Fixation clamp with thumbwheel

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F03651

TITLE

Fixation Clamp with thumbwheel

TECHNICAL FIELD

The present invention relates to a fixation clamp and, more particularly, to a fixation clamp for use in an external fixation system for holding bone fragments adjacent to each other.

PRIOR ART

External fixation systems are widely used to connect two or more bone fragments to each other. Such systems comprise bone screws, pins, wires which are inserted directly into the bone material and these systems use external structural elements as fixation rods, bars and rings. In order to connect the rods and bars to form a rigid frame, fixation clamps are used. Furthermore, fixation clamps are used to connect this screws and pins to the rigid frame to specifically hold bone fragments at an intended place.

One adjustable fixation clamp is known from EP 0 700 664 comprising two pairs of jaws allowing clamping of a rod as well as of a pin.

A clamp for multiple rod-shaped elements is known from EP 1 627 609 having one single pair of jaws. However, such a clamp allows clamping more than two, e.g. three or four rodshaped elements as pins with one single clamp, thus reducing the number of clamps. However, one further fixation clamp is necessary to fix the rod of said clamp to the frame of the fixation system.

WO 2007/001945 mentions that usual fixation clamps as e.g. known from EP 0 700 664 allow clamping of one single screw or pin to the frame and that this way to attach pins or rods leads to bulky fixation systems. Therefore WO 2007/001945 discloses a fixation

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65811-26 clamp addressing this problem and comprises two pairs of jaws within which each pair of jaws allows the introduction and clamping of two rods or pins etc. at the same time.

These clamps according to the prior art either provide different diameters of the receptions provided by the jaws to introduce different sizes of rods, pins or wires, or they rely on additional inserts as e.g. disclosed in EP 1 661 523. Such inserts reduce the diameter of the reception cavities to allow a secure fixing of differently sized rods, pins or wires.

From EP 2 250 968 a further fixation clamp is known. Although the users such as surgeons provide very good feedback concerning the handling of such a fixation clamp, many of the users mentioned clamping process in some occasions is difficult.

Furthermore the fixation clamps as known from prior art have the drawback that the user is not able to recognize, if the fixation clamp has been sterilized or if it was already used.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a fixation clamp which provides an easier clamping process, in particular the fixation clamp shall be pre-tensioned manually or handoperated respectively, and tensioned by means of a tool, such as a wrench.

According to an embodiment, there is provided a fixation clamp for use in an external fixation system for holding bone fragments adjacent to each other with the help of fixation elements, comprising at least one clamping assembly having at least one reception to accommodate a fixation element along the longitudinal axis of the reception and at least one locking element extending through the clamping assembly which locking element provides a clamping force to clamp the fixation element upon tensioning the locking element, wherein the fixation clamp comprises an actuation element which is in connection with the locking element such that the locking element is actuatable by means of the actuation element, the actuation element is designed such that it is detachable from the locking element after use and that remounting onto the locking element is prevented after having detached the actuation element from the locking element, and the actuation element is provided with at least one latching element which engages with the locking element.

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2a

According to another embodiment, there is provided a tool adapted to remount an actuation element according onto a fixation clamp as described herein, wherein the tool comprises a tool section adapted to engage with said latching elements and to push said latching elements away from the middle axis (M2) so that the actuation element is mountable onto said locking element of a sterilized fixation clamp.

Accordingly a fixation clamp, more particularly for use in an external fixation system for holding bone fragments adjacent to each other with the help of fixation elements, comprising at least one clamping assembly having at least one reception to accommodate a fixation element along the longitudinal axis of the reception and at least one locking element extending through the clamping assembly which locking element provides a clamping force to clamp the fixation element upon tensioning the locking element. The fixation clamp comprises an actuation element which is in connection with the locking element such that the locking element is actuatable by means of the actuation element, and the actuation element is designed such that it is detachable from the locking element after use and that remounting onto the locking element is prevented after having detached the actuation element from the locking element.

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By means of actuation element the locking element can be pre-tensioned or pre-tightened. After removal of the actuation element a conventional tool can be use to tighten the locking element firmly. Since the actuation element is provided such that it is not remountable once it has been detached from the locking element, the user is able to separate used or non-used fixation clamps.

Preferably the actuation element is designed as single-use or disposable element.

Preferably the actuation element is provided with at least one latching element which engages with the locking element Alternatively the actuation element comprises at least two or at least three latching elements which are arranged diagonal with respect to the locking element from each other. Thereby the latching elements are arranged such that it is not possible to spread the latching element by means of a tool such as a screwdriver which means that such a configuration the risk that the user remounts the actuation element becomes even smaller.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described in the following with reference to the drawings, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same. In the drawings,

Fig. 1

Fig. 2

Fig. 3

Fig. 4

Fig. 5 shows a perspective view of a first embodiment of a fixation clamp of the present invention;

shows a cross-section of the fixation clamp according to figure 1;

shows a top view of the fixation clamp for figure 1 ;

shows a perspective view from the top of an actuation element which is connectable to the fixation clamp of figure 1;

shows a perspective view from the bottom of the actuation element of figure 4;

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Fig. 6 shows a cross-sectional vie of the actuation element of figure 4;

Fig. 7 shows a perspective view of the fixation clamp of figure 1 and the actuation element of figure 4 before mounting the actuation element onto the fixation clamp;

Fig. 8 shows a cross-sectional view of figure 7;

Fig. 9 shows a cross-sectional view of the arrangement of figure 7 in a premounting state;

Fig. 10 shows a cross-sectional view of the arrangement of figure 7 in a mounting state; and

Fig. 11 shows a cross-sectional view of the arrangement of figure 7 in a mounted state.

DESCRIPTION OF PREFERRED EMBODIMENTS

Figure 1 und 2 show a preferred first embodiment of a clamping element or fixation clamp 10 pursuant to the invention. The clamping element 10 consists of a first clamping assembly 20 and a second clamping assembly 30 and a locking element or shaft 40 which is positioned through bores 21, 31 within the two clamp assemblies 20, 30 along the longitudinal axis M of shaft 40. The shaft 40 is preferably a locking element adapted to allow closing the clamp assemblies 20 and 30. Shaft 40 enters a first jaw 11 through a washer 41.

The shaft 40 comprises a head portion 44, a reduced diameter portion 43 which is followed by a shaft portion 42 and a thread portion 49. The outer threaded portion 49 is adapted to be screwed into a complementary inner thread within the distal jaw 11 so that turning the head of the shaft 40 changes the longitudinal position of the shaft 40 against the lower jaw 11, which allows opening or closing the entire clamp 10 against the force of a spring 15 provided between the two clamp assemblies 20 and 30. Said spring 15 is preferably positioned in corresponding receptions 16 in the jaws 12. Instead of a spring 15, provided around shaft 40, it is possible to provide a different spring means as Belleville washers or an elastic compressible solid or foam. Upon closing of the clamp assemblies 20 and 30 the jaws 12 adjacent to the spring 15 can eventually come into contact and then the antirotation surfaced 55 which are provided in both surfaces of the jaws 12 fixe the angular

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F03651 orientation of each clamping assembly 20 and 30 against the other.

Preferably after having mounted the shaft 40 with the thread 49 within the lower jaw 11, the end portion of the thread 49 is destroyed through pressure to ensure that the shaft 40 cannot be removed from the clamping assemblies 20, 30 to maintain the clamp as one single piece.

Each clamping assembly 20 or 30 comprises two opposing clamping jaws 11 and 12. These jaws 11 and 12 are essentially similarly shaped on the sides facing each other. Each of the jaws 12,11 comprises a respective contact surface 18, 19 facing the other surface of the jaw 11,12.

In order to prevent rotation between the jaw 11 and the jaw 12 as well as in order to prevent a misalignment of the jaw 11, 12 at least one orientation device 13, 14 is arranged on the surfaces 18, 19. In the present embodiment in the second clamping assembly 30 the jaw 11 comprises an opening 14 extending into surface 18 and the jaw 12 comprises a pin 13 extending from surface 19. The pin 13 extends into the opening 14. This pin-opening connection prevents therefore a possible rotation between the jaws 11, 12 and a possible misalignment between the jaws 11,12.

The jaws 11 and 12 are provided here with three grooves 51, 52 and 53. Grooves 51, 52 and 53 are all provided in a same plane perpendicular to the longitudinal axis of shaft 40. In that plane they are oriented perpendicular to the radial direction from the center of the bore 21 or 31. As such the grooves 51, 52 and 53 are substantially parallel to outer side wall 61,62 or 63 of each pair of jaws 11 and 12.

Each pair of grooves 51, 52 or 53, respectively, in each jaw 11 and 12, define one reception, i.e. a first reception 71, a second reception 72 and a third reception 73. The grooves 51, 52 and 53 are each formed as a rounded semi-spherical recess in section to provide receptions 71, 72 and 73 which accommodate cylindrical pins or rods with a defined diameter, if the clamp is closed. The outer side walls 61, 62 or 63 can comprise an inclined sliding surface to allow an easier clipping of such pins or rods 100 into the corresponding reception. The grooves 51, 52, 53 are called to form rounded semi-spherical

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F03651 recesses in a section. This means that the recesses provided by the grooves 51, 52, 53 have a hollow cylindrical shape to accommodate rod-shaped elements. Some or all of the grooves 51,52, and 53 are also provided with friction enhancing elements such as ribs 56.

All three grooves 51, 52 and 53 have different sizes so that the corresponding receptions 71, 72 and 73 have three different sizes. In other words each reception 71, 72 or 73 is adapted to accept a different fixation element, i.e. a rod, screw, pin or wire having a different diameter. One preferred embodiment of the first clamping assembly 20 has grooves to accept fixation elements having a diameter of 12 mm, 8 mm and 5 mm, respectively. A different embodiment may have a sequence of diameters of 8 mm, 6 mm and 4 mm, respectively.

The second clamping assembly 30 according to the embodiment of Fig. 1 also comprises two jaw portions 11 and 12 and these comprise three grooves 51, 52, 53. These grooves 51, 52, 53 also comprise a sequence of different sizes. In the embodiment shown the inner jaws portion 12 have an identical structure as have the outer jaws 11, especially in view of the anti-rotation device 55, the reception 16 for a spring 15.

Within a preferred embodiment the first clamping assembly 20 may comprise a sequence of smaller sizes, e.g. 7 mm, 5 mm and 3 mm; or 6 mm, 5mm and 4 mm; and the second clamping assembly 30 may comprise a sequence of larger sizes, e.g. 13.5 mm, 12 mm and 10 mm. Different sizes are possible, usually for wires starting from 2 mm diameter until thicker rods with a diameter of 30 mm are used within such a clamp 10. Such a clamp 10 allows using one single versatile clamp, wherein the first clamping assembly 20 is used to fix a specific pin or screw or wire having a diameter for which one of the receptions 71, 72 or 73 is adapted. The user takes the clamp 10 and orients the first clamping assembly 20 into the correct alignment so that the pin or screw can be clipped into the corresponding reception.

Then the clamp 10 can be clamped on a rod of an external fixator with the help of the second clamping assembly 30. Said second clamping assembly 30 can be oriented in a way so that the rod can be clipped into the corresponding reception. It is an advantage of the clamp 10 having two clamping assemblies 20 and 30 according to the invention, that a

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F03651 practitioner attaching such a clamp at a bone screw with one clamping assembly 20 and subsequently a rod of an external fixator to the other clamping assembly 30 can check the robustness of his external fixator, and if he finds that the rod he has used is not stiff enough, he simply opens the second clamping assembly 30, removes the thinner rod, turns the second clamping assembly 30 e.g. 60 degrees into one direction or the other around the longitudinal axis to align the larger reception with the new thicker rod and replaces it. This change does not necessitate the replacement of the clamp 10 itself as necessary with prior art systems. The method to replace such a rod is faster and more reliable since the clamping of the bone screw is not changed, and avoids use of a second sterile clamp at said time.

It is of course also possible that the second clamping assembly 30 is a traditional clamping assembly or even any other element known in the prior art with clamping elements. The object of a versatile clamping assembly is already achieved through one first clamping assembly 20, since it allows clamping one of three different sizes of screws, pins of wires through simple reorientation of the first clamping assembly 20.

Figure 2 shows a cross-section of the clamp according to figure 1, wherein the clamp 10 is shown in a premounted state, i.e. the spring 15 is under tension. The upper jaw 11 of the first clamping assembly 20 is therefore pushing the washer 41 against a flange 45 of the head of shaft 40. The bore 21 which accommodates part of the shaft portion 42 and the reduced diameter portion 43 is provided with a larger diameter than the respective diameter of the shaft 40 so that an angular or pivoting movement of the first clamping assembly 20 against the shaft 40 is possible. This is in particularly advantageous during the mounting process of the fixation clamp. With this regard it has to be noted that also bore 31 can be provided with a larger diameter than the respective section of the shaft 40 such that jaw 12 of the second clamping assembly becomes pivotable to the shaft 40.

The diameter DI, D2 of bore 21 of the first clamping assembly 20 is larger than the diameter of the locking element 40 extending through the bore 21. Thereby a pivoting movement or displacement between the locking element 40 and the first clamping assembly 20 during positioning the clamping assemblies 20, 30 and the pins or rods becomes possible. In the present embodiment the bore 21 in the first jaw 11 is a bore 21

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F03651 having an abutment surface 86. The abutment surface 86 is provided by means a step-like bore 21 having a first section with a first diameter DI and a second section with a second diameter D2. The first diameter DI is larger than the second diameter D2. The abutment surface 86 serves as abutment element for the locking element 40 in particular for the flange 45 in case washer 41 is removed. Hence the abutment surface 86 together with the flange 45 prevents that the first clamping assembly 20 will be separated from the second clamping assembly 30 when the washer is removed. Particularly during a cleaning or sterilization process the prevention of such a separation is very advantageous.

Alternatively the bore 21 can be provided with a conical section 32 as shown with bore 21 in the jaw 12 of the first clamping assembly. In the present embodiment there are two conical sections arranged, whereby the diameter of the bore 21 decreases with increasing length of the bore as seen from outside of the jaw 12. In case two conical sections 32 are present the degree of the pivoting motion can be increased.

The shaft 40 as part of a locking element is threaded into the lower jaw 11 of the second clamping assembly 30. Hence the lower jaw 11 comprises a threaded opening. Threading may be provided in the bore or the screw may exhibit self-tapping threading. Quite generally, a locking element may be provided which may be a lever locking element or a bayonet lock. Among these locking elements may also be supporting disks or toothed disks, which, for the sake of simplicity, are not shown in the drawings.

Therefore the two clamp assemblies 20, 30 can be opened and closed through turning the head of shaft 40 and thus turning said shaft 40 in the jaw thread.

In the cross-sectional view of figure 2 it can also be seen that the locking element 40 extends through the first clamping assembly 20 and is in contact with the second clamping assembly 30 by means of the threaded portion 49. In mounting position in which the rods or pins will be positioned in the receptions 71, 72, 73 the first clamping assembly 20 is moveable along the middle axis M of the threaded portion 49. Upon actuation of the locking element 40 the first clamping assembly 20 will be moved against the spring pressure towards the second clamping assembly 30 such that the anti-rotation surface 55 of the first clamping assembly 20 comes into contact with the respective anti-rotation surface

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F03651 of the second clamping assembly 30. Once the locking element 40 is firmly tightened the first clamping assembly 20 and the second clamping assembly 30 are in contact with each other via the anti-rotation surface 55.

In figure 2 the mounting position of clamping assemblies 20, 30 is shown. Thereby the clamping assemblies 20, 30 are positioned at the distance to each other with regard to the middle axis M. The second clamping assembly 20 is in contact with the locking element 40 and the spring 15 pushes the first clamping assembly away from the second clamping assembly 20 towards the washer 41 which is contact with the flange 45 of the locking element.

To summarize: The clamping assemblies 20, 30 will be moved due to actuation of the locking element 40 from a mounting position to a locking position and afterwards when fixation shall be cancelled from the locking position to the mounting position. After use the washer 41 will be removed as explained below in order to sterilize the clamping element 10 for further use.

Figure 3 shows a view from above on the clamp according to Figures 1 and 2. Since the embodiment of Fig. 1 comprises three grooves 51, 52 and 53, there are three side walls 61, 62 and 63, which provide, when looked from above as in Fig. 2 a triangular shape of each clamping assembly 20 or 30.

The clamping element 10 further comprises an actuation element 90 or thumbwheel which is used to prethighten the locking element 40 before it is tightened by means of a tool such as a wrench. Such an actuation element 90 is shown in figures 4 to 11, whereby in said figures the fixation clamp according to figure 1 and 3 is shown. For the sake of simplicity not all reference numerals regarding the fixation clamp 10 have been added.

Figures 4 to 6 show views of an actuation element 90 to actuate the locking element 40 in order to pretighten the fixation clamp 10 by hand. The actuation element 90 is designed as single use element. Preferably the actuation element 90 is mounted onto the locking element 40 during or shortly after the process of sterilizing the fixation clamp 10. After pretightening the fixation clamp 10 the actuation element 90 is removed by the user, e.g. a

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F03651 surgeon or an assistant of the surgeon. The user then is able to tighten the locking element 40 by means of a tool that engages the head portion 44 of the locking element. Since the actuation element 90 is designed as single use element it is not possible to remount the actuation element 90 onto the locking element 40 after having it detached from the locking element 90. This has the advantage the one can easily recognize, if the fixation clamp 10 has already been used or if it is still ready to be used, e.g. if it is still sterilized.

To summarize: the actuation element 90 is designed such that it is mountable by means of a mounting tool 110 onto the locking element 40, that it is detachable from the locking element 40 after use and that remounting onto the locking element 40 is prevented after having detached the actuation element 90 from the locking element 40.

Hence the actuation element 90 is provided in mainly three states, namely in a mounting state in which the actuation element 90 is mounted onto the fixation clamp 10, in a mounted state in which the actuation element 90 is fixedly connected with the locking element 40 and in a detached state in which the actuation element 90 is detached from the locking element 10 and in which it is impossible to remount the actuation element 90. In the mounted state the fixation clamp 10 is ready for use in a surgery.

The actuation element 90 comprises in the present embodiment, a cylindrical sidewall 93, a frontwall 95 extending substantially perpendicular to said sidewall 93, a central opening 92 extending along a middle axis M2 substantially parallel to said sidewall 93 and at least one, here four, latching elements 91. The sidewall 93 and the frontwall 95 encompass an interior space 94 in which the latching elements 91 extend. The latching elements 91 extend from the frontwall 95 in direction of middle axis M2 into said interior space 94 and are designed to engage with the locking element 40.

The latching elements 91 are provided as elastic or resilient beam elements having a first end 98 which is in contact with the sidewall 93 or the frontwall 95 and a second end 99 which is provided as loose end. In the present embodiment the first end 98 is in contact with the ffontwall 95 and the first end 98 extends over a first segment 101 substantially parallel to said frontwall 95 and over a second segment 102 substantially perpendicular or angular to said frontwall 95. Said latching elements 91 are by means of a mounting tool

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110 elastically deformable from a blocking position in which the locking element 40 is not insertable into the actuation element 90 to a mounting position in which the actuation element 90 is mounteable onto the actuation element 90.

The second end or loose end 99 is provided with an engaging element 97 which engages with the locking element 40. The engaging element 99 here has the shape of an embossment extending from the loose end 99 into the interior space 94.

Reference is made to the cross-sectional view of the actuation element 90 in figure 6. The actuation element 90 will be moved along its middle axis Ml with respect to the locking element 40. In the present embodiment the locking element 40 enters the interior space from below in figure 6 as indicated by arrow 200.

In the vicinity of the second end 99 there is arranged an abutment surface 96. The abutment surface 96 is arranged substantially perpendicular to said middle axis M2 and extends into the central opening 92. In case the user tries to remount the actuation element 90 onto the locking element 40 the abutment surface 96 blocks the locking element 40 from intruding into the interior space 94. Hence the abutment surface 96 blocks a movement of the locking element 40 into the interior space 94 as it extends into the path of the locking element 40.

The latching element 91 in the present embodiment is provided with an optional guiding slot 103 which extends as seen from the central opening 92 or the middle axis M2 into the latching element 91. Said guiding slot 103 serves to accommodate a respective counter part of the mounting tool 110.

The actuation element 90 comprises furthermore an outer surface on said cylindrical sidewall which outer surface comprises friction enhancing elements 100 in order to increase friction between a user’s hand and the actuation element. In the present embodiment the friction enhancing elements 100 are hollow channels extending in direction of the middle axis M2 into said sidewall 93. Furthermore the sidewall 93 comprises also recesses 104 extending into the sidewall 93.

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From figure 1 and 2 it can be seen that the locking element 40 comprises in its head portion 44 adjacent to flange 45 several recesses 46. In the present embodiment the head portion comprises several, here four side surfaces 48 extending from the flange 45 along middle axis M. The head portion 44 ends with a top surface 47 which is arranged substantially 5 perpendicular to the middle axis M and to the side surfaces 48. The top surface 47 here is slightly convex. The side surfaces 48 serve as engaging surface for a tool in order to tighten the locking element 40. In the present embodiment the recesses 46 extend into the head portion 44, in particular into the side surfaces 48 of the locking element 40.

Reference is now made to figure 7 und 8 in which the actuation element 90 is shown above the fixation clamp 10. Furthermore a mounting tool 110 to mount the actuation element 90 onto the fixation clamp 10 is shown. The mounting tool 110 is used to mount the actuation element 90 onto the locking element 40 during or shortly after sterilizing the fixation clamp 10. The mounting tool 110 mainly serves to push the latching element 91 away from the middle axis M2 so that the clearance between the latching elements 91 becomes larger in order to receive the head portion 44 of the locking element 40. With other words it can also be said that the abutment surfaces 96 will be moved away from the middle axis M2 such that they give way for the head portion 44.

The mounting tool 110 comprises a tool section 111 and a handle section 112. The tool section 111 is provided such that the mounting tool 110 can be inserted into the central opening 92 and pushes the latching elements 91 away from the middle axis M2 in order to enlarge the clearance between the latching elements 91. In case the latching elements 91 are provided with the guiding slots 103 the tool section 111 comprises a respective embossment 113 that is adapted to engage into the guiding slot 103. The handle section 112 is provided such that it can be grasped by a hand of a mounting person.

In figure 9 it is shown that the mounting tool 110 will be inserted with the tool section 111 into the central opening 92. This is shown by arrow 201. Thereby the latching elements 91 30 will be moved away from the middle axis M2. Hence the abutment surfaces 96 as well as the engaging elements 97 will be moved away from the middle axis M2 towards the sidewall 93.

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Figure 10 shows the actuation element 90 in the mounting state in which the actuation element 90 will be moved towards the fixation clamp 10 in direction of arrow 202, wherein the head portion 44 of the locking element 40 extends into the interior space 94 between the latching elements 91. The latching element 91 is thereby in contact with the side surface 48 of the locking element 40 and therefore it is possible to move the actuation element 90 with respect to the locking element 40.

Figure 11 shows the end position of the actuation element 90 with regard to the locking element 40. Thereby the actuation element 90 is in a position in which the engaging elements 97 are able to engage into the recesses 46 of the locking element 40. Once the actuation element 90 has reached its end position as shown in figure 11 the resilient latching elements 91 will move to their originating position and engage into the recesses 46. In this state the fixation clamp 10 is ready to be used by a user in a operating theatre during a surgery.

Once the user has pretensioned or pretightened the fixation clamp 10 by means of the actuation element 90, the actuation element 90 is detachable from the locking element 10. In order to enhance this detaching process the recesses 46 comprise chamfered edges 460 which are inclined towards the middle axis Ml such that the latching elements 91 will be moved away from the middle axis M2 upon a displacement of the actuation element 90 relative to the recess 46. Afterwards with increasing distance between the fixation clamp 10 and the actuation element 90 the latching elements 91 are in contact with the side surfaces 48 of the locking element 40 and slide on said surface. During detaching the actuation element 90 the user has to apply a force in direction of arrow 203 as shown in figure 11.

Once the actuation element 90 is completely detached from the locking element 40, the latching elements 91 will move back to their origin position due to the resilient structure. Thereby the abutment surfaces 96 are arranged such that the locking element 40 abuts with its top surface 47 on the abutment surfaces 96. Hence it is not possible to remount the actuation element 90.

The actuation element 90 is preferably made out of plastic material, in particular out of a

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F03651 thermoplast.

The actuation element 90 has the following advantages: First of all it is possible to pretighten the fixation clamp 10 by hand without the aid of an additional tool. Furthermore 5 the user is able to recognize, if the fixation clamp is ready for use when the actuation element 90 is still mounted or, if the fixation clamp has been used in which case the actuation element 90 is removed. Furthermore false use is prevented due to the fact that the actuation element 90 cannot be remounted without the aid of a respective tool.

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LIST OF REFERENCE SIGNS

10 fixation clamp 63 third side wall 11 jaw 71 first reception 12 jaw 72 second reception 13 pin 73 third reception 14 bore 90 actuation element 15 spring 91 lachting element 16 reception 92 central opening 18 contact surface 93 sidewall 19 contact surface 94 interior space 20 first clamping assembly 95 frontwall 21 bore 96 abutment surface 30 second clamping assembly 97 engaging element 31 bore 98 first end 32 conical section 99 second end 40 shaft, locking element 100 friction enhancing elements 41 washer 101 first segment 42 shaft portion 102 second segment 43 reduced diameter portion 103 guiding slot 44 head portion 110 mounting tool 45 flange 111 tool section 49 threaded portion 112 handle section 51 first groove 46 recesses 52 second groove 47 top surface 53 third groove 48 side surface 54 limiting edges 460 chamfered edges 55 anti-rotation surface DI diameter 56 ribs D2 diameter 61 first side wall Ml middle axis 62 second side wall M2 middle axis actuation element