Abstract:
This disclosure provides a spinal stabilization system and method for stabilizing at least two vertebrae. The system holds together the vertebrae while allowing a limited amount of relative movement between the vertebrae. The system may include a flexible braid having two free ends, at least one spacer interposed between the spinous processes of the vertebrae, and a securing mechanism for securing the two ends of the braid to hold the at least one spacer between the spinous processes of the vertebrae. In some embodiments, the securing mechanism may comprise parts movable relative to each other. Portions of the braid may be placed between the movable parts. A mechanical member may cause the movable parts to move towards each other to secure the two ends of the braid.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims a benefit of priority under 35 U.S.C. 119(a) of the filing date of European Patent Application No. 08305183, filed May 20, 2008, entitled “SYSTEM FOR STABILIZING AT LEAST TWO VERTEBRAE,” which is fully incorporated herein by reference. 
     TECHNICAL FIELD OF THE DISCLOSURE 
     The present disclosure relates to a system and method for stabilizing at least two vertebrae, including but not limited to dynamic stabilization. 
     BACKGROUND OF THE RELATED ART 
     With certain pathologies of the vertebral column, the surgeon might need to perform surgery for securing at least two vertebrae to each other. Sometimes, the surgeon will need to secure a larger number of vertebrae to one another, e.g., 3 or 4. 
     In order to perform this operation, when it is desired to stabilize only two vertebrae, it is known to place between them an intervertebral implant constituted by a spacer that is usually disposed between the spinous processes of the vertebrae, together with securing means such as braids or ties that surround the spinous processes in order to hold the spacer between the vertebrae. For that purpose, in addition to the spacer, it is known to use a braid that presents two free ends that are secured to the spacer, e.g., with the help of a self-locking system of the type described in PCT patent application WO 2005/120277. Nevertheless, making such a spacer with usually releasable locking means presents certain drawbacks. 
     SUMMARY OF THE DISCLOSURE 
     A first object of the present disclosure is to provide a stabilization system that is dynamic, i.e., a system that, while holding together at least two vertebrae, nevertheless allows a limited amount of relative movement between these two vertebrae. 
     Another object of the disclosure is to provide such a system that enables the surgeon to exert the required amount of traction on the free ends of the braid system under improved conditions, and regardless of the number of vertebrae that are to be stabilized. 
     To achieve these objects, according to the present disclosure, there is provided a system for stabilizing at least two vertebrae, the system comprising:
         a flexible braid having two ends and a length defined by the two ends, the length of the flexible braid forming a single loop around spinous processes of the at least two vertebrae;   at least one spacer interposed between the spinous processes of the two vertebrae and the single loop of the flexible braid, the spacer including a body and elements for engaging portions of the single loop of the flexible braid; and   a securing mechanism for securing the two ends of the flexible braid to hold the at least one spacer between the spinous processes of the two vertebrae.       

     Because the system has at least one spacer, if the stabilization system involves only two vertebrae, then only one spacer is used and the securing mechanism for securing the two free ends of the braid is a component that is distinct from the spacer. 
     In addition, regardless of whether the braid system has one or more braids, since it forms a single loop around the spinous processes of the vertebrae to be stabilized, having functionally only two free ends suitable for achieving traction, the surgeon can easily exert said traction. 
     In addition, regardless of whether the braid system has one or more braids, since it is flexible and possibly presents a certain amount of elasticity, a limited amount of relative movement remains possible between the vertebrae even after the surgeon has exerted traction on the free ends of the braid system is an amount appropriate to obtain the desired stabilization. 
     In a first embodiment of the stabilization system, the braid system has only one braid, the co-operating elements of the spacer merely comprising means for guiding the braid, and the securing mechanism for securing the free ends of the braid is distinct from the spacers. 
     An advantage of this embodiment is that all of the spacers can be identical. In some embodiments, the spacers can have a simple construction. 
     In a second embodiment of the stabilization system, the braid system comprises only one braid, and a securing mechanism for securing the two free ends of the braids is secured to one of the spacers. 
     The securing mechanism for securing the free ends of the braid may form an integral portion of the spacer to which it is secured, or it may be removably mounted thereon. 
     In this second embodiment, the spacers that do not have a securing mechanism need only include elements for guiding portions of the braid, or they may include elements for clamping to a portion of the braid, or indeed both types may be involved. 
     In a third embodiment, the stabilization system has two braids, the body of one of the spacers having two side faces, the securing mechanism comprising a first securing member secured to a first side face and a second securing member secured to a second side face, each braid presenting a first end permanently secured to the body of said spacer and a second end that is free, suitable for receiving traction, and retractably secured to one of the securing members. 
     In all of the above-defined embodiments, one or more braids or ties are used and that the braid may be made of a material that is flexible, or possibly elastic, so that the braid allows a limited amount of relative movement to the two or more vertebrae while providing a stabilizing effect. 
     In addition, regardless of whether there is only braid or more, the braid system may form a single loop passing, directly or indirectly, around the spinous processes of the set of vertebrae for stabilizing. This single loop functionally presents only two free ends, on which it is easy for the surgeon to exert traction. 
     Under certain circumstances, the braid system may physically present two pairs of free ends. Nevertheless, functionally, traction is exerted by the surgeon on only one of the pairs of free ends of the braid system. The surgeon can then select the pair of free ends that is easier to access. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other characteristics and advantages of the disclosure are described below. The following description provides examples of several embodiments. The description refers to the accompanying figures, in which: 
         FIG. 1  is an elevation view of one embodiment of a stabilization system for two vertebrae, using an embodiment of a securing mechanism for securing the free ends of a braid; 
         FIG. 2  is an elevation view of one embodiment of a stabilization system for three vertebrae, using two spacers and the securing mechanism of  FIG. 1 ; 
         FIG. 3A  is a cross-sectional view of an embodiment of a securing mechanism for securing the ends of a braid; 
         FIG. 3B  is an exploded perspective view of the securing mechanism of  FIG. 3A ; 
         FIG. 4A  is a cross-sectional view of a second embodiment of a securing mechanism for securing the ends of the braid; 
         FIG. 4B  is an exploded perspective view of the securing mechanism of  FIG. 4A ; 
         FIG. 5  is a vertical section view of a third embodiment of a securing mechanism for securing the ends of the braid; 
         FIG. 6  is a cross-sectional view of a fourth embodiment of a securing mechanism for securing the ends of the braid; 
         FIG. 7  is an elevation view of a system for stabilizing three vertebrae, having a simple spacer and a spacer with a braid-securing mechanism; 
         FIG. 8  is an elevation view of a system for stabilizing four vertebrae, using two simple spacers and a spacer with a braid-securing mechanism; 
         FIG. 9  is a perspective view of a spacer provided with a first type of braid-securing mechanism; 
         FIG. 10  is a view of the underside of the spacer in  FIG. 9  positioned between two vertebrae; 
         FIG. 10A  is a cross-sectional view along the length of the spacer in  FIG. 9 , showing a movable part; 
         FIG. 11  is a perspective view of a second embodiment of a spacer fitted with a braid-securing mechanism suitable for use in the stabilization system of the disclosure; 
         FIGS. 12A ,  12 B, and  12 C show the various component parts of the spacer shown in  FIG. 11 ; 
         FIG. 13A  is a perspective view of a third embodiment of a spacer fitted with a braid-securing mechanism; 
         FIG. 13B  is an exploded view of the spacer shown in  FIG. 13A ; 
         FIG. 13C  is a cross-sectional view along the length of the spacer in  FIG. 13A , showing a movable part; 
         FIG. 14A  is a perspective view of a fourth embodiment of a spacer with a braid-securing mechanism, suitable for use in the stabilization system of the disclosure; 
         FIG. 14B  is a cross-sectional view along the length of the spacer in  FIG. 14A , showing a movable part; 
         FIG. 15  is a perspective view of a fifth embodiment of a spacer with a securing mechanism; 
         FIG. 16  is a cross-sectional view along the length of the spacer in  FIG. 15 ; 
         FIG. 16A  is a cross-sectional view along the width of the spacer in  FIG. 15 , showing the securing mechanism; 
         FIG. 17  is an elevation view of an embodiment of the stabilization system for four vertebrae comprising simple spacers and an embodiment of an intervertebral spacer fitted with a braid-securing mechanism; 
         FIGS. 18A and 18B  are perspective views of the intervertebral spacer fitted with a braid-securing mechanism shown in  FIG. 17 ; 
         FIG. 18C  is a cross-sectional view along the width of the spacer in  FIGS. 18A and 18B , showing the braid-securing mechanism; 
         FIG. 19  is an elevation view, partially cross-sectional, showing an embodiment of the system for stabilizing four vertebrae comprising simple spacers and an embodiment of a spacer fitted with a securing mechanism for securing the ends of the braid; 
         FIG. 20  is an elevation view of a first variant of the stabilization system shown in  FIG. 7 ; 
         FIG. 21  is an overall view of a second variant of the stabilization system shown in  FIG. 7 ; 
         FIG. 22  is an elevation view of a variant of the stabilization system shown in  FIG. 8 ; and 
         FIGS. 23 and 24  show two other embodiments of the stabilization system. 
     
    
    
     DETAILED DESCRIPTION 
     With reference initially to  FIGS. 1 and 2 , there follows a description of a first embodiment of the stabilization system of the disclosure.  FIG. 1  shows a stabilization system  10  for stabilizing two vertebrae V 1  and V 2 ,  FIG. 2  showing a similar stabilization system  10 ′ for stabilizing three vertebrae V 1 , V 2 , and V 3 . 
     In this first embodiment, use is made solely of intervertebral spacers that are simple, i.e., spacers that do not include their own securing mechanism for securing the free ends of the braid on the spacer, with there being only one braid. 
     More precisely, in  FIG. 1 , the stabilization system  10  has a simple intervertebral spacer  12  with ends  12   a  and  12   b  provided with recesses  14   a  and  14   b  for receiving the spinous processes of the vertebrae V 1  and V 2 . Preferably, the distal prongs  16  defining the recesses  14   a  and  14   b  are much smaller in height than are the proximal prongs  18  that also define the same recesses. As is known, this asymmetry of the prongs makes it possible to use a lateral approach for putting the spacer into place between the processes of the vertebrae V 1  and V 2  (see PCT patent application WO 2007/099258, which is incorporated herein by reference). The lateral portions  20  and  22  of the spacer that terminate in the prongs  16  and  18  are provided with passages  24 ,  26  that extend over their full length so as to allow a securing tie or braid  28  to pass freely. The braid  28  is made of a material that confers a certain amount of flexibility thereto and possibly also a certain amount of elasticity in order to obtain the desired dynamic stabilization effect as mentioned above. The braid  28  has portions  28   a ,  28   b  that pass around the spinous processes of the vertebrae V 1  and V 2  in part, intermediate portions  28   c  and  28   d  that are engaged in the passages  24  and  26 , and two free ends  28   e  and  28   f . The ends  28   e  and  28   f  of the braid  28  are secured to each other by a securing mechanism  30  represented symbolically in  FIG. 1 . This braid-securing mechanism is described in greater detail below. 
     It should be understood that the structure of the simple spacer  12  is very simple, since it does not itself include any braid-securing mechanism. To provide dynamic stabilization for dynamically stabilizing the vertebrae V 1  and V 2 , it is possible to have a hollow  32  in the central portion of the body of the spacer, thereby giving it a certain amount of elasticity or a certain amount of deformability that is additional to the flexibility of the braid  28 . In addition, as explained below, when putting the stabilization system into place, the surgeon can exert appropriate traction on the ends  28   e  and  28   f , with the help of a traction instrument that is itself known, so as to find a compromise between the desired stabilization and the desired possibility of relative movement between the vertebrae in order to obtain the dynamic stabilization effect. Such a traction instrument is described in particular in PCT patent application WO 2007/034112, which is incorporated herein by reference. 
       FIG. 2  shows a system for stabilizing three vertebrae that is very similar to the system shown in  FIG. 1 . The only difference lies in the fact that two simple spacers  12   a  and  12   b  are interposed between the spinous processes of vertebrae V 1 , V 2 , and V 3 . The braid  28  is itself identical to that of  FIG. 1 , but longer, passing around portions of the spinous processes of vertebrae V 1  and V 3 , and passing freely within the internal passages  24   a ,  26   a , and  24   b ,  26   b  of the simple spacers  12   a  and  12   b . As in  FIG. 1 , the ends  28   a  and  28   f  are secured to each other by a securing mechanism  30  that may be identical to that of  FIG. 1 , and that is described below. 
     It should be understood that the embodiment shown in  FIG. 2  enables three vertebrae to be stabilized with the help of intervertebral spacers of a structure that is very simple, since none of them includes any means for securing a braid. It is possible to provide a system of the type shown in  FIG. 2  for stabilizing more than three vertebrae, by providing a corresponding number of simple spacers. As in the embodiment of  FIG. 1 , the tension in the braid  28  can be adjusted prior to locking the braid in place with the securing mechanism  30 . 
     It should be understood that in this first embodiment, the spacers act relative to the braid  28  solely to provide guidance, as is achieved by the various internal passages  24 ,  26 ,  24   a ,  24   b ,  26   a ,  26   b.    
     With reference to  FIGS. 3A to 6 , there follows a description of several embodiments of a securing mechanism for securing the ends of the braid  28 , which is given overall reference  30  in  FIGS. 1 and 2 . 
     In the first embodiment, the securing mechanism  30   1 , as shown in  FIGS. 3A and 3B , essentially comprises a cylindrical sleeve  40  having a first slot  42  to allow the free ends  28   e  and  28   f  of the braid  28  to pass therethrough, and second and third slots  44  and  4  in its sides also to allow the braid  28  to pass through, after it has passed through the cylindrical housing  48  defined by the sleeve  40 . A locking part  50  of substantially semicylindrical shape can be inserted in the cylindrical housing  48  of the sleeve  40  so that portions  52  and  54  of the braid  28  are interposed between the inside wall of the cylindrical housing  48  and the outside face of the semicylindrical part  50 . The securing mechanism  30   1  also including a clamping screw  56  capable of co-operating with a tapped orifice  58  formed in the cylindrical sleeve  40  in a position diametrically opposite to the first slot  42 . When the screw  56  is engaged in the tapped orifice  58 , its end  56   a  comes to bear against the top face  50   a  of the part  50 , thereby providing claiming by wedging the braid portions  52  and  54  between the part  50  and the wall of the housing  48 . By exerting appropriate traction on the free ends  28   e  and  28   f  of the braid  28  before tightening the screw  56 , the surgeon can obtain suitable tension in the braid  28  when it passes around the spinous processes of the vertebrae that are to be stabilized in dynamic manner, thereby adjusting of the dynamic stabilization effect, in part. 
     With reference now to  FIGS. 4A and 4B , there follows a description of a second embodiment  30   2  of the securing mechanism for securing the ends of the braid. 
     In this embodiment, the securing mechanism comprises a body  60  presenting a side wall  62  defining a cylindrical inside housing  64  and an end wall  66 . The end wall  66  is provided with a slot  68  for passing the free ends  28   e  and  28   f  of the braid  28  going towards the vertebrae. The side wall  62  of the body  60  is subdivided into two portions by diametrically opposite notches  70  and  72 . Finally, the side wall of the body  62  is provided with two side slots  7   4  and  76  for passing braid portions  28  going towards the vertebrae. The braid-securing mechanism also includes a locking part  78  of generally semicylindrical shape that can be put into place in the inside housing  64 , projecting through the notches  70  and  72 . Finally, the securing mechanism  302  includes a screw  80  that can co-operate with tapping  64   a  formed in the inside portion of the housing  64 . As shown better in  FIG. 4A , portions  82  and  84  of the braid  28  are disposed between the inside wall of the end  66  of the body  60  and the side face  78   a  of the locking part  78 . By tightening the screw  80  in the taping  64   a , the end  80   a  of the screw  80  comes to bear against the top face  78   b  of the locking part  78 . Thus, by tightening the screw  80 , the surgeon can secure the braid  28  by wedging it between the locking part  78  and the inside face of the body  60 . 
       FIG. 5  shows a third embodiment of the braid-securing mechanism  30   3 . This embodiment is similar to that of  FIGS. 4A and 4B . It comprises a body  60 ′ that is identical to the body  60  of the securing mechanism  30   2  except that it does not have the side slots  74  and  76 , and the top portion of its outside face is provided with a thread  83 . The clamping screw  80  is replaced by a tapped ring  85  that co-operates with the thread  84  of the body  60 ′. By tightening the tapped ring  85 , the side wall of the body  60 ′ is deformed elastically, thereby securing portions of the braid  28  by wedging them, this securing effect being accompanied by the action of the tapped ring  85  against the ends of the top face  78   a  of the locking part  78 . 
       FIG. 6  shows a fourth embodiment of the braid-securing mechanism  30   4 . The securing mechanism  30   4  is constituted by two jaws  90  and  92  that are hinged relative to each other at a first end about an axis  95 . The facing faces  92   a  and  90   a  of the jaws  90  and  92  have shapes that are complementary, and in particular that define a substantially semicylindrical convex portion  94  and a substantially semicylindrical concave portion  96 . The jaw  92  is provided with a slot  98  for passing the braid  28 , and the jaw  90  is also provided with a slot  100  for passing the free ends  28   e  and  28   f  of the braid  28 . 
     Thus, the braid  28  passing through the slots  98  and  100  is to be found between the complementary semicylindrical surfaces  94  and  96  of the two jaws. A locking screw  102  co-operates with a tapped orifice  104  and a smooth orifice  106  formed in the second ends of the jaws  90  and  92  respectively. By tightening the screw  102 , the two jaws are caused to move towards each other and the wedge portions are secured by being wedged between the complementary surfaces  94  and  96  of the two jaws. 
     It would also be possible to use other systems for securing the ends of the braid, providing, in this embodiment, they are distinct from the simple spacers that are used and providing that they enable the surgeon to exert traction on the ends  28   e  and  28   f  of the braid  28  so as to obtain the desired traction. 
     Whatever the type of securing mechanism used, the stabilization system can be put into place via a lateral approach. Consequently, the spacers  110 ,  114 , and  116  need to be of an appropriate shape. More precisely, the transverse height of the distal end of each spacer is smaller, while the transverse height of the proximal end of each spacer is larger, since it does not need to be capable of being inserted between the vertebrae. 
       FIGS. 7 and 8  show a second embodiment of the stabilization system which involves, in  FIG. 7 , stabilizing three vertebrae V 1 , V 2 , and V 3 , and in  FIG. 8 , stabilizing four vertebrae V 1 , V 2 , V 3 , and V 4 . 
     This second embodiment differs from that described with reference to  FIGS. 1 and 2  essentially by the fact that the securing mechanism for securing the free ends  28   e  and  28   f  of the braid  28  is mounted on or forms an integral part of one of the spacers interposed between the vertebrae V 1 , V 2 , and V 3 . In  FIG. 7 , there can be seen the intervertebral spacer  110  that has its own system for clamping and securing the ends of the braid  28 , which system is described below, together with a simple spacer  114  that is identical to the simple spacers as described above. In this embodiment, the braid  28  surrounds the spinous processes of the end vertebrae V 1  and V 3  and passes freely along the internal passages in the simple spacer  114 . The braid  28  shown in this figures has the same properties as the braid shown in  FIGS. 1 and 2  for providing stabilization. 
     In  FIG. 8 , in addition to the intervertebral spacer  112  and the simple spacer  114 , there is a second simple spacer  116  interposed between the spinous processes of vertebrae V 1  and V 2 . The simple spacer  116  is identical to the simple spacer  114 . 
     The second embodiment of the disclosure shown in  FIGS. 7 and 8  presents all of the advantages of the embodiments described with reference in particular to  FIGS. 1 and 2 , and in particular it is possible to insert the intervertebral spacers using a lateral approach and it is possible to exert traction laterally on the ends of the securing braid  28 . 
     In the embodiments shown in  FIGS. 7 and 8 , the simple spacers  114  and  116  merely perform a function of guiding the braid  28 . 
     With reference now to  FIGS. 9 ,  10 , and  10 A, there follows a description of a first embodiment  110   1  of the spacer  112  incorporating the securing element. 
     In this embodiment, the securing mechanism for securing the ends of the braid forms an integral portion of the spacer  110   1 . The locking system is constituted by a stationary portion formed by the body  120  of the spacer  110   1 , and by a movable or movable portion  122 . The various spacer embodiments  110   1 ,  110   2 ,  110   3 ,  110   4 , and  110   5  differ essentially in the embodiment of the movable portion or part  122  for locking the ends  28   e  and  28   f  of the braid  28 . 
     The movable part  122  of the spacer  110   1  is mounted in a housing  124  made in the body of the spacer  120  and opening out into its bottom face  120   a . The movable part  122  presents a sloping top face  126  that co-operates with the sloping top face  128  of the housing  124 . By the face  126  sliding against the face  128 , the end  130  of the movable part  122  can be moved towards the front wall  132  of the housing  124 . The spacer body  120  also has two slots  134  and  136  for passing the braid  28  that can thus penetrate into the inside of the housing  124 . The front face  130  of the movable portion  122  defines two clamping surfaces  130   a  and  130   b  that co-operate with clamping faces  132   a  and  132   b  defined by the front wall  132  of the cavity  124 . Since the braid  28  is disposed between these two pairs of clamping surfaces, movable the movable portion  122  towards the face  132  of the cavity  124  of the spacer body serves to clamp two portions of the braid  28  close to their free ends  28   e  and  28   f . In  FIG. 10A , it can be seen that the front wall  132  of the cavity  124  is provided with a slot  139  that enables the ends  28   e  and  28   f  of the braid  28  to pass through after the braid portions have been passed between the clamping faces  130   a ,  132   a ,  130   b ,  132   b.    
     The movable portion  122  is preferably moved relative to the stationary body  120  with the help of a screw  138  having its threaded portion  138   a  co-operating with a tapped bore  142  formed in the movable portion  122 . In addition, the head  138   b  of the screw  138  is held pressed against the top face  120   b  of the body  120  of the spacer. It will be understood that by turning the screw  138  in one direction or the other, it is possible to move the movable portion  122  in one direction or the other. The spacer body  120  also has a passage  140  for a portion of the braid  28 , through which portion the braid can slide freely. 
       FIGS. 11 ,  12 A,  12 B, and  12 C show a second embodiment of the spacer provided with the securing mechanism, this spacer being referenced  110   2 . 
     This second embodiment of the spacer  110   2  is very similar to that shown in  FIGS. 9 and 10 . The spacer body  150  constitutes the stationary portion of the securing mechanism and the part  152  constitutes the movable portion. The spacer body  150  is provided with a cavity  154  presenting a sloping end wall  156  and an inside front wall  158 . The cavity  154  opens out into the top face  150   a  of the body  150 . The movable part  152  has a bottom face  160  that can slide against the sloping end wall  156  of the cavity  154 . 
     As in the above embodiment, the spacer body  150  has two side slots  162  and  164  for passing the braid  28 , and an axial slot  166  for passing the ends  28   e  and  28   f  of the braid  28 . The inside front face of the cavity  154  defines two clamping surfaces  154   a  and  154   b . The movable part  152  presents a front face  168  that itself defines two clamping surfaces  168   a  and  168   b  suitable for co-operating with the clamping surfaces  154   a  and  154   b  of the spacer body  150 . 
     As in the above embodiment, by moving the movable part  152  in the cavity  154  relative to the stationary part  150 , the pairs of clamping surfaces  154   a  &amp;  168   a , and  154   b  &amp;  168   b  are moved towards or away from each other. This movement is preferably obtained with the help of a screw  170  whose head  172  bears against the top face  152   a  of the movable part  152  and whose threaded portion  174  passes freely through an oblong bore  176  formed in the movable part  152 , and co-operates with tapping  178  formed in the end wall of the spacer body  150 . By turning the screw  170 , with its head  172  bearing against the top face  152   a  of the movable part  152 , the movable part  152  is caused to move relative to the stationary part  150 , thereby securing the braid  28  to the spacer  110   2 . 
     With reference to  FIGS. 13A to 13C , there follows a description of a third embodiment of the spacer fitted with the securing mechanism, which spacer is given reference  110   3 . Like the other spacers  110   1 , and  110   2 , the spacer  110   3  comprises a body  180  that constitutes the stationary portion of the securing mechanism together with a movable part  182  that is mounted to slide in a cavity  184  formed in the body of the spacer body  180  and opening out into the proximal face  180   a  of the spacer body  180 . The cavity  184  has a substantially horizontal end wall  186  on which the likewise substantially horizontal end wall  188  of the movable part  182  can slide. The movable part  182  has an axial channel  190  and two flanges  192  and  194 . 
     As shown better in  FIG. 13C , the end wall  196  of the axial channel  190  in the movable part  182  has a portion  196   a  that is substantially horizontal and a portion  196   b  that is inclined. The flanges  192  and  194  of the movable part  188  are provided with respective free passages  198  and  200  for passing portions of the braid  28  that extend parallel to the movement direction of the movable part  182 . The spacer body  180  includes in its top face  180   b  a tapped bore  202  suitable for cooperating with a screw  204 . The bore  202  opens out into the housing  184 . The spacer body  180  also has two side slots  206  for passing portions of the braid  28 , as shown more clearly in  FIG. 13A . Its distal end  208  presents a free passage  210  for the braid  28 , as shown more clearly in  FIG. 13A . A portion of the braid  28  penetrates into the housing  184  via the side slots  206  and passes through the slots  198  and  200  of the movable part  188  so that the free ends  28   e  and  28   f  of the braid  28  exit from the movable part  188 , as shown more clearly in  FIG. 13A . The distal faces  192   a  and  194   a  of the flanges  192  and  194  of the movable part  182  constitute clamping faces suitable for co-operating with the distal vertical face  184   a  of the housing  184 . 
     As shown more clearly in  FIG. 13C , the bottom end  204   a  of the screw  204  co-operates with the inclined portion  196   b  of the end wall  196  of the channel  190  in the movable part  188 . Thus, by turning the screw  204 , it is possible to move the movable part  188  in one direction or the other relative to the wedge body  180 . This serves to clamp portions of the braid  28  between the clamping face  184   a  of the stationary portion  180  and the clamping faces  192   a  and  194   a  of the movable part  188 . 
     The spacer  110   4  with a clamping system as shown in  FIGS. 14A and 14B  is very similar to the spacer  110   2 . In this embodiment, the movable part is subdivided into two independent movable parts  210  and  212 . These two movable parts  210  and  212  can be moved in translation inside the housing  214  that is formed in the spacer body  216 . Each movable half-part  210  and  212  is fitted with a screw  218  and  219  for controlling its movement, each of these screws having exactly the same function as the screw  172  in the spacer  110   2 . The braid  28  is clamped and thus secured to the spacer by co-operation between each of the clamping faces  210   a  and  212   a  as defined by the proximal ends of the movable half-parts  210  and  212  and by a common clamping surface  220   a  defined by a portion of the wall of the housing  214  in the spacer body  216 . The advantage of this embodiment is that it enables each end of the braid  28  to be secured separately to the spacer, which makes it possible under certain circumstances to enable the surgeon to perform special adjustment. 
     In  FIGS. 15 ,  16 , and  16 A, there can be seen a fifth embodiment of a spacer  110   5  that is provided with a securing mechanism. 
     In this embodiment, the stationary portion of the securing mechanism is constituted by the spacer body  270 . In the proximal portion  270   a  of the spacer body there is provided a housing  272  for receiving the movable portion  274 . The end wall  276  of the housing  272  constitutes a first clamping surface for the portions of the braid  28 . The bottom face  278  of the movable part  274  constitutes the second clamping surface. The movable part  274  is moved in translation along the direction XX′ by a control screw  280  having a threaded portion  280   a  that co-operates with tapping  282  formed in the spacer body  270 . The head  280   b  of the screw  280  bears against the bottom of a counterbore  284  formed in the movable part  274 . 
     Portions of the braid  28  penetrate between the clamping surface  276  and  278  via slots  286  formed in the spacer body  270 , and the free ends  28   e  and  28   f  of the braid  28  exit via slots  288  formed in the movable part  274 . By acting on the screw  280 , the clamping surfaces  276  and  278  can be moved away from or towards each other. 
     It should be observed that the above-described securing mechanisms are all of the same general structure. They comprise two parts that are movable relative to each other and between which two portions of the braid close to its free ends  28   e  and  28   f  are interposed. A mechanical member, usually a screw, serves to cause the parts to move towards or away from each other. When the two parts are moved towards each other, the two braid portions are secured to each other and to the securing mechanism by being wedged or clamped. 
     This applies regardless of whether the securing mechanism is independent of the spacer ( FIGS. 1 to 6 ), or whether the securing mechanism is mounted in a spacer ( FIGS. 7 to 16 ). 
       FIG. 17  shows a first variant of the second embodiment of the stabilization system of the disclosure. 
     In this variant of the second embodiment of the stabilization system of the disclosure, as shown in  FIG. 17 , the difference compared with the stabilization system shown in  FIG. 8  consists solely in the fact that the spacer  220  provided with a securing mechanism is of a different type. The stabilization system as a whole also comprises simple spacers  114  and  116  interposed between vertebrae V 1  and V 2  and between vertebrae V 3  and V 4 , and a braid  28  that co-operates with the spacers in exactly the same manner as in  FIG. 8 . 
     The spacer  220  differs essentially from the spacers  210  by the fact that the securing mechanism  222  that is associated therewith for securing the braid  28  with this spacer is removable from the body  224  of the spacer  220 . More precisely, the securing mechanism is preferably secured of the spacer body  224  by a clip system as described below. 
       FIGS. 18A ,  18 B, and  18 C show the spacer  220  and its securing mechanism  222 . This spacer, which is preferably suitable for lateral insertion, is described in detail in PCT patent application WO 2007/099258, which is incorporated herein by reference. 
     The securing mechanism  222  can be fastened to the proximal prong  226  of the spacer body  224  by a clip-fastener system that is constituted, for example, by two studs  228  carried by two side faces of the securing mechanism  222  suitable for co-operating with elastically deformable notches  230  formed in the faces of the proximal prong  226  of the spacer body  224 . As shown more clearly in  FIGS. 18A-18C , the braid  28  is secured to the spacer  220  by a system of slots made in the body  232  of the securing mechanism  222 . This braid-securing mechanism comprising two systems that are self-locking is described in detail in PCT patent application WO 2007/120277, which is incorporated herein by reference. There are two inclined side slots  234  and  236  and an axial slot  238 . The side slots  234  and  236  co-operate with the inside face  232   a  of the body  232  of the securing mechanism  222  to define edges  240  and  242 .  FIG. 18C  shows the path followed by the braid  28  inside the body  232  of the securing mechanism  222 . The traction free ends  23   e  and  28   f  of the braid are identified as its portions  28   g  and  28   h  going towards the simple spacers  114  and  116 . 
     When the securing mechanism  222  has been clipped onto the spacer body  224  and when the surgeon is exerting appropriate traction on the free ends  28   e  and  28   f  of the braid using the above-mentioned surgical instrument, the braid becomes wedged in the body  232  of the securing mechanism, in particular because of the presence of the edges  240  and  242 . The body  224  of the spacer  220  also has a free passage  244  for a braid portion  28 . 
       FIG. 19  shows a second variant of the second embodiment of the stabilization system in accordance with the disclosure. This system again comprises a braid  28  and spacers  114  and  116  interposed between the vertebrae V 4  and V 3  and also between the vertebrae V 2  and V 1 . In this embodiment of the spacer  250 , the difference lies in the means for securing the ends of the braid  28 . The spacer  250  with its securing mechanisms is described in PCT patent application WO 2002/071960, which is incorporated herein by reference. The spacer  250  comprises a spacer body  252  presenting two side faces  254  and  256 . Each of the side faces  254  and  256  can have a locking member  258  or  260  clipped thereto, the set of two locking members forming the braid-securing mechanism. Two braids  28 ′ a  and  28 ′ b  are used. A first end of each braid is secured to a respective portion  260  or  262  of the spacer body  252 . The other free end  28 ′ ae  or  28 ′ bf  is engaged in a respective one of the locking systems  258  and  260 . Each locking system  258  and  260  corresponds to exactly half of the locking system shown in  FIG. 18C . 
     It should be observed that if two distinct braids  28 ′ a  and  28 ′ b  are used, then the surgeon needs to exert traction on only one braid portion end  28 ′ ae  or  28 ′ bf , as in the other embodiments of the disclosure. 
     It should also be observed that since the locking members are disposed on both side faces of the spacer body the technique of insertion by a lateral approach is not usable. 
     Finally, in the embodiments shown in  FIGS. 17 and 19 , the free end of the braid is secured to the securing mechanism by locking the braid because it follows a sinuous path through the securing mechanism, thereby ensuring that it becomes self-blocking by friction when a traction force is exerted on the main portion of the braid. 
       FIGS. 20 to 22  show other variants of the second embodiment of the disclosure. 
     The first variant as shown in  FIG. 20  is very similar to the embodiment shown in  FIG. 7 . The difference lies in the structure of the simple spacer  115 . Instead of having solely the function of guiding the braid  28 , the spacer  115  also has a function of clamping a portion of the braid  28 . The spacer  115  may have the same structure as the spacer  110 , but it is used differently. The braid  28  enters via the slot  134  of  FIG. 9  and leaves via the analogous second slot. Consequently, the simple spacer  115  not only performs a guidance function, but it also performs a function of clamping a portion of the braid  28  by acting on the movable part  122  relative to the stationary portion  120 . In contrast, the simple spacer  115  does not under any circumstances serve to secure the free ends of the braid  28 , which function is performed by the spacer  110 . 
       FIG. 21  shows a variant of  FIG. 20  that differs therefrom by the fact that the spacers  110  and  115  are inserted between the spinous processes of the vertebrae V 1 , V 2 , and V 3  using different approaches. 
     In  FIG. 22 , there is shown another variant of the second embodiment of the disclosure. In this variant, there are two simple spacers  115  and  117  having functions of clamping portions of the braid  28 . It is possible to use stabilization systems comprising a spacer  112  provided with a securing mechanism for the free ends of the braid  28 , at least one simple spacer such as the spacer  114  shown in  FIG. 17  that serves solely to guide the braid  28 , and at least one simple spacer of the same type as the spacer  115  that has a function of clamping a portion of the braid. 
       FIGS. 23 and 24  show another variant of the second embodiment of the disclosure. In this variant, the stabilization system comprises two braids  28   a  and  28   b  and two spacers  300  and  302 , each provided with a system  304  and  308 , each of which is physically suitable for securing to one end of each of the braids  28   a  and  28   b . It should be understood that one of the spacers  300  or  302  serves for securing the two braids  28   a  and  28   b , while the other spacer serves for securing the free end of each braid after the surgeon has exerted an appropriate amount of traction on the free ends of the braid exiting one of the spacers  300 ,  302 . 
     This solution makes it possible, as a function of ease of access, to exert traction on the braid via one or the other of the spacers  300  and  302  or to begin by exerting traction on the free ends of the braid via one of the spacers and to finish off applying traction to the braids via the other spacer.