EP2434966A1

EP2434966A1 - Surgical instrument

Info

Publication number: EP2434966A1
Application number: EP10715805A
Authority: EP
Inventors: Theodor Lutze; Olaf Hegemann
Original assignee: Aesculap AG
Current assignee: Aesculap AG
Priority date: 2009-05-29
Filing date: 2010-04-21
Publication date: 2012-04-04
Also published as: DE102009042150A1; US8353898B2; CN102448387B; CN102448387A; AU2010252203A1; US20120123396A1; JP2012527916A; WO2010136270A1; DE202009012793U1

Abstract

The invention relates to a surgical instrument comprising a proximal and a distal end respectively comprising an articulation region, and a rigid central section resistant to bending arranged between said ends. The proximal end section can be connected to an actuating device, and a cutting, abrasive or milling tool that can be driven by means of a drive element is connected to the distal end section. The aim of the invention is to improve such a surgical instrument such that it can be used in a flexible manner and has a larger working surface. To this end, the instrument is provided with an outer hollow cylindrical shaft, an inner hollow cylindrical shaft, and a control element arranged between said shafts, with at least two longitudinal elements transmitting tractive and/or pressure forces and extending at least essentially from the proximal articulation region to the distal articulation region. The longitudinal elements are arranged in the peripheral direction of the instrument at essentially regular angular distances and are interconnected at their proximal and distal ends in the peripheral direction.

Description

Surgical instrument

The invention relates to a surgical instrument, in particular for use in combination with a trocar or the like., With a proximal and a distal, each having a joint zone end portion and an interposed, bending-resistant central portion.

The proximal end section is connectable to an actuating device, in particular also a motor drive device, and to the distal end section a cutting, abrading or milling tool drivable by means of a drive element is connected.

It is known to form such surgical instruments for enlarging their working area in the distal end section slightly angled, for example by 20 ° relative to the longitudinal direction of the instrument, as is known from EP 0 677 276 Bl or DE 10 2004 046 539 Al.

Despite the angulation of the distal end portion of the work area, which can thus be achieved with the patient, is still relatively limited and particularly hard to reach tissue parts in part still require the re-placement of the trocar, which is generally undesirable.

The object of the present invention is to further develop the above-mentioned surgical instrument so that it can be used more flexibly and has a larger working area.

This object is achieved in the case of the surgical instrument described above in that the instrument has an outer hollow cylindrical shaft, an inner hollow cylindrical shaft and a control element arranged between these shafts with two or more at least substantially from the proximal to the distal joint zone the instrument extending, tensile and / or compressive forces transmitted longitudinal elements. The longitudinal elements are arranged in the circumferential direction of the instrument at substantially regular angular intervals and connected at their proximal and distal ends with each other in the circumferential direction.

Due to this configuration of the surgical instrument, pivotal movements can now be performed on the proximal end section, to which pivoting movements at the distal end section then correspond.

Compared with the prior art instruments, instead of the straight-line (linear) or fixed-cranked configuration, a straight-line or adjustable-cranked configuration is possible, which can be varied within predetermined limits even during surgery.

The coupling of the pivotal movement at the proximal and distal end portion is achieved by the control element and its force transmitting longitudinal elements.

If two force-transmitting longitudinal elements are used, the pivoting movement is limited to one plane. If several, in particular four or more, for example, eight force-transmitting longitudinal elements used, it is possible to pivot the surgical instrument in two mutually perpendicular planes or to pivot, in particular in the use of eight control elements or more in virtually arbitrary levels.

The pivoting movements are not limited to an angle of about 20 °, but can quite swing movements reach well over 90 °. In a preferred embodiment of the invention, the instrument has a control element, which comprises a hollow cylindrical component, the cylinder wall is divided at least in the region of a portion between the proximal and distal ends in two or more wall segments which form the force-transmitting longitudinal elements.

Here, the two or more wall segments at the distal end of the hollow cylindrical component can be firmly connected to each other via a collar.

Furthermore, the two or more wall segments in the region of the proximal end of the hollow cylindrical member may be firmly connected to each other.

Particularly preferably, the hollow cylindrical component is formed integrally. Here, the handling when assembling the instrument is particularly simple. In addition, the one-piece component can be produced with particular precision with respect to the mutual alignment of the wall segments.

Instruments of this embodiment have, in particular, a hollow-cylindrical component which is manufactured from a single tube, wherein the subdivision of the cylinder wall into wall segments preferably takes place by means of laser beam cutting.

As a material for the production of the control element, in particular of the hollow cylindrical component, steel alloys or nitinol are particularly suitable.

In a particularly preferred embodiment of the invention, the inner shaft of the instrument is designed as a drive element, so that the largest possible inner lumen remains free, for example, for discharging ablated from the tool tissue parts of the treated patient. The drive element in this case has two flexible sections, which are arranged in the assembled state of the instrument respectively in the proximal and distal joint zones within the outer shaft. This ensures that the typically rotating drive movement can also be transmitted in an angled state to the tool connected to the distal end section.

In order to achieve the most effective possible transmission of torques, the drive element is formed substantially torsionally stiff.

Also, the outer shaft is preferably formed torsionally stiff to accommodate the reaction forces occurring during operation of the tool and to avoid twisting of the instrument. Warping the instrument would cause the instrument to be moved away from its intended location, an effect that could lead to significant complications in high-precision operations.

In a further embodiment of the present invention, the articulation zones are formed elastically, preferably flexurally elastic, so that the surgical instrument will be restored to the straight shape in the event of an elimination of the forces which force a pivotal movement at the proximal end.

The force-transmitting longitudinal elements are arranged laterally spaced from each other in a variant of the present invention, so that they do not rub against each other during the pivoting movement and so the pivoting movement can be made with a minimum of effort.

Alternatively, a spacer may be arranged in each case between the laterally spaced-apart longitudinal elements, so that the position in the circumferential direction of the longitudinal elements remains substantially unchanged even for larger forces to be introduced for carrying out the pivoting movement. Alternatively it can be provided that the force-transmitting longitudinal elements along the longitudinal direction are arranged at least partially in direct contact with each other. Here, too, it is ensured that the longitudinal elements, viewed in the circumferential direction, remain in their positions even when the force is introduced, and thus exact control of the pivoting movement of the distal end can be achieved.

More preferably, the longitudinal force-transmitting elements are radially guided by the outer and inner shafts, resulting in a further improvement in the accuracy of the pivotal movement made at the distal end.

According to a further embodiment of the present invention it can be provided that in the control element to be used according to the invention, the distal ends of the longitudinal elements are fixed in the circumferential direction in angular positions which are different from the angular positions in which the respectively associated proximal ends are fixed.

This allows pivotal movements of the distal end in a plane other than that in which the pivotal movement of the proximal end is performed.

The angular difference in which the angular positions of the distal and proximal ends of a longitudinal element are fixed may range from about 10 ° to about 350 °. In particular, differences in the angular positions at the proximal and distal ends in the range of about 45 ° to about 315 ° are of interest, more preferably in the range of about 150 ° to about 210 °.

To achieve this, the force-transmitting longitudinal elements are preferably arranged helically at least in sections. In view of the typical length of a surgical instrument and the consequent length of the longitudinal elements and the relatively small diameter at the same time result angular positions of the longitudinal elements in their helical path, which differ to a very small extent from the axial direction of the instrument. This means that even with a very large angular offset of, for example, 180 ° secure handling of the instrument is ensured and in particular the pivoting movement of the distal end can be performed with precision and predictable.

In a further embodiment of the invention it can be provided that the force-transmitting longitudinal elements in the region of the proximal and / or distal end portion are arranged with a substantially parallel orientation to the longitudinal axis of the instrument.

Alternatively, one or more sections may be arranged parallel to the longitudinal direction of the instrument.

Again, in view of the typical length of the required control element of mostly more than 10 cm and with a typical diameter of the instrument of a few millimeters, an extremely high pitch of the helical line or in other words a very small deviation from the parallelism to the longitudinal direction of the instrument, which is a few angular degrees to a fraction of an angular degree.

According to a variant of the instrument according to the invention, the force-transmitting longitudinal elements are formed as cables or wires.

In another variant, the force-transmitting longitudinal elements have a banana-shaped cross-section. As already stated above, in a particularly preferred embodiment, the force-transmitting longitudinal elements are formed from a hollow cylindrical component in which, for example by means of laser beam cutting, the cylinder wall transmits over the largest part, in particular almost over the entire length in the axial direction to form the force Slotted longitudinal elements. The longitudinal elements are formed by cylinder wall segments, which have a circular arc shape in cross section.

The wall segments preferably have a circular arc shape in cross-section which corresponds to an arc angle of approximately 20 ° or more, in particular 30 ° or more.

The number of wall segments is preferably in the range of 4 to 16, more preferably in the range of 6 to 12.

The distance between the wall segments in the circumferential direction of each other (corresponds to the slot width) is measured in degrees, preferably about 2 ° to 15 °, more preferably about 4 ° to about 8 °.

The slot width, as produced by laser beam cutting, can be increased if necessary, so that the remaining strip-shaped wall segments can be moved without contact relative to each other. Due to the circular segment-like cross sections of the longitudinal elements of the non-contact state of the longitudinal elements is retained even in the case of tensile or compressive stress in the joint areas; This is especially true in a leadership of the longitudinal elements in the radial direction between an inner and an outer shaft.

The two end portions of the hollow cylindrical element remain uncut, so that the longitudinal elements remain connected to each other via annular collars. The proximal and distal articulation zones of the instrument can be realized in various ways.

If the inner shaft is used as a drive element, it has flexible sections in the area of the joint zones, which may be sufficient for the realization of the proximal and distal joint zones, from the front. This means that the outer shaft must be correspondingly flexible in order to also follow the pivot movements initiated by the control element.

Alternatively, both the inner and the outer shank can have a proximal and distal joint section in the region of the proximal and distal joint zones, wherein, when the inner shaft is used as the drive element, its flexible sections correspond to the proximal and distal joint sections.

Preferably, the articulation zones of the outer and / or inner shaft have a plurality of slots extending in the circumferential direction, which are separated from each other by wall areas in the circumferential direction or axial direction.

Preferably, a respective wall section in the circumferential direction two or more, in particular three or more slots arranged one behind the other. The slots are preferably arranged in the circumferential direction at equal distances from each other.

In the axial direction, the joint zones of preferred instruments have three or more slots arranged side by side, wherein preferably the juxtaposed slots are arranged offset from one another in the circumferential direction. The distances in which the slots are arranged in the axial direction to each other spaced, may be equal or vary, hereby the joint properties, in particular the bending radius, can be influenced. Typically, it is provided that the slots are the cylinder wall completely penetrating slots. However, good bending properties can also be achieved if the slots do not completely penetrate the wall of the shaft, but in particular end before reaching the inner circumference. Thus, the wall of the shaft remains closed as a whole, which may be desirable in some applications, in particular the outer shaft.

A preferred geometry of the slots is when the wall surfaces delimiting the slots are disposed at an acute angle to the radial direction. Preferably opposite wall surfaces of the same slot are arranged in mirror image, so that the outer circumference of a shaft results in a larger slot width than adjacent to the inner circumference.

Axially spaced apart slots are preferably circumferentially overlapping but offset from each other so as to provide a regular arrangement of the slots.

The wall surfaces of the slots may be inclined at an angle to the axial direction, which deviates from 90 °, so that the width of the slots on the outer circumference is greater than on the inner circumference of the outer shaft. This makes it possible to realize sufficiently large pivoting angles even with small slot widths without the number of slots having to be increased or the joint area having to extend over a greater axial length.

While in many cases the proximal and distal joint zones are of identical design and in particular have the same extension in the longitudinal direction of the instrument, this is not absolutely necessary.

In particular, it may be provided that the proximal and distal joint zones are formed differently, in particular also of different lengths. This can be achieved, for example, that a corresponding Pivoting movement of the proximal joint zone results in less or increased pivotal movement at the distal end portion of the instrument.

In particular, it can be provided that the pivoting movement of the proximal and / or distal joint zone is adjustable. This can be done, for example, by varying the extent of the proximal and / or the distal joint zone and thus changing the pivoting behavior of the two joint zones relative to one another.

In particular, it can be provided that the instrument comprises a holding device with which parts of one of the joint zones can be fixed in terms of bending with respect to the central section or a functional unit adjoining the proximal or distal end section of the instrument.

Thus, in a variant of the instrument according to the invention, the holding device can comprise a displaceable, rigid sleeve parallel to the longitudinal axis of the bending-resistant middle section. Depending on the position of the sleeve in the longitudinal direction to the central portion of the proximal and / or distal end portion and the joint zone provided there may be influenced in their length and thus also influenced in their pivoting behavior.

Preferably, the rigid sleeve is arranged on the outer circumference of the rigid shaft, so that not only the lumen of the control device remains unaffected, but also the position of the sleeve is easily changeable and in particular also can be fixed.

According to another variant, the holding device on the functional unit, which is coupled to the proximal end of the control device, comprise a supporting holding element. In this way, the joint zone can be influenced by the proximal end in their pivoting behavior. According to a further variant of the instrument according to the invention, the holding device can be positioned in a predetermined position and in particular also fixed. This makes it possible to pre-set or readjust the pivoting behavior of the distal and proximal end sections in a repeatable and precisely definable manner.

These and other advantages of the invention will be explained in more detail below with reference to the drawing. They show in detail:

FIG. 1A shows a surgical instrument in the form of a shaver according to the prior art;

Figure IB shows a surgical instrument in the form of a shaver according to the present invention;

Figure 2A, B and C an outer shaft, a control element and an inner shaft of the instrument according to the invention according to Figure IB; and

FIG. 2D shows an alternative embodiment of the control element of FIG. 2B;

Figures 2E and F show two alternative embodiments of hinge portions for the outer shaft of Figure 2A;

FIGS. 3A and B show two variants of an alternative embodiment of a control element for the inventive surgical instrument of FIG. 1B.

FIG. 1A shows a conventional surgical instrument in the form of a shaver 10 having a proximal end 12, a straight, rigid shaft 14, and a slightly angled distal end portion 16 to which a tool, such as a cutting, Abrasiv- or milling tool connected, in particular also formed.

For details of such an instrument may be made, for example, to DE 10 2004 046 539 Al.

Drilling tools can also be used in the instrument according to the invention, in which case the distal end of the instrument is not closed and, instead of the lateral opening, there is an opening in the axial direction for the passage of the drilling tool.

The angle at which the distal end portion 16 deviates from the longitudinal direction of the instrument 10 is predetermined during manufacture and remains invariably preserved.

The instrument can cover a limited working range by rotation about the longitudinal axis of the shaft 14, which is typically performed in a trocar, which is already significantly expanded compared to the also known, straight-line design of the instrument.

According to the present invention, a surgical instrument is provided with a proximal and a distal joint zone, as shown by the example of the shaver 20 of Figure IB and will be discussed below.

The shaver 20 according to the invention has a shaft which is divided into a proximal end section 22, a rigid central section 24 and a distal end section 26.

At the distal end portion 26, a tool 28 is connected or formed, which may correspond in its construction to that described for example in DE 10 2004 046 539 Al. The proximal and distal end portions 22, 26 of the instrument 20 each include a hinge zone 30, 32 which allow pivotal movement of the proximal end portion 22 which translates into pivotal movement of the distal end portion 26 on the hinge portion 32 due to a control element of the instrument 20. This can be done with the shaver 20 of Figure IB both in straight alignment, with slight bending of the distal end portion 26 and with a nearly vertical angulation of the end portion 26, which gives the instrument a considerably enlarged work area and also makes difficult accessible working positions accessible.

The construction of the shaver 20 according to the invention will be explained in more detail with reference to the detail figures of Figures 2A - 2C.

FIG. 2A shows an outer hollow-cylindrical shaft 40 with a proximal end region 42, a proximal flexible section 44 adjoining it, and a rigid center section 46 adjoining it in the direction of the distal end 52, on which a flexible section 50 first follows at the distal end section 48 to which then a component of a tool 52 is connected or formed. In the present case, the component of the tool is formed on the distal end of the outer shaft 40.

In this outer shaft 40, a control element 60 shown in Figure 2B is then inserted, which has a plurality, in this case eight, parallel to the longitudinal direction of the instrument extending force transmitting longitudinal elements 62, for example in the form of cables or wires.

The longitudinal elements 62 are connected to each other at their proximal and distal ends in the circumferential direction to form a collar 64, 66. The length of the control member 60 extends from the proximal hinge portion, as can be seen by comparing the illustration in FIGS. 2A and 2B 44 of the outer shaft 40 to the distal hinge portion 50 of the outer shaft 40th

Figure 2D shows an alternative embodiment of a control element 60 ', which is made of a one-piece tube 61, for example by laser beam cutting.

The slits 63 formed in the tube 61 by laser beam cutting extend almost the entire length of the tube 61, so that only at the proximal and distal end unslotted annular collars 64 ', 66' remain, which connect the force acting longitudinal elements wall segments 65 each with each other.

Finally, an inner shaft 80, as shown in FIG. 2C, is inserted into the interior of the hollow-cylindrical control element 60.

Also, the inner shaft 80 includes at the proximal end a hinge portion 82 and a flexure resistant center portion 84 and a distal hinge portion 86. Attached to the distal hinge portion 86 is a tool component 88 which, after the inner shaft 80 passes through the control member 60, into the outer shaft 40 is inserted in the same position as the tool component 52 of the outer shaft 40 is arranged.

According to a preferred embodiment of the invention it is provided that the inner shaft 80 simultaneously acts as a drive element, so that during a rotational movement then the tool components 88 and 52 interact and, for example, in this area coming into contact tissue parts via a cutting, Abrasiv- or milling function can remove. After the inner shaft 80 has a free lumen, such tissue parts may be delivered and removed via the lumen of the inner shaft 80 out to the proximal end 42 of the instrument.

The design of the joint sections in the form of the flexible sections 44, 50 and 82, 86 of the inner and outer shank can be varied.

FIGS. 2E and 2F show two variants of related embodiments of the flexible sections, here in the form of the sections 44 'and 44 ", respectively. The same type of configuration is also suitable for the flexible section 50.

Common to the two variants is the use of a slot structure with circumferentially extending slots 47 in the hollow cylindrical shaft. Preferably, two or more slots separated from one another via webs are present along a circumferential line. Since the arrangement of slots along only one perimeter line would allow only a very small pivot angle, typical slot structures of hinge zone 44 'have a plurality of axially spaced circumferential lines with slots 47 therein. Slits 47 which are arranged adjacent to one another in the axial direction are preferably offset relative to one another in the circumferential direction, so that bending possibilities result in several levels.

In FIG. 2F, there are two slots 47 per circumferential line, which are separated from one another by webs 49. In Figure 2E, there are three slots 47. The slot structure in both cases typically includes a plurality of slots 47 arranged along a plurality of imaginary and axially spaced circumferential lines. By choosing the slot structure and the number of slots, it is very easy to specify the permissible swivel angle and also to adapt other properties of a joint section, such as the flexural strength, to the particular application. FIG. 3A shows an alternative control element 90 in which the longitudinal force-transmitting elements 92 are connected at their proximal and distal ends to proximal and distal annular collars 94, 96, respectively. In contrast to the control element 60 shown in FIG. 2B, the longitudinal force-transmitting elements 92 are not rectilinear and arranged parallel to the longitudinal axis of the control element 90, but along helical lines such that the ends of the longitudinal elements 92 are circumferentially angularly offset Ringbünd 94, 96 end. The angular offset in the circumferential direction in the embodiment shown in Figure 3A is about 180 °, with the result that a pivoting movement of the proximal end of the instrument leads to a pivotal movement of the distal end portion, which runs in the same pivoting plane but in the opposite direction. Instead of the S-shape shown in Figure IB, a U-shaped angled instrument configuration is then obtained.

Other angular differences are possible, in principle in the full range of 0 to 360 °, with notable advantages in the range of about 10 ° to about 350 ° are achieved. For example, with an angular offset of 90 °, a pivoting movement of the distal end section perpendicular to the pivoting plane of the proximal end section is achieved.

FIG. 3B shows a variant of a control element 90 'which, like the control element 60' of FIG. 2D, is formed from a one-piece tube by laser cutting. The resulting wall segments 92 'are separated by slots 93' of each other and only in the region of annular collars 94 ', 96' positively connected to each other. The advantages of the helical course of the wall segments are the same as in the control element 90 with the helical longitudinal elements 92.

Claims

claims

1. Surgical instrument, in particular for use in combination with a trocar or the like., With a proximal and a distal, each comprising a joint zone end portion and an interposed, bending-resistant central portion, wherein the proximal end portion is connectable to an actuating device and wherein the distal end portion of a drivable by a drive element drivable cutting, Abrasiv- or milling tool is connected, wherein the instrument an outer hollow cylindrical shaft, an inner hollow cylindrical shaft and arranged between these shafts control element with two or more at least substantially from the proximal to the distal hinge zone The elongate elements arranged in the circumferential direction of the instrument at substantially regular angular intervals and at its proximal and distal End are connected to each other in the circumferential direction.

2. Instrument according to claim 1, characterized in that the inner shaft is designed as a drive element for the cutting, Abrasiv- or milling tool.

3. Instrument according to claim 2, characterized in that the drive element is formed substantially torsionally stiff.

4. Instrument according to one of claims 1 to 3, characterized in that at least one of the articulation zones is formed flexurally elastic.

5. Instrument according to one of claims 1 to 4, characterized in that the force-transmitting longitudinal elements are arranged laterally spaced from each other.

6. Instrument according to claim 5, characterized in that between the force transmitting longitudinal elements spacers are arranged.

7. Instrument according to one of claims 1 to 4, characterized in that the force-transmitting longitudinal elements are arranged along the longitudinal direction at least partially in direct contact with each other.

8. Instrument according to one of claims 1 to 7, characterized in that the force-transmitting longitudinal elements are guided by the outer and the inner shaft in the radial direction.

9. Instrument according to one of claims 1 to 8, characterized in that the force-transmitting longitudinal elements in the circumferential direction in different angular position at the proximal end and end at the distal end portion.

10. Instrument according to claim 9, characterized in that the force-transmitting longitudinal elements are at least partially helically arranged in the form of a spiral.

11. Instrument according to one of claims 1 to 10, characterized in that the force-transmitting longitudinal elements in the region of the proximal and / or distal end portion are arranged with a substantially parallel orientation to the longitudinal axis of the instrument.

12. Instrument according to claim 10 or 11, characterized in that the force-transmitting longitudinal elements one or more sections have, which are arranged parallel to the longitudinal direction of the instrument.

13. Instrument according to one of claims 1 to 12, characterized in that the force-transmitting longitudinal elements are formed as cables or wires.

14. Instrument according to one of claims 1 to 12, characterized in that the force-transmitting longitudinal elements have a bananenförmi- gene cross section.

15. Instrument according to one of claims 1 to 14, characterized in that the control element comprises a hollow cylindrical member whose cylinder wall is divided at least in the region of a portion between the proximal and distal ends in two or more wall segments which form the force-transmitting longitudinal elements.

16. Instrument according to claim 15, characterized in that the two or more wall segments are connected to one another at the distal end of the hollow cylindrical member via a collar.

17. Instrument according to claim 15 or 16, characterized in that the two or more wall segments are firmly connected to each other in the region of the proximal end of the hollow cylindrical member.

18. Instrument according to one of claims 15 to 17, characterized in that the hollow cylindrical member is integrally formed.

19. Instrument according to claim 18, characterized in that the hollow cylindrical component is made from a single tube, wherein the subdivision of the cylinder wall into wall segments is preferably carried out by means of laser beam cutting.

20. Instrument according to one of claims 15 to 19, characterized in that the hollow cylindrical member is made of a steel alloy or Nitinol.

21. Instrument according to one of claims 1 to 20, characterized in that at least one of the outer and inner shafts have a rigid portion disposed between the proximal and distal hinge zones.

22. Instrument according to claim 21, characterized in that the proximal joint zone has an extension in the longitudinal direction of the instrument, which is different from the extension of the distal joint zone.

23. Instrument according to claim 22, characterized in that the extent of the proximal and / or distal joint zone is adjustable.

24. Instrument according to claim 23, characterized in that the instrument comprises a holding device with which parts of a joint zone can be fixed in a bending-resistant manner with respect to the longitudinal direction of the instrument or a functional unit adjoining the proximal or distal end portion thereof.

25. Instrument according to claim 24, characterized in that the holding device comprises a relative to the longitudinal axis of the instrument displaceable rigid sleeve.

26. Instrument according to claim 25, characterized in that the rigid sleeve is arranged on the outer circumference of the outer shaft.

27. Instrument according to one of claims 24 to 26, characterized in that the holding device comprises a support member supported on the functional unit.

28. Instrument according to one of claims 24 to 27, characterized in that the holding device can be positioned in predetermined positions and preferably can be fixed.

29. Instrument according to one of claims 1 to 28, characterized in that the joint zone (s) of the outer and / or inner shaft comprise a wall portion in which a plurality of spaced apart spaced apart, extending in the circumferential direction slots are arranged.

30. Instrument according to claim 29, characterized in that in the circumferential direction two or more, in particular three or more slots are arranged one behind the other.

31. Instrument according to claim 29 or 30, characterized in that three or more slots are arranged side by side in the axial direction.

32. Instrument according to claim 31, characterized in that the juxtaposed slots are arranged offset from each other in the circumferential direction.

33. Instrument according to one of claims 29 to 32, characterized in that the slots are the cylinder wall completely penetrating slots.

34. Instrument according to one of claims 29 to 33, characterized in that the slots delimiting wall surfaces are arranged at an acute angle to the radial direction.

35. An instrument according to claim 34, characterized in that opposite wall surfaces of the same slot are arranged in mirror image, so that the outer circumference of a shaft results in a larger slot width than adjacent to the inner circumference.