Abstract:
A surgical connector useful to link spine rods together. The connector may be used adjacent a pair of mounting screws in one vertebra to limit movement between the screws or may be used to apply a lateral force to a portion of the spine to change curvature. A method of performing spinal surgery is also provide to reinforce a patient&#39;s spine.

Description:
FIELD OF INVENTION 
       [0001]    A device for use in spine surgery to extend between and connect rods used to reinforce portions of a spine. The device includes a cross connector used to connect rods secured to the spine on opposite sides of the spine. The device includes a flexible connector and a rigid connector that act together to limit bilateral movement between the rods. 
       BACKGROUND OF THE INVENTION 
       [0002]    Spinal surgery can be performed through large incisions or percutaneously, i.e., through small incisions using instruments specifically designed to allow the performance of surgery through small incisions. Such procedures are well known. Percutaneous procedures are often preferred because they are less invasive and leave less external scar tissue. However, some procedures are difficult to perform percutaneously because of the configuration of the devices to be installed. 
         [0003]    In the performance of spine surgery for such things as scoliosis, disc removal or replacement, spine fusion, bone grafts and spine deformity or weakness from cancer, metal (used to mean metal alloys and metal) rods are secured to the spine to help support the spine and/or straighten the spine. Rods may also be used to redistribute load on various vertebrae. Rods may be secured to the spine on opposite sides of the spine for extra support and rigidity. 
         [0004]    For scoliosis, surgery is used primarily for severe cases or for curves that do not respond to bracing. Surgery has two main goals—to stop a curve from progressing and to correct spinal deformity. 
         [0005]    There are various techniques used for scoliosis surgery. One type of surgery involves posterior spinal fusion with instrumentation and bone grafting. This surgery is performed through the patient&#39;s back while the patient lies on their stomach. During this type of surgery, the surgeon attaches a metal rod to each side of the patient&#39;s spine by using hooks or screws attached to the vertebral bodies. Then, the surgeon fuses the spine with a piece of bone from the patient&#39;s hip (a bone graft). The bone grows in between the vertebrae and holds them together and straight. This process is called spinal fusion. The metal rods attached to the spine ensure that the backbone remains straight while the spinal fusion takes place. 
         [0006]    The only lateral support for the rods is the vertebral bodies to which the rods are attached and the rods themselves. Additionally, the only support for the screws installed in the bones to support the rods is the bones themselves and perhaps to some extent, the rods and adjacent screws on the same rod. In the treatment spinal curvature as in the treatment of scoliosis, the spine needs to be brought to a less laterally curved condition which is difficult to do in percutaneous surgery since very little of the length of the rods is exposed. 
         [0007]    There is thus a need for an improved means to perform back surgery when rods are utilized. 
       SUMMARY 
       [0008]    The present invention involves the provision of a cross connector for use in spine surgery such as percutaneous spine surgery. The cross connector includes first and second hooks each having a throat partially defined by a shank with the throats opening generally toward one another. The throats are adapted to receive a respective rod secured to a spine therein. A flexible connector is secured to the first hook and extends to the second hook. The second hook includes means to facilitate securement of the second hook to the flexible connector and fix the maximum separation between the first and second hooks. A rigid connector is secured to and extends between the first and second hooks to fix the distance of their separation. 
         [0009]    The present invention also involves the provision of a method of conducting spinal surgery wherein rods are connected to opposite sides of the spine. The method includes providing access to the posterior of the spine on opposite sides thereof. First and second hooks are associated with first and second rods secured to a patient&#39;s spine in laterally spaced relationship. The first and second hooks are each associated with a respective said rod by tensioning a flexible connector associated with and extending between the hooks. A rigid connector is mounted to the first and second hooks to extend therebetween to fix the lateral spacing between the hooks. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a rear elevation view of a spine with attached rods and a plurality of cross connectors. 
           [0011]      FIG. 2  is an enlarged perspective view of a cross connector as shown in  FIG. 1 . 
           [0012]      FIG. 3  is a sectional view of the cross connector of  FIG. 2 . 
           [0013]      FIG. 4  is an elevation view of a tool usable in the installation of the cross connector. 
       
    
    
       [0014]    Like numbers used throughout this application represent like or similar parts and/or construction. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    While the present invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described presently preferred embodiments with the understanding that the present disclosure is to be considered an exemplification of the invention and is not intended to limit the invention to the specific embodiments illustrated. 
         [0016]    The reference numeral  1  designates generally a cross connector for attachment to a pair of laterally spaced apart rods  3 L,  3 R ( FIGS. 1 ,  3 ) secured to a spine  5  and positioned on opposite sides  7 L,  7 R of the spine. The rods  3  may be held in place via screw mounts  9  secured to a vertebra  10 . Such screw mounts  9  are well known in the art. The rods  3  extend longitudinally between various vertebrae  10  and may be attached to alternate vertebrae  10 A,  10 C on alternate sides  7 L,  7 R. Two forms of mounting of the connector  1  are shown, one form where the connector  1  is mounted between the rods  3 L,  3 R adjacent screws  9  attached to one vertebra  10  and one form where the connector  1  is mounted between the rods  3 L,  3 R with one rod at that location being mounted to one vertebra while the other rod is free of mounting to that vertebra to assist in straightening the spine  5 . That is, a rod  3  bridges one or more vertebrae without attachment thereto. 
         [0017]    The connector  1 , as best seen in  FIGS. 2 ,  3 , includes a pair of hooks  12 . Preferably, the hooks  12  have substantially the same configuration and include a shank  14 , a bight  16 , a leg  18  and a latch  20  defining a throat  22  therebetween and a mouth  24  defined by the latch  20  and the shank  14 . As configured for use, the throats  22  of the hooks  12  open generally toward one another. Preferably the hooks  12  are made of a metal and their component parts are integral. One hook  12  is shown as having an attached flexible connector  26  such as a multi strand metal cable on the order of ⅛ inch in diameter or smaller. As shown, the connector  26  is secured to a shank  14  and in use extends to the other hook  12  of a pair of hooks for securement thereto to effect mounting of the hooks each to a respective rod  3  by having a rod  3  positioned in a respective throat  22  after moving through a respective mouth  24 . The hooks  12  and the connector  26  form a connector hook assembly with flexible link when assembled. In a preferred embodiment, the hooks  12  have a generally rectangular transverse cross sectional shape particularly in the shank  14 . The edges and corners of a hook  12  (and other components of the connector  1 ) are preferably rounded. The latches  20  may also be provided with inclined surfaces  27  to facilitate mounting to a rod  3 . 
         [0018]    One of the shanks  14  of a pair of hooks  12  is configured to be associated with the flexible connector  26  to form an attached hook assembly. As shown, the shank  14  of one hook  12  is provided with a through passage  28  extending along a portion of the length of the shank  14 . The flexible connector  26  is inserted into the passage  28  and has a free end portion  29  extend beyond the shank  14  for gripping by a tool  30  adapted to induce tension in the flexible connector  26  to effect attachment of the hook assembly to the rods  3 . When the appropriate amount of tension is in the connector  26 , the connector  26  and the hooks  12  are secured together to make an assembly as with a fastener  31  as described below. This attachment fixes the maximum spacing between the hooks  12  during use. Other means of attaching the free end portion  29  of the connector  26  may be utilized. 
         [0019]    A rigid connector  34  is associated with the hook assembly and is operable to fix the hooks  12  against moving toward and away from one another and for tensile loading, it is redundant to the flexible connector  26 . The connector  34  can resist both tensile and compression axial loading while the connector  26  can resist axial tensile loading. The connector  34  can be loaded in tension to resist hook separation or divergence and in compression to resist convergence toward one another. As shown, the connector  34  has opposite end portions  35  for connection to the shanks  14  of hooks  12  and a central rigid load bearing portion  36  extending between the hooks  12 . Each of the end portions  35  includes a pair of longitudinally extending fingers  38  with a channel  39  therebetween. The shank  14  of a hook  12  is received in a respective channel  39  and is sandwiched between the fingers  38 . As shown, the finger  38  in the throat  22  is positioned between a rod  3  and a shank  14  to lock it against bending. The outer fingers  38  overlie a respective shank  14  and can be used to secure the connector  34  to the shanks  14 . As shown, a fastener  31 , such as a set screw or a hex head screw may be threadably engaged in holes  41  and received in recesses  42  in the shanks  14 . In the hook  12  with the passage  28  containing the connector  26 , the fastener  31  may be used to engage the connector  26  to secure it to the hook  12 . The connectors  34  can be provided in various lengths to accommodate different spacings between rods  3 . Shoulders  40  are provided in the channels  39  to abut the ends  43  of the hooks  12  to help resist movement of one hook  12  toward the other hook  12  when the connector  1  is assembled and installed. 
         [0020]    The connector  34  is also provided with means to allow the flexible connector  26  to extend between the hooks  12  preferably in a generally straight line. In the illustrated embodiment, an open sided groove  44  is positioned on the side of the central portion  36  and opens into each of the channels  39 . This allows for the mounting of the connector  34  to the assembly of hooks  12 . 
         [0021]    The mouth  24  has an opening size less than the cross sectional dimension of the throat  22  and preferably less that the diameter of a rod  3  plus the thickness of a finger  38  to be received therein so the hook  12  can lock onto a rod  3  after mounting on a rod. The latch  20  and leg  18  are preferably resiliently deformable to form a resiliently deformable lock. The channels  39  and the hook shanks  14  are configured to resist rotational movement of the shanks  14  on the connector  34 . 
         [0022]    The present invention is better understood by a description of the use of the cross connector  1 . A patient has rods  3  mounted to a spine  5  in laterally spaced relationship on opposite sides  7 L,  7 R of the spine. The rods  3  may have been previously installed or installed as part of the current procedure. Preferably, the procedure for installing the connector  1  is done percutaneously. Openings are formed on opposite sides of the spine  5  and a cannula or the like is inserted into each of the openings to provide access to surgical site. After rod installation, the rigid connector  34 , the flexible connector  26  with hook  12  and the unattached hook  12  may be moved into place through an opening on one side under the skin to bridge the spine for attachment to the rods  3 . As shown, the connector  1  may be mounted adjacent two rod mount screws  9  on one vertebra as at  48  or where there is a screw  9  for one rod in a vertebra and not the other rod so tension in the flexible connector  26  can either move a portion of the spine laterally or retain it in a less curved condition. An opening in the skin of the patient is made to provide access to the spine  5  and the rods  3  when installed. A hook  12  with the attached connector  26  is positioned in the surgery site and the connector  26  has its free end portion  29  exposed for access. The hook  12  is placed on a rod  3 . The rigid connector  34  is then moved into place with an installation tool  49  and the flexible connector  26  is positioned in the groove  44  and the shank  14  of the inserted hook  12  is positioned in its respective channel  39  at which time, the fastener  31  may be installed to couple the connectors  26 ,  34  together. The tool  49  has a handle  55  and a shank  56  connected thereto. An end portion  57  is configured to have a connector  34  removably mounted thereon as with a cable  63  and threaded fastener  61 . A foot  60  is removably mounted to the connector  34  and the cable  63  as with a fastener  61 . The foot  60  may be provided with a tapered lead-in section  65 . The free hook  12  has the connector  26  inserted through the passage  28  with the free end portion  29  being exposed for attachment to a tensioning tool  30 . Such a tool can function like a pop rivet tool or a cable tie tightener. The tool  30  tensions the connector  26  and pulls the hooks  12  together. The connector  34  has its fingers  38  guided over the shanks  14  with the shanks each moving into a respective channel  39  if not already there. Tensioning the connector  26  also urges the rods  3  to each move through a respective mouth deforming a respective latch  20  to move into a respective throat. The rods  3  may each already be positioned in a respective throat  22  and a finger  38  may move into the throat  22  to lock the rod  3  in a respective throat. When the appropriate tension is reached, the holes  41  are properly aligned each with a respective recess  42  and the shoulders  40  abut the ends  43  of the shanks  14 , the fasteners  31  may be installed and tightened to secure the connector  1  as an assembly and to retain tension in the connector  26  if desired. The free end portion  29  of connector  26  may cut off if desired. When installed, the connector  1  can maintain a spine&#39;s lateral curvature and can also be used to reinforce the screw mounts  9  in a vertebra by limiting relative movement between the screw mounts. 
         [0023]    It is to be understood that while a certain form of the invention is illustrated, it is not to be limited to the specific form or arrangement herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown and described in the specification and any drawings/figures included herein. 
         [0024]    One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objectives and obtain the ends and advantages mentioned, as well as those inherent therein. The embodiments, methods, procedures and techniques described herein are presently representative of the preferred embodiments, are intended to be exemplary and are not intended as limitations on the scope. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention and are defined by the scope of the appended claims. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in the art are intended to be within the scope of the following claims.