Abstract:
A spinal fixation system includes a first clip body having a pair of opposed spaced apart arcuate rod engaging hooks depending from a first side thereof for engaging a first elongated spinal rod, and a transverse connector extending laterally from a second side thereof; a second clip body having a pair of opposed spaced apart arcuate rod engaging hooks depending from a first side thereof for engaging a second elongated spinal rod, and a transverse connector extending laterally from a second side thereof; and a fastener for securing the transverse connector of the first elongated clip body and the transverse connector of the second elongated clip body to one another.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of U.S. patent application Ser. No. 08/856,916, filed May 15, 1997, currently pending, the entire disclosure of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to implantable spinal fixation systems for the surgical treatment of spinal disorders. More particularly, this invention relates to a transverse rod connector clip for connecting cylindrical rods to each other. 
     For years doctors attempted to restore stability to the spine by fusion (arthrodesis) of the problem area. This treatment yielded marginal results due to the inherently flexible spinal column. Over the past ten years spinal implant systems have been developed to add stability to the spine to enhance the arthrodesis rates. Such systems often include spinal instrumentation having connective structures such as a pair of plates and/or rods which are placed on opposite sides of the portion of the spinal column which is intended to be fused. These spinal systems consist of screws and hooks for segmental attachment to the spine and longitudinal rods connected to screws or hooks. These components provide the necessary stability both in tension and compression yet yield minimal torsional control. 
     It has been found that when a pair of spinal rods are fastened in parallel on either side of the spinous process, the assembly can be significantly strengthened by using at least one additional rod to horizontally bridge the pair of spinal rods. A cross brace assembly is disclosed in U.S. Pat. No, 5,084,049. Devices such as these commonly consist of a threaded rod for providing the desired lateral support. The threaded rod is fastened to each of the spinal rods by clamps located on each end of the threaded rod. However, this configuration is bulky and can cause irritation of the patient&#39;s back muscles and other tissue which might rub against the device. A cross brace assembly that fits closer to the spine, preferably in the same general plane as the vertical spinal rods, would reduce the complications associated with bulkier devices. 
     Most existing transverse connectors consist of rods, plates, and bars linked to the longitudinal rods by coupling mechanisms with set screws, nuts, or a combination of each. These connectors require several components and instruments to build the constructs. Each additional component or instrument required to assemble the connectors adds to the “fiddle factor” of the surgical technique. Examples of these transverse connectors include Tranverse Link Device (DLT) and Crosslink manufactured by Sofamor Danek, Trans-Connector manufactured by Synthes, and Modular Cross Connector and Transverse Rod Connector (TRC) manufactured by AcroMed. 
     Telescopic rod to rod couplers for use in a spinal implant systems have also been described. Prior to the locking member being engaged, the telescoping sections may be easily slid past their extremes and out of engagement with one another. While this is a convenient method of connecting and disconnecting the coupler sections, it can be inconvenient during surgery if the sections accidentally disengage. U.S. Pat. No. 5,275,600 describes a telescopic rod to rod coupler in which the telescopic rod sections are assembled together using a 180 degree twisting motion. This is designed to minimize the risk of the rod sections accidentally disconnecting during the implant procedure. 
     Presently available spinal fixation systems frequently require careful alignment of the hardware used to connect the components of the spinal instrumentation with each other. A need has thus arisen for improved rod connectors to transversely connect spinal rods without requiring additional manipulation of the spinal instrumentation and to minimize the use of pedicle screws while at the same time reducing requirements to assemble small pieces of hardware during the surgical procedure. 
     SUMMARY OF THE INVENTION 
     According to one or more aspects of the present invention, a spinal fixation system includes: a first clip body having a pair of opposed spaced apart arcuate rod engaging hooks depending from a first side thereof for engaging a first elongated spinal rod, and a transverse connector extending laterally from a second side thereof; a second clip body having a pair of opposed spaced apart arcuate rod engaging hooks depending from a first side thereof for engaging a second elongated spinal rod, and a transverse connector extending laterally from a second side thereof; and a fastener for securing the transverse connector of the first elongated clip body and the transverse connector of the second elongated clip body to one another. 
     According to one or more further aspects of the present invention, a spinal fixation system includes: a first clip body having a first pair of opposed spaced apart arcuate engaging hooks depending from a first side thereof for engaging a first elongated spinal rod, and a second pair of opposed spaced apart arcuate engaging hooks depending from a second side thereof for engaging an elongated transverse connector; and a second clip body having a first pair of opposed spaced apart arcuate engaging hooks depending from a first side thereof for engaging a second elongated spinal rod, and a second pair of opposed spaced apart arcuate engaging hooks depending from a second side thereof for engaging the elongated transverse connector. 
     According to one or more further aspects of the present invention, a spinal fixation system includes: an elongated spinal rod; a transverse member; and a connector having a pair of opposed spaced apart arcuate rod engaging hooks for receiving and engaging the elongated spinal rod, the connector securing the elongated spinal rod and the transverse member in a transverse orientation in which the elongated spinal rod are substantially coplanar. 
     The transverse connector clips of the present invention can be used to transversely connect spinal rods without requiring additional manipulation of the spinal instrumentation. Because the clips of the present invention do not require any additional locking mechanism, they reduce the assembly of small pieces of hardware during the surgical procedure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top perspective view of one embodiment of a transverse connector clip of the present invention; 
     FIG. 2 is a perspective view of one embodiment of the transverse connector clip of the present invention with a short, laterally extending bar; 
     FIG. 3 is a top perspective view of another embodiment of a transverse connector clip of the present invention with a laterally extending bar having a plurality of vertical teeth; 
     FIG. 4 is a bottom perspective view of the invention clip of FIG. 3; 
     FIG. 5 is a perspective view of a pair of the connecting transverse connector clips of FIG. 3; 
     FIG. 6 is a perspective view of the clip of FIG. 2 securing the transverse connector clips of FIG. 5; 
     FIG. 7 is a schematic view of the present invention connected to spinal rods implanted in a human spine and illustrating the method of assembly; 
     FIG. 8 is a top perspective view an another embodiment of the present invention; 
     FIG. 9 is a bottom perspective view of the invention of FIG. 8; 
     FIG. 10 is perspective view of the invention of FIG. 8 illustrating the connecting mechanism of the connector clip; 
     FIG. 11 is a perspective view of the invention of FIG. 8 connected to the ends of an T-bar; 
     FIG. 12 is a perspective view of an another embodiment of the present invention illustrating the method of assembly of two connector clips having laterally extending tapered bars connected together with a tapered sleeve; 
     FIG. 13 is a perspective view of the invention of FIG. 12 illustrating a range of lateral adjustment between the two clips; 
     FIG. 14 is a schematic view of the invention of FIG. 13 connected to spinal rods implanted in a human spine and illustrating the method of assembly; 
     FIG. 15 is a perspective view of another embodiment of the present invention illustrating the method of assembly; and 
     FIG. 16 is a perspective view of the assembled invention of FIG.  15 . 
    
    
     DETAILED DESCRIPTION OF INVENTION 
     The present invention is directed to a transverse connector clip  10  and assemblies used in spinal fixation systems. Spinal fixation systems typically include spinal instrumentation having connective structures such as a pair of plates and/or rods which are placed on opposite sides of the spinal column near vertebrae that are intended to be fused. These spinal systems consist of screws and hooks for segmental attachment to the spine and longitudinal rods connected to screws or hooks. These components provide the necessary stability both in tension and compression yet yield minimal torsional control. In addition, it has been found that when a pair of spinal rods are fastened in parallel on either side of the spinous process, the assembly can be significantly strengthened by using at least one additional rod to horizontally bridge the pair of spinal rods. 
     The transverse connector clips  10  of the present invention consist of a component with a means to clip the device on a spinal or cylindrical rod  11  and a component with a means to link two rod connectors together laterally. Transverse connector clip  10  concept consists of a clip body  12  with a first side  14  and a second side  16  (FIG.  1 ). On first side  14  are two, mirror image hemi-cylindrical shells  18  and  20 . These two, mirror image hemi-cylindrical shells  18  and  20  have an inner surface  24  that defines a rod bore  26  through which the cylindrical rod  11  can extend. Rod bore  26  has an inner diameter  22  that is designed to be slightly smaller than the outer diameter of the cylindrical rod  11  it will receive. Top surface  28  of the hemi-cylindrical shells  18  and  20  defines an outer diameter  30 . 
     It should be noted that the two, mirror image hemi-cylindrical shells  18  and  20  can be connected to the first side  14  of clip body  12  as shown in clip  10 A of FIG. 2 or in mirror image relationship as shown in clip  10 A of FIG.  6 . 
     Clip body  12  is placed on the cylindrical rod  11  at 90 degrees and turned so that the hemi-cylindrical shells  18  and  20  spread around the rod  11 . The deflection of the hemi-cylindrical shells  18  and  20  and the inner diameter of the shells  22  allow the clip  10  to securely clamp on the rod  11 . 
     The second side of the clip body  12  can include, but is not limited to, a short hemi-cylinder rod (Clip  10 A, FIG.  2 ), a laterally extending hemi-cylinder rod with a plurality of vertical teeth (Clip  10 B, FIGS.  3 - 4 ), a second pair of mirror image hemi-cylindrical shells (Clip  10 C, FIGS.  8 - 9 ), a laterally extending rod tapering from a proximal cylindrical shape to a distal hemi-cylinder shape (Clip  10 D, FIG.  12 ), or an outwardly extending U-shaped receptacle designed to receive a semi-cylindrical or cylindrical rod and a locking cap device (Clip  10 E, FIGS.  15 - 16 ). Each of these embodiments will be described below. 
     One embodiment of the transverse connector clip  10 A is shown in FIG.  2 . Here, the clip body  12  consists of a first side  14  as previously described (FIG. 1) and a second side  16  that comprises a preferably short laterally extending hemi-cylinder rod  40 , however, any shaped rod could be utilized. The short hemi-cylinder rod  40  integral to the second side  16  of clip body  12  is shaped to facilitate installation of clip  10 A by a user. A user can use the short rod  40  to manually engage and disengage the clip body  12  from a cylindrical rod  11  of two rods joined together in a spinal fixation system. Clip  1  GA can be used to connect transverse connector clips having laterally extending hemi-cylinder rods  10 B (FIG.  6 ). One advantage of the inventive connector clip  10 A over prior art connectors is that clip  10 A is a single piece connector, thereby reducing the amount of assembly of the spinal fixation system required by prior art connectors during surgery. 
     Another embodiment of the present invention is the transverse connector clip  10 B (FIG.  3 ). Here, the clip body  12  consists of a first side  14  as previously described (FIG. 1) and a second side  16  that includes a laterally extending hemi-cylinder rod  50  having a first side  52 , a second side  54 , and a longitudinal axis LA1—LA1. However, other shapes can be utilized for the laterally extending hemi-cylinder rod  50 . The first side  52  contains a plurality of vertically placed teeth  56  extending along the longitudinal axis LA1—LA1. FIG. 4 shows a perspective view of the second side  54  of connector clip  10 B. 
     Clip  10 B is designed to be interlocked to a second clip  1  GB (FIG.  5 ). The first sides  52  of the hemi-cylinder rods  50  are connected to each other via the plurality of vertical teeth  56  extending along the longitudinal axes LA1—LA1 of the hemi-cylinder rods  50 . The clips  10 B can transversely connect two longitudinal rods  11  placed at varying distances from each other with the plurality of teeth  56  accommodating the variable distance. This variable distance is indicated by the lateral motion arrows LM1—LM1 (FIG.  5 ). This ability of the clips  10 B provides a significant advantage during surgery where many such adjustments are necessary to fine tune the alignment of the assembly in the patient. 
     The connection between clips  10 B can be maintained by using transverse connector clip  10 A (FIG.  6 ). When the first sides  52  of the hemi-cylinder rods  50  are engaged by the interlocking of the plurality of vertical teeth  56 , the second sides  54  form a cylindrical rod having a diameter that is slightly larger than the inner diameter  22  defined by the inner surface  24  of the hemi-cylindrical shells  18  and  20  of clip  10 A. Thus, the hemi-cylindrical shells  18  and  20  of clip  10 A can snap onto the connected hemi-cylinder rods  50  of clips  10 B as if the connected hemi-cylinder rods  50  were a single cylindrical rod  11 . 
     While FIG. 6 illustrates a transverse connector clip  10 A of the present invention connecting the laterally extended hemi-cylinder rods  50  of clips  10 B, it should be understood that any connecting device known to one skilled in the art can be used to connect the hemi-cylinder rods  50 . The advantage of using the transverse connector clip  10 A of the present invention, however, is that it consists of a single piece which facilitates surgery by reducing the number of pieces that need to be assembled. 
     The spinal rod assembly using transverse connector clips  10 A and  10 B of the present invention connects to longitudinal rods  11  that are connected to a human vertebrae  91  as schematically shown in FIG.  7 . Two cylindrical rods  11  are each connected to a transverse connector clip  10 B through the mirror image hemi-cylindrical shells  18  and  20 . The laterally extending hemi-cylinder rods  50  of clips  10 B are connected to each other by the interlocking of the plurality of vertical teeth  56 . This connection is maintained by clip  10 A. 
     Clip  10 C (FIGS. 8-9) is an alternate embodiment of the transverse clip connector  10  having a clip body  12  with a first side  14  and a second side  16 . The first side  14  is as previously described (FIG.  1 ). The second side  16  of the clip body  12  comprises a second set of mirror image hemi-cylindrical shells  60  and  62 . Like the hemi-cylindrical shells  18  and  20  on the first side  14  of clip body  12 , hemi-cylindrical shells  60  and  62  can be placed on the second side  16  of the clip body  12  as shown (FIG. 8) or in mirror image relationship (not shown). 
     The second set of hemi-cylindrical shells  60  and  62  have an outer surface  64  and an inner surface  68 . The inner surface  68  defines a rod bore  70  through which a cylindrical rod  88  can extend. Rod bore  70  has a diameter  72  that is slightly smaller than the diameter of the rod  88  it is designed to receive. 
     Clip  10 C is designed to simultaneously connect two longitudinal rods  11  and a transverse rod  88  together. The cylindrical rods  11  connect to the first side  14  of the clip body  12  as previously described. Cylindrical rod  88  connects to the second side  16  of clip body  12  in a similar fashion. Namely, clip body  12  is placed on a cylindrical rod  88  at 90 degrees and turned so that the hemi-cylindrical shells  60  and  62  spread around the rod  88 . The deflection of the hemi-cylindrical shells  60  and  62  and the inner diameter  72  allow the clip body  12  of clip  10 C to securely clamp on the rod  88 . 
     One advantage of having the second side  16  of the inventive clip body  12  comprising a second pair of hemi-cylindrical shells  60  and  62  is that it allows attachment of this second pair of shells  60  and  62  to various other rod types used in spinal surgery such as T-bar  80  (FIG. 10) and an I-bar (not shown). A T-bar  80  and an I-bar can horizontally bridge a pair of cylindrical rods  11  (FIG. 11) significantly strengthening the spinal fixation system. 
     T-bars  80  have a longitudinal body  82 , a first end  84  and a second end  86 . The first end  84  of T-bar body  82  has a cylindrical-shaped bar  88  perpendicularly connected to the T-bar body  82  (FIG.  10 ). This bar  88  can be connected to the second pair of hemi-cylindrical shells  60  and  62  of invention clip  10 C as described above. 
     Two inventive clips  10 C can be used to connect two cylindrical rods  11  via two T-bars  80  (FIG.  11 ). In this example, two clips  10 C are each connected to bars  88  on the first ends  84  of two separate T-bar bodies  82 . The second ends  86  of each T-bar body  82  is then connected to each other via a tapered locking sleeve  90  or by any means known to those of skill in the art. The relative placement of one cylindrical rod  11  to the other can be adjusted by adjusting the T-bar connection as indicated by circular motion arrows CM1—CM1 and CM2—CM2. In this way, the inventive clips  10 C can facilitate the creation of the desired transverse bridge between two cylindrical rods  11  using a minimum number of pieces. 
     While the embodiment shown here (FIG. 11) shows invention clips  10 C connected to two different T-bars  80 , it should be understood that two clips  10 C can also be connected to the opposite ends of a single I-bar (not shown). An I-bar has a longitudinal body and a first and second end. The first end has a first rod-shaped bar positioned perpendicular to the I-bar body. The second end has a second cylindrical-shaped bar positioned perpendicular to the I-bar body. The first pair of hemi-cylindrical shells  18  and  20  of clip  10 C is connected to a first cylindrical rod  11  while the second pair of hemi-cylindrical shells  60  and  62  is connected to the first bar on the first end of the I-bar body. A second invention clip  10 C is connected to a second cylindrical rod  11  through hemi-cylindrical shells  18  and  20  and then to the second bar on the second end of the I-bar body via hemi-cylindrical shells  60  and  62 . In this way, the I-bar provides a horizontal bridge between two cylindrical rods by connection via the invention clips  10 C. 
     In another embodiment of the inventive clip  10 , the first side of the clip body  12  is as previously described, while the second side of the clip body  12  comprises a laterally extending rod  100  having a first side  102 , a second side  104 , a longitudinal axis LA1—LA1, and a proximal  106  and distal  108  end (Clip  10 D, FIG.  12 ). The proximal end  106  is cylindrical in shape and tapers to a hemi-cylindrical shape at the distal end  108 . 
     Clip  10 D is designed to connect to another clip  10 D (FIGS. 12-14) via the laterally extending tapering rods  100 . The laterally extending tapered rods  100  are connected to each other by mating the first sides  102  together. This connection can be maintained with any of the devices known to those of skill in the art including, but not limited to, a tapered locking sleeve  90 . This tapered locking sleeve  90  consists of an inner  92  and outer  94  sleeve portion. Inner sleeve portion  92  has an inner surface  96  and outer surface  98 ; and outer sleeve portion  94  has an inner surface  110  and outer surface  112 . The outer surface  98  of the inner portion  92  has a diameter  114  slightly smaller than a diameter  116  of the inner surface  110  of the outer sleeve  94  so as to allow the inner sleeve portion  92  to be placed concentrically inside the outer sleeve  94  in order to lock the inner sleeve portion  92  and outer sleeve portion  94  together. 
     To assemble clips  10 D, the outer sleeve portion  94  is positioned on a laterally extending hemi-cylinder bar  100  of a first connector clip  10 D and the inner sleeve portion  92  is positioned on a laterally extending hemi-cylinder bar  100  of a second connector clip  10 D (FIGS.  12 - 14 ). The first sides  102  of the laterally extending hemi-cylinder bars  100  of the first and second clips  10 D are mated and held in locking engagement by the tapered sleeve  90 . 
     The distance between the two connector clips  10 D can be laterally adjusted by moving the laterally extending tapered rods  100  as indicated by the arrows LM2—LM2 in FIG.  13 . When the first sides  14  of each clip body  12  of clips  10 D are connected to two different cylindrical rods  11  via the hemi-cylindrical shells  18  and  20  on the first side  14  of the clip body  12  (FIG.  14 ), lateral adjustment of the tapered rods  100  laterally adjusts the relative position of the cylindrical rods  11  to which the connector clips  10 D are connected. This provides the user with some flexibility in adjusting the alignment of the cylindrical rods  11  in a spinal fixation apparatus during surgery. 
     A spinal rod assembly using connector clips  10 D and a tapered locking sleeve  90  connects to longitudinal rods  11  that are connected to a human vertebrae  91  as schematically shown in FIG.  14 . Two cylindrical rods  11  are each connected to a clip  10 D through the mirror image hemi-cylindrical shells  18  and  20 . The laterally extending tapered bars  100  of clips  10 D are held together with a tapered locking sleeve  90 . The assembly of the tapered locking sleeve  90  is also shown. 
     Several means of clamping the various types of laterally extending rods from the second side  16  of the invention clip body  12  have been described above including another transverse clip of the present inventive clip  10 A (FIG. 6) and a tapered sleeve  90  (FIGS.  12 - 14 ). However, it should be understood that laterally extending hemi-cylinder rods can be connected by any other connecting means known to one skilled in the art. 
     In yet another embodiment of the inventive transverse connector clip  10 , the first side  14  of the clip body  12  is as previously described, while the second side  16  of the clip body  12  comprises an outwardly extending rod holding portion  120  and a locking mechanism  130 . The rod holding portion has a longitudinal axis positioned perpendicular to the longitudinal axis LA1—LA1 of the first side  14  of the clip body  12 . The locking mechanism  130  is configured to engage with the rod holding portion  120  in order to locking the longitudinal rod into the rod holding portion  120 . The rod holding portion can be in the shape of a solid holding portion having a through bore for receiving a hemi-cylindrical or cylindrical rod and the locking mechanism can be of any locking mechanism known to one skilled in the art, such as tapered locking caps, set screws or locking nuts. In one embodiment, the holding portion is a U-shaped holding portion  120  having a longitudinal axis LA3—LA3 positioned perpendicular to the longitudinal axis LA1—LA1 of the first side  14  of connector clip  10 E (FIGS.  14 - 15 ). The U-shaped holding portion  120  has an upper portion  122  and a lower portion  124 . The lower portion  124  is configured to receive a flat side  126  of a hemi-cylindrical rod  128 . Alternatively (not shown), the lower portion  124  of the U-shaped portion  120  can be configured to receive a cylindrical rod  11 . A locking mechanism for the U-shaped portion  120  can include a locking cap  130  with an upper  132  and lower side  134  configured to slide into and mate with the upper portion  122  of U-shaped portion  120 . Upper side  132  of locking cap  130  has a tapered portion  136  that engages and mates with a tapered portion  138  in the upper portion  122  of the U-shaped portion  120 . The lower side  134  of the locking cap  130  is configured to accommodate an arcuate side  140  of the hemi-cylindrical rod  128 . 
     The advantage of the inventive clip  10 E, when used in combination with the locking cap  10 G, the hemi-cylinder support bar  128 , and cylindrical rod  11  (FIGS. 15-16) is that connecting clip  10 E is a single piece that connects two rods together, thus reducing the requirement of the prior art connectors to assemble small pieces of hardware during the surgical procedure. 
     It should be understood that in keeping with spinal surgery techniques, a plurality of cylindrical rods  11  can be used, each with a plurality of attachment devices affixed thereto, with the present attachment devices transversely connecting either two rods  11  together or connecting portions of rods together in other alignments. 
     The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the details of the illustrated apparatus and construction and method of operation may be made without departing from the spirit of the invention.