Patent Publication Number: US-2009240290-A1

Title: Buffer type vertebral pedicle screw

Description:
TECHNICAL FIELD 
     The present invention relates to a vertebral pedicle screw used when conducting spine surgery in the field of orthopedics, and more particularly, to a buffer type vertebral pedicle screw which can absorb a shock using a relative sliding characteristic between a screw body driven into a vertebral pedicle and a rod, thereby relieving the pain of a patient and ensuring the stabilization of abody part receiving a surgical operation. 
     BACKGROUND ART 
     In general, a patient having the damaged spine cannot lead an active life. Even though the patient can be active to some extent due to the lesser degree of the damage to the spine, as the damaged portion of the spine is pressed by or brought into contact withan adjacent portion, a pain is caused to the patient, and a recovery is likely to be retarded. 
     Therefore, for the patient having the damaged spine, a surgical operationis conducted to support the adjacent portion of the spine using artificial prosthetics so that the damaged portion of the spine is not pressed by the adjacent portion. 
     In this case, the artificial prosthetics for supporting the spine is composed of a plurality of vertebral pedicle screws and a rod. The vertebral pedicle screws are driven into vertebral pedicles over and under a damaged vertebral pedicle and serve as fasteners, and the rod is securely held by the plurality of vertebral pedicle screws and serves as a support. 
       FIG. 4  is a sectional view illustrating the assembled state of a conventional vertebral pedicle screw, and  FIG. 5  is a perspective view illustrating the use of the conventional vertebral pedicle screw. 
     A vertebral pedicle screw  10  has a screw body  11  which is driven into a vertebral pedicle  100 , a housing  16  which is assembled to the upper portion of the screw body  11  and has U-shaped grooves  13  for placing a rod  12  therein and a threaded portion  15  to be locked with a fastening bolt  14 , the fastening bolt  14  being locked to the threaded portion  15  of the housing  16  to press the rod  12  positioned thereunder as it is threaded downwards, and a fastening ring  18  which is disposed in the housing  16  to press a screw head  17  of the screw body  11 . 
     The unexplained reference numeral  19  designates punched portions for fixing the position of the fastening ring  18 . 
     A procedure for connecting vertebral pedicles  100  using vertebral pedicle screws  10  and the rod  12  will be described below. 
     First, screw bodies  11  of the vertebral pedicle screws  10  are vertically driven into the respective vertebral pedicles  100  which are to be connected with one another. Then, fastening rings  18  are respectively inserted into housings  16  of the vertebral pedicle screws  10 , and the rod  12  is placed in the U-shaped grooves  13  of the housings  16 . 
     In this state, by locking respective fastening bolts  14  into threaded portions  15  of the housings  16 , as the lower surfaces of the fastening bolts  14  press the rod  12 , the rod  12  which connects the vertebral pedicles  100  with one another is securely held. 
     In succession, by punching the housings  16  on both sides of the respective fastening rings  18  which press the screw heads  17  on the lower ends thereof and support the rod  12  on the upper ends thereof and thereby forming punched portions  19 , the surgical operation for the spine using the vertebral pedicle screws  10  and the rod  12  is completed. 
     However, in the conventional vertebral pedicle screw  10 , since the screw body  11  and the fastening ring  18  are coupled with each other such that they are secured tight to each other and are not moved relative to each other, that is, such that the fastening ring  18  firmly grasps the screw head  17  of the screw body  11 , a problem is caused in that the body part receiving the surgical operation can be unstabilized even by slight motion of a patient. 
     For example, as the shock or vibration transferred to the screw body  11  through the rod  12  due to the motion of the patient is applied as it is, to the entire body part receiving the surgical operation, a pain is caused in the body part receiving the surgical operation, which acts as a factor impeding the stabilization of the body part receiving the surgical operation. As a result, inconvenience is rendered to thepatient due to the pain, and the recovery of the patient is likely to be retarded. 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a vertebral pedicle screw, which can realize a novel configuration of a vertebral pedicle screw by allowing a screw body driven into and fastened to a vertebral pedicle and a rod-side assembly to be slidingly moved relative to each other in all directions within a predetermined angle, so that, when a shock is applied, the shock can be absorbed throughthe relative sliding movement between the screw body and the rod-side assembly, thereby relieving the pain of a patient and ensuring the stabilization of the body part receiving a surgical operation, and the entire surgical operation including a rod connection task can be easily carried out due to the slidable structure of the rod-side assembly, thereby enabling spine surgery to be effectively conducted in terms of time and precision. 
     Technical Solution 
     In order to achieve the above object, according to the present invention, there is provided a vertebral pedicle screw including a screw body driven into a vertebral pedicle, a housing assembled to an upper end of the screw body and having U-shaped grooves for seating a rod and a threaded portion for locking a fastening bolt, the fastening bolt locked to the threaded portion of the housing to press the rod positioned thereunder as it is threaded downward, and a fastening ring inserted into thehousing, the vertebral pedicle screw comprising an insert placed on an outer surface of a screw head of the screw body in the housing, installed to be partially come into contact with the fastening ring on an upper portion thereof, and accommodating the screw head of the screw body on a curved inner surface thereof such that the insert and the screw head are brought into sliding contact with each other, whereby an entire rod-side assembly can be slidingly moved in all directions with respect to the screw body driven into the vertebral pedicle. 
     Advantageous Effects 
     Thanks to the above features, the vertebral pedicle screw according to the present invention provides advantages in that, since a slidable structure between a screw body and a rod-side assembly is adopted, when a shock is applied, the entire rod-side assembly can slidingly move in all directions within a predetermined angle and can thereby absorb or reduce the shock so that the pain of a patient can be relieved to the maximum degree, and it is possible to prevent a shock or vibration from being applied to the vertebral pedicle into which the screw body is driven so that the body part receiving a surgical operation can be kept stabilized. 
     Also, when conducting a surgical operation for the spine, because the rod-side assembly can slidingly move to some extent depending upon the status of the operation, the entire surgical operation including a rod connection task can be easily carried out so that the surgical operation for the spine can be effectively conducted in terms of time and precision. 
     As a result, the overall efficiency associated with the surgical operation for the spine can be increased, whereby it is possible to be of help to the operation and the medical treatment of a patient. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above objects, and other features and advantages of the present invention will become more apparent after a reading of the following detailed description taken in conjunction with the drawings, in which: 
         FIG. 1  is a perspective view illustrating the exploded state of a buffer type vertebral pedicle screw in accordance with an embodiment of the present invention 
         FIG. 2  is a sectional view illustrating the assembled state of the buffer type vertebral pedicle screw in accordance with the embodiment of the present invention; 
         FIG. 3  is a sectional view illustrating the sliding characteristic of the buffer type vertebral pediclescrew in accordance with the embodiment of the present invention 
         FIG. 4  is a sectional view illustrating the assembled state of a conventional vertebral pedicle screw; and 
         FIG. 5  is a perspective view illustrating the use of the conventional vertebral pedicle screw. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Reference will now be made in greater detail to a preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like parts. 
       FIG. 1  is a perspective view illustrating the exploded state of a buffer type vertebral pedicle screw in accordance with an embodiment of the present invention, and  FIG. 2  is a sectional view illustrating the assembled state of the buffer type vertebral pedicle screw in accordance with the embodiment of the present invention. 
     Referring to  FIGS. 1 and 2 , a vertebral pedicle screw  10  in accordance with an embodiment of the present invention is made of titanium(Ti) and serves as a medical subsidiary for securely holding a rod connecting vertebral pedicles with one another. 
     The vertebral pedicle screw  10  includes a screw body  11  which is driven into each of vertebral pedicles  100  positioned upwardly and downwardly adjacent to the damaged portion of the spine. 
     The screw body  11  is directly locked to the vertebral pedicle  100  by a threaded portion thereof, and is assembled to a housing  16  via a spherical screw head  17  thereof. 
     The housing  16  functions to grasp a rod  12 . The housing  16  has grooves downwardly extendingfrom the upper end thereof, that is, U-shaped grooves  13 , such thatthe rod  12  can be placed and seated in the U-shaped grooves  13 . 
     A threaded portion  15  is formed on the inner wall surface of the housing  16 , and a fastening bolt  14  is locked to the threaded portion  15  of the housing  16 . As the fastening bolt  14  is threaded downward, it can press and fasten the rod  12  positioned thereunder. 
     The vertebral pedicle screw  10  according to the present invention further includes the fastening bolt  14  which is locked to the threaded portion  15  of the housing  16  to press the rod  12 , and a fastening ring  18  which is disposed in the housing  16  to stably support the rod  12  placed in the grooves  13  of the housing  16  on the upper end thereof and to come into contact with an insert  21 , to be described later, on the lower end thereof. 
     The fastening ring  18  can be fixedly held at the inserted position by punched portions  19  of the housing  16  which are formed by punching the sidewall of the housing  16  to protrude inward. By forming the punched portions  19  in this way, it is possible to prevent the fastened state of the rod  12  from being released due to the fluctuation of the fastening ring  18 . 
     In particular, the present invention provides a structure for allowing the screw body  11  driven into the vertebral pedicle  100  and a rod-side assembly to be slidingly moved relative to each other. 
     The rod-side assembly, that is, the entire housing  16  including the fastening bolt  14 , the rod  12 , the fastening ring  18  and the insert  21  can be slidingly moved with respect to the screw body  11  in all directions within a predetermined angle. 
     To this end, the insert  21  is provided to surround the circumferential surface of the screw head  17  of the screw body  11 . The insert  21  has the sectional shape of a ring. The insert  21  has the configuration of a truncated hollow sphere which has a curved convex outer surface and a curved concave inner surface  20 . 
     The insert  21  is inserted into the housing  16  and is placed at the lower end of the housing  16 . The insert  21  is installed such that it surrounds the screw head  17  of the screw body  11  at the lower portion thereof and comes into contact with the lower surface of the fastening ring  18  at the upper portion thereof. 
     At this time, as the fastening bolt  14  is threaded, the insert  21  can be fixedly held not to be moved, by the rod  12  and the fastening ring  18  which are sequentially pressed by the fastening bolt  14 . 
     The fastening ring  18  has a lower surface which is composed of a curved surface  22 , i.e., having the same curvature as the curved outer surface of the insert  21 . Since the outer surface of the upper portion of the insert  21  can be partially brought into contact with the curved surface  22  of the fastening ring  18 , the insert  21  is fixedly held against movement with respect to the fastening ring  18 . 
     Specifically, the insert  21  has a structure in which the sphericalscrew head  17  of the screw body  11  is accommodated on the curved inner surface  20  of the insert  21  such that the spherical screw head  17  and the insert  21  can be slidingly moved with respect to each other. 
     According to this, the screw head  17  and the insert  21  can slide with respect to each other in all directions within a predetermined angle. As a result, through the sliding contact between the screw head  17  and the insert  21 , an entire rod-side assembly can be moved on the screw body  11  serving as a fixed element. 
     Here, it is preferred that the angle, within which the rod-side assembly can be moved in all directions, be set to about 10-15° when measured from the axis of the screw body  11 . 
     A procedure for installing vertebral pedicle screws  10  and thereby fastening the rod  12  when conducting a surgical operation for the spine using the rod  12  and the vertebral pedicle screws  10  according to the present invention, configured as described above, will be described below. 
     Referring to  FIG. 3 , first, each screw body  11  having the insert  21  on the screw head  17  thereof is threadedly driven into each of the vertebral pedicles  100  to be connected with one another. Then, after inserting the fastening ring  18  into the housing  16  which is coupled to the screw head  17  of the screw body  11 , the rod  12  is fitted into the housing  16 . 
     At this time, the rod  12  is seated in the U-shaped grooves  13  which are defined on both sides of the housing  16 . 
     In this state, the fastening bolt  14  is locked to the threaded portion  15  of the housing  16 . 
     The threading of the fastening nut  14  can be conducted by inserting a tool into the groove defined on the upper end of the fastening bolt  14  and then rotating the tool. 
     When the fastening bolt  14  is locked in this way, since the rod  12 , which is seated on the fastening ring  18  positioned thereunder, is pressed downward by the fastening bolt  14 , sufficient and precise pressing force (locking force) can be applied to the rod  12  and the rod  12  can be held in the fastened state. The curved surface  22  of the fastening ring  18 , which is positioned under and pressed by the rod  12 , is brought into close contact with the outer surface of the upper portion of the insert  21  and fixedly holds the insert  21 . 
     At this time, because a predetermined interval is defined between the screw head  17  of the screw body  11  and the fastening ring  18 , the possibility of them to come into contact witheach other is eliminated. 
     In succession, by forming the punched portions  19  by punching the sidewall of the housing  16  on both sides of the fastening ring  18 , the fastening ring  18  is secured, by which the installation of the vertebral pedicle screw  10  and the rod  12  is completed. 
     Accordingly, in the state in which the vertebral pedicle screw is installed, the entire rod-side assemblycan be slidingly moved to some extent within a predetermined angle with respect to the screw body which is driven into the vertebral pedicle, due to the slidingcontact between the screw head and the insert, etc., and as a result, even when a shock is applied to the rod due to the motion of a patient, the shock can be absorbed as the rod-side assembly is slidingly moved, whereby it is possible to minimize the shock transferred to the vertebral pedicle through the screw body. 
     In the conventional art, due to the fact that the screw body is integrally coupled to the rod-side assembly, the shock is directly transferred from the rod-side assembly through the screw bodyto the vertebral pedicle. In the present invention, unlike the conventional art, since the shock can be absorbed through the sliding movement of the rod-side assembly, the pain of the patient can be relieved to the maximum. Also, due to the absorption of the shock, it is possible to prevent the body part receiving the surgical operation, in particular, where the screw body is driveninto the vertebral pedicle, from being distorted, and thereby, the stabilization of the body part receiving the surgical operation can be ensured. 
     Also, when placing the rod into the housing after driving the screw body into the vertebral pedicle, since the entire housing including the rod can be adjusted in the angle thereof, the rod placing task can be easily and precisely carried out in a short period, whereby the surgical operation for the spine can be more efficiently conducted. 
     Although a preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.