WO2017082720A1

WO2017082720A1 - Elongated steerable tubular body and steerable instrument comprising the same

Info

Publication number: WO2017082720A1
Application number: PCT/NL2015/050798
Authority: WO
Inventors: Mattheus Hendrik Louis THISSEN
Original assignee: Fortimedix Surgical B.V.
Priority date: 2015-11-13
Filing date: 2015-11-13
Publication date: 2017-05-18

Abstract

The invention relates to an elongated steerable tubular body (18) and a steerable instrument (10; 2201) comprising the same. The elongated steerable tubular body comprises at least one flexible zone (15, 17; 14, 16) and at least one intermediate cylindrical element (102; 2203) that comprises at least three longitudinal steering elements (4; 2338). In said at least one flexible zone, at least two longitudinal steering elements comprise respective first (64) and second (65) flexible strips being provided with one or more of respective first (67a) and second (68b) spacers. Each spacer (67a, 68b) comprises a respective strip (71, 72) having at least one first curved section (51a, 52a). Each strip being attached to its respective flexible strip (64, 65) with at least two portions of said respective strip. Said first (67a) and second (68b) spacers are alternatingly arranged in the axial direction of the elongated steerable tubular body.

Description

ELONGATED STEERABLE TUBULAR BODY AND STEERABLE

INSTRUMENT COMPRISING THE SAME

FIELD OF THE INVENTION

[0001] The invention relates to an elongated steerable tubular body for use in a steerable instrument for at least one of endoscopic and invasive type of applications. The invention further relates to a steerable instrument comprising such an elongated steerable tubular body. The steerable instrument according to the invention can be used in both medical and non-medical applications. Examples of the latter include at least one of inspection and repair of at least one of mechanical and electronic hardware at locations that are difficult to reach. Hence, terms used in the following description such as endoscopic application or invasive instrument, must be interpreted in a broad manner. BACKGROUND OF THE INVENTION

[0002] 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 that respect the possibility to use a natural orifice of the body would even be better. 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.

[0003] Surgical invasive instruments and endoscopes through which these instruments are guided towards the target area are well-known in the art. Both the invasive instruments and endoscopes can comprise a elongated steerable tubular body that enhances its navigation and steering capabilities. Such an elongated steerable tubular body preferably comprises a proximal end part including at least one flexible zone, a distal end part including at least one flexible zone, and a rigid intermediate part, wherein the elongated steerable tubular body 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 rigid intermediate part into a related deflection of at least a part of the distal end part.

[0004] Furthermore, the elongated steerable tubular body preferably comprises a number of co-axially arranged cylindrical elements including an outer element, an inner element and one or more intermediate 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 element or the steering members are divided in different sets and each set of steering members is arranged in a different intermediate member. The steering arrangement may comprise conventional steering cables with sub 1 millimeter diameters as steering members, wherein the steering cables are arranged between related flexible zones at the proximal and distal end parts of the tube. However, as steering cables have many well-known disadvantages, it is preferred to avoid them and to implement the steering members by one or more sets of longitudinal steering elements that form integral parts of the one or more intermediate elements. Each of the intermediate elements can be fabricated either by using a suitable material addition technique, such as inj ection moulding or plating, or by 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. 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. Further details regarding the design and fabrication of the abovementioned elongated steerable tubular body and the steering arrangement thereof have been described for example in WO 2009/1 12060 Al, WO 2009/127236 Al, US 13/160,949, and US 13/548,935 of the applicant, all of which are hereby incorporated by reference in their entirety.

[0005] Steerable invasive instruments typically comprise a handle that is arranged at the proximal end part of the elongated steerable tubular body for at least one of steering the tube and manipulating a tool that is arranged at the distal end part of the elongated steerable tubular body. 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.

[0006] In this application, the terms "proximal" and "distal" are defined with respect to an operator, e.g. a physician that operates the instrument or endoscope. For example, a proximal end part is to be construed as a part that is located near the physician and a distal end part as a part located at a distance from the physician.

[0007] A disadvantage of the elongated steerable tubular bodies described above is that in the flexible zones of the elongated steerable tubular body, the longitudinal steering elements at least have a tendency to move in a tangential direction especially when significant deflections are required. As a consequence of this uncontrolled movement of the longitudinal steering elements, the accuracy and the magnitude of the control of the deflection of the distal end part of the elongated steerable tubular body relative to the rigid intermediate part by the deflection of the proximal end part of the elongated steerable tubular body relative to the rigid intermediate part becomes more complicated or might even be lost.

[0008] From the prior art it is known that this problem can at least be mitigated by providing spacers that are arranged between adj acent longitudinal steering elements as seen in a circumferential direction of the elongated steerable tubular body.

[0009] EP 2 259 710 B l discloses embodiments of an elongated steerable tubular body for use in a steerable instrument for at least one of endoscopic and invasive type of applications, the elongated steerable tubular body comprising a bend-resistive zone that is arranged to interconnect one bendable zone at a proximal end part and one bendable zone at a distal end part of the elongated steerable tubular body. These bendable zones are bendable in a radial direction of the elongated steerable tubular body relative to the bend-resistive zone via steering members that in the bend-resistive zone comprise strips that, as seen in the circumferential direction of the elongated steerable tubular body, are much broader than the wires in the respective bendable zones. The narrow wires in the respective bendable zones being separated, as seen in the circumferential direction of the elongated steerable tubular body, by apertures. In order to maintain the distance between the narrow wires in the respective bendable zones, the apertures are provided with one or more spacers. [0010] EP 2 259 710 B l discloses that spacing between the wires may be maintained by employing one or more spacers on a wire, in fixed attachment thereto, configured for slidable contact with an adjacent wire, thereby maintaining its distance therefrom. The aforementioned wire-bound spacer is formed by one or more bends in the actual wire. The wire so bent may have an undulating or meandering shape. The undulations, having a concave and convex part, are in slidable contact with straight (non-bent) wires adjacent on both sides. It is also possible that the bent wire has a concave or convex undulation, and that the undulation is in slidable contact with a straight region of an adjacent wire on one side. The number of undulations per wire, where present, may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more, depending on the size of the undulation and the length of the wire.

[0011] Application of longitudinal steering elements or narrow wires and spacer arrangements like the ones known from EP 2 259 710 B 1 has disadvantages regarding the reliability and hence the performance of especially elongated steerable tubular bodies comprising more than one flexible zone in both the proximal and distal end parts in order to make more complicated curves allowing at least one of better access to locations that are difficult to reach and more versatile use of the steerable instrument comprising such an elongated steerable tubular body. For example, in the case that each one of the proximal and distal end parts of the elongated steerable tubular body comprises two flexible zones, it is possible to make S-shaped curves allowing triangulation and hence the use of two steerable instruments at a same distal location of operation. In such elongated steerable tubular bodies the longitudinal steering elements that allow the two flexible zones in at least one of the proximal and distal end parts to be independently deflectable with respect to each other, are commonly arranged in different neighbouring cylindrical elements that are coaxially arranged in a radial direction of the elongated steerable tubular body.

The disadvantages regarding reliability and performance of such elongated steerable tubular bodies and the steerable instruments in which they are used include at least one of degraded flexibility of the flexible zones in at least one of the proximal and distal end parts at least due to degraded flexibility of the longitudinal steering elements, interference in at least one of the proximal and distal end parts between at least one of spacers of neighbouring cylindrical elements, longitudinal steering elements of neighbouring cylindrical elements, spacers and longitudinal steering elements of neighbouring cylindrical elements, and spacers and longitudinal steering elements within the same cylindrical element, and insufficient tensile load or pulling strength of the longitudinal steering elements in an axial direction of the elongated steerable tubular body in at least one of the proximal and distal end parts.

SUMMARY OF THE INVENTION

[0012] It is an object of the invention to provide an elongated steerable tubular body for use in a steerable instrument for at least one of endoscopic and invasive type of applications that preempts or at least reduces the disadvantages of known elongated steerable tubular bodies described above. It is also an obj ect of the invention to provide a steerable instrument comprising an elongated steerable tubular body according to the invention.

[0013] This is achieved by an elongated steerable tubular body having a proximal end part, a distal end part and a rigid intermediate part that is arranged to interconnect the proximal end part and the distal end part; at least one of the proximal end part, the rigid intermediate part and the distal end part comprises a set of at least three coaxially arranged cylindrical elements, namely an inner cylindrical element, a first intermediate cylindrical element, and an outer cylindrical element; at least one of the proximal end part and the distal end part comprises at least one first flexible zone that is arranged to be deflectable in at least one first radial direction of the elongated steerable tubular body relative to the rigid intermediate part; said first intermediate cylindrical element comprises a first set of at least three longitudinal steering elements that are arranged in at least said at least one first flexible zone and said intermediate rigid part and arranged to allow said at least one first flexible zone to be deflectable in said at least one first radial deflection of the elongated steerable tubular body through a movement of at least one of said first set of at least three longitudinal steering elements in an axial direction of the elongated steerable tubular body; wherein in at least one of said at least one first flexible zone, a first one of said first set of at least three longitudinal steering elements comprises a first flexible strip and a second one of said first set of at least three longitudinal steering elements comprises a second flexible strip; a first gap being present between said first flexible strip and said second flexible strip as seen in a circumferential direction of the elongated steerable tubular body; said first flexible strip being provided with at least one first spacer extending in said first gap towards said second flexible strip; said at least one first spacer comprising a first strip comprising at least one first curved section with a first tip that is arranged to prevent, in use, movement of the second flexible strip in the circumferential direction of the elongated steerable tubular body towards said first flexible strip; said first strip being attached to said first flexible strip with at least two portions of said first strip; said second flexible strip being provided with at least one second spacer extending in said first gap towards said first flexible strip; said at least one second spacer comprising a second strip comprising at least one second curved section with a second tip that is arranged to prevent, in use, movement of the first flexible strip in the circumferential direction of the elongated steerable tubular body towards said second flexible strip; said second strip being attached to said second flexible strip with at least two portions of said second strip.

[0014] In an embodiment of the elongated steerable tubular body according to the invention, said first flexible strip is provided with a plurality of said first spacers and said second flexible strip is provided with a plurality of said second spacers, said plurality of said first spacers and said plurality of said second spacers being alternately arranged in the axial direction of the elongated steerable tubular body in said first gap.

[0015] In an embodiment of the elongated steerable tubular body according to the invention, a third one of said first set of at least three longitudinal steering elements comprises a third flexible strip which as seen in a circumferential direction of the elongated steerable tubular body is arranged adj acent to said second flexible strip at a side of said second flexible strip that is opposite the side at which said first flexible strip is arranged, such that a second gap is present between said second flexible strip and said third flexible strip; said second flexible strip being provided with at least one third spacer extending in said second gap towards said third flexible strip; said at least one third spacer comprising a third strip comprising at least one third curved section with a third tip arranged to prevent, in use, movement of the third flexible strip in the circumferential direction of the elongated steerable tubular body towards said second flexible strip; said third strip being attached to said second flexible strip with at least two portions of said third strip; said third flexible strip being provided with at least one fourth spacer extending in said second gap towards said second flexible strip; said at least one fourth spacer comprising a fourth strip comprising at least one fourth curved section with a fourth tip arranged to prevent, in use, movement of the second flexible strip in the circumferential direction of the elongated steerable tubular body towards said third flexible strip; said fourth strip being attached to said third flexible strip with at least two portions of said fourth strip.

[0016] In an embodiment of the elongated steerable tubular body according to the invention, said second flexible strip is provided with a plurality of said third spacers and said third flexible strip is provided with a plurality of said fourth spacers, said plurality of said third spacers and said plurality of said fourth spacers are alternately arranged in the axial direction of the elongated steerable tubular body in said second gap.

[0017] In an embodiment of the elongated steerable tubular body according to the invention, in said rigid intermediate part comprising said set of at least three coaxially arranged cylindrical elements, at least one of said first set of at least three longitudinal steering elements of said first intermediate cylindrical element has a first width as seen in the circumferential direction of the elongated steerable tubular body that is larger than a second width of said at least one of said first set of at least three longitudinal steering elements in said at least one of said at least one first flexible zones such that at least one first slit is present as seen in the circumferential direction of the elongated steerable tubular body between said at least one longitudinal steering element and at least one adj acent longitudinal steering element of said at least one longitudinal steering element; said at least one first slit allowing, in use, independent movement of said at least one longitudinal steering element and said at least one adj acent longitudinal steering element relative to each other in the axial direction of the elongated steerable tubular body.

[0018] In an embodiment of the elongated steerable tubular body according to the invention, the set of cylindrical elements further comprises a second intermediate cylindrical element that is arranged between said first intermediate cylindrical element and said outer cylindrical element; at least one of the proximal end part and the distal end part comprising said at least one first flexible zone comprises at least one second flexible zone and at least one first rigid zone that is arranged to interconnect said at least one first flexible zone and said at least one second flexible zone; said at least one second flexible zone is arranged to be deflectable in at least one second radial direction of the elongated steerable tubular body relative to the rigid intermediate part independently from said at least one first radial direction in which said at least one first flexible zone is deflectable; said second intermediate cylindrical element comprises a second set of at least three longitudinal steering elements that are arranged in at least said at least one second flexible zone and said intermediate rigid part and arranged to allow said at least one second flexible zone to be deflectable in said at least one second radial direction of the elongated steerable tubular body through a movement of at least one of said second set of at least three longitudinal steering elements in the axial direction of the elongated steerable tubular body; wherein in at least one of said at least one second flexible zone, a first one of said second set of at least three longitudinal steering elements of said second intermediate cylindrical element comprises a fourth flexible strip and a second one of said second set of at least three longitudinal steering elements of said second intermediate cylindrical element comprises a fifth flexible strip; a third gap being present between said fourth flexible strip and said fifth flexible strip as seen in a circumferential direction of the elongated steerable tubular body; said fourth flexible strip being provided with at least one seventh spacer extending in said third gap towards said fifth flexible strip; said at least one seventh spacer comprising a seventh strip comprising at least one seventh curved section with a seventh tip that is arranged to prevent, in use, movement of said fifth flexible strip in the circumferential direction of the elongated steerable tubular body towards said fourth flexible strip; said seventh strip being attached to said fourth flexible strip with at least two portions of said fourth strip; said fifth flexible strip being provided with at least one eighth spacer extending in said third gap towards said fourth flexible strip; said at least one eighth spacer comprising an eighth strip comprising at least one eighth curved section with an eighth tip that is arranged to prevent, in use, movement of said fourth flexible strip in the circumferential direction of the elongated steerable tubular body towards said fifth flexible strip; said eighth strip being attached to said fifth flexible strip with at least two portions of said eighth strip.

[0019] In an embodiment of the elongated steerable tubular body according to the invention, said fourth flexible strip of said first one of said second set of at least three longitudinal steering elements of said second intermediate cylindrical element is provided with a plurality of said seventh spacers and said fifth flexible strip of said second one of said second set of at least three longitudinal steering elements of said second intermediate cylindrical element is provided with a plurality of said eighth spacers, said plurality of said seventh spacers and said plurality of said eighth spacers being alternately arranged in the axial direction of the elongated steerable tubular body in said third gap.

[0020] In an embodiment of the elongated steerable tubular body according to the invention, a third one of said second set of at least three longitudinal steering elements of said second intermediate cylindrical element comprises a sixth flexible strip which as seen in a circumferential direction of the elongated steerable tubular body is arranged adjacent to said fifth flexible strip at a side of said fifth flexible strip that is opposite the side at which said fourth flexible strip is arranged, such that a fourth gap is present between said fifth flexible strip and said sixth flexible strip; said fifth flexible strip being provided with at least one ninth spacer extending in said fourth gap towards said sixth flexible strip; said at least one ninth spacer comprising a ninth strip comprising at least one ninth curved section with a ninth tip arranged to prevent, in use, movement of said sixth flexible strip in the circumferential direction of the elongated steerable tubular body towards said fifth flexible strip; said ninth strip being attached to said fifth flexible strip with at least two portions of said ninth strip; said sixth flexible strip being provided with at least one tenth spacer extending in said fourth gap towards said fifth flexible strip; said at least one tenth spacer comprising a tenth strip comprising at least one tenth curved section with a tenth tip arranged to prevent, in use, movement of said fifth flexible strip in the circumferential direction of the elongated steerable tubular body towards said sixth flexible strip; said tenth strip being attached to said sixth flexible strip with at least two portions of said tenth strip.

[0021] In an embodiment of the elongated steerable tubular body according to the invention, said fifth flexible strip of said second one of said second set of at least three longitudinal steering elements of said second intermediate cylindrical element is provided with a plurality of said ninth spacers and said sixth flexible strip of said third one of said second set of at least three longitudinal steering elements of said second intermediate cylindrical element is provided with a plurality of said tenth spacers, said plurality of said ninth spacers and said plurality of said tenth spacers are alternately arranged in the axial direction of the elongated steerable tubular body in said fourth gap.

[0022] In an embodiment of the elongated steerable tubular body according to the invention, in at least one of said first rigid zone of the proximal end part, said rigid intermediate part, and said first rigid zone of the distal end part, at least one of said second set of at least three longitudinal steering elements of said second intermediate cylindrical element has a first width as seen in the circumferential direction of the elongated steerable tubular body that is larger than a second width of said at least one of said second set of at least three longitudinal steering elements in said at least one of said at least one first and second flexible zones such that at least one second slit is present as seen in the circumferential direction of the elongated steerable tubular body between said at least one longitudinal steering element and at least one adj acent longitudinal steering element of said at least one longitudinal steering element, said at least one second slit allowing, in use, independent movement of said at least one longitudinal steering element and said at least one adj acent longitudinal steering element relative to each other in the axial direction of the elongated steerable tubular body.

[0023] In an embodiment of the elongated steerable tubular body according to the invention, in at least one of said at least one second flexible zones at least one of said first, second, third and fourth spacers of at least one of said first, second and third flexible strips of said first intermediate cylindrical element and at least one of said seventh, eighth, ninth and tenth spacers of at least one of said fourth, fifth and sixth flexible strips of said second intermediate cylindrical element are arranged to at least partially overlap as seen in the axial direction of the elongated steerable tubular body.

[0024] In an embodiment of the elongated steerable tubular body according to the invention, at least one of said first and second strips which is attached to a respective one of said first and second flexible strips has a meandering shape comprising at least three curved sections with at least three tips; two of said at least three tips are arranged as seen in the circumferential direction of the elongated steerable tubular body next to an adj acent one of said respective one of said first and second flexible strips such as to prevent, in use, movement of said adjacent one of said respective one of said first and second flexible strips in the circumferential direction of the elongated steerable tubular body towards said respective one of said first and second flexible strips; a third one of said at least three tips is arranged next to said respective one of said first and second flexible strips such as to prevent, in use, movement of said respective one of said first and second flexible strips in the circumferential direction of the elongated steerable tubular body towards said adjacent one of said respective one of said first and second flexible strips.

[0025] In an embodiment of the elongated steerable tubular body according to the invention, at least one of said third and fourth strips which is attached to a respective one of said second and third flexible strips has a meandering shape comprising at least three curved sections with at least three tips; two of said at least three tips are arranged as seen in the circumferential direction of the elongated steerable tubular body next to an adjacent one of said respective one of said second and third flexible strips such as to prevent, in use, movement of said adjacent one of said respective one of said second and third flexible strips in the circumferential direction of the elongated steerable tubular body towards said respective one of said second and third flexible strips; a third one of said at least three tips is arranged next to said respective one of said second and third flexible strips such as to prevent, in use, movement of said respective one of said second and third flexible strips in the circumferential direction of the elongated steerable tubular body towards said adjacent one of said respective one of said second and third flexible strips.

[0026] In an embodiment of the elongated steerable tubular body according to the invention, at least one of said seventh and eighth strips which is attached to a respective one of said fourth and fifth flexible strips has a meandering shape comprising at least three curved sections with at least three tips; two of said at least three tips are arranged as seen in the circumferential direction of the elongated steerable tubular body next to an adjacent one of said respective one of said fourth and fifth flexible strips such as to prevent, in use, movement of said adjacent one of said respective one of said fourth and fifth flexible strips in the circumferential direction of the elongated steerable tubular body towards said respective one of said fourth and fifth flexible strips; a third one of said at least three tips is arranged next to said respective one of said fourth and fifth flexible strips such as to prevent, in use, movement of said respective one of said fourth and fifth flexible strips in the circumferential direction of the elongated steerable tubular body towards said adjacent one of said respective one of said fourth and fifth flexible strips.

[0027] In an embodiment of the elongated steerable tubular body according to the invention, at least one of said ninth and tenth strips which is attached to a respective one of said fifth and sixth flexible strips has a meandering shape comprising at least three curved sections with at least three tips; two of said at least three tips are arranged as seen in the circumferential direction of the elongated steerable tubular body next to an adj acent one of said respective one of said fifth and sixth flexible strips such as to prevent, in use, movement of said adjacent one of said respective one of said fifth and sixth flexible strips in the circumferential direction of the elongated steerable tubular body towards said respective one of said fifth and sixth flexible strips; a third one of said at least three tips is arranged next to said respective one of said fifth and sixth flexible strips such as to prevent, in use, movement of said respective one of said fifth and sixth flexible strips in the circumferential direction of the elongated steerable tubular body towards said adj acent one of said respective one of said fifth and sixth flexible strips.

[0028] An aspect of the invention is a steerable instrument for at least one of endoscopic and invasive type of applications comprising an elongated steerable tubular body according to any one of the preceding claims, said steerable instrument comprising a tool that is arranged at said distal end part of said elongated steerable tubular body and a handle that is arranged at said proximal end part of said elongated steerable tubular body such as to control, in use, at least one of said tool and at least one of said at least one first flexible zones and said at least one second flexible zones. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] 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. 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:

[0030] Figure 1 shows a schematic perspective view of a non-limiting embodiment of an invasive instrument assembly having two steerable instruments.

[0031] Figure 2a shows a side view of a non-limiting embodiment of a rigid invasive instrument. [0032] Figure 2b shows a side view of a non-limiting embodiment of a steerable invasive instrument.

[0033] Figure 2c provides a detailed perspective view of a non-limiting embodiment of the elongated tubular body of the steerable instrument.

[0034] Figure 2d provides a more detailed view of the distal end part of the elongated tubular body as shown in figure 2c.

[0035] Figure 2e shows a longitudinal cross-sectional view of the elongated tubular body of the steerable instrument as shown in figure 2c.

[0036] Figure 2f shows a longitudinal cross-sectional view of the elongated tubular body of the steerable instrument as shown in figure 2c, wherein the first proximal and first distal flexible zones are bent, thereby illustrating the operation of the steering arrangement.

[0037] Figure 2g shows a longitudinal cross-sectional view of the elongated tubular body of the steerable instrument as shown in figure 2f, wherein additionally the second proximal and second distal flexible zones are bent, thereby further illustrating the operation of the steering arrangement.

[0038] Figure 2h shows a perspective view of a part of the elongated tubular body as shown in figure 2c, wherein the outer cylindrical element partially has been removed to show an exemplary embodiment of the longitudinal steering elements that have been obtained after providing longitudinal slits to the wall of an intermediate cylindrical element that interconnects the first proximal flexible zone and the first distal flexible zone of the elongated tubular body.

[0039] Figure 2i shows a longitudinal cross-sectional view of an exemplary embodiment of a steerable instrument having one proximal and one distal flexible zone.

[0040] Figure 2j shows a perspective exploded view of the three cylindrical elements of the steerable instrument shown in figure 2i.

[0041] Figure 2k shows a top view of an unrolled version of an exemplary embodiment of the intermediate cylindrical element of the steerable instrument shown in figure 2j . The intermediate cylindrical element can be formed by rolling the unrolled version into a cylindrical configuration and attaching adj acent sides of the rolled-up configuration by any known attaching means such as by a welding technique. [0042] Figures 3a, 3b and 3c show schematic representations of unrolled views of embodiments of flexible proximal and distal parts of inner, outer and intermediate cylindrical elements.

[0043] Figure 4 shows a perspective exploded view of three cylindrical elements of a elongated steerable tubular body analogous to the exploded view of figure 2j , but with a varying diameter of the cylindrical elements.

[0044] Figure 5a shows a schematic cross-section of a first exemplary embodiment of a steerable instrument with cylindrical elements comparable as shown in figures 3a, 3b and 3c. The proximal actuating portion of the cylindrical elements has a larger diameter compared to the distal handling end portion. A frusto-conical part schematically representing a cylindrical diameter adaptation section has been incorporated in the intermediate rigid part that is arranged between the proximal end part and the distal end part to connect the parts of the elongated tubular body having different diameters.

[0045] Figure 5b shows a schematic cross-section of a second exemplary embodiment of a steerable instrument in which a proximal actuation flexible zone of the actuating portion of the cylindrical elements as well as an intermediate rigid part that is arranged between said proximal actuation flexible zone and a distal actuation flexible zone have a larger diameter than the other parts of the elongated tubular body. A frusto-conical part is shown that schematically represents a diameter adaptation section according to the invention.

[0046] Figure 6 shows a schematic perspective view of an exemplary embodiment of a proximal end part of an elongated steerable tubular body according to the invention comprising one intermediate cylindrical element. The elongated steerable tubular body furthermore comprises a frusto-conical part that schematically represents the diameter adaptation section.

[0047] Figure 7a shows a top view of an unrolled version of an exemplary embodiment of a first intermediate cylindrical element of the elongated steerable tubular body according to the invention comprising one flexible zone in the proximal end part and one flexible zone in the distal end part of the elongated steerable tubular body. Meandering or wave-shaped spacers are only provided in the flexible zone of the proximal end part and the flexible zone of the distal end part. [0048] Figure 7b shows a top view of an unrolled version of an exemplary embodiment of said first intermediate cylindrical element of the elongated steerable tubular body according to the invention comprising one flexible zone in the proximal end part and one flexible zone in the distal end part of the elongated steerable tubular body. Compared to figure 7a, meandering or wave-shaped spacers are now also provided in the rigid intermediate part of the elongated steerable tubular body.

[0049] Figure 8a shows a top view of an unrolled version of an exemplary embodiment of a first intermediate cylindrical element of the elongated steerable tubular body according to the invention comprising two flexible zones in the proximal end part and two flexible zones in the distal end part of the elongated steerable tubular body. Meandering or wave-shaped spacers are only provided in the first and second flexible zones of the proximal end part and in the first and second flexible zones of the distal end part.

[0050] Figure 8b shows a top view of an unrolled version of an exemplary embodiment of a first intermediate cylindrical element of the elongated steerable tubular body according to the invention comprising two flexible zones in the proximal end part and two flexible zones in the distal end part of the elongated steerable tubular body. Compared to figure 8a, meandering or wave-shaped spacers are also provided in the first rigid zone of the proximal end part, the rigid intermediate part and the first rigid zone of the distal end part of the elongated steerable tubular body.

[0051] Figure 9a shows a top view of an unrolled version of an exemplary embodiment of a second intermediate cylindrical element of the elongated steerable tubular body according to the invention. Meandering or wave-shaped spacers are provided in the second flexible zone of the proximal end part and the second flexible zone of the distal end part but not in the rigid intermediate part of the elongated steerable tubular body.

[0052] Figure 9b shows a top view of an unrolled version of an exemplary embodiment of a second intermediate cylindrical element of the elongated steerable tubular body according to the invention. Meandering or wave-shaped spacers are provided in the second flexible zone of the proximal end part, the second flexible zone of the distal end part and also in the rigid intermediate part of the elongated steerable tubular body.

[0053] Figure 10a shows a schematic perspective view of an exemplary embodiment of a second flexible zone of a proximal end part of an elongated steerable tubular body according to the invention comprising first and second intermediate cylindrical elements.

[0054] Figure 10b shows an exploded view of the exemplary embodiment of the second flexible zone of the proximal end part of the elongated steerable tubular body shown in figure 10a.

DETAILED DESCRIPTION

[0055] Embodiments of the present invention are described in the following with reference to the accompanying drawings.

[0056] Figure 2a shows a side view of a non-limiting embodiment of a rigid invasive instrument 240 and figure 2b shows a non-limiting embodiment of a steerable invasive instrument 10. Figure 1 shows a non-limiting embodiment of an invasive instrument assembly 1 having an introducer with two such steerable invasive instruments 10. Details of the non-limiting embodiment of the steerable invasive instruments 10 are explained in relation to figures 2c to 2k.

[0057] The rigid invasive instrument 240 as shown in figure 2a comprises an elongated shaft 242 having a proximal end part 241 and a distal end part 243. At the distal end part 243 a tool 2, for example a forceps, is arranged. At the proximal end part 241 a handle 3 is arranged that is adapted for manipulating the tool 2, i.e. opening and closing the jaw of the forceps. To that effect, a control rod (not shown) is present within the elongated shaft 242, which rod connects the handle 3 with the tool 2. The rod can be moved by the handle 3 and the movement of the rod is translated into a predetermined movement of the tool 2, as is known to persons skilled in the art and need no further explanation here. Also, the shaft 242 may comprise conducting wires to allow a current to flow to a tool, e.g. to heat said tool in order to perform a heat treatment within a human or animal body.

[0058] Figure 2b shows a side view of a steerable invasive instrument 10. The steerable instrument 10 comprises an elongated tubular body 18 having a proximal end part 1 1 including two actuation flexible zones 14, 15, a distal end part 13 including two distal flexible zones 16, 17, and a rigid intermediate part 12. The actuation flexible zones 14, 15 in the present embodiment are configured as flexible proximal zones, and will further be referred to as flexible proximal zones. At the distal end part 13 a tool, like a forceps 2 is arranged. At the proximal end part 1 1 a handle 3 is arranged that is adapted for opening and closing the jaw of the forceps 2.

[0059] Figure 2c provides a detailed perspective view of the distal portion of the elongated tubular body 18 of the steerable instrument 10 and shows that the elongated tubular body 18 comprises of a number of co-axially arranged layers or cylindrical elements including an outer cylindrical element 104 that ends after the first distal flexible zone 16 at the distal end portion 13. The distal end portion 13 of the outer cylindrical element 104 is fixedly attached to the cylindrical element 103 located within and adjacent to the outer cylindrical element 104, e.g. by means of spot welding at welding spots 100. However, any other suitable attachment method can be used, including gluing by a suitable glue.

[0060] Figure 2d provides a more detailed view of the distal end part 13 and shows that it includes three co-axially arranged layers or cylindrical elements being an inner cylindrical element 101 , a first intermediate cylindrical element 102 and a second intermediate cylindrical element 103. The distal ends of inner cylindrical element 101, first intermediate cylindrical element 102 and second intermediate cylindrical element 103 are all three fixedly attached to one another. This may be done by means of spot welding at welding spots 100. However, any other suitable attachment method can be used, including gluing by a suitable glue. The points of attachment may be at the end edges of inner cylindrical element 101 , first intermediate cylindrical element 102 and second intermediate cylindrical element 103, as shown in the figures. However, these points of attachment may also be located some distance away from these edges, be it, preferably, between the end edges and the locations of the flexible zone 17.

[0061] It will be clear to the skilled person that the elongated tubular body 18 as shown in figure 2c comprises four cylindrical elements in total. The elongated tubular body 18 according to the embodiment shown in figure 2c comprises two intermediate cylindrical elements 102 and 103 in which the steering members of the steering arrangement are arranged. The steering arrangement in the exemplary embodiment of the elongated tubular body 18 as shown in figure 2c comprises the two flexible zones 14, 15 at the proximal end part 1 1 of the elongated tubular body 18, the two flexible zones 16, 17 at the distal end part 13 of the elongated tubular body 18 and the steering members that are arranged between related flexible zones at the proximal 1 1 and distal 13 end parts. An exemplary actual arrangement of the steering members is shown in figure 2e, which provides a schematic longitudinal cross-sectional view of the exemplary embodiment of the elongated tubular body 18 as shown in figure 2c.

[0062] Figure 2e shows the four layers or cylindrical elements mentioned above, i.e. the inner cylindrical element 101 , the first intermediate cylindrical element 102, the second intermediate cylindrical element 103, and the outer cylindrical element 104.

[0063] The inner cylindrical element 101 , as seen along its length from the distal end to the proximal end of the instrument, comprises a rigid ring 1 1 1, which is arranged at the distal end part 13 of the steerable instrument 10, a first flexible portion 1 12, a first intermediate rigid portion 1 13, a second flexible portion 1 14, a second intermediate rigid portion 1 15, a third flexible portion 1 16, a third intermediate rigid portion 1 17, a fourth flexible portion 1 18, and a rigid end portion 1 19, which is arranged at the proximal end portion 1 1 of the steerable instrument 10.

[0064] The first intermediate cylindrical element 102, as seen along its length from the distal end to the proximal end of the instrument, comprises a rigid ring 121 , a first flexible portion 122, a first intermediate rigid portion 123, a second flexible portion 124, a second intermediate rigid portion 125, a third flexible portion 126, a third intermediate rigid portion 127, a fourth flexible portion 128, and a rigid end portion 129. The longitudinal dimensions of the rigid ring 121, the first flexible portion 122, the first intermediate rigid portion 123, the second flexible portion 124, the second intermediate rigid portion 125, the third flexible portion 126, the third intermediate rigid portion 127, the fourth flexible portion 128, and the rigid end portion 129 of the first intermediate element 102, respectively, are aligned with, and preferably approximately equal to the longitudinal dimensions of the rigid ring 1 1 1 , the first flexible portion 1 12, the first intermediate rigid portion 1 13, the second flexible portion 1 14, the second intermediate rigid portion 1 15, the third flexible portion 1 16, the third intermediate rigid portion 1 17, the fourth flexible portion 1 18, and the rigid end portion 1 19 of the inner cylindrical element 101, respectively, and are coinciding with these portions as well. In this description "approximately equal" means that respective same dimensions are equal within a margin of less than 10%, preferably less than 5%.

[0065] The second intermediate cylindrical element 103, as seen along its length from the distal end to the proximal end of the instrument, comprises a first rigid ring 131 , a first flexible portion 132, a second rigid ring 133, a second flexible portion 134, a first intermediate rigid portion 135, a first intermediate flexible portion 136, a second intermediate rigid portion 137, a second intermediate flexible portion 138, and a rigid end portion 139. The longitudinal dimensions of the first rigid ring 131 , the first flexible portion 132 together with the second rigid ring 133 and the second flexible portion 134, the first intermediate rigid portion 135, the first intermediate flexible portion 136, the second intermediate rigid portion 137, the second intermediate flexible portion 138, and the rigid end portion 139 of the second intermediate cylinder 103, respectively, are aligned with, and preferably approximately equal to the longitudinal dimensions of the rigid ring 1 1 1 , the first flexible portion 1 12, the first intermediate rigid portion 1 13, the second flexible portion 1 14, the second intermediate rigid portion 1 15, the third flexible portion 1 16, the third intermediate rigid portion 1 17, the fourth flexible portion 1 18, and the rigid end portion 1 19 of the first intermediate element 102, respectively, and are coinciding with these portions as well.

[0066] The outer cylindrical element 104, as seen along its length from the distal end to the proximal end of the instrument, comprises a first rigid ring 141 , a first flexible portion 142, a first intermediate rigid portion 143, a second flexible portion 144, and a second rigid ring 145. The longitudinal dimensions of the first flexible portion 142, the first intermediate rigid portion 143 and the second flexible portion 144 of the outer cylindrical element 104, respectively, are aligned with, and preferably approximately equal to the longitudinal dimension of the second flexible portion 134, the first intermediate rigid portion 135 and the first intermediate flexible portion 136 of the second intermediate element 103, respectively, and are coinciding with these portions as well. The rigid ring 141 has approximately the same length as the rigid ring 133 and is fixedly attached thereto, e.g. by spot welding or gluing. Preferably, the rigid ring 145 overlaps with the second intermediate rigid portion 137 only over a length that is required to make an adequate fixed attachment between the rigid ring 145 and the second intermediate rigid portion 137, respectively, e.g. by spot welding or gluing. The rigid rings 1 1 1, 121 and 13 1 are attached to each other, e.g., by spot welding or gluing. This may be done at the end edges thereof but also at a distance of these end edges. [0067] In an embodiment, the same may apply to the rigid end portions 1 19, 129 and 139, which can be attached together as well in a comparable manner. However, as will be explained hereinafter, the construction may be such that the diameter of the cylindrical elements at the proximal portion is larger, or smaller, with respect to the diameter at the distal portion. In such embodiment the construction at the proximal portion differs from the one shown in figure 2e. As a result of the increase in diameter an amplification is achieved, i.e., the bending angle of a flexible zone at the distal portion will be larger than the bending angle of a corresponding flexible portion at the proximal portion. This will be further described below with reference to figure 4.

[0068] The inner and outer diameters of the cylindrical elements 101 , 102, 103, and 104 are chosen in such a way at a same location along the elongated tubular body 18 that the outer diameter of inner cylindrical element 101 is slightly less than the inner diameter of the first intermediate cylindrical element 102, the outer diameter of the first intermediate cylindrical element 102 is slightly less than the inner diameter of the second intermediate cylindrical element 103 and the outer diameter of the second intermediate cylindrical element 103 is slightly less than the inner diameter of the outer cylindrical element 104, in such a way that a sliding movement of the adjacent cylindrical elements with respect to each other is possible. The dimensioning should be such that a sliding fit is provided between adjacent elements. A clearance between adjacent elements may generally be in the order of 0.02 to 0.1 mm, but depends on the specific application and material used. The clearance preferably is smaller than a wall thickness of the longitudinal steering elements to prevent an overlapping configuration thereof. Restricting the clearance to about 30% to 40% of the wall thickness of the longitudinal steering elements is generally sufficient.

[0069] As can be seen in figure 2e, flexible zone 14 of the proximal end part 1 1 is attached to the flexible zone 16 of the distal end part 13 by portions 134, 135 and 136, of the second intermediate cylindrical element 103, which form a first set of longitudinal steering members of the steering arrangement of the steerable instrument 10. Furthermore, flexible zone 15 of the proximal end part 1 1 is attached to the flexible zone 17 of the distal end part 13 by portions 122, 123, 124, 125, 126, 127, and 128 of the first intermediate cylindrical element 102, which form a second set of longitudinal steering members of the steering arrangement. The use of the construction as described above allows the steerable instrument 10 to be used for double bending. The working principle of this construction will be explained with respect to the examples shown in figures 2f and 2g.

[0070] For the sake of convenience, as shown in figures 2e, 2f and 2g,the different portions of the cylindrical elements 101, 102, 103, and 104 have been grouped into zones 151 - 160 that are defined as follows. Zone 151 comprises the rigid rings 1 1 1 , 121 , and 131. Zone 152 comprises the portions 1 12, 122, and 132. Zone 153 comprises the rigid rings 133 and 141 and the portions 1 13 and 123. Zone 154 comprises the portions 1 14, 124, 134 and 142. Zone 155 comprises the portions 1 15, 125, 135 and 143. Zone 156 comprises the portions 1 16, 126, 136 and 144. Zone 157 comprises the rigid ring 145 and the parts of the portions 1 17, 127, and 137 coinciding therewith. Zone 158 comprises the parts ofthe portions 1 17, 127, and 137 outside zone 157. Zone 159 comprises the portions 1 18, 128 and 138. Finally, zone 160 comprises the rigid end portions 1 19, 129 and 139.

[0071] In order to deflect at least a part of the distal end part 13 of the steerable instrument 10, it is possible to apply a bending force, in any radial direction, to zone 158. According to the examples shown in figures 2f and 2g, zone 158 is bent downwards with respect to zone 155. Consequently, zone 156 is bent downwards. Because of the first set of steering members comprising portions 134, 135, and 136 of the second intermediate cylindrical element 103 that are arranged between the second intermediate rigid portion 137 and the second rigid ring 133, the downward bending of zone 156 is transferred by a longitudinal displacement of the first set of steering members into an upward bending of zone 154 with respect to zone 155. This is shown in both figures 2f and 2g.

[0072] It is to be noted that the exemplary downward bending of zone 156, only results in the upward bending of zone 154 at the distal end of the instrument as shown in figure 2f. Bending of zone 152 as a result of the bending of zone 156 is prevented by zone 153 that is arranged between zones 152 and 154. When subsequently a bending force, in any radial direction, is applied to the zone 160, zone 159 is also bent. As shown in figure 2g, zone 160 is bent in an upward direction with respect to its position shown in figure 2f. Consequently, zone 159 is bent in an upward direction. Because of the second set of steering members comprising portions 122, 123, 124, 125, 126, 127 and 128 of the first intermediate cylindrical element 102 that are arranged between the rigid ring 121 and the rigid end portion 129, the upward bending of zone 159 is transferred by a longitudinal displacement of the second set of steering members into a downward bending of zone 152 with respect to its position shown in figure 2f.

[0073] Figure 2g further shows that the initial bending of the instrument in zone 154 as shown in figure 2f will be maintained because this bending is only governed by the bending of zone 156, whereas the bending of zone 152 is only governed by the bending of zone 159 as described above. Due to the fact that zones 152 and 154 are bendable independently with respect to each other, it is possible to give the distal end part 13 of the steerable instrument 10 a position and longitudinal axis direction that are independent from each other. In particular the distal end part 13 can assume an advantageous S-like shape. In known instruments such as described in EP 1 708 609 A, the position and the direction of the longitudinal axis are always coupled and cannot be individually controlled. The skilled person will appreciate that the capability to independently bend zones 152 and 154 with respect to each other, significantly enhances the maneuverability of the distal end part 13 and therefore of the steerable instrument 10 as a whole.

[0074] Obviously, it is possible to vary the lengths of the flexible portions shown in figures 2e to 2g as to accommodate specific requirements with regard to bending radii and total lengths of the distal end part 13 and the proximal end part 1 1 of the steerable instrument 10 or to accommodate amplification or attenuation ratios between bending of at least a part of the proximal end part 1 1 and at least a part of the distal end part 13.

[0075] The steering arrangement of the steerable invasive instrument 10 may comprise conventional steering cables as steering members that are fixedly attached to the respective rigid rings 121 , 133. However due to well-known disadvantages of conventional steering cables, the steering members preferably comprise one or more sets of longitudinal steering elements that form integral parts of the one or more intermediate cylindrical elements 102, 103. Preferably, the longitudinal steering elements comprise remaining parts of the wall of an intermediate cylindrical element 102, 103 after the wall of the intermediate cylindrical element 102, 103 has been provided with longitudinal slits that define the remaining longitudinal steering elements.

[0076] Further details regarding the fabrication of the latter longitudinal steering elements are provided with reference to figures 2i to 2k regarding an exemplary embodiment of a steerable instrument that comprises only one flexible zone at both its proximal 1 1 and distal end 13 parts.

[0077] Figure 2i shows a longitudinal cross-section of a steerable instrument 2201 comprising three co-axially arranged cylindrical elements, i.e. inner cylindrical element 2202, intermediate cylindrical element 2203 and outer cylindrical element 2204. Suitable materials to be used for making the cylindrical elements 2202,

2203, and 2204 include stainless steel, cobalt-chromium, shape memory alloy such as Nitinol®, plastic, polymer, composites or other cuttable material.

[0078] The inner cylindrical element 2202 comprises a first rigid end part 2221 , which is located at the distal end part 13 of the instrument 2201, a first flexible portion 2222, an intermediate rigid portion 2223, a second flexible portion 2224 and a second rigid end part 2225, which is located at the proximal end part 1 1 of the instrument 2201.

[0079] The outer cylindrical element 2204 also comprises a first rigid end part 2241 , a first flexible portion 2242, an intermediate rigid portion 2243, a second flexible portion 2244 and a second rigid end part 2245. The lengths of the different portions and parts of the cylindrical elements 2202 and 2204 are substantially the same so that when the inner cylindrical element 2202 is inserted into the outer cylindrical element

2204, the different portions and parts are positioned against each other.

[0080] The intermediate cylindrical element 2203 also has a first rigid end part 2331 and a second rigid end part 2335 which in the assembled condition are located between the corresponding rigid parts 2221, 2241 and 2225, 2245 respectively of the two other cylindrical elements 2202, 2204. The intermediate portion 2333 of the intermediate cylindrical element 2203 comprises three or more separate longitudinal steering elements which can have different forms and shapes as will be explained below. After assembly of the three cylindrical elements 2202, 2203 and 2204 whereby the element 2202 is inserted in the element 2203 and the two combined elements 2202, 2203 are inserted into the element 2204, at least the first rigid end part 2221 of the inner cylindrical element 2202, the first rigid end part 2331 of the intermediate cylindrical element 2203 and the first rigid end part 2241 of the outer cylindrical element 2204 at the distal end of the instrument are attached to each other. In the embodiment shown in figures 2i and 2j, also the second rigid end part 2225 of the inner cylindrical element 2202, the second rigid end part 2335 of the intermediate cylindrical element 2203 and the second rigid end part 2245 of the outer cylindrical element 2204 at the proximal end of the instrument are attached to each other such that the three cylindrical elements 2202, 2203, 2204 form one integral unit.

[0081] In the embodiment shown in figure 2j the intermediate portion 2333 of intermediate cylindrical element 2203 comprises a number of longitudinal steering elements 2338 with a uniform cross-section so that the intermediate portion 2333 has the general shape and form as shown in the unrolled condition of the intermediate cylindrical element 2203 in figure 2k. From figure 2k it also becomes clear that the intermediate portion 2333 is formed by a number of over the circumference of the intermediate cylindrical element 2203 equally spaced parallel longitudinal steering elements 2338. Advantageously, the number of longitudinal steering elements 2338 is at least three, so that the instrument 2201 becomes fully controllable in any direction, but any higher number is possible as well. Preferably, the number of longitudinal steering elements 2338 is 6 or 8.

[0082] The production of such an intermediate part is most conveniently done by injection moulding or plating techniques or starting from a cylindrical tube with the desired inner and outer diameters and removing parts of the wall of the cylindrical tube required to end up with the desired shape of the intermediate cylindrical element 2203. However, alternatively, any 3D printing method can be used.

[0083] The removal of material can be done by means of different techniques such as laser cutting, photochemical etching, deep pressing, conventional chipping techniques such as drilling or milling, high pressure water jet cutting systems or any suitable material removing process available. Preferably, laser cutting is used as this allows for a very accurate and clean removal of material under reasonable economic conditions. The above mentioned processes are convenient ways as the cylindrical element 2203 can be made so to say in one process, without requiring additional steps for connecting the different parts of the intermediate cylindrical member as required in the conventional instruments, where conventional steering cables must be attached in some way to the end parts. The same type of technology can be used for producing the inner and outer cylindrical elements 2202 and 2204 with their respective flexible portions 2222, 2224, 2242 and 2244.

[0084] Figure 2h shows an exemplary embodiment of longitudinal (steering) elements 4 that have been obtained after providing longitudinal slits 5 to the wall of the second intermediate cylindrical element 103 that interconnects proximal flexible zone 14 and distal flexible zone 16 as described above. I.e., longitudinal steering elements 4 are, at least in part, spiraling about a longitudinal axis of the instrument such that an end portion of a respective steering element 4 at the proximal portion of the instrument is arranged at another angular orientation about the longitudinal axis than an end portion of the same longitudinal steering element 4 at the distal portion of the instrument. Were the longitudinal steering elements 4 arranged in a linear orientation, than a bending of the instrument at the proximal portion in a certain plane would result in a bending of the instrument at the distal portion in the same plane but in a 180 degrees opposite direction. This spiral construction of the longitudinal steering elements 4 allows for the effect that bending of the instrument at the proximal portion in a certain plane may result in a bending of the instrument at the distal portion in another plane, or in the same plane in the same direction. A preferred spiral construction is such that the end portion of a respective steering element 4 at the proximal portion of the instrument is arranged at an angularly shifted orientation of 180 degrees about the longitudinal axis relative to the end portion of the same longitudinal steering element 4 at the distal portion of the instrument. However, e.g. any other angularly shifted orientation, e.g. 90 degrees, is within the scope of this document. The slits are dimensioned such that movement of a longitudinal element is guided by adjacent longitudinal steering elements when provided in place in a steerable instrument.

[0085] The flexible portions 1 12, 132, 1 14, 142, 1 16, 144, 1 18, and 138 as shown in figure 2e, as well as the flexible portions 2222, 2224, 2242, and 2244 shown in figures 2i and 2j can be obtained by the methods described in the European patent application 08 004 373.0 filed on 10.03.2008, page 5, lines 15-26, but any other suitable process can be used to make flexible portions.

[0086] Such flexible parts may have a structure as shown in figures 2c and 2d. I.e., the flexibility may be obtained by a plurality of slits 14a, 15a, 16a, 17a. E.g., two circumferential slits may be provided in a cylindrical element along a same circumferential line where both slits are located at a certain distance from one another. A plurality of identical sets of circumferential slits 14a, 15a, 16a, 17a is provided at a plurality of distances in the longitudinal direction of the instrument , where consecutive sets are arranged at an angularly rotated position, e.g. each time 90 degrees rotated. In such an arrangement, all parts of the cylindrical element are still attached to each other. [0087] Figures 3a, 3b and 3c show alternative manners of how such flexibility in part can be obtained. Figure 3a shows a schematic representation of a flat rolled-out flexible proximal or distal cylindrical zone. The intermediate cylindrical elements are then made by rolling-up the flat element and attaching the side edges together in any suitable fashion that is known as such, such as by a welding technique. In the embodiment shown in figure 3a, the part of the cylindrical tube to become flexible has been provided with slits 14a, 15a, 16a, 17a extending in a helical manner over the length of the flexible zone. The flexibility can be controlled by the number of slits and/or the angle of the slits with respect to the axial direction of the cylindrical member. In the embodiment of figure 3b the part of the cylindrical tube to become flexible has been provided with a number of short slits 14a, 15a, 16a, 17a. The slits can be divided into groups, the slits in each group being located in the same line extending perpendicular to the axis of the cylindrical member. The slits of two neighbouring groups are offset. In the embodiment of figure 3c the part of the cylindrical tube to become flexible has been provided by making slits 14a, 15a, 16a, 17a producing a number of swallow's tails between the slits, which fit into each other as shown. It will be obvious that other systems of providing a flexible zone in a cylindrical tube wall may be used as well. More specifically it is possible to use combinations of the systems shown above. However, any other suitable flexible construction may be used instead. For instance, any of the flexible constructions shown and described in EP 0 764 423 A and EP 0 782 836 A may be used as well.

[0088] Furthermore, if the portions 122, 123, 124, 125, 126, 127, and 128 of the first intermediate cylindrical element 102 and the portions 134, 135, and 136 of the second intermediate cylindrical element 103 that respectively form the first and second set of longitudinal steering members, as shown in figure 2e, are implemented as longitudinal steering elements 4 as shown in figure 2h, the fabrication methods described above can be used. The same applies to the longitudinal steering elements 2338 of figures 2j and 2k. Moreover, any embodiment described in EP 2 762 058 A can be used according to the invention.

[0089] Otherwise, the longitudinal steering elements 4, 2338 can also be obtained by any other technique known in the art such as for example described in EP 1 708 609 A. The only restriction with respect to the construction of the longitudinal steering elements used in these portions is that the total flexibility of the instrument in these locations where the flexible portions coincide must be maintained.

[0090] The different co-axially arranged layers or cylindrical elements 101, 102, 103, 104, 2202, 2203 and 2204 as described above in relation to the exemplary embodiments of the steerable instruments shown in figures 2e and 2i, respectively, may be produced by any of the known methods, provided that they are suitable to make a multilayer system. A multilayer system is to be understood as being a steerable instrument that comprises at least two separate sets of longitudinal steering elements 4, 2338 for transferring the movement of the proximal end part to the distal end part. The assembly of the different cylindrical elements can be realized in the same way as well. Preferred methods of producing the different cylindrical elements have been described in the above mentioned EP 2 762 058 A which is hereby incorporated by reference in its entirety.

[0091] In the above embodiments, the proximal portions and distal portions are constructed in a similar way. However, that need not be the case always as will be explained now.

[0092] For example, the proximal portion may have a wider diameter as shown in figure 4, which shows a special embodiment of an instrument according to the invention. The inner cylindrical element 2202 is composed of a first rigid end part 2225, a first flexible portion 2224, an intermediate rigid portion 2223, a second flexible portion 2222 and a second rigid end part 2221 which is normally used as the operating part of the instrument in that it serves to steer the other end of the unit. The outer cylindrical element 2204 is in the same way composed of a first rigid end part 2245, a first flexible portion 2244, an intermediate rigid portion 2243, a second flexible portion 2242 and a second rigid end part 2241. The intermediate cylindrical element 2203 also has a first rigid end part 2335 and a second rigid end part 2331 which in the assembled condition are located between the corresponding rigid end parts 2225, 2245 and 2221 , 2241 , respectively, of the two other cylindrical elements 2202, 2204. In the embodiment shown the longitudinal steering elements 2338 are of the type shown in figure 2j, but it will be obvious that any other type described above may be used as well. So far the construction is comparable to the instruments described above. The main difference with respect to the above embodiments is the use of a different set of diameters for some parts of the instrument. In the embodiment shown in figure 4 the portions 2222, 2242 and the end parts 2221 , 233 1 and 2241 have a larger diameter than the other portions and parts. In the sections 2223, 2333 and 2243, frusto-conical portions 2212, 2213, 2214 have been made in order to connect the small diameter portions with the large diameter portions. As shown in figure 4 the different elements can easily be assembled by inserting one into the other. The main reason, however, to have such an instrument with different diameters is that by using an operating end with a larger diameter, the movement of the other end is amplified, whereas if a smaller diameter is used the movement of the other end is attenuated. Dependent of the application and its requirements larger diameters can be used to have the amplified movement or smaller diameters can be used to attenuate the movement and increase manoeuvrability accuracy of the handling head.

[0093] Such widening of the instrument with increasing diameter towards the proximal portions can also be applied in an instrument with more than two bendable portions, as shown in figures 5a and 5b.

[0094] In figure 5a there is shown a first exemplary embodiment of a steerable instrument according to the invention having four layers and as such the instrument is comparable to the instrument of figure 2e but the distal actuation flexible zone 156 and the proximal actuation flexible zone 159 of the proximal end part of the instrument have a larger diameter compared to the respective corresponding distal flexible zones 154 and 152 of the distal end part of the instrument. In the zone 155 a frusto-conical part has been incorporated that schematically represents a cylindrical diameter adaptation section 162 of a steerable instrument according to the invention. The cylindrical diameter adaptation section 162 in the context of this invention comprises at least a distance in an axial or longitudinal direction of the elongated tubular body over which the longitudinal steering elements change from a second diameter at a first side of the cylindrical diameter adaptation section to a third diameter at a second side of the cylindrical diameter adaptation section. As a result of the larger diameter of the proximal actuation flexible zone 156 and the proximal actuation flexible zone 159 of the proximal end part, the flexion of the respective corresponding distal flexible zones 154 and 152 will be amplified upon bending, thereby amplifying the flexion of the handling head. It is also possible to work in the opposite direction with distal flexible zones 154 and 152 having a larger diameter than the proximal actuation flexible zones 156 and 159, whereby the degree of flexion is attenuated, thereby improving accuracy of movement of the handling head.

[0095] Figure 5b shows a schematic cross-section of a second exemplary embodiment of a steerable instrument according to the invention in which a proximal actuation flexible zone 159 of the actuating portion of the cylindrical elements as well as an intermediate rigid zone 158, that is arranged between said proximal actuation flexible zone 159 and a proximal actuation flexible zone 156, have a larger diameter than the other parts of the elongated tubular body. A frusto-conical part schematically representing a cylindrical diameter adaptation section 164 of a steerable instrument according to the invention has been incorporated in zone 158. The cylindrical diameter adaptation section 164 in the context of this invention comprises at least a distance in an axial or longitudinal direction of the elongated tubular body over which the longitudinal steering elements change from a second diameter at a first side of the cylindrical diameter adaptation section to a third diameter at a second side of the cylindrical diameter adaptation section. It will be clear to the skilled person that only the flexion of the corresponding distal flexible zone 152 will be amplified upon bending of the corresponding proximal actuation flexible zone 159 of the proximal end part. The degree of flexion of the distal flexible zone 154 will in principle be the same as the degree of flexion of the corresponding proximal actuation flexible zone 156, because of the fact that the intermediate cylindrical element, which comprises the longitudinal steering elements that are configured and arranged to transfer the flexion of the proximal actuation flexible zone 156 to the corresponding distal flexible zone 154, has the same diameter in these zones. In practice there may be slight differences between these degrees of flexion due to stretching of the longitudinal steering elements.

[0096] Figure 6 shows a schematic perspective view of an exemplary embodiment of a proximal end part 1 1 of an elongated steerable tubular body 18 according to the invention comprising one intermediate cylindrical element 102 and an inner cylindrical element 101 that is arranged coaxially with and inside of the intermediate cylindrical element 102. The elongated steerable tubular body 18 furthermore comprises the cylindrical diameter adaptation section described above, which is schematically represented by a frusto-conical part 164. The proximal end part 1 1 comprises one flexible zone 15 that is arranged at a distal side of the proximal rigid end part 129.

[0097] In the exemplary embodiment of the proximal end part 1 1 of the elongated steerable tubular body 18 as shown in figure 6, the longitudinal steering elements 4 in the flexible zone 15 are arranged at a larger diameter than the longitudinal steering elements that are arranged at a distal side of the cylindrical diameter adaptation section 164 (not shown). A detailed explanation of the construction of the cylindrical diameter adaptation section 164 is provided in the yet unpublished Dutch patent application NL 2015185 by the applicant. NL 2015185 is hereby incorporated by reference in its entirety. Specifically with reference to figures 7a-8b and the related text in the description of NL 2015185, the construction of the cylindrical diameter adaptation section is explained in detail. Due to the larger diameter of the intermediate cylindrical element in the flexible zone 15 of the proximal end part, the radial deflexion of a corresponding distal flexible portion (not shown) will be amplified upon deflection of the flexible zone 15 in a radial direction of the elongated steerable tubular body 18.

[0098] Figure 6 shows that parts of the longitudinal steering elements 4 of the intermediate cylindrical element 102 that coincide with the flexible zone 15 comprise first 64, second 65 and third 66 flexible strips that are provided with meandering or wave-shaped spacers 67a, 68b, 69a, 67b, respectively, such as to preserve the geometrical integrity of the longitudinal steering elements in the flexible zone 15 during operation, i.e. bending thereof, to operate a corresponding flexible zone located at a distal end part of the elongated steerable tubular body (not shown).

[0099] With regard to for example figures 6 and 7a, it can be seen that first spacer 67a comprises a first strip 71 that is attached to first flexible strip 64 with two of its portions 71a, 71b. In order to minimize degradation of the flexibility of the first flexible strip 64 and thereby of the longitudinal steering element due to the application of first spacer 67a, it is noted that first strip 71 has a width that is at most equal to the width of the first flexible strip 64. It will be clear to the skilled person that first strip 71 can be attached to first flexible strip 64 with more than two of its portions at more than two axial positions. However, by doing so the flexibility of first flexible strip 64 might be compromised too much. Furthermore, it will be clear that the two different axial positions at which the two portions 71 a, 71b of the first strip 71 are attached to the first flexible strip 64 can be chosen such that the influence on the flexibility of the first flexible strip 64 is minimized.

[00100] Analogously, second spacer 68b comprises a second strip 72 having a width that is at most equal to the width of the second flexible strip 65 to which second strip 72 is attached with two of its portions 72a, 72b. Third spacer 68a comprises a third strip 73 having a width that is at most equal to the width of the second flexible strip 65 to which third strip 73 is attached with two of its portions 73a, 73b. Fourth spacer 69b comprises a fourth strip 74 having a width that is at most equal to the width of the third flexible strip 66 to which fourth strip 74 is attached with two of its portions 74a, 74b. Fifth spacer 69a comprises a fifth strip 75 having a width that is at most equal to the width of the third flexible strip 66 to which fifth strip 75 is attached with two of its portions 75a, 75b. Sixth spacer 67b comprises a sixth strip 76 having a width that is at most equal to the width of the first flexible strip 64 to which sixth strip 76 is attached with two of its portions 76a, 76b.

[00101] It is observed that the longitudinal portion of for example first flexible strip 64 that is located between the two portions 71a, 71b of first strip 71 of first spacer 67a is actually slightly reinforced in its longitudinal direction by the first spacer 67a. However, at the same time, the radial flexibility of this longitudinal portion is not, or hardly not degraded by the first spacer 67a. This is an advantageous effect since the first flexible strip 64 must be designed such that it is both flexible as much as possible and as rigid as possible which are clearly conflicting requirements. The first strip 71 of first spacer 67a hardly negatively influences the flexibility of first flexible strip 64 but aids in at least one of the rigidity and tensile strength of the first flexible strip 64. Consequently, the longitudinal steering element comprising said first flexible strip 64 and first strip 71 in the flexible zone 15 of the proximal end part 1 1, is provided with both a hardly uncompromised radial flexibility and at least one of an improved rigidity and tensile strength or pulling load in an axial direction of the elongated steerable tubular body 18. The skilled person will appreciate that analogous considerations apply to the second 65 and third 66 flexible strips that are provided with second 68b and third 68a spacers and fourth 69b and fifth 69a spacers, respectively.

[00102] Furthermore, either one of figures 6-8b shows that for example starting from the first flexible strip 64, first 67a and sixth 67b spacers extend in opposite circumferential directions of the elongated steerable tubular body 18. In addition, either one of figures 6-8b shows that for example first 67a and second 68b spacers almost completely bridge a gap 91 that is present between the first 64 and second 65 flexible strips as seen in the circumferential direction of the elongated steerable tubular body 18. Either one of figures 6-8b also shows that for example the first 67a and the second 68b spacers are arranged alternatingly in the axial direction of the elongated steerable tubular body 18. The skilled person will appreciate that an analogous reasoning applies to the third 68a, fourth 69b, fifth 69a and sixth 67b spacers which are attached to either one of the first 64, second 65 and third 66 flexible strips as shown in at least one of figures 6-8b.

[00103] In the case of an elongated steerable tubular body 18 comprising a set of cylindrical elements having one intermediate cylindrical element, such as intermediate cylindrical element 102 as shown in figure 6, application of the meandering or wave-shaped spacers according to the invention described above, enables prevention of interference such as entanglement between spacers and flexible strips within said one intermediate cylindrical element.

[00104] In the case of an elongated steerable tubular body comprising a set of cylindrical elements having at least two neighbouring intermediate cylindrical elements, e.g. first intermediate cylindrical element 102 and second intermediate cylindrical element 103 as shown in figures 2e, 10a and 10b, application of the meandering or wave-shaped spacers according to the invention enables at least reduction and ultimately even prevention of interference between at least one of spacers of said two neighbouring intermediate cylindrical elements 102, 103, flexible strips of said two neighbouring intermediate cylindrical elements 102, 103, spacers and flexible strips of neighbouring intermediate cylindrical elements 102, 103 and spacers and flexible strips within the same intermediate cylindrical element.

[00105] As a result of the arrangement of the first 67a, second 68b, third 68a, fourth 69b, fifth 69a and sixth 67b spacers and the first 64, second 65 and third 66 flexible strips in at least one of the flexible zones 15, 17 of the proximal end part 1 1 and in at least one of the flexible zones 14, 16 of the distal end part 13 of the exemplary embodiments of the elongated steerable tubular body 18 shown in at least one of figures 6-8b, the reliability and consequently the performance of the exemplary embodiments of the elongated steerable tubular body according to the invention is improved compared to elongated steerable tubular bodies known from the prior art. The same applies to steerable instruments comprising an elongated steerable tubular body according to the invention.

[00106] A further advantage of the arrangement of the meandering or wave- shaped spacers and the flexible strips according to the invention is that a tendency of the longitudinal steering elements to rotate about their longitudinal axis is reduced as the effective width of for example the longitudinal steering element comprising first flexible strip 64 is increased as a result of the arrangement of first 67a and sixth 67b spacers at both sides of the first flexible strip 64. The reduced tendency of the longitudinal steering elements to rotate about their longitudinal axis also contributes to an improved reliability and hence performance of the elongated steerable tubular body according to the invention and the steerable instruments comprising such elongated steerable tubular bodies.

[00107] Furthermore, according to the exemplary embodiments of the elongated steerable tubular body 18 as shown in at least one of the figures 6-8b and particularly illustrated in figures 7a-8b, the strips of the spacers have an "M"-shape comprising three curved sections with each one tip, e.g. first strip 71 of first spacer 67a has a first 51a, a second 51b and a third 51c curved section having a first 81a, a second 81b and a third 81c tip, respectively. From each one of the figures 6-8b it can be seen that neither one of the three curved sections of each of the first 71 , second 72, third 73, fourth 74, fifth 75 and sixth 76 strips is attached to any one of the flexible strips, i.e. neither to the respective flexible strip from which the strip to which the curved sections belong originates, nor to its neighbouring flexible strips. For example in the case of the first spacer 67a, it can be observed that neither one of the first 81a, second 81b and third 81 c tips of the respective first 51 a, second 51b and third 51 c curved sections of the first strip 71 is attached to first flexible strip 64 from which first strip 71 originates nor to second flexible strip 65 next to which the first tip 81a and the third tip 81 c are arranged to prevent, in use of the elongated steerable tubular body, movement of the second flexible strip 65 towards the first flexible strip 64. The second tip 81b is arranged next to the first flexible strip 64 to prevent, in use of the elongated steerable tubular body, movement of the first flexible strip 64 towards the second flexible strip 65.

[00108] Analogously, in the case of the second spacer 68b, it can be observed that neither one of the first 82a, second 82b and third 82c tips of the respective first 52a, second 52b and third 52c curved sections of the second strip 72 is attached to second flexible strip 65 from which second strip 72 originates nor to first flexible strip

64 next to which the first tip 82a and the third tip 82c are arranged to prevent, in use of the elongated steerable tubular body, movement of the first flexible strip 64 towards the second flexible strip 65. The second tip 82b is arranged next to the second flexible strip 65 to prevent, in use of the elongated steerable tubular body, movement of the second flexible strip 65 towards the first flexible strip 64.

[00109] In the case of the third spacer 68a, it can be observed that neither one of the first 83a, second 83b and third 83c tips of the respective first 53a, second 53b and third 53c curved sections of the third strip 73 is attached to second flexible strip

65 from which third strip 73 originates nor to third flexible strip 66 next to which the first tip 83a and the third tip 83c are arranged to prevent, in use of the elongated steerable tubular body, movement of the third flexible strip 66 towards the second flexible strip 65. The second tip 83b is arranged next to the second flexible strip 65 to prevent, in use of the elongated steerable tubular body, movement of the second flexible strip 65 towards the third flexible strip 66.

[00110] In the case of the fourth spacer 69b, it can be observed that neither one of the first 84a, second 84b and third 84c tips of the respective first 54a, second 54b and third 54c curved sections of the fourth strip 74 is attached to third flexible strip 66 from which fourth strip 74 originates nor to second flexible strip 65 next to which the first tip 84a and the third tip 84c are arranged to prevent, in use of the elongated steerable tubular body, movement of the third flexible strip 66 towards the second flexible strip 65. The second tip 84b is arranged next to the third flexible strip 66 to prevent, in use of the elongated steerable tubular body, movement of the third flexible strip 66 towards the second flexible strip 65.

[00111] In the case of the fifth spacer 69a, it can be observed that neither one of the first 85a, second 85b and third 85c tips of the respective first 55a, second 55b and third 55c curved sections of the fifth strip 75 is attached to third flexible strip 66 from which fifth strip 75 originates nor to first flexible strip 64 next to which the first tip 85a and the third tip 85c are arranged, in use of the elongated steerable tubular body, to prevent movement of the first flexible strip 64 towards the third flexible strip 66. The second tip 85b is arranged next to the third flexible strip 66 to prevent, in use of the elongated steerable tubular body, movement of the third flexible strip 66 towards the first flexible strip 64.

[00112] Finally, in the case of the sixth spacer 67b, it can be observed that neither one of the first 86a, second 86b and third 86c tips of the respective first 56a, second 56b and third 56c curved sections of the sixth strip 76 is attached to first flexible strip 64 from which sixth strip 76 originates nor to third flexible strip 66 next to which the first tip 86a and the third tip 86c are arranged, in use of the elongated steerable tubular body, to prevent movement of the third flexible strip 66 towards the first flexible strip 64. The second tip 86b is arranged next to the first flexible strip 64 to prevent, in use of the elongated steerable tubular body, movement of the first flexible strip 64 towards the third flexible strip 66.

[00113] From figures 9a and 9b it can be seen that neither one of the three curved sections of each of the seventh 271 , eighth 272, ninth 273, tenth 274, eleventh 275 and twelfth 276 strips is attached to any one of the flexible strips, i.e. neither to the respective flexible strip from which the strip to which the curved sections belong originates, nor to its neighbouring flexible strips. For example in the case of the seventh spacer 267a, it can be observed that neither one of the tips 281a, 281b, 281c of the respective curved sections 251a, 251b, 251 c of the seventh strip 271 is attached to fourth flexible strip 264 from which seventh strip 271 originates nor to fifth flexible strip 265 next to which the tips 281a and 281 c are arranged to prevent, in use of the elongated steerable tubular body, movement of the fifth flexible strip 265 towards the fourth flexible strip 264. Tip 281b is arranged next to the fourth flexible strip 264 to prevent, in use of the elongated steerable tubular body, movement of the fourth flexible strip 264 towards the fifth flexible strip 265.

[00114] Analogously, in the case of the eighth spacer 268b, it can be observed that neither one of the tips 282a, 282b, 282c of the respective curved sections 252a, 252b, 252c of the eighth strip 272 is attached to fifth flexible strip 265 from which eighth strip 272 originates nor to fourth flexible strip 264 next to which tips 282a and 282c are arranged to prevent, in use of the elongated steerable tubular body, movement of the fourth flexible strip 264 towards the fifth flexible strip 265. Tip 282b is arranged next to the fifth flexible strip 265 to prevent, in use of the elongated steerable tubular body, movement of the fifth flexible strip 265 towards the fourth flexible strip 264. [00115] In the case of the ninth spacer 268a, it can be observed that neither one of the tips 283a, 283b, 283c of the respective curved sections 253a, 253b, 253c of the ninth strip 273 is attached to fifth flexible strip 265 from which ninth strip 273 originates nor to sixth flexible strip 266 next to which tips 283a and 283c are arranged to prevent, in use of the elongated steerable tubular body, movement of the sixth flexible strip 266 towards the fifth flexible strip 265. Tip 283b is arranged next to the fifth flexible strip 265 to prevent, in use of the elongated steerable tubular body, movement of the fifth flexible strip 265 towards the sixth flexible strip 266.

[00116] In the case of the tenth spacer 269b, it can be observed that neither one of the tips 284a, 284b, 284c of the respective curved sections 254a, 254b, 254c of the tenth strip 274 is attached to sixth flexible strip 266 from which tenth strip 274 originates nor to fifth flexible strip 265 next to which tips 284a and 284c are arranged to prevent, in use of the elongated steerable tubular body, movement of the sixth flexible strip 266 towards the fifth flexible strip 265. Tip 284b is arranged next to the sixth flexible strip 266 to prevent, in use of the elongated steerable tubular body, movement of the sixth flexible strip 266 towards the fifth flexible strip 265.

[00117] In the case of the eleventh spacer 269a, it can be observed that neither one of the tips 285a, 285b, 285c of the respective curved sections 255a, 255b, 255c of the eleventh strip 275 is attached to sixth flexible strip 266 from which eleventh strip 275 originates nor to fourth flexible strip 264 next to which tips 285a and 285c are arranged, in use of the elongated steerable tubular body, to prevent movement of the fourth flexible strip 264 towards the sixth flexible strip 266. Tip 285b is arranged next to the sixth flexible strip 266 to prevent, in use of the elongated steerable tubular body, movement of the sixth flexible strip 266 towards the fourth flexible strip 264.

[00118] Finally, in the case of the twelfth spacer 267b, it can be observed that neither one of the tips 286a, 286b, 286c of the respective curved sections 256a, 256b, 256c of the twelfth strip 276 is attached to fourth flexible strip 264 from which twelfth strip 276 originates nor to sixth flexible strip 266 next to which tips 286a and 286c are arranged, in use of the elongated steerable tubular body, to prevent movement of the sixth flexible strip 266 towards the fourth flexible strip 264. Tip 286b is arranged next to the fourth flexible strip 264 to prevent, in use of the elongated steerable tubular body, movement of the fourth flexible strip 264 towards the sixth flexible strip 266. [00119] It will be clear to the skilled person that the number of curved sections of the strips can be any one of one, three, five, seven etc. depending on the specific requirements for the elongated steerable tubular body, e.g. regarding flexibility of the longitudinal steering elements. The skilled person will also appreciate that the number of curved sections determines the distance between the two axial positions at which the two portions of the strips are attached to their respective flexible strip. Furthermore, it will be clear to the skilled person that it is also possible to provide a flexible strip with meandering or wave-shaped spacer elements having different numbers of curved sections.

[00120] As shown in any one of the drawings 6- 10b, the meandering or wave shape may have the form of a sinusoid. However, the skilled person will appreciate that other shapes may be used instead, like sawtooth shapes. Preferably, the tips of the spacers that, in use of the elongated steerable tubular body may touch a flexible strip have a rounded shape such as to prevent wear as much as possible when this rounded tip moves relative to an adjacent flexible strip.

[00121] Figure 7a shows a top view of an unrolled version of an exemplary embodiment of a first intermediate cylindrical element 2303 of an elongated steerable tubular body according to the invention comprising three longitudinal steering elements 2338. The first intermediate cylindrical element 2303 shown in figure 7a can replace the intermediate cylindrical element of the set of cylindrical elements of an elongated steerable tubular body having one flexible zone in the proximal end part and one flexible zone in the distal end part as is shown in figures 2i, 2j and 2k. In the exemplary embodiment of said first intermediate cylindrical element 2303 shown in figure 7a, only in the flexible zone 15 of the proximal end part 1 1 and in the flexible zone 17 of the distal end part 13 the longitudinal steering elements 2338 comprise flexible strips 64, 65, 66 that are provided with meandering or wave-shaped spacers 67a, 67b, 68a, 68b, 69a, 69b comprising strips 71, 72, 73, 74, 75, 76. Each one of the latter strips has three curved sections each of which curved sections comprises one tip as described above.

[00122] Furthermore, figure 7a shows that in the rigid intermediate part 12 of the elongated steerable tubular body, each one of the three longitudinal steering elements 2338 of the first intermediate cylindrical element 2203 has a first width as seen in the circumferential direction of the elongated steerable tubular body that is larger than a second width in the flexible zone 15 in the proximal end part 1 1 and in the flexible zone 17 in the distal end part 13, respectively. In this way a first slit 95 is present between neighbouring longitudinal steering elements as seen in the circumferential direction of the elongated steerable tubular body. The first slit 95 allows, in use of the elongated steerable tubular body, independent movement of neighbouring longitudinal steering elements relative to each other in the axial direction of the elongated steerable tubular body. The width of the first slit 95 as seen in the circumferential direction of the elongated steerable tubular body can be less than 40 micrometer, preferably less than 20 micrometer.

[00123] Figure 7b shows a top view of an unrolled version of an exemplary embodiment of a first intermediate cylindrical element 2303 of the elongated steerable tubular body according to the invention comprising three longitudinal steering elements 2338. The first intermediate cylindrical element 2303 shown in figure 7b can also replace the intermediate cylindrical element of the set of cylindrical elements of an elongated steerable tubular body having one flexible zone in the proximal end part and one flexible zone in the distal end part as is shown in figures 2i, 2j and 2k. In the exemplary embodiment of the first intermediate cylindrical element 2303 shown in figure 7b, also in the rigid intermediate part 12 of the elongated steerable tubular body one or more of at least one of the first 67a, second 68b, third 68a, fourth 69b, fifth 69a and sixth 67b meandering or wave-shaped spacers as described above are provided to respective ones of the first 64, second 65 and third 66 flexible strips. In this way the flexibility of the longitudinal steering elements 2338 can further be reduced.

[00124] Figure 8a shows a top view of an unrolled version of an exemplary embodiment of a first intermediate cylindrical element 102 of the elongated steerable tubular body according to the invention comprising three longitudinal steering elements 4. The first intermediate cylindrical element 102 shown in figure 8a can replace the first intermediate cylindrical element of the set of cylindrical elements of an elongated steerable tubular body having two flexible zones 14, 15 in the proximal end part 1 1 and two flexible zones 16, 17 in the distal end part 13 as is shown in figure 2e. In the exemplary embodiment of the first intermediate cylindrical element 102 shown in figure 8a, only in the first 15 and second 14 flexible zones of the proximal end part 1 1 and in the first 17 and second 16 flexible zones of the distal end part 13 of the elongated steerable tubular body first 67a, second 68b, third 68a, fourth 69b, fifth 69a and sixth 67b meandering or wave-shaped spacers as described above are provided to respective ones of the first 64, second 65 and third 66 flexible strips.

[00125] Figure 8a shows that the proximal end part 1 1 comprises a first rigid zone 158 that is arranged to interconnect the first 15 and second 14 flexible zones and that the distal end part 13 comprises a first rigid zone 153 that is arranged to interconnect the first 17 and second 16 flexible zones. Furthermore, it can be seen that in the first rigid zones 153, 158 of the proximal 1 1 and distal 13 end parts, respectively and in the rigid intermediate part 12 of the elongated steerable tubular body, each one of the three longitudinal steering elements 4 of the first intermediate cylindrical element 102 has a first width as seen in the circumferential direction of the elongated steerable tubular body that is larger than a second width in the first 15 and second 14 flexible zones in the proximal end part 1 1 and in the first 17 and second 16 flexible zones in the distal end part 13, respectively. In this way a first slit 95 is present between neighbouring longitudinal steering elements 4 as seen in the circumferential direction of the elongated steerable tubular body. The first slit 95 allows, in use of the elongated steerable tubular body, independent movement of neighbouring longitudinal steering elements 4 relative to each other in the axial direction of the elongated steerable tubular body. The width of the first slit 95 as seen in the circumferential direction of the elongated steerable tubular body can be less than 40 micrometer, preferably less than 20 micrometer.

[00126] Figure 8b shows a top view of an unrolled version of an exemplary embodiment of a first intermediate cylindrical element 102 of the elongated steerable tubular body according to the invention comprising three longitudinal steering elements 4. The first intermediate cylindrical element 102 shown in figure 8b can also replace the first intermediate cylindrical element of the set of cylindrical elements of an elongated steerable tubular body having two flexible zones 14, 15 in the proximal end part 1 1 and two flexible zones 16, 17 in the distal end part 13 as is shown in figure 2e. In the exemplary embodiment shown in figure 8b, also in the first rigid zone 158 of the proximal end part 1 1, the rigid intermediate part 12 and the first rigid zone 153 of the distal end part 13 of the elongated steerable tubular body one or more of at least one of the first 67a, second 68b, third 68a, fourth 69b, fifth 69a and sixth 67b meandering or wave-shaped spacers as described above are provided to respective ones of the first 64, second 65 and third 66 flexible strips. In this way the flexibility of the longitudinal steering elements 4 can further be reduced.

[00127] Figure 9a shows a top view of an unrolled version of an exemplary embodiment of a second intermediate cylindrical element 103 of the elongated steerable tubular body according to the invention comprising three longitudinal steering elements 24. The second intermediate cylindrical element 103 shown in figure 9a can replace the second intermediate cylindrical element of the set of cylindrical elements of an elongated steerable tubular body having two flexible zones in the proximal end part and two flexible zones in the distal end part as is shown in figure 2e. In the exemplary embodiment shown in figure 9a, seventh 267a, eighth 268b, ninth 268a, tenth 269b, eleventh 269a and twelfth 267b meandering or wave-shaped spacers as described above are provided to respective ones of the fourth 264, fifth 265 and sixth 266 flexible strips in both the second flexible zone 14 of the proximal end part 1 1 and in the second flexible zone 16 of the distal end part 13 but not in the rigid intermediate part 12 of the elongated steerable tubular body.

[00128] Furthermore, figure 9a shows that in the rigid intermediate part 12 of the elongated steerable tubular body, each one of the three longitudinal steering elements 24 of the second intermediate cylindrical element 103 has a first width as seen in the circumferential direction of the elongated steerable tubular body 18 that is larger than a second width in the second flexible zone 14 in the proximal end part 1 1 and in the second flexible zone 16 in the distal end part 13, respectively. In this way a second slit 96 is present between neighbouring longitudinal steering elements 24 as seen in the circumferential direction of the elongated steerable tubular body. The second slit 96 allows, in use of the elongated steerable tubular body, independent movement of neighbouring longitudinal steering elements 24 relative to each other in the axial direction of the elongated steerable tubular body. The width of the second slit 96 as seen in the circumferential direction of the elongated steerable tubular body can be less than 40 micrometer, preferably less than 20 micrometer.

[00129] Figure 9b shows a top view of an unrolled version of an exemplary embodiment of a second intermediate cylindrical element 103 of the elongated steerable tubular body according to the invention comprising three longitudinal steering elements 24. The second intermediate cylindrical element 103 shown in figure 9b can also replace the second intermediate cylindrical element of the set of cylindrical elements of an elongated steerable tubular body having two flexible zones in the proximal end part and two flexible zones in the distal end part as is shown in figure 2e. In the exemplary embodiment shown in figure 9b, in the second flexible zone 14 of the proximal end part 1 1, in the second flexible zone 16 of the distal end part 13 and also in the rigid intermediate part 12 of the elongated steerable tubular body one or more of at least one of the seventh 267a, eighth 268b, ninth 268a, tenth 269b, eleventh 269a and twelfth 267b meandering or wave-shaped spacers as described above are provided to respective ones of the fourth 264, fifth 265 and sixth 266 flexible strips. In this way the flexibility of the longitudinal steering elements 24 can further be reduced.

[00130] By replacing at least one of the first intermediate cylindrical element of the set of cylindrical elements shown in figure 2e by any one of the exemplary embodiments of the first intermediate cylindrical element 102 shown in figures 8a and 8b, and the second intermediate cylindrical element of the set of cylindrical elements shown in figure 2e by any one of the exemplary embodiments of the second intermediate cylindrical element 103 shown in figures 9a and 9b, an elongated steerable tubular body can be obtained that at least reduces and ultimately even prevents interference such as entanglement between at least one of the longitudinal steering elements 4 of the first intermediate cylindrical element 102 and the longitudinal steering elements 24 of the second intermediate cylindrical element 103, meandering or wave-shaped spacers 67a, 67b, 68a, 68b, 69a, 69b and first 64, second 65 and third 66 flexible strips of the first intermediate cylindrical element 102 and meandering or wave-shaped spacers 267a, 267b, 268a, 268b, 269a, 269b and fourth 264, fifth 265 and sixth 266 flexible strips of the second intermediate cylindrical element 103, and meandering or wave-shaped spacers and flexible strips within the same intermediate cylindrical element, i.e. within the first intermediate cylindrical element 102 and within the second intermediate cylindrical element 103. As a result, the reliability and consequently the performance of an elongated steerable tubular body according to the invention is significantly improved compared to elongated steerable tubular bodies known from the prior art. The same applies to steerable instruments comprising an elongated steerable tubular body according to the invention. [00131] Figure 10a shows a schematic perspective view of an exemplary embodiment of a second flexible zone 14 of a proximal end part 1 1 of an elongated steerable tubular body according to the invention comprising an inner cylindrical element 101 , a first intermediate cylindrical element 102 and a second intermediate cylindrical element 103. Said cylindrical elements 101 , 102, 103 are arranged coaxially with respect to each other. The inner cylindrical element 101 is arranged inside of the first intermediate cylindrical element 102 and the pair of inner cylindrical element 101 and first intermediate cylindrical element 102 is arranged inside of the second intermediate cylindrical element 103.

[00132] Figure 10a shows that in the second flexible zones 14 the meandering or wave-shaped spacers of the second intermediate cylindrical element 103 at least partially overlap with the meandering or wave-shaped spacers of the first intermediate cylindrical element 102. In this way, meandering or wave-shaped spacers of neighbouring intermediate cylindrical elements are confined as seen in a radial direction of the elongated steerable tubular body. Consequently, interference between spacers of neighbouring intermediate cylindrical elements can at least be reduced and ultimately be prevented. As a result, the reliability and hence the performance of the elongated steerable tube according to the invention is improved.

[00133] Figure 10b shows an exploded view of the exemplary embodiment of the second flexible zone 14 of the proximal end part 1 1 of the elongated steerable tubular body shown in figure 10a. Figure 10b shows an exemplary arrangement of the first 67a, second 68b, fifth 69a and sixth 67b meandering or wave-shaped spacers and the first 64, 65, 66 flexible strips in the second proximal flexible zone 14 of the first intermediate cylindrical element 102 and an exemplary arrangement of the seventh 267a, eighth 268b, eleventh 269a and twelfth 267b meandering or wave-shaped spacers and the fourth 264, fifth 265, sixth 266 flexible strips in the second proximal flexible zone 14 of the second intermediate cylindrical element 103.

[00134] Accordingly, it has been described that this invention relates to an elongated steerable tubular body 18 and a steerable instrument 10; 2201 comprising the same. The elongated steerable tubular body comprises at least one flexible zone 15, 17; 14, 16 and at least one intermediate cylindrical element 102; 2203 that comprises at least three longitudinal steering elements 4; 24; 2338. In said at least one flexible zone, at least two longitudinal steering elements comprise respective first 64 and second 65 flexible strips being provided with one or more of respective first 67a and second 68b spacers. Each spacer 67a, 68b comprises a respective strip 71 , 72 having at least one first curved section 51 , 52. Each strip being attached to its respective flexible strip 64, 65 with at least two portions of said respective strip. Said first 67a and second 68b spacers are alternatingly arranged in the axial direction of the elongated steerable tubular body.

[00135] It will be clear to a person skilled in the art that the scope of the invention is not limited to the examples discussed in the foregoing, but that several amendments and modifications thereof are possible without deviating from the scope of the invention as defined in the attached claims. While the invention has been illustrated and described in detail in the figures and the description, such illustration and description are to be considered illustrative or exemplary only, and not restrictive. The present invention is not limited to the disclosed embodiments but comprises any combination of the disclosed embodiments that can come to an advantage.

[00136] Variations to the disclosed embodiments can be understood and effected by a person skilled in the art in practicing the claimed invention, from a study of the figures, the description and the attached claims. In the description and claims, the word "comprising" does not exclude other elements, and the indefinite article "a" or "an" does not exclude a plurality. In fact it is to be construed as meaning "at least one". The mere fact that certain features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope of the invention.

Claims

1. An elongated steerable tubular body (18) for use in a steerable instrument (10; 2201) for at least one of endoscopic and invasive type of applications, the elongated steerable tubular body (18) having a proximal end part (1 1), a distal end part (13) and a rigid intermediate part (12) that is arranged to interconnect the proximal end part and the distal end part;

at least one of the proximal end part (1 1), the rigid intermediate part (12) and the distal end part (13) comprises a set of at least three coaxially arranged cylindrical elements, namely an inner cylindrical element (101; 2202), a first intermediate cylindrical element (102; 2203), and an outer cylindrical element (104; 2204);

at least one of the proximal end part (1 1) and the distal end part (13) comprises at least one first flexible zone (15; 17) that is arranged to be deflectable in at least one first radial direction of the elongated steerable tubular body (18) relative to the rigid intermediate part (12);

said first intermediate cylindrical element (102; 2203) comprises a first set of at least three longitudinal steering elements (4; 2338) that are arranged in at least said at least one first flexible zone (15; 17) and said intermediate rigid part (12) and arranged to allow said at least one first flexible zone (15; 17) to be deflectable in said at least one first radial deflection of the elongated steerable tubular body (18) through a movement of at least one of said first set of at least three longitudinal steering elements (4; 2338) in an axial direction of the elongated steerable tubular body (18);

wherein in at least one of said at least one first flexible zone (15; 17), a first one of said first set of at least three longitudinal steering elements comprises a first flexible strip (64) and a second one of said first set of at least three longitudinal steering elements comprises a second flexible strip (65);

a first gap (91) being present between said first flexible strip (64) and said second flexible strip (65) as seen in a circumferential direction of the elongated steerable tubular body (18);

said first flexible strip (64) being provided with at least one first spacer (67a) extending in said first gap (91) towards said second flexible strip (65); said at least one first spacer (67a) comprising a first strip (71) comprising at least one first curved section (51a) with a first tip (81a) that is arranged to prevent, in use, movement of the second flexible strip (65) in the circumferential direction of the elongated steerable tubular body (18) towards said first flexible strip (64);

said first strip (71) being attached to said first flexible strip (64) with at least two portions (71a, 71b) of said first strip (71);

said second flexible strip (65) being provided with at least one second spacer (68b) extending in said first gap (91) towards said first flexible strip (64);

said at least one second spacer (68b) comprising a second strip (72) comprising at least one second curved section (52a) with a second tip (82a) that is arranged to prevent, in use, movement of the first flexible strip (64) in the circumferential direction of the elongated steerable tubular body (18) towards said second flexible strip (65);

said second strip (72) being attached to said second flexible strip (65) with at least two portions (72a, 72b) of said second strip (72).

2. The elongated steerable tubular body (18) according to claim 1, wherein said first flexible strip (64) is provided with a plurality of said first spacers (67a) and said second flexible strip (65) is provided with a plurality of said second spacers (68b), said plurality of said first spacers (67a) and said plurality of said second spacers (68b) being alternately arranged in the axial direction of the elongated steerable tubular body (18) in said first gap (91).

3. The elongated steerable tubular body (18) according to claim 1 or 2, wherein a third one of said first set of at least three longitudinal steering elements comprises a third flexible strip (66) which as seen in a circumferential direction of the elongated steerable tubular body (18) is arranged adjacent to said second flexible strip (65) at a side of said second flexible strip (65) that is opposite the side at which said first flexible strip (64) is arranged, such that a second gap (92) is present between said second flexible strip (65) and said third flexible strip (66);

said second flexible strip (65) being provided with at least one third spacer (68a) extending in said second gap (92) towards said third flexible strip (66); said at least one third spacer (68a) comprising a third strip (73) comprising at least one third curved section (53a) with a third tip (83a) arranged to prevent, in use, movement of the third flexible strip (66) in the circumferential direction of the elongated steerable tubular body (18) towards said second flexible strip (65);

said third strip (73) being attached to said second flexible strip (65) with at least two portions (73a, 73b) of said third strip (73);

said third flexible strip (66) being provided with at least one fourth spacer (69b) extending in said second gap (92) towards said second flexible strip (65); said at least one fourth spacer (69b) comprising a fourth strip (74) comprising at least one fourth curved section (54a) with a fourth tip (84a) arranged to prevent, in use, movement of the second flexible strip (65) in the circumferential direction of the elongated steerable tubular body (18) towards said third flexible strip (66);

said fourth strip (74) being attached to said third flexible strip (66) with at least two portions (74a, 74b) of said fourth strip (74).

4. The elongated steerable tubular body (18) according to claim 3, wherein said second flexible strip (65) is provided with a plurality of said third spacers (68a) and said third flexible strip (66) is provided with a plurality of said fourth spacers (69b), said plurality of said third spacers (68a) and said plurality of said fourth spacers (69b) are alternately arranged in the axial direction of the elongated steerable tubular body (18) in said second gap (92).

5. The elongated steerable tubular body (18) according to any one of claims 1-4, wherein in said rigid intermediate part (12) comprising said set of at least three coaxially arranged cylindrical elements, at least one of said first set of at least three longitudinal steering elements of said first intermediate cylindrical element (102; 2203) has a first width as seen in the circumferential direction of the elongated steerable tubular body (18) that is larger than a second width of said at least one of said first set of at least three longitudinal steering elements in said at least one of said at least one first flexible zones (15; 17) such that at least one first slit (95) is present as seen in the circumferential direction of the elongated steerable tubular body (18) between said at least one longitudinal steering element and at least one adjacent longitudinal steering element of said at least one longitudinal steering element;

said at least one first slit (95) allowing, in use, independent movement of said at least one longitudinal steering element and said at least one adjacent longitudinal steering element relative to each other in the axial direction of the elongated steerable tubular body (18).

6. The elongated steerable tubular body (18) according to any one of the claims 1-5, wherein the set of cylindrical elements further comprises a second intermediate cylindrical element (103) that is arranged between said first

intermediate cylindrical element (102) and said outer cylindrical element (104); at least one of the proximal end part (11) and the distal end part (13) comprising said at least one first flexible zone (15; 17) comprises at least one second flexible zone (14; 16) and at least one first rigid zone (158; 153) that is arranged to interconnect said at least one first flexible zone (15; 17) and said at least one second flexible zone (14; 16);

said at least one second flexible zone (14; 16) is arranged to be deflectable in at least one second radial direction of the elongated steerable tubular body (18) relative to the rigid intermediate part (12) independently from said at least one first radial direction in which said at least one first flexible zone (15; 17) is deflectable; said second intermediate cylindrical element (103) comprises a second set of at least three longitudinal steering elements (24) that are arranged in at least said at least one second flexible zone (14; 16) and said intermediate rigid part (12) and arranged to allow said at least one second flexible zone (14; 16) to be deflectable in said at least one second radial direction of the elongated steerable tubular body (18) through a movement of at least one of said second set of at least three longitudinal steering elements in the axial direction of the elongated steerable tubular body (18); wherein in at least one of said at least one second flexible zone (14; 16), a first one of said second set of at least three longitudinal steering elements of said second intermediate cylindrical element (103) comprises a fourth flexible strip (264) and a second one of said second set of at least three longitudinal steering elements of said second intermediate cylindrical element (103) comprises a fifth flexible strip (265); a third gap (291) being present between said fourth flexible strip (264) and said fifth flexible strip (265) as seen in a circumferential direction of the elongated steerable tubular body (18);

said fourth flexible strip (264) being provided with at least one seventh spacer (267a) extending in said third gap (291) towards said fifth flexible strip (265);

said at least one seventh spacer (267a) comprising a seventh strip (271) comprising at least one seventh curved section (251a) with a seventh tip (281a) that is arranged to prevent, in use, movement of said fifth flexible strip (265) in the circumferential direction of the elongated steerable tubular body (18) towards said fourth flexible strip (264);

said seventh strip (271) being attached to said fourth flexible strip (264) with at least two portions (271a, 271b) of said fourth strip (271);

said fifth flexible strip (265) being provided with at least one eighth spacer (268b) extending in said third gap (291) towards said fourth flexible strip (264); said at least one eighth spacer (268b) comprising an eighth strip (272) comprising at least one eighth curved section (252a) with an eighth tip (282a) that is arranged to prevent, in use, movement of said fourth flexible strip (264) in the circumferential direction of the elongated steerable tubular body (18) towards said fifth flexible strip (265);

said eighth strip (272) being attached to said fifth flexible strip (265) with at least two portions (272a, 272b) of said eighth strip (272).

7. The elongated steerable tubular body (18) according to claim 6, wherein said fourth flexible strip (264) of said first one of said second set of at least three longitudinal steering elements of said second intermediate cylindrical element (103) is provided with a plurality of said seventh spacers (267a) and said fifth flexible strip (265) of said second one of said second set of at least three longitudinal steering elements of said second intermediate cylindrical element (103) is provided with a plurality of said eighth spacers (268b), said plurality of said seventh spacers (267a) and said plurality of said eighth spacers (268b) being alternately arranged in the axial direction of the elongated steerable tubular body (18) in said third gap (291).

8. The elongated steerable tubular body (18) according to claim 6 or 7, wherein a third one of said second set of at least three longitudinal steering elements of said second intermediate cylindrical element (103) comprises a sixth flexible strip (266) which as seen in a circumferential direction of the elongated steerable tubular body (18) is arranged adjacent to said fifth flexible strip (265) at a side of said fifth flexible strip (265) that is opposite the side at which said fourth flexible strip (264) is arranged, such that a fourth gap (292) is present between said fifth flexible strip

(265) and said sixth flexible strip (266);

said fifth flexible strip (265) being provided with at least one ninth spacer (268a) extending in said fourth gap (292) towards said sixth flexible strip (266); said at least one ninth spacer (268a) comprising a ninth strip (273)

comprising at least one ninth curved section (253a) with a ninth tip (283a) arranged to prevent, in use, movement of said sixth flexible strip (266) in the circumferential direction of the elongated steerable tubular body (18) towards said fifth flexible strip (265);

said ninth strip (273) being attached to said fifth flexible strip (265) with at least two portions (273a, 273b) of said ninth strip (273);

said sixth flexible strip (266) being provided with at least one tenth spacer (269b) extending in said fourth gap (292) towards said fifth flexible strip (265); said at least one tenth spacer (269b) comprising a tenth strip (274) comprising at least one tenth curved section (254a) with a tenth tip (284a) arranged to prevent, in use, movement of said fifth flexible strip (265) in the circumferential direction of the elongated steerable tubular body (18) towards said sixth flexible strip (266);

said tenth strip (274) being attached to said sixth flexible strip (266) with at least two portions (274a, 274b) of said tenth strip (274).

9. The elongated steerable tubular body (18) according to claim 8, wherein said fifth flexible strip (265) of said second one of said second set of at least three longitudinal steering elements of said second intermediate cylindrical element (103) is provided with a plurality of said ninth spacers (268a) and said sixth flexible strip

(266) of said third one of said second set of at least three longitudinal steering elements of said second intermediate cylindrical element (103) is provided with a plurality of said tenth spacers (269b), said plurality of said ninth spacers (268a) and said plurality of said tenth spacers (269b) are alternately arranged in the axial direction of the elongated steerable tubular body (18) in said fourth gap (292).

10. The elongated steerable tubular body (18) according to any one of the claims 6-9, wherein in at least one of said first rigid zone (158) of the proximal end part (1 1), said rigid intermediate part (12), and said first rigid zone (153) of the distal end part (13), at least one of said second set of at least three longitudinal steering elements of said second intermediate cylindrical element (103) has a first width as seen in the circumferential direction of the elongated steerable tubular body (18) that is larger than a second width of said at least one of said second set of at least three longitudinal steering elements in said at least one of said at least one first (15; 17) and second (14; 16) flexible zones such that at least one second slit (96) is present as seen in the circumferential direction of the elongated steerable tubular body (18) between said at least one longitudinal steering element and at least one adjacent longitudinal steering element of said at least one longitudinal steering element, said at least one second slit (96) allowing, in use, independent movement of said at least one longitudinal steering element and said at least one adjacent longitudinal steering element relative to each other in the axial direction of the elongated steerable tubular body (18).

1 1. The elongated steerable tubular body (18) according to any one of the claims 6-10, wherein in at least one of said at least one second flexible zones (14; 16) at least one of said first (67a), second (68b), third (68a) and fourth (69b) spacers of at least one of said first (64), second (65) and third (66) flexible strips of said first intermediate cylindrical element (102) and at least one of said seventh (267a), eighth (268b), ninth (268a) and tenth (269b) spacers of at least one of said fourth (264), fifth (265) and sixth (266) flexible strips of said second intermediate cylindrical element (103) are arranged to at least partially overlap as seen in the axial direction of the elongated steerable tubular body (18).

12. The elongated steerable tubular body (18) according to any one of the claims 1-1 1, wherein at least one of said first (71) and second (72) strips which is attached to a respective one of said first (64) and second (65) flexible strips has a meandering shape comprising at least three curved sections (51a, 51b, 51c; 52a, 52b, 52c) with at least three tips (81a, 81b, 81c; 82a, 82b, 82c);

two (81a, 81c; 82a, 82c) of said at least three tips are arranged as seen in the circumferential direction of the elongated steerable tubular body (18) next to an adjacent one of said respective one of said first (64) and second (65) flexible strips such as to prevent, in use, movement of said adjacent one of said respective one of said first (64) and second (65) flexible strips in the circumferential direction of the elongated steerable tubular body (18) towards said respective one of said first (64) and second (65) flexible strips;

a third one (81b; 82b) of said at least three tips is arranged next to said respective one of said first (64) and second (65) flexible strips such as to prevent, in use, movement of said respective one of said first (64) and second (65) flexible strips in the circumferential direction of the elongated steerable tubular body (18) towards said adjacent one of said respective one of said first (64) and second (65) flexible strips.

13. The elongated steerable tubular body (18) according to claim 12, wherein at least one of said third (73) and fourth (74) strips which is attached to a respective one of said second (65) and third (66) flexible strips has a meandering shape comprising at least three curved sections (53a, 53b, 53c; 54a, 54b, 54c) with at least three tips (83a, 83b, 83c; 84a, 84b, 84c);

two (83a, 83c; 84a, 84c) of said at least three tips are arranged as seen in the circumferential direction of the elongated steerable tubular body (18) next to an adjacent one of said respective one of said second (65) and third (66) flexible strips such as to prevent, in use, movement of said adjacent one of said respective one of said second (65) and third (66) flexible strips in the circumferential direction of the elongated steerable tubular body (18) towards said respective one of said second (65) and third (66) flexible strips;

a third one (83b; 84b) of said at least three tips is arranged next to said respective one of said second (65) and third (66) flexible strips such as to prevent, in use, movement of said respective one of said second (65) and third (66) flexible strips in the circumferential direction of the elongated steerable tubular body (18) towards said adjacent one of said respective one of said second (65) and third (66) flexible strips.

14. The elongated steerable tubular body (18) according to any one of the claims 6-13, wherein at least one of said seventh (271) and eighth (272) strips which is attached to a respective one of said fourth (264) and fifth (265) flexible strips has a meandering shape comprising at least three curved sections (251a, 251b, 251c; 252a, 252b, 252c) with at least three tips (281a, 281b, 281c; 282a, 282b, 282c); two (281a, 281c; 282a, 282c) of said at least three tips are arranged as seen in the circumferential direction of the elongated steerable tubular body (18) next to an adjacent one of said respective one of said fourth (264) and fifth (265) flexible strips such as to prevent, in use, movement of said adjacent one of said respective one of said fourth (264) and fifth (265) flexible strips in the circumferential direction of the elongated steerable tubular body (18) towards said respective one of said fourth (264) and fifth (265) flexible strips;

a third one (281b; 282b) of said at least three tips is arranged next to said respective one of said fourth (264) and fifth (265) flexible strips such as to prevent, in use, movement of said respective one of said fourth (264) and fifth (265) flexible strips in the circumferential direction of the elongated steerable tubular body (18) towards said adjacent one of said respective one of said fourth (264) and fifth (265) flexible strips.

15. The elongated steerable tubular body (18) according to claim 14, wherein at least one of said ninth (273) and tenth (274) strips which is attached to a respective one of said fifth (265) and sixth (266) flexible strips has a meandering shape comprising at least three curved sections (253a, 253b, 253c; 254a, 254b, 254c) with at least three tips (283a, 283b, 283c; 284a, 284b, 284c);

two (283a, 283c; 284a, 284c) of said at least three tips are arranged as seen in the circumferential direction of the elongated steerable tubular body (18) next to an adjacent one of said respective one of said fifth (265) and sixth (266) flexible strips such as to prevent, in use, movement of said adjacent one of said respective one of said fifth (265) and sixth (266) flexible strips in the circumferential direction of the elongated steerable tubular body (18) towards said respective one of said fifth (265) and sixth (266) flexible strips;

a third one (283b; 284b) of said at least three tips is arranged next to said respective one of said fifth (265) and sixth (266) flexible strips such as to prevent, in use, movement of said respective one of said fifth (265) and sixth (266) flexible strips in the circumferential direction of the elongated steerable tubular body (18) towards said adjacent one of said respective one of said fifth (265) and sixth (266) flexible strips.

16. A steerable instrument (10; 2201) for at least one of endoscopic and invasive type of applications comprising an elongated steerable tubular body (18) according to any one of the preceding claims, said steerable instrument comprising a tool (2) that is arranged at said distal end part (13) of said elongated steerable tubular body (18) and a handle (3) that is arranged at said proximal end part (11) of said elongated steerable tubular body (18) such as to control, in use, at least one of said tool (2) and at least one of said at least one first flexible zones (15; 17) and said at least one second flexible zones (14; 16).