Abstract:
The present invention relates to a screw for fixing vertebra comprising a cage as a prosthesis which can be extended to be protruded beyond an external diameter of a screw, and improving the drawback from detaching from the spine following surgical procedures.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to PCT Patent Application No. PCT/KR2010/000218, filed on Jan. 14, 2010, and Korean Patent Application No. 10-2009-0081516, entitled SCREW FOR FIXING VERTEBRA, in the name of MinSeok Kim, the entire disclosures of which are hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a screw for fixing vertebra, and more specifically to a screw for fixing vertebra which can prevent the screw from separating from a pedicle after surgery by providing a prosthesis that can be expanded in protrusion more than the outer diameter of the screw. 
       BACKGROUND OF THE INVENTION 
       [0003]    In general, spinal diseases include prolapsed intervertebral disk (spinal disk) and spinal scoliosis, and a patient with part of the spine damaged cannot engage in activities necessary for daily life in such a condition. Even if the extent of damage is not so serious, if the damaged part of the spine is pressed or touched by another adjacent part it may cause pain. 
         [0004]    Therefore, a patient with part of the spine broken or damaged cannot lead a stable daily life unless the damaged part is corrected by carrying out a surgery for supporting it by using an artificial aid in the damaged part. 
         [0005]    Of such spinal diseases, spinal scoliosis is a disease in which vertebrae are bent and twisted. If the spinal scoliosis is left alone, deformation of the spine progresses to eventually bring about serious deformity, followed by complications such as deformation of internal organs. 
         [0006]    Such spinal scoliosis can be cured completely by wearing a brace or surgery according to the bent angle of vertebrae. 
         [0007]    In the methods of operating on spinal scoliosis, there is a method known as a pedicle screw inserting technique for correcting by inserting screws into bent vertebrae. The pedicle screw inserting technique is a method for helping the spine recover to a normal condition by inserting pedicle screws into bent vertebrae and connecting the pedicle screws with each other using a rod. 
         [0008]    The patient leads a life with the pedicle screws transplanted semi-permanently. But the pedicle screws inserted in the human body may be deformed by body activity over time or the screws may separate from the pedicle as the fastening is loosened. A patient with osteoporosis has a higher possibility of the pedicle screw separating from the pedicle due to a low bone density. 
       SUMMARY OF THE INVENTION 
       [0009]    Accordingly, to solve the above problems, it is an object of the present invention to provide a screw for fixing vertebrae which can prevent screws from separating from the pedicle after surgery by providing a prosthesis that can be expanded in protrusion more than the outer diameter of the screw. 
         [0010]    Another object of the present invention is to provide a screw for fixing vertebrae that can be stably utilized also in vertebrae with a low bone density. 
         [0011]    In order to accomplish the foregoing objects, according to an embodiment of the present invention, there is provided a screw for fixing vertebrae including: a screw head with a screw head inserting hole formed therein; a screw body, which is formed monolithically with the screw head, having a screw body inserting hole formed longitudinally therein in communication with the screw head inserting hole, and a screw body screw part formed on the outer circumference thereof; a moving member which is inserted in the screw body inserting hole slidably lengthwise and has a protrusion means protruded through one or more through holes formed on the outer circumference of the screw body, and a moving member screw part formed inside of the screw body; an actuating bolt having an actuating bolt screw part screw-joined with the moving member screw part to be rotatably mounted in the screw head inserting hole; and a stripper bolt which is inserted into the screw head inserting hole to fix a connecting rod arranged on the actuating bolt. 
         [0012]    Preferably, the protrusion means is at least one protrusion leg which is extended from the moving member and has elasticity that makes it possible to pass through the through holes. 
         [0013]    Preferably, the protrusion means is at least one protrusion pin, one end of which is pivotly connected to a connecting bar extended from the bottom end of the moving member by a joint and the other end of which is passed through the through hole. 
         [0014]    Preferably, the protrusion means is protruded outwardly more than the screw body screw part. 
         [0015]    Preferably, the actuating bolt head of the actuating bolt is formed concavely so as to contact the outer circumference of the connecting rod. 
         [0016]    According to the present invention, it is possible to provide a screw for fixing vertebrae that can maintain the fixed state after surgery more securely than the conventional screw for fixing vertebrae. In particular, the screw for fixing vertebrae of the present invention can also be stably used for patients with osteoporosis related spinal disease. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The above objects, features and advantages of the present invention will become more apparent to those skilled in the related art in conjunction with the accompanying drawings. In the drawings: 
           [0018]      FIG. 1  is a sectional view of a screw for fixing vertebrae according to a first embodiment of the present invention; 
           [0019]      FIG. 2  is a plane view showing a state that the screws for fixing vertebrae of the  FIG. 1  are mutually connected by a connecting rod; and 
           [0020]      FIG. 3  is a sectional view of a screw for fixing vertebrae according to a second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. When inserting reference numerals into the constituents in the respective drawings, although the constituents are illustrated in different drawings, so far as the constituents are the same, they are described to have the same reference numeral, where possible. The detailed description for the well-known function and constitution, judged to make the gist of the invention obscure, will be omitted. 
         [0022]    The screw  100  for fixing vertebrae of the present invention includes a screw head  102  and a screw body  126  that make up the contour. Such a screw  100  for fixing vertebrae may be made of a metal material such as titanium or a polymer material such as PEEK. 
         [0023]    Inside the screw body  126  is formed a screw body inserting hole  128 , and inside the screw head  102  is formed a screw head inserting hole  101 . The screw body inserting hole  128  and the screw head inserting hole  101  are communicated with each other. 
         [0024]    On the outer circumference of the screw body  126  is formed a screw body screw part  130 , which comes into direct contact with the patient&#39;s vertebrae. And a screw front end  136 , which is a front end of the screw body  126 , is processed into a cone shape so as to be easily inserted into the vertebrae. 
         [0025]    And through holes  132  and  134  are formed between screw body screw parts  130  on the outer circumference of the screw body  126 . Protrusion legs  122  and  124 , which will be described later, are protruded outside from the inside of the screw body  126 . 
         [0026]    A moving member  118  is inserted in the screw body inserting hole  128 , which is an internal space of the screw body  126 . The moving member  118  is slidably moved while it is in contact with the inside of the screw body inserting hole  128 . The moving member  118  is roughly of a tube shape and has a moving member screw part  120  formed inside. At one end of the moving member  118  are formed protrusion legs  122  and  124  that can be protruded out through the through holes  132  and  134 . 
         [0027]    Accordingly, since the protrusion legs  122  and  124  should be protruded from the through holes  132  and  134  accordingly as the moving member  118  is moved up and down, it is preferable that the whole of the moving member  118 , and at least the protrusion legs  122  and  124 , are made of material having elasticity like rubber. 
         [0028]    An actuating bolt  114  is fastened to the inside of the moving member  118 , and the actuating bolt has an actuating bolt male screw  116  screw-joined with the moving member screw part  120 . 
         [0029]    In addition, an actuating bolt head  115  of the actuating bolt  114  is rotatably seated on the stepped portion formed in the screw head inserting hole  101  of the screw head  102 , as shown in  FIG. 1 . 
         [0030]    Accordingly, if the actuating bolt  114  is rotated, it rotates in its position only, and the rotation of the moving member  118  is prohibited by the protrusion legs  122  and  124 , so the moving member  118  moves up and down. 
         [0031]    And on the actuating bolt  114  is arranged a connecting rod  110  that connects two or more screws  100  for fixing vertebrae as shown in  FIG. 2 . 
         [0032]    The connecting rod  110  is fixed by a stripper bolt  106 . The stripper bolt has a stripper bolt male screw  108  to which is screw-joined a screw head female screw  104  formed on the inner circumference of the screw head inserting hole  101 , that is, the upper inside of the screw head inserting hole  101 . 
         [0033]    At this time, the top surface of the actuating bolt head  115  is formed in a concave shape having a radius of curvature the same as the outer circumference of the connecting rod for a secure contact with the connecting rod  110 . It is desirable because the area of contact with the connecting rod  110  can be increased as the top surface of the actuating bolt head has a shape corresponding to the inner circumference of the connecting rod  110 . 
         [0034]    The screw  100  for fixing vertebrae according to the first embodiment of the present invention is constructed basically as mentioned above. Below will be described the method of installing the screw  100  for fixing vertebrae. 
         [0035]    First, the initial state of the screw  100  for fixing vertebrae is a state in which the protrusion legs  122  and  124  are hung in the through holes  132  and  134  of the moving member  118  but are not protruded more than the screw body screw part  130 . In this case, it is preferable that the moving member  118  is screw-joined with the actuating bolt  114  so as to maintain the initial state. 
         [0036]    Next, the screw  100  for fixing vertebrae is inserted and fixed in the necessary position of the spine and the actuating bolt  114  is rotated to move the moving member  118  downward. Accordingly, the protrusion legs  122  and  124  are protruded outwardly more than the screw body screw part  130 . 
         [0037]    Then, connect the installed screws  100  for fixing vertebrae with each other to the connecting rod  100  and tightly connect the connecting rod  110  by use of the stripper bolt  106 . 
         [0038]    And apply and solidify cement to fix each of the vertebrae and the screws  100  for fixing vertebrae fixed to the vertebrae. 
         [0039]    Next, a screw  200  for fixing vertebrae according to a second embodiment of the present invention will be described with reference to  FIG. 3 . Description will be omitted in the second embodiment for the components identical to the first embodiment. 
         [0040]    The screw  200  for fixing vertebrae of the second embodiment is different in that it has protrusion pins  222  and  224  instead of the protrusion legs  122  and  124  of the screw  100  for fixing vertebrae of the first embodiment. 
         [0041]    The protrusion pins  222  and  224  are pivotly connected to a connecting bar  221  extended from the bottom end of the moving member  218  by joints  223  and  225 . 
         [0042]    The end portions of the protrusion pins  222  and  224  are inserted in the through holes  232  and  234  in the initial state, so they are not protruded out more than the screw body screw part  230 . 
         [0043]    When the moving member  218  is moved up and down by the rotation of the actuating bolt  214 , the protrusion pins  222  and  224  may be protruded out more than the screw body screw part  230 . 
         [0044]    At this time, it is preferable that the protrusion pins  222  and  224  are made of a metal material such as titanium. 
         [0045]    Although the present invention has been described in connection with the exemplary embodiments illustrated in the drawings, it is only illustrative. It will be understood by those skilled in the art that various modifications and equivalents can be made to the present invention. Therefore, the true technical scope of the present invention should be defined by the appended claims. 
         [0046]    The drawings refer to the following items: 
         [0047]      100 ,  200 : Screw for fixing vertebrae 
         [0048]      101 ,  201 : Screw head inserting hole 
         [0049]      102 ,  202 : Screw head,  104 ,  204 : Screw head female screw 
         [0050]      106 ,  206 : Stripper bolt,  108 ,  208 : Stripper bolt male screw 
         [0051]      110 ,  210 : Connecting rod,  112 ,  212 : Connecting rod seat 
         [0052]      114 ,  214 : Actuating bolt,  115 ,  215 : Actuating bolt head 
         [0053]      116 ,  216 : Actuating bolt male screw 
         [0054]      118 ,  218 : Moving member,  120 ,  220 : Moving member screw part 
         [0055]      122 ,  124 : Protrusion leg,  126 ,  226 : Screw body 
         [0056]      128 ,  218 : Screw body inserting hole 
         [0057]      130 ,  230 : Screw body screw part 
         [0058]      132 ,  134 ,  232 ,  234 : Through hole 
         [0059]      136 ,  236 : Screw front end,  221 : Connecting bar 
         [0060]      222 ,  224 : Protrusion pin,  223 ,  225 : Joint