Abstract:
A plate and screw assembly for fixation of at least a first vertebrate to a second vertebrate in a spinal column is disclosed. The plate and screw assembly includes a plate member that extends over a portion of at least the first vertebrate. At least a first screw hole extends through the plate and is sized to receive a first screw. The first screw extends through the first screw hole to engage the cylindrical side section of the first vertebrate to secure the first vertebrate to the plate member. At least a second screw hole extends through the plate member and is sized to receive a second screw. The second screw extends through the second screw hole to engage one of the flat base sections of the second vertebrate.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to spinal fixation plates. More specifically, the invention relates to a plate and screw assembly for the fixation of vertebrae. 
       BACKGROUND OF THE INVENTION 
       [0002]    The human vertebral column, also called the spinal column, consists of thirty three irregular shaped bones known as the vertebral column.  FIG. 1  depicts a vertebral column  100 . The vertebral column has an anterior side  104  and a posterior side  108 . 
         [0003]    A top view of a vertebra  200  is depicted in  FIG. 2 . The vertebra  200  has a main body region  204  and a spinous process region  208 . An opening  212  between the main body region  204  and the spinous process region  208  allows a spinal cord to pass. 
         [0004]      FIG. 3A  shows the main body regions  304  and  308  separated by an intervertebral disk  312 . The intervertebral disk  312  resides in the intervertebral space  314 . The main body region  304  (or  308 ) is drum-shaped having a cylindrical side section  306  and flat base sections  316  and  320 . 
         [0005]      FIG. 3B  shows a perspective view of the main body region  304  with the cylindrical side section  306  and flat base sections  316  and  320 . The intervertebral disk  312  is attached to the flat base sections of the main body regions. The intervertebral disk  312  cushions and softens the forces created by walking or jumping that might otherwise fracture the vertebrae. 
         [0006]    Referring back to  FIG. 2 , the vertebra  200  moves relative to its adjacent vertebra, providing a range of flexibility to the vertebral column. The movement between the adjacent vertebrae is limited to prevent pressure on the spinal cord or bending of the spinal cord. Excessive pressure or bending of the vertebral column  100  may result in a disorder such as a ruptured or herniated disk or a bone spur. A ruptured or herniated disk may cause tissue to protrude from the disk to compress the spinal cord causing pain. Also, bone spur or osteophyte may impinge the spinal cord causing pain. Surgery is often required to correct problems with osteophytes and herniations of the intervertebral disks. Typically, during surgery one or more vertebrae are exposed and the intervertebral disk is removed, thus removing the protruding tissue or providing access for the removal of the bone osteophytes. The removal of the intervertebral disk causes the adjacent vertebrae to be disconnected. A spinal implant is inserted into the intervertebral space and a spinal fusion or fixation is performed to connect the adjacent vertebrae. The spinal fixation may be performed by a vertebral plate that connects two or more vertebrae. 
         [0007]      FIG. 4  illustrates a section of a vertebral column  400  including vertebrae  404 ,  408 ,  412 ,  416 ,  420 , and  424 . Consider for example, that an intervertebral disk (not shown in  FIG. 4 ) between the vertebrae  416  and  420  becomes herniated. Consequently, the herniated intervertebral disk is removed by surgery and an implant is inserted into the intervertebral space  432 . Since the intervertebral disk connects the vertebra  420  to the vertebra  416 , the removal of the intervertebral disk causes the vertebrae  420  to be disconnected or detached from the vertebra  416 . Consequently, a vertebral fixation becomes necessary to re-attach the vertebra  420  to the vertebra  416  and to the vertebrae  404 ,  408  and  412 . 
         [0008]    A vertebral plate  440  is used attach the vertebra  420  to the vertebra  416  (and also to the vertebrae  412 ,  408 ). As shown in  FIG. 4 , the vertebral plate  440  extends at least partially over the cylindrical side sections  456  of the vertebrae  408 - 420 . The vertebral plate  440  includes 4 pairs of screw holes, each screw hole being aligned to enable a screw to engage the cylindrical side section  456  of a single vertebra. The screws extend generally perpendicularly through the vertebral plate  440  to engage the cylindrical side section  456  of the vertebra. 
         [0009]      FIG. 5  is a cross-sectional view of the vertebral column  400  including the vertebrae  404 ,  408 ,  412 ,  416 ,  420 , and  424 . As discussed before, the intervertebral disk (not shown in  FIG. 5 ) between the vertebrae  416  and  420  is removed and an implant  430  is inserted into the intervertebral space  432 . Consequently, the vertebra  420  became disconnected from the vertebra  416 , requiring fixation. The vertebral plate  440  is used to connect the vertebra  420  to the vertebrae  416  (and also to the vertebrae  412 ,  408 ). 
         [0010]    As shown in  FIG. 5 , the vertebral plate  440  is used to fixate the vertebra  420  to the vertebrae  416  (and also to the vertebrae  412 ,  408 ). The vertebral plate  440  receives a plurality of screws  444   x  each extending through the vertebral plate  440  to engage a vertebra. The screws are generally perpendicular to the vertebral plate  440  to enable the screws to extend through the cylindrical side of the vertebrae. 
         [0011]    If subsequent to the fixation of the vertebra  420  to the vertebrae  416 , an intervertebral disk  450  between the vertebra  420  and  424  is herniated or ruptured, removal of the intervertebral disk  450  may be necessary. If the intervertebral disk  450  is removed and an implant is inserted into the intervertebral space  452 , the vertebra  424  will become disconnected from the vertebrae  420 . Thus, a fixation will be necessary to connect the vertebra  424  to the vertebra  420 . However, since the vertebral plate  440 , which was implanted during a previous surgery, extends over at least a part of the cylindrical side section  456  of the vertebra  420 , there is insufficient space remaining along the cylindrical side section  456  of the vertebra  420  to accommodate a new vertebral plate necessary to connect the vertebra  424  to the vertebra  420 . As can be seen in  FIG. 5 , the edge of the vertebral plate  440  extends over at least part of the cylindrical side section  456  of the vertebra  420 , leaving insufficient space remaining for another vertebral plate to extend over the cylindrical side section  456  of the vertebra  420  in order to fixate the vertebra  424  to the vertebra  420 . Furthermore, even if space is available to accommodate a new vertebral plate to extend over the cylindrical side section  456  of the vertebra  420 , an additional pair of screws into the cylindrical side sections  456  of the vertebra  420  may shatter or otherwise damage the vertebra  420 . As will be appreciated, the cylindrical side section  456  of the vertebra  420  may be unable to sustain the impact from an additional pair of screws. 
       SUMMARY 
       [0012]    A plate and screw assembly for fixation of at least a first vertebrate to a second vertebrate in a spinal column is disclosed. The first and second vertebrae are adjacent to one another. Each vertebrae has a cylindrical side section and an upper and a lower flat base section. The plate and screw assembly includes a plate member that extends over a portion of at least the first vertebrate. At least a first screw hole extends through the plate and is sized to receive a first screw. The first screw extends through the first screw hole to engage the cylindrical side section of the first vertebrate to secure the first vertebrate to the plate member. At least a second screw hole extends through the plate member and is sized to receive a second screw. The second screw extends through the second screw hole to engage one of the flat base sections of the second vertebrate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    For a more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description of the invention along with the accompanying figures and in which: 
           [0014]      FIG. 1  depicts a vertebral column. 
           [0015]      FIG. 2  depicts a top view of a vertebra. 
           [0016]      FIG. 3A  shows main body regions of a vertebra separated by an intervertebral disk. 
           [0017]      FIG. 3B  shows a perspective view of a main body region with the flat base sections. 
           [0018]      FIG. 4  illustrates a section of a vertebral column. 
           [0019]      FIG. 5  is a cross-sectional view of a vertebral column. 
           [0020]      FIG. 6  illustrates a plate and screw assembly in accordance with one embodiment of the invention. 
           [0021]      FIG. 7  illustrates a cross-sectional view of a plate and screw assembly in accordance with another embodiment of the invention. 
           [0022]      FIG. 8  shows another view of the plate and screw assembly in accordance with one embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0023]      FIG. 6  illustrates a plate and screw assembly  600  in accordance with one embodiment. The plate and screw assembly  600  enables fixation of a first vertebra to a second vertebra when the second vertebra has inadequate space on its cylindrical side section to accommodate a conventional plate. As shown in  FIG. 6 , a conventional plate and screw assembly  604  is used to fixate a vertebra  616  to a vertebra  612 . Since the conventional plate and screw assembly  604  extends over at least part of the cylindrical side section  618  of the vertebra  616 , there is insufficient space remaining on the cylindrical side section  618  to accommodate a second conventional plate and screw assembly. However, the intervertebral disk (not shown in  FIG. 6 ) in the intervertebral space  640  became ruptured or herniated, thus requiring removal of the intervertebral disk. As will be appreciated, the intervertebral disk in the intervertebral space  640  connects the vertebra  620  to the vertebra  616 . Thus, the removal of the intervertebral disk from the intervertebral space  640  causes the vertebra  620  to be detached or disconnected from the vertebra  616 . 
         [0024]    An implant is inserted into the intervertebral space  640 , and the plate and screw assembly  600  is used to attach or fixate the vertebra  620  to the vertebra  616 . The plate and screw assembly  600  has a unique construction enabling the plate and screw assembly  600  to attach the vertebra  620  to the vertebra  616  without significantly extending over the cylindrical side section  618  of the vertebra  616 . The plate and screw assembly  600  includes a first pair of screw holes configured to receive a first pair of screws  644  and a second pair of screw holes configured to receive a second pair of screws  648 . The first pair of screws  644  extends generally perpendicularly through the plate and screw assembly  600  and engages the cylindrical side section  622  of the vertebra  620 . As will be appreciated, the cylindrical side section refers to the side section of the main body region of the vertebra as discussed before. The second pair of screws  648  extends through the plate and screw assembly  600  at an angle to engage the flat base section  652  of the vertebra  620 . As shown in  FIG. 6 , the angle at which the second pair of the screws  648  extend through the plate and screw assembly is a non-perpendicular angle in relation to the plate and screw assembly. In one example embodiment, the angle is 40 degrees, but other suitable values can be used. Thus, by extending at a non-perpendicular angle through the plate and screw assembly  600 , the second pair of screws  648  can engage the flat base section  652  of the vertebra  620 , thereby avoiding the cylindrical side section  618  of the vertebra  616 . The angular orientation of the second pair of screws  648  enables the screws  648  to avoid the cylindrical side section  618  of the vertebra  616 , thereby preventing damage to the vertebra  616 . Since the cylindrical side section  618  of the vertebra  616  is already inserted with a pair of screws from the conventional plate and screw assembly  604 , insertion of another pair of screws into the cylindrical side section of the vertebra  616  may cause the vertebra  616  to be shattered or otherwise damage. Accordingly, the plate and screw assembly  600  enables the second pair of screws  648  to engage the flat base section of the vertebra  616 , thus attaching the vertebra  620  to the vertebra  616  without causing damage to the vertebra  616 . 
         [0025]    Furthermore, it is believed that since the second pair of screws  648  engages the flat base section  652  of the vertebra  616 , the fixation of the vertebra  620  to the vertebra  616  is comparatively stronger than conventional fixation means as the flat base section  652  is structurally stronger than the cylindrical side section. 
         [0026]    It will be appreciated that the plate and screw assembly  600  enables the fixation of the vertebra  620  to the vertebra  616  that would otherwise be difficult with the conventional plate and screw assembly. The plate and screw assembly  600  attaches the vertebra  620  to the vertebra  616  without engaging the cylindrical side section  618  of the vertebra  616 . Especially in those circumstances where a conventional plate and screw fixates a first vertebra to a second vertebra, if a third vertebra is required to be fixated to the second vertebra but there is inadequate space to accommodate another conventional plate and screw assembly, the plate and screw assembly  600  enables the third vertebra to be fixated to the second vertebra. 
         [0027]      FIG. 7  illustrates a cross-sectional view of a plate and screw assembly  700  in accordance with another embodiment. The plate and screw assembly  700  enables the fixation of the vertebra  708  to the vertebra  704 . As shown in  FIG. 7 , a conventional plate and screw assembly  750  has fixated the vertebra  704  to other vertebrae (not shown in  FIG. 7 ). Since the conventional plate and screw assembly  750  extends over the cylindrical side section  702  of the vertebra  704 , there is inadequate space remaining on the cylindrical side section  702  of the vertebra  704 . Consequently, a second conventional plate and screw assembly is unsuitable to fixate the vertebra  708  to the vertebra  704 . 
         [0028]    However, the plate and screw assembly  700  due to its unique construction enables the vertebra  708  to be attached or fixated to the vertebra  704  in spite of the space limitation. The plate and screw assembly  700  includes a plate member  712  extending over at least a portion of the vertebrate  708 . The plate and screw assembly  700  includes a cantilever member  716  attached to the plate member  712 . The cantilever member  716  extends between the vertebrae  704  and  708  into the intervertebral space  720  to a selected length. By extending into the intervertebral space  720 , the cantilever member  716  provides structural support to the vertebrae  704  and  708 . A first pair of screws  724   x  extends perpendicularly through the plate member  712  and engages the cylindrical side section  710  of the vertebra  708 . The first pair of screws  724   x  secures the vertebra  708  to the plate and screw assembly  700 . The plate and screw assembly  700  includes a second pair of screws  728   x  extending through the plate member  712  and at least through a portion of the cantilever member  716 . As will be appreciated, there are appropriate screw holes drilled into the plate member  712  and into the cantilever member  716  to receive the screws. The second pair of screws  728   x  engages the flat base section  705  of the second vertebrate  704 . 
         [0029]    The second pair of screws  728   x  is not perpendicular to the plate member  712 , which enables the second pair of screws  728   x  to engage the flat base section of the vertebrate  704  without engaging the cylindrical side section  702  of the vertebrate  704 . In one embodiment, the plate member  712  may extend over at least a portion of the cylindrical side section  702  of vertebrate  704  as shown in  FIG. 7 . It will be appreciated that in  FIG. 7 , a first pair of screw holes are drilled through the plate member  712  to enable the first pair of screws to extend perpendicularly through the plate member  712  to engage the cylindrical side section of the plate member  712 . A second pair of screw holes are drilled through the plate member  712  and partially through the cantilever member  716  to enable the second pair of screws to extend through at an angle to engage the flat base section of the vertebra  708 . 
         [0030]      FIG. 8  shows another view of the plate and screw assembly  600 . The plate and screw assembly  600  enables fixation of the vertebra  620  to the vertebra  616 . A conventional plate and screw assembly  604  is used to fixate the vertebra  616  to a vertebra  612 . Since the conventional plate and screw assembly  604  extends over at least part of the cylindrical side section  618  of the vertebra  616 , there is insufficient space remaining on the cylindrical side section  618  to accommodate a second conventional plate and screw assembly. However, as discussed before, due to the unique construction of the plate and screw assembly  600 , the vertebra  620  is attached to the vertebra  616 . 
         [0031]    While the compositions, structures, apparatus and methods of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the compositions, structures, apparatus and/or methods and in the steps or in the sequence of steps of the method described herein without departing from the concept, spirit and scope of the invention. All such substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined by the appended claims.