Patent Abstract:
A depth gauge and method provide for accurate measurement of a socket portion of a bone tunnel in an ACL reconstruction.

Full Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to a system and method for reconstructing an anterior cruciate ligament (ACL) and more particularly to a method and gauge for dimensioning a femur tunnel in such a reconstruction. 
         [0003]    2. Description of the Related Art 
         [0004]    An injured ACL is commonly reconstructed by placing a replacement graft through tunnels prepared in a patient&#39;s tibia and femur. In one type of such procedure described in U.S. Pat. No. 5,306,301, the contents of which are incorporated herein by reference, 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 a loop attached to an elongated bar. The bar is able to pass in one direction up through the tunnel and then out adjacent the superior end of the tunnel. The bar is reoriented such 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. The tunnel has sufficient diameter at its inferior portion to accommodate the graft. The tunnel is preferably made narrower at the superior portion, which carries only the loop and not the graft, to minimize bone removal. For convenience, the inferior portion of the tunnel can be termed the socket. Determining a proper depth of the socket quickly, accurately and easily is desired. 
       SUMMARY OF THE INVENTION 
       [0005]    An instrument according to the present invention provides for determining a depth of a bone tunnel in an ACL reconstruction. The instrument comprises a measuring pin having an elongated body having a first end and a first indicia spaced apart from the first end. A first tube co-axially receives the first end of the measuring pin body, the first tube having in internal diameter sized to accommodate the measuring pin body first end, an open first end and a second end. A second tube at the first tube second end has an internal diameter larger than the first tube internal diameter and an first end connected to the first tube second end. A measuring block is disposed at least partially within the second tube and has an abutment and a socket depth scale indicia thereon. A first indicator on the second tube is oriented relative to the socket depth scale indicia being oriented such that when the measuring pin body first end abuts the measuring block abutment the alignment of the indicator and the socket depth scale indicia provides a reading indicative of a desirable depth of the bone tunnel. 
         [0006]    Preferably, the measuring block is biased toward the first tube. Also preferably, the first indicator is the second tube second end. Preferably, a loop size indicia is provided thereon. 
         [0007]    Preferably, the reading on the socket depth scale indicia represents the distance between the first indicia and the first tube first end minus a loop size indicated by the loop size indicia plus a predetermined flip length. The flip length is a distance beyond the femur necessary to reorient an elongated bar carrying a loop from which the graft is suspended into the bone tunnel from an orientation which allows it to pass through the bone tunnel into a sideways orientation which prevents its passage back into the bone tunnel. 
         [0008]    Preferably, a second loop size indicia indicating a different value than the loop size indicia and a second socket depth indicia associated therewith. Accordingly, the reading on the socket depth scale indicia represents the distance between the first indicia and the first tube first end minus a loop size indicated by the loop size indicia plus a predetermined flip length and the reading on the second socket depth scale indicia represents the distance between the first indicia and the first tube first end minus a loop size indicated by the second loop size indicia plus the predetermined flip length. Multiple loop size indicia and associated socket depth indicia can be provided to provide socket depth readings for different loop sizes with a single instrument. 
         [0009]    Preferably, the second tube has a graft implantation depth indicia thereon and wherein the measuring block has an associated second indicator associated therewith to provide a reading of a depth of implantation of a graft into the bone tunnel. In such case the reading on the implantation depth scale indicia preferably represents the distance between first indicia and the first tube first end minus the loop size indicated by the loop size indicia. 
         [0010]    A method according to the present invention provides for measuring a depth of a socket portion of a bone tunnel in an ACL reconstruction. The method comprises the steps of: creating a pilot hole through a femur so that the pilot hole has a first end at a condylar notch surface of the femur and a second end at a superior portion of the femur, the pilot hole being oriented along a path desired for a replacement ligament in the femur; positioning a measuring pin so that a first indicia on the measuring pin is located at the pilot hole first end and a second end of the measuring pin extends out of the pilot hole second end; placing a first tube over the measuring pin such that a portion of the measuring pin is coaxially received therein and a first end of the first tube abuts the femur at the pilot hole second end; abutting the second end of the measuring pin against an abutment on a measuring block having a distance scale indicia thereon, the measuring block having a lateral dimension larger than a largest lateral dimension of the measuring pin; and reading a desired depth for the socket portion of the bone tunnel from the distance scale indicia, the socket portion extending from the pilot hole first end along the path defined by the pilot hole. 
         [0011]    Preferably, the pilot hole is created with the measuring pin. Also preferably, an indicator is associated with the first tube, and the indicator provides the reading on the distance scale. 
         [0012]    Preferably, the desired depth read on the distance scale correlates to a distance separating the first tube first end and the first indicia on the measuring pin, more specifically the desired depth represents the distance separating the first tube first end and the first indicia on the measuring pin minus a predetermined loop size plus a predetermined flip length. Preferably, the predetermined loop size is indicated adjacent the distance scale. 
         [0013]    The method preferably further comprises the step of drilling the socket portion into the femur to the indicated depth from the condylar notch along the path. The method preferably further comprises the steps of: suspending the graft over a loop of the predetermined loop size, the loop being connected to an elongated bar; passing the elongated bar lengthwise through the bone tunnel and positioning the bar against the superior portion of the femur in a sideways orientation to prevent its passage back into the bone tunnel leaving the loop depending down into the socket portion and the graft suspended at least partially in the socket portion from the loop. The predetermined flip length is a distance beyond the femur sufficient to manipulate the bar from its lengthwise orientation into its sideways orientation after is has been passed through the tunnel and with the loop depending back into the tunnel. 
         [0014]    Preferably, a further reading is made of an implantation depth length of the implant in the socket portion from a socket depth indicia associated with the first tube, the implantation depth representing the distance separating the first tube first end and the first indicia on the measuring pin minus the predetermined loop size. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    In what follows, preferred embodiments of the invention are explained in more detail with reference to the drawings, in which: 
           [0016]      FIG. 1  is a side elevation view of a first embodiment of a beath pin according to the present invention; 
           [0017]      FIG. 1A  is a side elevation view of a second embodiment of a beath pin according to the present invention; 
           [0018]      FIG. 1B  is a side elevation view of a further embodiment of a beath pin according to the present invention; 
           [0019]      FIG. 2  is a side elevation view of a portion of a depth gauge according to the present invention; 
           [0020]      FIG. 3  is a side elevation view in cut-away of the depth gauge of  FIG. 2 ; 
           [0021]      FIG. 3A  is a perspective view in partial phantom of a second embodiment of a depth gauge according to the present invention; 
           [0022]      FIG. 3B  is a side elevation view of a further embodiment of a depth gauge according to the present invention; 
           [0023]      FIG. 4  is a perspective view of a graft construct for use in the procedure according to the present invention; 
           [0024]      FIG. 5  is a side elevation view in cut-away of a knee having an ACL reconstruction according to the present invention; 
           [0025]      FIG. 6  is a front elevation view of a femur of the knee of  FIG. 5  showing the creation of a pilot hole using the beath pin of  FIG. 1 ; 
           [0026]      FIG. 7  is a front elevation view of a femur of the knee of  FIG. 5  showing the beath pin of  FIG. 1  inserted to a pre-determined depth; 
           [0027]      FIG. 8  is a perspective view of the depth gauge of  FIGS. 2 and 3  being placed onto the beath pin; 
           [0028]      FIG. 9  is a perspective view of the depth gauge and beath pin of  FIG. 8  with an end of the depth gauge engaging a surface of the femur; 
           [0029]      FIG. 10  is a side elevation view of the depth gauge of  FIG. 8  showing the indicated reading for socket depth; 
           [0030]      FIG. 11  is a front elevation view of the femur of the knee of  FIG. 5  showing the socket being drilled; 
           [0031]      FIG. 12  is a front elevation view of the femur of the knee of  FIG. 5  showing the passing channel being drilled; and 
           [0032]      FIG. 13  is a front elevation view of the femur of the knee of  FIG. 5  showing the graft construct being passed. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]      FIGS. 1 to 3  illustrate primary components of the present invention.  FIG. 1  depicts a beath pin  10  having an elongated body  12 , sharp distal tip  14 , optional drill flutes  16  adjacent the distal tip  14  and a laser etched depth indicia  18  located about 15 cm from the distal tip  14 .  FIG. 1A  depicts an alternative beath pin  20  having an elongated body  22 , sharp distal tip  24 , drill flutes  26  adjacent the distal tip  24  and an annular flange  28  in place of the laser etched depth indicia  18  of the beath pin  10 . The pins  10  or  20  will be passed into a femur (not shown in  FIGS. 1 to 3 , to either the indicia  18  or the flange  28  and the flange provides a tactile feedback to a surgeon that the correct depth of passage into the femur has occurred.  FIG. 1B  depicts an alternative beath pin  27  having a reverse annular flange  29  that provides a visual feedback that the correct depth of passage into the femur has occurred. The reverse flange  29  also allows the beath pin  27  to be removed by pulling it through the passage forwardly and out of the femur. 
         [0034]      FIGS. 2 and 3  illustrate a depth gauge  30  for measuring and sizing the tunnel in the femur. The gauge comprises an elongated cylindrical first tube  32  sized to accommodate the beath pin  10 , the first tube  32  has a first end  34  and a second end  36  attached to a larger second tube  38 . The second tube  38  has a first end  40  attached to the first tube  32 , a free second end  42 . The second end  36  may be releasably attached via threads, snaps, bayonet fittings, or other means to the second tube  38  to allow the tube  32  to be disposable. A measuring block  44  travels within the second tube  38  and is preferably biased toward the first end  40  by a tension spring  46 . A first end  48  of the measuring block  44  acts as an abutment against the tip  14  of the beath pin  10 . It can be slightly countersunk for more positive engagement. A depth indicia scale  50  is provided on the measuring block and a loop size indicia  52  is provided toward a second end  54  of the measuring block  44 . 
         [0035]    The beath pins  10 ,  20  and  27  are preferably of small diameter, such as 2.4 mm. Markings thereon would be quite difficult to see due to its small size and could become obscured by body tissue. The measuring block  44  has an increased size making reading the indicia scale  50  easy. Preferably, the measuring block  44  has a width of at least 8 mm. The present arrangement also covers the sharp distal tip  14  of the beath pin  10  to enhance safety. 
         [0036]      FIGS. 3A  and B depict an alternative embodiments in which similar parts are identified with similar numerals with the subscripts “a” and “b” respectively. In  FIG. 3A , a measuring block  44   a  has a projection  45  extending into the second tube  38   a  and it is against this projection  45  which the beath pin tip  14  abuts. This provides for a shorter and thus safer beath pin. In  FIG. 3B  a second tube  38   b  is provided with an additional marking scale  51  on a window  53  through which can be seen an indicator  55  on a measuring block  44   b.  The marking scale  51  indicates the length of the graft disposed within the femur as will be discussed ahead. Additionally, the measuring block  44   b  and second tube  38   b  can be provided with multiple faces disposed circumferentially thereabout, each with its own corresponding indicia scale  50   b,  additional marking scale  51  and loop size indicia  52   b . For instance, one face could be arranged to work with a 20 mm loop size, a second face with a 25 mm loop size etc. with the loop size indicia  52   b,  indicia scale  50   b  and additional scale  51  arranged accordingly. 
         [0037]      FIG. 4  illustrates a graft construct  60  comprising an elongated bar  62  having a thick suture loop  64  through a pair of central openings  66  along with first and second guiding sutures  68  and  70  through first and second outside holes  72  and  74  respectively. A replacement graft  76  is looped over the loop  64 .  FIG. 5  illustrates the graft construct  60  in place in a patient&#39;s leg  78 . A tunnel  80  in the leg&#39;s femur  82  comprises a larger diameter inferior portion or socket  84  sized to accommodate the graft  76  and a smaller diameter superior portion or passing channel  86  sized to accept the bar  62  in a lengthwise orientation. The bar  62  sits against the femur  82  in a sideways orientation with the loop  64  depending down through the passing channel  86  and into the socket in which is placed the graft  76 . An opposite end of the graft  76  is placed into a tibial tunnel  88  in the leg&#39;s tibia  90  and held in place with an anchor  92  such as the INTRAFIX® anchor available from DePuy Mitek Inc. of Raynham, Mass. 
         [0038]      FIGS. 6 to 13  illustrate measurement and creation of the tunnel  80 . First a beath pin  10  is drilled in the desired orientation through the femur  82  creating a pilot hole  94  therethrough. The pin  10  is then advanced until the laser mark  18  is flush with the surface femur  82  (See  FIGS. 6 and 7 ). An appropriate sized gauge  30  is selected based upon the length of the loop  64 , with that size being printed  52  on the gauge  30 . Alternatively, if the gauge  30  has multiple faces with indicias  50  etc. as heretofore described the appropriate loop size face is oriented toward the surgeon. The first tube  32  of the gauge  30  is passed over the beath pin  10  and advanced until its first end  34  abuts the femur (See  FIGS. 8 and 9 ). The puts the beath pin through the femur  82  along the path (the pilot hole  94 ) which the soon to be drilled tunnel  80  will follow with the laser mark  18  at an inferior end  96  of the pilot hole  94  at a condylar notch surface  98  of the femur  82  and with the gauge first tube first end  34  at an opposite superior end  100  of the pilot hole  94 . 
         [0039]    The distal tip  14  of the pin  10  abuts the measuring block first end  48  and pushes the measuring block  44  out of the second tube  38  against the resistance of the spring  46  and the indicia scale  50  can be read at the second tube second end  42  (see  FIGS. 3 and 10 ). It returns the desired depth of the socket  84  from the condylar notch surface. A cannulated drill  102  of appropriate diameter for the socket  84  and having drilling depth indicia  104  thereon is passed over the beath pin  10  and the socket is drilled to the appropriate depth as indicated by the indicia scale  50  (see  FIG. 11 ). Then a separate, smaller cannulated drill  106  is passed over the pin  10  and the passing channel  86  is drilled through the femur  82  (see  FIG. 12 ). The graft construct  60  is then pulled up through the tunnel  80  with the bar  62  in a lengthwise orientation via the first suture  68  and then the bar  62  is manipulated into a sideways orientation via the second suture  70  and placed into abutment against the femur  82 . 
         [0040]    The depth gauge  30  provides the surgeon with the necessary information to drill the socket  84  for a given loop size. The length of the tunnel  80  is determined by the anatomy of the femur  82  and the path of the tunnel  80  therethrough. The gauge  30  measures this length by the spacing of the laser mark  18  and the gauge first tube first end  34 . This spacing is then translated into an appropriate socket  84  depth by the size and orientation of parts of the gauge  30 . The gauge  30  determines this depth by subtracting the loop length from the total length and then adding a length sufficient to allow the bar  62  to be pulled free of the femur and flip its orientation, about 8 to 10 mm. The graft length in the socket  84  shown by the scale  51  represents the socket  84  depth minus the flipping length. Rather than the surgeon having to perform calculations the gauge scales are oriented to read out the proper socket depth and graft length in the tunnel for a given loop size. 
         [0041]    Thus, while there have been shown, described, and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions, substitutions, and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit and scope of the invention. For example, it is expressly intended that all combinations of those elements and/or steps that perform substantially the same function, in substantially the same way, to achieve the same results be within the scope of the invention. Substitutions of elements from one described embodiment to another are also fully intended and contemplated. It is also to be understood that the drawings are not necessarily drawn to scale, but that they are merely conceptual in nature. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto. 
         [0042]    Every issued patent, pending patent application, publication, journal article, book or any other reference cited herein is each incorporated by reference in their entirety.

Technology Classification (CPC): 0