Surgical instrument having a shaft assembly with a kinematic chain

Abstract

A surgical instrument comprising an elongate shaft assembly, an end effector movably mounted at the distal end of the elongate shaft assembly, an optical fibre arranged in or on the shaft assembly to transmit an optical signal between the distal part of the shaft assembly and the proximal part of the shaft assembly. Wherein the shaft assembly comprises a kinematic chain, comprising a first kinematic link, a second kinematic link, and a kinematic joint coupling the first and second kinematic links such that the first and second kinematic links are movable with respect to each other. Wherein the optical fibre is guided through or along the first and second kinematic link and through or along the kinematic joint therein between and wherein the kinematic joint comprises at least one fibre guide to guide the optical fibre along or through the joint, the fibre guide having a curved guiding surface with a radius the same or larger than a desired minimum radius of curvature of the optical fibre.

Description

[0001] Title: Surgical instrument having a shaft assembly with a kinematic chain

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a surgical instrument, for example a surgical instrument for minimally invasive surgery.

[0004] BACKGROUND OF THE INVENTION

[0005] EP4241721 discloses a surgical instrument, for example a surgical instrument for minimally invasive surgery comprising an elongate frame, a forceps at the distal end of the frame, a handle part with a trigger device to operate the forceps at the proximal end of the frame, an actuation rod between the trigger device and the forceps and a sensor to provide a signal representative for a force exerted at the jaw elements of the forceps. The sensor may comprise an optical fibre that is arranged in the shaft and in the handle part and which may transmit an optical signal from a sensing element to an interrogator device that is placed in the handle part or in an external device.

[0006] A drawback of a surgical instrument such as described in EP4241721 with a rigid elongate shaft, is that the operational range of the end effector is limited. Especially during minimally invasive procedures, when the size of the surgical incision is limited to reduce wound healing time, providing an instrument shaft comprising one or more kinematic joints may be advantageous to increase the operational range of the end effector inside the body. However, when an optical fibre is used to transmit optical signals between a distal part of the instrument body and a proximal part of the instrument body, this poses extra challenges when the instrument body comprises a kinematic joint along which the optical fibre is routed. For example, bending of an optical fibre causes losses in the optical signal. As the radius of curvature decreases, the loss may increase exponentially until at a certain critical radius of curvature the optical signal cannot be used to provide accurate measurements anymore.

[0007] US2009 / 324160 describes an apparatus with an optical fibre that is used to detect the fibre’s position and orientation in a kinematic chain, where localized strain in the optical fibre at the exits of the links in the chain is decreased by using a curved exit surface with a minimum radius of curvature that is adapted to a minimum bend radius that the fibre will experience during shape sensing. The minimum bend radius is defined in this solution as the point where the joint reaches a limit in its range of motion. However, this solution solely considers local stress at the exit of the kinematic links and does not take into account the optical fibre losses that can occur when the optical fibre is bent in or along the joint itself due to hinging of the respective links connected to the joint.

[0008] OBJECT OF THE INVENTION

[0009] It is an object of the present invention to provide a surgical instrument, for example for minimally invasive surgery, that may have a relatively large operational range of the end effector inside a body, while at the same time preventing optical signal losses that may occur due to bending of an optical fibre that is comprised in the surgical instrument.

[0010] SUMMARY OF THE INVENTION

[0011] The present invention provides a surgical instrument, for example a surgical instrument for minimally invasive surgery as claimed in claim 1 .

[0012] The surgical instrument of the invention comprises an elongate shaft assembly, having a proximal and a distal end, to allow the operator to reach inside the body with at least one end effector that is movably mounted at the distal end of the elongate shaft assembly. An optical fibre is routed through and / or along the shaft assembly to transmit an optical signal between the distal part of the shaft assembly and the proximal part of the shaft assembly. The proximal part of the elongate shaft assembly may for example be connected to a handle part of the surgical instrument or be connected to a positioning system, e.g. a robot arm, of a surgical robot system. The optical fibre may be extended further from the proximal part of the shaft assembly through a handle part, robot arm, and / or other part of a surgical instrument to an interrogator device for signal processing.

[0013] According to the invention the shaft assembly comprises a kinematic chain to increase the operational range of the end effector inside the body. The kinematic chain comprises a first and a second kinematic link and a kinematic joint coupling the first and second kinematic link. The first kinematic link may for example comprise a distal part of the shaft assembly and the second kinematic link may for example comprise a proximal part of the shaft assembly.

[0014] The kinematic joint may be arranged in the distal half of a length of the shaft assembly, for example in the distal quarter of the length of the shaft assembly, i.e. within 50% and 25% of the length of the shaft assembly, respectively. It may be advantageous to provide the kinematic joint near the end-effector.

[0015] The optical fibre is guided through and / or along the kinematic links and through or along the kinematic joint in such a way that a minimum radius of curvature of the optical fibre at the joint of the kinematic chain is guaranteed to prevent optical signal losses. To this end, the kinematic joint comprises at least one fibre guide that has a curved surface to guide the optical fibre through or along the kinematic joint with a radius the same or larger than a desired minimum radius of curvature of the optical fibre. The desired minimum radius of curvature can be determined based on the bending characteristics of the optical fibre in regards to optical signal losses and / or other performance losses of the optical fibres due to bending.

[0016] The at least one fibre guide is arranged at the kinematic joint in such a way that it maintains at least the desired minimum radius of curvature of the optical fibre at the kinematic joint when the position of the first kinematic link with respect to the second kinematic link is changed. The at least one fibre guide may be arranged to keep the radius of curvature of the optical fibre anywhere between the first kinematic link and the second kinematic link the same or larger than the desired minimum radius of curvature of the optical fibre at the kinematic joint. The at least one fibre guide may be mounted on any suitable part of the kinematic joint, the first dynamic link and / or the second dynamic link.

[0017] The at least one fibre guide may have two or more curved surfaces to guide the optical fibre through or along the kinematic joint with a radius the same or larger than a desired minimum radius of curvature of the optical fibre. The two or more curved surfaces may have the same or different curvatures. The radius of each curved surface may differ at different locations along the curved surface as long as the radius at any location is the same or larger than a desired minimum radius of curvature of the optical fibre.

[0018] In an embodiment, the kinematic joint may be a hinge joint. The hinge joint may have one degree of freedom in rotation, or multiple degrees of freedom in rotation. A hinge joint enables pivoting of the first kinematic link with respect to the second kinematic link, such that a direction of a longitudinal axis of the first kinematic link changes with respect to a direction of a longitudinal axis of the second kinematic link. As a result, it is possible to pivot the at least one end effector out of a main direction of extension of the shaft assembly. This allows the operator to handle tissue at locations which are not or not easily accessible with shaft assemblies having a completely straight shaft.

[0019] In an embodiment, a joint angle range of the hinge joint may be a limited range. This limited range may provide an acceptable degree for the operator to provide adequate operational range and at the same time be limited as relatively large joint angles, e.g. more than 180 degrees in either rotation direction, could further complicate arrangement of the optical fibre inside the joint. The joint angle of the kinematic rotational joint may for example be limited to maximally 360 degrees, e.g. + / -180 degrees with respect to a middle position. In a further embodiment, the joint angle of the kinematic rotational joint may for example be limited to maximally 270 degrees, e g. + / - 135 degrees with respect to a middle position, or even 180 degrees, e g. + / - 90 degrees with respect to a middle position.

[0020] The kinematic joint may also be any other joint that allows movement of the first kinematic link with respect to the second kinematic link.

[0021] In an embodiment, the at least one fibre guide is arranged at or near an interface of a joint towards the first or towards the second kinematic link. In addition to maintaining at least the desired minimum radius of curvature, this may also prevent local strain at the exit of the joint due to movement of the first kinematic link with respect to the second kinematic link. Further fibre guides may be arranged at other locations of the kinematic joint.

[0022] In an embodiment, the kinematic joint comprises two fibre guides to guide the optical fibre along or through the joint. Providing two fibre guides may provide more freedom in the arrangement of the optical fibre at the kinematic joint while maintaining at least the desired minimum radius of curvature of the optical fibre. For example, the optical fibre may be bent along different axes or in different directions in the same plane. Additional length of the optical fibre may be contained inside the joint for example to account for bending when the joint angle is adjusted. The fibre guides may constrain the movement of the optical fibre inside the joint to account for this additional length. In an embodiment, the two fibre guides are arranged such that the optical fibre is guided in between the two fibre guides. The optical fibre guides may be arranged close near each other to constrain the path along which the optical fibre is guided or may be arranged further apart to give the optical cable more freedom to move.

[0023] In an embodiment, the two fibre guides are arranged next to each other perpendicular to a direction in which the first and second kinematic links extend when the first kinematic link and the second kinematic link are in an aligned position. This allows the hinging of the joint in two directions, because the optical fibre may bend in two directions along the curved surfaces of the fibre guide.

[0024] In an embodiment, the two fibre guides are arranged such that the optical fibre is guided in an S-shape from the first kinematic link to the second kinematic link when the first kinematic link and the second kinematic link are in an aligned position. This allows the hinging of the joint in two directions, because the optical fibre may bend in two directions along the curved surfaces of the fibre guide. This embodiment may be advantageous depending on for example joint angle constraints or arrangement of other features inside the joint such as additional cabling.

[0025] In an embodiment, the at least one fibre guide comprises a guiding groove or guiding channel, the guiding groove or guiding channel having a curved guiding surface with a radius the same or larger than a desired minimum radius of curvature of the optical fibre. The optical fibre may need additional length to be contained within the joint for example to allow for bending of the optical fibre. The optical fibre may move within the guiding groove or guiding channel away from or towards the curved guiding surface to allow more or less length of the optical fibre to be contained by the fibre guide without bending or twisting the fibre to prevent optical signal losses.

[0026] In an embodiment, the guiding groove or guiding channel is spirally shaped. The spirally shaped guiding groove or guiding channel has a curved guiding surface with a radius the same or larger than a desired minimum radius of curvature of the optical fibre. The optical fibre may be wound in a spiral through the guiding groove or guiding channel to accommodate additional length of the optical fibre. It may be wounded loosely or tighter towards the curved guiding surface depending on how much optical fibre length should be contained by the fibre guide. In an embodiment, the guiding groove or guiding channel comprises side walls extending from the curved guiding surface, wherein the side walls are arranged to keep the optical fibre within the guiding groove or guiding channel.

[0027] In an embodiment, the kinematic chain comprises one or more additional kinematic joints, wherein each additional kinematic joint comprises at least one additional fibre guide to guide the optical fibre along or through the joint, the fibre guide having a curved guiding surface with a radius the same or larger than the desired minimum radius of curvature of the optical fibre, wherein the at least one additional fibre guide is arranged at the kinematic joint such that an actual minimal radius of curvature of the optical fibre at the kinematic joint is the same or larger than the desired minimum radius of curvature of the optical fibre. The kinematic chain may have one or more additional kinematic joints and associated links. Each additional link is coupled with a joint to the distal end of the kinematic chain. Each additional kinematic joint may comprise at least one fibre guide to guide the optical fibre along a curved surface to maintain a desired minimum radius of curvature of the optical fibre. The optical fibre is routed through or along the entire kinematic chain between the proximal end of the shaft assembly and the distal end of the shaft assembly. The joints may be arranged such that they hinge around the same or different axes to increase mobility of the end effector of the surgical instrument.

[0028] In an embodiment, the kinematic chain comprises a multitude of kinematic links coupled by kinematic joints. Such kinematic chain may have a snake-like configuration comprising a multitude of kinematic links coupled by kinematic joints along at least a part of the shaft assembly. To establish a snake-like shape the length of the links may be relatively short, for example the length of the links may be the same or smaller than the diameter of the links. The snake-like shape increases mobility of the end effector of the surgical instrument.

[0029] In an embodiment, the optical fibre comprises one or more Fibre Bragg Gratings (FBGs). The FBGs may be used as sensing elements for strain or temperature by causing a shift in the Bragg wavelength. An example of the FBG sensor is described in W001 / 84097 A1 and will not be explained here in detail.

[0030] In an embodiment, one or more FBGs are used as strain sensing elements to transmit an optical signal representative for a force exerted on the at least one end effector. The FBGs may be arranged in various configurations to be able to measure this force. Examples of these configurations are described in EP4241721 and will not be explained here in detail.

[0031] In an embodiment, the at least one end effector is a jaw element operating as part of a forceps manipulator. Examples of such a forceps construction are described in WO2009145632 and W02020101496, the contents of which are hereby incorporated by reference and will not be described here in detail.

[0032] BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Fig. 1 depicts a schematic view of an embodiment of a surgical instrument according to the invention;

[0034] Fig. 2 depicts a schematic view of the kinematic chain of an embodiment of the surgical instrument of Fig. 1 wherein a fibre guide is arranged at the centre of the joint.

[0035] Fig. 3 depicts a schematic view of the kinematic chain of an embodiment of the surgical instrument of Fig. 1 wherein a fibre guide is arranged at the side of the joint.

[0036] Fig. 4 depicts a schematic view of the kinematic chain of an embodiment of the surgical instrument of Fig. 1 wherein two fibre guides are arranged near the exit of a kinematic link perpendicular to the direction of the kinematic links when they are in an extended position.

[0037] Fig. 5 depicts a schematic view of the kinematic chain of an embodiment of the surgical instrument of Fig. 1 wherein two fibre guides are arranged such that the optical fibre is guided in an S-shape from the first kinematic link to the second kinematic link when they are in an extended position.

[0038] Fig. 6 depicts a schematic side view of a fibre guide of an embodiment of the surgical instrument of Fig. 1 comprising an elongate indentation to guide an optical fibre through.

[0039] Fig. 7 depicts a schematic view of the kinematic chain of an embodiment of the surgical instrument of Fig. 1 wherein the optical fibre is wound around the fibre guide.

[0040] Fig. 8 depicts a schematic view of an embodiment of a surgical instrument according to the invention, wherein the kinematic chain has a snake-like configuration.

[0041] DETAILED DESCRIPTION OF THE DRAWINGS

[0042] Fig. 1 depicts a schematic view of an embodiment of a surgical instrument according to the invention. The surgical instrument 1 is in particular configured for minimally invasive surgery. The surgical instrument 1 comprises an elongate shaft assembly 2 and at least one end effector 3 movably mounted at the distal end of the elongate shaft assembly 2. The at least one end effector 3 may be part of a forceps construction as described in W02020101496.

[0043] The surgical instrument 1 further comprises an optical fibre 4 arranged in or on the shaft assembly 2 to transmit an optical signal between the distal part of the shaft assembly and the proximal part of the shaft assembly. The shaft assembly 2 comprises a kinematic chain, comprising a first kinematic link 5, formed by a distal part of the shaft assembly 2, a second kinematic link 6, formed by a proximal part of the shaft assembly 2, and a kinematic hinge joint 7 coupling the first kinematic link 5 and the second kinematic link 6. The kinematic hinge joint 7 allows the first kinematic link 5 and the second kinematic link 6 to pivot with respect to each other to increase the operational range of the end effector.

[0044] The first kinematic link 5 and the second kinematic link 6 may be in an aligned position in which a longitudinal axis of the first kinematic link 5 is parallel or coincident with a longitudinal axis of the second kinematic link 6. This aligned position is shown in Figure 1. From this aligned position, the first kinematic link 5 may be pivoted with respect to the second kinematic link 6 such that a longitudinal axis of the first kinematic link 5 is arranged at a joint angle with respect to the longitudinal axis of the second kinematic link 6.

[0045] The joint angle range of the may be a limited range. The joint angle of the kinematic rotational joint may for example be limited to maximally 360 degrees, e.g. + / -180 degrees with respect to the aligned position, wherein the aligned position is assumed to be at 0 degrees. In a further embodiment, the joint angle of the kinematic rotational joint may for example be limited to maximally 270 degrees, e.g. + / - 135 degrees with respect to the aligned position, or maximally 180 degrees, e.g. + / - 90 degrees with respect to the aligned position. It is also possible that from the aligned position, the second kinematic coupling 6 can only rotate in a single direction, for example over an angle of 0-180 degrees, 0-135 degrees, 0-90 degrees or any other suitable range.

[0046] The optical fibre may comprise one or more fibre Bragg gratings (FBGs) 8 to measure strain at a position distal of the kinematic hinge joint 7. The shaft assembly 2 is, at its proximal end, coupled to a handle assembly 9 of a hand-held surgical instrument. Strain measurements by the FBGs may be transmit between the distal end of the shaft assembly 2 and the proximal part of the shaft assembly. The optical fibre 4 may further extend through the handle assembly 9. In other embodiments, the shaft assembly may be coupled to other operating devices, such as a robotic arm of a robotic surgical system.

[0047] Figs. 2a and 2b depict schematic views of the kinematic chain of an embodiment of the surgical instrument of Fig. 1, wherein a fibre guide 10 is arranged at the centre of the kinematic hinge 7. When the fibre guide 10 is arranged at the centre of the joint, the optical fibre 4 may be routed through the kinematic hinge joint 7. Fig. 2a depicts the embodiment when the kinematic links are in the aligned position. Fig. 2b depicts the embodiment when the joint 7 is hinged, i.e. the longitudinal axis of the first kinematic link 5 and the longitudinal axis of the second kinematic link 6 are arranged at a non-zero joint angle with respect to each other.

[0048] The optical fibre 4 is guided along a curved guiding surface 11 with a radius the same or larger than a desired minimum radius of curvature of the optical fibre to prevent that the optical fibre will be bent in the hinge joint with a radius of curvature smaller than a desired radius of curvature. It will be appreciated that the fibre guide 10 may have a different shape or size than the depicted circle, but may comprise a side with a convex curved guiding surface 11 along which the optical fibre 4 is guided. The curved guiding surface 11 may have a circular or oval shape, or other shape as long as it is ensured that the optical fibre 4 will not be bent with a radius of curvature smaller than the desired radius of curvature.

[0049] Figs. 3a and 3b depict a schematic view of the kinematic chain of an embodiment of the surgical instrument of Fig. 1 wherein a fibre guide 10 is arranged at the side of the kinematic hinge joint 7. The optical fibre 4 is guided along the curved guiding surface 11 of the fibre guide 10 along the side of the kinematic hinge joint 7. Fig. 3a depicts the embodiment when the kinematic links are in the aligned position and Fig. 3b depicts the embodiment when the joint 7 is hinged out of the aligned position. Placing the fibre guide 10 at the side of the joint may leave space in the centre for mechanical parts or other cabling through the kinematic hinge joint 7. It will be appreciated that the fibre guide 10 may have a different shape or size than the depicted circle, but may comprise a side with a convex curved guiding surface 11 along which the optical fibre 4 is guided.

[0050] Figs. 4a, 4b and 4c depict a schematic view of the kinematic chain of an embodiment of the surgical instrument of Fig. 1 wherein two fibre guides 101, 102 are arranged near the interface of the hinge joint 7 with the first kinematic link 5. The two fibre guides 101 , 102 are spaced in a direction perpendicular to a direction of the longitudinal axes of the first and second kinematic links 5, 6 in the aligned position. Fig. 4a shows the kinematic chain when the kinematic links 5, 6 are in the aligned position. The optical fibre 4 is routed through the kinematic hinge joint 7 in between the two fibre guides 101 , 102. Fig. 4b depicts the kinematic chain when the joint angle is adjusted counterclockwise. The optical fibre 4 is guided around the first fibre guide 101 to maintain a minimum radius of curvature for bending of the optical fibre 4. Fig. 4c depicts kinematic chain when the joint angle is adjusted clockwise. The optical fibre 4 is guided around the second fibre guide 102 to maintain a minimum radius of curvature for bending of the optical fibre 4. It will be appreciated that the fibre guides 101 , 102 may have a different shapes or sizes than the depicted circles, but may comprise a side with a convex curved guiding surface 11 along which the optical fibre 4 is guided. It will further be appreciated that the fibre guides 101 , 102 may be arranged close together or further apart. Finally, it may also be possible that only one fibre guide is arranged near the interface of the first kinematic link 5. In this case the kinematic hinge joint 7 may be constrained to the corresponding hinging direction.

[0051] Correspondingly to the embodiment of Figures 4a, b, and 4b, one or two fibre guides may be arranged near the interface of the hinge joint 7 with the second kinematic link 6, or at another suitable location in the kinematic hinge joint 7.

[0052] Fig. 5a and 5b depict a schematic view of the kinematic chain of an embodiment of the surgical instrument of Fig. 1 where two fibre guides 101 , 102 are arranged such that the optical fibre 4 is guided in an S-shape from the first kinematic link 5 to the second kinematic link 6 when they are in an aligned position. Fig. 5b depict the embodiment when the joint angle is adjusted counterclockwise. The optical fibre 4 is guided around the first fibre guide 101 to maintain a minimum radius of curvature for bending of the optical fibre 4. Fig. 5c depict the embodiment when the joint angle is adjusted clockwise. The optical fibre 4 is guided around the second fibre guide 102 to maintain a minimum radius of curvature for bending of the optical fibre 4. It will be appreciated that the fibre guides 101, 102 may have a different locations, shapes or sizes than the depicted circles, but may comprise a side with a convex curved guiding surface 11 along which the optical fibre 4 is guided. It will further be appreciated that the fibre guides 101 , 102 may be arranged close together or further apart.

[0053] Fig. 6 depicts a schematic side view of the fibre guide 10 of an embodiment of the surgical instrument of Fig. 1 comprising a guiding groove12 to guide an optical fibre 4. The guiding groove 12 comprises a bottom surface and side walls 12a. The bottom surface of the guiding groove 12 forms the curved guiding surface 11 with a radius the same or larger than a desired minimum radius of curvature of the optical fibre to prevent that the optical fibre will be bent in the hinge joint with a radius of curvature smaller than a desired radius of curvature.

[0054] The guiding groove 12 allows the optical fibre 4to move towards and away from the curved guiding surface 11 , while the optical fibre 4 is still held in the guiding groove 12 by side walls 12a. This can be used to accommodate for path length differences of the optical fibre 4 between the first kinematic link 5 and the second kinematic link 6. For example, in the aligned position of the first kinematic link 5 and the second kinematic link 6, shown in Figure 2a, the shortest path of the optical fibre 4 between the first kinematic link 5 and the second kinematic link 6 has a smaller path length than in the pivoted position of the first kinematic link 5 and the second kinematic link 6, shown in Figure 2b.

[0055] In Fig. 6a the optical fibre 4 is located at a location further away from the curved guiding surface 11. In this position the guiding groove 12 of the fibre guide 10 may accommodate additional length of the optical fibre 4 as the bending radius of the optical fibre 4 is relatively large, for example such as in the situation of Fig. 2a. In Fig. 6b the optical fibre 4 is located closer to the curved guiding surface 11. In this position the bending radius of the optical fibre 4 is decreased to almost the minimum desired radius of curvature of the fibre guide 10, for example corresponding to the situation of Fig. 2b. It will be appreciated that the optical fibre 4 may move to different positions in the guiding groove 12 than depicted in Fig. 6a and Fig. 6b.

[0056] It may be advantageous that in all possible relative positions of the first kinematic link 5 with respect the second kinematic link 6, the optical fibre 4 will remain between the side walls 12a. In such embodiment the joint angle of the first kinematic link 5 with respect the second kinematic link 6 may have a limited range, wherein within the limited range the optical fibre will remain within the guiding groove 12 without moving to far away from the curved guiding surface 11 or being pulled on the curved guiding surface 11. For additional assurance that the optical fibre 4 will remain within the guiding groove the ends of the side walls 12a directed away from the curved guiding surface may be connected by a top wall to form a guiding channel.

[0057] Figs. 7a, 7b, 7c and 7d depict a schematic view of the kinematic chain of an embodiment of the surgical instrument of Fig. 1, wherein the optical fibre 4 is wound with one or more revolutions around the fibre guide 10. This allows additional length of the optical fibre 4 while maintaining the minimum radius for bending of the optical fibre 4. The fibre guide 10 may for example be configured to accommodate at least one or more complete revolutions, for example at least two, three, or four revolutions of the optical fibre along the curved guiding surface 11 of the fibre guide 10. Fig. 7a depicts the embodiment when the joint angle is adjusted counterclockwise. In this example, the optical fibre 4 is wound close to the inside of a guiding groove 12 of the fibre guide 10. Fig. 7b depicts a side view of the guiding groove 12. The guiding groove 12 may extend in a spiral shape around the complete circumference of the fibre guide 10. When additional length of the optical fibre is required, such as in Fig. 7a, the optical fibre 10 is wound around the fibre guide 20 such that it is relative close to the curved guiding surface 11. The curved guiding surface 11 maintain a minimum radius of curvature of the optical fibre 4. Fig. 7c depicts the embodiment when the joint angle is adjusted clockwise. In this example, the optical fibre 4 is wound in a spiral shape more loosely around the fibre guide 10. Fig. 7d depicts a side view of the fibre guide 10. Additional length of the optical fibre 4, such as in Fig. 7c, is contained within the guiding groove

[0058] 12 wherein the optical fibre 4 is paced further away from the inner guiding surface 11. lt will be appreciated that the embodiment of Figs. 7a-7d is an example of the principle of using a guiding groove 12 to accommodate additional length of an optical fibre 4 in the fibre guide 12.

[0059] Fig. 8 depicts a schematic view of an embodiment of a surgical instrument according to the invention, wherein the kinematic chain 15 has a snake-like configuration. The kinematic chain 15 comprises a multitude of kinematic links 13 coupled by kinematic hinge joints 14, wherein each kinematic hinge joint 14 allows pivoting of adjacent kinematic links 13 with respect to each other. In the shown embodiment, all hinge joints 14 allow pivoting of the adjacent kinematic links

[0060] 13 around parallel axes of rotation. In other embodiments, not all axes of rotation have to be parallel. The length of the kinematic links 13 may be relatively short, for example the length of the links may be the same or smaller than the diameter of the links. Each of the hinge joints 14 may have a fibre guide 10 as described hereinabove.

Claims

CLAIMS1. A surgical instrument, for example a surgical instrument for minimally invasive surgery, comprising: an elongate shaft assembly, having a proximal and a distal end, at least one end effector movably mounted at the distal end of the elongate shaft assembly, an optical fibre arranged in or on the shaft assembly to transmit an optical signal between the distal part of the shaft assembly and the proximal part of the shaft assembly, characterised in that: the shaft assembly comprises a kinematic chain, comprising: a first kinematic link, a second kinematic link, a kinematic joint coupling the first and second kinematic links such that the first and second kinematic links are movable with respect to each other, wherein the optical fibre is guided through or along the first and second kinematic link and through or along the kinematic joint therein between, wherein the kinematic joint comprises at least one fibre guide to guide the optical fibre along or through the joint, the fibre guide having a curved guiding surface with a radius the same or larger than a desired minimum radius of curvature of the optical fibre such that an actual minimal radius of curvature of the optical fibre at the kinematic joint will be the same or larger than the desired minimum radius of curvature of the optical fibre.

2. The surgical instrument of claim 1, wherein the kinematic joint is a hinge joint.

3. The surgical instrument of claim 1 , wherein a joint angle range of the hinge joint is a limited range.

4. The surgical instrument of any of the preceding claims, wherein the at least one fibre guide is arranged at or near an interface of the joint towards the first or towards the second kinematic link.

5. The surgical instrument of any of the preceding claims, wherein the kinematic joint comprises two fibre guides to guide the optical fibre along or through the joint.

6. The surgical instrument of claim 5, wherein the two fibre guides are arranged such that the optical fibre is guided in between the two fibre guides.

7. The surgical instrument of claim 6, wherein the two fibre guides are arranged next to each other perpendicular to a direction in which the first and second kinematic links extend when the first kinematic link and the second kinematic link are in an aligned position.

8. The surgical instrument of claim 6, wherein the two fibre guides are arranged such that the optical fibre is guided in an S-shape from the first kinematic link to the second kinematic link when the first kinematic link and the second kinematic link are in an aligned position.

9. The surgical instrument of any of the preceding claims, wherein the at least one fibre guide comprises a guiding groove or guiding channel, the guiding groove or guiding channel having a curved guiding surface with a radius the same or larger than a desired minimum radius of curvature of the optical fibre.

10. The surgical instrument of claim 9, wherein the guiding groove or guiding channel is spirally shaped.

11. The surgical instrument of claims 9 or 10, wherein the guiding groove or guiding channel comprises side walls extending from the curved guiding surface, wherein the side walls are arranged to keep the optical fibre within the guiding groove or guiding channel.

12. The surgical instrument of any of the preceding claims, wherein the kinematic chain comprises one or more additional kinematic joints, wherein each additional kinematic joint comprises at least one additional fibre guide to guide the optical fibre along or through the joint, the fibre guide having a curved guiding surface with a radius the same or larger than the desired minimum radius of curvature of the optical fibre, wherein the at least one additional fibre guide is arranged at the kinematic joint such that an actual minimal radius of curvature of the optical fibre at the kinematic joint is the same or larger than the desired minimum radius of curvature of the optical fibre.

13. The surgical instrument of any of the preceding claims, wherein the kinematic chain comprises a multitude of kinematic links coupled by kinematic joints.

14. The surgical instrument of any of the preceding claims, wherein the optical fibre comprises one or more Fibre Bragg Gratings (FBGs).

15. The surgical instrument of claim 13, where one or more FBGs are used as strain sensing elements to transmit an optical signal representative for a force exerted on the at least one end effector.

16. The surgical instrument of any of the preceding claims, wherein the at least one end effector is a jaw element operating as part of a forceps.

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