Abstract:
Apparatus for generating, applying and maintaining compression to a site in a human or animal body, the apparatus comprising: a staple comprising: a bridge configured to be elastically bendable; a first leg connected to the bridge by a first hinge region configured to be elastically bendable; and a second leg connected to the bridge by a second hinge region configured to be elastically bendable; wherein the first hinge region comprises a first hole configured to mate with a first element of a delivery device and the second hinge region comprises a second hole configured to mate with a second element of a delivery device; and wherein the first and second legs are angled toward one another when they are in an unstrained state; whereby, when the staple is mounted to a delivery device so that the first hole of the first hinge region mates with a first element of a delivery device and the second hole of the second hinge region mates with a second element of a delivery device, and when the delivery device applies a force to the bridge of the staple so as to reconfigure the bridge of the staple, the first and second legs are pivoted away from one another toward a parallel disposition.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This patent application is a continuation of U.S. application Ser. No. 15/079,770 filed on Mar. 24, 2016, which is a continuation-in-part of U.S. patent application Ser. No. 14/540,351 filed on Nov. 13, 2014, which claims priority to U.S. Provisional Application No. 62/137,496 filed on Mar. 24, 2015, U.S. Provisional Application No. 62/137,570 filed on Mar. 24, 2015 and U.S. Provisional Application No. 62/238,472 filed on Oct. 7, 2015. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to staples for generating, applying, and maintaining compression to a site in a human or animal body in order to facilitate healing of diseased or damaged tissue. The invention finds particular utility in the field of orthopedics and specifically for reducing fractures and maintaining compression between bone fragments, and/or for reducing openings and maintaining compression between bone segments in osteotomies, and/or for inducing fusion across the bones of a joint in an arthrodesis. While the invention has application throughout the body, its utility will be illustrated herein in the context of the repair of fractured or displaced bone tissue, such as during an Akin Osteotomy of the foot or an Isolated Lunocapitate Arthrodesis of the hand/wrist. 
       BACKGROUND OF THE INVENTION 
       [0003]    In the field of orthopedic surgery it is common to rejoin broken bones. The success of the surgical procedure often depends on the ability to re-approximate the bone fragments, the amount of compression achieved between the bone fragments, and the ability to sustain that compression over a period of time. If the surgeon is unable to bring the bone fragments into close contact, a gap will exist between the bone fragments and the bone tissue will need to fill that gap before complete healing can take place. Furthermore, gaps between bone fragments that are too large allow motion to occur between the bone fragments, disrupting the healing tissue and thus slowing the healing process. Optimal healing requires that the bone fragments be in close contact with each other, and for a compressive load to be applied and maintained between the bone fragments. Compressive strain between bone fragments has been found to accelerate the healing process in accordance with Wolf&#39;s Law. 
         [0004]    Broken bones can be rejoined using staples. Staples are formed from a plurality of legs (typically two legs, although sometimes more) connected together by a bridge. Staples are typically manufactured from stainless steel alloys, titanium alloys or Nitinol, a shape memory alloy. The legs of the staples are inserted into pre-drilled holes on either side of the fracture line, with the bridge of the staple spanning the fracture line. 
         [0005]    Existing staples need to be impacted so as to make the bottom of the staple bridge sit flush with the bone surface following implantation of the staple legs into the pre-drilled holes. This is because current staples and their associated delivery devices are typically designed to grip the staples under the bridge of the staple. After the staple has been deployed from the delivery device, there is a gap between the bottom of the bridge and the top surface of the bone. A tamp is typically used to fully seat the staple bridge against the bone surface. Thus, an additional step (i.e., the tamping step) is required. In addition, the action of tamping can cause the bone fragments to move out of position, impairing healing. 
         [0006]    Furthermore, current staple systems do not allow the surgeon to control the amount of compression that the staple will exert when it is released from the delivery device. While the shape memory and superelastic properties allow Nitinol staples to pull together the opposing bone fragments, the recovery forces and recoverable strain generated by these staples may be too great and may result in the staples “tearing through” the bone tissue and thus not providing a means to generate and maintain compression between the bone fragments. 
         [0007]    Additionally, current staple systems do not allow the surgeon to control the rate at which the staple loads the bone when it is removed from the delivery device. Current delivery devices load the bone nearly instantaneously. This may result in a large force impulse as the staple&#39;s legs rapidly undergo shape recovery. This force impulse may damage the bone and result in impaired healing. 
         [0008]    Current staple systems also do not allow the surgeon to control the extent to which the staple&#39;s legs are opened. This can make it particularly difficult to implant the staple into the pre-drilled holes if the holes were drilled slightly out of position. More particularly, if the pre-drilled holes are slightly too close together or slightly too far apart, it may be difficult to fit the staple legs into the holes and may result in impaired healing. 
         [0009]    Finally, current staple systems do not allow for the staple to be easily removed following implantation. Since the staples are tamped flush with the bone surface, there is no easy way for surgeons to grip and remove current staples. It is very time-consuming for surgeons to pry out deployed staples and it is difficult to cut deployed staples for removal. In addition, these actions may damage the underlying bone, thus impairing healing and may result in the patient needing to be under anesthesia for a longer period of time. 
         [0010]    Thus there exists a significant clinical need for a new staple and a new associated delivery device to implant the staple flush with the bone surface without the need for tamping to fully seat the staple. Additionally, there is a significant clinical need for a staple system that allows the surgeon to control the amount of compression the staple will generate across the fracture line after the staple has been implanted into bone, to control the rate at which the staple loads the bone, to allow the surgeon to adjust opening the staple legs for proper alignment with pre-drilled holes, and to allow the staple to be easily removed from the bone if desired. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention provides a novel fixation device which is able to bring bone fragments into close proximity with each other, generate a compressive load across a fracture line and maintain that compressive load across the fracture line while healing occurs. 
         [0012]    Among other things, the present invention comprises the provision and use of a novel staple which is manufactured from a shape memory material (e.g., a material capable of exhibiting superelasticity and/or a temperature-induced shape change). The shape memory material may comprise a metal alloy (e.g., Nitinol) or a polymer (e.g., appropriately processed polyether ether ketone (PEEK)). Alternatively, the novel staple may be manufactured from another suitable material, e.g., stainless steel, titanium, etc. The staple is designed to reduce fractures and generate and maintain compression across a fracture line between the bone fragments to aid in fracture healing. Note that in the preferred form of the invention, the staple is designed to generate and maintain compression between both the cortical bone and the cancellous bone of the bone fragments so as to promote effective healing. 
         [0013]    In one form of the invention, the staple comprises an elastic bridge and two elastic legs. The bridge and the legs meet at a pair of curved hinge regions which are also elastic. The hinge regions comprise holes that run through the full thickness of the hinge regions and are used to mate the staple to a delivery device. In the unrestrained state, the legs of the staple are oriented inwardly with an angle of less than 90° (relative to the bridge) and the bridge of the staple is bowed upward. Prior to implantation, the bridge of the staple can be reversibly bent and the legs of the staple can be reversibly pivoted (e.g., by bending at the elastic hinge regions) so that the bridge is more linear and the legs are substantially perpendicular to the longitudinal axis of the bridge. This allows for insertion of the staple into a prepared fracture site. A delivery device that mates with the holes in the staple&#39;s hinge region may be used to strain the staple, or the delivery device may act as a constraint, with the staple being strained while not loaded on the delivery device and then loaded onto the delivery device in the strained state. The constrained staple can then be inserted into the prepared fracture site (e.g., by positioning the staple&#39;s legs into pre-drilled holes on either side of the fracture line) and the staple can be released from the delivery device. Since the delivery device engages the staple at the holes in the hinge region, the staple can be fully seated during implantation (i.e., the bottom of the bridge can sit on the surface of the bone) and does not need to be tamped in order to fully seat the staple. Releasing the staple from the delivery device allows the bridge and legs of the staple to attempt to return to their original unrestrained state, thereby generating and maintaining a compressive load while healing occurs. 
         [0014]    In one preferred form of the invention, there is provided apparatus for generating, applying and maintaining compression to a site in a human or animal body, the apparatus comprising: 
         [0015]    a staple comprising:
       a bridge configured to be elastically bendable;   a first leg connected to the bridge by a first hinge region configured to be elastically bendable; and   a second leg connected to the bridge by a second hinge region configured to be elastically bendable;   wherein the first hinge region comprises a first hole configured to mate with a first element of a delivery device and the second hinge region comprises a second hole configured to mate with a second element of a delivery device; and   wherein the first and second legs are angled toward one another when they are in an unstrained state;       
 
         [0021]    whereby, when the staple is mounted to a delivery device so that the first hole of the first hinge region mates with a first element of a delivery device and the second hole of the second hinge region mates with a second element of a delivery device, and when the delivery device applies a force to the bridge of the staple so as to reconfigure the bridge of the staple, the first and second legs are pivoted away from one another toward a parallel disposition. 
         [0022]    In another preferred form of the invention, there is provided a method for generating, applying and maintaining compression to a site in a human or animal body, the method comprising: 
         [0023]    providing a staple comprising:
       a bridge configured to be elastically bendable;   a first leg connected to the bridge by a first hinge region configured to be elastically bendable; and   a second leg connected to the bridge by a second hinge region configured to be elastically bendable;   wherein the first hinge region comprises a first hole configured to mate with a first element of a delivery device and the second hinge region comprises a second hole configured to mate with a second element of a delivery device; and   wherein the first and second legs are angled toward one another when they are in an unstrained state;       
 
         [0029]    providing a delivery device comprising:
       a first element sized to be received in the first hole of the first hinge region of the staple;   a second element sized to be received in the second hole of the second hinge region of the staple; and   a plunger adapted to apply a force to the bridge of the staple so as to reconfigure the bridge of the staple;       
 
         [0033]    mounting the staple to the delivery device so that the first hole of the first hinge region mates with the first element of the delivery device and the second hole of the second hinge region mates with the second element of the delivery device; 
         [0034]    applying a force to the bridge of the staple with the plunger of the delivery device so as to reconfigure the bridge of the staple such that the first and second legs are pivoted away from one another toward a parallel disposition; 
         [0035]    inserting the staple into a site in a human or animal body; 
         [0036]    withdrawing the plunger of the delivery device from the bridge of the staple so as to cause the staple to apply compression to the site in a human or animal body as the staple reconfigures; and 
         [0037]    releasing the staple from the delivery device. 
         [0038]    In another preferred form of the invention, there is provided a staple comprising: 
         [0039]    a bridge configured to be elastically bendable; 
         [0040]    a first leg connected to the bridge by a first hinge region configured to be elastically bendable; and 
         [0041]    a second leg connected to the bridge by a second hinge region configured to be elastically bendable; 
         [0042]    wherein the first hinge region comprises a first hole and the second hinge region comprises a second hole; and 
         [0043]    wherein the bridge has a non-linear configuration when it is in an unstrained state, and wherein the first and second legs are angled toward one another when they are in an unstrained state. 
         [0044]    In another preferred form of the invention, there is provided apparatus for securing tissue to a site in a human or animal body, the apparatus comprising: 
         [0045]    a staple comprising:
       a bridge configured to be elastically bendable;   a first leg connected to the bridge by a first hinge region configured to be elastically bendable; and   a second leg connected to the bridge by a second hinge region configured to be elastically bendable;   wherein the first hinge region comprises a first hole and the second hinge region comprises a second hole; and   wherein the bridge has a non-linear configuration when it is in an unstrained state, and wherein the first and second legs are angled toward one another when they are in an unstrained state; and       
 
         [0051]    at least one suture extending through (i) at least one of the first hole and the second hole, and (ii) the tissue to be secured to the site in a human or animal body. 
         [0052]    In another preferred form of the invention, there is provided a staple comprising: 
         [0053]    a bridge configured to be plastically deformable; 
         [0054]    a first leg connected to the bridge by a first hinge region configured to be elastically bendable; and 
         [0055]    a second leg connected to the bridge by a second hinge region configured to be elastically bendable; 
         [0056]    wherein the first hinge region comprises a first hole and the second hinge region comprises a second hole; and 
         [0057]    wherein the bridge has a non-linear configuration when it is in an unstrained state, and wherein the first and second legs are angled toward one another when they are in an unstrained state. 
         [0058]    In another preferred form of the invention, there is provided a staple comprising: 
         [0059]    a bridge configured to be elastic; 
         [0060]    a first leg connected to the bridge by a first hinge region configured to be elastically bendable; and 
         [0061]    a second leg connected to the bridge by a second hinge region configured to be elastically bendable; 
         [0062]    wherein the first hinge region comprises a first hole and the second hinge region comprises a second hole; and 
         [0063]    wherein the first and second legs are angled toward one another when they are in an unstrained state. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0064]    These and other objects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts, and further wherein: 
           [0065]      FIG. 1  is a schematic view of a novel staple formed in accordance with the present invention, wherein the staple comprises a bridge which is capable of being elastically bent and legs which are capable of being elastically pivoted about elastic hinge regions, and further wherein the staple is shown in its unstrained condition; 
           [0066]      FIG. 2  is a schematic view of the novel staple shown in  FIG. 1 , wherein the bridge of the staple has been elastically bent (i.e., made to be more linear) and the legs of the staple have been elastically pivoted outwards (e.g., by bending at the elastic hinge regions) so as to be perpendicular to the bridge; 
           [0067]      FIG. 3  is a schematic view showing how the elastically bent staple of  FIG. 2  will have its legs “kick inward” when the strain on the staple is removed; 
           [0068]      FIGS. 4, 4A, 4B, 5, 6, 6A and 6B  are schematic views showing a novel delivery device which may be used with the novel staple shown in  FIG. 1  to strain and constrain the staple (e.g., with the staple legs perpendicular to the staple bridge); 
           [0069]      FIGS. 7 and 8  are schematic views showing the delivery device of  FIGS. 4, 4A, 4B, 5, 6, 6A and 6B  being used with the novel staple shown in  FIG. 1  to elastically bend the bridge of the staple and elastically pivot the legs of the staple (e.g., by bending at the elastic hinge regions); 
           [0070]      FIGS. 9 and 10  are schematic views showing how the novel staple of  FIG. 1  may be used to generate and maintain compression between bone fragments so as to aid in fracture healing; 
           [0071]      FIGS. 11-13  are schematic views showing another novel staple formed in accordance with the present invention, wherein the novel staple comprises a bridge which is capable of being elastically bent and legs which are capable of being elastically pivoted about elastic hinge regions—the novel staple of  FIGS. 11-13  has a concave bridge specifically engineered to match the anatomy of the fracture site (e.g., an Akin Osteotomy site), where  FIG. 11  shows the staple in its unstrained condition,  FIG. 12  shows the staple strained with its bridge elastically bent (i.e., made to be more concave) and its legs pivoted outwards (e.g., by bending at the elastic hinge regions) so as to be perpendicular to the bridge, and  FIG. 13  is a schematic view showing how the elastically bent staple of  FIG. 12  will have its legs “kick inward” when the strain on the staple is removed; 
           [0072]      FIGS. 14-16  are schematic views showing still another novel staple formed in accordance with the present invention, wherein the novel staple comprises a sloped bridge which is capable of being elastically bent and legs which are capable of being elastically pivoted about elastic hinge regions—the novel staple of this design has a slanted bridge specifically engineered to match the anatomy of the fracture site (e.g., an Akin Osteotomy site), where  FIG. 14  shows the staple in its unstrained condition,  FIG. 15  shows the staple strained with its bridge elastically bent (i.e., made to be more sloped) and its legs pivoted outwards (e.g., by bending at the elastic hinge regions) so as to be parallel with each other, and  FIG. 16  is a schematic view showing how the elastically bent staple of  FIG. 15  will have its legs “kick inward” when the strain on the staple is removed; 
           [0073]      FIGS. 17-19  are schematic views showing yet another novel staple formed in accordance with the present invention, wherein the novel staple comprises a bridge which is capable of being elastically bent and legs which are capable of being elastically pivoted about elastic hinge regions—the staple of this design has a stepped bridge specifically engineered to match the anatomy of the fracture site (e.g., sliding calcaneal osteotomies, calcaneocuboid fusions, Lapidus procedures, etc.), where  FIG. 17  shows the staple in its unstrained condition,  FIG. 18  shows the staple strained with its bridge elastically bent (i.e., made to be more linear) and its legs pivoted outwards (e.g., by bending at elastic hinge regions) so as to be perpendicular to the bridge, and  FIG. 19  is a schematic view showing how the elastically bent staple of  FIG. 18  will have its legs “kick inward” when the strain on the staple is removed; 
           [0074]      FIGS. 20-22  are schematic views showing another novel staple formed in accordance with the present invention, wherein the staple comprises a malleable bridge which is capable of being plastically bent (i.e., to take a set) and legs which are capable of being elastically pivoted about elastic hinge regions— FIG. 20  shows the staple in its unstrained condition,  FIG. 21  shows the staple strained with its malleable bridge plastically bent (i.e., made to take a set so as to be concave to match the fracture site anatomy) and its legs pivoted outwards (e.g., by bending at elastic hinge regions) so as to be perpendicular to the bridge, and  FIG. 22  is a schematic view showing how the elastically bent staple of  FIG. 21  will have its legs “kick inward” when the strain on the staple is removed; and 
           [0075]      FIG. 23  shows how the holes at the hinge region of the staple may be used by the surgeon to attach sutures for tying down tissue (e.g., ligaments, tendons, etc.). 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Novel Staple Comprising Bridge With Two Elastic Hinge Regions Incorporating Mounting Holes 
       [0076]    Looking first at  FIG. 1 , there is shown a novel staple  5  which is able to bring bone fragments into close proximity with each other, generate a compressive load across the fracture line, and maintain a compressive load across the fracture line while healing occurs. Staple  5  can be fully seated against the bone fragments without needing to be tamped after being released from the delivery device. 
         [0077]    Novel staple  5  is preferably manufactured from a shape memory material (e.g., a material capable of exhibiting superelasticity and/or a temperature-induced shape change). The shape memory material may comprise a metal alloy (e.g., Nitinol) or a polymer (e.g., appropriately processed PEEK). Alternatively, staple  5  may be manufactured from another suitable material, e.g., stainless steel, titanium, etc. Staple  5  is designed to reduce fractures and generate and maintain compression between bone fragments (e.g., across a fracture line) so as to aid in fracture healing. Staple  5  comprises an elastic bridge  10  and two elastic legs  15 . Bridge  10  and legs  15  meet at a pair of curved hinge regions  20  which are also elastic. Hinge regions  20  have holes  25  passing therethrough. Holes  25  may be round or may have other configurations consistent with the present invention. Legs  15  may have barbed teeth  30  to help the legs of the staple grip the bone after implantation into the bone and prevent the legs of the staple from working their way back out of the bone. In its unrestrained state, bridge  10  is bowed upwardly in the manner shown in  FIG. 1 . In the unrestrained state, legs  15  of staple  5  are elastically pivoted inwardly at elastic hinge regions  20  with an angle of less than 90° (relative to bridge  10 ). By way of example but not limitation, in one preferred form of the invention, legs  15  extend at an angle of about 65° to the longitudinal axis of bridge  10  when in their unrestrained state. 
         [0078]    Prior to implantation, bridge  10  of staple  5  can be reversibly bent (i.e., bent to nearly linear) and legs  15  of staple  5  can be reversibly pivoted at elastic hinge regions  20  (e.g., by bending at the elastic hinge regions  20 ) to a position substantially perpendicular to bridge  10  ( FIG. 2 ) so as to allow for insertion of the legs of the staple into a prepared fracture site, with the bridge of the staple spanning across the fracture line (see below). Note that where staple  5  is formed out of Nitinol, elastic deformations of up to approximately 8% are achievable. A delivery device (see below) can be used to elastically bend bridge  10  and pivot legs  15  at elastic hinge regions  20  (e.g., by bending at the elastic regions  20 ), constrain and hold the staple in its strained state prior to implantation, and then insert the staple into the prepared fracture site. 
         [0079]    Upon insertion of the strained staple  5  into the prepared fracture site, the constraint on bridge  10  and legs  15  is removed, whereupon staple  5  attempts to return to its original un-restrained state ( FIG. 3 ), thereby generating a compressive load across the fracture line and maintaining that compressive load across the fracture line while healing occurs. 
         [0080]    Looking next at  FIGS. 4, 4A, 4B, 5, 6, 6A, 6B, 7 and 8 , there is shown a novel delivery device  35  which may be used to selectively bend bridge  10  and to selectively pivot legs  15  of staple  5  at elastic hinge regions  20  (e.g., by bending at the elastic hinge regions  20 ). Delivery device  35  comprises a body  40  having an internal threaded region  45  ( FIG. 6 ) configured to mate with threaded screw  50 . Threaded screw  50  has a handle  55  mounted to its proximal end. Advancing threaded screw  50  into body  40  (e.g., by selectively rotating handle  55  so as to selectively rotate threaded screw  50  such that the threads of threaded screw  50  engage internal threaded region  45 ) causes the distal end of threaded screw  50  to push against the proximal end of a plunger  60 . The distal end of plunger  60  engages elastic bridge  10  of staple  5 . When plunger  60  is moved distally (i.e., by moving threaded screw  50  distally by rotating handle  55 ), the distal end of plunger  60  engages elastic bridge  10  of staple  5  and elastically bends elastic bridge  10  into a more linear configuration. Staple  5  is releasably mounted to delivery device  35  by a pair of pins  65  which are mounted to two arms  70  which are each pivotally mounted to body  40  of delivery device  35  by a pivot pin  75 . Pins  65  are received within holes  25  formed in staple  5 . When plunger  60  is moved distally against elastic bridge  10  of staple  5 , the deforming (i.e., straightening) bridge  10  of staple  5  causes arms  70  of delivery device  35  to pivot outwardly, with elastic hinge regions  20  of staple  5  bending about pins  65  so as to pivot staple legs  15  outwardly. 
         [0081]    More particularly, and looking now at  FIGS. 7 and 8 , when staple  5  is mounted to pins  65  of delivery device  35  (i.e., with pins  65  being received within holes  25  of staple  5 ) and handle  55  is rotated so as to advance threaded screw  50  distally, plunger  60  is also advanced distally, whereby to push against elastic bridge  10 , causing elastic bridge  10  to bend and become more linear, and causing arms  70  of delivery device  35  to articulate (i.e., pivot) outwardly. As this occurs, elastic hinge regions  20  of staple  5  bend about pins  65 , causing elastic legs  15  to be pivoted about elastic hinge regions  20  so as to be oriented generally perpendicular to elastic bridge  10  ( FIG. 8 ). 
         [0082]    Note that staple  5  is configured so that the force that is generated as staple  5  reconfigures (i.e., as bridge  10  and legs  15  attempt to return back to their original disposition) is less than the “tear through” force of the bone receiving legs  15 , i.e., staple  5  is specifically engineered so as to not “tear through” the bone tissue when staple  5  attempts to return to its original, unbiased shape. The compressive forces generated by staple  5  as staple  5  attempts to reconfigure (i.e., as bridge  10  contracts and as elastic legs  15  of staple  5  attempt to pivot inboard toward one another about elastic hinge regions  20 ) can be controlled by modulating the material properties of staple  5  and/or the geometry of staple  5 . 
         [0083]    By way of example but not limitation, the percentage of cold work in the shape memory material forming staple  5  affects the compressive force that is generated by the reconfiguring staple  5 . As the percentage of cold work increases, the compression force that is generated decreases. In one preferred form of the present invention, staple  5  has between about 15% and about 55% cold work in order to control the recovery force (i.e., the compressive force generated by bridge  10  and legs  15  as staple  5  reconfigures) of staple  5 ; however, if desired, other degrees of cold work may be used, and/or the material comprising staple  5  may not be cold worked at all. 
         [0084]    By way of further example but not limitation, another material property that affects the compression force generated by staple  5  as the staple reconfigures is the temperature differential between the body that staple  5  will be implanted into (assumed to be approximately 37° C., which is the temperature of a human body) and the austenite finish temperature of the shape memory material forming staple  5 . A smaller temperature differential between the two will result in staple  5  generating a smaller compressive load as staple  5  reconfigures; conversely, a larger temperature differential between the two will result in staple  5  generating a larger compressive load as staple  5  reconfigures. The shape memory material that staple  5  is made out of should, preferably, have an austenite finish temperature of greater than about −10° C., resulting in a temperature differential of about 47° C. when the staple is implanted (assuming that the staple is implanted in a human body). 
         [0085]    By way of further example but not limitation, staple geometry also affects the compression forces generated as staple  5  reconfigures. More particularly, the cross-sectional areas of elastic bridge  10 , elastic hinges  20  and elastic legs  15  affect the compression forces generated by the reconfiguring staple  5 . As the cross-sectional areas increase, the compression forces that the reconfiguring staple  5  generates also increase. 
         [0086]    Elastic legs  15  of staple  5  are critical for transmitting the compression force to the bone without “tearing through” the bone. The height, width, and length of the staple legs, and the geometry of the staple legs, are all significant factors relating to the staple&#39;s ability to not “tear through” the bone. Elastic legs  15  having greater surface area are better able to distribute the compression force and thus resist “tearing through” the bone. 
         [0087]      FIG. 9  shows how staple  5  may be used to reduce a fracture and generate and maintain compression between bone fragments  80  and  85 . 
         [0088]    More particularly, the fracture  90  which is to be fused is first re-approximated and reduced. A drill guide (not shown) of the sort well known in the art is used to drill two holes  95  the correct distance apart to accommodate the legs  15  of staple  5 . Staple  5  is mounted to pins  65  of delivery device  35 , and delivery device  35  is used to bend bridge  10  and straighten legs  15  of staple  5  in the manner discussed above (i.e., by turning handle  55  to advance plunger  60  which is used to bend bridge  10  and pivot legs  15  at elastic hinge regions  20 ). While still mounted to pins  65  of delivery device  35 , legs  15  of staple  5  are placed into the pre-drilled holes  95 . Staple  5  is then released from pins  65  of delivery device  35 , i.e., by turning handle  55  in the opposite (e.g., counter-clockwise) direction and sliding staple  5  off of pins  65 . This allows the bent bridge  10  and pivoted legs  15  of staple  5  to attempt to return (reconfigure) to their un-bent configuration, thereby applying compression across fracture  90 . 
         [0089]    Note that in the preferred form of the invention, staple  105  is designed to generate and maintain compression between both the cortical bone and the cancellous bone of the bone fragments so as to promote effective healing. In this respect note also that, while bridge  10 , elastic hinges  20  and the proximal (i.e., bridge-side) portions of legs  15  typically engage cortical bone, the pivoting nature of the reconfiguring distal portions of legs  15  will help apply enhanced compressive forces to the cancellous bone (i.e., the interior bone) of the bone fragments. 
         [0090]    Significantly, it should be appreciated that since staple  5  is mounted to delivery device  35  via pins  65  being inserted into holes  25 , staple  5  can be fully inserted into pre-drilled holes  95  with bridge  10  in direct contact with bone fragments  80  and  85 . Tamping is not needed in order to fully seat staple  5  ( FIG. 10 ). 
         [0091]    It should also be appreciated that, if desired, staple  5  can be used to attach soft tissue to bone (e.g., to attach a rotator cuff to bone). 
         [0092]    In some circumstances it can be desirable to modify delivery device  35  so as to ensure that legs  15  cannot be pivoted at hinge regions  20  beyond 90 degrees (relative to the longitudinal axis of bridge  10 ) when legs  15  of staple  5  are pivoted outboard. In other circumstances, it may be desirable for delivery device  35  to allow legs  15  of staple  5  to be pivoted outboard less than, or greater than, 90 degrees to allow insertion into slightly mispositioned (or angled) drill holes  95 . 
         [0093]    It should be appreciated that following implantation, if desired, delivery device  35  can also be used to remove staple  5  from the bone. More particularly, delivery device  35  can be used to re-engage staple  5  at the holes  25  (i.e., by inserting pins  65  of delivery device  35  into holes  25  of staple  5 ) in the hinge regions  20  of staple  5 . Turning handle  55  (e.g., clockwise) causes plunger  60  to bend staple bridge  10  and to reconfigure staple  5  such that bridge  10  is substantially perpendicular to staple legs  15 . Staple  5  can then be removed from the bone by pulling the staple out perpendicular to the bone. 
         [0094]    Additionally, staple delivery device  35  allows the surgeon to “sense” how much compression staple  5  will exert on the bone when it is released from delivery device  35  and attempts to reconfigure. More particularly, as the surgeon turns handle  55  to straighten bridge  10  and open staple legs  15  (e.g., by turning handle  55  clockwise), handle  55  requires greater levels of torque as staple  5  is opened (i.e, as bridge  10  is pushed down and legs  15  are pivoted outboard), thereby providing a degree of tactile feedback to the surgeon. The torque that the surgeon applies to handle  55  is proportional to the compression that staple  5  will exert on the bone as the staple reconfigures. 
         [0095]    Thus delivery device  35  also allows the surgeon to ascertain and control how much compression staple  5  will exert when the staple is released from delivery device  35 . The greater the degree to which bridge  10  is straightened and legs  15  of staple  5  are opened (i.e., pivoted outboard), the more compressive force staple  5  will exert on the bone when it is released from delivery device  35 . 
         [0096]    Additionally, delivery device  35  also allows the surgeon to control the rate at which staple  5  loads the bone as the staple is removed from delivery device  35 . More particularly, turning handle  55  of delivery device  35  counterclockwise releases the downward (i.e., distal) force that plunger  60  exerts on bridge  10  of staple  5 . This allows staple  5  to attempt to recover (i.e., reconfigure) to its original shape and apply compression across the fracture site. It may be desirable to allow the surgeon to be able to control this “release rate” so that the bone is not damaged as staple  5  reconfigures and so that staple  5  remains in the desired location. 
         [0097]    In one preferred form of the invention, staple  5  and delivery device  35  are provided in the form of a sterilized kit. Staple  5  may be “pre-loaded” (i.e, mounted) onto delivery device  35  (i.e., with pins  65  of delivery device  35  extending through holes  25  of staple  5 ). Staple  5  may be mounted on delivery device  35  in an unconstrained or a constrained state. The kit may include additional instruments to aid in the implantation of the staple (e.g., k-wire, drill bit, staple size guide, etc.). 
       EXAMPLE 
       [0098]    The compressive force generated by staples of the present invention formed out of Nitinol with greater than 20% cold work are able to generate 50 to 100 Newtons of force depending on the staple dimensions. This is more than twice the compression force able to be generated by conventional staples of a similar size. 
       Alternative Configurations of Novel Staple Formed in Accordance With the Present Invention 
       [0099]    Looking now at  FIGS. 11-19  it should be appreciated that staple bridge  10  may be formed so as to have a different configuration. By way of example but not limitation, it may be beneficial for staple bridge  10  to have a concave geometry ( FIGS. 11-13 ), such that when bridge  10  of staple  5  is reversibly bent (i.e., so that legs  15  are pivoted so that they are parallel to each other), bridge  10  can bend downwardly, i.e., so as to become more concave ( FIG. 12 ). Upon insertion of the strained staple  5  across the prepared fracture site, the constraint on bridge  10  and hinges  20  is removed, whereupon staple  5  attempts to return (i.e., reconfigure) to its original unrestrained state ( FIG. 13 ), thereby generating a compressive load across the fracture line and maintaining that compressive load across the fracture line while healing occurs. By way of example but not limitation, it may be beneficial to provide a staple  5  having a concave bridge  10  for the treatment of fractures where the anatomy is “hour-glass” shaped (e.g., in an Akin Osteotomy). 
         [0100]    It may also be desirable to provide a staple  5  having a bridge  10  formed with a sloped geometry ( FIG. 14 ). In this form of the invention, legs  15  can be elastically pivoted so as to be parallel to one another ( FIG. 15 ). Upon insertion of the strained staple  5  into the prepared fracture site, the constraint on bridge  10  and hinges  20  is removed, whereupon staple  5  attempts to return to its original un-restrained state ( FIG. 16 ), thereby generating a compressive load and maintaining that compressive load while healing occurs. It may be desirable to provide staple  5  having this configuration for the treatment of fractures where the anatomy is non-linear (e.g., at the metaphyseal flares). 
         [0101]    It may also be desirable to provide staple  5  with bridge  10  having a stepped geometry ( FIG. 17 ). In this form of the invention, when staple  5  is reversibly strained (i.e., so that legs  15  are pivoted outboard so as to be parallel to each other), bridge segments  10   a  and  10   b  are parallel to each other ( FIG. 18 ). Upon insertion of the strained staple  5  into the prepared fracture site, the constraint on bridge  10  and hinges  20  is removed, whereupon staple  5  attempts to return (i.e., reconfigure) to its original un-restrained state ( FIG. 19 ), thereby generating a compressive load across the fracture line and maintaining that compressive load across the fracture line while healing occurs. It may be desirable to provide a staple  5  having this configuration for the treatment of fractures where the anatomy is uneven (i.e., sliding calcaneal osteotomies, calcaneocuboid fusions, Lapidus procedures, etc.). 
       Novel Staple Having a Malleable Bridge Which Is Plastically Deformable to Take a Set 
       [0102]    It may also be desirable to provide a staple  5  having a malleable bridge  10  which is plastically deformable so as to be able to take a set ( FIG. 20 ). This allows the surgeon to shape staple bridge  10  in order to conform to the anatomy of the patient. With this form of the invention, delivery device  35  can be used to deform/shape staple bridge  10 . When a staple of this configuration has a force applied to its bridge  10  so that staple legs  15  are pivoted so as to be parallel to each other, malleable bridge  10  is plastically deformed so as to take a set ( FIG. 21 ). The more staple legs  15  are opened (i.e., pivoted outboard), the more staple bridge  10  is plastically deformed. Upon insertion of the strained staple  5  into the prepared fracture site, elastic hinges  20  attempt to return staple legs  15  to their original un-restrained state while staple bridge  10  remains deformed ( FIG. 22 ), thereby generating a compressive load and maintaining that compressive load across the fracture line while healing occurs. A staple of this configuration may be beneficial for the treatment of fractures where the anatomy is uneven (e.g., in an Akin Osteotomy). 
       Additional Use for Staple Mounting Holes 
       [0103]    While holes  25  are primarily used for releasably mounting staple  5  to delivery device  35  (i.e., via pins  65 ), holes  25  also may be used after implantation to aid the surgeon with tying ligaments and/or tendons directly down to the bone ( FIG. 23 ). Typically, a surgeon would use a suture anchor, bone tunnel or other method/device known in the art to re-secure a ligament and/or tendon to the bone. It should be appreciated that the staple of the present invention provides the surgeon with holes  25  which may be used to tie ligaments and/or tendons directly to the bone. This allows the surgeon to avoid having to use an additional implant or perform an additional procedure to achieve the same outcome. 
       Additional Applications 
       [0104]    In the foregoing disclosure, novel staple  5  and novel delivery device  35  are discussed in the context of rejoining a broken bone. However, it should be appreciated that novel staple  5  and novel delivery device  35  may be used to promote joinder of substantially any two (or more) bone segments, e.g., they may be used to reduce openings and maintain compression between bone segments in osteotomies, or they may be used for inducing fusion across the bones of a joint in an arthrodesis, etc. 
       Modifications of the Preferred Embodiments 
       [0105]    It should be understood that many additional changes in the details, materials, steps and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the present invention, may be made by those skilled in the art while still remaining within the principles and scope of the invention.