Abstract:
Systems, devices and methods are disclosed for limiting compression of a fracture imposed by a lag screw of a fixation system that includes a fixation device, a lag screw and a compression screw. The disclosed devices, systems and methods prevent over-compression of a fracture by a lag screw caused by over rotation of the compression screw. Specifically, implementations of a lag screw driver and a compression screw driver are provided whereby an engagement between the lag screw driver and compression screw driver prevents any further lateral movement of the lag screw, thereby providing a complete stop to further advancement of the lag screw and any additional compression.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the full benefit of U.S. Provisional Application No. 61/259,745, filed Nov. 10, 2009, and titled “TOOL FOR CONTROLLING LAG SCREW COMPRESSION,” the entire contents of which are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    This disclosure relates to controlling bone compression. 
       BACKGROUND 
       [0003]    A variety of devices are used to treat fractures of long bones, many of which are disclosed in co-pending and commonly-assigned U.S. patent application Ser. No. 12/074,320, which is incorporated herein by reference. Referring to  FIG. 1 , one such stabilizing assembly  30  includes an intramedullary nail  31  (in this case a humeral nail), a lag screw  32  and a compression screw  33 . As illustrated in  FIG. 1 , the compression screw  33  includes an enlarged head section  34  that, in this embodiment, bears against the humerus  35  to compress the humerus  35 . A threaded section  36  of the compression screw  33  passes through the nail  31  and engages a rack  35  disposed on a side of the lag screw  32  (the rack  35  is more clearly seen in  FIG. 8 ). In some implementations, the lag screw  32  can include a threaded portion that engages the threaded section  36  of the compression screw  33 . Rotating the compression screw  33  applies an axial force to the lag screw  32 , which has previously been anchored in a fragment of the humerus  35  by a threaded distal end  37 . Accordingly, rotating the compression screw  33  draws the lag screw  32 , and the bone fragment affixed to the end  37  of the lag screw  32 , in a direction along the length of the compression screw  33  and into position for proper healing. 
         [0004]    In another example illustrated in  FIG. 2 , a stabilizing assembly  40  coupled to a femur  41  includes a compression plate  42 , the compression screw  33  and the lag screw  32 . A head section  44  of the compression plate  42  extends into the femur  41  and supports the compression screw  33  and the lag screw  32 . As described above, the compression screw  33  bears against a surface of the compression plate  42  such that rotation of the compression screw  33  applies an axial force to the lag screw  32  to draw the lag screw  32  and a bone fragment in a direction along the length of the compression screw  33 . 
         [0005]      FIG. 3  illustrates another stabilizing assembly  50  applied to a proximal tibia  51 . The assembly  50  includes a periarticular plate  52 , the lag screw  32  and the compression screw  33 . Again, the head section  34  of the compression screw  33  bears against the plate  52  to limit further insertion of the compression screw and to provide a positive stop such that rotation of the compression screw  33  interacts with the lag screw  32  causing compression of the tibia  51 . 
         [0006]    In contrast to compression plate  42  of  FIG. 2 ,  FIGS. 4-6  illustrate a stabilizing assembly  60  which includes an antegrade femoral intramedullary nail  61 , the lag screw  32  and the compression screw  33  to stabilize a fracture  63  across a femoral neck  64 . The designs of the nails  31 ,  61 , plates  42 ,  52 , and screws  32 ,  33  may vary greatly and may be configured to be applicable to other parts of the anatomy not specifically illustrated here or specifically addressed in this disclosure. Regardless of the designs, the compression screw  33  interacts with the lag screw  32  to compress the bone. Alternatively, the fracture can be distracted by interaction of the compression screw  33  and the lag screw  32 . Additionally, the lag screw  32  and the compression screw  32  are configured to slide as a unit within the nail or plate. 
         [0007]    However, problems may result if bone adjacent to a fracture is weak and/or prone to damage when exposed to compression, or excessive compression, force. For example, excessive compression force could cause the femoral head  65  shown in  FIG. 4  to migrate towards or into the fracture site  63  resulting in misalignment. In extreme cases, excessive compression may cause the femoral head  65  to be compressed all the way into the trochanteric region  66  of the femur  41 . 
         [0008]    Further, compressing a bone more than a recommended or intended amount may cause the lag and compression screws  32 ,  33  to splay apart from each other, which can inhibit or prevent the screws from sliding within the intramedullary nail  31 ,  61  or plate  42 ,  52 . Thus, while applying compression force using a compression screw/lag screw system  32 ,  33  is an important orthopaedic technique, excessive compression can be problematic and should be avoided. 
         [0009]    Currently, separate compression screw and lag screw drivers are utilized. To limit the compressive force transmitted to the lag screw  32 , some compression screw drivers are equipped with a line indicating 0 mm and/or red line indicating to the surgeon or other use that rotation of the compression screw to apply compression force should be stopped. However, even with this type of visual aid, experienced surgeons may still apply excessive compression force across a fracture site. Hence, a more reliable system, that is less prone to operator error, and that controls bone and/or fracture compression, is needed. 
       SUMMARY 
       [0010]    Systems and assemblies are provided for limiting compression imposed by a compression screw on a lag screw of an orthopedic implant assembly. In one disclosed system, a lag screw driver is provided that includes a distal end for engaging the lag screw and a proximal end that includes a stop member or a stop in its structure. Hereinafter, this stop member or stop portion will be referred to simply as a “stop.” The system also includes a compression screw driver that comprises a distal end for engaging the compression screw and a proximal end. The compression screw driver comprises a radially outwardly extending member disposed between the proximal and distal ends thereof that engages the stop of the lag screw driver thereby preventing any further rotation of the compression screw driver or the compression screw. 
         [0011]    In some implementations, the system can include one or more of the following features. For example, the proximal end of the lag screw driver comprises a handle and the stop is disposed on the handle. The lag screw driver comprises an elongated cylindrical body extending between the proximal and distal ends of the lag screw driver and the elongated cylindrical body of the lag screw driver provides the stop. The lag screw driver comprises a retaining rod disposed within the elongated cylindrical body. The retaining rod comprises a proximal end that extends outward from the proximal end of the cylindrical body and serves as the stop for engaging the outwardly extending member of the compression screw driver. The retaining rod further comprises a threaded distal end for engaging interior threads disposed at the proximal end of the lag screw. The compression screw driver includes an elongated cylindrical body extending between the proximal and distal ends of the compression screw driver. The compression screw driver further comprises a retaining rod disposed within the elongated cylindrical body and the retaining rod of the compression screw driver includes a threaded distal end that threadably engages internal threads disposed at the proximal end of the compression screw. 
         [0012]    A system for limiting compression imposed by an orthopedic implant assembly is also disclosed. In one disclosed system, a lag screw and a compression screw are provided. The lag screw comprises a threaded distal end, a proximal end and an elongated body extending therebetween. The elongated body includes a middle rack. The middle rack has a predetermined axial length and the middle rack does not extend to either the distal or proximal ends of the lag screw. In other words, there are gaps between the middle rack and the distal and proximal ends of the lag screw. The distal end of the lag screw is threaded or includes an auger-type helical end for anchoring the lag screw into bone. The system also includes a compression screw that comprises a distal end, a proximal end and an elongated body extending therebetween. The elongated body of the compression screw includes a first threaded portion and a second unthreaded portion. The first threaded portion is disposed between the distal end of the compression screw and the second unthreaded portion. The second unthreaded portion is disposed between the proximal end of the compression screw and the first threaded portion. When the compression screw is located adjacent the lag screw so that the threads of the first portion of the compression screw are enmeshed with the middle rack of the lag screw, rotation of the compression screw results in axial movement of the lag screw until the middle rack reaches the second unthreaded portion of the compression screw (or the end of the threads of the first portion). At this point, continued rotation of the compression screw results in no additional axial movement of the lag screw as the middle rack has reached the end of the first threaded portion (or the middle rack has reached the second unthreaded portion of the compression screw). When the middle rack of the lag screw reaches the end of the first threaded portion of the compression screw, this action serves as a definitive stop and further axial movement of the lag screw is prevented. 
         [0013]    In some implementations, the system can include one or more of the following features. For example, the middle rack is disposed within a trough disposed along the elongated body of the lag screw. The trough configuration enables the side-by-side placement of the lag and compression screws to consume less cross-sectional space. 
         [0014]    An improved fracture stabilization assembly is also provided which includes a stabilization assembly that comprises a stabilization device selected from the group consisting of a compression plate or an intramedullary nail. The stabilization device comprises a shaped opening to accommodate a compression screw and a lag screw in a side-by-side fashion. A lag screw driver and a compression screw driver are provided as described above. Operation of the lag screw driver and compression screw driver in the manner described above provides a positive stop to prevent any over-compression of the fractured bone by excessive axial movement of the lag screw caused by over rotation of the compression screw. 
         [0015]    Similarly, a fracture stabilization assembly may include a stabilization device as described above in combination with the lag and compression screw combination described above. The lag screw includes a middle rack of a predetermined length and the compression screw includes a first portion that is threaded and a second portion that is unthreaded. When the compression screw is rotated to the extent whereby the middle rack of the lag screw reaches the second unthreaded portion of the compression screw, movement of the lag screw is positively stopped regardless of whether the compression screw continues to be rotated and over-compression of the fractured bone is avoided. 
         [0016]    Methods for stabilizing a fracture in a bone are also disclosed. One disclosed method includes installing a stabilization device such as a compression plate or an intramedullary nail as described above. The stabilization device may have a shaped opening to accommodate a compression screw and a lag screw in a side-by-side fashion as described above. The method includes providing a lag screw, a compression screw, a lag screw driver and a compression screw driver as described above. The method includes installing the stabilization device, inserting the lag screw through the shaped opening, rotating the lag screw with the lag screw driver and anchoring the lag screw in bone disposed on the distal side of the fracture site with the threaded distal end of the lag screw. The method further includes rotating the lag screw so that the middle rack faces the portion of the shaped opening that receives the compression screw. The method further includes inserting the compression screw through the shaped opening and engaging the threads of the compression screw with the middle rack of the lag screw. The method further includes rotating the compression screw with the compression screw driver until the radially outwardly extending member of the compression screw driver engages the stop of the lag screw driver. 
         [0017]    In some implementations, a lag screw with a middle rack as described above and a compression screw with the first threaded portion and second unthreaded portion as described above may be utilized. After the lag screw is anchored to bone disposed on a distal side of the fracture site, the compression screw is rotated until the middle rack of the lag screw reaches the second unthreaded portion of the compression screw to achieve a positive stop situation thereby avoiding over-compression of the fractured bone. 
         [0018]    In one general aspect, a system for the limiting compression force applied by an orthopaedic fastening assembly includes a first component driver comprising a distal end for engaging a first member of the fastening assembly and a proximal end including a stop, and a second component driver comprising a distal end for engaging a second member of the fastening assembly and a proximal end, the second component driver including a structure disposed between the proximal end and the distal end of the second member that engages the stop of the first component driver to limit axial translation of the first member relative to the second member. 
         [0019]    Implementations can include one or more of the following features. For example, the proximal end of the first component driver comprises a handle, and the stop is included on the handle. The first component driver further comprises an elongated cylindrical body extending between the proximal end and the distal end of the first component driver, and a retaining rod disposed within the elongated cylindrical body, the retaining rod comprising a proximal end that extends outward from the cylindrical body and serves as the stop. The retaining rod further comprises a threaded distal end for engaging the first member. The structure extends radially outwardly between the proximal end and the distal end of the second component driver. The structure includes a flange disposed between the proximal end and the distal end of the second component driver. The second component driver includes an elongated cylindrical body extending between the proximal end and the distal end of the second component driver, the second component driver further comprising a retaining rod disposed within the elongated cylindrical body and including a threaded distal end that threadably engages the second member. 
         [0020]    In another general aspect, a system for the limiting compression imposed by an orthopedic implant assembly includes a first fastener assembly member comprising a threaded distal end, a proximal end, and an elongated body extending therebetween, the elongated body of the first fastener assembly member having a cooperation structure having a predetermined axial length and not extending to the distal end or the proximal end of the first fastener assembly member, and a second fastener assembly member comprising a distal end, a proximal end, and an elongated body extending therebetween, the elongated body of the second fastener assembly member having a first portion and a second portion, the first portion being disposed between the proximal end and the distal end of the second fastener assembly member, and the second portion being disposed between the proximal end of the second fastener assembly member and the first portion, the first portion having a complimentary cooperation structure configured to engage the cooperation structure of the first fastener assembly member, and the second portion being configured to not engage the cooperation structure of the first fastener assembly member. When second fastener assembly member is located adjacent to the first fastener assembly member so that the complimentary cooperation structure of the first portion of the second fastener assembly member is engaged with the cooperation structure of the first fastener assembly member, adjustment of the second fastener assembly member results in axial movement of the first fastener assembly member relative to the second fastener assembly member until the cooperation structure of the first fastener assembly member reaches the second portion of the second fastener assembly member. 
         [0021]    Implementations can include one or more of the following features. For example, portions of the elongated body of the first fastener assembly member disposed between the cooperation structure of the first fastener assembly member and the proximal end of the first fastener assembly member and the distal end of the first fastener assembly member are configured to not engage the complimentary cooperation structure of the second fastener assembly member. The cooperation structure of the first fastener assembly member is disposed within a trough of the elongated body of the first fastener assembly member. 
         [0022]    In another general aspect, an orthopaedic device includes a stabilization structure selected from the group consisting of a plate and an intramedullary nail, the stabilization structure comprising a shaped opening configured to receive a first member and a second member in a side-by-side arrangement, a first driver having a distal end for engaging the first member and a proximal end having a stop surface, and a second driver having a distal end for engaging the second member and a proximal end, the second driver having a radially outwardly extending portion disposed between the proximal and distal ends thereof, the radially outwardly extending portion being configured to engage the stop surface of the first driver during use to limit relative movement between the first driver and the second driver. 
         [0023]    Implementations can include one or more of the following features. For example, the proximal end of the first driver comprises a handle, and the stop is located on the handle. The first driver further comprises an elongated cylindrical body extending between the proximal and distal ends thereof, the first driver further comprising a retaining rod disposed within the elongated cylindrical body, the retaining rod comprising a proximal end that extends outward from the cylindrical body and serves as the stop. The first driver further comprises an elongated cylindrical body extending between the proximal and distal ends thereof, the proximal end of the cylindrical body being connected to a handle, the first driver further comprising a retaining rod disposed within the elongated cylindrical body, the retaining rod comprising a proximal end that extends outward from the cylindrical body, at least one of the proximal end of the retaining rod, the handle, or the cylindrical body serving as the stop. The retaining rod of the first driver further comprises a threaded distal end for engaging the first member. The distal end of the retaining rod of the first driver is threaded for threadably engaging the first member. The distal end of the first driver is forked for engaging and rotating the first member. The distal end of the first driver comprises an element for rotating the first member that is selected from the group consisting of a female polygonal wrench socket, a male polygonal wrench, a transverse driver blade, an Allen-type driver element, a Phillips-type driver element, and a pair of prong members. 
         [0024]    In another general aspect, an orthopaedic device includes a stabilization structure selected from the group consisting of a plate and an intramedullary nail, the stabilization structure having a shaped opening configured to receive a first member and a second member in a side-by-side arrangement, the first member comprising a threaded distal end, a proximal end, and an elongated body extending therebetween that includes a cooperation structure, the cooperation structure having a predetermined axial length and not extending to either the distal or proximal ends of the first member, and the second member comprising a distal end, a proximal end, and an elongated body extending therebetween that includes a first portion and a second portion, the first portion being disposed between the proximal end and the distal end of the second member and the second portion being disposed between the proximal end of the second member and the first portion, the first portion having threads for engagement with the cooperation structure of the first member and the second portion being unthreaded. When the second member is located adjacent to the first member so that the threads of the first portion of the second member engage the cooperation structure of the first member, rotation of the second member results in axial movement of the first member relative to the second member until the cooperation structure reaches the second portion of the second member. 
         [0025]    Implementations can include one or more of the following features. For example, portions of the elongated body of the first member disposed between the cooperation structure and the proximal end of the first member and the threaded distal end of the first member are configured to not engage the threads of the second member. The cooperation structure is disposed within a trough of the elongated body of the first member. 
         [0026]    In another general aspect, a method for stabilizing a bone includes installing a stabilization structure selected from the group consisting of a plate and an intramedullary nail, the stabilization structure comprising a shaped opening configured to receive a first member and a second member in a side-by-side arrangement, providing the first member, the second member, a first driver, and a second driver, the first member comprising a threaded distal end, a proximal end for engagement with a first driver and a cooperation structure for engaging the second member, the first driver comprising a distal end for engaging the first member and a proximal end comprising stop, the second driver comprising a distal end for engaging the second member and a proximal end, the second driver comprising a radially outwardly extending member disposed between the proximal and distal ends thereof for engaging the stop of the first driver, inserting the first member through the shaped opening and engaging bone with the threaded distal end of the first member by rotating the first member with the first driver, inserting the second member through the shaped opening alongside the first member such that threads of the second member engage the cooperation structure of the first member, and rotating the second member with the second driver until the radially outwardly extending member of the second driver engages the stop of the first driver. 
         [0027]    Other advantages and features will be apparent from the following detailed description when read in conjunction with the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]      FIG. 1  is a perspective view of an intramedullary nail secured to a humerus by a fastening assembly. 
           [0029]      FIG. 2  is a perspective view of a fixation plate secured to a femur by a fastening assembly. 
           [0030]      FIG. 3  is a perspective view of a fixation plate secured to a tibia by a fastening assembly. 
           [0031]      FIG. 4  illustrates a fracture across a femoral neck and a stabilization assembly. 
           [0032]      FIG. 5  is a perspective view of the stabilization assembly of  FIG. 4 . 
           [0033]      FIG. 6  is an exploded view of the stabilization assembly of  FIG. 4 . 
           [0034]      FIG. 7  is a perspective view of a fastening assembly. 
           [0035]      FIG. 8  is an exploded view of the fastening assembly of  FIG. 7 . 
           [0036]      FIG. 9  is a side view of a driver tool for driving a fastener. 
           [0037]      FIG. 10  is a side view of a retaining rod for use with the tool of  FIG. 9 . 
           [0038]      FIG. 11  is a side view of the tool of  FIG. 9  with the retaining rod of  FIG. 10 . 
           [0039]      FIG. 12  is a side view of another tool for driving a fastener. 
           [0040]      FIG. 13  is a side view of another retaining rod for use with the tool of  FIG. 12 . 
           [0041]      FIG. 14  is a side view of the retaining rod of  FIG. 13  with the tool of  FIG. 12 ; 
           [0042]      FIGS. 15-17  are perspective views of a tool set for driving fasteners; 
           [0043]      FIGS. 18-20  are side views of another fastening assembly. 
       
    
    
       [0044]    It should be understood that the drawings are not necessarily to scale and that the figures are sometimes illustrated diagrammatically and in partial views. In certain instances, details which are not necessary for an understanding of the disclosure or which render other details difficult to perceive may have been omitted. It should be understood that this disclosure is not limited to the particular implementations illustrated herein. 
       DETAILED DESCRIPTION 
       [0045]    Referring to  FIGS. 7 and 8 , the lag screw  32  includes the threaded distal end  37  that engages or anchors the lag screw  32  into a bone. The compression screw  33  includes a threaded section  36 . A proximal end  68  of the lag screw is configured to engage a lag screw driver  80  ( FIGS. 9-11 ). Similarly, the compression screw  33  includes a proximal end  69  for engagement with a compression screw driver  90  ( FIGS. 12-14 ). 
         [0046]    Referring again to  FIG. 6 , the intramedullary nail  61  includes a shaped opening  67  for receiving both the lag screw  32  and the compression screw  33 . During a procedure, the lag screw  32  is inserted through a corresponding larger portion  67   a  of the shaped opening  67  and rotated until the threaded distal end  37  is anchored in a desired location distal of the fracture site. The lag screw  32  is then rotated until a trough area  71 , or other feature configured to engage the compression screw  33 , is facing smaller portion  67   b  of the shaped opening  67  that corresponds to the compression screw  33 . The proper alignment of the trough area  71  of the lag screw  32  and the compression screw  33  is illustrated in  FIGS. 4-6 . The compression screw  33  is then inserted through the smaller portion  67   b  of the shaped opening  67  alongside the lag screw  32 . The trough area  71  of the lag screw  32  extends generally along the length of the lag screw  32  and partially accommodates the circumference of the compression screw  33  as illustrated in  FIG. 7 . The trough area  71  includes a middle rack  72  between otherwise smooth trough sections  73 ,  74  as illustrated in  FIG. 8 . The middle rack  72  engages the threads  36  of the compression screw  33  when the compression screw  33  is inserted through the smaller portion  67   b  of the shaped opening  67  alongside the lag screw  32 . In some embodiments, the compression screw  33  and lag screw  32  may be inserted through the shaped opening  67  of the intramedullary nail  61  together. 
         [0047]    To provide compression force on the fracture  63  and/or the bone, the compression screw  33  is rotated with the threads  36  engaged with the middle rack  72  of the lag screw  32 . When the compression screw  33  engages the intramedullary nail  61 , rotation of the compression screw  33  results in the lag screw  32  being pulled back out of the shaped opening  67 , i.e., downward in the orientation of  FIG. 6 . 
         [0048]    In  FIGS. 7 and 8 , the proximal end  69  of the compression screw is designed to receive a hexagonally shaped Allen-type driving tool. Of course, other types of engagements between the compression screw  33  and a compression screw driver  90  ( FIGS. 12-14 ) could be utilized, as will be apparent to those skilled in the art. However, in  FIGS. 5-8 , two variations of the lag screw  32  are illustrated. In  FIGS. 5 and 6 , the proximal end  68  of the lag screw  32  is designed to be received in a hexagonal wrench socket, whereas in  FIGS. 7 and 8 , proximal end  68   a  includes a transverse slot  76  that can accommodate a blade-type driver or a forked-type driver, such as the driver  80  shown in  FIGS. 9-11 . 
         [0049]    Turning to  FIGS. 9-11 , a lag screw driver  80  is illustrated. In  FIG. 9 , an elongated cylindrical body  81  is shown attached to a handle  82 . A distal end  83  of the body  81  includes a pair of prongs or forks  84  for engaging the proximal end  68   a  of the lag screw  32 . The body  81  also includes proximal end  85  which is connected to the handle  82 . The body  81  accommodates a retaining rod  86  ( FIG. 10 ). The retaining rod  86  includes a proximal end  87  and a threaded distal end  88 . The threaded distal end  88 , which is optional, may be used to engage a threaded opening  89  in the lag screw  32 , as illustrated in  FIG. 6 . A threaded opening may also be disposed within the slot  76  of the lag screw  32  illustrated in  FIGS. 7-8 . The threaded end  88  of the retaining rod  86  captures the lag screw  32  and provides assurance that the lag screw  32  will not be dropped or misplaced during a procedure. The retaining rod  86  is received within the elongated body  81  of the lag screw driver  80 , as illustrated in  FIG. 11 . The proximal end  87  of the retaining rod  86  extends outward through the proximal end  85  of the elongated body  81 . As shown below, the proximal end  87  of the rod  86  may be used as a stop against further rotation of the compression screw  33  and/or compression screw driver  90  illustrated in  FIGS. 12-14 . Also, the retaining rod  86  is optional, and other portions of the handle  82  or proximal end  85  of the elongated body  81  of the lag screw driver  80  may be used as the stop. 
         [0050]    Turning to  FIGS. 12-14 , the compression screw driver  90  also includes an elongated body  91  with a distal end  92  and a proximal end  93 . Between the distal and proximal ends  92 ,  93 , the elongated body  91  includes a radially outwardly extending member, such as a flange  94  shown in  FIGS. 12 and 14 . Alternatively, other outwardly extending members may be employed as will be apparent to those skilled in the art. The elongated body  91  may be enlarged at the correct location, or may include a collar, retaining ring, clip or another structure to engage the proximal end  87  of the rod  86  and/or another stop provided on the lag screw driver  80 . The compression screw driver  90  may also include a retaining rod  95  also having a threaded distal end  96  and a proximal end  97 . Similar to the lag screw driver  80  discussed above, the threaded distal end  96  of the retaining rod  95  may be used to threadably engage an interior threaded portion of the compression screw  33  (not shown) to capture the compression screw and avoid the compression screw  33  being dropped or otherwise misplaced during a procedure. Like the retaining rod  86  of the lag screw driver  80 , the retaining rod  95  of the compression screw driver  90  is optional. The distal end  92  of the compression screw driver  90  is hexagonally shaped to be received in the proximal end  69  of the compression screw  33 , as illustrated in  FIGS. 6-8 . Alternatively, other coupling arrangements between the compression screw driver  90  and the compression screw  33  can be utilized, as will be apparent to those skilled in the art. 
         [0051]    Turning to  FIGS. 15-17 , operation of the flange or outwardly extending member  94  and the distal end  87  of the retaining rod  86  is illustrated. In  FIG. 15 , the lag screw  33  has been inserted through the fixation device (not shown in  FIGS. 15-17 ) and the handle  82  has been rotated so the threaded distal end  37  of the lag screw  32  is anchored into bone disposed distally of the fracture site (not shown in  FIGS. 15-17 ). The compression screw driver  90  is then engaged with the proximal end  69  of the compression screw  33  (not shown in  FIGS. 15-17 ) and, while leaving the lag screw driver  80  in place, the compression screw  33  is inserted alongside the lag screw  32  and the compression screw driver  90  engages the proximal end  69  of the compression screw  33  and is rotated. As the compression screw driver  90  is rotated while the compression screw  33  engages the intramedullary nail  61 , the threads  36  of the compression screw  33  engage the middle rack  72  of the lag screw  32  and draw the lag screw  32  and the lag screw driver  80  to the right in  FIGS. 15-17 , i.e., towards the flange  94 . 
         [0052]    In  FIG. 15 , little or no compression force is exerted by the lag screw  32  on the fracture  63 . In  FIG. 16 , the compression screw driver  90  has been rotated to an extent where at least some compression force is exerted by the lag screw  32  on the fracture  63 . As seen in  FIG. 16 , the handle  82  has moved from the position in  FIG. 15  towards the flange  94 . At the point reached in  FIG. 17 , the handle  82  and/or the distal end  87  of the retaining rod  86  of the lag screw driver  80  engage(s) the flange  94  of the compression screw driver  90  to prevent any further rotation of the compression screw driver  90  such that no additional movement of the lag screw  32  relative to the compression screw  33  is possible. Thus, in the position shown in  FIG. 17 , a complete stop is achieved and, with the dimensions properly designed, over-compression of the fracture  63  by the lag screw  32  is prevented. 
         [0053]    As mentioned above, the stop may be provided by the distal end  87  of the retaining rod  86 , by the handle  82 , and/or by the proximal end  85  of the elongated body  81  of the lag screw driver. Any area on the lag screw driver  80  may be employed as a stop to further rotation of the compression screw  33 . 
         [0054]    Turning to  FIG. 18 , the lag screw  32  is shown adjacent to a compression screw  33 . The compression screw  33  includes a proximal end  69 , a first threaded portion  36   a  and a second unthreaded portion  101 . The lag screw  32 , similar to the one illustrated in  FIGS. 7  and  8 , includes an elongated body and trough  71  ( FIG. 8 ) with a distinct middle rack  72 . To provide a complete stop against further movement of the lag screw  32  to the right in the orientation of  FIGS. 18-19  due to rotation of the compression screw  33 , the first threaded portion  36   a  of the compression screw  33  ends at the second unthreaded portion  101 . As seen in  FIG. 19 , when the compression screw  33  has been rotated, the rack  72  of the lag screw  32  has moved to the right relative to the compression screw  33  and partially into or over the unthreaded portion  101 . In the position shown in  FIG. 20 , the trailing edge of the middle rack  72  has reached the end of the first threaded portion  36   a  of the compression screw  33 . Therefore, further rotation of the compression screw  33  will not result in any additional lateral movement of the lag screw  32  to the right because the threaded portion  36   a  disengages the rack  72 , and a complete stop is obtained. 
         [0055]    Additionally, the proximal end  69  of the compression screw  33  can be configured to engage the rack  72  to limit further advancement of the compression screw  33  relative to the lag screw  32 . For example, when the compression screw  33  and the lag screw  32  are positioned as shown in  FIG. 20 , rotation of the compression screw will no longer cause further compression because the threaded portion  36   a  disengages from the rack  72  as described above. However, other forces may cause the compression screw  33  to advance further (or cause the lag screw  32  to retract relative to the compression screw  33 ), which could cause further compression. To limit further compression, the proximal end  69  can abut the rack  72  to provide a positive stop that prevents the compression screw  33  from moving relative to the lag screw  32  causing further compression. 
         [0056]    While selected implementations have been set forth, alternatives and modifications will be apparent from the above description to those skilled in the art that fall within the spirit and scope of this disclosure and the appended claims.