WO2012010869A1

WO2012010869A1 - Handle and surgical instrument

Info

Publication number: WO2012010869A1
Application number: PCT/GB2011/051332
Authority: WO
Inventors: David Main; Peter Moran
Original assignee: Surgical Innovations Limited
Priority date: 2010-07-22
Filing date: 2011-07-15
Publication date: 2012-01-26
Also published as: GB201012278D0

Abstract

A handle for a surgical instrument is described comprising: a body member for attachment to an outer shaft of a surgical instrument; a rotatable member at least partially disposed within the body member for rotation about a longitudinal axis and comprising a first helical thread formed on an outer surface and a second helical thread; a translatable member for attachment to an inner shaft of a surgical instrument, adapted for movement along the longitudinal axis relative to the rotatable member and having a helical thread engaged with the second helical thread of the rotatable member; a shuttle member disposed around the rotatable member comprising a ratchet mechanism having a pawl for engaging the first helical thread; and an actuation member having a first end pivotally attached to the body member and a second end coupled to the shuttle member. This construction provides greater mechanical advantage and control over movement of the translatable member, and therefore the relative movement of an inner shaft of a surgical instrument attached to the handle.

Description

HANDLE AND SURGICAL INSTRUMENT

The present invention relates to a handle for a surgical instrument and a surgical instrument comprising the handle. In particular, the present invention relates to handles for endoscopic surgical instruments and those surgical instruments which include an operative portion which is actuated by moving one part relative to another.

In endoscopic surgical techniques, it is known to provide an instrument which comprises an operative portion at the distal end of an elongate shaft. One part of the operative portion is coupled to the elongate shaft and another part is coupled to a second shaft, typically disposed within the outer shaft. Relative movement of the two shafts results in movement of the outer portion. Examples of surgical instruments operated in this way include scissors and bisectors. This form of actuation is also used in surgical retractors for use in endoscopic or laparoscopic surgery.

In order to be inserted through as small an incision as possible, a retractor for endoscopic or laparoscopic surgery has two configurations: a first, low profile configuration for insertion into the body and a second, larger configuration for engaging the part of the anatomy which is to be retracted. One form of retractor suitable for endoscopic surgery is a segment string. In a segment string instrument, a chain of connected segments have a filament running through them. Drawing the filament proximally shortens the length of the filament and causes the segment string to bend into a retraction configuration.

Handles for use with endoscopic surgical instruments are known. However, in general such handles are typically provided in the form of a pistol grip or scissors, with movement of the pistol grip or scissors directly corresponding to movement of the shafts of the operative portion. This limits the range of movement available from the handle to a single stroke of the pistol grip or scissors. It limits the force that can be applied, because the required range of movement at the operative portion places a limit on the mechanical advantage that can be achieved through a single operation of the pistol grip or scissor handles. This can make existing handles difficult to use with tools such as segment strings, which may require a high force to be applied to move the two portions of the shaft relative to each other.

Handles for endoscopic devices and retractors which include ratchets are known, examples include US-5441044 and US-A-2005/0070764.

Both of these documents discuss providing a ratchet mechanism within a handle. The ratchet mechanism enables a return spring to control one portion of the movement of the operative portion, for example an opening or a closing stroke, with the other controlled by a user operating an actuator. However, such instruments can have problems when improved mechanical advantage is required, because an opening or closing stroke is still controlled by a single stroke of the actuator.

It would be desirable to provide a handle for a surgical instrument which allows more control over the movement of an operative part or end effector attached to it.

Accordingly, it is an object of the present invention to provide a handle for a surgical instrument which can provide a greater mechanical advantage and/or a more controlled use of an operative portion.

Accordingly, the present invention provides a handle including a rotatable member which is engaged by a shuttle member having a ratchet mechanism. The rotatable member has a helical thread formed on an outer surface which is engaged by the ratchet in the shuttle member. As the shuttle member moves back and forth over the thread, the pawl of the ratchet only engages in one direction, therefore ensuring that the rotatable member rotates in a single direction. The rotation of the rotatable member is converted into a linear motion by a translatable member which engages a screw thread driven by the rotatable member. Thus, improved control and mechanical advantage can be gained in the handle and multiple strokes of the actuation member can be used to continually advance or retract a portion of an attached surgical instrument. According to a first aspect of the present invention, there is provided a handle for a surgical instrument, the handle comprising a body member for attachment to an outer shaft of a surgical instrument; a rotatable member at least partially disposed within the body member for rotation about a longitudinal axis and comprising a first helical thread formed on an outer surface and a second helical thread; a translatable member for attachment to an inner shaft of a surgical instrument, adapted for movement along the longitudinal axis relative to the rotatable member and having a helical thread engaged with the second helical thread of the rotatable member; a shuttle member disposed around the rotatable member comprising a ratchet mechanism having a pawl for engaging the first helical thread; and an actuation member having a first end pivotally attached to the body member and a second end coupled to the shuttle member.

The pivotal motion of the actuating member relative to the body member is converted into rotation of the rotatable member by the engagement with the first helical thread through the shuttle member. In turn, this rotation of the rotatable member is converted into translation of the translatable member by the engagement of the second helical thread. The relative pitch of the first and second thread on the rotatable member can be chosen to determine the mechanical advantage of the handle.

The actuation member may be formed with indentations for receiving a user's digits. The second helical thread may be formed on an outer surface of the rotatable member, longitudinally displaced from the first helical thread. Alternatively the second helical thread may be formed in a bore within the rotatable member, coaxial with the longitudinal axis. In that case the corresponding thread of the rotatable member may be formed on an outer surface of the rotatable member.

While prior art surgical instruments have employed a ratchet to drive rotation of a member, the rotation of the member has always been used directly, for example in orthopaedic drills or drivers. Examples of such surgical drivers include US-5911722 and WO-A-97/24991. This is consistent with the general use of helical scroll mechanisms in tools which rotate a driven end, such as a screwdriver. However, the translatable member of the present invention enables the improved mechanical advantage and control from the rotatable drive to be used in instruments which require linear actuation.

Preferably, the first helical thread comprises a double helix and the shuttle member further comprises means for selecting which of the threads of the double helix is engaged by the pawl of the ratchet. This enables the direction of rotation of the rotatable member to be selected by the user, depending on which thread the pawl engages. Therefore, the user can provide controlled actuation in two directions. This is not possible in prior ratchet mechanisms for surgical retractors, such as US-5441044 and US-A-2005/0070764, both of which rely on a return spring for actuation in one direction.

Providing control over the operation in both directions is particularly advantageous when applied to retractors which comprise a segment string. The tension under which the inner member of the segment string must be placed can be significant. Even without a return spring, the natural elasticity of the material of the inner member, can release significant amounts of energy when tension is removed from the inner member. This may cause recoil of the instrument and consequent damage to the body cavity in which the instrument is deployed. This embodiment therefore enables controlled movement in both directions, for example to move a segment string retractor between deployed and undeployed configurations.

In one embodiment, the ratchet may have two pawls, each associated with one of the helixes of the double helix. By operating a switch a user can engage one of the pawls with one of the helixes and disengage the other of the pawls.

The apparatus may further comprise a second actuating member having a first end pivotally attached to the body member; wherein the first and second actuating members are disposed symmetrically about the longitudinal axis. In one embodiment the second actuation member may be attached to the body member at the same point as the first actuation member. This symmetrical configuration enables easy operation of the handle by squeezing. The symmetrical configuration means that the torque is applied equally at either side of the body member, reducing a tendency of the instrument to twist during the squeezing operation.

Advantageously, the actuating member may be arranged to be moved between a first position, in which its second end is a first distance away from the body member, and a second position, in which its second end is a second distance away from the body member, wherein the second distance is smaller than the first distance. The handle may further comprise a resilient member for biasing the actuating member towards the first position. In this configuration, the resilient member allows the handle to return automatically ready for another actuation by the user, enabling simpler use with one hand. The resilient member may be a spring, elastomer or any other elastically deformable element. In the second position the second distance may be zero, i.e. the handle may be directly adjacent or touching the body member in the second position. In one embodiment, the apparatus may comprise a latch member on the handle for holding the actuating member in the second position. This enables the handle to be held in a low profile configuration which can be advantageous in reducing the profile of the instrument. During endoscopic or laparoscopic surgical procedures many instruments are often operated within close proximity to each other. In these circumstances, the low profile configuration can make it easier to manipulate other instruments at the same time as the handle of the present invention. By holding the actuation member in the second position, the latch may also ensure that the relative positions of inner and outer shafts and hence the operative portion of the instrument is substantially locked.

The actuating member may be coupled to the shuttle member by a link member. This provides a simple method of transforming the pivotal motion of the actuation member to linear motion of the shuttle.

Preferably, the handle further comprises a clutch disposed between the rotatable member and the translational member. The clutch can limit the torque applied to the thread of the translatable member. The design of the present handle enables a significant mechanical advantage to be obtained. In turn, this makes it easier for a user to apply excessive force. A clutch may be provided to limit the force which can be applied, avoiding failure of instrument components due to excessive stress supplied by the handle. It can also provide tactile feedback to a surgeon when the end of the movement range of an operative portion of a surgical instrument attached to the handle has been reached.

In one embodiment, the handle further comprises a clutch disposed between the rotatable member and the translatable member for limiting the torque applied to the thread of the translatable member. This allows a low profile clutch mechanism to be provided which can easily be tailored to slip at a specific torque.

According to another aspect of the invention, there is provided a surgical instrument comprising an operative portion at a distal end; an outer shaft having a longitudinal bore extending from the operative portion in a proximal direction and attached to a first part of the operative portion; an inner member which is disposed within the longitudinal bore and attached to a second part of the operative portion; and a handle as discussed above.

In one embodiment, the operative portion may be a surgical retractor. However, the handle of the present invention can be used in combination with a variety of surgical instruments for use in endoscopic or laparoscopic surgery. Examples of such instruments include biopsy forceps, tissue graspers, surgical scissors, surgical snares and retrieval baskets, all of which may be moved between operative positions by controlling an attached handle to move portions of the instrument attached to an inner shaft relative to an outer shaft.

According to another aspect of the present invention, there is provided a surgical retractor comprising a handle as described above.

It will be appreciated that the handle of the present invention may be removable or permanently attached to the surgical instrument. Likewise, the handle and surgical instrument may be disposable or reusable.

The embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 depicts a handle according to the present invention attached to a segment string retractor;

Figure 2 depicts a plan view of a handle according to the present invention in a first position;

Figure 3 depicts the handle of Figure 2 in a second position with a latch engaged;

Figure 4 depicts a partial cross-section of the handle of Figure 1 so that its operation can be understood more clearly; and

Figure 5 depicts a cross-section along line A-A in Figure 4 showing a clutch mechanism.

Figure 1 depicts a perspective view of a handle 2, connected to a segment string retractor 4. The segment string retractor 4 comprises a plurality of segments which can pivot relative to one another which are attached to an outer shaft that extends proximally and is attached to a body member 6 of the handle 4. Within the segment string, an internal flexible member, such as a metal wire, extends and is attached to a translation member 9 of the handle 2 (the inner member or wire is not visible in Figure 1). The handle also comprises two actuation members 8 which are both pivotally attached to the body member 6 to pivot about the same point, symmetrically about a longitudinal axis. The handle members 8 are connected via link members 10 to a shuttle member 12. The shuttle member 12 is disposed within the body member 6. It comprises a ratchet mechanism (not visible) which engages a helical track formed on an outer surface of a rotatable member 14. The shuttle member 12 comprises a switch 16 which enables selection of which of the two helical tracks formed on the rotatable member 14 are engaged by the ratchet mechanism. Figure 3 depicts the handle in a closed configuration. The two actuation members 8 have been squeezed towards the body member 6. This moves linkage members 10 and pushes the shuttle member 12 in a proximal direction. The ratchet within the shuttle member 12 engages the helical track on the rotatable member 14 and causes it to rotate. The rotation of the rotatable member 14 is converted into a translation of translatable member 9.

Translatable member 9 is constrained against rotation by the engagement of ridges or fins 18 with corresponding slots in the body member. A threaded portion of translatable member 9 is engaged with a corresponding thread of the rotatable member 14, so that rotation of rotatable member 14 is transformed to translation of translatable member 9. The mechanical advantage of the handle is determined by the relative pitch of the helical track on the outer surface of the rotatable member 14 and the pitch of the threaded portion of the translatable member 9.

As shown in Figure 3, a latch 20 has been engaged to hold the two actuation members in the closed position. The actuation members 8 are held in this position by the engagement of projections 22 on the latch 20 with corresponding slots 24 in the actuation member (best seen in Figure 2).

Figure 4 depicts a cross-section in which the actuation members have been omitted to enable the construction of the handle to be understood more clearly. Figure 4 shows how the linkage members 10 are connected to the shuttle member 12 which is contained within the body member 6. The shuttle member 12 can move over the rotatable member 14. As the shuttle member moves in a proximal direction, towards translating member 9, its internal ratchet engages one of the helical tracks formed on rotatable member 14, rotating the member. The construction of shuttle member 12 and the ratchet which engages the helical member 14 is as known in the art for use with screwdrivers and other rotating instruments. For example, it may use the construction discussed in US patent 593,157 (Furbish) and described in relation to Figures 22-27 thereof. The content of US-593,157 is herein incorporated by reference for all purposes.

The rotational motion of the rotatable member 14 is transferred to the translating member 9 by a clutch mechanism. The clutch mechanism limits the torque which can be applied to the thread of the translatable member 9, thereby limiting the force which can be applied to an operative portion of an attached surgical instrument. For example, in a segment string retractor, the clutch limits the force which is applied to the inner member, limiting the tension of the retractor. The construction of the clutch mechanism is depicted in cross-section in Figure 5. The rotatable member 14 is engaged with an inner threaded section 26 by resiliency biased teeth, which engage corresponding profiles formed on inner threaded member 26. As depicted in Figure 5, the profile of the teeth 28 and the corresponding profile they engage, defines the maximum torque which will be transmitted in an anticlockwise direction. As the torque increases, the vertical component of the force exerted on the tooth 28 is increased until it is sufficient to push the tooth 28 out of engagement against the resilient biasing. Choice of the angle of the tooth and the force exerted by the resilient biasing enables determination of the torque at which the clutch slips. The tooth may be biased against the rotatable shaft 26 by any suitable means, such as a spring, elastomer or any other resilient element. Thus, the present invention provides a handle for a surgical instrument which allows control over actuation in a single direction with a single hand, allowing the use of multiple actuation strokes to further advance the operative portion of the surgical instrument.

In alternative embodiments, the handle may be removable for use with a variety of different surgical instruments. Likewise, in other embodiments, the selection switch 16 may be omitted and the helical thread on the rotatable member may be a single helical thread allowing actuation in a single direction. In that embodiment, the release in the other direction may be provided by a torsion spring or other mechanism to provide movement in the other direction.

Claims

1. A handle for a surgical instrument, the handle comprising:

a body member for attachment to an outer shaft of a surgical instrument;

a rotatable member at least partially disposed within the body member for rotation about a longitudinal axis and comprising a first helical thread formed on an outer surface and a second helical thread;

a translatable member for attachment to an inner shaft of a surgical instrument, adapted for movement along the longitudinal axis relative to the rotatable member and having a helical thread engaged with the second helical thread of the rotatable member; a shuttle member disposed around the rotatable member comprising a ratchet mechanism having a pawl for engaging the first helical thread; and

an actuation member having a first end pivotally attached to the body member and a second end coupled to the shuttle member.

2. A handle according to claim 1 , wherein the first helical thread comprises a double helix and the shuttle member further comprises means for selecting which of the threads of the double helix is engaged by the pawl of the ratchet.

3. A handle according to claim 1 or 2, further comprising a second actuating member having a first end pivotally attached to the body member; wherein the first and second actuating members are disposed symmetrically about the longitudinal axis.

4. A handle according to any one of the preceding claims wherein the actuating member is arranged to be moved between a first position, in which its second end is a first distance away from the body member, and a second position, in which its second end is a second distance away from the body member, wherein the second distance is smaller than the first distance; and wherein the handle further comprises a resilient member for biasing the actuating member towards the first position.

5. A handle according to claim 4, further comprising a latch member on the handle for holding the actuating member in the second position.

6. A handle according to any one of the preceding claims, wherein the second end of the actuating member is coupled to the shuttle member by a link member.

7. A handle according to any one of the preceding claims, further comprising a clutch disposed between the rotatable member and the translatable member for limiting the torque applied to the thread of the translatable member.

8. A handle according to claim 7, wherein the rotatable member further comprises: a second rotatable member coaxial with the longitudinal axis which defines the threaded bore on an inner surface and has an outer surface defining radial teeth; and

a radial member biased to engage the radial teeth;

wherein the angle of the radial teeth and the force at which the radial member is biased against the teeth determine the torque at which the clutch slips.

9. A surgical instrument comprising:

an operative portion at a distal end;

an outer shaft having a longitudinal bore extending from the operative portion in a proximal direction and attached to a first part of the operative portion;

an inner member which is disposed within the longitudinal bore and attached to a second part of the operative portion; and

a handle according to any one of the preceding claims.

10. A surgical instrument according to claim 9, wherein the operative portion is a retractor.

11. A surgical retractor comprising a handle according to any one of the preceding claims.