Abstract:
A two-piece clamping element comprises two separate, i.e., non-integral, opposing first and second clamping jaws forming a laterally open cavity to receive a pin or rod-shaped element. Each clamping jaw has a bore aligned with one another to receive a screw, wherein a pivot bearing is arranged opposite said cavity allowing the two opposing clamping jaws to come in contact to one another. The pivot bearing comprises at least one set of complementary part-cylindrical bearing surface portions. An anti-rotation pin extends between the two jaw members.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a divisional of U.S. patent application Ser. No. 11/641,600, filed on Dec. 19, 2006, which claims priority from European Patent Application No. EP 06 110 244.8 filed on Feb. 21, 2006, all of which are incorporated herein by reference. 
    
    
     BACKGROUND 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 articulation element with two clamping elements and with one at least two-piece locking device, and optionally an anti-rotation device. 
     U.S. Patent Publication 2003/0181911 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 U.S. Pat. No. 5,752,954 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, 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. 
     SUMMARY OF THE INVENTION 
     Based on this state of technology, it is one role of the invention at hand to provide a two-piece clamping element which allows the lateral 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 two-piece clamping element with advantages of a single-piece clamping element, e.g. the working connection of the two clamping jaws. 
     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 U.S. Publication 2003/0181911. Especially it is an object of the invention to realize a disposable clamping element being able to support and transmit large pressure forces. 
     Based on the known state of technology, another role of the invention is also to provide an improved articulation element. Such an improved articulation element is shown in U.S. Patent Publication 2006/0039750 assigned to the assignee of the present invention. 
     A two-piece clamping element is provided comprising two separate non-integral opposing first and second clamping jaws forming a laterally open cavity to receive a rod-shaped element, with each clamping jaw having a bore aligned with one another. 
     A pivot bearing is arranged opposite the cavity bringing the two opposing clamping jaws in contact to one another and thereby making them movable towards and away from one another. Each clamping jaw has a bore, aligned with one another. The bores are arranged between the cavity and the pivot bearing. 
     A first clamping jaw has an anti-rotation device on its exterior or a receptacle for receiving an anti-rotation device. 
     An articulation element can be formed from two clamping elements in which the clamping elements are arranged on top of one another with their first clamping jaws adjacent one another. The articulation element has one at least two-piece locking shaft with a first part of the locking shaft insertable through a bore of the second clamping jaw of one clamping element, and with a second part of the locking shaft insertable through a bore of the first clamping jaw of the other clamping element. One or the other or both parts of the locking shaft being able to be brought in contact with one another through the bores in the first clamping jaws. The first and second clamping jaws of the clamping elements can be blocked with the locking device. The articulation element has an anti-rotation device is arranged between the first clamping jaws that are arranged on top of one another, the anti-rotation device having a central bore. The anti-rotation device is preferably a plate whose material is preferably harder than the material of the clamping elements and which has ridges formed on both sides of the plate. The anti-rotation device can also be a cylinder whose material in a floor and a lid area thereof is preferably harder than the material of the clamping elements, and which preferably consists of a flexible, compressible material in the solid material part, in particular synthetic foam. The locking device includes a cylindrical screw and a conical nut, the conical nut preferably has a stop shoulder for a self-locking screw, which can be inserted in an internal thread in the cylindrical screw. A hollow spring enveloping the locking device is used as an anti-rotation device or as an additional anti-rotation device. 
     By equipping the two-piece clamping elements with functionally different first and second clamping jaws, two clamping elements can be placed on top of one another each with their first clamping jaws, to form an articulation element in a simple manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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 per a first embodiment of the invention, 
         FIG. 2  shows a different perspective view of the articulation element of  FIG. 1 , 
         FIG. 3  shows a cross-section view of the articulation element of  FIG. 1  or  2 , 
         FIG. 4  shows a perspective view of an articulation element with two clamping elements per a second embodiment of the invention, 
         FIG. 5  shows a different perspective view of the articulation element of  FIG. 4 , 
         FIG. 6  shows a cross-section view of the articulation element of  FIG. 4  or  5 , 
         FIG. 7  shows a top view of an anti-rotation device for an articulation element per  FIG. 1  or  4 , 
         FIG. 8  shows a perspective view of another anti-rotation device for an articulation element, and 
         FIG. 9  shows a partially sectioned lateral view of a part of a locking screw, a nut and a self-locking bolt for an articulation element per one of the  FIGS. 1 to 6 . 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 to 3  show a first embodiment of an articulation element with two clamping elements  10  per the invention.  FIGS. 1 and 2  show two perspective views at different angles from the top. The two-part clamping element 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, comprising complementary pivotal surfaces comprising semi-cylindrical portions  36  and complementary grooves  38  contacting clamping jaws  12  and  13 . 
     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  23 . Screw receptacle  23 , for instance, has a conical shoulder area or a step shoulder, whose purpose will be described later, which merges into a continuous bore in the top clamping jaw  12 , which can be seen in  FIG. 3 . 
     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. Of course, the number of guide ribs may be chosen freely, preferably between three or five ribs. 
     One clamping element  10  with the jaw parts  12  and  13  comprises a semi-cylindrical portions  36  running over the whole width of the jaw  12  and being directed to a complementary groove  38  in jaw  13 . The stops  36  and  38  may be chosen shorter or in smaller portions with intermediate regions; however, the shown embodiment providing for a long pivotal bearing  17  is preferred. The stops  36  and  38  are running parallel to the cavity  11 . Between the stops  36  and  38  and the vertically oriented bores for the screw is provided a pin  136  and a corresponding reception bore  138 . The pin  136  can be seen in the cross-sectional view of  FIG. 3 , entering with play into the reception bore  138 , to ensure that the jaws  12  and  13  are not rotating one against the other and to allow an easy introduction of a larger rod into the cavity  11  whereas the complementary stop surfaces  36  and  38  can loose contact but are guided by elements  136  and  138 . The pin  136  can be symmetrical in view of his main axis but is preferably oblong in the transverse direction, e.g. parallel to surfaces  36  and groove  14 . 
       FIGS. 4 to 6  show a second embodiment of an articulation element with two clamping elements  20  per the invention.  FIGS. 4 and 5  show two perspective views at different angles from the top. The two-part clamping element has two clamping jaws  12  and  13  creating together one cavity  11  to receive a rod-shaped element. All identical or similar features have received the same reference numerals as cavity  11  and grooves  14 . Across from the cavity  11 , a pivotal bearing  17  is arranged, comprising complementary pivotal surfaces comprising semi-cylindrical portions  36  and complementary grooves  38  contacting clamping jaws  12  and  13 . 
     One clamping element  20  with the jaw parts  12  and  13  comprises two semi-cylindrical portions  36  running on the left and on the right side of a passage  238  of the jaw  12  and being directed to two complementary groove portions  38  on both sides of a blocking pin  236  in jaw  13 . The stops surfaces  36  and  38  may also be chosen shorter; however, the shown embodiment providing for two rather long pivotal bearing surfaces  17  is preferred. The blocking pin  236  and the corresponding reception bore  238  are provided on the outer open side of the jaws  12  and  13 . The pin  236  is—seen from above—rectangular to ensure that the jaws  12  and  13  of the clamping element  20  can not rotate one against the other. 
     In the first embodiment of  FIGS. 1 to 3  the pin  136  is provided in the jaw  12  whereas in the second embodiment of  FIGS. 4 to 6  the blocking pin  236  is provided in the jaw  13 . This clearly shows that the features of the two embodiments can be mixed, the blocking pin  236  of  FIG. 4  can be used within jaw  12  and the pin  136  of  FIG. 1  can be used within jaw  13  with the complementary bores in the other jaws  13  and  12 , respectively. However, the represented embodiments are preferred. 
     A spiral or coil spring  119  is arranged between the two clamping elements  10  or  20 , which is supported by the spring receptacle  121 . The spring receptacle  121  can form a hemispherical area; it can also be level and smooth; in particular, it can be rough to ensure a greater resistance of the spring  119  against twisting. The spring  119  pushes the two clamping elements  10  or  20  away from one another and is intended to secure the twisting of the two clamping elements  10  or  20  against one another. It does not secure the forcing apart of the jaws  12  and  13 ; they open against the forces acting upon the clipping in of the rods  101  and  102  in a radial direction with respect to grooves  14 . The spring  119  can also be a disk spring package or another resilient element. 
       FIG. 7  shows a top view of an anti-rotation device for an articulation element per  FIG. 1 . Anti-rotation device  90 , for instance, is a thin metal plate with a central bore  91 , a hub  92  and spokes  93 . The outer rim  94 , for instance, has successive punctured ridges  95  and recesses  96 . For instance, they are arranged so that recesses  96  are always arranged opposite the six spokes  93  in this case, with each of the ridges  95  located intermittently. 
     It is clear that, a simple punching process to manufacture the plates of the anti-rotation device  90  is used, that ridges  95  seen from above are recesses seen from below. Punctured ridges  95  and recesses  96  can be round, pyramidal or polygon shaped. They can run radially side by side in several rows, in a larger number than in  FIG. 7  etc. In another alternate design, radial ribs can be used as well. 
     The anti-rotation device  90  is to be positioned between the two clamping elements  10 ,  20  at the position  190  as indicated in  FIGS. 1 ,  2 ,  4  and  5 .  FIGS. 3 and 6  show that an anti-rotation device can also be achieved through the design of the material of the first clamping jaw  13 , comprising rough elements to avoid rotation between the contacting jaws  13 . 
     The anti-rotation device can also be a flexible synthetic foam element  199  as per  FIG. 8 . Only upon the tightening of screw  103  the anti-rotation device  199  interlock and determine the angle position of the articulation element. 
     This is a flexible cylindrical element  199  with a central bore  198  for receiving screw  103 . It can be used in the place of an anti-rotation device  90 . The advantage is that its material on the bottom and lid surfaces  197  is harder and, in particular, can also be structured or span hard inserts to engage in a ring-shaped step. The clamping element  10  is then designed similar to the embodiment per  FIG. 1 , only the depth and the sidewalls are intended to receive the anti-rotation device  199 . In the cylinder area, the element  199  is flexible to be compressed when screw  103  is tightened. The anti-twisting device is beveled and has conical slants  196  between the surface  195  and the lid or the floor area  197 . 
     It is advantageous that the material in the floor and lid area of the anti-rotation device  199  is harder than the material of the clamping elements utilized, and in the solid material preferably consists of a flexible, compressible material, particularly synthetic foam. 
     The diameter of the anti-rotation device  90  or  199  is 30 millimeters and the contact surface (radial width) for the outer rim  94  is 3 millimeters. Instead of placing the ridges on element  90 , the structures (ridges) can also be integrated in the material of the clamping jaw  13 , for instance radial grooves. 
       FIG. 9  shows a screw  103  which is to be inserted through the aligned bores, which can sit on the conical screw receptacle  23  with its conical flange  104 . For tightening, screw  103  for instance has a square drive head  105 . It is clear that instead of a square, a hexagon or a slit etc. can be utilized. Preferably, the shoulder  104  is designed to be complementary to the receptacle  23 . A nut  106  is attached from the other side. The nut  106  has a slightly conical sleeve  107  and a conical flange  108  as a covering cap. The shape of flange  108  corresponds to the shape of screw receptacle  23  of clamping element  10  or  20 . The sleeve  107  is inserted into one bore and, to the best advantage, protrudes into the other bore and/or through it. The sleeve  107  is fitted in the press fit; additionally, it can also have an external thread. It can be designed as a fit for one of the internal threads used in bore. 
     In another design version, not illustrated in the drawings, a clamping element is equipped with a tilting, but torsion rigid, bearing for the nut. The clamping jaw  12  again has the conically opening bore. This bore, however, has a recess on the side facing away from the cavity  11 , which can be a rectangular slit in particular. During the assembly, the cylindrical nut is inserted in the recess. A tolerance exists through the cylindrical nut, so that when a rod  102  is clipped into cavity  11  the top part  12  of the clamping element can be tilted as well. In order to ensure the fixation of screw  103  and to design the nut torsionally rigid, it has an appendage or projection, which protrudes into the said recess with lateral tolerance. In a lateral view of the clamping element, the projection has a tolerance in the recess to permit the tilting motion of top part  12 . In addition to the nut with projection, other design versions are possible, for instance, an L-shaped flattened nut, which, for example, has wobble rivets and is punched, so that an appendage protrudes into a corresponding nut in top part  12  and produces the torsion rigidity. 
     The nut  106  has an internal thread that fits the complementary external thread of screw  103 . Through the tightening of screw  103  opposite nut  106 , the two clamping elements  10  and  20  are pulled together. Then, by exerting pressure, a rod can be inserted laterally in the respective cavity. Since the diameters of the rods are larger than the opening at the free ends, it is protected from falling out. Through a roughening of grooves  14 , not illustrated in the drawings, it is also protected from a simple longitudinal displacement. 
     If screw  103  is tightened further, clamping jaws  12  and  13  are moved closer towards one another against the resetting force of the hinge bearing  17  and are finally completely blocked in their angled position through the use of the plate of anti-rotation device  90  placed between the clamp elements. At the same time, this fully secures the rods in grooves  14  against longitudinal displacement as well as against twisting by minimizing the cavity  11 . While self-locking screw  109  is not illustrated, it can be utilized here as well. Preferably the nut  106  is designed as a continuous sleeve. 
     When screw  103  is opened, nut  106  remains in the one clamping element. The anti-rotation device  90  has impressed itself into the softer material of jaw  13 . Said impression makes it preferable—with the exception of an immediate tightening of the screw in this or another place of an external fixator clamping element used for the same patient—to use said clamping element only once and to throw it away after use. The material used for the clamp may be PEEK (Poly Esther Ether Ketone), and may have chopped carbon fiber reinforcement for extra strength. This allows the two pieces of the polymeric clamp to be injection molded. The pressed in traces of the anti-rotation device in the step is a sign of use for the clamping element, so that the user can see that the reuse of the product can be excluded. 
     In the resting position of the clamping elements  10  and  20 , clamping jaws  12  and  13  urged together by the spring force and the distance of the slit  27  is reduced. When screw  103  is tightened, the slit is minimized. Through the central transfer of force via the screw and nut elements  104  and  108  on the identical areas, the slit  27  is minimized in its thickness until the groove  14  contacts the rod in the cavity  11 . Then the (upper) clamping jaw  12  with the ribs  21  deviates around the rod and the semi-cylindrical region  36  touches down on the complementary area  38 . When screw  103  is tightened further, the blocking effect sets in as of this time and the unit semi-cylindrical region  36 —complementary area  38  takes over the bearing function. 
     Instead of a screw  103 , another locking device can be used, for instance a clamping lever or a bayonet catch. 
     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 clamping element is an object of the invention, which has the bore and nut per  FIG. 3 , a counter nut  109  per  FIG. 9  and non-skid elements  99  for the rods per  FIG. 8  or a part thereof. A corresponding articulation element can be comprised of any two random above-mentioned clamping elements, if they can be utilized for the selected anti-rotation device. 
     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.