Abstract:
An insert ( 70 ) for a clamping element with two jaws to clamp a rod-shaped element comprises an inner cavity ( 144 ) to accommodate a rod-shaped element and at least one flange element ( 153 ) at one longitudinal end of the insert intended to abut against the clamping element. The flange element ( 153 ) comprises clamping members ( 161 ) to reduce the available room within the inner cavity ( 144 ) for the rod-shaped element to be clamped and to clamp the flange element ( 153 ) between the rod-shaped element and an outer clamping surface of the clamping element to prohibit any longitudinal movement of the clamped insert.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The invention pertains to a clamping element for the clamping of a rod-shaped element of an articulation element, particularly a clamping element of an articulation element for the stabilization of bone fractures. The invention also pertains to an insert for such a clamping element adapting such clamping element for rod-shaped elements of a smaller diameter. 
     TECHNICAL BACKGROUND OF THE INVENTION 
     EP 1 184 000 describes a single-piece clamping element with two opposing cavities and one laterally open cavity to receive a clamping jaw forming a rod-shaped element and a hinge, which is arranged opposite the cavity, connecting the clamping jaws so that they are movable on top of each other, with each clamping jaw having one bore each aligned flush with one another. 
     This clamping element has the advantage that an articulation can be produced with two identical clamping elements arranged next to one another, inserting a connecting screw through the bore, which is screwed into an internally threaded nut to close the clamping jaws. 
     From EP-A-0 700 664 an articulation is known consisting of two times two individual clamping jaw elements and one central screw. This articulation allows the lateral insertion of one or two rod-shaped elements into the corresponding cavities. U.S. Pat. No. 5,752,954 has a spring arranged between the two center clamping jaw elements, which spring tension allows the clipping in of the rod-shaped elements and holding the jaw elements on the rod-shaped elements before the articulation element is blocked. U.S. Pat. No. 6,616,664 provides for narrow lateral lever arms to hold laterally inserted rod-shaped elements before the articulation is blocked. U.S. Pat. No. 6,342,054 has an external spring. 
     Based on this state of technology, it is one role of the invention at hand to indicate a single-piece or two-piece clamping element which allows the longitudinal insertion of a rod-shaped element and which, when utilized dually, is directly applicable as an articulation element. It is another object of the invention to obtain a single-piece clamping element with advantages being usable for rod-shaped elements with different diameters. 
     Another goal of the invention is the creation of a cost-effective disposable clamping element, particularly made of, a synthetic material (such as plastic) injection molding, which does not have the structural disadvantages of X-ray transparent clamping elements as in EP 1 184 000. Especially it is an object of the invention to realize a disposable clamping element being able to support and transmit large pressure forces for rod-shaped elements with different diameters. 
     Based on the known state of technology, another, role of the invention is also to provide an improved articulation element. 
     SUMMARY OF THE INVENTION 
     An insert for a clamping element with two jaws to clamp a rod-shaped element is provided with an inner cavity to accommodate a rod-shaped element and at least one flange element at one longitudinal end of the insert intended to abut against a clamping element. Then the flange element comprises clamping members to reduce the available room within the inner cavity for the rod-shaped element to be clamped and to clamp the flange element between the rod-shaped element and an outer clamping surface of the clamping element to prohibit any longitudinal movement of the clamped insert. Such a combination of features allow the simple use of plastic material for the clamping element as well as for the insert itself without reducing the possible clamping force. 
     The clamping members can be slits provided within the insert itself or free ends of the flanges, which are clamped by corresponding outer surfaces of the jaws, to create an identity of clamped items, i.e. the rod at the innermost place, the surrounding insert and the encompassing clamping element with its jaws. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Now the invention is more closely described with reference to the drawings and with the aid of a number of embodiments: 
         FIG. 1  shows a perspective view of an articulation element with two clamping elements and an insert according to prior art, 
         FIG. 2  shows a perspective view of the articulation element of  FIG. 1  with two rod-shaped elements, 
         FIG. 3  shows a perspective view of a clamping element according to a first embodiment of the invention and an insert according to a first embodiment of the invention, 
         FIG. 4  shows a perspective view of a clamping element according to a second embodiment of the invention and an insert according to a second embodiment of the invention, 
         FIG. 5  shows a perspective view of the insert according to  FIG. 3 , 
         FIG. 6  shows a front view of the insert according to  FIG. 5 , 
         FIG. 7  shows a sectioned lateral view of the insert according to  FIG. 5 , 
         FIG. 8  shows a perspective view of the insert according to  FIG. 4 , 
         FIG. 9  shows a front view of the insert according to  FIG. 4 , and 
         FIG. 10  shows a sectioned lateral view of the insert according to  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIGS. 1 and 2  shows a perspective view of an articulation element  100  with two clamping elements  10 . The clamping element  10  has two clamping jaws  12  and  13  creating together one cavity  11  to receive a rod-shaped element. The cavity  11  is formed by transversely running grooves  14 . The outer edges  16  of the side facing clamping jaws  12  and  13  are slanted to simplify the lateral insertion of a rod-shaped element. Across from the cavity  11  and the slanted outer edges  16 , a pivotal bearing  17  is arranged. 
     When the clamping element  10  is intended for a rod with 4 to 6 millimeters in diameter, the opening at the free ends has a diameter of, for instance, 2 millimeters in a resting position. If the clamping element  10  is intended for a rod with a diameter of 12 millimeters, the opening at the free ends has a diameter of, for instance, 9 millimeters in a resting position. 
     In the upper area of the clamping jaw  12  the area between cross ribs  21  has been excluded with the exception of a round screw receptacle. Only the screw head  103  can be seen. Screw receptacle, for instance, has a conical shoulder area or a step shoulder, which merges into a continuous bore in the top clamping jaw  12 . 
     In the lower clamping jaw  13  cross ribs  21  end in a ring flange  22 , which, for instance, may have a flat recessed ring shaped step, where a weight and material saving recess advantageous for injection molding can be connected, with a bore in the center. 
     This continuous bore is aligned flush with the abovementioned bore in top clamping jaw  12 . At the clamping element  10 , it runs vertically to the axis of the cavity  11 . The bore is cylindrical and in its interior, it may have guide ribs arranged in regular intervals, preferably between three or five ribs. 
     One clamping element  10  with the jaw parts  12  and  13  comprises semi-cylindrical portions running over the whole width of the jaw  12  and being directed to a complementary groove in jaw  13 . The stops may be chosen shorter or in smaller portions with intermediate regions. The stops are running parallel to the cavity  11 . 
     An insert  50  is lodged within the cavity  11 , comprising cylindrical wall portions  51  defining inner and outer curved surfaces, wherein the wall portions  51  are connected by a web. The web is thinner than the wall portions  51 . The outer surfaces of the insert  50  are complementary to the surfaces of the grooves  14 . The insert  50  according to  FIG. 1  comprises two holding extensions  53  and  54 , extending away from the inner room of the insert  50  and engaging a respective corresponding surface between the ribs  21 . These corresponding surfaces of the insert  50  avoid lateral displacement of the insert  50  in the direction of a rod to be introduced. The holding extensions  53  and  54  also avoid the rotation of the insert itself. 
       FIG. 2  shows the use of an articulation element  100  according to  FIG. 1  as an articulation element with two clamping elements  10  and one insert  50 . All identical or similar features have received the same reference numerals. The rod-shaped element  102  having a greater diameter is directly clamped between the jaws  12  and  13 . The smaller diameter rod-shaped element  101  is not directly clamped between the jaws  12  and  13  but between the corresponding surfaces of the insert  50 . 
       FIG. 1  and  FIG. 2  show the principles of clamping rod-shaped elements. The following description discloses new clamping elements and especially inserts, which can be used with modified clamping elements according to  FIG. 1  as explained later. 
       FIG. 3  now shows a single-piece clamping element  20  according to a first embodiment of the invention, having received a single-piece insert  60 . The single-piece insert  60  is shown in three detailed views in  FIGS. 5 ,  6  and  7 , comprising three reception grooves  141 ,  142  and  143 , extending in the longitudinal direction of the insert  60 . The reception grooves  141 ,  142  and  143  show, in a cross-sectional view, parts of circles with a radius of 4, 5 or 6 millimeter, wherein the centers are placed on the axis of insert  60 . Instead of a holding extension  53  there is a flange  153 , having the shape of a C. The flange  153  has free ends  154 , engaging complementary recesses  61  within the clamping element  60 . The free ends  154  each comprise a nose  155 , engaging the recess  61  and forming a gripping element. The connecting portion  156  opposite to the free ends can be thinner or omitted in other embodiments, to improve the flexible movement of the web. The orifices of the grooves  141 ,  142  and  143  comprise chamfers  159  to enable a smoother longitudinal introduction of rods, preferably at both ends of the insert  60 . 
     The sequence of grooves  141 ,  142 ,  143  defines apertures for rods of different diameters. The distance of the central points of the grooves  141 ,  142 ,  143  is smaller then the diameter of the corresponding rods. The centered groove  142  is oriented concentrically to the outer surface  56  of the insert  60 . The distance between the center of this groove  142  to the center of the smallest groove  141  is smaller than the distance to the center of the larger groove  143 . 
     The clamping element  20  of the embodiment of  FIG. 3  is a single-piece clamping element encompassing the insert  60 . The free ends  154  are located between the upper outer rims  62  of the jaws  12  and  13  and inner noses  63  of the jaws. These noses  63  and the rims  62  form the above-mentioned recesses  61  to accommodate one free end  154 , respectively. The longitudinally oriented surface of each recess  61  provides an abutting surface for the insert  60 . It is also possible to provide larger free ends  154  encompassing the function of the noses  63 , wherein, when the flange  153  is clamped, the inner parts of the free ends  154  are pressed one against another. 
     Therefore the jaws  12  and  13  are pushing the free ends  154  one towards the other and, since they are provided within the recesses  61 , the inner noses  63  are moved one towards the other. Therefore the clamping force finally fixes the free ends  153  in the recesses  61  between the outer rims  62  and ensures that the insert  60  cannot be displaced in a longitudinal direction and therefore improves the holding properties, since the flanges  153  themselves are clamped by the jaws  12 ,  13 . 
     It is noted that within another embodiment not shown in the FIG. the insert  60  can also be turned by around 180 degree, wherein the noses  163  of the modified clamping element are then provided on the free ends of the jaws  12  and  13 . Then jaws  12 ,  13  and free ends  154  are oriented in the same direction allowing for a lateral introduction of a rod over the edge  55  of insert  60 . The web  156  is then thinner and can preferably by bent to allow a better closing of the jaws. Such an insert  60  would then be preferably used with a two-piece clamping element or with a clamping element similar to the clamping element of  FIG. 1  with noses  63  near the longitudinal ends of edges  16 . Although it is possible and preferred to use only one flange  153  it is possible that the insert  60  has two flanges  153  at opposite longitudinal ends. 
       FIG. 4  shows a perspective view of a clamping element  30  according to a second embodiment of the invention and an insert  70  according to a second embodiment of the invention. Clamping element  30  is a single-piece clamping element  30  encompassing the insert  70  with a semicircular shell surface  31 . Insert  70  comprises a flange  153  divided into four segments  162  with separating slits  161 . Each flange segment  162  continues in the longitudinal direction of the insert  70  as a hollow cylindrical portion  163 . Each hollow cylindrical portion  163  is separated from its neighbour portion  163  by a slit  161 . Each hollow cylindrical portion  163  is furthermore separated into a fork-like form through further slits  164  running from the opposite side of the insert. As can be seen from  FIG. 8  these slits  161  and  164  are creating a meander form for the insert  70 , defined between the flange  153  and the bottom surfaces  165 . Preferably, the slits  161  and  164  have the same width over the longitudinal length and the radial depth, they have parallel sides (and not radially tapering sides), the lengths are such that the remaining longitudinal portion is identical near surface  165  and flange  153 , and the angle  166  between two neighbouring slits  161  and  164  is 45 degrees. 
     At both ends there are chamfered surfaces  159  to facilitate introduction of rods. The diameter of the rods to be used depends on the inner hollow diameter  144  of the insert  70 . It is clear that different rods can be clamped since the eight segments  163  spanning around a rod at any cross-section in the middle of the insert and the four segments at the free ends of the insert  70  allow for a compression of the corresponding slits  161  and/or  164 . At the same occasion, the insert  70  is clamped between the jaws  12  and  13  ensuring the stop of any lateral displacement of the insert in relation to the clamping element. 
     It is emphasized that the term embodiment in the previously mentioned description does not mean that only the elements described with respect to the respective clamping element or articulation element are subject of the invention. In particular, these are also combinations of the characteristics described in objects of various embodiments and FIGS. For instance, a modified clamping element is an object of the invention, which has a groove  14  per  FIG. 1  and accepts an insert  50  per  FIG. 4 , thus comprising noses  63  as shown within the embodiment of  FIG. 3 . 
     Although the simplicity of the construction enables the use of low-cost plastic material for the clamping element as well as for the insert, it is also contemplated to use plastic inserts within metallic clamping elements. 
     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.