Abstract:
Disclosed are embodiments of a dynamic stabilizer system for dynamically stabilizing the sacrum and at least lumbar vertebra L5. The dynamic stabilizer system may comprise two anchoring members that can be implanted at distinct locations in the sacrum, a mechanical fastener element having two ends and a flexible portion that can be securely fastened on the spinous process of a lumbar vertebra, and two distinct rods, each securing onto the anchoring members and the mechanical fastener element. In some embodiments, the dynamic stabilizer system may further comprise one or more spacers, each interposed between two spinous processes. The mechanical fastener element further comprises features for securing the one or more spacers.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims a benefit of priority under 35 U.S.C. 119(a) of the filing date of European Patent Application No. 08305124, entitled “System for Stabilizing at Least a Portion of the Spine” by inventors Stephane Douget and Vincent Pointillart, filed on Apr. 24, 2008, the content of which application is hereby incorporated as if fully set forth herein. 
     TECHNICAL FIELD OF THE DISCLOSURE 
     The present disclosure includes a system and method for stabilizing at least a portion of the spine, including in at least one embodiment a system for dynamically stabilizing the sacrum and at least lumbar vertebra L5. 
     SUMMARY OF THE DISCLOSURE 
     PCT patent applications Nos. WO 2005/020860, WO 2006/106268, and WO 2007/023240, which are incorporated herein by reference, describe systems for stabilizing the sacrum to the fifth lumbar vertebra. 
     Those devices are very effective, but they prevent the vertebra(e) from moving relative to the sacrum in a manner that is practically total, thus leaving no degree of freedom between the sacrum and the last lumbar vertebra. In many circumstances, that situation is unfavorable. 
     To solve this problem, at least one object of the present disclosure is to provide a system for stabilizing the sacrum and at least the fifth lumbar vertebra that makes dynamic stabilization possible. For this particular embodiment of the disclosure, the term “dynamic stabilization” is used to mean that the sacrum and at least the last lumbar vertebra are indeed stabilized relative to each other, but that a limited amount of relative movement is nevertheless allowed between the vertebra and the sacrum so as to enable the patient to be more comfortable. 
     According to the disclosure, to achieve this particular object, a dynamic stabilizer system for dynamically stabilizing the sacrum and at least lumbar vertebra L5, is characterized in that it comprises:
         two anchoring members in the sacrum, said members being implanted at distinct locations;   two distinct rigid rods, each presenting a first end and a second end, each second end being secured to an anchoring member in such a manner that the point at which each rod is secured close to its second end can be adjusted; and   a mechanical fastener element fastened on the process of a lumbar vertebra, said mechanical fastener element presenting a first end and a second end, the first end of each rigid rod being secured to one of the ends of said mechanical fastener element, said mechanical fastener element including a flexible portion.       

     It will be understood that by means of the disclosure, effective stabilization is obtained for the vertebra(e) relative to the sacrum, in particular because of the presence of the two rigid rods, each of which is anchored at one end to the sacrum by the mechanical fastener element, and each of which is connected at its other end to the spinous process of at least the fifth lumbar vertebra, with adjustment being possible. The reader should appreciate that the mechanical fastener element may be a screw, nail, or any other type of fastener capable for fixation to bone. Nevertheless, since the mechanical fastener element includes a flexible portion connecting the process to one of the ends of the rigid rods, dynamic stabilization is indeed obtained that allows limited amounts of relative movement between the sacrum and the lumbar vertebra(e). 
     In a first embodiment, said mechanical fastener element includes at least one flexible tie completely surrounding the spinous process of the vertebra L5, said first and second ends of said mechanical fastener element being constituted by portions of said tie(s). 
     It will be understood that under such circumstances, the spinous process of the fifth lumbar vertebra is surrounded by one or more flexible ties and that the second ends of said rigid rods are rigidly anchored in the sacrum by the anchoring members. The dynamic stabilization is obtained by the presence of the tie(s) surrounding the process. 
     In a second embodiment, said mechanical fastener element comprises at least a first spacer interposed between the process of lumbar vertebra L5 and the process S1 of the sacrum, said spacer presenting said first and second ends; and a flexible tie co-operating with the process of a lumbar vertebra, said flexible tie presenting two ends secured to said spacer. 
     It will be understood that the stabilization between the sacrum and the last lumbar vertebra is obtained by co-operation between the spacer with the two rigid rods, each having one end anchored in the sacrum, and with the flexible tie that co-operates with the process of at least the fifth lumbar vertebra. This procures effective stabilization, while allowing limited amounts of relative movement between the vertebra and the sacrum by using the flexible tie in co-operation with the process of the vertebra or the processes of the vertebrae. 
     In a variant embodiment, said mechanical fastener element further comprises a second spacer interposed between the processes of lumbar vertebrae L5 and L4, said flexible tie co-operating with said second spacer and partially surrounding the process of lumbar vertebra L4. 
     It will be understood that because of the presence of the second spacer, the tie enables both the fifth and the fourth lumbar vertebrae to be stabilized with the sacrum, while also allowing relative movement between the sacrum, the fifth lumbar vertebra, and the fourth lumbar vertebra. Naturally, it is possible to provide more than one second spacer should it be appropriate to stabilize more than two vertebrae with the sacrum. 
     Other characteristics and advantages of the disclosure appear better on reading the following description of various embodiments of the disclosure given as non-limiting examples. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The description refers to the accompanying figures, in which: 
         FIG. 1  is a perspective view of a first embodiment of the dynamic stabilizer system; 
         FIG. 1A  shows an embodiment of the connection between the rigid rods and the mechanical fastener element for the embodiment of  FIG. 1 ; 
         FIG. 1B  is a vertical section view showing two fastener parts of the  FIG. 1A  embodiment; 
         FIG. 1C  is a plan view of the mechanical connection system of  FIG. 1A ; 
         FIG. 2  is a perspective view of a second embodiment of the dynamic stabilizer system; 
         FIG. 3  is an exploded view showing the connection between the spacer shown in  FIG. 2  and the rigid rods; 
         FIG. 4  is a perspective view, partially in section on plane IV-IV of  FIG. 2 , showing how the ends of the rods and the ends of the flexible tie are secured; 
         FIG. 5  is a perspective view of a variant of the second embodiment enabling two vertebrae to be stabilized dynamically relative to the sacrum; and 
         FIG. 6  is a perspective view showing a screw constituting the anchoring element for anchoring rigid rods in the sacrum. 
     
    
    
     DETAILED DESCRIPTION 
     With reference initially to  FIG. 1 , there follows a description of a first embodiment of the dynamic stabilizer system. 
     In this figure, there can be seen the upper portion of the sacrum S together with the lower lumbar vertebra L5 and its spinous process A. 
     The dynamic stabilizer system, given overall reference  10 , is constituted by two anchoring members  12  and  14  preferably constituted by screws screwed into the sacrum, by two rigid rods  16  and  18 , and by a mechanical fastener element fastened to the process A, and given reference  20 . As explained above, the mechanical element fastened to the process includes a flexible portion that is constituted, in this embodiment, by two flexible tie portions  22  and  24 . The ends  22   a ,  22   b  and  24   a ,  24   b  of these ties are secured to one another in such a manner that the assembly constituted by the tie portions  22  and  24  completely surrounds the spinous process A. The ends  22   a ,  24   a  and  22   b ,  24   b  of the tie portions constitute fastener ends of the mechanical fastener element  20 , which fastener ends are fastened to the first ends  16   a  and  18   a  of the rigid rods  16  and  18 . A preferred embodiment of the securing means between the ends of the rods  16  and  18  and the ends  26  and  28  of the mechanical fastener element  20  are described in greater detail below. The anchoring members  12  and  14 , which are preferably constituted by screws  30  and  32  screwed into suitable portions of the sacrum, are described in greater detail below. They serve to fasten the second ends  16   b  and  18   b  of the rigid rods  16  and  18 . The screws  30  and  32  cooperate with the ends  16   b  and  18   b  of the rigid rods in such a manner that, prior to the ends being secured on the screws, it is possible to adjust which portions of the rigid rods that are indeed held securely. In other words, it is possible to adjust the distance between the ends  16   a  and  18   a  of the rods and the zones in which the anchoring elements are clamped onto the rods. 
     This makes it possible to adjust the stabilization effect between the lumbar vertebra L5 and the sacrum S. 
     It will be understood that since the connection between the first ends  16   a  and  18   a  of the rigid rods  16  and  18  and the spinous process A of the lumbar vertebra L5 is provided via tie portions  22  and  24  that are flexible, the vertebra L5 is indeed stabilized dynamically relative to the sacrum, such that limited relative movement remains possible between the vertebra L5 and the sacrum S. The tie portions are made using a material that presents sufficient flexibility, and possibly also sufficient elasticity, to allow limited relative movement. For example, the material may be a polyester, a polyethylene, polyetheretherketone (PEEK) or any other material that provides the desired elasticity. 
       FIGS. 1A ,  1 B, and  1 C show a particular embodiment of the mechanical element  20  for fastening to the process. 
     The mechanical element  20  is essentially constituted by two securing parts  31  and  33  and by a flexible tie or braid  34  that performs the same function as the tie portions  22  and  24  in  FIG. 1 . The securing parts  31  and  33  are designed to be fastened on either side of the spinous process A with the help of the braid  34 . 
     Each securing part comprises a main portion  31   a ,  33   a  and a lug  31   b ,  33   b  extending substantially perpendicularly to the main portion. The lugs  31   b ,  33   b  are held by the braid  34  against the sides of the process A. The lugs  31   b  and  33   b  have slots  35 ,  36  for passing the braid  34 . The ends  16   a ,  18   a  of the rigid rods  16 ,  18  are welded to the main portions  31   a ,  33   a  of the parts  31 ,  33 . 
     In order to secure or block the free ends  34   a  and  34   b  of the braid  34 , the part  33  is provided with a movable clamping member  37 . The clamping member  37  presents a clamping face  37   a  facing the sloping face  38  of the lug  33   b  of the part  33 . A screw  39  passes freely through the clamping member  37  and its threaded portion  39   a  co-operates with a tapped hole  39 ′ formed in the main portion  33   a  of the fastener part  33 . 
     By tightening the screw  39 , the clamping surface  37   a  is caused to move towards the clamping surface  38  of the lug  33   b . This thus secures the ends  34   a ,  34   b  of the braid to the parts  31  and  33 . Nevertheless, since the braid  34  is flexible, limited movement remains possible between the process A and the parts  31  and  33 , i.e. limited relative movement is possible between the vertebra and the sacrum. 
       FIGS. 2 to 4  show a second embodiment of the disclosure that is described below. 
     In this second embodiment, the dynamic stabilizer system is given reference  10 ′ and it is constituted by two screws  40  and  42  that constitute the anchoring members in the sacrum S, by two rigid rods  44  and  46 , and by a mechanical fastener element referenced  20 ′ for fastening to the spinous process A of the vertebra L5. In this embodiment, the mechanical fastener element  20 ′ is essentially constituted by an intervertebral spacer  48  and by a flexible tie  50 . 
     The spacer  48  is interposed between the spinous process A of the vertebra L5 and the spinous process S1 of the sacrum S. More precisely, the spacer  48  has two end portions  52  and  54 , each provided with a recess  56 ,  58  for receiving the spinous processes A and S1. As explained in greater detail below, the spacer  48  serves both for fastening to one of the ends of each of the rigid rods  44  and  46 , and for securing the ends of the flexible braid  50 . 
     Preferably, the spacer  48  is elongate in shape in a direction perpendicular to the axis of the spine and includes a first end  60  and a second end  62 . Each of these ends  60  and  62  is pierced by a respective orifice  64 ,  66  into which the ends  46   a  and  44   a  of the rods  44  and  46  can penetrate. 
     Close to its ends  60  and  62 , the spacer  48  also has two orifices  68  and  70  that pass right through the spacer in its thickness direction, i.e. between its faces  52  and  54 . These orifices  68  and  70  communicate with the end orifices  64  and  66 . Finally, tapped holes  72  and  74  are provided in the side face  48   a  of the spacer  48 . These tapped holes  72  and  74  also open out into the orifices  68  and  70 . 
     When the dynamic stabilizer system is put into place, the flexible tie or braid  50  has its middle portion  50   a  that bears against the top face of the spinous process A of the vertebra L5 and has portions close to the ends  50   b  and  50   c  that are engaged in the orifices  68  and  70  so as to project beyond the spacer  48 . 
     Finally, as can be seen better in  FIG. 3 , it should be observed that each rod has a first end  44   a ,  46   a  that is angled relative to the main portion  44   b ,  46   b  of each of the rods, with the second end of each rod having a respective reference  44   c  and  46   c.    
     The screws  40  and  42  can be screws of the same type as the screws  30  and  32  as used in the first embodiment of the disclosure, and as described in greater detail below, and they enable adjustment to be performed. 
     There follows a description of how the dynamic stabilizer system  10 ′ is put into place by the surgeon. 
     After performing anatomic operations giving access to the lumbar vertebra L5 and to the upper portion of the sacrum S, the surgeon puts the spacer  48  into place between the process A of the lumbar vertebra L5 and the process S1 of the sacrum in such a manner that these processes are received in the recesses  56  and  58  of the spacer. Thereafter, the surgeon screws the screws  40  and  42  into the sacrum. The ends  46   c  and  46   c  of the rigid rods  44  and  46  are put into place in the heads of the screws. The flexible braid  50  is then put into place in such a manner that its middle portion  50   a  bears against the top face of the spinous process A of the lumbar vertebra L5, and the two ends of the braid are caused to penetrate into the through orifices  68  and  70  so that the free ends  50   b  and  50   c  of the braid project beyond the bottom face of the spacer  48 . The surgeon inserts the ends  44   a  and  46   a  of the rigid rods  44  and  46  into the end orifices  64  and  66  of the spacer  48 . The surgeon can adjust stabilization by inserting the ends  44   c  and  46   c  to a greater or lesser extent into the heads  40   a  and  42   a  of the screws  40  and  42 . Once adjustment has been achieved in satisfactory manner, i.e. once the desired degree of stabilization has been reached, the surgeon secures the screws  40  and  42  to the ends  44   c  and  46   c  of the rigid rods with the help of headless set screws  80  and  82  co-operating with tapped holes  80 ′ and  82 ′ formed in the heads of the screws  40  and  42 . 
     Thereafter, by inserting headless set screws  84  and  86  in the tapped holes  72  and  74 , the surgeon proceeds to secure the ends of the flexible braid  50  of the spacer  48  and the second ends  44   a  and  46   a  of the rigid rods  44  and  46 . As shown better in  FIG. 4 , an intermediate portion of the braid  50  engaged in the orifice  68  is placed between the end  44   a  of the rigid rod  44  and the wall of the orifice  68 . By acting on the set screw  84  engaged in the tapped hole  72 , the end  84   a  of the screw  84  exerts pressure on the end  44   a  of the rod  44  and on the intermediate portion of the braid  50 . Before ensuring that these various parts are finally blocked in position, the surgeon applies suitable traction on the ends  50   b  and  50   c  of the braid  50  in order to obtain the desired degree of stabilization and also the desired possibilities for relative movement between the sacrum and the vertebra L5, i.e. the desired dynamic stabilization. This traction may advantageously be exerted with the help of the traction instrument described in PCT patent application WO 2007/034112, which is incorporated herein by reference. When the set screws  84  and  86  are engaged to the maximum, the spacer  48 , the ends of the braid  50 , and the ends of the rigid rods  44  and  46  are secured effectively to one another. 
     With reference to  FIG. 5 , there follows a description of a variant of the second embodiment of the dynamic stabilizer system that makes it possible to obtain stabilization between the sacrum S and both lumbar vertebrae L5 and L4. The dynamic stabilizer system, now referenced  10 ″, has anchor screws  40  and  42  in the sacrum, a spacer  48 , and rigid rods  44  and  46 . All of these elements are analogous or identical to those described above with reference to the embodiment of  FIGS. 2 to 4 . The essential difference lies in the length of the flexible braid  50 ′ and in the addition of a simple intervertebral spacer  90  which is interposed between the spinous process A4 of the lumbar vertebra L4 and the spinous process AS of the lumbar vertebra L5. In conventional manner, the intermediate spacer  90  comprises an intermediate portion  92  that may present a certain amount of flexibility, and two end portions  94  and  96 , each defining a recess  98  or  100  for receiving a respective one of the spinous processes A4 and AS. In its side portions  102  and  104 , the simple intervertebral spacer  90  has two passages  106  and  108  extending along the entire length of the spacer in the axial direction of the spine. 
     The middle portion  50 ′ a  of the flexible tie or braid  50 ′ passes over the top face of the spinous process A4 of the lumbar vertebra L4. Intermediate portions of the same braid  50 ′ are engaged in the longitudinal passages  106  and  108  of the intermediate spacer and its ends  50 ′ b  and  50 ′ c  are engaged in the spacer  48  in exactly the same manner as that described with reference to  FIGS. 2 to 4 . 
     It can be understood that this obtains dynamic stabilization between the sacrum S and the lumbar vertebrae L5 and L4. 
     Naturally, it is possible to provide a larger number of simple intervertebral spacers of the type referenced  90 , and that are interposed between lumbar vertebra L4 and lumbar vertebra L3, etc.; such spacers being identical to the spacer  90 . This obtains dynamic stabilization between the sacrum and a larger number of lumbar vertebrae. 
     In  FIG. 6  there can be seen an example of a screw  120  suitable for constituting an anchor screw in the sacrum as described above. The screw, known as a “pedicular” screw, comprises a threaded shank  122  presenting a thread suitable for enabling it to be screwed into the sacrum, and it also possesses a head  124 . The head  124  presents a circular recess  126  provided with tapping  128 . The head  124  also has two notches  130  and  132  that are diametrically opposite and of dimensions suitable for receiving the ends  44   c  or  46   c  of the rigid rods. A headless set screw of the type shown under references  80  or  82  can be engaged in the tapped orifices  126  in the head of the screw for clamping purposes and thus for securing the ends of the rigid rods to the heads of the screws. It will be understood that the surgeon can initially position the appropriate portions of the ends  44   c  or  46   c  of the rods in the heads of the screws in appropriate manner for obtaining suitable positioning and clamping of the spacer  48  on the spinous process S1 of the sacrum S. 
     The forms of the disclosure shown and described herein are to be taken as examples of embodiments. Elements and materials may be substituted for or implemented from those illustrated and described herein, as would be apparent to those skilled in the art after having the benefit of the disclosure. Changes may be made in the elements or to the features described herein without departing from the spirit and scope of the disclosure as set forth in the following claims and their legal equivalents.