Abstract:
A fixation device for securing tissue to a bone. The fixation device includes an anchor having a hollow body defining a longitudinal passage, and a plug configured to be received in at least a portion of the passage.

Description:
INTRODUCTION 
     Various methods of attaching tissue, such as sift tissue, grafts or ligaments to bone are known. In anterior cruciate ligament reconstruction (ACL), for example, interference screws can be used to secure the graft against the walls of tunnels drilled in the tibia and the femur. The interference screws are wedged between the graft and a wall of the tunnel. To facilitate insertion and improve anchoring, some interference screws include cutting threads or other anchoring features. 
     SUMMARY 
     The present teachings provide a fixation device for securing tissue to a bone. The fixation device includes an anchor having a hollow body defining a longitudinal passage, and a plug configured to be received in at least a portion of the passage. 
     The present teachings provide a method for securing tissue to a bone. The method includes forming a tunnel in a bone, passing the tissue through the tunnel, providing a cannulated anchor defining a longitudinal passage, inserting the anchor between the tissue and the tunnel, and plugging the longitudinal passage of the cannulated anchor. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating various aspects of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a partially assembled perspective view of a fixation device according to the present teachings; 
         FIG. 2  is a perspective view of an anchor for a fixation device according to the present teachings; 
         FIG. 3  is a perspective view of an anchor for a fixation device according to the present teachings; 
         FIG. 3A  is a cross-sectional view of a cannulated anchor with a plug inserted therein for a fixation device according to the present teachings; 
         FIG. 4  is a perspective view of an anchor for a fixation device according to the present teachings; 
         FIG. 5  is a perspective view of an anchor for a fixation device according to the present teachings; 
         FIG. 6  is a perspective view of a plug for a fixation device according to the present teachings; 
         FIG. 7  is a perspective view of a driver for use with a fixation device according to the present teachings; 
         FIG. 8  is an environmental view of a fixation device according to the present teachings. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For example, although the devices and methods of the invention are illustrated for use in anterior cruciate ligament reconstruction (ACL) in knee surgery, use for securing any soft tissue, hard tissue, bone cartilage, ligament, natural or artificial graft, such as, for example, polylactide (PLA), polyglolide (PGA), polyurethane urea, and other grafts, to a bone is contemplated. 
     Referring to  FIG. 1 , an exemplary fixation device  100  according to the present teachings includes a cannulated anchor  102  and a plug  150  that can be received in the anchor  102 .  FIGS. 2-5  illustrate exemplary anchors  102  and plugs  150 . The cannulated anchor  102  includes a cylindrical portion  106  and a tapered tip portion  104 . The anchor  102  can be threaded. The cylindrical portion  106  can have threads  114  with pitch p 1 , and the tapered tip portion  104  can have threads  110  with pitch p 2 , where p 1  is greater than p 2 . For an exemplary 30 mm long anchor, for example, p 1  can be about 2.2 mm and p 2  about 1.8 mm, although other values can be used for these dimensions. The threads  114 ,  110  of both portions  106 ,  104  can have “blunt” edges that are herein defined as non-cutting edges  108 . The small pitch p 1  of the tapered tip portion  104  facilitates the insertion of the anchor  102  using only non-cutting edges  108  and avoiding the need for sharp or cutting edges. 
     Referring to  FIG. 8 , the shape of the tapered tip portion  104  together with the smaller pitch threads  110  facilitates the insertion of the anchor  102  into a bone tunnel  62  to wedge a ligament or graft  70  against the wall of the tunnel  62  by pushing apart, without cutting into, surrounding tissues. The threads  114  of the cylindrical portion  106  also push apart, without cutting into, surrounding tissue, and being of different pitch p 1  that is greater than the pitch p 2  of the threads  110  of the tapered tip portion  104 , do not follow any paths that may be opened by the pushing apart action of the threads  110  of the tapered tip portion  104 . The anchor  102  can be made any biocompatible material, including metal, such as titanium, for example. The anchor  102  can also be made of bioabsorbable material, such as Lactosorb® from Biomet, Inc., Warsaw, Ind., for example. 
     Referring to  FIGS. 3 ,  5  and  6 , the cannulated body of the anchor  102  defines a longitudinal passage  115  that extends throughout the entire body of the anchor  102  along a longitudinal center axis “A”. A plug-receiving portion  116  of the longitudinal passage  115  extends along the cylindrical portion  106  of the anchor and can have an enlarged opening of a shape such as a cruciate shape defined by four longitudinal ribs  118 , or any other shape, such as a fingered shape, a hexagonal, pentagonal, triangular or other polygonal shape. The plug  150  has a shape that is complementary to the shape of the plug-receiving portion  116 . For example, for the cruciate shape the plug  150  can have grooves  152  shaped for mating with the ribs  118  when the plug  150  is inserted into the passage  115 . The plug  150  can be made of osteoinductive and/or osteoconductive material to promote bone growth through the anchor  102 . The material of the plug  150  can be, for example, calcium phosphate, calcium sulfate, tricalcium phosphate, allograft bone, autograft bone, combinations thereof, etc. The plug  150  can be cannulated. 
     Referring to  FIGS. 4 and 5 , the cylindrical portion  106  of the anchor can be solid, without any apertures. Referring to  FIGS. 2 and 3 , the outer surface of the cylindrical portion  106  of the anchor  102  between the threads  114  can also include apertures  112 . The apertures  112  can be formed, for example, by cutting through from the inside to the outside the outer surface  130  of the anchor  102  between the threads  114 , using a cutting instrument that can be received in the anchor  102 , although other cutting methods can also be used. The apertures  112  are, therefore, confined in the direction of the longitudinal axis A between adjacent threads  114  of the cylindrical portion  106 . The apertures  112  extend substantially parallel to the threads  114  in the regions between adjacent ribs  118 . The size of the apertures  112  can be selected to occupy only a portion of the outer surface  130  between the threads  114 , as illustrated in  FIG. 2 . 
     Referring to  FIG. 3 , the size of the apertures  112  can also be selected to occupy the entire portion of the outer surface  130  between the threads  114  and the ribs  118 . In this respect, the structural integrity of the cylindrical portion  106  of the anchor  102  is provided by the threads  114  and the ribs  118 , with no material therebetween. The apertures  112  facilitate bone ingrowth or outgrowth through the anchor  102  and can also be used to distribute a biologic material, including osteoinductive/osteoconductive material, such as calcium phosphate, platelet concentrates, fibrin, etc., which may be injected through the passage  115 . The plug  150 , in addition to providing bone growth promoting benefits, closes the longitudinal passage  115  and can prevent such material from draining out. 
     Referring to  FIG. 3A , the outer surface  154  of the plug  150  is shaped to extend outward beyond a minor diameter “d” defined by the ribs  118 . The outer surface  154  of the plug mates with interior surface  117  of the anchor  102  at a major diameter “D” at which the apertures  112  are formed, such that portions of the plug  150  can contact tissue through the apertures  112  when the anchor  102  is implanted, thereby promoting tissue growth and better tissue attachment. 
     Referring to  FIG. 7 , a driver  160  can be used to rotate the anchor  102  and facilitate its insertion. The driver  160  includes a handle portion  164  and a suitably shaped portion  162  for engaging the plug-receiving portion  116  of the passage  115  of the anchor  102 . Alternatively, the plug  150  can be pre-inserted into the anchor  102  and the driver  160  can engage the cannulated plug  150 . The driver  160  can also be cannulated. The driver  160  can have a cruciate shape or any other shape that can engage the plug-receiving portion  116 . 
     Referring to  FIG. 8 , an exemplary, but not limiting, use of the fixation device  100  is illustrated in the context of arthroscopic knee surgery. A ligament or graft  70  passes through a tibial tunnel  52  and a femoral tunnel  62  and is fixed in the tibia  50  and femur  60  with sutures  72 . The fixation device  100  can be implanted in the tibial tunnel  52  or in the femoral tunnel  62 , or two fixation devices  100  can be implanted, one in each tunnel  52 ,  62 . A guide wire  170  is inserted between the wall of tibial tunnel  52 /femoral tunnel  62  and the graft  170  to guide the anchor  102  of the fixation device  100 , as needed. The anchor  102  is passed over the guide wire  170  and wedged between the graft  170  and the tibial tunnel  52 /femoral tunnel  62  by rotation using the cannulated driver  160 . The guide wire  170  is then removed. The passage  115  is then closed by inserting the plug  150 . 
     Osteoinductive/conductive material can be optionally injected through the passage  115  of the anchor  102  using, for example, the cannulated driver  160 , a syringe, a pump or other suitable delivery device before inserting the plug  150 . 
     While particular embodiments have been described in the specification and illustrated in the drawings, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention as defined in the claims. In addition, many modifications may be made to adapt a particular situation or material to the present teachings without departing from the essential scope thereof. Therefore, it is intended that the present teachings are not be limited to the particular embodiments illustrated by the drawings and described in the specification, but that the present teachings will include any embodiments falling within the foregoing description and the appended claims.