Abstract:
An orthopedic stabilization structure including a threaded fastener capable of articulation to accommodate various skeletal geometries, a rod, and a cup supporting the threaded fastener and the rod to be subsequently held in fixed position with respect to the skeletal structure.

Description:
FIELD OF THE INVENTION 
     The instant invention is directed generally to devices used by orthopedic surgeons to stabilize and align skeletal structures. More specifically, the instant invention includes a fastener capable of rotation about an axis within a supporting cup, the cup contoured to receive a rod therein and a means to fix the rod and rotationally oriented fastener in a fixed position. 
     BACKGROUND OF THE INVENTION 
     Orthopedic procedures involving stabilization of skeletal structure presently suffer from two common frailties: the first is the inability to orient the stabilizing structure for a multiplicity of common angulations and the second is the failure to provide a reliable thread portion which engages bone of the patient. 
     SUMMARY OF THE INVENTION 
     The instant invention provides the ability to address various skeletal components in a relational way by allowing articulation of the device in a multiplicity of angulations and to fasten to the skeletal structure to provide greater stabilization with an improved thread pattern which provides both axially compressive forces along the length of the fastener and radially inward drawing forces. 
     OBJECTS OF THE INVENTION 
     Accordingly, it is a primary object of the present invention to provide an orthopedic stabilization structure. 
     A further object of the present invention is to provide an improved threaded portion therefore. 
     A further object of the present invention is to accommodate a plurality of angulations when addressing a skeletal structure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top view of the fastener. 
     FIG. 2 is a side view of the fastener. 
     FIG. 3 is a sectional view of the fastener geometry. 
     FIG. 3A shows FIG. 3 with a taper. 
     FIG. 4 shows the fastener and stabilization structure. 
     FIG. 5 is another view of FIG.  4 . 
     FIG. 6 displays angulation of the FIG. 4 structure. 
     FIG. 7 details a bolt used in the structure. 
     FIG. 8 details the bolt receiving area. 
     FIG. 9 shows one side of the cup. 
     FIG. 10 shows an adjacent side (90 degrees) relative to FIG. 9, showing a diametrical slot. 
     FIG. 11 is a top view of FIGS. 9 and 10. 
     FIG. 12 is a bottom view of FIGS. 9 through 11. 
     FIG. 13 is a sectional view of FIG. 9 along lines  13 — 13 . 
     FIG. 14 is a sectional view similar to FIG.  4 . 
     FIG. 15 adds a fastener and rod to FIG.  14 . 
     FIG. 16 adds a fixing bolt to FIG.  15 . 
     FIG. 17 shows the device deployed by way of example. 
     FIG. 18 shows an alternative thread pattern. 
     FIGS. 19A and B show the bolt of the earlier drawings modified to include a stem. 
     FIG. 20 is a perspective of a clamp to be used with the FIG. 19 stem. 
     FIG. 21 shows the clamp mounted on the stem. 
     FIG. 22 shows two clamps on the stem from one side. 
     FIG. 23 shows two clamps on the stem from another side. 
     FIG. 24 shows a deployment of FIGS. 18 through 23. 
     FIG. 25 illustrates angulation of FIGS. 22 and 23. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Considering the drawings, wherein like reference numerals denote like parts throughout the various drawing figures, reference numeral  100  is directed to the orthopedic stabilization device according to the present invention. 
     The device  100  allows a threaded fastener  10  to move about the arrow C as shown in FIG. 4 such that although the long axis of the threaded shaft is depicted as presently aligned, it can be rotated and skewed from a vertical long axis of a cup  130  as in FIG. 6. A rotational means  120  embodied as a disc has a cylindrical outer face  122  and planar top and bottom faces  124 ,  126 . Thus, rotation about the arrow C occurs about a geometrical center  128 . The disc  120  is integrally fixed to fastener  10 . The rotational means  120  is constrained within a cup  130  having a central bore  132 , an upper portion of which is provided with threads  111 . In addition, a transverse slot  134  is cut along a diameter of the cup which allows slideable insertion therein of both the fastener  10  and integral disc  120  as well as a rod  136  transverse to a long axis of the cup  130 . Please see FIGS. 9 through 16. The cup  130  is dimensioned such that the rotational means  120  is in tangential registry along one cylindrical face  122  with the rod  136 . The threaded bore  132  receives a threaded fixing bolt  110  therewithin to press the rod  136  against the rotational means  120  to fix their relative relationship once appropriate orientation has occurred. 
     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 . 
     The second thread pattern  14  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. 
     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. 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 B as well as the compressive force A. 
     The threads  60  of fastener  10  for threads  12  and  14  are actually one continuous helically wound thread which begins at the ends and spirals towards the medial portion of shaft  32  as it migrates from the ends. Please see FIG.  3 . 
     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 . 
     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. 
     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°. 
     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. 
     It is the angulation of the surfaces, especially upper surface  66  which encourages the radially inward force. When the upper and lower thread patterns are combined, axial compressive forces can be seen. Note the flat wall  54  of FIG.  3 . This could replace point  16  and require a deeper pilot hole. 
     The second thread portion  14  has the same FIG. 3 geometry except that the threads  60   a  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 . 
     FIG. 3A shows a section of thread with a pronounced taper. For thread pattern  14 , FIG. 3A would be viewed upside down and with a reverse taper to that shown. 
     A bottom  129  of cup  130  (FIG. 4) has clearance  22  which extends within an included arc preferably approaching 90 degrees to allow a wide range of fastener  10  rotation about arrow C. Rotation beyond this clearance  22  is prevented by cup wall structure  24  that survives both the clearance aperture  22  and the slot  134  that runs diametrically down two sides of the substantially cylindrical cup  100 . Free ends  138  of the cup  100  need the support a bolt  110  (FIG. 16) to: (first) press the rod  136  in place by (second) applying pressure to the disk  120  and retaining it by (third) uniting the free ends  138 . 
     The threads  60  of the threaded bolt  110  (FIGS. 7 and 16) are actually one continuous helically wound thread which begins at the bottom  54  and spirals up to the top  52 . While this single thread design is preferred, other arrangements including compound series of threads which wind helically together from the bottom  54  to the top  52  could also be utilized. 
     The threads  60  include a crest  170  defining a major diameter  62  of the threads and root  80  defining a minor diameter  64  of the threads  60 . As shown in detail in FIG. 7, the threads  60  have an upper surface  66  which extends from a bottom edge  84  of the root  80  to the upper edge  72  of crest  170 . The threads  60  also include a lower surface  68  which extends from a top edge  82  of the root  80  to a lower edge  74  of the crest  170 . Both the upper surface  66  and lower surface  68  angle upwards as the surfaces  66 ,  68  extend from the root  80  to the crest  170 . Both the crest  170  and root  80  exhibit a constant distance from the central axis  2  between the top edge  82  and the bottom edge  84 . Compared to FIG. 3, crest  170  is blunt, while crest  70  is sharpened. Also, bolt  110  and thread  111  could have sharp contours like crest  70  (replacing crest  170 ) and vice versa. 
     In section, the surfaces  66 ,  68  extend linearly from the root  80  to the crest  170 . However, as this contour is rotated helically about the threaded bolt  110  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. 
     The upper surface  66  extends from the root  80  to the crest  170  at an upper surface angle α diverging from a reference plane  4  orthogonal to the central axis  2 . The upper surface angle α is preferably 20 degrees but could be any angle between 0 degrees and 90 degrees. The lower surface  68  extends from the root  80  to the crest  170  at a lower surface angle β with respect to the reference plane  4 . The lower surface angle β is preferably 40 degrees but could vary between 0 degrees and 90 degrees. 
     The upper surface angle α is preferably less than the lower surface angle β such that a thickness of the threads  60  at the crest  170  is less than a thickness of the threads  60  between adjacent roots  80 . In this way, the threads 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 threaded bore  132 . 
     Referring now to FIG. 8, details of the threaded bore  132  on free ends  138  are shown. The bore is preferably substantially complemental in form to the threaded shaft of the bolt  110 . The bore includes threads T. The thread geometry of the bolt  110  and threads T draw free ends  136  of cup  130  together along arrow D. 
     FIG. 17 shows a fractured bone and the device  100  being applied. The fasteners  10  with discs  120  and the cups  130  are located such that the fasteners  10  are located in the bone, but the disc can rotate within clearance  22  as described. Recall the threads  12 ,  14  axially compress and radially inwardly drawing in the bone. Next the rod  136  is placed within the slots  134  of the cups  130 . 
     The rod is shown as having a bend  165  to demonstrate the system&#39;s versatility. Next the bolts  110  are threaded into threads  111  in the free ends  138  of the cups  130 . As the bolts  110  bear on rod  136 , the rod  136 , disc  120  and fastener  10  become rigid. The free ends  138  also draw together tightly. 
     FIG. 18 is a view similar to FIG. 4 showing an embodiment where the first and second thread patterns have conventional geometry but the second thread pattern has a greater thread pitch density, defining finer threads than the first thread pattern. 
     FIGS. 19A and B are similar to FIG. 16 except that the bolt  110  includes an elongate stem  112  projecting from a top of the bolt  110  and projects from the cup  130 . The stem  112  may include a necked down area  113  adjacent bolt  110 . Stem is preferably cylindrical while the necked down area  113  can be faceted to rotate stem  112  with a tool. 
     FIG. 20 is a perspective view of a stem clamp  210  which fixes to stem  112 . Clamp  210  includes a cylindrical bore  212  dimensioned to receive stem  112  and includes a slit  214  on an outer wall and is diametrically aligned with a groove  216  extending into the clamp body. Slit and groove collectively cooperate with a bore  218  passing through clamp  210  perpendicular to groove  216 . When slit  214  and groove  216  and drawn together along arrow D, the stem  112  is fixed in position. Clamp  210  is substantially box shaped and includes a top surface  222  which is planar except for two outboard raised edgewalls  224  oriented parallel to the stem bore  212 . The edgewalls  224  in conjunction with top surface  222  define a receiving slot dimensioned to receive a projection  226  similar to the rectangular projection  226  shown in FIG. 20 on the bottom surface. The projection  226  thus includes projection walls leading to the body of the clamp  210  such that the span between the edgewalls  224  equals the span of the projection between the projection walls  228 . Note the projection  226  is offset from the top surface  222  (and its recess defined by edgewalls  224 ) by 90 degrees. This allows plural clamping blocks  210  to be stacked as shown in FIGS. 22 and 23 in a stabile manner. A bolt  230 , passing through plural bores  218  holds the clamps in place via a nut  232 . Corners  203  of clamp  210  may be chamfered. 
     FIG. 24 shows how this alternative embodiment uses the stem as an extension to accommodate the rod  136  discussed in FIG.  17 . Instead of rod  136  being interposed between disc  120  and bolt  110 , the rod is received through one bore  218  of one clamp  210  mated as shown in FIG. 23, while a second bore receives the stem  112 . This embodiment favors external deployment of rod  136  external the body of a patient. To use the FIG. 24 device, the fasteners  10  (with discs  120  and cups  130 ) are threaded along the bore. The stem  112  having the bolt  110  integral therewith is next threaded into the cup  130 . The stems  112  are not yet tightened, allowing the cups to angulate (e.g. FIG. 25) to follow the bone contour. The clamps  210  are next positioned on the stems  112  in pairs along with rod  136 . The stems  112  are next tightened against disc  120  to fix the cups  130  by pressing the bolt  110  against the cylindrical outer face  122  of disc  120 . Note that the geometry of the disc  120  and its placement in slot  134  prevents the fastener from working loose in the bone, particularly with the thread geometry  12 ,  14  discussed above. Next the rod  136 , the clamps  210  and stems  112  are fixed in position by bolts  230  and nuts  232 . At this point, the fracture (or other orthopedic anomaly) has been stabilized. While the necked down portion  113  may be faceted, the end  114  of stem  112  may have a drive head in lieu of or in addition to facets on stem  112 . 
     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.