Patent Publication Number: US-2005131410-A1

Title: Rotary device for retrieving spinal column under treatment

Description:
FIELD OF THE INVENTION  
      The present invention relates generally to a spinal surgical care device, and more particularly to a rotary device for retrieving spine column under treatment.  
     BACKGROUND OF THE INVENTION  
      The inventor of this application in US patent published No. 20030187434 A1 discloses a vertebral fixation device comprising a fixation seat, a fixation block, and a fastening bolt. The fixation seat is provided with a receiving slot for receiving a vertebral fixation rod. The fixation block is engaged with the fixation seat such that the vertebral fixation rod is pressed by the fixation block, and that two retaining edges of the fixation block are retained in two retaining recesses of the fixation seat. The fastening bolt is engaged with a threaded through hole of said fixation block such that one end of the fastening bolt presses against the vertebral fixation rod. Although this design improves the conventional backbone-fixing devices, there are at least the following defects which call for further improvements: 1) the contact of the spherical head fastening screw and the fixation rod is restricted to a thin line; and 2) the fixation block has to be fabricated precisely to well fasten the fixation rod in the receiving slot of the fixation seats. For this reason, the fixation rod is susceptible to unintentional displacement in a spinal surgery in progress. Such a displacement of the back-retrieving rod often affects adversely the outcome of the spinal surgery. U.S. Pat. No. 6,565,565 B1 discloses a device for securing spinal rods, which is similar to that described in the US patent published No. 20030187434 A1 with the common drawbacks.  
     SUMMARY OF THE INVENTION  
      A primary objective of the present invention is to provide a rotary device for fixing spinal column under treatment without the drawbacks of the prior art.  
      A vertebral retrieval device constructed according to the present invention comprises: 
          a retrieval rod which is used to retrieve spinal segments under treatment;     a fixation seat provided with a receiving slot for receiving the retrieval rod, said receiving slot being provided on two opposite side walls with a retaining recess, and in a bottom with a through hole;     a fastening screw is provided with a spherical head made integrally therewith, wherein said spherical head is rotatably received in said fixation seat when said fastening screw is inserted into said through hole of said fixation seat;     a C-shaped ring provided with a concave down surface on one side, said C-shaped ring being able to be elastically deformed, received in said fixation seat and retained in said fixation seat by an expansion force resulting from said deformation, while said concave down surface resting on the spherical head of said fastening screw and another side of said C-shaped ring being adapted to receive said retrieval rod;     a fixation assembly comprising a rotary fixation element provided with a threaded through hole, and two retaining edges opposite to each other; a pressing element having a projection at one side and a groove at another side; and a pressing screw having a round hole adapted to receive said projection of said pressing element, wherein said rotary fixation element is engaged with said fixation seat such that the two retaining edges are retained in said retaining recesses of said fixation seat, said pressing screw is threadably engaged in said threaded through hole of said rotary fixation element, and the pressing element is able to be pressed against said retrieval rod by threading said pressing screw, when the groove of said pressing element rests on said retrieval rod and said projection of said pressing element is received in said round hole of said pressing screw.        

      Preferably, said retaining recesses of said fixation seat are located in inner sides of the two side walls of said receiving slot; wherein said retaining edges of said rotary fixation element are located in outer edges of said rotary fixation element. More preferably, said retaining edges of said rotary fixation element are provided with an inclined plane having a higher outer side and a lower inner side; wherein said retaining recesses of said fixation seat are provided with an inclined plane having a higher outer side and a lower inner side, wherein said rotary fixation element is engaged with said fixation seat such that said inclined planes of said rotary fixation element and said fixation seat are in contact with each other, and thus the two side walls of said receiving slot of said fixation seat are further prevented from departing from each other.  
      Preferably, said C-shaped ring is provided with a groove on said another side thereof, and said groove of said C-shaped ring is adapted to receive said retrieval rod;  
      Preferably, a tool hole is provided in said pressing screw for facilitating the threadable engagement with said rotary fixation element.  
      Said C-shaped ring of the present invention is elastically retained in the fixation seat and is pressed against the spherical head of the fastening screw, creating more friction between the C-shaped ring and the fixation seat/the spherical head of the fastening screw, so that the fastening thereof is improved. The groove of the C-shaped ring further enhances the friction and the fastening effect.  
      The pressing screw of the present invention can be threaded to press the pressing element against the fixation rod, which presses the C-shaped ring, which presses the spherical head of the fastening screw, which presses the fastening seat, so that the retrieval rod is gripped firmly in the receiving slot of the fixation seat, and thus it is secured to the fastening screw which has be fastened to a pedicle of a vertebra in advance.  
      The features and the advantages of the present invention will be more readily understood upon a thoughtful deliberation of the following detailed description of the present invention with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows an exploded view of a first preferred embodiment of the present invention.  
       FIG. 2  shows a perspective view of the first preferred embodiment of the present invention shown in  FIG. 1 , when the fixation assembly  60  is assembled.  
       FIG. 3  shows a perspective view of the first preferred embodiment of the present invention shown in  FIG. 1  at work.  
       FIG. 4  shows a sectional view of the first preferred embodiment of the present invention shown in  FIG. 3 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      As shown in  FIGS. 1-4 , a vertebral retrieval device  10  of the present invention comprises a retrieval rod  20 , a fixation seat  30 , a fastening screw  40 , a C-shaped ring  50 , and a fixation assembly  60 .  
      The fixation seat  30  is provided with a U-shaped receiving slot  31  which has two retaining recesses  33  on the two inner walls, two clamping slots  34  on the outer walls, and a through hole  32  in the bottom.  
      The fixation assembly  60  has a rotary fixation element  61 , a pressing screw  62  and a pressing element  63 , which can be assemble before using, as shown in  FIG. 2 . The rotary fixation element  61  is provided with a threaded through hole  612  at the axial center, and two opposite retaining edges  611  protruding radically from the outer surface. The pressing element  63  has a cylindrical projection  632  at one side and a groove  631  at another side. The pressing screw  62  has a round hole  623  for receiving said projection  632  of said pressing element, and is threadably engaged in the threaded through hole  612  of the rotary fixation element  61 .  
      The fastening screw is provided with a shank  41  and a spherical head  42  made integrally therewith, wherein said spherical head  42  is rotatably received in said fixation seat  30  when said shank  41  is protruding from said through hole  32  of said fixation seat. The shank  41  of the fastening screw  41  is then fastened to a pedicle of a vertebra under treatment (not shown in the drawings).  
      The C-shaped ring  50  is provided with a concave down surface  51  on one side, and a groove  54  adapted to receive said retrieval rod  20  on another side  52  thereof. Said C-shaped ring  50  can be elastically deformed due to an opening  53 , received in said fixation seat  30  and retained in said fixation seat by an expansion force resulting from said deformation, while said concave down surface  51  resting on the spherical head  42  of said fastening screw  40 .  
      The retrieval rod  20  is received in the receiving slot  31  of the fixation seat  30  and on the groove  54  of the C-shaped ring  50 .  
      The fixation assembly  60  is rotated and connected to the fixation seat  30 , wherein the rotary fixation element  61  is engaged with said fixation seat  30  such that the two retaining edges  611  are retained in said retaining recesses  33  of said fixation seat  30 . The pressing element  63  is able to be pressed against said retrieval rod  20  by threading said pressing screw  62 , wherein the groove  631  of said pressing element rests on said retrieval rod  62  and said projection  632  of said pressing element is received in said round hole  623  of said pressing screw. The pressing screw  62  is provided with a tool hole  622  for facilitating the threadable engagement with said rotary fixation element  61  and the pressing.  
      As shown in  FIG. 4 , the retaining edges  611  of said rotary fixation element are provided with an inclined plane having a higher outer side and a lower inner side; and the retaining recesses  33  of said fixation seat  30  are provided with an inclined plane having a higher outer side and a lower inner side, wherein said rotary fixation element  61  is engaged with said fixation seat  30  such that said inclined planes of said rotary fixation element  61  and said fixation seat  30  are in contact with each other, and thus the two side walls of said receiving slot  31  of said fixation seat are held by the rotary fixation element  61 .