Patent Description:
It is of importance to apply an appropriate force to the first and the second jaw element such that tissue is manipulated with a suitable manipulation force. This force should not be too low to prevent that tissue is inadvertently released from the forceps, but also not too high to avoid damage of the tissue. Therefore, it is also of importance to provide accurate feedback of the applied force to the trigger device such that a surgeon can feel the actually applied force, or a force representative for this applied force.

An embodiment of an instrument for minimally invasive surgery is known from <CIT>. In the known embodiment of a surgical instrument the force exerted on the forceps by a surgeon is measured by a force sensor arranged on a jaw of the forceps and is fed back to the surgeon via a control unit. In this way the surgeon is provided with a better feeling of the applied force. The force sensor may for example be an optical sensor connected by means of an optical fibre to a suitable control unit.

<CIT> discloses a surgical instrument comprising a forceps construction in which force sensors are arranged on the forceps frame, instead of on the jaw elements, to determine the force applied on the first and second jaw elements.

<CIT> discloses ophthalmic surgical forceps having fiber bragg gratings as axial and lateral strain sensors. Further instruments for minimally invasive surgery are disclosed in <CIT> and <CIT>.

The forceps construction of <CIT> comprises:
a forceps frame having a distal end, the distal end comprising a first extension and a second extension, the first extension and the second extension of extending in distal direction from a main part of the forceps frame. The first extension and the second extension extend in parallel in the distal direction with a slot, slit or gap between the first extension and the second extension.

A first jaw element is rotatably mounted on the first extension and a second jaw element is rotatably mounted on the second extension. An actuation assembly connected to the first jaw element and the second jaw element is provided to rotate the first jaw element and the second jaw element with respect to the forceps frame.

The presence of the slit, slot or gap results in bending of the first extension and the second extension when a force is exerted on the first jaw element and/or the second jaw element. Thus, by measuring this bending of the first extension and/or the second extension, the force exerted on the first jaw element and/or second jaw element may be measured.

For this reason, a strain sensor is mounted at or near the end of the slit between the first extension and the second extension. However, at this location also other forces are present in the forceps frame, such as pulling or pushing forces in the forceps frame resulting from operating the first and second jaw elements. These other forces will also be measured by the strain sensor, and the force exerted on the first and/or second jaw element cannot reliably be determined on the basis of the force determined by the strain sensor at this location. Therefore, <CIT> proposes to mount a second strain sensor on the forceps frame on a location spaced from the slit between the first extension and the second extension. This location is selected such that the strain resulting from bending of the first extension and the second extension is not measured by the second strain sensor, but the other forces in the forceps frame are measured by the second strain sensor. A further strain sensor may be provided to determine temperature effects on the measurements.

By comparison of the measurement results of the first strain sensor and the second strain sensor, the strain resulting from bending of the first extension and/or the second extension may be determined. On the basis thereof, the force exerted on the first jaw element and/or the second jaw element may be calculated.

It is a drawback of the surgical instrument of <CIT> that multiple, at least three strain sensors are required to determine the force that is exerted on the first jaw element and/or the second jaw element of the forceps construction. This results in a relatively complex measuring system and requires an additional calculation effort, i.e. processing time, to determine the force that is exerted on the first jaw element and/or second jaw element.

It is an object of an aspect of the disclosure to provide a forceps construction, in particular a forceps construction for a surgical instrument to be used in minimally invasive surgery, wherein the force exerted on the first and/or second jaw element can be determined with a high degree of accuracy, or at least to provide an alternative forceps construction.

In an embodiment, the disclosure provides a forceps construction.

In the forceps construction of this aspect of the disclosure a strain element is provided between the first extension and the second extension. This strain element is fixed at its proximal end to the forceps frame and at its distal end to the proximal ends of the first distal extension part and the second distal extension part. This strain element is provided as a basis to mount a strain sensor.

Bending of the first extension and/or second extension due to forces being exerted on the first jaw element and/or second jaw element will result in elongation of the strain element. This elongation may be measured by the strain sensor mounted on or in the strain element.

Other forces exerted on the forceps frame, such as pulling or pushing forces resulting from actuating movement of the first and second jaw element will be transmitted through the first extension and the second extension, but these forces will substantially not be transmitted through the strain element. As a result, there is no need for an additional sensor to measure these forces separately and subsequently correct the measurement of the first strain sensor for these other forces. In other words, the strain element is mechanically substantially isolated from other forces, such as pulling or pushing forces, in the forceps frame, and will therefore substantially only measure the strain resulting from bending of the first extension and/or second extension. On the basis of this measured strain, the forces exerted on the first jaw element and/or the second jaw element may relatively easily be calculated.

The first extension comprises a first bridge element between the first distal extension part and the first proximal extension part, wherein the first bridge element is designed to facilitate bending of the first extension when a force is exerted on the first jaw element, and the second extension comprises a second bridge element between the second distal extension part and the second proximal extension part, wherein the second bridge element is designed to facilitate bending of the second extension when a force is exerted on the second jaw element.

To improve the measurement results it is advantageous that the first extension and the second extension relatively easily deform, e.g. bend, at a desired location. To facilitate bending of the first extension a first bridge element is arranged between the first distal extension part and the first proximal extension part. This first bridge element is designed such that the first extension will mainly bend at the first bridge element when a force is exerted on the first jaw element. The bridge element may for example have a smaller cross section than the cross section of the first distal extension part and the first proximal extension part to facilitate bending of the first extension at the first bridge element. Correspondingly, a second bridge element is arranged between the second distal extension part and the second proximal extension part to facilitate bending of the second extension.

In an embodiment, the strain element is an elongated element. An elongated strain element provides a suitable shape for mounting a strain sensor to measure strain of the strain element.

In an embodiment, a cross section of the strain element is small compared with the cross section of the first bridge element and the second bridge element. By giving the strain element a relatively small cross section, it may further be prevented, or at least minimized, that pulling or pushing forces in the forceps frame will be transmitted through the strain element.

In an embodiment, the strain sensor is a Fibre Bragg Grating (hereinafter also FBG), or multiple FBG's, arranged in an optical fibre that is fixed on or in the strain element. It is found to be advantageous to use FBG sensors. An example of the FBG sensor is described in <CIT> and will not be explained here in detail. An application of the FBG sensors as strain sensor is advantageous because a wavelength shift is proportional to a degree of strain, which is independent of any loss in the signal intensity thereby improving accuracy of force measurement. Furthermore, a FBG does not use any electrical signals near the sensitive measurement area. This is especially important in minimally invasive surgery instruments, which tend to include high voltage and high frequency electrical signals for surgical purposes, such as cutting.

In an embodiment, the optical fibre with the FBG is fixed in a hollow space in the strain element. In an alternative embodiment the optical fibre with the FBG may be fixed at any other suitable position on or in the strain element.

In an embodiment, the main part comprises in proximal direction from the strain element a hollow channel in which the optical fibre is arranged. From the strain element, the optical fibre comprising the Fibre Bragg Grating runs towards the proximal end of the forceps construction. By providing a hollow channel in the main part of the forceps frame, the optical fibre may run through the frame where it is protected from external influences.

In an embodiment, the optical fibre comprises a second Fibre Bragg Grating (FBG) arranged in the hollow channel to determine temperature effects. FBG sensors are sensitive for temperature differences. By providing a second FBG at a location relatively close to the first FBG, but where it will not measure any forces exerted on the forceps frame, it will only measure strain differences due to temperature effects. These measured strain differences can be used to compensate the measurements of the FBG fixed to the strain element for temperature effects.

In an embodiment, bending of the first extension with respect to the second extension is mechanically limited. Although elastic deformation due to bending of the first extension and the second extension is used to determine the forces exerted on the first jaw element and/or the second jaw element, it is desirable that the bending of the first extension and the second extension remains below certain maximum bending limits. In particular, it is undesirable that plastic deformation occurs in the first and/or second extension as a result of the bending of the first extension and second extension. To prevent that deformation beyond the maximum yield limits may occur, the bending range of the first extension and the second extension is limited by mechanical limiters, for example stop elements.

In such embodiment, the first extension may comprise a first bulge and the second extension may comprise a second bulge, wherein the first bulge and the second bulge have interlocking shapes to mechanically limit the bending of the first extension with respect to the second extension.

The forceps construction may be applied in any suitable device or instrument, in which accurate force feedback of the force exerted on the first jaw element and/or the second jaw element is required. The forceps construction is in particular suitable to be applied in a surgical instrument, for example for minimally invasive surgery.

There is provided a surgical instrument, for example for minimally invasive surgery, comprising:.

In an embodiment, the strain sensor is a Fibre Bragg Grating provided in an optical fibre.

In an embodiment, the surgical instrument comprises an interrogator device to interrogate the Fibre Bragg Grating. The interrogator device may be integrated in a handheld surgical instrument, but may also be arranged in a separate housing that can be arranged in a stationary location, whereby other parts of the surgical instrument such as the elongate frame, trigger device, actuation rod, actuator and the forceps construction are provided as a handheld device. In another embodiment, the surgical instrument may also be integrated in a surgical robot.

In an embodiment, the surgical instrument comprises a controller wherein the controller is arranged to control the actuator on the basis of the sensor signal. The controller may be part of a handheld surgical instrument or device, but may in another embodiment be provided at another location, for example in a separate housing and/or integrated with the interrogator device.

The invention relates to a surgical instrument, for example a surgical instrument for minimally invasive surgery, comprising:.

To allow different rotational positions of the at least one jaw element with respect to the handle part of the surgical instrument, the shaft may be rotatably mounted, about its longitudinal axis on the handle part of the surgical instrument. A rotatable connection device may be provided between the handle part and the shaft to allow this rotation of the shaft with respect to the handle part. By rotation of the shaft, the position of the at least one jaw element with respect to the shaft may be adapted. This rotation of the shaft can for example be a manual rotation. A rotation knob rotatably fixed on the shaft, may be provided to carry out the manual rotation of the shaft.

The rotation of the shaft about its longitudinal axis may for example be in the range of <NUM> degrees to <NUM> degrees, for example in the range of <NUM> degrees to <NUM> degrees in both rotation directions from a middle rotation position of the shaft.

When the sensor comprises an optical fibre, for example in case of a Fibre Bragg Grating, the optical fibre may run through both the handle part and the shaft. Such optical fibre has to be able to follow rotation of the shaft with respect to the handle part, i.e. rotation of the shaft with respect to the handle part should not result in damage and/or performance loss of the optical fibre. When the optical fibre is arranged on the axis of rotation of the shaft, the optical fibre should be able to torque or twist about its longitudinal axis to follow the rotation of the shaft. An optical fibre will easily damage when the optical fibre is subject to such torque. Moreover, it is desirable to arrange the actuation rod on the axis of rotation.

When the optical fibre is arranged at a distance from the axis of rotation, rotation of the shaft will lead to a difference in length of the path of the optical fibre in the handle part and/or the shaft. The optical fibre should be arranged in surgical instrument such that the surgical instrument allows this change in path length of the optical fibre.

Furthermore, it should be avoided that the bending radius of the optical fibre becomes too small as a bend below a minimum fibre bending radius may have a negative effect on the optical performance of the optical fibre. For example, the bending radius of an embodiment of a typical optical fibre, for example having a diameter of <NUM>, suitable for use in a surgical instrument, should not be lower than <NUM>.

To facilitate rotation of the shaft without increased risk on damage of the optical fibre, the surgical instrument may comprise a fibre guide to guide the optical fibre in a substantially helix shaped path concentric with the longitudinal axis of the shaft. This fibre guide ensures that the change in path length can be accommodated by allowing the diameter of the loops of the optical fibre in the helix shape to increase or decrease in dependence of the rotation of the shaft with respect to the handle part. At the same time, the fibre guide ensures that the bending radius of the optical fibre will not come below a minimal bending radius. This minimal bending radius should be selected such that the optical fibre will have sufficient optical performance for the sensor measurement with the optical fibre.

The fibre guide may be formed as an element with an outer cylindrical surface, wherein the outer cylindrical surface comprises a helical groove to guide the optical fibre. The helical groove comprises a bottom surface defining the minimum bending radius of the optical fibre guided in the helical groove.

The helical groove comprises a number of helical revolutions of <NUM> degrees around the longitudinal axis of the helical groove. The number of revolutions is for example at least <NUM>, preferably at least <NUM> revolutions. The number of revolutions is for example between <NUM> and <NUM> revolutions.

In an embodiment, the shaft is releasably mounted on the handle part, wherein the handle part supports a rotatable connection part arranged to mount the shaft on the handle part,.

It may be desirable to provide a shaft that is releasable from the handle part, for example to clean the shaft and the handle part separately. When an optical fibre is used as part of a sensor arranged in the shaft, a fibre connection device has to be provided to connect a first fibre part of the optical fibre arranged in the shaft with a second fibre part of the optical fibre arranged in the handle part.

Further, the shaft may be rotatable about its longitudinal axis. To enable a connection between the first fibre part and the second fibre part, a rotatable connection part may be supported by the handle part. The rotatable connection part may be fixed to the shaft to enable rotation of the shaft and to provide at the same time a connection between the first fibre part and the second fibre part. The fibre connection device may comprise a first connector arranged at the proximal end of the shaft and a second connector arranged at the distal end of the rotatable connection part.

To improve the connection between the first connector and the second connector the second connector may be biased by a spring element into the distal direction of the surgical instrument and/or the first connector may be biased by a spring element into the proximal direction of the surgical instrument.

In an embodiment, the trigger device comprises a trigger arranged to be manipulated by a user, wherein the trigger is rotatably mounted on the handle part of the frame,.

In this embodiment the actuator is provided as a linear direct drive motor comprising a coil mounted on the trigger of the trigger device and at least one permanent magnet assembly mounted on the handle part. The actuation force of this linear direct drive motor is created directly between the trigger and the handle part of the frame of the surgical instrument. No separate moving parts are required and the coil and at least one permanent magnet assembly are spaced with respect to each other. As a result, the linear direct drive motor can relatively easily be cleaned when needed.

In an embodiment, the coil will move along a path of movement upon rotation of the trigger, wherein the actuator comprises two permanent magnet assemblies, each aligned with the path of movement at opposite sides of the path of movement.

In an embodiment, the at least one permanent magnet assembly comprises one or more permanent magnets and a back iron at a side of the magnets opposite to the side of magnets facing the coil.

In an embodiment, the at least one permanent magnet assembly comprises multiple permanent magnets arranged in a Halbach array. The advantage of the use of a Halbach array of permanent magnets is that the magnetic field of the permanent magnets is augmented at one side of the permanent magnets, i.e. the side of the permanent magnets facing the coil, while the magnet field at the opposite side of the permanent magnets can be cancelled to close to zero.

In an embodiment, the direct drive motor is a linear Lorentz motor. A Lorentz motor is a suitable motor to be used as actuator in the surgical instrument, as the motor can provide an actuation force without any direct mechanical contact between the coil mounted on the trigger and the at least one permanent magnet assembly mounted on the handle part of the frame of the surgical instrument.

In an embodiment, the shaft is a hollow tube, wherein the shaft and the actuation rod are, at their proximal ends, releasably mounted on the handle part, wherein the surgical instrument comprises an actuation rod locking mechanism to connect the actuation rod, at its distal end, to an actuation assembly of the at least one jaw element, wherein, in the assembled state, the actuation rod extends through the hollow shaft.

It may be advantageous to use a hollow shaft through which the actuation rod extends. To properly clean the actuation rod and the hollow shaft, it is desirable that the actuation rod can be taken out of the hollow shaft. In such embodiment an actuation rod locking mechanism to connect the distal end of the actuation rod with a proximal end of a lock element of the actuation assembly of the at least one jaw element may be required to release the actuation rod from the lock element in order to take the actuation rod out of the hollow shaft.

In an embodiment, the actuation rod locking mechanism comprises a spherical element mounted at the distal end of the actuation rod, and a catch element and a lock element mounted at the proximal end of the actuation assembly, wherein the lock element comprises a recess in which the catch element is placed,
wherein the catch element comprises a catch space to receive the spherical element, wherein the catch element is rotatable between a locking position, in which the spherical element can be locked in the catch space of the catch element, and a non-locking position, in which the spherical element can move into and out of the catch space of the catch element.

It has been found that a catch element provided in a recess of the lock element can advantageously be used to lock the spherical element arranged at the distal end of the actuation rod.

In an embodiment, the actuation rod comprises a distal end surface and the lock element comprises a proximal end surface, wherein the catch element is arranged to pull, when the catch element is rotated from the non-locking position to the locking position the distal end surface against the proximal end surface. By exerting a pulling force on the actuation rod, while the proximal end surface of the lock element is pushed against the distal end surface of the actuation rod a tight connection between the lock element and the actuation rod can be obtained.

In an embodiment, the catch element comprises a driving surface, such as a slot, a groove, or a recess, to receive a tool head for rotation of the catch element between the locking position and the unlocking position, and wherein the shaft comprises an opening through which the tool head can be arranged on or in the driving surface. The rotation of the catch element between the locking position and the non-locking position can be performed by placing a tool head in the driving surface of the catch element. The driving surface is for example a groove in which a head of a screw driver can be arranged to transfer a rotating movement of the screw driver to the catch element.

Since the catch element is arranged in the hollow shaft an opening may be provided in the shaft through which a tool head of a tool, for example a screw driver, can be arranged in the groove of the catch element.

In an embodiment, the surgical instrument may comprise the forceps construction as described herein. In such embodiment the at least one jaw element mounted movably at a distal end of the elongate frame is part of the forceps construction.

Embodiments of the aspects of the disclosure will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference numerals indicate corresponding parts, and in which:.

<FIG> show side views of a forceps construction generally denoted by reference numeral <NUM>. <FIG> shows a cross section of the forceps construction <NUM>.

The forceps construction <NUM> comprises a forceps frame <NUM>. At the distal end of the forceps frame <NUM> a first extension <NUM> and a second extension <NUM> are provided. The first extension <NUM> and the second extension <NUM> extend in distal direction from a main part <NUM> of the forceps frame <NUM>. A slit <NUM> is provided between the first extension <NUM> and the second extension <NUM>. The first extension <NUM> and the second extension <NUM> in this embodiment are arranged parallel to each other. In other embodiments, the first extension <NUM> and the second extension <NUM> may be arranged at a non-zero angle with respect to each other.

The first extension <NUM> comprises a first distal extension part <NUM> and a first proximal extension part <NUM>. The first distal extension part <NUM> and the first proximal extension part <NUM> are connected to each other by a first bridge element <NUM>. The cross-section of the bridge element <NUM> is smaller than the cross sections of each of the first distal extension part <NUM> and the first proximal extension part <NUM>.

Correspondingly, the second extension <NUM> comprises a second distal extension part <NUM> and a second proximal extension part <NUM>, that are connected to each other by a second bridge element <NUM>. The cross-section of the second bridge element <NUM> is also smaller than the cross sections of each of the second distal extension part <NUM> and the second proximal extension part <NUM>.

The forceps construction <NUM> further comprises a first jaw element <NUM> and a second jaw element <NUM>. The first jaw element <NUM> is rotatably mounted on the first distal extension part <NUM> at a first axis of rotation <NUM>. The second jaw element <NUM> is rotatably mounted on the second distal extension part <NUM> at a second axis of rotation <NUM>.

An actuation assembly is provided to rotate the first jaw element <NUM> and the second jaw element <NUM> with respect to the first axis of rotation <NUM> and the second axis of rotation <NUM>. The actuation assembly comprises a first actuation element <NUM> connected to the first jaw element <NUM> and a second actuation element <NUM> connected to the second jaw element <NUM>. The first actuation element <NUM> and the second actuation element <NUM> are connected or configured to be connected to an actuation rod that, in its turn, is connected to a trigger device for operating the forceps construction <NUM> (as shown in <FIG>).

Between the first extension <NUM> and the second extension <NUM> a strain element <NUM> is provided. At its proximal end, the strain element <NUM> is connected to the main part <NUM> of the forceps frame <NUM>, while the distal end of the strain element <NUM> is connected via a first connection part <NUM> to the proximal end of the first distal extension part <NUM> and via a second connection part <NUM> to the proximal end of the second distal extension part <NUM>.

It is remarked that the first extension <NUM> and the second extension <NUM> are arranged at opposite sides of a midplane M. The first bridge element <NUM> and the second bridge element <NUM> are spaced from the midplane M, while the strain element <NUM> is arranged on the midplane M.

When a force Ft1 is exerted on the first jaw element <NUM>, for example by tissue held between the first jaw element <NUM> and the second jaw element <NUM>, this will result in a force Fh1 being exerted on the first axis of rotation <NUM>. Similarly, when a force Ft2 is exerted on the second jaw element <NUM>, for example by tissue held between the first jaw element <NUM> and the second jaw element <NUM>, this will result in a force Fh2 being exerted on the second axis of rotation <NUM>.

These forces Fh1 and Fh2 cause elastic deformation due to bending of the first extension <NUM> and the second extension <NUM>. The first bridge element <NUM> and the second bridge element <NUM> are provided to facilitate this bending. Due to the force Fh1 the first distal extension part <NUM> tilts at the first bridge element <NUM> with respect to the first proximal extension part <NUM>. Correspondingly, due to the force Fh2 the second distal extension part <NUM> tilts at the second bridge element <NUM> with respect to the second proximal extension part <NUM>. Due to the tilting movement of the first distal extension part <NUM> about the first bridge element <NUM> and the tilting movement of the second distal extension part <NUM> about the second bridge element <NUM>, the first connection part <NUM> and the second connection part <NUM> are pulled in the distal direction causing an elongation of the strain element <NUM>.

The forceps construction <NUM> is designed such that the strain element <NUM> will only or substantially only be elongated by forces acting on the first axis of rotation <NUM> and the second axis of rotation <NUM> due to forces being exerted on the first jaw element <NUM> and the second jaw element <NUM>, respectively. Other forces, in particular pushing and pulling forces caused by actuation of the first jaw element <NUM> and the second jaw element <NUM>, will not or substantially not be transmitted through the strain element <NUM>, but will be transmitted through the first bridge element <NUM> and the second bridge element <NUM>.

It is remarked that due to the location of the strain element <NUM> on the midplane and the relative small and long first connection part <NUM> and second connection part <NUM>, the strain element <NUM> will mainly elongate, but not bend, when the first distal extension part <NUM> tilts at the first bridge element <NUM> and the second distal extension part <NUM> tilts at the second bridge element <NUM>. This further improves the measurement of the strain in the strain element <NUM> as a basis for determination of forces exerted by tissue or other material on the first jaw element <NUM> and the second jaw element <NUM>.

A strain sensor, in particular a Fibre Bragg Grating (FBG) <NUM> provided in an optical fibre <NUM> is fixed in a hollow space in the strain element <NUM> (see <FIG>) to measure the elongation of the strain element <NUM>. The optical fibre <NUM> comprises a second FBG <NUM> that is not firmly fixed to the forceps frame <NUM>. This second FBG <NUM> is provided to measure the effects of (change in) temperature.

Since the strain element <NUM> will only measure elongation caused by forces exerted on the first jaw element <NUM> and the second jaw element <NUM>, there is no need for additional strain sensors to compensate other forces in the forceps frame <NUM>, such as pulling and pushing forces used to operate the first jaw element <NUM> and the second jaw element <NUM>. This results in a relatively simple measurement system comprising two Fibre Bragg Gratings provided in a single optical fibre <NUM>.

It is remarked that forces exerted on the first jaw element <NUM> and the second jaw element <NUM> in opposite direction of the forces Ft1 and Ft2, for example by opening the first jaw element <NUM> and the second jaw element <NUM> in a tissue opening in which the jaw elements <NUM>, <NUM> are placed, may result in a compression of the strain element <NUM> that can be measured by the FBG <NUM>.

To prevent that the first extension <NUM> and the second extension <NUM> are bent beyond certain mechanical yield limits, the first extension <NUM> comprises a first bulge <NUM> and the second extension <NUM> comprises a second bulge <NUM>. The first bulge <NUM> and the second bulge <NUM> have interlocking shapes to mechanically limit the extent of bending of the first extension <NUM> with respect to the second extension <NUM>. In the unstressed position of the first jaw element <NUM> and the second jaw element <NUM>, i.e. when no forces are exerted on the first jaw element <NUM> and the second jaw element <NUM>, the distance between the first bulge <NUM> and the second bulge <NUM> substantially corresponds with the width of the slit <NUM>. As a consequence, the first distal extension part <NUM> and the second distal extension part <NUM> can each bend until the first bulge <NUM> and the second bulge <NUM> have each moved over a distance of approximately half the width of the slit <NUM>. This distance has been selected such that no plastic deformation in the first extension <NUM> and the second extension <NUM> will occur due to bending of the first distal extension part <NUM> and the second distal extension part <NUM>.

It is thereby remarked that the first extension <NUM> and the second extension <NUM> are substantially symmetrical with respect to each other with respect to the midplane M. Only the first bulge <NUM> and the second bulge <NUM> are not symmetrical with respect to each other. This substantially symmetrical design has the advantage that when equal forces are exerted on the first jaw element <NUM> and the second jaw element <NUM>, the first extension <NUM> and the second extension <NUM> will substantially equally bend.

The forceps construction <NUM> described above may be applied in any device or instrument in which an accurate feedback of the force that is exerted on the first jaw element <NUM> and the second jaw element <NUM> is desirable. The forceps construction <NUM> is in particular suitable for a surgical instrument for minimally invasive surgery, since accurate feedback of forces exerted on and by manipulated tissue is important to properly manipulate tissue.

<FIG> shows a surgical instrument <NUM> for minimally invasive surgery, comprising the forceps construction <NUM> as shown in <FIG>.

The surgical instrument <NUM> comprises an elongate frame, formed by a handle part <NUM> and a shaft <NUM>. The handle part <NUM> comprises an inner frame and a housing mounted on the inner frame. The shaft <NUM> is releasably mounted on the handle part <NUM>, as will be described hereinafter. Further, the shaft <NUM> is rotatable about its longitudinal axis with respect to the handle part <NUM>. This allows different rotational positions of the jaw elements <NUM>, <NUM>, with respect to the handle part <NUM> of the surgical instrument <NUM>. A rotation knob <NUM> is provided to manually set a rotation position of the shaft <NUM> with respect to the handle part <NUM>.

The rotation of the shaft about its longitudinal axis may for example be in the range of <NUM> degrees to <NUM> degrees, for example in the range of <NUM> degrees to <NUM> degrees in both rotation directions from a middle rotation position of the shaft. One or more stop elements may be provided to limit the range of rotation of the shaft <NUM>.

A trigger device <NUM> is provided to operate the jaw elements <NUM>, <NUM> of the forceps construction. The trigger device <NUM> is rotatably mounted in the handle part <NUM> of the surgical instrument <NUM>.

The shaft <NUM> is hollow. Through the hollow shaft <NUM> an actuation rod <NUM> (see <FIG>) extends from the trigger device <NUM> to the actuation assembly of the forceps construction <NUM> to operate the forceps construction by manipulation of the trigger device <NUM>.

The optical fibre <NUM> of the FBG's also runs through the hollow shaft <NUM>. An actuator <NUM> (see <FIG>) is provided in the handle part <NUM> to exert a feedback force on the trigger device <NUM> on the basis of a sensor signal based on the sensor signal obtained from the FBG.

A cable <NUM> is connected to the handle part <NUM>. The cable <NUM> guides the optical fibre <NUM> from the handle part <NUM> to an interrogator device (not shown) arranged at a separate location. The interrogator device is configured to interrogate the one or more FBG's <NUM>, <NUM> provided in the optical fibre and to provide a sensor signal representative for the force exerted on the jaw elements of the forceps construction <NUM>.

The surgical instrument <NUM> comprises a controller, wherein the controller is arranged to control the actuator <NUM> on the basis of the sensor signal. The controller may be part of the handheld frame of the surgical instrument <NUM>. In this embodiment, the sensor signal obtained by the interrogator device is guided through the cable <NUM> back to the handle part <NUM>. In another embodiment, the controller may be provided as a separate device, or for example integrated with the interrogator device. In this embodiment the cable <NUM> is used to guide a control signal of the controller to the actuator <NUM>. In yet an alternative embodiment, the controller and the interrogator device may be integrated in the handheld frame of the surgical instrument <NUM>.

Since the optical fibre <NUM> runs through the handle part <NUM> and the shaft <NUM>, the optical fibre <NUM> has to be able to follow rotation of the shaft <NUM> with respect to the handle part <NUM>. The optical fibre <NUM> should not be damaged by the rotation of the shaft <NUM>. Moreover, it should be avoided that the optical performance of the optical fibre decreases below a desired level due to a too small bending radius of the optical fibre <NUM>.

<FIG> shows the distal side of the handle part <NUM> for the releasable and rotatable connection of the shaft <NUM> in more detail. The handle part <NUM> supports a rotatable connection part <NUM> which is rotatable about the axis of rotation A-A which coincides with the longitudinal axis of the shaft <NUM> when mounted in the handle part <NUM>. The rotatable connection part <NUM> is rotatably mounted on a fixed bearing <NUM> of the handle part <NUM>. A lock plate <NUM> is provided to lock the rotatable connection part <NUM> on the fixed bearing <NUM>.

The rotatable connection part <NUM> comprises a hollow channel <NUM> to receive the shaft <NUM> including the actuation rod <NUM> placed in the hollow shaft <NUM>. The longitudinal axis of the actuation rod <NUM> when placed in the hollow shaft <NUM> will coincide with the axis of rotation A-A of the rotatable connection part <NUM> and the shaft <NUM>.

The shaft <NUM> is releasably locked to the rotatable connection part <NUM> by a shaft locking mechanism <NUM> mounted on the frame of the handle part <NUM>. The proximal end of the actuation rod <NUM> is releasably connected to the trigger device <NUM>, for example comprising a ball catch mechanism. The rotation knob <NUM> is rotatably fixed to the rotatable connection part <NUM>, such that rotation of the rotation knob <NUM> will result in rotation of the rotatable connection part <NUM> and therewith in rotation of the shaft <NUM>, when connected to the rotatable connection part <NUM>. The rotatable connection part <NUM> comprises an alignment element <NUM> to properly align the shaft <NUM> with the rotatable connection part <NUM> when the shaft <NUM> is mounted on the handle part <NUM>. This alignment element <NUM> may also be used to transfer the rotational movement of the rotatable connection part <NUM> to the shaft <NUM>.

As the shaft <NUM> is releasable from the handle part <NUM>, the optical fibre <NUM> has to be provided in two parts that can be separated from each other. The shaft <NUM> comprises a first fibre part and a second fibre part of the optical fibre <NUM> is arranged in the handle part <NUM>. A fibre connection device <NUM> is provided to optically connect the first fibre part and the second fibre part to each other when the shaft <NUM> is mounted on the handle part <NUM>.

The fibre connection device <NUM> comprises a first connector arranged at the proximal end of the shaft <NUM> and a second connector <NUM> arranged at the distal end of the rotatable connection part <NUM>. When the shaft <NUM> is mounted on the handle part <NUM>, the first connector is pushed onto the second connector <NUM>. To improve the connection between the first connector and the second connector <NUM>, a spring element <NUM> is provided. The spring element <NUM> is biased in the distal direction to actively push a support element <NUM> supporting the second connector <NUM> on the first connector when the shaft <NUM> is mounted on the handle part <NUM>.

The second connector <NUM> is arranged at a distance from the axis of rotation A-A of the rotatable connection part <NUM>. As a result, rotation of the rotatable connection part <NUM> will lead to a difference in length of the path of the optical fibre <NUM> in the handle part <NUM>. The optical fibre <NUM> therefore should allow a change in path length in the handle part <NUM>. At the same time, it should be avoided that the bending radius of the optical fibre becomes too small as a small bending radius may have a negative effect on the optical performance of the optical fibre and/or may lead to damage of the optical fibre <NUM>. For example, the bending radius of the optical fibre <NUM> suitable for use in the shown embodiment of the surgical instrument <NUM>, should not be lower than a minimum fibre bending radius. Such minimum fibre bending radius may for example be <NUM> for a typical embodiment of an optical fibre having a diameter of <NUM>.

To facilitate rotation of the shaft <NUM> and the rotatable connection part <NUM> without increased risk on damage of the optical fibre <NUM> or substantial loss of optical performance of the optical fibre <NUM>, a fibre guide <NUM> is provided.

<FIG> shows the fibre guide <NUM> in more detail. The fibre guide <NUM> comprises an outer cylindrical surface <NUM> having a helical groove <NUM> to guide the optical fibre <NUM> in a substantially helix shaped path. The outer cylindrical surface <NUM> of the fibre guide <NUM> is arranged concentrically with the axis of rotation A-A of the rotatable connection part <NUM> and therewith the shaft <NUM> when connected to the handle part <NUM>.

The fibre guide <NUM> ensures that the change in path length of the optical fibre <NUM> can be accommodated by allowing the diameter of the loops of the optical fibre <NUM> in the helix shaped groove <NUM> to increase or decrease in dependence of the rotation of the rotatable connection part <NUM> with respect to the handle part <NUM>. The diameter of the bottom surface of the groove <NUM>, i.e. the smallest diameter of the groove <NUM> is larger than the minimum bending radius of the optical fibre <NUM> that can be allowed without having substantial performance loss. This ensures that the actual bending radius of the optical fibre will not come below this minimal bending radius.

The helical groove <NUM> defines a number of helical revolutions of <NUM> degrees around the longitudinal axis of the helical groove. The number of revolutions is in the shown embodiment between <NUM> and <NUM> revolutions. The number of revolutions may be adapted in dependence of the maximum rotation of the shaft <NUM> and the associated change in path length of the optical fibre <NUM> within the handle part <NUM>.

The fibre guide <NUM> has an inner cylindrical surface <NUM> adapted to fit on the fixed bearing <NUM> of the handle part <NUM>. The fibre guide <NUM> may be arranged to rotate together with the rotatable connection part <NUM> or may be fixed on the fixed bearing <NUM>.

<FIG> shows the actuator <NUM> of the surgical instrument <NUM> in perspective view. The actuator <NUM> is a linear direct drive motor arranged in the handle part <NUM>. The actuator <NUM> is provided to exert a feedback force on the trigger device <NUM>. The trigger device <NUM> comprises a trigger <NUM> which is rotatably mounted at rotation axis <NUM> on the inner frame <NUM> of the handle part. The inner frame <NUM> is fixedly connected to the housing of the handle part <NUM> shown in <FIG>.

The trigger <NUM> comprises an extension <NUM> on which a coil <NUM> is mounted. When the trigger is rotated about its rotation axis <NUM>, the coil <NUM> will move along a path of movement. The actuator <NUM> comprises two permanent magnet assemblies <NUM>, each aligned with the path of movement at opposite sides of the path of movement of the coil <NUM>.

<FIG> shows the coil <NUM> and the permanent magnet assemblies <NUM> in more detail. The coil <NUM> comprises an upper coil part <NUM> and a lower coil part <NUM> connected to each other by side coil parts <NUM>. The permanent magnet assemblies <NUM> each comprise a set of permanent magnets and a back iron <NUM>. The set of permanent magnets comprises a first pair of magnets <NUM>, <NUM> aligned with the upper coil part <NUM> and having an axial magnetization in a first direction and a second pair of magnets <NUM>, <NUM> aligned with the lower coil part <NUM> and having an axial magnetization in a second direction opposite to the first direction.

Between the first set of magnets <NUM>, <NUM> and the second set of magnets <NUM>, <NUM>, there is provided a third set of magnets <NUM>, <NUM> having a tangential magnetization. It is remarked that the axial and radial direction of the magnetization are related to the rotational movement of the trigger <NUM> with respect to the rotation axis <NUM>.

The arrangement of the permanent magnets is a Halbach array. The advantage of the use of a Halbach array of permanent magnets is that the magnetic field of the permanent magnets is augmented at one side of the permanent magnets, i.e. the side of the permanent magnets facing the coil <NUM>, while at the opposite side of the permanent magnets the magnetic field will be close to zero.

The coil <NUM> and the permanent magnet assemblies <NUM> form a Lorentz motor. The axial magnetization of the first set of permanent magnets <NUM>, <NUM> create a magnetic field in axial direction through the upper coil part <NUM>, such that a current through the coil results in a Lorentz force in the tangential direction. Correspondingly, the axial magnetization of the second set of permanent magnets <NUM>, <NUM> create a magnetic field in axial direction through the lower coil part <NUM>, such that a current through the coil <NUM> also results in a Lorentz force in the tangential direction. Since the directions of axial magnetization of the first set of permanent magnets <NUM>, <NUM> and the second set of permanent magnets <NUM>, <NUM> are opposite to each other, and also the directions of the current through the upper coil part <NUM> and the lower coil part <NUM> are opposite to each other the resulting Lorentz forces in the upper coil part <NUM> and in the lower coil part <NUM> act in the same tangential direction.

The dimensions of the coil <NUM> and the permanent magnet assemblies <NUM> are designed such that at both ends of the range of movement of the trigger <NUM> the upper coil part <NUM> is still positioned between the first sets of permanent magnets <NUM>, <NUM> and the lower coil part <NUM> is still positioned between the second sets of permanent magnets <NUM>, <NUM>.

An advantage of the Lorentz type direct drive motor as actuator <NUM> is that the actuation force of the motor is created directly between the trigger <NUM> and the handle part <NUM> of the surgical instrument. No separate moving parts are required and, furthermore, the coil <NUM> and the permanent magnet assemblies <NUM> are spaced with respect to each other. As a result, the linear direct drive motor can relatively easily be cleaned when needed and the actuator <NUM> will make little noise when actuated.

<FIG> show the distal end of the surgical instrument <NUM> comprising the forceps construction <NUM> arranged on the shaft <NUM>. As described above, the shaft <NUM> is a hollow tube in which the actuation rod <NUM> is arranged. The shaft <NUM> and the actuation rod <NUM> are releasably mounted to the handle part <NUM> and the trigger device <NUM>, respectively, as described with respect to <FIG>. At the distal end of the actuation rod <NUM>, an actuation rod locking mechanism <NUM> is provided to connect the actuation rod <NUM> to the actuation assembly of the forceps construction <NUM>. The actuation rod locking mechanism <NUM> makes it possible to remove the actuation rod <NUM> out of the shaft <NUM> to facilitate proper cleaning and disinfection of both the shaft <NUM> and the actuation rod <NUM>.

The actuation rod locking mechanism <NUM> comprises a spherical element <NUM> mounted at the distal end of the actuation rod <NUM>, and a catch element <NUM> and a lock element <NUM> mounted at the proximal end of the actuation assembly. The lock element <NUM> comprises a recess in which the catch element <NUM> is placed. The catch element <NUM> comprises a catch space <NUM> to receive the spherical element <NUM>. The catch element <NUM> is rotatable in the recess between a locking position, in which the spherical element <NUM> can be locked in the catch space <NUM> of the catch element <NUM>, and a non-locking position, in which the spherical element <NUM> can move into and out of the catch space <NUM> of the catch element <NUM>.

The catch element <NUM> comprises a groove <NUM> as a driving surface to receive a head of a screw driver. When the head of the screw driver is arranged in the groove <NUM> the catch element <NUM> can be rotated between the locking position and the non-locking position by rotation of the screw driver. Since the catch element <NUM> is arranged in the hollow shaft <NUM> an opening <NUM> is provided in the shaft <NUM> through which the screw driver can be arranged in the groove <NUM> of the catch element <NUM>. In an alternative embodiment the driving surface, may be any surface, such as a slot, groove, or recess, suitable to receive a corresponding tool head for rotation of the catch element <NUM> between the locking position and the non-locking position.

The actuation rod <NUM> comprises a distal end surface <NUM> and the lock element <NUM> comprises a proximal end surface <NUM>. When the spherical element <NUM> is arranged in the catch space <NUM>, and the catch element <NUM> is rotated from the non-locking position to the locking position, the catch element <NUM> is arranged to pull the distal end surface <NUM> against the proximal end surface <NUM>. This locking configuration in which the spherical element <NUM> is pulled by the catch element <NUM> in distal direction , while the proximal end surface <NUM> of the lock element <NUM> is pushed against the distal end surface <NUM> of the actuation rod <NUM> a tight connection between the lock element <NUM> and the actuation rod <NUM> can be obtained. The locking configuration can easily be released by rotation of the catch element <NUM> from the locking position to the unlocking position.

In the above embodiment, the surgical instrument may comprise the forceps construction <NUM>. Aspects of the disclosure as described with respect to <FIG> may also be applied in other embodiments of surgical instruments having at least one jaw element, but without the specific configuration of the forceps construction of <FIG>.

Claim 1:
A surgical instrument (<NUM>), for example a surgical instrument for minimally invasive surgery, comprising:
an elongate frame,
at least one jaw element (<NUM>, <NUM>) mounted movably at a distal end of the elongate frame,
a trigger device (<NUM>) to operate the at least one jaw element and arranged at a proximal end of the elongate frame,
an actuation rod (<NUM>) provided between the trigger device and the at least one jaw element,
a sensor (<NUM>) to provide a sensor signal representative for a force exerted on the at least one jaw element, and
an actuator (<NUM>) to exert a feedback force on the trigger device on the basis of the sensor signal,
wherein the elongate frame comprises a handle part (<NUM>) and a shaft (<NUM>), wherein the trigger device (<NUM>) and the actuator (<NUM>) are mounted on the handle part (<NUM>) and the at least one jaw element (<NUM>, <NUM>) is mounted on the shaft,
wherein
the shaft has a longitudinal axis, wherein the shaft is mounted rotatably about its longitudinal axis on the handle part,
the sensor comprises an optical fibre (<NUM>), characterized in that
the surgical instrument comprises a fibre guide (<NUM>) to guide the optical fibre in a substantially helix shaped path concentric with the longitudinal axis.