Patent Publication Number: US-9427263-B2

Title: Device for fixing a bony structure to a support member

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/906,880, filed May 31, 2013, which claims priority to EP12305614.5, filed on Jun. 1, 2012, the entire disclosures of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure generally relates to a device for fixing a bony structure to a support member, to a system comprising such a device and to a method using it. Such a device may be helpful for holding a bone (e.g. a vertebra) and a support member (e.g. a rod) in a desired configuration. In particular, the present disclosure relates to a system and method for stabilizing at least two vertebrae. 
     BACKGROUND OF THE INVENTION 
     One field of application for the invention is holding together a bone and a support member in a desired relative position, while allowing in some cases a limited amount of relative movement, for example to aid in healing of breaks or to correct bony structure deficiencies and abnormalities. In particular, sufferers of abnormal spine curvature or other spine deficiencies may benefit from the invention. 
     The spine is formed of superposed vertebrae, normally aligned along a vertebral axis, from the lumbar vertebrae to the cervical vertebrae, each having an anterior part: the vertebral body, and a posterior part: the vertebral arch (or neural arch), the anterior and posterior part enclosing the vertebral foramen. Each vertebral arch is formed by a pair of pedicles and a pair of laminae, with transverse processes and/or a spinous process (or neural spine) projecting therefrom. The transverse processes and the spinous process project opposite to the vertebral foramen. 
     When the vertebrae are articulated with each other, the vertebral bodies form a strong pillar for the support of the head and trunk. In between every pair of vertebral bodies, there is an intervertebral disc. 
     When the spine of a person has abnormal curvature (e.g. scoliosis) or other deficiencies (e.g. a damaged intervertebral disc), the vertebrae are typically too close together, too far apart or otherwise misaligned, and there is a need to stabilize the vertebrae in a correct position relative to one another. Mainly, there is either a need to compress the vertebrae (i.e. to bring and hold them closer together) or a need to distract the vertebrae (i.e. to move and keep them away from each other). 
     Devices known in the art for holding vertebrae relative to one another typically include one or more rods that are held by devices attached to the vertebrae by means of screws, hooks, or flexible ligatures. One such device is described in patent document EP2052689A1. This known device comprises a holding body having a receiving portion for receiving the rod and an engagement portion, a closure member for engagement with the engagement portion of the holding body to secure the rod within said receiving portion, and an anchor member for anchoring the holding body to the bony structure of a vertebra. 
     In the device of EP2052689A1, to create a connection, the receiving portion of the holding body has to be sized to the gauge of the rod used. Since, depending on the specific intervention and patient, a variety of different rod gauges may be required, different holding bodies adapted to accommodate each specific rod gauge need to be provided. 
     While known devices have proven effective, further improvements would be beneficial. 
     SUMMARY OF THE INVENTION 
     Described is a fixing device for fixing a bony structure to a support member. This fixing device comprises:
         a main body comprising first and second members defining between them a first passage configured for receiving the support member, the second member being pivotable with respect to the first member, around a first axis, and   a clamping mechanism engaging the main body and being configured to move the first and second members towards each other for clamping the support member therebetween.       

     In an exemplary fixing device, the first axis is movable in translation along a first direction so that the second member is movable in translation along the first direction, with respect to the first member. Such freedom of movement in translation allows the size of the first passage to be adjusted to the gauge of the support member to be used. Proper clamping of a variety of support members having different gauges can thus be obtained. 
     In certain embodiments, the clamping mechanism engages with the first and second members and is configured to move the second member in translation along the first direction, so as to narrow the first passage. Accordingly, the size of the first passage can be narrowed to the gauge of the support member to be used, by means of the clamping mechanism. 
     Configurations of the device that allow for the intraoperative adjustment of the first passage of the device that receives the support member can have the advantage of being adjustable to a variety of support members having different gauges, while being made of a limited number of parts, which makes the device simpler to produce and easier to handle. 
     In certain embodiments, the fixing device is adapted to receive a flexible member within the first passage, in a direction transverse to a longitudinal axis of the first passage. 
     The fixing device may be adapted to clamp the flexible member between at least one of the first and second members and the support member, when a support member is disposed within the first passage. In this case, the flexible member and the support member can be simultaneously clamped, i.e. the flexible member and the support member can be simultaneously held in position with respect to the fixing device. 
     At least one of the first and second members may be provided with at least one through opening, said through opening being in communication with the first passage and being configured to guide the flexible member therethrough. 
     In certain embodiments, the clamping mechanism comprises a clamping member which is configured to cooperate with the first and second members so as to exert a force on the second member, the force having a component along the first direction. 
     In certain embodiments, the resultant force exerted by the clamping member on the second member is oriented substantially along the first direction, which improves the clamping efficiency. 
     A variety of clamping mechanisms that cause the flexible member and support member to remain in a fixed position can be utilized. For example, a single clamping mechanism can be used to hold the flexible member and support member in a fixed position, or two or more separate clamping mechanisms can be used to hold the flexible member and support member in a fixed position individually. 
     In certain embodiments, the clamping member is a screw with a screw head and a shank, the shank being threadably engaged with the first member and the screw head being configured to exert said force on the second member when the screw is tightened (e.g. when it is screwed into the first member). Using a screw as the clamping member is one embodiment which allows the physician to (finely) adjust the clamping force to the needs. In particular, the physician (or other operative) may lock, unlock, move and/or remove the fixing device, merely by screwing or unscrewing the screw. 
     The fixing device can be preloaded onto a support member with the clamping mechanism partially tightened with final tightening occurring after the physician has the flexible member and support member in its desired position. 
     In certain embodiments, the screw head defines a first sloped or curved surface and the second member defines, on its outside face, a second sloped or curved surface. The force exerted by the screw onto the second member is exerted through those first and second surfaces when the screw head is tightened. The first sloped or curved surface may be symmetrical around the rotational axis of the screw. It may be, for instance, a circular part of a spherical (or substantially spherical), convex or conical surface of the screw head. 
     In certain embodiments, the second member is provided with an oblong opening through which the screw shank passes. The longitudinal direction of that oblong opening may be substantially perpendicular to the screw axis and/or to the first axis A. 
     In certain embodiments, the second member has an inside face defining an abutment for engagement against the support member. This abutment pushes the support member towards the first member when the second member is moved in translation in the first direction. The shape of the abutment is configured to transmit force to support members of different gauges in the best possible way. For example, the outline of the abutment, in a section plane perpendicular to the first axis, may be concave towards the support member. For instance, the abutment may be a groove, the support member being engaged in that groove. 
     In certain embodiments, a pivoting mechanism is provided between the first and second members, the pivoting mechanism comprising a pivot shaft being received in an oblong opening provided in at least one of the first and second members. 
     In certain embodiments, one of the first and second members is provided with a pivot shaft extending along the first axis, and the other one of the first and second members is provided with at least one oblong opening (i.e. an opening having an oblong cross-section) through which the pivot shaft passes, the oblong opening having a longitudinal direction substantially parallel to the first direction. The cooperation between the pivot shaft and the oblong opening is a simple and safe solution for the first and second members to move both in translation and rotation with respect to each other. In cross-section, the oblong opening may have an open outline, i.e. an outline with a gap, or a close outline. When the oblong opening has an open outline, the pivot shaft may be inserted into or taken out of the oblong opening sideways, through the gap of the open outline of the opening. The oblong opening may be open in its longitudinal direction, i.e. the gap of the open outline of the opening may be provided along the longitudinal direction of the groove. 
     In certain embodiments, the pivot shaft is a one-piece shaft extending through the first and second members. This one-piece shaft may be fixedly linked to the first or second member by friction, welding, swaging, crimping, pressing, clamping or any other appropriate solution. 
     The pivot shaft may also be defined by two pins protruding from one member, on opposite sides thereof, and extending through the oblong openings of the other member. 
     Also described is a system comprising at least one support member and at least one fixing device, as described above, for fixing a bony structure to the support member. 
     The support member may be rigid or not. Typically, the support member is a rod or equivalent. The cross-section of the support member may have different shapes. For instance, it may be round, flat or polygonal. The support member may be provided in a variety of gauges (e.g. different widths or diameters) that can be available to a physician for surgery, thus providing the physician with the ability to select an appropriate support member for the patient from a set of available sizes. In particular, the system may comprise a set of support members of different sizes and at least one fixing device. 
     The system may further comprise a flexible member passing through the first passage, between the support member and said first and/or second member, the flexible member extending outside or beyond the main body for attachment to the bony structure. In particular, the flexible member may form a loop around the bony structure. 
     The flexible member may be made of any suitable material that is flexible such as a band, wire, ligament, or cord. For instance, the flexible member may be made of a metal, a polymeric material or a combination thereof. 
     Such a system may be a system for stabilizing at least two vertebrae, which comprises: a first fixing device configured to be fastened to a first vertebra, a second fixing device configured to be fastened to a second vertebra, and a support member for connecting the first and second devices together, thereby providing stabilization between the first and second vertebrae; and wherein at least the first fixing device is a device as described above. 
     The second fixing device may be similar to or different from the first fixing device. 
     The stabilization system described herein may be used for providing “static stabilization” or “dynamic stabilization” between the vertebrae. Static stabilization typically refers to holding together the vertebrae in a particular relative position, while minimizing movement between the vertebrae, whereas dynamic stabilization typically refers to holding together the vertebrae in a particular relative position, while allowing a limited amount of relative movement between the vertebrae. For dynamic stabilization, the support member and/or the flexible member may have elastic properties. 
     As explained above, a variety of support members with different gauges (e.g., with different diameters in case of round section rods) may be used with the same fixing device. Different gauges may be needed to treat different pathologies or portions of the bony structure of the spine (e.g., cervical, thoracic, lumbar, sacral regions). Accordingly, the system may include several support members, of different gauges (or different shapes), and at least one fixing device. The gauge of the support member to be used is then chosen by the physician (or other operative), depending on the specific intervention and patient. 
     Also described is a method for connecting a bony structure to a support member, comprising the steps of: providing a support member and a fixing device as defined above; passing said loop around the bony structure and applying a force to (e.g., tensioning) said loop to change the position of the bony structure, and impeding movement of the bony structure relative to the support member by fixing the position of the flexible member and support member relative to the fixing device, e.g. by clamping the flexible member and the support member between the first and second members. 
     Such a method may be used for stabilizing at least two vertebrae. In this case, it comprises the steps of: providing a system as described above; fixing the first fixing device to a first vertebra, by passing said loop around a bony part of the vertebra and tensioning said loop; fixing the second fixing device to a second vertebra; and impeding relative movement between the first and second fixing devices by connecting each of them to the support member, relative movement between the first vertebra and the support member being impeded by fixing the position of the flexible member and support member relative to the first fixing device. 
     These methods have the advantages derived from using a fixing device or a stabilization system according to the present disclosure. 
     In particular, the physician (or other operative) may be provided with a system comprising one or several fixing devices as described above, and several support members (e.g., several rods) of different gauges. Since the physician is able to accommodate any of the different support members from the set in the fixing device(s), the physician can freely select one appropriate support member (with a particular gauge) without worrying about the compatibility between the selected support member and the fixing device(s). In other terms, regardless of the support member being selected, the physician can use the same type of fixing device. Accordingly, the physician does not waste time in choosing the fixing device. In addition, the physician needs to acquaint himself with the handling and use of one type of fixing device only. 
     Selection of the appropriate support member may be done depending, e.g., on the pathology or the type of bony structure to be treated. 
     Such methods may be used for correcting abnormal spine curvature (e.g., scoliosis) or other spine deficiencies (e.g., a damaged intervertebral disc) by compressing or distracting vertebrae. 
     Other features and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, some principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, like reference signs generally refer to the same parts throughout the different views. Moreover, parts belonging to different embodiments but having analogous functions are given like reference numbers incremented by 100, 200, etc. 
       The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. 
         FIG. 1  is a perspective view of an example of a fixing device. 
         FIG. 2  is an exploded view of the fixing device of  FIG. 1  with a support member. 
         FIG. 3  is a sectional view of the fixing device of  FIG. 1 , along plane III-III. 
         FIG. 4  is a sectional view, like that of  FIG. 3 , showing the fixing device in another position (a clamping position). 
         FIG. 5  is a perspective view of another example of a fixing device. 
         FIG. 6  is an exploded view of the fixing device of  FIG. 5 . 
         FIG. 7  is a diagrammatic view showing an example of a stabilization system in place on two vertebrae. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, it is referred to the accompanying drawings showing examples of fixing devices and stabilization systems. It is intended that these examples be considered as illustrative only, the scope of the invention not being limited to these examples. 
     A first example of fixing device  1  is shown in  FIGS. 1 to 4 . This device  1  is for fixing a support member, such as a rod  4  (see  FIGS. 2-4 ), to a bony structure. The bony structure may be, for instance, a vertebra V 1  or V 2 , as shown in  FIG. 7 . 
     The rod  4  is an example of support member according to the present disclosure. Here, the rod  4  is rigid and has a circular cross-section. It may be made of biocompatible metallic material. 
     The fixing device  1  may be made of biocompatible metallic material. It comprises a main body  2  forming a clamp. The main body  2  comprises a first member  1 J and a second member  2 J linked to the first member  1 J over a hinge of axis A. In the figures, the first and second members  1 J,  2 J are, respectively, the lower and upper portions of the main body  2 . The rod  4  extends substantially parallel to axis A. 
     The hinge comprises a pin or shaft  10  passing thought the first and second members  1 J,  2 J. When the first and second members are assembled, the shaft  10  extends along axis A and goes successively through an opening  13 A provided in a first lateral leg  13  of the second member  2 J, through an opening  14 A provided in a central part  14  of the first member  1 J, and through an opening  15 A provided in a second lateral leg  15  of the second member  2 J. The lateral legs  13 ,  15  of the second member  2 J are located on each side of the central part  14  of the first member  1 J. All openings  13 A,  14 A,  15 A are through holes. However, in other embodiments one or more of the openings  13 A,  14 A,  15 A may be blind holes. Openings  13 A and  15 A have a circular cross-section of substantially the same size (i.e. substantially the same diameter) as that of the shaft  10 . When the fixing device  1  is assembled, the shaft  10  is held by friction, welding, swaging, crimping, pressing, clamping or any other appropriate fixing solution inside the openings  13 A,  15 A, or otherwise attached to the legs  13 ,  15  of the second member  2 J. Opening  14 A has an oblong cross-section with a close outline. The longitudinal direction LD of oblong opening  14 A is perpendicular to axis A. The shaft  10  can turn inside the opening  14 A and can move along the longitudinal direction LD of the opening  14 A (see  FIGS. 3-4 : the position of the shaft  10  inside the opening  14 A is different). Accordingly, with respect to the first member  1 J, the second member  2 J is movable in rotation around the first axis A, while being movable in translation in a first direction D parallel to the longitudinal direction LD. In other embodiments, the oblong opening  14 A may be curved or arcuate, thus allowing the shaft  10  to move in the oblong opening  14 A in an arcuate path generally perpendicular to the axis A. 
     The fixing device  1  further comprises a flexible member  20  (shown in  FIGS. 3-4 , not depicted in  FIGS. 1-2 ) passing through the main body  2 —e.g. through the first member  1 , through the passage  5  between the members  1 J,  2 J, and through the second member  2 J—and extending from the main body  2  to form a loop  20 P around a bony structure (not shown in  FIGS. 1-4 ). Here, the flexible member  20  has two end portions  20 E and an intermediate portion forming said loop  20 P. The loop  20 P extends outside the main body  2  from a passage  21  provided in the first member  1 J, and the end portions  20 E extend from the main body  2  from a passage  22  provided in the second member  2 J. The loop  20 P is tightened or tensioned around a bony structure by pulling on the end portions  20 E, and the flexible member  20  is locked in position by clamping the portions  1 J,  2 J and thus pressing the flexible member  20  between the rod  4  and a surface of the first member  1 J. 
     In this example, there is only one exit passage  22  for the end portions  20 E and one loop passage  21  for the loop  20 P. However, in other examples, not shown, the main body  2  is provided with two exit passages, i.e. one for each end  20 E of the flexible member  20 . Similarly, the main body  2  may be provided with two loop passages, i.e. one for each branch of the loop  20 P. 
     The main body  2  is further provided with a first passage  5  for receiving a portion  4 A of the rod  4 . The first passage  5  is defined by recesses provided in the inside faces of the first and second members  1 J,  2 J. 
     The exit passage  22  and the loop passage  21  both communicate with the first passage  5 . In the appended figures, the exit passage  22  is located above the first passage  5  whereas the loop passage  21  is located below the first passage  5 . When the flexible member  20  is passed through the main body  2  and the rod portion  4 A is placed into the main body  2 , between the members  1 J,  2 J, portions of the flexible member  20  (located between the end portions  20 E and the loop  20 P) are held between the rod portion  4 A and the internal walls of the members  1 J,  2 J defining the first passage  5 . 
     In the example of  FIGS. 1-4 , the exit passage  22 , the first passage  5 , and the loop passage  21  are substantially aligned and the flexible member  20  passes on the same side of the rod  4 , near the first axis A. In other examples, not shown, the flexible member  20  passes on each side of the rod  4 , i.e., one branch of the flexible member  20  passes on one side of the rod  4 , while the other branch of the flexible member  20  passes on the other side of the rod  4 . 
     The fixing device  1  also comprises a clamping mechanism for bringing and maintaining the first and second members  1 J,  2 J in a clamping position in which the rod  4  and the flexible member  20  are held tight. 
     Here, the clamping mechanism comprises a screw  6 . The screw  6  has a shank  6 B going through the first and second members  1 J,  2 J, and a head  6 A having a profile (being internal or external) that allows the screw  6  to be driven in rotation. In more detail, the screw shank  6 B passes through an orifice  9  provided in an engagement portion  12 J of the second member  2 J, and can be screwed into a threaded hole  13  formed in an engagement portion  11 J of the first member  1 J. The screw shank  6 B is provided with an outside thread for engagement with the inside thread of the hole  13 . 
     The orifice  9  is oblong, the longitudinal direction N (see  FIG. 2 ) of this orifice  9  being oriented substantially perpendicular to the screw axis S and to the first axis A. Due to this oblong shape, the second member  2 J is movable in translation in the longitudinal direction N with respect to the screw  6  (when the screw  6  is screwed into the first member  1 J). 
     The screw  6  and the engagement portions  11 J,  12 J of the first and second members  1 J,  2 J are located on the side of the main body  2  which is opposite to the hinge (i.e., to axis A), with respect to the rod  4 . 
     By tightening the screw  6 , the first and second members  1 J,  2 J are moved toward each other and the rod portion  4 A is clamped inside the first passage  5 , between the first and second members  1 J,  2 J, while the flexible member  20  is simultaneously clamped between the rod portion  4 A and the members  1 J,  2 J. 
     The screw head  6 A has a generally spherical, convex or conical shape and the lower part of the screw head (i.e., the part close to the shank  6 B) defines a first sloped or curved surface  31 . When the screw  6  is tightened, the screw head  6 A comes into abutment with a second sloped or curved surface  32  defined on the outside face of the engagement portion  12 J, around the orifice  9 , and the screw head  6 A pushes on the engagement portion  12 J. Thus, a force F (see  FIG. 4 ) is exerted by the screw head  6 A on the second member  2 J, through the first and second surfaces  31 ,  32 . This force F has a component along the first direction D and, advantageously, the force F is aligned with the first direction D. 
     The tightening of the screw  6  makes the pivot shaft  10  move through the oblong opening  14 A in the first direction D, as illustrated in  FIGS. 3-4  (the device being shown in a non-clamping position in  FIG. 3 , and in a clamping position in  FIG. 4 ). So, when the screw  6  is tightened, the second member  2 J is moved in translation along the first direction D, with respect to the first member  1 J. The second member  2 J has an internal face with an abutment face  33  for the rod  4 , the abutment face  33  pushing the rod  4  towards the first member  1 J when the second member  2 J is moved relative to the first member  1 J. In turn, the rod  4  presses the portions of the flexible member  20  against the face  34  of the first member  1 J, thereby locking the flexible member  20  in position. 
     Another example of fixing device  101  is shown in  FIGS. 5-6 . This device differs from the one of  FIGS. 1-3  by the hinge linking the first member  101 J with the second member  102 J. The other parts are substantially the same and will not be described again, for the sake of conciseness. 
     In the example of  FIGS. 5-6 , the hinge between the first and second members  101 J,  102 J comprises two pins  110  aligned with each other and both extending along axis A in opposite directions from the first member  101 J. Those pins  110  extend from the lateral sides of the central part  114  of the first member  101 J and are respectively engaged through openings  113 A,  115 A respectively provided in first and second lateral legs  113 ,  115  of the second member  102 J. The lateral legs  113 ,  115  of the second member  102 J are located on each side of the central part  114  of the first member  101 J. 
     Openings  113 A,  115 A are oblong holes having a width corresponding substantially to the diameter of the pins  110 . The longitudinal direction LD of each opening (see  FIGS. 3-4 ) is parallel to the first direction D and is substantially perpendicular to the first axis A. Accordingly, the pins  110  are movable within the openings  113 A,  115 A both in rotation around their axis A and in translation in direction D. As a consequence, with respect to the first member  101 J, the second member  102 J is movable in rotation around the first axis A, while being movable in translation in direction D, generally perpendicular to the axis A. In other embodiments, the oblong openings  113 A,  115 A may be curved or arcuate, thus allowing the pins  110  to move in the oblong openings  113 A,  115 A in an arcuate path generally perpendicular to the axis A. 
     In cross-section, the outline of each opening  113 A,  115 A is open, meaning that this outline has a gap  140  and that each opening  113 A,  115 A opens out at the gap  140 . The gap  140  is provided at a longitudinal end of the oblong opening  113 A,  115 A. Thus, when assembling the first and second members  101 J,  102 J, the pins  110  are inserted into the openings  113 A,  115 A, through the gaps  140 . Then, the screw  106  is mounted on the members  101 J,  102 J. When the screw  106  is in position but not tightened, the translational movement of the second member  102 J with respect to the first member  101 J is possible while being limited, and the pins  110  cannot exit the openings  113 A,  115 A, through the gap  140 , because the length of the oblong openings  113 A,  115 A (i.e. their length along the longitudinal direction LD) is greater than the maximum length of possible translation of the second member  102 J along direction D. 
     When the screw  106  is not yet mounted on the members  101 J,  102 J, in order to impede the pins  110  from being removed from the openings  113 A,  115 A, small stops  142  protruding inside the opening  113 A,  115 A may be provided near the gap  140 . To assemble the members  101 J,  102 J together, the pins  110  are inserted in force into the openings  113 A,  115 A, past the stops  142 . The pins  110  cannot go backward, past the stops  142 , unless a sufficient force exceeding a threshold amount of force is exerted thereon. 
     Pins  110  may be made in one piece with the central part  114  of the first member  101 J or, alternatively, in separate pieces. In particular, pins  110  may be formed by the end portions of a shaft passing through the central part  114  and being fixedly linked thereto or by end portions of shafts extending from the part  114  in opposite directions. 
       FIG. 7  shows an example of a stabilization system for stabilizing at least two vertebrae V 1 , V 2 , the system comprising: a first fixing device configured to be fastened to a first vertebra V 1 , a second fixing device configured to be fastened to a second vertebra V 2 , and a support member—e.g. a rod  4 —for connecting the first and second anchors together, thereby providing stabilization between the first and second vertebrae. The first and second fixing devices may be the same or different and may be devices  1 ,  101  such as those of  FIGS. 1-6 . In this example, the first and second fixing devices  1 ,  101  are respectively fastened to the laminae of the vertebrae V 1 , V 2 .  FIG. 7  is diagrammatic and, in particular, the flexible members of the fixing devices  1 ,  101  are not shown.