Abstract:
This disclosure provides a system for securing a bone to a rod, the system comprising a ligature, a body, and two fasteners. The ligature has two free ends and an intermediate portion therebetween, the intermediate portion being configured to engage a bone. A portion of a rod can be fastened to the body using one of the fasteners. The ligature can be fastened to the body using another one of the fasteners. The two fasteners are distinct from one another and are adapted to fasten two free end portions of the ligature to the body independently from fastening the portion of the rod to the body.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This is a U.S. national stage application of International Application No. PCT/EP2010/061085, filed Jul. 30, 2010, entitled “BONE FIXING SYSTEM,” which claims priority from European Patent Application No. EP 09305720.6, filed Jul. 31, 2009. All applications referenced herein are hereby incorporated by reference in their entireties. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present disclosure relates generally to systems and methods for fixing a bone to a rod. Such systems and methods may be helpful for holding together a bone and a rod in a desired configuration or in a particular relative position. In particular, the bone may be a transverse process or a lamina of a vertebra. 
       BACKGROUND OF THE INVENTION 
       [0003]    One field of application for the invention is fixing bones in a desired position, for example to aid in healing of breaks or in the treatment of scoliosis or otherwise to correct abnormal curvatures of the spine. Other bone deficiencies and abnormalities may also benefit from the invention. 
         [0004]    The spine is formed of superposed vertebrae, normally aligned along a vertebral axis, from the lumbar vertebrae to the cervical vertebrae, each having an anterior part, which is the vertebral body, and a posterior part, which is the vertebral arch (or neural arch), the anterior and posterior part enclosing the vertebral foramen. Each vertebral arch is formed by a pair of pedicles and a pair of laminae, and transverse processes and/or a spinous process (or neural spine) project therefrom. The transverse processes and the spinous process project opposite to the vertebral foramen. 
         [0005]    When the vertebrae are articulated with each other, the vertebral bodies form a strong pillar for the support of the head and trunk, and the vertebral foramen constitute a canal for the protection of the spinal cord (or medulla spinalis). In between every pair of vertebrae, there are two apertures, the intervertebral foramina, one on either side, for the transmission of the spinal nerves and vessels. 
         [0006]    If the spine of a person has abnormal curvature, the vertebrae are typically inclined relative to one another and relative to said vertebral axis. The lateral edges of the vertebrae on one side are therefore closer together and define a concave outline, while the lateral edges on the other side are farther apart and define a convex outline. 
         [0007]    In order to straighten the vertebral column as a remedy for this situation, the lateral edges of the vertebrae on the concave side can be moved away from one another and supported at distances from one another substantially equivalent to the distances between the lateral edges on the convex side. To do so, different kinds of devices may be used. 
         [0008]    A first kind of device known in the art is a hook and rod system with hooks that are hooked on the internal wall of the vertebral foramen, and rods for connecting two or more hooks together, thereby holding the vertebrae in correct position relative to one another. Known examples of hook and rod system are disclosed, for instance, in the PCT Patent Application No. WO 2005/023126 and in U.S. Pat. No. 4,269,178. 
         [0009]    However, using hooks can be difficult because their use increases the risk that the physician (or other operative) might contact and potentially damage the spinal cord that extends along the vertebral foramen (which can result in paralysis of the patient). 
         [0010]    Another kind of known device is a screw and rod system with screws that are screwed into the vertebrae, and rods for connecting two or more screws together, thereby holding the vertebrae in correct position relative to one another. A known example of screw and rod system is disclosed, for instance, in the European Patent No. EP 157543381. 
         [0011]    The screws typically have tulip-shaped heads and are inserted in pairs into the pedicles on each side of the spinous process on the posterior wall of the vertebrae. The screws therefore constitute fixing points on the vertebrae for holding the vertebrae. However, the screws are inserted into the pedicles of the vertebrae, which in some cases are small or have deteriorated and can be damaged or do not provide sufficient purchase to permanently hold the screw. 
         [0012]    Another kind of known device is the system for fixing a bone to a rod, disclosed in WO 2009/047352. It comprises a rod, a blocking body and a conformable elongate member adapted to surround the bone, i.e. to form a loop around it. When using such a system, the elongate member is passed around said bone and through the blocking body and the rod is loaded into the blocking body. The ends of the elongate member are pulled so as to apply tension to the elongate member, and the elongate member and the rod are simultaneously fastened to the blocking body by means of the same fastening system, portion(s) of the elongate member being clamped between the rod and the blocking body. Such a system does not give complete satisfaction because it may be difficult to handle for the physician (or other operative). Indeed, the elongate member and the rod have to be fastened to the blocking body in one single step and, therefore, the elongate member needs to be kept under the desired tension while fastening the rod to the blocking body. 
       BRIEF SUMMARY OF THE INVENTION 
       [0013]    According to one embodiment of the present disclosure, there is provided a bone fixing system for fixing a bone to a rod comprising:
       a conformable elongate member having a first free end portion, a second free end portion, and an intermediate portion therebetween;   a main body;   first fastening device or means for fastening a portion of the rod to the main body; and   second fastening device or means for fastening the free end portions of the elongate member to the main body, the second fastening device or means being distinct from the first fastening device or means, and the second fastening device or means being suited to operated independently from the first fastening means.       
 
         [0018]    Compared to the bone fixing systems of the prior art, such a bone fixing system is safer and easier to handle. More particularly, since the first and second fastening means are distinct and since the second fastening means may be operated independently from the first fastening means, it is possible to adjust the tension of the elongate member and to fasten the elongate member to the main body, in a first step, and to fasten the rod to the main body in a second step (or vice-versa). 
         [0019]    Moreover, the elongate member may be made of a material that presents a certain amount of elasticity so that, even after the physician has pulled and locked in position the free end portions of the elongate member, the elongate member allows a limited amount of relative movement between the bone and the rod while providing a stabilizing effect, thereby providing what is called a dynamic stabilization. 
         [0020]    According to an embodiment, the second fastening means comprise a compression member which is movable relative to the main body, the compression member and the main body both defining clamping surfaces between which the free end portions of the elongate member may be inserted, said free end portions being clamped between said clamping surfaces by moving the compression member relative to the main body. 
         [0021]    According to an embodiment, the main body is hollow, extends along a first axis from a lower end to an upper end, and comprises:
       a main part with upwardly extending side walls defining between them a first internal passage extending along said first axis and opening onto the outside of the main body at its upper end; and   a bottom part located under the main part and provided with a second internal passage extending through the entire thickness of the bottom part and communicating with the first internal passage.       
 
         [0024]    In this embodiment, the compression member may be located under said bottom part and be movable relative to said bottom part, the compression member and the bottom part both defining said clamping surfaces, and the bone fixing system may comprise a locking mechanism that passes through the second internal passage and that is to be operated for causing the compression member to move relative to the bottom part. 
         [0025]    Thanks to such a conformation, the bone fixing system has a compact design and is easy to handle. Besides, the locking mechanism is accessible and operable through the first internal passage and, therefore, may be operated with a tool being passed through the first internal passage, so as to secure the elongate member to the main body. Thus, the locking mechanism is easily accessible and operable by the physician. 
         [0026]    According to an embodiment, the compression member is provided with a threaded hole and said locking mechanism comprises a first screw having a head and a shaft with an external thread, the screw shaft passing through the second internal passage, the screw head bearing on the upper face of the bottom part and having a profile that allows the first screw to be driven, and the external thread of the screw shaft engaging with the threaded hole of the compression member. 
         [0027]    According to another embodiment, the second internal passage of the bottom part is provided with an internal thread and the compression member has a protruding part forming said locking mechanism. Said protruding part extends upwardly, has on its upper end a profile that allows the protruding part to be driven, and is provided with an external thread engaging with said internal thread. 
         [0028]    According to one embodiment of the present disclosure, there is also provided a method for fixing a bone to a rod, comprising the steps of:
       passing a conformable elongate member around said bone and through a bone fixing system according to the present disclosure;   applying tension to the elongate member by pulling on the ends of the elongate member;   fastening the elongate member to the main body by means of said second fastening means;   loading a portion of the rod into the main body;   fastening the rod portion to the main body by means of said first fastening means.       
 
         [0034]    According to the above method, the elongate member may be fastened to the main body before fastening the rod portion to the main body, or vice-versa. 
         [0035]    For the physician, the method is easy to use and, more particularly, is effective for holding two or more vertebrae in correct position relative to each other. For so doing, the physician (or other operative) uses at least one bone fixing system and passes the elongate member of the system around a transverse process or a lamina of a vertebra. 
         [0036]    Preferably, the physician uses a number of elongate members and bone fixing systems corresponding to the number of vertebrae, with one rod connecting together the bone fixing systems. If the vertebrae need to be held on each side of the spinous processes, it is preferable, to use a number of elongate members and bone fixing systems corresponding to twice the number of vertebrae and two connecting rods (one rod being placed on each side of the spinous processes). 
         [0037]    The method has further advantages linked to the use of a bone fixing system according the disclosure. 
         [0038]    According to an embodiment, the method uses a bone fixing system according to the disclosure, and comprises the steps of operating the locking mechanism of the system, so as to secure the elongate member to the main body, with a tool which is passed through the first internal passage. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0039]    In the drawings, like reference signs generally refer to the parts throughout the different views. Moreover, parts of different embodiments that have analogous function are identified by the same reference numerals plus  100 ,  200 , etc. 
           [0040]    The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. 
           [0041]      FIG. 1  is a perspective view of an example of bone fixing system according to the present disclosure; 
           [0042]      FIG. 2  is a partial perspective view of the bone fixing system of  FIG. 1 ; 
           [0043]      FIG. 3  is a sectional view of the bone fixing system of  FIG. 1 , along the plane III-III; 
           [0044]      FIG. 4  is a sectional view of another example of bone fixing system according to the present disclosure; 
           [0045]      FIG. 5  is a perspective view of another example of bone fixing system according to the present disclosure; 
           [0046]      FIG. 6  is a sectional view of the bone fixing system of  FIG. 5 , along the plane VI-VI; 
           [0047]      FIG. 7  is a sectional view of another example of bone fixing system according to the present disclosure; 
           [0048]      FIG. 8  is a sectional view of another example of bone fixing system according to the present disclosure; 
           [0049]      FIG. 9  is a sectional view of another example of bone fixing system according to the present disclosure; 
           [0050]      FIG. 10  is a sectional view of the bone fixing system of  FIG. 9 , along the plane X-X; 
           [0051]      FIG. 11  is a sectional view of another example of bone fixing system according to the present disclosure; 
           [0052]      FIG. 12  is a sectional view of the one fixing system of  FIG. 11 , along the plane XII-XII; 
           [0053]      FIG. 13  is a sectional view of another example of bone fixing system according to the present disclosure; 
           [0054]      FIG. 14  is a sectional view of another embodiment of the compression member of the bone fixing system. 
           [0055]      FIG. 15  is a view showing the bone fixing system of  FIG. 1  put into place on a vertebra. 
           [0056]      FIG. 16  is a view showing the bone fixing system of  FIG. 1  fitted with the compression member of  FIG. 14  and put into place on a vertebra. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0057]    In the following detailed description, it is referred to the accompanying drawings showing several examples of bone fixing systems according to the present disclosure. It is intended that these examples be considered as illustrative but not limiting, the scope of the invention being given by the accompanying claims. 
         [0058]    An example of bone fixing system is shown on  FIGS. 1 to 3 . The bone fixing system  10  is for fixing a rod  5  (a portion of which is shown in  FIGS. 1 ,  3  and  15 ) to a bone (see  FIG. 15 ). The bone may be, for instance, a lamina of a vertebra or a transverse process TP of a vertebra V, as shown in  FIG. 15 . 
         [0059]    The bone fixing system  10  comprises
       a conformable elongate member  7 , such as a ligature, having a first free end portion  7   a,  a second free end portion  7   b,  and an intermediate portion  7   c  therebetween, said intermediate portion  7   c  being adapted to surround the bone (e.g. the transverse process TP);   a main body  12 ;   first fastening device or means for fastening a portion of the rod  5  to the main body  12 ; and   second fastening device or means for fastening the free end portions  7   a,    7   b  of the elongate member  7  to the main body  12 , said second fastening means being distinct from the first fastening means.       
 
         [0064]    The elongate member  7  may be any suitable material that is conformable such as a band, wire, or cord made of metal, a polymeric material, or a combination of the two. 
         [0065]    The second fastening means comprise a compression member  14  which is movable relative to the main body  12 , the compression member  14  and the main body  12  both defining clamping surfaces  14   c,    12   c,  between which the free end portions  7   a,    7   b  of the elongate member  7  may be inserted, said free end portions  7   a,    7   b  being clamped between said clamping surfaces  12   c,    14   c  by moving the compression member  14  relative to the main body  12 . 
         [0066]    The main body  12  is hollow, extends along a first axis Z from its lower end to its upper end, and comprises:
       a main part  12   a  with upwardly extending side walls  13  defining between them a first internal passage  20  extending along said first axis Z and opening onto the outside of the main body  12  at its upper end; and   a bottom part  12   b  located under the main part  12   a  and provided with a second internal passage  22  extending through the entire thickness of the bottom part  12   b  and communicating with the first internal passage  20 .       
 
         [0069]    The main body  12  further comprises third and fourth internal passages  43 ,  44  through which the first and second free end portions  7   a,    7   b  of the elongate member  7  may be inserted respectively. Each internal passage  43  ( 44 ) extends through the main body  12 , has two ends  4   43   b  ( 44   a,    44   b ) and opens, at one end  43   a  ( 44   a ), in front of the compression member  14  and, at the other end  43   b  ( 44   b ), onto an outer face of the main body and, more precisely, onto a side face of the main body  12 . The third and fourth internal passages  43 ,  44  form guiding means for the free end portions  7   a,    7   b  of the elongate member  7 . 
         [0070]    In the example the third and fourth internal passages  43 ,  44  extend, respectively, along third and fourth axis A, A′, each of the third and fourth axis forming with respect to said first axis Z an acute angle C which is preferably comprised between 0 and 70°. Thus, it is easier for the physician to pull on the ends  7   a,    7   b  of the elongate member  7  for tensioning it. 
         [0071]    On the other hand, the clamping surfaces  14   c,    12   c  of the compression member  14  and of the main body  12  define between them fifth and sixth passages  53 ,  54  extending, respectively, along fifth and sixth axis B, B′, each of the fifth and sixth axis forming with respect to said first axis Z an obtuse angle D. 
         [0072]    The compression member  14  is provided with a threaded hole  24 . Said locking mechanism comprises a first screw  26  having a head  26   a  and a shaft  26   b  with an external thread. The screw shaft  26   b  passes through the second internal passage  22  and the screw head  26   a  has a profile  28  that allows the first screw  26  to be driven. In the example, the screw head  26   a  is a socket head and, more particularly, a hex socket head which can be driven, for instance, by an Allen key. 
         [0073]    When the first screw  26  is driven, the external thread of the shaft  26   b  engages with the threaded hole  24  of the compression member  14  and the screw head  26   a  bears on the upper face  12   d  of the bottom part  12   b.  Thus, the clamping surfaces  14   c,    12   c  are brought closer together and the end portions  7   a,    7   b  are locked in position by clamping between the clamping surfaces  14   c,    12   c.    
         [0074]    Turning now to the first fastening means for fastening a portion of the rod  5  to the main body  12 , openings  30  are provided in the side walls  13  (see  FIG. 2 ), so that a portion of the rod  5  may be loaded into the main body  12  via said openings  30 , and a closure member  32  engages with the main body  12  so as to secure said portion of rod  5  to the main body. 
         [0075]    In the example, the main body  12  is provided with a first thread  13   b  for engagement with a second thread  32   a  provided on the closure member  32 , so that said portion of rod  5  may be clamped between the main body  12  and the closure member by threadably moving the closure member  32  relative to the main body  12 . More precisely, in the example, the rod portion is clamped between the edges  13   a  of the side walls  13  delimiting the bottom of the openings  30 , and the lower face of the closure member  32 . 
         [0076]    In the example, the closure member  32  has an external thread  32   a  engaging with an internal thread  13   b  provided on the inner face of the side walls  13 . The closure member  32  further comprises a socket head  32   b  for driving it in rotation. 
         [0077]    Another example of bone fixing system is shown on  FIG. 4 . The bone fixing system  110  of  FIG. 4  differs from that of  FIG. 3  by the locking mechanism. In  FIG. 3 , the second internal passage  22  of the bottom part  12   b  is provided with an internal thread  123 , and the compression member  114  has a protruding part  114   a  forming said locking mechanism. Said protruding part  114   a  extends upwardly, has on its upper end a profile  128  that allows the compression member  114  to be driven in rotation, and is provided with an external thread  114   b  engaging with said internal thread  123 . 
         [0078]    It should be noted that, in the examples of  FIGS. 1-4 , the bottom part  12   b  of the main body  12  is integral with the main part  12   a  of the main body  12 . This is not the case in the examples of  FIGS. 5-7 . 
         [0079]      FIGS. 5 and 6  show another example of bone fixing system  210  differing from that of  FIGS. 1-3  in that it comprises a main body  112  with a bottom part  212   b  and a main part  212   a  which are not integral with each other. 
         [0080]    In this example, the bottom part  212   b  and the main part  212   a  of the main body  212  are interconnected by a ball-and-socket connection. 
         [0081]    The main part  212   a  comprises a bottom wall  250 , the bottom wall  250  being provided with a through hole  251  delimited by an upper edge  251  a. The ball-and-socket type connection comprises a second screw  252  having a head  252   a  and a shaft  252   b.  The screw shaft  252   b  passes through said through hole  251  and through the second internal passage  222 . The screw head  252   a  has a convex lower face  252   c  bearing on said upper edge  251   a,  and a profile that allows the second screw  252  to be driven. For instance, the screw head  252   a  may be a hex-head or a socket-head. The screw head  252   a  further has a concave upper face  252   d.    
         [0082]    When the rod  5  is locked in position by means of the first fastening means, the rod  5  leans against the concave upper face  252   d  of the second screw  252 . More precisely, when the closure member  32  is screwed down, the closure member  32  pushes down on the rod  5  which in turn pushes down on the screw  252  until the convex lower face  252   c  of the screw head  252   a  leans against the upper edge  251   a  of the through hole  251 . Since the contact zones between the screw head  252   a  and the upper edge  251   a  and between the screw head  252   a  and the rod  5 , are limited, the screw head  252   a  is able to move with respect to the he main part  212   a  of the main body  212 . 
         [0083]    The above structure is one example of a ball-and-socket type connection but other examples could be used. 
         [0084]    A ball-and-socket type connection allows a limited amount of relative movement between the bottom part  212   b  and the main part  212   a  of the main body  212  and, thus, between the bone and the rod  5 , thereby providing or improving the desired dynamic stabilizing effect. 
         [0085]    The bottom part  212   b  is substantially the same as the bottom part  12   b  of  FIG. 3  except for the screw head  226   a  which has an outer driving profile  228  (instead of the inner driving profile  28 ), and apart from the fact that the screw  226  is provided with an internal threaded hole  227 . 
         [0086]    The screw shaft  252   b,  which has an external thread, passes through the second internal passage  222  and engages with the threaded hole  227 , so as to connect together the bottom part  212   b  and the main part  212   a  of the main body  212 . 
         [0087]    Another example of bone fixing system  310  with a ball-and-socket type connection is shown on  FIG. 7 . In this example, the main part  312   a  of the main body  312  and the second screw  352  are the same as those ( 212   a,    252 ) of  FIG. 6 , and the bottom part  312   b  of the main body  312  is substantially the same as the bottom part  12   b  of  FIG. 4  apart from the fact that the protruding part  314   a  of the compression member  314  has an outer driving profile  328  instead of the inner driving profile  128 , and that the compression member  314  is provided with an internal threaded hole  327 . 
         [0088]    The screw shaft  352   b,  which has an external thread, passes through the second internal passage  322  and engages with the threaded hole  327 , so as to connect together the bottom part  312   b  and the main part  312   a  of the main body  312 . 
         [0089]    In both examples of  FIGS. 6 and 7 , the screw shaft  252   b,    352   b  passes through the through hole  251 ,  351  of the bottom wall  250 ,  350  of the main part  212   a,    312   a  and through the second internal passage  222 ,  322  and engages with the compression member  214 ,  314 . On  FIG. 7 , it engages directly with the compression member  314 , whereas on  FIG. 6 , it engages indirectly with the compression member  214 , via the screw  226 . 
         [0090]    Other examples of bone fixing systems  410 ,  510 ,  610 ,  710 , for fixing a bone to a rod  5 , are shown on  FIGS. 8 to 13 . Each of them comprises:
       a conformable elongate member  7  having a first free end portion  7   a,  a second free end portion  7   b,  and an intermediate portion  7   c  therebetween, said intermediate portion  7   c  being adapted to surround said bone;   a main body  412 ,  512 ,  612 ,  712 ;   first fastening device or means for fastening a portion of the rod  5  to the main body  412 ,  512 ,  612 ,  712 ; and   second fastening device or means for fastening the free end portions  7   b  of the elongate member  7  to the main body  412 ,  512 ,  612 ,  712 , said second fastening device or means being distinct from the first fastening device or means.       
 
         [0095]    In the systems of  FIGS. 8-12 , the first fastening device or means for fastening a portion of the rod  5  to the main body  412 ,  512 ,  612 , are the same as those of  FIG. 1-4  and, therefore, do not need to be described again. 
         [0096]    In all the examples of  FIGS. 8-13 , the second fastening means comprise a compression member which is movable relative to the main body  412 ,  512 ,  612 , the compression member and the main body both defining clamping surfaces between which the free end portions  7   a,    7   b  of the elongate member  7  may be inserted, said free end portions being clamped between said clamping surfaces by moving the compression member relative to the main body. 
         [0097]    In the example of  FIG. 8 , the compression member  414  is provided with a thread  414   d  for rotative engagement with another thread  412   a  provided on the main body  412 , so that the free end portions  7   a,    7   b  of the elongate member  7  may be clamped between a compression part  412   e  of the main body  412  and the compression member  414  by threadably moving the compression member  414  relative to the main body  412 . 
         [0098]    In this example, the compression member  414  is a nut provided with an internal thread  414   d,  and the main body  412  is provided with an external thread  412   a.  When the compression member  414  is screwed or unscrewed, it moves closer or farther away from the compression part  412   e.    
         [0099]    The main body  412  comprises:
       a compression part  412   e  which is a flange protruding on the lateral faces of the main body  412 , and   two internal passages  453 ,  454  through which the first and second free end portions  7   a,    7   b  of the elongate member may be inserted respectively, each of the third and fourth internal passages  453 ,  454  extending through the main body, having two ends and opening, at one end, in front of the compression member  414  and, at the other end, onto an outer face of the main body  412  and, more precisely, onto the end face of the main body  412  which is opposite to the other end face receiving the rod  5 .       
 
         [0102]    When the compression member  414  is threadably engaged with the main body  412 , it moves closer or farther away from the compression part  412   e.    
         [0103]    In the example of  FIG. 9 , the compression member  514  is also a nut provided with an internal thread  514   d  (see  FIG. 10 ), and the main body  512  is also provided with an external thread  512   a,  but in this case, the compression member  514  is not in direct contact with the elongate member  7 . Indeed, the compression member  514  cooperates with two profiled rotating pieces  515  which are rotatably mounted (around the axis R) in recesses  512   i  provided on the lateral faces of the main body  512 . When the compression member  514  moves along the main body  512 , it pushes the rotating pieces  515  in the recesses  512   i,  and each free end portion  7   a,    7   b  of the elongate member is clamped between a rotating piece  515  and the bottom wall of the recess  512   i.    
         [0104]    In the example of  FIG. 11 , the compression member  614  is a circlip and the main body has a peripheral groove  612   i  for receiving the free end portions  7   a,    7   b  of the elongate member and the compression member  614 . The free end portions  7   a,    7   b  are inserted and clamped between the bottom of the groove  612   i  and the compression member  614 . 
         [0105]    The compression member  614  could also be a fastening collar. 
         [0106]    The peripheral groove  612   i  may extend along the entire circumference of the main body  612 , or along a part of it. 
         [0107]    In the example of  FIG. 13 , the second fastening device or means comprise a screw  764  and a compression member  714  which is provided with a through hole  760 . The main body  712  of the bone fixing system  710  is provided with a threaded hole  762  aligned with said through hole  760 . The shaft  764   b  of the screw  764  passes through said through hole  760  and is threadably engaged with the threaded hole  762 . The head  764   a  of the screw  764  is intended to lean against the upper surface of the compression member  714 . The compression member  714  and the main body  712  both define clamping surfaces between which the free end portions  7   a,    7   b  of the elongate member may be inserted and clamped, said free end portions being clamped by screwing the screw  764  into the main body  712 . 
         [0108]    In the example of  FIG. 13 , the first fastening device or means comprise a seat part  766  for receiving a portion of the rod  5 , the seat part  766  facing the intermediate portion  7   c  of the elongate member  7 , said portion of rod  5  being clamped between the seat part  766  and the intermediate portion  7   c  of the elongate member by tightening the elongate member  7  (i.e. by pulling on the free end portions  7   a,    7   b  of the elongate member  7 ). Preferably, the seat part  766  is a clip for holding the rod  5 . For instance, the seat part  766  is delimited by two open arms  763  with certain elasticity, said arms  763  partially surrounding the rod  5 . 
         [0109]    Turning now to  FIG. 15 , the bone fixing system  10  of  FIGS. 1-3  is shown in a tightened position around a vertebra V. More precisely, the intermediate portion  7   c  of the elongate member  7  surrounds the transverse process TP of the vertebra. 
         [0110]    By pulling on the ends of the elongate member  7 , the compression member  14  of the system  10  comes into contact with the transverse process TP. 
         [0111]    The compression member  14  may be made In a soft material, order to avoid damaging the vertebra V and/or to allow a limited amount of relative movement between the vertebra V and the system  10 , and thus between the vertebra V and the rod  5 , thereby providing a dynamic stabilization effect, More particularly, compared to the material which makes up the main body  12  and which is preferably rigid, the material the compression member  14  is softer. 
         [0112]    In order to improve the cushioning effect and/or the dynamic stabilization effect, the compression member  14 ′ may be provided with at least one peripheral groove  19 ′ on its side faces. Such a peripheral groove  19 ′ makes the deformation of the compression member  14 ′ easier and allows the member  14 ′ to bend laterally and to compress axially. Thus a limited amount of relative movement (including pivoting movement) between the vertebra V and the system  10  is allowed, as illustrated by the double arrow P on  FIG. 16 .