Abstract:
A suture anchor extension for converting a non-fully threaded base suture anchor to a fully threaded suture anchor. The extension comprises a hollow tubular sleeve adapted to be axially aligned with and attached to the base suture anchor. One end of the sleeve engages the non-circular drive member on the base suture anchor and the other end engages a driver for turning the extension and base anchor into tissue at the work site. Suture attached to the base anchor is directed through the interior of the sleeve and, during installation, through the cannulation of the driver.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to suture anchors for re-attaching soft tissue to bone or other tissue. More particularly, the invention relates to screw-in suture anchors and devices for enhancing the strength of the attachment of the suture anchors to bone or other tissue. 
       DESCRIPTION OF THE PRIOR ART 
       [0002]    Suture anchors are commonly used to attach soft tissue to bone or other tissue during either open or closed surgical procedures. Suture anchors come in a variety of configurations including threaded or screw-in anchors which may be directly screwed into bone at the surgical site or screwed into a pre-formed (and, optionally, tapped) hole made in the bone. Certain suture anchors may be inserted into a pre-formed bone hole and then deployed to actually engage the wall of the bone hole. Suture anchors also come in a push-in configuration in which the anchor may be pushed into a pre-formed hole. All suture anchors serve as an anchor point for suture or suture-like material to attach soft tissue to the anchor and hold it near the bone or other tissue during the healing process. 
         [0003]    One prior art suture anchor comprises an elongated, somewhat tapered body having a threaded outer surface, a tapered point at its distal end and an axially aligned drive portion at its proximal end. The drive portion is non-circular (e.g., hexagonal) and is designed to be engaged by a driver having a complementarily shaped non-circular, axially aligned recess to engage the drive portion to rotate the anchor relative to its axis in order to position it at the surgical site. This type of anchor is turned into the bone sufficiently so that the drive portion is recessed under the surface of the bone to avoid any abrasion of the re-attached soft tissue by the anchor. An eyelet or other suture attachment point is formed in the suture anchor, often transversely through the drive portion. While this structure is suitable for use as a suture anchor in bone and in tissue other than bone, a suture anchor has recently been developed primarily for use in bone. This anchor includes a thread along the entire length of its outer surface. This type of so-called fully threaded structure enables the thread at the proximal end of the suture anchor to engage the cortical layer of bone and thereby achieve a greater pull-out force. 
         [0004]    The manufacture of such fully threaded suture anchor is somewhat compromised in view of the need to provide some attachment mechanism for sutures to be retained by the suture anchor. Accordingly, it is an object of this invention to produce a suture anchor assembly combining the advantages of fully threaded prior art suture anchors with the advantages of eyelet-bearing suture anchors. 
         [0005]    It is another object of this invention to provide a device which is easily adaptable to a variety of thread configurations so that a fully threaded suture anchor assembly may be constructed for a variety of applications. 
         [0006]    It is another object of this invention to provide a device which can be easily assembled with a prior art non-fully threaded suture anchor in order to produce a fully threaded suture anchor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a front perspective, expanded view of the preferred embodiment of a suture anchor assembly, including a base suture anchor, suture anchor extension and a driver, constructed in accordance with the principles of this invention. 
           [0008]      FIG. 2  is a side elevation view of the components of  FIG. 1  assembled together. 
           [0009]      FIG. 3  is side elevation view, partially in cross-section, of  FIG. 1  in an assembled configuration. 
           [0010]      FIG. 4  is a front perspective view of the distal end of the driver shown in  FIG. 1 . 
           [0011]      FIG. 5  is a cross-sectional view of  FIG. 2  taken along the line  5 - 5 . 
           [0012]      FIG. 6  is a cross-sectional view of  FIG. 2  taken along the line  6 - 6 . 
           [0013]      FIG. 7  is a front perspective view of an alternate embodiment of a suture anchor driver. 
           [0014]      FIG. 8  is a side elevation view, partially in cross-section, of the driver of  FIG. 7  assembled with a suture anchor of  FIG. 1  and an alternate embodiment of a suture anchor extension. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0015]    As shown in  FIG. 1 , the invention is a suture anchor extension  10  which is attachable to an existing eyelet-bearing suture anchor  12  to thereby create a fully threaded suture anchor. The suture anchor  12 , sometimes herein called the base suture anchor, comprises an eyelet  14  through which one or more strands of suture  16  pass in a conventional manner. Anchor  12  comprises a body  20  having a point  22  at its distal end  24  and a non-circular driven member  26  at its proximal end  28 . The outer surface of body  20  is provided with a thread  30  along its length although the proximal end of the thread  30  ends at a point  32  just distal to driven member  26 . This enables driven member  26  to be engaged by the driving member of a driver during normal use of anchor  12  if it were to be used without the suture anchor extension. 
         [0016]    Suture anchor extension  10  comprises a tubular body  32  having an outer cylindrical surface  34 , a thread  36  extending along the entire length of the outer surface, and an inner surface  38  surrounding a hollow interior  40 . Inner surface  38  is provided with a non-circular driving member  42  at the distal end  44  of extension  10  and a non-circular driven member  46  at proximal end  48 . Driving member  42  is adapted to engage driven member  26  and driven member  46  is adapted to be engaged by non-circular driving member  50  formed at the distal end of cannulated driver  52 . The axially aligned lumens  54  and  56  of extension  10  and driver  52 , respectively, receive sutures  16  when the base anchor, extension and driver are assembled. The sutures pass through the cannulated driver and are secured to a cleat on the handle (not shown). 
         [0017]    Suture anchor extension  10  may be made in a variety of sizes and shapes in order to mate with any selected non-fully threaded base suture anchor. The mating of the two pieces, i.e. the anchor and the extension, produces a new fully threaded suture anchor as best seen in  FIG. 2 . In a preferred embodiment the extension thread  36  is designed with the same pitch and size as the anchor thread  30 . If the anchor assembly (i.e. extension  10  plus anchor  12 ) is inserted into a bone hole, the proximal end  48  of extension  10  will be flush with the bone surface (not shown). Also, the thread  36  will engage cortical bone lying near the bone surface. It will be understood that extension  10  and anchor  12  may be positioned rotationally about their common axes so that the threads  36  and  30  form essentially one continuous, unbroken thread. This may be accomplished by, for example, starting the distal end of thread  36  at a predetermined circumferential point relative to the hexagonal driving member  42  so that when drive members  42  and  26  become engaged the threads  36  and  30  will be automatically aligned. However, alignment is not essential. 
         [0018]    The term “drive member” as used herein can refer to either a driving member or a driven member. It will be understood that a driving member is the one providing the force to rotate an element and a driven member is the one receiving the force. In the configuration of the preferred embodiment the extension  10  has a driven member  46  at its proximal end and a driving member  42  at its distal end. 
         [0019]    In the preferred embodiment, suture anchor extension  10  is axially aligned with and attached to or placed on anchor  12  after suture  16  is threaded through eyelet  14 , as best seen in  FIG. 2  (with suture  16  removed for clarity). This requires the suture to be drawn through the interior  40  of extension  10  and through the axial cannulations  56  of driver  52 , as best seen in  FIG. 3 . Once the suture is so situated, the extension  10  may be placed on anchor  12  by engaging drive member  42  with drive member  26 , and driver  52  may be placed on extension  10  by engaging drive member  50  with drive member  46 . 
         [0020]    Extension  10  may be attached to anchor  12  via a press- or friction-fit or may be bonded, welded, ultrasonically welded or otherwise secured. Alternatively, extension  10  may be loosely placed on anchor  12  since the interaction between the tissue being attached, sutures  16  and anchor  12  will tend to hold the extension and base anchor together. It will be understood that the extension and base anchor may both be made out of the same biocompatible material or of different materials. One may be bioabsorbable and the other not. One may be a polymeric composite material including bone growth inducting/conducting material and the other may be simply bioabsorbable or not. Any variety of combinations is possible. 
         [0021]    The interior  40  of extension  10  may be formed in a variety of shapes to accommodate the anchor  12  and driver  50  with which the extension is intended to be used. In the embodiment shown in  FIGS. 1-3 , drive member  26  has a male hexagonal drive portion with an axial length L 1 , and an eyelet portion with an axial length L 2 . Consequently, to engage male drive member  26 , female drive member  42  preferably has a hexagonal profile with an axial length equal to or greater than L 1 . The male drive member  50  is adapted to fit into female drive member  46  and abut the proximal end of drive member  26 . 
         [0022]    In the preferred embodiment the outer diameter of extension  10  may be uniform along its length, and approximately equal to the greatest outer diameter of anchor  12 , or may be tapered outwardly from distal end  44  to proximal end  48 . The proximal and distal ends of extension  10  preferably abut the driver and base anchor, respectively, to facilitate installation and use of the extension. 
         [0023]    In an alternate embodiment of the invention the thread  60  on the extension  61  can have a different pitch than thread  62  on the base suture anchor  64 , as shown in  FIG. 8 . In this embodiment the screw pitch of the extension would be optimized for cortical bone engagement whereas that of the base anchor is optimized for cancellous bone engagement. 
         [0024]    Also shown in  FIGS. 7 and 8  is a configuration in which driver  70  is provided with a driving member  72  having a non-circular drive surface  76  facing inwardly and a non-circular drive surface  78  facing outwardly. Drive surface  76  is adapted to engage drive member  26  of the base anchor  64  while drive surface  78  is adapted to engage a complementarily shaped drive surface  80  on the interior of extension  61 . 
         [0025]    The dimensions of the various components are selected based upon the degree to which the pieces are to be secured together. Also, the relative sizes of the driving and driven members may vary as a function of the materials from which the components are made. For example, the surface area of a non-metallic driven member may need to be larger than if the driven member was made of metallic material. 
         [0026]    It will be understood by those skilled in the art that numerous improvements and modifications may be made to the preferred embodiment of the invention disclosed herein without departing from the spirit and scope thereof.