitable cutting pattern in outer tube 340. This may be any cutting pattern known in the art or still to be developed. An example may be the cutting pattern shown with reference number 360 in figure 7 and as explained in detail with reference to hinges 407(}) in figures 9-12C.

[76] Bendable body section 348 is provided with a desired flexibility by making a suitable cutting pattern in outer tube 340. This may be any cutting pattern known in the art or still to be developed. It may be the same cutting pattern as applied in flexible tip section 344.

[77] Rigid, ring-shaped section 346 may be attached to all solid fill spacers 318(1) in intermediate tube 312 at locations 350(j). Le, each one of solid fill spacers 318(1) in intermediate tube 312 is attached to at least one of ring-shaped section 336 of inner tube 330 or ring-shaped section 346 of outer tube 340. This may be done by (laser) welding or any other known attachment technique. To that end, outer tube 340 may have small lips at locations 350(j) which may be melted by a laser beam such that molten lip material is welded to the solid fill spacers 318(1).

[78] Figure 7 also shows that body section 348 is provided with one or more lips 352. Once intermediate tube 3 12 (and possibly also inner tube 330) each one of these lips 352 is bent inwards such each one is inserted in one of the through holes 324 in spacer pairs 320a(i), 320b(1). Once being inside these through holes 324 they will limit tangential and axial movement of spacer pairs 320a(1), 320b(1) relative to outer tube 340.

[79] In a further embodiment, force isolation elements 322(k) may themselves be provided with through holes 325, as shown in figure 6D, through which lips of inner tube 330 and/or outer tube 340 are inserted, like lips 352 shown in figure 7. Then, tangential movement of force isolation elements 322(k) relative to inner tube 330 and/or outer tube 340 is blocked as much as possible by these lips, whereas axial movement of force isolation elements 322(k) relative to inner tube 330 and outer tube 340 1s allowed until a certain maximum amount. Moreover, such through holes 325 are configured such as to provide force isolation elements 322(k) with a certain required flexibility to allow body section 309 to be bendable and yet with enough longitudinal stiffness. In this embodiment, one of the or both spacer pairs 320a(i), 320b(1) may be left out and force isolation elements 322(k) may be designed to act also as tangential spacers between adjacent steering wires 16(i).

[80] The embodiment of figures 5A, 5B, 5C, 5D, 6 and 7 is based on a continuous spiraling of all steering wires a positive integer number of times 180 degrees about intermediate tube 312. In an alternative embodiment, a discrete system may be used like the one shown in figure 4 in which the body section is divided in sub-body sections and the 180 degrees spiraling is only applied in some of the sub-body sections whereas the other sub-body sections comprise straight steering wires running in parallel to one another and to the central axis.

In a still further embodiment the total amount of spiraling may differ from a positive integer number of times 180 degrees about intermediate tube 312, e.g, when there are specific requirements as to the plane in which the tip section should be deflected. Then, the path length compensation may not be perfect but may be compensated for by implementing an extra Bowden cable arrangement for both the steering wires 16(1) and the force isolation elements 322(k), e.g., at the proximal end of the instrument, as schematically indicated with a box 355 in figure 5C. One may, e.g., apply one of the Bowden cable arrangements as shown and explained in WO2022260518A1.

[81] As mentioned hereinbefore, in the embodiment of figures SA, 5B, 5C, 5D, 6 and 7 all longitudinal force isolation elements 322(k) are at their distal ends attached to at least one of inner tube 330 or outer tube 340 at a location at the distal end of body section 309 and at their proximal ends attached to at least one of inner tube 330 or outer tube 340 at a location at the proximal end of body section 309. Thereby, axial loads on the body section of the instrument caused by bending the body section and/or operating steering wires 16(i) to deflect tip portion 358 are carried by these longitudinal force isolation elements 322(k). Consequently, push and pull forces exerted by steering wires 16(1) to deflect tip portion 358 are isolated from body portion 356. It has turned out that thereby these push and pull forces in the steering wires 16(i) are much more balanced than in prior art setups and, consequently, when operating tip portion 358 of the invasive instrument the spiraling steering wires 16(1) cause less undesired movements of body portion 356 due to resulting torque load.

[82] In practise, depending on the design and curvature of the curved channel in which the invasive instrument is inserted, full path length compensation may not be achieved, i.e., an offset error may remain. If only a short length of the flexible body section of the instrument is bent and if this length is shorter than one spiral period of 180 degrees a small difference in length offset between steering wires 16(1) and longitudinal force isolation elements 322(k) is created. This may result in muscling of the shaft of the instrument.

[83] Such an offset error in path length compensation will be larger for the above mentioned discrete systems. The length of the sub-body sections of these discrete systems in which the steering wires extend in a straight fashion, the length in between the sub-body sections in which both steering wires and longitudinal force isolation elements are spiraling 180 degrees, as well as the maximum angle these sub-body sections can bend, determine the maximum remaining offset error of the instrument. The higher the number of sub-body sections in which the steering wires and longitudinal force isolation elements are spiraling 180 degrees and the shorter the sub-body sections in which the steering wires and longitudinal force isolation elements run in a straight fashion, the smaller the possible remaining error.

[84] Even an instrument as shown in figures SA, 5B, 5C, SD, 6 and 7 in which the steering wires 16(i) and longitudinal force isolation elements 322(k) are continuously spiraling about the intermediate tube 312 along the entire body section 309, still a small error in path length compensation can occur, when the body section is bent only along a portion of its entire length especially if the bent portion is smaller than the length of a 180 degrees spiraling portion. This effect becomes smaller with decreasing pitch of the spiraling steering wires 16(1) and of the longitudinal force isolation elements 322(k).

[85] In order to avoid or at least minimize such an offset error and, as a consequence, any muscling effect in the body section of the instrument, an extra “coil pipe” or Bowden cable section proximal to the proximal end of the body section may be applied, as schematically indicated with reference number 355 in figure 5C. In figure 5C, Bowden cable section 355 is drawn inside steering section 354, however, it can, alternatively, be present between the proximal end of body section 356 and steering section 354. Examples of such coil pipe or Bowden cable sections entirely manufactured by (laser) cutting components from tubes are disclosed in WO2022260518A 1. They all compensate path length differences in the body section caused by bending the body section because the coil pipe or Bowden cable section absorbs more or less steering wire length in the body section without causing deflection of the deflectable tip section and without deflecting the proximal end of the instrument. All embodiments explained in WO2022260518A 1 may be used as an additional path length compensation mechanism both for steering wires 16(1) and force isolation elements 322(k) in the embodiments of the present invention. Since possible remaining offset errors in the present embodiments are relatively small, these known coil pipe or Bowden cable arrangements do not need to be large and may only need a relatively small space.

[86] It is observed that an invasive instrument with the path length compensation as explained with reference to figures 5A, 5B, 5C, 5D, 6 and 7 can be manufactured easily in only three tubes. The embodiment is simpler than the embodiments disclosed in WO2022260518A 1 and avoids a possible bending force of the flexible shaft to control an instrument at the proximal end of the instrument like in that patent application.

[87] It is observed that the embodiment of figures SA, 5B, 5C, 5D, 6 and 7 shows three tubes in which all components are made by making suitable cutting patterns in them. However, the invention is not limited to applications with three tubes. E.g., the instrument may have more tubes. Steering wires 16(i) may have mutually connected or attached separate portions made from the tube material of two or more such tubes, as explained in WO2017213491. Moreover, the instrument may have other longitudinal elements made from the tube material and configured to perform another function than steering the tip or isolating forces, e.g., to lock or unlock a curvature of a portion of the body portion, as explained in WO2023287289.

[88] Though the invasive instrument is shown with one deflectable tip portion, the invention is not restricted to this. I.e., the invasive instrument may have multiple deflectable tip portions.

[89] All tubes 330, 312, 340 may have one of a circular, oval, elliptical or rectangular cross section.

[90] All tubes 330, 312, 340 may, at least in part, be made of at least one of the following set of materials: a biocompatible polymeric material, including polyurethane, polyethylene or polypropylene, stainless steel, cobalt-chromium, shape memory alloy such as Nitinol®, plastic, polymer, composites, or other curable material.

[91] In an embodiment, components of the tubes, including the one or more steering wires 16(1) and the one or more longitudinal force isolation elements 322(k) result from a material removal technique applied on a wall of the at least one tube 312 to make suitable cutting patterns, including at least one of photochemical etching, deep pressing, chipping techniques, laser cutting or water cutting. The material removal means can be a laser beam that melts and evaporates material or a water jet cutting beam and this beam can have a width of 0.01 to 2.00 mm, more typically for this application, between 0.015 and 0.04mm.

[92] The wall thickness of tubes depend on their application. For medical applications the wall thickness may be in a range of 0.03-2.0 mm, preferably 0.03-1.0 mm, more preferably 0.05-0.5 mm, and most preferably 0.08-0.4 mm.

The diameter of the tubes depend on their application. For medical applications the diameter may be in a range of 0.5-20 mm, preferably 0.5-10 mm, more preferably 0.5-6 mm. The radial play between adjacent tubes may be in range of 0.01 — 0.3 mm.

[93] Features of the invention explained with reference to the preceding figures may be summarized as follows.

[94] The invention relates to a steerable instrument with a deflectable tip portion (358) at a distal side and a bendable body portion (356) proximal from the tip portion (358), the steerable instrument including at least one tube (312) and at least one of an inner tube (330) inside the at least one tube (312) or an outer tube (340) outside the at least one tube (312), one or more steering wires (16(1)) in the at least one tube (312), the at least one tube (312) including a deflectable tip section (301) in the deflectable tip portion (358) and a bendable body section (309) in the bendable body portion (356), the one or more steering wires (16(1)) spiraling in a circumferential direction of the steerable instrument in at least a portion of the flexible body section (309), the steerable instrument also including one or more longitudinal force isolation elements (322(k)) in the at least one tube (312), the longitudinal force isolation elements (322(k)) being arranged in parallel to the one or more steering wires (16(1)) in the flexible body section (309), wherein the one or more longitudinal force isolation elements (322(k)) have a distal end and a proximal end, and one of the following features is applied: if the steerable instrument includes the outer tube (340), the distal end of each longitudinal force isolation element (322(k)) is attached to the outer tube (340) at a distal end of the body section (309) and the proximal end of each longitudinal force isolation element (322(k)) is attached to the outer tube (340) at a proximal end of the body section (309), or if the steerable instrument includes the inner tube (330), the distal end of each longitudinal force isolation element (322(k)) is attached to the inner tube (330) at a distal end of the body section (309) and the proximal end of each longitudinal force isolation element (322(k)) is attached to the inner tube (330) at a proximal end of the body section (309), or if the steerable instrument includes the inner tube (330) and the outer tube (340), the distal end of each longitudinal force isolation element (322(k)) is attached to at least one of the inner tube (330) or the outer tube (340) at a distal end of the body section (309) and the proximal end of each longitudinal force isolation element (322(k)) is attached to at least one of the inner tube (330) or the outer tube (340) at a proximal end of the body section (309).

[95] The one or more steering wires (16(i)) may be spiraling 180 degrees in the circumferential direction of the steerable instrument in at least one portion of the flexible body section (309) in order to provide path length compensation caused by bending of the at least one portion of the flexible body section (309).

[96] The one or more steering wires (16(1)) may be spiraling a number of times 180 degrees in the circumferential direction of the steerable instrument in an equal number of portions of the flexible body section (309) in order to provide path length compensation caused by bending of one or more of the number of portions of the flexible body section (309).

[97] The one or more steering wires (16(1}) may be spiraling in a continuous fashion along the entire flexible body section (309).

[98] In such a steerable instrument multiple steering wires (16(1)) may be arranged at equidistant locations in the tangential direction of the at least one tube (312) in a parallel fashion, whereas the at least one tube may have multiple longitudinal force isolation elements (322(k)), at least one longitudinal force isolation element (322(k)) being located between two adjacent steering wires (161), 16(i+1)).

[99] Each longitudinal force isolation element (322(k)) may be attached to a spacer (318(1)) configured to keep two adjacent steering wires (16(1)) at a desired tangential distance and if the steerable instrument includes the outer tube (340), the distal end of each longitudinal force isolation element (322(k)) is attached to the outer tube (340) via an attachment of the spacer (318(1)) to the outer tube (340), or if the steerable instrument includes the inner tube (330), the distal end of each longitudinal force isolation element (322(k)) is attached to the inner tube (330) via an attachment of the spacer (318(1)) to the inner tube (330), or if the steerable instrument includes the inner tube (330) and the outer tube (340), the distal end of each longitudinal force isolation element (322(k)) is attached to at least one of the inner tube (330) or the outer tube (340) via an attachment of the spacer (318(1)) to at least one of the inner tube (330) or the outer tube (340).

[100] There may be one longitudinal force isolation element (322(k)) arranged between and at equal distances from two adjacent steering wires (16(1), 16(+1)).

[101] A pair of flexile spacers (320a(1), 320b(1)) may be provided between two adjacent steering wires (16(i}), 16(i+1)) proximally from the spacer (318(1), a first one of the pair of flexile spacers (320a(i), 320b(1)) being located between the single longitudinal force isolation element (322(k)) and a first one of the two adjacent steering wires (16(1), 16(1+1)) and a second one of the pair of flexile spacers (320a(1), 320b(1)) being located between the single longitudinal force isolation element (322(k)) and a second one of the two adjacent steering wires (16(1), 16(+1)).

[102] The at least one tube (312) may include a ring-shaped end portion (314) at its distal end to which the one or more steering wires (16(1)) are attached.

[103] At least one of the longitudinal force isolation elements (322(k)) may be provided with through holes (325), a lip extending from either the inner tube (330) or the outer tube (340), respectively, through the through holes (325), the lips and through holes (325) being configured to block tangential movement but allow axial movement of the longitudinal force isolation elements (322(k)) relative to the inner tube (330) or outer tube (340), respectively.

[104] The tip section of the at least one tube (312) may include a spacer (316(1)) between each two adjacent steering wires (16(1), 16(i+1)), each spacer (316(1)) having the form of a regular wave pattern like a block wave or sine wave pattern.

[105] The steerable instrument may have a Bowden cable section (355) at a proximal side of a proximal end of the body section (356) to compensate offsets in path length differences of the steering wires (16(1)).

Hinge structure

[106] In an other aspect, the invention relates to a hinge structure, i.e., the one shown with reference number 360 in figure 7. As an introduction to a detailed description of such a hinge structure, first figure 8 will be described which is a copy of figure 9 of WO2018067004.

[107] Figure 8 shows a hinge structure 402 in a tube 400. The hinge structure

402 is shown to have two identical hinges 401(1), 401(2) be it that these identical hinges 401(1), 401(2) are rotated 90 degrees in the tangential direction of tube 400. Like reference numbers without the “(1)’or “(2)” refer to the same components of the respective hinges 401(1), 401(2).

[108] Hinge 401(1) is made by a cutting pattern in tube 400. The cutting pattern defines a distal, i.e. left hand, side and a proximal, i.e. right hand, side of hinge 401(1). The distal side and proximal side are connected to one another by two identical longitudinal bridges, one being shown with reference number 404(1). The other one is not visible in figure 8 but located 180 degrees rotated in the tangential direction of tube 400 relative to longitudinal bridge 404(1).

Longitudinal bridge 404(1) is a strip made in the wall material of tube 400 by two parallel longitudinal slits 406(1), 408(2) extending in the longitudinal direction of tube 400. The two parallel longitudinal slits 406(1), 408(2) have the same length. Longitudinal bridge 404(1) has a center of rotation 426(1).

[109] A first tangential slit 410(1) extends from longitudinal slit 406(1) in a first tangential direction of tube 400. First tangential slit 410(1) is connected to longitudinal slit 406(1) at a center location of longitudinal slit 406(1). First tangential slit 410(1) covers a tangential range of less than 180 degrees. First tangential slit 410(1) is interrupted by a first lip shaped portion 412(1) of the distal side of hinge 401(1). First lip shaped portion 412(1) extends into the longitudinal direction of tube 400 in a first opening 414(1) in the proximal side of hinge 401(1). First lip shaped portion 412(1) and opening 414(1) are separated by a small slit 428(1) such that the outside surface of first lip shaped portion 412(1) matches the inside surface of first opening 414(1), and first lip shaped portion 412(1) can move freely inside first opening 414(1).

[110] A second tangential slit 418(1) extends from longitudinal slit 408(1)in a second tangential direction of tube 400. The second tangential direction is opposite to the first tangential direction. Second tangential slit 410(1) is connected to longitudinal slit 408(1) at a center location of longitudinal slit 408(1). Second tangential slit 418(1) covers a tangential range of less than 180 degrees. Second tangential slit 418(1) is interrupted by a lip shaped portion 420(1) of the distal side of hinge 401(1). Lip shaped portion 420(1) extends into the longitudinal direction of tube 400 in an opening 422(1) in the proximal side of hinge 401(1). Lip shaped portion 420(1) and opening 422(1) are separated by a small slit 430(1) such that the outside surface of lip shaped portion 420(1) matches the inside surface of opening 422(1), and lip shaped portion 420(1) can move freely inside opening 422(1).

[111] Lip shaped portion 412(1) has a first curved side extending along a portion of a first circle C1 having its center coinciding with center of rotation 426(1) of longitudinal bridge 404(1). Lip shaped portion 412(1) has a second curved side, opposite to the first curved side, extending along a portion of a second circle C2 having its center coinciding with center of rotation 426(1) of longitudinal bridge 404(1) as well.

[112] Lip shaped portion 420(1) has a third curved side extending along a portion of first circle C1 and a fourth curved side, opposite to the third curved side, extending along a portion of second circle C2.

[113] Longitudinal bridge 404(1), longitudinal slits 406(1), 408(1), tangential slits 410(1), 418(1), lip shaped portion 412(1), 420(1), and openings 414(1), 422(1) define a first cutting pattern in tube 400. A second cutting pattern, identical to the first cutting pattern, is present on 180 degrees rotated locations in tube 400. Figure 8 shows an end portion of a tangential slit 416(1) of the second cutting pattern which corresponds to tangential slit 418(1) of the first cutting pattern, and an end portion of a tangential slit 424(1) of the second cutting pattern which corresponds to tangential slit 410(1) of the first cutting pattern.

[114] Also tangential slits 416(1) and 424(1) extend in the tangential direction over a length shorter than 180 degrees. Tangential slit 410(1) of the first cutting pattern and tangential slit 416(1) of the second cutting pattern do not coincide in any location but are overlapping in the tangential direction such that a tangential bridge 403(1) extending in the tangential direction is present between them. Tangential bridge 403(1) is at one end attached to the distal side of hinge 401(1) and at its other end attached to the proximal side of hinge 401(1).

Tangential slit 418(1) of the first cutting pattern and tangential slit 424(1) of the second cutting pattern do not coincide in any location but are overlapping in the tangential direction such that a tangential bridge 405(1) extending in the tangential direction is present between them. Tangential bridge 405(1) is at one end attached to the distal side of hinge 401(1) and at its other end attached to the proximal side of hinge 401(1).

[115] The first and second cutting patterns allow bending of tube 400 by rotating the distal and proximal sides of hinge 401(1) in opposite directions in a first plane perpendicular to a virtual line through center of rotation 426(1) of longitudinal bridge 404(1) and the center of the longitudinal bridge of the second cutting pattern on the opposite side of tube 400.

[116] In use, one may wish to rotate tube 400 about its center axis 29 which results in torque in tube 400. Torsional forces may damage hinge 401(1) by deformation or rupture of wall material of tube 400. Tangential bridges 403(1), 405(1) will absorb such torsional forces to an extent depending on their elasticity which is determined by the wall material and their dimensions.

[117] Lip shaped portions 412(1), 420(1) inside openings 414(1), 422(1) — and their non-visible counterparts of the second cutting pattern — block relative tangential rotation between the distal side and proximal side of hinge 401(1) after a certain minimum amount of relative tangential rotation as allowed by the slit between lip shaped portions 412(1) and 420(1), respectively, and openings 414(1) and 422(1), respectively. In this way, lip shaped portions 412(1), 420(1) and their non-visible counterparts of the second cutting pattern further counteract potential damaging effects of torsional forces.

[118] Figure 8 shows some components of hinge 401(2) which is identical to hinge 401(1) be it 90 degrees rotated relative to hinge 401(1). Tube 400 has a distal portion located at the distal side of hinge 401(2) and a proximal portion located at the proximal side of hinge 401(2). Hinge 401(2) also has two opposite longitudinal bridges with respective centers. Therefore, hinge 401(2) allows rotation of these distal and proximal portions relative to one another in a second plane which is perpendicular to a virtual line through these two centers of these two longitudinal bridges. The second plane is perpendicular to the above mentioned first plane, allowing the hinge structure 402 comprising hinges 401(1), 401(2) to be bent in three dimensions. Hinge structure 402 as shown may be repeated multiple times in tube 400 such that tube 400 can bend in three dimensions along a longer length of tube 400.

[119] Lip shaped portions 412(1), 420(1), 412(2), and 420(2) should have a certain size, especially in the longitudinal direction, to be effective and not to be damaged themselves too easily due to torsional forces. Therefore, they may limit further miniaturization of tubes 400. The present aspect of the invention addresses this problem, as explained with reference to figures 9-12C.

[120] In figure 9, which shows a side view of a first hinge 407(1) of a hinge structure 360 of the invention, the same reference numbers as used in earlier figures have been used to refer to the same components. It is observed that this hinge structure may be applied in any bendable tube and not only in a device shown in figures 1A-7. Such a bendable tube may, e.g., be part of any type of bendable invasive instrument e.g. for endoscopic applications. Such bendable invasive instruments may have one or more deflectable tips which can be deflected by a suitable steering section 354 at the proximal end. Steering wires may be strips resulting from making suitable cutting patterns in one or more coaxial tubes or may be cables. They may be straight or spiraling in the instrument.

[121] In tube 400 of figure 9 (cf. also the three dimensional view of figure 10) tangential slit 410(1) comprises tangential slit portions 410a(1), 410b(1), and tangential slit 418(1) comprises tangential slit portions 418a(1), 418b(1).

Tangential slit portions 410a(1), 410b(1) are connected to one another and have respective ends 409(1), 419(1). Tangential slit portions 410a(1), 410b(1) extend from end 409(1) to end 419(1) partly surrounding the tube 400 in tangential direction E. In an embodiment, tangential slit portion 410a(1) is tapering towards end 409(1), and tangential slit portion 410b(1) is tapering towards end 419(1). However, tangential slit portions 410a(1), 410b(1) may have a single width along their lengths, which may be the same for both.

[122] Tangential slit portions 418a(1), 418b(1) are connected to one another and have respective ends 411(1), 413(1). Tangential slit portions 418a(1), 418b(1) extend from end 411(1) to the end 413(1) partly surrounding the tube in tangential direction F. In an embodiment, tangential slit portion 418a(1) is tapering towards end 41 1(1), and tangential slit portion 418b(1) is tapering towards end 413(1). The tapering of tangential slit portion 410a(1) may be equal to the tapering of tangential slit portion 418a(1) and the tapering of tangential slit portion 410b(1) may be equal to the tapering of tangential slit portion 418b(1). Moreover, tangential slit portions 418a(1), 418b(1) may have a single width along their lengths, which may be the same for both and the same as the ones of those of tangential slit portions 410a(1), 410b(1).

[123] The tangential direction E and the tangential direction F are opposite directions. The end 409(1) and the end 411(1) are located on a same circumference in a plane perpendicular to the central axis 29 which extends in the longitudinal direction of the tube 400. The end 409(1) and the end 411(1) are arranged facing each other.

[124] End 409(1) coincides with the center location of longitudinal slit 406(1) and end 411(1) coincides with the center location of longitudinal slit 408(1) which both extend longitudinally along the tube 400 such that they define longitudinal sides of longitudinal bridge 404(1). Ends 409(1) and 411(1), respectively, may coincide with another portion of longitudinal slits 406(1) and 408(1), respectively.

[125] As shown, both longitudinal slits 406(1) and 408(1) may be curved in opposite directions such that longitudinal bridge 404(1) has a smallest width 7 at a certain location which may be in the center of the total length of longitudinal bridge 404(1). Width 7 may have a value between 0.05-0.3mm. Longitudinal slit 406(1) has a length LB1 which may have a value between 0.3-4mm.

Longitudinal slit 408(1) has a length LB2 which may have a value between 0.3- 4mm. Length LB1 may be equal to length LB2. The shape of longitudinal slit 406(1) may coincide with a portion of a first circle CB1 having a first radius of 0.5-10mm. The shape of longitudinal slit 408(1) may coincide with a portion of a second circle CB2 having a second radius of 0.5-10mm. The radius of second circle CB2 may be equal to the radius of first circle CB1. The values provided here for width 7, lengths LB1 and LB2, and radius of CB1 and CB2 may be applicable for tube instruments with a radius between 1-15mm and a wall thickness between 0.08-2mm.

[126] Thus, longitudinal bridge 404(1) has a better defined center of rotation 426(1) in its center about which portions of tube 400 located at longitudinally opposite sides of bridge 404(1) may bend than if longitudinal bridge 404(1) has an equal width along its length, thus providing the instrument with more accuracy in movement.

[127] In an embodiment, the tangential directions E and F are located in a plane perpendicular to central axis 29 of the tube 400. However, direction E may form an angle with such a plane. The tangential direction F may also form an angle with such a plane. These angles may be between -20° and + 20°, or - 10° and +10" degrees, more preferably between -8° and +8” degrees. They may have the same value.

[128] Tangential slit portions 410a(1) and 410b(1) are located at longitudinally shifted positions and, respectively, connected at opposite ends of a longitudinal channel 425(1) which is extending in the longitudinal direction of the instrument 400 such as to form a tangential shoulder structure. Side walls of longitudinal channel 425(1) are defined by walls 442(1), 440(1) which are extending in the longitudinal direction of the instrument between tangential slit portions 410a(1), 410b(1). In an embodiment, walls 442(1), 440(1) are straight.

However, they may have a curvature coinciding with a portion of a circle having center of rotation 426(1) as its center to align movement during rotation of the hinge with the center of rotation 426(1). In the non-bent position of the distal and proximal sides of the hinge 407(1), walls 442(1), 440(1) are partly overlapping as seen in the tangential direction of the instrument. The amount of overlap may be between 0.05 — 3mm.

[129] Tangential slit portions 418a(1) and 418b(1) are located at longitudinally shifted positions and, respectively, connected at opposite ends of a longitudinal channel 427(1) which is extending in the longitudinal direction of the instrument 400 such as to form a tangential shoulder structure. Side walls of longitudinal channel 427(1) are defined by walls 446(1), 444(1) which are extending in the longitudinal direction of the instrument between tangential slit portions 418a(1), 418b(1). In an embodiment, walls 446(1), 444(1) are straight.

However, they may have a curvature coinciding with a portion of a circle having center of rotation 426(1) as its center to align movement during rotation of the hinge with the center of rotation 426(1). In the non-bent position of the distal and proximal sides of the hinge, walls 446(1), 444(1) are partly overlapping as seen in the tangential direction of the instrument. The amount of overlap may be between 0.05 — 3mm.

[130] In use, the instrument 400 may be rotated in its tangential direction, e.g., by providing a rotational force to the proximal end of the instrument 400. Then, the instrument may be located inside a channel, e.g, intestines of a living being, a blood vessel, or esophagus or the like. Rotating the instrument inside such a channel may cause friction between the channel wall and the instrument 400 resulting in torsion forces on the instrument. A hinge structure as shown in figures 9 and 10 limits torsion response loss because, during rotation, wall 442(1) may abut wall 440(1), and wall 446(1) may abut wall 444(1) which will limit (or block) a possible rotation difference between the distal and proximal sides of hinge 407(1) shown in these figures to a certain maximum. Thus, the hinge provides extra torsion stiffness due to the walls 442(1), 440(1), 446(1), and 444(1).

[131] Figure 10 shows a 3D view on tube 400 such that one can also look inside tube 400. Thus, more details of first hinge 407(1) shown in figure 9 can be seen in figure 10. Apart from the first hinge shown in figure 9, figure 10 shows a second hinge 407(2) which is identical to the one shown in figure 9 be it that the second one is rotated 90 degrees in the tangential direction, causing the total hinge structure to be bendable in all directions, as will be evident to persons skilled in the art. In figure 10, the individual features of first hinge 407(1) as shown in figure 9 are indicated with the same reference numbers. The features of second hinge 407(2) shown in figure 10 are shown with the same reference numbers but having the indicator “(2)” instead of “(1)” affixed to it.

[132] Now, features of first hinge 407(1) not (entirely) visible in figure 9 will be explained in detail. This explanation will not be repeated for second hinge 407(2) but is identical apart from changing “(1)” into “(2)”. As shown in figure 10, first hinge 407(1) has tangential slit portions 424a(1), 424b(1) and tangential slit portions 416a(1), 416b(1). Tangential slit portions 424a(1), 424b(1) have an end 423(1) and an end 415(1). Tangential slit portions 424a(1), 424b(1) extend from end 423(1) to end 415(1) partly surrounding the tube in a tangential direction H (cf. figure 9). Tangential slit portions 416a(1), 416b(1) have an end 421(1) and an end 417(1). Tangential slit portions 416a(1), 416b(1) extend from end 421(1) to end 417(1) partly surrounding the tube in a tangential direction G (cf. figure 9). The tangential direction H and the tangential direction G are opposite directions. The end 423(1) and the end 421(1) are located at the same plane perpendicular to the central axis 29 mentioned above on which ends 409(1) and 411(1) are located. End 423(1) and end 421(1) are arranged facing each other.

[133] End 423(1) coincides with a center location of a longitudinal slit 452(1) and end 421(1) coincides with a center location of a longitudinal slit 448(1) which both extend longitudinally along the tube 400 such that they define longitudinal sides of a longitudinal bridge 450(1).

[134] Like longitudinal slits 406(1) and 408(1), longitudinal slits 452(1) and 448(1) may be curved in opposite directions such that longitudinal bridge 450(1) has a smallest width 7 at a certain location which may be in the middle of the total length of longitudinal bridge 450(1). Width 7 may have a value between 0.05-0.3mm. Slit 452(1) has a length LB3 which may have a value between 0.3-4mm. Slit 448(1) has a length LB4 which may have a value between 0.3-4mm. Length LB3 may be equal to length LB4. Moreover, all lengths LB1, LB2, LB3, and LB4 may be equal. The shape of slit 452(1) may coincide with a portion of a third circle CB3 having a third radius of 0.5-10mm.

The shape of slit 448(1) may coincide with a portion of a fourth circle CB4 having a fourth radius of 0.5-10mm. The radius of fourth circle CB4 may be equal to the radius of third circle CB3. Moreover, the radius of all circles CB1,

CB2, CB3, and CB4 may be equal. The values provided here for width f, lengths 1. B3 and LB4, and radius of CB3 and CB4 may be applicable for tube instruments with a radius between 1-15mm and a wall thickness between 0.08- 2mm.

[135] Thus, longitudinal bridge 450(1) has a better center of rotation 458(1) in its center about which portions of tube 400 located at longitudinally opposite sides of bridge 450(1) may bend than if longitudinal bridge 450(1) would have an equal width along its entire length, providing the instrument with more accuracy in movement.

[136] Tangential slit portions 424a(1) and 424b(1) are located at longitudinally shifted positions and, respectively, connected at opposite ends of a longitudinal channel 429(1) which is extending in the longitudinal direction of the instrument 400 such as to form a tangential shoulder structure. Side walls of longitudinal channel 429(1) are defined by walls 454(1), 456(1) which are extending in the longitudinal direction of the instrument between tangential slit portions 424a(1), 424b(1). In an embodiment, walls 454(1), 456(1) are straight.

However, they may have a curvature coinciding with a portion of a circle having center of rotation 458(1) of longitudinal bridge 450(1) as its center to align movement during bending of the hinge with the center of rotation 458(1).

In the non-bent position of the distal and proximal sides of hinge 407(1), walls 454(1), 456(1) are partly overlapping as seen in the tangential direction of the instrument. The amount of overlap may be between 0.05 — 3mm.

[137] Tangential slit portions 416a(1) and 416b(1) are located at longitudinally shifted positions and, respectively, connected at opposite ends of a longitudinal channel 431(1) which is extending in the longitudinal direction of the instrument 400 such as to form a tangential shoulder structure. Side walls of longitudinal channel 431(1) are defined by walls 462(1), 464(1) which are extending in the longitudinal direction of the instrument between tangential slit portions 416a(1), 416b(1). In an embodiment, walls 462(1), 464(1) are straight.

However, they may have a curvature coinciding with a portion of a circle having center of rotation 458(1) as its center to align movement during bending of the hinge with the center of rotation 458(1). In the non-bend position of the two opposite sides of the hinge, walls 462(1), 464(1) are partly overlapping as seen in the tangential direction of the instrument. The amount of overlap may be between 0.05 — 3mm.

[138] As explained above, in use, the instrument 400 may be rotated in its tangential direction, e.g., by providing a rotational force to the proximal end of the instrument. Then, the instrument may be located inside a channel, e.g, intestines of a living being, a blood vessel, or esophagus or the like. Rotating the instrument inside such a channel may cause friction between the channel walls and the instrument resulting in torsion forces on the instrument. Hinge structures as shown in figures 9 and 10 can better cope with increased torsion forces because, during rotation, wall 454(1) may abut wall 456(1), and wall 462(1) may abut wall 464(1) which will limit (or block) any possible rotation difference between distal and proximal sides of the hinge shown in these figures to a certain maximum. Thus, the hinge structure shown in these figures provides extra torsion stiffness due to the walls 454(1), 456(1), 462(1), and 464(1).

[139] In an embodiment, the tangential directions G and H are in the above mentioned plane perpendicular to the central axis of the tube 400. However, direction G may form an angle with such a plane. The tangential direction H may also form an angle with such a plane. These angles may be between -10° and +10" degrees, more preferably between -8° and +8° degrees. They may have the same value.

[140] Longitudinal bridges 404(1) and 450(1) are, preferably, located on locations on tube 400 rotated 180 degrees away from each other on the circumference, thus allowing tube 400 to bend about a virtual line through centers of rotation 426(1) and 458(1).

[141] As shown in figures 9 and 10, tangential slit portion 410b(1) and tangential slit portion 416b(1) overlap circumferentially, i.e. a part of tangential slit portion 410b(1) is located adjacent to a part of tangential slit portion 416b(1) as seen in a longitudinal direction, however, without these parts engaging one another. A tangential bridge 403(1) is present between these parts of tangential slit portion 410b(1) and tangential slit portion 416b(1). The ends of tangential bridge 403(1) are attached to the distal side and to the proximal side of hinge 407(1), respectively. In an embodiment, tangential bridge 403(1) has a constant width BW(1) (seen in the longitudinal direction of the instrument). This width may be 0.05-0.3mm. Tangential bridge 403(1) may have a length equal to a value between 20-45% of the tube circumference.

[142] As is also shown in figure 10, tangential slit portion 418b(1) and tangential slit portion 424b(1) overlap circumferentially, i.e. a part of tangential slit portion 418b(1) is located adjacent to a part of tangential slit portion 424b(1) as seen in a longitudinal direction, however, without these parts engaging one another. A tangential bridge 405(1) is present between these parts of tangential slit portion 418b(1) and tangential slit portion 424b(1). The ends of tangential bridge 405(1) are attached to the distal side and to the proximal side of hinge 407(1), respectively. In an embodiment, tangential bridge 405(1) has a constant width BW(2) (seen in the longitudinal direction of the instrument). This width may be 0.05-0.3mm and may be the same as the width of tangential bridge 403(1). Tangential bridge 405(1) may have a length equal to a value between 20-45% of the tube circumference. The lengths of tangential bridges 403(1) and 405(1) may be equal.

[143] Though longitudinal bridges 404(]), 450(;) have been shown here as straight bridges other forms may be used as well, including, e.g., S-shaped, Z- shaped or block wave shaped forms, as shown in WO2018067004.

[144] Figure 11 shows an embodiment with three adjacent hinges. There may be more than three. They are identical and their features are indicated with indicators (1), (2) and (3) respectively. They are all arranged in the same tangential orientation causing the total hinge structure to be bendable in one plane only, i.e, a plane perpendicular to the virtual lines through centers of rotation 426(j) and 458(j) §j = 1, 2, … I} are located.

[145] In the embodiments shown with reference to figures 9-11, the channels defined by the side walls 442(j)/440()), 446(})/444(}), 454(j/456(j), and 462(j)/464()) have a certain width defined by, e.g., the width of a laser beam used to make all slit patterns in the tube 400, if a laser is used. The width of these channels define a maximum tangential play between adjacent sides of each hinge when they rotate relative to one another in the tangential direction. There is a desire to keep this width as small as possible to reduce such play. Figures 12A, 12B and 12C show ways of reducing this width of these channels.

[146] Figure 12A is identical to figure 9 apart from the following. When manufacturing the slit pattern in tube 400 opposing side walls 442(1), 440(1) are still attached to one another by means of a fracture element 480(1). Similarly, when manufacturing the slit pattern in tube 400 opposing side walls 446(1), 444(1) are still attached to one another by means of a fracture element 482(1). Figure 12B shows an example of a fracture element 482(1) in enlarged shape.

[147] The manufacturing process of making the slit pattern, e.g. by laser cutting, renders fracture element 482(1) such that it has a wider portion 484(1) and a smaller portion 488(1). Here, wider portion 484(1) is attached to side wall 446(1) and smaller portion 488(1) is attached to side wall 444(1), whereas wider portion 484(1) is attached to smaller portion 488(1). A first reason to manufacture such a fracture element 482(1) is to keep different opposite portions of the tube-like element 400 which are separated by slits still attached to one another which makes maneuverability of the tube 400 much easier, e.g. when it has to be inserted into another tube or another tube has to inserted into it. A second reason is, however, that one can use such fracture elements to reduce play between such opposite portions.

[148] When manufacturing side walls 446(1) and 444(1) by, e.g., a laser beam cutting longitudinal channel 427(1) between them, they will have a minimum distance w/ as caused by the width of the laser beam. Without applying a fracture element 482(1) as explained here, this minimum distance w/ will define the play between side walls 446(1) and 444(1) when opposite sides of the hinge rotate relative to one another in the tangential direction.

[149] When during use the hinge is forced to bend such that the two opposite sides of the hinge rotate about centers of rotation 426(1), 458(1) opposite side walls 446(1), 444(1) will be forced to move in opposite longitudinal directions. As indicated in figure 12B, side wall 446(1) may be forced to move in a first longitudinal direction by a force #2 and side wall 444(1) may be forced to move in a second, opposite, longitudinal direction by a force F'/. Fracture element 482(1) is designed such that when these forces #7 and #2 are above a certain threshold force smaller portion 488(1) will fracture while wider portion 484(1) will remain intact and the material of the hinge to which wider portion 484(1) is attached only deforms elastically but not plastically and also the material of the hinge to which smaller portion 488(1) is attached only deforms elastically but not plastically by the forces FH and F2. Also wider portion 484(1) may only deform elastically but not plastically by these forces but that is not necessary.

[150] Assuming smaller portion 488(1) has a length in the tangential direction of the instrument of w2 << w/, then, after smaller portion 488(1) has been fractured wider portion 484(1) is decoupled from side wall 444(1) and may be forced by tangentially rotating the tube 400 towards side wall 444(1) along a distance of at maximum w2. This reduces the maximum play between side walls 446(1), 444(1) to w2.

[151] Methods of manufacturing such fracture elements, as wells as examples of their shapes have been disclosed and explained in WO2016/089202 of the present applicant. Manufacturing fracture elements that can be used to reduce play between adjacent components of a tube which are separated by slits can be found in

W02020/080938 of the present applicant. Play reducing fracture elements as disclosed in these applications can be used as well.

[152] The detailed explanation provided here for fracture element 482(1) equally applies to fracture element 480(1). Moreover, similar or identical play reducing fracture elements can be applied between all opposite side walls 454(j)/456(j), and 462(1)/464).

[153] Figure 12C shows an alternative fracture element 490(1) to fracture element 482(1) of figure 12B.

[154] As shown in figure 12C, side wall 444(1) is divided into two portions: a first side wall portion 444a(1) located in the tangential extension of tangential slit 418a(1) and a second side wall portion 444b(1) defining the side wall of longitudinal channel 427(1) between tangential slits 418a(1) and 418(b(1). The tangential distance between second side wall portion 444b(1) and side wall 446(1) is indicated with width w/. Width w depends on the used manufacturing method, e.g., the size of a laser beam. The tangential distance between second side wall portion 444a(1) and side wall 446(1) is indicated with width w3 wherein w3 may be as small as 0 mm. Width w/ >w3. During manufacturing tube 400, a small fracture element or melt element 490(1) is kept between a transition area between first side wall portion 444a(1) and second side wall portion 444b(1).

[155] When element 490(1) is implemented as fracture element, this fracture element will be fractured by bending hinge 407(1) with a certain predetermined bending force. To that effect, fracture element 490(1) is designed such that when the bending force, schematically indicated with #7 and F2, is above a certain threshold force a reaction force as caused by the bending force inside the fracture element will cause fracture of fracture element 490(1) while the material of the side walls to which they are attached will remain intact because this material may only deform elastically but not plastically. Fracturing may also be caused by fatigue, i.e., by bending hinge 407(1) multiple times with a force less than this threshold force but strong enough to eventually rupture fracture element 490(1). This method causes less tension in material of tube 400 attached to fracture element 490(1).

[156] When element 490(1) is implemented as melt element, this melt element will be destroyed by melting them later in the manufacturing process. For instance, tube 400 in which hinge 407(1) is manufactured is inserted inside another tube having holes in its structure which are aligned with respective melt elements. Then, an energy beam, e.g. a laser beam, is directed through such holes to the melt elements 490(1) of which the energy is so high that it destroys the melt elements but does not or hardly not destroy the side walls to which the melt elements are attached.

[157] Fracture elements like fracture element 490(1) can be applied between all opposite side walls 440(j)/442(j), 454(1)/456(]), and 462(})/464(}). If so, after all these fracture elements are fractured, or destroyed by melting, and all hinges 407(j) are unbent — tube 400 1s 100% straight — then, there is no tangential play reduction yet. However, in practice, most of the times the invasive instrument may be inserted in a curved channel, e.g., in a human body, causing many if not most of hinges 407(j) to be bent more or less. In the bent condition, at least some of the first side wall portions 444a(1) (and their equivalents at respective other locations) will be moved opposite side wall 446(1) (and their respective equivalents at other locations) and actual play will be reduced from w/ to w3.

[158] The tubes of the invasive instrument may have a circular cross section.

The tubes may, however, have another suitable cross section. E.g., the tubes may have an oval or elliptical or rectangular cross section. tube

[159] The tubes may be formed using a suitable biocompatible polymeric material, such as polyurethane, polyethylene, polypropylene or other biocompatible polymers. The tubes may be made of any other suitable material and/or in any other suitable way. Other suitable materials may be stainless steel, cobalt-chromium, shape memory alloy, such as Nitinol®, plastic, polymer, composites or other curable material.

[160] The circumferential, longitudinal slits and other slits may be made by means of any known material removal technique such as photochemical etching, deep pressing, chipping techniques, however, preferably by laser or water cutting. All slits are open both to the outside and inside of the tubes.

[161] The longitudinal slits, the circumferential slits and the U-shaped slits may have any suitable length and width, as required by the envisaged application. The longitudinal slits, the circumferential slits and the U-shaped slits of an intermediate tube may have the same or different lengths and/or widths.

[162] Preferably, their length is between 25 and 50%, more preferably between 30 and 45%, and most preferably between 35 and 40% of the external circumference of the tube-like member. The circumferential slits may have any suitable width. The circumferential slits of the same tube-like member may have the same width or different widths. The circumferential slits may be narrower next to their ending points and wider in their central part.

[163] The longitudinal slits and the inclined slits may have also any suitable length and width, as required by the envisaged application. The longitudinal slits and the inclined slits of a tube-like member may have the same or different lengths and/or widths.

[164] Variations in bending and torsion fidelity along the length of the tube- like member can be achieved by varying the durometer rating of materials that are used to mold the different segments. Also, the flexibility of the tube-like member may be varied by changing the dimensions and locations of the circumferential slits, longitudinal slits and inclined slits and/or by varying the angles between the circumferential slits and the radial circumference.

[165] Tube 400 may have one of a circular, oval, elliptical or rectangular

Cross section.

[166] Tube 400 may, at least in part, be made of at least one of the following set of materials: a biocompatible polymeric material, including polyurethane, polyethylene or polypropylene, stainless steel, cobalt-chromium, shape memory alloy such as Nitinol®, plastic, polymer, composites, or other curable material.

[167] In an embodiment, the cutting patterns of hinges 407(j) result from a material removal technique applied on a wall of tube 400, including at least one of photochemical etching, deep pressing, chipping techniques, laser cutting or water cutting. The material removal means can be a laser beam that melts and evaporates material or a water jet cutting beam and this beam can have a width of 0.01 to 2.00 mm, more typically for this application, between 0.015 and 0.04mm.

[168] The wall thickness of tubes depend on their application. For medical applications the wall thickness may be in a range of 0.03-2.0 mm, preferably 0.03-1.0 mm, more preferably 0.05-0.5 mm, and most preferably 0.08-0.4 mm.

[169] Features of the invention explained with reference to figures 9-12C may be summarized as follows.

[170] The invention of these figures relate to a tube including a hinge structure, the hinge structure including one or more hinges (407(j), j = 1, 2, ...

J), each hinge (407(j) including a first cutting pattern in the tube (400) and a second cutting pattern in the tube (400), the first cutting pattern and the second cutting pattern being located between a proximal hinge side and a distal hinge side of the hinge (407(})), the first cutting pattern defining a first longitudinal bridge (404(})) located at a first location, extending in a longitudinal direction of the tube (400) and connecting the proximal hinge side and the distal hinge side, a first tangential slit (410a(j), 410b(j)) extending from the first longitudinal bridge (404(})) in a first tangential direction (E) of the tube (400), the first tangential slit including two first tangential slit portions (410a(j), 410b(})) located at longitudinally shifted positions and, respectively, connected at opposite ends of a first channel (425(})) having a first longitudinally extending wall (440(j)) and a second longitudinally extending wall (442(j)) opposite to the first longitudinally extending wall (440(3)) such as to block tangential rotation of the proximal hinge side relative to the distal hinge side, a second tangential slit (418a(}), 418b(j)) extending from the first longitudinal bridge (404(})) in a second tangential direction (F) of the tube (400), the first and second tangential directions being opposite directions, the second tangential slit including two second tangential slit portions (418a(j), 418b(})) located at longitudinally shifted positions and, respectively, connected at opposite ends of a second channel (427(})) having a third longitudinally extending wall (444(;)) and a fourth longitudinally extending wall (446(})) opposite to the third longitudinally extending wall (444(1)) such as to block tangential rotation of the proximal hinge side relative to the distal hinge side, the second cutting pattern defining a second longitudinal bridge (450()) located at a second location, extending in the longitudinal direction of the tube (400) and connecting the proximal hinge side and the distal hinge side, the second location being 180 degrees rotated relative to the first location, a third tangential slit (424a(}), 424b(})) extending from the second longitudinal bridge (450(})) in the first tangential direction (E) of the tube (400), the third tangential slit including two third tangential slit portions (424a(}), 424b(})) located at longitudinally shifted positions and, respectively, connected at opposite ends of a third channel (429(})) having a fifth longitudinally extending wall (454(})) and a sixth longitudinally extending wall (456(})) opposite to the fifth longitudinally extending wall (454(3)) such as to block tangential rotation of the proximal hinge side relative to the distal hinge side, a fourth tangential slit (416a(}), 416b(j)) extending from the second longitudinal bridge (450(})) in the second tangential direction (F) of the tube (400), the fourth tangential slit including two fourth tangential slit portions (416a(j), 416b(})) located at longitudinally shifted positions and, respectively, connected at opposite ends of a fourth channel (43 1(j}) having a seventh longitudinally extending wall (462(})) and an eighth longitudinally extending wall (444(})) opposite to the seventh longitudinally extending wall (462(3)) such as to block tangential rotation of the proximal hinge side relative to the distal hinge side.

[171] The first longitudinal bridge (404(j)) may have a first center of rotation

(426(})) and the second longitudinal bridge (450(;)) may have a second center of rotation (458(3)), each hinge (407(})) being able to bend about a virtual line through the first center of rotation (426(j)) and the second center of rotation (458(3)), each one of the first longitudinally extending wall (440(})), the second longitudinally extending wall (442(})), third longitudinally extending wall (444(})) and the fourth longitudinally extending wall (446(j)) being formed as a portion of a respective circle having its center in the first center of rotation (426(3)), and each one of fifth longitudinally extending wall (454(})), the sixth longitudinally extending wall (456(})), seventh longitudinally extending wall (462(})) and the eighth longitudinally extending wall (444(})) being formed as a portion of a respective circle having its center in the second center of rotation (458()).

[172] The first cutting pattern may have two longitudinal slits (406(}), 408(})) extending in the longitudinal direction and forming two longitudinal sides of the first longitudinal bridge (404(})), and the second cutting pattern may have two further longitudinal slits (448), 452(})) extending in the longitudinal direction and forming two longitudinal sides of the second longitudinal bridge (4500).

[173] The two longitudinal slits (406(}), 408(j)) may be curved such that the first longitudinal bridge (404(})) has a first width increasing to its ends.

[174] The two further longitudinal slits (448(}), 452(j)) may be curved such that the second longitudinal bridge (404(})) has a second width increasing to its ends.

[175] The first tangential slit (410a(j), 410b(j)) may extend from a center (409(3)) of one of the two longitudinal slits (4063), 408(j)) and the second tangential slit (418a(j), 418b(j)) may extend from a center (411(j)) of the other one of the two longitudinal slits (406(j), 408(})).

[176] The third tangential slit (424a(}), 424b(j)) may extend from a center (423(})) of one of the two further longitudinal slits (448(}), 452(j)) and the fourth tangential slit (416a(}), 416b(j)) extends from a center (421(})) of the other one of the two further longitudinal slits (4483), 452()).

[177] One of the two first tangential slit portions (410a(j), 410b(})) and one of the two fourth tangential slit portions (416a(}), 416b(j)) may be, at least partly,

tangentially overlapping such as to form a first tangential bridge (403(})) between them, the first tangential bridge (403(j)) having one end attached to the proximal hinge side and an other end to the distal hinge side.

[178] One of the two second tangential slit portions (418a(}), 418b(j)) and one of the two third tangential slit portions (424a(3), 424b(j)) may be, at least partly, tangentially overlapping such as to form a second tangential bridge (405(})) between them, the second tangential bridge (405(})) having one end attached to the proximal hinge side and an other end to the distal hinge side.

[179] The two first tangential slit portions (410a(j), 410b(j)) and the third two tangential slit portions (424a(j), 424b(j)) may be oriented forming a first angle with a plane perpendicular to a center axis of the tube (400), the first angle being between -10" and +10° degrees, more preferably between -8° and +8° degrees.

[180] The two second tangential slit portions (418a(}), 418b(})) and the two fourth tangential slit portions (416a(}), 416b(})) may be oriented forming a second angle with a plane perpendicular to a center axis of the tube (400), the second angle being between -10° and +10" degrees, more preferably between - 89 and +8° degrees.

[181] The tube may include at least one of the following features: the first longitudinally extending wall (440(})) and the second longitudinally extending wall (442(j)) have portions of a fractured first fracture element (480(})) such as to reduce play between them, the third longitudinally extending wall (444(3)) and the fourth longitudinally extending wall (446(})) have portions of a fractured second fracture element (482(})) such as to reduce play between them, the fifth longitudinally extending wall (454(})) and the sixth longitudinally extending wall (456(})) have portions of a fractured third fracture element such as to reduce play between them, or the seventh longitudinally extending wall (462(3)) and the eighth longitudinally extending wall (444(})) have portions of a fractured fourth fracture element such as to reduce play between them.

General remark

[182] The examples and embodiments described herein serve to illustrate rather than to limit the invention. The person skilled in the art will be able to design alternative embodiments without departing from the scope of the claims. Reference numbers placed in parentheses in the claims shall not be interpreted to limit the scope of the claims. Items described as separate entities in the claims or the description may be implemented as a single or multiple hardware items combining the features of the items described.

[183] It is to be understood that the invention is limited by the annexed claims and its technical equivalents only. In this document and in its claims, the verb "to comprise" and its conjugations are used in their non-limiting sense to mean that items following the word are included, without excluding items not specifically mentioned. In addition, reference to an element by the indefinite article "a" or "an" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements. The indefinite article "a" or "an" thus usually means "at least one".

Claims

Conclusions

1. A steerable instrument having a deflectable tip section (358) on a distal side and a flexible body section (356) proximal to the tip section (358), the steerable instrument comprising at least one tube (312) and at least one of an inner tube (330) within the at least one tube (312) or an outer tube (340) outside the at least one tube (312), one or more steering wires (16(i)) within the at least one tube (312), the at least one tube (312) comprising a deflectable tip section (301) within the deflectable tip section (358) and a flexible body section (309) within the flexible body section (356), the one or more steering wires (16(i)) being helically disposed in a circumferential direction of the steerable instrument in at least a portion of the flexible body section (309), the steerable instrument also includes one or more longitudinal force isolation elements (322(k)) in the at least one tube (312), the longitudinal force isolation elements (322(k)) being disposed parallel to the one or more steering wires (16(i)) in the flexible body section (309), the one or more longitudinal force isolation elements (322(k)) having a distal end and a proximal end and one of the following features being employed: if the steerable instrument includes the outer tube (340), the distal end of each longitudinal force isolation element (322(k)) is attached to the outer tube (340) at a distal end of the body section (309) and the proximal end of each longitudinal force isolation element (322(k)) is attached to the outer tube (340) at a proximal end of the body section (309), or if the steerable instrument includes the inner tube (330), the distal end of each longitudinal force isolation element (322(k)) is attached to the outer tube (340) at a proximal end of the body section (309), isolating element (322(k)) is attached to the inner tube (330) at a distal end of the trunk section (309) and the proximal end of each longitudinal force isolating element (322(k)) is attached to the inner tube (330) at a proximal end of the trunk section (309), or if the steerable instrument comprises the inner tube (330) and the outer tube (340), the distal end of each longitudinal force isolating element (322{k)) is attached to at least one of the inner tube (330) or the outer tube (340) at a distal end of the trunk section (309) and the proximal end of each longitudinal force isolating element (322(k)) is attached to at least one of the inner tube (330) or the outer tube (340) at a proximal end of the trunk section (309).

A steerable instrument as claimed in claim 1, wherein the one or more steering wires (16(i)) are helically disposed 180 degrees circumferentially of the steerable instrument in at least one portion of the flexible body section (309) to provide path length compensation caused by bending of the at least one portion of the flexible body section (309).

A steerable instrument as claimed in claim 2, wherein the one or more steering wires (16(i}) are spiraled a plurality of 180 degree times in the circumferential direction of the steerable instrument in an equal number of portions of the flexible body section (309) to compensate for path length caused by bending of one or more of the plurality of portions of the flexible body section (309).

4. A steerable instrument as claimed in any preceding claim, wherein the one or more steering wires (16(i)} are arranged in a continuous manner in a spiral fashion along the entire flexible body section (309).

5. A steerable instrument according to any one of claims 1 to 4, comprising a plurality of steering wires (16(i)) at equally spaced locations in the tangential direction of the at least one tube (312) in a parallel manner, and a plurality of longitudinal force isolating elements (322(k)), wherein at least one longitudinal force isolating element (322(k)) is located between two adjacent steering wires (16(i), 16(i+1)).

6. The steerable instrument of claim 5, wherein each longitudinal force isolating element (322(k)) is attached to a spacer (318(i)) configured to maintain two adjacent steering wires (16(i)) at a desired tangential distance and if the steerable instrument comprises the outer tube (340), the distal end of each longitudinal force isolating element (322(k)) is attached to the outer tube (340) via an attachment of the spacer (318(i)) to the outer tube (340), or if the steerable instrument comprises the inner tube (330), the distal end of each longitudinal force isolating element (322(k)) is attached to the inner tube (330) via an attachment of the spacer (318(i)) to the inner tube (330), or if the steerable instrument comprises the inner tube (330) and the outer tube (340), the distal end of each longitudinal force insulating element (322(k)) is attached to at least one of the inner tube (330) or the outer tube (340) via an attachment of the spacer (318(i)) to at least one of the inner tube (330) or the outer tube (340).

7. A steerable instrument according to claim 5 or 6, wherein a single longitudinal force isolating element (322(k)) is disposed between and equidistant from two adjacent steering wires (16(i}, 16(i+1)).

8. The steerable instrument of claim 7, wherein a pair of flexible spacers (320a(i), 320b(i)) are provided between two adjacent steering wires (16(i), 16(i+1)) proximal to the spacer (318(i), a first of the pair of flexible spacers (320a(i), 320b(i)) being located between the single longitudinal force isolating element (322(k)) and a first of the two adjacent steering wires (16(i}, 16(i+1)) and a second of the pair of flexible spacers (320a(i}, 320b(i)) being located between the single longitudinal force isolating element (322(k)) and a second of the two adjacent steering wires (16(i}, 16(i+1)).

A steerable instrument according to any preceding claim, wherein at least one of the longitudinal force isolating elements (322(k)) includes through-holes (325), a lip extending from the inner tube (330) or the outer tube (340), respectively, through the through-holes (325), the lips and through-holes (325) being configured to block tangential movement but permit axial movement of the longitudinal force isolating elements (322(k)) relative to the inner tube (330) or the outer tube (340), respectively.

A steerable instrument according to any preceding claim, wherein the at least one tube (312) comprises an annular end portion (314) at its distal end to which the one or more steering wires (16(i)) are attached.

The steerable instrument of claim 10, wherein the tip portion of the at least one tube (312) comprises a spacer (316(i)) between each two adjacent steering wires (16), 16(i+1)), each spacer (316(i)) having the shape of a regular wave pattern such as a square wave or a sine wave pattern.

A steerable instrument according to any preceding claim, wherein the at least one tube (312) has one of a circular, oval, elliptical or rectangular cross-section.

A steerable instrument according to any preceding claim, wherein the at least one tube (312) is made of at least one of the following set of materials: a biocompatible polymeric material, comprising polyurethane, polyethylene or polypropylene, stainless steel, cobalt-chromium, shape memory alloy such as Nitinol®, plastic, polymer, composites or other hardenable material.

A steerable instrument according to any preceding claim, wherein the one or more steering wires (16(i)) and the one or more longitudinal force isolating elements (322(k})) result from a material removing technique applied to a wall of the at least one tube (312), comprising at least one of photochemical etching, intaglio printing, machining techniques, laser cutting or waterjet cutting.

A steerable instrument according to any preceding claim, comprising a Bowden cable portion (355) on a proximal side of a proximal end of the body portion (356) to further compensate for path length differences of the steering wires (16(i)) and the force isolating elements (322(k)).

An invasive instrument comprising a steerable instrument according to any preceding claim and a steering unit configured to operate the steering wires (16(i)) to deflect the deflectable tip portion (358), the steering unit being one of a manually operated steering unit or a robotic steering unit.

17. A tube comprising a hinge structure, the hinge structure comprising one or more hinges (407(j), j= 1, 2, ... J), each hinge (407(j)) comprising a first cutting pattern in the tube (400) and a second cutting pattern in the tube (400), the first cutting pattern and the second cutting pattern being located between a proximal hinge side and a distal hinge side of the hinge (407(j)), the first cutting pattern defining a first longitudinal bridge (404(j)) located at a first location extending in a longitudinal direction of the tube (400) and interconnecting the proximal hinge side and the distal hinge side, a first tangential slot (410a(j), 410b{j)) extending from the first longitudinal bridge (404(j)) in a first tangential direction (E) of the tube (400), wherein the first tangential slot comprises two first tangential slot portions (410a(j), 410b(j)) located at longitudinally offset positions and respectively secured to opposite ends of a first channel (425(j)) having a first longitudinally extending wall (440(j)) and a second longitudinally extending wall (442(j)) opposite the first longitudinally extending wall (440(j)) to block tangential rotation of the proximal hinge side relative to the distal hinge side, a second tangential slot (418a(j), 418b(j)) extending from the first longitudinal bridge (404(j)) in a second tangential direction (F) of the tube (400), the first and second tangential directions being opposite directions, the second tangential slot comprising two second tangential slot portions (418a(j), 418b(j)} located at longitudinally offset positions and respectively attached to opposite ends of a second channel (427(j)} having a third longitudinally extending wall (444(j)) and a fourth longitudinally extending wall (446(j)) opposite the third longitudinally extending wall (444(j)), so as to block tangential rotation of the proximal hinge side relative to the distal hinge side, the second cutting pattern defining a second longitudinal bridge {450(j)} located at a second location extending in the longitudinal direction of the tube (400) and connecting the proximal hinge side and the distal hinge side, the second location being rotated 180 degrees relative to the first location, a third tangential slot (424a(j), 424b(j)) which extending from the second longitudinal bridge (450(j)) in a first tangential direction (E) of the tube (400), the third tangential slot comprising two third tangential slot portions (424a(j), 424b(j)) located at longitudinally offset positions and respectively secured to opposite ends of a third channel (429(j)) having a fifth longitudinally extending wall (454(j)) and a sixth longitudinally extending wall (456(j)) opposite the fifth longitudinally extending wall (454(j)) so as to block tangential rotation of the proximal hinge side relative to the distal hinge side, a fourth tangential slot (416a(j), 416b(j)) extending from the second longitudinal bridge (450(j)) in a second tangential direction (F) of the tube (400), the fourth tangential slot includes two fourth tangential slot portions (416a(j), 416b(j)) located at longitudinally offset positions and respectively secured to opposite ends of a fourth channel (431(j)) having a seventh longitudinally extending wall (462(j)) and an eighth longitudinally extending wall (444{j)) opposite the seventh longitudinally extending wall (462(j)), so as to block tangential rotation of the proximal hinge side relative to the distal hinge side.

18. The tube of claim 17, wherein the first longitudinal bridge (404(j)) has a first center of rotation (426(j)) and the second longitudinal bridge (450(j)) has a second center of rotation (458(j)), each hinge (407(j)) being capable of bending about a virtual line through the first center of rotation (426(j)) and the second center of rotation (458(j)), each of the first longitudinally extending wall (440(j)), the second longitudinally extending wall (442([)), the third longitudinally extending wall (444(j)) and the fourth longitudinally extending wall (446{j}) being formed as a portion of a respective circle having its center at the first center of rotation (426(j)) and each of the fifth longitudinally extending wall (454(j)), the sixth The longitudinally extending wall (456(j)), the seventh longitudinally extending wall (462(j)) and the eighth longitudinally extending wall (444(j)) are formed as a portion of a respective circle having its center at the second center of rotation (458(j)).

19. The tube of claim 17 or 18, wherein the first cutting pattern has two longitudinal slots (406), 408(j)) extending in the longitudinal direction and forming two longitudinal sides of the first longitudinal bridge (404(j)) and the second cutting pattern has a further two longitudinal slots (448(j), 452(j)) extending in the longitudinal direction and forming two longitudinal sides of the second longitudinal bridge (450(j)).

20. The tube of claim 19, wherein the two longitudinal slots (408(j), 408(j)) are curved such that the first longitudinal bridge (404(j)) has a first width that increases toward its ends.

21. A tube as claimed in claim 19 or 20, wherein the two further longitudinal slots (448(j), 452(j)) are curved such that the second longitudinal bridge (404(j)) has a second width increasing towards its ends.

22. The tube of claim 19, 20 or 21, wherein the first tangential slot (410a(j), 410b(j)) extends from a midpoint (409(j)) of one of the two longitudinal slots (406), 408(j)) and the second tangential slot (418a(j), 418b(j)) extends from a midpoint (411(j)) of the other of the two longitudinal slots (406(), 408(j)).

23. A tube according to any one of claims 19 to 21, wherein the third tangential slot (424a(j), 424b(j)) extends from a centre (423(j)) of one of the two further longitudinal slots (448(j), 452())) and the fourth tangential slot (416a(j), 416b(j)) extends from a centre (421(j)) of the other of the two further longitudinal slots (448(j), 452()).

24. The tube of any of claims 17 to 23, wherein one of the two first tangential slot portions (410a(j), 410b(j)) and one of the two fourth tangential slot portions (4164), 416b(j)) at least partially tangentially overlap to form a first tangential bridge (403(j)) therebetween, the first tangential bridge (403(j)) having one end attached to the proximal hinge side and another end attached to the distal hinge side.

25. The tube of any of claims 17 to 24, wherein one of the two second tangential slot portions (418a(j), 418b(j)) and one of the two third tangential slot portions (424a(j), 424b(j)) at least partially tangentially overlap to form a second tangential bridge (405(j)) therebetween, the second tangential bridge (405(j)) having one end attached to the proximal hinge side and another end attached to the distal hinge side.

26. A tube according to any one of claims 17 to 25, wherein the first two tangential slot portions (410a(j), 410b(j)) and the third two tangential slot portions (424a(j), 424b{j}) are oriented to form a first angle with a plane perpendicular to a central axis of the tube (400), the first angle being between -10 and +10 degrees, most preferably between -8 and +8 degrees.

27. A tube according to any one of claims 17 to 26, wherein the two second tangential slot portions (418a(j), 418b(j)} and the two fourth tangential slot portions (416a(j), 416b(j)) are oriented to form a second angle with a plane perpendicular to a central axis of the tube (400), the second angle being between -10 and +10 degrees, most preferably between -8 and +8 degrees.

28. A tube according to any one of claims 17 to 27, wherein the tube has one of a circular, oval, elliptical and rectangular cross-section.

29. A tube according to any one of claims 17 to 28, made from at least one of the following set of materials: a biocompatible polymeric material, comprising polyurethane, polyethylene or polypropylene, stainless steel, cobalt-chromium, shape memory alloy such as Nitinol®, plastic, polymer, composites or other curable material.

30. A tube according to any one of claims 17 to 29, wherein the first and second cutting patterns result from a material removal technique comprising at least one of photochemical etching, intaglio printing, machining techniques, laser cutting or waterjet cutting.

31. A tube according to any one of claims 17 to 30, wherein the two first tangential slot portions (410a(j), 410b(j)), the two second tangential slot portions (418agj), 418b(j)), the third two tangential slot portions (424a(j), 424b(j)) and the two fourth tangential slot portions (416a(j), 416b(j)) have a same length, which is preferably between 25 and 50%, more preferably between 30 and 45% and most preferably between 35 and 40% of an external circumference of the tube.

32. A pipe according to any one of claims 17 to 31, wherein the first two tangential slot portions (410a(j), 410b(j)) and the second two tangential slot portions (418a(j), 418b{j}) taper toward the first longitudinal bridge (404(j)) and taper toward their opposite ends and the third two tangential slot portions (424a(j), 424b(j)) and the fourth two tangential slot portions (416a(j), 416b(j)) taper toward the second longitudinal bridge (450(j)) and taper toward their opposite ends.

33. Pipe according to any one of claims 17 to 32, comprising at least one of the following features:

the first longitudinally extending wall (440(j)) and the second longitudinally extending wall (442(j)) have portions of a fractionated first fracture element (480(j)) to reduce the clearance therebetween, the third longitudinally extending wall (444(j)) and the fourth longitudinally extending wall (446(j)) have portions of a fractionated second fracture element (482(j)) to reduce the clearance therebetween, the fifth longitudinally extending wall (454(j)) and the sixth longitudinally extending wall (456(j)) have portions of a fractionated third fracture element to reduce the clearance therebetween, or the seventh longitudinally extending wall (462(j)) and the eighth longitudinally extending wall (444(j)) have portions of a fractional fourth fraction element, in order to reduce the clearance between them.

34. A steerable invasive instrument comprising a tube according to any one of claims 17 to 33 and a steering unit configured to deflect a deflectable tip section.

35. The steerable invasive instrument of claim 34, wherein the steering unit is one of a manually operated steering unit or a robotic steering unit.