Abstract:
An innovative bone anchor and methods for securing connective tissue, such as tendons, to bone are disclosed which permit a suture attachment which lies entirely beneath the cortical bone surface, and wherein the suturing material between the connective tissue and the bone anchor is oriented in a direction generally transverse to the longitudinal axis of the bone anchor, so that axial pull-out forces exerted on the bone anchor are minimized. The suture attachment to the bone anchor involves the looping of a substantial length of suturing material around a shaft of the anchor, thereby avoiding an eyelet connection which requires a knot and which concentrates stress on a very small portion of the suturing material. Thus, failure rates are greatly decreased over conventional techniques, and the inventive procedures are significantly easier to perform than conventional techniques.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to methods and apparatus for attaching soft tissue to bone, and more particularly to anchors and methods for securing connective tissue, such as ligaments or tendons, to bone. The invention has particular application to arthroscopic surgical techniques for reattaching the rotator cuff to the humeral head, in order to repair the rotator cuff. 
     It is an increasingly common problem for tendons and other soft, connective tissues to tear or to detach from associated bone. One such type of tear or detachment is a “rotator cuff” tear, wherein the supraspinatus tendon separates from the humerus, causing pain and loss of ability to elevate and externally rotate the arm. Complete separation can occur if the shoulder is subjected to gross trauma, but typically, the tear begins as a small lesion, especially in older patients. 
     To repair a torn rotator cuff, the typical course today is to do so surgically, through a large incision. This approach is presently taken in almost 99% of rotator cuff repair cases. Two types of open surgical approaches for repair of the rotator cuff, one known as the “classic open” and the other as the “mini-open”. The classic open approach requires a large incision and complete detachment of the deltoid muscle from the acromion to facilitate exposure. Following the suturing of the rotator cuff to the humeral head, the detached deltoid is surgically reattached. Because of this maneuver, the deltoid requires postoperative protection, thus retarding rehabilitation and possibly resulting in residual weakness. Complete rehabilitation takes approximately 9 to 12 months. 
     The mini-open technique, which represents the current growing trend and the majority of all surgical repair procedures, differs from the classic approach by gaining access through a smaller incision and splitting rather than detaching the deltoid. Additionally, this procedure is typically used in conjunction with arthroscopic acromial decompression. Once the deltoid is split, it is retracted to expose the rotator cuff tear. The cuff is debrided to ensure suture attachment to viable tissue and to create a reasonable edge approximation. In addition, the humeral head is abraded or notched at the proposed soft tissue to bone reattachment point, as healing is enhanced on a raw bone surface. A series of small diameter holes, referred to as “transosseous tunnels”, are “punched” through the bone laterally from the abraded or notched surface to a point on the outside surface of the greater tuberosity, commonly a distance of 2 to 3 cm. Finally, the cuff is sutured. and secured to the bone by pulling the suture ends through the transosseous tunnels and tying them together using the bone between two successive tunnels as a bridge, after which the deltoid muscle must be surgically reattached to the acromion. 
     Although the above described surgical technique is the current standard of care for rotator cuff repair, it is associated with a great deal of patient discomfort and a lengthy recovery time, ranging from at least four months to one year or more. It is the above described manipulation of the deltoid muscle together with the large skin incision that causes the majority of patient discomfort and an increased recovery time. 
     Less invasive arthroscopic techniques are beginning to be developed in an effort to address the shortcomings of open surgical repair. Working through small trocar portals that minimize disruption of the deltoid muscle, a few surgeons have been able to reattach the rotator cuff using various bone anchor and suture configurations. The rotator cuff is sutured intracorporeally and an anchor is driven into bone at a location appropriate for repair. Rather than thread the suture through transosseous tunnels which are difficult or impossible to create arthroscopically using current techniques, the repair is completed by tying the cuff against bone using the anchor and suture. Early results of less invasive techniques are encouraging, with a substantial reduction in both patient recovery time and discomfort. 
     Unfortunately, the skill level required to facilitate an entirely arthroscopic repair of the rotator cuff is inordinately high. Intracorporeal suturing is clumsy and time consuming, and only the simplest stitch patterns can be utilized. Extracorporeal knot tying is less difficult, but their tightness cannot later be adjusted. Knots tied arthroscopically are difficult to achieve, impossible to adjust, and are located in less than optimal areas of the shoulder. Suture tension is also impossible to measure and adjust once the knot has been tied. Consequently, because of the technical difficulty of the procedure, presently less than 1% of all rotator cuff procedures are of the arthroscopic type, and are considered investigational in nature. 
     A significant difficulty with current arthroscopic rotator cuff repair techniques are shortcomings related to currently available suture anchors. Suture eyelets in bone anchors available today are small in radius, and can cause the suture to fail at that location when the anchor is placed under high tensile loads. Additionally, the sutures must be preloaded into the anchor. Thus, if the suture breaks or is accidentally pulled out during manipulation, a new anchor must be used. The old anchor remains in the bone, because of a barbed construction designed to resist axial removal of the anchor. This presents a problem because of the limited bone space available for the insertion of bone anchors. The need to utilize additional bone anchors to satisfactorily complete a procedure, leaving extra useless anchors in the bone, can severely compromise the ability to perform subsequent procedures, should they be required. Furthermore, due to design, some anchors are limited in the way that they can be placed into the bone. For example, two Mitek anchors must not be placed too near one another or too near the edge of a bone as the “retention barbs” present on anchors of this particular design would interfere with each other or fall outside the surface of the bone. A major problem with existing suture anchor designs is the location of the suture attachment point (typically an eyelet) at the exposed proximal end of the anchor. This arrangement means that any tensile force applied on the suturing material attached to the anchor will result in an axial pull-out force applied to the anchor. As a consequence, if the suturing material itself does not break at the point of attachment, as discussed supra, then there is still a substantial risk that the bone anchor will pull out of the bone, causing the connective tissue to once again become at least partially detached from the bone. In the humerus, the cancellous bone is soft, making such an event more likely. If either suture failure or anchor pull-out occurs after the surgical procedure has been completed, then an entirely new repair procedure must be initiated, with its attendant costs, discomfort, inconvenience, and rehabilitation. 
     Other methods of securing soft tissue to bone are known in the prior art, such as staples and tacks, but are not presently considered to be feasible for shoulder repair procedures, because of physicians&#39; reluctance to leave anything but a suture in the capsule area of the shoulder. The reason for this is that staples, tacks, and the like could possibly fall out and cause injury during movement. Screws are also known for such attachment procedures, but suffer from a number of disadvantages, including their tendency to loosen over time, requiring a second procedure to later remove them, and their requirement for a relatively flat attachment geometry. As a result of this constraint, the attachment point often must be located at a less than ideal position. 
     What is needed, therefore, is a new approach for repairing the rotator cuff, wherein suture tension can be measured and adjusted, the suture resides completely below the cortical bone surface, there is no requirement for the surgeon to tie a knot to attach the suture to the bone anchor, and the skill level for correct placement is suitable for practitioners having average ability. 
     SUMMARY OF THE INVENTION 
     The present invention solves the problems outlined above by providing an innovative bone anchor and connective techniques which permit a suture attachment which lies entirely beneath the cortical bone surface, and wherein the suturing material between the connective tissue and the bone anchor is oriented in a direction generally transverse to the longitudinal axis of the bone anchor, so that axial pull-out forces exerted on the bone anchor are minimized. The suture attachment to the bone anchor involves the looping of a substantial length of suturing material around a shaft of the anchor, thereby avoiding an eyelet connection which requires a knot and which concentrates stress on a very small portion of the suturing material. Thus, failure rates are greatly decreased over conventional techniques, and the inventive procedures are significantly easier to perform than conventional techniques. 
     More particularly, there is provided an apparatus for attaching connective tissue to bone, comprising a shaft having a longitudinal axis and a periphery, which is adapted to be inserted into a bone. The shaft is adapted to have at least one loop of suturing material extending around the periphery thereof while the shaft is disposed in the bone. Advantageously, the shaft comprises structure, such as an anti-rotation cap, for retaining a portion of adjacent suturing material, so that subsequent rotation of the shaft causes a length of the suturing material to become wrapped about the shaft, thereby securing the suturing material to the shaft. The retaining structure preferably comprises a lumen disposed in the shaft, for channeling a length of the suturing material therealong in an axial direction. 
     In another aspect of the invention, there is provided an apparatus for attaching connective tissue to bone, which comprises a shaft having a longitudinal axis, which is adapted to be inserted into a bone. The apparatus also includes structure for retaining a portion of adjacent suturing material, so that subsequent rotation of the shaft causes a length of the suturing material to become wrapped about the shaft, thereby securing the suturing material to the shaft. Advantageously, an anti-rotation element, preferably comprising an anti-rotation cap or an anti-rotation bar, is disposed on the shaft, portions of which engage the bone surrounding the shaft in order to prevent the shaft from moving rotationally. 
     In still another aspect of the invention, an apparatus for attaching connective tissue to bone is provided which requires two or more portals in the bone to manage the tissue to bone attachment. A first one of the portals is adapted to receive suturing material which is attached at one end to the tissue to be attached to the bone. The apparatus comprises an anchoring mechanism which is adapted to be inserted into a second one of the two or more portals. The anchoring mechanism is further adapted to receiving a free end of the suturing material which extends through the first portal, and to employ rotational motion to both attach the suturing material to the anchoring mechanism and to selectively tighten the suturing material. 
     Importantly, the suturing material joining the tissue to the anchoring mechanism lies in a direction generally transverse to that of a longitudinal axis of the anchoring mechanism. This permits the inventive mechanism to be subjected to little or no axial “pull-out” forces, due to the attachment of the anchoring mechanism to the torn connective tissue, such as a tendon, relative to prior art suture anchors of this type, thereby sharply reducing the chance of failure of the anchoring mechanism because of its inadvertent separation from the bone. 
     An inventive method is disclosed for securing connective tissue to bone, which comprises a step of creating a slit in a bone, which slit is open along its length at a surface of the bone and which extends along an anticipated suture path between the connective tissue and a hole in the bone for securing an anchoring device. Other steps include attaching a first end of suturing material to the connective tissue which is to be attached to the bone, securing a second end of the suturing material to the anchoring device, and inserting the anchoring device into the hole, so that the suturing material is disposed in the slit between the anchoring device and the connective tissue. The disclosed inventive method is versatile, in that the securing step may be performed before the inserting step, the suturing material sliding downwardly into the slit through the opening on the bone surface as the anchoring device is advanced into the hole, or, alternatively, the securing step may be performed after the inserting step, if desired. 
     In yet another aspect of the invention, a method for securing connective tissue to bone is disclosed which comprises steps of attaching a first end of suturing material to connective tissue which is to be attached to a bone, and securing a second end of the suturing material to an anchoring device by wrapping a length thereof about the anchoring device. 
     In another aspect of the invention, a method for securing connective tissue to bone is disclosed which comprises steps of creating a first portal in the bone, for receiving a suture anchoring device, and creating a second portal in the bone, having an orientation generally transverse to that of the first portal, for receiving suturing material which attaches the suture anchoring device to the connective tissue. Preferably, the second portal has a slot-type geometry, while the first portal comprises a bore which is disposed generally parallel to and beneath the connective tissue, such that the second portal communicates with the first portal and with the connective tissue. 
     In still another aspect of the invention, there is provided an apparatus for attaching connective tissue to bone, comprising a structure having a longitudinal axis and a periphery, wherein the structure, preferably a shaft, is adapted to be inserted into a bone. At least one loop of suturing material extends around the periphery of the structure while the structure is inserted into the bone. 
     The invention, together with additional features and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying illustrative drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a humerus in partial cross-section, and a tendon, which together form part of a rotator cuff to be repaired, wherein a hole has been made in the humerus for accommodating a suture anchoring device which is constructed in accordance with the principles of the present invention; 
     FIG. 2 is a view similar to FIG. 1 illustrating a step in the inventive procedure wherein a slit is made in the humerus; 
     FIG. 2 a  is a schematic view of a portion of the device shown in FIG. 2, illustrating a sawblade which may be used to form the slit; 
     FIG. 3 is a view similar to FIGS. 1 and 2 illustrating the humerus after the slit has been completed; 
     FIG. 4 is a view similar to FIGS. 1-3, illustrating an alternative procedure wherein a second hole orthogonal to the first hole is created in the humerus; 
     FIG. 5 is a perspective view of the humeral head, illustrating a preferred method wherein three parallel holes have been created therein; 
     FIG. 6 is a partial cross-sectional view similar to FIGS. 1-3 illustrating the humeral head and tendon after they have been sutured together using the apparatus and methods of the present invention; 
     FIG. 6 a  is an enlargement of a portion of FIG. 6, illustrating in greater detail the structure and methods of the present invention; 
     FIG. 6 b  is a cross-sectional view similar to FIG. 6 a , wherein a knot has been tied at the proximal end of the suturing material extending from the inventive anchoring device for retentive purposes; 
     FIG. 7 is a perspective view of a first preferred embodiment of a knotless suture anchoring device constructed in accordance with the principles of the invention, in a partially assembled configuration; 
     FIG. 7 a  is a perspective view similar to FIG. 7, showing the first preferred embodiment of the knotless suture anchoring device in a fully assembled configuration; 
     FIG. 8 is a perspective view similar to FIG. 7, illustrating the first preferred embodiment of the knotless suture anchoring device in an initial unassembled configuration; 
     FIG. 9 is a perspective view similar to FIG. 8, illustrating a second modified embodiment of the preferred knotless suture anchoring device; 
     FIG. 10 a  is a perspective, schematic view of a modified embodiment of the distal portion of the inventive knotless suture anchoring device; 
     FIG. 10 b  is a plan view of the embodiment illustrated in FIG. 10 a;    
     FIG. 10 c  is another perspective view from another angle of the embodiment illustrated in FIG. 10 a;    
     FIG. 11 a  is a perspective view of another modified embodiment of the distal portion of the inventive knotless suture anchoring device, wherein the shaft thereof includes two longitudinal slits; 
     FIG. 11 b  is a perspective view from another angle of the embodiment illustrated in FIG. 11 a;    
     FIG. 12 a  is a perspective view of yet another modified embodiment of the distal portion of the inventive knotless suture anchoring device, wherein the shaft thereof includes three longitudinal slits; 
     FIG. 12 b  is a perspective view from another angle of the embodiment illustrated in FIG. 12 a;    
     FIG. 13 is a perspective view of yet another modified embodiment of the distal portion of the inventive knotless suture anchoring device, wherein the shaft thereof includes only one longitudinal slit; 
     FIG. 14 is a perspective view similar to FIG. 8, of a modified embodiment of the knotless suture anchoring device constructed in accordance with the principles of the present invention, wherein an anti-rotation bar is employed rather than an anti-rotation cylinder; 
     FIG. 15 is a perspective view of the embodiment illustrated in FIG. 14, wherein suturing material has been wrapped therearound; 
     FIG. 16 is a perspective view of another modified embodiment of the distal portion of the inventive knotless suture anchoring device, wherein the shaft includes one longitudinal slit and a portion of the shaft is threaded; 
     FIG. 17 is a perspective view of another modified embodiment of the distal portion of the inventive knotless suture anchoring device, wherein the shaft includes two longitudinal slits, and a portion of the shaft is threaded; 
     FIG. 18 is a perspective view of another modified embodiment of the distal portion of the inventive knotless suture anchoring device, wherein the shaft includes three longitudinal slits, and a portion of the shaft is threaded; 
     FIG. 19 is a perspective, schematic view of the point of attachment between a patient&#39;s humeral head and the end of the tendon to be re-attached thereto, in accordance with one method taught herein; 
     FIG. 20 a  is a perspective view of another modified embodiment of the distal portion of the inventive knotless suture anchoring device, wherein the shaft includes anti-rotation barbs and a portion of the shaft is threaded; 
     FIG. 20 b  is a perspective view similar to FIG. 20 a , wherein the shaft includes anti-rotation barbs but there are no threads; 
     FIG. 21 a  is a perspective view of another modified embodiment of the distal portion of the inventive knotless suture anchoring device, wherein the shaft includes guiding ridges for the suturing material to track in as it is wrapped thereabout; 
     FIG. 21 b  is another perspective view of the embodiment illustrated in FIG. 21 a , which shows suturing material wrapped about the shaft thereof; 
     FIG. 22 a  is a perspective view of another modified embodiment of the inventive device, having an open shaft configuration so that suturing material which is wrapped about the shaft is in direct contact with suturing material which extends along the length of the shaft and proximally from its proximal end; 
     FIG. 22 b  is a perspective view of the embodiment shown in FIG. 22 a , which shows the suturing material wrapped about the shaft; 
     FIG. 22 c  is a cross-sectional view along lines A—A of FIG. 22 b;    
     FIG. 23 a  is a perspective view showing yet another modified embodiment of the knotless suture anchoring device of the present invention, wherein the device comprises a flat bar; 
     FIG. 23 b  is a perspective view similar to FIG. 23 a , with the suturing material removed for clarity; 
     FIG. 23 c  is another perspective view of the device shown in FIGS. 23 a  and  23   b;    
     FIG. 24 a  is a perspective views of still another modified embodiment of the knotless suture anchoring device of the present invention, wherein the axially extending suturing material lies on the exterior of the shaft, and peaks and valleys are provided to create a more tortuous path therefor and thus reduce slippage; and 
     FIG. 24 b  is another perspective view of the device illustrated in FIG. 24 a , wherein the-suturing material has been removed for clarity. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now more particularly to the drawings, there is shown in FIG. 1 a  portion of a partially torn rotator cuff  11 . In the illustration, which is simplified for purposes of clarity, a globular head  13  of a humerus  15  is disposed in a glenoid cavity  17  formed by a scapula  19 . A supraspinatus tendon  21 , the end of which is normally fully attached onto a facet of a greater tuberosity  23 , is shown in a detached condition, resulting in a diagnosis that the rotator cuff has been torn. 
     Now with particular reference to FIGS. 7 and 8, there is illustrated one preferred embodiment of a knotless suture anchoring device  25  constructed in accordance with the principles of the invention. In its preferred configuration, the anchoring device  25  comprises a hollow stem or shaft  27 , having a longitudinal axis  28  and a periphery. A pair of longitudinal slits  29  extend along a portion of a distal section of the shaft  27  from its distal end  31 , and a wider and shorter recess  32  may also be disposed on the shaft distal end  31 , as shown. At the shaft&#39;s proximal end, there is disposed a hexagonal nut  33 , which is adapted to receive and engage an anti-rotation cap  35  onto it, for purposes to be described below. The anti-rotation cap  35 , in this embodiment, has an internally disposed hexagonal surface  36  which corresponds with the hexagonal nut  33  to permit a snug fit. An internal lumen  37 , which extends through both the shaft  27  and the hexagonal nut  33 , is adapted to receive suturing material  39 , as shown in FIG.  7 . 
     The anti-rotation cap  35  includes a radially extending flange portion  41 , which preferably has a flap member  43  disposed thereon. The purpose of the anti-rotation cap  35  is to prevent rotation of the anchoring device  25  about its axis once it has been inserted into, for example, the humeral bone of a patient, as will be described. The purpose of the flap member  43 , which extends angularly outwardly from the flange surface, as shown, is to prevent axial migration of the device, once in position, as will also be explained. The flap member  43  may be oriented at any desired angle, which may be either fixed or adjustable. 
     An alternative embodiment of the invention is illustrated in FIG. 9, wherein like elements to those depicted in FIGS. 7 and 8 are designated by like reference numerals, increased by  100 . Thus, there is shown a knotless suture anchoring device  125  which is substantially identical to anchoring device  25  shown in FIGS. 7 and 8, except that the internal surface  45  of the anti-rotation cap  135  is ribbed, rather than being hexagonal. The effect of the ribs on the surface  45  is similar to that of the internal hexagonal surface  36  of the cap  35 , namely, to provide a snug engagement between the anti-rotation cap  135  and the nut  133 . Other suitable configurations for both the cap  35 ,  135  and the nut  33 ,  133  may, of course, be utilized as well. 
     A preferred surgical technique for suturing the tendon  21  to the humeral head  13  will now be described, with particular reference to FIGS. 1-6 b  and  19 . Initially, the preferred technique proceeds in accordance with conventional arthroscopic techniques for rotator cuff repair, in that access or working ports are positioned in the shoulder in a conventional fashion. An endoscope is inserted through one of the access ports, and, once the endoscope is in place and functional, the rotator cuff tear is observed, and the site is prepared. Site preparation steps include preparing the bone surface by creating a notch or rough surface  47  in the humeral head  13  for accommodation of the detached or torn end  49  of the tendon  21 , and to encourage reattachment to the bone  15 . Then, suturing material  39  is introduced through a working port to the surgical site, and one end or both ends thereof is/are attached to the detached end  49  of the tendon  2   1 . The type of stitch  51  (FIGS. 6,  6   a ,  6   b , and  19 ) which is employed, and the type of suturing instrument, if any, which is utilized to perform the suturing step just described is beyond the scope of the invention. A number of different suturing techniques and devices are well known in the prior art for this type of surgical application, and any one of them could be appropriate. For example, a “mattress” stitch or a “Mason-Allen” stitch could be employed, if desired, and a preloaded suturing instrument for assisting in the suturing step could also be employed, depending upon the surgeon&#39;s preference. 
     Once the tendon  21  has been sutured, a hole  53  (FIGS. 1-6) is strategically created at the greater tuberosity  23  of the humerus  15 . It should be noted, at this juncture, that the inventive method does not require the torn end  49  of the tendon  21  to be sutured prior to the creation of the hole  53 . The hole  53  could just as easily be created first, followed by the aforementioned suturing step. The hole  53  may be created using known techniques. For example, the hole  53  could be created using a drill. At this point, in one preferred method, as illustrated in FIG. 2, a saw  55  having a blade  57 , which may reciprocate, if desired, is introduced axially into the hole  53 , and manipulated so that the blade  57  cuts a slit  59  (FIG. 4) into the bone  15 , extending from the hole  53  to the upper edge of the humeral head  13  (see FIG.  3 ). The saw  55  may be of any known construction. An alternative straight-bladed saw  55   a  is illustrated in FIG. 2 a , for example. The slit  59  is cut deeper into the bone as the saw  57  is advanced further into the hole  53 , by suitable manipulations of the saw, until a distal end  61  of the saw  57  reaches the terminus  63  of the hole  53 . When the slit-forming step is completed, the deep edge of the slit  60  should extend to the edge of the globular head  13  in a direction substantially orthogonal to the orientation of the hole  53 , along the anticipated suture path between the tendon  21  and the anchoring device  25 , as shown in FIGS. 3 and 6, which are cross-sectional views through the slit  59 . 
     The slit  59  extends upwardly all the way to the edge of the globular head  13 , and runs continuously along the surface of the greater tuberosity  23  from the hole  53  to the notch  47 . The open edge of the slit  59  along the greater tuberosity surface is uniquely advantageous, because it permits a convenient, direct passageway through the bone  15  between the detached end  49  of the tendon and the anchoring device  25 , to thereby permit anchoring of the free end of the suturing material  39  (that end which is not sutured to the detached end  49  of the tendon) to the bone  15 , as will be described below. Furthermore, once the tendon  21  is anchored in place, the slit  59  is sufficiently narrow that it quickly heals closed, so that there is no opportunity for the suturing material  39  to migrate out of the slit through the open upper edge. 
     After the slit  59  has been created, the free end or ends of the suturing material  39  is secured to the anchoring device  25  by holding it against the shaft  27  and rotating the shaft several times, thereby wrapping a portion of the length of suturing material  39  around the periphery of the shaft  27 . A preferred approach is to first slide the shaft  27  along the free end of the suturing material  39  so that the material  39  runs through the lumen  37 , as shown in FIG.  7 . Then, as the shaft  27  is rotated, to begin wrapping an additional length of the suturing material externally thereabout, the longitudinal slits  29  permit the distal end  31  of the shaft to be radially compressible responsive to the pressure of the suturing material being wrapped about the distal end, causing the outer walls of the shaft  27  at the distal end  31  to be reduced in diameter sufficiently to engage the suturing material  39  which is passing through the internal lumen  37 . This engagement or clamping effect is useful in helping to prevent the axial migration of the suturing material  39  through the internal lumen  37  over time, further increasing the reliability of the inventive device. 
     After a few turns, but while the length of suturing material  39  extending from the tendon  21  to the anchoring device  25  is still slack, the anchoring device  25  is inserted into the hole  53 , as shown in FIGS. 6 and 6 a . It should be noted that the inventive method is sufficiently broad to permit variation in the order in which these described steps are performed. For example, the anchoring device  25  may be inserted into the hole  53  prior to beginning the wrapping process by rotating the shaft  27 , with the wrapping of the suturing material  39  about the shaft  27  taking place only after the anchoring device  25  has been placed inside the hole  53 . 
     In the preferred method, the anchoring device  25  is advanced sufficiently far into the hole  53  so that the length of suturing material  39  which is not wrapped about the shaft  27  or passing through the lumen  37  runs along the deep edge of the slit  59 , as shown in FIGS. 6 and 6 a . Then, the shaft  27  is rotated through several additional revolutions, wrapping additional loops of suturing material  39  thereabout, until the torn tendon end  49  is drawn snugly against the bone  15 , and the length of suturing material  39  extending through the slit  59  is taut. The inventors have discovered that an additional benefit of the present inventive design is that, as the shaft  27  is rotated within the hole  53 , the portion of suturing material  39  which is wrapped about the shaft  27  acts to “thread” the soft cancellous bone which comprises the internal surface of the hole  53 , thereby providing an additional means for securing the anchoring device  25  within the hole  53 , and preventing unwanted axial migration thereof. 
     When the suturing material  39  has been wrapped sufficiently about the shaft  27  to secure the tendon  21  to the bone  15 , the anti-rotation cap  35  is installed onto the proximal end of the anchoring device  25 , as illustrated in FIGS. 7 and 7 a . As shown, a preferred method for doing this is to slide the cap  35  distally along the length of suturing material  39  which extends proximally from the shaft lumen  37 , until the cap  35  is engaged with the nut  33 ; i.e. slid coaxially thereover. For the FIGS. 7 and 7 a  embodiment, this involves aligning the internally disposed hexagonal surface  36  of the cap  35  with the exterior surface of the hexagonal nut  33 , and then sliding the cap  35  axially onto the hexagonal nut  33 , creating a slight interference fit to prevent disengagement. For the FIG. 9 embodiment, the procedure involves sliding the cap  135  axially over the nut  133 , and allowing the ribbed interior surface of the cap  135  to create an interference fit with the exterior surface of the nut  133 . As illustrated in FIGS. 6 and 6 a , the flange portion  41  of the anti-rotation cap  35  slides axially into the slit  59 , which will ultimately then close around it, retaining it in a fixed position, as the remaining cylindrical portion of the cap  35  slides axially into the hole  53 . 
     Functionally, when the anti-rotational cap  35  and associated flange portion  41  are in position on the anchoring device  25 , as shown in FIGS. 6 and 6 a , the anchoring device  25  is prevented from rotating because of the lodgment of the flange portion  41  in the slit  59 . This prevents the device from being inadvertently “backed out” of the hole  53 , or the suturing material  39  from being inadvertently unwrapped (partially or fully) from its disposition about the shaft  27 , either during the course of the procedure or afterwards. 
     In the preferred embodiment, as discussed above, the flange portion  41  of the anti-rotational cap  35  includes a flap member  43 , which is angularly displaced relative to the plane of the flange member. This flap member  43  functions to engage the bone surrounding the hole  53 , and to thereby assist in preventing undesired axial displacement of the anchoring device  25  proximally out of the hole  53 . In other words, it functions as an anchor to axially hold the shaft  27  in place, once it has been installed to a desired position within the hole  53 . 
     The above described anti-rotation cap  35 ,  135 , as shown in alternative embodiments in FIGS. 7-9, is just one preferred approach for preventing undesired rotation of the anchoring device  25 ,  125  once the device has been inserted into the bone  15 . Many other alternative anti-rotation systems could be employed as well. For example, in FIGS. 14-15, there is shown an alternative embodiment for such an anti-rotation system. In this embodiment, wherein like elements to those in FIGS. 7 and 8 are designated by like reference numerals, increased by  200 , an anti-rotation bar  65  is employed, rather than the anti-rotation cap  35  earlier described. The procedure for inserting the anchoring device  225  into the bone  15  is the same as that for inserting the devices  25  and  125 , except that, after the suturing material  239  has been wrapped about the shaft  227  a sufficient number of revolutions to secure the tendon  21  to the bone  15 , and to ensure that the anchoring device  225  will not inadvertently separate from the suturing material  39 , the anti-rotation bar  65  is installed onto the proximal end of the device  225 . As with the FIG. 7 embodiment, a hexagonal nut  233  is disposed on a proximal end of the shaft  227 . However, in the FIG. 14 embodiment, the nut  233  includes a recess or slot  67  at its proximal end for the purpose of accommodating the anti-rotation bar  65 . To prevent undesired rotation of the shaft  227 , the anti-rotation bar  65  is inserted into the recess  67 , after the device  225  has been inserted into the hole  53 . One end of the anti-rotation bar  65  will be inserted into a portion of the slit  59  as the bar  65  is inserted into the recess  67 , in a manner similar to that by which the flange portion  41  is inserted into the slit  59  in the FIG. 7 embodiment. A second slit or recess, opposed to the first slit  59 , and of sufficient size to accommodate the second end of the bar  65 , may be formed in the bone  15 , either by the prior use of suitable forming equipment, such as a saw, in a manner similar to that by which slit  59  is created, or by forcing, (i.e. pounding) the second end of the bar  65  into the soft cancellous bone  15  surrounding the hole  53 . 
     Functionally, when the anti-rotational bar  65  is in position on the anchoring device  225 , as shown in FIGS. 14 and 15, the anchoring device  225  is prevented from rotating because of the lodgment of the anti-rotation bar  65  in the slit  59 . This prevents the device from being inadvertently “backed out” of the hole  53 , or the suturing material  239  from being inadvertently unwrapped (partially or fully) from its disposition about the shaft  227 , either during the course of the procedure or afterwards. 
     In the preferred embodiment, the anti-rotation bar  65  includes one or more flap members or barbs  243 , each of which are angularly displaced relative to the plane of the anti-rotation bar. These flap members functions to engage the bone surrounding the hole  53 , and to thereby assist in preventing undesired axial displacement of the device  225  proximally out of the hole  53 . 
     Of course, other anti-rotation configurations, including, for example, radially deployable structure which is always present on the shaft  27 ,  127 ,  227 , which will act to rotationally lock the shaft in place may be employed, to the same effect. 
     Many alternative embodiments of the inventive anchoring device may be employed within the scope of the inventive concept. For example, FIGS. 10 a - 10   c , wherein like elements to those shown in FIGS. 1-8 are designated by like reference numerals, increased by  300 , illustrate a modified embodiment of a shaft portion  327  of the anchoring device, wherein the shaft  327  is of an open construction along its midsection, and has a curved configuration as well. The curved configuration of the shaft  327  in some circumstances may assist in equalizing the forces applied on the device  25  once the suturing material  39  has been wrapped about the shaft  327  by ensuring that substantially the entire surrounding internal wall of the hole  53  contacts the wrapped shaft  327  at some point along its length. This may improve the ability of the shaft  327  to resist undesired axial movement once the tendon  21  is properly attached to the bone  15  and the medical procedure is completed. 
     FIGS. 11 a - 11   b  illustrate another alternative embodiment of the inventive device, wherein like elements to those shown in FIGS. 1-8 are designated by like reference numerals, increased by  400 . In this embodiment, the shaft  427  is constructed to have two longitudinal slits  69  (only one is shown—the second slit is diametrically opposed to the visible one) disposed along a midportion thereof, as illustrated, and the outer diameter of the shaft  427  is bowed radially outwardly at a centerpoint  71  of the shaft  427 , relative to its diameter at each end. The slits  69  are substitutes for the slits  29  shown in FIGS. 7 and 8, and differ from slits  29  because their distal ends terminate proximally of the distal end of the shaft  427 . Though not shown, it is noted that the inner diameter of the lumen  437  of the shaft  427  is preferably substantially constant along its entire length. 
     In operation, as the suturing material  39  is wrapped about the shaft  427 , the slits  69  function to permit the diameter of the shaft  427  to be compressed at its centerpoint and adjacent regions on either side thereof, where the outside diameter is bowed outwardly, by the suturing material. Since the inner diameter is constant, this causes the inner diameter at the centerpoint to be compressed so that it is less than the inner diameter near either end of the shaft  427 , thereby causing the interior lumen walls to contact and compress the suturing material passing through the lumen  437  near the axial centerpoint of the shaft  427 . This contact assists in resisting undesirable axial migration of the suturing material through the lumen. 
     FIGS. 12 a  and  12   b  illustrate an embodiment identical to that of FIGS. 11 a  and  11   b , except that in the FIGS. 12 a  and  12   b  embodiment, three slits  69  are employed rather than two. In actuality, any number of slits  69  may be employed to obtain the inventive results which are described above. 
     FIG. 13 illustrates an embodiment similar to that of FIGS. 7 and 8, and for that reason like elements are designated by like reference numerals. The only substantive difference between the two embodiments is that in the FIG. 13 embodiment only one longitudinal slit  29  is employed, instead of two. In actuality, any number of slits  29  may be employed, as long as they function to cause the inner diameter of the shaft  27  to be reduced as a result of compression applied by the wrapped suturing material, thereby cinching the lumen walls down onto the suturing material disposed in the lumen  37  to clamp same in place. 
     FIGS. 16-18 illustrate three different modified embodiments of the shaft of the inventive anchoring device, wherein like elements to those shown in previously described embodiments are designated by like reference numerals, preceded by the numerals  5 ,  6 , and  7 , respectively. FIG. 16 illustrates an embodiment very similar to that of FIG. 13, except for the addition of external threads  73 , disposed on the shaft  527  proximally of the slit  529 . The function of the FIG. 16 embodiment is identical to that of the FIG. 13 embodiment, with a single slit  529 , except that the threads  73  create a threaded engagement with the bone  15  forming the internal walls of the hole  53 , as the shaft  527  is rotated to wrap the suturing material therearound. As described supra, the wrapped suturing material creates a threaded engagement itself with the soft cancellous bone in the humeral head  13 , but the employment of external threads  73  significantly enhances the effect, and provides a further mechanism for resisting unwanted axial pull-out of the anchoring device  25  from the hole  53 . 
     FIG. 17 illustrates an embodiment very similar to that of FIGS. 7 and 8, with two longitudinal slits  629 , except for the addition of external threads  673 , which function in the manner above described with respect to threads  73  in FIG.  16 . 
     FIG. 18 illustrates an embodiment very similar to that of FIGS. 11 a ,  11   b , and  12 , employing one or more longitudinal slits  769  along a central portion of the shaft  727 , and functioning in a manner identical to that described supra in connection with the FIGS. 11 a ,  11   b , and  12  embodiments, except for the addition of external threads  773 . These threads function to create an enhanced threaded engagement with the surrounding bone  15 , as above described. 
     FIGS. 20 a  and  20   b  illustrate embodiments similar to those illustrated in the above described figures, wherein like elements are designated by like reference numerals, preceded by an  8 . Thus, the embodiment shown in FIG. 20 a  functions in a manner essentially identical to that of the embodiment shown in FIGS. 16 or  17 , except that anti-rotational barbs  75  have been added on the circumference of the shaft  827 , in order to provide an additional impediment to undesired rotation of the shaft  827  once it has been inserted into the hole  53  and has been wrapped by the suturing material  39 . FIG. 20 b  also functions in a similar manner, but does not include external threads  873 . In the preferred embodiments, the barbs  75  are disposed on a collar  77 , though other arrangements may be suitable as well. It is noted that, depending upon a number of factors, including the desired application, differing combinations of anti-rotational mechanisms may be employed. FIG. 20 b  represents an embodiment where the external threads  873  shown in FIG. 20 a  are not deemed to be necessary to achieve adequate anti-rotational performance. Either of the embodiments shown in FIG. 20 a  and  20   b  may be employed with or without additional anti-rotational mechanisms, such as those shown in FIGS. 7-9. 
     FIGS. 21 a  and  21   b  illustrate a further modified embodiment, wherein like elements to those of prior described embodiments are denoted by like reference numerals, preceeded by the numeral  9 . This embodiment functions in a manner substantially identical to that of the embodiment of FIGS. 7 and 8, for example, except that in this embodiment the external surface of the shaft  927  has been fabricated to include a spiral groove  79  which extends along the length of the shaft  927  for the purpose of guiding the suturing material  929  as it is wrapped about the shaft. 
     FIGS. 22 a - 22   c  illustrate still another modified embodiment, wherein like elements to those of prior described embodiments are denoted by like reference numerals, preceded by the numeral  10 . In this embodiment, the shaft  1027  is partially open, comprising only a hemispherical section through a portion of its length, as shown in FIGS. 22 a  and  22   b . Thus, as shown particularly in FIG. 22 b , the portion of the suturing material  1039  which lies axially along the open portion of the shaft  1027  is exposed to the outside of the shaft, as opposed to prior described embodiments wherein the suturing material  1039  extending through the shaft lumen is entirely enclosed by the shaft. Functionally, the result is that the outer wrap of suturing material  1039  is in direct contact with the suturing material extending through the center of the shaft, thereby acting to impede undesired axial migration of the suturing material  1039  which extends axially along the shaft  1027 . 
     FIGS. 23 a - 23   c  illustrate yet another modified embodiment, wherein like elements to those of prior described embodiments are denoted by like reference numerals, preceded by the numeral  11 . This embodiment is somewhat similar to that of FIGS. 22 a - 22   c , in that in this embodiment the suturing material  1139  which extends along the center longitudinal axis of the shaft  1127  is also exposed, and the wrapped suturing material  1139  also directly contacts the center-lying suturing material in this embodiment. However, in this embodiment, the shaft  1127  comprises only a flat bar having two bend regions  81  and  83 , respectively, in which are disposed first and second apertures  85  and  87 , respectively. The apertures  85  and  87  function to receive the portion of suturing material which lies axially along the length of the shaft bar  1127 , as shown in FIG. 23 a.    
     FIGS. 24 a  and  24   b  show a further modified embodiment, wherein like elements to those of prior described embodiments are denoted by like reference numerals, preceded by the numeral  12 . In this embodiment, the shaft  1227  is formed of a solid cylindrical biocompatible material. The external surface of the shaft  1227  includes a spiral groove  89 , forming a series of peaks and valleys, over which the suturing material lies. First and second apertures  91  and  93 , respectively, function to receive the suturing material  1239  at both ends of the shaft  1227  which includes the groove  89 , and to channel it axially along the peaks and valleys created by the groove  89 . The effect is to create a tortuous path for the suturing material which increases its resistance to axial slippage. Of course, alternative approaches may be taken to the creation of such a tortuous path along the external surface of the shaft  1227 , without departing from the spirit of the present invention. 
     The inventors have found that the foregoing relatively simple techniques function remarkably better than prior art suture anchoring approaches to minimize the possibility that the anchor will pull out of the bone or that the suturing material will somehow become dislodged from the anchoring device during or after the shoulder repair procedure. Either of these occurrences, of course, jeopardizes the success of the procedure, and may result in the necessity of further repair of the rotator cuff. As shown particularly in FIGS. 5 and 19, in a preferred repair procedure, a plurality of suture anchoring devices  25  are inserted into a corresponding plurality of holes  53 , adjacent to one another in the bone  15 , in order to properly secure the tendon  21  to the bone  15 . Although three adjacent holes  53  and associated anchoring devices  25  are shown, any number of anchoring devices (one or greater), may be employed, depending upon the particular case. If one or more of these anchoring devices were to fail, there is no feasible way to withdraw it from the bone, because of barbs which are disposed on the anchor to prevent its inadvertent withdrawal due to applied axial forces. Thus, it becomes useless, and another hole must be created, for the insertion of a new suture anchoring device. Each extra anchor weakens the bone, and reduces available “real estate” for possible future repair procedures. 
     An important reason for the vastly improved results afforded by the inventive procedure is that the tension placed on the suturing material by the tendon  21  is substantially normal or perpendicular to the axial direction of the anchoring device, so that the applied tension does not act to tend to pull the anchoring device axially out of the hole, as with prior art devices. Another reason is that, rather than merely being knotted to a suture eyelet on the anchoring device, as with many prior art devices, it is wrapped numerous times about the shaft of the anchoring device  25 . This makes release of the suturing material  39  from the anchoring device  25  nearly impossible. In contrast, by anatomical necessity, the available prior art suture anchors are small, and all have a suture eyelet. Because the suture eyelet has a small radius, it concentrates stress on the suture at that point and creates a weak spot on the suture. In the inventive device, in contrast, the suture engagement radius is much larger, and is much less likely to impart stress on the suture. 
     Another important advantage of the present invention is the ability to control the tension on the suture. In existing devices, the tension on the suture is determined by how tightly or loosely the practitioner ties the securing knot on the suture eyelet. In contrast, in the inventive device, the tension is completely adjustable and may even be measured in torque-wrench fashion during the tightening process, if desired. The inventive device  25  has a substantial length of free suturing material wrapped about its shaft, as opposed to the very small length of suturing material which is knotted to the suture eyelet in prior art anchors. The increased length of suturing material  39  wrapped about the anchor shaft  27  of the present invention creates more compliance (slack) in the suturing material, and, thus, a much lower chance of failure. This compliance factor, in combination with the unique feature of the present invention, in that the tension applied to the anchor  25  by the suturing material attached to the tendon  21  is orthogonal to the axis of the anchor, rather than axial, reduces the risk of failure of the inventive anchor substantially. 
     In an alternative procedure, which may be preferred in some operating embodiments where space considerations are different than for rotator cuff procedures, once the tendon  21  has been sutured, and the hole  53  has been created, as described above, a transosseous tunnel  95  (FIG. 4) may be created, rather than a slit  59 . The tunnel traverses the same path as the deep edge of the slit  60 , as shown in FIG. 4, i.e. the anticipated suture path. Then, a suture snare device, such as are well known in the art, may be used to capture the free end of the suturing material  39 , and to draw. it through the transosseous tunnel  95  and into the hole  53 . At the practitioner&#39;s option, the snare may be slid in either direction through the transosseous tunnel to capture the suturing material; i.e. the practitioner may elect either to snare the free end of the suture and then push it through the transosseous tunnel  95  into the hole  53 , or to advance the snare down through the hole  53  and outwardly through the tunnel  95  until its distal end extends from the tunnel. The suture can then be captured with the distal end of the snare, and then pulled back through the tunnel  95  and the hole  53 . Once the suturing material  39  has been captured and extends through the tunnel  95 , the procedure concludes in a manner substantially identical to that of the previously disclosed method, wherein a free end of the suturing material is engaged with the anchoring device  25 , preferably by sliding the device along a length thereof with that length of suturing material extending through the lumen  37 . Then, the shaft is rotated to wrap several loops of suturing material therearound, taking advantage of rope friction effects to help to secure the suture, after which it is dropped into the anchor hole  53 , the wrapping process is completed to snugly secure the tendon  21  to the bone  15 , and the anchoring device is finally secured by one of the aforementioned anti-rotation devices. 
     Some of the advantages of the present invention can be summarized as follows: 
     1) The inventive anchoring device utilizes the principle of rope friction to secure the suturing material to the anchoring device. In other words, the present inventive configuration permits the contacting of the anchor device  25  with a substantial length of the suturing material (the portions either wrapped about the shaft or extending through the shaft lumen, for example), wherein that contact, because of frictional effects, functions to resist the axial migration of the suturing material relative to the anchoring device. Thus, no knots are required; 
     2) The inventive suture anchoring device does not include a suture eyelet. There is no requirement that a suture be passed through a small radius eyelet. Rather, the suture is wrapped around the entire shaft of the anchoring device, thereby increasing the radius of suture engagement with the anchoring device. As a result, in the inventive system, the suture is far less likely to break at the suture-to-anchoring device engagement point than in prior art systems; 
     3) No knots are required to secure the suturing material to the anchoring device. However, as shown in FIG. 6 b , a knot  97  may be tied at the proximal end of the suturing material, if desired, in the inventive system, in order to provide even more assurance that the suturing material and anchoring device will not be separated; 
     4) The tension on the suture can be adjusted and even measured in the inventive system; and 
     5) An open slit may be employed for accommodating the suturing material connection between the bone anchoring device and the tendon  21 , rather than the known transosseous tunnel. 
     Accordingly, although an exemplary embodiment of the invention has been shown and described, it is to be understood that all the terms used herein are descriptive rather than limiting, and that many changes, modifications, and substitutions may be made by one having ordinary skill in the art without departing from the spirit and scope of the invention. In particular, it is noted that, while the procedure described relates to repair of torn rotator cuffs, the methods and devices disclosed are suitable for many other orthopedic application involving the re-attachment of connective tissue to bones.