Abstract:
A bone bolt assembly is designed for attaching supporting implants between adjacent bones, for holding adjacent bones relative to each other, and for holding together fractured bone fragments. The functions performed by the bone bolt assembly are achieved without the use of bone screws that are implanted into the bone.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    None. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable. 
       APPENDIX 
       [0003]    Not Applicable. 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Field of the Invention 
         [0005]    The present invention pertains to a bone bolt assembly that is designed for attaching supporting implants between adjacent bones, for holding adjacent bones relative to each other, and for holding together fractured bone fragments. These functions performed by the bone bolt assembly are achieved without the use of bone screws that are inserted into the bone that could potentially fracture the bone. 
         [0006]    2. Description of the Related Art 
         [0007]    Surgical screws are commonly used to hold bones or bone fragments together or attach anatomical body parts to bones. Surgical screws employed in these types of orthopedic procedures are commonly referred to as bone screws. 
         [0008]    The typical bone screw is a metal implant screwed into the bone. The bone is prepared by first drilling a hole into the bone where the bone screw is to be implanted. The drilled hole diameter is larger than the minor diameter of the screw and less than the major diameter of the screw. This allows the threads of the screw to cut into the bone surrounding the drilled hole as the screw is advanced through the hole. Bone screws are commonly used to set or hold a bone in position relative to an adjacent bone, to immobilize fractured bone fragments to aid in the healing of the fracture, and to secure an implant in place relative to a bone. 
         [0009]    A particular type of bone screw used in spine fusion surgery to hold implants in place is called a pedicle screw. Pedicle screws are implanted into the pedicle of a vertebra to hold supporting rods or plates to the spine. Pedicle screws are commonly implanted in two or more consecutive vertebra segments with a rod or plate connected between the screws to support the section of the spine. 
         [0010]    A problem encountered with the use of bone screws implanted in bone is the strength of the connection between the screw and the bone is dependent on the strength of the surrounding bone. If the strength of the bone has been deteriorated due to smoking, disease, or other causes, the portion of the bone surrounding the screw could fracture or split during insertion of the screw. 
       SUMMARY OF THE INVENTION 
       [0011]    The bone bolt assembly of the invention is designed to secure together adjacent bones, bone fragments, and to secure implants to bones without requiring a bone screw to be implanted into the bone. By eliminating the need for a bone screw implanted into the bone, the assembly of the invention avoids the potential problem of bone screws causing fracturing of the bone in and around the location where the assembly is secured to the bone, and also avoids the potential problem of bone screws becoming loose over time. 
         [0012]    The bone bolt assembly of the present invention is basically comprised of a tubular member, a guide tip that is removably attached to one end of the tubular member, and a proximal bolt and distal bolt that are removably attached to opposite ends of the tubular member in use of the assembly. Each of these component parts of the assembly is constructed of surgical steel. However, the component parts could also be constructed of other biocompatible materials. 
         [0013]    The tubular member is a straight, elongate cylindrical member. An interior bore having internal screw threading extends through the length of the tubular member. In one embodiment, the interior bore is surrounded by internal screw threading that extends the entire length of the bore. In an alternate embodiment, the interior bore and the internal screw threading do not extend entirely through the tubular member. Instead, two separate interior bores having internal screw threading extend short distances into the opposite ends of the tubular member. In a still further embodiment, external screw threading is formed on the exterior of the tubular member and extends along the entire length of the tubular member. 
         [0014]    The guide tip has external screw threading at one end and a conical-shaped surface or other equivalent shaped surface at the opposite end. The external screw threading is complementary to the internal screw threading of the tubular member. Screwing the tip external screw threading into the internal screw threading at one end of the tubular member removably attaches the tip to the tubular member. 
         [0015]    The proximal and distal bolts are substantially identical in construction. Each has external screw threading at one end and a head at the opposite end. The external screw threading is complementary to the internal screw threading of the tubular member. Each head is adapted for engagement with an appropriate driving tool to rotate the bolt in response to rotating the tool. In addition, each head can be adapted for attachment to a spinal fixation system, for example, a spinal instrumentation rod or a spinal instrumentation plate. In addition, each head could be constructed to swivel or pivot relative to the external screw threading of the bolt. 
         [0016]    In use of the assembly, the guide tip is removably attached at one end of the tubular member and the proximal bolt is attached at the opposite end of the tubular member. In an alternate embodiment of the assembly, the proximal bolt could be an integral part of one end of the tubular member. 
         [0017]    A straight hole is drilled through the bone, adjacent bones, or bone fragments into which the assembly is to be inserted. The tubular member is inserted guide tip first through the drilled hole. The proximal bolt head prevents the tubular member from passing completely through the drilled hole. The length of the tubular member is determined so that, with the tubular member inserted into the drilled hole to where the proximal bolt head is positioned adjacent the bone, the guide tip attached to the opposite end of the tubular member projects from the drilled hole at the opposite side of the bone, bones, or bone fragments. With this positioning of the assembly, the tip can then be removed from the end of the tubular member and replaced with the distal bolt that is attached to the tubular member after the tip is removed. If needed, spinal instrumentation can then be attached to the tubular member by being attached to the heads of the proximal and distal bolts. In addition, the spinal instrumentation can be attached to the tubular member by being positioned between the opposite ends of the tubular member and the proximal and distal bolts prior to the attachment of the proximal and distal bolts to the tubular member. 
         [0018]    In the embodiment of the bone bolt assembly that comprises the tubular member having external screw threading formed on the tubular member along the length of the tubular member, the tubular member is again inserted guide tip first into the drilled hole. The tubular member is advanced through the hole by turning the proximal bolt head with an appropriate tool. The tubular member is advanced through the hole until the tip can be removed from the end of the tubular member and replaced with the distal bolt in the manner described above. The external screw threading of the tubular member grips the bone, bones, or bone fragments. 
         [0019]    In the above manner, the bone bolt assembly of the invention is attached to a bone, between adjacent bones or between bone fragments without requiring external screw threading to secure the bone bolt assembly inside the hole drilled through the bone. The bone bolt assembly thereby eliminates the potential problem of fracturing of the bone in and around the location of the bone bolt assembly, or the potential for screw threads backing out of the drilled hole in the bone. If these potential problems are not present, then the embodiment of the bone bolt assembly comprising the tubular member with the external screw threading may be used to secure the tubular member to the bone, bones, or bone fragments. 
         [0020]    Other features of the bone bolt assembly are set forth in the following detailed description of the preferred embodiments of the assembly and in the drawing figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a side, partially sectioned view of one embodiment of the bone bolt assembly. 
           [0022]      FIG. 2  is a side, partially sectioned view of the assembly shown in  FIG. 1  showing the guide tip removed from the tubular member and the distal bolt that replaces the guide tip. 
           [0023]      FIG. 3  is a side, partially sectioned view of the assembly showing the tip replaced with a distal bolt. 
           [0024]      FIG. 4  is a side, partially sectioned view of a further embodiment of the assembly. 
           [0025]      FIG. 5  is a side, partially sectioned view of the assembly shown in  FIG. 4  with the proximal bolt and tip removed from the tubular member and showing the distal bolt that replaces the tip. 
           [0026]      FIG. 6  is a side, partially sectioned view of the embodiment shown in  FIG. 5  with the proximal bolt and distal bolt assembled to the tubular member. 
           [0027]      FIG. 7  is a side, partially sectioned view of the embodiment of  FIGS. 5 and 6  shown used with spinal instrumentation. 
           [0028]      FIG. 8  is a view of the bone bolt assembly similar to that of  FIGS. 4-7  but showing an embodiment of the tubular member having external screw threading formed on the tubular member along the length of the tubular member. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0029]    As stated earlier, the basic component parts of the bone bolt assembly comprise a tubular member  10 , a guide tip  12 , a proximal bolt  14  and a distal bolt  16 . Each of these component parts is preferably constructed of surgical steel. However, other biocompatible materials may be used in the component part&#39;s construction. 
         [0030]      FIGS. 1-3  show a first embodiment of the assembly that is comprised of the tubular member  10 , the guide tip  12 , and the distal bolt  16 . The size of the component parts shown in the drawing figures is enlarged to facilitate the description of the component parts. In actual use of the bone bolt assembly, the tubular member  10  would typically have a length dimension of about 1½ to 2½ inches and a diameter dimension of about one quarter of an inch. The other component parts would be dimensioned accordingly. 
         [0031]    The tubular member  10  shown in  FIG. 1  has an elongate, straight length with opposite proximal  18  and distal  20  ends. The tubular member  10  has a smooth, cylindrical exterior surface  22  that extends the entire length of the tubular member. The cylindrical exterior surface  22  has a center axis  24  that defines mutually perpendicular axial and radial directions relative to the bone bolt assembly. In the embodiment shown in  FIG. 1 , the tubular member  10  has a hollow interior bore defined by internal screw threading  26  that extends a short distance axially into the distal end  20  of the tubular member  10 . In an alternate embodiment, the center bore could extend entirely through the length of the tubular member  10  and could have internal screw threading along its entire length, or could have portions of internal screw threading adjacent the opposite proximal  18  and distal  20  ends of the tubular member. The internal bore extending entirely through the tubular member  10  is represented by the dashed lines  28  shown in the drawing figures. 
         [0032]    The guide tip  12  has an axial length with external screw threading  30  at one end and a conical-shaped surface  32  at the opposite end. The external screw threading  30  is complementary to the internal screw threading  26  at the tubular member distal end  20 . As shown in  FIG. 1 , the tip  12  is removably attached to the tubular member  10  by screwing the tip external screw threading  30  into the internal screw threading  26  at the tubular member distal end  20 . The tip conical-shaped surface  32  has a diameter dimension at its base that is substantially the same as the diameter dimension of the tubular member  10 . From the base of the conical-shaped surface  32 , the tip extends axially away from the tubular member  10  and tapers to the distal end of the tip  12 . Although the tip  12  is shown with a conical-shaped surface  32 , other equivalent surface shapes, for example, a parabolic surface shape or a semi-circular surface shape, could be provided on the tip  12 . It is only necessary that the configuration of the tip surface  32  facilitate guiding the insertion of the tip  12  and tubular member  10  through a hole drilled in a bone or bones. 
         [0033]    In the embodiment of the assembly shown in  FIG. 1 , the proximal bolt  14  is formed as an integral part of the tubular member  10  at the tubular member proximal end  18 . The proximal bolt  14  has a head  34  that is shown projecting radially from the tubular member exterior surface  22 . In alternate embodiments, the proximal bolt head  34  could have a diameter dimension that is substantially the same as that of the tubular member  10 . The proximal bolt head  34  is shown only schematically in the drawing figures. The bolt head  34  is intended to be adapted for attachment to any known type of spinal instrumentation (for example, rods or plates) and thereby attach the instrumentation to the tubular member  10 . It is also possible that the bolt head  34  be attached to the tubular member  10  by a connection that enables the bolt head  34  to move (for example, pivot or swivel) relative to the tubular member  10 . 
         [0034]    The distal bolt  16  has an axial length with external screw threading  36  at one end and a head  38  at the opposite end. The external screw threading  36  is complementary to the internal screw threading  26  at the distal end of the tubular member  10 . The head  38  of the distal bolt  16  is substantially the same as the head  34  of the proximal bolt  14 . 
         [0035]    The assembly of  FIGS. 1-3  is intended for use in securing or attaching spinal instrumentation to a bone, in securing together adjacent bones, or in securing together bone fragments. In use of the assembly, a hole is drilled through the bone, adjacent bones or bone fragments. The hole diameter is slightly larger than the exterior diameter of the tubular member  10  and the base of the guide tip  12 . With the tip  12  attached to the tubular member distal end  20 , the assembly is inserted tip first through the drilled hole. When the assembly is entirely inserted through the drilled hole, the tip  12  is accessible at the opposite end of the bone from which the assembly was inserted. The tip  12  can then be removed from the tubular assembly  10  and replace with the distal bolt  16  that is screwed to the tubular member distal end  20 . In this manner, the bone bolt assembly of  FIGS. 1-3  is secured to a bone, to adjacent bones, or to bone fragments without requiring external screw threading cutting into bone which could cause fracturing or splitting of the bone around the drilled hole. 
         [0036]    Once the assembly of  FIGS. 1-3  is in place, if needed, spinal instrumentation can be secured to the proximal bolt head  34  and the distal bolt head  38 . 
         [0037]      FIGS. 4-6  show an alternate embodiment of the bone bolt assembly from that shown in  FIGS. 1-3 . The embodiment of  FIGS. 4-6  employs the same tip  12  and distal bolt  16  of the embodiment of  FIGS. 1-3  and therefore the features of these component parts are identified by the same reference numbers used in identifying these features in  FIGS. 1-3 . However, in  FIGS. 4-6  these reference numbers are followed by a prime (′). 
         [0038]    The tubular member  42  of  FIGS. 4-6  is substantially the same as the tubular member  10  of  FIGS. 1-3  except for an additional interior bore at the tubular member proximal end  44 . The proximal end interior bore is defined by internal screw threading  46  that extends axially into the tubular member  42  from the tubular member proximal end  44 . As shown in  FIGS. 4-6 , the internal screw threading  46  extends only a short distance into the tubular member  42  from the tubular member proximal end  44 . As an alternative, the internal screw threading  46  could extend entirely through the interior of the tubular member  44  as represented by the dashed lines  28 ′. In such an alternate embodiment, the internal screw threading  56  at the tubular member distal end  58  and the internal screw threading  46  at the tubular member proximal end  44  are two portions of the internal screw threading  28 ′ that extends entirely through the length of the tubular member  42 . 
         [0039]    The embodiment of the bone bolt assembly shown in  FIGS. 4-6  also differs from the previously described embodiment of  FIGS. 1-3  in that it comprises a separate proximal bolt  50 . The proximal bolt  50  has an axial length with external screw threading  52  at one end and a head  54  formed at the opposite end. The external screw threading  52  is complementary to the internal screw threading  46  that extends into the tubular member proximal end  44 . By screw threading the proximal bolt external screw threading  52  into the tubular member internal screw threading  46 , the proximal bolt  50  is removably attached to the tubular member  42  at the proximal end  44 . The head  54  of the proximal bolt  50  has the same construction as the head of both the proximal bolt  14  and the distal bolt  16  described earlier. 
         [0040]    The use of the embodiment of the bone bolt assembly shown in  FIGS. 4-6  is substantially the same as that of the embodiment of  FIGS. 1-3 . The only difference is that the proximal bolt  50  is removably attached to the tubular member  42  at the tubular member proximal end  46  with the guide tip  12 ′ being removably attached to the tubular member  42  by screwing the tip external screw threading  28 ′ into the internal screw threading  56  provided at the tubular member distal end  58 . With the proximal bolt  50  removably attached to the tubular member  42  and the tip  12 ′ removably attached to the tubular member  42 , the assembly is inserted through a hole previously drilled through the bone, bones, or bone fragments and is secured in place in the same manner as the embodiment of  FIGS. 1-3  described previously. 
         [0041]      FIG. 7  shows the embodiment of the bone bolt assembly of  FIGS. 4-6  with schematic representations of spinal instrumentation  62 ,  64  removably attached to the assembly. The left side of the assembly shown in  FIG. 7  represents a spinal instrumentation  62  that is removably attached to the assembly, or more specifically to the tubular member,  42  by the external screw threading  52  of the proximal bolt  50 . The proximal bolt threading  52  is first inserted through an opening provided in the spinal instrumentation  62  before the screw threading  52  is screwed into the internal screw threading  46  at the tubular member proximal end  44 . By tightening the proximal bolt  50  to the tubular member  42 , the proximal bolt  50  secures the spinal instrumentation  62  to the tubular member  42  of the assembly. 
         [0042]    The right side of  FIG. 7  shows the schematic representation of spinal instrumentation  64  being removably attached to the tubular member  42  of the assembly by any known attachment mechanism provided on the head  38 ′ of the distal bolt  16 ′. In this manner, the distal bolt  16 ′ removably attaches the spinal instrumentation  64  to the tubular member  42 . 
         [0043]      FIG. 8  shows a further embodiment of the bone bolt assembly that is substantially the same as that shown in  FIGS. 4-7  except for the tubular member  66  having external screw threading  68  that extends along the length of the tubular member. Because all of the component parts of the bone bolt assembly shown in  FIG. 8  are the same as those shown in  FIGS. 4-7  and described earlier, those component parts will not be described again. The same component parts shown in  FIG. 8  are identified by the same reference numbers shown in  FIGS. 4-7 , with the reference numbers being followed by a prime (′) or a double prime (″). 
         [0044]    The use of the embodiment of the bone bolt assembly shown in  FIG. 8  is substantially the same as that of the embodiment shown in  FIGS. 4-7 . The only difference is that with the proximal bolt  50 ′ removably attached to the tubular member  66  and the tip  12 ″ removably attached to the tubular member  66 , the assembly is advanced through a hole previously drilled through the bone, bones, or bone fragments by turning the bolt  50 ′ with an appropriate tool which in turn screw threads the tubular member  66  through the hole due to the external screw threading  68  on the tubular member  66 . The tubular member external screw threading  68  secures the tubular member  66  to the bone, bones, or bone fragments. The tubular member  66  is further secured in place in the same manner as the previously discussed embodiments. 
         [0045]    In view of the foregoing, it will be seen that the several advantages of the invention are achieved and attained. 
         [0046]    The embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. 
         [0047]    As various modifications could be made in the constructions and methods herein described and illustrated without departing from the scope of the invention, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.