Abstract:
The present invention relates to apparatus and methods for securing tissue to bone using a suture anchoring system that provides enhanced tactile feedback and does not require tying a suture knot. In each embodiment, a surgeon can individually tension the free ends of the suture to fine-tune the placement of the tissue with respect to the bone, and then secure the suture without tying a knot. In several embodiments of the present invention, the device may be transformed between locked and unlocked suture states, thereby allowing further fine-tuning of the tension in the suture.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to the field of surgical arthroscopy, and more particularly, to apparatus and methods for facilitating the attachment of tissue to bone using a suture anchoring system that provides enhanced tactile feedback and does not require tying a suture knot.  
       BACKGROUND OF THE INVENTION  
       [0002]     Many attempts have been made to provide devices that allow the arthroscopic securing of torn tissue to a substrate bone. For example, there have been numerous devices designed for the shoulder to allow a torn rotator cuff to be secured to the humeral head.  
         [0003]     Typically, in a first step, a hole is drilled into the bone under arthroscopic visualization. A length of a suture generally is employed to permit securing of the tissue to the bone. The suture length is threaded through a portion of the tissue, and also is coupled to a bone anchor configured to be inserted into the hole in the bone. One or both of the suture ends may extend outside of the arthroscopic site, so that the suture can be manipulated by a physician.  
         [0004]     Once the suture is coupled between the tissue and the bone anchor, the bone anchor is inserted into the hole. The bone anchor generally is configured to lock itself within the hole in the bone upon deployment therein. Several means for securing the bone anchor within the hole of a bone are known in the art.  
         [0005]     Once the bone anchor is secured within the hole in the bone, a physician may tension one or both ends of the suture to approximate the positioning of the tissue with respect to the bone. Once the tissue is positioned as desired, the suture is locked in place to maintain the tension in the suture. The free end or ends of the suture then are clipped under arthroscopic visualization to complete the procedure.  
         [0006]     There are various drawbacks associated with such previously-known suture anchoring systems. For example, many of the previously-known systems require the physician to tie a knot to lock the suture, thereby maintaining the tensile forces that hold the tissue in place. However, when performing the procedure under arthroscopic visualization and having minimal clearance, it is often difficult for the surgeon to perform the maneuvers necessary to tie a knot in the confined working space.  
         [0007]     Further, previously-known suture anchoring systems generally do not allow the surgeon direct tactile feedback of the tension in the suture between the tissue and the bone. For example, in those systems where only one free end of the suture may be manipulated by a physician, difficulties may arise in approximating the position of the tissue with respect to the bone. By contrast, when a physician can manipulate both ends of a suture independently, two different forces may be applied to the tissue to facilitate positioning of the tissue with respect to the bone.  
         [0008]     Still other previously-known suture anchoring systems have relied on urging tissue towards a bone anchor by tightening a knot. In such systems, the suture is threaded through tissue and a knot is tied proximal to the tissue. As the knot is tightened, the tissue is pushed towards the bone. However, such systems have various drawbacks, including not being able to manually determine the tension of the tissue, and also risking the possibility that the knot will become embedded within the tissue.  
         [0009]     An example of a previously-known method and apparatus for attaching tissue to bone using a knotless suture anchoring device is described in U.S. Pat. No. 6,585,730 to Foerster. Foerster describes a device having a distal anchor portion and a wedge body. A suture length has a bound end and a free end. The bound end of the suture is coupled to the tissue, and the suture extends around the wedge body at the distal end of the device, such that a free end of the suture may be manipulated by a physician.  
         [0010]     Once the distal anchor portion is secured within the bone, the practitioner pulls the free end of the suture to draw the soft tissue towards the bone. Tension in the suture draws the wedge body up into the lumen of the distal anchor portion. At this time, the length of suture wrapped around the wedge body becomes pinched between the wedge body and the distal anchor portion.  
         [0011]     The Foerster patent suggests that the pinching force imposed upon the suture creates a self-locking mechanism. Further, the patent suggests that applying a tensile force to the free suture end, after it has been clamped, will cause the wedge body to move distally to unlock the previously-pinched suture and enable “reversibility” of the device for further fine-tuning.  
         [0012]     The device described in the Foerster patent has several drawbacks. First, the device appears to rely on tension alone to secure the tissue to the bone. Specifically, merely tensioning the free end of the suture is expected to lock the device, since the suture is clamped between the wedge body and the distal anchor portion. Then, the Foerster patent suggests that simply pulling the free end of the suture will unlock the device, since the pinched suture wants to straighten out when the free end is tensioned. Therefore, the device is both locked and unlocked by tensioning the free end of the suture. Accordingly, it is possible that incidental tensile forces applied to the free suture end may unexpectedly unlock the device. In short, when tensioning the free end of the suture is the means for locking and unlocking the device, it may be difficult to lock the device in a desired position, or the device may come unlocked at an undesirable time.  
         [0013]     Another drawback of the device described in the Foerster patent is that one of the suture ends is “bound” to the tissue. It is expected that if a physician can tension both ends of the suture, it will facilitate positioning of the tissue with respect to the bone.  
         [0014]     Another previously-known knotless suture anchor is described in U.S. Pat. No. 6,692,516 to West et al. (“West”). The embodiment of  FIGS. 11-17  of the West patent describes a device having a shaft with a distal crown portion. The shaft is disposed through an outer member, such that the crown portion is disposed distal to the outer member.  
         [0015]     The shaft has an elongated opening through which the two free suture ends can be threaded. Therefore, in use, the suture is threaded through tissue to form a loop, and the two free ends of the suture are threaded through the elongated opening in the shaft, such that the free ends then can be manipulated by a physician.  
         [0016]     In operation, a physician approximates the positioning of the tissue with respect to the bone. A proximally-directed force then is applied to the shaft to cause the shaft to move proximally with respect to the outer member. This causes the suture, which is threaded through the opening in the shaft, to be pinched between the shaft and the outer member, thereby locking the suture in place. At the same time, the proximal retraction of the shaft with respect to the outer member causes radially expandable fingers on the crown portion to be deployed outward, thereby securing the device within the hole in the bone.  
         [0017]     The device described in the West patent does not appear to permit suture adjustments after the suture is locked in place. This is because the proximal retraction of the shaft with respect to the outer member both pinches the suture in place, and also deploys the expandable fingers to secure the device in the borehole. Therefore, it is not possible to adjust the suture further because it would be necessary to distally advance the shaft to do so, i.e., to remove the compressive force imposed upon the suture. However, the shaft cannot be advanced distally because the expandable members, secured within the bone, would prohibit such movement.  
         [0018]     In view of these drawbacks of previously known suture anchoring systems, it would be desirable to provide apparatus and methods for securing tissue to bone that are easy to use and do not require a large incision.  
         [0019]     It further would be desirable to provide apparatus and methods for securing tissue to bone that allow a surgeon direct tactile feedback of the tension in the suture between the tissue and the bone.  
         [0020]     It also would be desirable to provide apparatus and methods for securing tissue to bone that allow a surgeon to tension both ends of a suture individually to fine-tune the placement of the tissue with respect to the bone.  
         [0021]     It still further would be desirable to provide apparatus and methods for securing tissue to bone that allows a suture to be locked in place without tying a knot.  
       SUMMARY OF THE INVENTION  
       [0022]     In view of the foregoing, it is an object of the present invention to provide apparatus and methods for securing tissue to bone that are easy to use and do not require a large incision.  
         [0023]     It is also an object of the present invention to provide apparatus and methods for securing tissue to bone that allow a surgeon direct tactile feedback of the tension in the suture between the tissue and the bone.  
         [0024]     It is a further object of the present invention to provide apparatus and methods for securing tissue to bone that allow a surgeon to tension both ends of a suture individually to fine-tune the placement of the tissue with respect to the bone.  
         [0025]     It is still a further object of the present invention to provide apparatus and methods for securing tissue to bone that allow a suture to be locked in place without tying a knot.  
         [0026]     These and other objects of the present invention are accomplished by providing apparatus comprising a bone anchor member configured to be securely disposed in a hole drilled in a bone. A suture length may be coupled between the bone anchor member and tissue, or alternatively, between a plug portion that fits within a bore of the bone anchor member and the tissue. In each embodiment, a surgeon can individually tension each end of the suture to fine-tune the placement of the tissue with respect to the bone, and then secure the suture without tying a knot.  
         [0027]     In a first embodiment of the present invention, the apparatus comprises a bone anchor member comprising first and second passages that extend laterally through the bone anchor member. A suture is threaded through the first passage, then threaded through the tissue, and finally threaded back through the second passage, such that the first and second free ends of the suture can be manipulated by a physician. Alternatively, the suture can be threaded through the tissue first, such that the free ends extend from the tissue. The free ends then are threaded through the respective first and second passages of the bone anchor member.  
         [0028]     In this embodiment, the first and second passages each comprise a plurality of cleated members that are configured to permit one-way movement of the first and second suture ends, i.e., each suture end can be tensioned in a proximal direction. Accordingly, a physician can incrementally fine-tune the positioning of the tissue with respect to the bone by individually tensioning the suture ends. When a desired tension is achieved, as determined by tactile feedback, the suture ends are locked in place via the one-way cleated members.  
         [0029]     In an alternative embodiment of the present invention, the bone anchor member comprises a bore disposed therein. The bore is configured to receive a plug portion, which may have various configurations. In one embodiment, the plug portion may comprises first and second passages having a plurality of cleated members. The plurality of cleated members are configured to permit one-way movement of the first and second suture ends in their respective passages.  
         [0030]     The plug portion may be secured within the bone anchor bore using any number of means, as described hereinbelow. Either before or after the plug portion is secured within the bone anchor member, a physician may individually tension the first and second suture ends, which are disposed through the first and second one-way passages of the plug portion, to secure the tissue to the bone.  
         [0031]     In further alternative embodiments of the present invention, the suture may be transformed between locked and unlocked state, as desired. In one of these fully reversible embodiments, the bone anchor member and the plug portion each comprise first and second laterally extending passages. When the plug portion is disposed within the bore of the bone anchor member, the first passage of the plug portion can align with the first passage of the bone anchor member, and the second passage of the plug portion can align with the second passage of the bone anchor member.  
         [0032]     In this embodiment, a first suture end is threaded through the first passage of the plug portion and the first passage of the bone anchor member, while the second suture end is threaded through the second passage of the plug portion and the second passage of the bone anchor member. When the first and second passages of the plug portion are aligned with the first and second passages of the bone anchor member, respectively, then the first and second suture ends may be individually tensioned by a physician. When the passages of the plug portion and bone anchor member are misaligned, then the suture ends are pinched and locked in place.  
         [0033]     In further alternative embodiments, the plug portion may be rotated with respect to the bone anchor member. When the plug portion is rotated in a first direction, the plug portion pinches the suture to lock the suture in place. When the plug portion is rotated in an opposing direction, the suture ends are unlocked and may be manipulated by a physician.  
         [0034]     In still further alternative embodiments, the bone anchor member may comprise a flexible member disposed therein, and a laterally extending passage disposed distal to the flexible member. The first and second suture ends are configured to be threaded through the passage. When a physician desires to lock the suture in place, a distally-directed force is applied to the flexible member, via the bore, to cause the flexible member to pinch the suture ends and lock the suture in place. If a physician wishes to further adjust the suture ends, then the distally-applied force is removed, thereby allowing movement of the suture.  
         [0035]     Alternatively, a threaded cap may be disposed within the bore of the bone anchor member, and configured for movement within a grooved inner portion of the bore. A passage through which the first and second suture ends passes is situated distal to the threaded cap. If a physician wishes to lock the suture in place, then the threaded cap is advanced distally within the bore, e.g., by rotating the cap in a first direction, to cause the cap to pinch the suture. If a physician wishes to unlock the suture, then the threaded cap is rotated in an opposing direction so that it is retracted proximally within the bore.  
         [0036]     Several further embodiments of the present invention also are disclosed in detail hereinbelow. Each embodiment permits the incremental tensioning of first and second suture ends and locking of the suture without tying a knot.  
         [0037]     Methods for using the apparatus of the present invention to facilitate the attachment of tissue to bone also are disclosed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0038]     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments, in which:  
         [0039]      FIG. 1  is a schematic of a bone and tissue interface;  
         [0040]      FIG. 2A-2C  are, respectively, a side view, a front view, and a side-sectional view along line A-A of  FIG. 2B  showing a first embodiment of the present invention;  
         [0041]      FIGS. 3A-3C  are, respectively, a side-sectional view of an alternative embodiment of the present invention having a bone anchor member and a plug portion, a side view of the plug portion of  FIG. 3A , and an opposing side view of the plug portion;  
         [0042]      FIGS. 4A-4C  are, respectively, a side-sectional view of a further alternative embodiment of the present invention having a bone anchor member and a plug portion, a side view of the plug portion of  FIG. 4A , and an opposing side view of the plug portion;  
         [0043]      FIG. 5  is a side sectional view of an alternative embodiment of the present invention having at least one adhesive delivery channel;  
         [0044]      FIGS. 6A-6B  are, respectively, a side-sectional view of a further alternative embodiment of the present invention, and the device of  FIG. 6A  shown deployed in a hole of a bone;  
         [0045]      FIG. 7  is a side sectional view of a further alternative embodiment of the present invention;  
         [0046]      FIG. 8  is a side view of an alternative embodiment of the present invention, which is configured for use with a through hole drilled in a bone;  
         [0047]      FIGS. 9A-9C  are side sectional views illustrating the use of an alternative embodiment of the present invention;  
         [0048]      FIG. 10  is an alternative embodiment of the bone anchor member described in  FIGS. 9A-9C ;  
         [0049]      FIGS. 11A-11C  are, respectively, a top view of an alternative embodiment of the present invention in an unlocked state, a side sectional view of the device along line B-B of  FIG. 11A , and a top view of the device of  FIG. 11A  in a locked state;  
         [0050]      FIG. 12  illustrates use of a suture in connection with the embodiment described in  FIGS. 11A-11C ;  
         [0051]      FIGS. 13A-13B  are side sectional views of an alternative embodiment of the present invention in unlocked and locked states, respectively;  
         [0052]      FIGS. 14A-14B  are side sectional views of a further alternative embodiment of the present invention in unlocked and locked states, respectively;  
         [0053]      FIGS. 15A-15B  are side sectional views of yet a further alternative embodiment of the present invention in unlocked and locked states, respectively;  
         [0054]      FIGS. 16A-16B  are, respectively, a top sectional view and a side view of an alternative embodiment of the present invention in an unlocked state;  
         [0055]      FIGS. 17A-17B  are, respectively, a top sectional view and a side view of the embodiment of  FIGS. 16A-16B  in a locked state;  
         [0056]      FIGS. 18A-18B  are side sectional views of a further alternative embodiment of the present invention; and  
         [0057]      FIGS. 19A-19C  are, respectively, a side sectional view, a side view, and a bottom view of an alternative embodiment of the plug portion of  FIGS. 18A-18B . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0058]     Referring now to  FIG. 1 , a schematic of a bone and tissue interface is shown primarily for illustrative purposes. In  FIG. 1 , tissue T has a torn end and it is desirable to secure the torn end to a section of bone B. In a first step, hole H having diameter d H  is drilled in bone B, as depicted, using techniques that are well known in the art.  
         [0059]     Bone anchor member  20 , which will be described in greater detail in  FIGS. 2A-2C  hereinbelow, is shown as a means for securing tissue T to bone B. Bone anchor member  20  is configured to be used in conjunction with a suture length  30 . Suture  30  has first and second ends  32   a  and  32   b,  which are coupled to bone anchor member  20 , as described in  FIGS. 2A-2C  hereinbelow. It should be noted that a central region of suture  30  forms loop  34 , which is threaded through a section of tissue T near the torn end of the tissue, as depicted in  FIG. 1 , using techniques that are known in the art.  
         [0060]     Referring now to  FIGS. 2A-2C , features of bone anchor member  20  are described in greater detail. Bone anchor member  20  has proximal region  22  and distal region  24 , as depicted in  FIG. 2A . The apparatus further comprises means for securing bone anchor member  20  within hole H of bone B (see  FIG. 1 ). As depicted, the means for securing bone anchor member  20  comprises plurality of cleated members  42 , which preferably are formed on or attached to an exterior surface of bone anchor member  20 . Alternatively, other means for securing bone anchor member  20  within hole H may be used, such as radially expandable members (not shown) that dig into surrounding bone B, or threaded exterior members that screw into surrounding bone.  
         [0061]     Referring now to  FIGS. 2B-2C , bone anchor member  20  preferably further comprises first and second guide channels  50  and  52 , respectively, which preferably are formed within opposing surfaces of bone anchor member  20 . First and second guide channels  50  and  52  are configured to accommodate regions of suture  30 , so that the suture regions do not extend outside of the confines of the guide channels when in use.  
         [0062]     Bone anchor member  20  further comprises first and second passages  60  and  70 . First and second passages  60  and  70  extend laterally through a main body of bone anchor member  20 , as depicted in  FIG. 2C . First passage  60  communicates with first guide channel  50  via opening  61 , and further communicates with second guide channel  52  via opening  62 . Similarly, passage  70  communicates with first guide channel  50  via opening  71 , and further communicates with second guide channel  52  via opening  72 .  
         [0063]     In the embodiment of  FIGS. 2A-2C , first passage  60  is shown disposed proximal to second passage  70 , i.e., the first passage is closer to proximal region  22  of bone anchor member  20 . However, as will be apparent to one skilled in the art, the passages also may be disposed adjacent one another, or otherwise positioned, to achieve the objects of the present invention.  
         [0064]     First passage  60  and second passage  70  each comprise at least one cleated member  74 . Each cleated member comprises angled sections  75  and substantially orthogonal sections  76 , which are disposed adjacent one another, thereby forming a cleated shape, as shown in  FIG. 2C .  
         [0065]     The cleated members are configured such that angled sections  75  are angled towards openings  62  and  72  of passages  60  and  70 , respectively, as shown in  FIG. 2C . In accordance with one aspect of the present invention, cleated passages  60  and  70  are configured to permit oneway movement of first and second suture ends  32   a  and  32   b,  respectively. For example, when first end  32   a  is pulled in a proximal direction by a physician, angled sections  75  permit movement of the suture end in the proximal direction. However, a physician cannot distally advance suture end  32   a  within passage  60 .  
         [0066]     In a preferred embodiment, suture  30  has an outer diameter that is slightly larger than an inner diameter of cleated passages  60  and  70 . Therefore, first and second suture ends  32   a  and  32   b  can pass through cleated passages  60  and  70  in a proximal direction with relatively little resistance. However, the suture will hold significantly greater force in the distal direction.  
         [0067]     In a preferred method, a central region of suture  30  can be looped through tissue T first, such that free ends  32   a  and  32   b  extend from the tissue. Free end  32   a  then is threaded through one-way cleated passage  60  in a proximal direction, while free end  32   b  is threaded through one-way cleated passage  70 , also in a proximal direction.  
         [0068]     As will be apparent to one skilled in the art, suture  30  may be coupled between tissue T and bone anchor member  20  using other threading techniques, so long as the suture ultimately is situated in a manner depicted in  FIG. 2C .  
         [0069]     At this time, first end  32   a  of suture  30  is disposed through first passage  60 , then transitions into loop portion  34   a.  Loop portion  34   a  transitions into loop portion  34   b,  forming loop  34  therebetween, which is coupled to tissue T (see  FIG. 1 ). Loop portion  34   b  transitions into second end  32   b,  which is disposed through passage  70 , as shown in  FIG. 2C . Accordingly, first and second ends  32   a  and  32   b  of suture  30  may be independently manipulated by a physician for purposes described hereinbelow.  
         [0070]     In operation, after suture  30  is coupled to bone anchor member  20  and tissue T as described hereinabove, bone anchor member  20  is distally advanced into hole H of bone B under arthroscopic guidance. Cleated members  42  of bone anchor member  20  allow the bone anchor member to be advanced distally within hole H when an appropriate force is applied, but cleated members  42  inhibit proximal movement of bone anchor member  20  to provide a secure anchor within hole H.  
         [0071]     At this time, the surgeon can approximate the positioning of tissue T with respect to bone B (see  FIG. 1 ) by pulling first end  32   a  and/or second end  32   b  proximally through cleated passages  60  and  70 . Advantageously, the use of two separate passages allows the surgeon to tension each end of the suture independently, which is often desirable when tissue is torn irregularly.  
         [0072]     Further, the use of a plurality of cleated passages  60  and  70  permits incremental tensioning of first and second suture ends  32   a  and  32   b.  This allows a physician to incrementally adjust the positioning of the tissue, using tactile feedback as a guide. Once a desired tension is achieved, the physician simply needs to stop retracting the suture ends, and the suture is automatically locked in place. Advantageously, there is no need to tie a knot.  
         [0073]     In accordance with another object of the present invention, guide channels  50  and  52  permit the retraction of first and second suture ends  32   a  and  32   b  when bone anchor member  20  is secured within hole H by providing a clearance between the bone anchor member and the bone itself.  
         [0074]     Referring now to  FIGS. 3A-3C , an alternative embodiment of the present invention is described. In  FIG. 3A , apparatus  100  comprises bone anchor member  102  and plug portion  110 . Bone anchor member  102  comprises main body  103  having bore  104  disposed therein, as depicted in  FIG. 3A . Further, main body  103  of bone anchor member  102  comprises exterior cleated members  106 , which are similar to cleated members  42  of bone anchor member  20 . Cleated members  106  are configured to be inserted into hole H of bone B (see  FIG. 1 ) using a frictional force fit.  
         [0075]     In operation, once bone anchor member  102  is secured in hole H, then plug portion  110  may be inserted into bore  104  of bone anchor member  102 . Cleated members  116  of plug portion  110  are configured to permit distal advancement of the plug portion into bore  104 , with some friction provided between cleated members  116  and inner wall  105 . However, cleated members  116  ensure that plug portion  110  cannot be retracted proximally after advancement into bore  104 , thereby securing the plug portion to the bone anchor member.  
         [0076]     Referring now to  FIGS. 3B-3C , further features of plug portion  110  are described. Plug portion  110  comprises first and second passages  118  and  120 . First and second suture ends  32   a  and  32   b  preferably are coupled to plug portion  110  of apparatus  100  in a manner similar to that described in  FIG. 2C  hereinabove. Specifically, in the embodiment of  FIGS. 3A-3C , first end  32   a  of suture  30  is disposed through first passage  118 . After exiting through first passage  118 , first end  32   a  then transitions into loop portion  34   a,  forms loop  34 , and transitions into loop portion  34   b  (see  FIGS. 2A-2C ). Loop portion  34   b  transitions into second end  32   b,  which extends through second passage  120  of  FIGS. 3A-3C .  
         [0077]     If desired, passages  118  and  120  of  FIGS. 3A-3C  may comprise cleated members  74 , as described hereinabove with respect to  FIG. 2C . If cleated members  74  are employed, then tissue T may be secured to bone B by individually tensioning first and second ends  32   a  and  32   b  of suture  30 , as described hereinabove with respect to  FIG. 2C .  
         [0078]     Plug portion  110  preferably comprises one or more guide channels  125  disposed in a lateral surface of plug body  113 . Guide channel  125  preferably is substantially similar to guide channels  50  and  52  of  FIG. 2C . In  FIG. 3C , guide channel  125  is configured to permit retraction of first and second suture ends  32   a  and  32   b  when plug portion  110  is secured within bore  104  by providing a clearance between the plug portion and the bone anchor member.  
         [0079]     Alternatively, in the embodiment of  FIGS. 3A-3C , passages  118  and  120  may be substantially smooth passages, such that cleated members  74  are not employed. In this case, passages  118  and  120  permit substantially unimpeded movement of suture  30  through the passages. In operation, a physician may individually tension suture ends  32   a  and  32   b  prior to insertion of plug portion  110  into bone anchor member  102 . When a physician deems that tissue T is appropriately secured to bone B, then plug portion  110  is forced into bore  104  of bone anchor member  102 . This causes suture ends  32   a  and  32   b  to be sandwiched between plug portion  110  and bone anchor member  102  when guide channels  125  are not present. Accordingly, the suture is secured between the two portions using a force fit.  
         [0080]     Referring now to  FIGS. 4A-4C , an alternative embodiment of the present invention is described. In  FIG. 4A , apparatus  140  comprises bone anchor member  142  and plug portion  150 . Bone anchor member  142  comprises main body  143  having bore  144  disposed therein, as depicted in  FIG. 4A . Further, main body  143  of bone anchor member  142  comprises exterior cleated members  146  and interior cleated members  145 . Exterior cleated members  146  are configured to be inserted into hole H of bone B (see  FIG. 1 ) using a force fit, as described hereinabove.  
         [0081]     Plug portion  150  comprises main body  153 , which preferably has a substantially cylindrical shape and smooth exterior surface  156 . Taper  157  preferably is disposed at a distal region of main body  153 , as shown in  FIG. 4A .  
         [0082]     Suture  30  having first and second ends  32   a  and  32   b  is coupled to plug portion  150  of apparatus  140 , preferably in a manner described hereinabove with respect to  FIGS. 2-3 . More specifically, suture  30  passes through first and second passages  158  and  160  of plug portion  150  in a manner described hereinabove, e.g., with respect to  FIG. 2C .  
         [0083]     In operation, bone anchor member  142  is advanced into hole H (see  FIG. 1 ). Exterior cleated members  146  of bone anchor member  142  permit one-way movement of the bone anchor member into the hole.  
         [0084]     In a next step, plug portion  150  then is inserted into bore  144  of bone anchor member  142 . Exterior surface  156  of plug portion  150  preferably has an outer diameter that is slightly larger than an inner diameter of bore  144 . Accordingly, when plug portion  150  is urged distally, a force fit is achieved to secure plug portion  150  within the bore of bone anchor member  142 .  
         [0085]     Taper  157  of plug portion  150  facilitates the distal advancement of the plug portion with respect to bone anchor member  142 . Further, interior cleated members  145  are configured to permit advancement of plug portion  110  into bore  144  in a distal direction only.  
         [0086]     First and second suture ends  32   a  and  32   b  may be coupled to plug portion  150  in a manner described hereinabove with respect to  FIGS. 3A-3C . Specifically, in the embodiment of  FIGS. 4A-4C , first end  32   a  of suture  30  is disposed through first passage  158 , then forms a loop that is threaded through tissue T, and second end  32   b  of suture  30  then extends through second passage  160 .  
         [0087]     First and second passages  158  and  160  of  FIGS. 4A-4C  may comprise cleated members  74  of  FIG. 2C . If cleated members  74  are employed, then tissue T may be secured to bone B by individually tensioning first and second ends  32   a  and  32   b  of suture  30 . Cleated members  74  permit incremental tensioning of each suture end, and serve to lock the suture ends within their respective passages  158  and  160 , as generally set forth hereinabove with respect to  FIG. 2C .  
         [0088]     Plug portion  150  preferably comprises one or more guide channels  165  disposed in a lateral surface of plug body  153 , as shown in  FIG. 4C . Guide channel  165  preferably is substantially similar to guide channel  50  of  FIG. 2C , and is configured to permit retraction of first and second suture ends  32   a  and  32   b  when plug portion  150  is secured within bore  144 .  
         [0089]     Alternatively, in the embodiment of  FIGS. 4A-4C , passages  158  and  160  may be substantially smooth passages, such that cleated members  74  are not employed and guide channels  165  are not present. In this case, a physician may individually tension suture ends  32   a  and  32   b  prior to insertion of plug portion  150  into bone anchor member  142 . When a physician deems that tissue T is appropriately secured to bone B, then plug portion  150  is forced into bore  144  of bone anchor member  142 . This causes suture ends  32   a  and  32   b  to be sandwiched between plug portion  150  and bone anchor member  142 . Accordingly, the suture is secured between the two portions using a force fit.  
         [0090]     Referring now to  FIG. 5 , a further alternative embodiment of the present invention is described. In  FIG. 5 , bone anchor member  180  is similar to bone anchor member  20  of  FIGS. 2A-2C , except as noted hereinbelow. Cleated members  182  of bone anchor member  180  preferably are similar to cleated members  42  of bone anchor member  20 , as described hereinabove, and facilitate anchoring of bone anchor member  180  within hole H. Further, guide channels  190  and  192  preferably are similar to guide channels  50  and  52  of  FIGS. 2A-2C .  
         [0091]     Unlike the embodiments described hereinabove, bone anchor member  180  comprises at least one adhesive delivery channel  188 , which is provided within main body  181  as shown in  FIG. 5 . Adhesive delivery channel  188  may be formed by drilling a hole into an upper surface of main body  181 , such that the hole extends through first passage  184  and second passage  186 . As will be apparent to one skilled in the art, however, channel  188  may be formed using other known techniques.  
         [0092]     In the embodiment of  FIG. 5 , first and second passages  184  and  186  may comprise cleated members  74  of  FIG. 2C , thereby permitting one-way movement of suture ends  32   a  and  32   b  through the passages. Alternatively, in the embodiment of  FIG. 5 , passages  184  and  186  may comprise substantially smooth inner surfaces that permit movement of suture  30  through the passages in either direction.  
         [0093]     After bone anchor member  180  is secured in hole H of bone B, a physician may approximate the positioning of tissue T with respect to bone B by individually tensioning first and second ends  32   a  and  32   b  of suture  30 , as described hereinabove. When the suture ends are tensioned as desired, an adhesive is delivered to adhesive delivery channel  188 , preferably using a needle-like tube (not shown) disposed within a working cannula (not shown). The needle-like tube preferably has a distal opening that may be placed in close proximity to, or within, adhesive delivery channel  188  to deliver an adhesive thereto.  
         [0094]     The adhesive flows distally through adhesive delivery channel  188  and into portions of first and second passages  184  and  186 . The adhesive contacts portions of suture  30  that extend through corresponding regions of first and second passages  184  and  186 , thereby locking the suture in place. As will be apparent to one skilled in the art, although one adhesive delivery channel  188  is depicted in  FIG. 5 , multiple adhesive delivery channels may be employed to secure the suture, irrespective of whether cleated members  74  are employed.  
         [0095]     Referring now to  FIGS. 6A-6B , yet another alternative embodiment of the present invention is described. In  FIG. 6A , apparatus  200  comprises bone anchor member  202  and plug portion  210 . Apparatus  200  is similar to apparatus  140  of  FIGS. 4A-4C , except as noted below.  
         [0096]     Bone anchor member  202  comprises main body  203  having bore  204  disposed therein, as depicted in  FIG. 6A . Further, main body  203  of bone anchor member  202  comprises exterior cleated members  206 , which are configured to be inserted into hole H of bone B (see  FIG. 1 ) using a force fit, as described hereinabove.  
         [0097]     Plug portion  210  preferably comprises a substantially cylindrical shape and comprises main body  213  having substantially smooth exterior surface  216 . Further, taper  217  preferably is disposed at a distal region of main body  213 , as shown in  FIG. 6A .  
         [0098]     Suture  30  having first and second ends  32   a  and  32   b  is coupled to plug portion  210 , preferably in a manner described hereinabove with respect to  FIGS. 2-4 . More preferably, suture  30  passes through first and second passages  218  and  219  of plug portion  210  in a manner described hereinabove with respect to  FIG. 2C .  
         [0099]     Main body  213  of plug portion  210  has an outer diameter that is slightly larger than an inner diameter of bore  204 . The diameters are selected such that main body  213  of plug portion  210  may be distally advanced into bore  204  when forced distally. Taper  207  of bone anchor member  202  is configured to facilitate advancement of plug portion  210  into bore  204 .  
         [0100]     In operation, bone anchor member  202  is secured within hole H when the bone anchor member is distally advanced into the hole, as depicted in  FIG. 6B . Exterior cleated members  206  of bone anchor member  202  permit oneway movement of the bone anchor member into hole H.  
         [0101]     In a next step, plug portion  210  is advanced distally into bore  204  of bone anchor member  202  and secured therein using a force fit, as described hereinabove. At this time, surrounding regions of bone B will apply a compressive force upon bone anchor member  202 , as indicated by the larger directional arrows in  FIG. 6B . This compressive force upon bone anchor member  202  in turn causes compression upon plug portion  210 , as indicated by the smaller directional arrows in  FIG. 6B , thereby securely retaining the plug portion within bore  204 .  
         [0102]     In the embodiment of  FIGS. 6A-6B , passages  218  and  219  may comprises cleated members  74  as described hereinabove with respect to  FIG. 2C , as a means for locking suture  30 . Alternatively, passages  218  and  219  may comprise substantially smooth interior surfaces that permit advancement of suture  30  in either direction.  
         [0103]     In either embodiment, it may be desirable to approximate the positioning of tissue T (not shown in  FIG. 6B ) to bone B by individually tensioning suture ends  32   a  and  32   b  prior to insertion of plug portion  210  into bone anchor member  202 . In a preferred embodiment of the method, the tissue position is approximated when passage  219  is disposed just above bore  204 . Once the desired positioning of the tissue is achieved, plug portion  210  is advanced distally into bore  204 , thereby locking the suture. Specifically, the suture will be sandwiched between exterior surface  216  of plug portion  210  and inner wall  205  of bone anchor member  202 .  
         [0104]     Referring now to  FIG. 7 , a further alternative embodiment of the present invention is described. In  FIG. 7 , apparatus  220  comprises bone anchor member  222  and plug portion  230 . Apparatus  220  is similar to apparatus  200  of  FIGS. 6A-6B , except as noted below.  
         [0105]     Bone anchor member  222  comprises main body  223  having bore  224  disposed therein, as depicted in  FIG. 7 . Further, main body  223  comprises exterior cleated members  226 , which are configured to be inserted into hole H of bone B (see  FIG. 1 ) using a force fit, as described hereinabove. Unlike previous embodiments, bone anchor member  222  comprises a proximal protrusion having inward taper  227 . Proximal stop  228  is formed between inward taper  227  and inner wall  225  of bone anchor member  222 , as shown in  FIG. 7 .  
         [0106]     Plug portion  230  preferably comprises main body  233  having proximal region  235 , central region  234  and tapered distal region  237 . Tapered distal region  237  is sized to pass through taper  227  of bone anchor member  222  when a distally-directed force is applied to plug portion  230 . When further force is applied, central region  234  of plug portion  230  is advanced into bore  224  via taper  227 . Finally, when yet further force is applied to plug portion  230 , proximal region  235  will be advanced past taper  227 . Once proximal region  235  is fully inserted into bore  224 , proximal stop  228  is configured to abut proximal edge  236  of plug portion  230 , thereby securing the plug portion within bone anchor member  222 .  
         [0107]     As will be apparent to one skilled in the art, apparatus  220  of  FIG. 7  may comprise any other features described hereinabove with respect to the embodiments of  FIGS. 2-6 . For example, passages  238  and  239  may comprise cleated members  74  of  FIG. 2C , or alternatively may comprise substantially smooth interior surfaces. Further, the operation of apparatus  220  preferably is substantially similar to the methods described hereinabove with respect to the embodiments of  FIGS. 2-6 .  
         [0108]     Referring now to  FIG. 8 , a further alternative embodiment of the present invention is described. In  FIG. 8 , bone anchor  240  is similar to bone anchor member  20  of  FIGS. 1-2 , but is configured for use in applications where through hole H T  is employed. For example, bone B may be a thin bone, such that it is possible to arthroscopically operate from both sides of the bone.  
         [0109]     Bone anchor  240  comprises main body  242  having proximal and distal ends, flange  245  disposed at the proximal end and taper  246  formed at the distal end. Main body  242  further comprises exterior surface  243  disposed between flange  245  and taper  246 , as shown in  FIG. 8 .  
         [0110]     Bone anchor  240  further comprises first and second passages  250  and  252 , each having a plurality of cleated members  254 , as shown in  FIG. 8 . Each of the cleated members comprises angled sections  255  and substantially orthogonal sections  256 , which are disposed adjacent one another thereby forming a cleated shape, as described hereinabove with respect to cleated members  74  of  FIG. 2C .  
         [0111]     In operation, a central region of suture  30  can be looped through tissue T first, such that free ends  32   a  and  32   b  extend from the tissue. Free end  32   a  then is threaded through first passage  250  in a proximal direction, while free end  32   b  is threaded through second passage  252 , also in a proximal direction. The suture may be threaded through passages  250  and  252  and tissue T by arthroscopically operating on one or both sides of bone B.  
         [0112]     As will be apparent to one skilled in the art, suture  30  may be coupled between tissue T and bone anchor  240  using other arthroscopic threading techniques, so long as the suture ultimately is situated in a manner depicted in  FIG. 8 .  
         [0113]     Once the suture is threaded as shown in  FIG. 8 , a physician may proximally retract first and second suture ends  32   a  and  32   b,  one at a time, to approximate the positioning of tissue T with respect to bone B. As the suture ends are tensioned, flange  245 , which has an outer diameter larger than the diameter of through hole H T , abuts bone B. The system becomes tensioned because flange  245  and tissue T are drawn against the bone from opposing directions.  
         [0114]     In accordance with one aspect of the present invention, cleated passages  250  and  252  are configured to permit one-way movement of first and second suture ends  32   a  and  32   b,  respectively. For example, when first end  32   a  is pulled in a proximal direction by a physician, angled sections  255  permit movement of that particular suture end in the proximal direction. However, a physician cannot distally advance suture end  32   a  within passage  250 . Advantageously, the use of two separate passages allows the surgeon to tension each end of the suture separately, which is often desirable when tissue T is torn irregularly.  
         [0115]     As will be apparent to one skilled in the art, the methods described in  FIG. 8  may be accomplished using a separate bone anchor member and plug portion. For example, the principles of the embodiments in  FIGS. 3-4  and  6 - 7 , in which separate bone anchor and plug portions are employed, may be implemented in lieu of one-piece bone anchor  240 .  
         [0116]     Further, the suture securing methods described in  FIG. 8  may be accomplished using substantially smooth passages  250  and  252 . Where substantially smooth passages are employed, an interference fit or adhesive may be employed in lieu of the cleated passages to facilitate securing of the suture. The interference fit or adhesive may be used, for example, as described hereinabove with respect to the embodiments of  FIGS. 3-7 .  
         [0117]     Referring now to  FIGS. 9A-9C , still a further alternative embodiment of the present invention is described. In  FIG. 9A , apparatus  270  comprises bone anchor member  272  and plug portion  280 .  
         [0118]     Bone anchor member  272  comprises main body  273  having bore  274  disposed therein, as depicted in  FIG. 9A . Further, main body  273  comprises exterior cleated members  276 , which are configured to be inserted into hole H of bone B (see  FIG. 1 ) using a force fit, as described hereinabove. Like the embodiment of  FIG. 7 , bone anchor member  272  comprises a proximal protrusion having inward taper  277 . Proximal stop  278  is formed between inward taper  277  and an inner wall of bone anchor member  272 , as shown in  FIG. 9A .  
         [0119]     Bone anchor member  272  further comprises first and second spring elements  292   a  and  292   b,  which are disposed at a distal region of bore  274 . First and second spring members  292   a  and  292   b  may be integrally formed with bone anchor body  273 , as depicted in  FIG. 9A , or may be separate elements coupled to body  273 . As will be described in further detail hereinbelow, first and second spring elements  292   a  and  292   b  may be deformed to accommodate plug portion  280  within bore  274 , and also to enable locking and unlocking of a suture (not shown in  FIGS. 9A-9C ) used in conjunction with apparatus  270 . As will be apparent to one skilled in the art, one or more spring elements may be employed.  
         [0120]     First and second passages  298  and  299  extend laterally through main body  273  of bone anchor member  272 , as depicted in  FIG. 9A . First and second passages  298  and  299  are configured to be selectively aligned with first and second passages  288  and  289  of plug portion  280 , for the purposes described hereinafter.  
         [0121]     Referring still to  FIG. 9A , plug portion  280  of apparatus  270  preferably comprises main body  283  having proximal and distal ends. The proximal end comprises flange  284 . Taper  286  is disposed between flange  284  and main body  283 , as shown in  FIG. 9A . Further, distal taper  287  is disposed at the distal end of plug portion  280 .  
         [0122]     Plug portion  280  further comprises first and second passages  288  and  289 , which extend laterally through main body  283 , as shown in  FIG. 9A . In the embodiment of  FIGS. 9A-9C , first and second passages  288  and  289  preferably comprise a substantially smooth interior surfaces.  
         [0123]     Referring now to  FIG. 9B , in a first step, plug portion  280  is inserted into bore  274  of bone anchor member  272 , preferably using insertion tool  294 . Specifically, when an appropriate force is applied to plug portion  280 , tapered distal end  287  is configured to pass through taper  277  of bone anchor member  272 . When further force is applied, a central region of plug portion  280  is advanced into bore  274  via taper  277 . Finally, when yet further force is applied to plug portion  280 , the proximal region having taper  286  and flange  284  will be advanced past taper  277 .  
         [0124]     When plug portion  280  is fully inserted into bore  274 , first and second spring elements  292   a  and  292   b  will be inclined to urge plug portion  280  in a proximal direction, such that flange  284  will abut proximal stop  278  (see  FIG. 9C ). However, when a sufficient distally-directed force is applied to plug portion  280 , e.g., using insertion tool  294 , first and second spring elements may be deformed distally, as shown in  FIG. 9B .  
         [0125]     Insertion tool  294  may be a rod or other substantially rigid member configured to transfer a distally-directed force from a physician to plug portion  290 . In a preferred embodiment, insertion tool  294  is configured to engage mating slot  295 , as shown in  FIG. 9B .  
         [0126]     The provision of a distally-directed force acting on plug portion  280  causes first and second passages  288  and  289  to become substantially aligned with first and second passages  298  and  299  of bone anchor member  27 , respectively, as shown in  FIG. 9B . At this time, suture  30  is threaded through aligned first passages  288  and  298 . The suture then is threaded through tissue T, as described hereinabove, and then threaded back through aligned second passages  289  and  299 . In effect, first suture end  32   a  extends through first passages  288  and  298 , while second suture end  32   b  extends through second passages  289  and  299 .  
         [0127]     Once the suture is coupled to apparatus  270  in this manner, apparatus  270  is inserted into hole H of bone B under arthroscopic guidance. Cleated members  276  secure apparatus  270  within hole H, as described hereinabove. At this time, first and second suture ends  32   a  and  32   b  will extend outside of the arthroscopic site for manipulation by a physician.  
         [0128]     A physician may selectively tension first and second suture ends  32   a  and  32   b  to approximate the positioning of tissue T with respect to bone B when first and second passages  288  and  289  are aligned with first and second passages  298  and  299 , respectively. During tensioning of the suture ends, insertion tool  294  urges plug portion distally to cause the passages to align, as shown in  FIG. 9B .  
         [0129]     When a desired positioning of tissue T is achieved, the force applied to plug portion  280  is removed, e.g., by proximally retracting insertion tool  294 , as shown in  FIG. 9C . At this time, first and second spring elements  292   a  and  292   b  are inclined to bias proximally, thereby urging flange  284  of plug portion  280  against proximal stop  278  of bone anchor member  272 . This movement of plug portion  280  with respect to bone anchor member  272  causes a misalignment between first passage  288  of plug portion  280  and first passage  298  of bone anchor member  272 . Also, a misalignment occurs between second passages  289  and  299 . Accordingly, the misalignments cause first suture end  32   a  to become pinched between first passages  288  and  298 , while second suture end  32   b  is pinched between second passages  289  and  299 . These misalignments lock the suture in place.  
         [0130]     If it becomes necessary to adjust the positioning of tissue T with respect to bone B during the procedure, then insertion tool  294  may be inserted into mating slot  295 , as shown in  FIG. 9B , to urge plug portion  280  distally. As described hereinabove, when first and second passages of plug portion  280  and bone anchor member  272  are aligned (see  FIG. 9B ), a physician may manipulate suture ends  32   a  and  32   b  to adjust the positioning of tissue T.  
         [0131]     Referring now to  FIG. 10 , an alternative embodiment of the invention of  FIGS. 9A-9C  is described. In  FIG. 10 , alternative bone anchor member  272 ′ comprises spring element  292 ′ disposed at a distal end of main body  273 . Spring element  292 ′ comprises a distally concave configuration having a central region  293 , as shown in  FIG. 10 .  
         [0132]     Alternative bone anchor member  272 ′ is used in conjunction with plug portion  280  in a manner similar to that described hereinabove with respect to  FIGS. 9A-9C . Specifically, after plug portion  280  is inserted into bore  274 , the provision of a further distally-directed force acting on plug portion  280  will cause central region  293  of spring element  292 ′ to be deformed in a distal direction. When the central region of spring element  292 ′ is deformed distally, first and second passages  288  and  289  of plug portion  280  are substantially aligned with first and second passages  298  and  299  of bone anchor member  272 ′, respectively. In this state, first suture end  32   a  may move substantially unimpeded through aligned first passages  288  and  298 , while second suture end  32   b  may move through aligned second passages  289  and  299 , respectively, as described hereinabove with respect to  FIG. 9B .  
         [0133]     When a desired positioning of tissue T is achieved, the force imposed upon plug portion  280  is removed, e.g., by proximally retracting insertion tool  294 , as described in  FIG. 9C . At this time, central region  293  of spring elements  292 ′ will return in a proximal direction to its preferred orientation. This causes flange  284  of plug portion  280  to be urged against proximal stop  278  of bone anchor member  272 ′. As described hereinabove, the movement of plug portion  280  with respect to bone anchor member  272 ′ causes a misalignment between first passages  288  and  298 , and also a misalignment between second passages  289  and  299 . These misalignments pinch suture ends  32   a  and  32   b  to lock the suture in place.  
         [0134]     Referring now to  FIGS. 11-12 , a further alternative embodiment of the present invention is described. Apparatus  300  comprises bone anchor member  302  and plug portion  310 , as shown in  FIGS. 11A-11B . Bone anchor member  302  is similar to the bone anchor members described hereinabove and comprises main body  303  having plurality of cleated members  306 , which are configured to anchor plug portion  302  within hole H of bone B (see  FIG. 1 ). Bone anchor member  302  further comprises central bore  304 , which is configured to receive plug portion  310 , as described hereinbelow.  
         [0135]     Plug portion  310  of apparatus  300  comprises main body  311  having distal region  318  and central bore  312 , as shown in  FIG. 11B . Main body  311  has an outer diameter that is slightly smaller than an inner diameter of bore  304 . Accordingly, plug portion  310  is configured for circumferential rotation within bore  304  of bone anchor member  302 , as described hereinbelow.  
         [0136]     Bone anchor member  302  further comprises first and second semi-circular channels  305   a  and  305   b,  which preferably are formed at diametrically opposing surfaces of main body  303 , as shown in  FIGS. 11A-11B . Further, plug portion  310  comprises first and second semi-circular channels  315   a  and  315   b,  which preferably are formed at diametrically opposing surfaces on main body  311 , as shown in  FIGS. 11A-11B .  
         [0137]     Apparatus  300  also comprises actuation knob  321 , which is disposed on an outer surface of plug portion  310 , as shown in  FIG. 11A . Actuation knob  321  is configured to be disposed within first recess  322  of bone anchor member  302  in an unlocked state, and disposed within second recess  323  in a locked state, as described in further detail hereinbelow.  
         [0138]     When actuation knob  321  is disposed within first recess  322 , first and second semi-circular channels  305   a  and  305   b  of bone anchor member  302  are aligned with first and second semi-circular channels  315   a  and  315   b  of plug portion  310 , respectively, thereby forming first and second circular channels, as shown in  FIGS. 11A-11B .  
         [0139]     When actuation knob  321  is disposed within second recess  323 , first and second semi-circular channels  305   a  and  305   b  of bone anchor member  302  are not aligned with corresponding channels  315   a  and  315   b  of plug portion  310 , as shown in  FIG. 11C .  
         [0140]     In operation, suture  30  preferably is coupled to apparatus  300  in a manner shown in  FIG. 12 . Specifically, first suture end  32   a  extends through central bore  312  of plug portion  310 . First suture end  32   a  passes through aperture  327  in plug portion  310  (see  FIG. 11B ) and transitions into loop portion  34   a.  Loop portion  34   a  is threaded through the first circular channel formed by semi-circular channels  305   a  and  315   a,  as shown in  FIG. 12 .  
         [0141]     Loop portion  34   a  then is threaded through tissue T and transitions into loop portion  34   b.  Loop portion  34   b  is threaded through the second circular channel formed by semi-circular channels  305   b  and  315   b,  as shown in  FIG. 12 . Loop portion  34   b  passes through a second aperture  327  and transitions into second suture end  32   b.  Second suture end  32   b  extends through central bore  312  of plug portion  310 , as shown in  FIG. 12 .  
         [0142]     In accordance with one aspect of the present invention, a physician may selectively tension first and second suture ends  32   a  and  32   b  when actuation knob  322  is disposed within first recess  322 , as shown in  FIGS. 11A-11B . This is because first and second semi-circular channels  305   a  and  305   b  of bone anchor member  302  are aligned with first and second semi-circular channels  315   a  and  315   b  of plug portion  310 , respectively, to form the first and second circular channels through which the suture can freely pass.  
         [0143]     It should be noted that, as first and second ends  32   a  and  32   b  are individually tensioned, rounded edges  328  of plug portion  310  (see  FIG. 11B ) serve to reduce the shear stresses imposed upon the suture ends as they pass through apertures  327 .  
         [0144]     When a physician desires to lock the suture in place, plug portion  310  is rotated with respect to bone anchor member  302  to cause actuation knob  321  to be advanced into second recess  323 . The rotation of plug portion  310  may be achieved by inserting an actuation tool such as a hexagonal key (not shown) into mating slot  325 . Once knob  321  is secured within second recess  323 , as shown in  FIG. 11C , the suture will be locked in place because the misaligned semi-circular channels pinch the first and second ends of the suture.  
         [0145]     Advantageously, if a physician desired to tweak the positioning of tissue T with respect to bone B after the suture has been locked, then a physician simply needs to insert the actuation tool into mating slot  325  to cause knob  322  to rotate in an opposing direction into first recess  322 . As described above, this forms two fully circular channels through which the suture may be advanced or retracted to facilitate positioning of the tissue with respect to the bone.  
         [0146]     Referring now to  FIGS. 13A-13B , a further alternative embodiment of the present invention is described. In  FIG. 13A , bone anchor member  340  comprises main body  343  having proximal and distal regions. Bone anchor member  340  preferably comprises plurality of cleated members  346 , and further comprises opposing guide channels  348  and  349 , which preferably are similar to guide channels  50  and  52  of  FIG. 2C .  
         [0147]     Bone anchor member  340  further comprises at least one passage  352 , which extends laterally through main body  343 , and further comprises flexible member  350 , which is disposed proximal to passage  352 , as shown in  FIGS. 13A-13B . Flexible member  350  has a preferred relaxed configuration in which it assumes a convex shape, i.e., bowed away from passage  352 . In the relaxed configuration, shown in  FIG. 13A , there is sufficient clearance between flexible member  350  and passage  352  to permit suture  30  to move substantially unimpeded through the passage.  
         [0148]     In operation, suture  30  may be coupled between apparatus  340  and tissue T, for example, in a manner described hereinbelow with respect to  FIG. 18A . Specifically, before bone anchor member  340  is inserted into hole H in bone B, first suture end  32   a  is passed through passage  352 . The first suture end then becomes loop portion  34   a,  which is threaded through tissue T, as described hereinabove. Loop portion  34   a  extends through the tissue to become loop portion  34   b.  Loop portion  34   b  passes back through passage  352  and becomes second suture end  32   b.  First and second suture ends  32   a  and  32   b  extend outside of the arthroscopic site and may be individually tensioned by a physician.  
         [0149]     After suture  30  is coupled to apparatus  340  and tissue T, bone anchor member  340  is advanced distally into hole H of bone B (see  FIG. 1 ), whereby cleated members  346  serve to anchor the device in hole H. As described above, a physician then may individually tension first and second suture ends  32   a  and  32   b  to approximate the positioning of tissue T with respect to bone B. During this time, no external forces are applied to flexible member  350 , thereby permitting movement of the suture within passage  352 .  
         [0150]     Once a desired tissue positioning is achieved, the suture may be locked in place by apply a distally-directed force upon flexible member  350 , as depicted in  FIG. 13B . Flexible member  350  preferably assumes a concave shape in which distal knob  354  is urged towards corresponding pocket  355  in bone anchor member  342 . The distally-directed force locks the suture in place by pinching the suture and inhibiting its movement within passage  352 .  
         [0151]     As will be apparent to one skilled in the art, any number of mechanisms may be employed to apply a distally-directed force upon flexible member  350 , and further, to lock the flexible member in the concave position depicted in  FIG. 13B . For example, a plug may be inserted into bore  358 , and then wedged against flexible member  350  to hold the flexible member in place. Alternatively, bone anchor member  340  may comprise taper  277  and proximal stop  278  (see  FIG. 9A ) such that the plug will remain in place within bore  358 . In either case, the plug will serve to apply a compressive force to hold the suture in the locked state.  
         [0152]     Alternatively, the flexible member may be “bi-stable,” such that the flexible member has only two stable states. In the first state, the flexible member is positioned as shown in  FIG. 13A . When a sufficient distally-directed force is applied, the flexible member is configured to “snap” from the first state into a second state, as shown in  FIG. 13B . There are no stable positions between the first and second state. Accordingly, the flexible member is either provided in a locked or unlocked state. Means for applying a proximally-directed force to the flexible member may be used to cause the flexible member to snap from the second state, shown in  FIG. 13B , to the first state, shown in  FIG. 13A , thereby unlocking the device.  
         [0153]     In an alternative embodiment, a threaded member may be used to hold the suture in a locked state. As shown in  FIGS. 14A-14B , threaded cap  360  has exterior thread  361 , which is adapted to engage grooved interior section  371  of bore  358 ′. In a preferred embodiment, threaded cap  360  further comprises a proximal region having mating slot  365  and a distal region having distal protrusion  362 .  
         [0154]     In an unlocked state, threaded cap  360  is situated proximally within bore  358 ′, as shown in  FIG. 14A . Once a physician wishes to lock the suture in place, locking tool  375  may be inserted into mating slot  365  and then rotated clockwise to advance threaded cap in a distal direction, in a manner similar to tightening a screw. This causes a distal region of threaded cap  360 , and preferably, distal protrusion  362 , to urge flexible member  350  distally, thereby impinging upon a suture length disposed through passage  352 . This effectively locks the suture in place.  
         [0155]     If a physician subsequently desires to re-adjust the suture, then locking tool  375  can be rotated counterclockwise within mating slot  365  to proximally retract the threaded cap. This will remove the forces imposed upon the suture, as depicted in  FIG. 14A .  
         [0156]     In the embodiment of  FIGS. 14A-14B , it will be apparent to one skilled in the art that flexible member  350  may be omitted entirely. In this case, threaded cap  360  will directly pinch the suture in passage  352  to lock the suture in place.  
         [0157]     Referring now to  FIGS. 15A-15B , a further alternative embodiment of the bone anchor of  FIGS. 13A-13B  is described. Operation of bone anchor member  340 ″ is substantially the same as that of bone anchor  340 , with the main exception that locking member  380  is provided in lieu of flexible member  350 .  
         [0158]     Locking member  380  preferably comprises cylindrical body  381 , which is configured to be confined within recess  391  of main body  343 ″, as shown in  FIG. 15A . Locking member  380  further comprises distal protrusion  382 , which is configured to extend at least partially through aperture  390  of main body  343 ″.  
         [0159]     First and second support members  383   a  and  383   b  are disposed beneath cylindrical body  381 , and preferably are formed integrally with locking member  380 . As shown in  FIG. 15A , the first and second support members  383   a  and  383   b  rest on support ledge  395  of main body  343 ″, thereby elevating locking member  380  within recess  391 .  
         [0160]     In operation, suture  30  is secured to tissue T and disposed through passage  352 ″, as described hereinabove with respect to  FIGS. 13A-13B . Bone anchor member  340 ″ then is advanced distally into hole H of bone B (see  FIG. 1 ), such that cleated members  346  anchor the device in hole H.  
         [0161]     When locking member  380  is elevated within recess  391 , distal protrusion  382  does not substantially extend into passage  352 ″, thereby permitting movement of the suture within passage  352 ″. At this time, a physician may individually tension first and second suture ends  32   a  and  32   b  to approximate the positioning of tissue T with respect to bone B.  
         [0162]     Once a desired positioning is achieved, the suture may be locked in place by any number of techniques that cause first and second support members  383   a  and  383   b  to be lowered or eliminated, thereby lowering cylindrical body  381  within recess  391  and urging distal protrusion  382  towards corresponding pocket  355 ″, as depicted in  FIG. 15B . The distally-directed force applied by distal protrusion  382  secures the suture in place.  
         [0163]     In one embodiment, first and second support members  383   a  and  383   b  may be fused with support ledge  395  of main body  343 ″. In this embodiment, ultrasonic energy may be delivered to a proximal surface of locking member  380 , via bore  358 ″, using techniques that are known in the art. The provision of ultrasonic energy causes first and second support members  383   a  and  383   b  to fuse with support ledge  395 , thereby lowering locking device  380  and locking the suture disposed within passage  352 ″ in place.  
         [0164]     In the embodiments of  FIGS. 13-15 , while only one passage  352  is depicted, it will be apparent to one skilled in the art that a second passage may be provided, e.g., disposed adjacent to the first passage. If two adjacent passages  352  are provided, then the suture can be threaded through the first passage, through tissue T, and threaded back through the second passage.  
         [0165]     Further, it will be apparent to one skilled in the art that an adhesive, for example, cyanoacrylate, epoxy, bone cement and so forth, may be employed in conjunction with any of the embodiments described in  FIGS. 13-15 . Such an adhesive may be used in conjunction with apparatus including, but not limited to, flexible member  350 , threaded cap  360 , locking member  380 , and any associated components.  
         [0166]     Referring now to  FIGS. 16-17 , a further alternative embodiment of the present invention is described. In the embodiment of  FIGS. 16-17 , apparatus  400  comprises bone anchor member  402  and plug portion  410 .  
         [0167]     Bone anchor member  402  comprises main body  403  having cleated members  406 , which are configured to secure bone anchor member  402  in hole H of  FIG. 1 , as described hereinabove. Further, bone anchor member  402  comprises first and second passages  408  and  412 , which extend laterally through main body  403 , as shown from a top view in  FIG. 16A .  
         [0168]     Bone anchor member  402  further preferably comprises guide channels  409   a,    409   b,    413   a  and  413   b,  which are disposed in exterior surfaces of main body  403 , as shown in  FIGS. 16A-16B . The guide channels preferably are similar to guide channels  50  and  52  of  FIGS. 2A-2C , except that four guide channels are employed in the present embodiment.  
         [0169]     In use, first suture end  32   a  passes through guide channel  409   a,  through passage  408  and through guide channel  409   b.  The first suture end then transitions into loop  34 , which is threaded through tissue T, as described in  FIGS. 1-2  hereinabove. Loop  34  of suture  30  then transitions into second suture end  32   b.  Second suture end  32   b  passes through guide channel  413   b,  through passage  412 , and through guide channel  413   a.  Accordingly, the suture is coupled between the tissue and apparatus  400 .  
         [0170]     Plug portion  410  having main body  411  is configured to be disposed within a central bore of bone anchor member  402 . Plug portion  410  comprises actuation knob  422 , which is configured to be disposed in first recess  423  of bone anchor member  402  in an unlocked state, and disposed within second recess  424  in a locked state.  
         [0171]     In the unlocked state, i.e., when knob  422  is disposed within first recess  423 , plug portion  410  is oriented such that main body  411  does not substantially overlap with first and second passages  408  and  412  of bone anchor member  410 , as depicted in  FIGS. 16A-16B .  
         [0172]     In accordance with one aspect of the present invention, a physician may selectively tension first and second ends  32   a  and  32   b  of suture  30  when knob  422  is disposed within first recess  423 , as shown in  FIGS. 16A-16B . This is because first and second passages  408  and  412  provide a substantially unimpeded circular channel within which the suture can pass.  
         [0173]     When a physician desires to lock the suture in place, plug portion  410  is rotated to cause knob  422  to be advanced into second recess  424 . The rotation of plug portion  410  with respect to bone anchor member  402  may be achieved by inserting an actuation tool such as a rectangular key (not shown) into mating slot  427 . Once knob  422  is secured within second recess  424 , the suture will be locked in place because main body  411  of plug portion  410  impinges upon passages  408  and  412 , as depicted in  FIGS. 17A-17B .  
         [0174]     Advantageously, if a physician desires to tweak the positioning of tissue T with respect to bone B after the suture is in the locked state, then the physician simply needs to insert the actuation tool into mating slot  427  to cause knob  422  to rotate back into first recess  423  (see  FIGS. 16A-16B ). This removes the compressive forces imposed upon the suture, such that the first and second ends of the suture may be individually tensioned to facilitate re-positioning of the tissue.  
         [0175]     Referring now to  FIGS. 18A-18B , yet a further alternative embodiment of the present invention is described. In  FIG. 18A , apparatus  440  comprises bone anchor member  442  and plug portion  450 . Bone anchor member  442  comprises main body  443  having cleated members  446 , which are configured to secure bone anchor member  442  in hole H of  FIG. 1 , as described hereinabove. Further, bone anchor member  442  comprises central bore  444  and circumferential protrusion  449 , which is disposed near a distal end of bore  444 , as shown in  FIG. 18A .  
         [0176]     Plug portion  450  has main body  451  having proximal and distal regions. The proximal region comprises first and second guide channels  456  and  457 , which are recessed in opposing lateral surfaces of main body  451 . The distal region of main body  451  comprises circumferential recess  453  and distal taper  454 , as shown in  FIG. 18A . Plug portion  410  also has a central region having passage  448  disposed laterally therethrough, as depicted in  FIG. 18A .  
         [0177]     Before plug portion  450  is inserted into bore  444 , first suture end  32   a  is passed through passage  448 . The first suture end then becomes loop portion  34   a,  which is threaded through tissue T. Loop portion  34   a  extends through the tissue to become loop portion  34   b.  Loop portion  34   b  passes back through passage  448  and becomes second suture end  32   b.  First and second suture ends  32   a  and  32   b  may be manipulated by a physician, as described in further detail hereinbelow.  
         [0178]     Alternatively, as described hereinabove, a central region of suture  30  may be threaded through tissue T, and the free ends of the suture then may be passed through passage  448  in a proximal direction to achieve the suture positioning depicted in  FIG. 18A .  
         [0179]     In a preferred method of use, bone anchor member  442  is inserted into hole H of bone B before plug portion  450  is inserted into bore  444 . Once bone anchor member  442  is securely disposed within hole H, plug portion  450  is positioned slightly above bone anchor member  442 , so that passage  448  is proximal to bore  444 . At this time, a physician may individually tension first and second suture ends  32   a  and  32   b  to approximate the positioning of tissue T with respect to bone B (see  FIG. 1 ).  
         [0180]     Once the desired positioning is achieved, the physician advances plug portion  450  distally into bore  444  of bone anchor member  442 . An insertion tool, such as insertion tool  294  of  FIGS. 9A-9C , may be inserted into mating slot  458  to advance plug portion  450  distally. The provision of a sufficient distally-directed force urges taper  454  over circumferential protrusion  449 , thereby locking the plug portion within the bone anchor member, as shown in  FIG. 18B .  
         [0181]     At this time, first and second suture ends  32   a  and  32   b  are compressed within guide channel  456 , while suture loop portions  34   a  and  34   b  are compressed within guide channel  457 , as depicted in  FIG. 18B . Guide channels  456  and  457  may be sized to ensure that the suture is completely locked in place when plug portion  450  is inserted into bore  444 . Alternatively, guide channels  456  and  457  may be sized to permit incremental adjustments of the suture, such that applying a sufficient tension to free ends  32   a  and  32   b  will overcome the frictional forces between the suture, plug portion  450  and bone anchor member  442 .  
         [0182]     Referring now to  FIGS. 19A-19C , an alternative plug portion, which may be used in lieu of plug portion  450  of  FIGS. 18A-18B  is described. In  FIG. 19A , plug portion  450 ′ comprises distal passage  466 , in lieu of passage  448  of  FIGS. 18A-18B . Distal passage  466  is formed as a slot recessed in the distal end of main body  451 , as shown in  FIGS. 19A-19C . Distal passage  466  preferably is in communication with opposing guide channels  456  and  457 .  
         [0183]     The operation of a bone anchor system using plug portion  450 ′ is substantially similar to the steps described in  FIGS. 18A-18B , with the exception that first and second suture ends  32   a  and  32   b  are disposed within distal passage  466 . Specifically, in use, the suture ends can be looped around the distal end of plug portion  450 ′, and need not be inserted by threading through central passage  448 . Once the suture ends are looped around the distal end of plug portion  450 ′ and confined within passage  466 , then a physician may hold the suture in place while inserting plug portion  450 ′ into bone anchor member  442 . Once the plug portion is locked into place via circumferential protrusion  449 , as described in  FIG. 18B , then the suture is compressed between plug portion  450 ′ and bone anchor member  442 .  
         [0184]     In each of the embodiments described hereinabove, it will be apparent to those skilled in the art that various means for securing a bone anchor member within hole H of bone B may be employed. Cleated members  42  of  FIG. 2A , which are depicted in most of the embodiments herein, are merely one exemplary means for securing. Other alternative means for securing may be used in conjunction with the apparatus and methods of the present invention. As an example, the bone anchor member may employ one or more radially expandable members that extend into the surrounding bone.  
         [0185]     Further, while some of the embodiments of the present invention describe use of a bone anchor member only, and other embodiments describe use of a bone anchor member and a plug portion, many of these features may be interchanged. It will be apparent to one skilled in the art that many embodiments depicting a bone anchor member only may be performed using a bone anchor member and plug portion, and vice versa.  
         [0186]     Also, for those embodiments described hereinabove having a bone anchor member and a plug portion, it will be apparent to those skilled in the art that the suture ends may be tensioned either before or after the plug portion is inserted into the bore of the bone anchor member.  
         [0187]     It will also be apparent to one skilled in the art that the plug portion may be securely disposed within the bore of the bone anchor member using various means not specifically disclosed herein. For example, after the plug portion is inserted into the bore of the bone anchor member, an adhesive, for example, cyanoacrylate, epoxy, bone cement and so forth, may be delivered to affix the plug portion to the bone anchor member. Alternatively, an exterior surface of the plug portion may be coated with a biocompatible adhesive that affixes to the bone anchor member after the plug portion is inserted into the bore of the bone anchor member. In yet a further alternative embodiment, heat energy may be applied to fuse the plug portion to the bone anchor member. It will be apparent to one skilled in the art that still further means for securing the plug portion to the bone anchor member may be employed.  
         [0188]     In still further embodiments of the present invention, the objective of the present invention may be achieved using multiple bone anchor members, or multiple bone anchor members coupled to respective plug portions. In each embodiment, one or more sutures may be coupled between a desired tissue region and the bone anchor member or plug portion. If multiple sutures and bone anchor members are employed, enhanced sequential tensioning of the tissue may be achieved.  
         [0189]     Finally, while the above-described embodiments reference use of apparatus and methods for facilitating attachment of tissue to bone, it will be apparent to one skilled in the art that such apparatus and methods may also be used to secure tissue to tissue and bone to bone.  
         [0190]     While preferred illustrative embodiments of the invention are described above, it will be apparent to one skilled in the art that various changes and modifications may be made therein without departing from the invention. The appended claims are intended to cover all such changes and modifications that fall within the true spirit and scope of the invention.