Patent Publication Number: US-2018036049-A1

Title: Bone plate and bone plate system

Description:
TECHNICAL FIELD 
     The present invention relates to a bone plate and a bone plate system. 
     BACKGROUND ART 
     There has been known a bone plate to be fixed to a bone through use of a screw having a male thread formed on a head portion. For example, a bone plate having a fixation hole is disclosed in Patent Literature 1. The fixation hole has a female thread formed so as to be engaged with the male thread formed on the head portion of the screw. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Patent Translation Publication No. 2015-511859 
     SUMMARY OF INVENTION 
     Technical Problem 
     The female thread is formed in advance on an inner surface of the fixation hole of the bone plate disclosed in Patent Literature 1. Thus, an axial direction of the screw driven into the fixation hole is determined by a center axis direction of the fixation hole. However, an angle of the screw to the bone is required to be appropriately determined in consideration of a surface shape of the bone, strength of the bone, and the like. With the bone plate disclosed in Patent Literature 1, it is difficult to fasten the screw to the bone at a desired angle unless a surgeon deforms the bone plate or reprocesses the fixation hole. 
     It is an object of the present invention to provide a bone plate and a bone plate system that enable a screw to be fastened to a bone at a desired angle. 
     Solution to Problem 
     In order to solve the above-mentioned problem, according to one embodiment of the present invention, there is provided a bone plate, including: an upper surface on a side opposite to a bone; a lower surface on a side closer to the bone; and at least one first hole connecting the upper surface and the lower surface and being configured to allow insertion of a screw. The first hole has an upper inner peripheral surface on an upper surface side and a lower inner peripheral surface on a lower surface side. The upper inner peripheral surface has an inner diameter decreasing toward the lower surface, and the lower inner peripheral surface has an inner diameter increasing toward the lower surface. The lower inner peripheral surface includes at least one first region inclined at a first angle with respect to a center axis of the first hole and at least one second region inclined at a second angle with respect to the center axis of the first hole. 
     In the above-mentioned bone plate, the screw may include a head portion and a shaft portion, each having a male thread formed thereon. The lower inner peripheral surface may have no female thread formed in advance, and the female thread may be formed through rotation of the head portion after the screw is inserted into the first hole. 
     In the above-mentioned bone plate, the lower inner peripheral surface may include one set of the first regions facing each other across the center axis of the first hole and one set of the second regions facing each other across the center axis of the first hole. 
     In the above-mentioned bone plate, the one set of first regions may be arranged so as to face each other in a longitudinal direction of the bone plate, and the one set of second regions may be arranged so as to face each other in a direction intersecting with the longitudinal direction of the bone plate. 
     In the above-mentioned bone plate, the first angle maybe larger than the second angle. 
     In the above-mentioned bone plate, a plurality of the first holes may be arranged at intervals in a longitudinal direction of the bone plate, and at least one of the plurality of first holes may include the one set of first regions arranged so as to face each other in the longitudinal direction of the bone plate and the one set of second regions arranged so as to face each other in the direction intersecting with the longitudinal direction of the bone plate. 
     The above-mentioned bone plate may further include at least one second hole connecting the upper surface and the lower surface and being configured to allow insertion of the screw. The second hole may have an upper inner peripheral surface on the upper surface side and a lower inner peripheral surface on the lower surface side. The upper inner peripheral surface may have an inner diameter decreasing toward the lower surface, and the lower inner peripheral surface may have an inner diameter in a predetermined direction increasing toward the lower surface. The lower inner peripheral surface may include at least one first region inclined at a first angle with respect to a center axis of the second hole and at least one second region in parallel to the center axis of the second hole. 
     In order to solve the above-mentioned problem, according to another embodiment of the present invention, there is provided a bone plate system including the above-mentioned bone plate and the screw. The screw includes a head portion and a shaft portion, each having a male thread formed thereon. The lower inner peripheral surface has no female thread formed in advance, and the female thread is formed through rotation of the head portion after the screw is inserted into the first hole. 
     Advantageous Effects of Invention 
     According to the present invention, the screw can be fastened to a bone at a desired angle. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a bone plate system according to one embodiment of the present invention. 
         FIG. 2  is a side view of the bone plate system in a longitudinal direction. 
         FIG. 3A  and  FIG. 3B  are side views of the bone plate system in a width direction.  FIG. 3A  is a view for illustrating screws in a center, and  FIG. 3B  is a view for illustrating screws at an end portion. 
         FIG. 4  is a side view of the screw. 
         FIG. 5  is a perspective view of an upper surface side of a bone plate. 
         FIG. 6  is a perspective view of a lower surface side of the bone plate. 
         FIG. 7  is a plan view of the bone plate. 
         FIG. 8  is a bottom view of the bone plate. 
         FIG. 9  is a side view of the bone plate in the longitudinal direction. 
         FIG. 10  is a side view of the bone plate in the width direction. 
         FIG. 11  is a partially enlarged view of the bone plate (portion F of  FIG. 5 ). 
         FIG. 12  is a partially enlarged view of the bone plate (portion G of  FIG. 6 ). 
         FIG. 13  is a sectional view of the bone plate (taken along the line A-A of  FIG. 7 ) in the longitudinal direction. 
         FIG. 14A ,  FIG. 14B , and  FIG. 14C  are enlarged partial sectional views of the bone plate (portion E of  FIG. 13 ).  FIG. 14A  is a view for illustrating a state before a screw is inserted.  FIG. 14B  is a view for illustrating a state in which the screw is driven straight.  FIG. 14C  is a view for illustrating a state in which the screw is driven obliquely. 
         FIG. 15A ,  FIG. 15B , and  FIG. 15C  are enlarged partial sectional views of the bone plate (portion C-C of  FIG. 7 ).  FIG. 15A  is a view for illustrating a state before the screw is inserted.  FIG. 15B  is a view for illustrating a state in which the screw is driven straight.  FIG. 15C  is a view for illustrating a state in which the screw is driven obliquely. 
         FIG. 16  is an enlarged partial sectional view of the bone plate (portion D of  FIG. 13 ). 
         FIG. 17  is an enlarged sectional view of the bone plate (taken along the line B-B of  FIG. 7 ). 
         FIG. 18A ,  FIG. 18B ,  FIG. 18C , and  FIG. 18D  are side views for illustrating a schematic configuration of a jig.  FIG. 18A  is a view for illustrating an internal configuration of the jig.  FIG. 18B  is a view for illustrating a state in which the jig is placed upright.  FIG. 18C  is a view for illustrating a state in which the jig is placed obliquely.  FIG. 18D  is another view for illustrating a state in which the jig is placed obliquely. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Now, one embodiment of the present invention is described with reference to the drawings. 
       FIG. 1  is a perspective view of a bone plate system according to one embodiment of the present invention.  FIG. 2  is a side view of the bone plate system in a longitudinal direction.  FIG. 3A  and  FIG. 3B  are side views of the bone plate system in a width direction.  FIG. 3A  is a view for illustrating screws in a center, and  FIG. 3B  is a view for illustrating screws at an end portion.  FIG. 1  to  FIG. 3D  are views for illustrating an example in which a plurality of screws  2  ( 2   a  to  2   i ) are fastened to a bone plate  1 .  FIG. 3A  is a view of the three screws  2   c,    2   d,  and  2   e  as viewed from the screw  2   e  side.  FIG. 3B  is a view of the two screws  2   h  and  2   i.    FIG. 4  is a side view of the screw  2 . In  FIG. 4 , the screw  2  is illustrated in an enlarged manner. 
       FIG. 5  is a perspective view of an upper surface side of the bone plate.  FIG. 6  is a perspective view of a lower surface side of the bone plate.  FIG. 7  is a plan view of the bone plate.  FIG. 8  is a bottom view of the bone plate.  FIG. 9  is a side view of the bone plate in the longitudinal direction.  FIG. 10  is a side view of the bone plate in the width direction. Both side surfaces of the bone plate in the longitudinal direction have the same shape. Further, both side surfaces of the bone plate in the width direction have the same shape. 
     The bone plate system includes the bone plate  1  and at least one screw  2 . The bone plate  1  is formed into an elongated flat plate-like shape as a whole. Further, the bone plate  1  is formed so as to curve in an arc-like shape as viewed in the longitudinal direction so that a lower surface of the bone plate  1  (surface on a lower side in  FIG. 2 ) is formed along a surface shape of a bone. As one example, the bone plate system is used to join and reinforce bones of small animals including dogs and cats. For example, a dimension of the bone plate  1  in the longitudinal direction can be set to about 100 mm. A dimension of the bone plate  1  in the width direction can be set to about 10 mm. A dimension of the bone plate  1  in a thickness direction can be set to about 2.5 mm. A material of the bone plate  1  is, for example, metal such as a titanium alloy, a resin, or the like. 
     The bone plate  1  includes a center portion  3  and end portions  4  at both ends of the center portion  3 . A maximum width dimension of each of the end portions  4  is larger than a maximum width dimension of the center portion  3 . 
     In the center portion  3  of the bone plate  1 , a plurality of (seventeen in  FIG. 1 ) holes  5  are formed in line at equal intervals in the longitudinal direction. The width dimension of the center portion  3  repeatedly changes so as to be maximum at a center of each of the holes  5  in the longitudinal direction and minimum at each of intermediate positions between the adjacent holes  5 . Further, the width dimension of the center portion  3  is minimum at a position at which the center portion  3  is connected to each of the end portions  4  in the longitudinal direction. A thickness dimension of the center portion  3  repeatedly changes so as to be maximum at the center of each of the holes  5  in the longitudinal direction and minimum at each of the intermediate positions between the adjacent holes  5 . The shape of the lower surface of the bone plate  1  can reduce a contact area with a surface of the bone as compared to a case where the shape of the lower surface of the bone plate is flat. 
     In each of the end portions  4  of the bone plate  1 , a hole  6  is formed on a side closer to the center portion  3 . Further, in each of the end portions  4 , two holes  7  are formed on a side farther from the center portion  3  with an interval in the width direction. The width dimension of each of the end portions  4  is increased so as to be minimum at a position at which the end portion  4  is connected to the center portion  3  and maximum at a center of the two holes  7  in the longitudinal direction. 
     Each of the screws  2  includes a head portion  21  and a shaft portion  22 . A male thread  23  is formed on a lower portion of the head portion  21 . A male thread  24  is formed on the shaft portion  22 . The screw  2  can also be called a “locking screw”. An outer diameter of the head portion  21  is larger than an outer diameter of the shaft portion  22 . The outer diameter of the shaft portion  22  is smaller than each of inner diameters (minimum inner diameters) of the holes  5  to  7 . The outer diameter of the head portion  21  is larger than each of inner diameters (minimum inner diameters) of the holes  5  to  7 . Through rotation of the screw  2 , an inner wall of a corresponding one of the holes  5  to  7  is scraped by the male thread  23  of the head portion  21  (corresponding one of the holes  5  to  7  is subjected to tapping). As a result, the head portion  21  of the screw  2  is fixed to the corresponding one of the holes  5  to  7 . 
     The holes  5  connect an upper surface (surface on an upper side in  FIG. 2 ) of the bone plate  1  and a lower surface (surface on a lower side in  FIG. 2 ) of the bone plate  1  to each other. A center axis of each of the holes  5  is approximately perpendicular to the upper surface and the lower surface of the bone plate  1 . Each of the holes  5  has an approximately cylindrical shape as a whole. A female thread is not formed in advance on an inner surface of each of the holes  5  (the inner surface of each of the holes  5  is not subjected to tapping). The female thread is cut by the male thread  23  of the head portion  21  of the screw  2 . The screws  2  can be driven into the holes  5  at various angles. For example, as illustrated in  FIG. 1  to  FIG. 3B , the screw  2   e  is driven into a hole  5   e  so that an axis of the screw  2   e  matches a center axis of the hole  5   e.  The screw  2   d  is driven into a hole  5   d  so that an axis of the screw  2   d  is inclined with respect to a center axis of the hole  5   e  in the width direction of the bone plate  1 . The screw  2   f  is driven into a hole  5   f  so that an axis of the screw  2   f  is inclined with respect to a center axis of the hole  5   f  in the longitudinal direction of the bone plate  1 . A structure of each of the holes  5  for achieving the above-mentioned function is described later in detail. 
     The holes  6  connect the upper surface of the bone plate  1  and the lower surface of the bone plate  1  to each other. Each of the holes  6  has an approximately cylindrical shape as a whole. A center axis of each of the holes  6  is approximately perpendicular to the upper surface and the lower surface of the bone plate  1 . A female thread is not formed in advance on an inner surface of each of the holes  6  (the inner surface of each of the holes  6  is not subjected to tapping). The female thread is cut by the male thread  23  of the head portion  21  of each of the screws  2 . The screws  2  can be driven into the holes  6  at a predetermined angle. For example, the screw  2  is driven into a corresponding one of the holes  6  so that the axis of the screws  2  matches a center axis of the corresponding one of the holes  6 . A structure of each of the holes  6  for achieving the above-mentioned function is described later in detail. 
     The holes  7  connect the upper surface of the bone plate  1  and the lower surface of the bone plate  1  to each other. A center axis of each of the holes  7  is approximately perpendicular to the upper surface and the lower surface of the bone plate  1 . Each of the holes  7  has an approximately cylindrical shape as a whole. A female thread is not formed in advance on an inner surface of each of the holes  7  (the inner surface of each of the holes  7  is not subjected to tapping). The female thread is cut by the male thread  23  of the head portion  21  of each of the screws  2 . The screws  2  can be driven into the holes  7  at various angles. For example, as illustrated in  FIG. 1  to  FIG. 3B , the screw  2   h  is driven into a hole  7 h so that an axis of the screw  2   h  matches a center axis of the hole  7 h. The screw  2   a  is driven into a hole  7   a  so that an axis of the screw  2   a  is inclined with respect to a center axis of the hole  7   a  in the longitudinal direction of the bone plate  1 . A structure of each of the holes  7  for achieving the above-mentioned function is described later in detail. 
       FIG. 11  is a partially enlarged view of the bone plate (portion F of  FIG. 5 ).  FIG. 12  is a partially enlarged view of the bone plate (portion G of  FIG. 6 ).  FIG. 13  is a sectional view of the bone plate (taken along the line A-A of  FIG. 7 ) in the longitudinal direction.  FIG. 14A ,  FIG. 14B , and  FIG. 14C  are enlarged partial sectional views of the bone plate (portion E of  FIG. 13 ).  FIG. 14A  is a view for illustrating a state before a screw is inserted.  FIG. 14B  is a view for illustrating a state in which the screw is driven straight.  FIG. 14C  is a view for illustrating a state in which the screw is driven obliquely.  FIG. 15A ,  FIG. 15B , and  FIG. 15C  are enlarged partial sectional views of the bone plate (portion C-C of  FIG. 7 ).  FIG. 15A  is a view for illustrating a state before a screw is inserted.  FIG. 15B  is a view for illustrating a state in which the screw is driven straight.  FIG. 15C  is a view for illustrating a state in which the screw is driven obliquely.  FIG. 16  is an enlarged partial sectional view of the bone plate (portion D of  FIG. 13 ). In  FIG. 14A  to  FIG. 15C , a black area represents a cross section of a region where the screw  2  and the hole  5  are engaged with each other. 
     As illustrated in  FIG. 11  and  FIG. 12 , each of the holes  5  has an upper inner peripheral surface  51  on an upper surface side of the bone plate  1  and a lower inner peripheral surface  52  on a lower surface side of the bone plate  1 . The upper inner peripheral surface  51  is formed along a shape of the upper portion of the head portion  21  of the screw  2 . The upper inner peripheral surface  51  is formed of a conical surface so that an inner diameter thereof decreases toward the lower surface. The lower inner peripheral surface  52  includes a plurality of conical surfaces so that an inner diameter thereof increases toward the lower surface as a whole. The lower inner peripheral surface  52  includes first regions  53  facing each other, each being inclined at a first angle (larger than 0 degrees) with respect to the center axis of the hole  5 . The lower inner peripheral surface  52  also includes second regions  54  facing each other, each being inclined at a second angle (larger than 0 degrees) with respect to the center axis of the hole  5 . One set of the first regions  53  facing each other across the center axis of the hole  5  is formed on the lower inner peripheral surface  52  so as to face each other in the longitudinal direction of the bone plate  1 . Further, one set of the second regions  54  facing each other across the center axis of the hole  5  is formed on the lower inner peripheral surface  52  so as to face each other in the width direction of the bone plate  1 . On an upper side of the second regions  54 , third regions  55  facing each other in parallel to the center axis of the hole  5  are formed so as to face each other in the width direction of the bone plate  1 . 
     The screw  2  can be driven into the hole  5  described above so that the axis of the screw  2  matches the center axis of the hole  5 . Further, the screw  2  can be driven into the hole  5  so that the axis of the screw  2  is inclined in the longitudinal direction or the width direction of the bone plate  1  with respect to the center axis of the hole  5 . 
     As illustrated in  FIG. 14A , the first regions  53  face each other, each being inclined at the first angle (15 degrees in  FIG. 14A ) with respect to a center axis Z 1  of the hole  5 .  FIG. 14B  is an illustration of a case where the screw  2  is driven into the hole  5  so that an axis z 1  of the screw  2  matches the center axis Z 1 . In this case, an entire periphery of the male thread  23  of the head portion  21  is engaged with the female thread formed on the first regions  53  and the second regions  54 . An outer peripheral surface of the upper portion of the head portion  21  is held in contact with the upper inner peripheral surface  51  to receive a reactive force generated by tightening the screw  2 .  FIG. 14C  is an illustration of a case where the screw  2  is driven into the hole  5  so that the axis z 1  of the screw  2  is inclined at the first angle (15 degrees in  FIG. 14C ) in the longitudinal direction of the bone plate  1  (direction in which the first regions  53  face each other) with respect to the center axis Z 1 . In this case, the periphery of the male thread  23  of the head portion  21  is at least partially engaged with the female thread formed on the first regions  53  and the second regions  54 . In  FIG. 14C , the male thread  23  of the head portion  21  is engaged with the first region  53  corresponding to the direction of inclination and the one set of second regions  54 . The outer peripheral surface of the upper portion of the head portion  21  is held in contact with the upper inner peripheral surface  51  to receive a reactive force generated by tightening the screw  2 . 
     As illustrated in  FIG. 15A , the second regions  54  face each other, each being inclined at the second angle (6 degrees in  FIG. 15A ) with respect to the center axis Z 1  of the hole  5 .  FIG. 15B  is an illustration of a case where the screw  2  is fastened into the hole  5  so that the axis z 1  of the screw  2  matches the center axis Z 1 . In this case, the entire periphery of the male thread  23  of the head portion  21  is engaged with the female thread formed on the first regions  53  and the second regions  54 . The outer peripheral surface of the upper portion of the head portion  21  is held in contact with the upper inner peripheral surface  51  to receive a reactive force generated by tightening the screw  2 .  FIG. 15C  is an illustration of a case where the screw  2  is driven into the hole  5  so that the axis z 1  of the screw  2  is inclined at the second angle (6 degrees in  FIG. 15C ) in the width direction of the bone plate  1  (direction in which the second regions  54  face each other) with respect to the center axis Z 1 . In this case, the periphery of the male thread  23  of the head portion  21  is at least partially engaged with the female thread formed on the first regions  53  and the second regions  54 . In  FIG. 15C , the entire periphery of the male thread  23  of the head portion  21  is engaged with the female thread formed on the first regions  53  and the second regions  54 . The outer peripheral surface of the upper portion of the head portion  21  is held in contact with the upper peripheral surface  51  to receive a reactive force generated by tightening the screw  2 . 
     The two first regions  53  that face each other can be formed in the following manner. Specifically, a hole is formed along the center axis Z 1  through use of a drill, and the upper inner peripheral surface  51  is formed by machining through use of a ball-end mill along the center axis Z 1 . After that, the first regions  53  are formed by machining through use of the ball-end mill along an axis Z 2  and an axis Z 3  respectively inclined at the first angle (15 degrees in  FIG. 14A ) in both directions in the longitudinal direction with respect to the center axis Z 1 . 
     The two second regions  54  that face each other can be formed in the following manner. Specifically, the hole is formed along the center axis Z 1  through use of a drill, and the upper inner peripheral surface  51  is formed by machining through use of a ball-end mill along the center axis Z 1 . After that, the second regions  54  are formed by machining through use of the ball-end mill along an axis Z 4  and an axis Z 5  respectively inclined at the second angle (6 degrees in  FIG. 15A ) in both directions in the width direction with respect to the center axis Z 1 . The third regions  55  are formed when the hole is formed along the center axis Z 1 . 
     As illustrated in  FIG. 16 , the hole  6  includes an upper inner peripheral surface  61  on the upper surface side of the bone plate  1  and a lower inner peripheral surface  62  on the lower surface side of the bone plate  1 . The upper inner peripheral surface  61  is formed along the shape of the upper portion of the head portion  21  of the screw  2 . The upper inner peripheral surface  61  is formed of a conical surface so that an inner diameter thereof decreases toward the lower surface. An inner diameter of the lower inner peripheral surface  62  is formed uniformly. Specifically, the lower inner peripheral surface  62  is entirely parallel to a center axis of the hole  6 . 
     The screw  2  can be driven into the hole  6  described above so that the axis of the screw  2  matches the center axis of the hole  6 . 
     As illustrated in  FIG. 3B ,  FIG. 10 , and  FIG. 17 , each of the end portions  4  curves in an arc-like shape so that center axes Z 6  of the two holes  7  intersect with each other at a center C of the arc. An angle of inclination (angle formed between an axis Z 7  that connects a center point between the two holes  7  on the arc and the center C of the arc and the center axis Z 6 ) of each of the holes  7  is set so that the axis of the screw  2  matches the center axis Z 6  to prevent interference with the screw  2  driven similarly into the neighboring hole  7  when the screw  2  is driven into the hole  7 . 
     The hole  7  does not have a region corresponding to the second regions  54  of the hole  5 , but is otherwise formed similarly to the hole  5 . The hole  7  includes an upper inner peripheral surface  71  on the upper surface side of the bone plate  1  and a lower inner peripheral surface  72  on the lower surface side of the bone plate  1 . The upper inner peripheral surface  71  is formed along the shape of the upper portion of the head portion  21  of the screw  2 . The upper inner peripheral surface  71  is formed of a conical surface so that an inner diameter thereof decreases toward the lower surface. The lower inner peripheral surface  72  includes a plurality of conical surfaces so that an inner diameter of the bone plate  1  in the longitudinal direction increases toward the lower surface as a whole. The lower inner peripheral surface  72  includes first regions  73  facing each other, each being inclined at a first angle (larger than 0 degrees; 15 degrees in  FIG. 17 ) with respect to a center axis of the hole  7 . The lower inner peripheral surface  72  includes second regions  74  facing each other in parallel to the center axis of the hole  7 . One set of the first regions  73  facing each other across the center axis of the hole  7  therebetween is formed on the lower inner peripheral surface  72  so as to face each other in the longitudinal direction of the bone plate  1 . Further, one set of the second regions  74  facing each other across the center axis of the hole  7  therebetween is formed on the lower inner peripheral surface  72  so as to face each other in the width direction of the bone plate  1 . 
     The screw  2  can be driven into the hole  7  described above so that the axis of the screw  2  matches the center axis of the hole  7 . Further, the screw  2  can be driven into the hole  7  so that the axis of the screw  2  is inclined in the longitudinal direction of the bone plate  1  with respect to the center axis of the hole  7 . 
     One example of a method of using the above-mentioned bone plate system is now described. The holes  5  are described here, and the same applies to the holes  6  and the holes  7 . 
     First, a surgeon places the lower surface of the bone plate  1  in contact with a target portion of a bone and determines an angle of the screw  2  with respect to the hole  5  in consideration of a surface shape of the bone, strength of the bone, and the like. 
     In this embodiment, the angle of the screw  2  is determined through use of a jig.  FIG. 18A  to  FIG. 18D  are side views for illustrating a schematic configuration of the jig.  FIG. 18A  is a side view for illustrating an internal configuration of the jig.  FIG. 18B  is a side view for illustrating a state in which the jig is placed upright.  FIG. 18C  is a side view for illustrating a state in which the jig is placed obliquely.  FIG. 18D  is another side view for illustrating a state in which the jig is placed obliquely. FIG.  18 B and  FIG. 18C  are partial sectional views of the bone plate  1 , taken along the longitudinal direction.  FIG. 18D  is a partial sectional view of the bone plate  1 , taken along the width direction. 
     As illustrated in  FIG. 18A , a jig  9  has an approximately cylindrical shape as a whole, and has a guide hole  91  configured to allow passage of a drill (for example, a drill having the same outer diameter as that of the shaft portion  22  of the screw  2 ) in a vertical direction therethrough. Further, the jig  9  has a distal end portion  92  to be brought into abutment against the hole  5 . The distal end portion  92  includes an upper abutment portion  93  to be brought into abutment against the upper inner peripheral surface  51  of the hole  5  and a lower abutment portion  94  to be brought into abutment against the lower inner peripheral surface  52  of the hole  5 . The upper abutment portion  93  is formed to have a spherical surface so as to perform a smooth rotational operation along the upper inner peripheral surface  51 . An outer diameter (maximum outer diameter) of the upper abutment portion  93  is larger than the inner diameter (minimum inner diameter) of the hole  5 . The lower abutment portion  94  is formed to have a cylindrical shape. An outer diameter of the lower abutment portion  94  is smaller than the inner diameter (minimum inner diameter) of the hole  5 . 
       FIG. 18B  is an illustration of a case where the jig  9  is placed into the hole  5  so that an axis z 2  of the jig  9  matches the center axis Z 1 .  FIG. 18C  is an illustration of a side view for illustrating a case where the jig  9  is placed into the hole  5  so that the axis z 2  of the jig  9  is inclined at the first angle (15 degrees in  FIG. 18C ) in the longitudinal direction of the bone plate  1  with respect to the center axis Z 1 . The angle of inclination of the jig  9  in the longitudinal direction of the bone plate  1  is limited up to the first angle by abutment of an outer peripheral surface of the lower abutment portion  94  against the first region  53  that is located on the side opposite to the direction of inclination. As a result, the angle of inclination of the guide hole  91  in the longitudinal direction is also limited up to the first angle.  FIG. 18D  is an illustration of a case where the jig  9  is placed into the hole  5  so that the axis z 2  of the jig  9  is inclined at the second angle (6 degrees in  FIG. 18D ) in the width direction of the bone plate  1  with respect to the center axis Z 1 . The angle of inclination of the jig  9  in the width direction of the bone plate  1  is limited up to the second angle by abutment of the outer peripheral surface of the lower abutment portion  94  against the second region  54  that is located on the side opposite to the direction of inclination. As a result, the angle of inclination of the guide hole  91  in the width direction is also limited up to the second angle. 
     The surgeon determines the angle of inclination of the guide hole  91  (also an angle of the drill and an angle of the screw  2 ) through use of the jig  9 . The surgeon can determine angles of the screw  2  to be fastened in the width direction and the longitudinal direction of the bone plate  1 . 
     Next, the surgeon inserts the drill into the guide hole  91  of the jig  9  inclined at the determined angle to form in the bone a prepared hole for driving the shaft portion  22  of the screw  2  thereinto. A female thread may be formed on an inner surface of the prepared hole. 
     Finally, the surgeon inserts a distal end of the screw  2  into the prepared hole through the hole  5 , and then tightens the screw  2  through use of a screw driver. The male thread  24  of the shaft portion  22  is engaged with the prepared hole. When the screw  2  is further tightened, the male thread  23  of the head portion  21  forms a female thread on the inner surface of the hole  5  so as to be engaged therewith. 
     In the above-mentioned manner, the screw  2  is fastened to the bone at an angle desired by the surgeon. Further, the screw  2  is fastened even to the bone plate  1  at an angle desired by the surgeon. The screw  2  is fastened to the bone at an appropriate angle in consideration of the surface shape of the bone, the strength of the bone, and the like, and hence the bone plate  1  is fixed to the bone and the screws  2 . 
     The one embodiment of the present invention is described above. With the bone plate system of this embodiment, the screw can be fastened to the bone at a desired angle. 
     For example, the hole  5  of the bone plate  1  includes the first regions  53  and the second regions  54 , each being inclined with respect to the center axis of the hole  5 . As a result, the screw  2  can be fastened at a desired angle within a range of the angle of inclination of the first regions  53  and a range of the angle of inclination of the second regions  54 . Further, for example, the female thread is not formed in advance on the inner surface of the hole  5  of the bone plate  1 . As a result, the desired angle can be more easily determined. 
     Further, for example, the first regions  53  are arranged so as to face each other in the longitudinal direction of the bone plate  1 , whereas the second regions  54  are arranged so as to face each other in the width direction of the bone plate  2 . In general, the bone plate  1  is placed in contact with the bone so that the longitudinal direction of the bone plate  1  corresponds to a longitudinal direction of the bone. Therefore, the surgeon can simply set an axial direction of the screw  2  so that the axial direction of the screw  2  corresponds to the longitudinal direction of the bone or a width direction of the bone through use of the first regions  53  or the second regions  54 . 
     The above-mentioned embodiment of the present invention is intended to exemplify the gist and the scope of the present invention without being limited thereto. For example, dimensions, shapes, and the like of the bone plate  1 , the screws  2 , and the jig  9  are not limited to the illustrated examples as long as the object of the present invention can be achieved. Further, for example, arrangements, numbers, dimensions, shapes, and the like of the holes  5 ,  6 , and  7  are not limited to the illustrated examples as long as the object of the present invention can be achieved. Still further, a region and a range in which the head portion  21  of the screw  2  and the inner peripheral surface of each of the holes  5  to  7  are engaged with each other are not limited to the illustrated examples as long as the object of the present invention can be achieved. Still further, for example, the holes  5  may be arranged in place of the holes  6 . Still further, for example, the holes  5  maybe arranged in place of the holes  7 . Still further, for example, the holes  5  and the holes  7  do not strictly limit the inclinations of the screws  2  only in the longitudinal direction and the width direction, and may have play for allowing inclination in another direction. Still further, the holes  6  do not strictly limit the axial direction of the screw  2  to match the center axis of the hole  6 , and may have play for allowing inclination in another direction. 
     The present invention can be carried out with various modifications within the gist of the present invention. Further, the above-mentioned embodiment and each of modified examples may be appropriately combined. 
     In the embodiment described above, the first angle (for example, 15 degrees) corresponding to the longitudinal direction of the bone plate  1  is set larger than the second angle (for example, 6 degrees) corresponding to the width direction of the bone plate  1 . As another example of this configuration, for example, the lower inner peripheral surface  52  may be formed so that the first angle and the second angle are equal to each other. Further, for example, the lower inner peripheral surface  52  may be formed so that the first angle becomes smaller than the second angle. Still further, for example, the four angles (respective angles of the one set of first regions  53  and the one set of second regions  54 ) maybe freely set. Further, all the holes  5  are not required to have the same configuration. A configuration of at least one of the holes  5  may be changed. The first angle of the hole  7  may be set equal to the first angle or the second angle of the hole  5 , or maybe set different from the first angle and the second angle of the hole  5 . Further, all the holes  7  are not required to have the same configuration. A configuration of at least one of the holes  7  may be changed. 
     In the embodiment described above, the lower inner peripheral surface  52  is formed so that the screw  2  can be inclined in the longitudinal direction and the width direction of the bone plate  1 . The direction of inclination is not limited to the longitudinal direction and the width direction of the bone plate  1 . The lower inner peripheral surface  52  may be formed so that the screw  2  can be inclined in another direction (for example, a first direction intersecting with the longitudinal direction at 45 degrees and a second direction perpendicularly intersecting with the first direction). Further, all the holes  5  are not required to have the same configuration. A configuration of at least one of the holes  5  may be changed. Even for the holes  7 , the lower inner peripheral surface  72  may be formed so that the screw  2  can be inclined in another direction different from the longitudinal direction. Still Further, all the holes  7  are not required to have the same configuration. A configuration of at least one of the holes  7  may be changed. 
     In the embodiment described above, the four inclined regions in total (the two first regions  53  and the two second regions  54 ) are formed on the lower inner peripheral surface  52  of the hole  5  so that the screw  2  can be inclined in the longitudinal direction and the width direction of the bone plate  1 . The number of inclined regions may be from one to three, or may also be five or more. Further, in the embodiment described above, the two inclined regions in total (the two first regions  73 ) are formed on the lower inner peripheral surface  72  of the hole  7  so that the screw  2  can be inclined in the longitudinal direction of the bone plate  1 . The number of inclined regions may be one, or may also be three or more. 
     The present invention can be provided in various forms, such as the bone plate system, the bone plate, and the method of fixing the bone plate. The present invention is applicable not only to small animals including dogs and cats but also to various creatures including human beings.