Abstract:
A tissue fixation system provides a primary fixation plate with a depending graft retention loop and a longer auxiliary fixation plate which fits to the primary fixation plate via upwardly projecting pegs which fit into suture holes in the primary fixation plate. The system has particular utility in cortical fixation procedures in which a graft channel is over-drilled and a longer fixation plate is indicated.

Description:
BACKGROUND 
       [0001]    The present invention relates to tissue fixation plate system and more specifically to such systems having a primary fixation plate with a depending graft retention loop and a longer auxiliary fixation plate. 
         [0002]    Tissue fixation plates fix tissue to bone adjacent a bone tunnel. One common usage occurs in Anterior Cruciate Ligament (ACL) reconstruction. A bone tunnel is formed through a femur. It comprises a graft channel wide enough to accommodate a replacement graft tissue and terminates in a smaller passing channel that exits through the cortical bone and is wide enough to pass the fixation plate. The graft is carried by a loop depending from the fixation plate and the plate is guided lengthwise up through the bone tunnel whereupon its orientation is flipped approximately ninety degrees to rest against the surface of the femur and be thus prevented from passing back through the tunnel. Examples of such flipping-type fixation devices are disclosed in U.S. Pat. Nos. 5,306,301 and 5,645,588 incorporated herein by reference. 
         [0003]    If the graft channel is drilled too deeply there may be no passing channel or insufficient bone thickness to support a preferred size of fixation plate. A surgeon may also desire to prepare a single diameter bone tunnel. In each case a larger fixation plate will be required for proper fixation. An expanded size accessory plate is typically employed having a length exceeding that of the primary fixation plate and having an upper recess into which the primary fixation plate fits. 
         [0004]    Current accessory plates are difficult to use because of the difficulty in attaching them seamlessly to the primary fixation plate. Often the graft must first be removed from the graft loop so that the graft loop can be threaded into a hole through the accessory plate that accepts the loop. Then, the graft must be re-loaded on the graft loop prior to the construct being used. Also, the existing plates do not tend to interconnect well. 
         [0005]    Other solutions include simply using a larger fixation plate, but again, the graft must be offloaded from the original loop and then loaded onto the second plate&#39;s graft loop. 
       SUMMARY OF THE INVENTION 
       [0006]    The present innovation improves on the prior art by reducing the number of steps and allowing the graft to remain on the loop while loading the accessory plate onto the construct. Also, there is a perception among many surgeons that it is desirable to maintain an axial load on the graft prior to insertion in the body to remove stretch. The present innovation improves on prior art by permitting the graft to remain in its loaded configuration for longer than other technologies. 
         [0007]    A tissue fixation device according to the present invention comprises a first fixation plate comprising an elongated body having a first end and a second end with a length therebetween. A first suture aperture is provided at the first end, and a central graft support loop depending from the body. A second fixation plate receives the first fixation plate and comprises an upper surface having a first peg projecting upwardly therefrom through the first suture aperture of the first fixation plate. The second fixation plate has a length exceeding the length of the first fixation plate. 
         [0008]    Preferably, the first fixation plate further comprises a second suture aperture and the second fixation plate further comprises a second peg projecting upwardly therefrom through the second suture aperture of the first plate. 
         [0009]    Preferably, the length of the second fixation plate exceeds the length of the first fixation plate by at least 15 percent. 
         [0010]    Preferably, the length of the second fixation plate exceeds the length of the first fixation plate by at least 65 percent. 
         [0011]    In one aspect of the invention, the second fixation plate further comprises a first suture receiving aperture with a first suture therethrough and a second suture receiving aperture with a second suture therethrough. 
         [0012]    In one aspect of the invention the second fixation device has a first suture receiving aperture with a suture therethrough which comprises a cannulation through the first peg. 
         [0013]    Preferably, the second fixation plate has a lower surface opposite its upper surface and the graft support loop depends below the second fixation plate lower surface. 
         [0014]    Preferably, the first peg fits closely within the first suture aperture of the first fixation plate. The first peg can be provided to fit with a compression fit within the first suture aperture of the first fixation plate to hold together the first fixation plate and the second fixation plate. 
         [0015]    In one aspect of the invention the first fixation plate and second fixation plate interlock with each other. The interlocking can comprise a snap-fit engagement between the first fixation plate and the second fixation plate. 
         [0016]    In one aspect of the invention the second fixation plate further comprises a side opening slot through which depends the graft support loop. The second fixation plate could comprise a pair of side opening slots with a separator in-between, and with the separator passing through the graft support loop laterally and the graft support loop depending downwardly through the side opening slots. 
         [0017]    A method according to the present invention provides for anchoring a tissue graft to bone. The method comprising the steps of: preparing a bone tunnel through a bone; affixing a first fixation plate to a second fixation plate to form a construct, the first fixation plate comprising an elongated body having a first end and a second end with a length therebetween, a first suture aperture at the first end, and a central graft support loop depending therefrom, the second fixation plate receiving the first fixation plate and comprising an upper surface having a first peg projecting upwardly therefrom through the first suture aperture of the first fixation plate and wherein the second fixation plate has a length exceeding the length of the first fixation plate; affixing the tissue graft to the graft support loop; passing the construct lengthwise through the bone tunnel and then reorienting the construct to place the lower plate lower surface against the bone adjacent the bone tunnel with the graft support loop and graft depending downwardly into the bone tunnel. 
         [0018]    Preferably, the first fixation plate further comprises a second suture aperture and the second fixation plate further comprises a second peg projecting upwardly therefrom through the second suture aperture. 
         [0019]    Preferably, a suture affixed to the second fixation plate is used to pass the construct through the bone tunnel. The suture can be first removed from the first fixation plate and affixed to the second fixation plate. In one aspect of the invention, the suture is passed through the first peg. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is an exploded perspective view of a tissue fixation device according to the present invention; 
           [0021]      FIG. 2  is a side elevation view showing the tissue fixation device of  FIG. 1 ; 
           [0022]      FIG. 3 . Is a side elevation view in cross-section showing the tissue fixation device of  FIG. 1  in use in a bone; 
           [0023]      FIG. 4A  is a top plan view of an auxiliary plate of an alternative embodiment of a tissue fixation device according to the present invention; 
           [0024]      FIG. 4B  is an exploded side elevation view in cross-section of the tissue fixation device of  FIG. 4A ; 
           [0025]      FIG. 4C  is a side elevation view in cross-section of the tissue fixation device of  FIG. 4B ; and 
           [0026]      FIGS. 5A to 5C  are top plan views of alternative embodiments of auxiliary tissue fixation plates according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]      FIG. 1  illustrates a tissue fixation device  10  according to the present invention. It comprises in gross a primary fixation plate  12  and an auxiliary fixation plate  14  which is longer than the primary fixation plate  12 . The primary fixation plate  14  can be used by itself to provide fixation and when a longer length is desired it can be used with the auxiliary fixation plate  14  to form the fixation device  10  having a length exceeding that of the primary fixation plate  12 . 
         [0028]    A typical dimension for the primary fixation plate when used in ACL reconstruction would be about 4 mm wide by 12 mm long by 1 mm thick. Complimentary dimensions on the auxiliary fixation plate  14  in such case would be between about 14 mm to 26 mm long with a width of 4 mm matching that of the primary fixation plate or slightly wider, and a thickness of about 2 mm or as needed to meet the strength requirements. The dimensions can be varied to accommodate different sized patients and for different procedures. The length of the auxiliary plate  14  exceeds that of the primary fixation plate  12 , preferably by between about 15% and 115% and most preferably by about 67%. Preferably they are formed of surgical grades of titanium or stainless steel or other biocompatible material having sufficient strength and rigidity. 
         [0029]    The primary fixation plate  12  comprises an elongated body  16  having a first end  18  and a second end  20  with a first suture aperture  22  at the first end  18  and a second suture aperture  24  at the second end  20 . A first guiding suture  26  is received through the first suture aperture  22  and a second guiding suture  28  is received through the second suture aperture  24 . A pair of central apertures  30 , having a bridge  32  therebetween, passes through the body  16  from an upper surface  34  to a lower surface  36  thereof and carries a flexible graft support loop  38  which depends from the body  16 . The graft support loop  38  shown is a continuous loop of woven fibers but other configurations are possible including adjustable size loops. 
         [0030]    The auxiliary fixation plate  14  is longer than and adapted to fit together with the primary fixation plate  12 . It has a first end  40 , second end  42 , upper surface  44  and lower surface  46 . A first peg  48  projects upwardly from the upper surface  44  and fits closely within the first suture aperture  22  of the primary fixation plate  12 . A second peg  50  projects upwardly from the upper surface  44  and fits closely within the second suture aperture  24 . An elongated central aperture  52  is sized to receive the loop  38  therethrough so that the when the primary fixation plate  12  and auxiliary fixation plate  14  are fitted together with the pegs  48  and  50  received through the suture apertures  22  and  24  the loop  38  depends downwardly through the aperture  52  to depend below the lower surface  46  of the auxiliary fixation plate  14  (see  FIG. 2 ). The central aperture  52  can be sized to allow the primary fixation plate  12  to be passed upwardly therethrough so that it can be affixed to the auxiliary fixation plate  14  with a graft (not shown in  FIGS. 1 and 2 ) attached to the loop  38 . 
         [0031]    A first guiding suture  54  is received through a first suture aperture  56  near the first end  40  of the auxiliary fixation plate  14  and a second guiding suture  58  is received through a second suture aperture  60  at the second end  42 . The auxiliary plate  14  can be provided with only the suture apertures  56  and  60  and without the guiding sutures  54  and  58  in which case the guiding sutures  26  and  28  from the primary fixation plate can be removed and threaded through the suture apertures  56  and  60  in the auxiliary plate. If the auxiliary fixation plate  14  has its own sutures  54  and  58  then the guiding sutures  26  and  28  of the primary fixation plate  12  would be removed and discarded when used with the auxiliary fixation plate  14 . This would negate the need to rethread these sutures  26  and  28  during a procedure. 
         [0032]    Turning now also to  FIG. 3 , a typical use for the auxiliary fixation plate  14  is when a graft channel  62  in a bone tunnel  64  is drilled too deeply through a bone  66  such as a femur leaving a short passing channel  68  (or no passing channel  68  if the graft channel  62  is completely overdrilled) and thus leaving insufficient bone  66  to support the primary fixation plate  12  by itself. The added length of the auxiliary plate  14  allows it to sit securely atop adjacent bone  66  and provide a secure repair. 
         [0033]    After a surgeon determines the need for the auxiliary fixation plate  14  the auxiliary plate is affixed to the primary fixation plate  12 . If a graft  70  is already attached to the loop  38  of the primary fixation plate  12  it need not be removed. The primary fixation plate  12  is passed upwardly through the central aperture  52  with its sutures  26  and  28  already removed and the pegs  48  and  50  of the auxiliary fixation plate  14  fitted into the empty suture apertures  22  and  24  of the primary fixation plate  12  with the loop  38  depending from the thus formed construct of the tissue fixation device  10 . This construct is then passed lengthwise up through the bone tunnel  64  as would have been the primary fixation plate  12  but employing the sutures  54  and  58  of the auxiliary fixation plate  14 . It is then reoriented to lay flat with the auxiliary fixation plate lower surface  46  bearing against the bone  66  and the loop  38  and graft  70  depending down into the bone tunnel  64 , after which the guiding sutures  54  and  58  can be removed. For an ACL reconstruction an opposite end of the graft  70  would be fixed into a tibial tunnel (not shown). 
         [0034]      FIGS. 4A to 4C  illustrate an alternative embodiment of a tissue fixation device  72  according to the present invention. It comprises the primary fixation plate  12  with an alternative auxiliary fixation plate  74  which has a structure similar to the auxiliary fixation plate  14  with several alternative features which can be employed together as shown here or separately. It differs in having first and second pegs  76  and  78  with respective first and second cannulations  80  and  82  extending axially therethrough and which replace the separate first and second suture apertures  56  and  60  of the auxiliary fixation plate  14 . The first and second guiding sutures  26  and  28  can then be located at the same location with respect to the primary fixation plate  12  as its normal operation and their path through both the primary fixation plate  12  and auxiliary fixation plate  74  help to hold these two structures together. 
         [0035]    It is contemplated that the sutures  26  and  28  would be repurposed from the primary fixation plate  12  to the cannulated pegs  76  and  78  and to this end the auxiliary fixation plate  74  can be provided with suture threaders (not shown) such as an elongated wire with a distal suture capture kite threaded therethrough to simplify the task of rethreading the sutures  26  and  28 . Alternatively, the pegs  76  and  78  can be preloaded with new sutures in disposable holder plugs (not shown) in the cannulations  80  and  82  which can assist in completing the threading of the new sutures after the primary and auxiliary fixation plates  12  and  74  are configured together. 
         [0036]    The auxiliary fixation plate  74  also differs from the first embodiment by having instead of the single enclosed, elongated central aperture  52 , first and second side facing slots  84  and  86  with a dividing tang  88  formed therebetween. This allows the loop  38  to be loaded from the side into the slots  84  and  86  with the tang inserted through the loop  38 . 
         [0037]    To hold the auxiliary fixation plate  74  firmly to the primary fixation plate  12  it may be desirable to have an interlocking feature such as a snap-fit engagement between these two parts. For instance, each peg  76  and  78  could be provided with a slight distal and radial lip and one or more axial slots (not shown) so that they compress and reduce in diameter slightly as they are loaded into the suture apertures  22  and  24  and then as the lip passes past the body  16  the pegs spring back to lock the parts together. The parts need not have a snap-fit but could just have a sufficient interference fit to hold them together and thereby accomplish a similar objective. 
         [0038]      FIGS. 5A to 5C  show three alternatives to the auxiliary fixation plate  74  for use with the primary fixation plate  12  of  FIG. 1 .  FIG. 5A  shows a plate  90  having cannulated pegs  92  and a single central aperture  94  for receipt of the loop  38 .  FIG. 5B  shows a plate  96  having a single side-loading slot  98  for receipt of the loop  38 .  FIG. 5C  shows a plate  100  having a pair of opposed side-loading slots  102  and  104  with a bridge  106  therebetween. The plate  100  would be passed partly through the loop  38  and rotated to load it into the slots  102  and  104 . 
         [0039]    While the invention has been particularly described in connection with specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation, and that the scope of the appended claims should be construed as broadly as the prior art will permit.