Patent Publication Number: US-2011077690-A1

Title: Rod holder and minimally invasive spine surgery system using the same

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a rod holder, and more particularly, to a rod holder which is configured to operate in a two-stage loading manner to allow a rod to be easily mounted. 
     In addition, the present invention relates to a minimally invasive spine surgery system, and more particularly to, a minimally invasive spine surgery system, which allows a rod to be more accurately and stably mounted to a pedicle screw inserted into a vertebra by using the rod holder, a rod guide and a rod guide holder during a spinal surgical operation using a minimally invasive method, thereby minimizing a damage of tissues or nerves in a surgical site. 
     2. Description of the Related Art 
     In general, the spine is commonly composed of 24 vertebras (except a sacral vertebra) which are connected with each other by means of joints, called disks, interposed between them so as to support the spine and give a buffering act. In this way, the spine helps a person to keep his/her posture and also plays important roles such as giving a basis for motions and protecting the internal organs. 
     However, if a person maintains an abnormal posture for a long time, suffers from degenerative diseases caused by aging or receives a shock from the outside, the disk between joints of the vertebras may be damaged to cause a spine disk disease. This spine disk disease compresses nerves connected to various portions of a human body through the joints of the vertebras, which gives a pain to the person. 
     Thus, for disk patients, a disk near a damaged portion is removed so that the damaged portion of a spine is not pressed or compressed, and an artificial aid (e.g., cage) made of hollow metal or plastic material is filled with bone fragments and then inserted into a region from which the disk is removed. After that, a pedicle screw is inserted into and fixed to vertebra at upper and lower locations of the damaged disk, and a rod is then connected to the pedicle screw to allow a distance between the vertebras to be secured, thereby ensuring a normal bone fusion. 
     In such a spine surgical operation, the skin around the damaged vertebra is cut to remove the damaged disk or left as it was, and the pedicle screw is then inserted into vertebras above and below the damaged disk and the fixed. After that, a rod is connected thereto, and a bolt is then fastened to couple the disk to the pedicle screw. 
     However, this surgical operation causes a large invasive region which delays the recovery of the patient and results in bad satisfaction for the surgery due to a large wound, though it may reduce an operation time and ensure easier operation. Thus, in recent, minimally invasive surgery manners being capable of minimizing an invasive region during a spine surgery operation have been developed and used. 
     In the minimally invasive surgical operation, when a pedicle screw is inserted into vertebras above and below a damaged disk, in a state where a patient&#39;s skin is not cut, a canula is put into the patient&#39;s skin without cutting the patient&#39;s skin, the pedicle screw is then inserted into the canula and fixed to the vertebras, and a rod is subsequently inserted through the canula and a bolt is then inserted into and fixed to a head portion. The rod used herein has a bar shape, so that it is extremely difficult to insert the rod through the canula. Thus, in order to facilitate easy insertion of the rod, the shape of the rod is modified or various kinds of operation tools have been developed for the insertion of the rod. 
       FIG. 1  is a schematic view showing a minimally invasive surgery operation tool disclosed in Korean Laid-open Patent Publication No. 2009-5316. 
     Referring to  FIG. 1 , a holding assembly  20  is connected to a pedicle screw  10  inserted into a vertebra to form a path through which a rod  40  can be inserted, and the rod  40  is then held at one end of the rod holder  30  and inserted through the path formed by the holding assembly  20 . 
     However, in this method, while a surgeon grips the rod holder  30  and inserts the rod  40  into a surgical site, since the surgeon must grip a handle of the rod holder  30  and inset the rod holder into a patient&#39;s body at the same time, there is an inconvenience that the surgeon should pay careful attention to all two operations (that is, gripping and insertion). Due to the above, in a case where the gripping is released by a surgeon&#39;s carelessness before the rod is mounted, there is a danger that a surgical site should be enlarged to find the rod, so that the minimally invasive spine surgical method can be regarded as meaningless one. 
     In such surgical method, in the meantime, while a surgeon grips the rod holder  30  and inserts the rod  40  into a surgical site, if the holding assembly  20  connected to the pedicle screw  10  is shaken or the posture of the surgeon is unstable, it is difficult to control accurately an insertion direction of the rod  40 , so that it is not easy to mount accurately the rod  40  to the pedicle screw  10 . Accordingly, while the rod  40  is inserted, the rod  40  may damage or injure surrounding tissues or nerves, which may give a great pain to the patient after the surgery operation. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the present invention is to provide a minimally invasive spine surgery system which may solve the aforementioned problems in the prior art. 
     Another object of the present invention is to provide a rod holder which is easily manipulated and can make a rod be easily inserted thereto and be easily mounted thereto. 
     A further object of the present invention is to provide a minimally invasive spine surgery system which may allow a rod to be mounted to a pedicle screw more accurately and stably to minimize any damage of nerves or tissues around an operation portion when the rod is inserted. 
     A rod holder according to the present invention for gripping a rod, which connects a pair of pedicle screws inserted into and fixed to a vertebra with each other, to mount the rod to the pair of pedicle screws comprises a grip serving as a handle; a loading unit mounted to an upper portion of the grip in such a manner that the loading unit passes through the grip in a front and rear direction; a button unit mounted to the upper portion of the grip in such a manner that the button unit passes through the grip in a right and left direction, thereby cooperating with the loading unit; and an insert unit partially inserted into a human body and comprising a rod gripping portion for gripping the rod and a connection member for transmitting a forward or backward movement of the loading unit to the rod gripping portion. The rod holder is configured to adjust a gripped state of the rod through three sequential stage including a first loading stage for moving backward and fixing the loading unit to fixedly grip the rod; a second loading stage for partially moving the loading unit forward and fixing the loading unit to the button unit, thereby rotatably gripping the rod; and a rod mounting stage for completely moving the loading unit forward by operating the button unit so that the rod is separated from the rod holder. 
     A minimally invasive spine surgery system according to the present invention is to insert and fix a pair of pedicle screws into and to a vertebra and installing a rod for connecting the pair of pedicle screws with each other. The system comprises a pair of rod guides connected to upper ends of the pair of pedicle screws to form a moving path of the rod; a rod holder for gripping the rod; and a rod guide holder for guiding an insert position of the rod. Here, the rod guide holder includes a first fixing unit connected to upper ends of the pair of rod guides to keep a distance between the pair of rod guides constant; a guide connected to a center of the first fixing unit and having an arc shaped slit formed thereon; and a second fixing unit connected to the guide and moved circularly along the slit in a state where the rod holder is inserted therein, thereby guiding an insert position of the rod. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view showing a conventional minimally invasive spine surgery system; 
         FIG. 2  is a schematic view showing a minimally invasive spine surgery system according to the present invention; 
         FIG. 3  is a perspective view of a pedicle screw; 
         FIG. 4  is a schematic view showing a rod; 
         FIG. 5  is a side sectional view showing an overall configuration of a rod holder according to the present invention; 
         FIG. 6  is an exploded view showing an insert unit of the rod holder of  FIG. 5 ; 
         FIG. 7  is a schematic view of a rod gripping portion of the insert unit of  FIG. 6 ; 
         FIG. 8  is an exploded view of a loading unit of the rod holder of  FIG. 5 ; 
         FIG. 9  is a schematic view showing a connection unit and a cover unit mounted to a grip; 
         FIG. 10  is a schematic view showing a two-stage loading adjusting member of the loading unit of  FIG. 8 ; 
         FIG. 11  is a schematic view showing a button unit and a grip to which the button unit is mounted, provided in the rod holder of  FIG. 5 ; 
         FIGS. 12   a  to  12   c  are schematic views showing the rod holder in a first loading stage; 
         FIGS. 13   a  to  13   c  are schematic views showing the rod holder in a second loading stage; 
         FIGS. 14   a  to  14   c  are schematic views showing the rod holder in a rod mounting stage; 
         FIG. 15  is a schematic side sectional view of a rod holder according to another embodiment and an exploded and enlarged view of a locking unit; 
         FIGS. 16   a  and  16   b  are a rear sectional view and a schematic perspective view of a rod holder according to another embodiment in a case where the locking unit is in a locked state and a rear sectional view and a schematic perspective view of the rod holder according to another embodiment in a case where the locking unit is in an unlocked state; 
         FIG. 17  is a schematic view showing a first embodiment of the rod guide; 
         FIG. 18  is a schematic view showing a second embodiment of the rod guide; 
         FIG. 19  is a sectional view of a rod guide of  FIG. 18 ; 
         FIG. 20  is a view showing an inner body of the rod guide of  FIG. 18 ; 
         FIG. 21  is a view showing an outer sleeve of the rod guide of  FIG. 18 ; 
         FIG. 22  is a view showing a rod pusher of  FIG. 2 ; 
         FIG. 23  is a schematic side view of a sleeve of a rod guide separator; 
         FIG. 24  is a partial enlarged view and schematic view of a circled portion A of  FIG. 23 ; 
         FIG. 25  is a schematic side view of an insert bar of the rod guide separator; 
         FIG. 26  is a schematic view showing an operation mechanism of the rod guide separator; 
         FIG. 27  is a perspective view of the rod guide holder of  FIG. 2 ; 
         FIGS. 28   a  and  28   b  are a side view and a plane view of the rod guide holder of  FIG. 27 ; 
         FIG. 29  is a view showing a state where the rod guide holder of  FIG. 27  is installed; 
         FIG. 30  is a view showing a gap adjuster of  FIG. 2 ; 
         FIG. 31  is a schematic perspective view of a gap adjuster according to another embodiment; 
         FIG. 32  is a schematic view showing an operation mechanism of the gap adjuster of  FIG. 31 ; and 
         FIG. 33  is a schematic view showing that the gap adjuster of  FIG. 31  adjusts a gap between pedicle screws. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereinafter, a preferred embodiment of the present invention will be explained in detail with reference to the accompanying drawings. For reference, when illustrating the present invention, any related known function or configuration may not be explained in detail herein if such function or configuration has a possibility to make the present invention unclear. 
     Prior to explaining the embodiments of the present invention, in the below description, a direction toward the spine to be surgically operated is defined as a ‘front’ direction, and a direction toward a surgeon is defined as a ‘rear’ direction based on a location of a rod holder. Similarly, a movement toward the spine is defined as a ‘forward’ movement, and a movement toward the surgeon is defined as a ‘backward’ movement. 
       FIG. 2  shows a schematic view illustrating an entire configuration and connection relations among all components of a minimally invasive spine surgery system according to the present invention. As described above, the minimally invasive spine surgery system  1000  is a kind of operation system in which a pair of pedicle screws  100  are inserted into and fixed to the vertebra and a rod  200  for connecting the pair of pedicle screws  100  with each other is installed. Referring to  FIG. 2 , the minimally invasive spine surgery system  1000  of the present invention comprises a pair of pedicle screws  100  inserted into and fixed to the pedicle, a rod  200  for connecting the pair of pedicle screws  100  with each other, a rod holder  300  for gripping the rod  200 , a pair of rod guides  500 ,  600  connected to upper ends of the pair of pedicle screws  100  to form a moving path of the rod  200 , and a rod guide holder  800  connected to upper ends of the pair of rod guides  500 ,  600  to define a path through which the rod holder  300  gripping the rod is inserted into a patent&#39;s body. 
     Also, the minimally invasive spine surgical system  1000  may comprise a rod pusher  700  selectively for mounting closely the rod  200  to a pedicle screw and a gap adjuster  900  connected to sides of the rod guides  500 ,  600  to adjust a gap between the pedicle screws. 
       FIG. 3  is a view showing a configuration of the pedicle screw  100 . As shown in  FIG. 3 , the pedicle screw  100  has a U shaped receiving groove  114  with a predetermined depth for receiving the rod  200 , and the pedicle screw  100  includes a head portion  110  having a female thread  112  formed along an inner circumference surface of the receiving groove  114  and a screw portion  120  connected to a lower portion of the head portion  110  to be inserted into the vertebra. Here, although the pedicle screw  100  in which the head portion  110  and the screw portion  120  extend and are integrated with each other is illustrated herein, the pedicle screw  100  in which the head portion  110  is pivotally connected to one end of the screw portion  120  may be utilized. Preferably, a symmetrical groove is formed in an outer circumference surface of the head portion  110  to enable the rod guides  500 ,  600  explained later to grip the head portion  110 . 
       FIG. 4  is a view showing the rod  200  constituting the minimally invasive spine surgery system  1000  according to the present invention. As shown in  FIG. 4 , the rod  200  has a curved-bar shape, and one end of the rod  200  has a streamlined shape to facilitate easier insertion into a surgical site and an insertion portion  201  having a rectangular section extends from the other end of the rod  200 . The insertion portion  201  is inserted into the rod holder  300 , and a through hole  203  or a pair of fixing grooves to be gripped by the rod holder  300  may be formed on the insertion portion  201 . As explained below, since the insertion portion  201  has a rectangular shape, if the insertion portion  201  is inserted into the rod holder  300  explained later, flat upper and lower surfaces of the insertion portion  201  are fixed and supported in the rod holder  300 , so that the rod  200  cannot be rotated upward or downward. 
       FIGS. 5 to 14  are schematic views showing a structure and an operation mechanism of the rod holder  300  of the minimally invasive spine surgery system  1000  according to the present invention. 
       FIG. 5  is a side sectional view showing an overall configuration of the rod holder  300  according to the present invention. The rod holder  300  is one of surgical tools of the minimally invasive spine surgery system  1000 , which grips the rod  200  connecting a pair of pedicle screws  100  inserted into and fixed to the vertebra to mount the rod  200  to the pair of pedicle screws  100 . Referring to  FIG. 5 , the rod holder  300  includes a grip  310  serving as a handle; a loading unit  350  passing through the grip  310  in a forward and backward direction and mounted to an upper portion of the grip  310 ; a button unit  370  passing through the grip  310  in a right and left direction and mounted to an upper portion of the grip  310  to allow the loading unit  350  to cooperate therewith; and an insert unit  330  located at a front of the loading unit  350  and inserted partially into a human body while gripping the rod  200 . The rod holder  300  is operated in three stages, namely a first stage in which a surgeon grips securely the rod  200  so as to easily insert the rod  200  into a patient&#39;s body, a second stage in which the surgeon mounts safely the rod  200  to the head portion of the pedicle screw  100 , and a mounting stage in which the grip of the rod  200  is released. This operating mechanism will be explained in more detail after each component of the rod holder  300  is described. 
     Referring to  FIG. 6 , the insert unit  330  includes a rod gripping portion  331  for gripping the rod  200 , a connection member  333  fixedly connected to a rear end  331   a  of the rod gripping portion  331  and a hollow insert body  335  surrounding the rod gripping portion  331  or the connection member  333 . 
     The connection member  333  is fixedly connected to the rear end  331   a  of the rod gripping portion  331  by means of welding or the like. Preferably, the connection member  333  may be formed integrally with the rod gripping portion  331 . The connection member  333  is configured to transmit a forward or backward movement of the loading unit  350 . In other words, the connection member  333  is configured to enable the rod gripping portion  331  to be moved by a distance corresponding substantially to a moving distance of the loading unit  350  when the loading unit  350  is moved forward or backward. For this purpose, in particular, it is preferable that the connection member  333  is made of wire, cable, bar shaped member or the similar mean, each of which having a rigidity for preventing the connection member from being buckling when the connection member  333  is moved forward. As explained below, the rear end of the connection member  333  is fixedly connected to an intermediate member  351  of the loading unit  350 . 
     As shown in  FIGS. 6 and 7 , the rod gripping portion  331  includes a rear end  331   a  fixedly connected to the front end of the connection member  333  by means of welding or the like and two arms  331   b  extending into two parts from the rear end  331   a  toward the front. Two arms  331   b  are divided into a Y shape to be elastically compressed inward, so that the gripping state of the rod  200  (or, a gripping state or a grip-releasing state) may be adjusted depending on whether two arms  331   b  are compressed inward. Protrusions  331   c  are formed on facing inner surface of the ends of the two arms  331   b,  and the protrusions  331   c  have a shape complementing to that of a pair of fixing grooves or through holes  203  of the rod  200 . Thus, when the two arms  331   b  are compressed inward, the rod  200  may be firmly gripped. 
     As shown in  FIG. 6 , the insert body  335  receives the rod gripping portion  331  or the connection member  333  (see  FIG. 5 ), and a front end portion of the insert body  335  is directly inserted into a patient&#39;s body. The insert body  335  is located at the front of the loading unit  350  and connected to the connection unit  311  (explained later) through a fitting manner or a fixedly-coupling manner such as welding. The insert body  335  includes a rear end  335   a  for receiving the intermediate member  351  of the loading unit  350  explained later, a connection member-guide unit  335   b  for defining a path of the connection member  333  and a rod gripping portion receiver  335   c  extending from the front end of the connection member-guide unit  335   b.    
     Preferably, the connection member guide unit  335   b  of the insert body  335  has a plurality of slot shaped openings. Due to the plurality of slot-like openings, it is possible to clean easily the insert body  335  after a surgical operation. 
     The rear end  335   a  may receive an elastic means such as a spring  337  to make the loading unit  350  be elastically moved forward. Also, the rear end  335   a  forms a path through which the loading unit  350  may be elastically moved forward or backward. 
     Preferably, the connection member guide unit  335   b  may make a predetermined angle with the rod gripping portion receiver  335   c  to place the rod  200  easily at the pedicle screw  100 . 
     The interior of the rod gripping portion receiver  335   c  is configured to press two arms  33   ab  of the rod gripping portion  331  when the rod gripping portion  331  is inserted into the rod gripping portion receiver  335   c  by the connection member  333 , to enable the two arms  331   b  of the rod gripping portion  331  to be shrunken inward. Preferably, the rod gripping portion receiver  335   c  may be configured to receive the rod gripping portion  331  entirely, 
       FIG. 8  is a schematic view showing a configuration of the loading unit  350 . As shown in  FIG. 8 , the loading unit  350  includes an intermediate member  351  fixedly connected to a rear end of the connection member  333 , a two-stage loading adjustment member  353  connected to a rear end of the intermediate member  351  and a loading handle  355  fixedly connected to a rear end of the two-stage loading adjustment member  353 . 
     Referring to  FIG. 8 , the intermediate member  351  is partially or entirely received in the rear end  335   a  of the insert body  335  and moved forward or backward in the rear end  335   a.  A protrusive rim  351   a  is formed on a front end of the intermediate member  351  (in this reason, as shown in  FIG. 8 , overall the intermediate member  351  has a T shape), and an elastic member (e.g., spring  337 ) to be inserted into the rear end  335   a  of the insert body  335  is provided at the protrusive rim  351   a,  so that the intermediate member  351  is elastically moved forward or backward in the rear end  335   a  of the insert body  335 . Preferably, a restoring force of the spring  337  is utilized for moving the intermediate member  351  or the entire loading unit  350  forwards. 
     As shown in  FIGS. 5 and 9 , it is preferable that a connection unit  311  defining a path of the intermediate member  351  and connected to the insert unit  330  is installed at a front of the upper side of the grip  310  through which the loading unit  350  passes. Also, a cover unit  313  having a stop formed thereon is connected to the rear end of the connection member  311 , the stop of the cover unit being configured such that a first catching step  353 d which will be described later can be fixed to the stop of the cover unit in a first loading stage. 
     As shown in  FIG. 10 , the two-stage loading adjustment member  353  includes a front end  353   a  fixedly connected to a rear end of the intermediate member  351 , a centre portion  353   b  allowing the loading unit  350  to be loaded into two stages and a rear end  353   c  to which the loading handle  355  is fixedly installed. 
     A first catching step  353   d  forming the first loading stage is formed at the upper portion of the center portion  353   b  of the two-stage loading adjustment member  353 , and a second catching step  353   e  arranged at the front of the first catching step  353   d  to form the second loading stage is formed at the lower portion of the two-stage loading adjustment member  353 . A location of the first catching step  353   d  may be changed with that of the second catching step  353   e.  However, the following explanation is based on the first catching step  353   d  and the second catching step  353   e  arranged as above. Now, the operating mechanism of the rod holder  300 , which will be explained in more detail later, will be explained. The first catching step  353   d  is fixed at the stop formed at the rear end of the cover unit  313  to set the first loading stage, and the catching step  353   e  is fixed to a second loading stage adjuster  373  of the button unit  370  (explained later) to set the second loading stage. In other words, the two-stage loading adjustment member  353  may adjust the entire loading process of the loading unit  350  through a stage in which the first catching step  353   d  and the second catching step  353   e  are fixed and a stage in which the two-stage loading adjustment member  353  is moved forward by a release of fixing of the first catching step  353   d  and the second catching step  353   e.    
     As shown in  FIG. 11 , the button unit  370  is mounted such that the button unit passes through the grip  310  in a right and left direction, and the button unit  370  is located below the loading unit  350  and cooperates with the loading unit  350 . The button unit  370  includes a housing  371  mounted in an upper portion of the grip  310 , a second loading stage adjuster  373  received in the housing  371  and a button  375  secured to an end of the second loading stage adjuster  373 . 
     One end of the housing  371  is closed, and the other end of the housing  371  is opened to allow the button  375  to be located in the housing. Also, an opening  371   a  is formed in a part of the upper portion of the housing  371  to enable the two-stage loading adjustment member  353  of the loading unit  350  to pass through the upper portion of the housing  371  and be moved forward or backward. In addition, a groove  371   b  having a shape complementing to the protrusion formed on the grip  310  is formed on a lower portion of the housing  371  in order to prevent the housing  371  from being separated due to the force occurring when the button  375  is pressed (that is, to fix the housing  371  to the grip  310 ). 
     The second loading stage adjuster  373  includes a hollow portion  373   a  receiving a spring  377  by which the second loading stage adjuster can elastically reciprocate, a center portion  373   b  extending from the hollow portion  373   a,  and a button fixing unit  373   c  extending from the center portion  373   b  and to which the button  375  is fixed. An anti-separation protrusion  373   d  extends toward a rim between the center portion  373   b  and the button fixing unit  373   c  so as to prevent the second loading stage adjuster  373  from being separated outward. 
     Preferably, a step portion  373   e  is formed at an upper portion of the center portion  373   b,  so that a fixing or a forward movement of the second catching step  353   e  formed on the lower portion of the two-stage loading adjustment member  353  of the loading unit  350  can be adjusted. In other words, when the second loading stage adjuster  373  is pushed to the right (based on  FIG. 11 ) due to the tensile restoring force of the spring  377 , the step portion  373   e  is stopped at the second catching step  353   e  of the second loading stage adjuster  373  to set a second loading stage, and when the button unit  370  is pressed, an engagement between the step portion  373   e  and the second catching step  353   e  is released so that the two-stage loading adjustment member  353  is moved forward to achieve a rod mounting stage in which the gripping of the rod  200  is released. Even at this time, although the tensile restoring force of the spring  377  is still exerted to push the second loading stage adjuster  373  to the right (based on  FIG. 11 ), the right side of the step portion  373   e  (based on  FIG. 11 ) is contacted and engaged with a side surface of the two-stage loading adjustment member  353 , so that it is prevented that the second loading stage adjuster  373  is restored to a location before the button  375  is pressed. In addition, a plurality of protrusions  373   f,  which are contacted and engaged with the protrusions formed on the inside of the housing  371  in correspondence with the grooves formed in the housing  371 , are formed on the lower portion of the second loading stage adjuster  373  to define a reciprocating range in the second loading stage. 
     Hereinafter, an operating mechanism of the rod holder  300  according to the present invention is described with reference to  FIGS. 12 to 14 . 
     Seeing the operating mechanism of the rod holder  300  in general, the rod holder  300  is operated to control a grip state of the rod  200  in a three-stage manner, including a first loading stage in which the loading unit  350  is moved backward to grip fixedly the rod  200 ; a second loading stage in which the loading unit  350  is partially moved  350  forward from the first loading stage and is then fixed to the button unit  370  to rotatably grip the rod  200 ; and a rod mounting stage in which the button unit  370  is operated from the second loading stage to completely move the loading unit  350  forward such that the rod  200  is separated from the rod holder  300 . 
     At this time, the rod  200  in a gripped state, the rod gripping portion  331  gripping the rod  200 , the connection member  333  fixedly connected to the rear end of the rod gripping portion  331 , the intermediate member  351  fixedly connected to the rear end of the connection member  333 , the two-stage loading adjustment member  353  fixedly connected to the rear end of the intermediate member  351 , and the loading handle  355  fixedly connected to the rear end  353   c  of the two-stage loading adjustment member  353  (hereinafter, an assembly consisting of these components are called as ‘a movable assembly’) are integrally moved forward or backward. Preferably, the fixed connection among the components of the movable assembly may be achieved by welding, hole or pin connection or similar means. 
     Here, the force causing the forward movement of the movable assembly is a compressive restoring force of an elastic member (e.g., sprig  337 ) received in the rear end portion  335   a  of the insert body  335  and having one end fixed to the protrusive rim  351   a  of the intermediate member  351  of the loading unit  350  and the other end fixed in the rear portion  335   a  of the insert body  335 , and the force causing the backward movement of the moving assembly is an external force exerted by a surgeon who pulls the loading handle  355  backward. 
       FIGS. 12   a  to  12   c  illustrate the first loading stage.  FIG. 12   a  is a side view of the rear portion of the rod holder  300  in the first loading stage,  FIG. 12   b  is a side sectional view of the rear portion of the rod holder  300  in the first loading stage, and  FIG. 12   c  is a side sectional view of the front portion of the rod holder  300  in the first loading stage. 
     As shown in  FIG. 12   a , in the first loading stage, a surgeon holds the grip  310  with one hand and holds the loading handle  355  with the other hand, and the surgeon pulls backward the loading handle  355  until the first catching step  353   d  of the loading unit  350  and the stop of the cover unit  313  are located on a straight line and then slightly lifts up the loading handle  355  to fix the two-stage loading adjustment member  353 . 
     Even while the surgeon pulls the loading handle backward for setting the first loading stage, the movable assembly tends to move forward due to a compressive restoring force of the elastic member  337  installed to the protrusive rim  351   a  of the intermediate member  351 . As shown in  FIG. 12   b , the loading handle  355  is slightly lifted up such that the first catching step  353   d  formed at the upper portion of the two-stage loading adjustment member  353  is engaged with the stop provided at the rear end of the cover unit  313  mounted to the upper end of the grip  310 . As a result, a forward movement of the movable assembly may be controlled. A circled portion A of  FIG. 12   b  illustrates the state that the first catching step  353   d  of the two-stage loading adjustment member  353  is engaged with the stop of the cover unit  313 . 
     When the movable assembly is moved backward until the first catching step  353   d  of the loading unit  350  and the stop of the cover unit  313  are located on a straight line, the rod gripping portion  331  is moved backward by a distance as much as a backward moving distance of the movable assembly due to the connection member  333 . At this time, the rod gripping portion  331  is completely inserted into the rod gripping portion receiver  335   c  of the insert body  335 , and in this inserting process, the end or inner shape of the rod gripping portion receiver  335   c  compresses two arms  331   b  of the rod gripping portion  331  to shrink the two arms  331   b  elastically inwards, so that the protrusions formed on the two arms  331   b  grip firmly the fixing groove or the through hole  203  of the rod  200 . In this state, as shown in  FIG. 12   c , the insertion portion  201  of the rod  200  on which the fixing groove or the through hole  203  are formed, which is gripped by the rod gripping portion  331 , is inserted into the rod gripping portion receiver  335   c,  and the end of the rod gripping portion receiver  335   c  becomes substantially identical to the rear end of the rod in shape and height, thereby supporting the rod  200  in both upper and lower directions and thus enabling the rod  200  not to be rotated. In other words, the insertion portion  201  has a rectangular sectional shape (see  FIG. 4 ), and so, in case where the insertion portion  201  is inserted into the rod holder  300  explained later, the flat upper and lower surfaces of the insertion portion  201  are fixed and supported by the upper and lower surfaces in the rod gripping portion receiver  335   c,  as a result, the rod  200  cannot be rotated upward or downward. A circled portion B of  FIG. 12   c  illustrates a state that the rear end of the rod  200  is inserted into the rod gripping portion receiver  335   c  and thus the rod  200  can not be rotated. 
     In the first loading stage, the movable assembly is integrally moved forward or backward, so that a distance from a position at which the loading process is initiated to a position at which the first catching step  353   d  of the loading unit  350  and the stop of the cover unit  313  are located together on a straight line is substantially identical to a distance from a position at which the loading process is begun to a position at which the rod gripping portion  331  connected to the connection member  333  is completely inserted into the rod gripping portion receiver  335   c  (see  FIG. 12   c ) by pulling backward the rod gripping portion. 
     In a state that the first loading stage is completed, the rod  200  is firmly gripped by the rod gripping portion  331  and can not be rotated, so that a surgeon may not worry about whether the rod  200  is fixed or rotated, so that the surgeon may insert the rod safely and easily into a patient&#39;s body while holding the grip  310  of the rod holder  300 . 
       FIGS. 13   a  to  13   c  illustrate the second loading stage.  FIG. 13   a  is a side view of a rear portion of the rod holder  300  in the second loading stage,  FIG. 13   b  is a plane view of the rear portion of the rod holder  300  in the second loading stage, and  FIG. 13   c  is a side sectional view of a front portion of the rod holder  300  in the second loading stage. 
     As shown in  FIG. 13   a , in the second loading stage, if a surgeon holds the grip  310  with one hand and slightly moves down the loading handle  355  fixed in the first loading stage with the other hand, the movable assembly is partially moved forward by the elastic member installed to the intermediate member  351 , and during the forward movement, the second catching step  353   e  formed at the two-stage loading adjustment member  353  is caught to the step portion  373   e  of the second loading stage adjuster  373 . 
     In other words, as shown in  FIG. 13   b , since the button  375  is not yet pressed in the second loading stage, the button  375  is located spaced apart from the grip  310  by a predetermined distance by means of the spring received in the hollow portion  373   a  of the second loading stage adjuster  373  (see a circled portion C of  FIG. 13   b ), and the step portion  373   e  is located to block a forward movement path of the second catching step  353   e  of the two-stage loading adjustment member  353  (see a circled portion E of  FIG. 14   b ). 
     As shown in  FIG. 13   c , due to the partial forward movement of the movable assembly, the rod gripping portion  331  is partially moved forward out of the rod gripping portion receiver  335   c,  so that a gripping state of the rod  200  is maintained, but the insertion portion  201  of the rod is not supported by the rod gripping portion receiver  335   c,  so that the rod  200  can be rotated in upper and lower directions (see a circled portion D of  FIG. 13   c ). At this time, since the movable assembly is integrally moved forward or backward, a moving distance of the movable assembly from the first loading stage to a state where the second catching step  353   e  of the two-stage loading adjustment member  353  is engaged with the step portion  373   e  of the second loading stage adjuster  373  is substantially identical to a forward movement distance of the rod gripping portion  331  from the first loading stage to a state where the rod is rotatably gripped. 
     In a state that the second loading stage is completed, the rod  200  is rotatable. Thus, after the rod  200 , explained later, passes through a cut portion of the rod guide, a surgeon may freely adjust an inserting angle of the rod, so that the surgeon may mount the rod to the head portion of the pedicle screw  100  easily and safely. 
       FIGS. 14   a  to  14   c  illustrate a rod mounting stage.  FIG. 14   a  is a side view of a rear portion of the rod holder  300  in the rod mounting stage,  FIG. 14   b  is a sectional view of a rear portion of a button unit  370  and shows an operating location of the button unit  370  in the rod mounting stage, and  FIG. 14   c  is a plane view of a front portion of the rod gripping portion  331  and shows a state of the rod gripping portion  331  in the rod mounting stage. 
     As shown in  FIGS. 14   a  and  14   b , if the button  375  of the rod holder  300  in the second loading stage is pressed in an arrow direction of  FIG. 14   b , the step portion  373   e  of the second loading stage adjuster  373  is pushed in the arrow direction to open the forward movement path of the second catching step  353   e  of the two-stage loading adjustment member  353  (see a circled portion E of  FIG. 14   b ), so that the movable assembly is completely moved forward by means of the elastic member (e.g., spring  337 ) installed to the intermediate member  351  to form the rod mounting stage. 
     As shown in  FIG. 14   c , in the rod mounting stage, two arms  331   b  of the rod gripping portion  331  are almost completely moved out of the rod gripping portion receiver  335   c,  so that the pressing force is eliminated. Accordingly, the two arms  331   b  are elastically restored into an original Y shape. In this reason, the protrusions  331   c  formed on the two arms  331   b  are released from the fixing groove or the through hole  203  of the rod to separate the rod  200  from the rod holder  300 . 
     In order to grip the rod  200  again for a reloading, the fixing groove or the through hole  203  of the rod  200  are located at the protrusions  331   c  of the two arms  331   b,  and the loading handle  355  is then pulled to a location of the first loading stage. At this time, the second loading stage adjuster  373  is moved in the right direction again due to the spring  377  received in the hollow portion  373   a  thereof (based on  FIG. 14   b ), so that the step portion  373   e  of the second loading stage adjuster  373  is re-located again to block the forward movement path of the second catching step  353   e  of the two-stage loading member. 
     As shown in  FIG. 15 , as another embodiment of the rod holder, the rod holder may further include a locking unit  390 . 
     The locking unit  390  includes a circular body  391  located below the two-stage loading adjustment member  353  of the loading unit  350 , a wing shaped locking projection  393  extending outward from one side of the circular body  391  in the radial direction to press the two-stage loading adjustment member  353  upwards, a bar shaped arm  397  extending outward in the radial direction from the other side of the circular body  391  and having a handle pin  395  mounted thereto, and a rotary central shaft  399  inserted into a through opening  398  formed at the center of the circular body  391  to fix the circular body  391  to the grip  310  rotatably. An angle between the arm  397  and a central line of the locking projection  393  is preferably 90° or above, more preferably 120°. 
     Seeing the operating mechanism of the locking unit  390 , as shown in  FIGS. 16   a  and  16   b , in case where the rod holder  300  is in the first loading stage, if a surgeon rotates the handle pin  395  mounted to the arm  397  in the counterclockwise direction, the locking projection  393  pushes up a lower portion of the two-stage loading adjustment member  353  (i.e., pressing it), and thus the two-stage loading adjustment member  353  is maintained in the first loading stage (a locked state). In this state, after the rod  200  is inserted into the pedicle screw  100  by means of the rod holder  300 , once a surgeon rotates the handle pin  395  in the clockwise direction, the locking projection  393  is swerved from the lower portion of the two-stage loading adjustment member  353  so that a pressed state of the two-stage loading adjustment member  353  is released (releasing a locking state). Due to the above state, a surgeon may freely manipulate the rod holder  300  from the first loading stage to the second loading stage. 
     By using such locking unit  390 , an unintentional downward movement of the loading handle  355  caused by a mistake of the surgeon can be prevented, so that it is possible to prevent the first loading stage from being converted into the second loading stage. 
     By employing the rod holder  300  configured as illustrated above, a surgeon may adjust easily a gripped state of the rod  200  through three stages including a gripped state in which the rod  200  is firmly fixed, a rotatably gripped state, and a grip released state by means of a simple manipulation such as pulling the loading handle  355  or pressing the button  375 . 
       FIGS. 17 to 21  show schematically rod guides  500 ,  600  constituting the minimally invasive spine surgery system  1000  according to the present invention.  FIG. 17  shows the first embodiment of the rod guide  500 , and  FIGS. 18 to 21  show the second embodiment of the rod guide  600 . 
     As shown in  FIG. 17 , the rod guide  500  of the first embodiment has a hollow cylindrical shape and a pair of cuts  510  are formed at a lower end of the rod guide in opposite directions such that the rod  200  may be inserted therein. Also, a flat fixed surface  530  is formed at an upper end of the rod guide to be perpendicular to the cut  510  such that the rod guide may be inserted in and fixed to a rod guide holder  800  explained later. The fixed surface  530  makes it possible to prevent the rod guide  500  from being rotated in the rod guide holder  800  explained later, so that it is possible to fundamentally prevent locations of the cuts  510  serving as a moving path of the rod from being changed. In addition, a pair of plane grooves  521 , which can be gripped by a rod pusher  700  explained later, may be symmetrically formed on an upper end surface of the rod guide  500 , wherein the groove and the cut  510  are formed on a straight line. 
       FIGS. 18 to 21  show the rod guide  600  of the second embodiment.  FIG. 18  is a perspective view showing the second embodiment of the rod guide  600 ,  FIG. 19  is a sectional view showing the second embodiment of the rod guide  600 ,  FIG. 20  is a sectional view of an inner body  610  of the rod guide  600  of the second embodiment, and  FIG. 21  is a sectional view of an outer sleeve  650  of the rod guide  600  of the second embodiment. 
     As shown in  FIGS. 18 and 19 , the rod guide  600  includes a hollow cylindrical inner body  610  for griping the pedicle screw  100  and an outer sleeve  650  surrounding the inner body  610  in an axial direction and slid in two stages along the inner body  610 . 
     As shown in  FIG. 20 , the inner body  610  includes a hollow tube  611 , a plurality of elastic arms  613  extending from the hollow tube  611  into a V shape, a pair of cuts  615  formed between the elastic arms  613  and facing to each other, and a gripping portion  617  formed at an end of the elastic arm  613  to grip the pedicle screw  100 . 
     Preferably, as shown in  FIGS. 18 and 19 , a thread may be formed on an upper end of the hollow tube  611  to allow a driver to be connected thereto. Also, a pair of plane grooves  621  to be gripped by the rod pusher  700  or the gap adjuster  900  (explained later) may be formed on the surface below the upper end of the hollow tube  611  on which the thread is formed. Here, the plane grooves  621  are symmetrically formed on a surface of the hollow tube rod, wherein the groove and the cut  615  are formed on a straight line. Preferably, the flat fixed surface  630  is formed on a side of the upper end of the hollow tube  611  to be perpendicular to the cut  615  such that the hollow tube can be inserted in and fixed to the rod guide holder  800  (see  FIG. 18 ). As mentioned above, by using the fixed surface  630 , it is possible to prevent the rod guide  600  from being rotated in the rod guide holder  800 , so that it is possible to fundamentally prevent location of the cut  615  serving as a moving path of the rod  200  being changed. Preferably, in addition, the groove  631  guiding an installing direction of the rod guide separator  400  explained later may be formed at the upper end of the fixed surface  630 . 
     A guide groove  623  defining a path of a guide pin  653  formed in the outer sleeve  650  explained later is formed at a side of the hollow tube  611  placed below the plane groove  621 . The guide groove  623  includes, as shown in  FIG. 20 , a first vertical sliding guide  623   a,  a horizontal guide  623   b  formed perpendicular to the lower portion of the first vertical sliding guide  623   a,  and a second vertical sliding guide  623   c  formed perpendicular to the horizontal guide  623   b  in a lower direction of the inner body  610 . The role of the guide groove  623  will be described in detail when an operating mechanism of the rod guide  600  is explained. 
     In order to enhance the elastic characteristics of the elastic arm  613 , the elastic arm  613  is divided in a longitudinal direction into plural parts, and the elastic arm  613  is widen into a V shape so that the elastic arm can be shrunken inward or expansively restored. A gripping portion  617  having a protrusion  618  formed thereon for gripping the groove formed on an outer surface of the head portion of the pedicle screw  100  is provided at an end of the elastic arm  613 . The gripping portion  617  grips the pedicle screw  100  as follows. In a state where the elastic arm  613  is shrunken inward, the pedicle screw  100  is gripped by the protrusion  618  of the gripping portion  617 . Also, in a state where the elastic arm  613  is restored outward, the protrusion  618  releases the gripping of the pedicle screw  100 . In other words, due to an elastic movement of the elastic arm  613 , a gripping state of the pedicle screw  100  is adjusted. 
     The cut  615  serves as a path through which the rod  200  is inserted, and the cut  615  is formed in a longitudinal direction between the elastic arms  613  and in opposite directions to enable the rod to be inserted therein. Preferably, among four cuts formed on the pair of rod guides  600 , the cut into which the rod  200  is inserted at first has a height causing an exposure out of the patient&#39;s skin so that the rod  200  may be inserted from the outside of the skin. Due to the cut  615  having such a height, a surgeon may easily insert the rod  200  from the outside of a human body without expanding a surgical site such that the minimally invasive spine surgical operation can be performed pertinently. 
     As shown in  FIG. 21 , the outer sleeve  650  has a cylindrical hollow shape, and the inner body  610  is received in the outer sleeve  650 . A protrusive rim  651  serving as a handle is formed at the upper end of the outer sleeve  650 . Preferably, opposite surfaces of the protrusive rim  651  are bilateral symmetric and has flat shape, so that a surgeon may easily rotate the outer sleeve  650 . The protrusive rim  651  also plays a role of a pressing unit against the rod pusher  700  explained later. A guide pin  653  corresponding to the guide groove  623  is formed in an upper inner surface of the outer sleeve  650  such that the outer sleeve  650  may be guided along the guide groove  623  formed in the inner body  610 . Due to the guide pin  653  and the guide groove  623  as described above, the path of the outer sleeve  650  is defined as a vertical sliding path and a lateral rotating path with respect to the inner body  610 . 
     On a lower end of the outer sleeve  650 , a pair of cuts  655  extend in opposite directions, so that the rod  200  may be inserted into the rod guide  600  through the cuts  655 . The cut  655  of the outer sleeve  650  may be located on a straight line with the cut  615  of the inner body  610  so as to enable the outer sleeve  650  to be rotated in a right or left direction to insert the rod into the rod guide  600 . Among four cuts  615  formed on the pair of rod guides  600 , the cut  655  into which the rod is inserted at first has a height causing an exposure out of the patient&#39;s skin so that the rod  200  may be inserted from the outside of the skin. Due to the cut  655  having such a height, a surgeon may insert easily the rod  200  from the outside of a human body without expanding a surgical site such that the minimally invasive spine surgical operation can be performed pertinently. 
     At least one rod pressing unit  657  is formed at a lower end of the outer sleeve  650  and extends in a longitudinal direction toward a downstream. Thus, when the rod  200  is located to the head portion of the pedicle screw  100  by means of the rod holder  300 , the outer sleeve  650  can be moved in a lower direction to press the rod such that the rod is closely contacted to the head portion of the pedicle screw  100 . It is preferable that the rod pressing unit  657 is formed at a portion near the cut  655  such that a distance between a central axis of the rod pressing unit  657  and a central axis of the cut  655  is substantially identical to a length of the horizontal guide unit  623   b  of the rod guide groove  623 . The end of the rod pressing unit  657  preferably has a concave shape corresponding to an outer shape of the rod in order to press surely the rod. 
     It is preferable that, among the pair of rod guides  600 , the rod guide  600  to which the rod is inserted at first has only one rod pressing unit  657  formed on a side of the outer sleeve  650  located in an opposite direction to the insertion direction of the rod. Since the rod holder  300  is arranged at the cut into which the rod  200  is inserted at first and the surgical operation is performed, the above configuration does not disturb the movement of the rod holder  300 . 
     Due to the above rod pressing unit  657 , the possibility that the rod  200  is suspended at a mid portion of the head portion of the pedicle screw  100  may be removed, so that it is possible to eliminate any inconvenience that the thread is not well fit when the set screw is fastened due to unstable mounting of the rod. In other words, the rod  200  may be closely contacted with the head portion of the pedicle screw  100  by the rod pressing unit  657 , so that the rod  200  may be more securely mounted to the head portion of the pedicle screw  100 . 
     In order to allow the rod pressing unit  657  to be in contact with rod  200  in a pressing manner, the rod pusher  700 , explained later, is preferably used. In particular, it is preferable to employ the rod pusher  700  when the outer sleeve  650  is moved in a lower direction along the second vertical sliding guide unit  623   c.  Hereinafter, the rod pusher  700  is explained. 
       FIG. 22  is a schematic view showing configuration and operating mechanism of the rod pusher  700  which may constitute the minimally invasive spine surgery system  1000  according to the present invention. As shown in  FIG. 22 , the rod pusher  700  includes an upper handle  720  having a fixed gripping portion  710  for gripping a plane groove  621  formed in the inner body  610  of the rod guide  600  and a lower handle  740  connected to the upper handle  720  by a hinge  730 . Preferably, the upper handle  720  and the lower handle  740  are connected by means of the hinge  730  in an X-like shape. 
     A pressing head  741  for generating a downward pressing force is formed at an end of the lower handle  740 , and a shaft  743  to which a downward pressing force is exerted is connected to a lower portion of the pressing head  741  by a connection means such as a pin  745 . Also, a movable gripping portion  747  is fixedly installed to a lower end of the shaft  743 . 
     In addition, it is preferable that a sliding tube  713  is installed to a lower portion of the fixed gripping portion  710  of the upper handle  720  such that the shaft  743  may slide and a distance between the movable gripping portion  747  and the fixed gripping portion  710  is kept constant before the upper handle  720  and the lower handle  740  are pressed and gripped. The length of the sliding tube  743  is substantially identical to a distance between the protrusive rim  651  of the outer sleeve  650  and the plane groove  621  in case where the sliding tube is located above the second vertical sliding guide unit  623   c  so that the sliding tube  743  can make the rod pusher  700  be mounted easily to the rod guide  600  before the upper handle  720  and the lower handle  740  are pressed and gripped. 
     If the upper handle  720  and the lower handle  740  are pressed and gripped, the movable gripping portion  747  is in contact with the protrusive rim  651  of the outer sleeve  650  to press the outer sleeve  650  toward the pedicle screw while the fixed gripping portion  710  grips fixedly the plane groove  721 . In other words, when the upper handle  720  and the lower handle  740  are pressed and gripped, a distance between the fixed gripping portion  710  and the movable gripping portion  747  is increased though a distance between the end of the upper handle  720  and the end of the lower handle  740  is decreased. Due to such a handle pressing process, the rod pressing unit  657  of the outer sleeve  650  presses the rod in a seesaw manner. 
     A distance adjusting means  760  for adjusting a moving distance of the movable gripping portion  747  is provided at ends of the upper handle  720  and the lower handle  740  located at a side opposite to the gripped portion of the rod guide  600 . In other words, the bar shaped distance adjusting means  760  having toothed first projections  761  formed at one side thereof is further provided between the other end of the upper handle  720  and the other end of the lower handle  740  to adjust a moving distance of the movable gripping portion  747 . An insertion hole  765  having a tooth shaped second projection formed at a portion contacted with the first projections is formed with a predetermined depth at the other end of the lower handle  740 , so that the distance adjusting means  760  may be inserted thereto. One end of the distance adjusting means  760  is connected to the other end of the upper handle  720  by a hinge  763 , and the other end of the distance adjusting means  760  is inserted into the insertion hole  765 , so that one of concave portions between the first projections  761  is engaged with the second projection. Due to the above configuration of the distance adjusting means  760 , if the upper handle  720  and the lower handle  740  are pressed, a moving distance of the movable gripping portion  747  may be adjusted step by step. 
     Also, it is preferable that the rod pusher  700  further includes an elastic member  770  provided between the upper handle  720  and the lower handle  740 . Due to the above elastic member  770 , when the fixed state of the distance adjusting means  760  is released, it is possible to recover the upper handle  720  and the lower handle  740  to a state where the handles are not yet pressed. 
     By using the rod pusher  700  as above, the outer sleeve  650  of the rod guide  600  of the second embodiment may be easily slid with a small power, and the rod pressing unit  657  may also compress the rod  200  more strongly with a small power. 
     Hereinafter, an operating mechanism of the rod guide  600  and the rod pusher  700  is explained. 
     First of all, the head portion  110  of the pedicle screw  100  is located at the gripping portion  617  of the inner body  610 . At this time, the guide pin  653  of the outer sleeve  650  is located at the upper portion of the first vertical sliding guide unit  523   a  among the guide grooves  623  of the inner body  610 . Due to the above, since the lower end of the outer sleeve  650  is located in the hollow tube  611  of the inner body  610 , any pressing force is not yet transferred to the elastic arm  613  of the inner body  610 , so that the gripping portion  617  does not still grip the pedicle screw  100 . Also, in this state, one pair of cuts  655  of the outer sleeve  650  are overlapped with one pair of cuts  615  of the inner body  610 , so that the rod  200  can be inserted. 
     Then, until the guide pin  653  of the outer sleeve  650  is located below the first vertical sliding guide unit  623   a  among the guide grooves  623 , the outer sleeve  650  is slid in a downward direction along the inner body  610 . During this sliding process, the end of the outer sleeve  650  partially presses the plurality of elastic arms  613  elastically widen into a V shape to shrink inward the elastic arms  613 , and the gripping portion  617  is also shrunken inwards according to the above inward shrinkage, so that the protrusion  618  formed on the gripping portion  617  firmly grips the groove of the head portion  110  of the pedicle screw in a spring collet manner. For reference, in this state, a screw driver is connected to the thread formed on the upper portion of the inner body  610  to fix the pedicle screw  100  gripped by the rod guide  600  to the vertebral pedicle. Also, even in this state, one pair of cuts  655  of the outer sleeve  650  are still overlapped with one pair of cuts  615  of the inner body  610 , so that the rod may be inserted therein. 
     After that, the pedicle screw  100  is fixed to the vertebral pedicle, and the rod  200  is located to the head portion  110  of the pedicle screw  100  through the cuts  615 ,  655  of the rod guide  600  by using the rod holder  300 . Then, the protrusive rim  623   b  of the outer sleeve  650  is gripped and then rotated in the left direction in  FIG. 20  (namely, in a clockwise direction) with respect to the inner body  610  such that the guide pin  653  of the outer sleeve  650  is located at the left side (in  FIG. 20 ) of the horizontal guide unit  623   b  of the guide groove  623 . In this state, since the rod pressing unit  657  is formed near the cut  655  such that a distance between the central axis of the rod pressing unit  657  and the central axis of the cut  655  is substantially identical to a length of the horizontal guide unit  623   b  of the rod guide groove  623 , the rod pressing unit  657  of the outer sleeve  650  and the cut  615  of the inner body  610  are located on a straight line as shown in  FIG. 19  due to the above clockwise rotation. 
     In the state where the rod pressing unit  657  and the cut  615  of the inner body  610  are located on a straight line, the fixed gripping portion  710  of the rod pusher  700  is fit into the plane groove  621  of the inner body  610 , and the movable gripping portion  747  is located on the protrusive rim  651  of the outer sleeve  650  such that the movable gripping portion  747  of the rod pusher  700  comes in contact with the protrusive rim  651  of the outer sleeve  650 . Then, the upper handle  720  and the lower handle  740  of the rod pusher  700  are pressed and gripped to move the movable gripping portion  747  downward (see the left side of  FIG. 22 ). As shown in  FIG. 22 , due to the downward movement of the movable gripping portion  747 , the outer sleeve  650  is also pressed downward, so that the rod pressing unit  657  of the outer sleeve  650  presses the rod  200  to be closely contacted with the head portion  110  of the pedicle screw  100 . At this time, the guide pin  653  of the outer sleeve  650  is moved up to a lower position along the second vertical sliding guide unit  623   c.    
     After the rod is safely mounted to the pedicle screw  100 , a surgeon grips the protrusive rim  651  of the outer sleeve  650  and then moves it in a reverse order to the above. In other words, the surgeon manipulates the outer sleeve  650  such that the guide pin  653  of the outer sleeve  650  is moved from the lower portion to the upper portion of the second vertical sliding guide unit  623   c,  from a left side to a right side of the horizontal guide unit  623   b  (based on  FIG. 20 ), and from the lower portion to the upper portion of the first vertical sliding guide unit  623   a,  thereby releasing the gripping of the pedicle screw  100  and then removing the rod guide  600 . 
     After the surgical operation is completed, in order to separate easily the pedicle screw  100  from the rod guide  600 , the minimally invasive spine surgery system  1000  may further include a rod guide separator  400 .  FIGS. 23 to 26  show the rod guide separator  400 . The rod guide separator  400  includes a hollow sleeve  410  fixedly connected to the end of the inner body  610  of the rod guide  600  and mounted to two facing grooves formed in the end portion of the fixed surface  630  of the inner body  610  and a T shaped insert bar  420  inserted into the sleeve  410 . 
     As shown in  FIG. 23 , the sleeve  410  includes a fixed unit  411  having an opening formed thereon and screw-coupled to the inner body  610 , a hollow body  413  extending downward from the fixed unit  411 , two rigid arms  415  extending from end of the hollow body  413  to face each other and two flexible arms  416  extending from the end of the hollow body  413  and being adjacent to sides of the rigid arms  415  and facing each other. Also, a protrusion  417  is formed on an outer surface of the flexible arm  416 , and the flexible arm  416  is shrunken inward rather than the rigid arm  415  as shown in  FIG. 24 . A protrusion having a shape complementing to that of the groove  631  of the inner body  610  is formed on the fixed unit  411 , so that the protrusion is mounted in the groove  631  of the inner body. Accordingly, the rod guide separator  400  is guided such that the protrusion  417  formed on the flexible arm  416  and the gripping portion  617  of the inner body  610  are located on one straight line. Preferably, outer diameters of the hollow body  413  and the rigid arm  415  are substantially identical to an inner diameter of the inner body  610  of the rod guide  600 , and an outer diameter of the flexible arm is smaller than an inner diameter of the inner body  610 . 
     As shown in  FIG. 25 , the insert bar  420  includes a circular handle  421  and a cylindrical bar  423  extending downward from the center of the circular handle  421  and passing through the hollow body  413 . Also, the cylindrical bar has a length greater than the entire length of the sleeve  410 . Preferably, the outer diameter of the cylindrical bar  423  is substantially identical to the inner diameters of the hollow body  413  and the rigid arm  415 , and the end of the cylindrical bar  423  is tapered. 
     The operating mechanism of the rod guide separator  400  is explained with reference to  FIG. 26 . First, the fixed unit  411  of the sleeve  410  is mounted to the groove  631  of the inner body  610  of the rod guide  600 . At this time, the hollow body  413 , the rigid arm  415  and the flexible arm  416  of the sleeve are completely received or inserted into the inner body  610 , and the protrusion  417  formed on the flexible arm  416  is located near the flexible arm  613  of the inner body  610 . Then, the insert bar  420  is inserted into the sleeve  410 . Since the outer diameter of the cylindrical bar  423  of the insert bar  420  is substantially identical to the inner diameter of the rigid arm  415  and greater than the inner diameter of the flexible arm  416 , when the insert bar  420  is inserted into the sleeve  410 , the end of the circular bar  423  expands the flexible arm  416  outwards. Due to the above, the protrusion  417  formed on the flexible arm  416  of the sleeve  410  expands the flexible arm of the inner body  610  of the rod guide  600  outwards, thereby separating the pedicle screw  100  from the rod guide  600 . 
     By using the above rod guide separator  400 , the pedicle screw  100  may be easily separated from the rod guide  600 , so that it is possible to prevent any muscle or tissue around a surgical operation region from being damaged during the rod guide separating process. 
       FIGS. 27 to 29  are schematic views showing a structure and an installation state of the rod guide holder  800  constituting the minimally invasive spine surgery system  1000  according to the present invention.  FIG. 27  is a perspective view of the rod guide holder  800  of the present invention,  FIGS. 28   a  and  28   b  are a side view and a plane view of the rod guide holder  800  of the present invention, and  FIG. 29  is a schematic view showing a state where the rod guide holder  800  of the present invention is installed on the rod guides  500 ,  600 . 
     Referring to  FIGS. 27 and 28 , the rod guide holder  800  includes a first fixing unit  830 , a guide  840  and a second fixing unit  850 . Here, the first fixing unit has a rectangular first fixture  810  formed at body center thereof for inserting one of the pair of rod guides  500 ,  600  therein and a U shaped second fixture  820  formed at both sides of the first fixture  810  for inserting the remaining rod guide therein, and the guide  840  is connected to one side of the first fixture  810  of the first fixing unit  830  and has an arc slit  841  formed thereon. Also, the second fixing unit  850  is connected to the guide  840  and rotated and moved along the slit  841  to guide an insert position of the rod in a state where the rod holder  300  is inserted in the second fixing unit. 
     A knob  811  is formed at one side of the first fixture  810  for fixing the rod guides  500 ,  600  after the rod guides  500 ,  600  are inserted therein, and a screw is formed on the knob  811  to enable the rod guides  500 ,  600  to be fixed or released according to a rotating direction of the knob  811 . 
     Also, the second fixture  820  has a U shape, so that the cylindrical rod guides  500 ,  600  may be moved along the second fixture  820  as much as a predetermined distance. Preferably, the inner shape of the first fixture  810  and the inner shape and size of the second fixture  820  are determined such that the planed fixed surfaces  530 ,  630  formed perpendicularly to one pair of cuts  510 ,  515  can be mounted at the upper end of the rod guides  500 ,  600  without rotating. By using the above configuration, it is possible to prevent the rod guides  500 ,  600  from being rotated in the rod guide holder  800 , so that it is fundamentally possible to prevent a location of the cuts  510 ,  615  serving as a path of the rod from being changed.  FIG. 23  illustrates that one rod guide is inserted into the first fixture  810  and fixed by the knob  811 , and the remaining rod guide is inserted into the second fixture  820  located at the right side (based on  FIGS. 27 to 29 ) such that the rod guide holder  800  is installed to the rod guides  500 ,  600 . 
     The second fixing unit  850  has an insert hole  851  into which the rod holder  300  may be inserted and is connected such that the second fixing unit can be moved circularly at the slit  841  formed in the guide  840  and rotated freely, so that the rod  200  gripped by the rod holder  300  may be accurately mounted to the pedicle screw  100  while freely adjusting an insert angle into the rod guides  500 ,  600 . 
     By the above configuration, the rod guides  500 ,  600  and the rod holder  300  may be located on a straight line, so that it is possible to prevent the rod holder  300  from being separated from the insertion path of the rod  200 . In addition, since the path along which the rod holder  300  is moved is placed within a radius of rotation, the rod may be easily inserted. Moreover, during a surgical operation, a scattering of the arrangement of four cuts on the straight line caused by a rotation of rod guides  500 ,  600  can be prevented due to the contact between the rod holder  300  and the rod guide, thereby improving the accuracy of the rod inserting process. 
       FIG. 30  is a schematic perspective view showing configuration and operating mechanism of the gap adjuster  900  for suitably adjusting a gap between the head portions of the pedicle screw  100 . 
     As shown in  FIG. 30 , the gap adjuster  900  includes a fixed gripping portion  910 , two legs  930  connected to a lower portion of the fixed gripping portion  910  by a hinge  920 , arms  940  rotatably connected to the two legs  930 , respectively, an adjustment gripping portion  950  fixedly connected to the arm  940 , and a bar member  960  having a male thread screw-coupled to a bore formed in the arm  940  and having a female thread formed therein. 
     The fixed gripping portion  910  includes a horizontal portion  911  and a vertical portion  913  so that the fixed gripping portion has a ‘┐’ shape as a whole when being seen from a side. The horizontal portion  911  has a ‘3’ shape and grips fixedly the plane grooves  521 ,  621  formed on the upper portions of the pair of rod guides  500 ,  600 , and the vertical portion  913  has a slit  915  formed thereon. 
     By means of the hinge  920 , two legs  930  are connected to the slit  915  formed in the fixed gripping portion  910 , so that an angle between two legs  930  may be changed as the two legs  930  are widened or narrowed. 
     The arms  940  are rotatably connected to ends of the two legs  930 , respectively, preferably by pins. A bore on which a female thread is formed is formed on the arm  940 . 
     The bar member  960  having a male thread formed thereof passes through the bore of the arm  940  having the female thread formed therein. At this time, the bar member  960  and the bore are screw-coupled to each other like a bolt and screw. A handle  929  is installed at one end of the bar member  960  to facilitate a rotation of the bar member  960 , and a knob  931  is installed at the front of the handle  929 . The knob  931  plays a role of fixing the adjusted gap during a surgical operation process after a gap between the pedicle screws  100  is adjusted by turning the handle  929 . 
     The adjustment gripping portion  950  is fixedly and perpendicularly mounted to one end of the arm  940  and grips central sides of the rod guides  500 ,  600  or a central side of the outer sleeve  650 . Preferably, the adjustment gripping portion  950  has shape and size complementing to those of central sides of the rod guides  500 ,  600  or a central side of the outer sleeve  650 , so that the adjustment gripping portion  950  may firmly grip the rod guide or the outer sleeve  650 . 
     Hereinafter, the operating mechanism of the gap adjuster  900  is illustrated. 
     First of all, the horizontal portion  911  of the fixed gripping portion  910  is located in the plane grooves  521 ,  621  of the inner body  610 , and the adjustment gripping portion  950  is located at the central side of the rod guide  500  or the central side of the outer sleeve  650 . In case where a gap between pedicle screws fixed to the vertebral pedicle is wider than a required value, the handle  929  is rotated to move the bar member  960  to a position opposite to the handle  929 . Due to the above movement of the handle  929  in the opposite direction, two arms  940  become closer, so that the distance between the adjustment gripping portions  950  fixed to two arms  940  is also decreased. Thus, the distance between the head portions of the pedicle screws  100  gripped by the rod guides  500 ,  600  can be decreased. When the gap of the adjustment gripping portion  950  is decreased as above, the angle between the legs  930  is decreased, and the hinge  920  connecting the legs  930  is moves upward along the slit  915  formed on the vertical portion  913  of the fixed gripping portion  910 . 
     On the contrary, in case where the gap between the pedicle screws fixed to the vertebral pedicle is narrower than a required value, by rotating the bar member  960  in a direction opposite to the case where that the gap between the pedicle screws fixed to the vertebral pedicles is wider than a required value, the gap between the pedicle screws may be widened in the same principle as described above. 
     By using the gap adjuster  900  configured as above, it is possible to solve an inconvenience caused by manipulating directly the long rod guides  500 ,  600  by hand to adjust a gap between the pedicle screws  100  and a problem that the force is not accurately transferred to the screw portion of the pedicle screw  100  due to such a manual manipulation. In other words, by means of the gap adjuster  900 , a gap between the pedicle screws  100  may be decreased just by determining a rotating direction of the handle  929 , and it is possible to easily adjust a gap of the pedicle screws  100  by rotating the handle  929  with a small force. 
     As another embodiment of the gap adjuster, as shown in  FIGS. 31 to 33 , the gap adjuster  950  may comprise a first handle  953  and a second handle  955  respectively having adjustment gripping portions  951  mounted to one ends thereof, a T shaped hinge shaft  957  connecting the first handle  953  and the second handle  955  in a hinge manner and mounted vertically at connection portions of the first handle  953  and the second handle  955 , and a cylindrical bar  959  mounted to one end of the hinge shaft  957  such that the cylindrical bar can be rotated with respect to the hinge shaft  957 . 
     Preferably, the adjustment gripping portions  951  are rotatably mounted to the first handle  953  and the second handle  955 . By mounting rotatably the adjustment gripping portions  951  as mentioned above, although a gap between the adjustment gripping portions  951  is changed by pressing the first handle  953  and the second handle  955 , a contact between the adjustment gripping portions  951  and the rod guide can be maintained (in other words, a contact area between the adjustment gripping portion  951  and the rod guide may be maintained), so that the gap between the pedicle screws may be stably adjusted without a slip of the adjustment gripping portion  951 . 
     Preferably, a bar shaped distance adjusting means  960  having toothed first projections  961  formed on one side thereof is additionally provided between the other end of the first handle  953  and the other end of the second handle  955  to adjust a moving distance of the adjustment gripping portions  951 . An insertion hole  965  having a toothed second projection formed at a portion to be in contact with one of concave portions between the first projections  961  is formed with a predetermined depth on the other end of the second handle  955  to enable the distance adjusting means  960  to be inserted therein. Also, one end of the distance adjusting means  960  is connected to the other end of the first handle  953  by means of a hinge  963 , and the other end of the distance adjusting means  960  is inserted into the insertion hole  965  such that one of concave portions between the first projections  961  and the second projection are engaged with each other, so that if the first handle  953  and the second handle  955  are pressed, a moving distance of the adjustment gripping portions  951  may be adjusted step by step. 
     Preferably, the gap adjuster  950  further includes an elastic member  970  provided between the first handle  953  and the second handle  955  to restore the first handle  953  and the second handle  955  to an original state before being pressed. More preferably, the elastic member  970  consists of two flexible metal plates, but not limited thereto. 
       FIGS. 32 and 33  show an operating mechanism of the gap adjuster  950 . The adjustment gripping portions  951  of the first handle  953  and the second handle  955  are located at outer sides of two rod guides  500 ,  600  fixed to the vertebra, and the cylindrical bar  959  is inserted between the two rod guides  500 ,  600 . At this time, in order to decrease a gap between the pedicle screws  100 , the cylindrical bar  959  is located above the rod guides  500 ,  600 , and the adjustment gripping portions  951  are located below the rod guides. Meanwhile, in order to increase a gap between the pedicle screws  100 , the cylindrical bar  959  is located below the rod guides  500 ,  600 , and the adjustment gripping portions  951  are located above the rod guides. Then, the first handle  953  and the second handle  955  are pressed to adjust a gap between the pedicle screws  100 . At this time, the gap adjuster is operated in a lever principle, and the hinge shaft plays a role of a support of the lever. 
     By using the gap adjuster  950  according to the above embodiment, a gap between the pedicle screws  10  may be adjusted more easily with a small force. 
     The rod holder according to the present invention has an advantage that the rod can be securely gripped and easily inserted and mounted at the same time. 
     Further, the rod holder according to the present invention can be easily manipulated. 
     Accordingly, the rod holder according to the present invention can shorten a time required for spine surgical operation. 
     In addition, according to the present invention, the rod can be placed on a pedicle screw in a more accurate and stable way, thereby minimizing a damage of nerves and tissues around a surgical site when the rod is inserted. 
     Due to the above effects, the time required for recovering a surgical site of a patient may be shortened so that additional costs after the surgical operation can be reduced. 
     The preferred embodiments of the present invention have been illustrated and explained herein, but the scope of the present invention is not limited to the embodiment described and illustrated herein, but is defined by the appended claims. It will be apparent that those skilled in the art can make various modifications and changes thereto within the scope of the invention defined by the claims. Therefore, the true scope of the present invention should be defined by the technical spirit of the appended claims.