Abstract:
Method and apparatus for securing first and second bones together by forming a cavity in the first and second bones, with the cavity including a shaped first anchor portion in the first bone and a shaped second anchor portion in the second bone, with a channel extending therebetween, fixating a first tissue anchor onto a first portion of tissue, fixating a second tissue anchor onto a second portion of the tissue, and inserting the first tissue anchor into the cavity first anchor portion and the second tissue anchor into the cavity second tissue anchor, wherein the tissue first and second portions are secured to the first and second bone, and the tissue extends along the channel. The tissue will form a strong biological construct with the sidewalls of the channel, whereby the tissue anchors may optionally dissolve away.

Description:
[0001]     This application claims the benefit of U.S. Provisional Application No. 60/543,633, filed Feb. 10, 2004. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to ligament repair, and more particularly to a method and apparatus that provides standardized attachment points for attaching ligaments to bone that enhances bone association and ligament repair.  
       BACKGROUND OF THE INVENTION  
       [0003]     Presently it can be difficult to repair injured ligaments that connect between separate bones. For example, when the ligament connecting the scaphoid and lunate bones in the wrist is injured, where the ligament is torn or ruptured from the bone causing the bone positions to disassociate, the injury is often repaired by simply fusing these bones together, where mobility between these bones is permanently lost. Instead of bone fusion, these bones can be reconnected together in a mobile fashion by grafting soft tissue on the surfaces of the bone. However, the strength of the soft tissue bond can be weak, and the ideal separation between these bones can be hard to achieve. Tissue grafts can have high failure or re-injury rates, even if the bones are pinned together during the initial healing process.  
         [0004]     There is a need for a ligament repair apparatus and method that reliably connects bones together, that promotes bone to connective tissue healing to create a permanent reliable bone/tissue/bone fixation, that simplifies the actual operative techniques to implement, and that maintains bone mobility even during the healing process.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention solves the aforementioned problems by providing tissue anchors that crimp or swag onto the ends of connective tissue, a compression assembly for ensuring the tissue anchors are separated along the tissue by the desired distance, and a drilling template to ensure the bone cavity is formed with the correct dimensions. The present invention essentially transforms non-standard sized tissue and standardizes its dimensions for insertion into bone cavities of predetermined dimensions.  
         [0006]     The anchor system of the present invention, for fixating portions of tissue in a bone cavity, includes a pair of tissue anchors each having an aperture, wherein the aperture includes side walls for receiving and exerting a fixating force onto a portion of the tissue.  
         [0007]     In another aspect of the present invention, an anchor system for securing first and second bones together utilizing tissue having first and second portions and utilizing a bone cavity having a first anchor portion formed in the first bone and a second anchor portion formed in the second bone and a channel extending between the first and second anchor portions, includes a first tissue anchor dimensioned for insertion into the cavity first anchor portion, the first tissue anchor including a first aperture in which the first portion of the tissue is fixated, and a second tissue anchor dimensioned for insertion into the cavity second anchor portion, the second tissue anchor including a second aperture in which the second portion of the tissue is fixated, wherein the first and second bones are secured together by the first and second tissue anchors inserted in the cavity first and second anchor portions, and by the tissue extending between the first and second tissue anchors and through the channel.  
         [0008]     In yet one more aspect of the present invention, a method of securing first and second bones together with tissue includes forming a cavity in the first and second bones, the cavity including a first anchor portion formed in the first bone, a second anchor portion formed in the second bone, and a channel extending between the first and second anchor portions, fixating a first tissue anchor onto a first portion of the tissue, fixating a second tissue anchor onto a second portion of the tissue, and inserting the first tissue anchor into the cavity first anchor portion and the second tissue anchor into the cavity second anchor portion such that the tissue extends along the channel.  
         [0009]     Other objects and features of the present invention will become apparent by a review of the specification, claims and appended figures.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a perspective view of the tissue anchor assembly of the present invention.  
         [0011]      FIG. 2  is a perspective view of the tissue anchor of the present invention.  
         [0012]      FIG. 3  is a top view of the bone cavity formed to receive the tissue anchor assembly of the present invention.  
         [0013]      FIG. 4  is a perspective view showing the formation of the tissue anchor using a mold insert.  
         [0014]      FIGS. 5A and 5B  are perspective views of the compression plates of the present invention.  FIGS. 6A  to  6 D are perspective views illustrating the positioning plates of the present invention.  
         [0015]      FIG. 7A and 7B  are perspective views of the compression assembly of the present invention.  
         [0016]      FIGS. 8A and 8B  are perspective views of the drilling template of the present invention.  
         [0017]      FIG. 9  is a top view illustrating the tissue anchor assembly implemented in the bone cavity.  
         [0018]      FIG. 10  is a perspective view of the tissue carrier of the present invention.  
         [0019]      FIG. 11  is a top view illustrating a scalloped surface of the tissue anchor assembly implemented in the bone cavity for use with an interference screw. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]     The present invention is a tissue anchor assembly and method of implementation of the same that securely connects two bones together with tissue while preserving mobility and promoting healing. The present invention is described in the context of reconstructing the ligament complex between the scaphoid and lunate carpal bones using harvested donor ligament tissue, but any bones can be connected together using the present invention, with any appropriate organic or inorganic connective tissue.  
         [0021]      FIG. 1  illustrates the tissue anchor assembly  10  of the present invention, which includes a pair of tissue anchors  12  fixated to the ends of tissue  14 . Tissue  14  can be any appropriate organic or inorganic, synthetic or natural, connective or muscular tissue, and/or any combinations thereof. Each of the tissue anchors  12  is a generally cylindrically shaped rigid member with an aperture  16  (e.g. a thin slot) formed therethrough, as shown in  FIG. 2 . Tissue anchors  12  may be made of any appropriate biocompatible material (preferably a polymer or copolymer), which also may be bio-absorbable, osteoconductive, and/or osteoinductive.  
         [0022]     Each end of the tissue  14  is inserted into the slot (aperture)  16  of one of the tissue anchors  12 , and then the tissue anchors  12  are crimped down (swaged) onto the tissue  14  so that sidewalls  16   a  of slot  16  exert a tissue fixating force onto the tissue to create a compressive lock that secures the tissue  14  in slots  16 . The tissue anchors  12  are separated by a predetermined distance D, and provide a standardized shape for connecting the ends of tissue  14  to bone.  
         [0023]      FIG. 3  illustrates the bone cavity  18  in which the tissue anchor assembly  10  is inserted. The bone cavity  18  is formed in the bones  20   a  and  20   b  which are to be connected together (separated by cartilage  62 ) using conventional bone drilling and channeling techniques. Bone cavity  18  includes a pair of cylindrical holes  22  (one in each of the bones  20   a/b ) which are preferably sized to match the size the tissue anchors  12 . A channel  24  extends between the cylindrical holes  22  and is sized to receive the tissue  14 . With the bones  20   a/b  ideally positioned with the desired separation (if any), holes  22  are separated by the distance D.  
         [0024]     To anchor the bones  20   a/b  together, the tissue anchors  12  are inserted into the holes  22 , such that the tissue  14  is inserted into the channel  24 . Ideally, the tissue  14  and channel  24  are dimensioned to gently press the tissue  14  against the bone sidewalls of channel  24  to promote the healing of the tissue  14  to the bones  20   a/b,  and to ultimately result in a strong biological construct therebetween (without any excessive forces sufficient to cause bone erosion, tissue necrosis, etc.). Once the biological construct is formed between tissue  14  and bones  20   a/b,  tissue anchors  12  are no longer necessary. Thus, tissue anchors  12  can be made of a bio-absorbable material that dissolves after the healing period has ended and bone regeneration fills the void left from implanting the anchors.  
         [0000]     Tissue Anchor Swaging  
         [0025]     The tissue anchors  12  are preferably swaged onto the tissue ex-vivo in the following manner. First, the tissue anchors  12  are formed via molding with the slots  16  preferably having the smallest possible width.  FIG. 4  illustrates one of the tissue anchors  12  molded around a very thin mold insert  26 , which leaves slot  16  in tissue anchor  12  after being removed therefrom. The slots  16  are then manually expanded in width, for example, by driving a mandrel through each slot  16  to expand it. Depending upon the material used to form tissue anchors  12 , the slots therein can be expanded while the tissue anchor material is at room temperature, or can be expanded while in an excited state (“excite expanded”, where the molecules of the tissue anchor material have been sped up). The excited state can be achieved by, for example, subjecting the tissue anchor material to heat (e.g. via conduction), ultrasonic waves, radiation (e.g. visible, ultraviolet, and/or infrared light from a laser, RF, etc.) and so on.  
         [0026]     After the tissue  14  is inserted into slots  16 , the tissue anchors  12  are mechanically compressed by a swaging or crimping action so that each tissue anchor  12  (via i.e. aperture sidewalls  16   a ) exerts a tissue fixation force that prevents the tissue  14  from sliding out of slot  16 . Depending upon the material used to form tissue anchors  12 , they can be compressed at room temperature, or can be compressed while in an excited state (“excite compressed”, where the molecules of the tissue anchor material have been sped up during compression). Once the excitation source and/or mechanical compressive force have been removed, the tissue anchor exerts an inward force on the tissue  14  that secures it with slot  16  in a very strong and reliable manner. It has been discovered that by expanding the slot  16  before compression, better fixation forces can be achieved.  
         [0027]      FIGS. 5A and 5B  illustrate tooling for compressing the tissue anchors  12 . The tooling includes a pair of compression plates  28   a/b  having engagement tabs  30  and compression tabs  32  extending therefrom. The engagement tabs  30  engage each other to ensure the compression tabs  32  are properly aligned to each other as the plates  28   a/b  are pressed together. Each of the compression tabs  32  has an end (e.g. preferably concave) to engage with the cylindrical sidewall of the tissue anchors  12 . For each compression plate  28   a/b,  the compression tabs  32  are separated by the distance D.  FIG. 5A  illustrates the alignment of the plates  28   a/b  before engagement, and  FIG. 5B  illustrates the plates  28   a/b  pressed together.  
         [0028]     During the process of compressing the tissue anchors  12  on to the tissue  14 , features can be created on the surface of the tissue anchors  12  in the form of ribs, barbs or bumps corresponding to features made in the compression tabs  32 . The added features to the tissue anchors  12  would create a positive locking interference fit when pushed into the bone cavity  18 .  
         [0029]     To swage the tissue anchors  12  onto the tissue  14 , each tissue anchor is placed between opposing compression tabs  32 , and then the plates  28   a/b  are pressed together so the compression tabs  32  swage (crimp) the tissue anchors  12  down onto the tissue  14 . So long as the tissue is pulled taught before or during this process, the tissue anchors  12  are reliably distanced apart along the tissue  14  by the distance D. Interlocking positioning plates  34   a/b  can be used to reliably position tissue anchors  12  between opposing compression tabs  32 , as illustrated in  FIGS. 6A  to  6 D. The compression plates  28   a/b  can be pressed together using a compression assembly  36  as shown in  FIGS. 7A and 7B . The compression assembly includes drive shafts  38  that press the compression plates  28   a/b  together by the operation of leverage handles  40 . Positioning blocks  42  hold the compression plates  28   a/b  in place. The ends of drive shafts  38  preferably include rotatable bolts  44  that allow the user to adjust the amount of compression exerted on the compression plates  28   a/b  during the full action of the leverage handles  40 .  
         [0000]     Bone Cavity Formation  
         [0030]     The bone cavity  18  is preferably performed using a drilling template  46  (as shown in  FIG. 8A ), which is a plate  48  having an aperture  50  formed therethrough with a shape to match the desired dimensions of the bone cavity  18 . Forming the bone cavity  18  through the aperture  50  (i.e. using aperture  50  to guide the bone drilling/cutting tools) ensures that the cylindrical holes  22  and channel  24  have the desired dimensions, and holes  22  have the desired separation D. Other aperture(s) and/or slot(s) can be added to the drilling template to help position, or maintain position of, the template  46  on the target bones. Separate apertures for the holes and the channel portions of the bone cavity can be formed on separate inserts, which fit into the template  46  as shown in  FIG. 8B .  
         [0031]     Different matching sets of drilling templates  46  and compression plates  28   a/b,  with different matching values of separation D, can be provided to the surgeon so that, given the size of the bones to be connected together, the ideal tissue anchor separation value D can be selected and reliably achieved. Thus, the tissue anchor assembly  10  and bone cavity  18  have known and matching shapes. After tissue anchor assembly  10  has been implemented into bone cavity  18  (see  FIG. 9 ), the two bones  20   a/b  are connected together in a manner that allows motion between the bones during and after the healing process.  
         [0032]     The present invention has many advantages: tissue reconstruction is made at or below the interfacing bone surfaces where the original connection tissue existed to encourage re-growth, initial mechanical fixation allows early motion critical for successful healing and preservation of range of motion, and a better means to reliably position and repair the disassociation between bones.  
         [0033]     It is to be understood that the present invention is not limited to the embodiment(s) described above and illustrated herein, but encompasses any and all variations falling within the scope of the appended claims. For example, the tissue anchors  12  and bone cavity holes  22  need not necessarily be cylindrical in shape or even the same shape. In order to increase the friction and reduce any possible creep between the tissue anchors  12  and tissue  14 , the walls forming slots  16  can be roughened or include a textured pattern (e.g. knurled pattern, tines, pins, intermeshing patterns or grooves, etc.) to better engage with tissue  14 . Each tissue anchor could include separate parts or halves that attach together to clamp onto tissue  14 , or suture holes so that sutures can be used to help secure the tissue  14  to the tissue anchor  10 . Alternately, a tissue carrier  54  could be used, where tissue  14  is attached to one, both sides, or in between layers of the tissue carrier  54  that is shaped to fit the bone cavity, as illustrated in  FIG. 10 . Lastly, the outer surface of tissue anchors  12  could be irregularly shaped or mismatched in shape in comparison to that of the bone cavity. For example, as shown in  FIG. 1 , the outer surface is scalloped so that the tissue anchor  12  can be rotated within hole  22  and then fixed in place (e.g. with an interference screw  60  between the tissue anchor surface and the bone) for adjusting (post implementation) the tightness of the joint if necessary. Alternately, other mismatched shapes can be used to ensure there are gaps in which interferences screws can be used to fix rotation (e.g. square anchor in round cavity, etc.