Abstract:
A device and method of stabilizing a fracture of a bone is provided. The device includes an intramedullary rod having a shaped distal end, and an insertion jig detachably connectable to the proximal end of the rod and used with the rod to apply a compressive force to the fracture site. The jig may also be used to correctly place fixation screws in a proximal end of the rod. The device achieves both fixation of the rod to the bone regardless of rod or bone diameter and allows for compression at the fracture site. In addition, fixation of the rod to the bone is accomplished without requiring a precise alignment of a distal end fixation screw. The device uses headless fixation screws, which, when in place, are disposed below cortical surface of bone, reducing damage to overlying soft tissues.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     This invention relates to devices and methods for fixation and compression of bone fractures. 
     Description of the Background Art 
     It is well known to use rigid internal fixation devices including rods, plates and wires to position and stabilize fractures of the long bones of the body to achieve successful bone healing. Known internal fixation devices are typically fixed to a bone using one or more screws. In some fractures of the long bones, a common approach for aligning the bone fragments is to insert a rod through the intradullary cavity. The rod may be held in place by screws until the fracture has healed, or may be left in the bone after healing is complete. 
     Conventional intramedullary rods, such as those used in the femur, often include an elongate rod that extends across the fracture and is fixed to the bone on each side of the fracture using screws that pass through holes provided in the rod. However, it is difficult to fix smaller diameter long bones such as the ulna of the forearm using this type of device because of the small bone diameter. In particular, the small rod diameter required for use in a small diameter long bone such as the ulna precludes providing through holes in the rod. As a result, it is difficult to fix the rod to the bone. Thus, a need exists for an intramedullar rod for use in small diameter long bones. 
     SUMMARY 
     A device and method of stabilizing a fracture of a bone is provided. The device may include an intramedullary rod. The distal end (furthest away from the body) of the rod is shaped to engage a distally placed screw, and a proximal end (nearest the body) of the rod may include through holes to receive fixation screws. The device may further include an insertion jig that detachably connects to the proximal end of the rod and may be used to apply a compressive force to the fracture site whereby displaced fractures may be closed. The jig may also be used to correctly place proximal end fixation screws in a proximal end of the rod. Among other advantages, the device provides an intramedullary rod that achieves fixation of the rod to the bone on opposed sides of the fracture regardless of rod or bone diameter, providing rotational control of the fracture, and also allows for compression at the fracture site. In addition, fixation of the rod to the bone is accomplished without requiring a precise alignment of a distal end fixation screw. Still further, the device uses headless fixation screws, which, when in place, are disposed below cortical surface of bone, reducing damage to overlying soft tissues. 
     In some approaches, an intermedullary device is provided for use in stabilizing a fracture of a bone. The device includes a rod having a longitudinal axis. A plurality of recesses are formed along an outer surface of the rod in a direction transverse to the axis. Each recess includes an engaging surface extending substantially transverse to the axis, and a sliding surface extending longitudinally from the engaging surface. The device further includes a rod engaging member having a first surface configured to engage a respective one of the plurality of sliding surfaces of the rod, and a second surface configured to engage a respective one of the plurality of engaging surfaces of the rod. 
     The intramedullary device may include one or more of the following features: 
     Each recess is elongate such that the dimension parallel to the longitudinal axis of the rod is greater than the dimension transverse to the longitudinal axis of the rod. Each recess further includes a curved surface opposed to the engaging surface, and the curved surface faces an insertion end of the rod. The rod engaging member is a headless screw. The rod includes a first end, a second end, and a midpoint between the first and second ends, and the recesses are disposed between the first end and the midpoint. The second end of the rod includes at least one through hole configured to receive an interlock screw. The interlock screw is configured to simultaneously engage bone on transversely opposed sides of the rod when received in a corresponding through hole. An end of the rod includes a first through hole configured to receive a first interlock screw and a second through hole configured to receive a second interlock screw. The first through hole extends transverse to the longitudinal axis, and the second through hole extends both transverse to the longitudinal axis and at an angle to the at least one first through hole. The intermedullary device further comprises a compression generating device configured to engage the proximal end of the rod and axially move the rod relative to the bone. 
     In some approaches, a rod insertion jig is provided for use with an intramedullary rod. The jig includes a threaded connector member including one end detachably connected to threads formed in an opening provided in an end of the rod. The jig includes a main body having a main body through hole in which is positioned a first mid-portion of the threaded connector member. The jig includes a receiving shaft disposed between the second end of the rod and the main body. The receiving shaft has a shaft first end which engages the second end of the rod, a shaft second end opposed to the shaft first end and having exterior threads, and a shaft axial through hole in which is positioned a second mid-portion of the threaded connector member. The jig includes a compression device coaxially disposed on the receiving shaft, the compression device including interior threads configured to engage the exterior threads of the receiving shaft. The jig further includes a securing nut disposed on the threaded connector member adjacent the main body and on a side of the main body opposed to receiving shaft, the securing nut serving to maintain the relative positions of the rod and receiving shaft with respect to the main body, and a buttress plate having a plate through hole that receives the shaft first end therethrough. In the rod insertion jig, a rotation of the compression device relative to the receiving shaft results in an axial movement of the buttress plate relative to the second end of the rod. 
     The jig may include one or more of the following features: 
     The buttress plate includes a first face which abuts an end of the compression device and a second face opposed to the first face, the buttress plate further including a plurality of axially-extending protrusions formed on the second face. The buttress plate freely axially slides relative to the receiving shaft. The main body includes a base portion including a first base arm and second base arm, and the base portion lies in a plane transverse to a longitudinal axis of the receiving shaft. In addition, a posterior arm extends orthogonally from an end of the first base arm toward the rod such that the posterior arm extends substantially parallel to the longitudinal axis, and a lateral arm extends orthogonally from an end of the second base arm toward the rod such that the lateral arm extends substantially parallel to the longitudinal axis. The posterior arm includes one or more posterior arm guide holes which extend through the posterior arm, and the lateral arm includes one or more lateral arm guide holes which extend through the lateral arm. The posterior and lateral guide holes are each respectively oriented to extend along an axis that intersects the longitudinal axis of the rod. 
     In some approaches, a bone compression device is provided for stabilizing a bone fracture. The device includes an intramedullary rod and rod insertion jig detachably connected to the rod. The intramedullary rod includes a first end configured to be fixed relative to the bone on a first side of the bone fracture, a second end configured to be fixed relative to the bone on a second side of the bone fracture, and a rod longitudinal axis. The rod insertion jig includes a threaded connector member including one end detachably connected to threads formed in an opening provided in the second end of the rod, and a main body including a main body through hole in which is positioned a first mid-portion of the threaded connector member. The jig includes a receiving shaft disposed between the second end of the rod and the main body, the receiving shaft having a shaft first end which engages the second end of the rod, a shaft second end opposed to the shaft first end and having exterior threads and a shaft axial through hole which in which is positioned a second mid-portion of the threaded connector member. The jig includes a compression device coaxially disposed on the receiving shaft, the compression device including interior threads configured to engage the exterior threads of the receiving shaft. The jig includes a securing nut disposed on the threaded connector member adjacent the main body and on a side of the main body opposed to receiving shaft, the securing nut serving to maintain the relative positions of the rod and receiving shaft with respect to the main body. The jig further includes a buttress plate having a plate through hole that receives the shaft first end therethrough. A rotation of the compression device relative to the receiving shaft results in an axial movement of the buttress plate relative to the second end of the rod. 
     The bone compression device may include one or more of the following features: 
     The buttress plate includes a first face which abuts an end of the compression device and a second face opposed to the first face, the buttress plate including a plurality of axially-extending protrusions formed on the second face. The buttress plate freely axially slides relative to the receiving shaft. The intramedullary rod further comprises a plurality of recesses formed along an outer surface of the rod in a direction transverse to the axis, each recess including an engaging surface extending substantially transverse to the axis, and a sliding surface extending longitudinally from the engaging surface. The intramedullary rod further includes a plurality of through holes formed adjacent the second end configured to receive second end fixation screws. The device further includes a first end fixation screw including a first surface configured to engage one of the sliding surfaces of the rod and a second surface configured to engage one of the engaging surfaces of the rod. 
     In some approaches, a method is provided for stabilizing a bone fracture using an intramedullary rod and rod insertion jig detachably connected to the rod. The rod includes a first end, a second end opposed to the first end, a longitudinal axis, a plurality of through holes formed at the second end, and a plurality of recesses formed along an outer surface of the first end in a direction transverse to the axis. Each recess includes an engaging surface extending substantially transverse to the axis, and a sliding surface extending longitudinally from the engaging surface. The jig includes a main body, a connector that detachably connects the main body to the second end of the rod, and a compression generating device configured to move the rod in an axial direction relative to the bone. The method includes the following method steps:
         Inserting the rod in a medullary cavity of the bone so that the rod longitudinal axis is aligned with a longitudinal direction of the bone, and the first end of the rod and the second end of the rod reside on opposed sides of the fracture;   Inserting a first screw in the bone in a direction transverse to longitudinal axis and at a location between the first end of the rod and the fracture;   Actuating the compression generating device to axially move the rod whereby the engaging surface of one of the recesses engages a side surface of the first screw;   Further actuating the compression generating device to axially move the rod until the rod and bone are in a desired relative position;   Inserting one or more second screws in corresponding ones of the through holes so that the second screws reside within and extend outwardly from opposed sides through holes; and   Detaching the rod insertion jig from the second end of the rod.       

     The method may include one or more of the following: 
     The step of inserting a first screw further includes inserting the first screw to the extent that an end of the first screw contacts the sliding surface of the rod, and the other end of the screw is engaged with cortical bone. After the step of further actuating the compression generating device, the method further includes advancing the first screw until a surface of the rod contacts an interior surface of the medullary cavity. After the rod insertion jig is detached from the second end of the rod, the second end of the rod resides at or below the cortex of the bone. After insertion, at least one of the first screw and one or more second screws is seated at or below the cortex of the bone. The step of further actuating the compression generating device is continued until a compression force is applied to the bone at the fracture. The first screw comprises a flat tip, and wherein when the flat tip is in contact with the sliding surface of the rod, rotation of the rod relative to the bone is prevented. 
     In some approaches, a bone compression device is provided for stabilizing a bone fracture. The device includes an intramedullary rod and rod insertion jig detachably connected to the rod. The device is configured to achieve and maintain compression of the fracture, and control rotation of the fracture. 
     The bone compression device may include one or more of the following features: 
     Control of rotation of the fracture comprises preventing rotation of a bone portion on one side of the fracture relative to a bone portion on an opposed side of the fracture. The intramedullary rod is configured to be fixed to the bone on opposed sides of the fracture whereby rotational control of the fracture is achieved. The fracture divides the bone into a first bone portion and a second bone portion, and the intramedullary rod is configured to engage with the first bone portion, and the rod insertion jig is configured to draw the first bone portion toward the second bone portion, whereby compression of the fracture is achieved. 
     Modes for carrying out the present invention are explained below by reference to an embodiment of the present invention shown in the attached drawings. The objects, characteristics and advantages of the present invention will become apparent form the detailed description of the embodiment of the invention presented below in conjunction with the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a bone compression device including an intramedullary rod disposed within the medullary cavity of an ulna and an insertion jig connected to a proximal end of the rod. 
         FIG. 2  is a perspective view of the bone compression device of  FIG. 1 . 
         FIG. 3  is a perspective view of the proximal end of the rod of  FIG. 1 . 
         FIGS. 4 a -4 c    are side sectional views of a distal end of the rod disposed within the medullary cavity. 
         FIG. 5 a    is an exploded perspective view of the insertion jig of  FIG. 1 . 
         FIG. 5 b    is a side sectional view of the insertion jig connected to the rod. 
         FIG. 6  is an end view of the insertion jig as seen in the direction of arrow A as shown in  FIG. 5   b.    
         FIG. 7  is a perspective view of the forearm bones illustrating the rod disposed in the ulna and the radius shown lying in its normal position next to the ulna. 
         FIG. 8  is a side view of an ulna including a mid shaft displaced fracture. 
         FIG. 9  is a side view of the ulna of  FIG. 8  with the rod inserted in the medullary canal of the ulna. 
         FIG. 10  is a side view of the ulna of  FIG. 9  with a distal screw provided in the ulna at a location corresponding to a distal end of the rod. 
         FIG. 11  is a side view of the ulna of  FIG. 10  with the distal screw engaged with the distal end of the rod and the fracture reduced. 
         FIG. 12  is a side view of the ulna of  FIG. 11  with proximal screws fixing the proximal end of the rod relative to the ulna. 
         FIG. 13  is a sectional view of the distal end of the bones of the forearm with the rod inserted in the medullary canal of the ulna and distal screw in place. 
         FIG. 14  is a sectional view of the proximal end of the ulna. 
         FIG. 15  is a schematic side view of the distal end of the rod of  FIG. 1  to use as comparison for  FIG. 16A-D . 
         FIG. 16A-D  are schematic side views of alternative embodiments of the distal end of the rod. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , an ulna  2  is shown connected to a humerus  14  via an elbow joint  16 . A fracture  8  is shown in the mid-shaft of the ulna  2 , dividing the ulna  2  into a proximal bone portion  4  and a distal bone portion  6 . A compression device  100 , including an intramedullary rod  102  and rod insertion jig  104 , is shown with the rod  102  disposed within the medullary canal  200  ( FIGS. 4, 13 ) of the ulna  2 . The rod  102  is fixed relative to the distal bone portion  6  using a distal screw  108 , and is fixed relative to the proximal bone portion  4  using one or more proximal interlock screws  106 . When used in combination with the rod insertion jig  104 , the rod  102  serves to compress the proximal and distal bone portions  4 ,  6  of the ulna  2  together. Once the proximal and distal bone portions  4 ,  6  are properly mutually positioned, the rod insertion jig  104  may be disconnected from the rod  102 , and the rod  102  remains within the medullary canal  200  of the ulna  2  to provide compression and fixation of the proximal and distal bone portions  4 ,  6 . 
     Referring to  FIG. 2 , the compression device  100  is shown isolated from the ulna  2 . As seen in this figure, the rod  102  is an elongate, solid member including a generally cylindrically shaped proximal end  112  that is configured to connect to the rod insertion jig  104 . The rod  102  includes a distal end  116  opposed to the proximal end  112 . An elongate cylindrical mid-portion  114  extends along a longitudinal axis  10  between the proximal and distal ends  112 ,  116 , and has a cross-sectional diameter that is less than that of the proximal end  112 . In some embodiments the cross sectional diameter of the mid portion  114  is about half that of the proximal end  112 . 
     The proximal end  112  of the rod  102  has a tapered portion  118  to provide a smooth transition between the proximal end  112  and the mid-portion  114 , a feature which reduces injury to the interior surface of the medullary canal  200  during insertion of the rod  102  in the ulna  2 . The proximal end  112  includes one or more through holes  120  that receive the proximal interlock screws  106  to maintain proximal and distal positioning of the rod  102  and prevent rotation of the rod  102  with respect to the proximal bone portion  4 . In the illustrated embodiment, five through holes  120  are provided. In some embodiments, a first subset of through holes  120  are aligned transverse to the longitudinal axis  10  of the rod  102 , and a second subset of through holes  120  are aligned at an acute angle with respect to both the longitudinal and transverse axes of rod  102 . At least one proximal interlock screw  106  is required to achieve sufficient fixation of the proximal end  112  of the rod  102  with respect to the proximal end  4  of the ulna  2 , and a more secure fixation is achieved if more than one proximal interlock screws are used. 
     Referring to  FIG. 3 , the most proximal portion of the rod  102  includes a triangular shaped jig interface  122 . The triangular interface  122  is received in a complimentarily shaped opening in the alignment jig  104 , and serves to prevent rotation of the rod  102  with respect to the rod insertion jig  104  when connected thereto. The interface is not limited to a triangular shape, and other noncircular (e.g. square, oval, etc.) interfaces or interlocking tabs could be used to prevent the rod  102  from rotating relative to the rod insertion jig  104 . A threaded receiving hole  124  is drilled longitudinally in the center of the triangular shaped jig interface  122 . The receiving hole is sized to receive a correspondingly threaded connector  134  (described below) when the rod  102  is connected to the insertion jig  104 . 
     Referring to  FIG. 4 a   , an enlarged view of the distal end  116  of the rod  102  is shown positioned within the medullary canal  200  of the ulna  2 . The distal tip  117  of the rod  102  is rounded to allow it to pass easily through the medullary canal  200 . The distal end  116  of the rod  102  includes several recesses  184  formed along an outer surface of the rod  102  in a direction transverse to the axis  10 . Each recess  184  is elongate in the axial direction of the rod  102 . That is, the recess dimension parallel to the longitudinal axis  10  is greater than the recess dimension transverse to the longitudinal axis  10 . Each  184  recess includes a flat face  204  which faces toward the proximal end  112  of the rod  102  and which provides an engaging surface for a rod-engaging distal screw  108  (discussed below) placed in the posterior cortex  180  of the ulna  2 . The flat face  204  extends substantially transverse to the axis  10 . Each recess  184  also includes a flat portion  190  which serves as a sliding surface for the distal screw  108 . The flat portion  190  extends longitudinally from the engaging surface  204 . Each recess  184  further includes a curved surface  206  opposed to the engaging surface  204 . The curved surface  206  faces an insertion (distal) end of the rod  102 . The curved shape of the surface  206  eases insertion of the rod  102  and helps to minimize injury to the interior bone surfaces during insertion. 
     The recesses  184  are separated by portions of the rod referred to as protrusions  186 . The protrusions  186  are approximately ½ to ⅓ the diameter of the mid portion  114  of the rod in height. They extend outwardly from the flat portion  190  and therefore the overall diameter of the distal end of the rod  116  including the protrusions  186  is no greater in diameter than the mid portion  114  of the rod. Each protrusion  186  is defined by the flat face  204  of one recess  184 , and the curved face  206  of the adjacent recess  184 . In some embodiments, the protrusions  186  are spaced at regular intervals. The interval spacing may be, for example, approximately 1.5 cm, but is not limited to this spacing. The protrusions  186 , particularly the flat faces  204  thereof, are used to engage the distal screw  108 . 
     Compression of the Displaced Fracture 
     Initially, or prior to compression of the displaced fracture  160  (described below), the distal screw  108  is directed transverse to the axis of the rod  102  and set proximally to distally between protrusions  186  on the distal end of the rod  116 . The distal screw  108  is advanced until it just touches but does not exert pressure against the flat portion  190  of the rod  102  ( FIG. 4A ). During the initial placement of the distal screw  108 , prior to compression of the displaced fracture  160  (described below), the posterior aspect of the rod  196  is not firmly pressed up against the far endosteal surface  194  of the ulna  2 . 
     Compression of the displaced fracture  160  is achieved by retracting the rod  102  proximally through actuation of compression nut  127  on the rod insertion jig  104  (discussed below). As the rod  102  is retracted proximally (the retraction direction is indicated by the long arrow in  FIG. 4B ), the distal screw  108  slides along the flat portion  190  until it engages the flat face  204  of a protrusion  186 . At this point, a proximally directed force (indicated by the short arrow in  FIG. 4B ) is transmitted from the protrusion  186  of the rod  102  to the distal end of ulna  6  through the distal screw  108 , providing compression of the displaced fracture  160 . The tip  208  of the distal screw  108  is flat so that as it abuts the flat portion  190  of the rod  102 , it provides rotational control of the distal portion  6  of the ulna  2  and the distal end  116  of the rod  102 , preventing rotation of the distal portion  6  of the ulna  2  relative and the distal end  116  of the rod  102 . 
     After the displaced fracture has been sufficiently compressed, the distal screw  108  is seated firmly against the flat face  204  of the protrusion  186 . The distal screw  108  is then advanced until it pushes the posterior aspect of the rod  196  against the far endosteal surface of the bone  194  ( FIG. 4C ). The distal screw  108  is configured without a head so that the base  210  of the distal screw  108  is no greater in diameter than the main body  212  of the distal screw  108 . In addition, the length of the distal screw  108  is such that, once in position, the base  210  is seated at or below the edge of the ulnar cortex  198 . These features are advantageous since they minimize hardware irritation to overlying soft tissue. Additional distal screws  108  can be inserted to provide additional strength to the construct as needed. 
     Referring to  FIG. 5 a    (an exploded view) and  FIG. 5 b    (a side section view), the insertion jig  104  includes a jig main body  212 , a receiving shaft  131 , a compression nut  127 , a securing nut  140 , a buttress plate  126 , and a threaded connector member  134 . 
     The jig main body  212  is a rigid structure on which the remaining components of the insertion jig  104  are mounted. The main body  212  includes an L-shaped base portion  162  including a first base arm  164 , and second base arm  166  that intersects the first base arm  164  at a right angle ( FIG. 6 ). The base portion  162  is arranged to lie in a plane transverse to a longitudinal axis of the receiving shaft  131  (described below), which in turn is coaxial with the longitudinal axis  10  of the rod  102 . The main body  212  includes a through hole  238  disposed substantially at the intersection of the first and second base arms  164 ,  166 . The through hole  238  extends in parallel to the longitudinal axis  10  and is dimensioned to receive the threaded connector member  134  therethrough. 
     The jig main body  212  also includes a posterior arm  142  and a lateral arm  144  which extend in parallel to each other and the longitudinal axis  10  of rod  102 .  FIG. 6  illustrates the orthogonal orientation of the posterior arm  142  relative to the lateral arm  144  of the rod insertion jig  104 . In addition, the posterior arm  142  extends orthogonally from an end  170  of the first base arm  164  toward the rod  102  such that the posterior arm  142  extends substantially parallel to the rod longitudinal axis  10 . Similarly, the lateral arm  144  extends orthogonally from an end  174  of the second base arm  166  toward the rod  102  such that the lateral arm  144  extends substantially parallel to the rod longitudinal axis  10 . 
     The posterior arm  142  includes one or more posterior arm guide holes  146   a  which extend through the posterior arm  142 , and the lateral arm  144  includes one or more lateral arm guide holes  146   b  which extend through the lateral arm  144 . The posterior and lateral guide holes  146   a ,  146   b  are each respectively oriented to extend along an axis that intersects the rod longitudinal axis  10 , and are dimensioned to accommodate an outer diameter of proximal interlock screws  106  used to fix the rod  102  with respect to the proximal portion of the ulna  2 . More specifically, when the alignment jig  104  is connected to the rod  102 , the each of the guide holes  146   a ,  146   b  are arranged to be aligned with a corresponding hole  120  formed in the proximal end  112  of the rod  102 . The guide holes  146   a ,  146   b  are dimensioned and arranged to facilitate both properly locating a drill site and subsequent drilling of the proximal end of the ulna  2 , as well as placement of the proximal interlock screws  106  into the proximal end of the rod  112  (described below) once a corresponding bone hole has been drilled. 
     The receiving shaft  131  is disposed between the proximal end  112  of the rod  102  and the jig main body  212 , and abuts one side of the base portion  162 . The receiving shaft  131  includes a shaft first end  132  which engages the proximal end  112  of the rod  102 , a shaft second end  129  opposed to the shaft first end  132  and having exterior threads, and a shaft axial through hole  138 . The shaft axial through hole  138  is dimensioned to receive the threaded connector member  134  therethrough, and is continuous with the through hole  238  of the main body  212 . 
     The shaft first end  132  has a smooth exterior surface and an outer diameter that is substantially the same as that of the rod  102 . In addition, the shaft first end  132  has a triangular opening  136  sized to received the triangular shaped jig interface  122  provided on the proximal portion  112  of the rod  102 . The jig interface  122  mates with the triangular hole  136  formed in the end face  132   a  of the shaft first end  132  to provide a secure connection and prevent relative rotational motion between the rod  102  and the receiving shaft  131 . The exterior threads of the shaft second end  129  cooperatively engage threads formed on an inner surface of a compression nut  127  which is co-axially disposed on the proximal threaded end  129 . 
     The compression nut  127  is long relative to its cross-sectional diameter. In some embodiments, the compression nut  127  has a hexagonal cross-sectional shape to permit the nut  127  to be easily manually grasped and rotated. In other embodiments, the compression nut has other polygonal cross-sectional shapes such as square or pentagonal. 
     The buttress plate  126  is a generally disc-shaped body that is larger in diameter than the proximal end of the rod  112 . The buttress plate  126  includes a first, proximally-directed face  262  which abuts an end  264  of the compression nut  127 , and a second, distally-directed face  260  opposed to the first face  262 . Sharp protrusions  128  are formed on the distally-directed face  260  of the buttress plate  126  and extend longitudinally toward the proximal end  112  of the rod  102 . In some embodiments, the buttress plate  126  is approximately 5 mm greater in diameter than the proximal end of the rod  112 . This size allows the buttress plate  126  to be small enough to pass inside the skin incision and large enough to distribute compressive forces against the proximal end of the ulna  2  and associated soft tissues. However, the diameter of the buttress plate  126  is not limited to this size. 
     The buttress plate  126  is disposed on the distal end  132  of the receiving shaft so that an end  264  of the compression nut  127  abuts the proximally-directed face  262  of the buttress plate  126 . There exists a center hole  130  in the buttress plate  126 , which is sized to permit the buttress plate  126  to slide freely over top of both the proximal end  112  of the rod  102  and/or over the smooth distal end  132  of the receiving shaft  131 . Since the smooth distal end  132  of the receiving shaft  131  has the same diameter as the proximal end  112  of the rod  102 , the proximal end  112  of the rod  102 , as well as a portion of the smooth distal end  132  of the insertion jig  104  can be passed completely into the medullary canal  200  of the ulna  2 . As a result, when the rod insertion jig  104  is removed, the triangular shaped jig interface  122  does not protrude proximally outside the edge of the bone  2 . 
     The threaded connector member  134  is an elongate, rigid threaded rod used to interconnect the components of the insertion jig  104  and to connect the insertion jig  104  to the rod  102 . In particular, when the rod  102  is assembled with the insertion jig  104 , a first end of the threaded connector member  134  is received within the threaded receiving hole  124  of the proximal end  112  of the rod  102 . The threaded connector member  134  extends serially through the buttress plate  126 , compression nut  127  and main body  212  so that a mid portion of the threaded connector member  134  passes through axially aligned hole  138  formed in the receiving shaft  131  and axially aligned hole  238  formed in the main body  212  of the insertion jig  104 . When the securing nut  140  on the proximal end of the threaded connector member  134  is tightened, the rod insertion jig  104  is firmly fixed to the rod  102  and the assembled configuration of the insertion jig  104  and the rod  102  is maintained. 
       FIG. 7  demonstrates a foreshortened view of the rod  102  as it is placed in the ulna bone  2 . The radius bone  12  is shown lying in its normal position next to the ulna bone  2 . 
     A method of using the rod  102  and insertion jig  104  will now be described with reference to  FIGS. 8-12 . 
       FIG. 8  shows the ulna  2  with a displaced fracture  160 , whose ends are not perfectly coapted, dividing the ulna into proximal bone portion  4  and distal bone portion  6 . The humerus  14  helps clarify the proximal bone portion  4  of the ulna  2 . 
     Prior to insertion of the rod  102 , a first hole is drilled in the proximal cortex of the ulna  2  in a direction aligned with the longitudinal axis of the ulna to provide access to the intramedullary cavity  200 . The first hole has a diameter just large enough to accommodate the outer diameter of the insertion rod  102 . 
     The insertion rod  102 , pre-assembled to compression jig  104 , is inserted into the intermedullary cavity  200  so that the rod  102  extends axially within the cavity  200  and so that the proximal end  112  of the rod  102  and the distal end  112  of the rod  102  reside on opposed sides of the displaced fracture  160 .  FIG. 9  shows the ulna  2  with the rod  102  inserted. The proximal end of the rod  112  is seated so that it passes deep/distal to the proximal cortex  172  of the ulna  2 . 
     Once the proximal end of the rod  112  is properly seated, a second hole is drilled in the posterior cortex  180  of the ulna  2  at a location distal to the displaced fracture  160  and which is aligned radiographically to be between any two protrusions  186 . The second hole is drilled transverse to the longitudinal direction of the rod.  FIG. 10  shows a distal screw  108  placed in the posterior cortex  180  of the ulna directed transverse to the axis of the rod  102  and set proximally to distally between protrusions  186  on the distal end of the rod  116 . The distal screw  108  is advanced until it just touches but does not exert pressure against the flat part  190  of the rod  102 . Advancement of the distal screw  108  may be done both by feeling for resistance against advancement by the surgeon and also by intraoperative x-ray. 
     With the distal screw  108  in place with respect to the distal end  116  of the rod  102 , the compression nut  127  is turned to retract the rod  102  (that is, move the rod  102  in a proximal direction) relative to the ulna  2  ( FIG. 11 ). As the compression nut  127  is tightened, the buttress plate is pushed  126  against the proximal cortex of the ulna  172  as the distal end  116  of the rod  102  is pulled proximally. Once the protrusions  186  on the distal end  116  of the rod  102  engage the distal screw  108 , the distal bone portion  6  is then pulled proximally to compress against the proximal bone portion  4 . The displaced fracture  160  is now a reduced and compressed fracture  8 . Adequate compression may be assessed by intraoperative x-ray. 
     Once the desired compression is achieved, the distal screw  108  is further advanced to seat the posterior aspect of the rod  196  against the far endosteal surface of the bone  194  as described above. At this time, additional holes are drilled in the proximal portion  4  of the ulna  2  by using the guide holes  146   a ,  146   b  provided in the main body  212  of the insertion jig  104 . As discussed above, the guide holes  146   a ,  146   b  assure that the drilled holes are correctly aligned with the holes  120  in the proximal end  112  of the rod  102 . After the holes are drilled, the guide holes  146  are used place proximal interlock screws  106  into the proximal end of the rod  112  ( FIG. 12 ). The proximal interlock screws  106  are long relative to the diameter of the proximal end  112  of the rod  102  so that when in place, the opposed ends of the proximal interlock screws extend outwardly from opposed sides of the rod  102 . In particular, the proximal interlock screws have a length on the order of that of the diameter of the proximal end of the ulna to maximize engagement with available cortical bone in this region, thus maximizing fixation of the proximal end  112  of the rod  102 . 
     The proximal interlock screws  106  are placed to prevent rotation of the proximal portion  4  of the ulna  2  relative to the rod  102 . Since the distal portion  6  of the ulna  2  was earlier fixed relative to the rod  102  via the distal screw  108 , the ulna  2  is fixed to the rod  102  on opposed sides of the fracture, and thus the distal portion  6  and proximal portion  4  of the ulna  2  are prevented from relative rotation. In addition, this configuration maintains compression of the ulna  2  and fracture  8 . 
     With the rod  102  fixed proximally and distally of the fracture  108 , the rod insertion jig  104  is removed from the proximal end  112  of the rod  102 , and the rod  102  remains in place within the intramedullary canal. 
       FIG. 13  shows a cross sectional view of the distal end of the forearm as seen looking toward the hand, illustrating from a different view the position of the rod  102  within the intramedullary canal  200  after the distal screw  108  has been tightened. The protrusion  186  seats firmly against the distal screw  108  and the distal screw  108  pushes the posterior aspect of the rod  196  against the far endosteal surface of the bone  194 . Once in position, the distal screw  108  is seated below the edge of the ulnar cortex  198  to minimize hardware irritation to overlying soft tissue. 
       FIG. 14  is a cross sectional view of the proximal end of the forearm as seen looking toward the elbow, illustrating placement of the rod  102  along with the proximal interlock screws  106 . This shows the orthogonal orientation of proximal screw  106  placement which provides secure fixation and can be beneficial when fracture lines propagate proximally. It also demonstrates that the proximal screws  106  are also headless constructs allowing them to be buried at or below the level of the cortex  220  to minimize soft tissue irritation. The proximal interlock screws  106  have a shaft  222  that is the same diameter as the outer part of the thread  224  of the screw. This provides for a secure fit between the interlock screw shaft  222  and the holes  120  in the rod  102 . 
       FIG. 15  is a schematic side view of the distal end  116  of the rod  102  which can be used for a basis of comparison to other configurations of the distal end of the rod demonstrated in  FIGS. 16A-D , which would achieve the same ability to lock the distal end and provide compression, but are of slightly different shape. 
     In the embodiment shown in  FIG. 16A , the distal end  116  includes protrusions  186   i  that extend out beyond the outer diameter of the distal end  116   i  of the rod  102 . 
     In the embodiment shown in  FIG. 16B , the distal end  116   ii  includes protrusions  186   ii  that are not curved on their distal aspect but still have a surface  204  to abut the distal screw  108 . 
     In the embodiment shown in  FIG. 16C , the distal end  116   iii  includes protrusions  186   iii  that are flat and long relative to protrusions  186 , and further includes relatively short recesses  184 ′ for capturing a distal screw  108  to allow compression at the fracture site. 
     In the embodiment shown in  FIG. 16D , the distal end  116   iv  includes circumfrential protrusions  186   iv  and recesses  184 ″ with a surface  204  to abut the edge of a distal screw  108 . 
     Although the preceding description details the use of the compression rod  102  in the ulna, there are other applications within the scope of the invention. For example, the rod  102  could be used in a nearly identical manner in other long bones with an intramedullary canal, including, but not limited to, the radius, humerus, tibia, fibula, femur, clavicle, metacarpal, or phalanx. The device  100  is demonstrated with a mid-shaft fracture, but it could be used with fractures at locations all along the bone with the exception of fractures at locations corresponding to the distal end of the rod  102 . The rod  102  could also be used as a minimally invasive fixation for ulnar shortening osteotomies or other long bone osteotomies. 
     A selected illustrative embodiment of the invention is described above in some detail. It should be understood that only structures considered necessary for clarifying the present invention have been described herein. Other conventional structures, and those of ancillary and auxiliary components of the system, are assumed to be known and understood by those skilled in the art. Moreover, while a working example of the present invention has been described above, the present invention is not limited to the working example described above, but various design alterations may be carried out without departing from the present invention as set forth in the following claims.