DETAILED DESCRIPTION OF THE INVENTION

[0073] In accordance with the principles of the present invention, methods and apparatus are provided for intraluminally forming and securing gastrointestinal (“GI”) tissue folds, for example, to reduce the effective cross-sectional area of a GI lumen. These methods and apparatus may be used to treat obesity by approximating the walls of a gastrointestinal lumen to narrow the lumen, thus reducing the area for absorption in the stomach or intestines. More particularly, the present invention involves endoscopic apparatus that engages a tissue wall of the gastrointestinal lumen, creates one or more tissue folds and disposes one or more anchor assemblies through the tissue fold(s). Preferably, the anchor assemblies are disposed through the muscularis and/or serosa layers of the gastrointestinal lumen. In operation, a distal tip of the probe engages the tissue and then moves the engaged tissue to a proximal position relative to the catheter tip, thereby providing a substantially uniform plication of predetermined size.

[0074] Formation of a tissue fold preferably is accomplished using at least two tissue contact points that are separated by a linear or curvilinear distance, wherein the separation distance between the tissue contact points affects the length and/or depth of the fold. In operation, a tissue grabbing assembly engages the tissue wall in its normal state (i.e., non-folded and substantially flat), thus providing a first tissue contact point. The first tissue contact point then is moved to a position proximal of a second tissue contact point to form the tissue fold. An anchor assembly then may be extended across the tissue fold at the second tissue contact point. Optionally, a third tissue contact point may be established such that, upon formation of the tissue fold, the second and third tissue contact points are disposed on opposing sides of the tissue fold, thereby providing backside stabilization during extension of the anchor assembly across the tissue fold from the second tissue contact point.

[0075] Preferably, the first tissue contact point is used to engage and then stretch or rotate the tissue wall over the second tissue contact point to form the tissue fold. The tissue fold is then articulated to a position wherein a portion of the tissue fold overlies the second tissue contact point at an orientation that is substantially normal to the tissue fold. An anchor then is delivered across the tissue fold at or near the second tissue contact point.

[0076] Referring to FIG. 1 , apparatus 10 of the present invention comprises torqueable catheter 11 having distal region 12 from which first and second interconnected flexible tubes 13 and 14 extend, and proximal region 15 having handle 16 and actuator 17 . Catheter 11 is configured for insertion through a patient's mouth and esophagus into the gastrointestinal lumen. Tissue grabbing assembly 18 is disposed on the distal end of flexible tube 13 , and is coupled to actuator 17 via control wire 19 that extends through flexible tube 13 .

[0077] As better illustrated in FIG. 1 B, flexible tubes 13 and 14 are connected via hinge assembly 20 that comprises link 21 attached to flexible tube 13 at pivot point 22 and attached to flexible tube 14 at pivot point 23 . Hinge assembly 20 prevents tissue grabbing assembly 18 from moving more than a predetermined distance relative to distal end 24 of flexible tube 14 .

[0078] Still referring to FIG. 1 B, flexible tubes 13 and 14 preferably include bendable sections 25 and 26 , respectively. The bendable sections may comprise, for example, a plurality of through-wall slots 27 to enhance flexibility of the tube. Preferably, flexible tubes 13 and 14 are made from stainless steel with an etched or laser-cut slot pattern. More preferably, the slot pattern is a sinusoidal repeating pattern of slots perpendicular to the longitudinal axis of tubes 13 and 14 . Alternative flexible patterns will be apparent to those of skill in the art.

[0079] Referring to FIGS. 2A and 2B , tissue grabbing assembly 18 comprises pair of jaws 28 a , 28 b arranged to rotate about pivot point 29 between an open configuration ( FIG. 2A ) and a closed configuration ( FIG. 2B ). Control wire 19 is coupled via pivot point 30 to arms 31 a and 31 b . Arms 31 a and 31 b are in turn pivotally coupled to jaws 28 a and 28 b , respectively, at pivot points 32 a and 32 b . Each of jaws 28 a and 28 b preferably includes sharpened teeth 33 disposed near its distal ends to facilitate grasping of the tissue wall of the GI lumen.

[0080] Control wire 19 is coupled to actuator 17 of handle 16 so that translation of the wire within flexible tube 13 causes the jaws to open or close. In particular, urging control wire distally (as indicated by arrow A in FIG. 2A ) moves pivot point 30 distally, thereby forcing the jaws to open. Urging control wire 19 proximally (as indicated by arrow B in FIG. 2B ) moves pivot point 30 proximally, thereby forcing the jaws to close together. In alternative embodiments, tissue grabbing assembly 18 may comprise a grappling hook or fork, or plurality of needles coupled to the distal end of flexible tube 13 .

[0081] Flexible tube 14 is affixed to and immovable within catheter 11 , while flexible tube 13 is coupled to catheter 11 only via hinge 20 . Accordingly, when control wire 19 is extended in the distal direction, flexible tube 13 is carried in the distal direction. When control wire 19 is retracted in the proximal direction, flexible tube remains stationary until jaws 28 a and 28 b close together, after which further retraction of control wire 19 by moving actuator 17 causes flexible tube 13 to buckle in bendable region 25 , as described hereinafter.

[0082] Referring now to FIGS. 1 and 3 A- 3 E, operation of apparatus 10 is described to create a tissue fold in a tissue wall of a GI lumen. In FIG. 3 A, distal region 12 of catheter 11 is positioned within a patient's GI lumen transesophageally, and jaws 28 a and 28 b of tissue grabbing assembly 18 are opened by moving actuator 17 to the distal-most position on handle 16 . As depicted in FIG. 3 B, actuator 17 may then be moved proximally until the jaws of tissue grabbing assembly 18 engage a portion of tissue wall W at contact point P 1 .

[0083] Referring to FIG. 3 C, after the tissue wall has been engaged at contact point P 1 , flexible tube 13 is urged proximally within catheter 11 by further proximal retraction of control wire 19 to stretch tissue wall W and create tissue fold F. During this movement of flexible tube 13 , link 21 of hinge assembly 20 causes tissue grabbing assembly 18 to move from a position distal to distal end 24 of flexible tube 14 , to a position proximal of distal end 24 of flexible tube 14 . Bendable sections 25 and 26 of flexible tubes 13 and 14 , respectively, accommodate any lateral motion caused by operation of hinge assembly 20 . Advantageously, formation of fold F facilitates the penetration of the tissue wall by a needle and subsequent delivery of an anchor assembly, as described hereinafter.

[0084] Referring to FIG. 3 D, additional proximal movement of actuator 17 causes flexible tubes 13 and 14 to buckle at bendable sections 25 and 26 . Hinge assembly 20 transmits force applied to flexible tube 13 via control wire 19 and actuator 17 to the distal tip 24 . Preferably, flexible tube 14 is configured so that distal tip 24 contacts, and is substantially perpendicular, to tissue fold F at contact point P 2 . As illustrated in FIG. 3 E, once tissue fold F is stretched across distal tip 24 of flexible tube 14 , sharpened needle or obturator 34 may be extended from distal tip 24 of flexible tube 14 to pierce all four layers of the tissue wall W. Sharpened needle or obturator 34 is inserted via inlet 35 to flexible tube 14 on handle 16 (see FIG. 1A ).

[0085] As discussed above, the GI lumen comprises an inner mucosal layer, connective tissue, the muscularis layer and the serosa layer. To obtain a durable purchase, e.g., in performing a stomach reduction procedure, the staples or anchors used to achieve reduction of the GI lumen must engage at least the muscularis tissue layer, and more preferably, the serosa layer as well. Advantageously, stretching of tissue fold F across distal tip 24 permits an anchor to be ejected through both the muscularis and serosa layers, thus enabling durable gastrointestinal tissue approximation.

[0086] As depicted in FIG. 3 E, after tissue fold F is stretched across distal tip 24 of flexible tube 14 to form contact point P 2 with tissue wall W, needle 34 may be extended from distal tip 24 and through tissue fold F. Because needle 34 penetrates the tissue wall twice, it exits within the gastrointestinal lumen, thus reducing the potential for injury to surrounding organs. Once the needle has penetrated tissue fold F, an anchor assembly is ejected through distal tip 24 as described hereinbelow.

[0087] With respect to FIGS. 4 A- 4 C, a first embodiment of an anchor assembly suitable for use with the apparatus of the present invention is described. Anchor assembly 36 comprises T-anchor assembly having distal rod 38 a and proximal rod 38 b connected by suture 39 . The precise shape, size and materials of the anchors may vary for individual applications. In addition, the suture material also may vary for individual applications. By way of example, the suture material may consist of monofilament wire, multifilament wire or any other conventional suture material. Alternatively, suture 39 may comprise elastic material, e.g. a rubber band, to facilitate adjustment of the distance between the proximal and distal rods. Suture 39 extends through a pair of through-holes 40 in each rod, thereby forming a loop. Alternatively, suture 39 may be attached to the rods via an eyelet or using a suitable adhesive. Preferably, through-holes 40 are located near the center of the rods 38 a and 38 b.

[0088] Referring to FIG. 4 B, rods 38 a and 38 b may be delivered through needle 34 (see FIG. 3E ) using push rod 42 . Push rod 42 is adapted to freely translate through flexible tube 14 and needle 34 . Push rod 42 is preferably flexible, so that it may slide through bendable section 26 of flexible tube 14 . In addition, push rod 42 may include notch 43 near its distal end to facilitate grasping and tensioning suture 39 after anchor delivery.

[0089] During anchor delivery, the longitudinal axis of distal rod 38 a is substantially parallel to the longitudinal axis of needle 34 . However, once distal rod 38 a is ejected from needle 34 , suture tension induces the rod to rotate approximately 90 degrees about its longitudinal axis, so that its longitudinal axis is substantially perpendicular to the longitudinal axis of needle 35 . This rotation of distal rod 38 a prevents it from being pulled back through tissue wall W.

[0090] Referring to FIG. 4 C, once rod 38 a is ejected on the distal side of fold F, needle 35 is retracted and push rod 42 is used to eject rod 38 b on the proximal side of tissue fold F. Like distal rod 38 a , tension in the suture causes proximal rod 38 b to rotate about 90 degrees once it is ejected from the needle. Notch 43 in push rod 42 then may be employed to tighten suture 39 by any of a variety of mechanisms. Alternatively, suture 39 may comprise an elastic material that dynamically tightens the rods against tissue fold F.

[0091] Referring now to FIG. 5 A, according to other embodiments, the anchor assembly comprises a T-anchor assembly suitable to be disposed over obturator 50 . More particularly, distal rod 38 a includes through-hole 51 dimensioned for the passage of obturator tip 52 , and obturator 50 is translatably inserted through flexible tube 14 via inlet 35 of handle 16 (see FIG. 1A ). Proximal rod 38 b may be a solid rod that does not include a through-hole for passage of obturator 50 . Alternatively, proximal rod 38 b may include a through-hole for the passage of the obturator. Preferably, obturator tip 52 is sharpened to facilitate tissue penetration.

[0092] With respect to FIG. 5 B, once rod 38 a is ejected on the distal side of fold F, it rotates into a position substantially parallel to tissue wall W and perpendicular to the longitudinal axis of the obturator. Obturator 50 then is retracted and proximal rod 38 b is ejected from flexible tube 14 . More particularly, when flexible tube 14 is retracted from tissue wall W, proximal rod 38 b is pulled through distal tip 24 . Proximal rod 38 b then rotates substantially 90 degrees as it is ejected from flexible tube 14 so that rod 38 b is urged against tissue wall W.

[0093] Referring to FIG. 6 A, according to further embodiments, anchor assembly 55 comprises a T-anchor assembly similar to the embodiment depicted in FIG. 4A . However, anchor assembly 55 includes fine wire tether 56 that may be twisted to maintain the tension between rods 38 a and 38 b.

[0094] With respect to FIG. 6B, a method of delivering anchor assembly 55 is described. Initially, distal rod 38 a is delivered across both tissue walls using needle 34 . The needle then is retracted to release distal rod 38 a so that it engages the tissue wall. Next, needle 34 is retracted to release proximal rod 38 b , so that it too rotates into engagement with the tissue wall. A proximal portion of the wire tether is captured by notch 43 of push rod 42 (see FIG. 4B ), and the push rod is rotated to cause proximal rod 38 b to clamp down on the tissue fold. Because wire tether 56 is twisted by rotation of push rod 42 , it maintains the desired force on the tissue walls.

[0095] Referring now to FIG. 7, a unidirectionally adjustable anchor assembly suitable for use with apparatus of the present invention is described. Anchor assembly 60 comprises distal anchor 62 and unidirectionally adjustable proximal anchor 64 , which are connected by suture 39 . Distal anchor 62 is translationally fixed with respect to suture 39 . Such fixation may be achieved in a variety of ways. For example, as seen in FIG. 7 A, distal anchor 62 may comprise a pair of through-holes 63 , located near the center of anchor 62 and through which suture 39 is threaded and tied off at knot 65 .

[0096] FIG. 7B provides alternative techniques for fixing the distal anchor. As seen in FIG. 7 B(i), distal anchor 62 may comprise hollow tube T having opening O. A distal end of suture 39 is passed through opening O and formed into knot K, which is dimensioned such that it cannot pass through opening O, thereby fixing the distal anchor with respect to the suture. In order to facilitate formation of knot K, distal anchor 62 optionally may comprise distal opening DO, which is dimensioned such that knot K may pass therethrough. The distal end of suture 39 may be passed through distal opening DO, knotted, and then pulled back within hollow tube T of anchor 62 until it catches at opening O.

[0097] A drawback of the fixation technique described with respect to FIG. 7 B(i) is a risk of suture 39 being torn or cut due to rubbing against opening O. In FIG. 7 B(ii), hollow tube T comprises first end E to which is connected wire loop L, which may be formed, for example from a nickel-titanium alloy (“Nitinol”). Suture 39 passes through the wire loop before terminating at knot K. Knot K is dimensioned such that it cannot pass back through the wire loop. Wire loop L directs suture 39 through opening O, thereby reducing rubbing of the suture against the opening and reducing a risk of tearing or cutting of suture 39 .

[0098] FIG. 7 B(iii) provides yet another alternative technique for fixing the distal anchor with respect to the suture. Distal anchor 62 again comprises hollow tube T having opening O. Rod R is disposed within tube T, and the ends of the tube may be either closed or crimped to rod R, such that the rod is maintained within the tube. The distal end of suture 39 is threaded through opening O, around rod R, and back out opening O. The suture is then knotted at knot K, thereby fixing distal anchor 62 with respect to suture 39 .

[0099] In addition to the techniques shown in FIGS. 7A and 7B , suture 39 alternatively may be fixed with respect to anchor 62 by other means, for example, via a knotted eyelet or via a suitable adhesive. Additional techniques will be apparent to those of skill in the art. While anchor 62 is illustratively shown as a rod- or T-type anchor, any of a variety of anchors, per se known, may be used as distal anchor 62 . Exemplary anchors are described in co-pending U.S. patent application Ser. No. 10/612,170, filed Jul. 1, 2003, which is incorporated herein by reference in its entirety. Additional anchors are described hereinbelow with respect to FIG. 17 . For the purposes of the present invention, anchors and anchor assemblies should be understood to include clips for securing tissue, as well as suture knots and knot replacements. Furthermore, anchor assemblies may comprise multiple components that are not initially coupled to one another; the components may be brought together and/or coupled within a patient at a treatment site.

[0100] Referring again to FIG. 7 A, adjustable proximal anchor 64 comprises outer cylinder 66 having first end 67 a and second end 67 b , as well as first opening 68 a and second opening 68 b . First and second openings 68 are preferably disposed near the center of cylinder 66 and approximately 180° apart. Anchor 64 further comprises first flexible rod 70 a and second flexible rod 70 b , both of which are disposed within outer cylinder 66 and coupled to first and second ends 67 of cylinder 66 . Rods 70 may be formed, for example, from Nitinol or from a polymer, and may be separated from one another by small gap G. As with the previous anchor assemblies, the precise shape, size and materials of the anchors and suture may vary as required for specific applications.

[0101] As best seen in FIG. 7 C, suture 39 passes from distal anchor 62 through first opening 68 a of proximal anchor 64 , around second flexible rod 70 b , around first flexible rod 70 a , between rods 70 a and 70 b , and out through second opening 68 b . This suture winding provides a unidirectional adjustment capability that allows a length L of suture 39 disposed between distal anchor 62 and proximal anchor 64 to be shortened. However, the suture winding precludes an increase in length L. FIG. 8 illustrate the mechanism of this unidirectional adjustment capability in greater detail. Optionally, suture 39 may be tied off proximal of anchor 64 at knot 69 , thereby forming a proximal loop of suture to facilitate deployment and/or adjustment of anchor assembly 60 .

[0102] In FIG. 8A, a proximally-directed force F ₁ is applied to suture 39 proximal of adjustable anchor 64 , while anchor 64 is held stationary or is advanced distally. A portion of force F ₁ is transferred through suture 39 to second flexible rod 70 b , which causes rod 70 b to bow, thereby increasing gap G and allowing suture 39 to freely pass between rods 70 a and 70 b and through proximal anchor 64 , facilitating unidirectional adjustment. When anchor 64 is held stationary while suture 39 is retracted proximally, distal anchor 62 retracts proximally towards anchor 64 . Alternatively, when anchor 64 is advanced distally while suture 39 is retracted proximally, distal anchor 62 either remains stationary or retracts proximally towards proximal anchor 64 , depending upon a degree of distal advancement of proximal anchor 64 . Regardless, length L of suture 39 disposed between anchors 62 and 64 is decreased, thereby unidirectionally adjusting a distance between the anchors.

[0103] In FIG. 8B, a distally-directed force F ₂ is applied to suture 39 distal of adjustable anchor 64 . Force F ₂ may be applied, for example, by tissue compressed between anchors 62 and 64 . Compressed tissue stores energy in a manner similar to a compression spring and seeks to push anchors 62 and 64 apart after unidirectional tightening. Force F ₂ causes the loop of suture 39 around first and second rods 70 to tighten, thereby bowing both rods inward and closing gap G such that suture 39 is friction locked between first and second flexible rods 70 . In this manner, the length L of suture between anchors 62 and 64 may be selectively decreased but cannot be increased.

[0104] As will be apparent to those of skill in the art, the magnitude of force required to unidirectionally adjust length L may be altered in a variety of ways. For example, a length, flexibility or diameter of rods 70 may be altered. Likewise, the elasticity or diameter of suture 39 may be altered. Initial gap G may be increased or decreased. Furtherstill, the materials used to form rods 70 and suture 39 may be changed to alter material properties, such as coefficients of friction, and/or rods 70 or suture 39 may comprise a lubricious coating. Additional methods for varying the magnitude of force, a few of which are described hereinbelow with respect to FIG. 9 , will be apparent in view of this disclosure and are included in the present invention.

[0105] Referring now to FIG. 9 , alternative anchors 64 are described. In FIG. 9 A, flexible rods 70 of proximal adjustable anchor 64 ′ are rotated with respect to openings 68 (or vice versa). When utilizing the suture winding described in FIGS. 7 and 8 , rotation of rods 70 up to 180° clockwise progressively increases friction when force is applied to anchors 62 and 64 . The magnitude of the friction lock is increased when force is applied in the manner described with respect to FIG. 8B . However, friction is also increased when unidirectionally adjusting the length of suture between the proximal and distal anchors by applying force in the manner described with respect to FIG. 8A . Rotation of rods 70 more than about 180° clockwise would cause anchor 64 ′ to friction lock regardless of which direction force were applied to suture 39 , thereby negating the unidirectional adjustment capability. Counterclockwise rotation of rods 70 with respect to openings 68 would initially reduce friction during force application to suture 39 in either direction. It is expected that counterclockwise rotation in excess of about 90° would eliminate the friction lock described in FIG. 8 B and allow bidirectional adjustment. Continued counterclockwise rotation beyond about 450° would reverse the directions of friction lock and unidirectional adjustment, while counterclockwise rotation beyond about 720° would result in friction lock regardless of which direction force were applied to suture 39 .

[0106] As discussed previously, openings 68 of cylinder 66 of anchor 64 are preferably disposed approximately 180° apart from one another. However, in order to increase the friction lock force without significantly increasing friction during unidirectional adjustment, first opening 68 a may be rotated counterclockwise with respect to second opening 68 b (or vice versa), as seen with anchor 64 ″ of FIG. 9B . In this manner, first opening 68 a is no longer in line with rods 70 , while second opening 68 b remains in line with rods 70 . When force F ₁ is applied to anchor 64 ″, second flexible rod 70 b is able to bow outward and increase gap G, thereby facilitating unidirectional adjustment. Likewise, when force F ₂ is applied to the anchor, gap G is closed more tightly upon suture 39 , thereby increasing the friction lock force. If first opening 68 a alternatively were rotated clockwise with respect to the second opening, it is expected that the friction lock force would be decreased.

[0107] In FIG. 9 C, proximal adjustable anchor 64 ′″comprises an alternative suture winding. Suture 39 passes from distal anchor 62 through first opening 68 a of anchor 64 ′″, around second flexible rod 70 b , around first flexible rod 70 a , back around second flexible rod 70 b , between rods 70 a and 70 b ., and out through second opening 68 b . As with the suture winding described with respect to anchor 64 of FIGS. 7 and 8 , the suture winding illustrated in FIG. 9C provides a unidirectional adjustment capability that allows a length L of suture 39 disposed between distal anchor 62 and proximal anchor 64 ′″ to be shortened. However, this suture winding precludes an increase in length L. Additional unidirectionally adjustable suture windings will be apparent to those of skill in the art.

[0108] With reference to FIG. 10 , an alternative unidirectionally adjustable anchor comprising three rods is described. Anchor assembly 80 comprises distal anchor 62 and proximal anchor 82 . Unidirectionally adjustable proximal anchor 82 comprises outer cylinder 84 having first end 85 a and second end 85 b (not shown), as well as first opening 86 a and second opening 86 b . First and second openings 86 are preferably disposed near the center of cylinder 84 and approximately 180° apart. Anchor 82 further comprises first flexible rod 88 a , second flexible rod 88 b and third flexible rod 88 c , all of which are disposed within outer cylinder 66 and coupled to first and second ends 85 of cylinder 64 . Rods 88 are separated from one another by gaps G ₁ and G ₂ .

[0109] Suture 39 passes from distal anchor 62 through first opening 86 a of proximal anchor 82 , around first rod 88 a , between first rod 88 a and second rod 88 b , between second rod 88 b and third rod 88 c , around third rod 88 c , back to and around first rod 88 a , and out through second opening 86 b . As seen in FIG. 10 A, when force F ₁ is applied to suture 39 , gaps G ₁ and G ₂ remain open, thereby facilitating unidirectional adjustment/shortening of length L of suture 39 disposed between distal anchor 62 and proximal anchor 82 . As seen in FIG. 10 B, when force F ₂ is applied to suture 39 , gaps G _{1 and G 2} close down upon suture 39 , thereby forming a friction lock that precludes an increase in length L of suture 39 .

[0110] Referring now to FIG. 11 , an alternative three rod anchor assembly is described. The unidirectionally adjustable anchors described hereinabove with respect to FIGS. 7 - 10 all comprise rods disposed within a cylinder having openings for passage of a suture. The openings act to center the suture with respect to the rods and can be used to alter magnitudes of force applied during adjustment and friction locking, as discussed previously. However, such openings present a risk of tearing or cutting the suture as the suture slides through the openings.

[0111] As seen in FIG. 11 , anchor assembly 90 comprises distal anchor 62 and proximal anchor 92 . Unidirectionally adjustable proximal anchor 92 comprises first flexible rod 94 a and second flexible rod 94 b , as well as rigid rod 96 , which is preferably larger in diameter than first and second rods 94 . Flexible rods 94 are preferably fabricated from Nitinol or a polymer, while rigid rod 96 is preferably fabricated from stainless steel or a polymer. Alternative materials will be apparent to those of skill in the art.

[0112] Anchor 92 further comprises first outer cylinder 98 a and second outer cylinder 98 b , which are crimped to the ends of first and second rods 94 , and rigid rod 96 . As an alternative to crimping, first and second cylinders 98 may each comprise an end cap (not shown) to which the rods are coupled. First and second cylinders 94 do not span a central portion of anchor 92 . Flexible rods 94 are separated from one another by gap G ₁ , while rods 94 are separated from rigid rod 96 by gap G ₂ .

[0113] Anchor 92 comprises three rods, but, unlike anchor 82 of FIG. 10 , suture 39 is only wrapped around two of them to achieve unidirectional adjustment. As best seen in FIGS. 11B and 1C , the illustrative suture winding of anchor assembly 90 is similar to that described previously with respect to anchor assembly 60 of FIGS. 7 and 8 . The break between first and second cylinders 98 acts to center suture 39 with respect to the rods, as seen in FIG. 11 A, while rigid rod 96 acts to stiffen and reduce rotation of anchor 92 as it directs suture 39 about flexible rods 94 .

[0114] Suture 39 passes from distal anchor 62 to proximal anchor 92 , between rigid rod 96 and flexible rods 94 , around second flexible rod 94 b , around first flexible rod 94 a , between rigid rod 96 and first flexible rod 94 a , between flexible rods 94 a and 94 b , and out. As seen in FIG. 11 A, when force F ₁ is applied to suture 39 , flexible rods 94 are forced apart and gap G ₁ widens while gap G ₂ remains substantially constant, thereby allowing unidirectional adjustment of length L of suture 39 disposed between distal anchor 62 and proximal anchor 92 . As seen in FIG. 11 B, when force F ₂ is applied to suture 39 , gap G ₁ closes down upon suture 39 , thereby forming a friction lock that precludes an increase in length L of suture 39 . Gap G ₂ again remains substantially constant.

[0115] With reference to FIG. 12 , an alternative unidirectionally adjustable anchor assembly comprising pivots is described. Anchor assembly 100 comprises distal anchor 62 and proximal anchor 102 . Unidirectionally adjustable proximal anchor 102 comprises outer cylinder 103 having first end 104 a and second end 104 b (not shown), as well as first opening 105 a and second opening 105 b . First and second openings 105 are preferably disposed near the center of cylinder 103 and approximately 180° apart. Anchor 102 further comprises first rod or paddle 106 a and second rod or paddle 106 b , both of which are disposed within outer cylinder 103 and coupled to the first and second ends of cylinder 103 by pins 107 , which pass through pivot holes 108 . In this manner, first and second paddles 106 are able to rotate about pivot holes 108 . Paddles 106 may be formed, for example, from stainless steel or a polymer, and are separated from one another by gap G. As with the previous anchor assemblies, the precise shape, size and materials of the anchors, as well as suture 39 , may vary as required for specific applications.

[0116] Suture 39 illustratively passes from distal anchor 62 through first opening 105 a of proximal anchor 102 , around second paddle 106 b , around first paddle 106 a , between paddles 106 a and 106 b , and out through second opening 105 b . The placement of pivot holes 108 ensures that application of force F ₁ , as described hereinabove, causes paddles 106 to rotate apart from one another and expand gap G, thereby enabling unidirectional adjustment. Likewise, application of previously discussed force F ₂ causes paddles 106 to rotate together, thereby closing gap G and pinching suture 39 between the paddles in a friction lock. An increase in the magnitude of force F ₂ serves to rotate paddles 106 together more tightly, thereby increasing the magnitude of the friction lock acting upon suture 39 between the paddles. In this manner, unidirectional adjustment is achieved.

[0117] Referring now to FIG. 13 , an alternative unidirectionally adjustable anchor assembly comprising spring material is described. Anchor assembly 110 comprises distal anchor 62 and proximal anchor 112 . Unidirectionally adjustable proximal anchor 112 comprises outer cylinder 113 having first end 114 a and second end 114 b (not shown), as well as first opening 115 a and second opening 115 b . First and second openings 115 are preferably disposed near the center of cylinder 113 and approximately 180° apart. Anchor 112 further comprises first rod 116 a and second rod 116 b that are separated by gap G, as well as spring material 118 , all of which are disposed within outer cylinder 113 . Spring material 118 abuts rods 116 , which preferably are substantially the same length as cylinder 113 , and may either move freely within cylinder 113 or may be coupled to the ends (not shown) of cylinder 113 . Spring material 118 may also move freely within cylinder 113 or may be coupled to the cylinder, and comprises lumen 119 having a diameter that is preferably equal to or less than the diameter of suture 39 . Spring material 118 may comprise, for example, a compressible biocompatible foam, which acts as a compression spring.

[0118] Suture 39 passes from distal anchor 62 to proximal anchor 112 through first opening 115 a of cylinder 113 , between rods 116 , through lumen 119 of spring material 118 , and out through second opening 115 b . Lumen 119 snugly contacts suture 39 such that application of force F ₁ causes friction between the suture and the spring material to compress the spring material against the wall of cylinder 114 , thereby reducing a stress applied to rods 116 by spring material 118 and increasing gap G such that unidirectional adjustment of length L of suture 39 disposed between distal anchor 62 and proximal anchor 102 may proceed. Application of force F ₂ stretches spring material 118 against rods 116 , thereby increasing the stress applied to the rods by the spring material and closing gap G such that suture 39 is friction locked between rods 116 .

[0119] With reference to FIG. 14 , alternative unidirectionally adjustable anchor assemblies comprising one-way valves are described. In FIG. 14 A, anchor assembly 120 comprises distal anchor 62 and proximal anchor 122 . Unidirectionally adjustable proximal anchor 122 comprises outer cylinder 124 having first and second ends 125 a and 125 b , as well as first opening 126 a and second opening 126 b . First and second openings 126 are preferably disposed near the center of cylinder 124 and approximately 180° apart. Anchor 122 further comprises first inclined plane 128 a and second inclined plane 128 b , which are forced into apposition by compression springs 129 a and 129 b , thereby forming one-way valve V at the junction of the two inclined planes. Inclined planes 128 and springs 129 are disposed within outer cylinder 124 ; springs 129 abut ends 125 of cylinder 124 , as well as the ends of the inclined planes. Suture 39 ′ comprises a plurality of knots or beads B adapted to actuate one-way valve V.

[0120] Suture 39 ′ passes from distal anchor 62 to proximal anchor 122 through first opening 126 a of cylinder 124 , between inclined planes 128 , through one-way valve V, and out through second opening 126 b . Application of force F ₁ to suture 39 ′ causes a bead B to contact inclined planes 128 and gradually coax them apart by compressing springs 129 , thereby opening valve V and allowing the bead to pass through the valve. Once the bead has passed through valve V, springs 129 force inclined planes 128 back into apposition, thereby closing the valve. Continued application of force F ₁ allows multiple beads to pass through the valve, which facilitates unidirectional adjustment of suture length L disposed between distal anchor 62 and proximal anchor 122 . Application of force F ₂ causes a bead B of suture 39 ′ to impinge upon the proximal sides of inclined planes 128 . However, force transferred to the planes by the bead is perpendicular to the direction required to compress springs 129 and urge planes 128 apart. As such, the bead B impinging upon the proximal sides of planes 128 is not able to open one-way valve V and pass back through the valve in a distal direction, thereby ensuring only unidirectional adjustment, i.e. shortening, of the length L of suture disposed between the proximal and distal anchors.

[0121] In FIG. 14 B, an alternative unidirectionally adjustable anchor having a one-way valve is described. Anchor assembly 130 comprises distal anchor 62 and proximal anchor 132 . Unidirectionally adjustable proximal anchor 132 comprises lumen 134 having cantilevered inclined plane 136 disposed therein, which forms one-way valve V. ‘Zip-tie’ fastener 138 , having a plurality of inclined planes 139 , connects proximal anchor 132 and distal anchor 62 . The plurality of inclined planes 139 are disposed about 180° out of phase with inclined plane 136 of anchor 132 .

[0122] Fastener 138 passes from distal anchor 62 to proximal anchor 132 , through lumen 134 and past inclined plane 136 . Inclined planes 139 of fastener 138 mesh with inclined plane 136 and bend or cantilever plane 136 , such that planes 139 of fastener 138 may proximally pass one-way valve V when force F ₁ is applied to the fastener, thereby enabling unidirectional adjustment of length L of fastener 138 disposed between the proximal and distal anchors. Conversely, when force F ₂ is applied to the fastener, the proximal side of inclined plane 136 of anchor 132 abuts the distal side of an inclined plane 139 of fastener 138 , and the fastener cannot be drawn distally through proximal anchor 132 , nor can the length L of fastener disposed between the anchors be increased significantly.

[0123] Referring now to FIG. 15 , alternative unidirectionally adjustable anchor assemblies comprising a slipknot are described. In FIG. 15 A, anchor assembly 140 comprises distal anchor 142 and proximal anchor 144 . Through-holes 143 a and 143 b extend through distal anchor 142 , while through-holes 145 a and 145 b extend through proximal anchor 145 . Preferably, through-holes 143 and 145 are located near the center of anchors 142 and 144 , respectively.

[0124] The distal end of suture 39 passes through through-hole 145 a of proximal anchor 144 to distal anchor 142 , where it passes through through-hole 143 a and back through through-hole 143 b . It then extends from distal anchor 142 back to proximal anchor 144 , where it passes through through-hole 145 b of the proximal anchor. The distal end of suture 39 is tied off at unidirectional slipknot S, which is located proximal of anchor 144 . FIG. 15B provides a detail view illustrating formation of slipknot S.

[0125] As will be apparent to those of skill in the art, application of force F ₁ causes suture 39 to slide through through-holes 143 and 145 , and decrease the length L of suture 39 disposed between anchors 142 and 144 . Suture 39 may readily pass through slipknot S in a proximal direction, thereby facilitating unidirectional adjustment of length L. However, application of force F ₂ tightens slipknot S and prohibits passage of suture 39 through the slipknot in a distal direction, thereby precluding an increase in length L.

[0126] FIG. 15C illustrates an alternative embodiment of anchor assembly 140 wherein the slipknot is disposed within the proximal anchor. Anchor assembly 140 ′ comprises distal anchor 142 and proximal anchor 144 ′. Proximal anchor 144 ′ comprises hollow cylinder or tube 146 having distal openings 147 a and 147 b , and proximal opening 148 .

[0127] The distal end of suture 39 passes through proximal opening 148 into the interior of tube 146 . It then passes through distal opening 147 a of proximal anchor 144 ′ to distal anchor 142 , where it passes through through-hole 143 a and back through through-hole 143 b . Next, suture 39 extends from distal anchor 142 back to proximal anchor 144 ′, where it passes through distal opening 147 b into the interior of tube 146 of the proximal anchor. The distal end of suture 39 is tied off at unidirectional slipknot S, which is disposed within tube 146 of anchor 144 ′. Anchor assembly 140 ′ may be unidirectionally adjusted in a manner similar to that described hereinabove with respect to anchor assembly 140 of FIG. 15A .

[0128] FIGS. 7 - 15 have illustrated anchor assemblies comprising various mechanisms for achieving unidirectional adjustment of the distance between the proximal and distal anchors. These mechanisms have been provided solely for the sake of illustration and should in no