Abstract:
A spinal fixation system connector for maintaining a predetermined positions of a spinal linkage members fastened to vertebrae of a patient. The connector includes a body having first and second openings extending along first and second axes, respectively. The connector includes a first fastener for fastening the first member in the first opening and a second fastener for fastening the second member in the second opening. Prior to the first fastener fastening the first spinal linkage member in the first opening and the second fastener fastening the second spinal linkage member in the second opening, the body is manipulatable to adjust an angle between the first axis and the second axis. When the first fastener fastens the first member in the first opening and the second fastener fastens the second member in the second opening, the angle between the first axis and the second axis is fixed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from U.S. Provisional Patent Application No. 60/795,718 filed Apr. 29, 2006, which is hereby incorporated by reference. 
    
    
     BACKGROUND 
     The present invention relates to a spinal fixation system connector for maintaining predetermined positions of vertebrae in the spinal column of a patient. More particularly, the present invention relates to a component of a spinal fixation system for connecting a first spinal linkage member (e.g., a rod) to a second spinal linkage member. The component allows angles between the connected spinal linkage members to vary. 
     Spinal fixation systems are commonly used to align, adjust and/or stabilize portions of a spinal column of a patient. These systems frequently include vertebral anchors such as pins, bolts, screws, hooks and/or cables that attach to vertebrae in the spinal column. The spinal linkage members can be connected to the anchors to maintain the relative positions of the corresponding vertebrae. Thus, the members maintain the spacing and alignment of the connected vertebrae. To provide desired alignment across several levels of the spine, more than one spinal linkage member may be used and connected by one or more fixation system connectors. 
     Frequently, the connector is used to connect portions of two linkage members positioned side-by-side. The connector spans between linkage members to maintain the positions of the members relative to each other. Frequently, the portions of the spinal linkage members connected by the connector are not parallel. Instead, the members are non-parallel so they are oriented at various angles and in various positions due to the anatomical structure of the spine and alignment desired by the surgeon. 
     Many conventional connectors are designed to accommodate linkage members aligned at a particular angle. Variations in angular alignment from the particular angle accepted by the linkage may make it difficult to optimally align members using the conventional connectors. When there is a difference between the desired alignment and the fixed alignment of conventional connectors, the linkage members must be deformed. Deforming members may weaken portions of the spinal fixation system or cause the vertebrae to fail. 
     BRIEF SUMMARY 
     The present invention relates to a spinal fixation system connector for maintaining a predetermined position of a first spinal linkage member fastened to vertebrae of a patient to a second spinal linkage member fastened to vertebrae of the patient. The connector comprises a body having a first opening extending through the body along a first axis. The first opening is sized and shaped for receiving the first spinal linkage member. The connector also includes a second opening extending through the body along a second axis. The second opening is sized and shaped for receiving the second spinal linkage member. Further, the connector includes a first fastener mounted on the body for fastening the first spinal linkage member in the first opening of the body and a second fastener mounted on the body for fastening the second spinal linkage member in the second opening of the body. Prior to the first fastener fastening the first spinal linkage member in the first opening of the body and the second fastener fastening the second spinal linkage member in the second opening of the body, the body is manipulatable to adjust an angle between the first axis and the second axis. When the first fastener fastens the first spinal linkage member in the first opening of the body and the second fastener fastens the second spinal linkage member in the second opening of the body, the angle between the first axis and the second axis is fixed. 
     In another aspect, the invention includes a surgical system for maintaining a predetermined position of vertebrae of a patient. The system comprises a first elongate spinal linkage member, a first anchor for attaching the first member to a first vertebra, a second elongate spinal linkage member, a second anchor for attaching the second member to a second vertebra, and a connector. The connector includes a body having a first opening extending through the body along a first axis. The first opening is sized and shaped for receiving the first spinal linkage member. In addition, the connector includes a second opening extending through the body along a second axis. The second opening is sized and shaped for receiving the second spinal linkage member. The system also comprises a first fastener mounted on the body for fastening the first spinal linkage member in the first opening of the body and a second fastener mounted on the body for fastening the second spinal linkage member in the second opening of the body. Prior to the first fastener fastening the first spinal linkage member in the first opening of the body and the second fastener fastening the second spinal linkage member in the second opening of the body, the body is manipulatable to adjust an angle between the first axis and the second axis. When the first fastener fastens the first spinal linkage member in the first opening of the body and the second fastener fastens the second spinal linkage member in the second opening of the body, the angle between the first axis and the second axis is fixed. 
     The invention also includes a method of connecting a first spinal linkage member fastened to vertebrae of a patient to a second spinal linkage member fastened to vertebrae of the patient and maintaining a predetermined position of the first spinal linkage member to the second spinal linkage member. The method comprises inserting a portion of the first spinal linkage member into a first opening in the connector and inserting a portion of the second spinal linkage member into a second opening in the connector. The connector is manipulated so the first spinal linkage member and the second spinal linkage member are aligned in a predetermined orientation with respect to one another. The method also includes fastening the connector to the first spinal linkage member and fastening the connector to the second spinal linkage member. 
     Other aspects of the present invention will be in part apparent and in part pointed out hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective of a connector of one embodiment of the present invention having a closed passage including a variable angle mechanism for receiving a linkage member and an open lateral groove to receive a linkage member. 
         FIG. 2  is a top plan of the connector shown in  FIG. 1  connecting two linkage members. 
         FIG. 3  is a perspective of the connector connecting two linkage members. 
         FIG. 4  is a side elevation of the connector shown in  FIG. 1 . 
         FIG. 5  is a rear elevation of the connector connected two linkage members. 
         FIG. 6  is a top plan of a connector of a second embodiment of the present invention having a closed passage including a variable angle mechanism for receiving a linkage member and an open lateral groove to receive a linkage member. 
         FIG. 7  is a rear elevation of the connector of the second embodiment connecting two linkage members. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. Directional terms such as top and side are used for convenience and correspond only to one orientation of the connector. 
     DETAILED DESCRIPTION 
     Referring now to the drawings and in particular  FIG. 1 , a first embodiment of a connector of the present invention is designated in its entirety by the reference number  10 . The connector  10  includes a closed passage or opening  12  for receiving a first spinal linkage member (designated  20  in  FIG. 2 ) and an open lateral groove or slot or opening  14  for receiving a second spinal linkage member (designated  22  in  FIG. 2 ). The connector  10  may be used adjacent all areas of the spine. 
       FIG. 2  illustrates a top plan of the connector  10 . The connector  10  includes a closed passage  12  having a variable angle mechanism, generally designated by  24 , for receiving a spinal linkage member (e.g., member  20 ) and an open lateral groove  14  for receiving another linkage member (e.g., member  22 ) according to one embodiment of the invention. The connector  10  has a body  30  having an opening  32  sized and shaped for receiving the variable angle mechanism  24 . The mechanism  24  includes a housing  34  that is pivotally mounted in the opening  32  on axles formed by pins  36  rotatably mounted in recesses  38  in the body  30 . The housing  34  has the closed passage  12  through which the spinal linkage member  20  is passed. A threaded hole  40  extends through the housing  34  intersecting the passage  12  generally perpendicular to the passage. A fastener such as a setscrew  42  is inserted into the threaded hole  40  for securing the connector  10  to the spinal linkage member  20  received in the closed passage  12 . As shown in  FIG. 3 , the connector body  30  includes an opening  44  for accessing the fastener  42  to tighten the fastener once the connector  10  is in place. 
     As illustrated in  FIGS. 2 and 4 , at least one surface  50  of the housing  34  and a corresponding surface  52  of the connector body  30  are spherical. Further, the pins  36  are smaller (both shorter and narrower) than the recesses  38 , allowing the housing  34  to pivot in any direction within the body  30 . The housing  34  includes a slot  54  that extends from the surface  50  to the closed passage  12 . As the fastener  42  is tightened, the linkage member  20  presses against the slot  54  so the slots spreads open. As the slot  54  spreads, the corresponding spherical surfaces  50 ,  52  of the housing  34  and body  30  frictionally engage to prevent the housing from moving in the body. Thus, as the fastener  42  is tightened, the spinal linkage member  20  is locked in place in the closed passage  12  and the housing  34  is locked in place in the body  30 . 
     The open groove or slot  14  in the body  30  receives the second spinal linkage member  22 . A threaded hole  60  extends through the body  30  and intersects the passage  14  generally perpendicular to the passage. A fastener such as a setscrew  62  is inserted into the threaded hole  60  for securing the connector  10  to the spinal linkage member  22  received in the open groove  14 . In one embodiment, the groove  14  includes a hooked lip  64  which ensures the spinal linkage member  22  is retained in the groove when the fastener  62  is tightened to firmly lock of the member in place in to the body  30  of the connector  10 . Although the slot  14  faces laterally in the illustrated embodiment, those skilled in the art will appreciate that the slot may have alternative orientations without departing from the scope of the present invention. 
       FIG. 5  shows the connector  10  with both spinal linkage members  20 ,  22  seated in the body  30 . As will be apparent to those skilled in the art, the selectively pivotable nature of the variable angle mechanism  24  allows the spinal linkage members  20 ,  22  to be angled relative to each other. Further, once the connector  10  accepts the spinal linkage members  20 ,  22 , the fasteners  42 ,  62  are tightened to lock the connector in position on the members and the members in position relative to one another. 
       FIG. 6  illustrates another embodiment of a connector of the present invention, generally designated in its entirety by the reference number  70 . The connector  70  of the this embodiment includes a body constructed in two pieces  72 ,  74 . The first piece  72  includes a closed passage  82  for receiving a first spinal linkage member (designated  20  in  FIG. 7 ) and the second piece  74  includes an open lateral groove or slot  84  for receiving a second spinal linkage member (designated  22  in  FIG. 7 ). The slot  84  of connector  70  of the second embodiment is substantially identical to the slot  14  of the first embodiment. A threaded hole  90  similar to hole  60  of the first embodiment extends through the piece  74  and intersects the passage  84  generally perpendicular to the passage. A fastener such as a setscrew  92  is inserted into the threaded hole  90  for securing the connector  70  to the spinal linkage member  22  received in the open groove  84 . As the open lateral groove  84  is similar to the slot  14  in the connector  10  of the first embodiment, it will not be described in further detail. 
     As further illustrated in  FIG. 6 , the second piece  74  includes a post  100  extending generally perpendicular to both the threaded hole  90  and the slot  84 . The first piece  72  has an opening  102  having a shape that complements the post  100 . The post  100  is sized relative to the opening  102  to permit the first piece  72  and second piece  74  to move relative to each other. Although the post  100  and opening  102  may have other shapes without departing from the scope of the present invention, in one embodiment both the post and opening have generally conical shapes. It is envisioned that the post and opening may have generally spherical shapes in an alternate embodiment (not shown). In the illustrated embodiment, both the post  100  and the opening  102  include ridges and grooves to improve gripping between surfaces when they are engaged. In an alternate embodiment (not shown), it is envisioned that the surfaces may have other treatments (e.g., grit blasting or knurling) to improve gripping during engagement. 
     A threaded hole  120  extends through the first piece  72  and intersects the closed passage  82  generally perpendicular to the passage. A fastener such as a setscrew  122  is inserted into the threaded hole  120  for securing the first piece  72  to the spinal linkage member  20  received in the closed passage  82 . As the fastener  122  is tightened, the linkage member  20  presses against the post  100  and forces it to seat in the opening  102 . When the post  100  seats in the opening  102 , the corresponding conical surfaces of the post and opening frictionally engage to prevent the first and second pieces  72 ,  74  of the connector  70  from moving relative to each other. Thus, as the fastener  122  is tightened, the spinal linkage member  20  is locked in place in the closed passage  82  and the first and second pieces of the connector  70  are locked in place. 
       FIG. 7  shows the connector  70  with both spinal linkage members  20 ,  22  seated in the body  80  and the halves of the body immobilized relative to each other. As will be apparent to those skilled in the art, the post  100  and opening  102  of the first and second pieces  72 ,  74  form a variable angle mechanism  140  of a second embodiment that allows the spinal linkage members  20 ,  22  to be angled relative to each other. Further, once the connector  70  accepts the spinal linkage members  20 ,  22 , the fasteners  92 ,  122  are tightened to lock the connector in position on the members and the members in position relative to one another. 
     As will be appreciated by those skilled in the art, the spinal linkage members may extend at any suitable angle within a predetermined range of angles to accommodate a particular configuration of spinal instrumentation and spinal alignment. 
     The sizes of the closed passages and the open grooves that accommodate the spinal linkage members are selected so the linkage members can move laterally in the corresponding passage and groove. In one embodiment, the radii of the passages and grooves vary around their circumferences so that the radii at positions opposite the fasteners are approximately equal to or small than those of the linkage members to improve engagement between the connectors and members. One skilled in the art will recognize that the shape and size of the passages and grooves are not limited to the illustrated embodiments, and that any suitable size and/or shape, as well as relative location in the connector is envisioned. 
     According to an alternate embodiment, a locking mechanism for securing the position of the rods within the connector may comprise a plurality of setscrews. For example, the locking mechanism may comprise a first screw and a second screw disposed around the closed passage for the first linkage member for locking the connector components together and fixing the angular relation of the spinal linkage member relative to the body. 
     The present invention provides an improved connector for a spinal fixation system intended for connecting a first spinal linkage member to a second spinal linkage member. The connector provides an angled or non-parallel connection between the linkage members allowing for desired alignment or angular variation between portions of the spinal fixation system. The connector may include a first passage for receiving a portion of the first spinal linkage member, and a groove or slot for receiving a portion of the second spinal linkage member. Thus, the orientation of the first linkage member may vary relative to the second linkage member. The connector may comprise a variable connection mechanism functionally separating the passage of the first member and the groove of the second member. The variable connection mechanism may include a swivel type joint and surface treatments to reliably lock angular offset between portions of the connector and thus the angle between the linkage members. 
     The invention will be described relative to illustrative embodiments, though one skilled in the art will recognize that the invention is not limited to the described embodiments. While the connector may be primarily applied in spinal surgery, the connector may also be employed to couple any type of components of an implant system. The material composition of the connector and its components may be formed of any suitable bio-compatible material, including, but not limited to stainless steel, titanium, nitinol, metal alloys, plastic, polymers, carbon based materials, ceramics, and mixtures or combinations thereof. 
     When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
     As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.