Abstract:
A spinal cage system for inserting a spinal cage assembly into a spine to separate and support adjacent spinal vertebrae, includes a first cage member; a second cage member; and an articulating mechanism adapted to connect the first cage member to the second cage member and to permit the first and second cage members to move relate to each other. An insertion instrument is adapted to capture the spinal cage assembly for insertion of the spinal cage assembly into a spine and to rotate the first and second cage members relative to each other to achieve a desired orientation in the spine.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation-in-part of application Ser. No. 11/742,873, filed on May 1, 2007, which claims the filing benefit of U.S. Provisional Application Ser. No. 60/796,691, filed May 2, 2006, the disclosures of which are hereby incorporated herein by reference in their entirety. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
       [0002]    Not applicable. 
       BACKGROUND 
       [0003]    The present disclosure relates generally to the field of orthopedic surgery and, more particularly, to the field of spinal implants. 
         [0004]    Fusion cages generally have been used in orthopedic surgery for fixing bones in a pre-selected spacial orientation. However, in inserting such fusion cages using minimally invasive surgical techniques, it is oftentimes difficult to insert a fusion cage without making an incision that is larger than desired or significantly displacing the neural element. Typically, interbody fusion cages of the prior art require considerable space to be rotated into the proper position between adjacent vertebrae. To properly position such prior art cages, it generally was necessary to make a larger incision or displace the nerve roots more than desirable, or both, to properly position the fusion cage. 
       BRIEF SUMMARY 
       [0005]    The present disclosure overcomes the foregoing and other shortcomings and drawbacks of the interbody fusion cages heretofore known. While the new fusion cage design and insertion method will be described in connection with certain embodiments, it will be understood that the disclosure is not limited to these embodiments. On the contrary, the disclosure includes all alternatives, modifications and equivalents as may be included within the spirit and scope of the present disclosure. 
         [0006]    The present disclosure relates to a fusion cage that is used to separate and support adjacent vertebrae in the spine. The fusion cage may be designed for use in the lumbar region of the spine, although it is possible to use the fusion cage of the present disclosure in other areas of the spine as well. The fusion cage has a first spacer member or chamber and a second spacer member or chamber that are pivotally interconnected by an articulating mechanism such as a hinge. The first and second spacer members are designed for insertion between adjacent vertebrae to properly support and separate the vertebrae. An advancing mechanism is located between the first and second spacer members to pivotally move the first spacer member relative to the second spacer member around the hinge. The angular position of the first spacer member relative to the second spacer member facilitates the insertion of the fusion cage around the dural sac and reduces the space necessary for the insertion of the cage. The advancing mechanism is operable to adjust the angular position of the first and second spacer members so that the first and second spacer members are in the desired position relative to the adjacent vertebrae when the cage is fully inserted. 
         [0007]    In another embodiment, the spinal cage system includes a first cage member; a second cage member; and an articulating mechanism adapted to connect the first cage member to the second cage member and to permit the first and second cage members to move relate to each other. An insertion instrument is adapted to capture the spinal cage assembly for insertion of the spinal cage assembly into a spine and to rotate the first and second cage members relative to each other to achieve a desired orientation in the spine. 
         [0008]    One advantage of the present fusion cage design is the use of an articulated fusion cage that can be displaced during the insertion process to move around the neural element in a manner that takes less room. Such articulation has the advantage of facilitating insertion of the cage during minimally invasive spinal surgery and reducing the need to displace the spinal cord more than is desirable. Another advantage is that, as the present fusion cage is maneuvered into position, the angular relationship between the two portions of the cage can be adjusted so that the cage is in the proper orientation when finally inserted. These and other advantages will be readily apparent to those skilled in the art based on the disclosure set forth herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0009]    For a fuller understanding of the nature and advantages of the present device, system, and insertion method, reference should be had to the following detailed description taken in connection with the accompanying drawings, in which: 
           [0010]      FIG. 1  is a top view showing a fusion cage according to one embodiment of the present fusion cage design in an open or expanded position; 
           [0011]      FIG. 2  is a top view showing the fusion cage of  FIG. 1  in a closed or collapsed position; 
           [0012]      FIG. 3  is a right side view of the fusion cage of  FIG. 1  in a collapsed or inserted position and showing serrations on the top and bottom of the cage; 
           [0013]      FIG. 4  is an overhead view of the insertion instrument and open positioned fusion cage assembly of another design with the fusion cage being captured and held by the insertion instrument; 
           [0014]      FIG. 5  is a side view of the captured fusion cage assembly and insertion instrument of  FIG. 4 ; 
           [0015]      FIG. 6  is a perspective view of the captured fusion cage assembly in and open and rotated position, but still captured by the insertion instrument; 
           [0016]      FIG. 7  is a perspective view of the fusion cage assembly in a closed (inserted) position; 
           [0017]      FIG. 8  is a side, elevation view of the fusion cage assembly of  FIG. 7 ; 
           [0018]      FIG. 9  is a side elevation view of the captured fusion cage assembly and insertion instrument of  FIG. 4 , as it is inserted adjacent to the spine during practice of the fusion cage assembly insertion method disclosed herein; 
           [0019]      FIG. 10  is a section view taken along line  10 - 10  of  FIG. 9 , where the insertion instrument is inserted to place the fusion cage assembly adjacent to the spine; 
           [0020]      FIG. 11  is the same view as in  FIG. 10 , but with the insertion instrument withdrawn to an intermediate withdrawal position; 
           [0021]      FIG. 12  is the same view as in  FIGS. 10 and 11 , but with the insertion instrument being advanced further into the body to commence rotation of the fusion cage; 
           [0022]      FIG. 13  is the same view as in  FIGS. 10-12 , but with the insertion instrument being advanced further into the body to complete rotation of the fusion cage into position in the spine; 
           [0023]      FIG. 14  is the same view as in  FIGS. 10-13 , but with the insertion instrument being removed from the body to leave the fusion cage into position in the spine; 
           [0024]      FIG. 15  is the same view as in  FIGS. 10-14 , but with insertion instrument fully removed from the body to leave the spinal fusion cage assembly in position in the spine; 
           [0025]      FIG. 16  is a perspective view of the insertion instrument and captured fusion cage assembly as depicted in  FIG. 13 ; and 
           [0026]      FIG. 17  is a perspective view of the inserted fusion cage assembly, as depicted in  FIG. 15 , 
       
    
    
       [0027]    The drawings will be described in greater detail below. 
       DETAILED DESCRIPTION  
       [0028]    The present disclosure is directed to an interbody fusion cage assembly that is used in spinal fusion procedures, such as a transforaminal lumbar spinal fusion procedure, by way of example. More particularly, the present disclosure is directed to an articulated fusion cage assembly that can be adjusted in configuration to facilitate the insertion of the cage assembly between adjacent vertebrae in the spine, such as the lumbar region. The fusion cage assembly of the present disclosure may be inserted by the use of minimally invasive surgical techniques wherein relatively small incisions are made in the patient and instruments are utilized to guide the cage assembly to the desired location between adjacent vertebrae. The articulated nature of the cage assembly allows the cage assembly to be disposed at an angle that facilitates the insertion of the cage assembly around the neural elements and reduces the displacement or impact on the nerve roots during the insertion process. 
         [0029]    Referring now to the embodiment depicted in  FIGS. 1-3 , and to  FIGS. 1-2  in particular, a fusion cage assembly,  10 , has a first spacer member or chamber,  15 , and a second spacer member or chamber,  19 , that are connected together by an articulating mechanism, such as a hinge,  25 , to form the complete fusion cage assembly. The cage assembly may be made of reinforced carbon fiber, PEEK (poly ether ether ketone) polymer material, titanium, or other suitable biomaterial. Hinge  25  may be made of nitinol, titanium, or other biocompatible material. Hinge  25  may incorporate holes,  29 , in the hinge material to assist in connecting to the cage assembly material. Holes  29  provide an opening in which the bone or bone replacement material can protrude to form a secure bond between the cage assembly and the hinge. 
         [0030]    Alternatively, hinge  25  could be created by using a mechanism similar to one seen in a door hinge, wherein one chamber of the fusion cage assembly pivots in relation to the other. Chambers  15 ,  19  of fusion cage assembly  10  interdigitate at hinge  25 , allowing them to pivot in relation to each other. It will be appreciated that other types of hinge or articulating mechanisms known to those of ordinary skill in the art are possible as well without departing from the spirit and scope of the present disclosure. 
         [0031]    In one embodiment, first space member  15  and second spacer member  19  may be generally elliptical in shape when looked at from above; and openings  17  and  21  may be provided in first and second spacer members, respectively, as shown in  FIGS. 1 and 2 . In one embodiment, fusion cage assembly  10  may have a “lordotic” shape, wherein the front of cage assembly  10  is taller than the back. Cage assembly  10  may have serrations,  73 , provided on the top and bottom of the cage assembly. First and second spacer members  15 ,  19  of cage assembly  10  may be the same length or may vary in length and size with, for example, second spacer member  19  being longer and making up to 70% of the total length of cage assembly  10 . First and second spacer members  15 ,  19  may be designed to fit between and properly space adjacent vertebrae in the lumbar region of the spine. Fusion cage assembly  10  may be used when a disk is removed from between the vertebrae and it is necessary to use cage assembly  10  to provide the necessary spacing between the vertebrae and to stabilize the vertebrae after the disc has been removed. In most applications, bone or bone graft substitute will be positioned in openings  17 ,  21  of first and second spacer members  15 ,  19 , so that the bone can fuse with the adjacent vertebrae to complete the repair on the spine. 
         [0032]    In one embodiment, a threaded passageway,  31 , extends from opening  21  in second spacer member  19  to an end,  33 , of second spacer member  19  that is adjacent to first spacer member  15 . Threaded passageway  31  may be metallic and made of material such as, for example, titanium. Passageway  31  may be encased within the wall of trailing chamber  19 . An advancement mechanism, such as a threaded rod/screw,  35 , may be positioned in threaded passageway  31 , so that the threads on the rod engage the threads on threaded passageway  31 . An end,  37 , of rod  35  that is spaced apart from opening  21  in second spacer member  19  is disposed to engage an edge,  43 , of first spacer member  15 . A pivoting foot or ball in a socket,  47 , design may be employed on the end of threaded rod  35  that engages edge  43  of first spacer member  15 . The pivoting foot or ball and socket design facilitates angulation of the cage assembly as the hinge is deployed. A port,  51 , may extend through a portion of second spacer member  19  that is on the opposite side of opening  21  from threaded passageway  31 . Port  51  may extend into opening  21  and is disposed to be in alignment with threaded passageway  31 . Port  51  may be threaded to facilitate placement of a cage assembly inserter or tool,  57 , having a shaft,  61 , as shown in  FIG. 2 , which can be inserted into port  51  and advanced to engage threaded rod  35  so that tool  57  can used to rotate and advance threaded rod  35 . Port  51  may be placed as far anteriorly (in the front) as possible so that inserted tool device  57  occupies the least amount of space within chamber  21 . 
         [0033]    In use, fusion cage assembly  10  of the present disclosure is in the collapsed position shown in  FIG. 2  with end  33  of second spacer member  19  positioned immediately adjacent edge  43  of first spacer member  15  when the cage assembly is initially beginning to be inserted into the patient. Fusion cage assembly  10  in this collapsed positioned is advanced into an incision made in the patient to position fusion cage assembly  10  between adjacent vertebrae in the spine, such as in a transforaminal lumbar spinal fusion procedure. As fusion cage assembly  10  is inserted, it must move around the neural elements that are positioned adjacent the area where fusion cage assembly  10  will be located between the adjacent vertebrae. Essentially, fusion cage assembly  10  must be inserted and rotated around the neural elements to position the fusion cage assembly in the desired location. 
         [0034]    To reduce the intrusion of fusion cage assembly  10  into the body of the patient and to reduce the amount of displacement that may be necessary for the spinal cord it is desirable to articulate or bend the fusion cage assembly so that it will more easily move around the spinal column. This becomes especially important when fusion cage assembly  10  is inserted through relatively small incisions utilizing an access tube or cannula. In such situations, there is little room for maneuverability, and a straight position of the cage assembly during the initial insertion process is desirable. When fusion cage assembly  10  is inserted into the body so that first spacer member  15  is extending past the dural sac, tool  57  can be turned, much like a screwdriver, to advance threaded rod  35  in threaded passageway  31 . Pivoting foot or ball in socket  47  on the end of threaded rod  35  permits edge  43  of first spacer member  15  to be advanced away from end  33  of second spacer member  19  as threaded rod  35  is advanced via operation of tool  57 . The advancement of threaded rod  35  causes first spacer member  15  to pivot away from second spacer member  19  around pivot point or hinge  25  that connects first spacer member  15  to second spacer member  19 . Threaded rod  35  is advanced until first spacer member  15  is in the desired angular relationship with respect to second spacer member  19  and fusion cage assembly  10  can be advanced into the patient in a direction that is less intrusive and not injurious to the body of the patient. Tool  57  can be used to adjust the angular position between first spacer member  15  and second spacer member  19  to facilitate the insertion of fusion cage assembly  10 . As first spacer member  15  is advanced between the adjacent vertebrae and around the spine, threaded rod  35  can be advanced to increase the angle between first spacer member  15  and second spacer member  19 . Increasing the angle allows fusion cage assembly  10  to progressively move to the angulated position so as to allow fusion cage assembly  10  to be positioned into the proper location between the adjacent vertebrae. 
         [0035]    When fusion cage assembly  10  is fully inserted between the adjacent vertebrae, threaded rod  35  will have been advanced so that fusion cage assembly  10  is in the angulated position shown in  FIG. 1 . When fusion cage assembly  10  has been angulated, tool  57  can be disengaged from threaded rod  35  and retracted until the threads in tool  57  are engaged with threads within port  51 . The cage assembly is then further advanced by using an impactor and properly located between the adjacent vertebrae. Tool  57  then is removed from second spacer member  19 . The end of tool  57  that engages threaded rod  35  will have a mechanism, as is well known in the art, to engage the threaded rod so that the tool can cause the threaded rod to be rotated in threaded passageway  31 . It will be appreciated that other advancement mechanisms for opening and collapsing first and second spacer members  15  and  19 , and other types of tools for selectively advancing the advancement mechanism are possible as well without departing from the spirit and scope of the present disclosure. Further details of this new fusion cage assembly method will be detailed below in connection with another embodiment of the disclosed fusion cage assembly. 
         [0036]    If desired, a shoulder (not shown) can be positioned in threaded passageway  31  adjacent opening  21  to act as a stop for threaded rod  35 . The shoulder will prevent threaded rod  35  from being advanced into opening  21  in second spacer member  19 . 
         [0037]    First and second spacer members  15 ,  19  of cage assembly  10  could be symmetric or asymmetric in size. Leading chamber  15  could be smaller (with 40:60 ratio with trailing chamber  19 . Such a configuration would decrease stresses on leading chamber  15  as the tallest portion of cage assembly  10  would be located on trailing chamber  19 . This would, in turn, decrease the risk of shearing and stripping of advancing mechanism  35 . 
         [0038]    If desired, hinge  25  could be created with a scored metal rod. Hinge  25  is contained between chambers  15 ,  19 , and the wings of the scored metallic rod are initially deployed to keep cage assembly  10  in a collapsed position. As cage assembly  10  is partially inserted, the wings of the scored metallic rod could be retracted allowing the rod to elongate between chambers  15 ,  19 , which would angulate the cage assembly. 
         [0039]    Referring now to another embodiment of the disclosed fusion cage assembly, reference is made to  FIGS. 4-17 , where a fusion cage assembly,  100  (see  FIGS. 7 and 8 ), is seen captured by an insertion instrument,  102  ( FIGS. 4-6 ). Like the embodiment depicted in  FIGS. 1-3 , fusion cage assembly  100  is composed of two spacer members or elements, a leading spacer member,  104 , and a trailing spacer member,  106 . The top and bottom surfaces of both spacer members are serrated in order to assist the adjacent vertebrae in retaining the inserted fusion cage assembly in position. Again like before, insertion instrument  102  captures fusion cage assembly  100  for its insertion into position where a disk has been removed from the spine. Like the previously described embodiment, fusion cage assembly is articulated about a pivot point. Insertion instrument  102  is elongate having a handle region,  108 , and a capture region,  110 . Its operation will be described in greater detail below in connection with the fusion cage assembly procedure. 
         [0040]    Referring now to  FIG. 9 , insertion instrument  102  and captured fusion cage assembly  100  have been placed in position adjacent to a spine,  112 , and adjacent to a space,  114 , created by the prior removal of a disk (similar to a disk,  115 ) located between an upper vertebra,  116 , and a lower vertebra,  118 . Shown in phantom disposed in the interior of annular instrument handle  102  is a rod,  120 , that actually captures fusion cage assemble  100 . Handle  108  contains a dial,  122 , that provides a readout to the surgeon indicating the distance rod  120  has been extended or retracted with respect to instrument  102 . 
         [0041]    In particular, spacer members  104  and  106  are held together by a pivot pin,  124 , which is located in a body,  126 , having a forward surface,  128 . The distal end,  130 , of rod  120  bears against surface  128  of body  126  and, thus, keeps fusion cage assembly  100  in an open position, as depicted in  FIG. 10 . When the surgeon rotates handle region  108  a defined amount as determined by dial  122 , rod  120  withdraws towards the proximal end of insertion instrument  102  and, thus, no longer is in contact with surface  128 . This partially withdrawn position of rod  120  now permits leading spacer member  104  to rotate about pin  124  to form an arcuately shaped fusion cage assembly and also rotate about another pin,  132 , with respect to trailing spacer member  106 , because spacer member  106  still is held by road  120 . 
         [0042]    At this juncture of the insertion procedure and as depicted in  FIGS. 12 and 13  (and associated  FIG. 16 ), the surgeon commences to again push insertion instrument further into the patient. Leading spacer member  104 , however, encounters tissue that causes it to rotate about pins  124  and  132  into space  114 . Such rotational movement prevents leading spacer member  104  from contacting the spinal cord or any nerves and other sensitive tissue associated with spine  112 . The arcuate or closed position of fusion cage  100  is maintained when insertion instrument  102  is withdrawn by the surgeon and out of contact with fusion cage assembly  100 , as depicted in  FIGS. 14 and 15 . At this juncture, the procedure is complete and insertion instrument  102  is totally removed from the patient, as seen in  FIG. 17 . While the spinal cord is shown moved aside from the path of the advancing fusion cage assembly, the retractor that is used therefor has been omitted for ease in illustrating the disclosed spinal cage assembly. 
         [0043]    While the device, system, and insertion method has been described with reference to various embodiments, those skilled in the art will understand that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope and essence of the disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiments disclosed, but that the disclosure will include all embodiments falling within the scope of the appended claims. In this application all units are in the metric system and all amounts and percentages are by weight, unless otherwise expressly indicated. Also, all citations referred herein are expressly incorporated herein by reference.