Abstract:
The connecting element ( 1 ) has the shape of a rod with longitudinal axis ( 2 ), a rear end ( 6 ), and a front end ( 7 ), and serves to span a number of bone anchoring elements ( 12 ) implanted in the bone. The connecting element ( 1 ) comprises at least one longitudinal slot ( 5 ). This provides it with a greater elasticity during implantation so that it can be reversibly deformed. The connecting element can then be stiffened once it has been fixed in the bone anchoring elements (e.g. pedicle screws).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation of International Application No. PCT/CH2004/000129, filed Mar. 4, 2004, the entirety of which is incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates to a connecting element.  
       BACKGROUND OF THE INVENTION  
       [0003]     Connecting elements are suitable for bridging several bone-anchoring elements, which are implanted in the bone, particularly in the region of the spinal column, that is, for bridging pedicle screws. They have been known for a long time. However, such elements are always relatively rigid longitudinal supports, which must be bent with special measures in order to adapt them to the configuration required anatomically or clinically.  
         [0004]     The WO 02/085217 discloses a connecting element, which, instead of a single longitudinal support, consists of a plurality of elastic wires (rod bundles), lying loosely next to one another. The danger that the individual wires may cross, which would lead to unstable connections, is a disadvantage of this known device.  
         [0005]     The invention is to provide a remedy here. It is an object of the invention to provide a connecting element, which has a greater elasticity during the implantation, so that it can be shaped reversibly, and which can be reinforced after it is fixed in the bone-anchoring elements (such as pedicle screws).  
       SUMMARY OF THE INVENTION  
       [0006]     The advantages, achieved with the invention, may be seen to lie essentially therein that, due to its elasticity, the connecting element may be implanted in a minimally invasive manner through a bent tube and then stiffened by fixation with the bone-anchoring elements. In comparison to the above-mentioned, known bundle of rods, the advantage results that an accurately defined external shape is always present, that is, in the state at rest as well as in radially braced state, that is, after fixation in the bone-anchoring elements.  
         [0007]     In the case of a particular embodiment, the connecting element has a cavity, which extends in the direction of the longitudinal axis and by means of which a sheath is defined. This permits a central rod to be introduced into the cavity. It is an advantage of such an embodiment that the slotted sheath has the same external diameter in the clamped as well as in the not clamped state. In the case of a slotted rod with a full cross section, the material losses due to the slotting must be compensated for by a reduction in the external diameter. An additional advantage lies therein that the cross section of the rod is divided among two elements, so that, as a result, the bending stiffness can be reduced.  
         [0008]     Preferably, the slots penetrate the sheath radially and, advisably, the cavity extends continuously from the rear end to the front end, so that the connecting element is tubular.  
         [0009]     In the case of a further embodiment, the slots are disposed in such a manner, that the sheath continues to hang together.  
         [0010]     In the case of a further embodiment, the ends of the slots lie within the connecting element. The advantage of this embodiment lies in an increased bending stiffness of the connecting element, since the connecting element is closed at both sides and minimizes relative movement of the individual sheath elements under a bending stress.  
         [0011]     In the case of an alternative embodiment, the ends of the slots break through the rear end and/or the front end on one side. In the case of this embodiment, there is increased bending elasticity. In the bent state of the connecting element, the radially external elements of the sheath are able to shift relatively to the radially internal elements.  
         [0012]     The connecting element may be made from known metallic materials or from plastic.  
         [0013]     In the case of a further embodiment, the connecting element has a circular, external cross section. As a result, the connecting element has uniform mechanical properties, independently of the orientation of the rotation of the connecting element.  
         [0014]     In the case of an alternative embodiment, the connecting element has a polygonal, external cross section. In conjunction with pedicle screws, the rod seat of which is also constructed polygonally, a connecting element with a polygonal cross section may be oriented in a defined manner. Advantageously, the mechanical properties, such as the stiffness, may be predefined differently, depending on the direction of stress.  
         [0015]     The slots may have a width of not more than 1.0 mm and preferably of not more than 0.6 mm.  
         [0016]     In the case of a further embodiment, the connecting element ( 1 ) has uniform mechanical strength and stiffness over the whole of its length. The uniform stiffness of the connecting element over the whole of it length causes the bending moments applied to be distributed over the whole length of the connecting element and, by so doing, prevents stress concentrations at the transitions.  
         [0017]     The slots may be filled at least partially with a material softer than that of the connecting element, preferably with PEEK, as a result of which undesirable growth of tissue into the connecting element is prevented.  
         [0018]     In the case of a further embodiment, the slots, as viewed radially to the longitudinal axis, are disposed offset. A uniform bending stiffness and bending elasticity in different directions can be achieved in this way.  
         [0019]     In the case of an alternative embodiment, several slots, when viewed axially, are disposed one behind the other, so that several radially offset groups of such slots, disposed one behind the other axially, are present. Here also, there is a uniform bending stiffness and bending elasticity in different directions. Subdividing the slots among several slots, which, viewed in the axial direction, are disposed one behind the other, is suitable especially for long connecting elements. By these means, the torsional rigidity and the bending strength may be increased and/or adapted.  
         [0020]     In yet another embodiment, the individual slots of a group are offset axially with respect to the slots of the radially adjacent group. This results in the advantage of a uniform mechanical strength and stiffness.  
         [0021]     In the case of a further embodiment, the connecting element additionally has a central rod, which is introduced into the cavity. This central rod may be made from a metal, preferably from titanium, a titanium alloy or steel. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     The invention and further developments of the invention are explained in greater detail in the following by means of the partially diagrammatic representations of several embodiments:  
         [0023]      FIG. 1  shows a perspective view of an inventive connecting element,  
         [0024]      FIG. 2  shows a side view of the connecting element of  FIG. 1 ,  
         [0025]      FIG. 3  shows a front view of the connecting element of  FIG. 1 ,  
         [0026]      FIG. 4  shows a side view of a modified connecting element with a slot closed at either end,  
         [0027]      FIG. 5  shows a side view of a modified connecting element with a slot open at one side,  
         [0028]      FIG. 6  shows a side view of a modified connecting element with two slots, separated by a bridge, open at one side,  
         [0029]      FIG. 7  shows a side view of a modified connecting element with two closed slots, separated by a bridge,  
         [0030]      FIG. 8  shows a side view of a modified connecting element with a plurality closed slots, disposed offset to one another,  
         [0031]      FIG. 9  shows a side view of a modified connecting element with a plurality of closed slots, which are disposed one behind the other,  
         [0032]      FIG. 10  shows a cross section, which is orthogonal to the longitudinal axis of a hollow connecting element, with one slot,  
         [0033]      FIG. 11  shows a cross section, which is orthogonal to the longitudinal axis of a hollow connecting element, with two slots, which are diametrically opposite to one another,  
         [0034]      FIG. 12  shows a cross section, which is orthogonal to the longitudinal axis of a hollow connecting element, with four uniformly disposed slots,  
         [0035]      FIG. 13  shows a cross section, which is orthogonal to the longitudinal axis of a hollow connecting element, with three uniformly disposed slots,  
         [0036]      FIG. 14  shows a cross section, which is orthogonal to the longitudinal axis of a hollow connecting element, with eight uniformly disposed slots,  
         [0037]      FIG. 15  shows a cross section, which is orthogonal to the longitudinal axis of a connecting element that does not have a longitudinally extending hole, with a longitudinal slot.  
         [0038]      FIG. 16  shows a cross section, which is orthogonal to the longitudinal axis of a connecting element that does not have a longitudinally extending hole, with two longitudinal slots,  
         [0039]      FIG. 17  shows a cross section, which is orthogonal to the longitudinal axis of a connecting element that does not have a longitudinally extending hole, with four longitudinal slots,  
         [0040]      FIG. 18  shows a longitudinal section through a modified connecting element, into which a central rod has been introduced,  
         [0041]      FIG. 19  shows an enlarged section of a variation of the connecting element of  FIG. 18 , which has an internal thread on one side,  
         [0042]      FIG. 20  shows an enlarged section of the variation of  FIG. 19  with a central rod screwed into the internal thread,  
         [0043]      FIG. 21  shows a cross section, orthogonal to the longitudinal axis of an inventive connection element with four slots, in the not clamped state,  
         [0044]      FIG. 22  shows the cross section of  FIG. 21  in the clamped state, the clamping of the individual tube segments of the connecting element being indicated by arrows,  
         [0045]      FIG. 23  shows a cross section, which is orthogonal to the longitudinal axis of an inventive connecting element with four slots and a central rod introduced therein, in the not clamped state,  
         [0046]      FIG. 24  shows the cross section of  FIG. 23  in the clamped state, the clamping of the individual tube segments and of the central rod being indicated by arrows,  
         [0047]      FIG. 25  shows a diagrammatic longitudinal section through a pedicle screw, into the seating head of which the connecting element with the central rod of  FIG. 24  has been introduced in the not clamped state,  
         [0048]      FIG. 26  shows the longitudinal section of  FIG. 25  in the clamped state,  
         [0049]      FIG. 27  shows a diagrammatic representation of a section through a spinal column with four with four implant anchoring elements introduced into adjacent vertebrae with a guiding instrument for the inventive connecting element,  
         [0050]      FIG. 28  shows the representation of  FIG. 27  with the guiding instrument, brought into position in the vicinity of the first implant-anchoring element, with the connecting element guided therein,  
         [0051]      FIG. 29  shows the representation of  FIG. 27  with the connecting element, introduced into the first implant-anchoring element,  
         [0052]      FIG. 30  shows the representation of  FIG. 27  with a manipulator mounted on the second implant-anchoring element,  
         [0053]      FIG. 31  shows the representation of  FIG. 27  with the connecting element introduced into the first and second implant-anchoring elements,  
         [0054]      FIG. 32  shows the representation of  FIG. 27  with the connecting element introduced into all four implant-anchoring elements and a manipulator for aligning the individual implant-anchoring elements,  
         [0055]      FIG. 33  shows the representation of  FIG. 32  with a diagrammatic representation of the way, in which the manipulator functions and  
         [0056]      FIG. 34  shows the representation of  FIG. 27  with the connecting elements, introduced into all four implant-anchoring elements and locked therein. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0057]     An embodiment is shown in FIGS.  1  to  3 , which comprises a tubular connecting element  1 , with a cavity  3 , which passes through the connecting element  1  from the rear end  6  up to the front end  7  and is coaxial with the longitudinal axis  2 , and several longitudinal slots  5 , which are distributed uniformly over the periphery of the connecting element  1  and pass radially through the sheath  4 . The longitudinal slots  5  extend parallel to the longitudinal axis  2  and are closed at the two ends  6 ;  7  of the connecting element  1 .  
         [0058]     Further embodiments of the connecting element  1  are shown in FIGS.  4  to  9 . These differ from the embodiments of FIGS.  1  to  3  only in that the geometry and the axial arrangements of the longitudinal slot or slots  5  are different. In  FIG. 4 , a connecting element  1  with a longitudinal slot  5  is shown, which is closed axially at the rear end  6  as well as at the front end  7 . In  FIG. 5 , a connecting element  1  with a longitudinal slot  5  is shown, which is open at the rear end  6  and closed at the front end  7 . In  FIG. 6 , the connecting element  1  comprises two longitudinal slots  5   a ;  5   b , which are separated axially from one another, and in each case one longitudinal slot  5   a ;  5   b  is open at one end  6 ;  7 . In  FIG. 7 , the connecting element  1  also comprises two longitudinal slots  5   a ;  5   b , which are disposed one behind the other axially and are separated axially from one another, each longitudinal slot  5   a ;  5   b  being axially outside at the appropriate end  6 ;  7  of the connecting element  1 . In  FIG. 8 , the connecting element  1  comprises four longitudinal slots  5   a ;  5   b ;  5   c ;  5   d , which are disposed offset from one another axially as well as on the periphery. The longitudinal slots  5   a ;  5   b ;  5   c ;  5   d  overlap axially at their ends. Furthermore, the two longitudinal slots  5   a ;  5   d  axially on the outside are closed at the end  6 ,  7  in question of the connecting element  1 . In  FIG. 9 , the connecting element  1  also comprises four longitudinal slots  5   a ;  5   b ;  5   c ;  5   d , which are separated axially from one another here and lie in the same diametrical planes. The axially external, longitudinal slots  5   a ;  5   d  are closed off at the corresponding ends  6 ;  7  of the connecting element  1 .  
         [0059]     Further embodiments, in turn, of the connecting element  1  are shown in FIGS.  10  to  14 . The connecting element  1  may have one or more longitudinal slots  5  of one of the embodiments shown in FIGS.  4  to  9 . It is evident from the cross sections, orthogonal to the longitudinal axis  2  ( FIG. 4 ) and shown in FIGS.  10  to  14 , that the connecting element  1 : of  FIG. 10  comprises one or more longitudinal slots  5 , which penetrate the sheath  4  radially from the cavity  3  up to the external surface; of  FIG. 11  comprises at least two diametrically opposite longitudinal slots  5   a ;  5   b , penetrating the sheath  4  radially from the cavity  3  up to the external surface; of  FIG. 12  comprises at least four longitudinal slots  5   a ;  5   b ;  5   c ;  5   d , which, in pairs, penetrate the sheath  4  radially from the cavity  3  up to the external surface; of  FIG. 13  comprises at least three longitudinal slots  5   a ;  5   b ;  5   c , penetrating the sheath  4  radially from the cavity  3  up to the external surface; and of  FIG. 14  comprises at least four longitudinal slots  5   a ;  5   b ;  5   c , which are distributed uniformly on the periphery and penetrate the connecting element  1  diametrically.  
         [0060]     In FIGS.  15  to  17 , different embodiments are shown, which comprise a connecting element  1  without a cavity. Here also, the connecting element  1  may comprise one or more longitudinal slots  5 , similarly to one of the embodiments shown in FIGS.  4  to  9 . It is evident from the cross sections, shown in FIGS.  15  to  17  and orthogonal to the longitudinal axis  2  ( FIG. 4 ), that the connecting element  1 : of  FIG. 15  comprises at least one longitudinal slot  5 , passing diametrically through the connecting element  1 ; of  FIG. 16  comprises at least two longitudinal slots  5   a ;  5   b , which are perpendicular to one another and pass through the connecting element  1  diametrically; and of  FIG. 17  comprises at least four longitudinal slots  5   a ;  5   b ;  5   c ;  5   d , which are distributed uniformly on the periphery and penetrate the connecting element  1  diametrically.  
         [0061]     An embodiment of the connecting element  1  is shown in  FIG. 18 . It has a cavity  3  and a central rod  8 , which is introduced into this cavity  3 . The central rod  8  has a circularly cylindrical structure and is pushed into the cavity  3  without axial fixation.  
         [0062]      FIG. 20  shows a different embodiment of a connecting element, which also has a coaxial cavity  3 . At the front end  7 , the coaxial cavity is provided with an internal thread  9  ( FIG. 19 ). A central rod  8 , having a complementary external thread  11 , may be screwed into this internal thread  9  and can thus be fixed axially, so that the central rod  8  cannot slide unintentionally out of the connecting element  1 .  
         [0063]      FIGS. 21 and 22  show an embodiment of the connecting element  1  with four longitudinal slots  5  and a cavity  3 , which is coaxial with the longitudinal axis  2  ( FIG. 1 ). The connecting element  1  is shown in the not clamped state in  FIG. 21  and in the clamped state in  FIG. 22 . As shown in  FIG. 22 , the clamping forces, acting on the connecting element  1  and indicated by arrows, cause the individual tube segments of the connecting element  1  to be compressed until the longitudinal slots  5  are closed and the tubular segments are pressed against one another at their side walls, which form the boundaries of the longitudinal slots  5 . The compressive forces, acting on the side walls of the longitudinal slots  5 , are also represented by arrows.  
         [0064]     Similarly, an embodiment of the connecting element  1  with four longitudinal slots  5  and a central rod  8 , introduced into the cavity  3 , is shown in  FIGS. 23 and 24 , the connecting element  1  being shown in the not clamped state in  FIG. 23  and in the clamped state in  FIG. 24 . The forces, acting radially on the connecting element  1  and indicated by arrows, compress the individual tube segments radially only until the wall of the cavity  3  comes into contact with the surface of the central rod  8 , so that the tube segments are pressed against the central rod and the longitudinal slots are not compressed.  
         [0065]      FIGS. 25 and 26  show an embodiment of the connecting element  1  of  FIG. 12  together with a pedicle screw  12 . The connecting element  1  is placed in a channel  15 , which passes through the seating head  13  of the pedicle screw  12  transversely to the central axis  14  of the latter.  FIG. 25  shows the clamping screw  16 , which, in the loosened state, can be screwed parallel to the central axis  14  into the seating head  13 , so that the connecting element  1  can be shifted parallel to its longitudinal axis  2 . In  FIG. 26 , the clamping screw  16  is tightened and the connecting element  1  is firmly clamped in the seating head  13  of the pedicle screw  12 . The arrows represent the forces acting on the connecting element  1  during the tightening of the clamping screw  16 .  
         [0066]     The surgical technique for the inventive connecting element  1  is described briefly below.  
         [0067]     The connecting element  1  with longitudinal slots  5  permits posterior spinal column repair with a minimally invasive surgical technique. The objective of this minimally invasive surgical technique is to implant the implant-anchoring elements  20 , such as screws, hooks, jaws, etc., as well as the longitudinal support by way of minimal accesses. The flexibility of the longitudinal support enables it to be implanted by means of a curved implantation aid, such as a curved tube. With that, the surgical access is reduced to the dimensions of the tube. The implant-anchoring elements  20 , lengthened by means of manipulators, enable the individual vertebrae to be manipulated during the introduction of the slotted connecting elements  1 , such as the correction of the spinal column if the connecting element  1  is horizontal. After the desired correction has been achieved, the connecting element  1  is fixed in the individual implant anchoring elements  20 . As a result, stiffening of the slotted connecting element  1  is achieved and sufficient stiffness of the fracture repair is attained.  
         [0068]     The individual steps of the surgery are now explained in detail by means of FIGS.  27  to  34 : 
        1. Percutaneous implantation, guided over pulling wires if necessary, of the implant-anchoring elements  20   a ;  20   b ;  20   c ;  20   d  at the vertebrae  25 , which are to be treated ( FIG. 27 ).     2. Percutaneous introduction of the guiding instrument  21  for the slotted connecting element  1  ( FIG. 28 ).     3. Locating the first implant-anchoring element  20   a  with the guiding instrument  21  ( FIG. 29 ). This may be accomplished over image processors or guided by way of an external targeting device, which is connected with the first implant-anchoring element  20   a.       4. Bringing the slotted connecting element  1  by means of the guiding instrument  21  into the first implant-anchoring element  20   a  ( FIG. 30 ).     5. Further introduction of the connecting element  1  and threading into the second implant-anchoring element  20   b  ( FIG. 31 ). The threading may be supported by the external manipulators  22 , which are connected with the implant-anchoring elements  20   b.       6. Further introduction of the connecting element  1  and threading into the third and last implant-anchoring element  20   c ;  20   d  ( FIG. 32 ).     7. After the connecting element  1  has been implanted in all implant-anchoring elements  20   a ;  20   b ;  20   c ;  20   d , a desired correction of the spinal column can be made by way of the external manipulators  22  of the implant-anchoring elements  20 .     8. After the correction has been made, it is fixed by clamping the connecting element  1  in the individual implant-anchoring elements  20   a ,  20   b ,  20   c ,  20   d  ( FIG. 33 ). This fixation leads to the stiffening of the connecting element  1  and makes possible a stress-resistant correction of the spinal column.     9. After removal of the guiding instrument and the anchoring manipulators ( FIG. 34 ), the stab incision is closed off.