Patent Document

CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of U.S. patent application Ser. No. 12/909,355, entitled KNOTLESS SUTURE ANCHOR, filed Oct. 21, 2010, which is incorporated herein by reference. 
    
    
     BACKGROUND 
     The present application relates to suture anchors and more particularly to a knotless suture anchor. 
     Suture anchors have wide use in surgery particularly for reattaching soft tissue to bone. It is preferred to perform most of these surgeries endoscopically. While working through a long narrow endoscope knot tying takes on added difficulty. Accordingly it is frequently preferred to employ a suture anchor which can capture the suture without the need of the surgeon having to tie a knot. It is also preferred that while capturing the suture to lock it to the anchor that the anchor not disturb the tension on the suture. Typically the soft tissue is carefully positioned just prior to locking the suture and if the act of locking the suture causes it to move it can affect the position of the soft tissue. 
     SUMMARY OF THE INVENTION 
     A suture anchor according to the present invention comprises an outer body having a distal end a proximal end and an axial bore therethrough. An inner body is receivable within the outer body. A suture limb is captured between the inner body and the outer body by being wrapped around the inner body. 
     Preferably, the inner body and the outer body are formed of a bioabsorbable material, as for example a material comprising PLGA. 
     Preferably, the inner body and outer body are threaded together. 
     Preferably, the suture anchor is configured such that as the inner body is moved toward the proximal end of the outer body the proximal end of the outer body expands outwardly radially. 
     Preferably, the suture limb is wrapped around the inner body at least two times. Enhanced holding is provided when the suture limb is wrapped around the inner body at least five times. 
     Preferably, the inner body comprises at least one tab extending outwardly radially whereby to effect wrapping of the suture about the inner body upon rotation of the inner body. 
     Preferably, the inner body has a distal end and a proximal end and wherein the inner body proximal has outer threads which mate with inner threads on the proximal end of the outer body. Preferably, an inserter is provided having a distal end which mates with the proximal end of the inner body and which has outer inserter threads engageable with the inner threads on the outer body. Preferably, the outer body has a first configuration in which at least a portion thereof is radially contracted inwardly and a second configuration in which the portion is radially expanded outwardly, and wherein when the outer inserter threads are engaged into the outer body inner threads it holds the portion in the second configuration. Similarly, when the outer threads on the inner body are engaged into the outer body inner threads it holds the portion in the second configuration. Preferably, a naturally relaxed position of the portion is in the second configuration. Thus, when the outer body is expanded into the bone internal stresses on the outer body are minimized. 
     In one aspect of the invention, the suture limb passes into a space formed between the inner body and the outer body at their proximal ends, passes out of the space at their distal ends and then passes proximally along an outer surface of the outer body. 
     Preferably, the outer body has at its proximal end at least one axially extending slit therein whereby to relieve stresses upon radially outward expansion of the outer body proximal end. 
     In one aspect of the invention, at least one more suture limb is captured between the inner body and the outer body or perhaps at least three more suture limbs captured between the inner body and the outer body. 
     A method according to the present invention provides for attaching tissue to a bone. It comprises the steps of: passing a limb of suture from the tissue between a suture anchor outer body, which has a distal end a proximal end and an axial bore therethrough, and an inner body receivable within the outer body; inserting the outer body into the bone; sliding the suture between the inner body and the outer body to achieve a desired tension thereon or desired position of the tissue; capturing the suture limb between the inner body and the outer body, by wrapping at least a segment of the suture limb about the inner body, to prevent sliding of the suture limb therebetween. 
     Preferably, the distance between the tissue and the anchor stays substantially the same during the step of capturing. 
     Preferably, the suture limb is wrapped around the inner body at least two times. 
     Preferably, the inner body has at least one radially extending projection and the step of wrapping comprises rotating the inner body within the outer body during which the projection engages the suture limb to cause it to wrap about the inner body. 
     Preferably, the method further comprises the step of radially expanding at least a portion of the outer body to engage the suture anchor into the bone. For instance when a proximal end of the inner body has outer threads and the proximal end of the outer body has mating inner threads then the step of radially expanding can comprise engaging the inner body outer threads with the outer body inner threads. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective cut-away view of a suture anchor according to the present invention; 
         FIG. 2  is a perspective view of the suture anchor of  FIG. 1 ; 
         FIG. 3  is a perspective view of the suture anchor of  FIG. 1  pre-loaded with a suture capture device; 
         FIG. 4  is a side elevation view in cut-away of soft tissue and associated bone showing initial insertion of the suture anchor of  FIG. 1 ; 
         FIG. 5 . is a side elevation view in cut away of the soft tissue and bone of  FIG. 4  showing free ends of a suture between the soft tissue and the anchor being pulled to tension the suture and position the soft tissue; 
         FIG. 6  is a side elevation view in cut away of the soft tissue and bone of  FIG. 4  showing the anchor being actuated to lock the suture to the anchor and the anchor to the bone; 
         FIG. 7  is a side elevation view in cut away of the soft tissue and bone of  FIG. 4  showing the anchor fully deployed; 
         FIG. 8  is a side elevation view in cut away of the soft tissue and bone of  FIG. 4  showing the anchor in partial cut-away in its fully deployed position; 
         FIG. 9  is a perspective view of a further embodiment of a suture anchor according to the present invention; 
         FIG. 10  is a perspective cut-away view of the suture anchor of  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  depicts a suture anchor  10  according to the present invention. It comprises in gross an inner body  12  having a distal end  14  and proximal end  16  and a cannulated outer body  18  having a distal end  20 , proximal end  22  and a cannulation  24  therethrough. Towards the outer body proximal end  22  the cannulation  24  bears internal threads  26  which decrease in internal diameter at the proximal end  22 . On its exterior surface  28  the outer body  18  bears barb shaped annular flanges  30  to assist in bone fixation. 
     The inner body  12  has an annular flange  32  at its distal end  14  with a groove  34  therethrough passing over the distal end  14 . At its proximal end  16  the inner body  12  has exterior threads  36  which mate with the inner body threads  26 . A pair of radially extending projections  38  extend from the inner body  12  toward the outer body  18  at its distal end  20 . The tolerance between the projections  38  and the outer body  18  should be close enough to prevent suture  39  from passing therebetween. 
     A tool receiving recess  40  on the inner body proximal end  16  mates with a driver head  42  (such as for instance a hex driver) on a distal end of a driver  44 . Just proximal thereof on the driver  44  are threads  46  which mate with the threads  26  on the outer body  18 . The threads  46  have a reduced major diameter at a proximal portion  48  which in its starting configuration as shown in  FIG. 1  sits adjacent the decreased internal diameter of the outer body thread  26  at their proximal end  22 . The driver  44  operates within a tube  50  having a distal end  52  abutting the outer body proximal end  22  with distally projecting tangs  53  extending into slots  54  in the outer body proximal end. This interface assists in maintaining the position of the anchor  10  as it is employed, by resisting both rotation and proximal withdrawal thereof. 
     Turning also now to  FIG. 2 , two or more of the stress relief slots  54  extend axially into the outer body  18  from its proximal end  22 . This allows the proximal end to be made from somewhat brittle materials yet still be able to expand outwardly radially to provide fixation. Both the inner body  12  and outer body  18  are preferably formed of a bioabsorbable material such as BIOCRYL RAPIDE available from DePuy Mitek, Inc. of Raynham, Mass. BIOCRYL RAPIDE is a bioabsorbable polymer formed of homogenous blend of TriCalcium Phosphate (TCP) and Polylactic/polyglycolic Acid (PLGA). Other suitable materials include without limitation PEEK, PLA, titanium, stainless steel, metals, polymers and other biocompatible materials. 
     Turning also now to  FIGS. 3 to 7 , use of the suture anchor  10  will be described. The anchor  10  is sterile and packaged in bacteria proof packaging (not shown) pre-loaded onto the driver  44  and pre-loaded with a suture capture device  56  comprising an elongated filament  58  having a suture capture loop  60  at one end. One example is the CHIA PERCPASSER available from DePuy Mitek, Inc. of Raynham, Mass. The loop  60  in  FIG. 3  is shown adjacent the anchor  10  for ease of display but in practice sufficient length of the filament  58  would extend from the anchor  10  to allow suture  39  to be pulled out of a cannula (not shown) through which the procedure is being endoscopically performed. 
     The suture  39  would be loaded into the suture capture loop  60  exterior of the patient and the cannula. A tab  62  may be placed on an opposite end of the filament  58 . (This is also shown adjacent the anchor  10  for ease of display but would more conveniently be positioned outside of the cannula.) When the tab is pulled the loop  60  with the suture  39  captured therein is drawn down between the inner body  12  and outer body  18  pulling the suture  39  with it. The path of the suture  39  after passing between the inner body  12  and outer body  18  goes through the groove  34  to assist in sliding. Additional sutures can also be employed, such as additional suture loops in the suture capture loop  60  or addition suture loops each with their own suture capture device. 
     The anchor  10  with the suture  39  therein is now inserted into a pre-drilled hole  64  in a bone  66  to which a piece of soft tissue  68  is to be attached as shown in  FIG. 4 . The anchor  10  is positioned in the hole  64  such that the suture passes into the anchor  10  at one of the stress relief slots  54 . The suture  39  is shown looped through the soft tissue  68  but other arrangements are possible such as extending from another anchor (not shown and typically of a different configuration than anchor  10 ) which is positioned in the bone  66  below the soft tissue  68  and up through the soft tissue  68  to the anchor  10 , such as in a dual row rotator cuff repair. Also, the path from the soft tissue  68  through the anchor  10  could be reversed. 
     Free ends  70  of the suture  39  are drawn through the anchor  10  to position the soft tissue  68  and properly tension the suture  39  (see  FIG. 5 ). The tube  50  of the driver  44  holds the anchor  10  down and prevents rotation of the outer body  18  while the driver  44  is rotated to rotate the inner body  18  (see  FIG. 6 ). As the threads  46  of the driver  44  pass through the reduced inner diameter proximal portion  22  of the outer body  18  it causes it to expand outwardly radially to engage the bone  66  and reduces the stress on the inner body  18 . Preferably, the relaxed condition of the outer body  18  is slightly expanded radially and as it is inserted into the hole  64  it is compressed slightly inwardly; the expansion by the threads  46  move it back to its relaxed configuration thus reducing internal stress. As the rotation continues the threads  36  of the inner body move into the reduced inner diameter proximal portion  22  to keep the outer body proximal end  22  radially expanded. The projections  38  on the inner body  12  cause the suture  39  to wrap around the inner body  12 . The suture  39  feeds in from the free ends  70 , not from the soft tissue  68  so that the position of the soft tissue  68  and the tension on the suture  39  between the anchor  10  and the soft tissue  68  remains substantially unchanged as the inner body  12  is rotated. After sufficient rotation the driver  44  is disengaged from the anchor  10  and removed leaving the suture  39  locked to the anchor  10  by virtue of its being wrapped around the inner body  12  and the outer body proximal end  22  is expanded outwardly into the bone  66  to lock the anchor  10  thereto (see  FIGS. 7 and 8 ). Tests have shown three to five turns providing good locking of the suture  39 . 
       FIGS. 9 and 10  illustrate a further preferred embodiment of the invention which is essentially similar to that depicted in  FIGS. 1 and 2 . Like parts are denoted with like numerals with the addition of a prime symbol (′). It comprises a suture anchor  10 ′ having an inner body  12 ′ and cannulated outer body  18 ′ having a short internal thread  24 ′. The inner body  12 ′ has an annular flange  32 ′ at its distal end  14 ′ with a groove  34 ′. It also carries radially extending projections  38 ′.  FIG. 9  especially more clearly illustrates how a driver receiving tube  50 ′ abuts a proximal end  22 ′ of the outer body  18 ′ with distally projecting tangs  53 ′ extending into stress relief slots  54 ′. A loop of suture  39 ′ has free ends which pass into the outer body  18 ′ from its proximal end  22 ′, preferably through one of the stress relief slots  54 ′, passes down between the inner body  12 ′ and outer body  18 ′ and between the projections  38 ′, out of the outer body  18 ′ through its distal end  20 ′, through the groove  34 ′ on the inner body  12 ′ at its distal end  14 ′ and then back into the outer body  18 ′ between it and the inner body  12 ′ and also again between the projections  38 ″ and finally exit through the opposing stress relief slot  54 ′. This embodiment is used similarly to the previous one. However, the groove  34 ′ assists in wrapping the suture  39 ′ around the inner body  12 ′ and one could even dispense with the projections  38 ′ due to the wrapping action provided by the groove  34 ′. 
     Various modifications and alterations of this invention will be apparent to those skilled in the art without departing from the scope and spirit of this invention. It should be understood that the invention is not limited to the embodiments disclosed herein, and that the claims should be interpreted as broadly as the prior art allows.

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