Patent Publication Number: US-2012024937-A1

Title: Compression bone staple, apparatus and method of the invention

Description:
CROSS-REFERENCE 
     This application is a continuation application of U.S. Ser. No. 10/896,360, filed Jul. 20, 2004, which is a continuation application of U.S. Ser. No. 09/985,719, filed Nov. 6, 2001, now U.S. Pat. No. 6,783,531, issued Aug. 31, 2004, which is a continuation application of U.S. Ser. No. 09/500,060, filed Feb. 8, 2000, now U.S. Pat. No. 6,348,054, issued Feb. 19, 2002, which is a continuation-in-part application of U.S. Ser. No. 09/299,285, filed Apr. 26, 1999, now U.S. Pat. No. 6,059,787, issued May 9, 2000, which are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to devices and techniques for securing bone segments across a fracture site, and more particularly relates to a bone stapling method and apparatus for achieving compression between segments. 
     2. Description of the Prior Art 
     In treating a bone fracture it is common practice to fasten one bone segment to the other so as to stabilize and immobilize them for the duration of the bone consolidation process. Thus there is the technique of internal fixation or direct mechanical fastening of the bone segments. 
     Traditionally, fixation has been accomplished by variety of apparatus and techniques, the more common involving the use of metallic fastening devices such as screws, connector plates (secured to the bone by screws), pins and clips. These methods invariably involve the drilling of screw holes in the bone and the use of related equipment such as drill hole templates. 
     Conventional U-shaped clips have also been used, the clip legs being installed one each in holes in the opposing bone segments. The rigid structure of such clips, like the other fixation devices mentioned above, provide rigid immobilization of the fracture zone. Such devices also served to maintain the distance between segments, which was found however, among other things, to hinder compression induced by contractions of skeletal muscles in some cases, and prevent the establishment of compressive force between the bone segments which is favorable to bone consolidation or knitting. In this regard the concept of creating dynamic compressive force across an osteotomy or bone fracture site has become well recognized as a technique to promote primary bone healing, i.e. consolidation that is faster and of better quality. 
     Thus there has evolved a number of fastening devices such as clips and the like, designed to deliver compression. Accordingly in U.S. Pat. No. 3,939,294 there is provided a clasp or clip of spring material having a pair of spaced-apart, inwardly inclined legs connected by a Z-shaped upper portion. Sloped holes are drilled in adjoining bone segments and tools are used to manipulate and install one leg, and then the other leg is pulled toward the other hole , spreading the Z-shaped elastic portion, and then inserted in the other hole. Unfortunately this method requires the drilling of specially sloped holes, involves multiple steps and is time-consuming, and like the conventional rigid fastening techniques, requires relatively large surgical opening. Also, the manual installation of the clip using hemostats and the like is difficult, requires meticulous skill and handling. 
     In U.S. Pat. No. 4,838,254 the legs of a pair of metallic clips are, inserted in pairs of specially angled bores in respective opposing bone segments. The exposed tops of the two installed clips then serve as fastening heads for a spring that is connected between the clips. 
     In U.S. Pat. No. 4,841,960 the disclosed “compression” clip is essentially a clip with opposing legs that are installed in pre-drilled holes and features a crimpable web that joins the top ends of the legs. A crimping tool is used to crimp the web in an effort to set up compression between the embedded legs. 
     U.S. Pat. No. 4,852,558 also requires manual installation of separate legs in pre-drilled holes, the tops of the install legs then being interconnected with a ratchet mechanism which must be operated to draw the legs together. This design appears inherently limited regarding adjustability and maintenance of constant pressure. In U.S. Pat. No. 5,660,188 the two legs of a clip must also be installed in pre-drilled holes. The clip has a bridge of two side-by-side crimpable elements, and the jaws of a crimping tool must be used on the embedded clip to deformingly spread apart these elements, causing the legs to draw to each other. The foregoing techniques involving crimpable clips all appear to be imprecise in setting up suitable compressive&#39; forces, require hole drilling and related problems, and do not lend themselves to minimizing the size of the surgical opening. 
     In view of the limitations of the afore-mentioned methods, stapling has been looked to as a potentially quick and effective way for fastening bone segments, and as a way to produce compression. Thus in U.S. Pat. Nos. 5,053,038 and 5,662,655 “compression” staples are applied to the bone by a powered stapler. These staples have legs shaped with beveled ends and/or have divergent legs that will be forced apart from each other during implantation, which flexes springy upper parts of the legs thereby tending to set up compression. Unfortunately there is concern for trauma to the bone due to driving of the compound-shaped legs into the bone mass, and there is little apparent precision in establishing the desired compressive forces. 
     In view of the foregoing it is a general object of the present invention to provide an improved method and for interosseous fastening. 
     A more particular object is to provide quick and simple, yet effective method for fastening bone segments with compressive force between opposing bone ends. 
     Another object to provide such a method that minimizes the size of the required surgical opening and associated trauma. 
     A further object to provide a method of bone stapling that minimizes trauma to the bone tissue during implantation of the staple legs. 
     Yet another object is to provide a method for stapling that maximizes the capability of establishing a dynamic compression level that is optimal for enhanced osseous healing. 
     A still further object is to provide simple, effective bone fixation technique that is relatively easy to learn and practice. 
     Another object is to provide for compression fixation in applications where other techniques would not work or would not deliver compression. For example, conventional fastening techniques for handling a “Jones” fracture, i.e. one that is transverse to the longitudinal extent of the bone segment, is difficult to address using conventional fastening techniques, however the present invention is particularly suitable to provide fastening for such fractures. 
     Still another object is to provide stapling apparatus and method in which there is enhanced selection capability regarding the level of the compressive forces to be imparted. 
     There are a number of advantages in exterior bone fixation techniques, where surgical incisions are not required and fasteners are applied through the skin; and thus it is yet another object of the invention to provide a bone stapling method that lends itself well to exterior bone fixation. 
     These and other objects of the present invention are achievable by way of the present invention of a bone stapling method and apparatus that uses a generally U-shaped staple having pair of spaced apart legs with sharp free ends and proximal ends interconnected by bridge that has at least one resilient curved portion, whereby spreading apart of the parallel legs lessens the curvature of the curved portions which brings the staple to a tensioned configuration in which one leg is resiliently urged towards the other. In a preferred embodiment it is seen that the bridge portion comprises a single bowed spring element, the curvature of which lies in a plane normal to the axes of the staple legs. 
     The novel fastening method involves first positioning the fractured ends of a first and a second bone segment in proximate, face-to-face relationship. The next step involves spreading apart the staple legs by a certain amount and holding the staple in the resultant tensioned configuration. The extent to which the staple legs are separated can be varied in one preferred embodiment of the invention, the induced compressive forces between the legs being proportional to the amount of displacement of the legs as the bowed portion is moved through range of motion in which elastic behavior is exhibited. In this regard it should be evident that herein lies one of the advantages of the present invention, i.e. the capability of selecting the optimal compressive force for an application by spreading apart the staple legs by a predetermined amount. 
     Next, as the staple is held in its tensioned configuration, it is positioned with it sharp ends forward and aligned respectively with surfaces of one bone segments and the other. Finally the positioned staple, while maintained in its tensioned configuration, is driven into the bone by percussive force, such quick application being provided by a conventional air-powered striker of a stapler according to the present invention, or by a manually stuck staple applicator according to the invention. The embedded staple legs will cause the opposing bone faces to be pressed into each other with a predetermined amount of force. 
     Such stapling method lends itself advantageously to a staple with a relatively narrow profile, wherein apparatus according to the present invention include a staple applicator having within its housing means for supporting the staple and guiding its movement with legs pointed ends forwardly disposed, and adapted to receive the staple in its initial un-tensioned configuration engaging its legs and spreading them apart by certain amount and holding the staple in its tensioned configuration adjacent the front end of the housing, for ejection therefrom. One embodiment, of several, uses opposing first and second grooves for engaging the staple legs and means for adjustably moving one groove from the other. Another embodiment employs grooves that diverge to spread the staple legs as a staple is advanced there-along. Ejection means mounted for longitudinal movement in the housing has a front end adapted to strike the rear of the tensioned staple with percussive force which is provided by air power or electrical power in preferred embodiments. 
     The invention also includes a staple applicator that is adapted for being manually driven. 
     Another related bone stapling method for compressively securing adjoining bone segments uses a resilient metallic staple that has legs with an initial convergent configuration with respect to each other, and the legs are resiliently extendible into parallel relationship, in which configuration a predetermined amount of spring force will urge the legs towards their initial convergent orientation. This method includes holding the normally convergent staple in its legs-parallel configuration, positioning the so-tensioned staple with its sharp ends aligned respectively with adjacent bone surfaces; and then driving and embedding the legs of the tensioned staple in the bone segments and releasing the embedded staple, whereby the bone segments are joined, and opposing surfaces of the bone segments are caused to be pressed into engagement with each other with a certain amount of compressive force. 
     An applicator or tool for such a staple includes staple-engaging means on the front end of the applicator body. Opposing jaws support the staple in a pointed-ends forward position against lateral and rearward movement, and engage inside surfaces of the convergent legs, the jaws being adapted for adjustable movement apart to cause the legs to rotate to a generally parallel orientation. Thus supported on the front end of the tool, the staple can be aligned with the bone segments, and the rear end of the tool stuck with a percussive force to cause the staple legs to be embedded into the bone segments. 
     Another applicator according to the present invention has a trigger-controlled air-powered staple-driving mechanism, and has a staple feeding mechanism including ramp means that is shaped to receive and support a staple in its initial configuration on one end of said ramp means, the configuration of the ramp means gradually changing to a shape that will hold the staple with its legs generally parallel with each other. Thus the staple can be slidably pushed along the ramp means in a lateral direction, i.e. normal to the plane in which the staple legs and bridge portion lie, to bring it to a terminal position along the ramp means, in which position the rear of the tensioned staple can be struck by the front end of a powered striker. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is perspective view of a preferred embodiment of a compression staple according to the present invention; 
         FIG. 2  is top plan view of the embodiment of the staple of  FIG. 1 ; 
         FIG. 3  is a rear end elevational view of the staple of  FIG. 1 ; 
         FIG. 4  is a perspective view of variant of a staple according to the present invention; 
         FIG. 5  is an elevational view of staple applicator according to the present invention, with parts broken away for the sake of clarity; 
         FIG. 6  is a partial, perspective enlarged view of the front end of the staple applicator of  FIG. 5 ; 
         FIG. 7  is a sectional view taken long the line  7 - 7  of  FIG. 6 ; 
         FIG. 8  is sectional view taken long the line  8 - 8  of  FIG. 6 ; 
         FIG. 9  is an enlarged, partial perspective view of the front portion of a variant of a staple applicator according to the present invention; 
         FIG. 10  is an enlarged, partial perspective view of the front portion of another variant of a staple applicator according to the present invention; 
         FIG. 11  is a top plan view of a manually powered stapler according to the present invention; 
         FIG. 12  is a partial, enlarged perspective view of the front portion of the staple applicator of  FIG. 11 ; 
         FIG. 13  is a sectional view taken along the line  13 - 13  of  FIG. 12 ; 
         FIG. 14  is a perspective view of another variant of a compressive staple according to the present invention, wherein the staple legs have a convergent orientation with respect to each other; 
         FIG. 15  is a side elevational view of the staple of  FIG. 14 ; 
         FIG. 16  is a top plan view of a staple applicator according to the present invention; 
         FIG. 17  is an enlarged, partial perspective view of the front end of the applicator of  FIG. 16 ; 
         FIG. 18  is an enlarged partial, side elevational, partially sectional view illustrating the mounting of a staple on the front end of the staple applicator of  FIG. 16 ; 
         FIG. 19  is a view similar to  FIG. 18  showing a staple supported with legs parallel; 
         FIG. 20  is a perspective view of a convergent-legged staple that is adapted to be fed to a powered staple applicator; 
         FIG. 21  is a rear elevational view of the staple of  FIG. 20 ; 
         FIG. 22  is a side elevational view of another powered applicator according to the invention; 
         FIG. 23  is a perspective illustration showing means for feeding staples to the staple-driving means of the powered staple applicator shown in  FIG. 22 ; 
         FIG. 24  is a partial, enlarged , partial sectional side view of staple-delivering ramp member of the applicator shown in  FIG. 22 ; 
         FIG. 25  is a schematic illustration of the staple-striking region of the staple feeding means of  FIG. 23 ; 
         FIG. 26  is a perspective view of another variant of another compression staple similar to the staple of  FIG. 1 , and adapted for use with a staple-feeding magazine or cartridge; 
         FIG. 27  is a front end elevational view of the staple of  FIG. 26 ; and 
         FIG. 28  is a partial sectional perspective view, with parts broken away for the sake of clarity, illustrating a magazine or cartridge for feeding the staple of  FIG. 26  to a powered staple applicator. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now the drawings,  FIGS. 1-3  show that a preferred embodiment of a compression staple  11  according to the present invention has a pair of legs  13  with sharp front ends  15  and a bridge  17  that interconnects the rear end, portions of legs  13 . Staple  11  is fabricated of a surgical grade, bio-compatible metal, such as stainless steel, titanium alloy or other suitable alloy. Bridge  17  functions not only to hold legs  13  in approximate parallel relationship, but is selected to act as a spring by the flexing of its bow when the legs are spread apart as illustrated by the broken line image of  FIGS. 2 and 3 . This imparts an inward reacting force between the legs proportional to the degree of their displacement. It will be appreciated that the dimensions, gauge and curvature of bridge  17  are selected such that it can be flexed to a tensioned state that will deliver the compression requirements of the bone fixation to which staple  11  is to be applied. 
     It is preferred that the opposing inside surfaces of legs  13  are provided with serrations or barbs  19 . In this regard it is noted that, inasmuch as the insides of legs  13  will be pressed against bone mass when they are embedded in a manner to be described, the size of such serrations or barbs can be advantageously minimized, which minimizes trauma to the bone tissue during their implantation. 
     It will be evident that there can be several variations of compression staples according to the principles of the invention. For example, staple legs can have various cross sectional configurations, including diamond-shaped, square, triangular and rectangular.  FIG. 4  shows a variant  23  of a staple according to the present invention, having legs  25 . It is formed from metal rod having suitable strength and spring properties. It is also contemplated under the invention that the curvature of the bridge can take other forms than the single bow shown, and would include, among others a generally V-shape and a shape with double 90 degree bends. 
       FIG. 5  shows an air-powered staple applicator  29  for applying staple  11 , and it includes main body  31 , a conventional air piston assembly  33  within body  31 , air supply line  35  and a pistol grip and trigger assembly  37  for holding the stapler and for controlling the air-powered operation of the staple head  41 , to be described hereinafter. 
     As  FIG. 6  illustrates, the staple head  41  features an adjustable staple mount  43  that includes lower head  45  which is a forward extension of body  31 , and upper head  47 . A pair of parallel guide rods  51 , affixed to lower head  45  and extending upwardly therefrom, slidably engage twin bores  53  in the upper head  47  so as to guide the upper head in vertical motion relative to the lower head  45 . A screw jack assembly drives the upper head and includes thrust screw  55  that engages the threaded bore  57  in lower head  45 .  FIG. 7  best illustrates the screw jack assembly and shows turn knob  59  that has a socket for receiving a tool such as an Allen wrench for rotating the knob  59 .  FIGS. 6 and 7  also show a longitudinally extending groove  65  on the lower head  45  and a corresponding parallel groove  63  on the movable upper head  47 , these grooves being shaped to cradle the opposing sides of staple legs  13 , and the knob can be operated to set the spacing between grooves to allow staple  11 , in its initial un-tensioned configuration, to be mounted thereon as illustrated. 
     In a preferred embodiment, vertically extending gradations are provided at  67  on a forward surface of body  31 , adjacent the movable rear end of upper head  45 , so as to gauge the displacement of the staple legs when the invention is operated in a manner to be described below. 
     As  FIGS. 6 and 7  and  8  also show, staple applicator  29  includes mechanism for driving a staple forwardly from the staple head  41 , and includes longitudinally extending striker member  69  that is slidably mounted to grooves  71  and  73  for longitudinal movement, and the rear portion (not shown), is connected to the air piston assembly , and spring means (not shown) will hold the striker in an initial rearward position as illustrated in  FIG. 6 . Striker member  69  has front surface  75  that is adapted, as best shown in  FIG. 7 , to impact the rear legs of the staple bridge  17  when the striker member  69  is propelled to its forward position shown by the phantom lines in  FIG. 6 . 
     In the operation of staple applicator  29  for osteosynthesis, a staple  11  is mounted to the staple mount  43  which is operated to bring the staple to the desired tensioned configuration. Then bone segments are brought together by manual or mechanical manipulation as close as possible and aligned with each other. The stapler head  41  can then be positioned with its legs straddling the fracture line, and sharp ends  15  adjacent the surfaces of the bone segments. The stapler trigger can then be operated to cause the striker to drive the legs of the tensioned staple into the bone segments. 
     There is a variant of a staple applicator according to the invention that is identical to the embodiment of  FIGS. 6 and 7 , except that it has a striker member  69   a  is designed to engage the rear ends of staple legs  13  instead of the rear edge of the staple bridge  17 . Thus the sectional view of  FIG. 9  shows ends  79  and  80  that are adapted to strike respectively the upper and lower rear ends of staple legs  13 , of a staple  11  supported in tensioned configuration. It is contemplated under the invention that ‘strikers like striker  69   a , with differently spaced ends  79  and  80  can be provided so that different sized staples can be accommodated. 
       FIG. 10  shows the forward portion  81  of another variant of a power stapler applicator according to the present invention, having a main body  82 , an upper staple guide  83  and lower staple guide  85 . Opposing forward portions  87  of the guides are separated by a distance allowing it to hold staple  11  in tensioned configuration, and the rearward portions  89  will hold the staple in its initial configuration. The open-sided portions  91  allow a staple to be loaded by hand unto the staple guides. When the staple is pushed forwardly by hand from portion  89  to portion  87 , the divergent portions  93  will cause the spreading apart of the staple legs, and thus a tensioned staple is positioned for ejection. 
     A striker member  95  has upper and lower edges  97  and  99  slidably engaged in slots  101  and  103  so as to mount the striker member for longitudinal movement. The striker front ends  105  and  107  will align with and abut the rear ends of a tensioned staple. 
       FIGS. 11 ,  12  and  13  show a variant  113  of the invention, whereby percussive force is delivered by hand using a suitable mallet. Here the body  115  has a rear portion  117  designed for being struck by a mallet, and staple holder  119  at its front end.  FIGS. 12 and 13  show how the holder  119  includes lower portion  121  that has staple leg-receiving groove  129 , and an adjustable upper part  135  with groove  137 .  FIG. 12  best shows how a dove-tail portion  141  of part  135  fits in a complementary slot for guiding vertical movement of part  135 . Front surfaces  145  and  147  respectively of parts  121  and  135  are adapted to abut the rear ends of a staple mounted in grooves  137  and  129 . A screw  153  for driving the part  135  has threads  157  that engage a threaded bore  159  in the movable part  135 , and the knob  163  can be engaged by a suitable tool to rotate the screw  153 . 
     In using tool  113  the sharp ends of a tensioned staple  11  can advantageously be precisely positioned on the target spots on the bone segments, then the tool end  117  struck with a mallet to implant the staple. 
     Referring now to  FIGS. 14 and 15  there is shown in  FIG. 14  another compressive staple  161  according to the invention that is fabricated of a suitable resilient metal, and features legs  163  and  165  that converge with respect to each other, and interconnect by a bridge  167 . Staple  161  can also be made of a suitable resilient non-metallic bio-absorbable material. 
       FIG. 15  best shows how legs  163  and  165  each converge at a pre-selected angle φ with respect to parallel positions that the legs can be resiliently urged in a manner to be described hereinafter. It should be apparent that the material properties of the selected resilient material, the degree of convergence, and the dimensions and form of the staple will be selected by those with ordinary skill in the pertinent art so as to establish a certain force by which the parallel legs are urged to their convergent positions. 
       FIG. 16  shows one preferred embodiment of a bone-staple applicator  171  having a main body  173  with a rear end  175  adapted for being impacted by a force delivering instrument like a mallet. The front end  177  is designed to mount a staple  161  in its initial configuration and then move it to, and hold it in, a configuration where its legs are parallel. Thus it is seen in  FIG. 17  that front end  177  has an upper jaw  181  that can be adjustably spaced from to a lower jaw  183  using drive-screw mechanism similar to that used for the screw-driven spreadable parts  135  and  121  previously described above and shown in  FIGS. 12 and 13 .  FIG. 17  shows how the upper jaw  181 , and lower jaw  183  are shaped to mount a staple  161 , the slots  187  and  189  in the respective jaws being sized to receive the staple bridge  167 . A recessed portion  191  in the top of the jaw  181  is for supporting and stabilizing rearward portions of the upper staple leg  163 , and there is a similarly recessed portion on the under-surface of the lower jaw  183  (not shown) for supporting the rearward part  196  of lower staple leg  165 . The recessed portion  191  has a shelf  193  for engaging lower surfaces of leg  163 , and opposing edges  195  can hold the staple against lateral movement while the ledge  197  is adapted to abut the rear edge of the staple leg. 
       FIG. 18  best shows how an untensioned staple  161  is first mounted within the grasp of the opposing recessed portions of the jaws  181  and  183 , and it is noted how surfaces  193  and  194  engage inner surfaces  211  and  213  of opposing legs  163  and  165 . It should be appreciated how the screw mechanism  217  can be operated to move apart the opposing jaws, causing the opposing legs to be pushed into parallel relationship, as illustrated in  FIG. 19 . When a staple  161  is thusly mounted on the applicator tool  171 , it can be used much the same as the previously described device  113 , to apply a tensioned staple  161  to adjoining bone segments. Note that the jaw surfaces  193  and  194  can be appropriately sloped to ensure that the legs will be pushed into parallelism. 
       FIGS. 20 and 21  show another embodiment of a compression staple according to the present invention, i.e. the staple  261  which is particularly adapted for application by a powered applicator, for example an electrically powered or an air-powered staple applicator such as applicator  271  shown in  FIG. 22 , to be described. Like the previously described staple  161 , the staple  261  is fabricated of a suitable resilient metal using conventional metal-working techniques. The staple legs  263  and  265  extend from the bridge portion  267  and converge at a predetermined angle. It is noted how legs  263  and  265  are wider than the bridge portion  267 . The inside surfaces of the staple bridge and legs are adapted to slidably engage staple-feeding ramp structure, to be described. Furthermore,  FIG. 21  best shows how this staple structure provides to one side of the bridge  267 , opposing inside surfaces  270  and  274  respectively of legs  263  and  265 , which can be advantageously engaged for slidable forward movement of the staple along parallel guide surfaces in the powered staple applicator  271 , in a manner to be described. 
     The trigger-controlled applicator  271 , shown in  FIG. 22 , except for its forward end, is similar to the above-described applicator  29 , and includes a piston assembly  275 .  FIG. 23  illustrates how at the forward end of the applicator  271 , there is mounted a staple feeder  273  designed to supply and position staples for engagement by the front end  279  of a striker  281  that is connected to the piston assembly  275 . 
       FIG. 23  shows that the feeder  273  includes a housing  285  that is attached to a sidewall of the applicator and which supports a ramp member  287  that has a distal end  289  that is shaped to receive staples  261 . The walls  291 ,  292  and  293  are shaped so as to be slidably embraced by a number of staples  261  in their relaxed, legs-convergent configurations.  FIG. 24  also illustrates the ramp member  287  and shows how the ramp walls  291  and  292  vary from a convergent orientation at one ramp end to a generally parallel one at the opposite ramp end  294 .  FIG. 23  also illustrates that within the feeder housing  285  there is a spring-powered pusher  295 , connected to a suitable conventional spring (not shown) for urging the pusher  295  against the rear side edges of a staple  261  mounted on the ramp member  287 . Thus it can be appreciated how a staple  261 , or several side-by-side staples  261 , can be slidably pushed towards the end  294  of the ramp member. 
     The enlarged view of  FIG. 25  shows how the innermost end of the ramp member  287  has an end  299  that is spaced from a guiding surface  301  of applicator wall  304 . Surfaces  301  and the opposing upper and lower surfaces  303  and  305  form a channel as  FIG. 24  shows, for receiving the striker  281 .  FIG. 25  shows in broken lines a tensioned staple  261  in position for being driven by the striker  281 . Note that the bridge member  267  is spaced within the above-mentioned channel, clear of the end of the ramp member  287 , the staple being supported by virtue of the staple leg surfaces  270  and  274  ( FIG. 21 ) engaging the ramp member. Thus the striker front end  279  is aligned with the rear end of staple bridge portion  267 . 
     In operation of applicator  271  it is supported with its front end in close proximity to the relevant bone segments, and with the pointed ends of the staple appropriately aligned therewith. Pulling the trigger will cause the striker end  279  to impact the staple bridge and propel the staple forwardly as the staple legs are held generally parallel by sliding engagement with the generally parallel surfaces of the ramp member  287  during ejection. 
     The striker will have a stroke sufficient to cause the legs, in their parallel configuration, to be embedded in the bone tissue. The striker will return to its initial position rearward of the ramp member. Then spring force will cause another staple to be positioned in the ejection channel. 
     Although  FIGS. 22 and 23  show the feeder  273  connected adjacent the front end  260  of the applicator, it should be appreciated that in some cases it is desirable that the feeder  273  attaches to the applicator  271  at a location spaced a greater distance to the rear of the front  260 . In such cases the ramp walls  291  and  292  in the region of wall  301  are elongated forwardly as necessary to provide guide surfaces for the staple, and the stroke of the striker  281  is increased accordingly. 
       FIGS. 26 and 27  illustrate yet another variant  361  of the compression staple  11  described above ( FIG. 1 ), and has generally parallel legs  363  and  365  and resilient bridge  367 . This configuration provides opposing surfaces  370  and  374 , best shown in  FIG. 27 , that are adapted to engage parallel guide surfaces when the staple  361  is propelled from a powered staple applicator  371 ; to be described. In  FIG. 27  the tensioned configuration of staple  361  in shown in broken lines. 
       FIG. 28  shows a feeder  373  which is constructed similarly to the above-described feeder  273 , except that the ramp member  387  is adapted to handle the staple  361 . Thus the ramp walls  391  and  392  provide parallel surfaces for engaging inside surfaces of the staple legs and the wall  393  slidably abuts the wall  393 . 
     The distal end of the ramp  387  receives staples  361  in their untensioned condition, and the walls  391  and  392  gradually diverge from each other such that at the other end  395  of the ramp, a staple  361  will be supported in a legs-parallel tensioned configuration. A spring-powered pusher  399  is adapted to urge a number of nested staples  361  towards the end  395  of the ramp. 
     The ramp end  395  is spaced a predetermined distance from the guide surface  401  and provides surfaces that engage the opposing surfaces  370  and  374  of staple  361 . Thus the rear of a tensioned staple can be struck by the striker  397  and ejected from the applicator. 
     While particular embodiments of the invention have been described, it should be understood that the invention is not limited thereto, and includes other variants and modifications that will readily occur to those persons of ordinary skill in the art, given the benefit of this disclosure. Thus it is intended that the invention be given its full scope and breath as defined in the claims which follow.