Patent Publication Number: US-9408637-B2

Title: Device for compression across fractures

Description:
PRIORITY CLAIM 
     The present application is a Continuation Application of U.S. patent application Ser. No. 13/693,603 filed on Dec. 4, 2012, now U.S. Pat. No. 9,011,501, which claims the priority to U.S. Provisional Patent Application Ser. No. 61/570,527 filed on Dec. 14, 2011. The entire disclosure of these patents/applications are expressly incorporated herein by reference. 
    
    
     BACKGROUND INFORMATION 
     Fractures of the pelvis and, more specifically, of the sacroiliac joint are often treated by inserting a fixation device across the fracture site. Present fixation systems and methods are generally directed to the insertion of one or more sacral bars or cancellous screws across the fracture site. The sacral bars are formed as elongated planar rods passed through the pelvis posterior to the sacrum until a free, end of the rod extends out of an opposing wall of the pelvis. Threaded nuts are then screwed onto the ends of the sacral bar to create and maintain compression of the pelvis. Cancellous screws can be inserted to span across the pelvis or can be inserted from either side of the pelvis to maintain the stability of the sacroiliac joint. However, these screws rely heavily on an overall strength of the bone and thread purchase to maintain the compression of the pelvis. These devices are therefore susceptible to failure due to loss of bone strength (e.g., due to osteoporosis, etc.), loosening of the threaded bolts and/or a loss of bony purchase (e.g., through rotational and/or longitudinal movement of the sacral bars within the bone). 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a bone fixation device comprising a first element extending from a first head at a first end to a first shaft at a second end along a first central longitudinal axis and having a first channel extending therethrough, the first head extending transverse to the first shaft providing a first shoulder which, in an operative configuration, rests against a portion of bone adjacent to a first hole through which the first shaft is inserted to define a maximum extent to which the first element may be inserted into the hole. The bone fixation device also comprises a second element including a second shaft extending along a second central longitudinal axis from a third end to a head at a fourth end thereof and having a second channel extending therethrough, the second head extending transverse to the second shaft providing a second shoulder which, in an operative configuration, rests against a portion of bone adjacent to a second hole through which the second shaft is inserted to define a maximum extent to which the second element may be inserted into the second hole, the second channel being dimensioned to slidably receive the first shaft therein. The bone fixation device also comprises a tensioning element insertable through the first and second channels, the tensioning element including a first end sized to prevent the first end from entering one of the first and second channels so that, tension applied at a second end of the tensioning element imparts a compressive force to the first and second elements and, consequently to a bone into which the first and second elements are inserted. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a first perspective view of a exemplary bone fixation element according to the present invention in a first configuration; 
         FIG. 2  shows a perspective view of the bone fixation element of  FIG. 1  in a second configuration; 
         FIG. 3  shows a second perspective view of the bone fixation element of  FIG. 1 ; 
         FIG. 4  shows a perspective view of the bone fixation element of  FIG. 1  in an implanted configuration; and 
         FIG. 5  shows a side view of the bone fixation element of  FIG. 1  in an implanted configuration. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The present invention relates generally to devices and methods for the fixation of a fractured or otherwise damaged pelvic bone. Specifically, the present invention relates to methods and devices for inserting a bone fixation element into the bone. The exemplary bone fixation element according to the invention comprises a first elongated element and a second elongated element, each extending along a longitudinal axis. In an operative configuration, the first and second elements are inserted through first and second lateral openings provided on opposing sides of a pelvic bone. In one embodiment, the first and second lateral openings can be two ends of a single hole formed by drilling completely across the pelvis. In another embodiment, two openings may be drilled on opposing walls of the pelvis. A free end of the first element is then inserted into a channel extending through the second element until the first and second elements are securely seated against the pelvic bone. A cable is then inserted through the first and second elements. A first end of the cable comprises a cable stop configured to lockingly engage an opening on a lateral head of the first element. The cable is then locked in position at a lateral end of the second element using a crimp to secure the first and second elements in a desired position relative to one another and compress the fractured bone, as will be described in greater detail later on. It is noted that although the exemplary system and method are discussed with respect to a sacroiliac fixation system and method, the invention may be used in any other bone fixation procedure in any other bone of the body by modifying the dimensions and shape of the apparatus to suit the particular anatomy. The term “medial” as used herein refers to a direction approaching a medial plane of a body in an operative configuration while the term “lateral” refers to a direction extending away from the medial plane in a right and left direction. 
     As shown in  FIGS. 1-5 , a bone fixation device  100  according to an exemplary embodiment of the invention comprises a first element  102  and a second element  104 . The first element  102  extends from a lateral end  106  to a medial end  108  along a central longitudinal axis  110 . The first element  102  according to this embodiment is substantially cylindrical and comprises a lateral body portion  112  having a first outer diameter and a medial body portion  114  having a second outer diameter, the second outer diameter being smaller than the first outer diameter. An elongated first channel  116  extends through the first element  102  from the lateral end  106  to the medial end  108 . The first channel  116  is in longitudinal alignment with the longitudinal axis  110  and is configured and dimensioned to receive a cable  200  therethrough, as will be described in greater detail later on. The lateral end  106  comprises an increased diameter head  118  having an oblong cross-sectional shape. It is noted, however, that any other cross-sectional shape (e.g., oval, circular, rectangular, etc.) may be used without deviating from the scope of the invention. The head  118  also comprises an opening  120  extending therethrough, a hole axis of the opening  120  extending substantially parallel to the longitudinal axis  110 . In another exemplary embodiment, the hole axis of the opening  120  may extend at any other angle relative to the axis  110 . The opening  120  is positioned adjacent to the channel  116 . As shown in  FIGS. 4-5 , the head  118  may also comprise a countersunk portion  121  configured to aid in manipulation of the cable  200 , as will also be described in greater detail below. 
     The second element  104  extends from a lateral end  122  to a medial end  124  along the central longitudinal axis  110 . The second element  104  according to this embodiment is substantially cylindrical in shape and comprises a substantially uniform outer diameter which is substantially equivalent to the first outer diameter of the lateral body portion  112 . However, those skilled in the art will understand that the first and second elements  102 ,  104 , respectively, may take any desired shape so long as the medial body portion  114  is slidably receivable within an elongated second channel  126  extending through the second element  104 . The second channel  126  extends from the lateral end  122  to the medial end  124  in longitudinal alignment with the longitudinal axis  110  and is configured and dimensioned to permit insertion of the medial body portion  114  thereinto. In one exemplary embodiment, the channel  126  has a substantially uniform diameter substantially equivalent to the outer diameter of the medial body portion  114  with a slight clearance to permit the medial body portion  114  to slide therein. In another exemplary embodiment, as shown in  FIG. 3 , the channel  126  comprises a medial channel portion  128  and a lateral channel portion  130 . The medial channel portion  128  has a diameter substantially equivalent to or greater than second outer diameter of the medial body portion  114  and smaller than the first outer diameter of the lateral body portion  112 . This configuration permits the insertion of the medial body portion  114  into the channel  126  while preventing the lateral body portion  112  from being inserted therein. In an exemplary embodiment, the first and second portions  102 ,  104  are dimensioned so that, when inserted to an operative configuration, the medial body portion  114  is seated within the medial channel portion  128  with enough overlap to maintain stability. Varying a length of the overlap allows adjustment of the length of the device  100  to account for variations in anatomy in different patients. In another embodiment, the device  100  may be provided in a variety of lengths so that a physician may select a device having a length range conforming to the requirements of a particular procedure. In a preferred embodiment, the device  100  may be configured to prevent the medial body portion  114  from being fully seated in the medial channel portion  128 . That is, by having the medial body portion  114  only partially seated in the medial channel portion  128 , a greater amount of compression may be applied via the cable  200 , as will be described in greater detail later on. The lateral channel portion  130  has substantially the same diameter as the first channel  116  so that the cable  200  inserted through the device  100  follows a smooth, substantially unobstructed path. The lateral end  122  comprises an increased diameter head  132  having an oblong cross-sectional shape similar to the shape of the head  118 . It is noted, however, that the head  132  may comprise any other shape without deviating from the scope of the invention. The head  132  comprises an opening  134  extending therethrough, a hole axis of the opening  134  extending substantially parallel to the longitudinal axis  110 . As with the opening  120 , the hole axis of the opening  134  may also extend at any angle relative to the axis  110 . 
     In accordance with an exemplary method according to the invention, a physician or other user makes incisions open to the right and left lateral walls of a pelvis. The fracture is then reduced and provisionally stabilized using, for example, Kirschner wires, as those skilled in the art will understand. A drill may then be used to form at least one longitudinal hole through the pelvis. A guide wire may first be inserted in the desired portion of the bone in a target insertion orientation. A cannulated drill may then be guided over the guide wire to open the bone to a desired diameter selected to accommodate the device  100 , as those skilled in the art will understand. In an exemplary embodiment, two holes may be drilled through the pelvis across the fracture to receive two devices  100 , although any number of holes may be drilled to conform to the requirements of the particular procedure, as those skilled in the art will understand. The cable  200  having the cable stop  202  on a first end thereof is then inserted into the opening  120  of the first element  102 . The cable stop  202  may be an enlarged end portion of the cable  200  having a diameter greater than a diameter of the opening  120 . In an exemplary embodiment, the cable stop  202  is inserted into the opening  120  from a medial direction so that when the first element  102  is positioned in the bone, the cable stop  202  is positioned toward the bone. As those skilled in the art will understand, this configuration minimizes stresses applied to the cable stop  202  in an operative configuration and helps to prevent loosening of the cable  200  relative to the bone. The first and second elements  102 ,  104  may then be inserted into the drilled hole from the left and right walls of the pelvis, respectively, until the medial body portion  114  is seated within the medial channel portion  128 , as described in greater detail earlier. In this configuration, the heads  118 ,  132  are in contact with the pelvis and the cable stop  202  is positioned adjacent the bone, as shown in  FIG. 3 . The cable stop  202  is seated within the concave portion of the head  118  so the head  118  is in direct contact with the bone without interference from the cable stop  202 . The free end of the cable  200  (not shown) is then inserted into the channel  116  from the lateral end  106 , forming a loop  204  adjacent the head  118 . As those skilled in the art will understand, the cable  200  may be configured and dimensioned to minimize a protrusion of the loop  204  out of the head  118  therefore minimizing a profile of the implanted device  100 . The loop  204  aids in removal of the device  100  from the body, as will be described in greater detail later on. The cable  200  is guided through the channel  116  and channel  126  until the free end exits the lateral end  122 . The free end of the cable  200  is then inserted into the opening  134  from the lateral end. A crimp is then advanced over the free end of the cable  200  and advanced until it contacts the head  132  of the second element  104 . The crimp may be any crimp known in the art. A tensioning mechanism threaded over the free end of the cable  200  is then operated as would be understood by those skilled in the art to apply a desired tension to the cable consequently applying a desired compressive force to the bone. The crimp is then crushed in a known manner to maintain the desired tension on the cable and the free portion of the cable  200  extending away from the crimp is trimmed. As would be understood by those skilled in the art, the countersunk portion  121  provides a space for into which the cable cutter may be advanced to allow a cable cutting device to snip the cable close in minimizing the protrusion of the free end of the cable  200 . 
     A physician may decide to remove the device  100  from the body after a predetermined amount of time has elapsed (e.g., once the bone has healed, etc.). To remove the device, a cable cutting mechanism may be used to cut the loop  204 , thereby removing the compressive force applied on the bone by the device  100 . The device  100  and cable  200  may then be removed from the body. 
     It will be apparent to those skilled in the art that various other modifications and variations may be made in the structure and the methodology of the present invention, without departing from the spirit or scope of the invention. For example, the exemplary system and method disclosed herein may be used for the treatment of any bone fracture wherein compression is required and opposing ends of the fractured bone are accessible to the physician. For example, the exemplary system and method may be used for the fixation of fractures of a patella, condyle, etc., wherein the compression may be aided by any number of additional bone fixation devices (e.g., intramedullary nail) without deviating from the scope of the invention. Thus, it is intended that the present invention cover modifications and variations of the invention provided that they come within the scope of the appended claims and their equivalents.