Abstract:
Embodiments disclosed herein provide a spinal interconnecting device and a stabilizing system using the same. The spinal interconnecting device has a connecting body and a hook member fixed to the connecting body for securing the connecting body to a vertebra. The connecting body has a first connecting member and a second connecting member. The first connecting member is adapted to receive the extremity of a spinal construction. The second connecting member is adapted to receive a first end of a separate rod, so that the direction of the separate rod is adaptable with respect to the direction of the spinal construction.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application claims a benefit of priority under 35 U.S.C. 119(a) of the filing date of European Patent Application No. 08305684, filed Oct. 15, 2008, entitled “A SPINAL INTERCONNECTING DEVICE AND A STABILIZING SYSTEM USING SAID DEVICE,” which is fully incorporated herein by reference. 
       TECHNICAL FIELD OF THE DISCLOSURE 
       [0002]    The present invention relates to a device for interconnecting the extremity of a spinal construction assembly with a separate rod and fixing them to a vertebra, and a stabilizing system including said interconnecting device. 
         [0003]    One field of application for the invention is holding bones in a relative position, for example, to aid in the healing of breaks or the positioning of bones, or the treatment of scoliosis, or otherwise to correct abnormal curvatures of the spine. 
       SUMMARY OF THE DISCLOSURE 
       [0004]    The spine is formed of superposed vertebrae, normally aligned along a vertebral axis from the lumbar vertebrae to the cervical vertebrae, each having a posterior wall from which projects a spinous process and two lateral edges from the walls of which project ribs and/or transverse process. Each vertebra also has two lateral pedicles and lamina surfaces. 
         [0005]    Accompanying  FIG. 1  shows vertebrae V and V′ with the different parts thereof. Reference TP designates the transversal processes, reference P designates the pedicles of the vertebra and reference L designates the lamina. 
         [0006]    In order to straighten or stabilize the vertebrae of the spine it is well known to use a stabilizing system which includes an interconnecting longitudinal rod and several fixing elements. Each fixing element is secured to one of the vertebrae to be stabilized and the longitudinal rod is secured to each fixing element. The fixing elements Include a head to be secured to the rod and a fixing member which may consist of a screw (for example a pedicle screw) or a hook. When the patient who is equipped with such a stabilizing system moves his spine, forces are developed by the fixing member of the fixing elements in the vertebrae. In particular, the fixing elements disposed at the extremities of the rod of the stabilizing system or spinal construction assembly develop the greatest forces. It is therefore apparent that it would be advantageous to try to decrease the forces developed at the extremities of the spinal construction assembly. 
         [0007]    Moreover, autostable claws are also well known. Such a system is described, for example, in EP 0 571 619. This system includes two fixing elements, each one being provided with a hook member, and a rod to interconnect the fixing elements and, consequently, the vertebrae on which the fixing elements are secured. When defining with the rod the appropriate distance between the two fixing elements, an appropriate stabilization of the vertebrae is obtained. 
         [0008]    In another use of the autostable claw system, the hook members of the autostable claw system can be secured to different parts of the same vertebra. 
         [0009]    A first object of the present Invention is to provide a device for interconnecting the extremity of a spinal construction assembly with a separate rod, said separate rod being preferably, but not necessarily, part of an autostable claw system, which is more easily implantable by the surgeon than the already known interconnecting devices. 
         [0010]    To achieve this goal, according to the invention, the device for interconnecting the extremity of a spinal construction with a separate rod and fixing them to a vertebra comprises a connecting body and a hook member for securing said connecting body to said vertebra, said hook member being fixed to said connecting body, said connecting body comprising a first connecting member, and a second connecting member, said first connecting member being adapted to receive said extremity of the spinal construction, said second connecting member being adapted to receive a first end of said separate rod so that the direction of said separate rod Is adaptable with respect to the direction of said spinal construction. 
         [0011]    It is understood that the extremity of the spinal construction system is connected to one end of the separate rod and fixed to the vertebra thanks to a unique device. 
         [0012]    Moreover, due to the fact that the second connecting member allows the separate rod to have an adaptable direction with respect to the direction of the spinal construction, the surgeon can choose freely the part of the vertebra to which the interconnecting device is fixed to the vertebra. 
         [0013]    Preferably, the second connecting member includes a first rotulating assembly for cooperating with a second rotulating assembly provided at said first end of said separate rod. 
         [0014]    According to a preferred embodiment of the invention, said hook member and said connecting body have a common median plane, said first connecting member having an axis and overlapping said hook member, said second connecting member having an axis contained in said median plane and substantially parallel to the axis of the first connecting member and being offset with respect to said first connecting member in a direction perpendicular to the axis of said first connecting member. 
         [0015]    It is apparent that, because the second connecting member is offset with respect to the first connecting member in a direction which is perpendicular to the direction of the axis of the connecting member, the thickness of the head of the interconnecting device is not increased. 
         [0016]    The hook member can overlap the first connecting member or the second connecting member in a direction of the axes of said connecting member. 
         [0017]    A second object of the invention is to provide a stabilizing system which uses an interconnecting device of the type described above. 
         [0018]    According to the invention, the stabilizing system comprises a spinal construction assembly having a first end, a separate rod having first and second ends, an interconnecting device of the type defined above for Interconnecting the first end of said spinal construction assembly and the first end of said separate rod, and a fixing element for fixing the second end of said separate rod to a vertebra. 
         [0019]    It can be understood that the stabilizing system is basically a combination of a spinal construction system and of an autostable claw system which is formed by the second connecting member of the interconnecting device, the separate rod, and the fixing element. The purpose of the autostable claw system is to permit a decrease in the forces developed within the vertebra by the extremity of the spinal construction system. 
         [0020]    Moreover, as the separate rod can have an adaptable direction with respect to the direction of the rod of the spinal construction, the surgeon can freely choose the part of the vertebra to which the interconnecting device is fixed and the part of the vertebra to which the fixing element is secured. This part can be the transverse process, the pedicle or the lamina. The hook member of the interconnecting device and the fixing member of the fixing element (preferably by a hook) can be fixed to two different parts of the same vertebra or to two adjacent different vertebrae. 
         [0021]    In both cases, the rods of the spinal construction and of the separate rod can form an angle of less than 90 degrees. This means that the separate rod “returns” towards the rod of the spinal construction. 
         [0022]    In both cases, the angle between the two rods can also be more than 90 degrees. This means that the separate rod extends “beyond” the rod of the spinal construction. 
         [0023]    These and other aspects and advantages of the invention will be better appreciated and understood when considered In conjunction with the following description and the accompanying drawings. The following description, while indicating various embodiments of the invention and numerous specific details thereof, is given by way of illustration, and not limitation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]      FIG. 1 , already described, is a perspective view of a vertebra showing the different parts of the vertebra. 
           [0025]      FIG. 2  is a perspective view of a preferred embodiment of the interconnecting device according to the invention. 
           [0026]      FIG. 3  is a sectional view of the connecting device according to plane P of  FIG. 2 . 
           [0027]      FIG. 4  is an exploded view which shows the combination of a spinal construction assembly with a separate rod, the connecting device being provided with a pellicle hook. 
           [0028]      FIG. 5  is similar to  FIG. 4  but the connecting device is provided with a lamina hook. 
           [0029]      FIG. 6  is similar to  FIG. 4  but with the components assembled; and 
           [0030]      FIGS. 7A to 7D  are schematic drawings which show four different combinations of a spinal construction assembly with an autostable claw system. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    With reference to  FIGS. 2 and 3 , a preferred embodiment of the interconnecting device will be described. 
         [0032]    The interconnecting device  10  comprises a connecting body  12  and a hook member  14 . 
         [0033]    The connecting body  12  includes a first connecting member  16  and a second connecting member  18 . Preferably, the first connecting member  16 , the second connecting member  18  and the hook member  14  are formed as a single piece. 
         [0034]    Preferably, the first connecting member, which forms a connecting head, is provided with an opening or slot  20  which terminates into two opposable faces  22  and  24  of the head  16 . The slot  20  has a bottom wall  26  which is substantially semi-cylindrical and two lateral walls  28  and  30  which are substantially flat. 
         [0035]    The upper portion  28   a  and  30   a  of the lateral walls  28  and  30  defines portions of cylindrical surfaces. These upper portions  28   a  and  30   a  are provided with a threading  32 . 
         [0036]    Preferably, the hook member  14  is formed by a hook  34 . In the case of the embodiment shown by  FIG. 2 , the hook member  14  is a pedicle hook. However, the hook member  14  might be a lamina hook. The hook  34  is disposed below the first connecting head  14 . 
         [0037]    Preferably, the second connecting member  18  is provided with an opening  40  which terminates in the face  42  of the second connecting member  18 . The bottom  44  of the opening  40  has a wall having substantially the shape of a portion of a half spherical surface. As will be explained hereinafter, the surface  44  forms the female part of a rotulating system. 
         [0038]    The upper part  46  of the opening  40  is formed by a wall  48  having the shape of a portion of a cylindrical surface. The upper part  46  is provided with an internal threading  50 . 
         [0039]    The first connecting member  16  has a longitudinal axis X, X′ and the second connecting member  18  has a longitudinal axis Y, Y′. These two axes are parallel one with the other and are disposed on a plane P. The plane P forms a median plane for the interconnecting device  10 . The first and second connecting members  16  and  18  are placed side by side in the direction perpendicular to the direction of the axis X, X′ and Y, Y′. As a result, the axis X, X′ and Y, Y′ are offset by a length E in the plane P. 
         [0040]    Referring now to  FIG. 4 , according to a preferred use of an interconnecting device  10  according to the invention, it is used to form a spinal stabilizing system and combines a spinal construction system A, and an adjustable claw system B. The function of the device  10  is to interconnect the extremity  60  of the spinal construction system A with an end  62  of a separate rod  64  which forms a part of the autostable claw B which will be described in more detail hereinafter. 
         [0041]    In  FIG. 4  the spinal construction A is symbolically represented by a longitudinal connecting rod  66  having the free end  60 . As is well known, the entire spinal construction A comprises the connecting rod  66  and a plurality of fixing devices (not shown in the figure) to secure intermediate portions of the rod with the vertebrae to be stabilized by the spinal construction A. 
         [0042]    The free end  60  of the rod  66  of the spinal construction A is adapted to be engaged into the opening  20  of the first connecting member  16  of the interconnecting device  10 . For this purpose, the diameter of the bottom wail  26  of the opening  20  is slightly greater than the diameter D of the rod  66 . When the end  60  of the rod  66  is engaged into the slot  20 , this end is connected to the connecting member by means of a screw  68  which cooperates with the threading  32 . 
         [0043]    As shown in  FIG. 4 , the end  62  of the separate rod  64  is provided with a spherical member  70  which forms the male part of a rotulating system adapted to be engaged within the partially spherical part  48  of the opening  40  of the second connecting member  1 B. The spherical member  70  can be connected to the connecting member  18  by means of a screw  72  which can cooperate with the threading  50  of the opening of connecting member  18 . 
         [0044]    The second end  74  of the separate rod  64  can be connected to a fixing element  76 . Preferably, the fixing element  76  comprises a connecting head  78  provided with a slot  80  to receive the rod  64  and a hook  79  to fix the fixing element  76  to a vertebra. In the example shown in  FIG. 4 , the hook  79  is a lamina hook. The end  74  of the rod  64  can be secured to the head  78  by means of a screw  82 . In  FIG. 5 , the connecting device is provided with a lamina hook  84 . 
         [0045]    In view of the above description, it is clear that a preferred use of the interconnecting device  10  is to interconnect an autostable claw system B and a spinal construction system A. 
         [0046]    The autostable claw system consists in the rod  64 , the fixing element  76  with its hook  79 , and the second connecting member  18  and the hook  34  of the interconnecting device  10 . 
         [0047]    As already explained, the connection between the end  62 ,  70  of the separate rod  64  and the second connecting member  18  is achieved by a rotulating system consisting in the spherical member  70  and the partially spherical bottom wall  44  of the connecting member  18 . As a result, the direction of the separate rod  64  can be chosen by the surgeon before screwing the screw  72  with the connecting member  18 . As a result, the surgeon can freely choose the part of the vertebra to which the fixing element  76  is fixed. This feature significantly simplifies the action of the surgeon as will be explained below with reference to  FIGS. 7A and 7D . 
         [0048]    Moreover, the two connecting members  16  and  18  are disposed side by side. Consequently, the interconnecting device is less aggressive than a device where the two connecting members are superposed. 
         [0049]      FIGS. 7A to 7D  illustrate the great number of possible positions of the autostabie claw system B and the spinal construction A. These figures also illustrate the great number of possible fixing locations of the stabilizing system to the vertebrae. 
         [0050]    In the case of  FIG. 7A , the interconnecting device  10  and the fixing element  76  are both fixed to a lamina of vertebrae V 1  and V 2 , and the autostable claw system B extends beyond the spinal construction A. The angle C between the rods of the systems A and B is substantially equal to 180 degrees. 
         [0051]    In the case of  FIG. 7B , the interconnecting device  10  and the fixing element  76  are still secured to a lamina of vertebrae VI and V 2  but the angle C between the autostable claw system B and the spinal construction A is greatly reduced. The rods of the systems A and B are substantially parallel and the system B “returns” towards the system A. In the case of  FIG. 7C , the fixing element  76  is fixed to a lamina of vertebra VI and the interconnecting device  10  is fixed to a pedicle of vertebra V 2  and the angle C is approximately 150 degrees. 
         [0052]    Finally, in the case of  FIG. 7D , the interconnecting device  10  is fixed to a lamina of vertebra V 1  and the fixing element  76  is secured to a pedicle of vertebra V 2 . The angle C is about 10 degrees. 
         [0053]    In the above description, the fixing element  76  and the Interconnecting device  10  are fixed to two different vertebrae. Obviously, these two securing components can be fixed to two different parts of the same vertebra. In this case, the rod  64  of the autostable claw system B has a reduced length. 
         [0054]    However, in both cases, the anchoring of the extremity of the spinal construction A into the vertebra is improved by the provision of the autostable claw system B. 
         [0055]    Moreover, in the above description, the hook member  34  or  84  has the same axis (XX′) as the first connecting member  16 . Of course, the hook member could be “aligned” with the second connecting member  18 . 
         [0056]    The advantage of this variant of the invention has exactly the same advantages as the previously described preferred embodiments.