Abstract:
An anchor device and system for coupling soft tissue to osseous tissue includes a stopper member that supports a loop of suture material. A fixing member includes features that allow it to be rigidly coupled to surrounding bone and thus hold the stopper member in a cavity within the bone. The loop of suture material, in turn, supports a second suture device, which is coupled to, and thus retains, the soft tissue. In certain embodiments, the stopper member includes a mechanical linkage for coupling it to the fixing member, and surface features that resist withdrawal of the fixing member from the bone.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. provisional patent applications numbered 60/983,159 filed on 27 Oct, 2007 and 61/127,315 filed on 12 May, 2008, the disclosures of which are herewith incorporated by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to surgical devices and more particularly to devices for surgical attachment. 
     BACKGROUND 
     Various surgical procedures require the temporary or permanent coupling of tissue to hard tissue such as bone. For example, when a tendon or ligament becomes detached from the bone which normally supports it, reattachment of the soft tissue to the bone with a supporting device helps to position the soft tissue for regrowth and recovery. Under other circumstances it is desirable to have a secure means of attaching a length of suture material between one or more bony regions. With this in mind, a variety of approaches have been developed for securing suture to hard tissue such as bone. Classed generally as bone anchors, these approaches have met with varying success. 
     Certain devices among those in this class have provided limited coupling strength with respect to a surrounding bone substrate matrix. Other devices have provided limited coupling strength and durability with respect to a suture material. Others have provided inadequate positional adjustability of the suture material. These and other deficiencies persist despite long and well-funded efforts by many investigators to secure improved methods and devices. 
     SUMMARY 
     Being aware of the long and previously incompletely effective efforts of others to address these problems, the present inventor has arrived at a new and important understanding of the problems, and of the mechanisms underlying those problems. Having developed this knowledge through careful and diligent effort, the inventor has now conceived and, out of similarly diligent efforts, reduced to practice novel and effective solutions to these problems. In particular, it is understood that earlier efforts to anchor soft tissue to bone have been inconsistently effective. The inventor now presents new and effective methods, devices and systems to effect these and other purposes. 
     As discussed above, it is necessary in some surgical procedures to provide a mechanism for coupling soft tissue to a particular location within the body. For example, in some circumstances it is necessary to couple a ligament or tendon to a bone. In other circumstances soft tissue such as muscle or skin must be similarly fixed in place. 
     One method of achieving such a coupling is to embed at least a portion of an anchor within a bone, and couple a suture between the anchor and the soft tissue. To this end, the present invention includes methods, systems and apparatus for providing an anchor device including a suture for coupling between, for example, bone and soft tissue. 
     In one embodiment, the anchor device includes a stopper portion and a fixing portion. The stopper portion is adapted to be coupled to a loop of suture material. A further length of suture material is disposed in a bent configuration through the suture loop. The stopper portion is disposed within a substrate matrix of osseous tissue and held in place by the fixing portion. 
     In certain embodiments according to the invention, the fixing portion includes a threaded feature on an external surface thereof. In other embodiments according to the invention a fixing portion includes a barbed feature on an external surface thereof. In still other embodiments according to the invention a fixing portion includes a vaned feature on an external surface thereof. 
     In certain embodiments of the invention, the fixing portion includes a plurality of projecting features disposed between longitudinal grooves at an external surface of the fixing portion. In other embodiments of the invention, the fixing portion includes a plurality of barb projections where the barb projections include substantially circular barb projections disposed coaxially about a longitudinal axis of the fixing portion. In other embodiments, the barb projections include a plurality of projections disposed between longitudinal grooves at a surface of the fixing portion. 
     In certain embodiments of the invention, the stopper portion is disposed between two or more fixing portions. In certain embodiments of the invention, fixing portions are provided with opposite threads and a coupling mechanism. In still further embodiments of the invention, the stopper portion includes a threaded surface feature oppositely handed with respect to a threaded surface feature of a fixing portion. In certain embodiments, the stopper portion includes a detent mechanism adapted to couple the stopper portion in substantially fixed spatial relationship with respect to the fixing portion. 
     These and other advantages and features of the invention will be more readily understood in relation to the following detailed description of the invention, which is provided in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows, in perspective side view, an exemplary anchor device including a stopper portion and a fixing portion according to one embodiment of the invention; 
         FIG. 2  shows, in perspective side view, an exemplary anchor device including a fixing device having a longitudinal groove according to one embodiment of the invention; 
         FIG. 3  shows, in perspective side view, an exemplary anchor device including a stopper device having a radial suture loop bore according to one embodiment of the invention; 
         FIG. 4  shows, in perspective side view, an exemplary anchor device including a stopper device having a projection according to one embodiment of the invention; 
         FIG. 5  shows, in cross-section, an anchor according to one embodiment of the invention; 
         FIGS. 6A-6H  show a respective plurality of projection profiles according to respective exemplary embodiments of the invention; 
         FIG. 7  shows, in distal perspective view, an anchor device according to one embodiment of the invention; 
         FIG. 8  shows, in proximal perspective view, an anchor device according to one embodiment of the invention; 
         FIG. 9  shows, in cross-section, a suture loop according to one embodiment of the invention; 
         FIG. 10  shows, in cross-section, a portion of an anchor device and an insertion tool according to one embodiment of the invention; 
         FIG. 11  shows, in cross-section, a portion of an anchor device including a stopper portion, a fixing portion and a detent mechanism, according to one embodiment of the invention; 
         FIG. 12  shows, in cross-section, an anchor device according to a further embodiment of the invention; 
         FIG. 13  shows, in cross-section, an anchor device according to another embodiment of the invention; 
         FIG. 14  shows, in cross-section, an anchor device according to still another embodiment of the invention; 
         FIG. 15  shows, in perspective view, a stopper having an anti-rotation vane according to one embodiment of the invention; 
         FIG. 16  shows, in cutaway perspective view, a stopper according to one embodiment of the invention; 
         FIG. 17  shows, in quasi-cross-sectional view, a stopper including a detent mechanism according to one embodiment of the invention; 
         FIG. 18  shows, in cutaway perspective view, a stopper including a detent mechanism according to another embodiment of the invention; 
         FIG. 19  shows, in cutaway perspective view, a stopper including a piercing point according to one embodiment of the invention; 
         FIG. 20  shows, in cross-section, an anchor according to one embodiment of the invention; 
         FIG. 21  shows, in cross-section, an anchor according to another embodiment of the invention; 
         FIG. 22  shows, in cross-section, an anchor according to still another embodiment of the invention; 
         FIG. 23  shows in cross-section, a portion of an anchor and insertion tool kit according to one embodiment of the invention; and 
         FIG. 24  shows, in cross-section, a portion of an anchor and insertion tool kit as used in a method according to one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows part of an exemplary anchor  100  according to one embodiment of the invention. The anchor  100  includes a first stopper portion  102  and a second fixing portion  104 . The stopper portion  102  has a substantially circular cylindrical peripheral surface  106  disposed coaxially about a longitudinal axis  108 . A distal surface  110  of the stopper  102  is disposed substantially normal to the longitudinal axis  108 . In the illustrated embodiment, first and second bores are defined within the stopper  102 . Each bore is defined by a respective substantially cylindrical internal surface  112 ,  114 . Internal surfaces  112 ,  114  have respective longitudinal axes disposed substantially parallel to one another and to longitudinal axis  108 . 
     In the illustrated embodiment, fixing portion  104  of the anchor  102  is generally cylindrical about longitudinal axis  108 . A circumferential surface  116  of fixing portion  104  includes a plurality of detent formations. As illustrated, the detent formations include a substantially helical flange  118  or ridge disposed generally equidistant to longitudinal axis  108 . As illustrated, the helical flange  118  includes a first distal surface region  120  and a second proximal surface region  122 . As illustrated in  FIG. 1 , the detent formation is shown as a push-in style detent feature. One of skill in the art will appreciate, however, that other detent features, such as, for example, cortical bone threads and cancellous bone threads are to be used in other respective embodiments of the invention. Also, as shown, the push-in detent features extend over the full length of the fixing portion  104 , as shown. In other embodiments partial coverage is employed. 
     As will be discussed in additional detail below, the fixing portion  104  includes an internal surface defining a bore that is substantially coaxial with longitudinal axis  108 . In the configuration illustrated, where the stopper portion  102  is disposed adjacent to a proximal end of the fixing portion  104  open regions within bores  112  and  114  are contiguous with an open region within the longitudinal bore of the fixing portion  104 . 
     According to one embodiment of the invention, the stopper portion  102  is removably coupled to the fixing portion  104  in the illustrated orientation. According to one methodical aspect of the invention stopper portion  102  is removably coupled to fixing portion  104  prior to insertion of the resulting assembly into osseous tissue. In an alternative it embodiment of the invention stopper portion  102  is disposed within a region of osseous tissue and fixing portion  104  is subsequently disposed adjacent to stopper portion  102 . In a further embodiment, stopper portion  102  is substantially non-removal. 
     In one embodiment of the invention, the helical flange  118  is configured as a thread, whereby a method of rotating fixing portion  104  about longitudinal axis  108  causes a threading interaction between helical flange  118  and a surrounding bone tissue. Consequently the rotation of the fixing portion  104  causes a distal advancement of the fixing portion  104  into the bone tissue. 
     As will be described below in further detail, a method according to one embodiment of the invention includes disposing respective first and second portions of a length of suture substantially coaxially within bores  112  and  114 . The length of suture includes a further U-shaped portion disposed within the bore of the fixing portion  104  and contiguous with the first and second suture portions. According to one embodiment of the invention, first and second knots are formed at respective ends of the length of suture and are disposed distally of surface  108  so as to slidingly couple the length of suture to the stopper portion  106 . 
       FIG. 2  shows an oblique generally distal perspective view of a portion of an anchor  200  according to one embodiment of the invention. Like anchor  100 , anchor  200  includes a stopper portion  202  and a fixing portion  204 . The stopper portion  202  includes first and second generally longitudinal bores  212  and  214 . In the embodiment shown, the longitudinal bores  212  and  214  are defined by respective substantially cylindrical internal surfaces of the stopper portion  202 . According to one embodiment of the invention, these substantially cylindrical internal surfaces are substantially smooth and uninterrupted. The stopper portion  202  is adapted to be disposed adjacent to, and in some embodiments coupled to, a distal end  226  of fixing portion  204 . 
     The fixing portion  204  includes a generally cylindrical external surface  216  having a helical flange  218  formation. A groove  228  is disposed longitudinally along surface  216  and defines respective first and second ends of flange  218 . In the illustrated embodiment, flange  218  is generally helical. Consequently, flange end  230  is distally offset along a longitudinal axis  208  with respect to flange end  232 . 
     In another embodiment of the invention, the flange  218  formation is substantially circular, rather than helical, so that flange ends  230 ,  232  are disposed generally adjacent to one another across groove  228 . It should be noted that in either case, flange  218  does not form an uninterrupted helical thread about longitudinal axis  218 . In a further embodiment, fixing portion  204  includes a plurality of longitudinal grooves disposed generally parallel to groove  228  around longitudinal axis  208 . 
       FIG. 3  shows an anchor  300  including a stopper portion  302  and a fixing portion  304  according to still another embodiment of the invention. While the configuration of anchor  300  is generally similar to that of anchor  200 , it should be noted that stopper portion  302  includes a bore  213  disposed generally perpendicular to a longitudinal axis  308 . One of skill in the art will appreciate that bore  213  defines an internal right angle within stopper portion  302  so as to open at a distal end of an internal longitudinal bore within the fixing portion  304 . Thus a length of suture can be passed through bore  213  to form an internal loop within the longitudinal bore of the fixing portion. An end of the length of suture projects perpendicular to longitudinal axis to emerge through the illustrated orifice where it is knotted to retain the length of suture in sliding relation to the stopper portion. One of skill in the art will appreciate that this arrangement contrasts to the longitudinal bores  212 ,  214  of anchor  200 . 
       FIG. 4  shows, in perspective view, a portion of an anchor  400  according to a further embodiment of the invention. The anchor includes a stopper portion  402  and a fixing portion  404 . The fixing portion  404  has a generally circular symmetry about a longitudinal axis  408 . A circumferential external surface  410  of the fixing portion has a first relatively smaller radius perpendicular to longitudinal axis  408  at a distal end  412  of the fixing portion. In comparison a corresponding radius at a second proximal end  414  of the fixing portion  404  is relatively larger. Consequently, external surface  410  of the fixing portion  404  describes, generally, a frustum of a cone. In the illustrated embodiment, the external surface  410  includes a projecting ridge or flange  418  disposed in a generally spiral/helical configuration about longitudinal axis  408 . In various embodiments, the ridge or flange  418  is interrupted by one or more longitudinal grooves like that shown in anchor  300  of  FIG. 3 . It should be noted that while  FIG. 4  exemplifies an anchor having a cortical thread alternative threading and other retaining features are used in alternative embodiments respectively. 
     In the illustrated embodiment, stopper portion  402  includes a generally circular cylindrical external surface  406  disposed coaxially to axis  408  at a distal region of the stopper. The stopper  402  also has a projecting portion  420  at a proximal region thereof. In various embodiments, as will be described below in additional detail, the projecting portion  420  is adapted to be received within a corresponding cavity of the fixing portion  404 . According to one embodiment the corresponding cavity consists of a portion of a longitudinal bore. 
       FIG. 5  shows, in cross-section, a portion of an exemplary anchor  500 . Anchor  500  includes a stopper portion  502  and a fixing portion  504 . The fixing portion  504  has a generally circular symmetry about a longitudinal axis  508 . A circumferential external surface  510  of the fixing portion has a first relatively smaller radius  511  perpendicular to longitudinal axis  508  at a distal end  512  of the fixing portion. In comparison a corresponding radius at a second proximal end  514  of the fixing portion  504  is relatively larger. Consequently, external surface  510  of the fixing portion  504  describes, generally, a frustum of a cone. 
     As shown, longitudinal bores  515 ,  517  traverse the stopper portion  502 . The longitudinal bores are disposed generally parallel to longitudinal axis  508 . As will be discussed below in further detail, the longitudinal bores  515 ,  517  are adapted to receive respective portions of a suture loop. 
     In the illustrated embodiment, stopper portion  502  includes a generally circular cylindrical external surface  506  disposed coaxial to axis  508  at a distal region of the stopper. The stopper  502  also has a projecting portion  520  at a proximal region thereof. As illustrated, the projecting portion  520  is adapted to be received within a corresponding cavity  522  of the fixing portion  504 . As illustrated, cavity  522  is defined by a plurality of substantially planar surface regions, e.g.,  524 . Consequently, a cross-sectional profile of the cavity  522  is, in certain embodiments, polygonal. A corresponding cross-section of projecting portion  520  matches the polygonal cross-section of the cavity  522 , in size and shape, so that the cavity is adapted to receive the projecting portion  520  firmly therewithin. 
     The creative practitioner of ordinary skill in the art will appreciate that a wide variety of cross-sections are used in corresponding embodiments of the invention. Thus, while the cross-section of projecting portion  520  is shown as generally hexagonal, other useful cross-sections include, as shown in  FIG. 6 , triangular ( FIG. 6A ), square ( FIG. 6B ), pentagonal ( FIG. 6C ), elongate ( FIG. 6D ), stellate ( FIG. 6E ), circular ( FIG. 6F ), irregular ( FIG. 6G ) and combinations thereof, (e.g.,  FIG. 6H ). 
       FIG. 7  shows, in distal perspective view, an exemplary anchor  700  including a stopper portion  702  and a fixing portion  704 . As is evident on inspection, longitudinal bores  706  and  708  in the stopper portion  702  form a contiguous passage with a longitudinal bore of the fixing portion  704 . 
       FIG. 8  shows, in proximal perspective view, an exemplary anchor  800  including a stopper portion  802  and a fixing portion  804 . A portion of a longitudinal bore  806  within the fixing portion  804  is visible. As shown, an internal surface of the longitudinal fixing portion  804  includes a plurality of substantially planar surface regions e.g.,  808  defining a substantially hexagonal tool engagement region  806 . 
     The substantially hexagonal tool engagement region  806  is adapted to receive a portion of a driving tool of corresponding cross-section therewithin. One of skill in the art will appreciate that such a tool can be used to rotate or otherwise manipulate the fixing portion as part of an anchor insertion procedure and method. It will also be evident to one of skill in the art that, while the illustrated embodiment shows a tool engagement region of the longitudinal bore having a substantially hexagonal cross-section, a wide variety of other cross-sections and configurations can readily be used in various embodiments of the invention. 
       FIG. 9  shows, in cross-section, a portion of anchor  900  including a suture loop according to one embodiment of the invention. As shown, the anchor includes a stopper portion  902  and a fixing portion  904 . The stopper portion  902  includes first  906  and second  908  longitudinal bores that, when the stopper portion  902  is disposed adjacent to the fixing portion  904 , open onto a longitudinal bore  910  of the fixing portion  904 . A first length of suture  912  is adapted to be knotted  914  at first end, to pass through the first stopper portion bore  906  into the fixing portion bore  910  and back through the second stopper portion bore  908 . 
     A further knot  916  is adapted to retain the first length of suture  912  in place in the illustrated suture loop configuration. A portion of a further length of suture material  918  is disposed within the bore  910  and engages with the first length of suture  912  as shown. As will be understood by one of ordinary skill in the art, an interface between the surfaces of the first  912  and second  918  lengths of suture material will exhibit desirably low friction. Further, the illustrated arrangement serves to couple the length of suture  918  effectively in relation to the anchor  900 . 
       FIG. 10  shows, in cross-section, a portion of a combination of an anchor  1000  with an insertion tool  1002 . In the illustrated embodiment, the insertion tool  1002  includes a shaft portion  1005  having a longitudinal internal bore  1004  (i.e., a cannulated shaft). As shown, a distal portion  1006  of the shaft portion  1005  is adapted to engage with a tool engagement region  1008  of a fixing portion  1010  of anchor  1000 . As a consequence of this arrangement, the fixing portion  1010  is adapted to receive a force such as a torque, transmitted by the shaft portion  1005 . 
     As shown, the longitudinal bore  1004  of the shaft portion  1005  is adapted to receive a length of suture  1012  therewithin. This arrangement allows the shaft portion  1005  to engage with the tool engagement region  1008  without interference from the length of suture  1012 . In certain embodiments of the invention, a kit is provided including an anchor having a stopper portion with a suture loop and a further length of suture, a fixing portion, and an insertion tool, all packaged together as a preassembled unit. 
     It should be noted that the various anchors illustrated and discussed above exhibit a variety of surface features including helical thread features and circular barb features and interrupted helical and circular barb features. In various embodiments of the invention particular features are selected for engagement with a particular substrate. Thus in one embodiment of the invention, an anchor is provided with a surface feature adapted to engage advantageously with cortical bone tissue. 
     In another embodiment, an anchor is provided with a surface feature adapted to engage with cancellous bone tissue. In certain other embodiments of the invention, a single anchor device may include surface features adapted to engage different substrates. Thus in one embodiment, an anchor is provided having a first surface feature adapted to engage cortical bone and a second surface feature adapted to engage cancellous bone tissue. 
     According to a further embodiment of the invention, it is advantageous to provide a stopper portion adapted to be substantially fixedly coupled to a corresponding fixing portion of a bone anchor. Such a fixing coupling can be advantageous both in terms of keeping the stopper portion and the fixing portion together during insertion of a bone anchor and also in terms of providing a robust coupling between the anchor and surrounding substrate, such as bone tissue. 
       FIG. 11  shows, in cross-section, a further embodiment of an anchor  1100 . Anchor  1100  includes a first stopper portion  1102  and a second fixing portion  1104 . Advantageously, the anchor  1100  includes a detent device  1106  adapted to substantially fixedly couple stopper portion  1102  to fixing portion  1104 . In the embodiment illustrated as anchor  1100  the detent device  1106  includes a plurality of quasi-elastic arms (e.g.,  1108 ) supporting a respective plurality of barbed hooks (e.g.  1110 ) or barbs. The arms  1108  are, in certain embodiments, coupled to or integral with stopper portion  1102 . Each hook  1110  is adapted to be received within a corresponding cavity (e.g.,  1112 ). Cavity  1112  opens into bore  1114  within fixing portion  1104 . 
     Following a method according to one embodiment of the invention, stopper portion  1102  and fixing portion  1104  are aligned substantially coaxially along a longitudinal axis  1116 . Forces are applied that urge stopper portion  1102  and fixing portion  1104  to move into proximity, each relative to the other. As this motion proceeds, proximal surface regions  1118  of barbs  1110  interfere mechanically with oblique surface regions  1120  of the fixing portion  1104 . This mechanical interference motivates a pivotal deflection of the arms  1108  with respect to stopper portion  1102 , moving the barbs  1110  progressively towards longitudinal axis  1116 . This trend proceeds until the barbs  1110  reach the cavities  1112 , whereupon elastic forces exerted by the arms move the barbs  1110  into the cavities  1112 . Thereafter, the same elastic forces tend to retain barbs  1110  within cavities  1112 . 
     One of skill in the art will appreciate that this arrangement tends to retain the stopper portion  1102  and fixing portion  1104  in substantially fixed relation to one another. In particular, it should be noted that the illustrated arrangement inhibits both further linear motion along the longitudinal axis  1116  with respect to one another and rotary motion of the stopper portion and fixing portion around longitudinal axis  1116  with respect to one another. 
     According to one embodiment of the invention, the stopper portion  1102  and fixing portion  1104  are urged together coaxially during assembly of an anchor device. As in the case of embodiment  1100 , however, assembly of the stopper portion  1102  to the fixing portion  1104  is advantageously performed in situ within substrate tissue. 
     Accordingly, in one aspect of the invention, the illustrated stopper portion  1102  includes a first externally threaded surface feature  1122  including a substantially helical surface ridge  1124 . It should be noted that first externally threaded surface feature  1122  is configured as a left-handed thread. The fixing portion  1104  includes a second externally threaded surface feature  1126  including a substantially helical surface ridge  1128 . It should be noted that second externally threaded surface feature  1126  is configured as a right-handed thread. One of skill in the art will appreciate that the handedness identified above is merely exemplary and is readily reversed in alternative embodiments of the invention so that the stopper portion includes a right-handed thread and the fixing portion includes a left-handed thread. 
     According to one embodiment, the invention includes a method of inserting a first anchor portion by a left-handed rotation of the stopper portion so as to screwingly advance the stopper portion within a substrate; and thereafter inserting a fixing portion by a right-handed rotation of the fixing portion so as to screwingly advance the fixing portion within the substrate. According to one aspect of the invention as the fixing portion arrives in proximity to the stopper portion a substantially permanent coupling between the two anchor portions is made, whereupon the opposite threading of the two portions serves to substantially limit further rotation of either anchor portion of the combined anchor portion assembly. 
     In light of the here-described method it should be noted that, according to one embodiment, stopper portion  1102  includes a first receiving feature  1130  adapted to receive a first portion of a first insertion tool, and fixing portion  1104  includes a second receiving feature  1132  adapted to receive a second portion of a second insertion tool. It should be noted, however, that in certain embodiments, receiving portions can be configured so that a single insertion tool can be used in relation to both a stopper portion and a fixing portion. Although not shown, one of skill in the art will readily understand that a suture loop arrangement, as described above, can be disposed in relation to the illustrated bores  1134 ,  1136  of anchor  1100 . 
       FIG. 12  shows, in cross-section, a portion of a further embodiment of an anchor  1200  including a stopper portion  1202  and a fixing portion  1204 . The anchor  1200  includes a detent device  1206 . In the illustrated embodiment, detent device  1206  includes at least one reasonably flexible arm  1208  having a barbed hook portion  1210 . The barbed hook  1210  is adapted to be received within a corresponding cavity  1212  of fixing portion  1204 . It should be noted that, during an assembly process, reasonably flexible arm  1208  is adapted to be deflected outwardly away from longitudinal axis  1214  by interference between a first surface region  1216  of barbed hook portion  1210  and a corresponding external surface region  1218  of fixing portion  1204 . 
     One of skill in the art will observe that whereas arm  1108  of anchor  1100  is deflected during assembly inwardly towards longitudinal axis  1116  and then relaxes hook  1110  outwardly into an internal cavity  1112  of fixing portion  1104 , arm  1208  of anchor  1200  is deflected during assembly outwardly away from longitudinal axis  1214  and then relaxes inwardly into an external cavity  1212  of fixing portion  1204 . In both illustrated embodiments  1100  and  1200 , interfering surfaces  1120  and  1218  exhibit substantially circular symmetry about respective longitudinal axis  1116 , 1214  and are disposed generally obliquely with respect to the respective longitudinal axes. It should be noted that, in various embodiments, these interfering surfaces may exhibit simple and/or compound curvature. 
     As with the embodiment of anchor  1100 , anchor  1200  includes opposing left-handed threads  1220  and right-handed threads  1222  so that once the stopper portion  1202  and fixing portion  1204  are assembled in situ within a substrate, and detent portion  1206  is activated to lock the two portions together, the opposing threads tend to prevent further rotation and other motion of the completed assembly. 
     It should be noted that, in certain embodiments, a first, relatively narrow, receiving hole is bored in a substrate to receive the stopper portion. In some embodiments, this receiving hole is in advance of insertion of the stopper portion. In other embodiments, the stopper portion includes a self-tapping thread. In still other embodiments, the stopper portion includes a self-punching self-tapping thread adapted to allow insertion of the stopper portion without the pre-drilling of a receiving hole. In certain embodiments no receiving hole is predrilled, but a lead hole of substantially smaller diameter than the stopper portion is predrilled in the substrate. 
     In other embodiments, a receiving hole is drilled that includes a relatively narrow diameter portion adapted to receive the stopper portion and a relatively wider diameter portion adapted to receive the fixing portion of the anchor. According to certain methods of the invention, a plural-diameter hole is prepared in a single operation using an appropriate tool of stepped diameter. Likewise, an appropriate tool may be used to simultaneously drill and tap a receiving hole of a single or of a plural diameter. 
       FIG. 13  shows an anchor  1300  including a stopper portion  1302  and a fixing portion  1304 . The stopper portion  1302  includes one or more substantially radially projecting vanes  1306 . The vanes  1306  are adapted to prevent rotation of stopper portion  1302  about a longitudinal axis  1308  when the stopper portion  1302  is disposed within a substrate matrix such as, for example, osseous tissue. 
     According to one method within the scope of the invention, an appropriately sized receiving hole is prepared in a region of substrate bone tissue. The receiving hole is configured to have a diameter appropriately less than a corresponding diameter  1310  across the vanes  1306  of stopper portion  1302 . Stopper portion  1302  is disposed coaxially at a mouth of the receiving hole and urged along longitudinal axis  1308  into the receiving hole. According to one embodiment of the invention, vanes  1306  are adapted to cut into, or otherwise displace, a portion of the substrate bone disposed radially with respect to the receiving hole as the stopper portion  1302  is advanced into the receiving hole. Consequently, when the stopper portion  1302  has been sufficiently received into the receiving hole its rotation about longitudinal axis  1308  is substantially inhibited by a mechanical interference between external surfaces (e.g.  1312 ) of the vanes and the surrounding substrate. 
     Thereafter, fixing portion  1304  is advanced with rotation into the receiving hole until a detent mechanism  1314  engages. Thereafter, the mechanical engagement between the stopper portion  1302  and the fixing portion  1304 , in combination with the action of the vanes  1306  to inhibit rotation of the stopper portion  1302  serves to substantially prevent undesirable counter-rotation and consequent withdrawal of the fixing portion  1304 . 
       FIG. 14  shows a further embodiment of an anchor  1400  according to principles of the invention. The anchor  1400  includes a stopper portion  1402  and a fixing portion  1404 . The stopper portion  1402  has at least one anti-rotation vane  1406 . The fixing portion  1404  has an external surface thread feature  1408 . A detent mechanism  1410  includes a plurality of substantially flexible arms  1412  that are integral with or coupled to fixing portion  1404 . The arms  1412  include respective barbed hooks  1414  adapted to be received internally within stopper portion  1402 . 
       FIG. 15  shows a further perspective view of stopper  1402  including four illustrative vanes  1406 . 
       FIG. 16  shows a further cutaway view of stopper  1402 . In the illustrated embodiment, stopper portion  1402  includes a plurality of receiving cavities  1418  adapted to receive and retain the barbed hooks  1414 . The illustrated receiving cavities have a substantially rectangular circumferential profile  1420 , however alternative profiles including, without limitation, circular, triangular, polygonal and curved are contemplated. In addition, it is anticipated that the number of receiving cavities  1418  may differ from a number of barbed hooks  1414 . For example, there may be more receiving cavities than barbed hooks or more barbed hooks than receiving cavities. 
     It should be understood that the above-described barbed hooks are merely exemplary of a wide variety of other detent mechanisms that are contemplated within the scope of the invention. Thus,  FIG. 17  shows a stopper  1700  according to a further embodiment of the invention including a first barbed-hook detent feature  1702  adapted to prevent linear withdrawal of a fixing portion (not shown) along longitudinal axis  1704  with respect to stopper  1700 . A separate hemispherical detent feature  1706  is adapted to be received within a corresponding cavity of the fixing portion to inhibit rotation about longitudinal axis  1704  of the fixing portion with respect to the stopper portion  1700 . 
     It will be appreciated that, while detent feature  1706  is shown as a substantially hemispherical projection, well adapted to be received in a corresponding substantially concave hemispherical recess of a fixing portion, alternative arrangements are possible. For example a concave recess may be provided on the stopper portion while a corresponding convex projection may be provided on the fixing portion. Likewise, each of the stopper portion and the fixing portion may include both convex and concave features. Further, the hemispherical shape of the projection is merely illustrative of a wide variety of possible shapes and configurations that fall within the scope of the invention in its various embodiments. Thus, for example,  FIG. 18  shows a portion of a stopper  1800  including an anti-rotation detent feature  1802  having a generally flexible arm  1804  and a barbed hook  1806  at one end thereof. 
     The generally flexible arm  1804  is integral with or coupled to a body  1808  of the stopper portion  1800  at an end  1810  opposite to the barbed hook  1806 . In the illustrated embodiment, the arm  1804  is adapted to deflect, so as to allow the barbed hook  1806  to be displaced generally radially outward with respect to longitudinal axis  1812 . Thereafter, the arm  1804  is adapted to resile so as to position a portion of the barbed hook  1806  within a corresponding cavity of a fixing portion (not shown). Consequently, as will be understood by one of skill in the art, the fixing portion and stopper portion  1800  are adapted to be locked in substantially fixed spatial relation to one another and to a surrounding substrate. 
       FIG. 19  shows, in cutaway cross-sectional view, a stopper portion  1900  according to a further embodiment of the invention. The stopper portion  1900  is adapted to be coupled to an exemplary piercing point  1902 . In the illustrated embodiment, the piercing point includes a fastener, shown here for example as an externally threaded stud  1904 , adapted to be received within an internally threaded bore  1906  of the stopper  1900 . In the illustrated embodiment, the piercing point includes an annular cavity or channel  1908  adapted to accommodate a knot  1910  of a suture loop (not shown). 
     While the piercing point  1902  is shown here as a discrete component adapted to be assembled to stopper portion  1900 , one of skill in the art will appreciate that stopper  1900  could equally well be prepared to include an integral piercing point. In the case of a stopper having an integral piercing point, suture channels (e.g.,  1912 ) can be configured to exit the stopper longitudinally and/or radially with respect to a longitudinal axis  1914  of the stopper  1900 . It should also be understood that the stopper and piercing point can be made of the same or differing materials according to the requirements of a particular embodiment and application. 
     Thus, in one embodiment a fixing portion, a stopper portion, and a piercing point may each be made of any one of a biocompatible material including natural and synthetic polymers such as, for example, poly-ether-ether-ketone (PEEK); reinforced polymer materials including reinforcing sheets and/or particles and/or fibers of, for example, one or more of, carbon fibers, carbon nano-materials, glass fibers and metallic fibers; precious metals, stainless steel, titanium and other metals; porcelain, alumina and other ceramics including, for example, aluminum oxide, calcium oxide, calcium phosphate hydroxyapatite, and zirconium, and combinations thereof. 
       FIG. 20  shows an anchor  2000  according to a further embodiment of the invention. Anchor  2000  includes a first stopper portion  2002  and a second fixing portion  2004 . The stopper portion  2002  includes a piercing point  2006 . According to one embodiment of the invention, piercing point  2006  includes a cavity  2008 , here shown as a generally hemispherical cavity adapted to receive a suture knot therewithin. The exemplary piercing point illustrated here also has a depressed region  2010  and a cutting edge  2012  adapted to facilitate a substrate piercing function of the piercing point  2006 . 
       FIG. 21  shows, in cross section, an anchor  2100  according to a further embodiment of the invention. Anchor  2100  includes a first piercing point  2101 , a second stopper portion  2102 , and a third fixing portion  2104 . As shown, the piercing point  2101  includes a first surface feature, here shown as left-handed threads  2106 . The fixing portion  2104  includes a second surface feature, here shown as right-handed threads  2108 . In the presently illustrated embodiment, the stopper portion  2102  does not include a surface feature adapted to prevent rotation or withdrawal along longitudinal axis  2112  of the stopper portion  2102 . The stopper portion  2102  does include, however, detent devices  2114 ,  2116 , adapted to substantially fixedly couple the stopper portion  2102  to the piercing point  2101  and the fixing portion  2104  respectively. 
     It should be appreciated that in other embodiments, the stopper portion includes an anti-rotation or anti-extraction surface feature such as a plurality of vanes. In other embodiments, one or more of the piercing point  2101  and the fixing portion  2104  includes an alternative anti-rotation or anti-extraction surface feature such as, for example, a plurality of vanes. 
       FIG. 22  shows, in cross section, a further anchor  2200 . Anchor  2200  includes a first stopper portion  2202 , a second fixing portion  2204 , and a retainer portion  2206 . The retainer portion  2206  includes at least one longitudinal bore  2208  adapted to receive a portion of a suture therewithin. As illustrated, the stopper portion  2202  includes a surface feature, here shown as left-handed threads, for example. The fixing portion  2204  includes a surface feature, here shown as right-handed threads, for example. Both the stopper portion  2202  and in the fixing portion  2204  include respective tool receiving features  2210 ,  2212 . In one embodiment, the retainer portion  2206  includes a contact surface  2214  adapted to engage a corresponding surface of stopper portion  2202 . 
     In the illustrated embodiment, the retainer portion  2206  also includes a contact surface  2216  adapted to engage a corresponding surface of fixing portion  2204 . According to one embodiment of the invention, contact surfaces  2214  and  2216  are adapted to frictionally engage corresponding surfaces of the stopper portion  2202  and fixing portion  2204 . In other embodiments, the anchor  2200  is adapted to receive, for example, a chemical adhesive material, at surfaces  2214  and  2216 . In still other embodiments, the anchor  2200  is adapted to be treated after insertion into a substrate to form a physical bond at surfaces  2214  and  2216 . For example, one or more of a thermal weld and an ultrasonic weld may be formed at surfaces  2214  and  2216  to prevent decoupling of the stopper portion  2202  from the fixing portion  2204  and the retainer portion  2206 . 
     One of skill in the art will appreciate that a variety of methods are evident from the above-provided description and included within the scope of the present invention as disclosed. Thus, according to one method of the invention, a first hole is drilled or pierced into a substrate such as a bone. A cannulated insertion tool  2300 , as shown in  FIG. 23  has a suture  2302  disposed generally longitudinally adjacent to a first substantially solid shaft  2304  thereof. The first shaft  2304  is used to drive a self-tapping stopper portion  2306  into the hole by a leftward rotation of the first shaft  2304 . Subsequently, a further portion of the cannulated insertion tool, including a second cannulated shaft  2308  coaxially encircling the first substantially solid shaft  2304  is used to drive a self-tapping fixing portion  2310  into the hole by a rightward rotation of the second shaft  2308  until the stopper portion  2306  and the fixing portion  2310  engage and lock together. Thereafter the opposing sense of the threads  2312 ,  2314  of the stopper portion and of the fixing portion respectively prevent subsequent rotation and withdrawal of the resulting anchor assembly  2320 . 
       FIG. 24  shows the relationship of the stopper portion  2306 , including suture loop  2322  and fixing portion  2310  in additional detail. In a typical application, the fixing portion  2310  will be installed in a substrate bone so that proximal surface  2320  is ultimately disposed substantially flush with an external surface of the bone. In another embodiment of the invention, surface  2320  is ultimately disposed a short distance inwardly of the external surface of the bone. For example surface  2320  may be disposed between about 0 mm and at least about 0.5 mm below the external surface of the substrate bone. It should be further noted that in certain cases, elements of the anchor are tapped, pounded and/or pressed into place, rather than rotated into place. 
     One of skill in the art will appreciate that a threaded suture anchor can be deployed into cortical bone. Purchase in cortical bone is enhanced by a narrow (e.g., approximately 1.5 mm) thread pitch. A wider thread pitch (e.g., approximately 3 mm) is advantageously deployed in cancellous bone. The push-in anchor has very broad application in areas such as the foot, the hand, and the shoulder. Advantageously, the push-in anchor has a compact size. This compact size is advantageous and allows for greater maneuverability in tight articular spaces. 
     While the exemplary embodiments described above have been chosen primarily from the field of soft tissue to bone reattachment, one of skill in the art will appreciate that the principles of the invention are equally well applied, and that the benefits of the present invention are equally well realized, in a wide variety of other applications, for example, the relative repositioning of multiple bone pieces and prosthetic devices. Further, while the invention has been described in detail in connection with the presently preferred embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions, or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.