Abstract:
An interbody fusion device related to implants for orthopedic surgery has a hollow skeleton made of titanium alloy to hold nonstructural cancellous bone graft. The skeleton is a U-shaped plate, whose front wall is disposed with holes. The upper and the lower end of the bottom of the U-shaped plate have inclined holes of ladder shape. The bigger end of the inclined hole is placed on the bottom surface of the bottom of the U-shaped plate, and the smaller end of the inclined hole is placed on the corresponding surface of the bottom of the U-shaped plate; the inclined hole of the U-shaped plate is disposed with screw inside. The present invention has small volume and the vertebra is partial removal, so it is more reliable for interbody fusion.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an implant for orthopedic surgery. 
       BACKGROUND OF THE INVENTION 
       [0002]    To repair the damaged vertebrae, artificial vertebral body is come out in the medical community aboard, such as titanium cage (TMC). The titanium cage is a hollow skeleton made of titanium alloy formed by titanium alloy plate of several meshes and set in a circle, the inner of the titanium cage is disposed with ring-shaped support. When insert the TMC, the corpectomy or the total removal of the vertebral body needs to be done, and then pack the bone graft in it. The raised spots on the both ends of the titanium cage withstand the cephalad and the caudad endplates separately. With bone growth between vertebral body and bone graft inside the TMC, the fusion of the index level and adjacent vertebral body will be achieved. The minute vessels will grow with the bone graft through the meshes of the titanium cage, achieving the treatment of interbody fusion. 
         [0003]    But the titanium cage has these disadvantages below: 
         [0000]    1). To implant the bulky size of cylindrical titanium cage, corpectomy or the total removal of the damaged vertebral body needs to be done, the patient will blood much and it will damage the blood supply to the vertebrae.
 
2). The titanium cage is fixed to the vertebrae by the raised spots on the both ends of the titanium cage withstanding the cephalad and the caudad endplates separately, which will be easily caved in.
 
3). Bone grafting could not be took in the surrounding of the titanium cage, and the titanium cage does not have the effect of damper to keep out the vertebrae canal, so that the bone graft could enter in and compress the nerve structure.
 
4). The titanium cage would encase the implant bone, keep off the X-ray and prevent from observing the growth of the bone.
 
       SUMMARY OF THE INVENTION 
       [0004]    The object of the present invention is to provide interbody fusion device, which could prevent the disadvantages of the titanium cage. 
         [0005]    The present invention provides interbody fusion device, which is a hollow skeleton made of titanium alloy for holding bone graft, wherein the skeleton is a U-shaped plate, the front wall is equipped with several holes while the back wall has not; the upper end and the lower end of the bottom of the U-shaped plate are configured separately with inclined hole of ladder shaped, the bigger end of the inclined hole is placed on the bottom surface of the bottom of the U-shaped plate, and the smaller end of the inclined hole is placed on the corresponding surface of the bottom of the U-shaped plate; the inclined hole of the U-shaped plate is disposed with screw inside. 
         [0006]    The outward of the cap of the two screws are circle-arc surface, the boundary between the bigger end and the smaller end of the inclined holes is circle arc section, which is coupled to the circle-arc surface. 
         [0007]    The outer surface of the back wall of the U-shaped plate is configured with slope along the free end; the outer surface of the front wall is configured with slope along the free end. The slope provides an insert guide head for the U-shaped plate in the surgery. 
         [0008]    The upper ends and lower ends of the back wall, front wall and the bottom of the U-shaped plate are configured with flanges. The flanges produce friction between the U-shaped plate and the caudad endplate of the upper vertebral body and the cephalad endplate of the lower one, which improves the stability of the U-shaped plate. 
         [0009]    The upper and the lower ends of the U-shaped plate is configured parallel to each other or not. The upper and the lower ends of the U-shaped plate parallel to each other makes it more fit to the thoracic vertebrae end-plate; the upper and the lower ends of the U-shaped plate unparallel to each other makes it more fit to the lumbar vertebrae end-plate; they could prevent collapse or fracture of the upper and the lower lumbar vertebrae due to the partial pressure. 
         [0010]    The present invention of interbody fusion device (it could be also called U-shaped artificial vertebrae) comprises a titanium alloy U-shaped plate of 0.6 cm and two screws locking the U-shaped plate between the caudad endplate of the upper vertebral body and the cephalad endplate of the lower one. The inner and the front of the U-shaped plate could be implanted with large amount of bone graft, making it easily to form biological connection. Corpectomy or the total removal of the damaged vertebral body is not needed and only one-third of posterior part of vertebral body is removed because of the small volume of the U-shaped plate. It keeps the anterior column and part of middle column of the damaged vertebral body. It retains most of the vertebrae bone, which reduces blooding and supports the vertebrae blood supply, beneficial to the interbody fusion of the anterior-middle column of the damaged vertebrae. The back wall of the U-shaped plate serving as a gate is disposed without holes, which prevent the entry of the bone graft to the vertebrae canal and the compression to the nerve structures. The front wall of the U-shaped plate is disposed with holes, making it easier for the biological connecting. The minute vessel grows accompanying with the bone by the holes. The inclined holes at the upper and the lower end of the bottom of the U-shaped plate are disposed with screws inside, the screws lock to the caudad endplate of the upper vertebral body and the cephalad endplate of the lower one, preventing the collapse of the implant. The interbody fusion situation could be direct evaluated by the observing the healing of the front two-third vertebrae when taking imaging examination. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  illustrates the structure of the first embodiment of the present invention; 
           [0012]      FIG. 2  illustrates the structure of the U-shaped plate of the first embodiment; 
           [0013]      FIG. 3  illustrates the upward view of the U-shaped plate of the first embodiment; 
           [0014]      FIG. 4  illustrates the cross-section view of the U-shaped plate of the first embodiment; 
           [0015]      FIG. 5  illustrates the structure of the screw of the first embodiment; 
           [0016]      FIG. 6  illustrates the status of used in the first embodiment; 
           [0017]      FIG. 7  illustrates the structure of the second embodiment of the present invention; 
           [0018]      FIG. 8  illustrates the U-shaped plate of the second embodiment; 
           [0019]      FIG. 9  illustrates the upward view of the U-shaped plate of the second embodiment; 
           [0020]      FIG. 10  illustrates the sectional structure of the U-shaped plate of the second embodiment; 
           [0021]      FIG. 11  illustrates the status of used in the second embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The First Embodiment 
       [0022]    The object of the present invention is to provide a preferred embodiment of fusion device for vertebral body. The  FIG. 1  illustrates the structure of the first embodiment; it comprises a U-shaped plate  1  and two screws  2 . 
         [0023]    The U-shaped plate  1  is hollow skeleton made of titanium alloys with thickness of 0.6 cm.  FIG. 2  illustrates the structure of the U-shaped plate. The back wall  11  of the U-shaped plate  1  connects to the front wall  12  by the bottom  14 . The upper end and the lower end of the U-shaped plate  1  are disposed unparallel to each other and configured with included angle of slope. The upper ends of the back wall  11 , front wall  12  and the bottom  14  are configured with flanges  13 . The lower ends of the back wall  11 , the front wall  12  and the bottom  14  are configured with flanges  15 . The back wall  11 , the front wall  12  and the bottom  14  are circling around forming the inside groove  16 . 
         [0024]    The outer surface of the back wall  11  of the U-shaped plate  1  is configured with slope  111  along the free end. The middle section of the back wall  11  near the bottom  14  is configured with a back groove  112  extending to the edge. 
         [0025]    Refer to the  FIG. 1 : The outer surface of the front wall  12  of the U-shaped plate  1  is configured with slope  121  along the free end. The middle section of the front wall  12  near the bottom  14  is configured with a front groove  122  extending to the edge. Several holes  123  are disposed on the front wall  12  evenly disposed. 
         [0026]    The slope  111  on the back wall  11  and the slope  121  on the front wall  12  of the U-shaped plate  1  provide a leading section for the placement of the U-shaped plate in the surgery. The back groove  112  on the back wall  11  and the front groove  122  on the front wall  12  of the U-shaped plate provide a gripper for holding the U-shaped plate in the surgery. 
         [0027]    Refer to the  FIG. 3 : the upper and the lower ends of the bottom  14  are disposed with inclined hole  141  of ladder shaped separately; the angle of the axis of the inclined hole  141  with the normals of the bottom  14  is 50 degrees. The bigger end of the two inclined holes  141  is disposed on the bottom surface of the bottom  14  and the smaller end on the corresponding surface of the bottom  14 . The boundary between the bigger end and the smaller end of the inclined hole  141  is circle- arc section  1411 . The middle of the bottom  14  is disposed with screw hole  142 , to fix an assistant potable bar to put the U-shaped plate  1  to the opening position of the damaged vertebrae. 
         [0028]    The screw  2  is made of titanium alloy.  FIG. 5  illustrates the structure of the screw  2 . The forward part of the screw body  21  is configured with cone thread section  22 , which could be easily screwed to the bone and have good performance of anti-pull out. The backend of the screw body  21  is disposed with cap  23 . Refer to  FIG. 1 ; the end face of the cap  23  has hexagon jack  231 , adapting to the hexagon screw-driver of high safety in the surgery. The outward of the cap  23  is circle arc surface  232 , which is coupled to the circle-arc section  1411  of the inclined hole  141 . 
         [0029]    Refer to the  FIG. 6 , the usage status of the first embodiment of the interbody fusion device. The rear edge of the damaged lumbar vertebrae  3  is disposed with a longitudinal groove to contain the U-shaped plate. Retain the anterior column  31  and part of the middle column of the damaged lumbar vertebrae. Put the bone graft into the inner groove  16  of the U-shaped plate, observe the bone graft filling status through the holes  123  on the front wall  12  and adjust the filler to make the inner groove  16  of the U-shaped plate filling with bone graft. Hold the back groove  112  on the back wall  11  and the front groove  122  of the front wall  12  with gripper; put the free ends of the back wall  11  and the front wall  12  towards the longitudinal groove of the damaged lumbar vertebrae  3 . The front wall  12  goes towards the anterior column  31 . And the front of the front wall  12  can be implanted with bone for biological connecting. 
         [0030]    The back wall  11  of the U-shaped plate  1  goes towards the vertebrae canal, preventing the entry of the bone graft to the vertebrae canal. If the bone graft gets into the vertebrae canal, nerve compression would occur. The flanges  13  and flanges  15  on the both ends of the u-shaped plate  1  withstand the caudad endplate of the upper vertebral body  4  and the cephalad endplate of the lower vertebral body  5  separately. Two screws  2  pass though the corresponding inclined holes  141  on the both end of the bottom of the U-shaped plate  1 , and the two screws  2  reach out of the both ends of the bottom. The cone thread sections  22  of the two screws  2  lock the bottom of the cephalad lumbar vertebrae  4  and the top of the caudad lumbar vertebrae  5 , and the circle arc surface  232  on the cap  23  of the screw  2  contact with the circle- arc section  1411  of the inclined hole  141 . The U-shaped plate  1  is fixed between the cephalad lumbar vertebrae  4  and the caudad lumbar vertebrae  5  by the two screws  2 . 
       The Second Embodiment 
       [0031]    The present invention provides with the second embodiment of the interbody fusion device for the thoracic vertebral body.  FIG. 7  illustrates the structure of the second embodiment, which comprises of a U-shaped plate  6  and two screws  2 . The structure of the screws  2  is the same with that of the first embodiment. 
         [0032]    The U-shaped plate  6  is hollow skeleton made of titanium alloys with thickness of 0.6 cm.  FIG. 8  illustrates the structure of the U-shaped plate. The back wall  61  of the U-shaped plate  6  connects to the front wall  62  by the bottom  64 . The upper end and the lower end of the U-shaped plate  6  are disposed parallel to each other and configured with included angle of slope, which makes it more fit to the thoracic vertebrae end-plate. The upper ends of the back wall  61 , front wall  62  and the bottom  64  are configured with flanges  63 . The back wall  61 , the front wall  62  and the bottom  64  are circling around forming the inside groove  65 . 
         [0033]    The outer surface of the back wall  61  of the U-shaped plate  6  is configured with slope  611  along the free end. The middle section of the back wall  61  near the bottom  64  is configured with a back groove  612  extending to the edge. 
         [0034]    The outer surface of the front wall  62  of the U-shaped plate  6  is configured with slope  621  along the free end. The middle section of the front wall  62  near the bottom  64  is configured with a front groove  622  extending to the edge. Four holes  623  are disposed on the front wall  62  evenly disposed. 
         [0035]    The slope  611  on the back wall  61  and the slope  621  on the front wall  62  of the U-shaped plate  6  provide a leading section for the placement of the U-shaped plate in the surgery. The back groove  612  on the back wall  11  and the front groove  622  on the front wall  62  of the U-shaped plate provide a gripper for holding the U-shaped plate in the surgery. 
         [0036]    Refer to the  FIG. 10 : the upper and the lower ends of the bottom  64  are disposed with inclined hole  641  of ladder shaped separately; the angle of the axis of the inclined hole  641  with the normals of the bottom  64  is 50 degrees. The bigger end of the two inclined holes  641  is disposed on the bottom surface of the bottom  64  and the smaller end on the corresponding surface of the bottom  64 . The boundary between the bigger end and the smaller end of the inclined hole  641  is circle- arc section  6411 . The circle-arc section  6411  is coupled to the circle-arc surface  232  on the outward of the cap  23  of the screws  2 . The middle of the bottom  64  is disposed with screw hole  642 , to fix an assistant potable bar to put the U-shaped plate  6  to the opening position of the damaged thoracic vertebrae. 
         [0037]    Refer to the  FIG. 11 , the usage status of the second embodiment of the interbody fusion device. The rear edge of the damaged thoracic vertebrae  7  is disposed with a longitudinal groove to contain the U-shaped plate  6 . Retain the anterior column  71  and part of the middle column of the damaged thoracic vertebrae. Put the bone graft into the inner groove  65  of the U-shaped plate, observe the bone graft filling status through the holes  623  on the front wall  62  and adjust the filler to make the inner groove  65  of the U-shaped plate full with bone graft. Hold the back groove  612  on the back wall  61  and the front groove  622  of the front wall  62  with gripper; put the free ends of the back wall  61  and the front wall  62  towards the longitudinal groove of the damaged thoracic vertebrae  7 . The front wall  62  goes towards the anterior column  71 . And the front of the front wall  62  can be implanted with bone for biological connecting. 
         [0038]    The back wall  61  of the U-shaped plate  6  goes towards the vertebrae canal, and the back wall  61  can prevent the entry of the bone graft to the vertebrae canal. If the bone graft gets into the vertebrae canal, nerve compression would occur. The flanges  63  on the both ends of the u-shaped plate  6  withstand the caudad endplate of the upper vertebral body  8  and the cephalad endplate of the lower vertebral body  9  separately. Two screws  2  pass though the corresponding inclined holes  641  on the both end of the bottom of the U-shaped plate  6 , and the two screws  2  reach out of the both ends of the bottom. The cone thread sections  22  of the two screws  2  lock the bottom of the cephalad thoracic vertebrae  8  and the top of the caudad thoracic vertebrae  9 , and the circle arc surface  232  on the cap  23  of the screw  2  contact with the circle-arc section  6411  of the inclined hole  641 . The U-shaped plate  6  is fixed between the cephalad thoracic vertebrae  8  and the caudad thoracic vertebrae  3  by the two screws  2 . 
         [0039]    Although the present invention has been fully described by ways of preferred embodiments with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scopes of the present invention, they should be construed as being included therein.