Abstract:
A fastener assembly for repairing fractured bone material includes a wire having a wire leading end for forming a bore through the bone material and a wire trailing end for extending beyond a near-side cortex of the bone material. The fastener includes a head portion having spaced-apart grooves defining cutting edges, a lower portion having threads, and an axial aperture therethrough for receiving the wire. The fastener is adapted to slide axially over the wire trailing end and be driven toward the wire leading end to countersink in the bone material. A driver including a driver body having an axially disposed aperture therethrough for accommodating said guide wire, and a driver head having fingers adapted to engage the spaced-apart grooves of the fastener head portion, is adapted to drive the fastener in the bone material. A measuring sleeve including a tubular body adapted to be positioned generally coaxially relative the wire trailing end and abutting the bone material includes a graduated scale thereon for comparison to the wire trailing end, whereby the depth of the bore can be determined.

Description:
CLAIM FOR PRIORITY 
     This patent application claims priority to U.S. Provisional Patent Application No. 60/123,914, filed Mar. 12, 1999. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a fastener system for repairing a bone fracture and, more particularly, a driver, a measuring device, and a self-drilling, self-tapping, self-counter-sinking, cannulated fastener for use with a guide wire to repair a bone fracture. 
     BACKGROUND OF THE INVENTION 
     While forming a countersunk recess is known in the surgical arts, such recesses are conventionally formed using a separate step and tool. The use of self-countersinking bolts, threaded fasteners, or screws is known in the carpentry and metalworking arts, but such designs are not readily acceptable for use in bone repair. For example, U.S. Pat. No. 5,683,217 to Walther et al. teaches a self-counter-sinking screw wherein the head of the threaded screw has an underside including triangular recesses with edges for cutting or burring a conical countersink in a workpiece. The recesses accommodate material removed by the countersinking. Further, such conventional fasteners are inefficiently driven by applying torque near the rotation axis. A fastener having an improved structure at a reasonable cost, that can form a countersunk recess in a bone to be repaired, that is adapted for use with a guide wire, and that can be efficiently driven by applying torque at its periphery, is needed. Further, there is a need for a measuring device for determining the depth of a fractured bone to be repaired so that an appropriately sized fastener can be selected to repair the fracture. 
     SUMMARY OF THE INVENTION 
     A fastener assembly for repairing a bone fracture including a cannulated fastener, guide wire, measuring sleeve, and driver maximizes simplicity and cost effectiveness. The fastener provides an improved structure at a reasonable cost for self-tapping, self-drilling, and self-countersinking in a bone to be repaired. Further, the guide wire eases insertion of the fastener and, with the measuring device, simplifies measurement of a bore in bone material, whereby the depth of a fractured bone to be repaired can be easily determined so that an appropriately sized fastener can be selected to repair the fracture. The driver efficiently drives the fastener by applying torque at the periphery of the fastener head. 
     More particularly, a fastener assembly according to the invention includes a wire having a wire leading end for forming a bore through the bone material and a wire trailing end for extending beyond a near-side cortex of the bone material. The fastener includes a head portion having spaced-apart grooves defining cutting edges, a lower portion having threads, and an axial aperture therethrough for receiving the wire. The fastener is adapted to slide axially over the wire trailing end and be driven toward the wire leading end to countersink in the bone material. A driver including a driver body having an axially disposed aperture therethrough for accommodating the guide wire, and a driver head having fingers adapted to engage the spaced-apart grooves of the fastener head portion, is adapted to drive the fastener in the bone material. A measuring sleeve including a tubular body adapted to be positioned generally coaxially relative the wire trailing end and abutting the bone material includes a graduated scale thereon for comparison to the wire trailing end, whereby the depth of the bore can be determined. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial side view of a driver, fastener, and guide wire according to the invention; 
     FIG. 2 is a partial perspective view of a head for a driver according to the invention; 
     FIG. 3 is a top view of another embodiment of a head for a driver according to the invention; 
     FIG. 4 is a perspective view of a fastener according to the invention; 
     FIG. 5 is a perspective view of an alternative embodiment of a fastener according to the invention; 
     FIG. 6 is a side sectional view of the fastener along line  6 — 6  of FIG. 5; 
     FIG. 7 is a side view of the guide wire of FIG. 1; 
     FIG. 8 is an enlarged side view of a cutting tip of the guide wire of FIG. 7; 
     FIG. 9 is a partial sectional view of the guide wire in the bone material with a measuring device according to the invention; 
     FIG. 10 is a partial side sectional view of a fastener according to the invention partially driven in the bone material; 
     FIG. 11 is a partial side sectional view of the fastener of FIG. 10 fully driven in the bone material; 
     FIG. 12 is a partial perspective view of an alternative embodiment of a measuring device; 
     FIG. 13 is a partial side sectional view of a fastener being guided by a guide wire disposed within the measuring device of FIG. 12 prior to being driven in the bone material; 
     FIG. 14 is a partial side sectional view of the fastener of FIG. 13 partially driven in the bone material by a driver according to the invention; and 
     FIG. 15 is a partial side sectional view of the fastener of FIG. 14 fully inserted in the bone material by the driver. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The fastener system according to the invention includes a novel driver, guide wire, measuring device, and fastener for repairing a bone fracture. With reference to the drawings, a driver  150  according to the invention is particularly adapted to drive a threaded fastener  40  according to the invention. A fastener assembly according to the invention includes the threaded fastener  40 , a guide wire  70 , and a measuring device. Preferably the measuring device is a measuring sleeve  100 , but can alternatively be a ruler  90 . More particularly, the threaded fastener  40  is adapted for use in repairing fractured bone material  80 , which has a near side bone cortex  81  and a far side bone cortex  82 . When driven into the bone material  80 , the wire  70  guides the threaded fastener  40 . Preferably, the threaded fastener  40  is driven by the driver  150 , but can alternatively be driven by conventional driver, such as a phillips or slot screwdriver or a socket-type driver. 
     The threaded fastener  40  according to the present invention, as best shown in FIGS. 4-6, includes a head portion  16 , a shank portion  46 , and a threaded end portion  48 . The head portion  16  has a flat top surface  17  and a rounded outer peripheral region  18 . The outer peripheral region  18  slopes from the flat top surface  17  to the shank portion  46  at approximately 45 degrees, and is preferably in a range of 35 to 65 degrees. In an alternative embodinent shown in FIG. 5, a flat top surface  17 ′ includes a hexagonal recess  43 , which is adapted to receive, for example, a hexagonally shaped head of a conventional socket-type driver for applying torque to the threaded fastener  40  during insertion thereof into the bone material  80 , and for removal of the threaded fastener  40  from the bone material  80 . Other types of recesses or tool gripping portions can be used instead of the hexagonal recess  43 , and such variations are contemplated as being within the scope of the present invention. 
     The head portion  16  further includes a plurality of cutting edges  22  for countersinking the threaded fastener into the near side bone cortex  81  during insertion. The cutting edges  22  are preferably trailing edges of angularly disposed, equi-angularly-spaced arcuate grooves  23 . The cutting edges  22  are formed by cutting, grinding, or pressing the head portion  16  to form the grooves  23 , which terminate in the cutting edges  22 . The cutting edges  22  are preferably angled between 15 and 30 degrees relative the longitudinal axis of the fastener  40  to form an aggressive cutting angle. The angle of the cutting edges  22  and the outer peripheral region  18  can vary depending upon the particular application. The cutting edges  22  burr the bone material  80  to countersink the fastener  40  in the bone material  80  to form a nearly flush surface between the head portion  16  and the near side bone cortex  81 . The grooves  23  accommodate burred bone material during insertion of the fastener  40  into the bone material  80 . Preferably, three cutting edges  22  are provided, with more or fewer cutting edges  22  being provided depending on the application. By countersinking, the threaded fastener  40  is protected from accidental bumping or striking, which tends to weaken a repaired bone. Further, countersinking minimizes soft tissue irritation from the fastener head portion  16  and protects vital structures in the body that may lie in close approximation to the fastener head  16 . 
     The threaded end portion  48  includes threads  49  and at least two cutting edges  32 , which are preferably equi-angularly spaced. The threads  49  of the threaded portion  48  are preferably self-tapping. The cutting edges  32  are preferably fluted, which permits avoiding the necessity of a separate drilling step. Preferably, the cutting edges  32  are generally straight grooves formed in opposite sides of the threaded portion  48 . As a result of the shape of the cutting edges  32 , the tip portion  34  has a very sharp cutting edge, which assists self-tapping. As shown in FIG. 4, the cutting edges  32  are disposed at the lower end of the threaded end portion  48 . In an alternative embodiment, as shown in FIG. 5, the cutting edges  32  extend from the lower end to the upper end of the threaded end portion  48 , whereby the cutting edges  32  are able to self-cut during insertion as well as removal of the fastener  40 . While shown to be continuous in FIG. 5, the cutting edges  32  may alternatively be discontinuous. 
     With reference to FIG. 6, a through-passage  49  extends axially through the head portion  16 , the shank portion  46 , and the threaded end portion  48  of the fastener  40 . The through-passage  49  is sized to accommodate passage of the guide wire  70  while inserting the fastener  40 . According to the preferred embodiment, the through-passage  49  has a diameter of approximately 0.062 inches for a guide wire  70  having 0.050-inch diameter body. The diameters of the through-passage  49  and the guide wire  70  are variable depending on the particular application, but should be complimentary. 
     As best shown in FIGS. 7 and 8, the guide wire  70  includes an elongated cylindrical body  72  and a tip  74  that is slightly enlarged relative the body  72 . A neck  76  separates the body  72  and tip  74 . The body  72  is preferably substantially longer than the axial length of the threaded fastener  40 . Particularly, the length of the guide wire  70  should be long enough to guide the wire  70 , yet short enough to avoid injuring vital structures that may lie at the border of the far side bone cortex  82 . The guide wire  70 , which guides the threaded fastener  40  during insertion into the bone material  80 , may be relatively rigid or flexible, but is preferably sufficiently strong and resilient that it does not break off when inserted into the threaded fastener  40 . Further, the guide wire  70  is adapted for use with a measuring device to determine whether the threaded fastener  40  is at the desired depth in the bone material  80 , or for measuring the insertion depth of the threaded fastener  40  into the bone material  80 . 
     The tip  74  of the guide wire  70  is preferably shaped to cut bone material  80 , and is shown to have a generally arrowhead shape. Alternatively, the tip  74  may be blunt or rounded. Where a blunt tip is used, a separate drilling step may be necessary in order to insert the guide wire  70  into the bone material  80 . The tip  74  preferably includes cutting edges  75 , which facilitate insertion of the guide wire  70  into the bone material  80 . Preferably, the tip  74  has a length of approximately three to four millimeters, and a width of approximately 0.060 inches. The lengths and widths are variable depending on the particular application. 
     The neck portion  76  of the guide wire  70  should have a slightly tapered contour for strength, thereby reducing the risk of breaking off the tip  40  in the surgical site. The greater the difference between the diameter of the tip  74  and the guide wire  70 , the more precise the measurement of the length of the bore through the bone material  80 . This feature further avoids the tip  74  being retracted into the bone material  80  through the far side bone cortex  82  when the guide wire  70  is drawn towards the near side cortex  81  for measuring the depth of the bone to be repaired. 
     As shown in FIGS. 1 through 3, the driver  150  according to the invention is particularly adapted to drive a fastener by applying torque at a peripheral edge of the fastener head. For example, the driver  150  is particularly useful to drive the fastener  40  according to the invention, but can be used to drive any fastener with grooves or passages disposed along the periphery of the fastener head. More specifically, the threaded fastener  40  as shown in FIG. 4, which does not include a central hexagonal recess  43 , or any other conventional phillips or slot recess, can be driven by the driver  150 . 
     The driver  150  includes a body  151  and drive head  152 , which has a generally planar end surface  154  with generally perpendicularly extending prongs  156 . A through-passage  153  extends axially through the body  151  and drive head  152  to accommodate the guide wire  70  during insertion of the fastener  40 . The prongs  156  are particularly adapted to engage the arcuate grooves  23  of the fastener  40  to drivingly insert or remove the fastener  40  by applying torque along the periphery of the head  16 . Accordingly, as many prongs  156  are provided as grooves  23  in the fastener  40 , whereby the driver  150  is complimentary to the fastener  40 . As shown in FIG. 2, the prongs  156  are generally block-like extensions having a rectangular cross-section, and include sides  158 A and  158 B, which are adapted to drivingly engage the arcuate walls of the groove  23  to rotate the fastener  40 . More specifically, depending on the direction of rotation of the fastener  40 , either the wall  158 A or the wall  158 B engages a surface of the arcuate groove  23 . In this manner, the driver  150  is able to insert or remove the fastener  40 . 
     An alternative embodiment of the driver is shown in FIG. 3 as a driver  150 ′, and includes a generally planar surface  154 ′ from which prongs  156 ′ extend generally perpendicularly. The prongs  156 ′ are generally block-like extensions having a triangular cross-section, and include a wall  158 ′ disposed generally perpendicular to the surface  154 ′ and a relief wall  160  angularly extending from the surface  154 ′ to a distal end the wall  158 ′. The relief wall  160  provides a flow path for burred bone material to exit the arcuate groove  23  during insertion of the fastener  40 . Because of the relief walls  160 , however, the driver  150 ′ is not able to remove the fastener  40 ; i.e., the walls  158 ′ only allow the driver  150 ′ to rotate the fastener  40  in the insertion direction, allowing the relief walls  160  to accommodate the flow of burred bone material. Accordingly, a driver similar to driver  150  is necessary for removal of the fastener  40 . 
     In use, as illustrated in FIG. 9, the guide wire  70  is driven into the bone material  80  using a tool (not shown) to rotate the guide wire  70  such that the tip  74  forms a bore  83  through the near side bone cortex  81 , the bone material  80 , and the far side bone cortex  82 . Preferably, the cutting tip  74  includes a sharpened tip  75  capable of cutting or boring through the bone material  80 , thereby avoiding the step of drilling through the bone material  80  prior to insertion of the guide wire  70 . The guide wire  70  is able to slide axially in the bore  83 , encountering resistance during removal when the tip  74  attempts to re-enter the far side bone cortex  82 . More specifically, as the guide wire  70  is being moved in the direction opposite of the insertion direction, the neck portion  76  of the guide wire  70  contacts the far side bone cortex  82 . This encountered resistance during removal serves as a useful indicator of the location of the far side bone cortex  82 . 
     A measurement can be made of the bone depth by measuring the portion of the known-length guide wire  70 , from an end  71  thereof, using a ruler  90  or other similar measuring device. More specifically, the end  71  of the guide wire  70  extends from the near side bone cortex  81  of the bone material  80  by a distance D, which when compared with the known total length of the guide wire  70 , it is possible by simple subtraction to obtain the thickness of the bone to be repaired. With this information, a proper size threaded fastener  40  can be selected, which eliminates the need for a depth gage or separate measuring device in the screw set. Further, an x-ray may be taken while the guide wire  70  is inserted, or after the threaded fastener  40  is inserted, especially in circumstances where the guide wire  70  does not exit the far side bone cortex  82  and the threaded fastener  40  is purposefully fixed without exiting the far side cortex; i.e., the threads remain within the cancellous bone. 
     As shown in FIG. 10, after the guide wire  70  is used to initially penetrate the fractured bone, particularly driving through an undulated fracture  87 , the threaded fastener  40  is slid axially over the wire  70 , which guides the threaded fastener  40  during insertion in the bone material  80 . A driver drives the threaded fastener  40  into the bone material  80 , guided by the guide wire  70 . As shown in FIG. 11, the top of the head portion  16  is fully inserted into the bone material  80  and properly seated flush or nearly flush with the near side bone cortex  81 . Once the fastener  40  is fully inserted into the bone material  80  so that the head portion  16  is flush, the guide wire  70 , which serves as a guide for the threaded fastener  40  during insertion thereof into the bone material  80 , is removed by withdrawal through the through-passage  49  of the fastener  40 , thus completing the repair. 
     Preferably, the driver  150  is used to insert the fastener  40  by applying torque along the peripheral edge of the fastener head  16 , as shown in FIG.  10 . The fastener  40  is inserted until, as shown in FIG. 11, the threaded fastener  40  forms its own countersunk recess  87 . More particularly, the cutting edges  22  burr the bone material of the near-side cortex  81  until the head portion  16  of the threaded fastener  40  is embedded therein. The burred bone material passes through the arcuate grooves  23  as the fastener  40  is inserted, thereby easing resistance to insertion of the fastener  40 . Where the driver  150 ′ is used to drive the fastener  40 , the reliefs  160  of the prongs  156 ′ further accommodate the flow of burred bone material during insertion. Further, even when the driver  150  is used to insert the fastener  40 , the prongs  156 , while occupying more of the fastener head grooves  23  and thereby narrowing the flow path, do not block the flow of bone material. Finally, a conventional driver can be used to insert the fastener  40  by including the appropriate slot, phillips, or hex-socket head on the fastener  40 . 
     An alternative embodiment of the invention including a measuring device  100  having a cylindrical body  102  and a handle  104  disposed generally perpendicular to the longitudinal axis of the body  102  is shown in FIG.  12 . The cylindrical body  102  includes a graduated scale  106  along an axial slot  108  formed in the cylindrical body  102  to facilitate measurement of the depth of the bore  83  through the bone material  80 . Further, the measuring sleeve  100  serves to protect soft tissue from the fastener head  16  and threads  49  during insertion of the fastener  40  into the bone material  80 . Moreover, the measuring sleeve  100  facilitates closed or minimal incision conditions, which further simplify and quicken bone repair procedures. Finally, the measuring sleeve  100  is particularly useful for questionable or non-sterile surroundings or for veterinary use. 
     In use, the measuring device  100  is lowered over the guide wire  70  and through comparison of the length of the guide wire  70 , or a mark on the guide wire  70 , as visible through the slot  108 , to the calculated values on the body  102  of the measuring device  100 , the desired fastener  40  length can be determined visually. Preferably, the body  102  includes at least two different sets of measurement values, one corresponding to a technique where the end of the guide wire  70  exits the far side bone cortex  82  and the other corresponding to a technique where the end of the guide wire  70  does not exit the far side bone cortex  82 . 
     Also, the measuring device  100  allows the fastener  40  to be utilized under closed or minimal incision conditions, which will further simplify and quicken fixation procedures. For example, the guide wire  70  can fixate the fracture or osteotomy percutaneously (or through the skin without opening the site and fully exposing the bone). Then, via a small stab incision on either side of the guide wire  70 , the soft tissue  85  can be bluntly dissected down to the surface of the bone  81  and the measuring device slid over the guide wire  70  until it stops at the bone surface  81 . Then, fixation via the threaded fastener  40  is accomplished in the same manner as if the surgical site was open. The measuring device  100  further functions as a soft tissue protector from the threads  49  of the fastener  40  during fixation. 
     Overall, the cannulated fastener assembly for repairing a bone fracture including the threaded fastener  40 , guide wire  70 , measuring sleeve  100 , and driver  150 ,  150 ′ maximizes simplicity and cost effectiveness. The fastener  40  provides an improved structure at a reasonable cost for self-tapping, self-drilling, and self-countersinking in a bone to be repaired. Further, the guide wire  70  eases insertion of the fastener  40  and simplifies measurement of a bore in bone material, whereby the depth of a fractured bone to be repaired can be easily determined so that an appropriately sized fastener can be selected to repair the fracture. The driver  150  efficiently drives the fastener  40  by applying torque at the periphery of the fastener head  16 . 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.