Abstract:
An orthopedic fastener having compressive forces along the direction of the long axis of the fastener and radially inwardly directed forces towards the center of the fastener to draw in a bone providing an improved means for uniting a fractured bone.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    Orthopedic surgeons typically are required to repair fractures and use pins in support thereof. The conventional pin actually induces a radially outwardly directed spreading force which does little to assist (and actually retards) the bone to mend itself. Further these pins induce no axial, compressive forces.  
         SUMMARY OF THE INVENTION  
         [0002]    The instant invention is distinguished over the known prior art in that a fastener is disclosed which provides radially inwardly directed forces relative to the fastener shaft which draw in the bone with respect to the fastener to provide a preferred fastening structure. In addition, the instant invention induces compressive forces along the length of the fastener to facilitate a tight juncture at the area of the fracture to promulgate healing and resist flexing at the fracture.  
         OBJECTS OF THE INVENTION  
         [0003]    The object of the present invention is to provide an improved orthopedic fastener exhibiting axial compressive forces and radially inward directed forces.  
           [0004]    Viewed from a first vantage point, it is an object of the present invention to provide an orthopedic fastener having first and second thread portions disposed along a long axis of the fastener in which the first and second thread patterns induce radially inward drawing forces as well as axially compressive forces with respect to the direction of the long axis of the fastener.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    [0005]FIG. 1 is a view of one fastener.  
         [0006]    [0006]FIG. 1A is a top view of another fastener drive.  
         [0007]    [0007]FIG. 1B is a top view of a third fastener drive.  
         [0008]    [0008]FIG. 2 is a view of a longer fastener, having an unthreaded medial shaft portion.  
         [0009]    [0009]FIG. 3 is a sectional view of a variation of the fastener geometry along a small length in which the shaft is not tapered.  
         [0010]    [0010]FIG. 4 is a sectional view similar to FIG. 3 but includes the tapered shaft.  
         [0011]    [0011]FIG. 5 is an alternative to FIG. 1.  
         [0012]    [0012]FIG. 6 is an alternative to FIG. 2.  
         [0013]    [0013]FIG. 7 shows the FIGS. 5 and 6 fasteners deployed as one example.  
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0014]    Referring to the drawings, wherein like numerals denote like parts, reference numeral  10  is directed to the orthopedic fastener according to the present invention.  
         [0015]    In its essence, the fastener  10  includes a threaded shaft  32  having a first thread pattern  12  at one end and a second thread pattern  14  at an opposite end. As shown in FIGS. 1 and 2, the first end thread pattern  12  terminates in a point  16  and the threads increase in diameter to form a thread pattern with its spiral increasing as it extends away from the point  16 . A remote end  18 , proximate the second thread pattern  14  includes a driving head  18  which in the drawings is shown as hexagonal, but can be formed as an alien wrench recess  21  (FIG. 1B), an oval drive head  20  (FIG. 1A), which is also recessed or other configuration to reliably drive the fastener. The second thread pattern  14  adjacent the drive head  18  preferably has a larger diameter but a similar thread contour which shall be discussed in detail infra. Preferably, the shaft  32  is of variable length and tapers and narrows from end  18  to point  16 . Please see FIGS. 1 and 2.  
         [0016]    A further nuance of the first and second thread patterns is that the first thread pattern  12  has a coarser thread than the second thread pattern  14  which is a finer thread. The point  16  is the point of initiation for insertion into a bone during an orthopedic procedure at a fracture site. To facilitate same, a pilot hole may be drilled in the bone but thereafter, because of the tapering nature of the first thread  12 , this portion is thereafter self-threading. Notice that the crest  70  for both first and second thread patterns are sharp. This allows cutting into the bone which typically has a harder exterior than the interior. By providing a coarser thread pattern for the first thread  12 , this thread will insert into the bone faster than the second thread pattern  14 . As a consequence, when the bone begins to be engaged by the second thread pattern, an axial compression of the bone occurs along the direction of the two arrows A. In addition, because of the thread geometry, the threads will exert a radially inwardly directed force along the direction of the double-ended arrows B. Whereas in the prior art, conventional fasteners induced radially outwardly spreading (the opposite direction from arrow B), the instant invention provides radially inwardly or a drawing force as well as the compressive force A.  
         [0017]    Notice in FIG. 3 that the shaft  32  is not tapered, but of constant cross section along its length. The threads  60  for each the first and second threads  12  and  14  are actually continuous helically wound thread which begins at the ends and spirals towards the medial portion of the shaft  32  as it migrates from the end. Notice also flat wall  54  may replace point  16  for any of the embodiments. With flat wall  54  the pilot hole is cut deeper and perhaps wider.  
         [0018]    The threads  60  include a sharpened crest  70  defining a major diameter  62  of the threads and a root  80  defining a minor diameter  64  of the threads  60 . As shown in detail in FIG. 3, the threads  60  have an upper surface  66  which extends from a bottom edge  84  of the root  80  to the sharpened crest  70 . The threads  60  also include a lower surface  68  which extends from a top edge  82  of the root  80  to the sharpened crest  70 . Both the upper surface  66  and lower surface  68  angle toward the medial portion of the fastener as the surfaces  66 ,  68  extend from the root  80  to the crest  70 .  
         [0019]    In section, the surfaces  66 ,  68  extend linearly from the root  80  to the sharpened crest  70 . However, as this contour is rotated helically about the threaded shaft  32  along with the threads  60 , the upper surface  66  and lower surface  68  take on a curved surface appearance. This appearance is similar to that which would be formed by a linear section of the surface of a cone with a tip of the cone oriented downward and the cone rotated and translated upward along a central axis thereof. The upper surface  66  and lower surface  68  thus have a curved surface in three dimensions similar to that of a cone, but a linear character when viewed in section.  
         [0020]    The upper surface  66  extends from the root  80  to the sharpened crest  70  at an upper surface angle α diverging from a reference plane orthogonal to the central long axis  2  of the fastener. The upper surface angle α is preferably 20° but could be any angle between 0° and 90°. The lower surface  68  extends from the root  80  to the sharpened crest  70  at a lower surface angle β with respect to the reference plane. The lower surface angle β is preferably 40° but could vary between 0° and 90°.  
         [0021]    The upper surface angle α is preferably less than the lower surface angle β. In this way, the threads  60  are provided with greater thickness, and hence greater strength adjacent the minor diameter  64  than at the major diameter  62  and are thus more capable of bearing the loads experienced within the bone.  
         [0022]    It is the angulation of the surfaces, especially upper surface  66  which encourages the radially inward drawing force. When the upper and lower thread patterns are considered, axial compressive force can be seen.  
         [0023]    The second thread portion  14  has the same FIG. 3 geometry except that the threads are inverted, and as mentioned earlier are a finer thread (greater threads per inch axially) than the first thread portion  12 . In other words FIG. 3 would be viewed upside down for threads  14 .  
         [0024]    As mentioned in FIG. 3, the shaft  32  is not tapered, but of constant cross section, preferably along its length. Also FIG. 3 shows an end  54  which is flat and would benefit from predrilling a hole. FIG. 4 shows a similar thread detail, however the shaft  32  is tapered as per FIGS. 1 and 2. This depiction tracks the threads  12  of FIGS. 1 and 2. The threads  14  are similar but the taper of FIG. 4 is reversed.  
         [0025]    [0025]FIGS. 5 through 7 show a variation where the tapered shaft  32  uses the specialized threads  12  of the FIG. 1 embodiment but conventional threads  114  on the second thread portion. The drive head  18  can be that of FIGS. 1, 1A,  1 B or otherwise.  
         [0026]    The conventional threads  114  mate with threaded bores  116  on a member  118  which may have a contour which follows the anatomy of the bone to be supported. Thus member  118  may have a compound contour as exemplified by the angulation  119 . As shown, the thread  12  is embedded in the patient&#39;s bone. In the embodiment, the threads  12  coact with the threads  114  to provide the axial compression A and the threads  12  also provide the radically inward force B described in the earlier figures.  
         [0027]    Moreover, having thus described the invention, it should be apparent that numerous structural modifications and adaptations may be resorted to without departing from the scope and fair meaning of the instant invention as set forth hereinabove and as described hereinbelow by the claims.