Abstract:
A device and method for fastening one or more graft strands to a bone. The device may include a first member having a first opening and a second member having a second opening. The first member may include a plurality of radial projections defining recesses, wherein each graft is separately received in a corresponding recess. The device may also include a fastener passing through the first and second openings. The fastener may have a first portion engaging the first member and a second portion received into the bone, such that tightening the fastener against the first member compresses the graft strands between opposing faces of the first and second members.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    Ligaments are strong fibrous soft tissue connecting the articular ends of bones to bind them together and to facilitate or limit motion. Injuries to ligaments are common, and patients who are physically active are generally more susceptible to such ligament injuries. The anterior cruciate ligament (ACL) of the knee joint is a ligament frequently injured by such patients. ACL injuries cause instability in the knee joint which, when left untreated, may lead to degenerative arthritis. Because of this condition, ACL reconstruction may be required. Generally during ACL reconstruction, a substitute soft tissue ligament or graft is attached to the femur (femoral fixation) and/or to the tibia (tibial fixation) to facilitate regrowth and permanent attachment.  
           [0002]    There are several known methods for performing ACL reconstruction, and there are also several tibial or femoral fixation devices that may be used with these methods, some of which are reviewed in U.S. Pat. No. 6,482,232. Nevertheless, new methods and devices that reduce soft tissue damage, are easy to install, prevent slippage of the graft, promote healing and increase strength are still needed.  
         SUMMARY  
         [0003]    One embodiment of the invention provides a device for fastening one or more graft strands to a bone. The device may include a first member having a first opening and a second member having a second opening. The first member may include a plurality of radial projections defining recesses, and each graft may be separately received in a corresponding recess. The device may also include a fastener passing through the first and second openings. The fastener may have a first portion engaging the first member and a second portion received into the bone, such that tightening the fastener against the first member compresses the graft strands between opposing faces of the first and second members. Moreover, while the present invention is discussed in detail in relation to ACL reconstruction, it will be understood that the invention may be used to secure any type of soft tissue.  
           [0004]    Another embodiment of the invention provides a device for fastening one or more graft strands to a bone and may includes an annular member that has a central opening, and a fastener that may have a head and a body. The annular member includes a plurality of radial projections defining recesses, such that each graft may be separately received in a corresponding recess. The body of the fastener may pass through the central opening of the annular member. The body may have a first portion engaging the annular member and a second portion received into the bone, such that tightening the fastener against the annular member compresses the graft strands between opposing faces of the annular member and the head of the fastener.  
           [0005]    Another embodiment of the invention provides a method for fastening a plurality of graft strands to a tunnel in a bone. The method may include pulling the graft strands through the tunnel and into a central opening of a first member, and inserting the graft strands into corresponding recesses radiating from the central opening. The method may include inserting a fastener through the first member and into the tunnel, and compressing the graft strands between the first member and the fastener.  
           [0006]    Another embodiment of the invention provides another method for fastening a plurality of graft strands to a bone. The method may include drilling a bore for a fastener into the bone, drilling a counter bore for receiving first and second members into the bone and pulling the graft strands through a first opening in the first member and into corresponding radial recesses that extend from the first opening. The method may also include inserting the fastener through a second opening of the second member into the bore, engaging a threaded portion of the fastener with a portion of the first member, and compressing the graft strands between the first and second members. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    In the accompanying Figures, there are shown present embodiments of the invention, wherein like reference numerals are employed to designate like parts and wherein:  
         [0008]    [0008]FIG. 1 is a diagram of a knee prepared for ACL reconstruction according to an embodiment of the fixation device of the present invention;  
         [0009]    [0009]FIG. 2 is a perspective view of an embodiment of the fixation device of the present invention;  
         [0010]    [0010]FIG. 3 is a side view of an embodiment of a fastener of the fixation device of the present invention;  
         [0011]    [0011]FIG. 4 is a top view of an embodiment of a first member of the fixation device of the present invention;  
         [0012]    [0012]FIG. 5 is a sectional view of the first member taken along line  5 - 5  of FIG. 4;  
         [0013]    [0013]FIG. 6 a top view of an embodiment of a second member for the fixation device of the present invention;  
         [0014]    [0014]FIG. 7 is sectional view of the second member taken along line  7 - 7  of FIG. 6;  
         [0015]    FIGS.  8 ( a )-( h ) are diagrams of side profiles of various embodiments of the first member of the fixation device of the present invention;  
         [0016]    [0016]FIG. 9 is a top view of an embodiment of the first member of the fixation device of the present invention;  
         [0017]    [0017]FIG. 10 is a perspective elevated view of an embodiment of the first member of the fixation device of the present invention;  
         [0018]    [0018]FIG. 11 is a perspective view of an embodiment of the first member of the fixation device of the present invention;  
         [0019]    [0019]FIG. 12 is a perspective view of an embodiment of the first member of the fixation device of the present invention;  
         [0020]    [0020]FIG. 13 is a perspective view of an embodiment of the second member of the fixation device of the present invention;  
         [0021]    [0021]FIG. 14 is a side view of an embodiment of the fastener of the fixation device of the present invention;  
         [0022]    [0022]FIG. 15 is a perspective view of an embodiment of the fastener of the fixation device of the present invention; and  
         [0023]    [0023]FIG. 16 is a perspective view of an embodiment of the fastener of the fixation device of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]    Referring now to the drawings for the purpose of illustrating the invention and not for the purpose of limiting the same, it is to be understood that standard components or features that are within the purview of an artisan of ordinary skill and do not contribute to the understanding of the various embodiments of the invention are omitted from the drawings to enhance clarity. In addition, it will be appreciated that the characterizations of various components and orientations described herein as being “vertical” or “horizontal”, “right” or “left”, “upper”, “lower”, “distal”, “proximal”, “top” or “bottom”, are relative characterizations only based upon the particular position or orientation of a given component for a particular application.  
         [0025]    [0025]FIG. 1 is a simplified view of a knee prepared for ACL reconstruction and tibial fixation according to an embodiment of the present invention. A ligament or graft  50  extends from a femoral bone  52  and passes through a tunnel  54  that is bored into a tibial bone  56 . The graft  50  may be bundled into several separate graft strands  58 , such as four, for example. One example of a representative procedure to prepare the bore is set forth in U.S. Pat. No. 5,931,869, the entire contents of which are incorporated herein by reference. The graft  50  may be a natural graft harvested from the patient or from a donor using techniques that are known in the art. The graft  50  may also be synthetic, made from a polymer or other biocompatible material.  
         [0026]    [0026]FIG. 2 shows an embodiment of a fixation device or implant  100  that may be used to fasten the graft strands  58  into the tibial tunnel  54  during an ACL or similar procedure. The fixation device  100  may include a first member  102 , a second member  104  and a fastener  106 . The fastener  106  may include a body  108  having a first portion  110 , which may be threaded or include concentric locking ribs  127 , as shown in FIG. 16, and a second portion  112 , which may also be threaded, or may be blank and act as a plug in the tunnel  54 . In the embodiment shown in FIGS. 14 and 15, the second portion  112  of the fastener may be cannulated and may include a plurality of holes  113  to allow for graft passage.  
         [0027]    The fastener  106  may also include a head  114 , which may be tapered and/or segmented. In one embodiment, as shown in FIG. 3, the head  114  may include a top portion  116 , which can be removed using a tool, such as a wrench or a socket, after attaching the fastener  106  to the tibial bone  56 , to reduce the length of the fastener  106  after installation.  
         [0028]    Referring to FIG. 4, the first member  102  includes a central opening  120  and a plurality of recesses or openings  122  that radiate from the central opening  120  and are separated by radial projections  124 . In the embodiment shown in FIG. 4, the first member  102  includes four recesses  122  separated by four radial projections  124 . The recesses  122  may be arranged to define a symmetric pattern, such as, for example, a cross, a four-petal cloverleaf, etc., although the recesses may also be arranged asymmetrically. The number of recesses  122  may be chosen to correspond to a maximum desirable number of graft strands  58 . For example, the first member  102  may have four recesses  122 , all of which may receive graft strands  58  in some applications, while in other applications only two recesses  122  may receive graft strands  58 . The shape and the size of the recesses  122  may be determined to accommodate the size of the graft  50  and the size of the resulting graft strands  58 .  
         [0029]    In reference to FIGS. 2 and 5, the first member  102  has first and second faces  126 , 128 . The first face  126  may include a plurality of protuberances  131 , such as, for example, cleats or wedge-shaped protuberances, collectively wedges for short,  130 . The second face  128  may also include a plurality of protuberances  131  or wedges  132 . Each wedge  130 ,  132  may define an angle a, which may be selected such that the corresponding faces  126 ,  128  provide good grip without causing damage or tear to any bone or soft tissue surface that the wedge  130  may come into contact in use. The wedge angle a may be an obtuse angle, such as, for example, 96°. The wedges  130 ,  132  may be blunt and short rather than sharp and long. It will be appreciated that the protuberances  131  of the first member  102  may be other than wedge-shaped and may have, for example, circular or rectangular cross-sections.  
         [0030]    As shown in FIG. 4, the radial projections  124  of the first member  102  may include segments  134 , which may be threaded or otherwise shaped to engage the threaded portion  110  of the fastener  106  to enable the first member  102  to move up or down along the fastener  106  in a controllable and stable manner. In the embodiment shown in FIG. 11, the radial projections  124  include slots  125  that snap onto the locking ribs  127  of the first portion  110  of the fastener  106 .  
         [0031]    Referring to FIGS.  8 ( a )- 8 ( h ), the first member  102  may have a variety of side profiles, including: flat (rectangular), FIG. 8( g ); tapered FIG. 8( h ) and ( f ); curved, FIG. 8( e ) and ( c ); L-shaped, FIG. 8( a ); U-shaped, FIGS.  8 ( b ) and ( d ); etc, or combinations thereof.  
         [0032]    Referring to FIGS. 6 and 7, the second member  104  includes an opening  140  and has first and second faces  142 ,  144 . The first face  142  of the second member  104  may include plurality of protuberances  131  or wedges  146  similar to those of the first member  102 . The second face  144  of the second member may include a countersunk portion  148  sized to receive a lower portion  150  of the head  114  of the fastener  106 . The inner surface  152  of the opening  140  may be undulated or threaded such that second member  104  can move along the threaded portion  110  of the fastener  106  in a controllable manner while in engagement with the fastener  106 . The second member  104  may be pre-assembled onto the fastener  106  before the fastener  106  is inserted into the central opening  120  of the first member  102  and before the fixation device  100  is attached to the tibial bone  56 .  
         [0033]    In one embodiment, the second member  104  may be an integral portion of the fastener  106 . In another embodiment, the second member  104  may be eliminated and its function may be assumed by the lower portion  150  of the head of the fastener.  
         [0034]    The fixation device  100  may be implanted into the tibial bone  56  as follows. A step drill or other similar tool may be used to drill the tibial tunnel  54  to an appropriate length and size to receive the fixation device  100  as an implant. The step drill may create a counterbore  160  at a distal end  162  of the tunnel  54 . The graft  50  may then be pulled in the tibial tunnel  54  through a proximal end  164  of the tibial tunnel  54  and out of the distal end  162 . The graft  50  may be passed through the central opening  120  of the first member  102 , which may be pulled up the graft  50  to be received into the counterbore  160  at the distal end  162  of the tibial tunnel  54 . The graft strands  58  may be inserted into the individual recesses  122  of the first member  102  and made to lay flat and radially separated on the first face  126  of the first member  102 . The fastener  106 , having the second member  104  assembled thereon, may be threaded through the central opening  120  of the first member  102 . When the fastener  106  is fully inserted into the tunnel  54 , the graft strands  58  may be compressed against the tibial tunnel  54  and may also be securely compressed or clamped between the opposing surfaces  126  and  142  of the first and second members  102 ,  104 .  
         [0035]    In the embodiment in which the second member  104  is eliminated, the graft strands  58  may be compressed between the first member  102  and the lower portion  150  of the head  114  of the fastener. The top portion  116  of the head  114  of the fastener  106  may be twisted off with a wrench or similar tool, such that it does not protrude outside the tibial tunnel  54  and such that the fixation device  100  may implanted substantially in its entirety into the tibial tunnel  54  in a break-away manner.  
         [0036]    In operation, the fastener  106  may be substantially coaxial with the tunnel  54 . The first and second members  102 ,  104 , which may be substantially planar, may be perpendicular to the tunnel  54  when inserted into the tunnel  54 .  
         [0037]    Referring to FIGS. 5, 9,  11  and  12 , the first member  102  has a boundary surface  129 , which may have a shape that is circular, or non-circular, such as, for example oval, rectangular, polygonal, etc. Referring to FIG. 10, the boundary surface  129  may include one or more outer peripheral formations  166 , including ridges or grooves or threads, to provide better grip of the first member  102  in the tunnel  54 . In the embodiment of FIG. 9, the first member includes an outer tab  156  to prevent the first member  102  from rotating after implantation. In the embodiment of FIG. 11, the first member  102  may include one or more top spikes  158  mating with corresponding apertures  160  of the second member  104 . The first member  102  may also include one or more bottom spikes  163 , as shown in FIG. 12. Referring to FIGS. 9-12, the first member  102  may also include one or more substantially flat portions  164  for engagement with a tool holder that may be used to facilitate the installation of the first member.  
         [0038]    Each of the components of the fixation device  100  may comprise one or more resorbable materials, such as LactoSorb®, or other polymeric materials, or bone graft material or other biocompatible materials, including metals, such as titanium or titanium alloy, stainless steel, etc. The use of resorbable material combined with implantation of the fixation device  100  in the tunnel  54  of the tibial bone  56  may promote circumferential healing in the tunnel  54 . The first and second members  102 ,  104  may act as a cortical layer fixation device, in contrast with standard devices utilizing interference screws which only contact cancellous bone.  
         [0039]    The counterbore  160  at the distal end  162  of the tunnel  54  may provide a ledge on which the first and second members  102 ,  104  may securely rest, thereby dispensing with the need to anchor the fixation device  100  with sharp long spikes into the bone, and avoiding an unnecessary risk of damage to the bone.  
         [0040]    Whereas the fixation device  100  was described in connection with tibial bone fixation in an ACL procedure, it should be appreciated that the fixation device  100  may be readily used for securing grafts or ligaments in other types of bone and in other reconstruction procedures.  
         [0041]    Furthermore, whereas particular embodiments of the invention have been described for the purpose of illustrating the invention and not for the purpose of limiting the same, it will be appreciated by those of ordinary skill in the art that numerous variations of the details, materials and arrangement of parts may be made within the principle and scope of the invention without departing from the spirit of the invention. The preceding description, therefore, is not meant to limit the scope of the invention. Rather the scope of the invention is to be determined only by the appended claims and their equivalents.