BONE FUSION DEVICE

A bone fusion device includes: a shaft including a porous section and a threaded proximal section configured for facilitating a compression.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to tissue fusion devices, and, more particularly, to bone fasteners and methods for using same.

2. Description of the Related Art

Various types of bone fusion devices are known, various types of medical fasteners. Such fasteners include bone screws and bone pins. Further, the Arthrex suture product line provides for suture compression.

What is needed in the art is an improved way of providing compression to bone tissue using bone fusion devices.

SUMMARY OF THE INVENTION

The present invention provides bone fusion devices which provide for enhanced and thus improved compression to bone tissue.

The invention in one form is directed to a bone fusion device, including: a shaft including a porous section and a threaded proximal section configured for facilitating a compression.

The invention in another form is directed to a bone fusion device, including: a shaft including an expandable portion configured for facilitating a compression.

The invention in yet another form is directed to a method of fusing tissue together, the method including the steps of: providing a suture, a first button, and a second button, the suture including a first end and an opposing second end; attaching the second end to the second button; passing the second button through a mechanical bore extending through a first bone portion; affixing the second button to a second bone portion; and creating a linear compression between the first bone portion and the second bone portion by way of the suture, the first button, and the second button.

An advantage of the present invention is that it provides enhanced fixation of the medical fastener to bone, inhibiting the fastener from pull-out, slip-out, or otherwise working itself out of the bone during use.

Another advantage is that some embodiments provide enhanced compression for bone fusion using buttons and a bored pin or drill.

Yet another advantage is that the present invention can be used to span a sacrum-iliac joint for fusion surgery, but could be used in other similar surgical procedures.

Yet another advantage is that certain embodiments of the present invention are shown individually but can be combined into a single implant, such as a single bone screw or bone pin, as desired.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a medical fastener, or parts thereof, which enhance fixation in a tissue, such as bone tissue.

The present invention in one form is directed to a bone screw configured for fastening to bone, the bone screw including a shaft with a threaded proximal section, a porous central section, and a threaded porous distal section.

The present invention in another form is directed to a head of a medical fastener such as a bone screw, the head including at least one locking mechanism configured for locking to bone. The locking mechanism can include a first locking mechanism including a plurality of teeth which are configured for engaging and fixing to bone. The locking mechanism can include a second locking mechanism, alternatively or in addition to the first locking mechanism, annularly disposed about an inner radial wall of the head, the inner radial wall of the head configured for threadably engaging a shaft of the bone screw, the second locking mechanism forming a polymer ring configured for providing resistance to thread loosening relative to the shaft. The locking mechanism can include a third locking mechanism, alternatively or in addition to the first and second locking mechanisms, including a plurality of spikes disposed about an inner radial wall of the head, the inner radial wall of the head configured for threadably engaging a shaft of the bone screw, the spikes configured for moving between an engaged position and an unengaged position, the spikes in the engaged position configured for protruding radially inwardly from the inner radial wall and thereby for engaging the shaft so as to prevent rotation of the head relative to the shaft. The present invention can further include a method of using any of these embodiments of this head.

The present invention in another form is directed to a medical fastener such as a bone screw, the screw including a shaft with a bore configured for receiving an insert and a central section, which can be porous, configured for moving between a nonexpanded position and an expanded position, the insert moving the central section from the nonexpanded position to the expanded position when the insert is pushed into the bore and/or turned in the bore, the expanded position configured for locking the bone screw to the bone. The present invention can further include a method of using this bone screw, the method including the steps of inserting the insert into the bore, and moving the central section from the nonexpanded position to the expanded position so that the central section locks to the bone.

The present invention in yet another form is directed to a medical fastener such as a bone screw, the screw including a shaft with a bore and a distal end, the bore configured for receiving an insert, the distal end configured for moving between a closed position and an open position, the insert moving the distal end from the closed position to the open position when the insert is pushed into the bore, the open position configured for locking the bone screw to the bone. The present invention can further include a method of using this bone screw, the method including the steps of inserting the insert into the bore, and moving the distal end of the screw from the closed position to the open position so that the distal end locks to the bone.

The invention in yet another form is directed to a tissue fusion mechanism including a medical fastener such as a bone pin, first and second buttons, and a suture, the pin having a bore and being configured for being positioned in a bone portion, the first button seated in a groove on the head of a pin, the second button configured for being positioned adjacent another bone portion, the suture being connected at opposing ends respectively to the first and second buttons and proceeding through the bore of the pin and thereby for providing compression to the bone portions to thereby cause fusion of the bone portions.

The invention in yet another form is directed to a method of fusing tissue, such as bone, the method including the steps of inserting a medical fastener such as a bone pin or bone screw into a pre-drilled hole in a first bone portion, attaching a suture at opposing ends thereof to respective first and second buttons, passing the second button through the bore of the pin, affixing the second button to a second bone portion, pulling the suture tight to create linear compression between the two bone portions, seating the first button to a groove in the head of the pin.

The invention in yet another form is directed to a tissue fusion mechanism including first and second buttons and a suture, each button configured for positioning adjacent to a bone portion, the suture attached at opposing ends thereof to respective ones of the first and second buttons, the suture and buttons together configured for providing compression to thereby fuse the bone portions together.

The invention in yet another form is directed to a method of fusing tissue, such as bone, the method including the steps of drilling a hole in a first bone portion with a drill with a bore, attaching a suture at opposing ends thereof to respective first and second buttons, passing the second button through the bore of the drill, affixing the second button to a second bone portion, pulling the suture tight to create linear compression between the two bone portions, affixing the first button to the first bone portion after removing the drill.

Referring now to the drawings, and more particularly toFIG.1, there is shown a shaft12of a bone fusion device, namely, a medical fastener in the form of a bone screw configured for fastening to a bone, the shaft12generally including a threaded proximal section16configured for facilitating a compression, a porous central section18, and a threaded porous distal section19(such porosity can aid in bone ingrowth and fixation). The porosity can be formed through the entire radius of the shaft or only partly thereof. Further, as shown inFIG.1, shaft12can include a longitudinally extending bore13, which can be a through-bore and may also be referred to as a “cannulation”, extending from the proximal to the distal end16,19of the shaft12. The proximal end, corresponding with the proximal section16, is the end that is configured for being driven by a drill or a workpiece used by a user or otherwise contacted by the user, whereas the distal end is the leading end of the shaft12as it is inserted into the bone, likely a pre-drilled hole in the bone. Optionally, the shaft12may have no such bore13. The threads of the proximal section16are configured to receive a threaded head14which is configured for tightening the screw10into the bone and thereby providing increased linear compression into the bone.

FIG.2shows a bone screw10including a modular head14and a shaft12. The head14, which can be referred to as a compression head, is configured for providing additional linear compression. The shaft12ofFIG.2is similar to the shaft ofFIG.1and thus retains the same reference character as inFIG.1, except that, as in alternative embodiments, it lacks a bore or it can have in the bore an insert or filler material. The head14is shown here as being threaded onto, and thus threadably connected to, the threaded proximal section16of the shaft12. Further, the head14inFIG.2is understood to be a generic representation of the various embodiments of the head shown inFIGS.3-8, and could be used on the head of any other fastener in the remaining figures depending upon the application.

The bone screw10ofFIG.2, and any of the embodiments of fasteners described herein, including shaft12ofFIG.1, can comprise a metal such as titanium, a polymer such as polyether ether ketone (PEEK), or any suitable material, composite, or mixture thereof, and can be made using any suitable manufacturing process. Further, the shaft12can be used or combined with other embodiments disclosed herein to provide compression, and/or can be used in conjunction with Herbert/Whipple devices and/or a compression head. Such formations or combinations are not intended to be limiting.

As shown in inFIG.3, the head14includes an inner threaded wall that is configured for threadably engaging a shaft of the bone screw, specifically, the threaded proximal section16of the shaft. The head14can further include at least one locking mechanism configured for locking to bone.FIG.3shows the head14with a locking mechanism formed as a plurality of teeth15. The head14also includes teeth15on a distal side of the head14. The teeth15can be cut into the head14and are configured for engaging with bone and allowing tightening onto the bone and thereby preventing the screw10from backing out of the bone after insertion into the bone. Thus, the teeth15are configured for engaging and fixing to bone as the bone screw10is screwed into the bone, that is, cutting into the bone as the head14is turned and thereby gripping the bone. Such teeth15constitute a passive compression head locking mechanism.

As shown inFIG.4, the head14can include, alternatively or in addition to the teeth15, a locking mechanism formed as a polymer ring17, which can be made of PEEK. The polymer ring17is annularly disposed about and coupled with an inner threaded wall (which is an inner radial wall) of the head14and is configured for providing resistance to the head14loosening relative to the shaft12. The polymer ring17can be integrally formed with the inner threaded wall of the head14or otherwise affixed to the inner threaded wall. Polymer ring17is configured for securing head14with shaft12. Polymer ring17constitutes a passive compression head locking mechanism.

As shown inFIGS.5-8, the head14can include, alternatively or in addition to the teeth15and/or polymer ring17, a locking mechanism including a plurality of spikes20coupled with and disposed about the inner radial wall of the head14which is configured for engaging shaft12of the bone screw. Such spikes20constitute an active compression head locking mechanism. The spikes20are configured for selectively moving between an engaged position and an unengaged position, the spikes20in the engaged position being configured for protruding radially inwardly from the inner radial wall and thereby for engaging the shaft12so as to prevent rotation of the head14relative to the shaft12. In use, a screwdriver engages the four grooves22shown inFIGS.5and6at the 12, 3, 6, and 9 o'clock positions of a proximal side of the head14. It should be appreciated that while four grooves22that are equally spaced from adjacent grooves22are illustrated and described, the number of grooves and associated spikes20may be adjusted as desired. In the 9 o'clock groove ofFIG.5, a lever24(which can be formed as, for example, a lever, button, or wedge) is shown projecting from one or more walls of that groove22(head14includes lever24coupled with spikes20). When a screwdriver is not engaged in these grooves22, as shown inFIG.5the spikes20protrude from the inner radial wall of the head14(either from a nonthreaded section of the inner radial wall, a threaded section, or both the nonthreaded and threaded sections) and are thus in the engaged position. In this engaged position, the spikes20protrude and thereby cause interference with the shaft12and prevent the head14from rotating relative to the shaft12, locking the head14in position to reduce the risk of losing compression in the tissue due to the head14displacing. When the screwdriver is engaged with the grooves22(FIG.6does not show the screwdriver but does show how the head14appears when the screwdriver is in the grooves22), the screwdriver contacts the lever24in the 9 o'clock groove22and thereby triggers or otherwise causes the spikes20to retract into the inner radial wall such that the spikes20are then in an unengaged position. The retraction of the spikes20allows a user such as a surgeon to selectively tighten or loosen the head14relative to the shaft12. Once the user is done tightening or loosening the head14relative to the shaft12, the screwdriver is removed and the spikes20extend back into the engaged position with the shaft12.

FIGS.7-8show more clearly how the spikes20are moved between their engaged and unengaged (retracted) positions. Showing head14ofFIGS.5and6with portions broken away,FIG.7shows the spikes20in their engaged position, together with the lever24disposed within a groove22of the head14. When a screwdriver is not engaged with the head14and thus not seated in the grooves22of the head14and on the lever24, the lever24is out in the 9 o'clock groove22, which pulls an inner mechanism26moveably disposed within a body of the head14. The lever24and the inner mechanism26can be connected directly or indirectly with one another, or formed integral relative to one another, so that movement of one, such as the lever24, causes movement of the other. When the lever24is out as inFIG.7, the lever24pulls the inner mechanism26. The inner mechanism26includes one or more openings or holes28each configured to receive a corresponding spike20when the spikes20are in their unengaged (retracted) positions.FIGS.7-8show one spike20and thus one corresponding opening28. The opening28for the spike20is thus part of the inner mechanism26. The pulling of the lever24on the inner mechanism28forces the spike20out of its opening28in the inner mechanism26and thus into the radially inward space defined by the head14, that is the central bore that the inner radial wall of the head14defines, as clearly shown inFIG.6. The spike20rotates about a hinge29so as to pivot between the unengaged and engaged positions of the spike20; the hinge29can be disposed on the body of the head14, slidably disposed on the inner mechanism26, or on any suitable structure. When the spikes20are forced into this radially inward bore of screwhead14, the spikes20engage the shaft12of the screw and thereby prevent rotation of the head14relative to the shaft12. The lever24and the inner mechanism26can be biased by a biasing mechanism, such as a spring or shape-memory alloy, e.g., nitinol, driven mechanism (not shown), so that the spikes20are in the engaged position. That is, absent the screwdriver engaging the lever24, the biasing mechanism urges, directly or indirectly, the lever24to return into the 9 o'clock groove22and the inner mechanism26into the position that forces the spikes20out of their respective holes28.

Showing head14ofFIGS.5-7with portions broken away,FIG.8shows the positioning of the lever24, the inner mechanism26, and a spike20when a screwdriver (not shown) engages the lever24in the 9 o'clock groove22ofFIGS.5and7. When the screwdriver engages the lever24(such as by pushing on the lever24, causing the lever24to move laterally relative to a bottom surface of the groove22, optionally by way of a ramped surface on the lever24), the screwdriver pushes the lever24, which pushes the inner mechanism26and thus moves the inner mechanism26. This movement of the inner mechanism26exposes the respective opening or hole28to the spike20, and the spike20moves into or is otherwise forced into the opening28by the rotating motion as the head14is tightened onto the shaft12, the shaft12thereby cooperating with the spike20to urge the spike12into its corresponding hole28in the inner mechanism26.

The present invention can further include methods of using any of these embodiments of the head14.

Turning now toFIGS.9-13, and more particularly toFIG.9, according to an embodiment of the medical fastener of the present invention there is shown a bone screw30including a shaft32with an expandable, portion, namely, central section38and a bore40configured for receiving an insert42therethrough (central section38, forming the expandable portion, is configured for facilitating a compression of bone). As shown inFIG.9, central section38can be at least partially porous on an outer radial wall and is configured for moving between a nonexpanded (unexpanded) position and an expanded position. The insert42moves longitudinally in the bore40and can be inserted in a proximal end of the bore40and be pushed at least into the central section of the bore40, or optionally all the way to the distal tip of the shaft12(as shown inFIG.9). The central section38expands to provide radial compression onto the bone, thereby enabling the fastener to more securely fasten into the bone. As shown inFIG.9, the central section38can be split longitudinally (forming a split) and thereby include split ends, with the split ends being able to move away from each other and relative to proximal and distal sections36,39of the shaft32of the screw30. The split ends are relatively close to one another in the unexpanded position and relatively far away from one another in the expanded position. Opposite the split, the central section38can be affixed to the proximal and distal sections36,39of the shaft32. The insert42is configured for moving the central section38from the nonexpanded position to the expanded position when the insert42is pushed into the bore40and/or turned in the bore40, the expanded position configured for locking the bone screw30to the bone.

FIGS.10-11show one way of expanding the central section38. That is, the insert42can be inserted into and thus be received by the bore40to the distal end of the shaft32and then turned or rotated—optionally, 90 degrees as shown inFIGS.10-11—to radially expand the central section38. The inner radial wall of the shaft32can include a depression or longitudinally extending groove or channel44that is opposite the split ends of the central section (thus, bore40includes grooves44). The insert42can have opposing, longitudinally extending protrusions46, which may extend longitudinally along the outer radial wall of the insert42, optionally for a length corresponding to the length of the central section38of the shaft32or the entire length of the shaft32. A respective one of protrusions46is configured for selectively seating in a respective one of grooves44. Upon seating the insert42into the groove44opposite the split ends, the central section38is in the nonexpanded position, as shown inFIG.10. The user can turn the insert4290 degrees in either direction, thereby unseating the protrusion46from a 6 o'clock position inFIG.10and moving that protrusion to either the 3 or 9 o'clock position as shown inFIG.11. In so doing, the protrusions46cause the central section38to expand a distance approximately corresponding to the height of the protrusions46. Upon finishing the turn, the protrusions46can seat in grooves48in the bore40at the 3 and 9 o'clock positions, these grooves48at the 3 and 9 o'clock position being shallower than the groove44at the 6 o'clock position, providing a tactile feel to the user that the insert42has been rotated a sufficient amount, and preventing undesirable further rotation of the insert42. Optionally, the 3 and 9 o'clock grooves48need not be provided. The expanded position of the central section38further locks the bone screw30to the bone by producing a tighter interference fit.

FIGS.12-13show another way of expanding the central section38. That is, the insert42can be inserted into the bore40to the distal end of the shaft32. The bore40of the shaft32, as shown inFIG.12, can include a longitudinally extending groove44at the 6 o'clock position of the bore40opposite the split ends at the 12 o'clock position, as well as grooves48at the 3 and 9 o'clock positions of the bore40, the grooves44,48optionally running the length of the central section38. Rather than inserting the insert42all the way to the distal end of shaft32, seating a protrusion46in the 6 o'clock groove44, and then rotating the insert42to expand the central section38, the user can begin by inserting the opposing protrusions46on the insert42into the 3 and 9 o'clock grooves48at the proximal end of the central section38and then pushing the insert42all the way to the distal end of the shaft32. The 3 and 9 o'clock grooves48can be shallower than the 6 o'clock groove44so that the central section38indeed expands radially. Further, the 3 and 9 o'clock grooves48provide a tactile feel to the user that the insert42is in the correct position and prevents undesirable rotation of the insert42once seated in those grooves48. Inserting the insert42in the 3 and 9 o'clock grooves48and pushing it through the bore40expands the central section38.

The present invention employing an expanded center section is based off of a rotating cam concept designed for use in unicompartmental knee replacement.

Turning now toFIGS.14-15, according to an embodiment of the medical fastener of the present invention there is shown a medical fastener in the form of a bone screw50including a shaft52with a bore60and an expandable portion, namely, a distal end64, which can also be called a tip (shaft52can also include a central section which can be porous, as shown inFIG.14-15) (distal end64, forming the expandable portion, is configured for facilitating a compression of bone). The bore60receives an insert62(and is thus configured for receiving insert62). The distal end64is configured for moving between a closed position (an unexpanded position) as shown inFIG.14and an open position (an expanded position) as shown inFIG.15. As the insert62is pushed through the bore60of the shaft52, the insert62moves the distal end64from the closed position to the open position. The open position is configured for locking the bone screw50to the bone. That is, the insert62is pushed through the center of the implant50to expand the distal end64, thereby providing stability in a bone such as an iliac bone or a sacrum bone. More specifically, the distal end64includes pivotable flanges66, as shown inFIG.15. Four, or another number, such flanges66can be provided, as shown inFIGS.14-15. These flanges66are hinged to a more proximate portion of the shaft52and can be threaded on an outer radial wall of the distal end64. In a closed position (unexpanded position), the threads of a distal section59of the shaft62can be continuous. An inner radial wall of the flanges66can include a radius that is smaller than an inner wall radius of a more proximate portion of the distal section59of the shaft52. The reduction of the inner wall radius can be progressive, thereby facilitating movement of the insert62. Thus, as the insert62encounters the reduced radius of the inner radial wall of the distal end64and proceeds to the distal extent of the shaft52, the four flanges66expand radially outwardly as they pivot on their respective hinges (thus, flanges66are configured for moving between the closed position and the open position when bore60receives insert62). In use, the user is provided with this bone screw50and the insert62, screws the bone screw50into a hole in the bone (such as the sacrum), inserts the insert62into the bore60of the shaft52of the screw50to the distal end64, and thereby moves the flanges66of the distal end64from the closed position (unexpanded position) to the open position (expanded position) so that the distal end64locks to the bone.

Turning now toFIGS.16-18, there is shown another embodiment of a tissue fusion mechanism70of the present invention, which provides suture compression. As shown inFIG.16, the mechanism includes a bone pin72(other medical fasteners can be used, such as a bone screw), a first button74, a second button76, each button74,76of which can have an elliptical shape with generally flat sides, and a suture78that attaches to button holes in the respective buttons74,76. The buttons74,76can be identical to one another. The pin72can have a longitudinally extending bore80therethrough and a head82with at least one groove (pin72can also include a central section and a distal end each of which can be porous, as shown inFIG.16-18).FIG.16shows the suture78tied or otherwise attached to the buttons74,76via the button holes, the suture and button combination not yet having been inserted into the bore80of the pin72. The user positions the pin72in a first bone portion, such as a hole in a bone, which can be an iliac bone84(seen inFIG.19).FIG.16shows the pin72in position as if attached to an iliac bone, without showing the iliac bone, with the head82of the pin72being on a lateral side (outside surface) of the iliac. Thus, after the pin72is inserted into the iliac bone, the first button76is passed through the bore80of the pin72(such bore80is optionally referred to as a pin cannula80), as shown inFIG.17. The second button76is passed through the bore80of the pin72from the lateral side of the iliac bone84and is passed through a hole in another bone portion, such as a sacrum86(seen inFIG.19). Once the first button76reaches desired stable bone (for example, the sacrum), the first button76is turned so that it cannot return through the hole in the sacrum and the cannula of the pin72. That is, the second button76is turned so that one of its flat sides lies adjacent an opposing (posterior) side of the sacrum, the suture78passing back through the hole in the sacrum and extending back through the bore80of the pin72to the first button74, to which the suture78is tied. The suture78is pulled tight, thereby providing linear compression across the iliac-sacrum joint, and the first button74is affixed. That is, the first button74can be seated in a groove on the head82of pin72as shown inFIG.18. The suture78is tied tight to this fixation button74at the head82of the pin72so as to keep the desired amount of linear compression relative to the bone portions (for example, at the iliac-sacrum joint) to thereby cause fusion of the bone portions (for example, the iliac bone and sacrum). The pin72thus provides a conduit for the suture78. The pin72may, but optionally may not, span the space between the iliac and sacrum. When the pin72does span that space, then the head82of the pin72can rest on the lateral side surface of the iliac bone, and the distal end of the pin72can rest against an inner (anterior) surface of the sacrum at the hole of the sacrum for the suture.

Turning now toFIG.19, an embodiment of a tissue fusion mechanism similar to that shown inFIGS.16-18is illustrated, less the bone pin72or screw. Rather, according to the embodiment inFIG.19, a cannulated bone drill87(shown schematically inFIG.19as drill87with cannula88), in part, substitutes for the cannulated pin72. The suture78and the buttons74,76are still used, similar to that inFIGS.16-18. InFIG.19, each button74,76positions adjacent to a bone portion, such as to the lateral side of an iliac bone84for one button74and to the posterior side of a sacrum86for the other button76, with the suture78attached at opposing ends thereof to button holes in the buttons74,76, so that the buttons74,76and suture78together provide compression to thereby fuse the bone portions together. In use, a cannulated drill87is used to drill a hole in the iliac bone84. The same drill87, once passing through the iliac bone84, can proceed to drill a corresponding hole in the sacrum86; alternatively, the same drill87, or another drill87, can be repositioned to drill the hole in the sacrum86. The opposing ends of a suture78are attached to respective buttons74,76, such as by tying each respective end to two button holes in a respective button74,76. The button76will be referred to further herein as an “initial fixation button,” for reasons that will become clear further herein. The initial fixation button76is passed through the cannula (stated otherwise, the bore) of the drill87and thus through the hole in the iliac bone84; and if the drill87proceeds to drill also the hole in the sacrum86, then the initial fixation button76passes through the cannula of the drill87at the same time it passes through the hole in the sacrum86. The initial fixation button76is affixed to the sacrum86after the hole has been drilled into the sacrum86. The initial fixation button76is turned so that a flat surface engages adjacent to an outside (posterior) surface of the sacrum86, the suture78proceeding back through the hole in the sacrum86and through the cannulated drill87to the other button74. The drill87is removed from the bone(s), the suture78is pulled tight to create linear compression between the iliac bone84and sacrum86, and the other button74is affixed to a lateral side surface (outside surface) of the iliac bone84. As shown inFIG.19, this procedure can be done two or more times with respective sets of buttons74,76and sutures78. Accordingly, the sutures78and buttons74,76provide initial compression across a sacrum-iliac joint until fusion occurs.

Referring now toFIG.20, there is shown a flow diagram of a method90of fusing tissue84,86(such as bone tissue84,86) together, the method90including the steps of: providing91a suture78, a first button74, and a second button76, the suture78including a first end and an opposing second end; attaching92the second end to the second button76; passing93the second button76through a mechanical bore80,88extending through a first bone portion84; affixing94the second button76to a second bone portion86; and creating95a linear compression between the first bone portion74and the second bone portion86by way of the suture78, the first button74, and the second button76. Further, the mechanical bore80can be formed by a fastener72. Further, the mechanical bore88can be formed by a bone drill87.