Abstract:
Apparatus for securing an object to bone, the apparatus comprising:
       an anchor assembly comprising an anchor and an actuation element extending from the anchor, wherein applying a force to the actuation element when the anchor is disposed in a hole formed in a bone secures the anchor to the bone; and   an inserter for deploying the anchor assembly in a hole formed in a bone, the inserter comprising:
           a shaft for releasably engaging the anchor; and   a force delivery mechanism mounted to the shaft and connected to the actuation element, the force delivery mechanism being constructed so as to receive an input force from an external source and to selectively apply an output force to the actuation element, with the force delivery mechanism being constructed so that the magnitude of the output force is limited regardless of the magnitude of the input force.

Description:
REFERENCE TO PENDING PRIOR PATENT APPLICATIONS 
       [0001]    This patent application: 
         [0002]    (i) is a continuation-in-part of pending prior U.S. patent application Ser. No. 12/839,246, filed Jul. 19, 2010 by Chris Pamichev et al. for METHOD AND APPARATUS FOR RE-ATTACHING THE LABRUM TO THE ACETABULUM, INCLUDING THE PROVISION AND USE OF A NOVEL SUTURE ANCHOR SYSTEM (Attorney&#39;s Docket No. FIAN-4655), which in turn claims benefit of (1) prior U.S. Provisional Patent Application Ser. No. 61/271,205, filed Jul. 17, 2009 by Chris Pamichev et al. for METHOD AND APPARATUS FOR RE-SECURING THE LABRUM TO THE ACETABULUM, INCLUDING THE PROVISION AND USE OF A NOVEL NANO TACK SYSTEM (Attorney&#39;s Docket No. FIAN-46 PROV), and (2) pending prior U.S. Provisional Patent Application Ser. No. 61/326,709, filed Apr. 22, 2010 by Chris Pamichev et al. for METHOD AND APPARATUS FOR RE-SECURING THE LABRUM TO THE ACETABULUM, INCLUDING THE PROVISION AND USE OF A NOVEL SUTURE ANCHOR SYSTEM (Attorney&#39;s Docket No. FIAN-55 PROV); 
         [0003]    (ii) is a continuation-in-part of pending prior International (PCT) Patent Application No. PCT/US2011/021173, filed 13 Jan. 2011 by Pivot Medical, Inc. and Chris Pamichev et al. for METHOD AND APPARATUS FOR RE-ATTACHING THE LABRUM TO THE ACETABULUM, INCLUDING THE PROVISION AND USE OF A NOVEL SUTURE ANCHOR SYSTEM (Attorney&#39;s Docket No. FIAN-70 PCT); and 
         [0004]    (iii) claims benefit of pending prior U.S. Provisional Patent Application Ser. No. 61/502,621, filed Jun. 29, 2011 by Andrew Lantz et al. for FORCE-LIMITING (FORCE-CONTROLLING) DELIVERY MECHANISMS FOR THE CONTROLLED DELIVERY OF THE SUTURE ANCHOR (Attorney&#39;s Docket No. FIAN-74A PROV). 
         [0005]    The five (5) above-identified patent applications are hereby incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0006]    This invention relates to surgical methods and apparatus in general, and more particularly to surgical methods and apparatus for treating a hip joint. 
       BACKGROUND OF THE INVENTION 
     The Hip Joint In General 
       [0007]    The hip joint is a ball-and-socket joint which movably connects the leg to the torso. The hip joint is capable of a wide range of different motions, e.g., flexion and extension, abduction and adduction, medial and lateral rotation, etc. See  FIGS. 1A ,  1 B,  1 C and  1 D. 
         [0008]    With the possible exception of the shoulder joint, the hip joint is perhaps the most mobile joint in the body. Significantly, and unlike the shoulder joint, the hip joint carries substantial weight loads during most of the day, in both static (e.g., standing and sitting) and dynamic (e.g., walking and running) conditions. 
         [0009]    The hip joint is susceptible to a number of different pathologies. These pathologies can have both congenital and injury-related origins. In some cases, the pathology can be substantial at the outset. In other cases, the pathology may be minor at the outset but, if left untreated, may worsen over time. More particularly, in many cases, an existing pathology may be exacerbated by the dynamic nature of the hip joint and the substantial weight loads imposed on the hip joint. 
         [0010]    The pathology may, either initially or thereafter, significantly interfere with patient comfort and lifestyle. In some cases, the pathology can be so severe as to require partial or total hip replacement. A number of procedures have been developed for treating hip pathologies short of partial or total hip replacement, but these procedures are generally limited in scope due to the significant difficulties associated with treating the hip joint. 
         [0011]    A better understanding of various hip joint pathologies, and also the current limitations associated with their treatment, can be gained from a more thorough understanding of the anatomy of the hip joint. 
       Anatomy of the Hip Joint 
       [0012]    The hip joint is formed at the junction of the leg and the torso. More particularly, and looking now at  FIG. 2 , the head of the femur is received in the acetabular cup of the hip, with a plurality of ligaments and other soft tissue serving to hold the bones in articulating condition. 
         [0013]    More particularly, and looking now at  FIG. 3 , the femur is generally characterized by an elongated body terminating, at its top end, in an angled neck which supports a hemispherical head (also sometimes referred to as “the ball”). As seen in  FIGS. 3 and 4 , a large projection known as the greater trochanter protrudes laterally and posteriorly from the elongated body adjacent to the neck of the femur. A second, somewhat smaller projection known as the lesser trochanter protrudes medially and posteriorly from the elongated body adjacent to the neck. An intertrochanteric crest ( FIGS. 3 and 4 ) extends along the periphery of the femur, between the greater trochanter and the lesser trochanter. 
         [0014]    Looking next at  FIG. 5 , the hip socket is made up of three constituent bones: the ilium, the ischium and the pubis. These three bones cooperate with one another (they typically ossify into a single “hip bone” structure by the age of 25 or so) in order to collectively form the acetabular cup. The acetabular cup receives the head of the femur. 
         [0015]    Both the head of the femur and the acetabular cup are covered with a layer of articular cartilage which protects the underlying bone and facilitates motion. See  FIG. 6 . 
         [0016]    Various ligaments and soft tissue serve to hold the ball of the femur in place within the acetabular cup. More particularly, and looking now at  FIGS. 7 and 8 , the ligamentum teres extends between the ball of the femur and the base of the acetabular cup. As seen in  FIGS. 8 and 9 , a labrum is disposed about the perimeter of the acetabular cup. The labrum serves to increase the depth of the acetabular cup and effectively establishes a suction seal between the ball of the femur and the rim of the acetabular cup, thereby helping to hold the head of the femur in the acetabular cup. In addition to the foregoing, and looking now at  FIG. 10 , a fibrous capsule extends between the neck of the femur and the rim of the acetabular cup, effectively sealing off the ball-and-socket members of the hip joint from the remainder of the body. The foregoing structures (i.e., the ligamentum teres, the labrum and the fibrous capsule) are encompassed and reinforced by a set of three main ligaments (i.e., the iliofemoral ligament, the ischiofemoral ligament and the pubofemoral ligament) which extend between the femur and the perimeter of the hip socket. See, for example,  FIGS. 11 and 12 , which show the iliofemoral ligament, with  FIG. 11  being an anterior view and  FIG. 12  being a posterior view. 
       Pathologies of the Hip Joint 
       [0017]    As noted above, the hip joint is susceptible to a number of different pathologies. These pathologies can have both congenital and injury-related origins. 
         [0018]    By way of example but not limitation, one important type of congenital pathology of the hip joint involves impingement between the neck of the femur and the rim of the acetabular cup. In some cases, and looking now at  FIG. 13 , this impingement can occur due to irregularities in the geometry of the femur. This type of impingement is sometimes referred to as cam-type femoroacetabular impingement (i.e., cam-type FAI). In other cases, and looking now at  FIG. 14 , the impingement can occur due to irregularities in the geometry of the acetabular cup. This latter type of impingement is sometimes referred to as pincer-type femoroacetabular impingement (i.e., pincer-type FAI). Impingement can result in a reduced range of motion, substantial pain and, in some cases, significant deterioration of the hip joint. 
         [0019]    By way of further example but not limitation, another important type of congenital pathology of the hip joint involves defects in the articular surface of the ball and/or the articular surface of the acetabular cup. Defects of this type sometimes start out fairly small but often increase in size over time, generally due to the dynamic nature of the hip joint and also due to the weight-bearing nature of the hip joint. Articular defects can result in substantial pain, induce and/or exacerbate arthritic conditions and, in some cases, cause significant deterioration of the hip joint. 
         [0020]    By way of further example but not limitation, one important type of injury-related pathology of the hip joint involves trauma to the labrum. More particularly, in many cases, an accident or sports-related injury can result in the labrum being torn away from the rim of the acetabular cup, typically with a tear running through the body of the labrum. See  FIG. 15 . These types of injuries can be very painful for the patient and, if left untreated, can lead to substantial deterioration of the hip joint. 
       The General Trend Toward Treating Joint Pathologies Using Minimally-Invasive, And Earlier, Interventions 
       [0021]    The current trend in orthopedic surgery is to treat joint pathologies using minimally-invasive techniques. Such minimally-invasive, “keyhole” surgeries generally offer numerous advantages over traditional, “open” surgeries, including reduced trauma to tissue, less pain for the patient, faster recuperation times, etc. 
         [0022]    By way of example but not limitation, it is common to re-attach ligaments in the shoulder joint using minimally-invasive, “keyhole” techniques which do not require large incisions into the interior of the shoulder joint. By way of further example but not limitation, it is common to repair torn meniscal cartilage in the knee joint, and/or to replace ruptured ACL ligaments in the knee joint, using minimally-invasive techniques. 
         [0023]    While such minimally-invasive approaches can require additional training on the part of the surgeon, such procedures generally offer substantial advantages for the patient and have now become the standard of care for many shoulder joint and knee joint pathologies. 
         [0024]    In addition to the foregoing, in view of the inherent advantages and widespread availability of minimally-invasive approaches for treating pathologies of the shoulder joint and knee joint, the current trend is to provide such treatment much earlier in the lifecycle of the pathology, so as to address patient pain as soon as possible and so as to minimize any exacerbation of the pathology itself. This is in marked contrast to traditional surgical practices, which have generally dictated postponing surgical procedures as long as possible so as to spare the patient from the substantial trauma generally associated with invasive surgery. 
       Treatment for Pathologies of the Hip Joint 
       [0025]    Unfortunately, minimally-invasive treatments for pathologies of the hip joint have lagged far behind minimally-invasive treatments for pathologies of the shoulder joint and the knee joint. This is generally due to (i) the constrained geometry of the hip joint itself, and (ii) the nature and location of the pathologies which must typically be addressed in the hip joint. 
         [0026]    More particularly, the hip joint is generally considered to be a “tight” joint, in the sense that there is relatively little room to maneuver within the confines of the joint itself. This is in marked contrast to the shoulder joint and the knee joint, which are generally considered to be relatively “spacious” joints (at least when compared to the hip joint). As a result, it is relatively difficult for surgeons to perform minimally-invasive procedures on the hip joint. 
         [0027]    Furthermore, the pathways for entering the interior of the hip joint (i.e., the natural pathways which exist between adjacent bones and/or delicate neurovascular structures) are generally much more constraining for the hip joint than for the shoulder joint or the knee joint. This limited access further complicates effectively performing minimally-invasive procedures on the hip joint. 
         [0028]    In addition to the foregoing, the nature and location of the pathologies of the hip joint also complicate performing minimally-invasive procedures on the hip joint. By way of example but not limitation, consider a typical detachment of the labrum in the hip joint. In this situation, instruments must generally be introduced into the joint space using an angle of approach which is offset from the angle at which the instrument addresses the tissue. This makes drilling into bone, for example, significantly more complicated than where the angle of approach is effectively aligned with the angle at which the instrument addresses the tissue, such as is frequently the case in the shoulder joint. Furthermore, the working space within the hip joint is typically extremely limited, further complicating repairs where the angle of approach is not aligned with the angle at which the instrument addresses the tissue. 
         [0029]    As a result of the foregoing, minimally-invasive hip joint procedures are still relatively difficult to perform and relatively uncommon in practice. Consequently, patients are typically forced to manage their hip pain for as long as possible, until a resurfacing procedure or a partial or total hip replacement procedure can no longer be avoided. These procedures are generally then performed as a highly-invasive, open procedure, with all of the disadvantages associated with highly-invasive, open procedures. 
         [0030]    As a result, there is, in general, a pressing need for improved methods and apparatus for treating pathologies of the hip joint. 
       Re-Attaching the Labrum of the Hip Joint 
       [0031]    As noted above, hip arthroscopy is becoming increasingly more common in the diagnosis and treatment of various hip pathologies. However, due to the anatomy of the hip joint and the pathologies associated with the same, hip arthroscopy is currently practical for only selected pathologies and, even then, hip arthroscopy has generally met with limited success. 
         [0032]    One procedure which is sometimes attempted arthroscopically relates to the repair of a torn and/or detached labrum. This procedure may be attempted (i) when the labrum has been damaged but is still sufficiently healthy and intact as to be capable of repair and/or re-attachment, and (ii) when the labrum has been deliberately detached (e.g., so as to allow for acetabular rim trimming to treat a pathology such as a pincer-type FAI) and needs to be subsequently re-attached. See, for example,  FIG. 16 , which shows a normal labrum which has its base securely attached to the acetabulum, and  FIG. 17 , which shows a portion of the labrum (in this case the tip) detached from the acetabulum. In this respect it should also be appreciated that repairing the labrum rather than removing the labrum is generally desirable, inasmuch as studies have shown that patients whose labrum has been repaired tend to have better long-term outcomes than patients whose labrum has been removed. 
         [0033]    Unfortunately, current methods and apparatus for arthroscopically repairing (e.g., re-attaching) the labrum are somewhat problematic. The present invention is intended to improve upon the current approaches for labrum repair. 
         [0034]    More particularly, current approaches for arthroscopically repairing the labrum typically use apparatus originally designed for use in re-attaching ligaments to bone. For example, one such approach utilizes a screw-type bone anchor, with two sutures extending therefrom, and involves deploying the bone anchor in the acetabulum above the labrum re-attachment site. A first one of the sutures is passed either through the detached labrum or, alternatively, around the detached labrum. Then the first suture is tied to the second suture so as to support the labrum against the acetabular rim. See  FIG. 18 . 
         [0035]    Unfortunately, bone anchors of the sort described above are traditionally used for re-attaching ligaments to bone and, as a result, tend to be relatively large, since they must carry the substantial pull-out forces normally associated with ligament reconstruction. However, this large anchor size is generally unnecessary for labrum re-attachment, since the labrum is not subjected to substantial pull-out forces, and the large anchor size typically causes unnecessary trauma to the patient. 
         [0036]    Furthermore, the large size of traditional bone anchors can be problematic when the anchors are used for labrum re-attachment, since the bone anchors generally require a substantial bone mass for secure anchoring, and such a large bone mass is generally available only a substantial distance up the acetabular shelf. In addition, the large size of the bone anchors generally makes it necessary to set the bone anchor a substantial distance up the acetabular shelf, in order to ensure that the distal tip of the bone anchor does not inadvertently break through the acetabular shelf and contact the articulating surfaces of the joint. However, labral re-attachment utilizing a bone anchor set high up into the acetabular shelf creates a suture path, and hence a labral draw force, which is not directly aligned with the portion of the acetabular rim where the labrum is to be re-attached. As a result, an “indirect” draw force (also known as eversion) is typically applied to the labrum, i.e., the labrum is drawn around the rim of the acetabulum rather than directly into the acetabulum. See  FIG. 18 . This can sometimes result in a problematic labral re-attachment and, ultimately, can lead to a loss of the suction seal between the labrum and femoral head, which is a desired outcome of the labral re-attachment procedure. 
         [0037]    Alternatively, the suture path can also surround the labrum, thus placing a suture on both sides of the labrum, including the articular side of the labrum, and thus exposing the articular surface of the femur to a foreign body, which could in turn cause damage to the articular surface (i.e., the articular cartilage) of the femur. 
         [0038]    Accordingly, a new approach is needed for arthroscopically re-attaching the labrum to the acetabulum. 
       SUMMARY OF THE INVENTION 
       [0039]    The present invention provides a novel method and apparatus for re-attaching the labrum to the acetabulum. Among other things, the present invention comprises the provision and use of a novel suture anchor system. 
         [0040]    In one form of the invention, there is provided an inserter for deploying an anchor assembly in bone, wherein the anchor assembly comprises an anchor and an actuation element extending from the anchor, and further wherein deploying the anchor assembly in bone comprises positioning the anchor assembly in a hole formed in the bone and applying a force to the actuation element so as to secure the anchor to the bone, the inserter comprising: 
         [0041]    a shaft for releasably engaging the anchor; and 
         [0042]    a force delivery mechanism mounted to the shaft and connected to the actuation element, the force delivery mechanism being constructed so as to receive an input force from an external source and to selectively apply an output force to the actuation element, with the force delivery mechanism being constructed so that the magnitude of the output force is limited regardless of the magnitude of the input force. 
         [0043]    In another form of the invention, there is provided apparatus for securing an object to bone, the apparatus comprising: 
         [0044]    an anchor assembly comprising an anchor and an actuation element extending from the anchor, wherein applying a force to the actuation element when the anchor is disposed in a hole formed in a bone secures the anchor to the bone; and 
         [0045]    an inserter for deploying the anchor assembly in a hole formed in a bone, the inserter comprising:
       a shaft for releasably engaging the anchor; and   a force delivery mechanism mounted to the shaft and connected to the actuation element, the force delivery mechanism being constructed so as to receive an input force from an external source and to selectively apply an output force to the actuation element, with the force delivery mechanism being constructed so that the magnitude of the output force is limited regardless of the magnitude of the input force.       
 
         [0048]    In another form of the invention, there is provided a method for securing an object to bone, the method comprising: 
         [0049]    using an inserter to position an anchor in a hole formed in a bone; and 
         [0050]    applying an input force to the inserter from an external source so as to selectively apply an output force to the anchor whereby to secure the anchor to the bone, with the inserter being constructed so that the magnitude of the output force applied to the anchor is limited regardless of the magnitude of the input force. 
         [0051]    In another form of the invention, there is provided a method for securing an object to bone, the method comprising: 
         [0052]    providing (i) an anchor assembly comprising an anchor and an actuation element extending from the anchor, and (ii) an inserter comprising a shaft for releasably engaging the anchor and a force delivery mechanism mounted to the shaft and connected to the actuation element, the force delivery mechanism being constructed so as to receive an input force from an external source and to selectively apply an output force to the actuation element, with the force delivery mechanism being constructed so that the magnitude of the output force is limited regardless of the magnitude of the input force; 
         [0053]    using the inserter to position the anchor inside a hole formed in a bone; and 
         [0054]    using the force delivery mechanism to apply an output force to the actuation element, whereby to secure the anchor to the bone. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0055]    These and other objects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts, and further wherein: 
           [0056]      FIGS. 1A-1D  are schematic views showing various aspects of hip motion; 
           [0057]      FIG. 2  is a schematic view showing bone structures in the region of the hip joint; 
           [0058]      FIG. 3  is a schematic anterior view of the femur; 
           [0059]      FIG. 4  is a schematic posterior view of the top end of the femur; 
           [0060]      FIG. 5  is a schematic view of the pelvis; 
           [0061]      FIGS. 6-12  are schematic views showing bone and soft tissue structures in the region of the hip joint; 
           [0062]      FIG. 13  is a schematic view showing cam-type femoroacetabular impingement (i.e., cam-type FAI); 
           [0063]      FIG. 14  is a schematic view showing pincer-type femoroacetabular impingement (i.e., pincer-type FAI); 
           [0064]      FIG. 15  is a schematic view showing a labral tear; 
           [0065]      FIG. 16  is a schematic view showing a normal labrum which has its base securely attached to the acetabulum; 
           [0066]      FIG. 17  is a schematic view showing a portion of the labrum detached from the acetabulum; 
           [0067]      FIG. 18  is a schematic view showing a bone anchor being used to re-attach the labrum to the acetabulum; 
           [0068]      FIGS. 19-27  are schematic views showing a novel suture anchor system for use in arthroscopically re-attaching a detached labrum to the acetabulum; 
           [0069]      FIGS. 28 and 28A  are schematic views showing the suture anchor system of  FIGS. 19-27  being used to re-attach the labrum to the acetabulum; 
           [0070]      FIGS. 29-31  are schematic views showing an alternative form of the suture anchor system of the present invention; 
           [0071]      FIG. 32  is a schematic view showing another alternative form of the suture anchor system of the present invention; 
           [0072]      FIGS. 33-38  are schematic views showing alternative arrangements for coupling the anchor of the suture anchor system of  FIGS. 19-27  to the inserter of the suture anchor system of  FIGS. 19-27 ; 
           [0073]      FIGS. 39-41  are schematic views showing still another alternative form of the suture anchor system of the present invention; 
           [0074]      FIG. 42  is a schematic view showing yet another alternative form of the suture anchor system of the present invention; 
           [0075]      FIGS. 43-45  are schematic views showing another alternative form of the suture anchor system of the present invention; 
           [0076]      FIGS. 46-48  are schematic views showing still another alternative form of the suture anchor system of the present invention; 
           [0077]      FIGS. 49-50  are schematic views showing yet another alternative form of the suture anchor system of the present invention; 
           [0078]      FIG. 51  is a schematic view showing another alternative form of the suture anchor system of the present invention; and 
           [0079]      FIGS. 52-54  are schematic views showing still another alternative form of the suture anchor system of the present invention; 
           [0080]      FIGS. 55-60  are schematic views showing yet another alternative form of the present invention; 
           [0081]      FIGS. 61-68  are schematic views showing another form of the present invention, wherein the inserter comprises a force delivery mechanism which is force-limiting so as to provide for the controlled delivery of an actuation force to the anchor, and further wherein the force delivery mechanism comprises a wishbone force delivery mechanism (note that in  FIGS. 62-64  and  67 , only one suture strand is shown for clarity of illustration); 
           [0082]      FIGS. 69 and 70  are schematic views showing alternative constructions for the wishbone element of the wishbone force delivery mechanism of  FIGS. 61-68 ; 
           [0083]      FIGS. 71-74  are schematic views showing design alternatives for the wishbone force delivery mechanism of  FIGS. 61-68  (note that in  FIG. 72 , only one suture strand is shown for clarity of illustration); 
           [0084]      FIGS. 75-79  are schematic views showing another form of the present invention, wherein the force delivery mechanism comprises a spooling force delivery mechanism (note that in  FIGS. 75-79 , only one suture strand is shown for clarity of illustration); 
           [0085]      FIGS. 80 and 81  are schematic views showing another form of the present invention, wherein the force delivery mechanism comprises a double wedge force delivery mechanism (note that in  FIGS. 80 and 81 , only one suture strand is shown for clarity of illustration); 
           [0086]      FIGS. 82 and 83  are schematic views showing another form of the present invention, wherein the force delivery mechanism comprises a suture cutting force delivery mechanism (note that in  FIGS. 82 and 83 , only one suture strand is shown for clarity of illustration); 
           [0087]      FIGS. 84 and 85  are schematic views showing another form of the present invention, wherein the force delivery mechanism comprises an alternative form of suture cutting force delivery mechanism; 
           [0088]      FIG. 86  is a schematic view showing another form of the present invention, wherein the force delivery mechanism comprises a dogbone force delivery mechanism; and 
           [0089]      FIGS. 87-100  are schematic views showing still other forms of the present invention, wherein the force delivery mechanism comprises a “controlled component failure” design (note that in  FIGS. 87-100 , the inserter is omitted from the figures for clarity of illustration). 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The Novel Suture Anchor System of The Present Invention In General 
       [0090]    The present invention provides a novel method and apparatus for arthroscopically re-attaching the labrum to the acetabulum. Among other things, the present invention comprises the provision and use of a novel suture anchor system. 
         [0091]    More particularly, and looking now at  FIG. 19 , there is shown a novel suture anchor system  5  for use in arthroscopically re-attaching a detached labrum to the acetabulum. Suture anchor system  5  generally comprises an anchor  10 , a suture  15  secured to anchor  10 , and an inserter  20  for delivering anchor  10  into the acetabulum, whereby suture  15  may be used to secure a detached labrum to the acetabular rim as will hereinafter be discussed in further detail. Suture anchor system  5  preferably also comprises a hollow guide  25  for delivering components from outside of the body to the acetabulum, and a punch (or drill)  30  which may be used to prepare a seat for anchor  10  in the acetabulum. 
         [0092]    Looking next at  FIGS. 19-23 , anchor  10  comprises a generally cylindrical body  35  having a distal end  40 , a proximal end  45 , and a lumen  50  extending between distal end  40  and proximal end  45 . In one preferred form of the present invention, lumen  50  comprises a distal end reservoir  55 , a short intermediate portion  60 , and an elongated proximal portion  65 . As seen in  FIG. 23 , distal end reservoir  55  has a diameter which is greater than the diameter of short intermediate portion  60 , and short intermediate portion  60  has a diameter which is greater than the diameter of elongated proximal portion  65 . And in one preferred form of the present invention, the outer surface of generally cylindrical body  35  comprises a plurality of ribs  70  spaced along the length of generally cylindrical body  35 , so as to enhance the “holding power” of anchor  10  in bone. In one particularly preferred form of the present invention, ribs  70  sub-divide the length of generally cylindrical body  35  into a plurality of segments, with each segment having a generally frusto-conical configuration ( FIGS. 21 and 22 ). 
         [0093]    Near (but spaced from) the distal end  40  of generally cylindrical body  35 , there is provided a longitudinally-extending slit  75  which extends completely through one side wall (but not the other) of generally cylindrical body  35 . Thus, longitudinally-extending slit  75  communicates with lumen  50  of anchor  10 . The distal end of longitudinally-extending slit  75  terminates in a distal relief hole  80 , and the proximal end of longitudinally-extending slit  75  terminates in a proximal relief hole  85 . It will be appreciated that distal relief hole  80  is spaced from distal end  40  of generally cylindrical body  35 , so that a solid distal ring  90  is located at the distal end of generally cylindrical body  35 , whereby to provide the distal end of generally cylindrical body  35  with a degree of structural integrity. 
         [0094]    Looking now at FIGS.  20  and  24 - 26 , suture  15  generally comprises a distal loop  95  terminating in an enlargement  100  at its distal end and connected to a proximal open loop  105  at its proximal end. More particularly, distal loop  95  extends through short intermediate portion  60  and elongated proximal portion  65  of lumen  50 . Enlargement  100  may comprise a solid member (e.g., cylindrical, conical, etc.) attached to the distal end of distal loop  95 , or it may comprise a suture knot formed by knotting off the distal ends of distal loop  95  of suture  15 , etc. Where enlargement  100  comprises a suture knot, this suture knot may or may not be hardened, shaped or stabilized with cement, heat, etc. For purposes of illustration, enlargement  100  is shown in the drawings schematically, i.e., as a generally cylindrical structure, but it should be appreciated that this is being done solely for clarity of illustration, and enlargement  100  may assume any other shapes and/or configurations (including that of a suture knot) consistent with the present invention. Enlargement  100  is sized so that it is small enough to be seated in distal end reservoir  55  of generally cylindrical body  35  (see, for example,  FIGS. 24 and 25 ), but large enough so that it may not enter short intermediate portion  60  of generally cylindrical body  35  without causing radial expansion of generally cylindrical body  35  (see, for example,  FIG. 26 ). Proximal open loop  105  extends back through the interior of inserter  20  ( FIGS. 19 and 20 ) and provides a pair of free suture ends emanating from the proximal end of inserter  20  ( FIG. 19 ), as will hereinafter be discussed. 
         [0095]    Looking now at  FIGS. 19 and 20 , inserter  20  generally comprises a hollow push tube  110  having a lumen  115  extending therethrough. Inserter  20  terminates at its distal end in a drive surface  120  for engaging the proximal end  45  of anchor  10 , and terminates at its proximal end in a handle  125 . Handle  125  may include features to secure the free ends of suture  15 , e.g., one or more suture cleats, suture slots, suture clamps, etc. Where such features are provided, and where appropriate, handle  125  may also include one or more release mechanisms to release the free ends of suture  15 . Handle  125  may also have one or more mechanisms to apply tension to the secured free ends of suture  15 . Suture  15  (i.e., proximal open loop  105  of suture  15 ) extends through lumen  115  of hollow push tube  110 . By maintaining a slight proximally-directed tension on the proximal end of suture  15  (e.g., by maintaining a slight proximally-directed tension on the free suture ends of proximal open loop  105 ), anchor  10  can be held against the drive surface  120  of hollow push tube  110 , thereby providing a degree of control for maneuvering the anchor. 
         [0096]    Preferably anchor  10 , suture  15  and inserter  20  are pre-assembled into a single unit, with suture  15  extending back through lumen  115  of inserter  20  with a slight proximal tension so as to hold anchor  10  on the distal end of inserter  20 . 
         [0097]    Suture anchor system  5  preferably also comprises a hollow guide  25  for guiding components from outside of the body to the acetabulum. More particularly, hollow guide  25  generally comprises a lumen  130  for slidably receiving anchor  10  and inserter  20  therein, as will hereinafter be discussed. The internal diameter of hollow guide  25  is preferably approximately equal to the largest external feature of anchor  10  (e.g., one or more of the barbs  70 ), so that anchor  10  can make a close sliding fit within the interior of hollow guide  25 . Alternatively, the internal diameter of hollow guide  25  may be slightly smaller or larger than the largest external feature of anchor  10  if desired. Where suture anchor system  5  also comprises a punch (or drill)  30 , lumen  130  of hollow guide  25  is preferably sized to slidably receive punch (or drill)  30 , as will hereinafter be discussed. The distal end of hollow guide  25  preferably includes a sharp tip/edge for penetrating the labrum and engaging the acetabulum, as will hereinafter be discussed. 
         [0098]    If desired, and looking now at  FIGS. 19 and 27 , suture anchor system  5  may also comprise a punch (or drill)  30  having a sharp distal end  135  and a proximal end  140  having a handle  145  mounted thereto. Where element  30  is a drill, handle  145  could comprise a mount for the drill so as to facilitate turning the drill with a powered driver, etc. Again, the sharp distal end  135  of punch (or drill)  30  is adapted to penetrate the acetabulum, as will hereinafter be discussed. 
       Method for Arthroscopically Re-Attaching the Labrum to the Acetabulum Using the Novel Suture Anchor System of the Present Invention 
       [0099]    Suture anchor system  5  is preferably used as follows to secure a detached labrum to the acetabulum. 
         [0100]    First, the sharp distal end  136  of hollow guide  25  is passed through the labrum and positioned against the acetabulum at the location where anchor  10  is to be deployed. Preferably the sharp distal end of hollow guide  25  penetrates through the labrum and a short distance into the acetabulum so as to stabilize the hollow guide vis-à-vis the acetabulum. A stylet (e.g., an obturator) may be used to fill the hollow guide  25  during such insertion and thus prevent tissue coring of the labrum during insertion. The distal portion of the punch (or drill)  30  may also be used to fill the hollow tip of the hollow guide  25  during such insertion. 
         [0101]    Next, if desired, punch (or drill)  30  may be used to prepare a seat in the acetabulum to receive anchor  10 . More particularly, if punch (or drill)  30  is used, the sharp distal end  135  of punch (or drill)  30  is passed through hollow guide  25  (thereby also passing through the labrum) and advanced into the acetabulum so as to form an opening (i.e., a seat) in the bone to receive anchor  10 . Then, while hollow guide  25  remains stationary, punch (or drill)  30  is removed from hollow guide  25 . 
         [0102]    Next, inserter  20 , carrying anchor  10  thereon, is passed through hollow guide  25  (thereby also passing through the labrum) and into the seat formed in the acetabulum. As anchor  10  is advanced into the bone, the body of anchor  10  (e.g., ribs  70 ) makes an interference fit with the surrounding bone, whereby to initially bind the anchor to the bone. At the same time, the solid distal ring  90  located at the distal end of the anchor provides the structural integrity needed to keep the anchor intact while it penetrates into the bone. When anchor  10  has been advanced an appropriate distance into the acetabulum, the proximal end of suture  15  (i.e., proximal open loop  105 ) is pulled proximally while the distal end of inserter  20  is held in position, thereby causing enlargement  100  to move proximally relative to the generally cylindrical body  35 , forcing the distal end of generally cylindrical body  35  to split and expand, in the manner shown in  FIG. 26 , whereby to further bind anchor  10 , and hence suture  15 , to the bone. In one preferred form of the present invention, expansion of generally cylindrical body  35  occurs along some or all of the circumference of the generally cylindrical body, and there may be variations in the amount of expansion about the circumference of the generally cylindrical body, e.g., with the construction shown in  FIG. 26 , there may be greater expansion in a direction perpendicular to the direction of longitudinally-extending slits  75  (for example, in the direction of the arrows shown in  FIG. 26 ). It will be appreciated that the location and magnitude of expansion of generally cylindrical body  35  can be controlled by the number and location of longitudinally-extending slits  75 , the configuration of enlargement  100 , the configuration of generally cylindrical body  35  (e.g., its lumen  50  and the associated side wall of the cylindrical body  35  adjacent the lumen), etc. In one preferred form of the present invention, expansion of generally cylindrical body  35  occurs at the zone where distal end reservoir  55  meets short intermediate portion  60 , with expansion occurring as enlargement  100  moves out of the comparatively larger diameter distal end reservoir  55  and into the comparatively smaller diameter intermediate portion  60 . 
         [0103]    Significantly, in view of the modest holding power required to secure the labrum in place, anchor  10  can have a very small size, much smaller than a typical bone anchor of the sort used to hold a ligament in place. By way of example but not limitation, anchor  10  may have a length of 0.325 inches, an outer diameter (unexpanded) of 0.063 inches, and an outer diameter (expanded) of 0.080 inches. This small size enables a minimal puncture to be made in the labrum (and hence a minimal hole to be made in the labrum), thus reducing potential damage to the labral tissue and enabling a more accurate puncture location through the labrum. The small size of anchor  10  also allows the anchor to be placed closer to, or directly into, the rim of the acetabular cup, without fear of the anchor penetrating into the articulating surfaces of the joint. See, for example,  FIG. 28 , which shows anchor  10  placed close to the rim of the acetabular cup, and  FIG. 28A , which shows anchor  10  placed directly into the rim of the acetabular cup. This significantly reduces, or entirely eliminates, the labrum eversion problems discussed above. Furthermore, the small size of the anchor significantly reduces trauma to the tissue of the patient. 
         [0104]    Once anchor  10  has been set in the acetabulum, guide  25  is removed from the surgical site, leaving anchor  10  deployed in the acetabulum and suture  15  extending out through the labrum. 
         [0105]    This process may then be repeated as desired so as to deploy additional anchors through the labrum and into the acetabulum, with each anchor having a pair of associated free suture ends extending out through the labrum. 
         [0106]    Finally, the labrum may be secured to the acetabular cup by tying the labrum down to the acetabulum using the free suture ends emanating from the one or more anchors. 
       Some Alternative Constructions for the Novel Suture Anchor System of the Present Invention 
       [0107]    If desired, and looking now at  FIGS. 29-31 , a deployment cylinder  150  may be disposed on distal loop  95  of suture  15  just proximal to enlargement  100 . Deployment cylinder  150  can be advantageous where enlargement  100  comprises a suture knot, since the deployment cylinder can ensure the uniform application of a radial expansion force to the wall of the anchor body even where the suture knot has a non-uniform configuration. Deployment cylinder  150  may have a beveled proximal end  155  to facilitate expansion of anchor  10  when suture  15  is pulled proximally.  FIG. 29  depicts anchor  10  in an unexpanded state, while  FIGS. 30-31  depict the anchor  10  in an expanded state. 
         [0108]    Furthermore, one or more of the ribs  70  may utilize a different construction than that shown in  FIGS. 21-23 . More particularly, in  FIGS. 21-23 , each of the ribs  70  comprises a proximal portion which comprises a cylindrical surface  160 . Such a cylindrical surface provides increased surface area contact for engaging the adjacent bone when anchor  10  is disposed in the acetabulum. However, if desired, one or more of the ribs  70  may terminate in a sharp proximal rim  165  ( FIGS. 29-31 ) for biting into adjacent bone when suture  15  is pulled proximally. 
         [0109]    Or one or more of the ribs  70  may be slotted as shown in  FIG. 32  so as to provide a rib with increased flexibility. Such a construction can be useful since it allows the slotted rib  70  to be radially compressed so as to fit within inserter  20  and then radially expanded, in a spring-like manner, when deployed in the acetabulum. 
         [0110]    If desired, alternative arrangements can be provided for coupling anchor  10  to the distal end of inserter  20 . More particularly, in  FIGS. 33 and 34 , a male-female connection is used to couple anchor  10  to inserter  20 , with anchor  10  having a male projection  170  and inserter  20  having a corresponding female recess  175 . In  FIGS. 35 and 36 , inserter  20  includes the male projection  170  and anchor  10  has the corresponding female recess  175 . In  FIGS. 37 and 38 , inserter  20  has a convex surface  180  and anchor  10  has a corresponding concave surface  185 . Still other constructions of this type will be apparent to those skilled in the art in view of the present disclosure. 
         [0111]    Looking next at  FIGS. 39-41 , in another form of present invention, suture  15  is intended to exit anchor  10  at proximal relief hole  85  and extend along the exterior of the generally cylindrical body  35 . If desired, slots  190  may be provided in ribs  70  so as to accommodate suture  15  therein. 
         [0112]    In another form of the present invention, and looking now at  FIG. 42 , suture  15  can be replaced by a solid shaft  195 . More particularly, solid shaft  195  extends through lumen  50  of anchor  10  and lumen  115  of inserter  20 , and has enlargement  100  formed on its distal end. Proximal movement of solid shaft  195  causes enlargement  100  to expand the distal end of anchor  10  so as to cause anchor  10  to grip adjacent bone. 
         [0113]    If desired, one or both of distal relief hole  80  and proximal relief hole  85  may be omitted, with longitudinally-extending slit  75  terminating in a blind surface at one or both ends. 
         [0114]    Furthermore, if desired more than one longitudinally-extending slit  75  may be provided in anchor  10 , e.g., two diametrically-opposed longitudinally-extending slits  75  may be provided. Additionally, if desired, longitudinally-extending slit  75  may extend all the way to the distal end of the anchor body, rather than stopping short of the distal end of the anchor body. See, for example,  FIGS. 43 and 44 , which show two diametrically-opposed, longitudinally-extending slits  75 , wherein the slits extend all the way to the distal end of anchor  10 , and with the two figures showing examplary rib configurations. See also  FIG. 45 , which shows an anchor  10  having a single longitudinally-extending slit  75 , wherein the slit extends all the way to the distal end of the anchor. 
         [0115]    If desired, and looking now at  FIGS. 46-48 , lumen  50  may extend along a longitudinal axis  200  which is eccentric to the longitudinal axis  205  of generally cylindrical body  35 . Such an eccentric construction can provide a thinner side wall on one side of the anchor and a thicker side wall on another side of the anchor, so as to create preferential body expansion. 
         [0116]    Or anchor  10  may be provided with an angled through-hole to create varying wall thicknesses and non-symmetric effects as shown in  FIGS. 49 and 50 . 
         [0117]    If desired, and looking now at  FIG. 51 , anchor  10  can be constructed so that longitudinally-extending slit  75  is omitted entirely. In this form of the invention, anchor  10  is preferably formed with one or more thin-walled sections  210  ( FIGS. 52-54 ) which fracture when enlargement  100  is forced proximally. 
         [0118]    Alternatively, in another form of the invention, anchor  10  is constructed so that its generally cylindrical body  35  expands radially when enlargement  100  moves proximally, but the distal end of the anchor does not split open. See  FIGS. 55-60 . Again, the direction and extent of the expansion of cylindrical body  35  may be controlled by the number and location of the longitudinally-extending slits  75 , the configuration of enlargement  100 , the configuration of generally cylindrical body  35  (e.g., its lumen  50  and the associated side wall of the cylindrical body  35  adjacent the lumen), etc. 
       Additional Construction Details 
       [0119]    Anchor  10  can be made out of any material consistent with the present invention, e.g., anchor  10  can be made out of a biocompatible plastic (such as PEEK), an absorbable polymer (such as poly-L-lactic acid, PLLA), bio-active materials such as hydrogels, or metal (such as stainless steel or titanium). 
         [0120]    Suture  15  can be made out of any material consistent with the present invention, e.g., common surgical suture materials. One such material is woven polymer such as PE or UHMWPE. Another material is a co-polymer material such as UHMWPE/polyester. Yet another material is an absorbable polymer such as polyglycolic acid, polylactic acid, polydioxanone, or caprolactone. Proximal loop  105  is preferably a #1 suture size; alternatively, it is a #2 suture size, a #0 suture size, or a #2-0 suture size. Distal loop  95  is preferably a #2-0 suture size; alternatively, it is a #2 suture size, a #1 suture size, or a #0 suture size. 
         [0121]    As noted above, enlargement  100  may comprise a solid member attached to the distal end of distal loop  95 , or it may comprise a suture knot formed by knotting off the distal ends of distal loop  95  of suture  15 . In this latter construction, enlargement  100  can be formed out of a single knot or multiple knots. It can be an overhand knot or other knot such as a “FIG.  8 ” knot. Suture  15  can also be heat formed so as to create the enlargement  100 . This will create a more rigid feature that better enables movement of enlargement  100  from its distal position to its more proximal position. Such heat forming could also be done on a knot or to seal the suture ends distal to the knot. 
       Force Delivery Mechanisms which are Force-Limiting so as to Provide for The Controlled Delivery of an Actuation Force to the Anchor 
       [0122]    In the preceding sections, there was disclosed a novel suture anchor system  5  which may be used for, among other things, arthroscopically re-attaching a detached labrum to the acetabulum. As discussed above, novel suture anchor system  5  generally comprises an anchor  10 , a suture  15  secured to anchor  10 , and an inserter  20  for delivering anchor  10  into the acetabulum. As also discussed above, novel suture anchor system  5  is constructed so that after inserter  20  has delivered anchor  10  into the acetabulum, tensioning of suture  15  causes the body of anchor  10  to expand laterally so that the anchor is secured to the bone, whereby to secure suture  15  to the bone. 
         [0123]    In one preferred form of the present invention, suture  15  may comprise a pair of sutures, e.g., a thinner distal suture  95  extending through anchor  10  and a thicker proximal suture  105  extending from thinner distal suture  95  to the proximal end of inserter  20  (e.g., to the handle of inserter  20 ), such that thicker proximal suture  105  can be used to actuate the anchor by pulling proximally on thinner distal suture  95  and to secure an object (e.g., the labrum) to the bone in which anchor  10  is deployed, e.g., the acetabulum. 
         [0124]    And in one preferred form of the present invention, novel suture anchor system  5  is intended to be constructed on a very small scale, e.g., so that anchor  10  has a diameter on the order of 1.5 mm, thinner distal suture  95  is a “Size 2-0 suture” with a diameter of approximately 0.3 mm, and thicker proximal suture  105  is a “Size 1 suture” with a diameter of approximately 0.4 mm. 
         [0125]    In view of this unusually small construction, it can be extremely important to limit the magnitude of the tension applied to the suture, since applying too much tension to the suture can result in unintentional damage to the body of anchor  10  and/or in breakage of the suture (particularly the thinner distal suture  95 ). At the same time, however, it is also important that an adequate amount of force be applied to the anchor in order to ensure proper actuation of the anchor. 
         [0126]    In the following sections of this document, there is disclosed force delivery mechanisms which are force-limiting so as to provide for the controlled delivery of an actuation force to anchor  10 . 
         [0127]    In accordance with the present invention, there is disclosed apparatus that may be used to deliver an anchor into bone and to actuate that anchor (i.e., by pulling proximally on an element) while the anchor is disposed in the bone, so as to set the anchor in the bone. In one preferred form of the present invention, the anchor is an expandable anchor that requires the application of a force at the anchor (preferably by tensioning a suture) in order to expand and/or deform the anchor (either a section of the anchor or the entire body of the anchor). In accordance with the present invention, the apparatus for actuating the anchor (e.g., for tensioning the suture) comprises a force delivery mechanism which is force-limiting in the sense that the mechanism allows the user to manually apply force to the anchor (e.g., by tensioning a suture) up to a specific, desired force limit, whereupon the mechanism automatically disengages and the force thereafter applied to the anchor (e.g., by tensioning the suture) drops to zero (or substantially zero). The disengagement and force-limiting aspect of the force delivery mechanism is automatic and does not require any additional action by the user. In other words, the force delivery mechanism is configured so that when the magnitude of the tension applied to the anchor (e.g., to the suture connected to the anchor) exceeds a certain, pre-determined limit, the force delivery mechanism automatically disengages and no further tension is applied to the anchor. 
         [0128]    The alternative to such a force-limiting mechanism is a mechanism that either (i) applies a variable force over a fixed distance of travel, or (ii) a mechanism that requires the user to actively control the delivery of the activation force to the anchor. Neither approach is preferable to a force-limiting mechanism of the sort provided by the present invention. Significantly, a force-limiting mechanism is independent of device variables such as suture stretch, anchor material properties and required actuation travel, and anatomical variables such as bone type and bone quality. For example, in equivalent bone quality, a device that has greater suture stretch may only see partial actuation at the anchor; however, a force-limiting mechanism is independent of suture stretch and hence will actuate the anchor to a consistent, specific force. By way of example but not limitation, the amount of stretch in a suture may significantly exceed the actuation travel required by an anchor, e.g., the suture might stretch 10 mm-15 mm along the length of an inserter when the suture is tensioned, whereas the anchor may only require an actuation travel of 1 mm. In this situation, suture stretch can make it virtually impossible to reliably apply the desired actuation force to the anchor. Furthermore, dense bone will resist the lateral expansion of an anchor more than soft bone will resist the lateral expansion of the anchor. So where the bone is dense, the force applied to the actuation suture may be taken up (i.e., absorbed) by the suture and hence incomplete anchor expansion may occur. Additionally, a device which requires the user to actively control the delivery of the actuation force to the anchor introduces the possibility of user error and unnecessary complications to the device function. 
         [0129]    On account of the foregoing, the present invention provides a force delivery mechanism which is force-limiting so as to provide for the controlled delivery of an actuation force to an anchor. 
         [0130]    For purposes of clarity of description, the novel force-limiting mechanism will hereinafter generally be discussed in the context of applying an actuation force to an anchor  10  by pulling proximally on its thicker proximal suture  105 , whereby to cause its thinner distal suture  95  to move a suture knot (e.g., enlargement  100 ) or a PEEK cylinder (e.g., deployment cylinder  150 ) proximally, whereby to expand anchor  10  and set it in bone. 
       Wishbone Mechanism 
       [0131]    Looking now at  FIGS. 61-68 , there is shown a wishbone force delivery mechanism  300  which is force-limiting so as to provide for the controlled delivery of an actuation force to an anchor, e.g., to the thicker proximal suture  105  of anchor  10 . Wishbone mechanism  300  is intended to be incorporated into the handle  125  of the inserter  20  discussed above, which may cause handle  125  to take on a modified configuration from that previously shown. In one preferred form of the invention, wishbone mechanism  300  generally comprises a handle  305 , a cap  310 , a cleat  315 , a wishbone  320  and a finger pull  325 . Wishbone apparatus  300  also comprises a proximal spring  330 , a distal spring  335  and a wishbone spring  340 . 
         [0132]    Wishbone  320 , finger pull  325  and wishbone spring  340  are the critical components that enable the force-limiting aspect of wishbone mechanism  300 , and handle  305  and cap  310  act to contain and guide the actuation. Additionally, proximal spring  330  dampens the hard stop at the end of actuation (i.e., when wishbone  320  pops out of finger pull  325 , as will hereinafter be discussed) and distal spring  335  maintains tension on the suture (e.g., thicker proximal suture  105 ) while the apparatus is in its packaging and/or prior to the delivery of an actuation force to finger pull  325 , as will hereinafter be discussed. 
         [0133]    Wishbone mechanism  300  is integrated into inserter  20  by mounting cap  310  to the proximal end of hollow push tube  110  of inserter  20 , with thicker proximal suture  105  of anchor  10  extending up hollow push tube  110  for releasable connection to cleat  315 , with handle  305  configured to be grasped by the hand of a user, and with finger pull  325  configured to be grasped by the index finger and middle finger of the user. 
         [0134]    Delivery of the suture anchor (e.g., anchor  10 ) requires a hole in the bone, created by either a drill bit or a punch; the anchor is then inserted into the hole to a specific depth indicated by markings (not shown) provided on the hollow push tube  110 . Once the anchor is located at the proper depth, the anchor requires an actuation step in which a suture knot (e.g., enlargement  100 ) and/or a PEEK cylinder (e.g., deployment cylinder  150 ) at the distal end of the suture (e.g., the thinner distal suture  95 ) are pulled proximally through the anchor, causing the anchor to expand in the manner previously described. The proximal advancement of the suture knot (e.g., enlargement  100 ) and/or the PEEK cylinder (e.g., deployment cylinder  150 ) within anchor  10 , and thereby expansion of the anchor, is controlled by the force-limiting wishbone mechanism  300  which is disposed at, and constitutes, the proximal (i.e., handle) end of the inserter  20 , with cap  310  being connected to the hollow push tube  110  of the inserter  20 . The force-limiting wishbone mechanism  300  is single-handedly actuated by the user via finger pull  325  which is disposed at the proximal (handle) end of the inserter  20 . 
         [0135]    To ensure optimal expansion of the anchor and maximum resistance to pullout, the expansion of the anchor is effected by the application of a pre-determined actuation force. The force-limiting wishbone mechanism  300  allows the user to actuate and expand the anchor up to the pre-determined maximum level of force and, upon reaching that pre-determined maximum level of force, the wishbone mechanism automatically disengages and thereby prevents the user from applying any further force to the anchor, but it does not disengage the force delivery mechanism until after that pre-determined maximum level of force has been applied to the anchor. Thus, wishbone mechanism  300  ensures that the correct level of tension is applied to anchor  10  every time (provided, of course, that an adequate level of force is supplied to finger pull  325  during actuation). 
       Overview of Wishbone Mechanism  300   
       [0136]    As discussed above, after anchor  10  has been positioned in a bone hole, it is set by expanding the anchor body, which is effected by pulling the thinner distal suture  95  (and hence suture knot  100  and/or PEEK cylinder  150 ) proximally. As also discussed above, the thinner distal suture  95  is pulled proximally by pulling the thicker proximal suture  105  (which extends to the handle) proximally. With wishbone mechanism  300 , the proximal end of the thicker proximal suture  105  is secured to cleat  315 , which is itself releasably connected to finger pull  325  via wishbone  320 , as will hereinafter be discussed. From the user&#39;s point of view, anchor actuation is effected by pulling finger pull  325  proximally until wishbone apparatus  300  has automatically disengaged ( FIG. 68 ), whereupon any further proximal movement of finger pull  325  is dampened by proximal spring  330 . During anchor actuation and prior to finger pull  325  engaging proximal hard stop  345 , the wishbone apparatus  300  will make an audible “snap” and, simultaneously, the resistance at finger pull  325  will drop significantly—this signifies that the pre-determined maximum level of force has been reached and that the wishbone apparatus  300  has automatically disengaged (i.e., by virtue of wishbone  320  popping free of finger pull  325 , as will hereinafter be discussed). At this point, the anchor has been expanded in the bone, and the proximal end of the thicker proximal suture  105  can be then unwrapped from cleat  315  and the inserter  20  (which includes wishbone mechanism  300 ) can be removed from the patient, leaving anchor  10  secured to the bone, and suture  105  extending out of the bone. 
       The Step-By-Step Function of Wishbone Apparatus  300   
       [0137]    1. The user pulls on finger pull  325  with two fingers. This causes the user-applied force to be transmitted from finger pull  325  to wishbone  320 , with the two arms  350  ( FIG. 62 ) of wishbone  320  being pulled in tension. The two arms  350  of wishbone  320  are initially held together via a spring-assisted snap fit in bore  355  ( FIG. 62 ) of finger pull  325 . This snap fit is preferably formed by engagement of wishbone projections  356  ( FIG. 62 ) and finger pull narrowings  357  ( FIG. 62 ). 
         [0138]    2. Force is then transmitted from wishbone  320  to the thicker proximal suture  105  (i.e., the suture  105  which extends through the hollow push tube  110  of inserter  20  and which is attached to the thinner distal suture  95  extending through anchor  10 ). More particularly, the proximal end of the thicker proximal suture  105  is wrapped around cleat  315 , and cleat  315  is attached to wishbone  320 , so that pulling proximally on wishbone  320  pulls proximally on the thicker proximal suture  105 . The thicker proximal suture  105  that is wrapped around cleat  315  exits through a hole  360  ( FIGS. 63 and 64 ) formed in the middle of cleat  315  and extends down the center axis of wishbone  320 , e.g., via opening (e.g., a groove or hole)  365  ( FIG. 62 ), through cap  310  and then down hollow push tube  110  of inserter  20 . 
         [0139]    3. The thicker proximal suture  105  that is wrapped around cleat  315  and extends down to and through the thinner distal suture  95  transmits force from finger pull  325  to the thinner distal suture  95 , which causes the knotted distal end  100  of the thinner distal suture  95  and/or the PEEK cylinder  150  to move proximally and hence causes anchor expansion. See  FIG. 65  (which shows the anchor  10  in its undeployed configuration) and  66  (which shows the anchor  10  in its deployed configuration). 
         [0140]    4. The initial force applied by the user at finger pull  325  is low and primarily accounts for the stretch in the suture; this low force creates very little compression of wishbone  320 . 
         [0141]    5. After the suture has stretched, the extension force between finger pull  325  and wishbone  320  increases, and arm  350  of wishbone  320  begins to compress inwardly, against the force of wishbone spring  340 , as the wishbone projections  356  ride on the finger pull narrowings  357  ( FIG. 62 ) in finger pull  325 . See  FIG. 67 . 
         [0142]    6. At a pre-determined maximum level of force (e.g., 10±2 lbf), arms  350  of wishbone  320  compress enough to allow finger pull  325  and wishbone  320  to separate. The force at which wishbone  320  disengages finger pull  325  is dictated by material selection and the geometry of the wishbone  320  and finger pull  325 , including the characteristics specific to the wishbone projections  356  and finger pull narrowings  357 . Among other things, the force at which disengagement occurs is determined by the amount of overlap (i.e. compression distance) between wishbone projections  356  and finger pull narrowings  357 , the angles of the contact surfaces, the surface finishes of the contact surfaces, the power of spring  340 , etc. See  FIGS. 67 and 68 . 
         [0143]    7. Once wishbone  320  and finger pull  325  have separated, the user is unable to apply any further force to the suture, and hence is unable to apply any further force to the anchor. 
       Wishbone Mechanism Variations 
       [0144]    In addition to the foregoing, the force-limiting feature of the wishbone mechanism can be provided via the following design alternatives. 
         [0145]    (i) No Wishbone Spring. The compression spring  340  between arms  350  of wishbone  320  can be omitted, and the function of wishbone compression spring  340  can be provided by using the spring characteristics of the material used to form the wishbone, or by using the geometry of the wishbone, or both. More particularly, wishbone  320  can be manufactured from a resilient metal such as spring steel or from a resilient polymer, whereby to provide the required spring characteristics to arms  350  of wishbone  320 . Alternatively, wishbone  320  can be manufactured as a steel/polymer hybrid, where arms  350  are formed out of spring steel and body  370  is formed out of polymer ( FIG. 69 ). As will be appreciated by those skilled in the art, the thickness and shape of wishbone  320  can be designed so as to achieve a moment of inertia that has the same effect as the compression spring ( FIGS. 69 and 70 ). 
         [0146]    (ii) Stationary Cleat. Cleat  315  can be formed integral with handle  305 , i.e., so that cleat  315  is effectively fixed to handle  305  ( FIG. 71 ). In this case, the suture path runs distally from cleat  315 , wraps around handle  305  at the junction between handle  305  and cap  310  (e.g., at  371 ), and wraps around wishbone  320  (e.g., at  372 ) before going into the interior of hollow push tube  110  of inserter  20  ( FIG. 72 ). With this design, the thicker proximal suture  105  slides relative to the wishbone  320  as the finger pull  325  is moved proximally by the user. And with this design, the actuation force felt by the user at finger pull  325  is approximately twice the force applied at the anchor. 
         [0147]    (iii) Rotational Actuation. Instead of the user pulling proximally on finger pull  325  to actuate the anchor, the user can rotate a knob  375  at the proximal end of handle  305  that translates this user-applied rotation into a linear actuation that pulls on wishbone  320  (which is secured to cleat  315 ) so as to actuate the anchor. See  FIG. 73 . More particularly, in this form of the invention, rotation of knob  375  causes longitudinal motion of a pull tube  376  within handle  305  by virtue of the engagement of helical thread  377  of pull tube  376  with helical groove  377  of knob  378 . The distal end of pull tube  376  has a configuration similar to corresponding portions of finger pull  325 , i.e., pull tube  376  includes the bore  355  for receiving the arms  350  of wishbone  320 , and narrowings  357  for engagement with projections  356  of wishbone  320 . As a result of this construction, when knob  375  is appropriately rotated, pull tube  376  will traverse longitudinally in the proximal direction pulling on wishbone  320 , whereby to apply force to the thicker proximal suture  105  attached to cleat  315  (since the cleat  315  is attached to wishbone  320 ). In an alternative embodiment, and looking now at  FIG. 74 , cleat  315  is mounted on the handle  305 , and the suture is tensioned by passing the suture around a portion of the wishbone (e.g., in a manner analogous to that shown at  372  in  FIG. 72 ) so that proximal movement of the wishbone pulls the suture proximally. 
         [0148]    (iv) Furthermore, instead of the user pulling proximally on finger pull  325  to actuate the anchor, or rotating knob  375  to actuate the anchor, other forms of user controls may be provided for actuating the anchor. By way of example but not limitation, the user may actuate the anchor by pulling a lever, squeezing a trigger, pulling a tab, etc. These and other constructions will be apparent to those skilled in the art in view of the present disclosure. 
       Spooling Mechanism 
       [0149]    In another form of the invention, and looking now at  FIGS. 75-79 , wishbone mechanism  300  may be replaced by a spooling mechanism  380  wherein the force-limiting mechanism is completely contained within finger pull  325 . More particularly, in this form of the invention, the thicker proximal suture  105  is wrapped around a shaft  385  which is disposed within finger pull  325  and selectively rotatable. In accordance with this form of the invention, shaft  385  is prevented from rotating until the pre-determined maximum level of force is reached, whereupon shaft  385  is permitted to rotate freely, and thicker proximal suture  105  is unwrapped from the shaft, whereupon to terminate the application of force to thicker proximal suture  105 . 
         [0150]    The following step-by-step description further describes the structure and function of spooling mechanism  380 . 
         [0151]    1. The user pulls on finger pull  325  with two fingers—within the finger pull, an equal and opposite force is transmitted to the thicker proximal suture  105  spooled on shaft  385 . See  FIG. 75 . 
         [0152]    2. The thicker proximal suture  105  is wrapped around shaft  385  and, as force is applied to thicker proximal suture  105  due to the proximally-directed force applied to finger pull  325 , a keyed collar  390 , which is fixedly secured to shaft  385  and has a finger  395  that is normally disposed within a slot  400  in finger pull  325 , prevents shaft  385  from rotating by virtue of the engagement of finger  395  with the walls of slot  400 . See  FIG. 76 . 
         [0153]    3. Additionally, as a retracting force is applied to shaft  385  via finger pull  325 , an equal and opposite force is applied from shaft  385  to its two axle mounts  401  which rotatably support shaft  385 , and hence to two compression springs  405  which resiliently support the two axle mounts  401  within finger pull  325  (and hence resiliently support shaft  385  within the finger pull  325 ). Compression springs  405  initially prevent shaft  385  from being pulled distally within finger pull  325  (and hence initially prevent keyed collar  390  from withdrawing its finger  395  from slot  400  in finger pull  325 ). As a result, the initial application of force to finger pull  325  is transferred to thicker proximal suture  105 . 
         [0154]    4. As noted above, the initial force applied by the user at finger pull  325  is low, and primarily accounts for the stretch in the suture—this low force creates very little compression of two compression springs  405  supporting shaft  385  in finger pull  325 . As a result, finger  395  of keyed collar  390  remains engaged in slot  400  in finger pull  325 , shaft  385  remains rotationally locked to finger pull  325 , and force applied to finger pull  325  is transferred to thicker proximal suture  105 . 
         [0155]    5. After the suture has stretched, the force applied to compression springs  405  supporting shaft  385  in finger pull  325  increases, and shaft  385  begins to move distally, against the force of springs  405 , relative to finger pull  325 . See  FIG. 77 . 
         [0156]    6. At the pre-determined maximum level of force (e.g., 10±2 lbf), springs  405  supporting shaft  385  compress to the point where finger  395  of keyed collar  390  is withdrawn slot  400  in finger pull  325 . At this point a spring  406  in finger pull  325  forces shaft  385  and keyed collar  390  laterally, so that finger  395  of keyed collar  390  steps away from slot  400  in finger pull  325  and is aligned with a large cavity  407  formed in the finger pull  325 , and so that shaft  385  is now free to rotate within finger pull  325 . Shaft  385  will thereupon rotate freely within finger pull  325  and thereby release the tension in the thicker proximal suture  105 . See  FIG. 78 . 
         [0157]    7. Upon such shaft rotation, the user is unable to apply any further force to thicker proximal suture  105 , and hence the user is unable to apply any further force to anchor  10 . See  FIG. 79 . 
         [0158]    8. The user is then able to remove the inserter from the body of the patient without any additional steps needing to be taken with respect to spooling mechanism  380 —as the inserter is removed, thicker proximal suture  105  simply unwinds (i.e., unspools) from shaft  385 . 
       Double Wedge Mechanism 
       [0159]    In another form of the invention, the force-limiting (force-controlling) mechanism may comprise the double wedge mechanism  435  shown in  FIGS. 80 and 81 . This double wedge mechanism uses two spring-loaded wedges  440  to hold cleat  315  to finger pull  325  as force is applied to finger pull  325 , whereby to apply force to the thicker proximal suture  105  secured to cleat  315 . At the pre-determined maximum level of force, the force applied to spring-loaded wedges  440  by cleat  315  causes the spring-loaded wedges to slide distally and sideways, away from cleat  315 , thereby freeing cleat  315  from finger pull  325 , and allowing cleat  315  to remain stationary as finger pull  325  moves proximally, whereby to terminate the application of force to thicker proximal suture  105 . 
         [0160]    More particularly, and looking now at  FIGS. 80 and 81 , finger pull  325  comprises a plate  441  having an opening  442  extending therethrough, and a pair of opposing inclined guides  443  mounted thereon. Wedges  440  ride along guides  443  so that, as wedges  440  move proximally, the wedges move closer together, and so that, as wedges  440  move distally, the wedges move further part. Springs  444  bias wedges  440  proximally, and hence bias wedges  440  together. Wedges  440  include projections  440 A which clamp cleat  315  between the wedges  440  when the wedges are close together (e.g., in the position shown in  FIG. 80 ) but which fail to clamp cleat  315  between the wedges  440  when the wedges are spaced apart (e.g., in the position shown in  FIG. 81 ). 
         [0161]    In use, double wedge mechanism  435  starts in the position shown in  FIG. 80 . Proximal force is applied to finger pull  325 , which causes proximal force to be applied to plate  441 . As plate  441  begins to move proximally, thicker proximal suture  105  initially stretches, allowing springs  444  to keep wedges  440  proximal and together, but as the finger pull  325  and plate  441  move further proximally, the tension in thicker proximal suture  105  grows. At the pre-determined maximum level of force (e.g., 10±2 lbf), the power of springs  444  is overcome, so that wedges  440  are free to move distally and laterally ( FIG. 81 ), whereby to release cleat  315  from projections  440 A, and hence from plate  441  and finger pull  325 , and whereby to release the tension on thicker proximal suture  105 . Thus it will be seen that with double wedge mechanism  435 , force applied to finger pull  325  will be transferred to thicker proximal suture  105  via double wedge mechanism  435  until the level of that force reaches a certain pre-determined level, whereupon the force delivery mechanism is disabled and the application of force to thicker proximal suture  105  is completely terminated. 
       Suture Cutting Mechanism 
       [0162]    In another form of the invention, the force-limiting mechanism may comprise the suture cutting mechanism  445  shown in  FIGS. 82 and 83 . This suture cutting mechanism  445  allows the user to apply a force to the thicker proximal suture  105  and then, when the pre-determined maximum level of force is reached, the proximal end of the suture is cut by a blade  450  that is positioned on finger pull  325 . Cutting of the thicker proximal suture  105  disables the force delivery mechanism and terminates tension on the suture. 
         [0163]    In essence, with suture cutting mechanism  445 , the suture extends up hollow push tube  110  of inserter  20 , through handle  305  and is attached to finger pull  325  by wrapping the thicker proximal suture  105  around a freely rotating shaft  455  mounted to finger pull  325  and then securing the end of the suture to a mount  456  on finger pull  325 . As a result, as long as thicker proximal suture  105  is intact, a proximal force applied to finger pull  325  applies tension to the suture. When a pre-determined maximum level of force is reached, blade  450  cuts the proximal end of thicker proximal suture  105 . Once the proximal end of suture  105  has been cut, the tension on the suture  105  is released, since it has been wrapped around the freely rotating shaft  455  mounted to finger pull  325  and is no longer secured to mount  456  on finger pull  325 . With the tension on the suture  105  released, the suture  105  is free to unwind off rotating shaft  455  as the user removes the device from the patient. Thus, cutting thicker proximal suture  105  disengages the force delivery mechanism and terminates tension on the suture. 
         [0164]    More particularly, in the preferred form of the invention, finger pull  325  comprises a pair of axial rods  460  upon which is movably mounted a platform  465 . Blade  450  is fixedly mounted to finger pull  325  so as to face the underside of platform  465 , and finger pull  325  comprises an opening  466  for passing thicker proximal suture  105  therethrough. A pair of springs  470  bias platform  465  away from finger pull  325 . Platform  465  carries a freely rotating shaft  455  around which is coiled the thicker proximal suture  105 . The proximal end of suture  105  comes off freely rotating shaft  455 , passes around a post  471  and another post  472 , and then terminates at mount  456 . Thus, a suture segment  473  extends between post  472  and mount  456 . As a result of this construction, a proximal force applied to finger pull  325  causes tension to be applied to thicker proximal suture  105 , since the end of thicker proximal suture  105  is secured to mount  456 . 
         [0165]    When the pulling force applied to finger pull  325  is below the aforementioned pre-determined maximum level of force, springs  470  keep platform  465  biased proximally, away from finger pull  325 , and so as to keep suture segment  473  spaced from cutter blade  450 . However, when the pulling force applied to finger pull  325  exceeds the aforementioned pre-determined level of force, the power of springs  470  is overcome and the gap between finger pull  325  and platform  465  closes so that cutter blade  450  engages the suture segment  473 , whereby to sever the thicker proximal suture  105 . As a result, the thicker proximal suture  105  is no longer fixed to mount  456 , so that freely rotating shaft  455  can spin, allowing thicker proximal suture  105  to unwind from freely rotating shaft  455  whereby to release the tension on thicker proximal suture  105 . 
         [0166]    In an alternative embodiment, suture  105  mounts directly to platform  465  (i.e., there is no freely rotating shaft  455 ). When the pulling force applied to finger pull  325  exceeds the aforementioned pre-determined level of force, the power of springs  470  is overcome and the gap between finger pull  325  and platform  465  closes so that cutter blade  450  engages the suture segment  473 , whereby to sever the thicker proximal suture  105 . As a result, the thicker proximal suture  105  is no longer fixed to mount  456 , allowing thicker proximal suture  105  to be disconnected from platform  465 , whereby to release the tension on thicker proximal suture  105 . 
       Alternative Suture Cutting Mechanism 
       [0167]    In another form of the invention, the force-limiting mechanism may comprise the alternative suture cutting mechanism  485  shown in  FIGS. 84 and 85 . In this form of the invention, where anchor  10  comprises the deployment cylinder  150  which is moved by a thinner distal suture  95  having an enlargement  100  at its distal end, and where thinner distal suture  95  is itself moved by a thicker proximal suture  105  extending up into hollow push tube  110  of inserter  20 , the thicker proximal suture  105  is coupled to a movable shaft  486  disposed within hollow push tube  110  of inserter  20  (in this embodiment, suture  105  may not serve to secure tissue to bone, rather, another suture, not shown, may be secured to the body of the anchor and used to secure tissue to bone). Thicker proximal suture  105  may comprise a loop having a segment  487  extending through diametrically opposed openings  488  formed in movable shaft  486 , with segment  487  extending across the central lumen of the movable shaft  486 . The inserter  20  may have a blade  490  which is disposed in the central lumen of the movable shaft  486 . In this form of the invention, the blade  490  is secured to the finger pull  325  (e.g., via a connector  491 ), and the movable shaft  486  is secured to a body  495  which is spring biased away from finger pull  325  by virtue of springs  500 . In this form of the invention, as long as the level of force applied to the finger pull  325  is below the aforementioned pre-determined maximum level of force, springs  500  will keep body  495  biased away from finger pull  325 , and hence keep blade  490  away from the suture segment  487  formed by thicker proximal suture  105 , so that proximal movement of finger pull  325  will apply a proximal force to thicker proximal suture  105 , whereby to actuate the anchor. However, as soon as the level of force applied to finger pull  325  reaches the aforementioned pre-determined maximum level of force (e.g., 10±2 lbf), the power of springs  500  will be overcome and finger pull  325  will approach body  495 , whereby to bring the cutter blade  490  into engagement with the suture segment  487  formed by thicker proximal suture  105 , and whereby to sever thicker proximal suture  105  and terminate the application of an actuation force to the anchor. 
         [0168]    In other words, in this form of the invention, as long as the level of force applied to finger pull  325  is below the aforementioned maximum level of force, the force applied to finger pull  325  is transmitted to body  495 , and hence to movable shaft  486 , and hence to thicker proximal suture  105 , whereby to actuate the anchor, with springs  500  keeping body  495  sufficiently separated from finger pull  325  to keep blade  490  separated from segment  487  of thicker proximal suture  105 , whereby to maintain the integrity of thicker proximal suture  105 . However, as soon as the level of force applied to finger pull  325  reaches the aforementioned maximum level of force, the power of springs  500  is overcome, so that the gap between body  495  and finger pull  325  decreases, whereby to cause blade  490  to engage segment  487  of thicker proximal suture  105  and sever the suture. This disengages the force delivery mechanism and terminates the tension on the suture  105 . 
       Dogbone Mechanism 
       [0169]    In another form of the present invention, the force-limiting mechanism may comprise the dogbone mechanism  505  shown in  FIG. 86 . Dogbone mechanism  505  allows the user to apply force to the thicker proximal suture  105  which is secured to cleat  315  by pulling proximally on finger pull  325 , with dogbone  510  transmitting force between the two parts (i.e., between finger pull  325  and cleat  315 ). Dogbone  510  is constructed so that at force levels below the aforementioned pre-determined maximum level of force, dogbone  510  will remain intact and will transmit force between finger pull  325  and cleat  315 . However, dogbone  510  is also constructed so that at force levels above the aforementioned pre-determined maximum level of force, dogbone  510  will break and no longer transmit force between finger pull  325  and cleat  315 . Thus, in this form of the invention, dogbone  510  effectively acts as a mechanical fuse, in the sense that it terminates force transmission as soon as the force applied to finger pull  325  reaches the aforementioned pre-determined maximum level of force. It will be appreciated that the breaking force of dogbone  510  is dictated by material selection and dogbone geometry. 
       Additional “Controlled Component Failure” Designs 
       [0170]    It will be appreciated that in the dogbone mechanism  505  discussed above, the force-limiting feature of the force delivery mechanism is provided by the “controlled component failure” of the dogbone. In essence, with this design, a component is designed to act as a “mechanical fuse”, whereby it will intentionally fail when the applied force exceeds the aforementioned pre-determined maximum level of force, whereby to terminate the application of an actuation force to the anchor assembly. The component which acts as the “mechanical fuse” is selected so that the component failure will not undermine the integrity of the anchor fixation in the bone. 
         [0171]    It will be appreciated that numerous other designs can be provided which use the “controlled component failure” scheme of the dogbone mechanism. 
         [0172]    Thus, for example, and looking now at  FIGS. 87 and 88 , in one form of the invention, thicker proximal suture  105  can be engineered to break when the applied force exceeds the aforementioned pre-determined maximum level of force (it should be appreciated that in these figures, and the figures which follow, the inserter is omitted from the drawing in order to improve clarity of understanding). Of course, in this form of the invention, inasmuch as thicker proximal suture  105  is designed to break when the applied force exceeds the aforementioned pre-determined maximum level of force, an additional suture S is provided for securing tissue to bone. In an alternative form of the invention (not shown), the thinner distal suture  95  can be engineered to break when the applied force exceeds the aforementioned pre-determined maximum level of force. 
         [0173]    Or, as shown in  FIGS. 89 and 90 , where a mechanical hook  515  is used in place of thicker proximal suture  105  to apply a proximal force to thinner distal suture  95 , mechanical hook  515  can be engineered to fail (e.g., yielding by bending) when the applied force exceeds the aforementioned pre-determined maximum level of force. Of course, in this form of the invention, inasmuch as mechanical hook  515  is designed to fail when the applied force exceeds the aforementioned pre-determined maximum level of force, an additional suture S is provided for securing tissue to bone. 
         [0174]    Or, as shown in  FIGS. 91 and 92 , where a rod  520  is used in place of thicker proximal suture  105  to apply a proximal force to thinner distal suture  95 , rod  520  can be engineered to fail (e.g., by the thinner distal suture  95  tearing through a segment  521  of rod  520 ) when the applied force exceeds the aforementioned pre-determined maximum level of force. It will be appreciated that the force at which thinner distal suture  95  tears through segment  521  of rod  520  is dictated by material selection and geometry of rod  520  and thinner distal suture  95 . Of course, in this form of the invention, inasmuch as rod  520  is designed to fail when the applied force exceeds the aforementioned pre-determined maximum level of force, an additional suture S is provided for securing tissue to bone. 
         [0175]    Or, as shown in  FIGS. 93 and 94 , where a rod  525  is used in place of both thinner distal suture  95  and thicker proximal suture  105  to apply a proximal force to deployment cylinder  150 , deployment cylinder  150  can be engineered to fail when the applied force exceeds the aforementioned pre-determined maximum level of force. Specifically, in one form of the invention, rod  525  comprises an enlargement  526  which is positioned distal to a narrowed section  527  of deployment cylinder  150 . Enlargement  526  has a profile in at least one dimension which is larger than at least one dimension of narrowed section  527 . Enlargement  526  and narrowed section  527  are constructed so that at force levels below the aforementioned pre-determined maximum level of force, enlargement  526  and narrowed section  527  will both remain intact and will transmit force from rod  525  to deployment cylinder  150 . However, at force levels above the aforementioned pre-determined maximum level of force, one or the other, or both, of enlargement  526  and narrowed section  527  will deform, so that rod  525  can move proximally relative to deployment cylinder  150 , and—once free of narrowed section  527 —will no longer transmit force between rod  525  and deployment cylinder  150 . It will be appreciated that the breaking force of enlargement  526 , narrowed section  527 , or both, is dictated by material selection and geometry of both rod  525  and deployment cylinder  150 . Of course, in this form of the invention, inasmuch as enlargement  526 , narrowed section  527 , or both, are designed to fail when the applied force exceeds the aforementioned pre-determined maximum level of force, an additional suture S (threaded through an opening in the anchor) is provided for securing tissue to bone. 
         [0176]    Or, as shown in  FIGS. 95 and 96 , where a suture  15  (e.g., a thinner distal suture  95  or a thicker proximal suture  105 ) is used to apply a proximal force to deployment cylinder  150 , deployment cylinder  150  can be engineered to fail (e.g., by the suture  15  tearing through a segment  528  of deployment cylinder  150 ) when the applied force exceeds the aforementioned pre-determined maximum level of force. It will be appreciated that the force at which suture  15  tears through segment  528  of deployment cylinder  150  is dictated by material selection and geometry of deployment cylinder  150  and suture  15 . Of course, in this form of the invention, inasmuch as deployment cylinder  150  is designed to fail when the applied force exceeds the aforementioned pre-determined maximum level of force, an additional suture S (threaded through an opening in the anchor) is provided for securing tissue to bone. 
         [0177]    Or, as shown in  FIGS. 97 and 98 , where a hook  530  is used to apply a proximal force to deployment cylinder  150 , hook  530  can be engineered to fail when the applied force exceeds the aforementioned pre-determined maximum level of force. Again, it will be appreciated that the force at which hook  530  fails is dictated by the material selection and geometry of hook  530 . Of course, in this form of the invention, inasmuch as hook  530  is designed to fail when the applied force exceeds the aforementioned pre-determined maximum level of force, an additional suture S (threaded through an opening in the anchor) is provided for securing tissue to bone. 
         [0178]    Or, as shown in  FIGS. 99 and 100 , where a pull rod  535  is used to apply a proximal force to deployment cylinder  150 , pull rod  535  can be engineered to fail when the applied force exceeds the aforementioned pre-determined maximum level of force. For example, pull rod  535  can comprise a break section  536 . Break section  536  may be a narrowing in the pull rod  535  (i.e. creating a weak point in the pull rod  535 ) or other feature or geometry which forces the pull rod  535  to break at that location when the level of force applied to pull rod  535  exceeds the aforementioned pre-determined maximum level of force. Of course, in this form of the invention, inasmuch as pull rod  535  is designed to fail when the applied force exceeds the aforementioned pre-determined maximum level of force, an additional suture S (threaded through an opening in the anchor) is provided for securing tissue to bone. 
       Alternative Construction and Method of Use 
       [0179]    In one form of the present invention, anchor  10  of suture anchor system  5  may be delivered trans-labrally, i.e., through the labrum and into the acetabular bone, e.g., such as was described above. 
         [0180]    In an alternative embodiment of the present invention, anchor  10  may be placed directly into the acetabular bone, without passing through the labrum first, and then suture  15  may be passed through the labrum. In this form of the invention, the components of suture anchor system  5  may remain the same. Alternatively, in this form of the invention, the distal end of hollow guide  25  need not have a sharp tip/edge  136  for penetrating the labrum as described above, and may instead have engagement features for engaging the acetabular bone. One such feature may be a tooth or a plurality of teeth. In this form of the invention, the distal end of the hollow guide may also include a window for confirming that the anchor is properly placed into the bone. 
       Curved or Angled Configuration and Method of Use 
       [0181]    Suture anchor system  5  may also comprise a curved or angled configuration. More particularly, hollow guide  25  may comprise a curve or angle at its distal end. In this form of the invention, the punch (or drill)  30 , inserter  20  and anchor  10  are adapted to pass through the curved or angled hollow guide  25  so as to permit a curved or angled delivery of anchor  10 . 
       Use of the Novel Suture Anchor System for Other Tissue Re-Attachment 
       [0182]    It should be appreciated that suture anchor system  5  may also be used for re-attaching other soft tissue of the hip joint, or for re-attaching tissue of other joints, or for re-attaching tissue elsewhere in the body. In this respect it should be appreciated that suture anchor system  5  may be used to attach soft tissue to bone or soft tissue to other soft tissue, or for attaching objects (e.g., prostheses) to bone other tissue. 
       Modifications of the Preferred Embodiments 
       [0183]    It should be understood that many additional changes in the details, materials, steps and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the present invention, may be made by those skilled in the art while still remaining within the principles and scope of the invention.