Abstract:
A graft retention device has an elongated body with a first and second ends and a midpoint therebetween. A pair of elongated slots formed through the body defines a tang therebetween. A graft retention loop is disposed over the tang and is slidable therealong. A trailing line connects to the body adjacent the slots and extends therefrom through the graft retention loop toward the first end. Tension applied to the trailing line thus tends to urge the graft retention loop away from the first end and toward the midpoint.

Description:
BACKGROUND 
       [0001]    This application relates to graft fixation, and more particularly to graft tissue fixation employing flipping-type fixation devices. 
         [0002]    Flipping-type fixation devices, such as disclosed in U.S. Pat. Nos. 5,306,301 and 5,645,588 which are incorporated herein by reference, allow a simple procedure to be used for fixing tissue such as in an Anterior Cruciate Ligament (ACL) reconstruction. Such device comprises an elongated bar having a central suture loop depending therefrom. A tunnel is prepared in the femur from a position at or near the patellar surface up through a portion of the femur and exiting through the side of the femur at a superior location. A graft is looped over the loop attached to the elongated bar. The bar is able to pass in one direction up through the tunnel. After exiting the superior end of the tunnel, the bar is flipped approximately 90 degrees so that it will not pass back through the tunnel and is positioned against the femur with the loop and graft hanging down into the tunnel therefrom. Tension on the graft keeps the bar in place against the bone surface. 
         [0003]    To initiate the flipping, however, the bar must be passed completely outside of the tunnel. When it is then placed down against the bone the suture loop falls back into the tunnel by the amount that it was pulled free of the tunnel, about 50% of the length of the bar. This decreases the contact of the graft with the bone in the tunnel. Also, longer loop lengths have the potential to increase motion of the graft within the tunnel, thus potentially slowing the healing process in which the graft attaches to the bone. 
         [0004]    U.S. Patent Publication No. 20130204366, incorporated herein by reference, provides a bar in which the graft retention loop is able to move axially along the bar thereby reducing the distance the graft is pulled out of the tunnel during the flipping procedure. 
       SUMMARY OF THE INVENTION 
       [0005]    A graft retention device according to the present invention comprises an elongated body having a first end and a second end, a midpoint therebetween, and an upper surface and a lower surface. A pair of elongated slots formed through the body from the upper surface to the lower surface defines a tang therebetween. A graft retention loop is disposed over the tang and is slidable therealong from a first position closer to the first end and a second position closer to the midpoint. A trailing line connects to the body adjacent the slots and extends therefrom. When the graft retention loop is in the first position, the trailing line extends from the body through the graft retention loop toward the first end such that tension applied to the trailing line will thus tend to urge the graft retention loop away from the first position and toward the second position. 
         [0006]    Preferably, the trailing line is attached to the tang, more preferably by passing through a first aperture through the tang. The first aperture can be elongated longitudinally along the tang so as to comprise a slot therethrough whereby tension applied to the trailing line for reorienting the body will tend to urge the trailing line toward the midpoint and further enhance its urging of the graft retention loop toward the second position. 
         [0007]    Preferably, a leading line connects to the body at the second end. 
         [0008]    Preferably, the tang slopes downwardly away from the first end. 
         [0009]    Preferably, the graft retention device is provided in a sterile condition. 
         [0010]    Preferably, the second position is located near a midpoint of the body and more preferably within a central 25% of a length of the elongated body between its first end and its second end. 
         [0011]    In one aspect of the invention, the elongated slots are closed at the first end via a retention line passing through the tang and attached to the body. Preferably, the retention line extends beyond the first end of the body when the graft retention loop is in the first position whereby to minimize a flipping distance of the graft retention device. 
         [0012]    A method according to the present invention provides for fixing a graft ligament into a bone tunnel. The method comprises the steps of: a) forming a graft construct by disposing the graft ligament over a loop slidably disposed upon a tang of an elongated fixation buckle, the loop being slidable along the tang from a first position nearer a first end of the buckle to a second position nearer a midpoint of the buckle; b) pulling the graft construct up through the bone tunnel with a second end of the buckle leading; c) after the buckle has been pulled through the tunnel, applying tension to a trailing line connected to the body and passing through the loop and away from the second position, the tension urging the loop toward the second position and also reorienting the buckle to be crosswise to the tunnel on the bone adjacent the tunnel with the loop depending into the tunnel from the second position on the buckle. 
         [0013]    Preferably, the trailing line is connected to the body at the tang such as by being received through a trailing line aperture through the tang. Preferably, the trailing line is removed after step c). Preferably, step b) is performed via a leading line received through a leading line aperture at the second end of the buckle. Preferably, at least a portion of the loop above an upper surface of the buckle extends beyond the first end of the buckle when the loop is in its first position. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a perspective view of a fixation device buckle according to the present invention; 
           [0015]      FIG. 2  is a sectional view taken along line  2 - 2  of  FIG. 1 ; 
           [0016]      FIG. 3  is a side elevation view in cross-section of a ACL repair in a knee employing the fixation device of  FIG. 1 ; 
           [0017]      FIGS. 4A to 4D  are side elevation views in cross-section of an ACL repair procedure employing the fixation device of  FIG. 1 ; and 
           [0018]      FIG. 5  is a top perspective view of an alternative embodiment of a buckle according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]      FIGS. 1 and 2  show a graft fixation device  10  according to the present invention. It comprises an elongated bar or buckle  12  having a graft receiving loop  14  depending therefrom. The buckle  12  comprises a first end  16  and second end  18 , and an upper surface  20  and lower surface  22 . The terms “upper” and “lower” and related terms such as “upwards” are used herein with reference to the surfaces of the buckle  12  just defined, with the lower surface  22  being that surface which will face a bone (not shown in  FIG. 1 ) when the buckle  12  is employed.) 
         [0020]    A pair of longitudinal slots  32  penetrates the buckle  12  from the upper surface  20  to the lower surface  22  and extends from a first end  34  adjacent the buckle first end  16  to a second end  36  at a midpoint  38  of the buckle  12 . The slots  32  define a retention tang  40  therebetween. An upper surface  42  of the retention tang slopes downwardly from the first end  34  of the slots  32  to the second end  36  to encourage the loop  14  to migrate toward the midpoint  38  at implantation. The loop  14  is received through the slots  32  and slides along the retention tang upper surface  42 . 
         [0021]    A first hole  24  penetrates the tang  40  laterally adjacent the first end  16  and a second hole  26  penetrates the buckle  12  at the second end  18 , passing from the upper surface  20  to the lower surface  22 . The first hole  24  receives a trailing line  28  and the second hole  26  a leading line  30  for guiding the buckle  12  during implantation. As best seen in  FIG. 2 , when the loop  14  is toward the first end  34  it overlaps the first hole  24 . When the trailing line  28  is tightened upwardly during the flipping portion of implantation it will tend to push the loop  14  away from the first end  34 . Placement of the hole  24  inboard of the first end  34  also allows the first end  34  of the slots  32  to be closer to the first end  16  of the buckle  12  and thereby reduce the flipping distance. 
         [0022]    The trailing line  28  and leading line  30  are preferably formed of ORTHOCORD #2 suture available from Ethicon, Inc. of Somerville, N.J. The leading line  30  may experience higher stress than the trailing line  28  while placing the fixation device  10  as will become apparent as the placement procedure is described. The second hole  26  is shown slightly larger than the first hole  24  (although they could be made the same size) and the leading line  30  can be a higher strength suture such as with a larger diameter than the trailing line  28 . This difference can be used to differentiate the leading line  30  and trailing line  28 . They can also be differentiated in some other fashion such as via varying colors or visual patterns. 
         [0023]    Preferably, the vertical dimension of the retention tang  40  remains constant from the first end  34  to second end  36  to enhance its strength and rigidity, with the retention tang  40  thus depending slightly below the buckle lower surface  22  at the midpoint  38 . The tang  40  is shown with a slope below the upper surface  20  of 13.6 degrees but could be anywhere from zero to about 45 degrees. It could also vary in slope, such as getting progressively steeper toward the midpoint  38  to encourage the loop to stay at the midpoint  38  after implantation. 
         [0024]    Preferably, for an ACL repair the buckle  12  is approximately 12 mm long, 4 mm wide and 1.5 to 2.5 mm thick, with the thickest portion being the midpoint  38  where the tang  40  depends. The tang  40  is approximately 1.5 mm thick. The buckle  12  is preferably formed of a biocompatible material such as 6A1-4V Ti alloy. Preferably, the loop  14  is woven of ultra-high molecular weight polyethylene, such as DYNEEMA, and polyester. The material of the loop  14  is preferably about 2 mm in diameter, preferably being in a range of from #2-0 up through about 4 mm, and the loop  14  is preferably between about 8 mm and 60 mm long. The loop  14  can be woven onto the buckle  12  to form a continuous loop without knots. U.S. Pat. No. 6,352,603 to Bryant, incorporated herein by reference, illustrates one method for achieving such a construct. 
         [0025]    Turning also now to  FIG. 3 , a graft construct  44  comprises a tissue graft  46  looped over the loop  14  of the fixation device  10  and is show in place in a patient&#39;s leg  48 . A tunnel  50  in the leg&#39;s femur  52  comprises a larger diameter inferior portion or socket  54  sized to accommodate the graft  46  and a smaller diameter superior portion or passing channel  56  sized to accept the buckle  12  in a lengthwise orientation. The buckle  12  sits against the femur  52  in a sideways orientation with the loop  14  depending down through the passing channel  56  and into the socket  54  in which is placed the graft  46 . An opposite end of the graft  46  is placed into a tibial tunnel  58  in the leg&#39;s tibia  60  and held in place with an anchor  62  such as the INTRAFIX® anchor available from DePuy Mitek Inc. of Raynham, Mass. 
         [0026]    Turning also now to  FIGS. 4A to 4D  the process of passing the buckle  12  up through the tunnel  50  and especially the passing channel  56  will be described. At the start of the procedure, the graft tissue  46  is threaded through the loop  14 . A longitudinal axis  60  of the buckle  12  is oriented coaxially with a longitudinal axis  62  of the tunnel  50 , with the loop  14  depending from the first end  34  of the slots  32  ( FIG. 4A ). Tension on the leading line  30  pulls the second end  18  of the buckle  12  upwardly out of the passing channel  56  until the first end  16  is free of the passing channel  56  ( FIG. 4B ). Preferably, the loop  14  and the passing channel  56  are dimensioned so that if the graft construct  44  is pulled up until the graft tissue  46  abuts an end  55  of the socket  54  the first end  16  of the buckle  12  has just cleared the end of the passing channel  56  thus providing tactile feedback to the surgeon that the buckle  12  is properly positioned to be rotated. The graft  46  shown in  FIGS. 4A to 4D  is not to scale and is shown as a thin line so as to better illustrate the construction of the socket  54 . In reality the graft  46  would be fatter such that it entirely fills the width of the socket  54 . Contact between the graft  46  and the bone forming the socket  54  allows the graft to grow into and merge with the bone to form a permanent repair. 
         [0027]    Rotation is approximately 90 degrees and can occur by applying tension to the trailing line  28  ( FIG. 4C ). The final orientation depends upon the angle at which the tunnel  50  penetrates the femur  52 . As the buckle  12  is rotated, opposing tension supplied by the graft tissue  46  tends to cause the loop  14  to slide along the retention tang  40  leaving it depending down into the passing channel  56  from the midpoint  38  of the buckle  12 . This occurs with a distinct snapping motion that can be felt by the surgeon through the trailing line  28  to provide tactile feedback that the migration has occurred properly. The trailing line  28  and leading line  30  are then removed and tension from the graft tissue  46  pulls the buckle  12  lower surface  22  firmly against the femur  52  ( FIG. 4D ). The crosswise orientation of the buckle  12  versus the passing channel  56  and the loop  14  depending from the midpoint  38  of the buckle  12  prevent the buckle from migrating back into the passing channel  56  thus providing secure fixation of the graft tissue  46 . 
         [0028]    The slope of the tang upper surface  42  assists in urging the loop  14  toward the midpoint  38 . Its angle on the femur  52  versus the tunnel  50  also tends to pull the loop  14  across the buckle  12  to sit at the slot second ends  36  and the buckle  12 . Locating the ends  36  at the midpoint  38  thus helps keep the loop  14  seated at the midpoint  38 . In terms of final seating of the loop  14  the term “midpoint” can be broadly construed. Seating at the exact middle of the buckle  12  provides an equal amount of buckle to each side thereof to minimize any chance that the buckle  12  can slip along the bone in such a fashion that and end thereof could fall back into the passing channel  56 . In practical terms the loop  14  can be seated in other locations yet still be safely situated to prevent the buckle  12  from falling back into the passing channel  56 . Preferably, the loop  14  is seated somewhere in the middle 50% of the length of the buckle  12  and more preferably within the middle 25%. 
         [0029]    The flipping distance is representative of the gap between the graft  46  and the end of the socket  54 . Ideally this gap is zero and the graft  46  extends all the way to the end of the socket  54 . 
         [0030]      FIG. 5  illustrates a further embodiment of a buckle  100  according to the present invention. It comprises a body  102  having first and second ends  104  and  106  with holes  108  and  110  for trailing and leading lines  107  and  109  respectively. It also has slots  112  forming a tang  114  for supporting a graft support loop  115 . The slots  112  extend from a midpoint  116  to the first end  104  rather than being enclosed by the body  102  at the first end  104  as in the previous embodiment. To retain the loop on the tang  114  a retaining line  118  is provided through aperture  120  in the tang  114  and adjacent apertures  122  in the body  102 . 
         [0031]    The retaining line  118  can be a suture, wire or other material with sufficient tensile strength to retain the loop. It can be flexible, stretchable or rigid. As shown in  FIG. 5  it bows outwardly  124  between the tang  114  and adjacent body  102  to further minimize the flipping distance, but it could be made straight with no bowing. The bowing  124  can be present in a resting state such as being formed in a wire, or may by dynamically formed under force of the loop  115  against the retaining line  118  if the line  118  is formed of an elastic material which stretches to form the bowing  124 . For instance the line  118  could be formed of a suture with a lower than average modulus of elasticity such as PDS (Polydioxanone) or Prolene and multiple lengths of such suture could be employed to form the line  118  with sufficient strength. Rubber or silicone materials, as for instance silicone tubing, of an implantable grade could are other possibilities for an elastic material. The bowing  124  could be formed by the line  118  being flexible, such as a suture, with sufficient slack as to form the bowing  124  especially when the loop presses against it. 
         [0032]    Fixation of the line  118  in the apertures  122  can be effected by providing knots  126  the ends of the line  118 , particularly if it is formed of suture, such that the knots  126  cannot pass through the apertures  122 . Other methods for fixation include welding, adhesives, interference screws etc. 
         [0033]    With sufficient bowing  124  the buckle  100  could have a flipping distance of zero or even a negative value allowing the graft to be seated to the end  55  of the graft socket  54  (not shown in  FIG. 5 ). With sufficient bowing  124  and a negative flipping distance, the graft will reach the end  55  of the graft socket  54  as the buckle  100  is flipped. After the flipping is completed and the buckle  100  is seated against the bone the loop  115  would be pulled upwards versus its position during flipping such that a tension in the loop  115  would pull the graft into contact with the end  55  of the socket  54  with a contact force thereagainst thereby maximizing the bone to graft contact area of the completed repair. In prior devices this bone surface  55  is wasted as they do not allow the graft to contact it sufficient to achieve ingrowth between the graft and the bone. 
         [0034]    The loop  115  is preferably a continuous closed loop. Formation of such a structure through weaving etc. is made more difficult if it must be formed around the tang  114 . With the design of  FIG. 5  the loop  115  can be formed alone which is much easier and then slipped onto the tang  114  prior to placing the line  118  onto the buckle  100 . This simplifies manufacturing. 
         [0035]    Refinements and variations to the buckle could include slots which extend to both sides such that the second side mirrors the first, and the retention tang sloping down from both ends toward the center. This would allow a surgeon to pull the buckle up through the tunnel  50  by either end. Also, the upper surface of the retention tang could be rounded to provide a better surface for the loop  14  to ride over and lessen chafing of the loop  14 . 
         [0036]    Provision can be made to discourage the loop  14  from moving away from the midpoint  38 , such as by providing barbs (not shown) along the upper surface  42  or other areas of the buckle  12  where they may engage the loop  14  as it slides along the slots  32 . The tang can have a pronounced dip to capture and retain the loop  14  at the midpoint. 
         [0037]    The buckle is particularly suited to ACL repair, but can be useful in other repairs such as for example reattachment of a biceps brachii tendon. 
         [0038]    The invention has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.