GB2509523A

GB2509523A - Surgical instrument with flexible members and a motor

Info

Publication number: GB2509523A
Application number: GB201300165A
Authority: GB
Inventors: Zahraee Ali Hassan; Stewart Maddison Fox; Anish Kumar Mampetta
Original assignee: INNOVATIONS Ltd M
Current assignee: INNOVATIONS Ltd M
Priority date: 2013-01-07
Filing date: 2013-01-07
Publication date: 2014-07-09
Also published as: GB201300165D0

Abstract

A surgical instrument is disclosed comprising a handle 7, a shaft 3 and a tool 1. A proximal flexible member 4 is located between the proximal end of the shaft and the handle 7 and a distal flexible member 2 is located between the shaft and the tool. An actuation member 8, such as cables, extends between the proximal and distal flexible members 4,2, such that bending of the proximal flexible member 4 causes a proportional bending of the distal flexible member 2. A motor (21, Figure 2b) is located in the handle 7 of the instrument and actuation of the motor (21) causes rotation of the tool 1. An embodiment is disclosed where the instrument is modular, comprising an instrument module, a handle module and an electronics module. Preferably the motor (21) is controlled by a switch 6 such as a bi-directional analogue switch and is an electric DC servomotor. The instrument may further comprise a control unit 9.

Description

DESCRIPTION

Background

Keyhole surgery including but not limited to endoscopic, laparoscopic, thoracoscopic and arthroscopic surgeries are carried out by inserting narrow tubular instruments into the surgical site though small incisions made on the skin. Visualisation of the surgical site is obtained by using a specialised narrow elongated camera, referred to as endoscope, laparoscope, thoracoscope or arthroscope respectively depending up on the application.

A typical keyhole surgical instrument consists of an elongated hollow shaft (a tube) with a tool on one end and a handle on the other end. Examples of the tools are scissors, forceps, grasper, needle holder, etc. The tool is actuated from the handle by means of trigger pivoted on the handle which is connected to the tool by means of an actuation element. Simpler tools such a scalpel, electro cautery hook and spatula do not require tool actuation.

The instrument is inserted into the body cavity through a narrow incision made on the skin. A port, which is a short hollow access tube, is placed at the incision to facilitate access. In the case of laparoscopic surgery, the port is also used to create a pneumatic seal so that the body cavity can be expanded by inserting pressurised gas (typically C02) to increase the working space for the surgeon.

The narrow incision (or the port) constraint the movement of the instrument and reduces the range of motion of the tool. Specifically, two translational motion of the tool is lost due to the constraint imposed by the port. This reduces the dexterity with which the surgeon can manipulate tissue making it difficult or even impossible to accomplish certain task which are otherwise easy to accomplish in open surgery. The difficulty level is particularly high for performing complicated tasks such as intracorporeal suturing, fine dissection, blunt dissection along a tissue plane, etc. The surgeon has to use considerable amount of upper limp arm motion during the surgery to compensate for the lost range of motion of the instrument. Often, surgeons have to take ergonomically unfavourable upper arm poses, such as extended upper arm for a considerable duration of time to accomplish the surgical task. This may cause symptoms of repeated strain injury (RSI) in surgeons over time. The occurrence of RSI is estimated to be considerably higher in keyhole surgeons compared to open surgeons.

Moreover, when two instruments are used collaboratively for tasks such as suturing, it is required that the ends of the instrument intersect at the work site -commonly referred as triangulation. In order to achieve triangulation, the surgeon has to use one arm in extended position to insert the instrument through a port at a relatively distant location to the first port.

The range of motion of the instrument tip can be increased by incorporating a wrist member near the instrument tip. This will make it easier to perform complicated tasks and easier to achieve triangulation. Ideally, the wrist member should provide the same range of motion as that of the surgeon's wrist to provide full dexterity. This corresponds to bending motion in three orthogonal axes which is commonly referred to as -Yaw, Pitch and Roll.

Prior art US patent 5,330,502 to William et al. describes an articulating instrument with one joint providing Yaw motion. US patent 2004/0260355 Al to Marcus Braun describes an articulating instrument which provides bending in one direction (Yaw) as well as rotation of the instrument tip (Roll). Having a flexible member near the instrument tip is an alternative to using articulating joints.

US patent 3,557,780 to Masaaki et al. describes the method of incorporating flexible joints controlled by mechanical cables in an endoscope. This technique has also been adapted to instruments since. In US patent 7,338,513 B2 to Woojin et al., the instrument incorporates a distal flexible member near the instrument tip which is controlled by another proximal flexible member on the handle. Actuation cables extend between the distal and proximal flexible members to transfer bending. This allows bending in two direction (Yaw and Pitch) giving motion similar to a wrist. It also allows transferring a rotation applied on the proximal bending element to corresponding rotation of the instrument tip (Roll). US patent 2006/0201130 Al to David Danitz describes a similar device with flexible element consisting of plurality of links connected together and controlled by mechanical cabling. However no explicit means of tool rotation is provided.

As more joints are added to the tip of the instrument, it adds the burden of controlling these additional joints. Hence while additional joints increase the range of motion, it can make the instrument difficult to use. This is seen in aforementioned prior art 7,338,513 B2 (to Woojin et al.) where the user has to manually control two bending and one rotation. This can be quite a burden since force has to be applied through the fingers for rotating the tool while maintaining steady orientation of the handle with respect to the instrument axis. Moreover, the proximal flexible member is free to rotate with respect to the handle unless held in position by using the fingers.

Hence continuous force has to be applied to keep the proximal flexible member stationary with respect to the handle when rotation of the tool is not intended.

A subsequent prior art US 2008/0255420 Al to the same inventors provides an embodiment in which the position of the flexure mechanism can be locked to hold orientation, while rotation can be provided by means of a sliding switch that can be controlled by the thumb. Again, this adds additional control means that may cause difficulty in using the device.

Prior art is available that addresses this problem by incorporating motorised joints. Motorised joints can be controlled with very little physical effort from the user. It can also hold the position without the need for additional locking mechanism, further simplifying the use of the device. Patent EP 1915 967 Al describes such a device. Kyrnerax from Tumero, Japan (htt J±www.ki'merax.coml, website accessed on 15/11/2012) and JAiMY from EndoControl, France (httD:!iwww.endocontrol medicaLcorn/iaimyøhn. web site accessed on 15/11/2012) are examples of commercial devices in the market. However, adding motors tends to increase the complexity, size and weight of the device.

The additional weight can cause fatigue to the surgeon while the large handle size may cause collision with other instruments in adjacent ports. Moreover, having a large number of motions being controlled though switches renders the instrument non-intuitive to control. Hence these devices generally limit to two additional degrees of freedom -namely Yaw and Roll; which is functionally less than the three degrees of freedom offered by competing manual instruments.

Hence the need for a handheld instrument that has sufficient range of motion, that is easy to use, intuitive to control, light weight and that is not excessively complex still exists.

Summary of the Invention

Accordingly, an object of the innovation is to provide an instrument with three additional degrees of motion at the tool end of the instrument. Another object of the innovation is that the additional degrees of motion are easy and intuitive to control. Yet another object of the innovation is to provide the additional range of motion without considerable increase in size, weight and complexity of the instrument.

The additional degrees of motion are achieved by incorporating a wrist mechanism formed from a distal flexible member located between the distal end of the instrument shaft and the tool. The flexible member is constructed such that it has low stiffness in bending and relatively high stiffness in torsion. The yaw and pitch motions of the tool are achieved by bending the flexible member with respect to the instrument shaft. The bending of the distal flexible member is controlled from a proximal flexible member located between the proximal end of the instrument shaft and the handle of the instrument. A plurality of symmetrically placed constant length, flexible, actuator cables connect the distal and proximal flexible member such that a bending of the proximal flexible member with respect to the instrument shaft will causes a corresponding bending of the distal flexible member.

The roll of the tool is achieved by rotating the proximal end of the proximal flexible member with respect to the instrument handle using actuation provided by an electric motor incorporated inside the handle. Because of the high torsional stiffness of the flexible members, any roll of the proximal flexible member will be transferred in entirety to the instrument shaft, which in turn is transferred in entirety to the tool through the distal flexible member. The arrangement of constant length actuation cables between the proximal and distal flexible member is such that the orientation of the tool remains fixed with respect to the orientation of the handle even when the tool is in roll.

In addition to the yaw, pitch and roll motion provided by the wrist, the tool can be actuated manually from the handle of the instrument using a trigger hinged on the handle. A flexible constant length tool actuation cable extends from the tool to the handle, passing through a cavity along the axis of the distal flexible member, along the axis of the shaft and though a cavity along the axis of the proximal flexible member to connect to the tool actuation trigger on the handle.

Summary of the drawings

FIG 1 shows the isometric view of the instrument with the wrist in bent orientation.

FIG 2a shows the breakout section view of the side of the instrument showing the internal features of the handle. FIG 2b shows the detail of the pusher mechanism. FIG 2c shows the breakout view of the instrument from the top.

FigS shows the isometric view of the instrument showing motion relationship between various members of the instrument.

Fig 4a, 4b, and 4c show the side view of the instrument with the wrist bent down, wrist straight and wrist bent up orientations and the respective positions of the handle.

FIG Sa & 5b shows the actuator cable routing arrangement though the flexible members.

FIG 6a & 6b show the details of a second embodiment with flexure mechanism made from live hinges.

FIG 7a & 7b shows the third embodiment with detachable electronics module.

FIG 8a shows the internal details of the electronics module.

FIG 9 shows the internal details of the handle used in the third embodiment.

FIG ba & lob shows the fourth embodiment consisting of detachable instrument module and handle module.

FIG lb shows the cross section of the fourth embodiment showing the coupling mechanism used to couple the instrument module to the handle module.

FIG 12a & 12b shows the fifth, fully modular embodiment of the instrument consisting of detachable instrument module, handle module and electronics module.

Detailed Description

FIG 1 illustrates the basic embodiment of the instrument. It consists of a handle (7), a proximal flexible member (4), an elongated hollow shaft (3), a distal flexible member (2) and a tool (1). The rotation of the tool is controlled by a switch (6) located on the top of the handle. The switch is analog and bi-directional to control the speed and direction of rotation of the motor. The motor is powered and controlled by an external control unit (9). The motor and the control switch (6) are connected to the external control unit (9) by means of a flexible electric cable assembly (8). The tool (1) is actuated manually by using the trigger (5) hinged to the underside of the handle.

FIG 2a, 2b and 2c show the internal details of the handle. The motor unit (21) comprises of an electric geared dc servo motor with a rotary magnetic encoder to sense the direction and speed of rotation. An external control unit (9, Fig 1) is used to achieve closed loop speed control of the motor.

The motor unit (21) is connected to a hollow axle (22). A carriage block (23) is free to slide on the hollow axle. A flexible actuation cable (25) that passes through a conduit along the axis of the instrument links the tool (1) to the pin (24) on the carriage block. The carriage block is coupled to the pusher (26) by means of a spring (27). The pusher is enclosed in a pusher case (28) along with the roller bearing. The pusher case translates along the hollow axle while the pusher can translate and rotate on the shaft. The connecting rod (29) connects the trigger (5) to the pusher to complete the tool actuation mechanism.

The proximal end of the proximal flexible member is connected to the handle though a bearing block (30) consisting of two rotary bearings such that the proximal flexible member can rotate relative to the handle. The bearing block is hollow along the axis to let the tool actuation cable pass through.

The distal bearing flange (31) receives the proximal flange (32) of the proximal flexible member (4).

The proximal bearing flange (33) of the bearing block is connected to the hollow axle (22). The hollow axle is in turn connected to the motor (21) to complete the tool rotation mechanism.

FIG 3 shows the motion relationship between the various components of the instrument. The instrument is fully restrained when held by the handle and inserted through the access port (8) into the body cavity. Al and Bl represent the mutually orthogonal bending motions of the handle relative to the axis of the shaft (3). This motion causes proportional movements AZ and B2 respectively at the tool, relative to the shaft. The motion is effected by means of constant length flexible actuator cables that extend between specific locations of the distal flexible member and the proximal flexible members. The cables can be arranged such that a bending of the handle will cause a similar bending of the wrist or such that it will cause a bending in the opposite direction.

The tool can be rotated (rolled) by either actuating the motor by means of the switch (6) or by rolling the handle along the axis of the handle. Rolling of the handle will roll the tool because when the motor is not actuated it will lock the relative motion between the proximal flexible member and the handle. Hence the rotation at the tool (C2) is the superposition of the rotary actuation provided by the motor (Cm) and that of the rotation provided manually by rolling the handle (Ch).

It should be noted that the manual rotation of the tool by rotating the handle will only be used for imparting fine rotation. The bulk of the rotation of the tool will be executed by using the rotation provided by the motor. The motorised motion enables the surgeon to quickly and precisely control the rotation of the tool without extensive use of surgeon's arm rotation, providing better ergonomics.

The manual actuation Dl provided at the trigger (5) will cause the actuation (D2) of the tool.

FIG 4a, 4b and 4c show the side view of the instrument in the neutral, extended up and extended down poses.

FIG 5a shows the details of the distal flexible member used in this embodiment. It consists of five independent links (51,52 and 53), each coupled to the adjacent link in a chain, thus forming a hinge.

Two of similar links 51 and two of similar links 52 and one of link 53 form the distal flexible member.

The links are held in contact due to the tension in the four pairs of actuation cables (54a, 54b, 54c & 54d) displaced at 90 degree orientation. The paired cable that passes near the hinge contact provides torsional stiffness to the flexure mechanism by virtue of the sheering strength of the cable.

The tool actuation cable (25) used to actuate the tool passes through a tight fitting conduit along the axis of the flexible member.

FIG 5b shows the details of the proximal flexible member used in this embodiment. It consists of three independent links (two of 55, and one of 56) each coupled to the adjacent link thus forming two orthogonal hinges. The links are held in contact due to the tension in the four pairs of actuation cable (54a, 54b, 54c & 54d) that originates from the distal flexible member. The rotary stiffness of the member is provided by interconnecting links (57) on the side of the main links. Each main link is connected by means of a pair of interconnecting links (57) displaced at 180 degrees. A router link (58) is provided at the distal end of the flexible member to connect to the proximal end of the shaft.

FIG 6a, 6b & Gc show the second embodiment of the instrument. In this embodiment the proximal flexible member (62) and distal flexible member (61) are made of single links incorporating a series of orthogonally oriented live hinges. Four pairs of cables (63a, 63b, 63c, 63d), separated by 90 degrees originates at the distal flexible member and terminate at the proximal flexible member. The tool actuation cable (64) passes through along the axis of the flexible members and the shaft. The cable arrangement is similar to that used in embodiment one.

Since the instrument incorporates relatively expensive motors and sensors, the cost of the instrument is considerably higher than a comparable manual instrument. It is desirable to re-use the instrument to bring down the cost. To enable this, the instrument has to be capable of being re-sterilised after each use. However, having electronics components inside the instrument may pose challenges with re-sterilisation.

FIG 7a shows the third embodiment in which the electronic components of the instrument can be detached from the handle to make the rest of the instrument re-sterilizable. Additionally, in this embodiment the motor is powered by an on board battery and controlled by an on board controller making the instrument fully self-contained. All the electronic hardware including the motor, gearbox, the rotary magnetic encoder, the analog switch used to actuate the motor, the motion controller hardware and the battery is packed into a single electronics module (71) that fits detachably inside the handle. The electronics module (71) is inserted into the handle by opening the flip cap (72) located on the back side of the handle. FIG 7b shows the location of the electronics module inside the handle.

FIG 8a & 8b shows the details of the electronics module. The motor interface (81) is a tapered hexagonal shaft that couples to a receiving socket inside the handle to transfer actuation to the hollow axle (95, Fig 9). The motor assembly consists of the motor (83), gearbox (85) and rotary magnetic encoder (84). The switch (86) is connected to a switch interface (82) which is formed by a tapered hexagonal socket that couples to the switch rod (94, Fig 9). The electronics module also carries the motor controller (88) and the battery pack (87). The battery is charged after each use via the battery terminals (89) on the back side of the instrument by inserting the unit into a charging station (not shown in the figure).

FIG 9 shows the handle assembly with the covers removed to expose the mechanism used to activate the switch. In this embodiment the switch is located inside the electronics module and hence the motion applied on the top of the handle has to be transferred into the electronics module. The input tab (91) is connected to a sector gear (92) which transfers the input to the spur gear (93) on the switch rod (94). The terminal of the switch shaft is a tapered hexagonal feature that couples to the switch interface (82).

The hollow axle (95) couples to the motor interface (81) of the electronics module to transfer the actuation of the motor to the output flange of the handle. The tool actuation trigger mechanism is similar to the mechanism described in the previous embodiment.

Though re-use through re-sterilisation reduces the cost, it presents the risk of infection due to insufficient decontamination. Due to the complicated features of the distal flexible member and the presence of moving cables inside, special care has to be taken during cleaning and re-sterilisation of the instrument. Hence it is desirable to have the part of the instrument that comes into direct contact with tissue to be disposed of after each use.

FIG iDa & lob show the fourth embodiment of the device where the device consists of two detachable modules-the instrument module (100) and the handle module (108). The instrument module consists of tool (101), distal flexible member (102), the instrument shaft (103) and the proximal flexible member (104). Flexible cable assembly (109) connects the distal and proximal flexible members as in previous embodiments. A flexible tool actuation cable (not shown in figure) terminates in the tool actuation coupler (110, FIG 11). The back-end of the proximal flexible member has a thread feature (105) that is used to couple the instrument module to the handle module. FIG lob shows the device in the coupled mode ready for use.

Figure 11 shows the cross section view of the instrument showing the detail of the dual coupling mechanisms used to independently couple the tool actuation and the instrument module to the handle module. The tool actuation coupler (110)15 a threaded stud that is coupled to the receiver (111) to link the trigger (5) to the tool. The coupler nut (104) is then used to couple the proximal flexible member to the handle output flange (112) of the handle module using the thread feature (105).

The various features discussed in the previous embodiments come together in a final fifth embodiment shown in FIG lZa & 12b. In this embodiment, the device is made of three detachable modules that will come together to form the instrument. The modules are: the instrument module (100), the handle module (120) and the electronics module (71). The instrument module (100) couples to the handle module (120) as described in em bodiment four. The electronics module (71) fits into the back end of the handle module (120) as described in embodiment three.

This arrangement enables the re-use of the handle module and electronics module while the instrument module, which is most contaminated during use, to be discarded of after each use. The handle module is intended to be re-sterilised after each use; the electronics module is intended to be re-charged after each use; the instrument module is intended to be single use and disposable.

This arrangement enables to bring down the overall cost of the instrument while considerably reducing the risk of infection due to insufficient sterilisation.

Claims

CLAIMS1. A surgical instrument comprising: a distal flexible member located between the distal end of the shaft and the tool of the instrument; a proximal flexible member located between the proximal end of the said shaft and the handle of the instrument; actuation means extending between the said distal flexible member and the said proximal flexible member such that bending of the proximal flexible member will cause a proportional bending of the distal flexible member; a motor located in the handle of the instrument such that the actuation of the motor causes rotation of the said tool.
2. The surgical instrument of Claim 1 wherein the tool can be actuated from the said handle by means of a trigger hinged on the handle.
3. The surgical instrument of Claim 1 wherein the said motor consists of an electric DC servo motor unit comprising of a dc motor, a gearbox and a rotary encoder.
4. The surgical instrument of Claim 1 wherein the said motor is controlled by means of a switch located on the handle of the instrument.
5. The switch in claim 4 consisting of a bi-directional analog switch to control the speed and direction of rotation of the said motor.
6. The instrument of Claim 1 wherein the motor prevents relative rotation between the said proximal flexible member and the said handle when the motor is not actuated.
7. The instrument of Claim 1 wherein the power required to operate the motor is provided by a control unit that is located separate from the instrument and connect to by means of an electric cable assembly.
8. The instrument of Claim 1 wherein the electronic hardware required for closed loop speed control of the motor is provided by a control unit that is located separate from the instrument and connected to it by means of an electric cable assembly.
9. The instrument of Claim 1 wherein the electric power required to power the motor is supplied by a battery placed within the handle of the instrument.
10. The instrument of Claim 1 wherein the electronic hardware required for closed loop speed control of the motor is located within the handle of the instrument.
11. The instrument of Claim 1 wherein the said motor unit, the said switch, the electrical hardware required to control the motor and a battery unit for powering the motor is integrated into a single electronics module that can be detached from the instrument.
12. A modular surgical instrument comprising of: a. An instrument module comprising of a shaft; a tool; a distal flexible member located between the tool and the distal end of the shaft; and a proximal flexible member connected to the proximal end of the shaft; actuation means extending between the said distal flexible member and the said proximal member such that a bending of the proximal flexible member will cause a proportional bending of the distal flexible member.b. A handle module that can couple to the proximal flexible member of the said instrument module and incorporating a motor unit such that actuating the motor will rotate the instrument module with respect to the handle module.
13. The instrument module in Claim 12 wherein a tool actuation coupler on the instrument module couples to a receiving member on the handle module to enable tool actuation from the handle module.
14. The surgical instrument in Claim 12, wherein the said motor unit, the switch required to actuate the motor, the electrical hardware required to control the motor unit and the battery required to power the motor unit are integrated into a single electronics module that is placed detachably in the handle module.
15. A modular surgical instrument comprising of: a. An instrument module comprising of a shaft; a tool; a distal flexible member located between the tool and the distal end of the shaft; and a proximal flexible member connected to the proximal end of the shaft; and actuation means extended between the said distal flexible member and the said proximal member such that a bending of the proximal flexible member will cause a proportional bending of the distal flexible member.b. A handle module that can couple to the said instrument module.c. An electronics module that couples to the handle module and incorporating a motor.
16. The surgical instrument in Claim 15, wherein actuating the motor incorporated inside the electronics module will rotate the instrument module with respect to the handle module.
17. The surgical instrument in Claim 15, wherein the electronics module incorporate a battery pack to power the motor.