Abstract:
An intramedullary nail configured for use in a bone, the nail including at least one bore configured to receive a bone screw. The bore includes at least one member configured to engage the threads of the screw to prevent axial motion of the screw within the bore after application. The member may be integrally formed in the bore or may be a separate member added to the bore. The member may have a variety of cross sectional shapes, such as a rectangular shape, circular shape or a triangular shape.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to an intramedullary nail for use in assisting in the healing of bones. 
         [0003]    2. Description of the Related Art 
         [0004]    The usage of intramedullary nails to assist in the healing of bones by locating the intramedullary nail in the canal of a bone is known. Bone screws are often employed to help retain the nail at a desired location within the bone canal. Often the bone screws are inserted into bores formed in the intramedullary nail. The bores generally have substantially smooth side walls thereby allowing the screw to pass freely through the nail. 
       SUMMARY 
       [0005]    An intramedullary nail configured for use in a bone, the nail including at least one bore configured to receive a bone screw. The bore includes at least one member configured to engage the threads of the screw to prevent axial motion of the screw within the bore after application. The member may be integrally formed in the bore or may be a separate member added to the bore. The member may have a variety of cross sectional shapes, such as a rectangular shape, circular shape or a triangular shape. 
         [0006]    In one form, the present invention provides for an intramedullary nail configured to receive at least a portion of a bone screw, the nail including a body portion having first and second ends; and at least one bore in the body portion, the bore configured to receive the bone screw, wherein at least a portion of the bore is substantially smooth and the bore comprises at least one member configured to engage at least a portion of a thread of the screw. 
         [0007]    In another form, the present invention provides for an intramedullary nail configured for use in a canal of a bone, the nail includes a first end including at least one bore configured to receive a screw, a second end, a body portion intermediate the first end and the second end wherein the at least one bore includes a substantially smooth portion and means for preventing movement of the screw with respect to the nail when the screw is not rotating. 
         [0008]    In another form, the present invention provides for a method of forming a bore configured to engage a screw in an intramedullary nail having a distal end, a proximal end and a body positioned intermediate the distal end and the proximal end, the method including the steps of milling a bore sized to receive the screw in one of the proximal or distal ends, wherein a portion of the bore includes a substantially smooth portion, and fashioning a member in the bore configured to engage the screw as the screw is inserted into the bore. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
           [0010]      FIG. 1  is a perspective view of an intramedullary nail embodying an aspect of the present invention; 
           [0011]      FIG. 2  is an enlarged fragmentary view of a portion of the nail depicted in  FIG. 1 ; 
           [0012]      FIG. 3  is a side view of the portion of the nail depicted in  FIG. 2 ; 
           [0013]      FIG. 4  is a section view taken along section line  4 - 4  in  FIG. 2  depicting an embodiment of an engagement portion within a bore of the nail; 
           [0014]      FIG. 5  is a perspective view of a screw; 
           [0015]      FIG. 6  is a perspective view of the screw depicted in  FIG. 5  inserted into the nail depicted in  FIG. 1 ; 
           [0016]      FIG. 7  is a section view taken along the section line  7 - 7  of  FIG. 6 ; 
           [0017]      FIG. 8  is an enlarged section view of the area indicated in  FIG. 7 ; 
           [0018]      FIGS. 9A-9C  are section views depicting an exemplary method of forming a portion of the bores present within the nail depicted in  FIG. 1 ; 
           [0019]      FIG. 10  is a section view depicting an alternative embodiment of an engagement portion present within a bore of the nail; 
           [0020]      FIG. 11  is section view depicting an alternative embodiment of engagement portions present within a bore of the nail; 
           [0021]      FIG. 12  is a perspective view depicting an exemplary method of forming the engagement portions depicted in  FIG. 11 ; 
           [0022]      FIG. 13  is a side view of a bore including an alternative embodiment of an engagement portion formed in a bore of the nail depicted in  FIG. 1 ; 
           [0023]      FIGS. 14 through 17  are section views depicting an alternative configuration of engagement portions present within a bore of the nail; 
           [0024]      FIGS. 18A-18C  are section views depicting an exemplary method of forming a portion of the bores present within a nail; 
           [0025]      FIG. 19  is a perspective view of an intramedullary nail embodying aspects of the present invention; and 
           [0026]      FIG. 20  is a perspective view of an elongated bore embodying aspects of the present invention. 
       
    
    
       [0027]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
       DETAILED DESCRIPTION 
       [0028]      FIG. 1  depicts an intramedullary nail, generally indicated by numeral  10 , representing an embodiment of the presenting invention. Nail  10  includes a proximal end  12 , a distal end  14  and a body portion  16  located intermediate the ends  12 ,  14 . Nail  10  may be formed from any suitable biocompatible material, such as titanium or stainless steel. Nail  10  may also have any shape suitable for any surgical techniques. Nail  10  is not intended to be limited to use in any particular body part or bone, such as a femur. 
         [0029]    Nail  10  further includes a cannula  18 , shown in  FIG. 1  in phantom, extending substantially along the longitudinal axis  20  of nail  10 . In the depicted embodiment, cannula  18  begins at proximal end  12  and terminates at distal end  14 . In embodiments, cannula  18  may traverse only a portion of nail  10 , if desired. 
         [0030]    Referring still to  FIG. 1 , proximal end  12  includes a plurality of through bores, each indicated by numeral  22 . In the depicted embodiment, bores  22  extend completely through nail  10 , and generally have circular shapes. Proximal end  12  also includes an elongated bore, generally indicated by numeral  24 . Elongated bore  24  may have substantially the same structure as bores  22  but has an elongated shape. 
         [0031]    Distal end  14  of nail  10  may be configured to be inserted into a canal of a bone in a known manner. In the depicted embodiment, distal end  14  includes a plurality of bores, each indicated by numeral  26 . In the depicted embodiment, bores  26  each have a circular shape and extend entirely through nail  10 . 
         [0032]    With reference to  FIGS. 1-4 , in the depicted embodiment, bore  26  includes a first smooth portion, generally indicated by numeral  28 , a second smooth portion, generally indicated by numeral  30 , and engagement portions, generally indicated by numeral  32 . In the depicted embodiment, the smooth portions  28 ,  30  define substantially similar diameters, indicated by D in  FIG. 3 , of bore  26 . In the depicted embodiment, the substantially smooth portions  28 ,  30  form, or extending along, at least a majority of the length of bore  26 . The substantially smooth portions  28 ,  30  may form, or extend along, at least 85%, 90% or 95% of the length of bore  26 . In embodiments, the smooth portions  28 ,  30  may form a larger portion of the bore  26 , if necessary. 
         [0033]    Engagement portions  32  also define a diameter, indicated by D′, in bore  26 . In the present embodiment, diameter D is greater in magnitude than diameter D′. As depicted in  FIG. 4 , engagement portions  32  have a substantially rectangular cross section. In addition, as depicted in  FIG. 4 , engagement portions  32  are integrally formed with nail  10 . As shown in  FIG. 3 , cannula  18  bisects the engagement portions  32 , thereby forming the two engagement portions  32 . It should be noted that if desired, the engagement portions  32  may be formed at a position spaced apart from cannula  18  thereby creating an annular engagement portion. 
         [0034]      FIG. 5  depicts a perspective view of a bone screw, indicated by numeral  40 . Bone screw  40  may be of any type know in the art and may be configured for any surgical technique requiring screw  40  to mate with nail  10 . In general, bone screw  40  includes a distal end  42 , a proximal end  44  and a thread  46  extending from distal end  42  to proximal end  44 . In the depicted embodiment, proximal end  44  includes a head portion  48  configured to provide a mechanism for driving screw  40 . It should be noted that in embodiments of screw  40 , thread  46  need not extend entirely from distal end  42  to proximal end  44 , but may be interrupted with a substantially smooth portion. 
         [0035]      FIG. 6  depicts screw  40  inserted into a bore  26 , as would be accomplished in numerous surgical techniques in which nail  10  has been inserted into the canal (not shown) of a bone (not shown). A bone has been omitted from  FIG. 6  for the sake of clarity. In addition, it should be noted that nail  10  may be configured to be located within the canal of numeral bones, in accordance with numeral surgical techniques. Once nail  10  has been properly positioned within a bone, screw  40  may be inserted into both the bone and the nail  10  in order to retain the nail in a fixed position with respect to the bone. 
         [0036]      FIGS. 7 and 8  are section views taken along the section line  7 - 7  of  FIG. 6  depicting screw  40  inserted into bore  26  of nail  10 . As depicted in the Figures, the threads  46  engage engagement portions  32  of nail  10  by receipt of engagement portions  32  between adjacent crests of thread  46  of screw  42  as the same is threaded through bore  26  of nail  10 . The engagement between the engagement portions  32  and screw  40  is sufficient to ensure that the screw  40  and nail  10  remain in a relatively fixed position with respect to each other. It should be noted that without engagement portions  32 , the screw  40  would be able to freely traverse within bore  26 . Engagement portions  32 , however, require that the screw  40  be rotated in a traditional fashion whenever being inserted into or removed from bore  26 . Accordingly, engagement portions  32  result in a more robust engagement between screw  40  and nail  10  than would occur if engagement portions  32  were not present in nail  10 . It should be noted that in embodiments, the engagement portions may be sized and configured to allow the threads  40  of the screw  42  to deform, or tap, the engagement portions  32  during a first insertion of screw  42 . 
         [0037]    In the depicted embodiment, the substantially smooth portions  28 ,  30  may provide a surgeon with a guide when screw  40  is first being inserted into bore  26 . When screw  40  has traversed a sufficient distance of bore  26  with one of the smooth portions  28 ,  30  guiding screw  40 , thread  42  may then engage engagement portions  32 . 
         [0038]    Engagement portions  32  may be formed in any suitable manner, such as by the process depicted in  FIGS. 9A-9C .  FIG. 9A  depicts a section view of nail  10  including unformed through bore  34 . Unformed through bore  34  has a substantially uniform diameter approximately equal to diameter D′. A workpiece capable of removing material, such as a mill  36 , depicted in  FIG. 9B , may be inserted into unformed bore  34  in order to remove material from the bore  34 . As mill  36  removes material, mill  36  forms smooth portion  28  having a diameter D. Workpiece  36  may then inserted into the opposite end of bore  34  in order to form smooth second portion  30 , as shown in  FIG. 9C . As set forth above, smooth second portion  30  has a diameter substantially equal to diameter D. In forming smooth second portion  30 , the maximum distance workpiece  36  is inserted should not exceed a distance that allows workpiece  36  to reach smooth first portion  28 . By not reaching smooth first portion  28 , workpiece  36  forms the engagement portions  32 . As shown in  FIG. 9C , since workpiece  36  has a substantially flat bottom portion  38 , the engagement portions  36  have a substantially rectangular cross section. It should be noted that in embodiments, diameter D may be approximately equal to the outer diameter of screw  40  wherein the thread  42  of screw  40  would deform, or tap, the engagement portions  32  during insertion of screw  40 . 
         [0039]      FIG. 10  depicts a cross section of another embodiment of the through bore  22 . In the depicted embodiment, the engagement portions  32 ′ are formed with a workpiece such as a countersink, which has an angled end. Accordingly, the cross section of the engagement portions  32 ′ are triangular when formed in the manner depicted in  FIG. 9A-9C  and described above but utilizing a countersink rather than a mill  36 . 
         [0040]      FIG. 11  depicts a cross section of another embodiment of bore  26 . In the embodiment depicted in  FIG. 11 , the engagement portions  32 ″ are formed by swaging the bore  26 . For example,  FIG. 12  depicts a method of swaging bore  26 . As shown in  FIG. 12 , a bar  50  may be placed across the through bore  26 . Bar  50  may then be struck with an object capable of providing a force in the direction of arrow F, such as a hammer or mallet, for example. The force imparted upon the bore  26  by the bar  50  causes a portion of the bore  26  to deform, thereby forming engagement portions  32 ″. Swaging may also be used to create engagement portions  32 ″ on the opposite side of bore  26 , as depicted in  FIG. 11 , in a similar manner. In addition, other known mechanisms capable of swaging bore  26  may be utilized. Furthermore, if suitable, the bar  50  may be orientated in a variety of different positions than that depicted in  FIG. 12 , if desired. 
         [0041]      FIG. 13  depicts a side view of another embodiment of bore  26 . In the depicted embodiment, bore  26  includes at least one groove  52 , illustrated in phantom, formed therein in a suitable manner. For example, a key mill (not shown) may be utilized to form a groove  52  in a known manner. 
         [0042]    A c-ring  32 ′″ may then be located in each of the grooves  52  in a known manner. For example, the c-ring  32 ′″ may be compressed slightly thereby allowing the c-ring  32 ′″ to be moved to a groove  52 . Once c-ring  32 ′″ is located in groove  52 , c-ring  32 ′″ may be released thereby allowing c-ring  32 ′″ to expand and reside within groove  52 . If desired, an adhesive may be utilized to help retain the c-ring  32 ′″ within groove  52 . C-ring  32 ′″ may be formed from any suitable material, such as a plastic. 
         [0043]      FIGS. 14 through 17  depict additional modifications that may be made to the engagement portions  32  depicted in  FIG. 4 . For example, in  FIG. 14 , one of the engagement portions  32  has been removed, thereby leaving a single engagement portion  32 . The removed engagement portion may be removed in any suitable fashion, such as with a mill, for example. 
         [0044]    In  FIG. 15 , the engagement portions  32  are askew, i.e. projected at an angle with respect to the longitudinal axis of bore  26 . The configuration depicted in  FIG. 15  may be formed in any suitable manner, such as by impacting the engagement portions  32  with a forming device or machining the engagement portions with a countersink from one direction and a mill in the opposite direction. 
         [0045]      FIG. 16  depicts an embodiment including multiple engagement portions formed in bore  26  on opposite sides of cannula  18 . 
         [0046]      FIG. 17  depicts an embodiment wherein each engagement portion  32  is formed on opposite sides of cannula  18  and the engagement portions are axially spaced with respect to one another along the longitudinal axis of bore  26 . It should be noted that each of these configurations may be utilized in placing the engagement portions  32 ′,  32 ″,  32 ′″ depicted in previous figures. 
         [0047]      FIG. 18A  depicts a section view of an embodiment wherein the engagement portions  32  are formed proximate cannula  18 . The embodiment depicted in  FIG. 18A  may be formed from any suitable manufacturing process, including the process depicted in  FIGS. 18B and 18C . As shown in  FIG. 18B , nail  10  includes an unformed bore  34  having a diameter of D′. As shown in  FIG. 18C , a workpiece capable of removing material, such as a mill  36 , may be inserted into unformed bore  34  in order to remove material from the bore  34 . As mill  36  removes material, mill  36  forms smooth portion  28  having a diameter D, which is larger than diameter D′. Workpiece  36  may then be inserted into the opposite end of unformed bore  34  in order to form smooth portion  30 , as shown in  FIG. 18A . The resulting embodiment includes engagement portions  32  located proximate cannula  18 . 
         [0048]    As should be understood by one with skill in the art, bores  22 ,  24  may also include engagement portions representative of any embodiment previously described. It should also be noted that in embodiments, the bores  22 ,  24 ,  26  may be orientated an oblique angle with respect to longitudinal axis  20 . For example, as depicted an embodiment of nail  10 ′ illustrated in  FIG. 19 , bore  22 ′ is an example of a bore located at an oblique angle with respect to the longitudinal axis  20  of nail  10 ′. 
         [0049]    Furthermore, as is also depicted in  FIG. 19 , an additional elongated bore  24 ′ similar to elongated bore  24  may also be located proximate distal end  14  in embodiments. In addition, it should be noted that in any elongated bores  24 ,  24 ′, the engagement portions will allow for dynamization of the nail  10 ′ when desired. Moreover, the elongated bores  24 ,  24 ′ also allow for the insertion of a bone screw at an oblique angle with respect to the longitudinal axis  20  of nail  10 ′. 
         [0050]      FIG. 20  depicts an embodiment of elongated bore  24 ′ including an engagement portion  32 . As explained above, bore  24 ′ may include suitable engagement portion including those described previously. As illustrated in  FIG. 20 , in the depicted embodiment, bore  24 ′ includes smooth portions  28 ,  30  positioned with the engagement portion  32  located intermediate. Furthermore, as illustrated in  FIG. 20 , engagement portion  32  does not align with cannula  18 . In embodiments, engagement portion  32  may align with cannula  18  thereby ensuring the smooth portions  28 ,  30  are of approximately equivalent size. It should be noted that in all embodiments of the bores  22 ,  24 ,  26 , the engagement portion  32  may be located at any suitable position therein. 
         [0051]    While this invention has been described as having exemplary designs, the present invention may be further modified within the spirit and scope of the disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.