A wrist joint

Abstract

A wrist joint (100) for a surgical instrument (160) having a proximal end (164), a distal end (166), an end effector (102) mounted at the distal end and (166) at least one actuation tendon (108a, 108b) for actuating the end effector (102) The wrist joint (100) comprises proximal and distal parts (110, 120) having respective proximal and distal rolling surfaces (112, 122), wherein respective axes (114, 124) extend through the proximal and distal parts (110, 120) centrally with respect to the associated rolling surfaces (112, 122). The distal part (120) is rotatably coupled to the proximal part (110) with the proximal and distal rolling surfaces (112, 122) able to roll against one another. Proximal and distal guiding assemblies (130, 132) are mounted to the proximal and distal parts (110, 120) respectively. Respective guiding surfaces (131, 133) of the proximal and distal guiding assemblies (130, 132) are configured to guide the at least one actuation tendon (108a, 108b) therebetween as the at least one actuation tendon (108a, 108b) extends from the proximal end (164) to the end effector (102), thereby decoupling actuation of the end effector (102) from wrist movement.

Description

[0001] A WRIST JOINT

[0002] Field of the invention

[0003] This invention relates to a wrist joint for a surgical instrument. The invention has particular application in the field of surgical robotics to facilitate the movement of a surgical instrument end effector for minimally invasive surgical procedures, although the invention is not limited to such application and may also have use in other medical / surgical devices comprising a member that requires articulation.

[0004] Background

[0005] Known surgical instruments forming part of robotic surgical systems comprise a proximal end, a distal end and an end effector mounted at the distal end. The proximal end may be considered the base of the surgical instrument and may comprise components such as electrical motors for driving movement of the surgical instrument. The distal end is configured for carrying out surgical procedures, such as minimally invasive surgical procedures. In particular, the end effector located at the distal end is configured for performing surgical tasks, e.g. guiding optical equipment, manoeuvring body tissue and holding surgical tools such as suture needles.

[0006] In some known surgical instruments, there is at least one wrist joint, or equivalent wrist-like mechanism, providing a high range of mobility to the end effector. However, known end effectors are tendon driven, meaning that movement of the end effector is driven by actuation of one or more tendons, cables, wires or similar. Extending tendons through a highly mobile wrist joint presents challenges in overcoming frictional losses due to the tendon(s) being exposed to sharp bends, fatigue due to the frequency of exposure to those sharp bends and "crosstalk" wherein movement of the wrist joint causes unintended movement of the tendons leading to unintended actuation of the end effector.

[0007] Known surgical instruments utilise complex computer software to apply small actuations of the tendons to compensate for crosstalk actuation caused by wrist movement. However, the use of such software introduces additional risk of error when the surgical instrument is being controlled.

[0008] It is an aim of the present disclosure to address these challenges without the use of software to compensate for crosstalk. Summary of the invention

[0009] According to a first aspect of the invention there is provided a wrist joint for a surgical instrument having a proximal end, a distal end, an end effector mounted at the distal end and at least one actuation tendon for actuating the end effector, the wrist joint comprising: a proximal part having a proximal rolling surface, wherein a first axis extends through the proximal part; a distal part having a distal rolling surface, wherein a second axis extends through the distal part, the distal part being rotatably coupled to the proximal part such that the distal rolling surface is able to roll against the proximal rolling surface to provide wrist movement of the distal part relative to the proximal part; a proximal guiding assembly having a proximal guiding surface and mounted to the proximal part such that the proximal guiding surface is coaxial with the proximal rolling surface along the first axis; and a distal guiding assembly having a distal guiding surface and mounted to the distal part such that the distal guiding surface is coaxial with the distal rolling surface along the second axis, wherein the proximal and distal guiding assemblies are configured to guide the at least one actuation tendon therebetween as the at least one actuation tendon extends from the proximal end to the end effector, thereby decoupling actuation of the end effector from wrist movement.

[0010] The term "wrist movement" is to be understood as rotation of the distal part of the wrist joint relative to the proximal part, thereby providing rotation of the end effector relative to the rest of the surgical instrument.

[0011] By extending the at least one actuation tendon between the proximal and distal guiding assemblies, the bending angles applied to the at least one actuation tendon may be controlled to avoid extreme bending angles that can lead to increased frictional losses and tendon fatigue.

[0012] The proximal and distal guiding assemblies are also configured to eliminate crosstalk by decoupling actuation of the end effector from wrist movement.

[0013] To understand why crosstalk occurs in known surgical instruments, it is helpful to consider a plane extending centrally through the surgical instrument from the proximal end to the distal end, wherein the central plane folds in response to rotation of a particular joint in the surgical instrument. Actuation tendons extending through that joint are typically offset to one side of the central plane, meaning that the actuation tendon is required to extend further than the central plane if the joint rotates in one direction or not as far as the central plane if the joint rotates in the other direction.

[0014] In a wrist joint according to the invention, the rotation of the wrist joint is provided by the proximal and distal rolling surfaces rolling against one another, wherein the first axis, the second axis and the contact point between those two rolling surfaces are each aligned with the central plane referred to above. Meanwhile, the proximal and distal guiding surfaces are coaxial with the proximal and distal rolling surfaces respectively. Therefore, as the at least one actuation tendon passes between the proximal and distal guiding assemblies, it is essentially crossing from one side of the central plane to the other. As a result, for each rotation of the wrist joint, there is a first portion of the at least one actuation tendon that travels a longer distance than the central plane and a second portion that travels a shorter distance than the central plane. Moreover, the fact that the proximal and distal guiding assemblies are coaxial with the proximal and distal rolling surfaces respectively means that the at least one actuation tendon is guided to cross the central plane at the midpoint of the joint. This allows the difference between the distance travelled by the first portion of the at least one actuation tendon and the central plane to be equal to the difference between the distance travelled by the second portion of the at least one actuation tendon and the central plane. In other words, the discrepancies between the distance travelled by the at least one actuation tendon relative to the central plane can be entirely cancelled out so that the distance travelled by the at least one actuation tendon is decoupled from wrist movement. Accordingly, actuation of the end effector is decoupled from wrist movement and crosstalk is eliminated.

[0015] In one or more embodiments, the wrist joint may further comprise a drive disc configured such that actuation of the drive disc provides the wrist movement of the distal part relative to the proximal part. In some such embodiments, the drive disc may be mounted to the proximal part for rotation about the first axis. The wrist joint may further comprise a drive axle mounted to the drive disc along the second axis and coupled to the distal part such that rotation of the drive disc causes the distal rolling surface to roll against the proximal rolling surface.

[0016] In some embodiments, the wrist joint further may comprise a drive tendon having a middle portion coupled to the drive disc and opposing end portions extending towards the proximal end of the surgical instrument, wherein a first end portion is able to be pulled to rotate the drive disc in a first sense to provide wrist movement in a first direction and a second end portion is able to be pulled to rotate the drive disc in a second sense to provide wrist movement in a second direction. The middle portion may be coupled to the drive disc by any suitable means, such as by crimping, welding, glueing, ferrule or another commonly known approach.

[0017] The use of a drive tendon to actuate rotation of the wrist joint is preferable because tendons can occupy a relatively small footprint in the cross section of a surgical instrument, allowing the surgical instrument to be narrower than if another actuation mechanism were used, such as an electric motor positioned locally to the wrist joint.

[0018] The use of a drive disc mounted to the proximal part enables the use of a drive tendon without the drive tendon needing to extend through the wrist joint to be fixed to the distal part, for example. This provides a number of advantages including a reduction in the number of parts extending through the wrist joint, simplification of the structure of the wrist joint and protecting the drive tendon from the tendon fatigue it might experience if it extended through the wrist joint and was exposed to sharp bending angles.

[0019] In one or more embodiments, the ratio between a diameter of the proximal guiding surface and a diameter of the proximal rolling surface may be equal to a ratio between a diameter of the distal guiding surface and a diameter of the distal rolling surface. Making those two ratios equal ensures that the difference between the distance travelled by the first portion of the at least one actuation tendon and the central plane is always equal to the difference between the distance travelled by the second portion of the at least one actuation tendon and the central plane. I.e. it is ensured that the discrepancies between the distance travelled by the at least one actuation tendon relative to the central plane are entirely cancelled out so that the distance travelled by the at least one actuation tendon is decoupled from wrist movement and crosstalk is eliminated.

[0020] In some such embodiments, the proximal guiding surface and the proximal rolling surface may share an equal diameter (i.e. a ratio of 1 : 1), and the distal guiding surface and the distal rolling surface may share an equal diameter. In other words, the proximal and distal guiding surfaces may be the maximum diameter allowable to fit within the structure of the wrist joint. This maximises the support provided to the at least one actuation tendon by the proximal and distal guiding assemblies as it extends through the wrist joint, reducing tendon fatigue and reducing the likelihood of slack developing in the at least one actuation tendon, which would be detrimental to the actuation of the end effector.

[0021] In some embodiments, the proximal guiding assembly may comprise at least one proximal pulley mounted to the proximal part and rotatable about the first axis. Similarly, the distal guiding assembly may comprise at least one distal pulley mounted to the distal part and rotatable about the second axis. The provision of a pulley to guide the at least one actuation tendon further reduces frictional losses and tendon fatigue.

[0022] In some such embodiments, the proximal guiding assembly comprises a plurality of proximal pulleys and the distal guiding assembly comprises a plurality of distal pulleys. The plurality of proximal pulleys and the plurality of distal pulleys may be arranged symmetrically with respect to a central plane of the surgical instrument, the central plane extending perpendicular to the first and second axes.

[0023] In one or more embodiments, the proximal rolling surface may comprise a plurality of proximal gear teeth extending radially from the first axis and the distal rolling surface may comprise a plurality of distal gear teeth extending radially from the second axis, the plurality of proximal gear teeth and the plurality of distal gear teeth being engageable with one another such that the distal rolling surface is able to roll against the proximal rolling surface without slipping. The proximal rolling surface may have a proximal pitch diameter equal to a diameter of the proximal guiding assembly and the distal rolling surface may have a distal pitch diameter equal to a diameter of the distal guiding assembly.

[0024] In some embodiments, the first axis and the second axis each extend along a central longitudinal plane of the surgical instrument. Arranging the first and second axes centrally means that the proximal and distal rolling surfaces (and the proximal and distal guiding surfaces) are arranged longitudinally with respect to one another within the overall structure of the surgical instrument, rather than laterally. This, in turn, allows for a more compact construction as relatively large components such as the proximal and distal guiding assemblies are not protruding irregularly from the side of the wrist joint.

[0025] According to a second aspect of the invention, there is provided a surgical instrument comprising: a proximal end and a distal end; an end effector mounted at the distal end; at least one actuation tendon for actuating the end effector; a wrist joint according to the first aspect of the invention, or any one of its embodiments. The wrist joint is positioned between the proximal end and the distal end, wherein the at least one actuation tendon extends between the proximal and distal guiding assemblies.

[0026] The features and advantages of the first aspect of the invention and its embodiments apply mutatis mutandis to the second aspect of the invention and its embodiments.

[0027] In one or more embodiments, the end effector may comprise a first jaw rotatable about a first jaw axis extending perpendicularly to the first and second axes. The at least one actuation tendon may comprise a first actuation tendon having a middle portion coupled to the first jaw and opposing end portions each passing between the proximal and distal guiding assemblies before extending towards the proximal end of the surgical instrument, the first actuation tendon being movable to rotate the first jaw.

[0028] In some embodiments, the end effector may comprise a second jaw rotatable about a second jaw axis extending perpendicularly to the first and second axes. The at least one actuation tendon may comprise a second actuation tendon having a middle portion coupled to the second jaw and opposing end portions each passing between the proximal and distal guiding assemblies before extending towards the proximal end of the surgical instrument, the second actuation tendon being movable to rotate the second jaw.

[0029] The first and second jaws may be rotatable independently of one another. The first jaw axis and the second jaw axis may be the same axis or may be separate axes offset from but extending parallel to one another. In other words, the first and second jaws may rotate about the same axis or may rotate about separate parallel axes that are offset from one another.

[0030] The proximal guiding assembly may comprise four proximal pulleys mounted to the proximal part and independently rotatable about the first axis. The distal guiding assembly may comprise four distal pulleys mounted to the distal part and independently rotatable about the second axis. Each end portion of the first and second actuation tendons may pass between a respective pair of proximal and distal pulleys. While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that other embodiments, beyond the particular embodiments described, are possible as well.

[0031] The figures and Detailed Description that follow also exemplify various example embodiments. Various example embodiments may be more completely understood in consideration of the following Detailed Description in connection with the accompanying Drawings.

[0032] Brief Description of the Drawings

[0033] The invention will now be described by way of example only with reference to the accompanying drawings in which:

[0034] One or more embodiments will now be described by way of example only with reference to the accompanying drawings in which:

[0035] Figure 1 schematically shows a wrist joint according to an embodiment of the invention;

[0036] Figure 2 schematically shows proximal and distal rolling surfaces forming part of the wrist joint of Figure 1;

[0037] Figures 3 and 4 schematically show alternative configurations of proximal and distal rolling surfaces for wrist joints according to embodiments of the invention;

[0038] Figure 5 schematically shows a view of the wrist joint of Figure 1 when in a straight configuration;

[0039] Figure 6 schematically shows a view of the wrist joint of Figure 1 when in a rotated configuration;

[0040] Figure 7 schematically shows a cross-sectional view of the wrist joint of Figure 1 when in a straight configuration;

[0041] Figure 8 schematically shows a cross-sectional view of the wrist joint of Figure 1 when in a rotated configuration;

[0042] Figure 9 schematically shows a wrist joint according to another embodiment of the invention;

[0043] Figure 10 schematically shows a further view of the wrist joint of Figure 1 when in a straight configuration;

[0044] Figure 11 schematically shows a further cross-sectional view of the wrist joint of Figure 1 when in a straight configuration; and Figure 12 schematically shows a surgical instrument comprising the wrist joint of Figure 1.

[0045] Detailed Description

[0046] A surgical instrument may have a proximal end, a distal end, an end effector mounted at the distal end and at least one actuation tendon for actuating the end effector.

[0047] Figure 1 shows a wrist joint 100 which is suitable for forming part of such a surgical instrument. An example of such a surgical instrument is shown in Figure 11. In Figure 1, the wrist joint 100 is shown coupled to an end effector 102 having a first jaw 103 and a second jaw 104. The first jaw 103 is actuated by a first actuation tendon 108a and the second jaw 104 is actuated by a second actuation tendon 108b.

[0048] The wrist joint 100 comprises a proximal part 110 and a distal part 120 to which the end effector 102 is coupled. The proximal part 110 has a proximal rolling surface 112 wherein a first axis 114 extends through the proximal part 110. Similarly, the distal part 120 has a distal rolling surface 122 wherein a second axis 124 extends through the distal part 120. In this example, the first and second axes 114, 124 extend centrally with respect to the proximal and distal rolling surfaces 112, 122 respectively. The distal part 120 is rotatably coupled to the proximal part 110 such that the distal rolling surface 122 is able to roll against the proximal rolling surface 112 to provide wrist movement of the distal part 120 relative to the proximal part 110.

[0049] To assist with tracking the perspectives shown throughout the drawings, Figure 1 includes x-, y- and z- axes for reference. The axes are fixed relative to the orientation of the proximal part 110 of the wrist joint 100 throughout the various drawings. The x- and y-axes each extend laterally with respect to the proximal part 110, whereas the z-axis extends longitudinally. As a further point of reference, the first and second axes 114, 124 each extend parallel to the x-axis.

[0050] The proximal and distal rolling surfaces 112, 122 are shown more clearly in Figure 2. In this example, the proximal rolling surface 112 comprises a plurality of proximal gear teeth 116 extending radially from the first axis 114 and the distal rolling surface 122 comprises a plurality of distal gear teeth 126 extending radially from the second axis 124. The plurality of proximal gear teeth 116 and the plurality of distal gear teeth 126 engage with one another so that the distal rolling surface 122 is able to roll against the proximal rolling surface 112 without slipping. In other examples, the proximal and distal rolling surfaces may have different configurations to avoid slippage. For example, Figure 3 shows a wrist joint 200 comprising a proximal part 210 and a distal part 220 that include a proximal rolling surface 212 and a distal rolling surface 222 respectively. Rather than having gear teeth to avoid slippage, the wrist joint 200 comprises a pair of coupling tendons 216, 226 that extend along the rolling surfaces 212, 222, crossing between the rolling surfaces 212, 222 at a contact point between the two rolling surfaces 212, 222. Each coupling tendon 216, 226 is a fixed length and is fixed at one end to the proximal part 210 and at the other end to the distal part 220 so that the coupling tendon 216, 226 is taut. The tension in the two coupling tendons 216, 226 ensures that the rolling surfaces 212, 222 are only able to roll against one another rather than slip past one another.

[0051] Figure 4 shows a further example configuration of rolling surfaces. In particular, Figure 4 shows a wrist joint 300 comprising a proximal part 310 and a distal part 320 that include a proximal rolling surface 312 and a distal rolling surface 322 respectively. In this example, the wrist joint 300 comprises a single coupling tendon 316 fixed at one end to the proximal part 310 and at the other end to the distal part 320 wherein each of the fixed ends are arranged centrally relative to the rolling surfaces 312, 322. The single coupling tendon 316 may be elastic (i.e. resiliently extendable) and fixed to the proximal and distal parts 310, 320 so that it is always under tension, thereby biasing the proximal and distal parts 310, 320 towards one another. The tension in the coupling tendon 316 biases the gap between the fixed ends of the coupling tendon to be the smallest distance possible and thereby biases the proximal and distal rolling surfaces 312, 322 against slippage that would cause the distance between the fixed ends to increase.

[0052] Returning to Figure 1, the wrist joint 100 further comprises a proximal guiding assembly 130 having a proximal guiding surface 131 and mounted to the proximal part 110 such that the proximal guiding surface 131 is coaxial with the proximal rolling surface 112 along the first axis 112. The wrist joint 100 also comprises a distal guiding assembly 132 having a distal guiding surface 133 and mounted to the distal part 120 such that the distal guiding surface 133 is coaxial with the distal rolling surface 122 along the second axis 124. The proximal and distal guiding surfaces 131, 133 are configured to guide the actuation tendons 108a, 108b therebetween as they extend through the wrist joint 100 (from the proximal end to the end effector 102). In this example, a diameter of the proximal guiding surface 131 is equal to a pitch diameter of the proximal rolling surface 112. Similarly, a diameter of the distal guiding surface 133 is equal to a pitch diameter of the distal rolling surface 122.

[0053] Figures 5 and 6 show the wrist joint 100 from a perspective aligned with the x-axis. In other words, the first and second axes 114, 124 shown in Figure 1 are extending perpendicularly out of the page in Figures 5 and 6.

[0054] A central plane 101 is shown extending through the wrist joint 100 and the end effector 102. The central plane 101 extends along both the first axis 114 and the second axis 124 (shown in Figure 1). Arranging the first and second axes 114, 124 centrally and in sequence longitudinally contributes to a more compact overall construction of the wrist joint 100. In other words, it avoids components such as the proximal and distal guiding assemblies 130, 132 from protruding from the side of the wrist joint 100 and resulting in an unnecessarily large or bulky cross-section.

[0055] Figure 5 shows the wrist joint 100 in a straight configuration wherein the central plane 101 extends parallel to both the x-axis and the z-axis. As each actuation tendon 108a, 108b passes between the proximal and distal guiding assemblies 130, 132, it is essentially crossing from one side of the central plane 101 to the other. More particularly, as a result of the proximal and distal guiding surfaces 131, 133 being coaxial with the proximal and distal rolling surfaces 112, 122 respectively, each actuation tendon 108a, 108b is guided to cross the central plane 101 at the midpoint of the wrist joint 101. The midpoint is the point at which the proximal rolling surface 112 contacts the distal rolling surface 122.

[0056] Figure 6 shows the wrist joint 100 in a rotated configuration wherein the rotation results in the central plane 101 essentially folding along the first axis and the second axis so that the end effector 102 extends at an incline relative to the proximal part 110. The rotation of the wrist joint 100 causes the first actuation tendon 108a to be unwrapped from the proximal guiding assembly 130. However, as the first actuation tendon 108a unwraps from the proximal guiding assembly 130, it simultaneously wraps further around the distal guiding assembly 132. Conversely, the rotation of the wrist joint 100 causes the second actuation tendon 108b to wrap further around the proximal guiding assembly 130 while simultaneously unwrapping from the distal guiding assembly 132. The simultaneous wrapping and unwrapping of the actuation tendons 108a, 108b means that each actuation tendon 108a, 108b always crosses the central plane at the point at which the proximal rolling surface 112 contacts the distal rolling surface 122. By extension, the simultaneous wrapping and unwrapping of the actuation tendons 108a, 108b ensures that the length of actuation tendon 108a, 108b passing through the wrist joint remains constant irrespective of wrist movement.

[0057] Accordingly, actuation of the end effector 102 is decoupled from wrist movement, thereby eliminating crosstalk caused by wrist movement.

[0058] Figures 7 and 8 show cross-sectional views of the wrist joint 100 when in the same configurations shown in Figures 5 and 6 respectively. The cross-sectional views reveal the mechanism for driving wrist movement.

[0059] In this example, the wrist joint 100 comprises a drive disc 140 configured such that actuation of the drive disc 140 provides the wrist movement of the distal part 120 relative to the proximal part 110.

[0060] The drive disc 140 is mounted to the proximal part 110 and is rotatable about the first axis. The wrist joint 140 also further comprises a drive axle 142 mounted to the drive disc 142 along the second axis 124 (shown in Figure 1) and coupled to the distal part 120 such that rotation of the drive disc 140 causes the distal rolling surface 122 to roll against the proximal rolling surface 112 (as shown in Figures 5 and 6).

[0061] In this example, the drive disc 140 is substantially circular except for a protrusion where the drive axle 142 is mounted proximally to a peripheral edge of the drive disc 140. The drive axle 142 acts as the axle about which the distal part 120, distal rolling surface 122 and distal guiding assembly 132 rotates about. Accordingly, the drive axle 142 may be considered as defining the second axis 124.

[0062] The drive axle 142 may be rigidly fixed to the drive disc 140 and the distal part 120 may be rotatably mounted to the drive axle 142, or vice versa. Alternatively, the drive axle 142 may be rotatably mounted to the drive disc 140 and the distal part 120 may be rotatably mounted to the drive axle 142.

[0063] When the wrist joint 100 is in the straight configuration shown in Figure 7, the drive disc 140 is configured so that the drive axle 142 is aligned with the first axis 114 along a central axis of the proximal part 110. To provide wrist movement, the drive disc 140 may be rotated relative to the proximal part 110, as shown in Figure 8. Rotation of the drive disc 140 causes rotation of the drive axle 142, and therefore the second axis 124, about the first axis 114. Meanwhile, the proximal rolling surface 112 (shown in Figure 6) remains in a fixed position relative to the proximal part 110. Accordingly, the rotation of the drive disc 140 causes the distal rolling surface 122 to roll against the proximal rolling surface 112. As the distal rolling surface 122 is fixed to the distal part 120, the rolling action of the distal rolling surface 122 cases rotation of the distal part 120 relative to the proximal part 110.

[0064] Moreover, for each degree of rotation applied to the drive disc 140 about the first axis 114, additional rotation of the distal part 120 is exhibited about the second axis 124. In the example shown in Figure 6, the proximal and distal rolling surfaces 112, 122 share an equal diameter such that the distal part 120 rotates an additional degree for each degree that the drive disc 140 is rotated. The output rotation of the distal part 120 is therefore double the input rotation of the drive disc 140.

[0065] The use of the drive disc 140 and drive axle 142 therefore allows the wrist joint 100 to efficiently achieve high bending angles.

[0066] The drive disc 140 may be rotated by a variety of suitable means. In the example shown in Figures 7 and 8, the wrist joint 100 comprises a drive tendon 144 having a middle portion 146 coupled to the drive disc 140 and opposing first and second end portions 147, 148 extending towards the proximal end of the surgical instrument. The first end portion 147 may be pulled to rotate the drive disc 140 in a first sense to provide wrist movement in a first direction (as shown in Figure 8). Meanwhile, the second end portion 148 may be pulled to rotate the drive disc 140 in a second sense to provide wrist movement in a second direction opposite to the first direction.

[0067] The ratio of rotation of the distal part compared to the drive disc may be adjusted by adjusting the ratio between diameters of the proximal and distal rolling surfaces 112, 122.

[0068] Figure 9 shows a wrist joint 400 which differs from the wrist joint 100 shown in Figures 1, 2 and 5 to 8 in that the ratio between diameters of the proximal and distal rolling surfaces 412, 422 is not 1 : 1 as it is in the wrist joint 100. To simplify the drawing, the actuation tendons and the drive tendon are hidden. In this example, the diameter of the distal rolling surface 422 is larger than the diameter of the proximal rolling surface 412. More specifically, the pitch diameter of the distal rolling surface 422 is larger than the pitch diameter of the proximal rolling surface 412.

[0069] So that crosstalk is eliminated despite the varied sizes of the proximal and distal rolling surfaces 412, 422, the ratio between the diameter of the proximal guiding surface 431 and the pitch diameter of the proximal rolling surface 412 is equal to the ratio between the diameter of the distal guiding surface 433 and the pitch diameter of the distal rolling surface 422. In this example, the diameter of the proximal guiding surface 431 and the pitch diameter of the proximal rolling surface 412 are equal, such that their ratio is 1 : 1. Similarly, the diameter of the distal guiding surface 433 is equal to the pitch diameter of the distal rolling surface 422.

[0070] Figure 10 shows the wrist joint 100 in a straight configuration similar to Figure 5 except that the perspective has changed. Figure 10 shows a perspective aligned with the y- axis wherein the end effector 102 points to the right of the page rather than the top of the page. This means that the first and second axes 114, 124 extend vertically along the page.

[0071] A central plane 105 is shown extending through the wrist joint 100 and the end effector 102. Whereas the central plane 101 shown in Figure 5 extends along both the first axis 114 and the second axis 124, the central plane 105 shown in Figure 10 extends perpendicular to both the first axis 114 and the second axis 124.

[0072] In Figure 10, the distal part 120 is shown as comprising a body portion 150. Figure 11 shows the same view as Figure 10 except the body portion 150 has been removed so that the internal components are more readily visible.

[0073] With particular reference to Figure 11, the proximal guiding assembly 130 comprises a plurality of proximal pulleys 136 mounted to the proximal part 110 and rotatable about the first axis 114. Similarly, the distal guiding assembly 132 comprises a plurality of distal pulleys 138 mounted to the distal part and rotatable about the second axis 124. The proximal and distal pulleys 136, 138 are arranged symmetrically with respect to the central plane 105. The surfaces of the proximal and distal pulleys 136, 138 respectively provide the proximal and distal guiding surfaces 131, 133 described in reference to earlier figures.

[0074] In this example, the proximal guiding assembly 130 comprises four proximal pulleys 136 and the distal guiding assembly 132 comprises four distal pulleys 138. Figure 11 also more clearly shows how the first and second actuation tendons 108a, 108b are guided between the proximal and distal guiding assemblies 130, 132 by the pluralities of proximal and distal pulleys 136, 138. For example, one end of the first actuation tendon 108a extends through the proximal part 110 and between a first pair of proximal and distal pulleys 136, 138. A middle portion of the first actuation tendon 108a then wraps around the first jaw 103, to which it is coupled in order to actuate the jaw. The other end of the first actuation tendon 108a then extends between a second pair of proximal and distal pulleys 136, 138 located on the opposite side of the central plane 105 before extending back through the proximal part 110. The second actuation tendon 108b follows a corresponding route through respective pairs of proximal and distal pulleys 136, 138.

[0075] Lastly, Figure 12 shows the wrist joint 100 and end effector 102 coupled to an articulatable member 162 to form a surgical instrument 160 having a proximal end 164 and a distal end 166.

[0076] In this specification, example embodiments have been presented in terms of a selected set of details. However, a person of ordinary skill in the art would understand that many other example embodiments may be practiced which include a different selected set of these details. It is intended that the following claims cover all possible example embodiments.

Claims

CLAIMS1. A wrist joint for a surgical instrument having a proximal end, a distal end, an end effector mounted at the distal end and at least one actuation tendon for actuating the end effector, the wrist joint comprising: a proximal part having a proximal rolling surface, wherein a first axis extends through the proximal part; a distal part having a distal rolling surface, wherein a second axis extends through the distal part, the distal part being rotatably coupled to the proximal part such that the distal rolling surface is able to roll against the proximal rolling surface to provide wrist movement of the distal part relative to the proximal part; a proximal guiding assembly having a proximal guiding surface and mounted to the proximal part such that the proximal guiding surface is coaxial with the proximal rolling surface along the first axis; and a distal guiding assembly having a distal guiding surface and mounted to the distal part such that the distal guiding surface is coaxial with the distal rolling surface along the second axis, wherein the proximal and distal guiding surfaces are configured to guide the at least one actuation tendon therebetween as the at least one actuation tendon extends from the proximal end to the end effector, thereby decoupling actuation of the end effector from wrist movement.

2. The wrist joint of claim 1, further comprising a drive disc configured such that actuation of the drive disc provides the wrist movement of the distal part relative to the proximal part.

3. The wrist joint of claim 2, wherein the drive disc is mounted to the proximal part for rotation about the first axis; and wherein the wrist joint further comprises a drive axle mounted to the drive disc along the second axis and coupled to the distal part such that rotation of the drive disc causes the distal rolling surface to roll against the proximal rolling surface.

4. The wrist joint of claim 2 or claim 3, further comprising a drive tendon having a middle portion coupled to the drive disc and opposing end portions extending towards the proximal end of the surgical instrument, wherein a first end portion is able to be pulled to rotate the drive disc in a first sense to provide wrist movement in a first direction and a second end portion is able to be pulled to rotate the drive disc in a second sense to provide wrist movement in a second direction.

5. The wrist joint of any one of the preceding claims, wherein the ratio between a diameter of the proximal guiding surface and a diameter of the proximal rolling surface may be equal to a ratio between a diameter of the distal guiding surface and a diameter of the distal rolling surface.

6. The wrist joint of claim 5, wherein the proximal guiding surface and the proximal rolling surface share an equal diameter, and the distal guiding surface and the distal rolling surface share an equal diameter.

7. The wrist joint of any one of the preceding claims, wherein the proximal guiding assembly comprises at least one proximal pulley mounted to the proximal part and rotatable about the first axis; and wherein the distal guiding assembly comprises at least one distal pulley mounted to the distal part and rotatable about the second axis.

8. The wrist joint of claim 7, wherein the proximal guiding assembly comprises a plurality of proximal pulleys and the distal guiding assembly comprises a plurality of distal pulleys, and wherein plurality of proximal pulleys and the plurality of distal pulleys are arranged symmetrically with respect to a central plane of the surgical instrument, the central plane extending perpendicular to the first and second axes.

9. The wrist joint of any one of the preceding claims, wherein the proximal rolling surface comprises a plurality of proximal gear teeth extending radially from the first axis and the distal rolling surface comprises a plurality of distal gear teeth extending radially from the second axis, the plurality of proximal gear teeth and the plurality of distal gear teeth being engageable with one another such that the distal rolling surface is able to roll against the proximal rolling surface without slipping.

10. The wrist joint of claim 8, wherein the proximal rolling surface has a proximal pitch diameter equal to a diameter of the proximal guiding assembly and the distal rolling surface has a distal pitch diameter equal to a diameter of the distal guiding assembly.

11. A surgical instrument comprising: a proximal end and a distal end; an end effector mounted at the distal end; at least one actuation tendon for actuating the end effector;a wrist joint according to any one of the preceding claims positioned between the proximal end and the distal end, wherein the at least one actuation tendon extends between the first and second guiding assemblies.

12. The surgical instrument of claim 11, wherein the end effector comprises a first jaw rotatable about a first jaw axis extending perpendicularly to the first and second axes; and wherein the at least one actuation tendon comprises a first actuation tendon having a middle portion coupled to the first jaw and opposing end portions each passing between the proximal and distal guiding assemblies before extending towards the proximal end of the surgical instrument, the first actuation tendon being movable to rotate the first jaw.

13. The surgical instrument of claim 12, wherein the end effector comprises a second jaw rotatable about a second jaw axis extending perpendicularly to the first and second axes; and wherein the at least one actuation tendon comprises a second actuation tendon having a middle portion coupled to the second jaw and opposing end portions each passing between the proximal and distal guiding assemblies before extending towards the proximal end of the surgical instrument, the second actuation tendon being movable to rotate the second jaw.

14. The surgical instrument of claim 13, wherein the first and second jaws are rotatable independently of one another.

15. The surgical instrument of claim 13 or claim 14, wherein: the proximal guiding assembly comprises four proximal pulleys mounted to the proximal part and independently rotatable about the first axis; the distal guiding assembly comprises four distal pulleys mounted to the distal part and independently rotatable about the second axis; and each end portion of each of the first and second actuation tendons passes between a respective pair of proximal and distal pulleys.

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