Abstract:
A transverse connector system for coupling elongate elements to each other in a spinal fixation system. A trans-connector plate with at least one slot-like passage may have top and bottom elongated concave surface configurations. A cylindrical component of a coupling member may be configured to couple with an elongate fixation element by way of a helical slot. A male component on the coupling member may be inserted through the slot like passage and a locking member may be secured thereon to position and orient the coupling member. A second coupling member and locking member may be utilized through a passage in the trans-connector plate, which may be a second slot-like passage. Each locking member cooperates with its respective coupling member to prevent uncoupling, and each may be positioned at a desired lateral position along a slot-like passage.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/873,425, filed Dec. 7, 2006, the disclosure of which is incorporated herein by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a device for spinal fixation, and in particular to a transverse connector system for coupling spinal rods, plates, or other elongate members. 
       BACKGROUND 
       [0003]    It is often necessary to surgically treat spinal disorders such as scoliosis. Numerous systems for use in spinal correction and fixation have been disclosed. These systems usually include a pair of elongate members, typically either rods or plates, placed along the vertebral column. For the sake of simplicity, the term “rod” is used throughout to refer to any such elongate member. Each rod is attached to the spine with various attachment devices. These attachment devices may include, but are not limited to, pedicle screws, plates, transverse process hooks, sublaminar hooks, pedicle hooks, and other similar devices. 
         [0004]    It is also well known that the strength and stability of a dual rod assembly can be increased by coupling two rods with a cross-brace or transverse connector which extends substantially horizontal to the longitudinal axes of the rods, typically across the spine. The simplest situation in which a transverse connector may be used occurs when the two rods are geometrically aligned parallel to each other in all three dimensions. In such an alignment, there is no convergence or divergence between the rods in the medial-lateral direction, the two rods have the same orientation with respect to the coronal plane (viewed in the anterior-posterior direction), the rods are coplanar from a lateral view, and the two rods are located a uniform distance from each other. 
         [0005]    However, the two rods are rarely three dimensionally geometrically aligned in clinical situations. There are several ways to address the variations of geometrical alignment. First, one or both of the rods can be bent to accommodate a transverse connector. However, any bending in either of the rods can adversely affect the fixation to the spine and compromise the clinical outcome. Furthermore, such bending can also adversely affect the mechanical properties of the rods. Alternatively, a transverse connector can be bent so that disturbance to the rod positioning is minimized. As is the case with bending of the rods, the mechanical properties of the transverse connector may be compromised by such bending. 
         [0006]    In order to address this issue, transverse connectors with some adjustability have been designed to adapt for variations from geometrical alignment. However, most of such connectors are multi-piece systems which can be difficult to assemble and use in the surgical environment. For example, U.S. Pat. No. 5,980,523, the disclosure of which is incorporated herein by reference in its entirety, discloses a multi-piece transverse connector for spinal rods that can accommodate converging or diverging rods. However, accidental disassembly of this type of connector by the surgeon is possible. 
         [0007]    Other connectors which are one-piece designs do not allow for adjustments to compensate for all three modes in which there may be variation from geometrical alignment: convergence or divergence, non-coplanar rods, and variability in rod separation distances. For example, U.S. Pat. No. 5,947,966, the disclosure of which is incorporated by reference herein, discloses a device for linking adjacent spinal rods. In one embodiment, the device includes two members that are movable with respect to one another to accommodate different rod separation distances. A pin on one member engages a groove on the other member to provisionally couple the two members, thereby preventing a surgeon from separating the two members. Because the pin is sized to exactly fit the groove, no movement of the pin transverse to the longitudinal axis of the groove is possible. As a result, the devices similar to the &#39;966 patent device cannot accommodate non-coplanar rods or adjust for rod convergence or divergence. 
         [0008]    Thus, there exists a need for an improved transverse connector utilized for connecting or coupling elongate fixation elements to each other in a spinal fixation system that allows for adjustment in translational and/or rotational placement to adjust for convergence or divergence, non-coplanarity, and variability in separation between the elongate fixation elements. 
       SUMMARY 
       [0009]    In one illustrative embodiment, the present invention includes a transverse connector system for coupling first and second elongate spinal fixation elements which may have different three dimensional orientations to each other. A trans-connector plate with at least one slot-like passage may have top and bottom elongated concave surface configurations. A cylindrical component of a coupling member may be configured to couple with an elongate fixation element by way of a helical slot. A male component on the coupling member may be inserted through the slot-like passage, and a locking member may be secured thereon to position and orient the coupling member. A second coupling member and locking member may be utilized through a passage in the trans-connector plate, which may be a second slot-like passage. Each locking member cooperates with its respective coupling member to prevent uncoupling, and each may be positioned at a desired lateral position along a slot-like passage. By using separately adjustable coupling members and locking members, different separation distances and orientations between elongate fixation elements in a spinal fixation system may be accommodated. 
         [0010]    Additional embodiments, examples, advantages, and objects of the present invention will be apparent to those of ordinary skill in the art from the following specification. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0011]    It will be appreciated by those of ordinary skill in the art that the elements depicted in the various drawings are not to scale, but are for illustrative purposes only. The nature of the present invention, as well as other embodiments of the present invention may be more clearly understood by reference to the following detailed description of the invention, to the appended claims, and to the several drawings attached hereto. 
           [0012]      FIG. 1  is a cut-away side view of one illustrative embodiment of a transverse-connector system in accordance with the principles of the present invention. 
           [0013]      FIG. 2  is a bottom view of the transverse-connector system of  FIG. 1 . 
           [0014]      FIG. 3  is a top view of the transverse-connector system of  FIGS. 1 and 2 . 
           [0015]      FIG. 4A  is a side view of one illustrative embodiment of a coupling member for use in a transverse connector system in accordance with the present invention. 
           [0016]      FIG. 4B  is a front view of the coupling member of  FIG. 4A . 
           [0017]      FIG. 5A  shows a cut-away view of an illustrative embodiment of a locking member for use in a transverse-connector system in accordance with the present invention. 
           [0018]      FIG. 5B  is a top view of the locking member of  FIG. 5A . 
           [0019]      FIG. 5C  is a bottom view of the locking member of  FIGS. 5A and 5B . 
           [0020]      FIG. 6  is a partial cut-away side view of the coupling member of  FIGS. 4A and 4B  together with the locking member of  FIGS. 5A ,  5 B and  5 C in a transverse connector system in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. 
         [0022]    Referring generally to  FIG. 1 , a transverse connector system  10  in accordance with the present invention is depicted. Transverse-connector  10  system may include one or more coupling members  20 , a counterpart internally threaded female locking member  30 , and at least one trans-connector plate member  40 . 
         [0023]    Transverse connector system  10  may be used for coupling a first elongate fixation element R 1  to a second elongate fixation element R 2 . First and second elongate fixation elements R 1  and R 2  may be cylindrical rods, rectangular bars, plates, or any other device suitable for spinal fusion. In a spinal fixation application, first elongate fixation element R 1  may extend along one side of the vertebral column, attached thereto by separate attachment elements. Similarly, second elongate fixation element R 2  may extend along the opposite side of the vertebral column, attached thereto by separate attachment elements. 
         [0024]    The components of transverse-connector system  10  can be made of any sturdy biocompatible material suitable for an orthopedic application. Suitable materials may include titanium, stainless steel, and alloys containing the same. Where the components of transverse-connector system  10  are constructed from metallic materials, the materials may be similar, or identical to, the metallic materials used for the elongate fixation elements to avoid galvanic (mixed-metal) corrosion. 
         [0025]    As shown in  FIGS. 1 ,  2  and  3 , the trans-connector plate  40  may be formed as a generally planar member with an upper surface  44  and a lower surface  43 . It may include a solid section forming a medial bridge  45 , from which two wings extend outwards opposite one another to distal ends D 1  and D 2 . Each wing may contain an elongated slot S 1  or S 2  passing therethrough from the upper surface  44  to the lower surface  43 . Surrounding each slot S 1  or S 2 , a concave inset  41 A or  41 B may be formed in the upper surface. In some embodiments, insets  41 A and  41 B may have a concave spherical configuration. Similarly, a concave inset  42 A or  42 B may be formed in the lower surface  43  surrounding each slot S 1  or S 2 . In some embodiments, insets  41 A and  41 B may have a concave spherical configuration. The surface of the concave insets  41 A,  41 B,  42 A, and  42 B may be roughened or knurled to increase engagement to other components of the system  10 , as discussed further herein. 
         [0026]    The inclusion of medial bridge  45  in trans-connector plate  40  may provide additional strength and stability to the system  10 . However, it will be appreciated that in some alternate embodiments, a trans-connector plate  40 , which lacks a medial bridge  45  and includes a single slot formed by the union of slots S 1  and S 2 , may be used. It will be further appreciated that although embodiments with two opposite wings and slots S 1  and S 2  are depicted, that embodiments including multiple slots in a single wing, or including different numbers of wings (such as 3, 4, or more wings containing slots) may be used and are within the scope of the present invention. 
         [0027]    Turning to  FIGS. 4A and 4B , a coupling member  20  in accordance with the principles of the present invention is depicted. Coupling member  20  includes a lower portion  21  which may have a generally cylindrical shape. A helical slot  23  extends upwards into the body of the lower portion  21  from a bottom end  27 . The walls  25  of the slot  23  are thereby configured to couple with an elongate fixation element, such as a spinal fixation rod, when the coupling member  20  is rotated about a rod inserted into the slot  23  at bottom end  27 . Slot  23  may have a helical rotation angle of at least about 11 degrees about the axis of the cylindrical component. The interior surface of walls  25  may be roughened or knurled for increased contact with an inserted elongate member. 
         [0028]    Coupling member  20  also includes a top portion  22  formed at a top end of lower portion  21 . Top portion  22  includes a linking element  29 , which may be a post with threads  24  for receiving an internally threaded locking member  30  ( FIG. 5A ). Between upper portion  22  and lower portion  21 , the coupling member  20  has a convex surface  26 . Convex surface  26  may be formed as a protrusion  28  disposed on the top surface of lower portion  21  and surrounding the linking element  29 . Upon installation, linking element  29  passes through a slot S 1  or S 2  of a trans-connector plate  40  and convex surface  26  contacts the concave inset  42 A or  42 B formed in the bottom surface of the trans-connector plate  40 . Convex surface  26  may be roughened or knurled to increase the security of the contact with a trans-connector plate  40 . 
         [0029]      FIGS. 5A ,  5 B and  5 C depict an internally threaded locking member  30  for use in a transverse connector system  10 , in accordance with the present invention. Locking member  30  may be generally formed as an internally threaded nut. A bore  32  extends from an upper surface  31  to a lower convex surface  33 . The internal wall  36  of bore  32  may include threads  35  for securing the locking member  30  to the coupling member  20 . The external sidewall  34  of locking member  30  may have planar portions to allow for interaction with a turning tool, such as a wrench. It will, of course, be appreciated that alternative configurations, where a tool print is disposed on the upper surface  31  of the locking member  30  may be used. 
         [0030]    Upon installation, the locking member  30  may be threadably attached to a linking element  29  of a coupling member  20  that passes through a slot S 1  or S 2  of a trans-connector plate  40  and lower convex surface  33  brought into contact with a concave inset  41 A or  41 B formed in the upper surface of the trans-connector plate  40 . Lower convex surface  33  may be roughened or knurled to increase the security of the contact with a trans-connector plate  40 . 
         [0031]      FIG. 6  depicts an enlarged side view of one side of a transverse-connector system  10  in a partial cut-away to highlight the interfaces between the trans-connector plate  40 , locking member  30 , and coupling member  20 . For use in securing elongated members, such as spinal rods, the linking element  29  of a coupling member  20  is inserted into a slot S 1  or S 2  of a trans-connector plate  40 . A locking member  30  is then threaded onto the linking element  29 . The convex surface  28  of the coupling element  20  is drawn towards the concave inset  42 A or  42 B of the lower surface  43  of the trans-connector plate and the lower convex surface  33  of the locking member  30  is drawn towards the concave inset  41 A or  41 B of the upper surface  44  of the trans-connector plate  40 . 
         [0032]    An elongated member, such as a spinal fixation rod, may be placed in the helical slot  23  of the coupling member  20 . The joined coupling member  20  and locking member  30  are positioned in the desired lateral position along the slot S 1  or S 2 . The locking member  30  is tightened on the linking element  29 . The coupling member  20  is thereby rotated, drawing the elongated member R into slot  23  to secure therein. The trans-connector plate  40  is secured between the coupling member  20  and locking element  30 , as concave insets  41  and  42  are compressed between the lower convex surface  33  and convex surface  26 . This process may be repeated for a second elongated member R using the second slot S 1  or S 2  of the trans-connector plate  40  with a second coupling member  20  and locking element  30 . 
         [0033]    In this fashion, connector systems  10  in accordance with the present invention include adjustability for attachment to elongate elements R 1  and R 2  that are not coplanar along their entire axes. Adjustability is provided by the lateral movement of the coupling member  20 /locking element  30  construct in the slots S 1  and S 2 . Additionally, since each coupling member  20  is secured to an elongated member R by rotation of a separate individual cylinder, the long axis of each elongated member R may have a different angular relationship to the system  10 , while being secured thereto. 
         [0034]    While the present invention has been shown and described in terms of preferred embodiments thereof, it will be understood that this invention is not limited to any particular embodiment and that changes and modifications may be made without departing from the true spirit and scope of the invention as defined and desired to be protected.