Abstract:
An insert for an external fixation has two jaws for clamping a rod-shaped element. The insert includes a locking element and is an angled piece having two free ends, with at least one engagement edge for engagement into the rod-shaped element being provided at its one free end. The insert has a recess or bore for engagement with a locking shaft of the clamp provided at the free end thereof that lies opposite to the free end having the rod engagement edge. The insert is angled so that it may extend through a passageway in one of the jaws and into a cavity formed in the jaw for receiving the rod. The insert rod engaging edges are tapered to bite into the rod to prevent its movement.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a divisional of U.S. application Ser. No. 11/120,775, filed on May 3, 2005, the disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to an insert for a clamping element for clamping a rod-shaped element of an articulated connection, particularly for a clamping element of an articulated connection for stabilizing bone fractures. Furthermore, the invention relates to an articulated connection having two clamping elements and having a locking element. In particular, the invention relates to an insert for optimizing the fixation of round rods in an external fixation system. 
         [0003]    An articulated connection is known from U.S. Pat. Nos. 5,741,252, 5,752,954, 6,080,153, 6,342,054, 6,616,664, and 6,702,814, respectively, which consists of two or four individual clamping jaw elements and a central shaft or screw. In the case of this articulated connection, it is possible to introduce one or two rod-shaped elements into the corresponding cavities from the side. In U.S. Pat. No. 5,752,954, a spring is disposed between the two center clamping jaw elements, and it is possible to clip the rod-shaped elements in, counter to its spring force, and thereby hold the articulated connection in place against the rod-shaped elements, before it is locked in position. In U.S. Pat. No. 6,616,664, narrow lever arms disposed on the side are provided, in order to hold rod-shaped elements that have been inserted from the side in place before the articulated connection is locked in position. 
         [0004]    These known articulated connections are particularly used with frame-type systems for external treatment of bone fractures, also referred to as external fixators. By means of a suitable material pairing of the clamps of the articulated connection and of the rods, for example steels of different hardness or a combination of steel and aluminum, or also by means of suitable surface structures of the interior surface of the clamp and the mantle surface of the rod, the result can be achieved that the rod-shaped elements are sufficiently secured against rotation and axial displacement after the locking screws have been fixed in place. 
         [0005]    It is desirable to construct such external fixators using non-metallic materials, for example plastic materials, particularly in order to achieve a weight reduction of such a system. If the modules or parts of such a clamp are made of plastic injection-molded materials, there may be the difficulty in finding suitable material pairings with which sufficient fixation can be achieved. This is a problem particularly because many plastics are characterized by negative creep behavior, which causes connections that have been tightened to gradually come loose, i.e. to lose their gripping power. 
         [0006]    Another problem that arises with such configurations is the high pressure stress on the plastic parts when the screw connection has been tightened, and this stress can result in stress cracks due to irregular stress on the plastic structure. This is particularly dangerous because such defects only occur after a certain period of time, and are not clearly evident optically. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    It is an aspect of the present invention to provide an insert for a clamping element that allows insertion of rod-shaped elements from the side, and whereby the clamping element, used double, can be inserted directly as an articulated connection, whereby the aforementioned elements of the clamping element can consist of a non-metallic material, for example plastic, without any impairment of the safety of the resulting articulated connection in an external fixator. 
         [0008]    Furthermore, it is an aspect of the present invention to provide a simple clamping element designed for use of such inserts. 
         [0009]    Yet another aspect of the invention is an improved articulated connection. 
         [0010]    It is one goal of the invention to offer a suitable system that allows an optimal and, to the greatest extent possible, a direct friction lock between the connecting clamp and the rod-shaped elements, which remains constant. At the same time, the locking does not result in overly great stress on the plastic parts and therefore helps to prevent structural damage. The permanent stability of frame configurations for external fixators, which are predominantly made of plastic, is guaranteed, in other words the reliability known from previous metal designs is assured. Furthermore, this design should be a design that can be easily produced and advantageously assembled, in order to obtain a relatively inexpensive product. 
         [0011]    These and other aspects of the present invention are accomplished by a clamping element for engaging a rod of an external fixation system. The clamping element has a first jaw member having a bore therethrough and a rod receiving cavity spaced radially from the bore. The cavity may be part cylindrical shape extending along an axis. The clamp includes a second jaw member having a bore therethrough and a rod receiving cavity spaced from the bore. A locking shaft extends through the bores of the first and second jaw members in a direction generally perpendicular to the axes of the cavities in the jaw members. The locking shaft may be threaded at one or both ends to allow for the tightening of the clamping elements against the rod. The clamping element includes an insert having a first part with a bore or recess for receiving the locking shaft and a second part extending into the rod receiving cavity of at least one of the jaw members. The second part has a tapered or pointed edge for engaging an outer circumferential surface of the rod received within the cavities of the first and second jaw members. Once the jaws are tightened by the use of the locking shaft and any associated threaded locking element coupled thereto the tapered edge bites into the outer surface of the rod fixing it axially within the cavities. In addition, the insert takes part of the load clamping the rod between the jaw members. 
         [0012]    The insert may be either angled or L-shaped. The first part of the L-shaped including a bore for receiving the locking shaft with the second L-shaped portion extending through a passageway in at least one of the jaw members and into engagement with the cavity housing the rod. The tapered edge of the insert may be in the form of a plurality of points or may have a roughened surface for better biting into and engaging the rod and preventing its motion. The tapered engagement edge can extend both axially along the rod and perpendicular thereto to better prevent axial motion of the rod within the cavity. The insert may include an anti-rotation feature to prevent the insert from rotating out of alignment with the axis of the cavity. This can be accomplished by having a portion of the insert in the region of the bore engaging the locking shaft or a portion of the insert engaging a recess in the jaw member. Preferably, the passageway runs from the outside of the jaw member through the jaw member in a direction that is perpendicular to the axis of the cavity and through a surface that delimits the cavity so that the first part of the insert clamp can lie against the clamp outer surface with the second part extending generally at 90° thereto extending into the cavity which receives the rod. In a preferred embodiment of the outer side of the jaw with the insert has a recess extending along the face of the jaw member and recessed in the direction of the passageway to receive the first part of the jaw. The recess is sized to receive the first part of the insert as a press-fit so that the insert is retained on the outer side of the jaw member and is prevented from rotation with respect thereto. Also in the preferred embodiment the bore in the first part for receiving the locking shaft may be oblong so that the jaw member with the insert press-fit therein can be moved apart when a rod-shaped element is inserted in a direction perpendicular to the axis of the cavity. In a second embodiment the jaw member may have a beveled surface for engaging a beveled surface on the insert to provide support for the insert when engaging the rod. 
         [0013]    In particular, an insert according to the invention allows a direct transfer of force from the screw or another locking element to the rod, in order to relieve stress on the plastic component. 
         [0014]    In other embodiments, it is also possible to achieve the inserts as extrusion-coated parts. In this case, metallic parts are laid into the injection-molding mold and then coated with plastic by extrusion coating. This is a common technique, but it requires a complicated and accordingly expensive production process (robot-controlled placement of the metal parts or manual placement). A disadvantage of such a solution is that extrusion-coated parts are also subject to the creep phenomena mentioned. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The invention will now be explained in greater detail, making reference to the drawings, using exemplary embodiments. These show: 
           [0016]      FIG. 1  is a cross-sectional side view of an articulated connection having two clamping elements having inserts according to a first exemplary embodiment of the invention; 
           [0017]      FIG. 2  is a perspective view of the first exemplary embodiment according to the invention, with an inserted rod; 
           [0018]      FIG. 3  is a perspective view of the insert according to the first exemplary embodiment; 
           [0019]      FIG. 4  is a bottom view of the insert according to  FIG. 3 ; 
           [0020]      FIG. 5  is a side view of the insert according to  FIG. 3 ; 
           [0021]      FIG. 6  is a perspective view of an insert according to a second exemplary embodiment; 
           [0022]      FIG. 7  is a bottom view of the insert according to  FIG. 6 ; 
           [0023]      FIG. 8  is a side view of the insert according to  FIG. 6 ; 
           [0024]      FIG. 9  is a perspective view of an insert according to a third exemplary embodiment; 
           [0025]      FIG. 10  is a bottom view of the insert according to  FIG. 9 ; 
           [0026]      FIG. 11  is a side view of the insert according to  FIG. 9 ; 
           [0027]      FIG. 12  is a cross-sectional side view of an articulated connection having two clamping elements having inserts according to a fourth exemplary embodiment of the invention; 
           [0028]      FIG. 13  is a perspective view of the articulated connection according to  FIG. 12 , with an inserted rod; 
           [0029]      FIG. 14  is a perspective view of the insert according to the fourth exemplary embodiment; 
           [0030]      FIG. 15  is a bottom view of the insert according to  FIG. 14 ; 
           [0031]      FIG. 16  is a side view of the insert according to  FIG. 14 ; 
           [0032]      FIG. 17  is a top view of the insert according to  FIG. 14 ; 
           [0033]      FIG. 18  is a perspective view of the insert according to a fifth exemplary embodiment; 
           [0034]      FIG. 19  is a side view of the insert according to  FIG. 18 ; 
           [0035]      FIG. 20  is a perspective view of the insert according to a sixth exemplary embodiment; 
           [0036]      FIG. 21  is a side view of the insert according to  FIG. 20 ; 
           [0037]      FIG. 22  is a bottom view of the insert according to  FIG. 20 ; 
           [0038]      FIG. 23  is a perspective view of an articulated connection having inserts according to the sixth exemplary embodiment of the invention, with an inserted rod; 
           [0039]      FIG. 24  is a cut side view of the articulated connection according to  FIG. 23 ; and 
           [0040]      FIG. 25  is a side view of an insert with a roughened surface. 
       
    
    
     DETAILED DESCRIPTION 
       [0041]    Referring to  FIG. 1  there is shown a cross-sectional side view of a preferred articulated connector  100  having two clamping elements  10  having inserts  50  according to a first exemplary embodiment of the invention. 
         [0042]    Each clamping element  10  has two clamping jaws  12  and  13  that lie opposite one another and have a cavity  11  for accommodating a rod-shaped element  101 . Rod  101  may be formed of a polymeric or composite material such as carbon fiber reinforced PEEK. The clamping jaws  12  and  13  have a groove with a longer curvature portion  14  and having a short curvature portion  14   a  that runs crosswise, in each instance, at their free ends  15 , which grooves together define the cavity  11 . At the free ends  15 , the outer edges  16  of the sides of the clamping jaws  12  and  13  that face one another are rounded, in order to facilitate the insertion of a rod-shaped element from the side. Opposite the cavity  11  and the free ends  15 , a hinge means  17  is provided, which can be seen in  FIG. 2 , and which connects the clamping jaws  12  and  13  with one another to form a single piece. A screw  103  that passes through clamping elements  10  and can be screwed into a nut  106  closes the articulated element  100 , and locks rods  101  that can be inserted into the latter in place. This screw/nut connection is a locking element that can also be implemented by way of levers and other elements. 
         [0043]    Clamping elements  10  have a solid cross-section in their center region, forming two lateral cross-ribs  21 , which are particularly marked in the upper region of clamping jaw  12 . The region between cross-ribs  21  is recessed towards the front edge  16 , with the exception of a rectangular insert accommodation or recess  18  that can be seen in the top view of  FIG. 2 . Insert accommodation  18  has a continuous bore centrally in the clamping element  10 , to accommodate screw  103 . Ribs  21  can also run completely on the outside of the clamping element, depending on the width of an insert  50 . Insert accommodation  18  can also consist of a second step, at a distance from ribs  21 . 
         [0044]    In the inner or lower clamping jaw  13 , cross-ribs  21  end in a ring flange  22 , which can have a flat, recessed, ring-shaped segment, for example, which can be followed by a recess that saves weight and material and is advantageous for injection-molding production, in the center of which a bore is provided. This continuous bore is oriented to align with the aforementioned continuous bore in the upper clamping jaw  12 . In the clamping element  10 , it runs perpendicular to the axis of the cavity  11  and parallel to the back of the hinge means  17 . However, it could also run at a slant. The ring flange  22  can be a carrier of engagement elements such as radial teeth, in order to prevent rotation of the clamping elements  10  relative to one another. A separate rotation element for insertion between the two clamping elements  10  can also be provided. 
         [0045]    In the representation of  FIG. 1 , preferred articulated element  100  is formed from two clamping elements  10 . The clamping elements  10  are provided, for example, for a rod having a diameter of 12 millimeters, for example. Then, the opening at the free ends has a diameter of 8 millimeters, for example, in the resting state. If the upper clamping element  10  is now supposed to be provided for a rod having a diameter of 4 to 6 millimeters, then the opening at the free ends  15  would have a diameter of 2 millimeters, for example, in the resting state. 
         [0046]    In the preferred embodiment an insert  50  is inserted into insert accommodation or recess  18 ; the former consists of an L-shaped profile that will be described in greater detail in  FIG. 3  and others. A continuous slit bore  19  is provided in upper clamping jaw  12 , in insert accommodation  18 , through which the tips of the L-shaped profile of insert  50  can project, into the region of the cavity  11 ; slit bore  19  ends in groove  14 , preferably in the center of groove  14 . They can always project into the groove  14  by 1 millimeter, for example, because the profile surface of the insert  50  sits in the clamping jaw with a press fit. 
         [0047]      FIG. 2  shows a perspective view of the first embodiment according to the invention, with an inserted rod  101 . The same characteristics in the drawings are shown with the same reference symbols, in each instance. In lower clamping element  10 , the break-through of slit bore  19  and two teeth of lower insert  50 , which is held by the nut  106 , can be seen. Here, the connection between clamping elements  10  is pressed apart by way of a pressure spring  23  that has been inserted between them. 
         [0048]      FIG. 3  shows a perspective view of insert  50  according to the first embodiment,  FIG. 4  shows a bottom view of this insert  50 , and  FIG. 5  shows a side view of the insert  50 . In the top view, the insert  50  is essentially a rectangular plate having an oblong bore  52 . In cross-section, the insert  50  looks like an L-shaped small plate having a long side  51  and a shorter engagement side  53 . Here, the free end of the shorter engagement side  53  ends in two teeth  54 , which have a prism shape in cross-section. The insert  50  serves as an inserted part in the plastic part of clamping element  10 , which is placed into the coupling element  10  under screw head  103  or under nut  106 , respectively. Preferably, here insert  50  is a die-punched part. In this embodiment, metal part  50  is affixed to the outside of the articulated element  100 , making reference to  FIGS. 1 and 2 . Insert  50  is structured in such a manner that it can claw directly into a round rod-shaped element  101 , through the penetration or slit bore  19  in the clamping element  10 , with an angled front side  53 , and thereby results in a material deformation or notching in rod-shaped element  101 . As a result, an optimal friction lock between elements  10  (by way of insert  50 ) and a rod  101  is achieved. The advantage is, in particular, that the friction lock comes about directly between screw  103  (or nut  106 ) and rod-shaped element  101 , by way of insert part  50 , and plastic component  10  of coupling element  100  now serves only as a guide element. As a result, the stress on it is significantly relieved, and it can be optimally designed for this guide function. In this context, engagement edge  55  of teeth  54  is directed essentially axially in the direction of rod  101 , and prevents rotation in particularly excellent manner. 
         [0049]      FIG. 6  shows a perspective view of an insert  60  according to a second embodiment.  FIG. 7  shows a bottom view of the insert  60  according to  FIG. 6 , and  FIG. 8  shows a side view of the insert  60  according to  FIG. 6 . The insert  60  is essentially very similar to insert  50 , with the difference that here, four teeth  64  are provided, and that the engagement edge  65  of the teeth  64 , in each instance, stands crosswise to the longitudinal direction of rod  101 , into which it can engage. Therefore the engagement edge  65  of the teeth  64  stands essentially crosswise to the direction of rod  101  and prevents axial displacement of the clamping element  10  on rod  101 , in particularly excellent manner. 
         [0050]      FIG. 9  shows a perspective view of on insert  70  according to a third exemplary embodiment,  FIG. 10  shows a bottom view of the insert according to  FIG. 9 , and  FIG. 11  shows a side view of the insert according to  FIG. 9 . In this embodiment variant, the first and second exemplary embodiments are combined, in principle. The insert  70  has lengthwise teeth  74  having an engagement edge  75  that prevents rotation, and crosswise teeth  76  having an engagement edge that prevents axial displacements. Here, one central lengthwise tooth  74  and two crosswise teeth  76  disposed to the sides of the former are provided; two or more lengthwise teeth  74  and one crosswise tooth  76  on only one side, or, in advantageous manner, two or more crosswise teeth  76 , symmetrically, could be provided. It is essential in this exemplary embodiment that the teeth  74  and  76 , respectively, are oriented at a right angle to one another, in order to reliably prevent both lengthwise displacement of the rods  101  and their rotation. 
         [0051]      FIG. 12  shows a cross-sectional side view of a second articulated connection  110  having two clamping elements  20  having inserts  80  according to a fourth embodiment of the invention, and  FIG. 13  shows a perspective view of this fourth embodiment according to the invention, with an inserted rod  101 . The clamping elements  20  correspond to a second embodiment of clamping elements as compared with clamping elements  10 , since they have been appropriately modified to accommodate the inserts  80 , which will be described in connection with  FIG. 14 to 17 .  FIG. 14  shows a perspective view of insert  80  according to the fourth embodiment,  FIG. 15  shows a bottom view of it,  FIG. 16  shows a side view, and finally,  FIG. 17  shows a top view of insert  80  according to  FIG. 14 . 
         [0052]    The lower clamping jaw  13  has a flat contact surface on its underside, on which the inner side  86  of the insert  80  rests (in contrast to the riffled or serrated flange  22  shown in  FIGS. 1 and 2 ). 
         [0053]    Furthermore, the clamping element  20  has a slit bore  29  that corresponds to slit bore  19 , and opens into groove  14  of clamping jaw  13 , analogously. The insert  80  is structured in U shape, and, similar to insert  50 , has a plate surface  81  that is configured here to be round, and is flattened on the side of the engagement side  83 . In the embodiment shown, two teeth  84  having engagement edges  85  which may be tapered to a pointed edge, are provided. It is clear that other configurations corresponding to the above second and third exemplary embodiments can also be implemented. 
         [0054]    On the side lying opposite the engagement side  83 , a locking bar  88  is provided, which runs essentially parallel to the engagement side  83 . The locking bar  88  runs in a slit of clamping elements  20  that runs parallel to the bore that accommodates the screw, and has a locking projection  89  that can press into the material of clamping element  20  in the depth of the slit. 
         [0055]    In this embodiment variant, two inserts  80  come to rest on one another directly, between the two parts of the clamping elements  20 , which are made of plastic, for example, and additionally take on the function of a rotation lock  87  of clamping elements  20 . In this case, the plastic parts do not have any teeth on the underside. Preferably, the insert is produced as a die-punched part. The radial teeth of rotation lock  87  engage into one another when the screw  103  is tightened, and, in order to improve the rotation lock, the insert additionally has a locking bar  88  that engages into clamping jaw  13  of plastic part  20 . 
         [0056]    In addition, this insert  80  can be configured with hooks  89  and engagement side  83 , as a clip or snap, and this simplifies assembly, since the parts can thereby be clicked onto the clamping element  20 . In this variant, as well, the teeth that engage in the rods  101  can be configured in the most various forms, of which the exemplary embodiments shown only form an advantageous selection. For example, round conical points can also be provided, instead of teeth  54 ,  64 ,  74 ,  76 ,  84 , or in addition to them. These are engagement elements, in each instance. Any such means that can be referred to as a means for generating high friction forces can be viewed as being an engagement element. This can simply have a rough surface, one or very many carpet-like little points can be present, or the engagement element can assume other embodiment forms mentioned in the specification and in the claims. 
         [0057]      FIG. 18  shows a perspective view of an insert  90  according to a fifth embodiment, and  FIG. 19  shows a side view of this insert  90  according to  FIG. 18 . The only difference between the fourth and the fifth embodiment is that the insert  90  does not have a locking bar  88 . Therefore the teeth  84  that claw into rods  101  when the articulated element is fixed in place are the only elements that simultaneously prevent rotation of the plastic clamps  10  and  20 . Therefore the rotation lock  87  is secured only on one side, and particularly utilizes the positive lock in the slit bore  29  only asymmetrically. 
         [0058]    It is clear that insert  50  according to the first embodiment can also be equipped with a locking bar  88 , if a corresponding recess is provided in clamping jaw  12 . 
         [0059]    It is directly evident that two inserts  80  and  90 , respectively, provided for the inner clamping jaws  13 , have a round bore  82 , while the inserts  50 ,  60 , and  70 , respectively, provided for the outer clamping jaws  12 , have rectangular bores or oblong bores. This is due to the fact that in order to insert the rods  101 , the clamping jaws  12  and  13  must be pressed apart. In doing so, clamping jaws  12  move about a pivot point of hinge part  17  and thereby relative to screw  103  or nut  106 , thereby making it necessary for a corresponding clear space to be present for the path of the screw  103  or nut  106 . Instead of the closed bore, a U-shaped slit can also be provided, which at least partially surrounds a clamping element  103 ,  106 . 
         [0060]      FIG. 20  shows a perspective view of an insert  190  according to a sixth embodiment.  FIG. 21  shows a side view of the insert  190  according to  FIG. 20 , and  FIG. 22  shows a bottom view. 
         [0061]    Insert  190  is configured to be rectangular with rounded corners, and, similar to insert  50 , has a plate surface  51  that makes a transition into the engagement side  93  on one side, at a slant. This can be achieved by means of punching, for example. The angle between the surface  51  and the engagement side  93  can be 45 degrees, for example, but other values, advantageously between 30 and 60 degrees, are also possible. An oblong hole  92  is disposed in the surface  51 ; its longitudinal direction is oriented perpendicular to the punch line of the engagement side  93 . The smaller diameter of the oblong hole  92  essentially corresponds to the diameter of the screw  103  provided for the clamping element  30  according to  FIG. 23 . Oblong hole  92  has a region that extends into the slant of the engagement side  93 . This is advantageous because in this way, in the case of the clamping element  30 , groove  14  for rod  101  can be brought closely up to screw  103 , which runs crosswise. The region of the engagement side  93 , which is thereby shortened, is advantageous since two rods  101  are thereby rigidly coupled with one another, tightly, by way of screw  103 , and little load acts on the clamping elements  30  that compose the articulated element  120 . 
         [0062]    In the exemplary embodiment shown, two lateral teeth  94  are provided with engagement edges  95 . This can also be described as an engagement edge  95  that is set back in the center region. It is clear that other engagement configurations, in accordance with the above first through fifth exemplary embodiments, can also be implemented. 
         [0063]    On the side lying opposite the engagement side  93 , no locking bar is provided here, which would run perpendicular to the surface  51 . Such a locking element, similar to the locking bar  88 , is, of course, possible, in order to support the locking effect. 
         [0064]    In this embodiment variant, the two inserts  190  come to rest directly between the two clamping jaws  12  and  13  of each clamping element  30 . For this purpose, the clamping jaw  12  has a bevel  38  that can rest against the engagement side  93 . In this context, the screw  103  passes through the opening  92 , which is configured as an oblong hole, in order to allow a movement of insert  190  crosswise to the orientation of rod  101 . 
         [0065]      FIG. 23  shows a perspective view of an articulated connection  120  having two clamping elements  30  having inserts  190  according to the sixth exemplary embodiment of the invention, with an inserted rod  101 , and  FIG. 24  shows a cut side view of this articulated connection  120  according to  FIG. 23 . The clamping elements  30  correspond to a third embodiment as compared with the clamping elements  10 , since they are appropriately modified to accommodate the inserts  190 . 
         [0066]    In the lower part of  FIG. 24 , it can be seen that the insert  190  rests on the clamping jaw  12  due to gravity. In this context, the engagement side  93  can rest against the bevel  38  of the clamping jaw  12 , but it does not have to do so, because the oblong hole  92  permits a movement of the insert  190  relative to the screw  103 . The engagement edge  95  projects into the cavity  11 . In this context, engagement edge  95  is oriented approximately centered in height between the clamping jaws  12  and  13 . When the rod  101  is inserted by pressing it over the edges of the clamping jaws  12  and  13 , as shown in the upper part of  FIG. 24 , the rod  101  comes to rest in the groove  14 . In doing so, it displaces the engagement side  93  towards the edge of the groove  14  and, in particular, against the bevel  38 . Then engagement edge  95  engages in the rod  101 . 
         [0067]    In the case of this variant, as well, the teeth that engage in the rods can be configured in the most various shapes, of which the exemplary embodiments shown form only an advantageous selection. For example, round conical points can also be provided, instead of the teeth  54 ,  64 ,  74 ,  76 ,  84 , in each instance, or in addition to them. They are engagement elements, in each instance. 
         [0068]    In the case of all the exemplary embodiments shown, the insert forms an angled support that directly engages on a rod, with a friction lock. Therefore the clamping elements  10 ,  20 , or  30  are now used only as a guide and spacer part; they are therefore subject to less stress. This permits an even greater material selection for the clamping elements  10 ,  20 ,  30 . In this context, the insert  50 ,  60 ,  70 ,  80 ,  90  or  190  engages in the locking element, here  103 ,  106 , on the other side. 
         [0069]    The inserts  50 ,  60 , and  70  are shown fitted into a recess  18 . This recess  18  can be configured, in particular, in such a manner that inserts  50 ,  60 , and  70  have no play in it, but rather fit into a press fit. They can then not fall out, and form a single-piece unit for the user. The same can also be achieved for the insert  80 , by means of a corresponding deformation of the lower clamping jaw  13 . As a result, a similar effect as that of the locking bar can also be achieved with reference to the rotation lock, particularly if the insert  90  is configured to be angular rather than round, whereby the characteristics that prevent rotation, for example radial grooves, are provided on the side lying opposite the flat side  86 . 
         [0070]    Finally, the inserts can also be provided as injection-coated parts in a clamping element. 
         [0071]    The exemplary embodiments shown in the drawings, and the characteristics of various exemplary embodiments mentioned in the present description, respectively, should not necessarily be understood as embodiments independent of one another. Instead, it is possible that each characteristic described in one of the exemplary embodiments can be combined with one or more of any other characteristics of other exemplary embodiments, so that other exemplary embodiments result, which are not literally described or shown in the drawings, but lie within the scope of protection claimed in the present claims.