Abstract:
A helicoil interference fixation system comprising:
       a helicoil comprising a helical body comprising a plurality of turns separated by spaces therebetween, the helical body terminating in a proximal end and a distal end, and at least one internal strut extending between at least two turns of the helical body; and   an inserter for turning the helicoil, the inserter comprising at least one groove for receiving the at least one strut;   the helicoil being mounted on the inserter such that the at least one strut of the helicoil is mounted in the at least one groove of the inserter, such that rotation of the inserter causes rotation of the helicoil.

Description:
REFERENCE TO PENDING PRIOR PATENT APPLICATIONS 
       [0001]    This patent application: 
         [0002]    (i) is a continuation-in-part of pending prior U.S. patent application Ser. No. 11/893,440, filed Aug. 16, 2007 by Dennis M. McDevitt for COMPOSITE INTERFERENCE SCREW FOR ATTACHING A GRAFT LIGAMENT TO A BONE, AND OTHER APPARATUS FOR MAKING ATTACHMENTS TO BONE (Attorney&#39;s Docket No. INCUMED-02); and 
         [0003]    (ii) claims benefit of pending prior U.S. Provisional Patent Application Ser. No. 61/200,285, filed Nov. 26, 2008 by Dennis M. McDevitt et all for HELICOIL FIXATION DEVICE (Attorney&#39;s Docket No. INCUMED-4 PROV). 
         [0004]    The two above-identified patent applications are hereby incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0005]    This invention relates to medical apparatus and procedures in general, and more particularly to medical apparatus and procedures for reconstructing a ligament. 
       BACKGROUND OF THE INVENTION 
       [0006]    Ligaments are tough bands of tissue which serve to connect the articular extremities of bones, and/or to support and/or retain organs in place within the body. Ligaments are typically made up of coarse bundles of dense fibrous tissue which are disposed in a parallel or closely interlaced manner, with the fibrous tissue being pliant and flexible but not significantly extensible. 
         [0007]    In many cases, ligaments are torn or ruptured as the result of an accident. Accordingly, various procedures have been developed to repair or replace such damaged ligaments. 
         [0008]    For example, in the human knee, the anterior and posterior cruciate ligaments (i.e., the “ACL” and “PCL”) extend between the top end of the tibia and the bottom end of the femur. The ACL and PCL serve, together with other ligaments and soft tissue, to provide both static and dynamic stability to the knee. Often, the anterior cruciate ligament (i.e., the ACL) is ruptured or torn as the result of, for example, a sports-related injury. Consequently, various surgical procedures have been developed for reconstructing the ACL so as to restore substantially normal function to the knee. 
         [0009]    In many instances, the ACL may be reconstructed by replacing the ruptured ACL with a graft ligament. More particularly, in such a procedure, bone tunnels are generally formed in both the top of the tibia and the bottom of the femur, with one end of the graft ligament being positioned in the femoral tunnel and the other end of the graft ligament being positioned in the tibial tunnel, and with the intermediate portion of the graft ligament spanning the distance between the bottom of the femur and the top of the tibia. The two ends of the graft ligament are anchored in their respective bone tunnels in various ways well known in the art so that the graft ligament extends between the bottom end of the femur and the top end of the tibia in substantially the same way, and with substantially the same function, as the original ACL. This graft ligament then cooperates with the surrounding anatomical structures so as to restore substantially normal function to the knee. 
         [0010]    In some circumstances, the graft ligament may be a ligament or tendon which is harvested from elsewhere within the patient&#39;s body, e.g., a patella tendon with or without bone blocks attached, a semitendinosus tendon and/or a gracilis tendon. In other circumstances, the graft ligament may be harvested from a cadaver. In still other circumstances, the graft ligament may be a synthetic device. For the purposes of the present invention, all of the foregoing may be collectively referred to herein as a “graft ligament”. 
         [0011]    As noted above, various approaches are well known in the art for anchoring the two ends of the graft ligament in the femoral and tibial bone tunnels. 
         [0012]    In one well-known procedure, which may be applied to femoral fixation, tibial fixation, or both, the end of the graft ligament is placed in the bone tunnel, and then the graft ligament is fixed in place using a headless orthopedic screw, generally known in the art as an “interference” screw. More particularly, with this approach, the end of the graft ligament is placed in the bone tunnel and then the interference screw is advanced into the bone tunnel so that the interference screw extends parallel to the bone tunnel and simultaneously engages both the graft ligament and the side wall of the bone tunnel. In this arrangement, the interference screw essentially drives the graft ligament laterally, into engagement with the opposing side wall of the bone tunnel, whereby to secure the graft ligament to the host bone with a so-called “interference fit”. Thereafter, over time (e.g., several months), the graft ligament and the host bone grow together at their points of contact so as to provide a strong, natural joinder between the ligament and the bone. 
         [0013]    Interference screws have proven to be an effective means for securing a graft ligament in a bone tunnel. However, the interference screw itself generally takes up a substantial amount of space within the bone tunnel, which can limit the surface area contact established between the graft ligament and the side wall of the bone tunnel. This in turn limits the region of bone-to-ligament in-growth, and hence can affect the strength of the joinder. By way of example but not limitation, it has been estimated that the typical interference screw obstructs about 50% of the potential bone-to-ligament integration region. 
         [0014]    For this reason, substantial efforts have been made to provide interference screws fabricated from absorbable materials, so that the interference screw can eventually disappear over time and bone-to-ligament in-growth can take place about the entire perimeter of the bone tunnel. To this end, various absorbable interference screws have been developed which are made from biocompatible, bioabsorbable 
         [0000]    INCUMED-5 polymers, e.g., polylactic acid (PLA), polyglycolic acid (PGA), etc. These polymers generally provide the substantial mechanical strength needed to advance the interference screw into position, and to thereafter hold the graft ligament in position while bone-to-ligament in-growth occurs, without remaining in position on a permanent basis. 
         [0015]    In general, interference screws made from such biocompatible, bioabsorbable polymers have proven clinically successful. However, these absorbable interference screws still suffer from several disadvantages. First, clinical evidence suggests that the quality of the bone-to-ligament in-growth is somewhat different than natural bone-to-ligament in-growth, in the sense that the aforementioned bioabsorbable polymers tend to be replaced by a fibrous mass rather than a well-ordered tissue matrix. Second, clinical evidence suggests that absorption generally takes a substantial period of time, e.g., on the order of three years or so. Thus, during this absorption time, the bone-to-ligament in-growth is still significantly limited by the presence of the interference screw. Third, clinical evidence suggests that, for many patients, absorption is never complete, leaving a substantial foreign mass remaining within the body. This problem is exacerbated somewhat by the fact that absorbable interference screws generally tend to be fairly large in order to provide them with adequate strength, e.g., it is common for an interference screw to have a diameter (i.e., an outer diameter) of 8-12 mm and a length of 20-25 mm. 
         [0016]    Thus, there is a need for a new and improved interference fixation system which (i) has the strength needed to hold the graft ligament in position while bone-to-ligament in-growth occurs, and (ii) promotes superior bone-to-ligament in-growth. 
       SUMMARY OF THE INVENTION 
       [0017]    These and other objects are addressed by the provision and use of a novel heliCoil interference fixation system for attaching a graft ligament to a bone. 
         [0018]    In one preferred form of the invention, there is provided a novel helicoil interference fixation system comprising: 
         [0019]    a helicoil comprising a helical body comprising a plurality of turns separated by spaces therebetween, the helical body terminating in a proximal end and a distal end, and at least one internal strut extending between at least two turns of the helical body; and 
         [0020]    an inserter for turning the helicoil, the inserter comprising at least one groove for receiving the at least one strut; 
         [0021]    the helicoil being mounted on the inserter such that the at least one strut of the helical is mounted in the at least one groove of the inserter, such that rotation of the inserter causes rotation of the helicoil. 
         [0022]    In another preferred form of the invention, there is provided a novel method for attaching a graft ligament to a bone, the method comprising: 
         [0023]    providing a helicoil interference fixation system comprising:
       a helicoil comprising a helical body comprising a plurality of turns separated by spaces therebetween, the helical body terminating in a proximal end and a distal end, and at least one internal strut extending between at least two turns of the helical body; and   an inserter for turning the helicoil, the inserter comprising at least one groove for receiving the at least one strut;   the helicon being mounted on the inserter such that the at least one strut of the helicoil is mounted in the at least one groove of the inserter, such that rotation of the inserter causes rotation of the helicoil;       
 
         [0027]    forming a bone tunnel in the bone, and providing a graft ligament; 
         [0028]    inserting the graft ligament into the bone tunnel; and 
         [0029]    using the inserter to turn the helicon into the bone tunnel so as to secure the graft ligament to the bone using an interference fit. 
         [0030]    In another preferred form of the invention, there is provided a novel helicoil comprising a helical body comprising a plurality of turns separated by spaces therebetween, the helical body terminating in a proximal end and a distal end, and at least one internal strut extending between at least two turns of the helical body, wherein the at least one internal strut comprises a helical construction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]    These and other objects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts, and further wherein: 
           [0032]      FIGS. 1-7  are schematic views showing a first helicoil interference fixation system formed in accordance with the present invention; 
           [0033]      FIGS. 8-13  are schematic views showing a second helicoil interference fixation system formed in accordance with the present invention; 
           [0034]      FIGS. 14-20  are schematic views showing a femoral fixation using the second helicoil interference fixation system of  FIGS. 8-13 ; 
           [0035]      FIGS. 21-25  are schematic views showing a full ACL reconstruction using the second helicoil interference fixation system of  FIGS. 8-13 ; 
           [0036]      FIGS. 26-28  are schematic views showing a soft tissue ACL fixation using the second helicoil interference fixation system of  FIGS. 8-13 ; 
           [0037]      FIGS. 29-31  are schematic views showing a third helicoil interference fixation system formed in accordance with the present invention; 
           [0038]      FIG. 32  is schematic view showing a fourth helicoil interference fixation system formed in accordance with the present invention; 
           [0039]      FIG. 33  is a schematic view showing a fifth helicoil interference fixation system formed in accordance with the present invention; 
           [0040]      FIGS. 34-36  are schematic views showing a sixth helicoil interference fixation system formed in accordance with the present invention; 
           [0041]      FIG. 37  is a schematic view showing a seventh helicoil interference fixation system formed in accordance with the present invention; 
           [0042]      FIG. 38  is a schematic view showing an eighth helicoil interference fixation system formed in accordance with the present invention; and 
           [0043]      FIG. 39  is a schematic view showing a ninth helicoil interference fixation system formed in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0044]    The present invention comprises the provision and use of a novel helicoil interference fixation system for attaching a graft ligament to a bone or other tissue. 
         [0045]    For convenience, the present invention will hereinafter be discussed in the context of its use for an ACL tibial and/or femoral fixation; however, it should be appreciated that the present invention may also be used for the fixation of other graft ligaments to the tibia and/or the femur; and/or the fixation of other graft ligaments to other bones or to other tissue such as organs. 
         [0046]    Looking first at  FIGS. 1-7 , there is shown a novel helicoil interference fixation system  5  for securing a graft ligament to a bone. Helicoil interference fixation system  5  generally comprises a helicoil  10  for disposition in a bone tunnel so as to hold the graft ligament in position while bone-to-ligament in-growth occurs. Helicoil interference fixation system  5  also comprises an inserter  15  for deploying helicoil  10  in the bone tunnel. More particularly, and looking now at  FIGS. 1-6 , and particularly at  FIG. 5 , helicoil  10  generally comprises a helical body  20  terminating in a distal end  25  and a proximal end  30 . Helical body  20  is constructed so that there are substantial spaces or gaps  35  between the turns  40  of the helical body. Spaces or gaps  35  facilitate bone-to-ligament in-growth, i.e., by providing large openings through the helical body. These large openings facilitate the flow of cell- and nutrient-bearing fluids through the helicoil, and permit the in-growth of tissue across the helicoil, so as to enhance bone-to-ligament in-growth. 
         [0047]    One or more struts  45  are disposed within the interior of helical body  20 , with the one or more struts  45  being secured to the interior surfaces  50  of helical body  20 . The one or more struts  45  provide a means for turning helicoil  10  during deployment within the body, as will hereinafter be discussed in further detail. In addition, the one or more struts  45  can provide structural support for the turns  40  of helical body  20 . The one or more struts  45  may be formed integral with helical body  20  (e.g., by a molding process), or they may be formed separately from helical body  20  and then attached to helical body  20  in a separate manufacturing process (e.g., by welding). Where the one or more struts  45  are formed integral with helical body  20 , the one or more struts  45  can be used to help flow melt into position. 
         [0048]    In one preferred form of the invention, the one or more struts  45  comprise helical structures. And in one particularly preferred form of the invention, the one or more struts  45  comprise helical structures which spiral in the opposite direction from the spiral of helical body  20 , and the one or more struts  45  have a pitch which is substantially greater than the pitch of helical body  20 . See  FIG. 5 . 
         [0049]    Preferably, the number of struts  45 , and their size, are selected so as to close off an insignificant portion of the spaces or gaps  35  between the turns  40  of helical body  20 , whereby to substantially not impede the passage of fluids and tissue through the helicoil. At the same time, however, the number of struts  45 , their size, and composition, are selected so as to provide an adequate means for turning helicoil  10  during deployment, and to provide any necessary support for the turns  40  of helical body  20 . 
         [0050]    In one preferred form of the present invention, one strut  45  is provided. 
         [0051]    In another preferred form of the present invention, a plurality of struts  45  (e.g., two, three, four or more struts) are provided. 
         [0052]    And in one preferred form of the present invention, the struts  45  collectively close off less than fifty percent (50%) of the spaces or gaps  35  between the turns  40  of helical body  20 . 
         [0053]    And in one particularly preferred form of the present invention, the struts  45  collectively close off less than twenty percent (20%) of the spaces or gaps  35  between the turns  40  of helical body  20 . 
         [0054]    Helicoil  10  is formed out of one or more biocompatible materials. These biocompatible materials may be non-absorbable (e.g., stainless steel or plastic) or absorbable (e.g., a bioabsorbable polymer). In one preferred form of the present invention, helicoil  10  preferably comprises a bioabsorbable polymer such as polylactic acid (PLA), polyglycolic acid (PGA), etc. In any case, however, helicoil  10  comprises a material which is capable of providing the strength needed to set the fixation device into position and to hold the graft ligament in position while bone-to-ligament in-growth occurs. Inserter  15  is shown in  FIGS. 1-4  and  7 . 
         [0055]    Inserter  15  generally comprises a shaft  55  having a distal end  60  and a proximal end  65 . One or more grooves  70  are formed on the distal end of shaft  55 . Grooves  70  receive the one or more struts  45  of helicoil  10 , in order that helicoil  10  may be mounted on the distal end of shaft  55  and rotated by rotation of shaft  55 . A tapered seat-forming thread  75  (e.g., a tapered cutting thread, a tapered opening or dilating thread, etc.) is formed in shaft  55  distal to grooves  70 . Tapered seat-forming thread  75  serves to precede helicoil  10  into the space between the graft ligament and the wall of the bone tunnel, and then to form a lead-in or opening in the graft ligament and the wall of the bone tunnel for receiving the turns  40  of helical body  20 , in much the same manner as a tap that creates the thread form, as will hereinafter be discussed in further detail. A handle  80  is mounted on the proximal end of shaft  55  in order to facilitate rotation of shaft  55  by the surgeon. 
         [0056]    It should be appreciated that tapered seat-forming thread  75  is matched to helicoil  10  so that when helicoil  10  is mounted on inserter  15 , tapered seat-forming thread  75  provides the proper lead-in for helicoil  10 . 
         [0057]    Preferably, interior surfaces  50  of helical body  20  and distal end  60  of inserter  15  are tapered, expanding outwardly in the proximal direction, so that helicoil  10  and inserter  15  form a positive seat such that the interior surface of the helicoil is in direct contact with the tapered body diameter of the inserter. 
         [0058]    Thus it will be seen that, when helicoil  10  is mounted on the distal end of shaft  55 , inserter  15  may be used to advance the helicoil to a surgical site and, via rotation of handle  80 , turn helicoil  10  into the gap between a graft ligament and the wall of a bone tunnel, whereby to create an interference fixation of the graft ligament in the bone tunnel. Significantly, inasmuch as inserter  15  has a tapered seat-forming thread  75  formed on its distal end in advance of helicoil  10 , the tapered seat-forming thread can form a seat into the tissue in advance of helicoil  10 , whereby to permit the helicoil to advance easily into the tissue and create the desired interference fixation. Accordingly, helicoil  10  does not need to have any penetrating point on its distal end in order to penetrate the tissue. 
         [0059]    If desired, inserter  15  may be cannulated so that the inserter and helicoil  10  may be deployed over a guidewire, as will hereinafter be discussed. 
         [0060]      FIGS. 8-13  show another helicoil interference fixation system  5 , wherein helicoil  10  comprises two struts  45  and inserter  15  comprises two grooves  70 . The use of two struts  45 , rather than one strut  45 , may be advantageous since it may distribute the load imposed during rotation over a larger surface area. This may be important where helicoil  10  is formed out of a bioabsorbable polymer. 
         [0061]    Helicoil interference fixation system  5  may be utilized in a manner generally similar to that of a conventional interference screw system in order to attach a graft ligament to a bone. 
         [0062]    More particularly, and looking now at  FIGS. 14-25 , there are shown various aspects of an ACL reconstruction effected using helicoil interference fixation system  5 . 
         [0063]      FIG. 14  shows a typical knee joint  205 , with the joint having been prepared for an ACL reconstruction, i.e., with the natural ACL having been removed, and with a tibial bone tunnel  210  having been formed in tibia  215 , and with a femoral bone tunnel  220  having been formed in femur  225 . 
         [0064]      FIG. 15  is a view similar to that of  FIG. 14 , except that a graft ligament  230  has been positioned in femoral bone tunnel  220  and tibial bone tunnel  210  in accordance with ways well known in the art. By way of example, graft ligament  230  may be “towed” up through tibial bone tunnel  210  and into femoral bone tunnel  220  using a tow suture  235 . 
         [0065]      FIGS. 16 and 17  show graft ligament  230  being made fast in femoral tunnel  220  using helicoil interference fixation system  5 . More particularly, in accordance with the present invention, helicoil  10  is mounted on the distal end of inserter  15  by fitting the struts  45  of helicoil  10  into the grooves  70  of the inserter. Then the inserter is used to advance helicoil  10  through tibial tunnel  210 , across the interior of knee joint  205 , and up into the femoral tunnel  220 . If desired, inserter  15  may be cannulated, so that the inserter and helicoil are advanced over a guidewire of the sort well known in the art. As the distal tip of the inserter is advanced, the tapered seat-forming thread  75  first finds its way into the space between the graft ligament  230  and the side wall of femoral bone tunnel  220 . Then, as the inserter is turned, tapered seat-forming thread  75  forms a seat into the tissue in advance of helicoil  10 , and helicoil  10  is advanced into the tissue so that the turns of helical body  20  seat themselves in the seat formed by seat-forming thread  75 . As this occurs, the graft ligament is driven laterally, into engagement with the opposing side wall of the bone tunnel. This action sets helicoil  10  between the side wall of femoral bone tunnel  220  and graft ligament  230 , thereby securing the interference fit between graft ligament  230  and the side wall of the bone tunnel, whereby to secure graft ligament  230  to the bone. 
         [0066]    Thereafter, and looking now at  FIGS. 18 and 19 , inserter  15  is withdrawn, leaving helicon  10  lodged in position between the graft ligament and the side wall of the bone tunnel. As seen in  FIG. 20 , helicoil  10  maintains the interference fit established between graft ligament  220  and the side wall of the bone tunnel, thereby securing the graft ligament to the bone. 
         [0067]    If desired, helicoil interference fixation system  5  can then be used in a similar manner to form a tibial fixation. See  FIGS. 21-25 . 
         [0068]    Significantly, forming the fixation device in the form of an open helical coil has proven particularly advantageous, inasmuch as the open helical coil provides the strength needed to set the fixation device into position, and hold the graft ligament in position while bone-to-ligament in-growth occurs, while still providing extraordinary access through the body of the fixation device. Thus, cell- and nutrient-bearing fluids can move substantially unimpeded through the body of helicoil  10 , and tissue in-growth can occur across the body of helicoil  10 . 
         [0069]    Furthermore, it has been found that when the graft ligament thereafter imposes axial loads on the interference fit, struts  45  help maintain the structural integrity of turns  40  of helical body  20 , whereby to ensure the integrity of the interference fit. 
         [0070]    In  FIGS. 16-24 , graft ligament  230  is shown to include bone blocks at the ends of the ligament, e.g., graft ligament  10  may be a patella tendon with bone blocks attached. However, as seen in  FIGS. 26-28 , graft ligament  230  can also constitute only soft tissue, e.g., graft ligament  230  may comprise a semitendinosus tendon and/or a gracilis tendon, and/or a synthetic device. 
         [0071]    In  FIGS. 5 and 11 , the one or more struts  45  are shown as having a helical structure. However, the one or more struts  45  may also be formed with a straight configuration. See, for example,  FIGS. 29-30 , which show a helicoil  10  with a single straight strut  45 , and  FIG. 31  which shows a helicoil  10  with multiple straight struts  45 . 
         [0072]    Furthermore, as seen in  FIG. 32 , the one or more struts  45  may be interrupted between turns  40  or, as seen in  FIG. 33 , the one or more struts  45  may be selectively interrupted between turns  40 . 
         [0073]    It should also be appreciated that an interference fit may be formed using a plurality of helicoils  10 . Thus, as seen in  FIGS. 34-36 , a plurality of helicoils  10  may be loaded on an inserter  15  and used for a collective interference fit. 
         [0074]    If desired, and looking now at  FIG. 37 , the one or more struts  45  may be replaced with recesses  45 A. In this case, grooves  70  on inserter  15  are replaced by corresponding ribs (not shown), whereby to permit inserter  15  to rotatably drive helicoil  10 . 
         [0075]    As seen in  FIG. 38 , the period of turns  40  may change along the length of helicoil  10 . 
         [0076]    Additionally, if desired, helicoil  10  can be tapered between its distal end  25  and its proximal end  30 . 
       Modifications 
       [0077]    It will be appreciated that still further embodiments of the present invention will be apparent to those skilled in the art in view of the present disclosure. It is to be understood that the present invention is by no means limited to the particular constructions and method steps herein disclosed and/or shown in the drawings, but also comprises any modifications or equivalents within the scope of the invention.