Abstract:
A vertebral anchoring device includes connectors ( 2 ) linked to one another by connecting rods ( 3 ) and fixed on bone-anchoring screws ( 5 ) implanted in the vertebrae ( 4 ) of a vertebral column, each connector ( 2 ) being composed of a connection element ( 6 ) that includes receiving and fixing members to permit immobilization of the connecting rod ( 3 ) in translation and in rotation. Each connection element ( 6 ) includes, opposite the members for receiving and fixing the connecting rod ( 3 ), a seat ( 12 ) that cooperates with a connecting device ( 17 ) permitting assembly of the anchoring screw ( 5 ). The connecting device ( 17 ), before immobilization of the connecting rod ( 3 ) in the connection element ( 6 ), permits lateral and independent tilting movements of the connection element ( 6 ) and of the anchoring screw ( 5 ) relative to each other, and rotation of the anchoring screw ( 5 ) for fixing it in the body of the vertebra ( 4 ).

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a vertebral anchoring device comprising bone-anchoring connectors that are fixed, by way of anchoring screws, to the various osseous bodies or vertebrae of a vertebral column. 
     DESCRIPTION OF THE RELATED ART 
     The U.S. Pat. No. 2,346,346 has disclosed an external bone-anchoring device comprising connectors that are linked to one another by a connecting rod, while each connector is fixed to a support or to the osseous body by way of an anchoring screw with a spherical head. 
     Each connector is composed of a cylindrical sleeve having, at each end, a bore of different diameter which, respectively, allows the screw to be introduced through said sleeve and allows the spherical head to be held inside the latter. 
     Each connector comprises a blocking device that simultaneously permits immobilization of the connecting rod inside the sleeve and fixation thereof about the spherical head of the screw. 
     It will be noted that, in order to fit this anchoring device in place, it is essential to join the anchoring screw and the connector together before fixing said screw either to a support or to the corresponding bone. 
     In this case, the spherical head of the screw is housed inside the connector, making it difficult to use same for anchoring it to the support or bone. 
     The international patent WO 2004/047657 discloses a vertebral anchoring device comprising a connector, a connecting rod, and a polyaxial anchoring screw. The polyaxial screw comprises a spherical head and a threaded body whose external diameter d at the summit of the teeth of the thread is greater than the external diameter a of the spherical head. 
     Each connector of the vertebral anchoring device is composed of a connection element with vertical branches delimiting a U-shaped opening, and of a locking clip equipped with a press-screw for blocking the connecting rod in the bottom of the U. 
     The connection element of each connector is provided centrally with a vertical bore that is able to receive, opposite the opening, a blocking device formed by a ring and by a threaded bushing, for placing and positioning said connector on the spherical head of the anchoring screw. 
     SUMMARY OF THE PRESENT INVENTION 
     The object of the present invention is to make available a vertebral anchoring device in which each connector comprises connecting means that permit, on the one hand, angular adjustment of said connector about the anchoring screw and, on the other hand, rotation of the anchoring screw for fixing it in the body of the vertebra. 
     The vertebral anchoring device according to the present invention comprises connectors that are linked to one another by connecting rods and are fixed on bone-anchoring screws implanted in the vertebrae of a vertebral column, each connector being composed of a connection element that comprises receiving and fixing means to permit immobilization of the connecting rod in translation and in rotation, each connection element comprising, opposite the means for receiving and fixing the connecting rod, a seat that cooperates with a connecting device permitting assembly of the anchoring screw, which connecting device, before immobilization of the connecting rod in the connection element, permits, on the one hand, lateral and independent tilting movements of the connection element and of the anchoring screw relative to each other and, on the other hand, rotation of the anchoring screw for fixing it in the body of the vertebra. 
     The vertebral anchoring device according to the present invention comprises a connection element composed of a bushing that cooperates with the seat of the connection element and has first means of rotation which are formed respectively in the seat and the bushing and allow the latter to tilt laterally about rotation pins, and second means of rotation which are formed respectively in the bushing and the head of the anchoring screw and allow the latter to tilt laterally about another rotation pin. 
     The vertebral anchoring device according to the present invention comprises a bushing which has at its center, and extending in a vertical direction, a through-bore designed to receive the head of the anchoring screw. 
     The vertebral anchoring device according to the present invention comprises a bushing which has, extending in a first horizontal direction, a first bore that opens into the inner bore and permits placement of the rotation pins, such that the latter open into the bores formed in the seat of the connection element, so as to permit the first lateral tilting movement. 
     The vertebral anchoring device according to the present invention comprises a bushing which has, extending in a second horizontal direction perpendicular to that of the first bore, a second bore that also opens into the inner bore and permits placement of a fixation pin that passes through a bore formed in the head of the anchoring screw, so as to permit the second lateral tilting movement. 
     The vertebral anchoring device according to the present invention comprises a bushing with an upper peripheral edge which has, on the one hand, a hump arranged above each first through-bore and, on the other hand, ribs arranged above each second bore and inside the inner bore. 
     The vertebral anchoring device according to the present invention comprises a bushing joined to a ring which, at its center, has a hole extending in a vertical direction, and, on its outer circumference, has recesses cooperating with the ribs of said bushing. 
     The vertebral anchoring device according to the present invention comprises a connection element with means for receiving and fixing the connecting rod, said means being composed of upper vertical branches that delimit a U-shaped opening for receiving said connecting rod, said upper vertical branches comprising, above the bottom of the opening, a threaded section that allows a press-screw to be tightened in order to block the connecting rod in translation and in rotation. 
     The vertebral anchoring device according to the present invention has a connection element comprising, below the threaded section and at the base of each vertical branch, an opening that opens into the inside of said connection element, in the area of the communication between the bottom of the opening and the seat, in a horizontal direction perpendicular to that of the connecting rod. 
     In the vertebral anchoring device according to the present invention, each of the openings of the connection element arranged opposite each other has an oblong vertical profile. 
     In the vertebral anchoring device according to the present invention, the through-bores of the connection element are arranged in a direction that is horizontal and perpendicular to that of the oblong openings. 
     The vertebral anchoring device according to the invention comprises other features that are essential to the invention and that are described and protected in the secondary claims dependent directly or indirectly on the main claim. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       The attached drawings, given by way of example, will permit a better understanding of the invention, of its features, and of the advantages it is likely to afford. 
         FIG. 1  is a plan view showing vertebral bodies of a vertebral column in which bone-anchoring connectors according to the present invention are fixed. 
         FIG. 2  is an exploded perspective view illustrating the bone-anchoring connector and its anchoring screw according to the present invention. 
         FIGS. 3 to 7  are views showing the assembling of the bone-anchoring connector with its bone-anchoring screw according to the present invention. 
         FIGS. 8 and 10  are views showing the bone-anchoring connector receiving a connecting rod according to the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A vertebral anchoring device  1 , shown in  FIGS. 1 to 4 , comprises connectors  2  that are linked to one another by connecting rods  3 , while each connector  2  is fixed by an anchoring screw  5  in each vertebra  4  of a segment of the spine that is to be corrected. 
     Each connector  2  is composed of a connection element  6  that comprises upper vertical branches  7 ,  8  delimiting a U-shaped opening  9 , the bottom  10  of which opening  9  communicates, opposite the opening  9 , with a seat  12  which opens to the outside and whose inner profile can be in the shape of a portion of a sphere. 
     The inner part of the upper vertical branches  7 ,  8  of the connection element  6  comprises, above the bottom  10  of the opening  9 , a threaded section  13  that allows a press-screw  14  to be tightened in order to block a connecting rod  3  in translation and in rotation in the bottom of the U of each connector  2  ( FIG. 8 ). 
     The connection element  6  comprises, below the threaded section  13  and at the base of each vertical branch  7 ,  8 , an opening  11  that opens into the inside of said connection element, in the area of the communication between the bottom  10  of the opening  9  and the seat  12 , in a horizontal direction perpendicular to that of the connecting rod  3 . 
     Each of the openings  11  arranged opposite each other has an oblong vertical profile of sufficient height to permit introduction of a rotation pin  26  during assembly of the connector  2 . 
     The seat  12  of the connection element  6  comprises coaxial through-bores  15  that extend in a horizontal direction perpendicular to that of the oblong openings  11 . 
     Each connector  2  comprises a bushing  17  with an outer profile that complements the inner profile of the seat  12  formed in the lower part of the connection element  6 . 
     The bushing  17  is provided centrally, and along a vertical axis, with an inner bore  18  in which the anchoring screw  5 , and more particularly the head  16  thereof, is housed and immobilized. 
     The bushing  17  has, in a first horizontal direction, a first bore  19  that opens into the inner bore  18 , and, in a second horizontal direction perpendicular to the first, a second bore  22  that also opens out into the inner bore  18 . 
     The bushing  17  comprises an upper peripheral edge  23  which has a hump  24  arranged above each first through-bore  19 . 
     The bushing  17  comprises ribs  32  arranged above the second bores  22  and in the area of the upper edge  23  of and inside the bore  18 . 
     Each connector  2  comprises a ring  27  which, at its center, has a hole  28  extending in a vertical direction. 
     The ring  27  comprises, on its outer circumference, recesses  30  below which there are indents  31  shaped as a portion of a cylinder. 
     The connection elements  6  of each connector  2  are fixed in each vertebra  4  by the anchoring screw  5 . Each anchoring screw  5  comprises a head  16 , which is continued by a cylindrical body  33  with a thread  34  on its outer circumference. 
     The head  16  of the anchoring screw  5  has an outer profile that may or may not be of a shape complementing that of the inner bore  18  of the bushing  17 . 
     The head  16  of the anchoring screw  5  has a through-bore  25  designed to cooperate with the fixation pin  26  when placed inside the connection element  6  of each connector  2 . 
     Thus the fitting of each connector  2  of the vertebral anchoring device  1  around the anchoring screw  5  will be easily understood from the above description. 
     First, the bushing  17  is introduced into the seat  12  of the connection element  6  in such a way that each first bore  19  is arranged in line with those  15  of said seat ( FIG. 4 ). 
     The bushing  17  is immobilized inside the seat  12  by way of two rotation pins  20 ,  21  which are each introduced through the inside of the bore  18  of the bushing  17  so as to cooperate with the bores  19  and  15  provided for this purpose. 
     The rotation pins  20 ,  21  comprise a head  29  whose external diameter is greater than the internal diameter of the bores  19 ,  15 , so as to avoid any translation of these pins. 
     The introduction of the rotation pins  20 ,  21  into the horizontal bores  19 ,  15  makes it possible, on the one hand, to retain the bushing  17  in the seat  12  of the connection element  6  and, on the other hand, to permit a freedom of movement, that is to say a rotation or an angular clearance about said horizontal pins  20 ,  21  between said bushing  17  and the connection element  6  ( FIG. 4 ). 
     Second, the ring  27  is introduced into and immobilized inside the inner bore  18  of the bushing  17  by means of the recesses  30 , which cooperate with the ribs  32  provided in the area of the upper edge  23  ( FIG. 4 ). 
     The ring  27  is immobilized inside the bushing  17 , ensuring, on the one hand, that the indents  31  shaped as a portion of a cylinder are arranged above the horizontal bores  22  formed in said bushing  17 , and, on the other hand, that the outer circumference of said ring opposite said indents bears against the rotation pins  20 ,  21  in order to prevent these from moving inside the bores  19  and  15 . 
     The ring  27  is fixed in the bushing  17  in order to continue the latter above its upper edge  23 , such that said ring  27  takes up a position at the bottom  10  of the opening  9  of the connection element  6 . 
     Third, the head  16  of the anchoring screw  5  is introduced into the bore  18  of the bushing  17 , which is retained inside the seat  12  of the connection element  6 . For this purpose, the bushing  17  must be positioned in such a way that the lower opening of the bore  18  is in alignment with that of the seat  12  of the connection element  6  ( FIGS. 5 and 6 ). 
     The head  16  is introduced into the bore  18  of the bushing  17  such that its through-bore  25  is positioned in line with and as a continuation of those  22  of said bushing  17 . 
     When the head  16  has an outer profile complementing the inner profile of the bore  18  of the bushing  17 , said head can be fitted only in one position, leading automatically to the alignment of the bores  25  of the head  16  and that  22  of the bushing  17 . 
     The connection element  6  is then inclined laterally about the rotation pins  20 ,  21 , while maintaining the cylindrical body  33  of the anchoring screw  5  and the bushing  17  in a vertical position ( FIG. 6 ). 
     This first lateral tilting movement makes it possible to position the first bore  22  of the bushing  17  and a first end of the bore  25  of the head  16  with one of the oblong openings  11  formed in the connection element  6 . 
     This position permits introduction of the rotation pin  26 , such that the latter passes through the corresponding oblong opening  11  of the connection element  6  and is positioned completely within the bores  22  of the bushing  17  and the bore  25  of the head  16  of the anchoring screw  5 . 
     The fixation pin  26  is thus introduced completely inside the bores  22  of the bushing  17  and the bore  25  of the head  16  of the anchoring screw  5 , making it possible to retain said anchoring screw  5  inside the bushing  17  ( FIG. 7 ). 
     It will be noted that the dimensions of the fixation pin  26  are smaller than the external dimensions of the bushing  17 , which means that once it has been introduced completely into the bores  22  of the bushing  17  and the bore  25  of the head  16  of the anchoring screw  5 , the bushing  17  and the connection element  6  are able to tilt freely about the rotation pins  20 ,  21 . 
     It will be observed that each connector  2  of the vertebral anchoring device  1  has:
         a first lateral tilting movement about the rotation pins  20 ,  21  joining the bushing  17  to the connection element  6 ,   and a second lateral tilting movement about the retention pin  26  joining the head  16  of the anchoring screw  5  to the bushing  17 , the retention pin  26  being arranged in a direction that is horizontal and perpendicular to that of the horizontal rotation pins  20 ,  21 .       

     It will be noted that the connection of the anchoring screw  5  to the bushing  17  and of the latter to the connection element  6  by way of the horizontal pins  20 ,  21  and  26  also ensures that the anchoring screw  5  is moved in rotation about its longitudinal axis in order for its cylindrical body  33  to penetrate into the corresponding vertebral body or vertebra  4 . 
     The anchoring screw  5  is driven in rotation, so as to fix it in the corresponding vertebra  4 , by means of a special tool (not shown) that cooperates with the connection element  6 . 
     When the anchoring screw  5  of each connector  2  is fixed in the vertebral body  4 , the connection element  6  is positioned in the best angular position by tilting about the horizontal pins  20 ,  21  and  26 , so as to receive the connecting rod  3  that joins each connector  2  on the instrumented segment of the vertebral column. 
     Inside each connector  2 , the connecting rod  3  is immobilized, in terms of rotation about its longitudinal axis and in terms of translation, by the press-screw  14  that is screwed in between the upper vertical branches  7  and  8  of the connection element  6  ( FIGS. 8 to 10 ). 
     The immobilization of the connecting rod  3  in the bottom of the opening  9  of each connection element  6  by the press-screw  14  also makes it possible to simultaneously block the connection element  6  in a suitable angular position about the head  16  of the anchoring screw  5 . 
     This is because the ring  27 , by way of its central bore  28 , allows the head  16  of the anchoring screw  5  to take up a position at the bottom  10  of the opening  9  that receives the connecting rod  3 . 
     The fixation of the connecting rod  3  between the vertical branches  7 ,  8  and against the bottom  10  of the opening  9  by means of the press-screw  14  allows the latter to bear against the head  16  of the anchoring screw  5  and block the connection element  6  ( FIGS. 9 and 10 ). 
     It must be understood, moreover, that the above description has been given only by way of example and that it does not in any way limit the field of the invention, and that replacing the described details by other equivalent ones would not constitute a departure from said field of the invention.