Abstract:
An external fixation system for securing a first bone portion in a fixed relationship with respect to a second bone portion. The fixation system includes at least one cylindrical support rod and a plurality of universal clamp assemblies for engagement with at least one support rod. The fixation system additionally includes various other distinct components for interconnecting the support rod with bone pins engaged with the bone. Some of the other components are formed to include serrations for engaging corresponding serrations provided on the universal clamp assemblies. Some of the components include a cylindrical portion, whereas other of the components include a rod receiving portion adapted to receive the at least one support rod or one of the cylindrical portions. These interchangeable and distinct components allow for a greater degree of surgeon flexibility in producing a desired construction to secure bone portions with bone pins.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to an orthopedic surgical procedure, and more particularly to an external fixation system for bones. 
     2. Description of the Related Art 
     In various orthopedic surgical procedures, it is often necessary to secure two or more portions of bone in a relatively fixed relationship to each other. This need is often a result of a fracture which has occurred to the bone. To ensure that the bone can properly regenerate and fuse the fractures of the bone, it is important that the various bone portions be fixed at the desired position during bone regeneration. 
     Various external fixation devices for the repair of traumatized bone are known. For example, commonly assigned U.S. Pat. No. 5,620,442 to Bailey et al. discloses an apparatus for the external fixation of small bones. The apparatus is illustrated to include a bone screw clamp for receiving a first bone screw which is connected to a first bone portion. The external fixator further includes a bone screw clamp which is operable to receive a second bone screw connected to the second bone portion. The first and second bone screw clamps include a spherical portion. The external fixator further includes a connection member for securing the spherical portions of the bone screw clamps. The connection member defines a radiographic window to permit radiographic examination of the bone fracture without removing the apparatus. U.S. Pat. No. 5,620,442 is hereby incorporated by reference as if fully set forth herein. 
     While known fixators, including the type described above, have proven to be effective in fixating bones, they nevertheless can be the subject of certain improvements. In this regard, conventional external fixation devices often do not provide the flexibility required for particular applications. Thus, it would be advantageous to provide an external fixation system with a plurality of interchangeable and distinct components which allow for a greater degree of surgeon flexibility in producing a desired construction. 
     SUMMARY OF THE PRESENT INVENTION 
     According to one aspect of the present invention, the invention relates to an external fixation system operable for securing two portions of bone in a fixed relationship to each other including various interchangeable components which can be selected by a surgeon. 
     An advantage of the present invention is to provide an external fixation system for bones and a related method that permit independent placement of bone pins at various positions and angular orientations along a bone. 
     Another advantage of the present invention is to provide an external fixation system for bones and a related method that incorporate a universal base clamp which can be placed any free space along a support rod without requiring the removal of other elements that may be secured to the support rod. 
     Another advantage of the present invention is to provide an external fixation system for bones and a related method that include a compression/distraction arrangement for relatively translating a pair of spaced apart support rods. 
     Another advantage of the present invention is to provide an external fixation system for bones and a related method that include a telescoping bone screw clamp that allows a surgeon to displace a bone pin from a support rod. 
     Another advantage of the present invention is to provide an external fixation system for bones and a related method that include a plurality of distinct components including cooperating serrated portions for facilitating interconnection between the components. 
     A related advantage of the present invention is to provide an external fixation system for bones and a related method that include a plurality of distinct components each including one of a cylindrical rod and a rod receiving portion to facilitate interconnection between the components and a cylindrical support rod. 
     Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1A and 1B illustrate a first exemplary construct of components of the external fixation system according to the teachings of the preferred embodiment of the present invention in operative association with a tibia. 
     FIG. 2 illustrates a second exemplary construct of components of the external fixation system according to the teachings of the preferred embodiment of the present invention in operative association with a tibia, the second construct incorporating a compression/distraction arrangement. 
     FIGS. 3A and 3B illustrate a third exemplary construct of components of the external fixation system according to the teachings of the preferred embodiment of the present invention in operative association with a tibia, the third construct incorporating a ring assembly. 
     FIGS. 4A and 4B are views of a universal clamp assembly of the external fixation system according to the teachings of the preferred embodiment of the present invention. 
     FIGS. 5A through 5C are views of a bar-to-bar clamp body of the external fixation system according to the teachings of the preferred embodiment of the present invention. 
     FIGS. 6A and 6B are views of a three pin clamp assembly of the external fixation system according to the teachings of the preferred embodiment of the present invention. 
     FIGS. 7A and 7B are views of a five pin clamp assembly of the external fixation system according to the teachings of the preferred embodiment of the present invention. 
     FIGS. 8A and 8B are views of a telescoping post of the external fixation system according to the teachings of the preferred embodiment of the present invention. 
     FIGS. 9A and 9B are views of a first ring connector assembly of the external fixation system according to the teachings of the preferred embodiment of the present invention. 
     FIGS. 10A and 10B are views of a second ring connector assembly of the external fixation system according to the teachings of the preferred embodiment of the present invention. 
     FIGS. 11A through 11D are views of a bone pin clamp body of the external fixation system according to the teachings of the preferred embodiment of the present invention. 
     FIGS. 12A through 12C are views of a post assembly of the external fixation system according to the teachings of the preferred embodiment of the present invention. 
     FIG. 13 is a side elevational view a bar clamping unit of a compression/distraction arrangement of the external fixation system according to the teachings of the preferred embodiment of the present invention. 
     FIGS. 14A through 14C are views of a variable connector body of the external fixation system according to the teachings of the preferred embodiment of the present invention. 
     FIG. 15 is a side elevational view of the bar clamping unit and threaded rod receiving unit the compression/distraction assembly of the external fixation system according to the teachings of the preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following description of the preferred embodiment of the present invention is merely exemplary in nature and is in no way intended to limit the invention or its application or uses. 
     Referring initially to FIGS. 1 through 3, illustrated are three constructs of cooperating components of the system  10  for external fixation of bone according to the preferred embodiment of the present invention. In FIGS. 1A and 1B, a first construct of components of the system  10  is shown securing a fracture  12  of a bone  14 . In particular, the system  10  is illustrated as being used to secure a bone fracture  12  of a tibia  14 . The system  10  is used to secure the bone portions  16  and  18  in a fixed relationship so as to permit the fractured portions to fuse properly. FIG. 2 illustrates a second construct of the system  10  shown operatively attached to the tibia  14 . In FIG. 3, a third construct of the system  10  is illustrated attached to the tibia  14 . While the system  10  is shown throughout FIGS. 1 through 3 in conjunction with a tibia  14 , it will be appreciated that the system  10  may be used with other bones as well. It will also be appreciated that the three constructions illustrated in FIGS. 1 through 3 are merely exemplary applications. 
     The structure and function of the individual cooperating components of the system  10  will be described with general reference to FIGS. 1 through 15. The components of the present invention are illustrated to generally include a universal clamp assembly  20 , bar-to-bar clamp body  22 , a three pin clamp assembly  24 , a five pin clamp assembly  26 , a telescoping post  28 , a first ring connector assembly  30 , a second ring connector assembly  32 , a bone pin clamp body  34 , and a post assembly  36 . The components are illustrated to additionally include a compression/distraction arrangement  38  including a pair of clamping assemblies  40  and an externally threaded drive rod  42 . Further, the components include a variable connector body  44 , a ring assembly  46 , and a plurality of cylindrical, smooth support rods  48 . The support rods  48  include main support rods which are typically oriented to extend generally parallel to the axis of the bone  14  or at an acute angle relative to the bone  14  and supplemental support rods. The supplemental support rods  48 ′, one of which is shown in FIG. 1B, may be provided in various lengths. 
     As will become apparent below, the components of the system  10  of the present invention may be combined in an infinite number of combinations and orientations to secure and rigidly interconnect a plurality of bone screws or pins  50  which are engaged with the bone portions  16  and  18 . This flexibility of the system  10  permits a surgeon to independently place a bone  50  at a limitless number of positions along the bone  14  or angular orientations with respect to the bone  14 . 
     With reference to FIGS. 4A and 4B, the universal clamp assembly  20  of the present invention is illustrated. The universal clamp assembly  20  includes a clamp portion  52  having first and second halves  54  and  56  which cooperate to define a bar receiving aperture  58  for receiving one of the support rods  48 , the telescoping post  28  or the post assembly  36 . It will be understood that in the exemplary embodiment the support rods  48 , telescoping post  28  and post assembly  36  each have a substantially identical diameter. 
     The first and second halves  54  and  56  include aligning apertures  60  and  62 , respectively, for receiving a locking bolt or fastener  64 . The aperture  62  of the second half  56  includes a counterbored portion  66  for receiving a portion of a head  68  of the fastener  64 . An outer surface  70  of the first half  54  is formed to include a serrated portion  72  having a plurality of serrations radially extending from the opening of the aperture  60 . The serrated portion  72  is adapted to engage substantially identical serrated portions provided on cooperating components of the system  10  of the present invention as will be discussed below. 
     An end  74  of the fastener  64  opposite the head  68  is externally threaded. When the fastener  64  engages an internally threaded aperture of a cooperating component and is rotated to draw the cooperating component against the first half  56 , the first and second halves  56  of the clamp portion  52  are drawn together to thereby securely clamp one of the support rods  48 , for example, within the aperture  58 . The rod receiving aperture  58  is sized to receive one of the support rods  48 , the telescoping post  28  or the post assembly  36 . 
     The universal base clamp  20  is the fundamental component of the system  10  of the present invention. The universal base clamp  20  is designed to be easily placed anywhere along a support rod  48 , for example (even between two previously locked universal base clamps  20 ). This can be cone by sliding the first half  54  up the fastener  64  and then rotating the first half  54  ninety degrees. This feature allows a surgeon to add components during the application without the inconvenience of unlocking clamps  20  already in place. 
     With reference to FIGS. 5A through 5C, the bar-to-bar clamp body  22  of the present invention is illustrated. The bar-to-bar clamp body  22  is generally C-shaped to define a rod receiving aperture  80  and includes first and second ends  76  and  78  which are spaced apart by an opening  82 . The first and second ends  76  and  78  include aligning apertures  84  and  86 , respectively, for receiving a fastener such as the fastener  64  described above with respect to the universal clamp assembly  20 . The aperture  86  of the second end  78  is internally threaded. An outer surface  88  of the first end  76  is formed to include a serrated portion  72 . 
     In use, the bar-to-bar clamp body  22  is attached to a cooperating component of the system  10  of the present invention through engagement of the fastener  64  with the apertures  84  and  86 . In such engagement, the serrated portions  72  of the components are interlocked thereby preventing relative rotation. Tightening of the fastener  64  draws the ends  76  and  78  of the bar-to-bar clamp body  22  toward one another. As a result, a support rods  48 , telescoping post  28  or post assembly  36  positioned within the aperture  80  is secured relative to the bar-to-bar clamp body  22  and in turn secured relative to the cooperating component. 
     With reference to FIGS. 6A and 6B, the three pin clamp assembly  24  of the present invention is illustrated. The pin clamp assembly  24  is operative for receiving and securing up to three bone pins  50  engaged with the bone  14 . The bone pin clamp  28  includes a main body member  90  and a cover member  92 . The main body member  90  defines three bone pin rests  94 . The bone pin rests or grooves  94  are substantially V-shaped and are operable to engage the sides of the bone pins  50 . 
     The cover member  92  of the pin clamp assembly  24  is able to be inserted over the bone pins  50  when the bone pins  50  are located in the grooves  94 . The cover member  92  includes a pair of apertures  96  which each allow a threaded fastener  98  to pass through the cover member  32  and into a threaded aperture  100  of the main body member  90 . Tightening of the fasteners  98  rotationally and longitudinally secures the bone pins  50  relative to the pin clamp assembly  24 . 
     To facilitate secure attachment of the pin clamp assembly  24  to other cooperating components of the system  10  of the present invention, the base member  90  and the cover member  92  are both formed to integrally include cylindrical extensions  102  and  104 , respectfully. The ends of each of the cylindrical extensions  102  and  104  are both formed to include a serrated portion  72 . Each of the cylindrical extensions  102  and  104  includes an internally threaded aperture  106  sized to receive a fastener  64 . 
     The five pin clamp assembly  26  is shown particularly in FIGS. 7A and 7B. The construction of the five pin clamp assembly  26  is identical to the construction of the three pin clamp assembly  26 , with the exception that the five pin clamp assembly  26  is formed to include two additional bone pin rests  94 . In this regard, the five pin clamp assembly  26  includes three bone pin rests  94  between the fasteners  98 , whereas the three pin clamp assembly  24  includes a single bone pin rest  94  between the fasteners. Due to the similarity between the two pin clamp assemblies  24  and  26 , like reference numbers are used in the drawings. 
     Turning now to FIGS. 8A and 8B, the telescoping post  28  of the present invention is illustrated. The telescoping post  28  includes a cylindrical post portion  108  and a mounting flange portion  110 . The cylindrical post portion  108  has a diameter substantially equal to the diameter of the support rods  48  and thereby may be securely received within rod receiving apertures of cooperating components of the system  10  of the present invention. The mounting flange portion  110  includes an aperture  112  for receiving a fastener  64 . A lower side  114  of the mounting flange portion  110  includes a serrated portion  72  for cooperating with the serrated portions of cooperating components of the system  10  in a manner discussed above. 
     With reference to FIGS. 9A and 9B, the first ring connector assembly  30  of the present invention is illustrated. 
     The first ring connector assembly includes a main body  116  and a fastener  118 . An upper portion  120  of the main body  116  defines a vertically extending aperture  122  which is internally threaded to receive the externally threaded fastener  118 . A lower portion  124  of the main body  116  includes a pair of spaced apart sides  126  and  128  and an aperture  130  horizontally passing therethrough. Both of the sides  126  and  128  are formed to include a serrated portion  72  radially surrounding the aperture  130  which is adapted to interface with cooperating components of the system  10  including a serrated portion  72  in a manner discussed above. The fastener  118  is adapted to pass through one of a plurality of apertures formed in a frame  132  of the ring assembly  46  for securing the first ring connector assembly  32  thereto. 
     With reference to FIGS. 10A and 10B, the second ring connector assembly  32  of the present invention is illustrated. Rather than interfacing with cooperating components of the system  10  including a serrated portion  72 , the second ring connector assembly  32  is adapted to interface with cooperating components including a rod receiving aperture, such as the universal clamp assembly  20  and the bar-to-bar clamp body  22 . The second ring connector assembly  32  includes a main body portion  132  and a cylindrical extension  134 . To facilitate clamping within one of the rod receiving apertures, the cylindrical extension  134  has a diameter substantially equal to the support rods  48 . The main body  132  defines a pair of apertures  136  which are internally threaded for receiving a pair of threaded fasteners  118  identical to the fastener described with respect to the first ring connector assembly  30 . In a similar manner, the fasteners  118  are adapted to pass through a pair of the plurality of apertures formed in the frame  132  of the ring assembly  46  for securing the second ring connector assembly thereto. 
     With reference to FIGS. 11A through 11D, the bone pin clamp body  34  of the present invention is illustrated. The bone pin clamp body  34  defines an aperture  138  for receiving a bone pin  50 . The pin clamp body  34  includes an upper flange portion  140  and a lower flange portion  142  which are separated by a gap  144 . The gap  144  intersects the aperture  138 . The upper and lower flange portions  140  and  142  are formed to include aligning apertures  146  and  148  for receiving a fastener  64 . The aperture  148  of the lower flange portion  142  is internally threaded. 
     An upper surface  150  of the upper flange portion  140  includes a serrated portion  72  surrounding the aperture  146 . The serrated portion  72  is adapted to interface with serrated portions of cooperating components of the system  10  of the present invention in a manner discussed above. When a cooperating component is secured to the bone pin clamp body  34  with a fastener  64 , tightening of the fastener  64  causes the gap  144  between the upper and lower flange portions  140  and  142  to decrease and the aperture  138  to slightly constrict. As a result, a bone pin  50  disposed within the aperture  138  is longitudinally and rotationally fixed with respect to the bone pin clamp body  34 . 
     Turning now to FIGS. 12A through 12C, the post assembly  36  of the present invention is illustrated. The post assembly  36  generally includes a cylindrical sleeve  152  and a threaded fastener  154 . The cylindrical sleeve  152  includes a central portion  156  and first and second enlarged ends  158  and  160 . The cylindrical sleeve  152  has a diameter substantially equal to the diameter of the support rods  48  and can similarly interface with cooperating components including a rod receiving aperture, such as the universal clamp assembly  20 , in a manner discussed above. 
     The cylindrical sleeve  152  defines an elongated aperture  162  for receiving the fastener  154 . An outer end of the first enlarged end  158  includes a serrated portion  72  surrounding the aperture  162 . The fastener  154  extends beyond the serrated portion and is externally threaded. An opposite end of the fastener  154  includes a recess  164  for receiving a tool (not shown) used to rotate the fastener  154  relative to the cylindrical sleeve  152 . The serrated portion  72  is adapted to interface with serrated portions  72  of cooperating components of the system  10  of the present invention in a manner discussed above. The serrated portion  72  is particularly intended to cooperate with the 3 pin and 5 pin clamp assemblies. 
     With reference to FIGS. 14A through 14C the variable connector body  44  of the present invention will be described. The variable connector body  44  generally includes a main body  166  and a cylindrical portion  168  extending from the main body  166 . The main body  166  includes a pair of spaced apart sides  170  and  172  and an internally threaded aperture  174  passing therethrough. Both of the sides  170  and  172  are formed to include a serrated portion  72  radially surrounding the aperture  174  which is adapted to interface with cooperating components of the system  10  including a serrated portion  72  in a manner discussed above. The cylindrical portion  168  has a diameter substantially equal to the diameter of the support rods  48  and thereby may be securely received within rod receiving apertures of cooperating components of the system  10  of the present invention in a manner discussed above. 
     With reference to FIGS. 13 and 15, the compression/distraction arrangement  38  of the present invention will be described. The clamping assemblies  40  of the distraction arrangement  38  each include a bar clamping unit  178  and a threaded rod receiving unit  180 . The bar clamping unit  178  includes a lower portion  182  and a pair of substantially identical upper portions  184 . Each of the upper portions  184  cooperates with the lower portion  182  to define an aperture  186  for receiving one of the support rods  48 . The upper portions  184  each include an apertures  188  which each allow a threaded fastener  190  to pass therethrough and into an aligning threaded aperture  192  provided in the lower portion  182 . Tightening of the fasteners  190  secures the support rods  48 . When the bar clamping units  178  are used in tandem, a pair of the support rods  48  are non-rotatably retained in a parallel and spaced apart relationship. 
     The threaded rod receiving unit  180  of each of the clamping assemblies  40  includes a first aperture (not specifically shown) which is internally threaded for receiving the drive rod  42 . The clamping assemblies  40  additionally include a second aperture  194  oriented substantially perpendicular to the first aperture. The second aperture  194  allows a threaded fastener  196  to pass therethrough and into an aligning internally threaded aperture  198  provided in the lower portion  182  of the bar clamping unit  178  for securing the bar clamping unit  178  to the threaded rod receiving unit  180 . 
     When the compression/distraction arrangement  38  is incorporated into a construct, as shown in FIG. 2 for example, the threads of the apertures receiving the drive rod  42  progress in opposing directions. To operate the compression/distraction arrangement  38 , the fastener  190  of a first one of the bar clamping units  178  which is associated with one of the support rods  48  must be loosened to permit the support rod  48  to slide within the aperture  186 . Similarly, the fastener  190  of a second of the bar clamping units  178  which is associated with the other one of the support rods  48  must be loosened to permit the support rod  48  to slide in its aperture  186 . In this manner, one of the bar clamping units  178  is permitted to translate with respect to one of the support rods  48  and the other of the clamping units  178  is permitted to translate relative to the other of the support rods  48 . At this point, rotation of the drive rod  42  in a first direction causes relative movement between the clamping assemblies  40  such that they approach one another and the bone  14  is compressed. Conversely, rotation of the drive rod  42  in a second direction causes relative movement between the clamping assemblies  40  such that they diverge from one another and the bone  14  is distracted. 
     The ring assembly  46  of the present invention is shown in the exemplary construct of FIGS. 3A and 3B. A substantially identical ring assembly is shown and described in commonly assigned U.S. Ser. No. 09/086,256, filed Jun. 28, 1998. U.S. Ser. No. 09/086,256 is incorporated by reference as if fully set forth herein. 
     The foregoing discussion discloses and describes merely exemplary embodiments of the present invention. One skilled in the art will recognize from such discussion and from the accompanying drawings and claims, that various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention.